WO2014022823A2 - Inhibiting telomere synthesis by telomerase - Google Patents

Abstract

This invention relates to inhibition or modulation of telomerase activity.

Description

TITLE: INHIBITING TELOMERE SYNTHESIS BY TELOMERASE

STATEMENT OF GOVERNMENT SPONSORED RESEARCH

[001] This invention was supported in part by grant CA125453 from the National Cancer Institute and AG033747 of the National Institutes of Health. The Federal Government has certain rights in this invention.

RELATED APPLICATIONS

[002] This application claims priority to USSN 61/679,022, filed August 2, 2012.

FIELD OF THE INVENTION

[003] This invention relates to inhibition or modulation of telomerase activity.

BACKGROUND OF THE INVENTION

[004] In the following discussion certain articles and methods will be described for background and introductory purposes. Nothing contained herein is to be construed as an "admission" of prior art. Applicant expressly reserves the right to demonstrate, where appropriate, that the articles and methods referenced herein do not constitute prior art under the applicable statutory provisions.

[005] Telomeres, which define the ends of chromosomes, consist of short, tandemly repeated DNA sequences loosely conserved in eukaryotes. Human telomeres consist of many kilobases of (TTAGGG)_n together with various associated proteins. Small amounts of these terminal sequences or telomeric DNA are lost from the tips of the chromosomes during the S phase of the cell cycle because of incomplete DNA replication. Many human cells progressively lose terminal sequence with cell division, a loss that correlates with the apparent absence of telomerase in these cells. Resulting telomeric shortening has been demonstrated to limit cellular lifespan, thereby resulting in cellular senescence and inactivation.

[006] Telomerase is a ribonucleoprotein (RNP) that uses a portion of its RNA moiety as a template for telomeric DNA synthesis. The catalytic core of telomerase is comprised of two essential components: TERT, the telomerase reverse transcriptase, and TERC, the telomerase RNA component. Telomerase synthesizes telomeres through reverse transcription of the template sequence encoded in TERC and through protein interactions that facilitate telomere engagement. Genetic studies in yeast, murine, and human cells have established that TERT and TERC are obligate partners in telomere synthesis. Inactivation of either subunit abrogates enzymatic activity and prevents telomere addition, leading to progressive telomere shortening; thus, telomerase functions primarily to prevent telomere uncapping through enzymatic extension of telomeres.

[007] Telomerase serves a similar function during tumor development where it prevents telomere shortening and uncapping, thus enabling cancer cells to proliferate in an unlimited fashion, and it has been shown that the immortality conferred by telomerase plays a key role in cancer development. However, despite the fact that telomerase has been viewed as a target to control cancer, there has been little progress thus far in the commercial development of telomerase inhibitors. Accordingly, there continues to be a need for development of such compounds and methods.

[008] Thus, there is a need in the art for methods and compounds that inhibit the action of telomerase. The present invention addresses this need.

SUMMARY OF THE INVENTION

[009] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description, and is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other features, details, utilities, and advantages of the claimed subject matter will be apparent from the following written Detailed Description including those aspects illustrated in the accompanying drawings and defined in the appended claims.

[0010] The present invention provides compounds and methods for treating cancer and for screening for compounds that may be used for treating cancer, autoimmune diseases, and other diseases characterized by unchecked cell growth. The claimed compounds and methods are based on the observation that the telomerase recruiting action of TPP1, a telomere binding protein, can be blocked and done so without disrupting shelterin function. Specifically, the OB-fold domain of TPPlis key in recruiting telomerase to telomeres through an association with the telomerase reverse transcriptase TERT. By inhibiting the binding of telomerase to the OB-fold of TPP1, telomerase action can be blocked, thereby inhibiting telomerase action and telomere maintenance. TPPl and TERT inhibitors have broad application to human cancers and proliferative diseases of diverse tissue origins, including but not limited to cancers of the brain, head and neck, esophagus, stomach, breast, colon and digestive tract, liver, testis, ovary skin, kidney, bladder, bone, connective tissue and pancreas.

[0011] In one embodiment, the invention provides a method for screening for a composition of matter for the treatment of cancer or other cellular proliferative disease comprising identifying a moiety that binds to an OB domain of TPPl. In some aspects of this embodiment, the moiety binds one or more of D166, E168 or K170; and in some aspects of this embodiment, the moiety binds to two or more of D166, E168 or K170; and in yet other aspects of this embodiment, the moiety binds to all of D166, E168 and K170. In other aspects of this embodiment, the moiety is an antibody to the OB domain of TPPl or a small molecule.

[0012] Other embodiments of the invention provide a composition of matter for the treatment of cancer or other proliferative disease with a therapeutic comprising a TPPl peptide. Some aspects of this embodiment provide a peptide comprising 100 amino acids or less and comprises an OB domain of TPPl. In other aspects of this embodiment, peptides comprising 80 amino acids, 60 amino acids, 40 amino acids, 20 amino acids, 10 amino acids or less but comprising one or more of D166, E168 or K170.

[0013] Yet other embodiments of the invention provide a method for screening for a composition of matter for the treatment of cancer or other proliferative disease comprising identifying a moiety that binds to one or both of the TEN or CTE domains of TERT. In some aspects of this embodiment the moiety is a peptide, antibody or small molecule.

[0014] Yet other embodiments of the invention provide a method of treating cancer or another proliferative disease in an individual comprising administering to the individual one or more of 1) a moiety that binds to the OB domain of TPPl; 2) a TPPl peptide; or 3) a moiety that binds to one or both of the TEN or CTE domains of TERT. In some aspects of this embodiment the moiety that binds to the OB domain of TPPl binds one or more of D166, E168 or K170; and in some aspects, the moiety that binds to the OB domain of TPPlbinds to two or more of D166, E168 or K170; and in yet other aspects the moiety that binds to the OB domain of TPPl binds to all of D166, E168 and K170. In some aspects of this embodiment, the TPPl peptide is a peptide comprising 100 amino acids or less and comprises an OB domain of TPPl. In other aspects of this embodiment, peptides comprising 80 amino acids, 60 amino acids, 40 amino acids, 20 amino acids, 10 amino acids or less but comprising one or more of D166, E168 or K170.

[0015] In yet other aspects of this embodiment, the moiety that binds to one or both of the TEN or CTE domains of TERT binds to both the TEN or CTE domains of TERT.

[0016] Also provided by the invention is an embodiment including a transgenic animal, wherein the transgenic animal conditionally transcribes a nucleic acid coding for TPPl or one or both of the TEN or CTE domains of TERT. In some aspects, the animal is a rodent.

[0017] One embodiment of the invention provides a method for identifying a compound that is capable of preventing recruitment of telomerase by TPPl but does not disrupt shelterin comprising the steps of (a) activating a cell by conditionally increasing transcription of a coding sequence of TPPl one or both of the TEN or CTE domains of TERT; contacting the compound with the cell; and observing the effect of the compound on the cell. In some aspects of this embodiment, the compound is a small molecule, in other aspects, the compound is a peptide and in some aspects the peptide is an antibody to an OB domain of TPPl.

[0018] Yet another embodiment of the invention includes a research tool comprising a cell transfected with a vector comprising a nucleic acid that codes for TPPl or one or both of the TEN or CTE domains of TERT. In some aspects of this embodiment, the nucleic acid codes for an OB domain of TPPl, and in some aspects the nucleic acid codes for residues D166, E168 and K170 of the OB domain.

[0019] Also provided is a system for use in identifying a compound that is capable of modulating the recruitment of telomerase by TPPl comprising; (a) a transgenic animal conditionally transcribing a nucleic acid coding for TPPl or one or both of the TEN or CTE domains of TERT; and (b) an agent that activates conditional transcription of said nucleic acid. In some aspects, the nucleic acid codes for an OB domain of TPPl, and in some aspects the nucleic acid codes for at residues D166, E168 and K170 of the OB domain.

[0020] Other embodiments and aspects of the invention are described in the Detailed Description below.

DESCRIPTION OF THE FIGURES

[0021] Figure 1A shows the amino acid sequence of the TPPl OB-fold. Figure IB shows the amino acid sequence of the OB-fold L34 loop. [0022] Figure 2 is a structural representation of the TPP1 OB domain. Residues required for telomerase interaction are shaded.

DEFINITIONS

[0023] The terms used herein are intended to have the plain and ordinary meaning as understood by those of ordinary skill in the art. The following definitions are intended to aid the reader in understanding the present invention, but are not intended to vary or otherwise limit the meaning of such terms unless specifically indicated.

[0024] The term "antibody" as used herein is intended to refer to an entire immunoglobulin or antibody or any functional fragment of an immunoglobulin molecule that is capable of specific binding to an antigen (antibodies and antigens are "binding partners" as defined herein). "Antibody" as used herein is meant to include the entire antibody as well as any antibody fragments capable of binding the antigen or antigenic fragment of interest, e.g., TPP1 and particularly the OB domain thereof. Examples of such peptides include complete antibody molecules, antibody fragments, such as Fab, F(ab')2, CDRS, VL, VH, and any other portion of an antibody which is capable of specifically binding to an antigen. Antibodies for the therapeutic methods of the invention are immunoreactive or immuno specific for, and therefore specifically and selectively bind to, TPP1 and particularly the OB domain thereof.

[0025] A "binding agent" is any molecule that selectively binds to and inhibits TPP1 or binds to one or both of the TEN or CTE domains of TERT. Examples of binding agents and TPP1 or TERT inhibitors that can be used in this invention include, but are not restricted to: peptides, proteins (including derivatized or labeled proteins); antibodies or fragments thereof; small molecules; aptamers; carbohydrates and/or other non-protein binding moieties; derivatives and fragments of naturally-occurring binding partners; peptidomimetics; and pharmacophores. A "TPP1 inhibitor" is a binding agent that inhibits recruitment of telomerase to the telomere, but does not disrupt TPPl ' s function as a member of the shelterin complex; alternatively, a TPP1 inhibitor is a TPP1 peptide that functions by out-competing cellular TPP1 that is part of the shelterin complex. A "TERT inhibitor" as used herein is a binding agent that binds to one or both of the TEN or CTE domains of TERT so that TERT cannot be recruited into the shelterin complex by TPP1.

[0026] The term "diagnostic tool" as used herein refers to any composition or assay of the invention used in order to carry out a diagnostic test or assay on a patient sample. As a diagnostic tool, the composition of the invention may be considered a collection of analyte specific reagents, and as such may form part of a diagnostic test regulated by a federal or state agency.

[0027] The term "excipient" refers to an inert substance added to a pharmaceutical composition of the invention to further facilitate administration of the therapeutic cells.

[0028] The term "pharmaceutical composition" refers to a preparation of one or more of the TPP1 inhibitors described herein, with at least one pharmaceutically suitable excipient, carrier or other formulation.

[0029] The term "pharmaceutically acceptable carrier" refers to a carrier or a diluent that facilitates delivery and/or the biological activity and properties of the pharmaceutical compositions of the invention.

[0030] The term "proliferative disease" refers to a disease or condition characterized by cells that have expanded in number, become immortal or otherwise proliferative due in part to telomere maintenance.

