Classifications

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  • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
  • C12P21/00—Preparation of peptides or proteins
  • C12P21/02—Preparation of peptides or proteins having a known sequence of two or more amino acids, e.g. glutathione
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  • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
  • C12N15/09—Recombinant DNA-technology
  • C12N15/63—Introduction of foreign genetic material using vectors; Vectors; Use of hosts therefor; Regulation of expression
  • C12N15/67—General methods for enhancing the expression
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  • C12N5/00—Undifferentiated human, animal or plant cells, e.g. cell lines; Tissues; Cultivation or maintenance thereof; Culture media therefor
  • C12N5/0018—Culture media for cell or tissue culture
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K2319/00—Fusion polypeptide
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  • C12N2500/00—Specific components of cell culture medium
  • C12N2500/30—Organic components
  • C12N2500/36—Lipids
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  • C12N2501/00—Active agents used in cell culture processes, e.g. differentation
  • C12N2501/01—Modulators of cAMP or cGMP, e.g. non-hydrolysable analogs, phosphodiesterase inhibitors, cholera toxin
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
  • C12N2510/00—Genetically modified cells
  • C12N2510/02—Cells for production

Definitions

• the invention is in the field of polypeptide production, particularly recombinant polypeptide production in cell culture.
• Polypeptides are useful in a variety of diagnostic, therapeutic, agricultural, nutritional, and research applications. Although polypeptides can be isolated from natural sources, the isolation of large quantities of a specific polypeptide from natural sources may be expensive. Also, the polypeptide may not be of uniform quality due to variation in the source material. Recombmant DNA technology allows more uniform and cost-effective large-scale production of specific polypeptides.
• One goal of recombinant polypeptide production is the optimization of culture conditions so as to obtain the greatest possible productivity. Incremental increases in productivity can be economically significant.
• Some of the methods to increase productivity in cell culture include using enriched medium, monitoring osmolarity during production, decreasing temperatures during specific phases of a cell culture, and/or the addition of sodium butyrate (see, e.g., U.S. Patent No. 5,705,364).
• the invention provides a method for producing a polypeptide, which may be a recombinant polypeptide, comprising culturing a mammalian cell line in a growth phase followed by a production or induction phase, which can occur at a temperature of less than 37°C, and adding to the culture during the production phase a xanthine derivative.
• the addition of the xanthine derivative can increase the production of the polypeptide.
• the mammalian cell line can be a cell line that has been genetically engineered to produce the polypeptide or a hybridoma cell line that can produce an antibody.
• the xanthine derivative may be caffeine at a concentration from about 0.01 millimolar to about 5.0 millimolar or from about 0.01 millimolar to about 3.0 millimolar.
• the mammalian cell line is a CHO cell line, and it may have been transformed with a recombmant vector encoding the recombinant polypeptide.
• the vector can comprise a cytomegalovirus (CMV) promoter.
• CMV cytomegalovirus
• the cell does not naturally express the polypeptide or only naturally expresses the polypeptide at very low levels (in the absence of genetic engineering).
• the polypeptide may be a recombinant fusion polypeptide or a human or humanized antibody.
• the production or induction phase can occur at a temperature from about 29°C to about 36°C or from about 30°C to about 33°C.
• the growth phase can occur at a temperature from about 35°C to about 38°C.
• at least two different xanthine derivatives can be added.
• the xanthine derivative(s) can be selected from the group consisting of caffeine, 3-isobutyl-l- methylxanthine, theophylline, theobromine, pentoxyphylline, and aminophylline or from a subset of this group. If two different xanthine derivatives are added, they can be caffeine and 3-isobutyl-l-methylxanthine.
• Xanthine derivatives can be added multiple times during the culturing of the cell line, and the cell line can be cultured in the presence of the xanthine derivative for at least about 5 days. The concentration of each xanthine derivative added to the culture can be from about 0.001 millimolar to about 3 millimolar.
• the recombinant polypeptide can be collected from the medium and formulated.
• the medium may further comprise a hybrid polar compound and/or an alkanoic acid.
• the hybrid polar compound can be hexamethylene bisacetamide, optionally at a concentration from about 0.1 millimolar to about 5 millimolar.
• the xanthine derivative can be caffeine, optionally at a concentration from about 0.1 millimolar to about 4 millimolar.
• the alkanoic acid can be a salt of butyric acid, optionally at a concentration from about 0.1 millimolar to about 2 millimolar.
• the mammalian cells can be cultured at a temperature from about 29°C to about 36°C or from about 30°C to about 33°C.
• the mammalian cells can be cultured in a growth phase at a first temperature from about 35°C to about 38°C before they are shifted to a production phase at a second temperature from about 29°C to about 36°C, wherein the second temperature can be lower than the first temperature.
• the xanthine can be added at the time of the shift from the first temperature to the second temperature and/or before and/or after the shift.
• the invention provides a method for producing a recombinant polypeptide comprising growing in culture a mammalian cell line, optionally a CHO cell line that has been genetically engineered to produce the recombinant polypeptide, and adding to the culture medium at least one xanthine derivative selected from the group consisting of theobromine and caffeine.
• the addition of the xanthine derivative can increase the production of the recombinant polypeptide.
• the mammalian cell line may have been transformed with a recombinant vector encoding the recombinant polypeptide.
• the vector can comprise a cytomegalovirus (CMV) promoter.
• CMV cytomegalovirus
• the cell line does not naturally express the recombinant polypeptide or only naturally expresses the recombinant polypeptide at very low levels (in the absence of genetic engineering).
• the recombinant polypeptide may be a recombmant fusion polypeptide or a human or humanized antibody.
• the cell line can be cultured in a growth phase, which is distinct from a production or induction phase.
• the production phase can occur at a temperature less than 37°C.
• the cell line can be cultured at a temperature of from about 29°C to about 36°C or from about 30°C to about 33°C.
• at least two different xanthine derivatives can be added.
• Xanthine derivatives can be added multiple times during the culturing of the cell line.
• the concentration of each xanthine derivative added to the culture can be from about 0.001 millimolar to about 3 millimolar.
• the recombinant polypeptide can be collected from the medium and formulated.
• the mammalian cell line can be cultured at a first temperature from about 35°C to about 38°C before it is shifted to a second temperature from about 29°C to about 36°C, and the xanthine derivative can be added at the time of the shift from the first temperature to the second temperature and/or before and/or after the shift.
• the second temperature can be lower than the first temperature.
• the invention provides a culture comprising a CHO cell genetically engineered to produce a polypeptide, a production medium, and at least one xanthine derivative selected from the group consisting of caffeine, 3-isobutyl-l-methylxanthine, theophylline, theobromine, pentoxyphylline, and aminophylline or from a subset of this group.
• the culture can comprise at least two xanthine derivatives.
• the concentration of each xanthine derivative present can be from about 0.001 millimolar to about 3 millimolar or from about 0.01 millimolar to about 3 millimolar.
• the culture can comprise serum-free medium, and may comprise no added protein or may comprise insulin or IGF-1.
• the culture can comprise dimethylformamide, dimethylsulfoxide, or dimethylacetamide.
• the invention because of its low cost and convenience, is particularly useful for large scale culturing of CHO cells.
• the culture can be a large scale culture of at least 100 liters, or even at least 500 liters, in size.
• the culture can comprise a homogeneous CHO cell line.
• the invention encompasses a culture comprising a CHO cell genetically engineered to produce a polypeptide, a production medium, and at least one xanthine derivative, wherein the culture is grown at less than 37°C for at least part of its life.
• the xanthine derivative or derivatives present can be within the concentration range from about 0.001 millimolar to about 3 millimolar or from about 0.01 millimolar to about 3 millimolar, and the culture can contain at least two different xanthine derivatives.
• the xanthine derivatives can be selected from the group consisting of caffeine, 3-isobutyl-l- methylxanthine, theophylline, theobromine, pentoxyphylline, and aminophylline or from a subset of this group such as caffeine, theobromine and pentoxyphylline.
• the size of the culture can be at least 100 liters, and the production medium can be serum-free medium and can comprise either no added protein or insulin or IGF-1.
• the culture can comprise a homogeneous CHO cell line.
• the invention includes a method for producing a polypeptide in a culture of mammalian cells comprising incubating the culture at a temperature of about 37°C and thereafter incubating the culture at a temperature from about 29°C to 36°C, and adding to the culture a xanthine derivative during the incubation at a temperature from about 29°C to 36°C, wherein the polypeptide is a recombinant polypeptide or an antibody.
• the xanthine derivative can be selected from the group consisting of caffeine, 3-isobutyl-l-methylxanthine, theophylline, theobromine, pentoxyphylline, and aminophylline or from a subset of this group such as caffeine, theobromine, and pentoxyphylline.
• the mammalian cells can be hybridoma cells or CHO cells.
• the xanthine derivative or derivatives present can be within the concentration range from about 0.001 millimolar to about 3 millimolar or from about 0.01 millimolar to about 3 millimolar, and the culture can contain at least two different xanthine derivatives.
• Xanthine derivatives can be added multiple times during the culturing of the cell line.
• the invention provides a method for producing a recombinant polypeptide comprising culturing a mammalian cell line, in some embodiments a CHO cell line, at a temperature from about 29°C to about 36°C, optionally at temperatures between about 29°C and 35°C or from about 30°C to about 33°C, in a medium comprising a hybrid polar compound.
• the medium can be serum free.
• the addition of the hybrid polar compound can increase the production of the recombinant polypeptide.
• the hybrid polar compound can be hexamethylene bisacetamide, optionally at a concentration from about 0.1 millimolar to about 20 millimolar or from about 0.1 millimolar to about 5 millimolar.
