Vectors and methods for expression of human protein C activity

Abstract: The present invention relates to DNA compounds which encode human protein C activity. A variety of eukaryotic and prokaryotic recombinant DNA expression vectors have been constructed that comprise the novel protein C activity-encod­ ing DNA and drive expression of protein C activity when trans­ formed into an appropriate host cell. The novel expression vec­ tors can be used to produce protein C derivatives, such as non­ carboxylated, non-glycosylatedd, or non-hydroxylated protein C, and to produce protein C precursors, such as nascent or zymogen protein C, and to produce subfragments of protein C, such as active or inactive light and heavy chain. The recom­ binant-produced protein C activity is useful in the treatment and prevention of a variety of vascular disorders.

Description: The present invention relates to a method of producing a polypeptide with human protein C activity in a eukaryotic host cell. Protein C, a vitamin K dependent protein of blood plasma, is a protein of major physiological importance. In consort with other proteins, protein C functions as perhaps the most important down-regulator of blood coagulation resulting in thrombosis. In other words, the protein C enzyme system represents a major physiological mechanism for anticoagulation. The biological and potential therapeutic importance of protein C can be deduced from clinical observations. In congenital homozygous protein C deficiency, affected family members die in early childhood from purpura fulminans, an often lethal form of disseminated intravascular coagulation. In heterozygous protein C deficiency, affected members suffer severe, recurrent thromboembolic episodes. It is well established clinically that plasma protein concentrates designed to treat hemophilia B or factor IX deficiency and which contain protein C as an impurity are effective in the prevention and treatment of intravascular clotting in homozygous as well as heterozygous protein C deficiency. Protein C levels have also been noted to be abnormally low in thrombotic states and in disease states predisposing to thrombosis, such as disseminated intravascular coagulation, major trauma, major surgery, and cancer. Human protein C is a serine protease zymogen present in blood plasma and synthesized in the liver. For expression of complete biological activity, protein C requires a post-translational modification for which vitamin K is needed. The mature, two-chain, disulfide-linked, protein C zymogen arises from a single-chain precursor by limited proteolysis. This limited proteolysis is believed to include cleavage of a signal peptide of ∼33 amino acid residues (residues 1-33, below) during secretion of the nascent polypeptide from the liver, removal of a pro peptide of ∼9 amino acid residues (residues 34-42), and removal of amino acid residues 198 and 199 to form the two chains observed in the zymogen. The activation of the zymogen into the active serine protease involves the proteolytic cleavage of an ARG-LEU peptide bond (residues 211 and 212). This latter cleavage releases a dodecapeptide (residues 200-211) constituting the amino-terminus of the larger chain of the two-chain molecule. Protein C is significantly glycosylated; the mature enzyme contains ∼23% carbohydrate. Protein C also contains a number of unusual amino acids, including γ-carboxyglutamic acid and β-hydroxyaspartic acid. γ-carboxyglutamic acid (gla) is produced from glutamic acid residues with the aid of a hepatic microsomal carboxylase which requires vitamin K as a cofactor. Since prokaryotes usually neither glycosylate, γ-carboxylate, nor β-hydroxylate proteins expressed from recombinant genes, the present invention is significant in that it allows for the first time the synthesis of protein C derivatives which have not undergone many of the post-translational modifications of normal human protein C. These unique derivatives have enormous research and clinical value, as discussed more fully below. For purposes of the present invention, as disclosed and claimed herein, the following terms are as defined below. ApR - the ampicillin-resistant phenotype or gene conferring same. ep - a DNA segment comprising the SV40 early promoter of the t-antigen (F) gene, the t-antigen binding sites, and the SV40 origin of replication. Functional Polypeptide - a recoverable bioactive heterologous or homologous polypeptide or precursor, a recoverable bioactive polypeptide comprising a heterologous polypeptide and a portion or whole of a homologous polypeptide, or a recoverable bioinactive fusion polypeptide comprising a heterologous polypeptide and a bio-inactivating polypeptide which can be specifically cleaved. G418R - the G418-resistant phenotype or gene conferring same. May also be identified as KmR. IVS - DNA encoding an intron, also called an intervening sequence. MSV LTR - a DNA segment comprising the promoter activity of the Murine Sarcoma virus long terminal repeat. Nascent protein - the polypeptide produced upon translation of a mRNA transcript, prior to any post-translational modifications. pA - a DNA sequence encoding a polyadenylation signal. Promoter - a DNA sequence that directs transcription of DNA into RNA. Protein C activity any property of human protein C responsible for biological function or anti-human protein C antibody-binding activity. Recombinant DNA Cloning Vector - any autonomously replicating agent, including, but not limited to, plasmids and phages, comprising a DNA molecule to which one or more additional DNA segments can be or have been added. Recombinant DNA Expression Vector - any recombinant DNA cloning vector into which a promoter has been incorporated. Replicon - A DNA sequence that controls and allows for autonomous replication of a plasmid or other vector. Restriction Fragment - any linear DNA sequence generated by the action of one or more restriction endonuclease enzymes. RSV LTR - a DNA segment comprising the promoter activity of the Rous Sarcoma virus long terminal repeat. Sensitive Host Cell - a host cell that cannot grow in the presence of a given antibiotic or other toxic compound without a DNA segment that confers resistance thereto. Structural Gene - any DNA sequence that encodes a functional polypeptide, inclusive of translational start and stop signals. TcR - the tetracycline-resistant phenotype or gene conferring same. Transformation - the introduction of DNA into a recipient host cell that changes the genotype of the recipient cell. Transformant - a recipient host cell that has undergone transformation. Translational Activating Sequence - any DNA sequence, inclusive of that encoding a ribosome binding site and translational start codon, such as 5'-ATG-3', that provides for the translation of a mRNA transcript into a peptide or polypeptide. Zymogen - an enzymatically inactive precursor of a proteolytic enzyme. Brief Description of the Figures Figure 1 - the restriction site and function map of plasmid pHC7. Figure 2 - the restriction site and function map of plasmid pSV2-HPC8. Figure 3 - the restriction site and function map of plasmid pL133. Figure 4 - the restriction site and function map of plasmid pL132. Figure 5 - the restriction site and function map of plasmid pL141. Figure 6 - the restriction site and function map of plasmid pL142. Figure 7 - the restriction site and function map of plasmid pMSV-HPC. Figure 8 - the restriction site and function map of plasmid pMMTΔBPV-HPC. Figure 9 - the restriction site and function map of plasmid pL151. The present invention provides a method of producing a polypeptide with human protein C activity in a eukaryotic host which comprises: A. transforming the eukaryotic cell with a recombinant DNA vector comprising: (i) a DNA sequence that provides for autonomous replication or chromosomal integration of said vector in said host cell, (ii) a promoter and translational activating sequence functional in said host cell, which translational activating sequence does not encode a translational start codon; and (iii)double-stranded DNA positioned in transcriptional and translational reading phase with said promoter and translational activating sequence, the coding strand of said DNA being: wherein A is deoxyadenyl, G is deoxyguanyl, C is deoxycytidyl, and T is thymidyl; and B. culturing the host cell transformed in step A under conditions suitable for gene expression. The amino acid sequence of nascent human protein C, numbered to facilitate further discussion, is: wherein H 2 N- is the amino-terminus, -COOH is the carboxy-terminus, ALA is Alanine, ARG is Arginine, ASN is Asparagine, ASP is Aspartic acid, CYS is Cysteine, GLN is Glutamine, GLU is Glutamic Acid, GLY is Glycine, HIS is Histidine, ILE is Isoleucine, LEU is Leucine, LYS is Lysine, MET is Methionine, PHE is Phenylalanine, PRO is Proline, SER is Serine, THR is Threonine, TRP is Tryptophan, TYR is Tyrosine, and VAL is Valine. The DNA compounds used in the present invention are derived from cDNA clones prepared from human liver mRNA that encodes human protein C activity. In constructing the cDNA clones, a 5' poly G sequence, a 3' poly C sequence, and both 5' and 3' Pst l restriction enzyme recognition sequences were constructed at the ends of the protein C-encoding cDNA. Two of these cDNA clones were manipulated to construct a DNA molecule comprising both the coding sequence of nascent human protein C and also portions of the DNA encoding the untranslated mRNA at the 5' and 3' ends of the coding region. This DNA molecule was inserted into the Pst l site of plasmid pBR322 to construct plasmid pHC7. Plasmid pHC7 thus comprises both the coding sequence above, and, again depicting only one strand of the molecule, also contains these additional sequences: and wherein A is deoxyadenyl, G is deoxyguanyl, C is deoxycytidyl, and T is thymidyl, at the 5' and 3' ends, respectively, of the coding strand of the nascent human protein C coding sequence. Due to the complementary nature of DNA base-pairing, the sequence of one strand of a double-stranded DNA molecule is sufficient to determine the sequence of the opposing strand. Plasmid pHC7 can be conventionally isolated from E. coli K12 RR1/pHC7, a strain deposited with and made part of the permanent stock culture collection of the Northern Regional Research Laboratory (NRRL), Peoria, Illinois. A culture of E. coli K12 RR1/pHC7 can be obtained from the NRRL under the accession number NRRL B-15926. A restriction site and function map of plasmid pHC7 is presented in Figure 1 of the accompanying drawings. Many mammalian host cells possess the necessary cellular machinery for the recognition and proper processing of the signal peptide present on the amino-terminus of nascent human protein C. Some mammalian host cells also provide the post-translational modifications, such as glycosylation, γ-carboxylation, and β-hydroxyíation, as are observed in human protein C present in blood plasma. A wide variety of vectors exist for the transformation of eukaryotic host cells, and the specific vectors exemplified below are in no way intended to limit the scope of the present invention. The pSV2-type vectors comprise segments of the SV40 genome that constitute a defined eukaryotic transcription unit--promoter (ep), intervening sequence (IVS), and polyadenylation (pA) site. In the absence of SV40 t-antigen, the plasmid pSV2-type vectors transform mammalian and other eukaryotic host cells by integrating into the host cell chromosomal DNA. A variety of plasmid pSV2-type vectors have been constructed such as plasmids pSV2-gpt, pSV2-neo, pSV2-dhfr, and pSV2-β-globin, in which the SV40 promoter drives transcription of an inserted gene. These vectors are available either from the American Type Culture Collection (ATCC) in Rockville, Maryland or from the Northern Regional Research Laboratory (NRRL) in Peoria, Illinois. Plasmid pSV2-HPC8 is a vector of the