[0031] The term "research tool" as used herein refers to any method of the invention or use of the pharmaceutical compositions of the invention for scientific inquiry, either academic or commercial in nature, including the development of pharmaceutical and/or biological therapeutics. The research tools of the invention are not intended to be therapeutic or to be subject to regulatory approval; rather, the research tools of the invention are intended to facilitate research and aid in such development activities, including any activities performed with the intention to produce information to support a regulatory submission.

[0032] The term "small molecule" as used herein refers to a molecule of a size comparable to those organic molecules generally used in chemistry-based pharmaceuticals. The term excludes biological macromolecules (e.g., proteins, nucleic acids, etc.). Preferred small organic molecules range in size up to about 5000 Da, more preferably up to 2000 Da, and most preferably up to about 1000 Da.

[0033] As used herein, the terms "subject" and "patient" are used interchangeably, and refer to an animal (e.g., birds, reptiles, and mammals), such as a mammal including a non-primate or a primate (e.g., a monkey, chimpanzee, and a human). In a typical embodiment, the subject is a human.

[0034] As used herein, the terms "treat," "treatment," "treating," and the like, refer to obtaining a desired pharmacologic and/or physiologic effect. The effect may be prophylactic in terms of completely or partially preventing a disease or symptom thereof and/or may be therapeutic in terms of a partial or complete cure for a disease and/or adverse affect attributable to the disease. "Treatment," as used herein, covers any treatment of a disease in a mammal, particularly in a human, and includes: (a) preventing the disease from occurring in a subject which may be predisposed to the disease but has not yet been diagnosed as having it; (b) inhibiting the disease, i.e., arresting its development; and (c) relieving the disease, e.g., causing regression of the disease, e.g., to completely or partially remove symptoms of the disease.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The practice of the techniques described herein may employ, unless otherwise indicated, conventional techniques and descriptions of neurobiology, physiology, electrophysiology, data analysis, pharmaceutical chemistry, organic chemistry, polymer technology, molecular biology (including recombinant techniques), cell biology, mammalian cell culture, and biochemistry, which are within the skill of those who practice in the art. Specific illustrations of suitable techniques can be had by reference to the Examples herein. However, other equivalent conventional procedures can, of course, also be used. Such conventional techniques and descriptions can be found in standard laboratory manuals such as Butler (2004), Animal Cell Culture (BIOS Scientific); Ozturk and Hu (2006), Cell Culture Technology for Pharmaceutical and Cell-Based Therapies (CRC Press); Sambrook and Russell (2006), Condensed Protocols from Molecular Cloning: A Laboratory Manual; and Sambrook and Russell (2002), Molecular Cloning: A Laboratory Manual (both from Cold Spring Harbor Laboratory Press); Stryer, L. (1995) Biochemistry, Fourth Ed. (W.H. Freeman); Nelson and Cox (2000), Lehninger, Principles of Biochemistry , Third Ed. (W. H. Freeman); and Berg et al. (2002) Biochemistry, Fifth Ed. (W.H. Freeman); all of which are herein incorporated in their entirety by reference for all purposes.

[0036] Note that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a telomerase inhibitor" refers to one or more telomerase inhibitors, and reference to "administering" or "administration" includes reference to equivalent steps and methods known to those skilled in the art, and so forth. [0037] Unless defined otherwise, 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. All publications mentioned herein are incorporated by reference for the purpose of describing and disclosing devices, formulations and methodologies that may be used in connection with the presently described invention.

[0038] Where a range of values is provided, it is understood that each intervening value, between the upper and lower limit of that range and any intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the invention subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the invention.

[0039] In the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention. However, it will be apparent to one of skill in the art that the present invention may be practiced without one or more of these specific details. In other instances, features and procedures well known to those skilled in the art have not been described in order to avoid obscuring the invention.

The Invention in General

[0040] The addition of telomere repeats to chromosome ends by the enzyme telomerase is essential to counter the incomplete replication of telomeres that occurs with cell division in stem cells and in cancer cells (Cech, 2004; Palm and de Lange, 2008; Artandi and DePinho, 2010; O'Sullivan and Karlseder, 2010). Disruption of this process by mutations in telomerase components causes stem cell dysfunction and results in a number of diseases in humans, including dyskeratosis congenita, aplastic anemia, pulmonary fibrosis and multiple types of cancer (Savage and Alter, 2008; Calado and Young, 2009). Human telomerase consists of a minimal catalytic core including the reverse transcriptase subunit, TERT, and the telomerase RNA component, TERC, which are assembled into a mature enzyme along with additional holoenzyme proteins (Collins, 2008). To elongate telomeres, telomerase is thought to be recruited to chromosome ends through interactions with telomere binding proteins, but the precise mechanisms of telomerase recruitment remain incompletely understood. [0041] Telomerase undergoes a highly orchestrated process of assembly and trafficking within the nucleus of human cells. TERC encodes the template for the reverse transcription reaction in telomere addition, but also serves as the central scaffold for assembly of the telomerase RNP (Cech, 2004; Zappulla and Cech, 2006; Egan and Collins, 2012). A newly transcribed TERC RNA molecule is bound and stabilized by the dyskerin core complex, which includes dyskerin, NHP2 and NOP10 (Darzacq et al., 2006). Loading of TERT into telomerase complexes generates an enzymatically active RNP, but this complex is unable to act on telomeres without completing additional trafficking and assembly steps in vivo. In human cancer cells and embryonic stem cells, telomerase localizes within Cajal bodies, nuclear sites of RNP modification and assembly (Gall, 2000; Jady et al., 2004; Zhu et al., 2004; Batista et al., 2011). RNA FISH studies using probes specific for TERC revealed that telomerase-containing Cajal bodies associated with a subset of telomeres specifically in S- phase of the cell cycle (Jady et al., 2004; Zhu et al., 2004; Tomlinson et al., 2008). Concentration of telomerase within Cajal bodies depends upon an interaction between the CAB box motif within TERC and TCAB1, a WD40 repeat protein that is part of the active telomerase holoenzyme (Cristofari et al., 2007; Tycowski et al., 2009; Venteicher et al., 2009). TCAB1 is required for telomere maintenance and is mutated in an autosomal recessive form of dyskeratosis congenita (Venteicher et al., 2009; Zhong et al., 2011). Loss of TCAB1 function causes mislocalization of telomerase from Cajal bodies to nucleoli, cripples the ability of telomerase to maintain telomeres and impairs recruitment of telomerase to chromosome ends (Venteicher et al., 2009; Batista et al., 2011; Zhong et al., 2011; Stern et al., 2012). Depletion of the Cajal body scaffold coilin also blunts the ability of telomerase RNA to associate with telomeres, suggesting that Cajal bodies may be important for recruiting telomerase to telomeres (Stern et al., 2012).

[0042] In yeast, the telomere binding protein Cdcl3p positively regulates telomerase recruitment through an interaction with the telomerase component Estlp (Pennock et al., 2001; Taggart et al., 2002; Chan et al., 2008). In human cells, telomere-binding proteins exert both positive and negative effects on telomerase function. Human telomeres consist of long tracks of double- stranded repeats ending in a single- stranded overhang, which together are bound by the six-protein shelterin complex (Smogorzewska and de Lange, 2004; de Lange, 2005; Verdun and Karlseder, 2007; Xin et al., 2008; O'Sullivan and Karlseder, 2010). TRF1 and TRF2, factors that bind double stranded telomere repeats, inhibit telomerase function presumably by transducing telomere length information to the chromosome terminus (Smogorzewska et al., 2000). The single stranded overhang is bound by a subcomplex of shelterin components in which POTl directly contacts DNA and TPPl bridges POTl to TIN2, which connects to the TRF1-TRF2 double stranded DNA binding complex. Depletion of POTl or TPPl, or overexpression of a POTl variant with a deletion in the DNA binding domain (ΡΟΤ1ΔΟΒ), each leads to telomere elongation by telomerase, indicating that POTl and TPPl prevent telomerase action at telomeres (Loayza and De Lange, 2003; Ye and de Lange, 2004; Ye et al., 2004). In contrast to these genetic findings in cultured cells, biochemical studies in vitro have established that recombinant TPPl and POTl enhance processivity of telomerase on oligonucleotide substrates, suggesting that TPPl and POTl act as positive co-factors in telomerase catalysis (Wang et al., 2007; Zaug et al., 2010). These dual functions of the TPPl -POTl complex in regulating telomerase function remain to be resolved.

3] Experiments designed to address telomerase recruitment in human cells have exploited 'super- telomerase' cells, cancer cells in which both TERT and TERC are overexpressed, to enable telomerase detection at telomeres (Cristofari and Lingner, 2006; Cristofari et al., 2007; Abreu et al., 2010). Loss of function studies showed that TPPl and TIN2 were required for efficient recruitment of telomerase to telomeres in super-telomerase cells (Abreu et al., 2010). TERT has been shown to interact with the OB-fold of TPPl (Xin et al., 2007) and this same domain of TPPl was implicated in recruiting telomerase to telomeres in super-telomerase cells (Abreu et al., 2010). However, TPPl serves to tether POTl to telomeres, therefore inhibition of TPPl leads to loss of the TPP1-POT1 complex from telomeres and the induction of a DNA damage response at telomeres (Houghtaling et al., 2004; Liu et al., 2004; Ye et al., 2004; Kibe et al., 2010; Tejera et al., 2010; Takai et al., 2011). In addition, loss of TPPl in vivo is accompanied by reduced levels of TIN2 (Rai et al., 2011), suggesting that TPPl might serve a structural role in the shelterin complex. Therefore, separating the putative recruitment function of TPPl from its end-protection function is inherently challenging. Mechanisms of telomerase recruitment to telomeres in human cancer cells has been elucidated. The OB-fold domain of TPPl recruits telomerase to telomeres and this is an essential step in telomere maintenance. Thus, blocking the recruitment of telomerase to the telomere by TPPl without disrupting shelterin is an elegant method of regulating cellular proliferation. [0044] Figure 1A provides the amino acid sequence for the OB fold of TPPl, which corresponds to amino acids 87-250 of the full length TPPl protein. Figure IB is the L34 loop of the OB fold of TPPl (also underlined in Figure 1 A). Figure 2 is a structural representation of the TPPl OB domain. Residues required for telomerase interaction are indicated by the darkly shaded areas at the right of both representations of the OB domain.

Small Molecule Inhibitors of TPPl or TERT

[0045] Small molecules contemplated for use in the methods of the invention include small molecules that may serve as binding agents to TPPl, specifically to the OB domain of TPPl and even more specifically to the region comprising D166, E168 and K170, which blocks the recruitment of telomerase to the telomere by TPPl without disrupting shelterin. In addition or alternatively, small molecules include moieties that may serve as binding agents to one or both of the TEN or CTE domains of TERT. Generally, selection of small molecules to act as TPPl or TERT inhibitors requires routine screening, including high throughput screening of compounds as described herein.

