WO2006120667A2 - Expression constructs and methods of using same for expressing heparanase in plants - Google Patents

Abstract

Nucleic acid constructs suitable for expression of heparanase in plants and methods of using same are provided.

Description

EXPRESSION CONSTRUCTS AND METHODS OF USING SAME FOR EXPRESSING HEP ARANASE IN PLANTS

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to expression constructs and methods of using same for expressing heparanase in plants.

Heparan sulfate proteoglycans (HSPG) are ubiquitous macromolecules associated with the cell surface and extra cellular matrix (ECM) of a wide range of cells of vertebrate and invertebrate tissues (1-4). The basic HSPG structure includes a protein core to which several linear heparan sulfate chains are covalently attached. These polysaccharide chains are typically composed of repeating hexuronic and D- glucosamine disaccharide units that are substituted to a varying extent with N- and O- linked sulfate moieties and N-linked acetyl groups (1-4). They bind avidly to a variety of biologic effector molecules, including extracellular matrix components, growth factor, growth factor binding proteins, cytokines, cell adhesion molecules, proteins of lipid metabolism, degradative enzymes and protease inhibitors.

Studies on the involvement of ECM molecules in cell attachment, growth and differentiation reveal a central role of HSPG in embryonic morphogenesis, angiogenesis, neurite outgrowth and tissue repair (1-5). HSPG are prominent components of blood vessels (3). In large blood vessels they are concentrated mostly in the intima and inner media, whereas in capillaries they are situated mainly in the subendothelial basement membrane where they support proliferating and migrating endothelial cells and stabilize the structure of the capillary wall. The ability of HSPG to interact with ECM macromolecules such as collagen, laminin and fibronectin, and with different attachment sites on plasma membranes suggests a key role for this proteoglycan in the self-assembly and insolubility of ECM components, as well as in cell adhesion and locomotion.

Cleavage of the heparan sulfate (HS) chains may therefore result in degradation of the subendothelial ECM and hence may play a decisive role in extravasation of blood-borne cells. HS catabolism is observed in inflammation, wound repair, diabetes, and cancer metastasis, suggesting that enzymes which degrade HS play important roles in these pathologic processes. Heparanase is an important enzyme involved in the metabolism of HS. Together with other lysosomal hydrolases, heparanase participates in the sequential degradation of HS. Heparanase is an endo-beta.-glucuronidase that cleaves its subject at specific interchain sites. Heparanase activity has been described in activated immune system cells and highly metastatic cancer cells (6-8) The enzyme is released from intracellular compartments (e.g., lysosomes or specific granules) in response to various activation signals (e.g., thrombin, calcium ionophore, immune complexes, antigens and mitogens), suggesting its regulated involvement in inflammation and cellular immunity (6). A number of factors are capable of binding to HSPGs including those that belong to the fibroblast growth factor (FGF) family (9). Fibroblast growth factors are highly mitogenic for vascular endothelial cells and are among the most potent inducers of neovascularization (9, 10). Studies on the interaction of bFGF with ECM revealed that bFGF binds to HSPG in the ECM and are released in an active form by HS degrading enzymes (11, 12, and 13). This sequestering of bFGF and possibly other heparin-binding angiogenic factors (e.g. vascular endothelial cell growth factor, VEGF) from their site of action, may explain the fact that despite the ubiquitous presence of growth factors in normal tissues, endothelial cell proliferation in these tissues is usually very low. It was demonstrated that heparanase activity expressed by platelets, mast cells, neutrophils, and lymphoma cells is involved in the release of active bFGF from ECM and basement membranes (14). Not only does heparanase aid in bFGF release, but the generated HS fragments are thought to potentiate bFGF receptor binding, dimerization and signaling (15, 16, and 17). Similar results were also obtained with VEGF (18). Wound repair is a chain process necessary for the removal of damaged tissue or invading pathogens from the body and for the recovery of normal skin tissue. The healing process requires a sophisticated interaction between inflammatory cells, biochemical mediators including growth factors, extracellular matrix molecules, and microenvironment cell population. Inflammatory cells, keratinocytes and fibroblasts in the wound space and border produce and release a variety of growth factors such as platelet-derived growth factor (PDGF), epidermal growth factor (EGF), transforming growth factor (TGF) and fibroblast growth factor (FGF). These growth factors have biological activities which stimulate infiltration of inflammatory cells into the wound space and induce proliferation of keratinocytes and fibroblasts, leading to the formation of highly vascularized granulation tissue and extracellular matrix deposition. Topical application of some growth factors (FGF, PDGF) accelerate healing of full-thickness wounds in normal mice and normalize a delayed healing response of diabetic mice (19, 20). This suggests that heparanase activity may not only function in cell migration and invasion, but may also elicit an indirect neovascular response in normal and pathological situations such as wound healing, inflammation and tumor development.

Independent of its endoglycosidase activity, heparanase also comprises a cell adhesion property (21) that may also be relevant for such processes as wound healing and implantation.

Among the chronic complications of diabetes mellitus, impaired wound healing leading to foot ulceration is among the least well studied even though skin ulceration in diabetic patients causes grave personal as well as financial costs (22, 23). Moreover, foot ulcers and the subsequent amputation of a lower extremity are the most common causes of hospitalization among diabetic patients (24). In diabetes, the wound healing process is impaired and healed wounds are characterized by diminished wound strength. Thus, agents capable of increasing the release of bFGF would be highly desirable in the aid of wound repair, particularly in diabetically- compromised patients. Indeed, U.S. Pat. Appl. 20020068054 discloses use of a recombinant heparanase to accelerate wound repair.

Since accelerated healing by heparanase may contribute to the aesthetic appearance of a wound, heparanase may also comprise a potential cosmetic benefit for both skin and hair.

In addition, the angiogenic effect of bFGF may also be of benefit for the treatment of such diseases as ischemic heart disease and infracted myocardium (25, 26, and 27). bFGF is also one of the endogenous factors found in bone matrix. bFGF is a mitogen for many cell types, including osteoblasts and chondrocytes. A lower dose of bFGF increases bone calcium content and a higher dose reduces it. Thus, exogenous bFGF can stimulate proliferation during early phases of bone induction. bFGF stimulates bone formation in bone implants, depending on dose and its method of administration. Hyaluronate gel has been shown to be effective as a slow-release carrier for bFGF (28). bFGF infusion increases bone in-growth into bone grafts when infused at both an early and a later stage, but the effect can be measured only several weeks later (28).

Heparanase may also play a role in viral infections. The presence of heparan sulfate on cell surfaces have been shown to be the principal requirement for the binding of Herpes Simplex (29) and Dengue (30) viruses to cells and for subsequent infection of the cells. Removal of the cell surface heparan sulfate by heparanase may therefore abolish virus infection. In fact, treatment of cells with bacterial heparitinase (degrading heparin-like molecules) or heparanase (degrading heparan sulphate) reduced the binding of two related animal herpes viruses to cells and rendered the cells at least partially resistant to virus infection (29). There are some indications that the cell surface heparan sulfate is also involved in HIV infection (31).

Neurodegenerative diseases are further examples of diseases in which heparanase may be of therapeutic benefit. Heparan sulfate proteoglycans were identified in the prion protein amyloid plaques of Genstmann-Straussler Syndrome, Creutzfeldt-Jakob disease and Scrape (32). Heparanase may disintegrate these amyloid plaques which are also thought to play a role in the pathogenesis of Alzheimer's disease.

Heparanase may also be useful in the treatment of restenosis and atherosclerosis. Proliferation of arterial smooth muscle cells (SMCs) in response to endothelial injury and accumulation of cholesterol rich lipoproteins are basic events in the pathogenesis of atherosclerosis and restenosis (33). Apart from its involvement in SMC proliferation (i.e., low affinity receptors for heparin-binding growth factors), HS is also involved in lipoprotein binding, retention and uptake (34). It was demonstrated that HSPG and lipoprotein lipase participate in a novel catabolic pathway that may allow substantial cellular and interstitial accumulation of cholesterol rich lipoproteins (35). The latter pathway is expected to be highly atherogenic by promoting accumulation of apoB and apoE rich lipoproteins (i.e. LDL, VLDL, chylomicrons), independent of feed back inhibition by the cellular sterol content. Removal of SMC HS by heparanase is therefore expected to inhibit both SMC proliferation and lipid accumulation and thus may halt the progression of restenosis and atherosclerosis.

In summary, recombinant heparanase may be used in a wide variety of therapeutic modalities such as wound healing, bone formation, pulmonary diseases, angiogenesis, restenosis, atherosclerosis, inflammation, ischemic heart disease, infracted myocardium, neurodegenerative diseases and viral infections. Mammalian heparanase can be used to neutralize plasma heparin, as a potential replacement of protamine. Common use in basic research is also expected.

However, for recombinant heparanase to gain practical use in medicine, methods of expressing this protein on a large scale must be addressed.

The cloning procedures of human heparanase are described at length in U.S. Pat. No. 5,968,822; U.S. patent application Ser. Nos. 09/109,386, and 09/258,892; and PCT Application No. US98/17954. Recotnbinantly modified heparanases are also known. To this end, see U.S. patent application Ser. No. 09/260,038. Although the biotechnology industry has directed its efforts to eukaryotic hosts like mammalian cell tissue culture, yeast, fungi, insect cells, and transgenic animals, to express recombinant proteins, these hosts may suffer particular disadvantages. For example, although mammalian cells are capable of correctly folding and glycosylating bioactive proteins, the quality and extent of glycosylation can vary with different culture conditions among the same host cells. Yeast, alternatively, produces incorrectly glycosylated proteins that have excessive mannose residues, and generally exhibit limited post-translational processing. Other fungi may be available for high-volume, low-cost production, but they are not capable of expressing many target proteins. Although the baculovirus insect cell system can produce high levels of glycosylated proteins, these proteins are not secreted, however, thus making purification complex and expensive. Transgenic animal systems are hindered by lengthy lead times for developing herds with stable genetics, high operating costs, and potential contamination by prions or viruses.

Prokaryotic hosts such as E. coli may also suffer disadvantages in expressing heterologous proteins. For example, the post-translational modifications required for bioactivity may not be carried out in the prokaryote host. Some of these post- translational modifications include signal peptide processing, pro-peptide processing, protein folding, disulfide bond formation, glycosylation, γ-carboxylation, and β- hydroxylation. As a result, complex proteins derived from prokaryote hosts are not always properly folded or processed to provide the desired degree of biological activity. Consequently, prokaryote hosts have generally been utilized for the expression of relatively simple foreign polypeptides that do not require post- translational processing to achieve a biologically active protein. The biochemical, technical, and economic limitations on existing prokaryotic and eukaryotic expression systems has created substantial interest in developing new expression systems for the production of heterologous proteins. To that end, plants represent a suitable alternative to other host systems because of the advantageous economics of growing plant crops, plant suspension cells, and tissues such as callus; the ability to synthesize proteins in leaves, and storage organs like tubers, seeds, and fruits; the ability of plants to perform many of the post-translational modifications previously described, the capability of plants for protein bioproduction at very large scales; and the ability to produce the protein in an environment free of human pathogens. Plant-based expression systems may be more cost-effective than other large-scale expression systems for the production of therapeutic proteins.

Various recombinant polypeptides have been successfully produced in plants including human serum albumin, transgenic plant rabbit liver cytochrome P450, hamster 3-hydroxy-3-methylglutaryl CoA reductase, and the hepatitis B surface antigen (36, 37, 38, 39). Additionally, low level expression of murine GM-CSF has been reported in tobacco cell suspension culture, although the protein was not characterized (40).

