Skip to main content
PMC home page
The EMBO Journal logoLink to The EMBO Journal
. 1992 Dec;11(13):4825–4833. doi: 10.1002/j.1460-2075.1992.tb05588.x

Extracellular proteolytic cleavage by urokinase is required for activation of hepatocyte growth factor/scatter factor.

L Naldini 1, L Tamagnone 1, E Vigna 1, M Sachs 1, G Hartmann 1, W Birchmeier 1, Y Daikuhara 1, H Tsubouchi 1, F Blasi 1, P M Comoglio 1
PMCID: PMC556958  PMID: 1334458

Abstract

The extracellular protease urokinase is known to be crucially involved in morphogenesis, tissue repair and tumor invasion by mediating matrix degradation and cell migration. Hepatocyte growth factor/scatter factor (HGF/SF) is a secretory product of stromal fibroblasts, sharing structural motifs with enzymes of the blood clotting cascade, including a zymogen cleavage site. HGF/SF promotes motility, invasion and growth of epithelial and endothelial cells. Here we show that HGF/SF is secreted as a single-chain biologically inactive precursor (pro-HGF/SF), mostly found in a matrix-associated form. Maturation of the precursor into the active alpha beta heterodimer takes place in the extracellular environment and results from a serum-dependent proteolytic cleavage. In vitro, pro-HGF/SF was cleaved at a single site by nanomolar concentrations of pure urokinase, generating the active mature HGF/SF heterodimer. This cleavage was prevented by specific urokinase inhibitors, such as plasminogen activator inhibitor type-1 and protease nexin-1, and by antibodies directed against the urokinase catalytic domain. Addition of these inhibitors to HGF/SF responsive cells prevented activation of the HGF/SF precursor. These data show that urokinase acts as a pro-HGF/SF convertase, and suggest that some of the growth and invasive cellular responses mediated by this enzyme may involve activation of HGF/SF.

Full text

PDF
4831

Images in this article

4826Image
on p.4826
4827Image
on p.4827
4828Image
on p.4828
4828Image
on p.4828
4829Image
on p.4829
4830Image
on p.4830