• the medium may comprise an alkanoic acid, such as a salt of butyric acid, at a concentration, for example, from about 0.05 millimolar to about 10 millimolar, optionally from about 0.1 millimolar to about 2 millimolar.
• the medium may comprise a xanthine derivative, for example, caffeine, at a concentration from about 0.005 millimolar to 10 millimolar, optionally from about 0.01 millimolar to 4 millimolar or from about 0.1 millimolar to 4 millimolar.
• the mammalian cells can be cultured at a first temperature from about 35°C to about 38°C before they are shifted to a second temperature between about 29°C and 36°C, and the hybrid polar compound can be added after the shift from the first temperature to the second temperature.
• the mammalian cells may be genetically engineered to produce a polypeptide, optionally a secreted polypeptide that can be recovered from the medium, including RANK:Fc, type II interleukin-1 receptor, TNFR.Fc, CD40 ligand, TRAIL, jQt3-ligand, IL-4 receptor, G-CSF, erythropoietin, an antibody, or a substantially similar polypeptide, among others.
• the invention provides an improved method for producing a polypeptide by culturing mammalian cells comprising culturing the cells in a medium comprising a hybrid polar compound, optionally at temperatures from about 29°C to about 36°C, between about 29°C and 35°C, or from about 30°C to about 33°C.
• the hybrid polar compound may be hexamethylene bisacetamide, optionally at a concentration between about 0.1 millimolar and about 5 millimolar.
• the addition of the hybrid polar compound can increase the production of the polypeptide, which may be a recombinant polypeptide.
• the medium may comprise an alkanoic acid, for example, butyric acid, optionally at a concentration from about 0.05 millimolar to about 10 millimolar or from about 0.1 millimolar to about 2 millimolar.
• the medium may comprise a xanthine, such as, for example, caffeine, optionally at a concentration from about 0.005 millimolar to 10 millimolar or from about 0.01 millimolar to 5 millimolar.
• the polypeptide may be RANK:Fc, type II interleukin-1 receptor, TNFR:Fc, CD40 ligand, TRAIL, flt3-ligand, IL-4 receptor, GM-CSF, erythropoietin, an antibody, or a substantially similar polypeptide among others.
• the invention provides a method for obtaining a polypeptide, optionally a recombinant polypeptide, comprising recovering the polypeptide from medium in which mammalian cells have been grown, wherein the mammalian cells can secrete the polypeptide and are grown at temperatures between about 29°C and 35°C, optionally from about from about 30°C to about 33 °C, in medium comprising hexamethylene bisacetamide.
• the hexamethylene bisacetamide may be present at concentrations between about 0.1 millimolar and about 5 millimolar.
• the medium may comprise an alkanoic acid, for example, butyric acid, optionally at a concentration from about 0.05 millimolar to about 10 millimolar or from about 0.1 millimolar to about 2 millimolar.
• the medium may comprise a xanthine, for example, caffeine, optionally at a concentration from about 0.005 millimolar to 10 millimolar or from about about 0.01 millimolar to 5 millimolar.
• the polypeptide may be RANK:Fc, type II interleukin-1 receptor, TNFR:Fc, CD40 ligand, TRAIL, flt3-ligand, IL-4 receptor, G-CSF, erythropoietin, an antibody, or a substantially similar polypeptide, among others.
• the invention comprises method for producing a recombinant polypeptide comprising culturing mammalian cells in a medium comprising a hybrid polar compound and a xanthine, wherein the mammalian cells have been genetically engineered to express the recombinant polypeptide.
• the medium may further comprise an alkanoic acid, such as, for example, a salt of butyric acid, which may be at a concentration from about 0.1 millimolar to about 2 millimolar.
• the hybrid polar compound can be hexamethylene bisacetamide, which may be at a concentration from about 0.1 millimolar to about 5 millimolar, and/or the xanthine can be caffeine, which may be at a concentration from about 0.1 millimolar to about 4 millimolar.
• the cells can be cultured at a temperature from about 29°C to about 36°C or from about 30°C to about 33°C.
• the mammalian cells can be cultured at a first temperature from about 35°C to about 38°C before they are shifted to a second temperature from about 29°C to about 36°C, and the hybrid polar compound and the xanthine can be added at the time of the shift from the first temperature to the second temperature and/or before and/or after the shift.
• the can be medium can be serum free.
• the invention encompasses a method for producing a polypeptide, optionally a recombinant polypeptide, comprising culturing mammalian cells in a medium comprising a hybrid polar compound and an alkanoic acid, wherein the mammalian cells may have been genetically engineered to express the recombinant polypeptide.
• the hybrid polar compound can be hexamethylene bisacetamide, and the hybrid polar compound can be present at a concentration of from about 0.5 millimolar to about 10 millimolar or at a concentration between about 0.5 millimolar and 2.5 millimolar.
• the alkanoic acid can be a salt of butyric acid, and the alkanoic acid can be present at a concentration from about 0.1 millimolar to about 5 millimolar or at a concentration between about 0.1 millimolar and about 2.0 millimolar.
• the mammalian cells can be cultured at a temperature from about 29°C to about 36°C, and the medium can be serum free.
• the mammalian cell line can be cultured at a first temperature from about 35°C to about 38°C before they are shifted to a second temperature from about 29°C to about 36°C, and the hybrid polar compound and the alkanoic acid may be added after the shift from the first temperature to the second temperature.
• the medium can further comprise a xanthine derivative at a concentration from about 0.001 millimolar to about 5.0 millimolar.
• the mammalian cell line can be a hybridoma cell line or a CHO cell line.
• the invention provides a method for producing a polypeptide comprising culturing a mammalian cell line in a production phase at a second temperature from about 30°C to 34°C in a medium comprising a hybrid polar compound, wherein the production phase follows a growth phase at a first temperature from about 35°C to about 38°C.
• the polypeptide can be a recombinant polypeptide or an antibody.
• the hybrid polar compound can be hexamethylene bisacetamide, optionally at a concentration from about 0.1 millimolar to about 5 millimolar. The hybrid polar compound may be added after the shift from the first temperature to the second temperature.
• the medium can further comprise an alkanoic acid, which can be a salt of butyric acid, optionally at a concentration from about 0.05 millimolar to about 10.0 millimolar.
• the medium can also comprise a xanthine derivative, optionally at a concentration from about 0.001 millimolar to about 5.0 millimolar.
• the medium can be serum free.
• the mammalian cell line can be a hybridoma cell line or a CHO cell line.
• the invention also provides a method for producing a polypeptide comprising culturing a mammalian cell line in a medium comprising a hybrid polar compound at a concentration between about 0.5 millimolar and 2.5 millimolar, an alkanoic acid at a concentration from about 0.1 millimolar and 2.0 millimolar, and a xanthine derivative at a concentration from about 0.001 millimolar to about 4 millimolar.
• the invention provides a method for producing a polypeptide, optionally RANK:Fc, type II interleukin-1 receptor, TNFR:Fc, CD40 ligand, TRAIL, flt3-ligand, B -4 receptor, G-CSF, erythropoietin, an antibody, or a substantially similar polypeptide, comprising culturing mammalian cells, which may have been genetically engineered to produce any of these polypeptides, in a medium comprising between about 0.1 millimolar and about 5 millimolar HMBA, from about 0.1 millimolar to about 2 millimolar butyric acid, and from about 0.1 millimolar to about 4 millimolar caffeine at a temperature from about 29°C to about 36°C or from about 30°C to about 33°C.
• a medium comprising between about 0.1 millimolar and about 5 millimolar HMBA, from about 0.1 millimolar to about 2 millimolar butyric acid, and from about 0.1 millimolar to about
• Figure 1 shows the percentage of the total cells that are viable under the indicated conditions at 31°C for the #9 CHO cell line as a function of days in culture.
• Figure 2 shows the micrograms of protein per milliliter of cell culture, i.e., protein titer, under the indicated conditions at 31°C for the #9 CHO cell line as a function of days in culture.
• Figure 3 shows the micrograms of protein per 10 6 cells per day under the indicated conditions at 31 °C for #9 CHO cell line as a function of days in culture.
• Figure 4 shows a graph displaying the concentration of an antibody against murine IL-4 receptor recovered from medium as a function of days of growth of a CHO cell line comprising a vector encoding the antibody at the stated temperatures in the presence or absence of HMBA or sodium butyrate. Markings are as follows: A - , no inducer 37°C; — ⁇ — , no inducer 34°C; — ⁇ -— , 0.5 millimolar sodium butyrate 34°C; — ⁇ — , 2.0 millimolar HMBA 34°C; — • — , no inducer 31°C; — •— , 0.5 millimolar sodium butyrate 31°C; and — •— , 2.0 millimolar HMBA 31°C.
• an “antibody” is a polypeptide or complex of polypeptides, each of which comprises at least one variable antibody immunoglobulin domain and at least one constant antibody immunoglobulin domain.
• Antibodies may be single chain antibodies, dimeric antibodies, or some higher order complex of polypeptides including, but not limited to, heterodimeric antibodies.
• a "human antibody” is an antibody encoded by nucleic acids that are ultimately human in origin. Such an antibody can be expressed in a non-human cell or organism. For example, DNA encoding a human antibody can be introduced into tissue culture cells and expressed in transformed cell lines. Alternatively, human antibodies can be expressed in transgenic animals such as, for example, the transgenic mice described in Mendez et al. ((1997), Nature Genetics 16(4): 146-56).
• a "humanized antibody” is a chimeric antibody comprising complementarity determining regions (CDR1, CDR2, and CDR3) from a non- human source and other regions that conform to sequences in human antibodies (and may be of human origin) as explained in, e.g., US Patent Nos. 5,558,864 and 5,693,761 and International Patent Application WO 92/11018.
• a "constant antibody immunoglobulin domain” is an immunoglobulin domain that is identical to or substantially similar to a C L , C H 1, C H 2, C H 3, or C H 4, domain of human or animal origin. See e.g.