[0046] Naturally occurring or synthetic small molecule compounds of interest include numerous chemical classes, though typically they are organic molecules, preferably small organic compounds having a molecular weight of more than 50 and less than about 2,500 daltons. Candidate agents comprise functional groups necessary for structural interaction with proteins, particularly hydrogen bonding, and typically include at least an amine, carbonyl, hydroxyl or carboxyl group, preferably at least two of the functional chemical groups. The candidate agents often comprise cyclical carbon or heterocyclic structures and/or aromatic or polyaromatic structures substituted with one or more of the above functional groups. Candidate agents are also found among biomolecules including peptides, saccharides, fatty acids, steroids, purines, pyrimidines, derivatives, structural analogs or combinations thereof. Such molecules may be identified, among other ways, by employing the screening protocols described below. Small molecule agents of particular interest include pyrrole-imidazole polyamides, analogous to those described in Dickinson et al., Biochemistry, 38(33): 10801-7 (1999). Other agents include "designer" DNA binding proteins that bind to TPPl or the OB domain thereof, or one or both of the TEN or CTE domains of TERT.

TPPl Peptides and Pep tide-producin Polynucleotides [0047] TPP1 inhibitors of the invention include biologies in addition to small molecules, such as TPP1 peptides. TPP1 peptides, either synthesized and delivered directly to the cell or transcribed and translated from a vector or other exogenous nucleic acid act to out-compete cellular TPP1 that is part of the shelterin complex.

[0048] Where the agent is a polynucleotide, analog or mimetic thereof, e.g., the agent may be introduced into tissues or host cells by any number of routes, including viral infection, microinjection, or fusion of vesicles. Jet injection may also be used for intramuscular administration, as described by Furth et al., Anal Biochem 205:365-368 (1992). The DNA may be coated onto gold microparticles, and delivered intradermally by a particle bombardment device, or "gene gun" as described in the literature (see, for example, Tang et al., Nature 356: 152-154 (1992)), where gold microprojectiles are coated with the DNA, then bombarded into skin cells. For nucleic acid therapeutic agents, a number of different delivery vehicles find use, including viral and non-viral vector systems, as are known in the art. Delivery vehicles that target cancer cell surface proteins may be used in the compositions and methods of the invention.

[0049] Expression vectors for a polynucleotide agent used in some embodiments of the present invention comprise a bacterial backbone (plasmid DNA or pDNA) or a viral backbone. The bacterial backbone can be any bacterial backbone known to those with skill in the art. Backbones typically selected are those that, e.g., contain or lack appropriate restriction sites to allow ease of cloning, may be produced and isolated with ease, are not immunogenic, and the like. For example, bacterial backbones derived from E. coli are of use in the present invention. A plasmid vector of the present invention also comprises one or more DNA control sequences, such as promoter sequences, polyadenylation signals, transcription termination sequences, upstream regulatory domains, origins of replication, internal ribosome entry sites and the like, which collectively provide for the replication, transcription and translation of the anti-inflammatory cytokine coding sequence(s) in a recipient cell. Not all of these control sequences need always be present so long as the antiinflammatory cytokine coding sequences are capable of being replicated, transcribed and translated in an appropriate host cell. Promoter sequences of use in the present invention include but are not limited to chicken or human β-actin promoters, cytomegalovirus immediate early promoters, glyceraldehydes 3-phosphate dehydrogenase (GADPH) promoters, elongation factor la (eFl ) promoter, GFAP promoter, murine leukemia virus (MLV) promoter, herpes simples virus thymidine kinase (TK) promoter, and woodchuck hepatitis virus post- transcriptional regulatory element (WPRE) promoters; upstream regulatory domains of use in the present invention include but are not limited to cytomegalovirus immediate early promoter enhancers, mouse mammary tumor virus (MMTV) enhancer and simian virus 40 (SV40) enhancer; and polyadenylation signals of interest in the present invention include but are not limited to SV40 polyadenylation signal, bovine growth hormone polyadenylation signal, and synthetic polyadenylation signals. Optionally, the plasmid DNA of the present invention will also comprise a selection marker gene, such as that coding for antibiotic resistance. Marker genes of use in the present invention include but are not limited to neomycin, hygromycin-B, ampicillin, kanomycin, or puromycin.

[0050] Alternatively, the vector may be a viral vector. In general, the five most commonly used classes of viral systems used in gene therapy can be categorized into two groups according to whether their genomes integrate into host cellular chromatin (oncoretroviruses and lentiviruses) or persist in the cell nucleus predominantly as extrachromosomal episomes (adeno-associated virus, adenoviruses and herpesviruses). For example, in one embodiment of the present invention, viruses from the Parvoviridae family are utilized. The Parvoviridae is a family of small single-stranded, non-enveloped DNA viruses with genomes approximately 5000 nucleotides long. Included among the family members is adeno- associated virus (AAV), a dependent parvovirus that by definition requires co-infection with another virus (typically an adenovirus or herpesvirus) to initiate and sustain a productive infectious cycle. In the absence of such a helper virus, AAV is still competent to infect or transduce a target cell by receptor-mediated binding and internalization, penetrating the nucleus in both non-dividing and dividing cells.

[0051] Another viral delivery system useful with the polynucleotide expression constructs of the present invention is a system based on viruses from the family Retroviridae. Retroviruses comprise single-stranded RNA animal viruses that are characterized by two unique features. First, the genome of a retrovirus is diploid, consisting of two copies of the RNA. Second, this RNA is transcribed by the virion- associated enzyme reverse transcriptase into double-stranded DNA. This double-stranded DNA or provirus can then integrate into the host genome and-be passed from parent cell to progeny cells as a stably-integrated component of the host genome. [0052] In some embodiments, lentiviruses are the preferred members of the retrovirus family for use in the present invention. Lentivirus vectors are often pseudotyped with vesicular steatites virus glycoprotein (VSV-G), and have been derived from the human immunodeficiency virus (HIV), the etiologic agent of the human acquired immunodeficiency syndrome (AIDS); visan-maedi, which causes encephalitis (visna) or pneumonia in sheep; equine infectious anemia virus (EIAV), which causes autoimmune hemolytic anemia and encephalopathy in horses; feline immunodeficiency virus (FIV), which causes immune deficiency in cats; bovine immunodeficiency virus (BIV) which causes lymphadenopathy and lymphocytosis in cattle; and simian immunodeficiency virus (SIV), which causes immune deficiency and encephalopathy in non-human primates. Vectors that are based on HIV generally retain <5% of the parental genome, and <25% of the genome is incorporated into packaging constructs, which minimizes the possibility of the generation of reverting replication-competent HIV. Biosafety has been further increased by the development of self- inactivating vectors that contain deletions of the regulatory elements in the downstream long- terminal-repeat sequence, eliminating transcription of the packaging signal that is required for vector mobilization. The main advantage to the use of lentiviral vectors is that gene transfer is persistent in most tissues or cell types.

[0053] Adenoviruses (Ads) are a relatively well characterized homogenous group of viruses, including over 50 serotypes. See, e.g., International PCT Application No. WO 95/27071. Adenoviruses are medium-sized (90-100 nm), nonenveloped (without an outer lipid bilayer) icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome. There are 57 described serotypes in humans, which are responsible for 5-10% of upper respiratory infections in children, and many infections in adults as well. They are classified as group I under the Baltimore classification scheme, meaning their genomes consist of double- stranded DNA, and are the largest nonenveloped viruses. Because of their large size, they are able to be transported through the endosome (i.e., envelope fusion is not necessary). The virion also has a unique "spike" or fiber associated with each penton base of the capsid that aids in attachment to the host cell via the coxsackie-adenovirus receptor on the surface of the host cell.

[0054] The adenovirus genome is linear, non-segmented double- stranded (ds) DNA that is between 26 and 45 kb, allowing the virus to theoretically carry 22 to 40 genes. Although this is significantly larger than other viruses in its Baltimore group, it is still a very simple virus and is heavily reliant on the host cell for survival and replication. Once the virus has successfully gained entry into the host cell, the endosome acidifies, which alters virus topology by causing capsid components to disassociate. With the help of cellular microtubules, the virus is transported to the nuclear pore complex, where the adenovirus particle disassembles. Viral DNA is subsequently released, which can enter the nucleus via the nuclear pore. After this the DNA associates with histone molecules. Thus, viral gene expression can occur and new virus particles can be generated.

[0055] Unlike lentiviruses, adenoviral DNA does not integrate into the genome and is not replicated during cell division. The primary applications for adenovirus are in gene therapy and vaccination. Recombinant adenovirus-derived vectors, particularly those that reduce the potential for recombination and generation of wild- type virus, have also been constructed. See, International PCT Application Nos. WO 95/00655 and WO 95/11984.

[0056] Other viral or non-viral systems known to those skilled in the art also may be used to deliver IL-10 expression constructs of the present invention to the joint, including but not limited to gene-deleted adenovirus-transposon vectors that stably maintain virus-encoded transgenes in vivo through integration into host cells (see Yant, et al., Nature Biotech. 20:999-1004 (2002)); systems derived from Sindbis virus or Semliki forest virus (see Perri, et al., J. Virol. 74(20):9802-07 (2002)); systems derived from Newcastle disease virus or Sendai virus; or mini-circle DNA vectors devoid of bacterial DNA sequences (see Chen, et al., Molecular Therapy. 8(3):495-500 (2003)). Mini-circle DNA as described in U.S. Patent Publication No. 2004/0214329 discloses vectors that provide for persistently high levels of nucleic acid transcription.

[0057] Alternatively in some embodiments it may be optimal to select promoters that allow for inducible expression of the polynucleotide agents of the present invention. A number of systems for inducible expression are known in the art, including but not limited to the tetracycline responsive system and the lac operator-repressor system (see PCT publication WO 03/022052A1; and U.S. Patent Application Publication No. 2002/0162126A1), the ecdysone regulated system, or promoters regulated by glucocorticoids, progestins, estrogen, RU-486, steroids, thyroid hormones, cyclic AMP, cytokines, the calciferol family of regulators, or the metallothionein promoter (regulated by inorganic metals).

TPP1 and TERT Antibodies [0058] TPP1 and TERT inhibitors of the invention include other biologies, such as TPP1 or TERT antibodies that act to prevent the recruitment of telomerase without disrupting the action of shelterin. Generally, TPP1 or TERT antibodies may be made according to any method known in the art. For example, monoclonal antibodies may be made using the hybridoma method first described by Kohler et al., Nature 256:495 (1975), or may be made by recombinant DNA methods (see, e.g., U.S. Pat. No. 4,816,567). In the hybridoma method, a mouse or other appropriate host animal, such as a hamster or macaque monkey, is immunized to elicit lymphocytes that produce or are capable of producing antibodies that specifically bind to the protein used for immunization. Alternatively, lymphocytes may be immunized in vitro. Lymphocytes then are fused with myeloma cells using a suitable fusing agent, such as polyethylene glycol, to form a hybridoma cell (Goding, Monoclonal Antibodies: Principles and Practice, pp. 59-103, Academic Press (1986)). The hybridoma cells are then seeded and grown in a suitable culture medium that may contain one or more substances that inhibit the growth or survival of the unfused, parental myeloma cells. For example, if the parental myeloma cells lack the enzyme hypoxanthine guanine phosphoribosyl transferase (HGPRT or HPRT), the culture medium for the hybridomas typically will include hypoxanthine, aminopterin, and thymidine (HAT medium), which substances prevent the growth of HGPRT-deficient cells.