Expression of monoclonal antibodies in plant host systems has been widely studied primarily due to their potential value as therapeutic and clinical reagents including complex secretory antibodies such as IgA (U.S. Pat. No. 5,959,177). The synthesis of IgA in rice has been reported recently as well (WO 99/66,026).

There is thus a widely recognized need for, and it would be highly advantageous to have expression constructs and methods of using same for producing heparanase in plants.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a nucleic acid construct capable of directing heparanase expression in plants.

It is another object of the present invention to provide a heparanase polypeptide attached to a carbohydrate moiety being selected from the group consisting or a xylose and a fucose.

According to one aspect of the present invention there is provided a nucleic acid construct comprising a nucleic acid sequence encoding heparanase and a cis- acting regulatory element capable of directing an expression of the heparanase in a plant.

According to another aspect of the present invention there is provided a molecule comprising a heparanase polypeptide and at least one carbohydrate moiety attached to the heparanase polypeptide, the carbohydrate moiety being selected from the group consisting of a xylose and a fucose.

According to yet another aspect of the present invention there is provided a plant cell comprising the nucleic acid construct.

According to still another aspect of the present invention there is provided a plant comprising the nucleic acid construct.

According to an additional aspect of the present invention there is provided a pharmaceutical composition comprising, as an active ingredient, the heparanase polypeptide and at least one carbohydrate moiety attached to the heparanase polypeptide, the carbohydrate moiety being selected from the group consisting of a xylose and a fucose.

According to yet an additional aspect of the present invention there is provided a method of producing heparanase comprising: (a) introducing the nucleic acid construct of claim 1 into a plant; (b) cultivating the plant under conditions which allow expression of the heparanase; and (c) recovering the heparanase from the plant, thereby producing the heparanase.

According to further features in the described preferred embodiments the method further comprises modifying the heparanase prior to or following (c).

According to further features in preferred embodiments of the invention described below, the nucleic acid sequence encoding the heparanase is as set forth in SEQ ID NO: 3.

According to still further features in the described preferred embodiments the additional nucleic acid sequence encodes a signal sequence.

According to still further features in the described preferred embodiments the signal sequence is selected from the group consisting of an ER signal sequence, a cytosol signal sequence, a plastid signal sequence, a seed signal sequence, a vacuole signal sequence and an apoplast signal sequence.

According to still further features in the described preferred embodiments the additional nucleic acid sequence is a viral sequence. According to still further features in the described preferred embodiments the viral sequence comprises a plus sense RNA viral replication origin, the replicon being dependent for replication on a helper virus.

According to still further features in the described preferred embodiments the nucleic acid sequence encoding heparanase is as set forth in SEQ ID NO. 1.

According to still further features in the described preferred embodiments the nucleic acid sequence encodes a polypeptide which comprises an amino acid sequence is as set forth in SEQ ID NO. 2.

According to still further features in the described preferred embodiments the cis-acting regulatory element is a plant promoter.

According to still further features in the described preferred embodiments the plant promoter is selected from the group consisting of a constitutive promoter, a pre- harvest inducible promoter, a post-harvest inducible promoter, a developmentally regulated promoter and a tissue-specific promoter. According to still further features in the described preferred embodiments the nucleic acid construct is capable of integrating into the genome of the plant cell.

According to still further features in the described preferred embodiments the nucleic acid construct is an episomal construct.

According to still further features in the described preferred embodiments the xylose is attached to the heparanase polypeptide via a beta 1,2 linkage.

According to still further features in the described preferred embodiments the fucose is attached to the heparanase polypeptide via an alpha 1,3 linkage.

According to still further features in the described preferred embodiments the plant is a monocotyledonous plant. According to still further features in the described preferred embodiments the plant is a dicotyledonous plant.

According to still further features in the described preferred embodiments the modifying comprises de-glycosylating the heparanase.

According to still further features in the described preferred embodiments the de-glycosylating is effected by a glycosidase.

According to still further features in the described preferred embodiments the glycosidase is selected from the group consisting of a xylosidase and a 1,3-fucosidase.

According to still further features in the described preferred embodiments the modifying comprises glycosylating the heparanase. According to still further features in the described preferred embodiments the glycosylating is effected by a glycosyltransferase.

According to still further features in the described preferred embodiments the glycosyltransferase is selected from the group consisting of a galatosyltransferase or a sialyltransferase.

According to still further features in the described preferred embodiments the modifying comprises glucosylating and de-glycosylating the heparanase.

According to still further features in the described preferred embodiments the modifying comprises cleaving the heparanase. The present invention successfully addresses the shortcomings of the presently known configurations by providing a novel recombinant human heparanase protein expressed in plants.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the drawings: FIG. 1 is a schematic illustration • of the expression vector pB1121-hpa designed for the expression of heparanase in plants. The expression vector comprises T-DNA right and left borders (RB and LB); NOS-NPTII-NOS - a chimeric gene for kanamycin resistance - Neomycin phosphotransferase gene under the control of nopaline synthase promoter and terminator; and 35S/Hpa CDS - Human Heparanase coding sequence (CDS), Genbank Accession No. AF144325 controlled by the constitutive 35S promoter from CaMV.

FIG. 2 is a photograph of a Western blot analysis illustrating the presence of a 50 kDa protein in the heparanase transformed leaves. FIG. 3 is a bar graph illustrating heparanase activity in plant extracts derived from heparanase transformed and control tobacco leaves. Activity was measured using the 1,9-Dimethylmethylene blue (DMB) assay (Hepa — extracts of leaves transformed with heparanase expression vector, Con - control untransformed leaves, Bg-background, no cell extract).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to expression constructs and methods of using same for expressing heparanase in plants. The present invention can be used to treat a variety of disorders in which an increase in quantity of heparanase is of therapeutic benefit.

The principles and operation of the expression constructs and methods of using same according to the present invention may be better understood with reference to the drawings and accompanying descriptions.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details set forth in the following description or exemplified by the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. The genes for human heparanase [Vlodavsky et aL, Nat. Med., 5: 793-802

(1999); Hulett et aL, Nat. Med., 5: 803-809 (1999); Kussie et aL, Biochem. Biophy. Res. Commun., 261: 183-187 (1999)] and chicken heparanase [Toyoshima & Nakajima, J. Biol. Chem., 261: 183-187 (1999)] have been cloned. The complete sequence of bovine heparanase (gene bank: AF281160), rat heparanase (gene bank: NM.sub.13 022605) and a partial sequence (residues 150-535) of murine heparanase (gene bank: AX034647, see Hulett et al., supra) are known. In addition, GenBank accession number AX034647 (see EP 1032656-A) discloses another partial sequence (residues 156-535), along with the corresponding polynucleotide sequence, of murine heparanase.

Expression of active mature heparanase from its full length coding sequence was demonstrated in mammalian cells, while expression and secretion of the heparanase precursor were demonstrated in mammalian cells as well as in insect cells and in yeast [U.S. Pat. No. 6348344]. However, these expression systems fail to produce heparanase in an amount sufficient for clinical use.

The present invention provides a novel nucleic acid construct for the production of human heparanase in plants and methods of using same for large-scale production of the recombinant protein. As is shown in the Examples section which follows, transgenic tobacco plants generated according to the teachings of the present invention, were able to express the processed 50 kDa human heparanase polypeptide. Results from the heparanase activity assay suggest that the 50 kDa polypeptide is expressed in an active form. These results demonstrate that plant-produced heparanase may be used in therapeutic as well as in cosmetic applications.

Thus, according to one aspect of the present invention there is provided a nucleic acid construct comprising a nucleic acid sequence encoding heparanase and a cis-acting regulatory element capable of directing an expression of the heparanase in a plant. As used herein the term "plant" refers to a whole plant, portions thereof, plant cell or plant cell culture.

As used herein, the term "heparanase" refers to at least an active portion (i.e., having heparanase activity) of a heparanase polypeptide (e.g., SEQ ID NO: 2).

As used herein the phrase "heparanase activity" refers to any known heparanase activity (e.g., heparin or heparan sulfate cleavage activity, cell adhesion activity) or the effect of heparanase on biological processes such as cell migration, extravasation, angiogenesis, wound healing, and smooth muscle cell proliferation. It will be appreciated that cell adhesion activity of heparanase is independent of its catalytic activity [Goldshmidt, O. et al, The FASEB Journal. 2003;17:1015-1025]. Hence, an active portion of a heparanase polypeptide may or may not encompass the catalytic site of heparanase.

The term "nucleic acid sequence" refers to a deoxyribonucleic acid sequence composed of naturally-occurring bases, sugars and covalent internucleoside linkages (e.g., backbone) as well as oligonucleotides having non-naturally-occurring portions which function similarly to respective naturally-occurring portions. Such modifications are enabled by the present invention provided that recombinant expression is still allowed.

Nucleic acid sequence of heparanase according to this aspect of the present invention can be a complementary polynucleotide sequence (cDNA), a genomic polynucleotide sequence and/or a composite polynucleotide sequences (e.g., a combination of the above).

As used herein the phrase "complementary polynucleotide sequence" refers to a sequence, which results from reverse transcription of messenger RNA using a reverse transcriptase or any other RNA dependent DNA polymerase. Such a sequence can be subsequently amplified in vivo or in vitro using a DNA dependent

DNA polymerase.

As used herein the phrase "genomic polynucleotide sequence" refers to a sequence derived (isolated) from a chromosome and thus it represents a contiguous portion of a chromosome.

As used herein the phrase "composite polynucleotide sequence" refers to a sequence, which is at least partially complementary and at least partially genomic. A composite sequence can include some exonal sequences required to encode the polypeptide of the present invention, as well as some intronic sequences interposing therebetween. The intronic sequences can be of any source, including of other genes, and typically will include conserved splicing signal sequences. Such intronic sequences may further include cis acting expression regulatory elements.

Examples of human heparanase gene sequences and homologs and orthologs thereof are provided in GenBank Accession Nos. AF144325 (SEQ ID NO:1), AF165154, AF152376, AF084467, AF155510, BC051321, AY948074, AK222986,

AX034643, AX034645, AX136167, AX147946, CQ840768, CQ840772, CQ840860,

CQ840864, CQ971645, CQ971649, CS051203, NM_006665 as well as in, U.S. Pat.

No 5,968,822 and in U.S. Pat. No. 6,348,344. The nucleic acid sequence encoding heparanase according to this aspect of the present invention may be altered, to further improve expression levels in plant expression system. For example, the nucleic acid sequence of heparanase may be modified in accordance with the preferred codon usage for plant expression. Increased expression of heparanase in plants may be obtained by utilizing a modified or derivative nucleotide sequence. Examples of such sequence modifications include, but are not limited to, an altered G/C content to more closely approach that typically found in plants, and the removal of codons atypically found in plants commonly referred to as codon optimization. The phrase "codon optimization" refers to the selection of appropriate DNA nucleotides for use within a structural gene or fragment thereof that approaches codon usage within a plant. Therefore, an optimized gene or nucleic acid sequence refers to a gene in which the nucleotide sequence of a native or naturally occurring gene has been modified in order to utilize statistically-preferred or statistically-favored codons within a plant. The nucleotide sequence typically is examined at the DNA level and the coding region optimized for expression in plants determined using any suitable procedure, for example as described in Sardana et al. (1996, Plant Cell Reports 15:677-681). In this method, the standard deviation of codon usage, a measure of codon usage bias, may be calculated by first finding the squared proportional deviation of usage of each codon of the native heparanase gene relative to that of highly expressed plant genes, followed by a calculation of the average squared deviation. The formula used is: 1 SDCU = n = 1 N [ ( Xn - Yn ) / Yn ] 2 / N, where Xn refers to the frequency of usage of codon n in highly expressed plant genes, where Yn to the frequency of usage of codon n in the gene of interest and N refers to the total number of codons in the gene of interest. A table of codon usage from highly expressed genes of dicotyledonous plants is compiled using the data of Murray et al. (1989, Nuc Acids Res. 17:477-498).