• an "Fc portion of an antibody” includes human or animal immunoglobulin domains C H 2 and C H 3 or immunoglobulin domains substantially similar to these. For discussion, see Hasemann and Capra, supra, at 212-213 and Kabat et al., supra.
• Cells have been "genetically engineered” to express a specific polypeptide when recombinant nucleic acid sequences that allow expression of the polypeptide have been introduced into the cells using methods of "genetic engineering,” such as viral infection with a recombmant virus, transfection, transformation, or electroporation. See e.g. Kaufman et al. (1990), Meth. Enzymol. 185: 487-511; Current Protocols in Molecular Biology. Ausubel et al, eds. (Wiley & Sons, New York, 1988, and quarterly updates).
• genetic engineering refers to a recombinant DNA or RNA method used to create a host cell that expresses a gene at elevated levels or at lowered levels, or expresses a mutant form of the gene. In other words, the cell has been transfected, transformed or transduced with a recombmant polynucleotide molecule, and thereby altered so as to cause the cell to alter expression of a desired polypeptide.
• the antibodies produced by a hybridoma cell line resulting from a cell fusion are not “recombinant polypeptides.”
• viral polypeptides produced by a cell as a result of viral infection are also not “recombmant polypeptides” as meant herein unless the viral nucleic acid has been altered by genetic engineering prior to infecting the cell.
• the methods of "genetic engineering” also encompass numerous methods including, but not limited to, amplifying nucleic acids using polymerase chain reaction, assembling recombinant DNA molecules by cloning them in Escherichia coli, restriction enzyme digestion of nucleic acids, ligation of nucleic acids, and transfer of bases to the ends of nucleic acids, among numerous other methods that are well-known in the art. See e.g. Sambrook et al., Molecular Cloning: A Laboratory Manual, 2 nd ed., vol. 1-3, Cold Spring Harbor Laboratory, 1989. Methods and vectors for genetically engineering cells and/or cell lines to express a polypeptide of interest are well known to those skilled in the art.
• Genetic engineering techniques include but are not limited to expression vectors, targeted homologous recombination and gene activation (see, for example, US Patent No. 5,272,071 to Chappel) and trans activation by engineered transcription factors (see e.g., Segal et al, 1999, Proc. Natl. Acad. Sci. USA 96(6):2758-63).
• the polypeptides are expressed under the control of a heterologous control element such as, for example, a promoter that does not in nature direct the production of that polypeptide.
• the promoter can be a strong viral promoter (e.g., CMV, SV40) that directs the expression of a mammalian polypeptide.
• the host cell may or may not normally produce the polypeptide.
• the host cell can be a CHO cell that has been genetically engineered to produce a human polypeptide, meaning that nucleic acid encoding the human polypeptide has been introduced into the CHO cell.
• the host cell can be a human cell that has been genetically engineered to produce increased levels of a human polypeptide normally present only at very low levels (e.g., by replacing the endogenous promoter with a strong viral promoter).
• "Growth phase” means a period during which cultured cells are rapidly dividing and increasing in number. During growth phase, cells are generally cultured in a medium and under conditions designed to maximize cell proliferation.
• hybrid polar compound is compound having two polar groups separated by an apolar carbon chain. This includes hexamethylene bisacetamide (HMBA) and the other molecules discussed below and in the following references: Richon et al. (1998), Proc. Natl. Acad. Sci. 95: 3003-07; Marks et al. (1994), Proc. Natl. Acad. Sci. 91: 10251-54; and US Patent Nos. 5,055,608 and 6,087,367.
• HMBA hexamethylene bisacetamide
• the production of a polypeptide is "increased" by the addition of an inducing agent, such as hexamethylene bisacetamide (HMBA) or caffeine, if the amount the polypeptide produced in a culture containing the inducing agent is more than the amount of the polypeptide produced in an otherwise identical culture that does not contain the inducing agent.
• an inducing agent such as hexamethylene bisacetamide (HMBA) or caffeine
• a “multimerization domain” is a domain within a polypeptide molecule that confers upon it a propensity to associate with other polypeptide molecules through covalent or non-covalent interactions.
• a "naturally-occurring polypeptide” is a polypeptide that occurs in nature, that is, a polypeptide that can be produced by cells that have not been genetically engineered. Such a polypeptide may also be produced by cells genetically engineered to produce it. "Polypeptide” means a chain of at least 6 amino acids linked by peptide bonds.
• a polypeptide can comprise at least 10, 20, 30, 40, 50, 60 , 70, 80, 90, 100, 150, 200, 250, or 300 amino acids linked by peptide bonds.
• Production medium means a cell culture medium designed to be used to culture cells during a production phase.
• “Production phase” means a period during which cells are producing maximal amounts of recombinant polypeptide.
• a production phase is characterized by less cell division than during a growth phase and by the use of medium and culture conditions designed to maximize polypeptide production.
• a "recombinant fusion polypeptide” is a fusion of all or part of at least two polypeptides, which is made using the methods of genetic engineering.
• a “recombinant polypeptide” is a polypeptide resulting from the process of genetic engineering.
• the antibodies produced by a hybridoma cell line resulting from a cell fusion are not “recombinant polypeptides.”
• viral proteins produced by a cell as a result of viral infection with a naturally-occurring virus are also not “recombinant polypeptides” as meant herein unless the viral nucleic acid has been altered by genetic engineering prior to infecting the cell.
• Substantially similar polypeptides are at least 80%, optionally at least 90%, identical to each other in amino acid sequence and maintain or alter in a desirable manner the biological activity of the unaltered polypeptide.
• Conservative amino acid substitutions, unlikely to affect biological activity include, without limitation, the following: Ala for Ser, Val for lie, Asp for Glu, Thr for Ser, Ala for Gly, Ala for Thr, Ser for Asn, Ala for Val, Ser for Gly, Tyr for Phe, Ala for Pro, Lys for Arg, Asp for Asn, Leu for lie, Leu for Val, Ala for Glu, Asp for Gly, and these changes in the reverse. See e.g. Neurath et al., The Proteins.
• the groups are: 1) methionine, alanine, valine, leucine, and isoleucine; 2) cysteine, serine, threonine, asparagine, and glutamine; 3) aspartate and glutamate; 4) histidine, lysine, and arginine; 5) glycine and proline; and 6) tryptophan, tyrosine, and phenylalanine.
• the percent identity of two amino sequences can be determined by visual inspection and mathematical calculation, or more preferably, the comparison is done by comparing sequence information using a computer program such as the Genetics Computer Group (GCG; Madison, WI) Wisconsin package version 10.0 program, 'GAP' (Devereux et al. (1984), Nucl. Acids Res. 12: 387) or other comparable computer programs.
• GCG Genetics Computer Group
• 'GAP' Denssion et al. (1984), Nucl. Acids Res. 12: 387
• the preferred default parameters for the 'GAP' program includes: (1) the weighted amino acid comparison matrix of Gribskov and Burgess (1986), Nucl. Acids Res. 14: 6745, as described by Schwartz and Dayhoff, eds., Atlas of Polypeptide Sequence and Structure, National Biomedical Research Foundation, pp.
• Transition phase means a period of cell culture between a "growth phase” and a
• production phase During transition phase, the medium and environmental conditions are typically shifted from those designed to maximize proliferation to those designed to maximize polypeptide production.
• variable antibody immunoglobulin domain is an immunoglobulin domain that is identical or substantially similar to a V L or a V H domain of human or animal origin.
• the present invention is directed towards improved methods for culturing mammalian cells, which may have been genetically engineered to produce a particular polypeptide. h particular, the invention is directed towards culture methods that maximize the production of specific polypeptides. It is also directed towards methods of producing and obtaining such polypeptides from cultured mammalian cells. Polypeptides are useful in a large variety of diagnostic, therapeutic, agricultural, nutritional, and research applications.
• xanthine derivatives and hybrid polar compounds used separately or together can dramatically induce the production of recombinant polypeptide from CHO cell lines.
• addition of the xanthine derivative caffeine to the production phase of a cell culture enhances recombinant polypeptide production.
• the hybrid polar compound hexamethylene bisacetamide is also shown to be an effective inducer of recombinant polypeptide production.
• other inducers such as, for example, alkanoic acids, can also be added to either a xanthine derivative, a hybrid polar compound, or both.
• the invention relates to inducing increased production of a recombinant polypeptide from a cell grown in culture by exposing the cell to chemical inducers, including hybrid polar compounds and/or xanthine derivatives.
• the methods of the invention include culturing mammalian cells in medium comprising a hybrid polar compound, for example, hexamethylene bisacetamide (HMBA), optionally at temperatures between about 29°C and 35°C or from about 30°C to about 33°C.
• a hybrid polar compound for example, hexamethylene bisacetamide (HMBA)
• HMBA hexamethylene bisacetamide
• Other embodiments of the invention encompass culture conditions in which an alkanoic acid and/or a xanthine, in addition to the hybrid polar compound, are added to the culture medium.
• a xanthine and a hybrid polar compound and culture temperatures between about 29°C and 36°C are used.
• Another embodiment comprises the addition of an alkanoic acid and a hybrid polar compound plus culture temperatures between about 29°C and 36°C.
• Still another embodiment comprises addition of a xanthine, an alkanoic acid, and a hybrid polar compound plus culture temperatures between about 29°C and 36°C.
• cell culture using the methods of the invention can take place during a production phase, as distmguished from a growth phase.
• a growth phase can be distinguished from a production phase by, for example, a temperature shift and/or a change in medium such as, for example, the addition of one or more inducers.
• the invention provides a method comprising growing in culture a mammalian cell that has been genetically engineered to produce a polypeptide; and adding to the culture a xanthine derivative.