[0059] Exemplary myeloma cells are those that fuse efficiently, support stable high-level production of antibody by the selected antibody-producing cells, and are sensitive to a medium such as HAT medium. Among these, particular myeloma cell lines that may be considered for use are murine myeloma lines, such as those derived from MOPC-21 and MPC-11 mouse tumors available from the Salk Institute Cell Distribution Center, San Diego, Calif., and SP-2 or X63-Ag8-653 cells available from the American Type Culture Collection, Manassas, VA. Human myeloma and mouse-human heteromyeloma cell lines also have been described for the production of human monoclonal antibodies (Kozbor, J. Immunol. 133:3001 (1984)). Culture medium in which hybridoma cells are growing is assayed for production of monoclonal antibodies directed against the antigen (e.g., TPP1). The binding specificity of monoclonal antibodies produced by hybridoma cells can be determined by immunoprecipitation or by an in vitro binding assay, such as radioimmunoassay (RIA) or enzyme-linked immunoabsorbent assay (ELISA). [0060] After hybridoma cells are identified that produce antibodies of the desired specificity, affinity, and/or activity, clones may be subcloned by limiting dilution procedures and grown by standard methods (Goding, Monoclonal Antibodies: Principles and Practice, pp. 59-103, Academic Press (1986)). Suitable culture media for this purpose include, for example, D-MEM or RPMI-1640 medium. In addition, the hybridoma cells may be grown in vivo as ascites tumors in an animal. The monoclonal antibodies secreted by the subclones are suitably separated from the culture medium, ascites fluid, or serum by conventional immunoglobulin purification procedures such as, for example, protein A-Sepharose, hydroxylapatite chromatography, gel electrophoresis, dialysis, or affinity chromatography.

[0061] DNA encoding the monoclonal antibodies may be readily isolated and sequenced using conventional procedures (e.g., by using oligonucleotide probes that are capable of binding specifically to genes encoding the heavy and light chains of the monoclonal antibodies). The hybridoma cells serve as a source of such DNA. For recombinant production of an antibody, a nucleic acid encoding the antibody is isolated and inserted into a replicable vector for further cloning or for expression. Many vectors are available for this purpose. The vector components generally include, but are not limited to, one or more of the following: a signal sequence, an origin of replication, one or more marker genes, an enhancer element, a promoter, and a transcription termination sequence (e.g., as described in U.S. Pat. No. 5,534,615, which is specifically incorporated herein by reference).

[0062] Once isolated, the DNA may be placed into expression vectors, which are then transfected into host cells such as E. coli cells, simian COS cells, Chinese hamster ovary (CHO) cells, or myeloma cells that do not otherwise produce immunoglobulin protein, to obtain the synthesis of monoclonal antibodies in the recombinant host cells.

Pharmaceutical Formulation, Dosage and Administration of the TPPl or TERT Inhibitors

[0063] The present invention provides compounds and methods for inhibiting the telomerase recruitment activity of TPPl to prevent cell proliferation without disrupting TPPl's role as a member of the shelterin complex, as well as compounds and methods for rendering TERT incapable of being recruited by TPPl. As described, TPPl or TERT inhibitors contemplated for use in the methods of the invention include but are not limited to biologies, such as antibodies against TPPl or the TEN or CTE domains of TERT, and small molecules. [0064] In one regime, the TPPl or TERT inhibitor is administered orally using a capsule dosage form composition, where the capsule contains the TPPl or TERT inhibitor without an additional carrier, excipient or vehicle. In another formulation, pharmaceutical compositions comprise an effective amount of the TPPl or TERT inhibitor and a pharmaceutically acceptable carrier or vehicle, where the pharmaceutically acceptable carrier or vehicle can comprise one or more excipients, or a mixture thereof. In one embodiment, the composition is a pharmaceutical composition. The TPPl or TERT inhibitors can be administered to a patient orally or parenterally in a conventional form of preparation, such as capsules, microcapsules, tablets, granules, powder, troches, pills, suppositories, injections, suspensions and syrups. Suitable formulations can be prepared by methods commonly employed using conventional, organic or inorganic additives, such as an excipient selected from binders, disintegrants, fillers or diluents, lubricants, preservatives, stabilizers, flavoring agents, antioxidants, suspending agents, dispersing agents, surfactants, or solubilizers.

[0065] Excipients that may be selected are known to those skilled in the art and include, but are not limited to fillers or diluents (e.g., sorbitol, sucrose, starch, mannitol, lactose, glucose, talc, cellulose, calcium phosphate or calcium carbonate and the like), disintegrants (e.g., sodium starch glycolate, croscarmellose sodium and the like), lubricants (e.g. , light anhydrous silicic acid, magnesium stearate, talc or sodium lauryl sulfate and the like), binders (e.g., cellulose, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, polyvinylpyrrolidone, polypropylpyrrolidone, gum arabic, gelatin, polyethyleneglycol or starch and the like), flavoring agents (e.g., citric acid, or menthol and the like), stabilizers (e.g., citric acid, acetic acid or sodium citrate and the like), preservatives (e.g., sodium benzoate, sodium bisulfite, methylparaben or propylparaben and the like), suspending agents (e.g., methylcellulose, polyvinyl pyrrolidone or aluminum stearate and the like), dispersing agents (e.g., hydroxypropylmethylcellulose and the like), surfactants (e.g., sodium lauryl sulfate, polaxamer, polysorbates and the like), antioxidants (e.g., ethylene diamine tetraacetic acid (EDTA), butylated hydroxyl toluene (BHT) and the like) and solubilizers (e.g., SOLUTOL®, GELUCIRE®, polyethylene glycols and the like). The effective amount the TPPl or TERT inhibitor in the pharmaceutical composition should be at a level that will result in the desired effect.

[0066] In certain formulations, the TPPl or TERT inhibitor is purified. In specific formulations, the TPPl inhibitor is at least 75% pure, at least 80% pure, at least 85% pure, at least 90% pure, at least 95% pure, at least 96% pure, at least 97% pure, at least 98% pure, at least 99% pure, at least 99.5% pure, at least 99.9% pure, or at least 100% pure.

[0067] In accordance with the methods for treating a proliferative condition provided by the invention, the TPPl or TERT inhibitor can be administered to a subject in need thereof by a variety of routes in amounts that result in a beneficial or therapeutic effect. The TPPl or TERT inhibitor may be orally administered to a subject. Oral administration of the TPPl or TERT inhibitor may facilitate patient compliance with taking the TPPl or TERT inhibitor. Other routes of administration include, but are not limited to, intravenous, intradermal, intramuscular, subcutaneous, intranasal, inhalation, transdermal, topical, transmucosal, intracranial, intrathecal, intraocular, intraurethral, epidural and intra- synovial administration. In one embodiment, the TPPl or TERT inhibitor is administered systemically (e.g., parenterally) to a subject in need thereof. In another regime, the TPPl or TERT inhibitor is administered locally, such as directly to a tumor. In one preferred regime, the TPPl or TERT inhibitor or pharmaceutical composition thereof is administered via a route that permits the TPPl or TERT inhibitor to cross the blood-brain barrier (e.g., orally).

[0068] In other aspects of the invention, the methods for treating a subject suffering from cancer or other proliferative disease involve administration of a TPPl or TERT inhibitor in combination with another therapy (e.g., one or more additional therapies that do not comprise a TPPl inhibitor). In some aspects, both TPPl and TERT inhibitors are used in the treatment. Such methods may involve administering the TPPl or TERT inhibitor prior to, concurrent with, or subsequent to administration of the additional therapy. In such aspects, the methods have an additive or synergistic effect. In accordance with the methods for treating cancer or other proliferative disease that involve administration of the TPPl or TERT inhibitor in combination with one or more additional therapies, the TPPl or TERT inhibitor and one or more additional therapies may be administered by the same route or a different route of administration.

[0069] Administration of the TPPl or TERT inhibitor uses a dosage and dosing regime that is efficacious while minimizing side effects in the subject. The exact dosage and frequency of administration of the TPPl or TERT inhibitor can be determined by a practitioner, in light of factors related to the patient who requires treatment. Factors which may be taken into account include the severity of the disease state, general health of the patient, age, and weight of the patient, diet, time and frequency of administration, combination(s) with other therapeutic agents or drugs, reaction sensitivities, and tolerance/response to therapy. The dosage and frequency of administration of the TPPl or TERT inhibitor may be adjusted over time to provide sufficient levels of the TPPl or TERT inhibitor or to maintain the desired effect.

[0070] In certain regimes, the TPPl or TERT inhibitor is administered once a day, twice a day, three times a day, or four times a day. In some regimes, the TPPl or TERT inhibitor is administered to a subject once, twice, three times, or four times every other day (i.e., on alternate days); once, twice, three times, or four times every two days; once, twice, three times, or four times every three days; and so on. In some regimes, the TPPl or TERT inhibitor is administered to a subject once, twice, three times, or four times every week, once, twice, three times, or four times every two weeks; once, twice, three times, or four times every three weeks; and so on. In particular regimes, the TPPl or TERT inhibitor is administered to a subject in cycles, where the TPPl or TERT inhibitor is administered for a period of time, followed by a period of rest (i.e., the TPPl inhibitor or pharmaceutical composition is not administered for a period of time), e.g., 1 week cycles, 2 week cycles, 3 week cycles, 4 week cycles, 5 week cycles, and so on. In such cycles, the TPPl inhibitor may be administered once, twice, three times, or four times daily. In particular dosing regimes, the method for treating cancer or other proliferative disease involves the administration of the TPPl inhibitor twice daily in 4 week cycles.

[0071] In certain dosing regimes, the method for treating a proliferative disorder involves the administration of a unit dose of the TPPl or TERT inhibitor that ranges from about 0.1 milligram (mg) to about 2500 mg, from about 1 mg to about 2500 mg, from about 5 mg to about 2500 mg, from about 10 mg to about 2500 mg, from about 100 mg to about 2500 mg, from about 150 mg to about 2500 mg, from about 250 mg to about 2500 mg, from about 300 mg to about 2500 mg, or from about 500 mg to about 2500 mg, or any range in between.

[0072] In some regimes, the method for treating cancer or other proliferative condition involves administration of the TPPl or TERT inhibitor that is expressed as mg per meter

2 2

squared (mg/m ). The mg/m for the specific TPPl or TERT inhibitor may be determined, for example, by multiplying a conversion factor for an animal by an animal dose in mg per kilogram (mg/kg) to obtain the dose in mg/m for human dose equivalent. For regulatory submissions the FDA may recommend the following conversion factors: Mouse=3, Hamster=4.1, Rat=6, Guinea Pig=7.7. The height and weight of a human may be used to calculate a human body surface area applying Boyd's Formula of Body Surface Area. In specific regimes, the methods for treating a proliferative disorder involves administration of an amount of the TPP1 or TERT inhibitor in the range of from about 0.1 mg/m to about

2500 mg/m , or any range in between.