present invention derived from plasmid pSV2-gpt (ATCC 37145), plasmid pHC7, and two synthetic linkers. The designation "gpt" refers to the E . coli xanthine-guanosine phosphoribosyl transferase gene present on plasmid pSV2-gpt. Plasmid pSV2-HPC8 was constructed by first preparing a Hind lll- Apa l restriction fragment, derived from plasmid pHC7 and comprising the amino-terminal half of the nascent protein C coding sequence and a synthetic linker; then preparing an Apa I- Bg III restriction fragment, derived from plasmid pHC7 and comprising the carboxy-terminal half of the nascent protein C coding sequence and a synthetic linker; and then inserting the two restriction fragments into Hin dIII- BgI II-cleaved plasmid pSV2-gpt. A more detailed description of the construction of plasmid pSV2-HPC8 is provided in Example 2; a restriction site and function map of the plasmid is presented in Figure 2 of the accompanying drawings. Plasmid pSV2-HPC8 was used as a starting material in the construction of plasmid pL133, along with plasmid pSV2-β-globin (NRRL B-15928). Two restriction fragments of plasmid pSV2-HPC8, an ∼0.29 kb Hin dIII- Sal I fragment and an ∼1.15 kb Sal l- Bgl ll fragment, comprising the entire nascent protein C coding region were ligated into Hin dIII- BgI II-cleaved plasmid pSV2-β-globin. The resulting plasmid, designated pL133, has entirely replaced the β-globin coding region with the nascent protein C coding region. A more detailed description of the construction of plasmid pL133 is presented in Example 3; a restriction site and function map of the plasmid is presented in Figure 3 of the accompanying drawings. Plasmid pL132 was constructed in a manner analogous to the construction of plasmid pL133, except that the plasmid pSV2-HPCB Hin dIII- SaI I and Sal l- Bgl ll restriction fragments were introduced into plasmid pSV2-neo (ATCC 37149). "Neo" signifies the presence on the plasmid of a neomycin resistance-conferring gene, which also confers G418 resistance. This construction, described in Example 4, creates a polycistron, with both the nascent protein C and the G418 resistance-conferring coding sequences being transcribed as a polycistronic mRNA initiated by the same SV40 early promoter. Because G418 is toxic to most eukaryotic and other host cells, plasmid pL132 transformants can be selected by screening for G418 resistance. A restriction site and function map of plasmid pL132 is presented in Figure 4 of the accompanying drawings. Plasmid pSV2-dhfr (ATCC 37146) comprises a murine dihydrofolate reductase (dhfr) gene under the control of the SV40 early promoter. Under the appropriate conditions, the dhfr gene is known to be amplified, or copied, in the host chromosome. This amplification can involve DNA sequences closely contiguous with the dhfr gene. Plasmid pL141 is a vector of the present invention comprising both the dhfr gene and also the nascent protein C structural gene under the control of the SV40 early promoter. To construct plasmid pL141, a single Bam HI site on plasmid pSV2-dhfr was converted to an Xho l site, yielding plasmid pSV2-dhfr-X. Two restriction fragments of plasmid pL133, an ∼0.64 kb Pvu II- Bst EII fragment and an ∼2.7 kb Bst ElI- Eco RI fragment, comprising the nascent protein C structural gene, were isolated and, after first converting "the Pvu ll- Bst EIl fragment into an Xho I- BstE II fragment, ligated into Eco RI- Xho l-cleaved plasmid pSV2-dhfr-X. The resultant plasmid, designated pL141, is illustrated in Figure 5 of the accompanying drawings; the construction is also described in Example 5. Illustrative plasmids of the present invention which were constructed for expression of protein C activity in mammalian and other eukaryotic host cells also utilize promoters other than the SV40 early promoter. The present invention is in no way limited to the use of the particular eukaryotic promoters exemplified herein. Other promoters, such as the SV40 late promoter or promoters from eukaryotic genes, such as, for example, the estrogen-inducible chicken ovalbumin gene, the interferon genes, the glucocorticoid-inducible tyrosine aminotransferase gene, the thymidine kinase gene, and the major early and late adenovirus genes, can be readily isolated and modified for use on recombinant DNA expression vectors designed to produce protein C in eukaryotic host cells. Eukaryotic promoters can also be used in tandem to drive expression of protein C. Furthermore, a large number of retroviruses are known that infect a wide range of eukaryotic host cells. Long terminal repeats in the retrovirus DNA often encode promoter activity and can be used, in place of the SV40 early promoter described above, to drive expression of human protein C. Plasmid pRSVcat (ATCC 37152) comprises portions of the long terminal repeat of the Rous Sarcoma virus (RSV), a virus known to infect chicken and other host cells. The RSV long terminal repeat sequences can be isolated on an '∼0.76 kb Nde l- Hin dIII restriction fragment of plasmid pRSVcat. When cloned into the ∼5.1 kb Nde l- Hin dIII fragment of plasmid pL133, the promoter in the RSV long terminal repeat (Gorman et al ., 1982, P.N.A.S. 79:6777) replaces the SV40 early promoter and is positioned correctly to drive transcription and expression of the nascent human protein C structural gene. The resultant plasmid, designated pL142, is illustrated in Figure 6 of the accompanying drawings. The construction of plasmid pL142 is also described in Example 6. Another plasmid of the present invention utilizes the Rous Sarcoma virus long terminal repeat promoter to drive expression of protein C and contains the dhfr gene for purposes of selection and gene amplification. The plasmid, designated pL151, was constructed by ligating the ∼4.2 kb Eco Rl- Xho l restriction fragment of plasmid pSV2-dhfr-X to the ∼1.06 kb Bst Ell- Nde l restriction fragment of plasmid pL142 and to the ∼2.74 kb Bst Ell- Eco Rl restriction fragment of plasmid pL133. In order to accomplish the ligation and construction of plasmid pL151, the Nde l site of the pL142 restriction fragment used in the ligation was converted to an Xho l site by the addition of DNA linkers. The construction of plasmid pL151 is described in Example 9, below, and a restriction site and function map of the plasmid is presented in Figure 9 of the accompanying drawings. Plasmid pMSVi (NRRL B-15929) comprises the long terminal repeats of the Murine Sarcoma virus (MSV), a virus known to infect mouse and other host cells. Cloning the ∼1.4 kb BcI I restriction fragment of plasmid pSV2-HPC8 into the single Bgl ll restriction enzyme recognition sequence of plasmid pMSVi places the nascent protein C structural gene under the control of the MSV long terminal repeat promoter. The resulting plasmid, designated pMSV-HPC, is illustrated in Figure 7 of the accompanying drawings. The construction of plasmid pMSV-HPC is also described in Example 7. The mouse metallothionein (MMT) promoter has also been well characterized for use in eukaryotic host cells. The MMT promoter is present in the 15 kb plasmid pdBPV-MMTneo (ATCC 37224), which is the starting material for the construction of another plasmid of the present invention, designated pMMTΔBPV-HPC. To construct plasmid pMMTΔBPV-HPC, plasmid pdBPV-MMTneo was first digested with Bam Hl and then religated to form plasmid pMMTΔBPV. This Bam HI deletion removes ∼8 kb of bovine papillomavirus (BPV) DNA. Plasmid pMMTΔBPV was then digested with Bgl ll, and the ∼1.4 kb Bcl I restriction fragment of plasmid pSV2-HPC8 was ligated into the Bgl ll-digested plasmid. The resulting plasmid, designated pMMT ΔBPV-HPC, comprises the nascent protein C structural gene positioned for transcription and expression from the MMT promoter. Immediately adjacent to and downstream of the nascent protein C structural gene in plasmid pMMTΔBPV-HPC is the G418 resistance-conferring gene, which is controlled by the metallothionein promoter and allows for selection of hosts transformed with plasmid pMMTΔBPV-HPC. The construction of plasmid pMMTΔBPV-HPC is described in Example 8; a restriction site and function map of the plasmid is presented in Figure 8 of the accompanying drawings. The vectors described above, excluding plasmid pHC7, can be transformed into and expressed in a variety of eukaryotic, especially mammalian, host cells. Because plasmids pSV2-HPC8, pL142, and pL133 possess no selectable marker with which to isolate and identify stable transformants, these vectors are most useful for purposes of transient assay, as described in Example 12 below, or for purposes of cotransformation. All of the vectors, including plasmid pHC7, comprise sequences that allow for replication in E . coli , as it is usually more efficient to prepare plasmid DNA in E . coli than in other host organisms. Expression of the nascent human protein C structural gene contained on the above-described vectors occurs in those host cells in which the particular promoter associated with the nascent human protein C structural gene functions. The SV40 early promoter, the Rous Sarcoma virus long terminal repeat promoter, the Murine Sarcoma virus long terminal repeat promoter, and the mouse metallothionein promoter functior in a wide variety of host cells. Preferred host cells for plasmids pSV2-HPC8, pL133, pL132, pL151, pL141, pMSV-HPC, pMMTΔBPV-HPC and pL142 are listed in Table I, along with appropriate comments. Preferred transformants of the present invention are: HepG-2/pL132, HepG-2/pMSV-HPC, HepG-2/pL141, HepG-2/pL151, HepG-2/pMMTΔBPV-HPC, H4IIEC3/pL141, H4IIEC3/pL132, H4IIEC3/pMMTΔBPV-HPC, H4IIEC3/pMSV-HPC, H4IIEC3/pL151, LLC-MK 2 /pL132, LLC-MK 2 /pMMTΔBPV-HPC, LLC-MK 2 /pL141 LLC-MK 2 /pL151, C127I/pMMTΔBPV-HPC, C127I/pMSV-HPC, C127I/pL151, 3T3/pMSV-HPC, 3T3/pMMTΔBPV-HPC, 3T3/pL132, 3T3/pL141, 3T3/pL151, RPMI8226/pMSV-HPC, RPMI8226/pMMTΔBPV-HPC, RPMI8226/pL132, RPMI8226/pL141, RPMI8226/pL151, CHO-K1/pMSV-HPC, CHO-K1/pMMTΔBPV-HPC, CHO-K1/pL132, CHO-K1/pL141, CHO-K1/pL151, CHO-K1(dhfr - )/pMSV-HPC, CHO-K1(dhfr - )/pMMTΔBPV-HPC, CHO-K1(dhfr - )/pL132, CHO-K1(dhfr - )/pL141, and CHO-K1(dhfr - )/pL151 Those skilled in the art will recognize that the expression vectors of this invention are used to transform eukaryotic host cells, such that a polypeptide with human protein C activity is expressed by the host cell. If the host cell is transformed with a vector comprising a promoter that functions in the host cell and drives transcription of the nascent human protein C structural gene, and if the host cell possesses the cellular machinery with which to process the signal peptide, protein C activity can be isolated from the media. Under other expression conditions, the protein C activity must be isolated from the host cell. As stated above, protein C produced by recombinant methodology will have a profound effect on the treatment of thrombotic disease. Persons who are homozygous or heterozygous for protein C deficiency suffer from severe thrombosis and are presently treated with clotting Factor IX concentrate, which contains protein C. For treatment of these human protein C-deficient homozygotes, assuming ∼3000 ml of blood plasma and some diffusion into the extravascular space, recombinant-produced protein C can be administered twice daily at levels ranging from 5 mg to 100 mg per dose, assuming the zymogen form of the enzyme is administered. Heterozygotes for protein C deficiency will need lower doses of protein C than homozygotes, ranging from 2.5 mg to 50 mg per dose of the zymogen form of the enzyme. Recombinant-produced protein C will also be useful in the prevention and treatment of a wide variety of acquired disease states involving intravascular coagulation, including deep vein thrombosis, pulmonary embolism, peripheral arterial thrombosis, emboli originating from the heart or peripheral arteries, acute myocardial infarction, thrombotic strokes, and disseminated intravascular coagulation. Experimental and