The nucleic acid sequence encoding heparanase may be altered, to further improve expression levels for example, by optimizing the nucleic acid sequence in accordance with the preferred codon usage for a particular plant cell type which is selected for the expression of the heparanase polypeptide. Use of tobacco plants for the expression of heparanase (as described in the Examples section hereinbelow) may limit the need for optimizing the nucleic acid sequence in accordance with the preferred codon usage since tobacco plant codon usage/preference is generally very similar to humans

One method of optimizing the nucleic acid sequence in accordance with the preferred codon usage for a particular plant cell type is based on the direct use, without performing any extra statistical calculations, of codon optimization tables such as those provided on-line at the Codon Usage Database through the NIAS (National Institute of Agrobiological Sciences) DNA bank in Japan (http://www.kazusa.or.jp/codon/). The Codon Usage Database contains codon usage tables for a number of different species, with each codon usage table having been statistically determined based on the data present in Genbank

By using the above tables to determine the most preferred or most favored codons for each amino acid in a particular species (for example, rice), a naturally- occurring nucleotide sequence encoding a protein of interest can be codon optimized for that particular plant species. This is effected by replacing codons that may have a low statistical incidence in the particular species genome with corresponding codons, in regard to an amino acid, that are statistically more favored. However, one or more less-favored codons may be selected to delete existing restriction sites, to create new ones at potentially useful junctions (5' and 3' ends to add signal peptide or termination cassettes, internal sites that might be used to cut and splice segments together to produce a correct full-length sequence), or to eliminate nucleotide sequences that may negatively effect mRNA stability or expression.

The naturally-occurring or native heparanase encoding nucleotide sequence may already, in advance of any modification, contain a number of codons that correspond to a statistically-favored codon in a particular plant species. Therefore, codon optimization of the native heparanase nucleotide sequence may comprise determining which codons, within the native human heparanase nucleotide sequence, are not statistically-favored with regards to a particular plant, and modifying these codons in accordance with a codon usage table of the particular plant to produce a codon optimized derivative. The modified or derivative nucleotide sequence encoding heparanase may be comprised, 100 percent, of plant preferred codon sequences, while encoding a polypeptide with the same amino acid sequence as that produced by the native heparanase coding sequence. Alternatively, the modified nucleotide sequence encoding heparanase may only be partially comprised of plant preferred codon sequences with remaining codons retaining nucleotide sequences derived from the native heparanase coding sequence. A modified nucleotide sequence may be fully or partially optimized for plant codon usage provided that the protein encoded by the modified nucleotide sequence is produced at a level higher than the protein encoded by the corresponding naturally occurring or native gene. For example, the modified heparanase may comprise from about 60 % to about 100 % codons optimized for plant expression. As another example, the modified heparanase may comprise from 90 % to 100 % of codons optimized for plant expression.

Construction of synthetic genes by altering the codon usage is described in for example PCT Patent Application 93/07278. A preferred sequence suitable for high expression in both plants and mammalian cells is set forth in SEQ ID NO. 3.

As mentioned, the nucleic acid sequence encoding heparanase is operably linked to a cis- acting regulatory element.

As used herein, the phrase "cis acting regulatory element" refers to a polynucleotide sequence, preferably a promoter, which binds a trans acting regulator and regulates the transcription of a coding sequence located downstream thereto.

As used herein, the phrase "operably linked" refers to a functional positioning of the cis-regulatory element (e.g., promoter) so as to allow regulating expression of the selected nucleic acid sequence. For example, a promoter sequence may be located upstream of the selected nucleic acid sequence in terms of the direction of transcription and translation.

Preferably, the promoter in the nucleic acid construct of the present invention is a plant promoter which serves for directing expression of the nucleic acid molecule within plant cells.

As used herein the phrase "plant promoter" refers to a promoter which can direct transcription of the polynucleotide sequence in plant cells. Such a promoter can be derived from a plant, bacterial, viral, fungal or animal origin. The promoter may be constitutive, i.e., capable of directing high level of gene expression in a plurality of plant tissues, tissue specific, i.e., capable of directing gene expression in a particular plant tissue or tissues, developmentally regulated, inducible, i.e., capable of directing gene expression under a stimulus, or chimeric.

Plant promoters typically contain two types of recognition sequences, the TATA box and upstream promoter elements. The TATA box, located 25-30 base pairs upstream of the transcription initiation site, is thought to be involved in directing RNA polymerase to begin RNA synthesis. The other upstream promoter elements determine the rate at which transcription is initiated.

Enhancer elements can stimulate transcription up to 1,000 fold from linked homologous or heterologous promoters. Enhancers are active when placed downstream or upstream from the transcription initiation site. Many enhancer elements derived from viruses have a broad host range and are active in a variety of tissues. For example, the SV40 early gene enhancer is suitable for many cell types. Other enhancer/promoter combinations that are suitable for the present invention include those derived from polyoma virus, human or murine cytomegalovirus (CMV), the long term repeat from various retroviruses such as murine leukemia virus, murine or Rous sarcoma virus and HIV. See, Enhancers and Eukaryotic Expression, Cold Spring Harbor Press, Cold Spring Harbor, N. Y. 1983, which is incorporated herein by reference.

In the nucleic acid construct, the promoter is preferably positioned approximately the same distance from the heterologous transcription start site as it is from the transcription start site in its natural setting. As is known in the art, however, some variation in this distance can be accommodated without loss of promoter function.

Examples of constitutive plant promoters include, but are not limited to CaMV35S and CaMV 19S promoters, FMV34S promoter, sugarcane bacilliform badnavirus promoter, CsVMV promoter, Arabidpsis ACT2/ACT8 actin promoter, Arabidpsis ubiquitin UBQ 1 promoter, barley leaf thionin BTH6 promoter, and rice actin promoter.

In the case where a tissue-specific promoter is used, protein expression is particularly high in the tissue from which extraction of the protein is desired. Depending on the desired tissue, expression may be targeted to the endosperm, aleurone layer, embryo (or its parts as scutellum and cotyledons), pericarp, stem, leaves, tubers, trichomes, seeds, roots, etc. Examples of tissue specific promoters include, but are not limited to bean phaseolin storage protein promoter, DLEC promoter, PHSβ promoter, zein storage protein promoter, conglutin gamma promoter from soybean, AT2S1 gene promoter, ACTI l actin promoter from Arabidpsis, napA promoter from Brassica napus and potato patatin gene promoter.

An inducible promoter is a promoter induced by a specific stimulus such as stress conditions comprising, for example, light, temperature, chemicals, drought, high salinity, osmotic shock, oxidant conditions or in case of pathogenicity. Usually the promoter is induced before the plant is harvested and as such is referred to as a pre-harvest promoter. Examples of inducible pre-harvest promoters include, but are not limited to, the light-inducible promoter derived from the pea rbcS gene, the promoter from the alfalfa rbcS gene, the promoters DRE, MYC and MYB active in drought; the promoters INT, INPS₃ prxEa, Ha hsρl7.7G4 and RD21 active in high salinity and osmotic stress, and the promoters hsr2O3J and str246C active in pathogenic stress.

The inducible promoter may also be an inducible post-harvest promoter e.g. the inducible MeGA.™ promoter (U.S. Pat. No. 5,689,056). The preferred signal utilized for the rapid induction of the MeGA ™ promoter is a localized wound after the plant has been harvested.

As mentioned herein above, the nucleic acid construct of the present invention may also comprise an additional nucleic acid sequence encoding a signal peptide that allows transport of the heparanase in-frame fused thereto to a sub-cellular organelle within the plant, as desired. Examples of subcellular organelles of plant cells include, but are not limited to, leucoplasts, chloroplasts, chromoplasts, mitochondria, nuclei, peroxisomes, endoplasmic reticulum and vacuoles.

Compartmentalization of the heparanase recombinant protein within the plant cell followed by its secretion is one pre-requisite of making the product easily purifiable. It was shown that targeting a recombinant protein to the endoplasmic reticulum by fusion with an appropriate signal peptide allows the fused polypeptide to be targeted to a secretory pathway. Accumulation of the protein in a subcellular organelle of the cell, may also be preferred to allow the protein to be stored in relatively high concentrations without being exposed to degrading compounds present in the vacuole, for example. Signaling sequences may be derived from plants such as wheat, barley, cotton, rice, soy, and potato.

Preferably the signal sequence of the present invention directs the heparanase to the endoplasmic reticulum where processing of the pre-pro protein occurs, degrading it to a 65 IdDa pro-form. The protein is then further processed by removing an internal 6 kDa peptide (amino acids 111-157) to yield an active secretable heterodimer consisting of an 8 kDa subunit derived from the protein N-terminus and the C-terminal 50 IcDa subunit [Fairbanks et al. J. Biol. Chem. 274 29587.29590 (1999)]. Exemplary signal peptides that may be used herein include the tobacco pathogenesis related protein (PR-S) signal sequence (Sijmons et ah, 1990, Bio/technology, 8:217-221), lectin signal sequence (Boehn et ah, 2000, Transgenic Res, 9(6):477-86), signal sequence from the hydroxypro line-rich glycoprotein from Phaseolus vulgaris (Yan et ah, 1997, Plant Phyiol. 115(3):915-24 and Corbin et ah, 1987, MoI Cell Biol 7(12):4337-44), potato patatin signal sequence (Iturriaga, G et ah, 1989, Plant Cell 1:381-390 and Bevan et ah, 1986, Nuc. Acids Res. 41:4625- 4638.) and the barley alpha amylase signal sequence (Rasmussen and Johansson, 1992, Plant MoI. Biol. 18(2):423-7). Such targeting signals may be cleaved in vivo from the heparanase sequence, which is typically the case when an apoplast targeting signal, such as the tobacco pathogenesis related protein-S (PR-S) signal sequence (Sijmons et ah, 1990, Bio/technology, 8:217-221) is used.

Other signal sequences which may also be used in accordance with this aspect of the present invention include signal retention sequences. Use of these sequences result in increased accumulation in a particular location and therefore may provide for easier purification of the heparanase.

For example, Pat. Appl. No. 20050039235 teaches the use of signal and retention polypeptides for targeting recombinant insulin to the ER or in an ER derived storage vesicle (e.g. an oil body) in plant cells thereby increasing the accumulation of insulin in seeds.

Examples of ER retention motifs include KDEL, HDEL, DDEL, ADEL and SDEL sequences.

As mentioned above, signal polypeptides may also be used for targeting the associated recombinant protein to the apoplast. It has been shown that targeting of recombinant immunoglobulins (MAb) to the apoplast significantly increased protein yields in comparison to plants where MAb was targeted to the cytosol [Conrad and

Fiedler, 38 Plant MoI. Biol. 101-109 (1998)].