• a genetically engineered cell may be a cell that has been transformed with a recombinant vector encoding the polypeptide.
• the polypeptide can be expressed under the control of a heterologous promoter such as, for example, a CMV promoter.
• the cell does not naturally express the polypeptide or only naturally expresses the polypeptide at very low levels (in the absence of genetic engineering), h another aspect, the invention provides a culture containing a cell genetically engineered to produce a polypeptide, a production medium, and the xanthine derivative.
• compositions of the invention can be used in combination with any other known or yet to be discovered methods of inducing the production of recombinant polypeptides.
• Such techniques include cold temperature shift, alkanoic acid additions (as described in U.S. Patent No. 5,705,364 to Etcheverry et al., incorporated herein by reference), DMF, and DMSO, to name just a few examples, as well as any yet to be described and/or discovered induction techniques.
• inducing polypeptide production or “induction” refers to culturing cells under a set of conditions designed to maximize the total amount of a desired polypeptide made by the cells.
• An “inducer” is an agent that, when added to culture medium, can increase the production of a desired polypeptide in at least some cell lines.
• Combining the addition of xanthine derivatives with other protein induction techniques can have a synergistic effect on polypeptide induction, allowing for lower additions of xanthine derivatives and/or lower additions of other inducing agents and/or more conservative temperature shifts.
• the other methods of induction can take place at around the same time as xanthine addition, and/or before and/or after xanthine addition. For example, one can shift the temperature of the culture at day 0, and then add a xanthine derivative and/or a hybrid polar compound, and optionally other chemical inducers, later, e.g.
• xanthine derivatives and/or hybrid polar compounds can be added to the culture during the production phase, separated by about 12, 24, 48, and/or 72 hours or more, with or without additions of other inducing agents or changes in culture conditions.
• an inducer can be added at day 0 and again at day 4.
• an inducer can be added for the first time one, two, three, or four days after a temperature shift.
• the invention entails performing a low temperature shift (shifting the temperature of the medium from the optimal growth temperature, usually around 37°C, to a lower temperature, usually from about 29°C to about 36°C, and optionally about 30°C to about 34°C at the time of, before, and/or after adding the xanthine derivative or the hybrid polar compound.
• a low temperature shift shifting the temperature of the medium from the optimal growth temperature, usually around 37°C, to a lower temperature, usually from about 29°C to about 36°C, and optionally about 30°C to about 34°C at the time of, before, and/or after adding the xanthine derivative or the hybrid polar compound.
• an alkanoic acid or salt thereof e.g. sodium butyrate
• Alkanoic acid can be added at concentrations typically used for induction, or even at lower concentrations than would typically be used.
• xanthine derivatives have the structure illustrated below.
• X, Y, and Z can be independently selected from a straight or branched chain alkyl radical having from 1 to 12 carbons, a straight or branched chain alkynyl radical having from 1 to 12 carbons (including a propynyl radical), a straight or branched chain acyl radical having from 1 to 12 carbons, a straight or branched chain radical with the structure -R-acyl containing from 1 to 12 carbons where R is a saturated or unsaturated aliphatic group, a straight or branched chain allenyl radical having from 1 to 12 carbons, a straight or branched chain hydroxyalkyl radical having from 1 to 12 carbons, a straight or branched chain hydroxyallenyl radical having from 1 to 12 carbons, a straight or branched chain radical with the structure -allenyl- halogen having from 1 to 12 carbons, a cyclohexyl radical, and hydrogen.
• At least one of X, Y and Z is a methyl group.
• each of X and Y independently represents a hydrogen atom, a linear or branched alkyl radical having up to 5 carbon atoms, an allyl radical, a propynyl radical or a cyclohexyl radical, with the proviso that X and Y do not simultaneously represent a hydrogen atom
• Z represents a hydrogen, methyl, ethyl, hydroxymethyl, hydroxyethyl or heterocyclo radical.
• xanthine derivatives that can be used in the methods and compositions of the invention include, but are not limited to, caffeine (1,3,7- trimethylxanthine), theophylline (1,3-dimethylxanthine), theobromine (3,7- dimethylxanthine), 3-isobutyl-l-methylxanthine, 3-butyl-l-methylxanthine, 1,3,7- triethylxanthine, 3-cyclohexyl-l-ethylxanthine, 3-ethyl-l-propynylxanthine, 3-ethyl-l- pentylxanthine, pentoxifylline, and aminophylline.
• Aminophylline is theophylline compound with 1,2-ethylenediamine (2:1) dihydrate.
• the xanthine derivative is added at a concentration in the culture from about 0.0005 to about 25 millimolar, optionally from about 0.001 to about 10 millimolar, from about 0.005 to about 5 millimolar, or from about 0.01 to about 3 millimolar.
• concentration of the xanthine derivative will vary depending upon its activity and the cell line, and can be determined by those skilled in the art using the guidance provided herein.
• the xanthine derivative can be dissolved in any appropriate solvent.
• 3- isobutyl- 1-methylxanthine (IBX) can be dissolved in water, but must to be heated to almost the boiling point.
• IBX can be dissolved in the solvents DMSO (dimethylsulfoxide), DMF (dimethylformamide), or DMA (dimethylacetamide).
• IBX can also be easily dissolved as a 100 millimolar stock solution in 0.5 M NaOH. Dilutions of this stock solution can be added to the induction media as it is being prepared (pre-sterile) and the effects of the NaOH should be inconsequential since base must often be added to raise the pH of the medium to 7.0.
• xanthine derivatives for use in the invention are cAMP phosphodiesterase inhibitors.
• cAMP phosphodiesterase inhibitors that are not xanthine derivatives could also be used to induce polypeptide production in alternative methods of the invention.
• inducers include but are not limited to imidazopyrimidine, pyrazolopyridine, etazolate, pyrazoloquinoline, and triazoloquinazoline (Pflugers Archiv 407: S31, 1986).
• Other examples cAMP phosphodiesterase inhibitors can be found in US Patent No. RE37,234, which is incorporated by reference herein.
• the hybrid polar compounds can have two polar groups separated by a non-polar carbon chain, such as those described in Richon et al. (1998), Proc. Natl. Acad. Sci. 95: 3003-07, Marks et al. (1994), Proc. Natl. Acad. Sci. 91: 10251-54, US Patent Nos. 5,055,608 and 6,087,367.
• the hybrid polar compounds of the invention may have the property of inducing one or more changes characteristic of a terminally differentiated state of the host cells. These compounds include those with the structure:
• Ri and R 2 can be the same as or different from each other.
• Ri and R 2 can each be a carbonyl group to which a hydrogen atom, a hydroxyl group, a substituted or unsubstituted, branched or unbranched alkyl, alkenyl, cycloalkyl, aryl, alkynl, allenyl, allyl, alkyloxy, aryloxy, arylalkyloxy, which contains 12 or fewer carbon atoms, or pyridine group, may also be attached.
• the "n” can be an integer from about four to about eight.
• HMBA is included within this class of hybrid polar compounds, and its structure is:
• the present invention further encompasses the use of hybrid polar compounds with the following structure:
• R 3 and R can be the same as or different from each other.
• each is a substituted or unsubstituted arylamino, cycloalkylamino, pyridineamino, piperidino, 9-purine-6-amine, or thiozoleamino group containing 12 or fewer carbon atoms.
• R 3 is equal to R 5 — N — Re, where R 5 and R 6 are the same as or different from each other and are a hydrogen atom, a hydroxyl group, a substituted or unsubstituted, branched or unbranched alkyl, alkenyl, cycloalkyl, aryl, alkynl, allenyl, allyl, alkyloxy, aryloxy, arylalkyloxy, or pyridine group, which contains 12 or fewer carbon atoms, or R 5 and Re bond together to form a piperidine group, and R 4 is a hydroxylamino, hydroxyl, amino, alkylamino, dialkylamino, or alkyloxy group, which contains 12 or fewer carbon atoms.
• the "n" is an integer from about four to about eight.
• the invention further embraces the use of all compounds disclosed in US Patent No. 6,087,367, US Patent No. 5,055,608, Richon et al., supra, and Marks et al., supra, i some of these, the apolar carbon chain may be shorter than 4 carbons and longer than 8 carbons, and it may be interrupted by aromatic groups, apolar groups, and/or polar groups.
• HMBA HMBA
• it can be added at concentrations from about 0.1 millimolar to about 20 millimolar, optionally, between about 0.1 millimolar and about 5 millimolar.
• Other hybrid polar compounds may be active at lower or higher concentrations.
• the optimal concentration for a particular hybrid polar compound will vary depending on its activity and the cell line in which it is used and can be determined by one of skill in the art using routine methods and the guidance provided herein.
• compounds such as suberoylanilide hydroxamic acid or m-carboxycinnamic acid bishydroxamide can be used at concentrations about one thousand fold lower than those required for HMBA, from about 0.01 micromolar to about 10 micromolar. See Richon et al., supra.
• Concentrations of hybrid polar compounds required to induce cell differentiation as disclosed in Marks et al. (supra) and Richon et al. (supra) can be used as a guide for determining the concentration of a hybrid polar compound required to enhance polypeptide production. Determination of the concentration needed for a specific hybrid polar compound used in a specific cell line can be done using routine methods, as described herein and the guidance provided in Richon et al. (supra) and Marks et al. (supra).
• the alkanoic acids for use in the invention include the selected acid and/or a corresponding salt.
• the acids include straight or branched chain, saturated or unsaturated alkanoic acids or salts thereof.
• An alkanoic acid generally comprises from one to ten carbon atoms.
• alkanoic acids contemplated by the invention are pentanoic acid, butyric acid, isobutyric acid, propionic acid, and acetic acid.