[0073] Other non-limiting exemplary doses of the TPP1 or TERT inhibitor that may be used in the methods for treating cancer or other proliferative diseases include mg amounts per kg of subject or sample weight. In certain regimes, a method for treating a proliferative disorder involves the administration of a dosage of the TPP1 or TERT inhibitor that ranges from about 0.001 mg/kg to about 10 mg/kg, from about 0.01 mg/kg to about 10 mg/kg, from about 0.1 mg/kg to about 10 mg/kg, from about 1 mg/kg to about 10 mg/kg, from about 10 mg/kg to about 1000 mg/kg, from about 100 mg to about 1000 mg/kg, from about 150 mg/kg to about 1000 mg/kg, from about 250 mg/kg to about 1000 mg/kg, or from about 300 mg/kg to about 1000 mg/kg. In some regimes, the method for treating cancer or other proliferative conditions involves administration of a dosage of the TPP1 or TERT inhibitor that ranges from about 0.001 mg/kg to about 100 mg/kg, from about 0.001 mg/kg to about 50 mg/kg, from about 0.001 mg/kg to about 25 mg/kg, from about 0.001 mg/kg to about 7 mg/kg, from about 0.001 mg/kg to about 5 mg/kg; from about 0.001 mg/kg to about 1 mg/kg; or from about 0.001 mg/kg to about 0.01 mg/kg. In accordance with these regimes, the dosage may be administered once, twice or three times per day, every other day, or once or twice per week and the dosage may be administered orally.

[0074] In specific regimes, the methods for treating cancer or other proliferative diseases involve subcutaneous administration of a dosage of the TPP1 or TERT inhibitor of about 100 mg/kg to about 200 mg/kg, about 100 mg/kg to about 300 mg/kg, about 100 mg/kg to about 400 mg/kg, about 100 mg/kg to about 500 mg/kg, about 100 mg/kg to about 600 mg/kg once per day. In a specific regime, 50 mg/kg of the TPP1 inhibitor is administered once per day, subcutaneously.

[0075] In specific aspects, the method for treating a proliferative disorder involves administration of the TPP1 inhibitor at a dosage that achieves a target plasma concentration of the TPP1 or TERT inhibitor. The length of time that a subject is administered the TPP1 or TERT inhibitor will be the time period that is determined to be efficacious. In certain regimes, the method for treating the proliferative disorder involves the administration of the TPPl inhibitor until the severity and/or number of symptoms associated with the proliferative disorder decreases.

[0076] In some regimes, the method for treating cancer or other proliferative disease involves administration of the TPPl or TERT inhibitor for up to 48 weeks. In other dosing regimes, the method for treating cancer or other proliferative disease involves the administration of the TPPl inhibitor for up to 4 weeks, 8 weeks, 12 weeks, 16 week, 20 weeks, 24 weeks, 26 weeks, 1 year, 1.5 years, 2 years or more.

[0077] In certain formulations, the TPPl inhibitor is administered in a crystalline form that solubilizes in the gut of the patient and subsequently enters the bloodstream after solubilization in the gut. In one aspect of these embodiments, the crystalline form of the TPPl inhibitor is insoluble at neutral pH but soluble in acidic pH.

[0078] In other formulations, a slow-release formulation of the TPPl or TERT inhibitor is provided. In accordance with such formulations, the TPPl or TERT inhibitor is provided in a crystalline form that slowly solubilizes, thus slowly releasing the TPPl inhibitor. Slow- releasing formulations of the TPPl or TERT inhibitor allow for reduced administration of the TPPl or TERT inhibitor while retaining therapeutically effective doses of plasma and/or brain concentrations of the TPPl inhibitor.

Applicable Disease States

[0079] In general, the methods of the invention are useful for cancer or other proliferative disease or condition. Cancer, known medically as a malignant neoplasm, is a broad group of various diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. Cancer may also spread to more distant parts of the body through the lymphatic system or bloodstream. Not all tumors are cancerous, for example, benign tumors do not grow uncontrollably, do not invade neighboring tissues, and do not spread throughout the body. There are over 200 different known cancers that afflict humans.

[0080] Cancer can be detected in a number of ways, including the presence of certain signs and symptoms, screening tests, or medical imaging. Once a possible cancer is detected it is diagnosed by microscopic examination of a tissue sample. Cancer is usually treated with chemotherapy, radiation therapy and/or surgery. To date, treatments involving regulation of telomerase activity have not been approved for use. The chances of surviving the disease vary greatly by the type and location of the cancer and the extent of disease at the start of treatment. While cancer can affect people of all ages— and a few types of cancer are more common in children— the risk of developing cancer generally increases with age. In 2007, cancer caused about 13% of all human deaths worldwide (7.9 million). Rates are rising as more people live to an old age and as mass lifestyle changes occur in the developing world.

[0081] Cancers are primarily an environmental disease with 90-95% of cases attributed to environmental factors and 5-10% due to genetics. Environmental, as used by cancer researchers, means any cause that is not inherited genetically. Common environmental factors that contribute to cancer death include tobacco (25-30%), diet and obesity (30-35%), infections (15-20%), radiation (both ionizing and non-ionizing, up to 10%), stress, lack of physical activity, and environmental pollutants.

[0082] When cancer begins it invariably produces no symptoms with signs and symptoms only appearing as the mass continues to grow or ulcerates. The findings that result depend on the type and location of the cancer. Few symptoms are specific, with many of them frequently occurring in individuals who have other conditions. It is not uncommon for people diagnosed with cancer to have been treated for other diseases to which it was assumed their symptoms were due.

[0083] Local symptoms may occur due to the mass of the tumor or its ulceration. For example mass effects from lung cancer can cause blockage of the bronchus resulting in cough or pneumonia, esophageal cancer can cause narrowing of the esophagus making it difficult or painful to swallow, and colorectal cancer may lead to narrowing or blockages in the bowel resulting in changes in bowel habits. Masses of breast or testicles may be easily felt. Ulceration can cause bleeding which, if it occurs in the lung, will lead to coughing up blood, in the bowels to anemia or rectal bleeding, in the bladder to blood in the urine, and in the uterus to vaginal bleeding. Although localized pain may occur in advanced cancer, the initial swelling is usually painless. Some cancers can cause build up of fluid within the chest or abdomen.

[0084] General symptoms occur due to distant effects of the cancer that are not related to direct or metastatic spread. These may include: unintentional weight loss, fever, being excessively tired, and changes to the skin. Hodgkin disease, leukemias, and cancers of the liver or kidney can cause a persistent fever of unknown origin. Specific constellations of systemic symptoms, termed paraneoplastic phenomena, may occur with some cancers. [0085] Symptoms of metastasis are due to the spread of cancer to other locations in the body. They can include enlarged lymph nodes (which can be felt or sometimes seen under the skin and are typically hard), hepatomegaly (enlarged liver) or splenomegaly (enlarged spleen) which can be felt in the abdomen, pain or fracture of affected bones, and neurological symptoms. Cancers that may be treated by the compounds and methods of the invention include but are not limited to cancers of the brain, head and neck, esophagus, stomach, breast, colon and digestive tract, liver, testis, ovary skin, kidney, bladder, bone, connective tissue and pancreas.

Screening Assays

[0086] Also provided by the subject invention are screening methods and assays for identifying compounds that are capable of acting as a TPPl or TERT inhibitor. The conditions may be set up in vitro, e.g., in a cell that conditionally expresses the coding sequence for TPPl or TERT, or in vivo, in an animal model that conditionally expresses the coding sequence of TPPl or TERT, as further described below. The screening methods may be an in vitro or in vivo format, where both formats are readily developed by those of skill in the art.

[0087] Whether the format is in vivo or in vitro, the target cell is first activated by conditionally increasing transcription of a coding sequence for TPPl or TERT, then the candidate agent is administered to the target cell, and the effect of the candidate agent on the target cell is observed. In such embodiments, the cell is activated by introducing into the target cell an agent that conditionally modulates (i.e., increases or decreases) transcription of an endogenous coding sequence for TPPl or TERT by decreasing inhibition of transcription of the coding sequence, as described above.

[0088] In some embodiments, the cell is activated by introducing into the target cell a nucleic acid expression system, e.g., a plasmid, that includes a coding sequence for TPPl or TERT operably linked to conditional promoter system, as described above. As summarized above, following introduction of the nucleic acid expression system, the transcription of TPPl or TERT is conditionally increased by administering to the target cell an active regulatory agent. Once TPPl or TERT transcription is conditionally increased, a candidate agent is administered to the cell and the effect of the administration of the candidate agent is observed on the target cells, as compared to control cells that were not administered the candidate agent. For example, monitoring telomere length in the experimental and control groups.

[0089] A variety of different candidate agents may be screened by the above methods.

Candidate agents encompass numerous chemical classes, though typically they are organic molecules, preferably small organic compounds having a molecular weight of more than 50 and less than about 2,500 daltons. Candidate agents comprise functional groups necessary for structural interaction with proteins, particularly hydrogen bonding, and typically include at least an amine, carbonyl, hydroxyl or carboxyl group, preferably at least two of the functional chemical groups. The candidate agents often comprise cyclical carbon or heterocyclic structures and/or aromatic or polyaromatic structures substituted with one or more of the above functional groups. Candidate agents are also found among biomolecules including peptides, saccharides, fatty acids, steroids, purines, pyrimidines, derivatives, structural analogs or combinations thereof.

[0090] Candidate agents are obtained from a wide variety of sources including libraries of synthetic or natural compounds. For example, numerous means are available for random and directed synthesis of a wide variety of organic compounds and biomolecules, including expression of randomized oligonucleotides and oligopeptides. Alternatively, libraries of natural compounds in the form of bacterial, fungal, plant and animal extracts are available or readily produced. Additionally, natural or synthetically produced libraries and compounds are readily modified through conventional chemical, physical and biochemical means, and may be used to produce combinatorial libraries. Known pharmacological agents may be subjected to directed or random chemical modifications, such as acylation, alkylation, esterification, amidification, etc. to produce structural analogs. Agents identified in the above screening assays that inhibit recruitment of telomerase by TPP1 find use in the methods described above, e.g., blocking the action of telomerase.

Animal Models

[0091] Also provided by the subject invention are animal models for use in the subject screening methods described above. Such animal models for use in the subject screening methods are capable of activation of target cells by the conditional transcription of a coding sequence for TPP1 or for one or both of the TEN or CTE domains of TERT. [0092] In some embodiments, the conditional transcription animal model is capable of conditional transcription of a transgene, which transgene includes the coding sequence of TPPl or for one or both of the TEN or CTE domains of TERT. In further embodiments the conditional animal models of the present invention include a nucleic acid expression system, e.g., a plasmid, providing for the conditional transcription of TPPl or for one or both of the TEN or CTE domains of TERT, where the nucleic acid vector includes the coding sequence for TPPl operably linked to a conditional promoter system, as described above. An example of a conditional promoter system suitable for use with the subject conditional transcription animal models is the tetracycline inducible promoter system, such as the Tet-On and Tet-off tetracycline regulated systems, where the active regulatory agent is tetracycline, doxicycline, or an analog thereof.

[0093] In other embodiments, the conditional transcription animal model is capable of conditional transcription of an endogenous coding sequence for TPPl or for one or both of the TEN or CTE domains of TERT. As further described above, the subject conditional transcription animal model can be achieved by introducing into the target cell of a subject animal an agent that conditionally increases transcription of an endogenous coding sequence for one of TPPl . Examples of animals suitable for use include nonhuman animals such as apes, monkeys, pigs and rodents, such a rats, mice, and guinea pigs.