clinical data suggest that conventional anticoagulants, particularly warfarin, are useful in the treatment of invasive cancers and act to prevent or reduce the distant metastatic lesions of these malignancies. Recombinant-produced protein C represents an attractive alternative to conventional anticoagulants in these clinical situations for the reasons detailed below. Deep vein thrombosis and pulmonary embolism can be treated with conventional anticoagulants, but a far more attractive clinical approach is to prevent the occurrence of thromboembolic complications in identified high risk patients, such as, for example, patients undergoing surgery, patients who are chronically bedridden, and patients with congestive heart failure. Over 50% of surgical patients age 50 and over 20% of all surgical patients in general suffer from deep vein thrombosis following surgery, and about 20% of all post-surgical cases of deep vein thrombosis are complicated by one or more pulmonary emboli. Presently, low doses of heparin (e.g. 5,000 units every 8 hours) are administered both pre- and post-surgery to prevent deep vein thrombosis. Low-dose heparin occasionally causes heavy bleeding during and after surgery. Since activated protein C is more selective than heparin, being active only when and where thrombin is generated and fibrin thrombi are formed, protein C will be more effective and less likely to cause bleeding complications than heparin when used prophylactically for the prevention of deep vein thrombosis. The dose of recombinant-produced protein C for prevention of deep vein thrombosis is in the range from 1-10 mg/day, and administration of protein C should begin 6 hours prior to surgery and continue until the patient becomes mobile. In established, objectively-documented, deep vein thrombosis and/or pulmonary embolism, the dose of activated protein C ranges from 1-10 mg as a loading dose followed by a continuous infusion in amounts ranging from 3-30 mg/day. Similar dosage schedules are applicable for the treatment of peripheral arterial thrombi. Because of the lower likelihood of bleeding complications from activated protein C infusions, activated protein C can replace heparin intra- and post-surgically in conjunction with thrombectomies or embolectomies, surgical procedures which are often necessary to save ischemic limbs from amputation in the setting of an acute arterial obstruction. Arterial emboli originating from the heart are frequent complications in diseases of the heart involving heart valves, in patients with artifical heart valves, in acute myocardial infarction, and in certain types of heart arrhythmias. The treatment of these problems with conventional oral anticoagulants is not always entirely effective, and as always when oral anticoagulants are used, the risk of bleeding complications is substantial. Activated protein C administered long-term, in doses comparable to those for the treatment of established deep vein thrombin-pulmonary embolism, through continuous infusion using portable pump systems has substantial utility in the prevention of cardiogenic emboli. Similarly, emboli originating from thrombi in peripheral arteries, most notably the carotid arteries, are not treated or prevented satisfactorily with currently used regimens, which include drugs capable of suppressing platelet function, oral anticoagulants, or combinations thereof. As in the case of cardiogenic emboli, activated protein C administered long term in the same manner as outlined for cardiogenic emboli has major potential in the prevention of emboli originating from carotid artery thrombi and resulting in embolic strokes. Recombinant protein C is also useful in the treatment of thrombotic strokes. Today, strokes are not usually treated with conventional anticoagulants. Treatment of strokes with either heparin or oral anticoagulants, although occasionally beneficial, carries a high risk for bleeding into the infarcted brain area, thereby aggravating the neurological deficit accompanying the stroke. Because of its low potential for causing bleeding complications and its selectivity, protein C can be given to stroke victims and is beneficial in preventing the local extension of the occluding arterial thrombus, thereby reducing the neurological deficit resulting from the stroke. The amount of active protein C administered will vary with each patient depending on the nature and severity of the stroke. Recombinant-produced activated protein C will be a useful treatment in acute myocardial infarction because of the ability of activated protein C to enhance in vivo fibrinolysis. Activated protein C can be given with tissue plasminogen activator during the acute phases of the myocardial infarction. After the occluding coronary thrombus is dissolved, activated protein C can be given for additional days or weeks to prevent coronary reocclusion. In acute myocardial infarction, the patient is given a loading dose of 1-10 mg of activated protein C at the time tissue plasminogen activator treatment is initiated followed by a continuous infusion of activated protein C in amounts ranging from 3-30 mg/day. Protein C zymogen or activated protein C is useful in the treatment of disseminated intravascular coagulation, As mentioned above, the levels of protein C in disseminated intravascular coagulation are severely reduced, probably through a mechanism which involves the widespread activation of the protein by thrombomodulin-thrombin and the subsequent catabolism or inactivation of the activated enzyme. Heparin and the oral anticoagulants have been given to patients with disseminated intravascular coagulation in extensive clinical trials, but the results of these trials have been disappointing. Characteristically, patients with disseminated intravascular coagulation have widespread thrombi involving the microcirculation with concomitant and often severe bleeding problems, which result from "consumption" of essential clotting factors, which have been first activated and then inactivated during the formation of widespread microcirculatory fibrin thrombi. In disseminated intravascular coagulation, protein C has a distinct advantage over conventional anticoagulants. Because of its selectivity, protein C will not aggravate the bleeding problems associated with disseminated intravascular coagulation, as do heparin and the oral anticoagulants, but retards or inhibits the formation of additional microvascular fibrin deposits. The protein C zymogen, rather than the activated serine protease, is the preparation of choice in disseminated intravascular coagulation; the substantial quantities of thrombomodulinthrombin present in the microcirculation of these patients will insure complete activation of the zymogen into the active serine protease. The doses required are comparable to those used in homozygous or heterozygous protein C deficiency, depending on the quantities of protein C present in the circulation at the time of the start of treatment. Evidence has been presented that conventional anticoagulant drugs, particularly warfarin, are useful in the treatment of invasive malignant tumors. Many tumor cells produce substances which trigger the activation of the coagulation system resulting in local fibrin deposits. These fibrin deposits function as "nests" in which cancer cells can divide to form metastatic lesions. In one clinical study, it was shown that patients receiving warfarin in addition to cancer chemotherapy for treatment of small cell carcinoma of the lung live longer and have less extensive metastatic lesions than patients receiving chemotherapy alone. However, the cancer chemotherapy utilized in this study was less intensive than that considered optimal in clinical oncology today. The more intensive forms of cancer chemotherapy almost always produce a sharp drop in the platelet count, and thrombocytopenia combined with warfarin therapy puts the patient in an unacceptably high risk for serious bleeding complications. Activated protein C, being more selective than conventional anticoagulants and having a far higher therapeutic index than either heparin or the oral anticoagulants, can be given relatively safely to the thrombocytopenic patient thus enabling the treatment of patients with invasive cancers with effective intensive chemotherapy in combination with activated protein C. Treatment of invasive cancers with activated protean C will follow a dosage regimen comparable to that used in deep vein thrombosis-pulmonary embolism. Protein C prepared by the method of the present invention can be formulated according to known methods to prepare pharmaceutically useful compositions, whereby the human protein C product is combined in admixture with a pharmaceutically acceptable carrier vehicle. Suitable carrier vehicles and their formulation, inclusive of other human proteins, e.g., human serum albumin, are well known in the art. Such compositions will contain an effective amount of protein C together with a suitable amount of carrier vehicle in order to prepare pharmaceutically acceptable compositions suitable for effective administration to the host. The protein C composition can be administered parenterally, or by other methods that ensure its delivery to the bloodstream in an effective form. The following examples further illustrate the invention disclosed herein. The examples describe the procedures for the construction of the present invention, and explanations of the procedures are provided where appropriate. Example 1 Culture of E . coli K12 RRl/pHC7 and Isolation of Plasmid pHC7 A. Culture of E . coli K12 RRl/pHC7 One liter of L-broth (10 g peptone, 10 g NaCl, and 5 g yeast extract) containing 15 ug/ml tetracycline was inoculated with a culture of E . coli RR1/pHC7 (NRRL B-15926) and incubated in an air-shaker at 37°C until the optical density (O.D.) at 590 nm was ∼1 absorbance unit, at which time 150 mg of chloramphenicol were added to the culture. The incubation was continued for about 16 hours; the chloramphenicol addition inhibits protein synthesis, and thus inhibits further cell division, but allows plasmid replication to continue. B. Isolation of Plasmid pHC7 The culture prepared in Example 1A was centrifuged in a Sorvall GSA rotor (DuPont Co., Instrument Products, Biomedical Division, Newtown, CN 06470) at 6000 rpm for 5 minutes at 4° C. The resulting supernatant was discarded, and the cell pellet was washed in 40 ml of TES buffer (10 mM Tris-HCl, pH=7.5; 10 mM NaCl; and 1 mM EDTA) and then repelleted. After discarding the supernatant again, the cell pellet was frozen in a dry ice-ethanol bath and then thawed. The thawed cell pellet was resuspended in 10 ml of a 25% sucrose/50 mM EDTA solution. After adding and mixing: 1 ml of a 5 mg/ml lysozyme solution; 3 ml of 0.25 M EDTA, pH = 8.0; and 100 ul of 10 mg/ml RNAse A, the solution was incubated on ice for 15 minutes. Three ml of lysing solution (prepared by mixing 3 ml 10% Triton-X 100; 75 ml 0.25 M EDTA, pH = 8.0; 15 ml of 1 M Tris-HCl, pH=8.0; and 7 ml of water) were added to the lysozyme-treated cells, mixed, and the resulting solution incubated on ice for another 15 minutes. The lysed cells were frozen in a dry ice-ethanol bath and then thawed. The cellular debris was removed from the solution by centrifugation at 25,000 rpm for 40 minutes in an SW27 rotor (Beckman 7360 N. Lincoln Ave., Lincolnwood, IL 60646). After adding 30.44 g of CsCl and ∼1 ml of a 5 mg/ml ethidium bromide solution, the solution volume was adjusted to 40 ml and decanted into a Vti50 ultra-centrifuge tube (Beckman). After sealing the tube, the solution was centrifuged in a Vti50 rotor at 42,000 rpm for ∼16 hours. The resulting plasmid band, visualized with ultraviolet light, was isolated and then placed in a ti75 tube and rotor (Beckman) and centrifuged at 55,000 rpm for 16 hours. Any necessary volume adjustments were made using TES containing 0.761 g/ml CsCl. The plasmid