• Concentrations for alkanoic acids encompassed by the invention range from about 0.05 millimolar to about 10 millimolar, optionally from about 0.1 millimolar to about 2 millimolar. Appropriate concentrations of alkanoic acids will vary depending upon their activity and the cell line and can be determined by one of skill in the art using routine methods and the guidance provided herein.
• An exemplary salt of butyric acid is sodium butyrate.
• Appropriate salts of the alkanoic acids described above include those comprising sodium, potassium, or ammonium groups, among others.
• polypeptides for expression are polypeptide-based drugs, also known as biologies.
• the polypeptides are secreted as extracellular products.
• the polypeptide being produced can comprise part or all of a polypeptide that is identical or substantially similar to a naturally-occurring polypeptide, and/or it may, or may not, be a recombinant fusion polypeptide.
• the polypeptide may be a human polypeptide, a fragment thereof, or a substantially similar polypeptide that is at least 15 amino acids in length. It may comprise a non-antibody polypeptide and/or an antibody. It may be produced intracellularly or be secreted into the culture medium from which it can be recovered. It may or may not be a soluble polypeptide.
• the polypeptide being produced can comprise part or all of a polypeptide that is identical or substantially similar to a naturally-occurring polypeptide, and/or it may, or may not, be a recombinant fusion polypeptide. It may comprise a non-antibody polypeptide and/or an antibody. It may be produced intracellularly or be secreted into the culture medium from which it can be recovered.
• the invention can be used to induce the production of just about any polypeptide, and is particularly advantageous for polypeptides whose expression is under the control of a strong promoter, such as for example, a viral promoter, and/or polypeptides that are encoded on a message that has an adenoviral tripartite leader element.
• a strong promoter such as for example, a viral promoter
• polypeptides that are encoded on a message that has an adenoviral tripartite leader element.
• useful expression vectors that can be used to produce proteins are disclosed in International Application WO 01/27299 and in McMahan et al., (1991), EMBO J. 10: 2821, which describes the pDC409 vector.
• a protein is generally understood to be a polypeptide of at least about 10 amino acids, optionally about 25, 75, or 100 amino acids.
• a flt3 ligand as described in International Application WO 94/28391, incorporarted herein by reference
• CD40 ligand as described in US Patent No. 6,087,329 incorporated herein by reference
• erythropoeitin thrombopoeitin
• calcitonin leptin
• IL-2
• Fas ligand ligand for receptor activator of NF-kappa B (RANKL, as described in International Application WO 01/36637, incorporated herein by reference), tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL, as described in International Application WO 97/01633, incorporated herein by reference), thymic stroma-derived lymphopoietin, granulocyte colony stimulating factor, granulocyte-macrophage colony stimulating factor (GM-CSF, as described in Australian Patent No.
• mast cell growth factor a cell growth factor
• stem cell growth factor described in e.g. US Patent No.6,204,363, incorporated herein by reference
• epidermal growth factor keratinocyte growth factor
• megakaryote growth and development factor RANTES
• growth hormone insulin, insulinotropin, insulin-like growth factors, parathyroid hormone
• interferons including ⁇ interferons, ⁇ interferon, and consensus interferons (such as those described in US Patent Nos.
• receptors and antagonists include: both forms of tumor necrosis factor receptor (TNFR, referred to as p55 and p75, as described in US Patent No. 5,395,760 and US Patent No. 5,610,279, both of which are incorporated herein by reference), Interleukin-1 (IL-1) receptors (types I and II; described in EP Patent No. 0460 846, US Patent No.
• IL-1 receptor antagonists such as those described in US Patent No. 6,337,072, incorporated herein by reference
• IL-1 antagonists or inhibitors such as those described in US Patent Nos. 5,981,713, 6,096,728, and 5,075,222, all of which are incorporated herein by reference
• IL-2 receptors such as those described in US Patent No. 0367 566 and US Patent No.
• EL-15 receptors JL-17 receptors, IL-18 receptors, granulocyte-macrophage colony stimulating factor receptor, granulocyte colony stimulating factor receptor, receptors for oncostatin-M and leukemia inhibitory factor, receptor activator of NF-kappa B (RANK, described in WO 01/36637 and US Patent No. 6,271,349, both of which are incorporated by reference), osteoprotegerin (described in e.g. US. Patent No. 6,015,938, incorporated by reference), receptors for TRAIL (including TRAIL receptors 1, 2, 3, and 4), and receptors that comprise death domains, such as Fas or Apoptosis-inducing Receptor (AIR).
• TRAIL including TRAIL receptors 1, 2, 3, and 4
• AIR Apoptosis-inducing Receptor
• CD polypeptides polypeptides comprising all or part of the amino acid sequences of differentiation antigens
• ligands or polypeptides substantially similar to either of these are disclosed in Leukocyte Typing VI (Proceedings of the Vlth).
• CD antigens include CD22, CD27, CD30, CD39, CD40, and ligands thereto (CD27 ligand, CD30 ligand, etc.).
• CD antigens are members of the TNF receptor family, which also includes 4 IBB and OX40.
• the ligands are often members of the TNF family, as are 41BB ligand and OX40 ligand. Accordingly, members of the TNF and TNFR families can also be purified using the present invention.
• Enzymatically active polypeptides or their ligands can also be produced according to the methods of the invention.
• Examples include polypeptides comprising all or part of one of the following polypeptides or their ligands or a polypeptide substantially similar to one of these: metalloproteinase-disintegrin family members, various kinases, glucocerebrosidase, superoxide dismutase, tissue plasminogen activator, Factor VHI, Factor IX, apolipoprotein E, apolipoprotein A-I, globins, an IL-2 antagonist, alpha-1 antitrypsin, TNF-alpha Converting Enzyme, ligands for any of the above-mentioned enzymes, and numerous other enzymes and their ligands.
• the methods of the invention can also be used to produce antibodies or portions thereof and chimeric antibodies, i.e. antibodies having human constant antibody immunoglobulin domains coupled to one or more murine variable antibody immunoglobulin domain, fragments thereof, or substantially similar proteins.
• the method of the invention may also be used to produce conjugates comprising an antibody and a cytotoxic or luminescent substance.
• Such substances include: maytansine derivatives (such as DM1); enterotoxins (such as a Staphlyococcal enterotoxin); iodine isotopes (such as iodine-125); technium isotopes (such as Tc-99m); cyanine fluorochromes (such as Cy5.5.18); and ribosome-inactivating polypeptides (such as bouganin, gelonin, or saporin-S6).
• enterotoxins such as a Staphlyococcal enterotoxin
• iodine isotopes such as iodine-125
• technium isotopes such as Tc-99m
• cyanine fluorochromes such as Cy5.5.18
• ribosome-inactivating polypeptides such as bouganin, gelonin, or saporin-S6.
• the invention can also be used to produce chimeric proteins selected in vitro to bind
• antibodies, in vztr ⁇ -selected chimeric proteins, or antibody/cytotoxin or antibody/luminophore conjugates that can be produced by the methods of the invention include those that recognize any one or a combination of polypeptides including, but not limited to, the above-mentioned proteins and/or the following antigens: CD2, CD3, CD4, CD8, GDI la, CD14, CD18, CD20, CD22, CD23, CD25, CD33, CD40, CD44, CD52, CD80 (B7.1), CD86 (B7.2), CD147, IL-l ⁇ , IL-l ⁇ , IL-2, IL-3, IL-7, IL-4, IL-5, IL-8, DL-10, IL-2 receptor, IL-4 receptor, IL-6 receptor, IL-13 receptor, IL-18 receptor subunits, PDGF- ⁇ and analogs thereof (such as those described in US Patent Nos.
• VEGF vascular endothelial growth factor
• TGF TGF- ⁇ 2, TGF- ⁇ l
• EGF receptor including those described in US Patent No. 6,235,883 Bl, incorporated by reference
• VEGF receptor hepatocyte growth factor
• osteoprotegerin ligand interferon gamma
• B lymphocyte stimulator BlyS, also known as BAFF, THANK, TALL-1, and zTNF4; see Do and Chen- Kiang (2002), Cytokine Growth Factor Rev.
• the invention may also be used to produce all or part of an anti-idiotypic antibody or a substantially similar polypeptide, including anti-idiotypic antibodies against: an antibody targeted to the tumor antigen gp72; an antibody against the ganglioside GD3; an antibody against the ganglioside GD2; or antibodies substantially similar to these.
• the methods of the invention can also be used to produce recombinant fusion polypeptides comprising any of the above-mentioned polypeptides.
• recombinant fusion polypeptides comprising one of the above-mentioned polypeptides plus a multimerization domain, such as a leucine zipper, a coiled coil, an Fc portion of an antibody, or a substantially similar protein, can be produced using the methods of the invention.
• a multimerization domain such as a leucine zipper, a coiled coil, an Fc portion of an antibody, or a substantially similar protein
• TNFR:Fc or RANK:Fc polypeptides in which a portion of TNFR or RANK is fused to an Fc portion of an antibody
• TNFR:Fc comprises the Fc portion of an antibody fused to an extracellular domain of TNFR, which includes amino acid sequences substantially similar to amino acids 1-163, 1-185, or 1-235 of Figure 2A of US Patent No. 5,395, 760, which is incorporated by reference.
• RANK:Fc is described in International Application WO 01/36637, which is incorporated by reference.
• the polypeptides are expressed under the control of a heterologous control element such as, for example, a promoter that does not in nature direct the production of that polypeptide.
• a heterologous control element such as, for example, a promoter that does not in nature direct the production of that polypeptide.
• the promoter can be a strong viral promoter (e.g., CMV, SV40) that directs the expression of a mammalian polypeptide.
• the host cell may or may not normally produce the polypeptide.
• the host cell can be a CHO cell that has been genetically engineered to produce a human polypeptide, meaning that nucleic acid encoding the human polypeptide has been introduced into the CHO cell.