Yet another important strategy to facilitate purification is to fuse the recombinant heparanase with an affinity tag by including a sequence of the tag in the nucleic acid construct of the present invention. This method is widely utilized for in vitro purification of proteins. Exemplary purification tags for purposes of the invention include but are not limited to polyhistidine, V5, myc, protein A, gluthatione-S-fransferase, maltose binding protein (MBP) and cellulose-binding domain (CBD) [Sassenfeld, 1990, TIBTECH, 8, 88-9]. In the case of CBD fusion proteins, the heparanase is fused to a substrate-binding region of a polysaccharidase (cellulases, chitinases and amylases, as well as xylanases and the beta.- 1,4 glycanases). The affinity matrix containing the substrate such as cellulose can be employed to immobilize the heparanase. The heparanase can be removed from the matrix using a protease cleavage site.

The nucleic acid construct of the present invention may also comprise a sequence that aids in proteolytic cleavage, e.g., a thrombin cleavage sequence. Such a sequence may permit the heparanase to be separated from an attached co-translated sequence such as the ER retention sequences described above. The nucleic acid construct of the present invention may also comprise viral nucleic acid sequences that enable amplification of the heparanase transcript as described in U.S. Pat. No. 6,852,846. According to this embodiment, a chimeric multicistronic gene (replicon) is constructed containing a plant promoter, viral replication origins, a viral movement protein gene, and the heparanase gene. The viral replication origins have substantial sequence homology to a plus sense, RNA helper virus capable of infecting plants. The replicons of this embodiment of the present invention lack replication protein sequences, and therefore rely on genetic complementation with helper viruses for replication. After the replicon has been introduced into the host, the resulting transgenic plants are grown to an optimized stage at which point a helper virus strain is added. The replicons are then amplified by the introduced helper virus and the heparanase is expressed. The viral movement protein gene ensures that replicon-encoded genes are capable of moving away from the site of infection and are also capable of systemic expression.

The nucleic acid construct of the present invention may also comprise sequences resulting in N-and/or C-terminal stabilizing protein extensions. Such extensions may be used to stabilize and/or assist in folding of the heparanase polypeptide and additionally may be used to facilitate purification of heparanase. Polypeptide extensions that may be used in this regard include for example a nucleic acid sequence encoding a single chain antibody, a nucleic acid encoding an Affibody^R™ molecule (Affibody AB), a nucleic acid sequence encoding the nontoxic B subunit of cholera toxin (CTB) (Arakawa, T. et al., 1998, Nat. Biotechnol. 16:938) or combinations of such polypeptides.

The nucleic acid construct of this aspect of the present invention may also comprise a transcriptional terminator which besides serving as a signal for transcription termination, may further serve as a protective element capable of extending the mRNA half life (Guarneros et al, 1982, Proc. Natl. Acad. Sci. USA, 79: 238-242). The length of the transcriptional terminator may vary from about 200 nucleotides to about 1000 nucleotides. The nucleic acid construct is prepared so that the transcriptional terminator is located 3' of the nucleic acid sequence encoding heparanase. Termination sequences that may be used herein include, but are not limited to the nopaline termination region (Bevan et al., 1983, Nucl. Acids. Res., 11: 369-385), the phaseolin terminator (van der Geest et al., 1994, Plant J. 6: 413-423), the arcelin terminator (Jaeger G D, et al., 2002, Nat. Biotechnol.Dec; 20:1265-8), the terminator for the octopine synthase genes of Agrobacterium tumefaciens or other similarly functioning elements. Transcriptional terminators may be obtained as described An, 1987, Methods in Enzym. 153: 292.

The nucleic acid construct of the present invention preferably further includes additional nucleic acid sequences which provide a broad host range prokaryote replication origin; a prokaryote selectable marker; and, for Agrobacterium transformations, T DNA sequences for Agrobacterium-mediated transfer to plant chromosomes. Where the heterologous sequence (i.e., heparanase coding sequence) is not readily amenable to detection, the construct will preferably also have a selectable marker gene suitable for determining if a plant cell has been transformed. A general review of suitable markers for the members of the grass family is found in Wilmink and Dons, Plant MoI. Biol. Reptr. (1993)11:165-185.

Suitable prokaryote selectable markers include resistance toward antibiotics such as ampicillin, kanamycin or tetracycline.

Sequences suitable for permitting integration of the heterologous sequence into the plant genome are also recommended. These might include transposon sequences as well as Ti sequences which permit random insertion of a heterologous expression cassette into a plant genome.

The nucleic acid construct of the present invention may be capable of integrating into the plant genome and as such would direct the expression of a heparanase. Alternatively, the nucleic acid construct may be an episomal construct directing a transient heparanase expression.

The above-described nucleic acid construct can be used for producing heparanase in plants. This can be effected by (a) introducing the nucleic acid construct described hereinabove into a plant; (b) cultivating the plant under conditions M

which allow expression of the heparanase; and (c) recovering the heparanase from the plant, thereby producing the heparanase.

There are various methods of introducing foreign genes into plants (Potrykus, L, Annu. Rev. Plant. Physiol., Plant. MoI. Biol. (1991) 42:205-225; Shimamoto et al., Nature (1989) 338:274-276).

The principle methods of effecting stable integration of exogenous nucleic acid sequence into plant genomic DNA include two main approaches:

(i) Agrobacterium-mediated gene transfer: [Klee et al. (1987) Annu. Rev. Plant Physiol. 38:467-486; Klee and Rogers in Cell Culture and Somatic Cell Genetics of Plants, Vol. 6, Molecular Biology of Plant Nuclear Genes, eds. Schell, J., and Vasil, L. K., Academic Publishers, San Diego, Calif. (1989) p. 2-25; Gatenby, in Plant Biotechnology, eds. Kung, S. and Arntzen, C. J., Butterworth Publishers, Boston, Mass. (1989) p. 93-112].

(ii) direct DNA uptake: [Paszkowski et al., in Cell Culture and Somatic Cell Genetics of Plants, Vol. 6, Molecular Biology of Plant Nuclear Genes eds. Schell, J., and Vasil, L. K., Academic Publishers, San Diego, Calif. (1989) p. 52-68; including methods for direct uptake of DNA into protoplasts, Toriyama, K. et al. (1988) Bio/Technology 6:1072-1074 DNA uptake induced by brief electric shock of plant cells: Zhang et al. Plant Cell Rep. (1988) 7:379-384. Fromm et al. Nature (1986) 319:791-793. DNA injection into plant cells or tissues by particle bombardment, Klein et al. Bio/Technology (1988) 6:559-563; McCabe et al. Bio/Technology (1988) 6:923-926; Sanford, Physiol. Plant. (1990) 79:206-209; by the use of micropipette systems: Neuhaus et al., Theor. Appl. Genet. (1987) 75:30-36; Neuhaus and Spangenberg, Physiol. Plant. (1990) 79:213-217; or by the direct incubation of DNA with germinating pollen, DeWet et al. in Experimental Manipulation of Ovule Tissue, eds. Chapman, G. P. and Mantell, S. H. and Daniels, W. Longman, London, (1985) p. 197-209; and Ohta, Proc. Natl. Acad. Sci. USA (1986) 83:715-719].

The Agrobacterium system includes the use of plasmid vectors that contain defined DNA segments that integrate into the plant genomic DNA. Methods of inoculation of the plant tissue vary depending upon the plant species and the Agrobacterium delivery system. A widely used approach is the leaf disc procedure which can be performed with any tissue explant that provides a good source for initiation of whole plant differentiation. Horsch et al. in [Plant Molecular Biology Manual A5, Kluwer Academic Publishers, Dordrecht (1988) p. 1-9. A supplementary approach] employs the Agrobacterium delivery system in combination with vacuum infiltration. The Agrobacterium system is especially viable in the creation of transgenic dicotyledenous plants (as described in the Examples section which follows). Additional methods of transgenic plant propagation and transformation are described in U.S. Pat. Nos. 6,610,909 to Oglevee-O'Donavan et al, and 6,384,301 to Martinell et al, both incorporated herein by reference.

There are various methods of direct DNA transfer into plant cells. In electroporation, the protoplasts are briefly exposed to a strong electric field. In microinjection, the DNA (i.e. nucleic acid construct encoding heparanase) is mechanically injected directly into the cells using very small micropipettes. In microparticle bombardment, the DNA is adsorbed on microprojectiles such as magnesium sulfate crystals or tungsten particles, and the microprojectiles are physically accelerated into cells or plant tissues. Following stable transformation plant propagation is exercised. The most common method of plant propagation is by seed. Regeneration by seed propagation, however, has the deficiency that due to heterozygosity there is a lack of uniformity in the crop, since seeds are produced by plants according to the genetic variances governed by Mendelian rules. Basically, each seed is genetically different and each will grow with its own specific traits. Therefore, it is preferred that the transformed plant be produced such that the regenerated plant has the identical traits and characteristics of the parent transgenic plant. Therefore, it is preferred that the transformed plant be regenerated by micropropagation which provides a rapid, consistent reproduction of the transformed plants. Micropropagation is a process of growing new generation plants from a single piece of tissue that has been excised from a selected parent plant or cultivar. This process permits the mass reproduction of plants having the preferred tissue expressing the fusion protein. The new generation plants which are produced are genetically identical to, and have all of the characteristics of, the original plant. Micropropagation allows mass production of quality plant material in a short period of time and offers a rapid multiplication of selected cultivars in the preservation of the characteristics of the original transgenic or transformed plant. The advantages of cloning plants are the speed of plant multiplication and the quality and uniformity of plants produced. Micropropagation is a multi-stage procedure that requires alteration of culture medium or growth conditions between stages. Thus, the micropropagation process involves four basic stages: Stage one, initial tissue culturing; stage two, tissue culture multiplication; stage three, differentiation and plant formation; and stage four, greenhouse culturing and hardening. During stage one, initial tissue culturing, the tissue culture is established and certified contaminant-free. During stage two, the initial tissue culture is multiplied until a sufficient number of tissue samples are produced to meet production goals. During stage three, the tissue samples grown in stage two are divided and grown into individual plantlets. At stage four, the transformed plantlets are transferred to a greenhouse for hardening where the plants' tolerance to light is gradually increased so that it can be grown in the natural environment.

Although stable transformation is presently preferred, transient transformation of leaf cells, meristematic cells or the whole plant is also envisaged by the present invention.

Transient transformation can be effected by any of the direct DNA transfer methods described above or by viral infection using modified plant viruses.

Viruses that have been shown to be useful for the transformation of plant hosts include CaMV, TMV and BV. Transformation of plants using plant viruses is described in U.S. Pat. No. 4,855,237 (BGV), EP-A 67,553 (TMV), Japanese

Published Application No. 63-14693 (TMV), EPA 194,809 (BV), EPA 278,667 (BV); and Gluzman, Y. et al., Communications in Molecular Biology: Viral Vectors, Cold

Spring Harbor Laboratory, New York, pp. 172-189 (1988). Pseudovirus particles for use in expressing foreign DNA in many hosts, including plants, is described in WO 87/06261.

Construction of plant RNA viruses for the introduction and expression of non- viral exogenous nucleic acid sequences (i.e. nucleic acid construct of the present invention) in plants is demonstrated by the above references as well as by Dawson, W. 0. et al, Virology (1989) 172:285-292; Takamatsu et al. EMBO J. (1987) 6:307- 311; French et al. Science (1986) 231:1294-1297; and Takamatsu et al. FEBS Letters (1990) 269:73-76.