EXAMPLES

[0094] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present invention, and are not intended to limit the scope of what the inventors regard as their invention, nor are they intended to represent or imply that the experiments below are all of or the only experiments performed. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

[0095] Efforts have been made to ensure accuracy with respect to numbers used (e.g., amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. [0096] Recruitment of large protein complexes to their sites of action on chromatin is a critical rate-limiting step for many biological processes, such as the formation of kinetochores at centromeres and the origin-of-replication complexes on DNA. Similarly, telomerase must be recruited to telomeric chromatin to synthesize telomere repeats, although this process has been difficult to dissect in human cells. An obligatory interaction between the telomerase RNP and the OB-fold domain of the shelterin component TPPl that recruits telomerase from a Cajal body reservoir to telomeric chromatin was identified, leading to the present invention. Blocking the telomerase-TPPl OB-fold interaction inhibited telomerase recruitment to telomeres and abrogated telomere synthesis by telomerase in vivo.

[0097] A stepwise mechanism for recruitment of the telomerase RNP to telomeres was demonstrated. In the first step, telomerase localizes to Cajal bodies by virtue of the interaction between the TERC CAB-box sequence and the Cajal body-enriched telomerase holoenzyme component, TCAB1. The importance of the Cajal body is suggested by observations showing that mislocalization of telomerase to the nucleolus— either by TCAB1 depletion or by TERC CAB-box mutations— inhibits telomerase recruitment and telomere synthesis by telomerase (Cristofari et al., 2007; Venteicher et al., 2009; Zhong et al., 2011). Enhanced loading of telomerase on telomeres in super-telomerase cells leads to formation of neo-Cajal bodies at telomeres, and furthermore, depletion of the Cajal body protein coilin can reduce telomerase foci at telomeres (Stern et al., 2012). Together, these findings establish the Cajal body as an important reservoir for telomerase, but it remains uncertain precisely what function is served by Cajal bodies and whether the bodies themselves are required for telomere synthesis by telomerase.

[0098] In the second step, telomerase RNP is recruited to telomeres via an obligatory 'docking' step, whereby the TERT TEN and CTE domains interact with the OB-fold domain of TPPl. The importance of this interaction is supported by a number of observations. First, removal of TPPl from telomeres by using short interfering RNAs against TPPl or TIN2 abrogated the ability of overexpressed telomerase to localize to telomeres and led to strong accumulation in Cajal bodies (Abreu et al., 2010). Second, tethered TPP1-OB fold alone was able to recruit telomerase to a heterologous non-telomeric locus. Third, the expression of TPPl -OB fold competitively sequestered overexpressed telomerase away from telomeres into Cajal bodies. Furthermore, the TPP1-OB domain itself was captured by telomerase in this context, localizing in Cajal bodies. Fourth, mutations in TPPl OB-fold, such as OB-RR, or TERT mutations in the TEN and CTE domain abrogated this interaction and inhibited telomerase recruitment, again arresting telomerase in its pre-recruitment, Cajal body- localized state.

[0099] In the third step, telomerase engages with telomeric DNA substrates and processively synthesizes telomeric repeats. Previously, the TPPl-POTl heterodimer has been shown to aid telomerase catalysis by enhancing its processivity on oligonucleotide substrates in vitro. A single amino acid mutation in TERT(GIOOV) abrogated the processivity enhancement by TPPl-POTl (Zaug et al., 2010). The same mutation was found to severely impair TERT-TPP1 OB interaction and telomerase recruitment. Based on these observations, it was postulated that the processive elongation of telomeric DNA and telomerase recruitment rely on the same TERT TEN-CTE: TPP1-OB interaction, which persists after the docking step and throughout the entire duration of telomerase catalysis. In other words, TERT TEN- CTE: TPP1 OB interaction not only recruits telomerase to telomeres, but also allows telomerase to be tethered to the shelterin bound telomeric DNA substrate, preventing premature release of the telomere substrate and/or aiding telomerase translocation on telomeric tracts (Latrick and Cech, 2010). The residues identified in the TPP1 OB-fold - D166, E168 and K170 - contribute to the actual interface at which TPP1 and telomerase interact. These residues in the L34 loop are solvent-exposed and form a ridge along a groove running across the TPP1 OB-fold structure. The development of small molecules or biologies such as peptides and antibodies targeting this region of the OB-fold could act as telomerase inhibitors to block telomere synthesis, in an analogous fashion to the effects of overexpressed OB-fold which is described herein. Alternatively, TPP1 peptides can be delivered to or expressed in a cell to compete out and sequester telomerase so that it is not delivered to TPP1 that is in a shelterin complex associated with a telomere.

[00100] The shelterin complex has consistently been found to inhibit telomerase in its ability to lengthen telomeres. This role of the shelterin complex was supported by both loss-of- function and gain-of-function genetic experiments, which demonstrated that telomeres lengthen upon shRNA-mediated depletion of the shelterin components TIN2, POTl and TPP1 (Loayza and De Lange, 2003; Houghtaling et al., 2004; Liu et al., 2004; Ye and de Lange, 2004; Ye et al., 2004), or by overexpression of TRF1 and TRF2 (Smogorzewska et al., 2000). However, it has been challenging to study the function of a single shelterin protein using these approaches due to the interdependence among these proteins at telomeres (Rai et al., 2011; Takai et al., 2011). Furthermore, disrupting the stoichiometry of the shelterin complex causes a DNA damage response at telomeres, which could affect telomerase recruitment. By using a minimal TPPl -OB fold domain to recruit TERT to a heterologous chromatin locus and by specifically interfering with telomerase-shelterin interaction through expression of the isolated OB-fold domain, the capping function of TPPl was separated from its interaction with telomerase.

[00101] The results obtained and described herein are consistent with a model in which the TPPl -POTl module serves a dual function at telomeres, restricting telomerase access to the chromosome terminus through POTl in order to prevent unscheduled telomere elongation, while recruiting telomerase to telomeres via the TPPl -OB fold. POTl binds single stranded telomeric DNA with high affinity and is a potent inhibitor of telomere extension both in vivo and in vitro (Loayza and De Lange, 2003; Lei et al., 2004; Kelleher et al., 2005). Once telomerase has been recruited to telomeres it may compete with POTl for the terminal single- stranded overhang for productive elongation. Telomere lengthening upon the depletion of TIN2 or TPPl may occur because of concomitant decrease in POTl occupancy at telomeres, favoring telomerase-telomere binding following recruitment by residual TPPl. Alternatively, additional contacts between telomerase and shelterin components could facilitate recruitment in the context of depletion of TIN2 or TPPl.

[00102] Germline mutations in telomerase or in ΤΓΝ2 result in very short telomeres, which in turn precipitate several disease states including dyskeratosis congenita, aplastic anemia, cancer, liver fibrosis and pulmonary fibrosis (Calado and Young, 2009). Certain telomerase mutations can cause disease without an apparent change in telomerase enzymatic activity. Mutations in TCAB1 cause dyskeratosis congenita by disrupting telomerase trafficking to the Cajal body, while leaving telomerase enzymatic activity intact (Batista et al., 2011; Zhong et al., 2011). The results obtained with the TERT mutations V144M and E1116fsX from IPF patients reveal that disease mutations can arrest telomerase trafficking in Cajal bodies, rendering telomerase unable to be recruited to telomeres. These findings expand the understanding of the contribution of telomerase trafficking defects in disease: TCAB1 mutations can force mislocalization of telomerase to nucleoli, whereas certain TERT mutations can prevent recruitment and trap telomerase in Cajal bodies. Telomerase activation confers replicative immortalization to primary human cells and is a hallmark of cancer (Hanahan and Weinberg, 2011). Thus,t telomerase-TPPl OB interaction is rate limiting for telomere length maintenance in human cancer cells.

EXAMPLE 1: Neo-Cajal Bodies Form at Telomeres in Supertelomerase Cells

[00103] To investigate telomerase recruitment, a modified "super telomerase" assay was employed that uses transient, plasmid-based expression to overcome inherent limitations in expressing TERC from a retrovirus. Elevated expression of TERC together with HA-tagged TERT resulted in uniform colocalization of telomerase with telomeres by RNA FISH and by immunostaining with an anti-HA antibody, respectively. In the absence of co-expressed TERC, HA-TERT was detected by immunofluorescence in a nucleoplasmic pattern. When transfected alone in cells lacking overexpressed TERT, transient TERC was found in Cajal bodies and rarely colocalized with telomeres. To investigate whether other telomerase holoenzyme components were also found at telomeres, immunofluorescence for dyskerin and TCABl was performed. Dyskerin and TCABl efficiently colocalized with telomeres in S-T cells, but showed minimal overlap with telomeres in cells expressing HA-TERT alone, where they accumulated in their typical nuclear compartments, nucleoli and Cajal bodies, respectively. Taken together, these results indicate that telomerase foci at telomeres in supertelomerase (S-T) cells contain the entire holoenzyme.

[00104] The striking localization of telomerase holoenzyme components to telomeric foci in S-T cells suggested the possibility that Cajal bodies were forming de novo at telomeres. To test this idea, staining was performed for telomeric DNA and for coilin, a classical marker of Cajal bodies. Remarkably, colocalization of coilin was found at most telomeres in S-T cells, whereas in control cells coilin was detected in classical Cajal bodies that typically did not co- localize with telomeres. The number of total Cajal bodies in S-T cells (17.5+5.5 per nucleus, n=75) far exceeded that of cells expressing HA-TERT alone (3.0+1.5 per nucleus, n=150, p<0.001 by Fisher's Exact Test), suggesting that telomerase overexpression results in 'neo- Cajal bodies' at telomeres and that these new foci may contain other Cajal body components. To test this hypothesis, S-T cells were stained for other well-characterized Cajal body components, including the scaRNA U85, fibrillarin and SMN, which do not participate in telomerase function. In control cells expressing HA-TERT alone, scaRNA U85 was detected exclusively in 3-5 strong nuclear foci by RNA FISH, consistent with its Cajal body localization; fibrillarin was found in both Cajal bodies and the nucleolus consistent with its role in modification of splicing RNAs and rRNAs and SMN protein was detected primarily in 3-10 foci per nucleus consistent with its localization in both nuclear gems and Cajal bodies). In contrast, scaRNA U85, fibrillarin and SMN were each readily detected at telomeres in S-T cells, indicating that the foci at telomeres in S-T cells resemble bona fide Cajal bodies and that overexpression of telomerase forms neo-Cajal bodies at telomeres.