band was again isolated, the ethidium bromide extracted with salt-saturated isopropanol, and diluted 1:3 with TES buffer. Two volumes of ethanol were then added to the solution, followed by incubation overnight at -20° C. The plasmid DNA was pelleted by centrifuging the solution in an SS34 rotor (Sorvall) for 15 minutes at 10,000 rpm. The ∼1 mg of plasmid pHC7 DNA obtained by this procedure was suspended in 1 ml of TE buffer (10 mM Tris-HCl, pH = 8.0 and 1 mM EDTA) and stored at -20° C. A restriction site and function map of plasmid pHC7 is presented in Figure 1 of the accompanying drawings. Example 2 Construction of Plasmid pSV2-HPC8 A. Isolation of the ∼1.25 kb Ban I Restriction Fragment of Plasmid pHC7 Fifty µl of the plasmid pHC7 DNA prepared in Example 1 were mixed with 5 µl (∼50 Units) of restriction enzyme Ban I, 10 µl of 10X Ban I reaction buffer (1.5 M NaCl; 60 mM Tris-HCl, pH=7.9; 60 mM MgCl 2 ; and 1 mg/ml BSA), and 35 µl of H 2 O and incubated until the digestion was complete. The Ban l-digested plasmid pHC7 DNA was then electrophoresed on a 3.5% polyacrylamide gel (29:1, acrylamide:bisacrylamide), until the ∼1.25 kb Ban l restriction fragment was separated from the other digestion products. The DNA bands were visualized by first staining the gel with a dilute solution of ethidium bromide and then viewing the gel with ultra-violet light. The region of the gel containing the ∼1.25 kb Ban l restriction fragment was cut from the gel, placed in a test tube, and broken into small fragments. One ml of extraction buffer (500 mM NH 4 OAc, 10 mM MgOAc, 1 mM EDTA, 1% SDS, and 10 mg/ml tRNA) was added to the tube containing the fragments, which was placed at 37° C overnight. Centrifugation was used to pellet the debris, and the supernatant was transferred to a new tube. The debris was washed once with 200 µl of extraction buffer; the wash supernatant was combined with the first supernatant from the overnight extraction. After passing the supernatant through a plug of glass wool, two volumes of ethanol were added to and mixed with the supernatant. The resulting solution was placed in a dry ice-ethanol bath for ∼10 minutes, and then the DNA was pelleted by centrifugation. Approximately 8 ug of the ∼1.25 kb Ban I restriction fragment were obtained by this procedure. The purified fragment was suspended in 10 µl of TE buffer and stored at -20° C. B. Construction of the Hin dIII- Bcl I- Ban I Linker The DNA fragments used in the construction of the linker were synthesized either by using a Systec 1450A DNA Synthesizer (Systec Inc., 3816 Chandler Drive, Minneapolis, MN) or an ABS 380A DNA Synthesizer (Applied Biosystems, Inc., 850 Lincoln Centre Drive, Foster City, CA 94404). Many DNA synthesizing instruments are known in the art and can be used to make the fragments. In addition, the fragments can also be conventionally prepared in substantial accordance with the procedures of Itakura et al ., 1977, Science, 198:1056 and Crea et al ., 1978, Proc. Nat. Acad. Sci. USA, 75:5765. Five hundred picomoles of each single strand of the linker were kinased in 20 µl of reaction buffer containing: 15 units (∼0.5 µl) T4 polynucleotide kinase 2 µl 10X ligase buffer (300 mM Tris-HCl, pH=7.8; 100 mM MgCl 2 ; 100 mM dithiothreitol; and 1 mg/ml BSA), 10 µl 500 µM ATP, and 7.5 µl H 2 O. The kinase reaction was incubated at 37° C for 30 minutes, and the reaction was terminated by incubation at 100° C for 10 minutes. In older to ensure complete kination, the reaction was chilled on ice, 2 µl of 0.2 M dithiothreitol, 2.5 µl of 5 mM ATP, and 15 units of T4 polynucleotide kinase were added, mixed, and the reaction mix incubated another 30 minutes at 37° C. The reaction was stopped by another 10 minute incubation at 100° C and then chilled on ice. Although kinased separately, the two single strands of the DNA linker were mixed together after the kinase reaction. In order to anneal the strands, the kinase reaction mixture was incubated at 100° C for 10 minutes in a water bath containing ∼150 ml of water. After this incubation, the water bath was shut off and allowed to cool to room temperature, a process taking about 3 hours. The water bath, still containing the tube of kinased DNA, was then placed in a 4° C refrigerator overnight. This process annealed the single strands. The linker constructed had the following structure: The linker was stored at -20°C until use. C. Construction of the ∼1.23 kb Hin dIII- Apa I Restriction Fragment The ∼8 µg of ∼ 1.25 kb Ban l fragment isolated in Example 2A were added to and mixed with the ∼50 µl of linker (∼500 picomoles) constructed in Example 2B, 1 µl T4 DNA ligase (∼10 units), 10 µl 10X ligase buffer, 10 µl 10 mM ATP, and 19 µl H 2 O, and the resulting ligation reaction was incubated at 4° C overnight. The ligation reaction was stopped by a 10 minute incubation at 65° C. The DNA was pelleted by adding NaOAc to 0.3 M final concentration and 2 volumes of ethanol, chilling in a dry ice-ethanol bath, and then centrifuging the solution. The DNA pellet was dissolved in 10 µl 10X Apa l reaction buffer (60 mM NaCl; 60 mM Tris-HCl, pH =7.4; 60 mM MgCl 2 ; and 60 mM 2-mercaptoethanol) 5 µl (∼50 units) restriction enzyme Apa I, and 85 µl of H 2 O, and the reaction was placed at 37° C for two hours. The reaction was then stopped and the DNA pelleted as above. The DNA pellet was dissolved in 10 µl 10X Hin dIII reaction buffer (500 mM NaCl; 500 mM Tris-HCl pH = 8.0; and 100 mM MgCl 2 ), 5 µl (∼50 units) restriction enzyme Hin dIII, and 85 µl of H 2 O, and the reaction was placed at 37° C for two hours. After the Hin dIII digestion, the reaction mixture was loaded onto a 3.5% polyacrylamide gel, and the desired ∼1.23 kb Hin dIII- Apa I restriction fragment was isolated in substantial accordance with the teaching of Example 2A. Approximately 5 µg of the desired fragment were obtained, suspended in 10 µl of TE buffer, and stored at -20° C. D. Isolation of the ∼0.88 kb Pst I Restriction Fragment of Plasmid pHC7 Fifty µl of the plasmid pHC7 DNA prepared in Example 1 were mixed with 5 µl (∼50 units) of restriction enzyme Pst l, 10 µl of 10X Pst I reaction buffer (1.0 M NaCl; 100 mM Tris-HCl pH=7.5; 100 MM MgCl 2 ; and 1 mg/ml BSA), and 35 µl of H 2 O and incubated at 37° C for two hours. The Pst l-digested plasmid pHC7 DNA was then electrophoresed on a 3.5% polyacrylamide gel, and the desired ∼0.88 kb fragment was purified in substantial accordance with the procedure of Example 2A. Approximately 5 µg of the desired fragment were obtained, suspended in 10 µl of TE buffer, and stored at -20° C. E. Construction of the Pst I- Bcl I- Bgl II Linker The following linker was constructed and prepared for ligation in substantial accordance with the procedure of Example 2B: F. Construction of the ∼0.19 kb Apa I- Bgl II Restriction Fragment The ∼5 µg of ∼0.88 kb Pst I fragment isolated in Example 2D were added to and mixed with the ∼50 µl of linker (∼500 picomoles) constructed in Example 2E, 1 µl T4 DNA ligase (∼10 units), 10 µl 10X ligase buffer, 10 µl 10 mM ATP, and 19 µl H 2 O, and the resulting ligation reaction was incubated at 4° C overnight. The ligation reaction was stopped by a 10 minute incubation at 65° C. After precipitation of the ligated DNA, the DNA pellet was dissolved in 10 µl 10X Apa l reaction buffer, 5 µl (∼50 units) restriction enzyme Apa l, and 85 µl of H 2 O, and the reaction was placed at 37 ° for two hours. The reaction was then stopped and the DNA pelleted bnce again. The DNA pellet was dissolved in 10 µl 10X Bgl ll reaction buffer (1 M NaCl; 100 mM Tris-HCl, pH=7.4; 100 mM MgCl 2 ; and 100 mM 2-mercaptoethanol), 5 µl (∼50 units) restriction enzyme Bgl ll, and 85 µl H 2 O, and the reaction was placed at 37° C for two hours. After the Bgl ll digestion, the reaction mixture was loaded onto a 3.5% polyacrylamide gel, and the desired ∼ 0.19 kb Apa l- Bgl ll restriction fragment was isolated in substantial accordance with the teaching of Example 2A. Approximately 1 µg of the desired fragment was obtained, suspended in 10 µl of TE buffer, and stored at -20° C. G. Isolation of Hin dIII- Bgl II-Digested Plasmid pSV2-gpt Approximately 10 µg of plasmid pSV2-gpt DNA (ATCC 37145) were dissolved in 10 µl 10X Hin dIII reaction buffer, 5 µl (∼50 units) restriction enzyme Hin dIII, and 85 µl H 2 O, and the reaction was placed at 37° C for 2 hours. The reaction mixture was then made 0.25 M in NaOAc, and after adding two volumes of ethanol and chilling in a dry ice-ethanol bath, the DNA was pelleted by centrifugation. The DNA pellet was dissolved in 10 µl 10X Bgl ll buffer, 5 µl (∼50 units) restriction enzyme Bgl ll, and 85 µl H 2 O, and the reaction was placed at 37° C for two hours. After the Bgl ll digestion, the reaction mixture was loaded onto a 1% agarose gel, and the fragments were separated by electrophoresis. After visualizing the gel with ethidium bromide and ultraviolet light, the band containing the desired ∼5.1 kb Hin dIII- Bgl ll fragment was cut from the gel and placed in dialysis tubing, and electrophoresis was continued until the DNA was out of the agarose. The buffer containing the DNA from the dialysis tubing was extracted with phenol and CHCl 3 , and then the DNA was precipitated. The pellet was resuspended in 10 µl of TE buffer and constituted ∼5 µg of the desired ∼5.1 kb Hin dIII- Bgl ll restriction fragment of plasmid pSV2-gpt. H. Ligation of Fragments to Construct Plasmid pSV2-HPC8 Two µl of the ∼1.23 kb Hin dIII- Apa l restriction fragment prepared in Example 2C, 3 µl of the ∼0.19 kb Apa I- BgI II fragment prepared in Example 2F, and 2 µl of the ∼5.1 kb Hin dIII- Bgl ll fragment prepared in Example 2G were mixed together and then incubated with 10 µl 10X ligase buffer, 10 µl 10 mM ATP, 1 µl T4 DNA ligase (∼10 units), and 72 µl of H 2 O at 16° C overnight. The ligated DNA constituted the desired plasmid pSV2-HPC8; a restriction site and function map of the plasmid is presented in Figure 2 of the accompanying drawings. I. Construction of E . coli K12 RR1/pSV2-HPC8 A 50 ml culture of E . coli K12 RR1 (NRRL B-15210) in L-broth was grown to an O.D. at 590 nm of ∼0.2. The culture was chilled on ice for ten minutes, and the cells were collected by centrifugation. The cell pellet was resuspended in 25 ml of cold 100 mM CaCl 2 and incubated on ice for 25 minutes. The cells were once again pelleted by centrifugation, and the pellet was resuspended in 2.5 ml of cold 100 mM CaCl 2 and incubated on ice overnight. Two hundred µl of this cell suspension were mixed with the ligated DNA prepared in Example 2H and incubated on ice for 20 minutes. The mixture was then incubated at 42° C for 2 minutes, followed by a 10 minute incubation at room temperature. Three ml of L-broth were added to the cell mixture, and then the cells were incubated in an air-shaker at 37° C for two hours. Aliquots of the cell mixture were plated on L-agar (L-broth with 15 g/l agar) plates containing 100 µg/ml ampicillin, and the plates were then incubated at 37° C E . coli K12 RR1/pSV2-HPC8 transformants were verified by restriction enzyme analysis of their plasmid DNA. Plasmid DNA was obtained from the E . coli K12 RR1/pSV2-HPC8 in substantial accordance with the teaching of Example 1, except that ampicillin not tetracycline, was the antibiotic used for selection. Example 3 Construction of Plasmid pL133 A. Isolation of the ∼0.29 kb Hin dIII- Sal I Restriction Fragment of Plasmid pSV2-HPC8 Fifty µg of plasmid pSV2-HPC8 were dissolved in 10 µl 10X Hin dIII reaction buffer, 5 µl (∼50 units) restriction enzyme Hin dIII, and 85 µl H 2 O, and the reaction was incubated at 37° C for two hours. After the Hin dIII digestion, the DNA was precipitated, and the DNA pellet was dissolved in 10 µl 10X Sal I reaction buffer (1.5 M NaCl; 60 mM Tris-HCl, pH=7.9; 60 mM MgCl 2 ; 60 mM 2-mercaptoethanol; and 1 mg/ml BSA), 5 µl (∼50 units) restriction enzyme Sal I, and 85 µl of H 2 O. The resulting Sal l reaction mixture