When the virus is a DNA virus, suitable modifications can be made to the virus itself. Alternatively, the virus can first be cloned into a bacterial plasmid for ease of constructing the desired viral vector with the foreign DNA. The virus can then be excised from the plasmid. If the virus is a DNA virus, a bacterial origin of replication can be attached to the viral DNA, which is then replicated by the bacteria. Transcription and translation of this DNA will produce the coat protein which acts to encapsidate the viral DNA. If the virus is an RNA virus, the virus is generally cloned as a cDNA and inserted into a plasmid. The plasmid is then used to make all of the constructions. The RNA virus is then produced by transcribing the viral sequence of the plasmid and translation of the viral genes to produce the coat protein(s) which encapsidate the viral RNA.

Construction of plant RNA viruses for the introduction and expression in plants of non- viral exogenous nucleic acid sequences such as those included in the construct of the present invention is demonstrated by the above references as well as in U.S. Pat. No. 5,316,931.

In one embodiment, a plant viral nucleic acid is provided in which the native coat protein coding sequence has been deleted from a viral nucleic acid, a non-native plant viral coat protein coding sequence and a non-native promoter, preferably the subgenomic promoter of the non-native coat protein coding sequence, capable of expression in the plant host, packaging of the recombinant plant viral nucleic acid, and ensuring a systemic infection of the host by the recombinant plant viral nucleic acid, has been inserted. Alternatively, the coat protein gene may be inactivated by insertion of the non-native nucleic acid sequence within it, such that a protein is produced. The recombinant plant viral nucleic acid may contain one or more additional non-native subgenomic promoters. Each non-native subgenomic promoter is capable of transcribing or expressing adjacent genes or nucleic acid sequences in the plant host and incapable of recombination with each other and with native subgenomic promoters. Non-native (foreign) nucleic acid sequences may be inserted adjacent the native plant viral subgenomic promoter or the native and a non-native plant viral subgenomic promoters if more than one nucleic acid sequence is included. The non-native nucleic acid sequences are transcribed or expressed in the host plant under control of the subgenomic promoter to produce the desired products. In a second embodiment, a recombinant plant viral nucleic acid is provided as in the first embodiment except that the native coat protein coding sequence is placed adjacent one of the non-native coat protein subgenomic promoters instead of a non- native coat protein coding sequence. In a third embodiment, a recombinant plant viral nucleic acid is provided in which the native coat protein gene is adjacent its subgenomic promoter and one or more non-native subgenomic promoters have been inserted into the viral nucleic acid. The inserted non-native subgenomic promoters are capable of transcribing or expressing adjacent genes in a plant host and are incapable of recombination with each other and with native subgenomic promoters. Non-native nucleic acid sequences may be inserted adjacent the non-native subgenomic plant viral promoters such that the sequences are transcribed or expressed in the host plant under control of the subgenomic promoters to produce the desired product. In a fourth embodiment, a recombinant plant viral nucleic acid is provided as in the third embodiment except that the native coat protein coding sequence is replaced by a non-native coat protein coding sequence.

The viral vectors are encapsidated by the coat proteins encoded by the recombinant plant viral nucleic acid to produce a recombinant plant virus. The recombinant plant viral nucleic acid or recombinant plant virus is used to infect appropriate host plants. The recombinant plant viral nucleic acid is capable of replication in the host, systemic spread in the host, and transcription or expression of foreign gene(s) (isolated nucleic acid) in the host to produce the desired protein.

In addition to the above, the nucleic acid molecule of the present invention can also be introduced into a chloroplast genome thereby enabling chloroplast expression.

A technique for introducing exogenous nucleic acid sequences to the genome of the chloroplasts is known. This technique involves the following procedures.

First, plant cells are chemically treated so as to reduce the number of chloroplasts per cell to about one. Then, the exogenous nucleic acid is introduced via particle bombardment into the cells with the aim of introducing at least one exogenous nucleic acid molecule into the chloroplasts. The exogenous nucleic acid is selected such that it is integratable into the chloroplast's genome via homologous recombination which is readily effected by enzymes inherent to the chloroplast. To this end, the exogenous nucleic acid includes, in addition to a gene of interest, at least one nucleic acid stretch which is derived from the chloroplast's genome. In addition, the exogenous nucleic acid includes a selectable marker, which serves by sequential selection procedures to ascertain that all or substantially all of the copies of the chloroplast genomes following such selection will include the exogenous nucleic acid. Further details relating to this technique are found in U.S. Pat. Nos. 4,945,050; and 5,693,507 which are incorporated herein by reference. A polypeptide can thus be produced by the protein expression system of the chloroplast and become integrated into the chloroplast's inner membrane.

The transformed or transfected plant of the present invention may be any monocotyledonous or dicotyledonous plant or plant cell, as well as, coniferous plants, moss, algae, monocot or dicot and other plants listed in www.nationmaster.com/encyclopedia/Plantae. Examples of monocotyledonous plants include, which can be used in accordance with the present invention include, but are not limited to, corn, cereals, grains, grasses, and rice. Examples of dicotyledonous plants which can be used in accordance with the present invention include, but are not limited to, tobacco, tomatoes, potatoes, and legumes including soybean and alfalfa. The plant may also be treated using any method known for enhancing growth and/or increased commercial yields - e.g. U.S. Pat. App. No. 20050108790.

It will be appreciated that the production of heparanase according to the present invention may be effected in plants or plant cells expressing additional recombinant proteins as well. Examples of recombinant proteins that may be advantageously co-produced with heparanase for the treatment of wound healing, for example, include growth factors such as platelet derived growth factor (PDGF) or transforming growth factor-β (TGF-β); angiogenic factors such as TNF-α and antimicrobial peptides. Other examples of recombinant proteins that may be advantageously co-produced with heparanase are discussed hereinbelow with respect to heparanase cleavage.

Various construct schemes can be utilized to express both recombinant proteins from a single nucleic acid construct. For example, the two recombinant proteins can be co-transcribed as a polycistronic message from a single promoter sequence of the nucleic acid construct.

To enable co-translation of both growth factors from a single polycistronic message, the first and second polynucleotide segments can be transcriptionally fused via a linker sequence including an internal ribosome entry site (IRES) sequence which enables the translation of the polynucleotide segment downstream of the IRES sequence. In this case, a transcribed polycistronic RNA molecule including the coding sequences of both the first and the second growth factors will be translated from both the capped 5¹ end and the internal IRES sequence of the polycistronic RNA molecule to thereby produce both the heparanase and the second recombinant protein. Alternatively, the first and second polynucleotide segments can be translationally fused via a protease recognition site cleavable by a protease expressed by the cell to be transformed with the nucleic acid construct. In this case, a chimeric polypeptide translated will be cleaved by the cell expressed protease to thereby generate both the heparanase and the second recombinant protein.

Still alternatively, the nucleic acid construct of the present invention can include two promoter sequences each being for separately expressing the heparanase and the second recombinant protein. These two promoters which may be identical or distinct can be constitutive, tissue specific or regulatable (e.g. inducible) promoters functional in one or more cell types.

Following introduction of the nucleic acid construct, the plant is cultivated to allow expression of the heparanase protein (e.g. by providing the inducer which activates an inducible promoter linked to the expression of the heparanase polypeptide, as well as appropriate humidity, heat and nutrition conditions) and optionally recovered from the plant.

Heparanase may be clinically used directly with no further recovery, as described in US. Pat. App.20040175440.

Direct use of heparanase of the present invention may further comprise partitioning of the plant so that the concentration of heparanase is homogeneous throughout. Processing techniques may include slicing, dicing, blending and quartering. The intact or partitioned plant that produces heparanase may be dried or freeze/dried through food processing techniques known in the art. The dry homogenate product can then be used therapeutically without the need to further recover the pharmaceutical protein. Alternatively, heparanase may be clinically used following recovery. The term "recovery" refers to at least a partial purification to yield a plant extract, homogenate, fraction of plant homogenate or the like. Partial purification may comprise, but is not limited to disrupting plant cellular structures thereby creating a composition comprising soluble plant components, and insoluble plant components which may be separated for example, but not limited to, by centrifugation, filtration or a combination thereof. In this regard, proteins secreted within the extracellular space of leaf or other tissues could be readily obtained using vacuum or centrifugal extraction, or tissues could be extracted under pressure by passage through rollers or grinding or the like to squeeze or liberate the protein free from within the extracellular space. Minimal recovery could also involve preparation of crude extracts of heparanase, since these preparations would have negligible contamination from secondary plant products. Further, minimal recovery may involve methods such as those employed for the preparation of FlP as disclosed in Woodleif et ah, Tobacco Sci. 25, 83-86 (1981). These methods include aqueous extraction of soluble protein from green tobacco leaves by precipitation with any suitable salt, for example but not limited to KHSO₄. Other methods may include large scale maceration and juice extraction in order to permit the direct use of the extract.

Alternatively, recovery of the heparanase polypeptide from the plant (whole plant) or plant culture can be effected using more sophisticated purification methods which are well known in the art. For example, collection and/or purification of heparanase from plant cells or plants can depend upon the particular expression system and the expressed sequence. Separation and purification techniques can include, for example, ultra filtration, affinity chromatography and or electrophoresis. In particular instances, molecular biological techniques known to those skilled in the art can be utilized to produce variants having one or more heterologous peptides which can assist in protein purification (purification tags, as described above). Such heterologous peptides can be retained in the final functional protein or can be removed during or subsequent to the collection/isolation/purification processing. One method of aiding recovery of the recombinant protein is targeting expression of the protein to a seed using seed specific promoters and endoplasmic reticulum retention sequences as described herein above. The plant seeds may be ground using any comminuting process resulting in a substantial disruption of the seed cell membrane and cell walls. Both dry and wet milling conditions (U.S. Pat. No. 3,971,856; Lawhon et aL, 1977, J. Am. Oil Chem. Soc, 63:533-534) may be used. Suitable milling equipment in this regard includes colloid mills, disc mills, IKA mills, industrial scale homogenizers and the like. The selection of the milling equipment will depend on the seed type and throughput requirements. Solid seed contaminant such as seed hulls, fibrous materials, undissolved carbohydrates, proteins and other water insoluble contaminants may be removed from the seed fraction using for example size-exclusion based methodologies, such as filtering or gravitational based processes such as centrifugation. The use of organic solvents commonly used in oil extraction, such as hexane, is generally avoided because such solvents may damage the heparanase polypeptide. Substantially pure heparanase may be recovered from the seed using a variety of additional purification methodologies such as centrifugation based techniques; size exclusion based methodologies, including for example membrane ultrafiltration and crossflow ultrafiltration; and chromatographic techniques, including for example ion-exchange chromatography, size exclusion chromatography, affinity chromatography, high performance liquid chromatography (HPLC), fast protein liquid chromatography (FPLC), hydrophobic interaction chromatography and the like. Generally, a combination of such techniques will be used to obtain substantially pure recombinant heparanase.

The heparanase polypeptide may be isolated from the seed contaminants by contacting the heparanase polypeptide with oil bodies as described hereinabove. This method is considered to be particularly advantageous as it permits the removal of seed contaminants including seed proteins in a particularly efficacious and inexpensive manner. Such contacting of the heparanase polypeptide with the oil bodies may be achieved by linking the heparanase polypeptide to an oil body protein or by linking the heparanase polypeptide to a polypeptide with affinity for an oil body, such as a single chain antibody with affinity for an oil body. In the former embodiment, heparanase polypeptide will be sequestered within the cell on the oil bodies and hence co-purify with the oil bodies. In the latter embodiment, upon being expressed in a membrane enclosed intracellular compartment such as the ER, the heparanase polypeptide will associate with the oil body upon breakage of the seed cells during the comminuting process. A process for isolating oil bodies is described in U.S. Pat. No. 5,650,554.