• the host cell can be a human cell that has been genetically engineered to produce increased levels of a human polypeptide normally present only at very low levels (e.g., by replacing the endogenous promoter with a strong viral promoter).
• an expression vector encoding the recombinant polypeptide can be transferred, for example by transfection or viral infection, into a substantially homogeneous culture of host cells.
• the expression vector which can be constructed using the methods of genetic engineering, can include nucleic acids encoding the polypeptide of interest operably linked to suitable regulatory sequences.
• the regulatory sequences are typically derived from mammalian, microbial, viral, and/or insect genes.
• Examples of regulatory sequences include transcriptional promoters, operators, and enhancers, a ribosomal binding site (see e.g. Kozak (1991), J. Biol. Chem. 266:19867-19870), appropriate sequences to control transcriptional and translational initiation and termination, polyadenylation signals (see e.g. McLauchlan et al. (1988), Nucleic Acids Res. 16:5323-33), and matrix and scaffold attachment sites (see Phi-Van et al. (1988), Mol. Cell. Biol. 10:2302-07; Stief et al.
• Nucleotide sequences are operably linked when the regulatory sequence functionally relates to the polypeptide coding sequence.
• a promoter nucleotide sequence is operably linked to a polypeptide coding sequence if the promoter nucleotide sequence controls the transcription of the coding sequence.
• a gene encoding a selectable marker is generally incorporated into the expression vector to facilitate the identification of recombinant cells. Transcriptional and translational control sequences for mammalian host cell expression vectors can be excised from viral genomes.
• promoter and enhancer sequences are derived from polyoma virus, adenovirus 2, simian virus 40 (SV40), and human cytomegalovirus (CMV).
• SV40 adenovirus 2
• CMV human cytomegalovirus
• the human CMV promoter/enhancer of immediate early gene 1 may be used. See e.g. Patterson et al. (1994), Applied Microbiol. Biotechnol. 40:691-98.
• DNA sequences derived from the SV40 viral genome for example, SV40 origin, early and late promoter, enhancer, splice, and polyadenylation sites can be used to provide other genetic elements for expression of a structural gene sequence in a mammalian host cell.
• Viral early and late promoters are particularly useful because both are easily obtained from a viral genome as a fragment, which can also contain a viral origin of replication (Fiers et al. (1978), Nature 273: 113; Kaufman (1990), Meth. in Enzymol. 185:487-511). Smaller or larger SV40 fragments can also be used, provided the approximately 250 bp sequence extending from the Hind III site toward the Bgl I site located in the SV40 viral origin of replication site is included.
• a sequence encoding an appropriate native or heterologous signal peptide can be incorporated into the expression vector, to promote extracellular secretion of the recombinant polypeptide.
• the signal peptide will be cleaved from the recombinant polypeptide upon secretion from the cell.
• the choice of signal peptide or leader depends on the type of host cells in which the recombinant polypeptide is to be produced. Examples of signal peptides that are functional in mammalian host cells include the signal sequence for interleukin-7 (IL-7) described in US Patent No. 4,965,195, the signal sequence for interleukin-2 receptor described in Cosman et al.
• electroporation or bombardment with microprojectiles coated with nucleic acids can be used to transfect mammalian cells using procedures, such as those in Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd ed. Vol. 1-3, Cold Spring Harbor Laboratory Press (1989) and Fitzpatrick-McElligott (1992), Biotechnology (NY) 10(9): 1036-40. Selection of stable transformants can be performed using methods known in the art, such as, for example, resistance to cytotoxic drugs. Kaufman et al. ((1990), Meth. in Enzymology 185:487-511), describes several selection schemes, such as dihydrofolate reductase (DHFR) resistance.
• DHFR dihydrofolate reductase
• a suitable host strain for DHFR selection can be CHO strain DX-B11, which is deficient in DHFR. Urlaub and Chasin (1980), Proc. Natl. Acad. Sci. USA 77:4216-4220.
• a plasmid expressing the DHFR cDNA can be introduced into strain DX-B11, and only cells that contain the plasmid can grow in the appropriate selective media.
• selectable markers include cDNAs conferring resistance to antibiotics, such as G418 and hygromycin B. Cells harboring the vector can be selected on the basis of resistance to these compounds.
• Additional control sequences shown to improve expression of heterologous genes from mammalian expression vectors include such elements as the expression augmenting sequence element (EASE) derived from CHO cells (Morris et al., in Animal Cell Technology, pp. 529-534 (1997); US Patent Nos. 6,312,951 Bl, 6,027,915, and 6,309,841 Bl) and the tripartite leader (TPL) and VA gene RNAs from Adenovirus 2 (Gingeras et al. (1982), J. Biol Chem. 257:13475-13491).
• EASE expression augmenting sequence element
• TPL tripartite leader
• VA gene RNAs from Adenovirus 2
• IVS internal ribosome entry site
• a heterologous cDNA as part of a dicistronic mRNA followed by the gene for a selectable marker (e.g. DHFR) has been shown to improve transfectability of the host and expression of the heterologous cDNA (Kaufman et al. (1990), Methods in Enzymol. 185:487-511).
• exemplary expression vectors that employ dicistronic mRNAs are pTR-DC/GFP described by Mosser et al., Biotechniques 22: 150-161 (1997), and p2A5I described by Morris et al., in Animal Cell Technology, pp. 529-534 (1997).
• a useful high expression vector, pCAVNOT has been described by Mosley et al. ((1989), Cell 59:335-348).
• Other expression vectors for use in mammalian host cells can be constructed as disclosed by Okayama and Berg ((1983), Mol. Cell. Biol. 3:280).
• a useful system for stable high level expression of mammalian cDNAs in C127 murine mammary epithelial cells can be constructed substantially as described by Cosman et al. ((1986), Mol. Immunol. 23:935).
• Additional useful mammalian expression vectors are described in EP Patent No.-A-O 367 566 and WO 01/27299 Al.
• the vectors can be derived from retroviruses.
• a heterologous signal sequence can be added, such as one of the following sequences: the signal sequence for IL-7 described in US Patent No. 4,965,195; the signal sequence for IL-2 receptor described in Cosman et al. (Nature 312:768 (1984)); the IL-4 signal peptide described in EP Patent No. 0 367 566; the type I IL-1 receptor signal peptide described in US Patent No. 4,968,607; and the type II IL-1 receptor signal peptide described in EP Patent No. 0460 846.
• the polypeptides can be produced recombinantly in eukaryotic cells and are preferably secreted by host cells adapted to grow in cell culture.
• host cells for use in the invention are preferably mammalian cells.
• the cells can be also genetically engineered to express a gene of interest, can be mammalian production cells adapted to grow in cell culture, and/or can be homogenous cell lines.
• Examples of such cells commonly used in the industry are VERO, BHK, HeLa, CVl (including Cos), MDCK, 293, 3T3, myeloma cell lines (e.g., NSO, NS1), PC12, WI38 cells, and Chinese hamster ovary (CHO) cells, which are widely used for the production of several complex recombinant polypeptides, e.g. cytokines, clotting factors, and antibodies (Brasel et al. (1996), Blood 88:2004-2012; Kaufman et al. (1988), J-Biol Chem 263:6352-6362; McKinnon et al. (1991), J Mol Endocrinol 6:231-239; Wood et al.
• cytokines e.g. cytokines, clotting factors, and antibodies
• DHFR dihydrofolate reductase
• CHO cells and recombinant polypeptides expressed in them have been extensively characterized and have been approved for use in clinical commercial manufacturing by regulatory agencies.
• the methods of the invention can also be practiced using hybridoma cell lines that produce an antibody. Methods for making hybridoma lines are well known in the art. See e.g. Berzofsky et al. in Paul, ed., Fundamental Immunology, Second Edition, pp.315-356, at 347-350, Raven Press Ltd., New York (1989). Cell lines derived from the above-mentioned lines are also suitable for practicing the invention.
• a mammalian host cell is cultured under conditions that promote the production of the polypeptide of interest, which can be an antibody or a recombmant polypeptide.
• Basal cell culture medium formulations are well known in the art. To these basal culture medium formulations the skilled artisan will add components such as amino acids, salts, sugars, vitamins, hormones, growth factors, buffers, antibiotics, lipids, trace elements and the like, depending on the requirements of the host cells to be cultured.
• the culture medium may or may not contain serum and/or protein.
• tissue culture media including serum-free and/or defined culture media, are commercially available for cell culture.
• Tissue culture media is defined, for purposes of the invention, as a media suitable for growth of animal cells, and preferably mammalian cells, in in vitro cell culture.
• tissue culture media contains a buffer, salts, energy source, amino acids, vitamins and trace essential elements. Any media capable of supporting growth of the appropriate eukaryotic cell in culture can be used; the invention is broadly applicable to eukaryotic cells in culture, particularly mammalian cells, and the choice of media is not crucial to the invention.
• Tissue culture media suitable for use in the invention are commercially available from, e.g., ATCC (Manassas, VA).
• any one or combination of the following media can be used: RPMI-1640 Medium, RPMI-1641 Medium, Dulbecco's Modified Eagle's Medium (DMEM), Minimum Essential Medium Eagle, F-12K Medium, Ham's F12 Medium, Iscove's Modified Dulbecco's Medium, McCoy's 5A Medium, Leibovitz's L-15 Medium, and serum-free media such as EX-CELLTM 300 Series (available from JRH Biosciences, Lenexa, Kansas, USA), among others, which can be obtained from the American Type Culture Collection or JRH Biosciences, as well as other vendors.