EXAMPLE 2: Depletion of TIN2 or TPPl stalls telomerase recruitment in conventional Cajal bodies

[00105] To understand the requirements for formation of telomerase foci at telomeres, proteins implicated in telomerase recruitment to telomeres were depleted with siRNAs. Dyskerin depletion led to a loss of TERC and eliminated TERT foci at telomeres in S-T cells consistent with a requirement for TERC in telomerase recruitment to telomeres. Depletion of TCAB1 efficiently diminished the number of telomerase foci at telomeres and caused HA- TERT to mislocalize to nucleoli. Some HA-TERT foci persisted at telomeres in siTCABl- treated cells (17.6 + 0.8 in control siRNA treated vs 5.8 + 0.6 siTCABl treated cells, p<0.0001 by Fisher's exact test), likely due to incomplete depletion of the protein. These results indicate that TCAB1 is needed for efficient recruitment to telomeres, consistent with previous studies showing a requirement for TCAB1 in localization of endogenous TERC to telomeres (Venteicher et al., 2009; Stern et al., 2012). To determine whether Cajal bodies themselves are required for telomerase recruitment, cells were treated with coilin siRNA, which efficiently depleted coilin protein by Western blot and resulted in loss of coilin- positive Cajal bodies in both HeLa cells and S-T cells. Coilin depletion eliminated HA- TERT foci at telomeres in S-T cells, without affecting HA-TERT protein levels or telomerase activity. These data show that coilin, which serves as a scaffold for assembly of Cajal bodies, is required for formation of telomerase foci at telomeres in S-T cells.

[00106] To understand the determinants at telomeres that control formation of telomerase foci, RNA interference was used to deplete TIN2 or TPPl, each of which had been implicated in telomerase recruitment (Abreu et al., 2010). Treatment of S-T cells with siRNAs against TIN2 or TPPl efficiently depleted each protein, which compromised telomere end-protection, resulting in 53BP1 -positive DNA damage foci at telomeres (Takai et al., 2003). Loss of TIN2, but not TPPl, led to reduced TRF2 protein at telomeres, consistent with the role of TIN2 as a core shelterin component (de Lange, 2005; Takai et al., 2011). In agreement with previous work, depletion of either TIN2 or TPPl resulted in a loss of HA-TERT foci colocalizing with telomeres (Abreu et al., 2010). Interestingly, instead of colocalizing with telomeres, HA-TERT was detected in a small number of bright foci that also stained positive for coilin in cells treated with siRNA against either TIN2 or TPPl (2.5+0.2, 7.0+0.4 per nucleus for siTIN2 and siTPPl, respectively, vs. 22.4+0.8 in control treated cells). The number and morphology of these foci were indistinguishable from Cajal bodies in control HeLa cells, indicating that loss of TIN2 or TPPl arrests telomerase in Cajal bodies.

EXAMPLE 3: A tethered TPPl OB-fold domain recruits telomerase to a non-telomeric chromatin locus

[00107] Studying telomerase recruitment using loss-of-function approaches is limited by: (1) the interdependence of many shelterin components for optimal accumulation (Rai et al., 2011; Takai et al., 2011) and by (2) the fact that perturbing shelterin proteins induces a DNA damage response at telomeres, which could in turn affect recruitment of telomerase. To develop an assay that would facilitate testing potential interactions between telomerase and candidate interacting partners outside the context of both the shelterin complex and telomeric DNA, a tethering strategy was employed that allows the expression of a lacl fusion protein 'bait' to be visualized as a strong single nuclear focus at a multimerized lacO array stably integrated into a single genomic locus in U20S2-6-3 cells (Janicki et al., 2004). This approach was used to study potential interactions between telomerase and TPPl at a heterologous chromatin site and in isolation from the effects of DNA damage responses at uncapped telomeres. Whereas HA-lacI-mCherry localized only in a single lacO array focus in the nucleus, the HA-lacI-mCherry-TPPl fusion protein localized both to the lacO array and to telomeres, indicating that the TPPl fusion protein retains the ability to be incorporated into the shelterin complex at telomeres. In addition, telomere signals were readily detected within the HA-lacI-mCherry-TPPl focus at the lacO array using a telomere FISH probe, indicating that the immobilized TPPl fusion protein recruits telomeres to the lacO focus. In U20S2-6-3 cells cotransfected with the HA-lacI-mCherry tag, Flag-TERT and TERC, HA- lacI-mCherry remained in a single lacO array focus and did not interfere with the ability of telomerase to localize to telomeres. In contrast, in cells expressing HA-lacI-mCherry-TPPl, FLAG-TERT localization to telomeres was diminished, and instead, FLAG-TERT was detected together with HA-lacI-mCherry-TPPl in the lacO array focus. In this setting, HA- lacI-mCherry-lacI-TPPl acted as a sink to preferentially recruit telomerase to the lacO array, effectively competing for telomerase binding sites at telomeres.

[00108] To determine whether the OB-fold of TPPl, previously implicated in binding TERT, mediated recruitment of telomerase to the lacO array, a fusion protein lacking the OB-fold (HA-lacI-mCherry-ΤΡΡΙΔΟΒ) was constructed and a minimal fusion protein comprising only the OB-fold of TPPl (HA-lacI-mCherry-TPPlOB). HA-lacI-mCherry-ΤΡΡΙΔΟΒ localized to the lacO array and to telomeres, but was unable to recruit telomerase to the lacO array and could no longer compete telomerase away from telomeres. Conversely, HA-lacI- mCherry-TPPlOB, which localized only to the lacO array, effectively recruited FLAG-TERT to the lacO array and blocked telomerase binding to telomeres. Importantly, telomeres were not detected at the lacO focus in cells expressing HA-lacI-mCherry-TPPlOB, indicating that HA-lacI-mCherry-TPPlOB likely recruited telomerase in the absence of other shelterin components. Taken together, these results show that the OB-fold domain of TPPl, when isolated from telomeric DNA and other shelterin components, is necessary and sufficient to recruit telomerase to a heterologous chromatin locus.

EXAMPLE 4: Specific loop residues within the TPPl OB-fold mediate recruitment of telomerase to telomeres

[00109] To further understand the interaction between telomerase and the TPPl OB-fold domain, it was investigated whether overexpressed TPPl OB-fold could effectively compete with endogenous TPPl for telomerase binding. Because TPP1-OB lacks the ability to be incorporated into the shelterin complex at telomeres, it was reasoned that an isolated and un- tethered TPPl -OB would sequester telomerase away from telomeres in a dominant negative manner. To investigate this hypothesis, a 'competitive sequestration' assay was developed. Specifically, mCherry-tagged TPPl OB-fold was cotransfected along with GFP-TERT and TERC in HeLa cells. Similar to super- telomerase cells described above, GFP-TERT localized to telomeres in the presence of TERC. In contrast to the mCherry vector, expression of mCherry-TPPl OB (mCherry-OB) abolished localization of GFP-TERT to telomeres and caused GFP-TERT to be sequestered within conventional Cajal bodies, results reminiscent of TPPl depletion in S-T HeLa cells. Unexpectedly, mCherry-OB itself strongly accumulated within Cajal bodies together with GFP-TERT, indicating that a telomerase- mCherry-OB complex was sequestered in Cajal bodies. Localization of mCherry-OB in Cajal bodies was not observed without coexpressed TERT and TERC. Taken together, it was concluded that overexpressed TPPl OB-fold acts as a competitive inhibitor of telomerase recruitment, presumably by blocking an interacting surface on telomerase that is engaged by endogenous TPPl during normal telomerase action at telomeres. These results further support the necessity and sufficiency of TPP1-OB in recruiting telomerase from Cajal bodies to telomeres.

[00110] The structure of the TPPl -OB-fold domain is closely related to the structure of certain OB-folds in telomere- associated or telomerase-associated proteins from other species (Wang et al., 2007; Xin et al., 2007). In Saccharomyces cerevisiae and Candida albicans, Est3 is a telomerase-associated co-factor whose OB-fold shows structural similarity to TPP1- OB-fold when modeled using structure prediction algorithms. Sequences within Est3 responsible for binding yeast telomerase have been identified using functional and biochemical assays (Lee et al., 2008; Yu et al., 2008). Structure- guided mutagenesis was used to identify specific amino acids in the TPPl-OB-fold domain required for association with human telomerase. Residues that were solvent-exposed based on the TPPl-OB-fold crystal structure were chosen, including those that were conserved in mammals, present in loop regions connecting β-strands, and near the analogous Est3-yeast telomerase association site. Using the 'competitive sequestration' assay described above, each TPPl -OB variant was tested for its ability to inhibit telomerase localization to telomeres and sequester telomerase within Cajal bodies.

[00111] Many mutations in TPPl -OB had no effect on the efficiency of mCherry-OB in blocking localization of GFP-TERT to telomeres, indicating that these residues are dispensable for TPP1-OB association with TERT. These included double mutants R159A;E160A and D163A;T164A, both of which reside in a short alpha-helix (helix αβ). Mutation of a conserved serine in loop LAI (S 111 A) similarly had no effect on the activity of mCherry-OB). In marked contrast, a double charge swap mutation - D166R;E168R, hereafter referred to as OB-RR - in conserved residues in loop L34 completely eliminated the activity of mCherry-OB. mCherry-OB-RR was expressed at similar levels compared to wild- type mCherry-OB, but failed to inhibit localization of GFP-TERT to telomeres, and as a result was not detected in Cajal bodies. Deconvolution of this double mutant revealed that E168R was more severely impaired in its ability to sequester telomerase away from telomeres than D166R, suggesting that the inactivity of the OB-RR mutant is largely due to mutation of E168. Introduction of K170A at a nearby residue in the same loop caused a modest reduction in the activity of mCherry-OB in this assay. Introduction of the RR mutations into full length TPP1 revealed that both wild- type mCherry-TPPl and mCherry-TPPl-RR localized to telomeres in HeLa cells. Although wild- type mCherry-TPPl did not interfere with the localization of GFP-TERT at telomeres, mCherry-TPPl-RR effectively blocked the ability of GFP-TERT to localize to telomeres, resulting in localization of GFP-TERT to Cajal bodies. In this case, mCherry-TPPl-RR inhibited telomerase recruitment to telomeres presumably by competing away endogenous TPP1 from the shelterin complex, replacing it with a mutant defective in the ability to associate with telomerase. Taken together, these data show that residues D166, E168 and K170 are required for telomerase association and define a critical surface required for interaction between TPP1 and telomerase.

EXAMPLE 5: Disruption of the TPPl-telomerase association causes telomere shortening in cancer cells

[00112] To test the functional significance of the telomerase-TPPl OB interaction in telomere length maintenance, it was tested whether isolated TPP1-OB fold domain could prevent telomerase from elongating telomeres. Retroviral transduction was used to express wild- type TPPl-OB-fold domain, TPP1 -OB-RR or GFP as a negative control in HTC75 cells, a telomerase-positive fibrosarcoma cell line widely used to study telomere maintenance. After selection, each culture was transduced either with an empty vector or with a retrovirus expressing Myc-POTl(AOB), a POT1 variant that lacks the N-terminal OB- fold domain. Myc-POTl(AOB) causes rapid telomere elongation by telomerase, presumably by relieving inherent negative regulation at the chromosome terminus (Loayza and De Lange, 2003). As expected, telomeres significantly elongated in cells expressing GFP and Myc- Potl(AOB) through successive population doublings. In comparison, telomere elongation by Myc-Potl(AOB) was abrogated by prior expression of wild-type TPP1-OB. This inhibitory effect of TPP1-OB was dependent on its association with telomerase, because expression of TPP1 -OB-RR exerted no inhibitory effect on telomere elongation by telomerase in Myc- Potl(AOB) cells. Furthermore, telomeres in cells expressing wild-type TPP1-OB (without Myc-POTl(AOB)) showed rapid telomere shortening as compared to GFP-expressing cells in which telomere lengths were maintained with passage. By population doubling 12, the mean telomere length in cells expressing TPP1-OB was 1.5kb shorter than cells expressing GFP. In contrast, TPP1-OB-RR showed no effect on telomere maintenance, despite similar expression compared to wild-type TPP1-OB protein. The strong inhibitory effect of TPP1- OB was not due to a reduction in telomerase catalytic function; catalytic assays performed on extracts from these cells showed no inhibition of enzymatic activity by expression of TPP1- OB. In addition, TPP1-OB did not interfere with cell growth or telomere protection, as there was no increase in DNA damage foci at telomeres. These findings demonstrate the TPP1 OB-fold inhibits telomere length maintenance by telomerase both at the basal level and in the context of rapid telomere elongation induced by ΡΟΤΙ(ΔΟΒ).