For clinical use, heparanase of the present invention is preferably highly purified such as to medical grade purity (e.g., > 95 %). Recombinant proteins of the present invention may be modified prior to or following recovery as further described hereinbelow.

It will be appreciated that production of active heparanase comprises a sequence of events, starting with the expression of the heparanase precursor which involves appropriate folding and post translational modifications, i.e. glycosylation and ending with proteolytic processing. Heparanase is a glycoprotein comprising 6 potential N-glycosylation sites. The significance of the glycosylation to either the production or the function of the enzyme has not been demonstrated. Simizu et a\., suggested that glycosylation plays a role mainly in secretion of the heparanase protein (Simizu et al. J Biol Chem. 2004 Jan 23;279(4):2697-703). Although plants glycosylate human proteins at the correct position, the composition of fully processed complex plant glycans differ from mammalian N-linked glycans. Plant glycans do not have the terminal sialic acid residue or galactose residues common in animal glycans and often contain a xylose or fucose residue with a linkage that is generally not found in mammals (Jenkins et ah, 14 Nature Biotech 975-981 (1996); Chrispeels and Faye in transgenic plants pp. 99-114 (Owen, M. and Pen, J. eds. Wiley & Sons, N. Y. 1996; Russell 240 Curr. Top. Microbio. Immunol. (1999). Specifically, plants comprise additional beta 1-2 linked xylosyl- and alpha 1-3 linked fucosyl-residues which are not found in mammals. Conversely they do not comprise fucosyl-1-6- residues which are present in mammals. Thus, the present invention teaches of a novel human heparanase with a plant glycosylation pattern.

As used herein a plant glycosylation pattern comprises at least one beta 1-2 linked xylosyl or at least one alpha 1-3 linked fucosyl-residue. The glycosylation pattern may also partly comprise a human glycosylation pattern - e.g., galactose or sialic acid residues.

The presence of xylose/fucose residues has been associated with antigenic responses (Chrispeels and Faye, supra). Galactose residues are thought to play a role in IgG-complement interactions. Also, sialic acid residues are required for pharmacokinetic reasons extending the in-vivo half-life of the associated polypeptide in the human recipient. Thus, the present invention contemplates the use of various strategies to address the issue of "humanization" of glycans of heparanase products synthesized in plants so that the novel human heparanase comprises a part plant glycosylation pattern and a part human glycosylation pattern.

Therefore, one strategy for the vitro modification of recombinant proteins following recovery of the heparanase polypeptide is an alteration of its glycan component by chemical or enzymatic methods (e.g. with glycosidases such as xylosidases or 1,3 fucosidases, or glycosyltranferases such as galactosyltransferase or sialyltransferase)

As mentioned, the glycan component of heparanase may also be modified prior to its recovery from a plant system. For example, a particular embodiment of the present invention focuses on modifications of the glycan processing machinery of the transformed plant. This is feasible in plants because 1) complex glycans are not critical for plant growth and development (Van Schaewen et al, 102 Plant Physiol 1109-1118 (1993)), and 2) glycan processing is highly sequential and compartmentalized, facilitating metabolic engineering. Thus, down-regulation of the glycan processing gene expression may be affected in plants of the present invention. For example, anti-sense oligonucleotides capable of inhibiting tobacco α- mannosidase I and N-acetylglucosaminyltransferase may be introduced into the transgenic plants of the present invention as described in U.S. Pat. Appl. 20030033637 thus partially blocking plant glycosylation. The recombinant polypeptide would thus partially comprise a mannose-terminated glycan that lacks the plant xylose and fucose residues found on plant complex glycans.

Alternatively, the sequence encoding a plant glycosylation site may be modified (provided this does not affect the activity of the heparanase) such that glycosylation is inhibited.

Yet alternatively or additionally, plants of the present invention may be modified to express human glycan processing enzymes. Palacpac teaches expression of human beta.-l,4-galactosyl-transferase in tobacco cells yielding N-linked glycans having a much more "human" composition [Palacpac et al., 96 P.N.A.S. 4692-4697 (1999)] where less than 7 % contained xylose and almost 50 % comprised terminal galactoses. In a similar fashion human sialyltransferase may be expressed in plants.

As mentioned herein above the human heparanase nucleotide sequence of the present invention encodes a protein that is initially synthesized as a pre-proprotein which is processed into three smaller peptides, one of about 60 kDa, another of about 45 kDa and yet another one of about 8 kDa upon translocation into the endoplasmic reticulum. Active heparanase is a mature processed form with an apparent molecular weight of 53 kDa (H53), proteolytically cleaved from the latent heparanase precursor of about 60 kDa. This proteolytic cleavage occurs at two cleavage sites yielding a 8 kDa polypeptide at the N-terminus, a 45 kDa polypeptide at the C-terminus and a 6 kDa linker polypeptide that is released due to the cleavage. Proteases involved in this cleavage include cysteine proteases, aspartic proteases and serine proteases. The formation of the heterodimer between the 8 and 45 kDa subunits is essential for heparanase enzymatic activity [M B Fairbanks el al. J. Biol. Chem. 274, 29587, 1999].

Plant heparanase of the present invention may be modified such that a stable protein is produced which is not processed in the plant. For example, a signal sequence that prevents heparanase cleavage in the plant by mis-directing the synthesized pre-proprotein away from the endoplasmic reticulum may be fused to the heparanase coding sequence so that a stable non-cleavable heparanase is expressed in plants and cleaved immediately prior to (or following) administration. Alternatively, the heparanase of the present invention may be co-expressed in the plant (as described herein above) with a particular protease inhibitor i.e. a cysteine protease inhibitor (e.g. leupeptin), an aspartic protease inhibitor (pepstatin) and a serine protease inhibitor thereby preventing its cleavage. The co-expressed polypeptide may also be an antibody directed against a protease. Alternatively, the nucleotide sequence of the present invention may encode an antisense molecule capable of inhibiting the activity of a protease. Following recovery of the uncleaved form of heparanase, the recombinant polypeptide may be cleaved in vitro by the addition of proteases thereby activating it. In this way the activity of the heparanase may be regulated in vitro and heparanases of particular strengths may be formulated.

Heparanase of the present invention may be used to treat a wide variety of conditions or disorders in which heparanase is therapeutically beneficial such as pulmonary diseases, angiogenesis, restenosis, atherosclerosis, inflammation, ischemic heart disease, infracted myocardium, neurodegenerative diseases and viral infections (see also the Background section). Pharmaceutical heparanase formulations may also be used to promote wound healing and regeneration of bone as well as for the neutralization of plasma heparin, as a potential replacement of protamine. Additionally, heparanase may also be formulated for cosmetic purposes.

Heparanase of the present invention can be provided to the treated subject (i.e. mammal) per se (e.g., purified or directly as part of a plant) or can be provided in a pharmaceutical composition comprising. As used herein a "pharmaceutical composition" refers to a preparation of one or more of the active ingredients described herein with other chemical components such as physiologically suitable carriers and excipients. The purpose of a pharmaceutical composition is to facilitate administration of a compound to an organism.

Herein the term "active ingredient" refers to the recombinant heparanase accountable for the biological effect. Hereinafter, the phrases "physiologically acceptable carrier" and

"pharmaceutically acceptable carrier" which may be interchangeably used refer to a carrier or a diluent that does not cause significant irritation to an organism and does not abrogate the biological activity and properties of the administered compound. An adjuvant is included under these phrases. Herein the term "excipient" refers to an inert substance added to a pharmaceutical composition to further facilitate administration of an active ingredient.

Examples, without limitation, of excipients include calcium carbonate, calcium phosphate, various sugars and types of starch, cellulose derivatives, gelatin, vegetable oils and polyethylene glycols.

Techniques for formulation and administration of drugs may be found in "Remington's Pharmaceutical Sciences," Mack Publishing Co., Easton, PA, latest edition, which is incorporated herein by reference.

Suitable routes of administration may, for example, include oral, rectal, transmucosal, especially transnasal, intestinal or parenteral delivery, including intramuscular, subcutaneous and intramedullary injections as well as intrathecal, direct intraventricular, intravenous, inrtaperitoneal, intranasal, or intraocular injections.

Alternately, one may administer the pharmaceutical composition in a local rather than systemic manner, for example, via injection of the pharmaceutical composition directly into a tissue region of a patient.

Pharmaceutical compositions of the present invention may be manufactured by processes well known in the art, e.g., by means of conventional mixing, dissolving, granulating, dragee-making, levigating, emulsifying, encapsulating, entrapping or lyophilizing processes.

Pharmaceutical compositions for use in accordance with the present invention thus may be formulated in conventional manner using one or more physiologically acceptable carriers comprising excipients and auxiliaries, which facilitate processing of the active ingredients into preparations which, can be used pharmaceutically. Proper formulation is dependent upon the route of administration chosen.

For injection, the active ingredients of the pharmaceutical composition may be formulated in aqueous solutions, preferably in physiologically compatible buffers such as Hank's solution, Ringer's solution, or physiological salt buffer. For transmucosal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art.

For oral administration, the pharmaceutical composition can be formulated readily by combining the active compounds with pharmaceutically acceptable carriers well known in the art. Such carriers enable the pharmaceutical composition to be formulated as tablets, pills, dragees, capsules, liquids, gels, syrups, slurries, suspensions, and the like, for oral ingestion by a patient. Pharmacological preparations for oral use can be made using a solid excipient, optionally grinding the resulting mixture, and processing the mixture of granules, after adding suitable auxiliaries if desired, to obtain tablets or dragee cores. Suitable excipients are, in particular, fillers such as sugars, including lactose, sucrose, mannitol, or sorbitol; cellulose preparations such as, for example, maize starch, wheat starch, rice starch, potato starch, gelatin, gum tragacanth, methyl cellulose, hydroxypropylmethyl- cellulose, sodium carbomethylcellulose; and/or physiologically acceptable polymers such as polyvinylpyrrolidone (PVP). If desired, disintegrating agents may be added, such as cross-linked polyvinyl pyrrolidone, agar, or alginic acid or a salt thereof such as sodium alginate.

Dragee cores are provided with suitable coatings. For this purpose, concentrated sugar solutions may be used which may optionally contain gum arabic, talc, polyvinyl pyrrolidone, carbopol gel, polyethylene glycol, titanium dioxide, lacquer solutions and suitable organic solvents or solvent mixtures. Dyestuffs or pigments may be added to the tablets or dragee coatings for identification or to characterize different combinations of active compound doses.

Pharmaceutical compositions which can be used orally, include push-fit capsules made of gelatin as well as soft, sealed capsules made of gelatin and a plasticizer, such as glycerol or sorbitol. The push-fit capsules may contain the active ingredients in admixture with filler such as lactose, binders such as starches, lubricants such as talc or magnesium stearate and, optionally, stabilizers. In soft capsules, the active ingredients may be dissolved or suspended in suitable liquids, such as fatty oils, liquid paraffin, or liquid polyethylene glycols. In addition, stabilizers may be added. AU formulations for oral administration should be in dosages suitable for the chosen route of administration.

For buccal administration, the compositions may take the form of tablets or lozenges formulated in conventional manner.