• DMEM Dulbecco's Modified Eagle's Medium
• F-12K Medium Minimum Essential Medium Eagle
• Ham's F12 Medium Ham's F12 Medium
• Iscove's Modified Dulbecco's Medium McCoy's 5A Medium
• Leibovitz's L-15 Medium and serum-free media
• serum-free media such as EX-
• the medium When defined medium that is serum-free and/or peptone-free is used, the medium is usually highly enriched for amino acids and trace elements. See, for example, US Patent Nos. 5,122,469 to Mather et al. and 5,633,162 to Keen et al.
• cells can be grown in serum-free, protein-free, growth factor-free, and/or peptone-free media.
• serum-free as applied to media includes any mammalian cell culture medium that does not contain serum, such as fetal bovine serum.
• insulin-free as applied to media includes any medium to which no exogenous insulin has been added. By exogenous is meant, in this context, other than that produced by the culturing of the cells themselves.
• IGF-1-free as applied to media includes any medium to which no exogenous Insulin-like growth factor-1 (IGF-1) or analog (such as, for example, LongR3, [Ala31], or [Leu24][Ala31] IGF-1 analogs available from GroPep Ltd. of Thebarton, South Australia) has been added.
• growth-factor free as applied to media includes any medium to which no exogenous growth factor (e.g., insulin, IGF-1) has been added.
• protein-free as applied to media includes medium free from exogenously added protein, such as, for example, transferrin and the protein growth factors IGF-1 and insulin. Protein-free media may or may not have peptones.
• peptone-free as applied to media includes any medium to which no exogenous protein hydrolysates have been added such as, for example, animal and/or plant protein hydrolysates. Eliminating peptone from media has the advantages of reducing lot to lot variability and enhancing processing such as filtration.
• Chemically defined media are media in which every component is defined and obtained from a pure source, preferably a non-animal source.
• an enriched medium that could support increased polypeptide production may comprise a mixture of two or more commercial media, such as, for instance, DMEM and Ham's F12 media combined in ratios such as, for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, or even up to 1:15 or higher.
• a medium can be enriched by the addition of nutrients, such as amino acids or peptone, and/or a medium (or most of its components with the exceptions noted below) can be used at greater than its usual, recommended concentration, for example at 2X, 3X, 4X, 5X, 6X, 7X, 8X, or even higher concentrations.
• nutrients such as amino acids or peptone
• a medium or most of its components with the exceptions noted below
• concentration for example at 2X, 3X, 4X, 5X, 6X, 7X, 8X, or even higher concentrations.
• IX means the standard concentration
• 2X means twice the standard concentration
• medium components that can substantially affect osmolarity, such as salts cannot be increased in concentration so that the osmolarity of the medium falls outside of an acceptable range.
• a medium may, for example, be 8X with respect to all components except salts, which can be present at only IX.
• An enriched medium may be serum free and/or protein free.
• a medium may be supplemented periodically during the time a culture is maintained to replenish medium components that can become depleted such as, for example, vitamins, amino acids, and metabolic precursors.
• different media and temperatures may have somewhat different effects on different cell lines, and the same medium and temperature may not be suitable for all cell lines.
• mammalian cells may be cultured in suspension or while attached to a solid substrate.
• mammalian cells may be cultured, for example, in fluidized bed bioreactors, hollow fiber bioreactors, roller bottles, shake flasks, or stirred tank bioreactors, with or without microcarriers, and operated in a batch, fed batch, continuous, semi- continuous, or perfusion mode.
• the methods according to the present invention may be used to improve the production of recombinant polypeptides in both single phase and multiple phase culture processes.
• a single phase process cells are inoculated into a culture environment and the disclosed methods are employed during the single production phase.
• a multiple stage process cells are cultured in two or more distinct phases. For example cells may be cultured first in a growth phase, under environmental conditions that maximize cell proliferation and viability, then transferred to a production phase, under conditions that maximize polypeptide production.
• the growth and production phases may be preceded by, or separated by, one or more transition phases.
• the methods according to the present invention are employed at least during the production phase.
• a growth phase may occur at a higher temperature than a production phase.
• a growth phase may occur at a first temperature from about 35°C to about 38°C
• a production phase may occur at a second temperature from about 29°C to about 36°C, optionally from about 30°C to about 33°C.
• Chemical inducers of polypeptide production such as, for example, caffeine, butyrate, and HMBA, may be added at the same time as, before, and/or after a temperature shift. If inducers are added after a temperature shift, they can be added from one hour to five days after the temperature shift, optionally from one to two days after the temperature shift.
• the resulting expressed polypeptide can then be collected.
• the polypeptide can purified, or partially purified, from such culture or component (e.g., from culture medium or cell extracts or bodily fluid) using known processes.
• partially purified means that some fractionation procedure, or procedures, have been carried out, but that more polypeptide species (at least 10%) than the desired polypeptide is present.
• purified is meant that the polypeptide is essentially homogeneous, i.e., less than 1% contaminating polypeptides are present.
• Fractionation procedures can include but are not limited to one or more steps of filtration, centrifugation, precipitation, phase separation, affinity purification, gel filtration, ion exchange chromatography, hydrophobic interaction chromatography (EUC; using such resins as phenyl ether, butyl ether, or propyl ether), HPLC, or some combination of above.
• EUC hydrophobic interaction chromatography
• the purification of the polypeptide can include an affinity column containing agents which will bind to the polypeptide; one or more column steps over such affinity resins as concanavalin A-agarose, heparin-TOYOPEARL ® (Toyo Soda Manufacturing Co., Ltd., Japan) or Cibacromblue 3GA SEPHAROSE ® (Pharmacia Fine Chemicals, Inc., New York); one or more steps involving elution; and/or immunoaffinity chromatography.
• the polypeptide can be expressed in a form that facilitates purification.
• fusion polypeptide such as those of maltose binding polypeptide (MBP), glutathione-S-transferase (GST), or thioredoxin (TRX).
• MBP maltose binding polypeptide
• GST glutathione-S-transferase
• TRX thioredoxin
• Kits for expression and purification of such fusion polypeptides are commercially available from New England BioLab (Beverly, Mass.), Pharmacia (Piscataway, NJ.) and InVitrogen, respectively.
• the polypeptide can be tagged with an epitope and subsequently purified by using a specific antibody directed to such epitope.
• FLAG ® is commercially available from Kodak (New Haven, Conn.).
• an affinity column comprising a polypeptide-binding protein, such as a monoclonal antibody to the recombinant polypeptide, to affinity-purify expressed polypeptides.
• Other types of affinity purification steps can be a Protein A or a Protein G column, which affinity agents bind to proteins that contain Fc domains.
• Polypeptides can be removed from an affinity column using conventional techmques, e.g., in a high salt elution buffer and then dialyzed into a lower salt buffer for use or by changing pH or other components depending on the affinity matrix utilized, or can be competitively removed using the naturally occurring substrate of the affinity moiety.
• the desired degree of final purity depends on the intended use of the polypeptide.
• a relatively high degree of purity is desired when the polypeptide is to be administered in vivo, for example.
• the polypeptides are purified such that no polypeptide bands corresponding to other polypeptides are detectable upon analysis by SDS-polyacrylamide gel electrophoresis (SDS-PAGE). It will be recognized by one skilled in the pertinent field that multiple bands corresponding to the polypeptide can be visualized by SDS-PAGE, due to differential glycosylation, differential post-translational processing, and the like.
• the polypeptide of the invention is purified to substantial homogeneity, as indicated by a single polypeptide band upon analysis by SDS-PAGE. The polypeptide band can be visualized by silver staining, Coomassie blue staining, or (if the polypeptide is radiolabeled) by autoradiography.
• the invention also optionally encompasses further formulating the polypeptides.
• formulating is meant that the polypeptides can be buffer exchanged, sterilized, bulk-packaged, and/or packaged for a final user.
• sterile bulk form means that a formulation is free, or essentially free, of microbial contamination (to such an extent as is acceptable for food and/or drug purposes), and is of defined composition and concentration.
• sterile unit dose form means a form that is appropriate for the customer and/or patient administration or consumption.
• Such compositions can comprise an effective amount of the polypeptide, in combination with other components such as a physiologically acceptable diluent, carrier, or excipient.
• physiologically acceptable means a non-toxic material that does not interfere with the effectiveness of the biological activity of the active ingredient(s).
• Formulations suitable for administration include aqueous and non-aqueous sterile injection solutions which may contain anti-oxidants, buffers, bacteriostats, and solutes which render the formulation isotonic with the blood of the recipient; and aqueous and non-aqueous sterile suspensions which may include suspending agents or thickening agents.
• the polypeptides can be formulated according to known methods used to prepare pharmaceutically useful compositions.
• Suitable formulations for pharmaceutical compositions include those described in Remington's Pharmaceutical Sciences, 16th ed. 1980, Mack Publishing Company, Easton, PA.
• compositions can be complexed with polyethylene glycol (PEG), metal ions, or incorporated into polymeric compounds such as polyacetic acid, polyglycolic acid, hydrogels, dextran, etc., or incorporated into liposomes, microemulsions, micelles, unilamellar or multilamellar vesicles, erythrocyte ghosts or spheroblasts.
• PEG polyethylene glycol
• metal ions or incorporated into polymeric compounds such as polyacetic acid, polyglycolic acid, hydrogels, dextran, etc.
• liposomes such as polyacetic acid, polyglycolic acid, hydrogels, dextran, etc.
• Suitable lipids for liposomal formulation include, without limitation, monoglycerides, diglycerides, sulfatides, lysolecithin, phospholipids, saponin, bile acids, and the like.
• compositions will influence the physical state, solubility, stability, rate of in vivo release, and rate of in vivo clearance, and are thus chosen according to the intended application, so that the characteristics of the carrier will depend on the selected route of administration.
• Sustained- release forms suitable for use include, but are not limited to, polypeptides that are encapsulated in a slowly-dissolving biocompatible polymer (such as the alginate microparticles described in US Patent No. 6,036,978), admixed with such a polymer (including topically applied hydrogels), and or encased in a biocompatible semi-permeable implant.