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Appella E., Robinson E. A., Ullrich S. J., Stoppelli M. P., Corti A., Cassani G., Blasi F. The receptor-binding sequence of urokinase. A biological function for the growth-factor module of proteases. J Biol Chem. 1987 Apr 5;262(10):4437–4440. [PubMed] [Google Scholar]
  2. Axelrod J. H., Reich R., Miskin R. Expression of human recombinant plasminogen activators enhances invasion and experimental metastasis of H-ras-transformed NIH 3T3 cells. Mol Cell Biol. 1989 May;9(5):2133–2141. doi: 10.1128/mcb.9.5.2133. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Barr P. J. Mammalian subtilisins: the long-sought dibasic processing endoproteases. Cell. 1991 Jul 12;66(1):1–3. doi: 10.1016/0092-8674(91)90129-m. [DOI] [PubMed] [Google Scholar]
  4. Bernier M., Laird D. M., Lane M. D. Insulin-activated tyrosine phosphorylation of a 15-kilodalton protein in intact 3T3-L1 adipocytes. Proc Natl Acad Sci U S A. 1987 Apr;84(7):1844–1848. doi: 10.1073/pnas.84.7.1844. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Bottaro D. P., Rubin J. S., Faletto D. L., Chan A. M., Kmiecik T. E., Vande Woude G. F., Aaronson S. A. Identification of the hepatocyte growth factor receptor as the c-met proto-oncogene product. Science. 1991 Feb 15;251(4995):802–804. doi: 10.1126/science.1846706. [DOI] [PubMed] [Google Scholar]
  6. Burnette W. N. "Western blotting": electrophoretic transfer of proteins from sodium dodecyl sulfate--polyacrylamide gels to unmodified nitrocellulose and radiographic detection with antibody and radioiodinated protein A. Anal Biochem. 1981 Apr;112(2):195–203. doi: 10.1016/0003-2697(81)90281-5. [DOI] [PubMed] [Google Scholar]
  7. Coffer A., Fellows J., Young S., Pappin D., Rahman D. Purification and characterization of biologically active scatter factor from ras-transformed NIH 3T3 conditioned medium. Biochem J. 1991 Aug 15;278(Pt 1):35–41. doi: 10.1042/bj2780035. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Comoglio P. M., Di Renzo M. F., Tarone G., Giancotti F. G., Naldini L., Marchisio P. C. Detection of phosphotyrosine-containing proteins in the detergent-insoluble fraction of RSV-transformed fibroblasts by azobenzene phosphonate antibodies. EMBO J. 1984 Mar;3(3):483–489. doi: 10.1002/j.1460-2075.1984.tb01834.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Cooper C. S., Park M., Blair D. G., Tainsky M. A., Huebner K., Croce C. M., Vande Woude G. F. Molecular cloning of a new transforming gene from a chemically transformed human cell line. Nature. 1984 Sep 6;311(5981):29–33. doi: 10.1038/311029a0. [DOI] [PubMed] [Google Scholar]
  10. Cooper C. S., Tempest P. R., Beckman M. P., Heldin C. H., Brookes P. Amplification and overexpression of the met gene in spontaneously transformed NIH3T3 mouse fibroblasts. EMBO J. 1986 Oct;5(10):2623–2628. doi: 10.1002/j.1460-2075.1986.tb04543.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Danø K., Andreasen P. A., Grøndahl-Hansen J., Kristensen P., Nielsen L. S., Skriver L. Plasminogen activators, tissue degradation, and cancer. Adv Cancer Res. 1985;44:139–266. doi: 10.1016/s0065-230x(08)60028-7. [DOI] [PubMed] [Google Scholar]
  12. Di Renzo M. F., Narsimhan R. P., Olivero M., Bretti S., Giordano S., Medico E., Gaglia P., Zara P., Comoglio P. M. Expression of the Met/HGF receptor in normal and neoplastic human tissues. Oncogene. 1991 Nov;6(11):1997–2003. [PubMed] [Google Scholar]
  13. Furie B., Furie B. C. The molecular basis of blood coagulation. Cell. 1988 May 20;53(4):505–518. doi: 10.1016/0092-8674(88)90567-3. [DOI] [PubMed] [Google Scholar]
  14. Furlong R. A., Takehara T., Taylor W. G., Nakamura T., Rubin J. S. Comparison of biological and immunochemical properties indicates that scatter factor and hepatocyte growth factor are indistinguishable. J Cell Sci. 1991 Sep;100(Pt 1):173–177. doi: 10.1242/jcs.100.1.173. [DOI] [PubMed] [Google Scholar]