For administration by nasal inhalation, the active ingredients for use according to the present invention are conveniently delivered in the form of an aerosol spray presentation from a pressurized pack or a nebulizer with the use of a suitable propellant, e.g., dichlorodifluoromethane, trichlorofluoromethane, dichloro- tetrafluoroethane or carbon dioxide. In the case of a pressurized aerosol, the dosage unit may be determined by providing a valve to deliver a metered amount. Capsules and cartridges of, e.g., gelatin for use in a dispenser may be formulated containing a powder mix of the compound and a suitable powder base such as lactose or starch.

The pharmaceutical composition described herein may be formulated for parenteral administration, e.g., by bolus injection or continuos infusion. Formulations for injection may be presented in unit dosage form, e.g., in ampoules or in multidose containers with optionally, an added preservative. The compositions may be suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilizing and/or dispersing agents.

Pharmaceutical compositions for parenteral administration include aqueous solutions of the active preparation in water-soluble form. Additionally, suspensions of the active ingredients may be prepared as appropriate oily or water based injection suspensions. Suitable lipophilic solvents or vehicles include fatty oils such as sesame oil, or synthetic fatty acids esters such as ethyl oleate, triglycerides or liposomes.

Aqueous injection suspensions may contain substances, which increase the viscosity of the suspension, such as sodium carboxymethyl cellulose, sorbitol or dextran.

Optionally, the suspension may also contain suitable stabilizers or agents which increase the solubility of the active ingredients to allow for the preparation of highly concentrated solutions.

Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g., sterile, pyrogen-free water based solution, before use.

The pharmaceutical composition of the present invention may also be formulated in rectal compositions such as suppositories or retention enemas, using, e.g., conventional suppository bases such as cocoa butter or other glycerides.

Pharmaceutical compositions suitable for use in context of the present invention include compositions wherein the active ingredients are contained in an amount effective to achieve the intended purpose. More specifically, a therapeutically effective amount means an amount of active ingredients (nucleic acid construct) effective to prevent, alleviate or ameliorate symptoms of a disorder (e.g., ischemia) or prolong the survival of the subject being treated. Determination of a therapeutically effective amount is well within the capability of those skilled in the art, especially in light of the detailed disclosure provided herein.

For any preparation used in the methods of the invention, the therapeutically effective amount or dose can be estimated initially from in vitro and cell culture OO

assays. For example, a dose can be formulated in animal models to achieve a desired concentration or titer. Such information can be used to more accurately determine useful doses in humans.

Toxicity and therapeutic efficacy of the active ingredients described herein can be determined by standard pharmaceutical procedures in vitro, in cell cultures or experimental animals. The data obtained from these in vitro and cell culture assays and animal studies can be used in formulating a range of dosage for use in human. The dosage may vary depending upon the dosage form employed and the route of administration utilized. The exact formulation, route of administration and dosage can be chosen by the individual physician in view of the patient's condition. (See e.g., Fingl, et al., 1975, in "The Pharmacological Basis of Therapeutics", Ch. 1 p.l).

Dosage amount and interval may be adjusted individually to provide plasma or brain levels of the active ingredient are sufficient to induce or suppress the biological effect (minimal effective concentration, MEC). The MEC will vary for each preparation, but can be estimated from in vitro data. Dosages necessary to achieve the MEC will depend on individual characteristics and route of administration. Detection assays can be used to determine plasma concentrations.

Depending on the severity and responsiveness of the condition to be treated, dosing can be of a single or a plurality of administrations, with course of treatment lasting from several days to several weeks or until cure is effected or diminution of the disease state is achieved.

The amount of a composition to be administered will, of course, be dependent on the subject being treated, the severity of the affliction, the manner of administration, the judgment of the prescribing physician, etc. Compositions of the present invention may, if desired, be presented in a pack or dispenser device, such as an FDA approved kit, which may contain one or more unit dosage forms containing the active ingredient. The pack may, for example, comprise metal or plastic foil, such as a blister pack. The pack or dispenser device may be accompanied by instructions for administration. The pack or dispenser may also be accommodated by a notice associated with the container in a form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals, which notice is reflective of approval by the agency of the form of the compositions or human or veterinary administration. Such notice, for example, may be of labeling approved by the U.S. Food and Drug Administration for prescription drugs or of an approved product insert. Compositions comprising a preparation of the invention formulated in a compatible pharmaceutical carrier may also be prepared, placed in an appropriate container, and labeled for treatment of an indicated condition, as if further detailed above.

Additional objects, advantages, and novel features of the present invention will become apparent to one ordinarily skilled in the art upon examination of the following examples, which are not intended to be limiting. Additionally, each of the various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below finds experimental support in the following examples.

EXAMPLES

Reference is now made to the following examples, which together with the above descriptions, illustrate the invention in a non limiting fashion.

Generally, the nomenclature used herein and the laboratory procedures utilized in the present invention include molecular, biochemical, microbiological and recombinant DNA techniques. Such techniques are thoroughly explained in the literature. See, for example, "Molecular Cloning: A laboratory Manual" Sambrook et al., (1989); "Current Protocols in Molecular Biology" Volumes I-III Ausubel, R. M., ed. (1994); Ausubel et al., "Current Protocols in Molecular Biology", John Wiley and Sons, Baltimore, Maryland (1989); Perbal, "A Practical Guide to Molecular Cloning", John Wiley & Sons, New York (1988); Watson et al., "Recombinant DNA", Scientific American Books, New York; Birren et al. (eds) "Genome Analysis: A Laboratory Manual Series", VoIs. 1-4, Cold Spring Harbor Laboratory Press, New York (1998); methodologies as set forth in U.S. Pat. Nos. 4,666,828; 4,683,202; 4,801,531; 5,192,659 and 5,272,057; "Cell Biology: A Laboratory Handbook", Volumes I-III Cellis, J. E., ed. (1994); "Culture of Animal Cells - A Manual of Basic Technique" by Freshney, Wiley-Liss, N. Y. (1994), Third Edition; "Current Protocols in Immunology" Volumes I-III Coligan J. E., ed. (1994); Stites et al. (eds), "Basic and Clinical Immunology" (8th Edition), Appleton & Lange, Norwalk, CT (1994); Mishell and Shiigi (eds), "Selected Methods in Cellular Immunology", W. H. Freeman and Co., New York (1980); available immunoassays are extensively described in the patent and scientific literature, see, for example, U.S. Pat. Nos. 3,791,932; 3,839,153; 3,850,752; 3,850,578; 3,853,987; 3,867,517; 3,879,262; 3,901,654; 3,935,074; 3,984,533; 3,996,345; 4,034,074; 4,098,876; 4,879,219; 5,011,771 and 5,281,521; "Oligonucleotide Synthesis" Gait, M. J., ed. (1984); "Nucleic Acid Hybridization" Hames, B. D., and Higgins S. J., eds. (1985); "Transcription and Translation" Hames, B. D., and Higgins S. J., eds. (1984); "Animal Cell Culture" Freshney, R. L, ed. (1986); "Immobilized Cells and Enzymes" IRL Press, (1986); "A Practical Guide to Molecular Cloning" Perbal, B., (1984) and "Methods in Enzymology" Vol. 1-317, Academic Press; "PCR Protocols: A Guide To Methods And Applications", Academic Press, San Diego, CA (1990); Marshak et al., "Strategies for Protein Purification and Characterization - A Laboratory Course Manual" CSHL Press (1996); all of which are incorporated by reference as if folly set forth herein. Other general references are provided throughout this document. The procedures therein are believed to be well known in the art and are provided for the convenience of the reader. All the information contained therein is incorporated herein by reference.

Expression of active heparanase in tobacco leaves The objective of this study was to ascertain whether an active form of heparanase could be expressed in plant tissue. MATERIALS AND METHODS

Construct: A plant expression vector pBI121-hpa was constructed for the transformation of Agrobacterium and subsequent infiltration into tobacco leaves. The binary plasmid pBI121, an E.coli/A.tumefaciens shuttle vector (Clontech, San Francisco, Ca) was digested with Smal (New England Biolabs, Beverly). pSI-hpa, pSI vector (Promega, Medison, WI) containing the entire heparanase coding sequence (Genbank Accession No. AF144325) was digested with EcoRI (New England Biolabs, Beverly, MA) and Notl (New England Biolabs, Beverly, MA) filled in by klenow and thereafter ligated with the digested pBI 121, using a ligase enzyme to yield the plasmid pBI3-h60 (Figure 1).

Agrobacterium transformation: The expression of recombinant human heparanase in tobacco was attempted using the Agrobacterium mediated leaf disc transformation. The constructs were transformed into E. coli XLI-Blue cells, and then into A. tumefaciens strain LBA4404, by the tri-parental mating method (Horsch et al, Cold Spring Harb Symp Quant Biol. 1985;50:433-7) using the helper plasmid pRK2013. Agrobacterium were grown at 30 °C in AB minimal medium in the presence of 50 mg/L kanamycin and 10 mg/L rifampicin. Agrobacterium cells were harvested in log phase, washed, and resuspended in liquid MS media until reaching an OD₆₀₀ of 0.6- 0.8.

Plant transformation and regeneration - The leaf surfaces were sterilized by 10 % bleach, + Tween 20 and rinsed with sterile double distilled water. Leaf disks were cut and immersed in a suspension of Agrobacterium tumefaciens (~10⁷/ml). The disks were blot dried, following which they were incubated on plates at 28 °C for 3 days (MS salts, B₅ vitamins, sucrose, 1.0 μg/ml benzyladenine, 0.1 μg/ml naphalene acetic acid.

Analysis: Leaf discs were frozen in liquid nitrogen and ground by mortal and pestle. Ground plant tissue was suspended in 20 mM phosphate citrate buffer pH 5.4.

Plant tissue extracts were subjected to western blot analysis to confirm heparanase expression. Rabbit anti heparanase (P50) polyclonal antibody was used for Western blot analysis using an HRP conjugated Goat anti rabbit and ECL detection system.

The 1,9-Dimethylmethylene blue (DMB) heparanase activity assay, as described in WO02060375 was performed to measure heparanase activity. Briefly, leaf extracts were incubated with heparin sepharose beads (Pharmacia) at 37 °C for 3 hours in reaction mixtures containing 20 mM phosphate citrate buffer pH 5.4, 1 mM

CaCl2, and 1 mM NaCl, following which the samples were centrifuged. The supernatants were analyzed for heparin released by endogenous heparanase activity, using the DMB (Aldrich) assay system. Absorbance was determined at 530 nm.

RESULTS

Heparanase expression: The results obtained by western analysis are shown in Figure 2. While several bands appear in both extracts, a band of approximately 50 kDa, similar to the recombinant human heparanase standard, appears only in extracts of transformed tobacco leaves. The quantity of the 50 kDa band is consistent with the activity obtained in the activity assay (see below).

Heparanase activity: The activity measured in heparanase transformed extracts as compared to control extracts is illustrated in Figure 3. Leaf extracts, transformed with heparanase expression vector showed activity clearly above the activity in the background and in control leaf extracts. Plotting the data on a standard curve of purified recombinant human heparanase indicated that 50 μl of leaf extract possess activity which is equivalent to 22 ng of purified recombinant human heparanase.

CONCLUSION The heparanase coding sequence encodes for a 65 kDa heparanase precursor, which in mammalian cells undergoes processing to yield a heterodimer of 50 kDa and 8 kDa polypeptides. The results of the western analysis indicate the presence of a 50 kDa polypeptide in the extracts of transformed plant cells while the heparanase activity assay suggests the presence of active heparanase heterodimer. It is suggested that the heparanase precursor is expressed in the plant tissue where it is able to undergo activation through proteolytic processing.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Although the invention has been described in conj miction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

REFERENCES

1. Wight, T. N., Kinsella, M. G., and Qwarnstromn, E. E. (1992). The role of proteoglycans in cell adhesion, migration and proliferation. Curr. Opin. Cell Biol., 4, 793-801.