• the cells at initial cell densities of 2 x 10 6 cells/ml in 20 ml, were placed in 125 ml plastic Erlenmeyer flasks with plug seal caps and placed on shaker platforms in incubators set to the appropriate temperatures. Cell viability and number were monitored by haemocytometer counting using trypan blue dye. Recombinant polypeptide titers were assessed by ELISA-based assays. For this cell line, 0.2 mM was known to be the optimal concentration of sodium butyrate for induction. Accordingly, 0.2 mM sodium butyrate was compared against the inducing effects of 0.5, 1.0, and 2.0 mM caffeine. A flask containing no inducing compound was also included. The shaker flasks were incubated in this induction phase for 5 days at 31°C in incubators without carbon dioxide control.
• caffeine can be used as an inducing agent and can induce product titers equal or exceeding those observed using sodium butyrate as an inducing agent.
• product quality e.g., glycosylation, folding, and amino acid composition
• CHO cells were grown in spinner flasks at 37°C using serum-free growth medium containing methotrexate. When the appropriate cell mass was obtained, spent medium was removed by a five minute centrifugation at 1000 x g and replaced with production medium without methotrexate.
• the cells with initial cell densities of 2 x 10 6 cells/ml in 20 ml, were placed in 125 ml plastic Erlenmeyer flasks with plug seal caps. The following caffeine concentrations were tested: 0, 0.6, 0.8, 1.0, 1.2, and 1.4 mM caffeine. The flasks were then incubated in this induction phase for 5 days at 31°C in incubators without carbon dioxide control.
• CHO cell line (cell line #60) expressing a third recombmant product, a human antibody that recognizes epidermal growth factor receptor, was analyzed.
• the inducing effects of 0, 0.5, 1.0, 1.5, and 2.0 mM caffeine were tested, and the experiment was conducted as in the previous experiment except that the induction phase was performed at 36°C.
• the flask of cells with no inducer and the flask of cells induced with 0.5 mM caffeine exhibited the highest cell viabilities (about 76%) of all the conditions. Viabilities of cultures containing 1.0 mM and 1.5 mM caffeine were about 68% and 60%, respectively. Cultures containing 0.75 mM butyrate or 2.0 mM caffeine were about 51% viable.
• the purpose of this experiment was to test ranges of temperature and caffeme concentrations in shake flasks in order to optimize the induction conditions for the cell line
• Cells were collected via centrifugation from a spinner culture of cell line #60 (26.85 x 10 5 cells/ml, 95.2% viable) and inoculated into a 575 ml spinner flask at 2 x 10 6 cells/ml in serum-free production medium. The culture was then aliquoted into twelve shake flasks. Caffeine was added according to the experimental plan described in Table 1. The shake flasks were incubated at the designated temperatures for 7 days. Samples were taken on days 3, 5 and 7. Cell density and viability were measured using an automated system of cell counting that employs trypan blue staining to determine viability (the Cell Density Examination System or Cedex, developed by innovatis GmbH, Bielefeld, Germany).
• Glucose and lactate measurements were taken with the Yellow Springs Instruments 2700 Select (available from Yellow Springs Instruments, Yellow Springs, Ohio, USA). Glucose was added on demand to maintain a concentration of > 2g/l. C0 2 and external pH were measured using the Ciba-Corning 248 blood gas analyzer (available from Bayer Diagnostics, Tarry ton, New York, USA). Protein titers were determined via a pre-purification of the antibody on a Protein A column followed by a measurement of the absorbance of the protein bound and eluted from the column at 280 nanometers.
• Cumulative viable cell densities were calculated as follows: the CVCD for day 1 is the number of viable cells per milliliter of culture as measured on day 1; the CVCD for day 2 is the number of viable cells per milliliter of culture as measured on day 2 plus the number of viable cells per milliliter of culture as measured on day 1 ; the CVCD for day 3 is the number of viable cells per milliliter of culture as measured on day 3 plus the numbers of viable cells per milliliter of culture measured on days 1 and 2; and CVCDs for subsequent days are calculated in a similar manner. Results. Higher CVCDs were achieved in the presence of little or no caffeine.
• the highest protein titers resulted at the low to intermediate levels of caffeine for both temperatures.
• the highest day 7 titer was observed in the culture grown at 36°C in the presence of 0.5 mM caffeine, and its titer was about 124% of the titer seen in a control culture grown at 36°C for 7 days without inducers.
• Day 7 titers of 36°C cultures grown in the presence of 1.0 mM and 1.5 mM caffeine were about 116% and 111% of control levels, respectively.
• the day 7 titers of cultures grown at 37°C in the presence of 0.5 mM, 1.0 mM, and 1.5 mM caffeme were about 110%, 112%, and 109%, respectively, of the 37°C no inducer control culture.
• Aminophylline is theophylline compound with 1,2-ethylenediamine (2:1) dihydrate.
• Xanthine derivatives tested included caffeine (at 0.5 mM), theobromine (at 0.1 mM, 0.5 mM, and 1.0 mM), 3-isobutyl-l-methylxanthine (BX, at 0.05 mM, 0.1 mM, and 0.15 mM), and pentoxyphylline (at 0.1 mM, 0.5 mM, and 1.0 mM).
• caffeine at 0.5 mM
• theobromine at 0.1 mM, 0.5 mM, and 1.0 mM
• BX 3-isobutyl-l-methylxanthine
• pentoxyphylline at 0.1 mM, 0.5 mM, and 1.0 mM.
• butyrate, some combinations of inducers, and the non-xanthine compound papaverine were tested.
• the 31°C control culture yielded low protein titers compared to the 37°C control culture, probably due to the preference of cell line #60 for higher temperatures.
• Theobromine at a concentration of 0.1 mM increased protein titer over that seen in the 37°C control culture, but was counterproductive at higher concentrations (0.5 mM and 1.0 mM).
• caffeine, IBX, or pentoxyphylline increased protein titers above that seen in a control culture with no inducers. Protein titer was inversely proportional to theobromine, BX, and pentoxyphylline concentrations in the ranges tested.
• cell line #9 (Table 3, Example 5) showed increased protein titers with increasing pentoxyphylline concentrations within this same range, highlighting the variability in the responses of different cell lines incubated at different temperatures to inducing agents.
• 0.5 mM caffeine appears to be a better inducer than 0.5 mM butyrate for cell line #60, although both failed to increase protein titer over that seen in the control culture with no inducing agent in this experiment.
• caffeine had induced slightly higher protein production than that seen in a control culture at 37°C at day 7 (about 110% of the titer seen in the control culture), although a greater induction was observed at 36°C.
• Example 4 Example 4
• the failure of caffeine to induce increased protein production in this experiment may be explained by a variety of factors such as experimental variability, the small size of the positive effect at 37°C in cell line #60, and/or the possibility that 0.5 mM may not be an optimum caffeine concentration for induction of cell line #60 at 37°C.
• HMBA HMBA, as indicated in Table 4.
• Cells were grown for a total of 5 days in shaker flasks. Thereafter, all medium was harvested. The number of cells present in the culture was determined by staining with trypan blue and counting the cells in a hemocytometer. The titer of RANK:Fc per milliliter of harvested medium was determined by purifying RANK:Fc by Protein A high performance liquid chromatography (HPLC) and subsequently measuring absorbance at 280 nanometers. An average number of cells in the culture was calculated by averaging the starting and ending cell numbers. Specific productivity was determined from the total number of micrograms of RANK:Fc produced, an average cell number (calculated as described above), and the number of days of growth. Data from this experiment are shown in Table 4.
• EXAMPLE 8 Production of RANK-Fc in the Presence of HMBA, Caffeine, and/or Butyric Acid Nucleic acids encoding RANK:Fc inserted into a suitable vector (as described in
• Nucleic acids encoding a type II IL-1 receptor inserted into a suitable vector were introduced into CHO cells. About 500 thousand cells from a stably transformed line were inoculated into a one liter of serum-free medium in a bioreactor. Cells were grown for two days at 37°C. Thereafter, cells were shifted to 31°C, either without HMBA or in the presence of 2 mM HMBA, and grown for 12 more days. Thereafter, all medium was harvested. The titer of type II IL-1 receptor per milliliter of harvested medium was determined by purification by reverse phase HPLC followed by the measurement of absorbance at 280 nanometers. Data from this experiment are shown in Table 6 as a percentage of the average of the protein titers obtained from the two samples without HMBA rounded to the nearest whole number.
• Nucleic acids encoding an antibody against a murine IL-4 receptor inserted into a suitable vector were introduced into CHO cells. About two million cells from a stably transformed line propagated at 37°C were inoculated into 20 miUiliters of medium at the temperatures indicated in Figure 4 and in the presence or absence of HMBA (2 mM) or sodium butyrate (0.5 mM), as indicated in Figure 4. Cells were grown for a maximum of 14 days in a shaker flask. Aliquots were removed at the times indicated in Figure 4, and the titer of the antibody (in micrograms per milliliter of harvested medium) was determined by enzyme-linked immunosorbent assay (ELISA), a method well known in the art. See e.g.
• ELISA enzyme-linked immunosorbent assay
• Nucleic acids encoding human TNFR:Fc in a suitable vector were introduced into CHO cells. About 3 + 0.5 x 10 6 cells from a stably transformed cell line propagated at 37°C were introduced into each of three 1 liter bioreactors and cultured at 32.5°C in an enriched, serum-free medium. Sodium butyrate (0.5 mM) was added to all three cultures, and HMBA (2 mM) was added to two of the cultures (“day 1 + HMBA”) one day after the shift to 32.5°C. Cells were incubated for a total of 11 days at 32.5°C.

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