[00113] To understand how expression of TPP1-OB variants affected recruitment of endogenous telomerase to telomeres, RNA FISH for endogenous TERC was performed in HeLa cells stably transduced with TPP1-OB or TPP1-RR. The frequency of cells harboring TERC foci that overlapped with TRF2 was significantly diminished by overexpression of TPP1-OB, but not by TPP1-OB-RR. These findings corroborate our observations from the 'competitive sequestration' assay at the endogenous level and provide functional evidence that association between the OB-fold domain of TPP1 and telomerase is essential for telomerase to be efficiently recruited to telomeres and to synthesize telomere repeats.

EXAMPLE 6: IPF mutations in TERT block recruitment and show diminished association with TPP1 OB-fold

[00114] Based on these findings indicating a functionally important association between TPP1 and telomerase, it was hypothesized that specific amino acid residues within TERT are required for its recruitment to telomeres. To address this question domain mapping studies were carried out on TERT by generating a panel of TERT deletion mutants. HA-tagged TERT mutants and TERC were co-expressed in HeLa cells and assayed for their localization by triple immunofluorescence staining for HA-TERT, TRF2 and coilin. Three distinct classes of localization patterns for these deletion mutants. Whereas wild- type TERT showed robust colocalization with TRF2, the N-terminal truncations of TERT were detected in a nucleoplasmic pattern. C-terminal deletions within TERT abrogated telomere localization, but instead showed strong accumulation in coilin-positive Cajal bodies. Based on these results, it was concluded that Cajal body-localization and telomere association are each governed by distinct structural domains of TERT. The N-terminus of TERT, including the TEN and TRBD domains, is essential for Cajal body localization, while the CTE is required for recruitment to telomeres.

[00115] Upon establishing the roles of the TEN and CTE domains in telomerase trafficking, a panel of disease-associated or engineered TERT point mutants in the TEN and CTE domain were examined. Four mutants— G 100 V, V144M, E1117X and F1127NAA (C-DAT)— were found to be defective in localizing to telomeres when coexpressed with TERC and strongly accumulated in Cajal bodies. This pattern was reminiscent of the relocalization of TERT into Cajal bodies upon depletion of TPP1 or upon expression of the OB-fold of TPP1. To determine whether these mutants failed to be recruited to telomeres because of a defect in association with TPP1, each mutant was coexpressed with mCherry-TPPl-OB. Three of the four mutants - G100V, V144M, E1117X - were significantly impaired in capturing mCherry- TPP1-OB into Cajal bodies, consistent with a defect in association between these mutant TERT proteins and the OB-fold of TPP1. The C-DAT mutant retained the ability to colocalize within mCherry-OB in Cajal bodies, although mCherry fluorescence intensity was reduced in Cajal bodies as compared to wild-type TERT, evidence for weaker association with mCherry-OB. These data indicate that the mutations in the TEN and CTE domains of TERT block association with TPP1 OB-fold and this defect explains their inability to be recruited to telomeres.

[00116] Importantly, the ability of the examined TERT variants to localize to telomeres was unrelated to their catalytic activity measured in vitro. The V144M and E1117fsX mutants derive from patients with idiopathic pulmonary fibrosis (Yamaguchi et al., 2005; Armanios et al., 2007; Tsakiri et al., 2007). Although El 117fsX has diminished catalytic activity, V144M retained wild-type activity in in vitro assays (Tsakiri et al., 2007; Tsang et al., 2012). The results suggest that defective trafficking from Cajal bodies to telomeres underlies the telomerase dysfunction in patients with the V144M mutation. G100V is an engineered mutation in the TEN domain and has been shown to be essential for the enhancement of telomerase processivity mediated by recombinant TPP1-POT1 (Zaug et al., 2010). Thus, an impaired interaction between TERT-G100V and TPP1 -OB-fold likely explains both the absence of processivity enhancement in this mutant and the defect in telomerase recruitment. F1127NAA (C-DAT) is an engineered mutation that "dissociates activities of telomerase" (DAT) by preserving enzymatic function while interfering with the ability of telomerase to immortalize primary human cells (Banik et al., 2002; Armbruster et al., 2003). It is worth noting that all the recruitment-disrupting mutations lie within or close to the previously characterized DAT domains in the TEN and CTE domains, raising the possibility that the DAT domains represent structural motifs directly involved in recruitment. Taken together, these data show that specific residues within TERT govern recruitment to telomeres via interaction with the TPPl-OB-fold domain and that this recruitment step is impaired in a subset of patients with pulmonary fibrosis.

EXAMPLE 7: Experimental Procedures

[00117] Small-Scale Cell Culture, cDNA and siRNA Transfections, and Retroviral Transductions: HeLa, 293T, HTC75 (a gift from T. de Lange) and U20S2-6-3 cells (a gift from S. Janicki) were grown in DMEM/10 fetal bovine serum l\% penicillin- streptomycin. Lipofectamine 2000 (Life Technologies) was used for all cDNA transfection experiments with and without siRNAs. For transfection with siRNA alone, Dharmafect 4 (Dharmacon) was used. All siRNAs were purchased from Dharmacon as siGENOME pools. Cells were reseeded 24hrs post transfection and assayed 24-48hrs later. For transient overexpression, TERT and TPPl coding sequences were cloned into pCDNA3.1 (Invitrogen) with indicated amino terminal tags. To generate cells by retroviral gene transfer, 293T cells were first transfected with RSV Gag-pol and VSV-g packaging vectors together with retroviral plasmids. Viral supernatant was collected and 24, 48 and 72hrs post transfection and concentrated using Retro-X concentrator (Clontech). Infected cells were selected in antibiotic containing media up to 1 week. All TERT and TPPl point mutants were generated using site-directed mutagenesis (QuikChange II, Agilent). See Table S I for primer sequences.

[00118] Immunofluorescence and in situ hybridization: All immunofluorescence was carried out as previously described (Zhong et al., 2011) on cells seeded on coverslips. RNA FISH was carried out using Quasar 570 labeled oligonucleotide probes (Biosearch). Telomere DNA FISH using PNA probes was carried out as described (Kibe et al., 2010). For combined immunofluorescence (IF) and DNA/RNA FISH, IF was carried out first and cells re-fixed with ImM DSP in lxPBS for 5 mins. Images were subsequently acquired with a Leica wide- field fluorescence microscope. LAF AS Lite suite (Leica) and ImageJ were used for image analyses. [00119] Telomere Repeat Amplification Protocol (TRAP) and Telomere Restriction Fragment analysis (TRF): TRAP was carried out using Trapeze kit according to the manufacturer's protocol (Milipore) with minor modifications. Cells were lysed in NP40 buffer (25 mM HEPES-KOH, 400 mM NaCl, 1.5 mM MgC12, 10% glycerol, 0.5% NP40, and 1 mM DTT [pH 7.5] supplemented with protease inhibitors). Each reaction was programmed with 0.5ug to 2ug of protein lysate. To measure telomere lengths during extended culture, HTC75 cells were grown in 6 well plates and reseeded every 3 days. Harvested cells were pelleted and digested with Proteinase K at 6 μg/ml overnight. DNA was extracted using the standard phenol-chloroform based method and digested overnight with Hinfl and Rsal before electrophoresis and Southern blotting with an end-labeled (CCATTT)4 oligonucleotide probe.

[00120] The preceding merely illustrates the principles of the invention. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention as well as specific examples thereof, are intended to encompass both structural and functional equivalents. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The scope of the present invention, therefore, is not intended to be limited to the exemplary aspects shown and described herein. Rather, the scope and spirit of present invention is embodied by the appended claims. In the claims that follow, unless the term "means" is used, none of the features or elements recited therein should be construed as means-plus-function limitations pursuant to 35 U.S.C. § 112, ¾6. References

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Claims

We claim:

1. A method for identifying a test compound that is capable of preventing recruitment of telomerase but does not disrupt shelterin comprising the steps of (a) activating a cell by conditionally increasing transcription of a coding sequence of TPPl and/or one or both of the TEN or CTE domains of TERT; contacting the cell with the test compound; and observing the effect of the test compound on the cell.

2. The method of claim 1, wherein the test compound is a small molecule.

3. The method of claim 2, wherein the test compound is a peptide.

4. The method of claim 3, wherein the peptide is an antibody to an OB domain of TPPl.

5. A method for treating a disease characterized by cellular proliferation in an individual comprising administering to the individual one or more of 1) a moiety that binds to the OB domain of TPPl; 2) a TPPl peptide; or 3) a moiety that binds to one or both of the TEN or CTE domains of TERT.

6. The method of claim 5, wherein the moiety that binds to the OB domain of TPPl binds one or more of D166, E168 or K170.

7. The method of claim 6, wherein the moiety that binds to the OB domain of TPPlbinds to two or more of D166, E168 or K170.

8. The method of claim 8, wherein the moiety that binds to the OB domain of TPPl binds to all of D166, E168 and K170.

9. The method of claim 5, wherein the TPPl peptide is a peptide comprising 100 amino acids or less and comprises an OB domain of TPPl.

10. The method of claim 9, wherein the peptide comprising 100 amino acids or less comprises one or more of D166, E168 or K170.

11. The method of claim 5, wherein the moiety that binds to one or both of the TEN or CTE domains of TERT binds to both the TEN or CTE domains of TERT.

12. The method of claim 5, wherein the disease is cancer.

13. The method of claim 5, wherein the disease is an autoimmune disease.

14. A transgenic animal, wherein the transgenic animal conditionally transcribes a nucleic acid coding for the OB domain of TPPl or one or both of the TEN or CTE domains of TERT.

15. The transgenic animal of claim 14, wherein the animal is a rodent.

16. A research tool comprising a cell transfected with a vector comprising a nucleic acid that codes for an OB domain of TPP1 and/or a nucleic acid that codes for one or both of the TEN or CTE domains of TERT.

17. The research tool of claim 16, wherein the nucleic acid codes residues D166, E168 and K170 of the OB domain.

18. A system for use in identifying a compound that is capable of modulating the recruitment of telomerase by TPP1 comprising; (a) a transgenic animal conditionally transcribing a nucleic acid coding for an OB domain of TPP1 and/or one or both of the TEN or CTE domains of TERT; and (b) an agent that activates conditional transcription of said nucleic acid.

19. The system of claim 18, wherein the nucleic acid codes for at residues D166, E168 and K170 of the OB domain.