was incubated for 2 hours at 37° C. The Hin dIII- Sal l-digested plasmid pSV2-HPC8 was loaded onto a 3.5% polyacrylamide gel and electrophoresed until the desired ∼0.29 kb Hin dIII- Sal l restriction fragment was clearly separated from the other reaction products. The desired fragment was purified in substantial accordance with the teaching of Example 2A. The ∼2 ug of fragment obtained were suspended in 10 µl of TE buffer and stored at -20° C. B. Isolation of the ∼1.15 kb Sal I- Bgl II Restriction Fragment of Plasmid pSV2-HPC8 Fifty µg of plasmid pSV2-HPC8 were dissolved in 10 µl 10X BgIII reaction buffer, 5 µl (50 units) restriction enzyme Bgl ll, and 85 µl H 2 O, and the reaction was incubated at 37° C for two hours. After the Bgl ll digestion, the DNA was precipitated, and the DNA pellet was dissolved in 10 µl 10X Sal I reaction buffer, 5 µl restriction enzyme Sal I, and 85 µl of H 2 O. The resulting Sal l reaction mixture was incubated for 2 hours at 37°C. The Sal l- Bgl ll-digested plasmid pSV2-HPC8 was loaded onto a 3.5% polyacrylamide gel and electrophoresed until the desired ∼1.15 kb Sal l- Bgl ll restriction fragment was clearly separated from the other reaction products. The desired fragment was purified in substantial accordance with the teaching of Example 2A. The ∼8 µg of fragment obtained were suspended in 10 µl of TE buffer and stored at -20°C. C. Isolation of the ∼4.2 Kb Bgl II- Hin dIII Restriction Fragment of Plasmid pSV2-β-globin The isolation of the desired ∼4.2 kb Bgl ll- Hin dIII restriction fragment of plasmid pSV2-β-globin (NRRL B-15928) was accomplished in substantial accordance with the teaching of Example 2G, with the exception that plasmid pSV2-β-globin, rather than plasmid pSV2-gpt, was used. The ∼5 µg of DNA obtained were suspended in 10 µl of TE buffer and stored at -20° C. D. Ligation of Fragments to Construct Plasmid pL133 Two µl of the fragment obtained in Example 3A, 2 µl of the fragment obtained in Example 3B, and 2 µl of the fragment obtained in Example 3C were mixed together and ligated in substantial accordance with the procedure of Example 2H. The ligated DNA constituted the desired plasmid pL133; a restriction site and function map of the plasmid is presented in Figure 3 of the accompanying drawings. E. Construction of E . coli K12 RR1/pL133 The desired E . coli K12 RR1/pL133 transformants were constructed in substantial accordance with the teaching of Example 21, with the exception that plasmid pL133, rather than plasmid pSV2-HPC8, was used as the transforming DNA. Plasmid DNA was obtained from the E . coli K12 RR1/pL133 transformants in substantial accordance with the procedure of Example 1, except that the antibiotic used in culturing the cells was ampicillin, not tetracycline. Example 4 Construction of Plasmid pL132 A. Isolation of the ∼5.7 kb Hin dIII- Bgl II Restriction Fragment of Plasmid pSV2-neo The isolation of the ∼5.7 kb Hin dIII- Bgl ll restriction fragment of plasmid pSV2-neo (ATCC 37149) was accomplished in substantial accordance with the teaching of Example 2G, with the exception that plasmid pSV2-neo, rather than plasmid pSV2-gpt, was used. The ∼5 µg of DNA obtained were suspended in 10 µl of TE buffer and stored at -20° C. B. Ligation of Fragments to Construct Plasmid pL132 Two µl of the ∼5.7 kb Hin dIII- Bgl ll restriction fragment of plasmid pSV2-neo (prepared in Example 4A), 2 µl of the ∼0.29 kb Hin dIII- Sal I restriction fragment of plasmid pSV2-HPC8 prepared in Example 3A, and 2 µl of the ∼1.15 kb Sal I- Bgl II restriction fragment of plasmid pSV2-HPC8 prepared in Example 3B were mixed together and ligated in substantial accordance with the procedure of Example 2H. The ligated DNA constituted the desired plasmid pL132; a restriction site and function map of the plasmid is presented in Figure 4 of the accompanying drawings. C. Construction of E . coli K12 RR1/pL132 The desired E . coli K12 RR1/pL132 transformants were constructed in substantial accordance with the teaching of Example 21 with the exception that plasmid pL132, rather than plasmid pSV2-HPC8, was used as the transforming DNA. Plasmid DNA was obtained from the E . coli K12 RR1/pL132 transformants in substantial accordance with the procedure of Example 1, except that the antibiotic used in culturing the cells was ampicillin, not tetracycline. Example 5 Construction of Plasmid pL141 A. Construction of an Xho I Recognition Sequence on Plasmid pSV2-dhfr to Yield Plasmid pSV2-dhfr-X Ten µg of plasmid pSV2-dhfr (isolated from E. coli K12 HB101/pSV2-dhfr, ATCC 37146) were mixed with 10 µl 10X Bam HI salts, 2 µl (∼20 units) restriction enzyme Bam HI, and 88 µl of H 2 O, and the resulting reaction was incubated at 37° for two hours. The reaction was terminated by phenol and chloroform extractions, after which the Bam HI-digested plasmid pSV2-dhfr DNA was precipitated and collected by centrifugation. The DNA pellet was resuspended in 1 µl of 50 mM DTT, 4 µl of a solution 100 mM in each of the dNTPs, 1 µl of the Klenow fragment of DNA polymerase I (∼5 units, New England Biolabs), 34 µl of H 2 O, and 5 µl of 10X Klenow buffer (400 mM KPO 4 , pH=7.5; 66 mM MgCl 2 ; and 10 mM 2-mercaptoethanol) and incubated at 14° C for one hour. The reaction was stopped by the addition of 4 µl of 0.25 M EDTA and a subsequent phenol extraction. The DNA was precipitated from the reaction mix and pelleted by centrifugation. The ∼10 µg of DNA obtained were dissolved in 20 µl of TE buffer. Xho l linkers (New England Biolabs, 32 Tozer Road, Beverly, MA 09195) of sequence: were kinased and prepared for ligation by the following procedure. Four µl of linkers (∼2 µg) were dissolved in 20.15 µl of H 2 O and 5 µl of 10X kinase buffer (500 mM Tris-HCl, pH=7.6 and 100 mM MgCl 2 ), incubated at 90° C for two minutes, and then cooled to room temperature. Five µl of γ- 32 P-ATP (∼20 µCi), 2.5 µl of 1 M DTT, and 5 µl of polynucleotidekinase (∼10 units) were added to the mixture, which was then incubated at 37° C for 30 minutes. Then, 3.35 µl of 0.01 mM ATP and 5 more µl of kinase were added, and the reaction was continued for another 30 minutes at 37° C. The reaction was then stored at -20° C. Six and eight-tenths µl (∼3.4 µg) of the Bam Hl-digested, Klenow-treated, plasmid pSV2-dhfr and 10 µl (∼0.4 µg) of the kinased Xho l linkers were mixed and incubated with 11.3 µl of water, 3.5 µl 10X ligase buffer, 1.4 µl 10 mM ATP, and 2 µl T4 DNA ligase (∼10 units,) at 16° C overnight. The reaction was stopped by a 10 minute incubation at 65° C. Ten µl 10X Xho l reaction buffer (1.5 M NaCl; 60 mM Tris-HCl, pH=7.9; 60 mM MgCl 2 ; 60 mM 2-mercaptoethanol; and 1 mg/ml BSA), 5 µl restriction enzyme Xhol (∼100 units), and 50 µl of H 2 O were added to the reaction, which was then incubated at 37° C for four hours. The reaction was loaded onto a 1% agarose gel, and the desired fragment was isolated in substantial accordance with the teaching of Example 2G. The ∼2 µg of fragment obtained were suspended in 10 µl of TE buffer. The Bam HI-digested plasmid pSV2-dhfr with Xho l linkers attached was then ligated and transformed into E. coli K12 RR1 in substantial accordance with the teaching of Examples 2H and 2I, with the exception that the transforming DNA was plasmid pSV2-dhfr-X. The resulting E . coli K12 RR1/pSV2-dhfr-X transformants were identified by their ampicillin-resistant phenotype and by restriction enzyme analysis of their plasmid DNA. Plasmid pSV2-dhfr-X was isolated from the transformants in substantial accordance with the procedure of Example 1, except that ampicillin was the antibiotic used during the culturing of the cells. B. Isolation of the ∼4.2 kb Eco RI- Xho I Restriction Fragment of Plasmid pSV2-dhfr-X Fifty µg of plasmid pSV2-dhfr-X were mixed with 10 µl 10X Xho l reaction buffer, 5 µl (∼50 units) restriction enzyme Xho l. and 85 µl of H 2 O, and the resulting reaction was incubated at 37° C for two hours. After the reaction, the Xho I-digested plasmid pSV2-dhfr-X DNA was precipitated and collected by centrifugation. The DNA pellet was resuspended in 10 µl 10X Eco RI reaction buffer, 5 µl (∼50 units) restriction enzyme Eco RI, and 85 µl of H 2 O, and the resulting reaction was incubated at 37° C for two hours. After the Eco RI reaction, the Xh ol- Eco Rl-digested plasmid pSV2-dhfr-X DNA was loaded onto a 1% agarose gel, and the desired ∼4.2 kb Eco RI- Xho l restriction fragment was purified in substantial accordance with the procedure of Example 2G. The ∼10 µg of the fragment obtained were suspended in 20 µl of TE buffer and stored at 20° C. C. Construction of the Xho I- Bst EII Restriction Fragment from the ∼0.64 kb Pvu II- Bst EII Restriction Fragment of Plasmid pLl33 Fifty µg of plasmid pL133 were mixed with 10 µl 10X Pvu ll reaction buffer (600 mM NaCl; 60 mM Tris-HCl, pH=7.5; 60 mM MgCl 2 ; 60 mM 2-mercaptoethanol; and 1 mg/ml BSA), 5 µl (∼50 units) restriction enzyme Pvu ll, and 85 µl of H 2 O, and the resulting reaction was incubated at 37° C for two hours. After the reaction, the Pvu ll-digested plasmid pL133 DNA was precipitated and collected by centrifugation. Approximately 5 µg of Xho l linker, the same as that used in Example 5A, were kinased and ligated to the Pvu II-digested plasmid pL133 DNA in substantial accordance with the teaching of Example 5A. After the ligation reaction, the DNA was precipitated and collected by centrifugation. The DNA pellet was resuspended in 20 µl 10X Xho l reaction buffer, 10 µl (∼100 units) restriction enzyme Xho l, and 165 µl of H 2 O, and the resulting reaction was incubated at 37° C for 4 hours. Then, 5µl (∼50 units) of restriction enzyme Bst EIl were added to the reaction, which was then incubated at 60° C for 4 hours under mineral oil. The Xho l- Bst Ell-digested DNA was loaded onto a 3.5% polyacylamide gel, and the desired ∼0.64 kb Xho l- Bst Ell restriction fragment was purified in substantial accordance with the teaching of Example 2A. Approximately 3 µg of the fragment were obtained, resuspended in 6 µl of TE buffer, and stored at -20° C. D. Isolation of the ∼2.7 kb Eco RI- Bst EII Restriction Fragment of Plasmid pL133 Fifty µg of plasmid pL133 were mixed with 10 µl 10X Bst EII reaction buffer, 5 µl (∼50 units) restriction enzyme Bst EII, and 85 µl of H 2 O, and the resulting reaction was incubated at 60° C for two hours under mineral oil. After the reaction, the Bst EII-digested plasmid pL133 DNA was precipitated and collected by centrifugation. The DNA pellet was resuspended in 10 µl 10X Eco RI reaction buffer, 5 µl (∼50 units) restriction enzyme Eco RI, and 85 µl of H 2 O, and the resulting reaction was incubated at 37° C for two hours. After the Eco RI reaction, the Bst EII- Eco RI-digested plasmid pL133 DNA was loaded onto a 1% agarose gel, and the desired ∼2.7 kb Eco RI- Bst EII restriction fragment was purified in substantial accordance with the procedure of Example 2G. The ∼10 µg of the fragment obtained were suspended in 20 µl of TE buffer and stored at 20° C. E. Ligation of Fragments to Construct Plasmid pL141 and Transformation of E . coli K12 RR1 Two µl of the ∼4.2 kb Eco RI- Xho l restriction fragment of plasmid pSV2-dhfr-X prepared in Example 5B, 2 µl of the ∼0.64 kb Xho I- Bst EII restriction fragment constructed from plasmid pL133 in Example 5C, and 2 µl of the ∼2.7 kb Eco RI- Bst EII restriction fragment of plasmid pL133 prepared in Example 5D were mixed together, ligated, and the resulting plasmid pL141 DNA used to transform E . coli K12 RR1 in substantial accordance with the teaching of Examples 2H and 21. The desired E . coli K12 RR1/pL141 transformants were identified by their ampicillin-resistant phenotype and by restriction enzyme analysis of their plasmid DNA. Plasmid pL141 was isolated from the transformants in substantial accordance with the procedure of Example 1, except that ampicillin was the antibiotic used in culturing the cells. A restriction site and function map of plasmid pL141 is presented