  15. Garcia-Morales P., Minami Y., Luong E., Klausner R. D., Samelson L. E. Tyrosine phosphorylation in T cells is regulated by phosphatase activity: studies with phenylarsine oxide. Proc Natl Acad Sci U S A. 1990 Dec;87(23):9255–9259. doi: 10.1073/pnas.87.23.9255. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Gherardi E., Gray J., Stoker M., Perryman M., Furlong R. Purification of scatter factor, a fibroblast-derived basic protein that modulates epithelial interactions and movement. Proc Natl Acad Sci U S A. 1989 Aug;86(15):5844–5848. doi: 10.1073/pnas.86.15.5844. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Gherardi E., Stoker M. Hepatocyte growth factor--scatter factor: mitogen, motogen, and met. Cancer Cells. 1991 Jun;3(6):227–232. [PubMed] [Google Scholar]
  18. Gherardi E., Stoker M. Hepatocytes and scatter factor. Nature. 1990 Jul 19;346(6281):228–228. doi: 10.1038/346228b0. [DOI] [PubMed] [Google Scholar]
  19. Giordano S., Ponzetto C., Di Renzo M. F., Cooper C. S., Comoglio P. M. Tyrosine kinase receptor indistinguishable from the c-met protein. Nature. 1989 May 11;339(6220):155–156. doi: 10.1038/339155a0. [DOI] [PubMed] [Google Scholar]
  20. Gohda E., Tsubouchi H., Nakayama H., Hirono S., Sakiyama O., Takahashi K., Miyazaki H., Hashimoto S., Daikuhara Y. Purification and partial characterization of hepatocyte growth factor from plasma of a patient with fulminant hepatic failure. J Clin Invest. 1988 Feb;81(2):414–419. doi: 10.1172/JCI113334. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Hearing V. J., Law L. W., Corti A., Appella E., Blasi F. Modulation of metastatic potential by cell surface urokinase of murine melanoma cells. Cancer Res. 1988 Mar 1;48(5):1270–1278. [PubMed] [Google Scholar]
  22. Hecht P. M., Anderson K. V. Extracellular proteases and embryonic pattern formation. Trends Cell Biol. 1992 Jul;2(7):197–202. doi: 10.1016/0962-8924(92)90246-j. [DOI] [PubMed] [Google Scholar]
  23. Higuchi O., Nakamura T. Identification and change in the receptor for hepatocyte growth factor in rat liver after partial hepatectomy or induced hepatitis. Biochem Biophys Res Commun. 1991 Apr 30;176(2):599–607. doi: 10.1016/s0006-291x(05)80226-8. [DOI] [PubMed] [Google Scholar]
  24. Igawa T., Kanda S., Kanetake H., Saitoh Y., Ichihara A., Tomita Y., Nakamura T. Hepatocyte growth factor is a potent mitogen for cultured rabbit renal tubular epithelial cells. Biochem Biophys Res Commun. 1991 Jan 31;174(2):831–838. doi: 10.1016/0006-291x(91)91493-v. [DOI] [PubMed] [Google Scholar]
  25. Iyer A., Kmiecik T. E., Park M., Daar I., Blair D., Dunn K. J., Sutrave P., Ihle J. N., Bodescot M., Vande Woude G. F. Structure, tissue-specific expression, and transforming activity of the mouse met protooncogene. Cell Growth Differ. 1990 Feb;1(2):87–95. [PubMed] [Google Scholar]
  26. Kan M., Zhang G. H., Zarnegar R., Michalopoulos G., Myoken Y., McKeehan W. L., Stevens J. I. Hepatocyte growth factor/hepatopoietin A stimulates the growth of rat kidney proximal tubule epithelial cells (RPTE), rat nonparenchymal liver cells, human melanoma cells, mouse keratinocytes and stimulates anchorage-independent growth of SV-40 transformed RPTE. Biochem Biophys Res Commun. 1991 Jan 15;174(1):331–337. doi: 10.1016/0006-291x(91)90524-b. [DOI] [PubMed] [Google Scholar]
  27. Kasai S., Arimura H., Nishida M., Suyama T. Primary structure of single-chain pro-urokinase. J Biol Chem. 1985 Oct 5;260(22):12382–12389. [PubMed] [Google Scholar]