2. Jackson, R. L., Busch, S. J., and Cardin, A. L. (1991). Glycosaminoglycans: Molecular properties, protein interactions and role in physiological processes. Physiol.

Rev., 71, 481-539

3. Wight, T. N. (1989). Cell biology of arterial proteoglycans. Arteriosclerosis, 9, 1-20.

4. Kjellen, L., and Lindahl, U. (1991). Proteoglycans: structures and interactions. Annu. Rev. Biochem., 60, 443-475.

5. Ruoslahti, E., and Yamaguchi, Y. (1991). Proteoglycans as modulators of growth factor activities. Cell, 64, 867-869.

6. Vlodavsky, I., Eldor, A., Haimovitz-Friedman, A., Matzner, Y., Ishai- Michaeli, R., Levi, E., Bashkin, P., Lider, O., Naparstek, Y., Cohen, I. R., and Fuks, Z. (1992). Expression of heparanase by platelets and circulating cells of the immune system: Possible involvement in diapedesis and extravasation. Invasion & Metastasis, 12, 112-127.

7. Vlodavsky, I., Mohsen, M., Lider, O., Ishai-Michaeli, R., Ekre, H. -P., Svahn, C. M., Vigoda, M., and Peretz, T. (1995). Inhibition of tumor metastasis by heparanase inhibiting species of heparin. Invasion & Metastasis, 14, 290-302.

8. Nakajima, M., Irimura, T., and Nicolson, G. L. (1988). Heparanase and tumor metastasis. J. Cell Biochem., 36, 157-167.

9. Burgess, W. H., and Maciag, T. (1989). The heparin-binding (fibroblast) growth factor family of proteins. Annu. Rev. Biochem., 58, 575-606. 10. Folkman, J., and Klagsbrun, M. (1987). Angiogenic factors. Science, 235,

442-447.

11. Bashkin, P., Doctrow, S., Klagsbrun, M., Svahn, C. M., Folkman, J., and Vlodavsky, I. (1989). Basic fibroblast growth factor binds to subendothelial extracellular matrix and is released by heparitinase and heparin-like molecules. Biochemistry, 28, 1737-1743. 12. Folkman, J., Klagsbrun, M., Sasse, J., Wadzinski, M., Ingber, D., and Vlodavsky, I. (1980). A heparin-binding angiogenic protein-basic fibroblast growth factor—is stored within basement membrane. Am. J. Pathol., 130, 393-400.

13. Ishai-Michaeli, R., Svahn, C. -M., Chajek-Shaul, T., Korner, G., Ekre, H. - P., and Vlodavsky, I. (1992). Importance of size and sulfation of heparin in release of basic fibroblast factor from the vascular endothelium and extracellular matrix. Biochemistry, 31, 2080-2088.

14. Ishai-Michaeli, R., Eldor, A., and Vlodavsky, I. (1990). Heparanase activity expressed by platelets, neutrophils and lymphoma cells releases active fibroblast growth factor from extracellular matrix. Cell Reg., 1, 833-842.

15. Spivak-Kroizman, T. et al. Heparin-induced oligomerization of FGF molecules is responsible for FGF receptor dimerization, activation, and cell proliferation. Cell 79, 1015-1024 (1994);

16. Vlodavsky, L, Miao, H. Q., Medalion, B., Danagher, P. & Ron, D. 1996. Involvement of heparan sulfate and related molecules in sequestration and growth promoting activity of fibroblast growth factor. Cancer Metastasis Rev 15, 177-186 (1996);

17. Aviezer, D. et al. Perlecan, basal lamina proteoglycan, promotes basic fibroblast growth factor-receptor binding, mitogenesis, and angiogenesis. Cell 79, 1005-1013 (1994)].

18. Gitay-Goren, H., Soker, S., Vlodavsky, L, and Neufeld, G. (1992). Cell surface associated heparin-like molecules are required for the binding of vascular endothelial growth factor (VEGF) to its cell surface receptors. J. Biol. Chem., 267, 6093-6098 19. Tsuboi R. and D. B. Rifkin. 1991. Recombinant basic fibroblast growth factor stimulates wound healing-impaired db/db mice. J. Exp. Med. 172: 245-251

20. Brown R. E., M. P. Breeden and D. G. Greenhalgh. 1994. PDGF and TGF- alpha act synergistically to improve wound healing in the genetically diabetic mouse. J. Surg. Res. 56: 562-570]. 21. Goldshmidt O. et al, The FASEB Journal. 2003;17:1015-1025

22. Knighton, D. R. and Fiegel, V. D. Growth factors and comprehensive surgical care of diabetic wounds. Curr. Opin. Gen. Surg.:32-9: 32-39, 1993;

23. Shaw, J. E. and Boulton, A. J. The pathogenesis of diabetic foot problems: an overview. Diabetes, 46 Suppl 2: S58-S61, 1997]. 24. Gibbons, G. W. The burden of diabetic foot ulcers. Am. J. Surg., 176: 5S- 1OS, 1998]

25. Hasegawa T et al; Angiology 1999 50(6):487-95;

26. Scheinowitz M et al; Exp. Physiol. 1998, 83(5):585-93 27. Miyataka M et al; Angiology 1998, 49(5):381-90

28. Wang J S et al., Acta Orthop Scand 1996, 67(3): 229-36

29. Shieh, M-T., Wundunn, D., Montgomery, R. L₅ Esko, J. D., and Spear, P. G. J. (1992). Cell surface receptors for herpes simplex virus are heparan sulfate proteoglycans. J. Cell Biol., 116, 1273-1281. 30. Chen, Y., Maguire, T., Hileman, R. E., Fromm, J. R., Esko, J. D.,

Linhardt, R. J., and Marks, R. M. (1997). Dengue virus infectivity depends on envelope protein binding to target cell heparan sulfate. Nature Medicine 3, 866-871.

31. Putnak, J. R., Kanesa-Thasan, N., and Innis, B. L. (1997). A putative cellular receptor for dengue viruses. Nature Medicine 3, 828-829 32. Narindrasorasak, S., Lowery, D., Gonzalez-DeWhitt, P., Poorman, R. A.,

Greenberg, B., Kisilevsky, R. (1991). High affinity interactions between the Alzheimer's beta-amyloid precursor protein and the basement membrane form of theparan sulfate proteoglycan. J. Biol. Chem., 266, 12878-83.

33. Ross, R. (1993). The pathogenesis of atherosclerosis: a perspective for the 1990s. Nature (Lond.)., 362:801-809.

34. Zhong-Sheng, J., Walter, J., Brecht, R., Miranda, D., Mahmood Hussain, M., Innerarity, T. L. and Mahley, W. R. (1993). Role of heparan sulfate proteoglycans in the binding and uptake of apolipoprotein E-enriched remnant lipoproteins by cultured cells. J. Biol. Chem., 268, 10160-10167. 35. Eisenberg, S., Sehayek, E., Olivecrona, T., and Vlodavsky, I. (1992).

Lipoprotein lipase enhances binding of lipoproteins to heparan sulfate on cell surfaces and extracellular matrix. J. Clin. Invest., 90, 2013-2021.

36. Sijmons et al, 8 BIO/TECH. 217-21 (1990).

37. Kusnadi et al, 56(5) BIOTECH. & BIOENG¹G 473-84 (1997); 38. Saito et al, 88 P.N.A.S. 7041-45 (1991);

39. Mason et al, 89 P.N.A.S. 11745-49 (1992).

40. Li et al, 7(6) MoI. Cells 783-787 (1997).

Claims

WHAT IS CLAIMED IS:

1. A nucleic acid construct comprising a nucleic acid sequence encoding heparanase and a cis-acting regulatory element capable of directing an expression of said heparanase in a plant.

2. A molecule comprising a heparanase polypeptide and at least one carbohydrate moiety attached to said heparanase polypeptide, said carbohydrate moiety being selected from the group consisting of a xylose and a fucose.

3. A plant cell comprising the nucleic acid construct of claim 1.

4. A plant comprising the nucleic acid construct of claim 1.

5. A pharmaceutical composition comprising, as an active ingredient, the heparanase of claim 2.

6. A method of producing heparanase comprising:

(a) introducing the nucleic acid construct of claim 1 into a plant;

(b) cultivating said plant under conditions which allow expression of the heparanase; and

(c) recovering the heparanase from said plant, thereby producing the heparanase.

7. The nucleic acid construct of claim 1, wherein said nucleic acid sequence encoding the heparanase is as set forth in SEQ ID NO: 3.

8. The nucleic acid construct of claim 1, further comprising an additional nucleic acid sequence encoding a signal sequence.

9. The nucleic acid construct of claim 8, wherein said signal sequence is selected from the group consisting of an ER signal sequence, a cytosol signal sequence, a plastid signal sequence, a seed signal sequence, a vacuole signal sequence and an apoplast signal sequence.

10. The nucleic acid construct of claim 1, wherein said additional nucleic acid sequence is a viral sequence.

11. The nucleic acid construct of claim 10, wherein said viral sequence comprises a plus sense RNA viral replication origin, said replicon is dependent for replication on a helper virus.

12. The nucleic acid construct of claim 1, wherein said nucleic acid sequence encoding heparanase is as set forth in SEQ ID NO. 1.

13. The nucleic acid construct of claim 1, wherein said nucleic acid sequence encodes a polypeptide which comprises an amino acid sequence as set forth in SEQ ID NO. 2.

14. The nucleic acid construct of claim 1, wherein said cis-acting regulatory element is a plant promoter.

15. The nucleic acid construct of claim 14, wherein said plant promoter is selected from the group consisting of a constitutive promoter, a pre-harvest inducible promoter, a post-harvest inducible promoter, a developmentally regulated promoter and a tissue-specific promoter.

16. The nucleic acid construct of claim 1, wherein the nucleic acid construct is capable of integrating into the genome of the plant cell.

17. The nucleic acid construct of claim 1, wherein the nucleic acid construct is an episomal construct.

18. The heparanase of claim 2, wherein said xylose is attached to said heparanase polypeptide via a beta 1,2 linkage.

19. The heparanase of claim 2, wherein said fucose is attached to said heparanase polypeptide via an alpha 1,3 linkage.

20. The plant cell, plant or method of any of claims 3, 4 or 6, wherein the plant is a monocotyledonous plant.

21. The plant cell, plant or method of any of claims 3, 4 or 6, wherein the plant is a dicotyledonous plant.

22. The method of claim 6, further comprising modifying said heparanase prior to or following (c).

23. The method of claim 22, wherein said modifying comprises de- glycosylating said heparanase.

24. The method of claim 23, wherein said de-glycosylating is effected by a glycosidase.

25. The method of claim 24, wherein said glycosidase is selected from the group consisting of a xylosidase and a 1,3-fucosidase.

26. The method of claim 22, wherein said modifying comprises glycosylating said heparanase.

27. The method of claim 26, wherein said glycosylating is effected by a glycosyltransferase.

28. The method of claim 27, wherein said glycosyltransferase is selected from the group consisting of a galatosyltransferase or a sialyltransferase.

29. The method of claim 22, wherein said modifying comprises glucosylating and de-glycosylating said heparanase.

30. The method of claim 22, wherein said modifying comprises cleaving said heparanase.