in Figure 5 of the accompanying drawings. Example 6 Construction of Plasmid pL142 A. Isolation of the ∼0.76 kb Nde I- Hin dIII Restriction Fragment of Plasmid pRSVcat Fifty µg of plasmid pRSVcat (available from the ATCC in host E . coli HB101 under accession number ATCC 37152) were mixed with 10 µl 10X Hin dIII reaction buffer, 5 µl (∼50 units) restriction enzyme Hin dIII and 85 µl of H 2 O, and the resulting digest was incubated at 37° C for 2 hours. After the Hin dIII digestion, the DNA was precipitated and collected by centrifugation. The DNA pellet was dissolved in 10 µl 10X Nde l reaction buffer (1.5 M NaCl; 100 mM Tris-HCl, pH=7.8; 70 mM MgCl 2 ; and 60 mM 2-mercaptoethanol), 10 µl (∼30 units) restriction enzyme Nde l, and 85 µl of H 2 O, and the resulting reaction was incubated at 37° C until the digestion was complete. The Hin dIII- Nde l-digested plasmid pRSVcat DNA was loaded onto a 3.5% polyacrylamide gel, and the ∼0.76 kb Nde I- Hin dIII restriction fragment was isolated and purified in substantial accordance with the teaching of Example 2A. Approximately 5 µg of the fragment were obtained, suspended in 10 µl of TE buffer, and stored at -20° C. The fragment comprises the promoter activity of the long terminal repeat from Rous Sarcoma virus and functions as a promoter of DNA transcription in many eukaryotic cells. B. Isolation of the ∼5.1 kb Nde I- Hin dIII Restriction Fragment of Plasmid pL133 The isolation was accomplished in substantial accordance with the teaching of Example 6A, except that plasmid pL133, instead of plasmid pRSVcat, was digested. Furthermore the fragment was isolated from a 1% agarose gel, in substantial accordance with the teaching of Example 2G, instead of a 3.5% polyacrylamide gel. Approximately 5 µg of the desired fragment were obtained, suspended in 10 µl of TE buffer, and stored at -20° C. C. Ligation of Fragments to Construct Plasmid pL142 and Transformation of E . coli K12 RR1 Two µl of the ∼0.76 kb Nde l- Hin dIII restriction fragment of plasmid pRSVcat isolated in Example 6A were ligated to 1 µl of the ∼5.1 kb Nde l- Hin dIII restriction fragment of plasmid pL133 isolated in Example 6B. The ligation was carried out in substantial accordance with the teaching of Example 2H. The ligated DNA, constituting the desired plasmid pL142, was used to transform E . coli K12 RR1 in substantial accordance with the teaching of Example 21. The E . coli K12 RR1/pL142 transformants were identified by their ampicillin-resistant phenotype and by restriction enzyme analysis of their plasmid DNA. A restriction site and function map of plasmid pL142 is presented in Figure 6 of the accompanying drawings. Plasmid pL142 was isolated from the transformants in substantial accordance with the teaching of Example 1, with the exception that ampicillin was the antibiotic used in culturing the cells. Example 7 Construction of Plasmid pMSV-HPC Ten µg of plasmid pMSVi (NRRL B-15929) were dissolved in 10 µl 10X Bgl ll buffer, 2 µl (∼20 units) restriction enzyme Bgl ll, and 88 µl of H 2 O, and the resulting reaction was incubated at 37° C for 2 hours. After extracting the Bgl II-digested plasmid pMSVi DNA with both phenol and chloroform, the DNA was resuspended in 10 µl of H 2 O. Two µl of the Bgl ll-digested plasmid pMSVi DNA were mixed with 2 µl of the ∼1.425 kb Bcl l restriction fragment of plasmid pSV2-HPC8 prepared in Example 8C, below, and the two fragments were ligated and transformed into E . coli K12 RR1 in substantial accordance with the procedure of Examples 2H and 21. The desired pMSV-HPC transformants were identified by restriction enzyme analysis of their plasmid DNA and by their ampicillin-resistant and tetracycline-resistant phenotype. A restriction site and function map of plasmid pMSV-HPC is presented in Figure 7 of the accompanying drawings. Due to the presence of the Murine Sarcoma virus sequences on the plasmid, plasmid pMSV-HPC can be encapsidated to become a transmissible vector with trans-acting functions provided by a helper virus with a broad host range (e.g., amphotropic murine leukemia viruses) or by a cell line harboring such helper functions. This process greatly enhances the transformability of the vector and widens the range of host cells wherein the vector can be expressed. Example 8 Construction of Plasmid pMMTΔBPV-HPC A. Construction of Intermediate Plasmid pMMTΔBPV About one µg of plasmid pdBPV-MMTneo (ATCC 37224) was mixed with 10 µl 10X Bam HI reaction buffer, 5 µl (∼50 units) restriction enzyme Bam HI, and 85 µl of H 2 O, and the resulting reaction was incubated at 37° C for two hours. After a five minute incubation at 65° C, the Bam HI-digested plasmid pdBPV-MMTneo DNA was diluted to a concentration of about 0.1 µg/µl in ligase buffer and ligated with T4 DNA ligase, and the resulting plasmid pMMTΔBPV DNA was used to transform E . coli K12 RR1 in substantial accordance with the teaching of Examples 2H and 2I. The E . coli K12 RR1/pMMTΔBPV transformants were identified by their ampicillin-resistant phenotype and by restriction enzyme analysis of their plasmid DNA. Plasmid pMMTΔBPV DNA was isolated from the transformants in substantial accordance with the teaching of Example 1, except that ampicillin was the antibiotic used during culturing of the cells. B. Preparation of Bgl II-Digested Plasmid pMMTΔBPV Ten µg of plasmid pMMTΔBPV DNA were dissolved in 10 µl 10X Bgl ll buffer, 5 µl (∼50 units) restriction enzyme BgI II, and 85 µl of H 2 O, and the resulting reaction was incubated at 37° C for two hours. The reaction was then extracted once with phenol and once with chloroform, and the DNA was precipitated and collected by centrifugation. The ∼10 µg of Bgl ll-digested plasmid pMMTΔBPV DNA obtained by this procedure were suspended in 20 µl of TE buffer and stored at 20° C. C. Isolation of the ∼1.425 kb Bcl I Restriction Fragment of Plasmid pSV2-HPC8 In order to digest DNA completely with restriction enzyme BcI I, the deoxyadenyl residue in the recognition sequence must not be methylated. When preparing plasmid DNA in E . coli for subsequent digestion with BcI I, it is necessary to use a strain deficient in adenine methylase, such as E . coli K12 GM48 (NRRL B-15725). E . coli K12 GM48 was prepared for transformation and then transformed with plasmid pSV2-HPC8 in substantial accordance with the procedure of Example 2I. Plasmid pSV2-HPC8 DNA was isolated from the E . coli K12 GM48/pSV2-HPC8 transformants in substantial accordance with the teaching of Example 1, except that ampicillin was the antibiotic used during culturing of the cells. Fifty µg of the plasmid pSV2-HPC8 DNA isolated from the E . coli K12 GM48/pSV2-HPC8 transformants were dissolved in 10 µl 10X Bcl l reaction buffer (750 mM KCl; 60 mM Tris-HCl pH =7.4; 100 mM MgCl 2 ; 10 mM dithiothreitol; and 1 mg/mL BSA), 5 µl (∼50 units) restriction enzyme Bcl l, and 85 µl of H 2 O, and the resulting reaction was incubated at 50° C for two hours. The Bcl I-digested plasmid pSV2-HPC8 DNA was loaded onto a 1% agarose gel, and the desired ∼1.425 kb Bcl l restriction fragment was isolated and purified in substantial accordance with the teaching of Example 2G. The ∼5 µg of fragment obtained were dissolved in 10 µl of TE buffer and stored at -20° C. D. Ligation to Construct Plasmid pMMTΔBPV-HPC and Transformation of E . coli K12 RRI Two µl of the Bgl ll-digested plasmid pMMTΔBPV DNA prepared in Example 8B and 2 µl of the ∼1.425 kb Bcl I restriction fragment of plasmid pSV2-HPC8 isolated in Example 8C were mixed together, ligated, and the resulting plasmid pMMTΔBPV-HPC DNA used to transform E . coli K12 RR1 in substantial accordance with the procedure of Examples 2H and 2I. The desired E . coli K12 RR1/pMMTΔBPV-HPC transformants were identified by their ampicillin-resistant phenotype and by restriction enzyme analysis of their plasmid DNA. Plasmid pMMTΔBPV-HPC was isolated from the transformants in substantial accordance with the procedure of Example 1, except that ampicillin was the antibiotic used during culturing. A restriction site and function map of plasmid pMMTΔBPV-HPC is presented in Figure 8 of the accompanying drawings. Example 9 Construction of Plasmid pL151 A. Construction of an ∼1.06 kb Bst EII- Xho I Restriction Fragment Derived From Plasmid pL142 Fifty µg of plasmid pL142 DNA were dissolved in 10 µl 10X Nde l reaction buffer, 5 µl (∼50 units) restriction enzyme Nde l, and 85 µl of H 2 O, and the resulting reaction was placed at 37° C for two hours. After the reaction, the DNA was precipitated and collected by centrifugation. The DNA pellet was resuspended in Klenow buffer, and the Nde l-digested DNA was treated with Klenow enzyme in substantial accordance with the procedure of Example 5A. After the Klenow reaction, the DNA was again precipitated and collected by centrifugation. Xho l linkers (5'-CCTCGAGG-3') were kinased, prepared for ligation, and ligated to the Nde l-digested, Klenow-treated plasmid pL142 DNA in substantial accordance with the procedure of Example 5A. After heat-inactivating the ligation reaction, the DNA was precipitated and collected by centrifugation. The DNA pellet was dissolved in 20 µl 10X Xho l reaction buffer, 10 µl (∼100 units) restriction enzyme Xho l, and 170 µl of H 2 O, and the resulting reaction was incubated at 37° C for two hours. Then, 5 µl (∼50 units) restriction enzyme Bst EII were added to the reaction, which was incubated at 60° C for four hours under mineral oil. After phenol extraction, the digested DNA was loaded onto an acrylamide gel and the ∼1,06 kb Bst EII- Xho l restriction fragment was isolated and purified in substantial accordance with the procedure of Example 2A. Approximately 5 µg of the desired fragment were obtained, suspended in 10 µl of TE buffer, and stored at -20° C. B. Ligation and Final Construction of Plasmid pL151 and E . coli K12 RR1/pL151 Two µl of the ∼1.06 kb Bst EII- Xho l restriction fragment derived from plasmid pL142 and prepared in Example 9A were ligated to 2 µl of the ∼4.2 kb Eco Rl- Xho l restriction fragment of plasmid pSV2-dhfr-X prepared in Example 5B, and to 2 µl of the ∼2.74 kb BstE II- Eco RI restriction fragment of plasmid pL133 prepared in Example 5D. The ligation reaction was carried out in substantial accordance with the procedure of Example 2H. The ligated DNA constituted the desired plasmid pL151 and was used to transform E . coli K12 RR1 in substantial accordance with the procedure of Example 2I. The desired E . coli K12 RR1/pL151 transformants were selected on ampicillin-containing media and identified by restriction enzyme analysis of their plasmid DNA. A restriction site and function map of plasmid pL151 is presented in Figure 9 of the accompanying drawings. Example 10 Construction of HepG-2/pL133 Transformants Although the following procedure describes the construction of HepG-2/pL133 transformants, it is equally applicable for the construction of HepG2 transformants of any of the other plasmids of the present invention, such as plasmids pSV2-HPC8, pL132, pL151, pMSV-HPC, pL141, pL142, and pMMTΔBPV-HPC. Furthermore, the procedure given is generally applicable to the cell lines listed as preferred cell lines in Table I of the present specification. Transformation procedures for eukaryotic host cells are well known in the art, i.e., Wigler et al ., 1979, P.N.A.S. USA 76:1373 and Graham et al ., 1973, Virology 52:456. A. Preparation of the Cells A culture of human hepatoblastoma cells, HepG-2 (ATCC # HB 8065) was passaged one to two days prior to the transformation, so as to provide 40-50% confluency on the day of the transformation. The media was changed two to three hours before the transformation. One 25 cm 2 flask of cells is needed for each transformation. B. Preparation of the DNA Ten to twenty µg of plasmid pL133 DNA were added to 62.5 µl of 2M CaCl 2 and 437.5 µl of H 2 O. The 0.5 ml of DNA were then added dropwise to 0.5 ml of 2X HeBS (10 g/L Hepes; pH = 7.5; 16 g/L NaCl; 