title: Role of hepatocyte growth factor in breast cancer: a novel mitogenic factor secreted by adipocytes.
abstract: Stromal cells can dramatically affect the growth and metastatic capability of breast carcinoma cells. Growth factors, considered to be important mediators of this process, act as either mitogenic or mito-inhibitory regulators. We have developed an in vitro coculture system to examine the influence of adipocytes, a dominant mammary stromal cell type, on the growth of a murine mammary carcinoma, SP1. Previously, we have reported that conditioned medium (CM) from 3T3-L1 adipocytes can promote in vitro growth of SP1 cells. We now show that the major mitogenic signal derived from 3T3-L1 adipocyte CM is mediated by hepatocyte growth factor (HGF). Neutralizing antibody against HGF at 15 micrograms/ml completely abrogated mitogenic activity of 3T3-L1 CM. Furthermore, heparin, an inhibitor of biological activity of HGF, inhibited the mitogenic activity of 3T3-L1 CM. Western blot analysis also confirmed the presence of HGF in 3T3-L1 CM. Although basic fibroblast growth factor (bFGF) and insulin-like growth factor I (IGF-I) were mitogenic for SP1 cells, neutralizing antibodies against IGF-I, bFGF, platelet-derived growth factor (PDGF), and epidermal growth factor (EGF) did not inhibit the mitogenic activity of 3T3-L1 CM. Immunoprecipitation and immunoblotting of HGF receptor/c-met showed that c-met is expressed at high level in SP1 cells, and is phosphorylated following HGF ligation. Together, our present data demonstrate that 3T3-L1 adipocytes secrete HGF, which stimulates SP1 cell growth by a paracrine mechanism. Furthermore, the mitogenic effect of 3T3-L1 CM requires HGF receptor ligation and activation of tyrosine kinase signaling cascades in SP1 cells. These results highlight the importance of stromal-tumor cell interactions and suggest that HGF secreted by adipocytes may be a key regulator of mammary tumor growth.
authors: Department of Pathology, Queen's University, Kingston, Ontario, Canada.
authors: N
authors: N
authors: Rahimi
authors: R
authors: R
authors: Saulnier
authors: T
authors: T
authors: Nakamura
authors: M
authors: M
authors: Park
authors: B
authors: B
authors: Elliott
mesh_terms: D016475:3T3 Cells; D000230:Adenocarcinoma / Q000473:pathology*; D017667:Adipocytes / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000378:metabolism; D006133:Growth Substances / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D017228:Hepatocyte Growth Factor / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D008325:Mammary Neoplasms, Experimental / Q000473:pathology*; D051379:Mice; D008934:Mitogens / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D009500:Neutralization Tests; D010766:Phosphorylation; D019859:Proto-Oncogene Proteins c-met; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D017077:Culture Media, Conditioned; D006133:Growth Substances; D008934:Mitogens; D017228:Hepatocyte Growth Factor; D006493:Heparin; D019859:Proto-Oncogene Proteins c-met; D020794:Receptor Protein-Tyrosine Kinases