  28. Kirchheimer J. C., Wojta J., Christ G., Binder B. R. Functional inhibition of endogenously produced urokinase decreases cell proliferation in a human melanoma cell line. Proc Natl Acad Sci U S A. 1989 Jul;86(14):5424–5428. doi: 10.1073/pnas.86.14.5424. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Kirchheimer J. C., Wojta J., Christ G., Binder B. R. Proliferation of a human epidermal tumor cell line stimulated by urokinase. FASEB J. 1987 Aug;1(2):125–128. doi: 10.1096/fasebj.1.2.3038646. [DOI] [PubMed] [Google Scholar]
  30. Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
  31. Lawrence D., Strandberg L., Grundström T., Ny T. Purification of active human plasminogen activator inhibitor 1 from Escherichia coli. Comparison with natural and recombinant forms purified from eucaryotic cells. Eur J Biochem. 1989 Dec 22;186(3):523–533. doi: 10.1111/j.1432-1033.1989.tb15238.x. [DOI] [PubMed] [Google Scholar]
  32. Liu C., Park M., Tsao M. S. Overexpression of c-met proto-oncogene but not epidermal growth factor receptor or c-erbB-2 in primary human colorectal carcinomas. Oncogene. 1992 Jan;7(1):181–185. [PubMed] [Google Scholar]
  33. Lokker N. A., Mark M. R., Luis E. A., Bennett G. L., Robbins K. A., Baker J. B., Godowski P. J. Structure-function analysis of hepatocyte growth factor: identification of variants that lack mitogenic activity yet retain high affinity receptor binding. EMBO J. 1992 Jul;11(7):2503–2510. doi: 10.1002/j.1460-2075.1992.tb05315.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Mangel W. F., Lin B. H., Ramakrishnan V. Characterization of an extremely large, ligand-induced conformational change in plasminogen. Science. 1990 Apr 6;248(4951):69–73. doi: 10.1126/science.2108500. [DOI] [PubMed] [Google Scholar]
  35. Mann K. G., Jenny R. J., Krishnaswamy S. Cofactor proteins in the assembly and expression of blood clotting enzyme complexes. Annu Rev Biochem. 1988;57:915–956. doi: 10.1146/annurev.bi.57.070188.004411. [DOI] [PubMed] [Google Scholar]
  36. Massagué J. The transforming growth factor-beta family. Annu Rev Cell Biol. 1990;6:597–641. doi: 10.1146/annurev.cb.06.110190.003121. [DOI] [PubMed] [Google Scholar]
  37. Meissauer A., Kramer M. D., Hofmann M., Erkell L. J., Jacob E., Schirrmacher V., Brunner G. Urokinase-type and tissue-type plasminogen activators are essential for in vitro invasion of human melanoma cells. Exp Cell Res. 1991 Feb;192(2):453–459. doi: 10.1016/0014-4827(91)90064-2. [DOI] [PubMed] [Google Scholar]
  38. Michalopoulos G., Houck K. A., Dolan M. L., Leutteke N. C. Control of hepatocyte replication by two serum factors. Cancer Res. 1984 Oct;44(10):4414–4419. [PubMed] [Google Scholar]
  39. Miyazawa K., Tsubouchi H., Naka D., Takahashi K., Okigaki M., Arakaki N., Nakayama H., Hirono S., Sakiyama O., Takahashi K. Molecular cloning and sequence analysis of cDNA for human hepatocyte growth factor. Biochem Biophys Res Commun. 1989 Sep 15;163(2):967–973. doi: 10.1016/0006-291x(89)92316-4. [DOI] [PubMed] [Google Scholar]
  40. Montesano R., Matsumoto K., Nakamura T., Orci L. Identification of a fibroblast-derived epithelial morphogen as hepatocyte growth factor. Cell. 1991 Nov 29;67(5):901–908. doi: 10.1016/0092-8674(91)90363-4. [DOI] [PubMed] [Google Scholar]
  41. Morimoto A., Okamura K., Hamanaka R., Sato Y., Shima N., Higashio K., Kuwano M. Hepatocyte growth factor modulates migration and proliferation of human microvascular endothelial cells in culture. Biochem Biophys Res Commun. 1991 Sep 16;179(2):1042–1049. doi: 10.1016/0006-291x(91)91924-2. [DOI] [PubMed] [Google Scholar]
  42. Nagaike M., Hirao S., Tajima H., Noji S., Taniguchi S., Matsumoto K., Nakamura T. Renotropic functions of hepatocyte growth factor in renal regeneration after unilateral nephrectomy. J Biol Chem. 1991 Dec 5;266(34):22781–22784. [PubMed] [Google Scholar]