0.74 g/L KCl; 0.25 g/L Na 2 PO 4 ; and 2 g/L dextrose), forming a milky precipitate. The mixture was allowed to stand for 10-20 minutes at room temperature before it was added to the cells. A longer incubation time may result in a coarser precipitate that does not transform well, but sometimes a longer incubation time may be necessary to form a precipitate. C. Transformation of the Cells The 1 ml DNA solution prepared in Example 12B was added to a 25 cm 2 flask of HepG-2 cells with gentle agitation and incubated at 37° C for 3-4 hours. Using care not to detach the cells, the cells were washed twice with serum-free growth media (Dulbecco's Modified Eagle Medium, Gibco). One ml of HeBS with 15% glycerol was added to the cells, which were then incubated at 37° C for two minutes. The "glycerol-shock" incubation was terminated by the addition of serum-free growth media, followed by two washes with serum-free growth media. Complete fresh growth media containing a serum-substitute (either bovine serum albumin or Ultroser-G, which is marketed by Reactiff I.B.F. Foc. Chim. (LKB), Pointet Girard, 92390 Villeneuvela Garenne, France) and 12.5 µg/ml vitamin K 1 was then added, and the cells were returned to a 37° C incubator. Fetal calf serum was not used in the media, because it contains bovine factors and proteases that interfere with protein C assays. For transient assays, usually terminated about 96 hours post-transformation, sodium butyrate was added at 5 mM final concentration. For transformations involving a plasmid that comprised a selectable marker, such as the C418R or dhfr gene, when selection of stable transformants was desired, the sodium butyrate was not added, and the selective agent (e.g., 400 µg/ml G418) was added about two to four days post-transformation. At this time complete media containing fetal calf serum is added, and cells are allowed to propagate in selection media for two to three weeks with a change of media every 5-7 days. Individual clones are then isolated for further analysis. D. Assay for Protein C HepG-2/pL133 transformants and HepG-2 mock-transformed cells were assayed for protein C about 96 hours after transformation. Mock-transformed cells have been subjected to the transformation procedure but have not been exposed to transforming DNA. The assay requires antibody directed against protein C, as described below. Techniques for purification of protein C for subsequent use to prepare antibody against protein C are known in the art as are techniques for preparing polyclonal and monoclonal antibody. Goat anti-human protein C polyclonal antibody was incubated overnight in a 96-well tissue culture dish to bind the antibody to the plastic. After washing the wells with buffer, media samples from HepG-2/pL133 transformants and from mock-transformed HepG-2 cells were added to the wells. The media samples were taken 96 hours post-transformation. After incubating the media samples in the wells for two hours at 37° C, the wells were rinsed with buffer, and mouse anti-human protein C monoclonal IgG was added to the wells and incubated overnight at 4° C. After rinsing out the unbound monoclonal antibody with buffer, peroxidase-conjugated, sheep anti-mouse IgG was added to the wells and incubated at 37° C for 2 hours. After rinsing with buffer, a solution of ABTS (2,2'-azino-di-3-ethylbenzthiazoline-sulfonate) was added to the wells, and incubation in the dark at room temperature was continued, with optical density of the samples being measured at 405 nm every 30 minutes for 2 hours. In essence, the assay works by the protein C becoming bound to the polyclonal antibody which is attached to the dish. The monoclonal antibody then attaches to the protein C, and the peroxidase-conjugated, anti-mouse IgG becomes bound to the monoclonal antibody. The peroxidase reacts with ABTS in a time-dependent reaction to give a product that strongly absorbs at 405 nm. Simply stated, the more protein C in the sample, the higher the O.D. measurement at 405 nm. The HepG-2/pL133 transformants gave readings up to ten fold higher than those from mock-transformed cells, indicating plasmid-driven expression of protein C in the HepG-2/pL133 transformants. Because HepG-2 cells comprise a chromosomal protein C structural gene, mRNA was isolated from the transformants to determine if plasmid-encoded, protein C message was present. The transformants were shown to have ∼5X more plasmid-derived protein C mRNA than chromosomal-derived protein C mRNA. The readings correspond to about 100 ng to 300 ng of protein C per ml of conditioned media. Similar assays were conducted with CHO-K1 (dhfr - )/pL141 transformants, and about 1.8 µg of protein C were observed per ml of conditioned media. CHO-K1(dhfr - ) host cells, such as DXB11 host cells, lack the wild-type dihydrofolate reductase gene found in CHO-K1 cells. Such dhfr - CHO-K1 host cells can be generated in accordance with well known procedures. The DXB11/pL141 transformants express more protein C, because more copies of the recombinant protein C gene are present in DXB11/pL141 transformants than in HepG-2/pL133 transformants due to the amplification of the recombinant DNA. As stated above, this amplification is well known in the art and is accomplished by exposing the host cells transformed with a plasmid comprising a wild-type dhfr gene to increasing amounts of methotrexate. This methotrexate-mediated amplification can be accomplished in a wide variety of host cells and is not limited to dhfr - cell lines. Protein C assays conducted with LLC-MK 2 /pL132 transformants showed about 25 ng of protein C per ml of conditioned media. Example 11 Activation of Recombinant Human Protein C Zymogen This example applies to recombinant human protein C isolated from conditioned tissue culture medium from mammalian cells expressing and secreting recombinant human protein C. Protein C contained in conditioned tissue culture medium can also be activated directly, without prior purification. The activation makes use of rabbit thrombomodulin complexed with bovine thrombin; the complex is immobilized on agarose beads. The agarose beads are sedimentable and are therefore readily removed from the activation mixture. The thrombomodulin-thrombin may be immobilized to agarose beads in the following manner. A monoclonal antibody with high binding affinity for rabbit thrombomodulin is covalently linked to cross-linked agarose beads with 6-8 carbon atom arms (e.g., Affigel™ 102 or Affigel™ 202, Bio Rad, Richmond, California). The purified murine IgG monoclonal antibody, depending on the chemical structure of the arm of the crosslinked agarose, can be linked covalently via its free carboxyl or free amino groups using conventional carbodiimide compounds for covalent linkage. For example, approximately 0.15 OD units of IgG protein may be covalently linked to the agarose gel matrix. Next, a highly purified rabbit thrombomodulin preparation is diluted to 0.15 OD units/ml with a buffer that is 0.02 M Tris-HCl, pH 7.4, and 0.15 M in NaCl. Then, one volume of packed agarose beads with monoclonal anti-thrombomodulin antibody attached is mixed with one volume thrombomodulin and the mixture incubated overnight with gentle mixing. The beads are then centrifuged, and the amount of thrombomodulin bound is estimated by determining the A 280 of the supernatant, assuming an E 1% (extinction coefficient) of 8.8 and a M r (molecular weight) of 75 kd for the purified protein. Bovine thrombin purified to apparent homogeneity (specific activity: 2,000 NIH U/mg) is added in amounts slightly in excess of the amount calculated to be equimolar to the immobilized thrombomodulin. The beads are then incubated from 30 minutes to overnight at 4° C. Following this incubation, the beads are washed 6-10 times with the 0.02 M Tris-HCl, pH 7.4, and 0.15 M NaCl buffer, and the beads are then stored at 4° C in this buffer. One ml of the purified protein C solution or protein C-containing tissue culture media is added to 50 microliters of packed beads and incubated on a rocker for 30 minutes at 37° C. The activation of the zymogen to the activated serine protease readily occurs in a variety of physiological pH and ionic strength buffers usually containing one mg/ml bovine serum albumin (radioimmunoassay grade, Sigma, St. Louis, MO). The activation reaction requires calcium, and therefore, CaCl 2 is usually added to the activation mixture to a final concentration of 0.005-0.025 M. At the end of the incubation period, the beads are removed by centrifugation, and human antithrombin III, purified to apparent homogeneity, is added to quench any free thrombin which is still present. Twenty µl of purified antithrombin III (1 OD unit/ml) is added to each 500 microliters of activation mixture. After 15 minutes incubation at room temperature, the activation mixture is then tested for activated protein C activity using the synthetic peptide paranitroanilide (pNA) substrate, H-D-Phe-Pip-Arg-pNA (S-2238, Kabi-Vitrum, Stockholm, Sweden), or other tripeptide paranitroanilide substrates sensitive to activated protein C. By this technique, activation and expression of activated protein C activity is possible with protein C, irrespective of whether the post-translational γ-carboxylation modification has occurred. However, the activation rate of "gla-less" protein C is about 20% of the activation rate of the protein which has undergone post translational modifications. If the expressed product does not contain γ-carboxyglutamate residues, the activation incubation period is prolonged to the extent which takes this slower activation rate into account. Alternatively, activated protein C activity can be measured in a clotting assay which utilizes bovine clotting factor Xa, purified to apparent homogeneity, and which measures the rate of inactivation of clotting factor Va, the obligatory, activated protein C-sensitive cofactor in the factor Xa mediated conversion of prothrombin into thrombin. Conditioned media from HepG-2/pL133 transformants has been subjected to the activation procedure described above and, as demonstrated by the clotting assays, has been shown to have ∼2X to more activated protein C (∼250 ng/ml) than mock-transformed HepG-2 cells (∼125 ng/ml). Protein C isolated from the medium of CHO-K1-(dhfr - )/pL141 transformants was activated in accordance with the procedure of this Example and tested in the clotting and amidolytic assays. The assays demonstrated that the protein C was active and indicated that the transformed CHO-K1 host cells possessed substantial γ-carboxylase activity. Because many polypeptides, including, but not limited to, vitamin K-dependent serine proteases, such as protein C, require γ-carboxylation for at least a portion of their biological activity, and because few cell lines, such as, for example, the HepG-2 and H4IIEC3 cell lines, possess γ-carboxylase activity, the expression of substantial γ-carboxylase activity in CHO-K1 host cells was unexpected. Therefore, the present invention also comprises a method for using CHO-K1 host cells, including the dhfr - derivatives thereof, to produce γ-carboxylated polypeptides, especially the vitamin K-dependent serine proteases, such as human protein C. Whether an amidolytic or clotting assay is utilized, calibration curves are typically established using highly purified activated protein C derived from human plasma as the standard. The immobilized thrombomodulin-thrombin preparation is reuseable; full activating activity is readily regained after repeated washing of the beads in the 0.02 M Tris-HCl, pH 7.4, and 0.15 M NaCl buffer. This technique is suitable for the activation of large quantities of protein C in large volumes. If large volumes are to be activated, the beads are packed into a column of appropriate size for the amount of protein C to be activated, and the protein C solution is passed over the column at low flow rates (e.g. 6-10 ml/h).