  43. Nakamura T., Nawa K., Ichihara A., Kaise N., Nishino T. Purification and subunit structure of hepatocyte growth factor from rat platelets. FEBS Lett. 1987 Nov 30;224(2):311–316. doi: 10.1016/0014-5793(87)80475-1. [DOI] [PubMed] [Google Scholar]
  44. Nakamura T., Nawa K., Ichihara A. Partial purification and characterization of hepatocyte growth factor from serum of hepatectomized rats. Biochem Biophys Res Commun. 1984 Aug 16;122(3):1450–1459. doi: 10.1016/0006-291x(84)91253-1. [DOI] [PubMed] [Google Scholar]
  45. Nakamura T., Nishizawa T., Hagiya M., Seki T., Shimonishi M., Sugimura A., Tashiro K., Shimizu S. Molecular cloning and expression of human hepatocyte growth factor. Nature. 1989 Nov 23;342(6248):440–443. doi: 10.1038/342440a0. [DOI] [PubMed] [Google Scholar]
  46. Naldini L., Vigna E., Narsimhan R. P., Gaudino G., Zarnegar R., Michalopoulos G. K., Comoglio P. M. Hepatocyte growth factor (HGF) stimulates the tyrosine kinase activity of the receptor encoded by the proto-oncogene c-MET. Oncogene. 1991 Apr;6(4):501–504. [PubMed] [Google Scholar]
  47. Naldini L., Weidner K. M., Vigna E., Gaudino G., Bardelli A., Ponzetto C., Narsimhan R. P., Hartmann G., Zarnegar R., Michalopoulos G. K. Scatter factor and hepatocyte growth factor are indistinguishable ligands for the MET receptor. EMBO J. 1991 Oct;10(10):2867–2878. doi: 10.1002/j.1460-2075.1991.tb07836.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  48. Ossowski L. In vivo invasion of modified chorioallantoic membrane by tumor cells: the role of cell surface-bound urokinase. J Cell Biol. 1988 Dec;107(6 Pt 1):2437–2445. doi: 10.1083/jcb.107.6.2437. [DOI] [PMC free article] [PubMed] [Google Scholar]
  49. Ossowski L. Plasminogen activator dependent pathways in the dissemination of human tumor cells in the chick embryo. Cell. 1988 Feb 12;52(3):321–328. doi: 10.1016/s0092-8674(88)80025-4. [DOI] [PubMed] [Google Scholar]
  50. Ossowski L., Reich E. Antibodies to plasminogen activator inhibit human tumor metastasis. Cell. 1983 Dec;35(3 Pt 2):611–619. doi: 10.1016/0092-8674(83)90093-4. [DOI] [PubMed] [Google Scholar]
  51. Park M., Dean M., Cooper C. S., Schmidt M., O'Brien S. J., Blair D. G., Vande Woude G. F. Mechanism of met oncogene activation. Cell. 1986 Jun 20;45(6):895–904. doi: 10.1016/0092-8674(86)90564-7. [DOI] [PubMed] [Google Scholar]
  52. Park M., Dean M., Kaul K., Braun M. J., Gonda M. A., Vande Woude G. Sequence of MET protooncogene cDNA has features characteristic of the tyrosine kinase family of growth-factor receptors. Proc Natl Acad Sci U S A. 1987 Sep;84(18):6379–6383. doi: 10.1073/pnas.84.18.6379. [DOI] [PMC free article] [PubMed] [Google Scholar]
  53. Patthy L., Trexler M., Váli Z., Bányai L., Váradi A. Kringles: modules specialized for protein binding. Homology of the gelatin-binding region of fibronectin with the kringle structures of proteases. FEBS Lett. 1984 Jun 4;171(1):131–136. doi: 10.1016/0014-5793(84)80473-1. [DOI] [PubMed] [Google Scholar]
  54. Petersen L. C., Lund L. R., Nielsen L. S., Danø K., Skriver L. One-chain urokinase-type plasminogen activator from human sarcoma cells is a proenzyme with little or no intrinsic activity. J Biol Chem. 1988 Aug 15;263(23):11189–11195. [PubMed] [Google Scholar]
  55. Ponzetto C., Giordano S., Peverali F., Della Valle G., Abate M. L., Vaula G., Comoglio P. M. c-met is amplified but not mutated in a cell line with an activated met tyrosine kinase. Oncogene. 1991 Apr;6(4):553–559. [PubMed] [Google Scholar]
  56. Prat M., Narsimhan R. P., Crepaldi T., Nicotra M. R., Natali P. G., Comoglio P. M. The receptor encoded by the human c-MET oncogene is expressed in hepatocytes, epithelial cells and solid tumors. Int J Cancer. 1991 Sep 30;49(3):323–328. doi: 10.1002/ijc.2910490302. [DOI] [PubMed] [Google Scholar]
  57. Pyke C., Kristensen P., Ralfkiaer E., Grøndahl-Hansen J., Eriksen J., Blasi F., Danø K. Urokinase-type plasminogen activator is expressed in stromal cells and its receptor in cancer cells at invasive foci in human colon adenocarcinomas. Am J Pathol. 1991 May;138(5):1059–1067. [PMC free article] [PubMed] [Google Scholar]
  58. Rubin J. S., Chan A. M., Bottaro D. P., Burgess W. H., Taylor W. G., Cech A. C., Hirschfield D. W., Wong J., Miki T., Finch P. W. A broad-spectrum human lung fibroblast-derived mitogen is a variant of hepatocyte growth factor. Proc Natl Acad Sci U S A. 1991 Jan 15;88(2):415–419. doi: 10.1073/pnas.88.2.415. [DOI] [PMC free article] [PubMed] [Google Scholar]
  59. Russell W. E., McGowan J. A., Bucher N. L. Partial characterization of a hepatocyte growth factor from rat platelets. J Cell Physiol. 1984 May;119(2):183–192. doi: 10.1002/jcp.1041190207. [DOI] [PubMed] [Google Scholar]
  60. Saksela O., Rifkin D. B. Cell-associated plasminogen activation: regulation and physiological functions. Annu Rev Cell Biol. 1988;4:93–126. doi: 10.1146/annurev.cb.04.110188.000521. [DOI] [PubMed] [Google Scholar]
  61. Sato Y., Rifkin D. B. Inhibition of endothelial cell movement by pericytes and smooth muscle cells: activation of a latent transforming growth factor-beta 1-like molecule by plasmin during co-culture. J Cell Biol. 1989 Jul;109(1):309–315. doi: 10.1083/jcb.109.1.309. [DOI] [PMC free article] [PubMed] [Google Scholar]
  62. Sato Y., Tsuboi R., Lyons R., Moses H., Rifkin D. B. Characterization of the activation of latent TGF-beta by co-cultures of endothelial cells and pericytes or smooth muscle cells: a self-regulating system. J Cell Biol. 1990 Aug;111(2):757–763. doi: 10.1083/jcb.111.2.757. [DOI] [PMC free article] [PubMed] [Google Scholar]
  63. Steiner D. F. Prohormone convertases revealed at last. Curr Biol. 1991 Dec;1(6):375–377. doi: 10.1016/0960-9822(91)90198-6. [DOI] [PubMed] [Google Scholar]
  64. Stern C. D., Ireland G. W., Herrick S. E., Gherardi E., Gray J., Perryman M., Stoker M. Epithelial scatter factor and development of the chick embryonic axis. Development. 1990 Dec;110(4):1271–1284. doi: 10.1242/dev.110.4.1271. [DOI] [PubMed] [Google Scholar]
  65. Stoker M., Gherardi E., Perryman M., Gray J. Scatter factor is a fibroblast-derived modulator of epithelial cell mobility. Nature. 1987 May 21;327(6119):239–242. doi: 10.1038/327239a0. [DOI] [PubMed] [Google Scholar]
  66. Weidner K. M., Arakaki N., Hartmann G., Vandekerckhove J., Weingart S., Rieder H., Fonatsch C., Tsubouchi H., Hishida T., Daikuhara Y. Evidence for the identity of human scatter factor and human hepatocyte growth factor. Proc Natl Acad Sci U S A. 1991 Aug 15;88(16):7001–7005. doi: 10.1073/pnas.88.16.7001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  67. Weidner K. M., Behrens J., Vandekerckhove J., Birchmeier W. Scatter factor: molecular characteristics and effect on the invasiveness of epithelial cells. J Cell Biol. 1990 Nov;111(5 Pt 1):2097–2108. doi: 10.1083/jcb.111.5.2097. [DOI] [PMC free article] [PubMed] [Google Scholar]
  68. Yoshiyama Y., Arakaki N., Naka D., Takahashi K., Hirono S., Kondo J., Nakayama H., Gohda E., Kitamura N., Tsubouchi H. Identification of the N-terminal residue of the heavy chain of both native and recombinant human hepatocyte growth factor. Biochem Biophys Res Commun. 1991 Mar 15;175(2):660–667. doi: 10.1016/0006-291x(91)91616-k. [DOI] [PubMed] [Google Scholar]
  69. Zarnegar R., Michalopoulos G. Purification and biological characterization of human hepatopoietin A, a polypeptide growth factor for hepatocytes. Cancer Res. 1989 Jun 15;49(12):3314–3320. [PubMed] [Google Scholar]

Articles from The EMBO Journal are provided here courtesy of Nature Publishing Group

RESOURCES