Claims: Claims for the following Contracting States : BE, CH, DE, FR, GB, IT, LI, LU, NL, SE A method of producing a polypeptide with human protein C activity in a eukaryotic host which comprises: A. transforming the eukaryotic cell with a recombinant DNA vector comprising: (i) a DNA sequence that provides for autonomous replication or chromosomal integration of said vector in said host cell, (ii) a promoter and translational activating sequence functional in said host cell, which translational activating sequence does not encode a translational start codon; and (iii) double-stranded DNA positioned in transcriptional and translational reading phase with said promoter and translational activating sequence, the coding strand of said DNA being: wherein A is deoxyadenyl, G is deoxyguanyl, C is deoxycytidyl, and T is thymidyl; and B. culturing the host cell transformed in step A under conditions suitable for gene expression. The method of claim 1 wherein the host cell is a HepG-2, Aedes aegypti , CV-1, LLC-MK 2 , 3T3, CHO-K1, CHO-K1, CHO-K1(dhfr), Antheraea eucalypti , HeLa, RPM18226, H4IIEC3, C127I, or HS-Sultan cell. The method of claim 2 wherein the transformed host cell is a HepG-2, Aedes aegypti , C127I, LLC-MK 2 , 3T3, or H4IIEC3 cell transformed with a plasmid selected from: pL133 produced by ligating the ∼0.29 kb Hind III- Sal I restriction fragment of plasmid pSV2-HPC8, the ∼1.15 kb Sal I- Bgl II restriction fragment of plasmid pSV2-HPC8 and the ∼4.2 kb Bgl II-HindIII restriction fragment of plasmid pSV2-β-globin (NRRL B-15928), pSV2-HPC8 produced by ligating pHC-7 (NRRL B-15926) derived ∼1.23 kb Hin dIII- Apa I and ∼0,19 kb Apa I- Bgl II fragments to a plasmid pSV2-gpt (ATCC 37145) derived ∼5.1 kb Hin dIII- Bgl II fragment, and pL142 produced by ligating the ∼0.76 kb Nde I- Hin dIII restriction fragment of plasmid pRSVcat (ATCC 37152) and the ∼5.1 kb Nde I- Hin dIII restriction fragment of plasmid pL133. The method of claim 1 or 2 wherein the recombinant DNA vector further comprises a selectable marker that functions in said eukaryotic host cell. The method of claim 4 wherein the transformed cell is a HepG-2, Aedes aegypti , CV-1, LLC-MK 2 , 3T3, CHO-K1, CHO-K1 (dhfr - ), Antheraea eucalypti, HeLa, RPM18226, H4IIEC3, C127I, or HS-Sultan cell transformed with a plasmid selected from: pL132 produced by ligating the ∼0.29 kb Hin dIII- Sal I restriction fragment of plasmid pSV2-HPC8, the ∼1,15 kb SaI I- Bgl II restriction fragment of plasmid pSV2-HPC8 and the ∼5.7 kb Hin dIII- Bgl II restriction fragment of plasmid pSV2-neo (ATCC 37149), pL151 produced by ligating the plasmid pL142 derived ∼1.06 kb Bst Ell Xho I DNA sequence, the ∼4.2 kb Eco RI- Xho I restriction fragment of pSV2-dhfr-X (ATCC 37146), and the ∼2.74 kb Eco RI- Bst EII restriction fragment of plasmid pL133. pL141 produced by ligating the ∼4.2 kb Eco RI- Xho I restriction fragment of plasmid pSV2-dhfr-X (ATCC 37146), the plasmid pL133 derived ∼0.64 Xho I- Bst Ell DNA sequence, and the ∼2.7 kb Eco RI- Bst Ell restriction fragment of plasmid pL133. p2MSV-HPC produced by ligating the Bgl II digest of plasmid pMSVi (NRRL B-15929) and the ∼1.425 kb Bcl I restriction fragment of plasmid pSV2-HPC, and pMMTΔBPV-HPC produced by ligating the Bgl II digest of plasmid pMMTΔBPV derived by Bam HI treatment of plasmid pdBPV-MMtneo (ATCC 37224) and ligation with T4 DNA ligase, and the Bcl I digest of plasmid pSV2-HPC8. A eukaryotic host cell which is a HepG-2, Aedes aegypti , CV-1, LLC-MK 2 , 3T3, CHO-K1, CHO-K1 (dhfr - ), Antheraea eucalypti , HeLa, RPM18226, H4IIEC3, C127I, or HS-Sultan cell transformed with a plasmid selected from: pSV2-HPC8 defined in claim 3 pMSV-HPC defined in claim 5 pL133 defined in claim 3 pL132 defined in claim 5 pL151 defined in claim 5 pL141 defined in claim 5 pL142 defined in claim 3, and pMMTΔBPV-HPC defined in claim 5. Claims for the following Contracting State : AT A method of producing a polypeptide with human protein C activity in a eukaryotic host which comprises: A. transforming the eukaryotic cell with a recombinant DNA vector comprising: (i) a DNA sequence that provides for autonomous replication or chromosomal integration of said vector in said host cell, (ii) a promoter and translational activating sequence functional in said host cell, which translational activating sequence does not encode a translational start codon; and (iii) double-stranded DNA positioned in transcriptional and translational reading phase with said promoter and translational activating sequence, the coding strand of said DNA being: wherein A is deoxyadenyl, G is deoxyguanyl, C is deoxycytidyl, and T is thymidyl; and B. culturing the host cell transformed in step A under conditions suitable for gene expression. The process of claim 1 which comprises ligating the DNA segments into the form of a plasmid. The process of claim 2 which comprises ligating a coding strand derived from plasmid pHC7 to a eukaryotic transcriptional and translational activating sequence. The process of claim 1 which comprises ligating the coding strand to an SV40 promoter, the long terminal repeat promoter of the Rous sarcoma or the murine sarcoma virus, or the mouse metallothionein promoter. The process of claim 4 which comprises ligating the coding strand to an SV40 promoter. The process of claim 5 which comprises preparing plasmid pSV2-HPC8 by ligating plasmid pHC-7 derived ∼1.23 kb Hin dIII- Apa I and ∼0.19 kb Apa I- Bgl II fragments to a plasmid pSV2-gpt (ATCC 37145) derived ∼5.1 kb Hin dIII- Bgl II fragment. The process of claim 5 which comprises preparing plasmid pL133 by ligating the ∼0.29 kb Hin dIII- Sal I restriction fragment of plasmid pSV2-HPC8, the ∼1,15 kb Sal I- Bgl II restriction fragment of plasmid pSV2-HPC8, and the ∼4.2 kb Bg III- Hin dIII restriction fragment of plasmid pSV2-β-globin (NRRL B-15928). The process of claim 5 which comprises preparing plasmid pL132 by ligating the ∼0.29 kb Hin dIII- Sal I restriction fragment of plasmid pSV2-HPC8, the ∼1,15 kb Sal I- Bgl II restriction fragment of plasmid pSV2-HPC8, and the ∼5.7 kb Hin dIII- Bgl II restriction fragment of plasmid pSV2-neo (ATCC 37149). The process of claim 5 which comprises preparing plasmid pL141 by ligating the ∼4.2 kb Eco RI- Xho I restriction fragment of plasmid pSV2-dhfr-X (ATCC 37146), the plasmid pL133 derived ∼0.64 Xho I- Bst EII DNA sequence, and the ∼2.7 kb Eco RI- Bst EII restriction fragment of plasmid pL133. The process of claim 4 which comprises ligating the coding strand to the long terminal repeat promoter of the Rous sarcoma virus. The process of claim 10 which comprises preparing plasmid pL142 by ligating the ∼0.76 kb Nde I- Hin dIII restriction fragment of plasmid pRSV cat (ATCC 37152) and the ∼5.1 kb Nde I- Hind III restriction fragment of plasmid pL133. The process of claim 10 which comprises preparing plasmid pL151 by ligating the plasmid pL142 derived ∼1.06 kb Bst EII- Xho I DNA sequence, the ∼4.2 kb Eco RI- Xho I restriction fragment of plasmid pSV2-dhfr-X (ATCC 37146), and the ∼2.74 kb Eco RI- Bst EII restriction fragment of plasmid pL133. The process of claim 4 which comprises ligating the coding strand to the long terminal repeat promoter of the murine sarcoma virus. The process of claim 13 which comprises preparing plasmid pMSV-HPC by ligating the Bgl II digest of plasmid pMSVi (NRRL B-15929) and the ∼1.425 kb Bcl I restriction fragment of plasmid pSV2-HPC8. The process of claim 4 which comprises ligating the coding strand to the mouse metallothionein promoter. The process of claim 15 which comprises preparing plasmid pMMTΔBPV-HPC by ligating the Bgl II digest of plasmid pMMTΔBPV derived by Bam HI treatment of plasmid pdBPV-MMTneo (ATCC 37224) and ligation with T4 DNA ligase, and the BclI digest of plasmid pSV2-HPC8. The method of any preceding claim wherein the host cell is a cell of cell line HepG-2, Aedes aegypti, CV-1, LLC-MK 2 , 3T3, CHO-K1, CHO-K1 (dhfr-), Antheraea eucalypti , HeLa, RPMI8226, H4IIEC3, C127I, or HS-Sultan.

Inventors: BANG NILS ULRIK, BECKMANN ROBERT JOHN, JASKUNAS STANLEY RICHARD JR, LAI MEI-HUEI TSAI, LITTLE SHEILA PARKS, LONG GEORGE LOUIS, SANTERRE ROBERT FRANK, BANG, NILS ULRIK, BECKMANN, ROBERT JOHN, JASKUNAS, STANLEY RICHARD, JR., LAI, MEI-HUEI TSAI, LITTLE, SHEILA PARKS, LONG, GEORGE LOUIS, SANTERRE, ROBERT FRANK
Applicants: LILLY CO ELI, ELI LILLY AND COMPANY
Application year: 1986
Main classification: C12N15
IPC codes: C12P21, C12N5, A61K38, C12R1, A61K31, A61K35, C07H21, C12N1, C12N15, C07K14, A61P7, C12N9