Hepatocyte growth factor
(HGF)

Scatter factor (SF)
Lung fibroblast-derived mitogen
Hepatopoietin A
Met ligand

Gene: HGF maps to 7q21.1. The HGF cellular receptor gene, the MET oncogene, is also located on 7q. Thus, cells with polysomy of chromosome 7 may simultaneously overproduce both the factor and its receptor and acquire invasive properties through an autocrine mechanism.
mRNA: size: 6.0 kb.
Protein: HGF consists of 2 chains, heavy and light, with molecular weights of 54-69 kDa and 31-34 kDa, respectively. These chains are linked together by disulfide bonds. The sequence of the pre-pro-protein deduced from the mRNA consists of 728 amino acid residues. The heavy and light chains are encoded by the same mRNA and are produced from a common translation product by proteolytic processing.
HGF/SF is an essential mediator of allantoic mesenchyme-trophoblastic epithelia interaction required for placental organogenesis.
During development of the mammary gland, HGF is involved in branching duct formation in mammary gland epithelial cells. HGF affects growth of mammary epithelial cells as a stromal (fibroblast)-derived paracrine factor.
HGF is an in vivo potent angiogenic factor and in vitro induces endothelial cells to proliferate and migrate.
It appears that HGF production by MRC-5 human fetal lung fibroblast cell line is inhibited by several known peptide growth factors, including transforming growth factor beta, epidermal growth factor, and transforming growth factor alpha (Seslar S.P. et al., 1993).

HGF is an angiogenic growth factor that stimulates motility and invasion of carcinoma cells. HGF is present in the extracellular matrix (ECM) of breast cancers, where it might act to promote tumor cell invasion and angiogenesis.

Cell lines:
- It has been shown that several adult human primary fibroblast cultures from breast produced HGF. HGF expression in the MRC-5 human fetal lung fibroblast cell line was stimulated by conditioned media harvested from human breast cancer cell (BCC) lines (MCF-7, T47D, and MDA-MB-231). In contrast, both indirect and direct coculture of each of these BCC lines with MRC-5 fibroblasts down-regulated HGF expression (Seslar S.P. et al., 1993).

- HGF was found to bind in a dose-dependent fashion to extracellular matrix secreted by three human BCC lines. Binding of HGF to matrices from all three cell lines was significantly inhibited by preincubation of the matrices with antibodies against thrombospondin-1, whereas antibodies against several other ECM components were less effective or ineffective in inhibiting HGF binding (Lamszus K. et al., 1996).

- MDA-MB-231 BCC were transfected with HGF. When injected in the mammary fat pads of athymic nude mice, two HGF+ clones showed significantly increased tumor growth rates, reaching 3- to 4-fold larger primary tumor volumes and weights by time of killing (p < 0.001), as well as higher rates of axillary lymph node metastasis (p < 0.02), as compared with two HGF- clones. In contrast, in vitro proliferation rates, two-dimensional colony formation, and soft agar colony formation were no greater in HGF+ than in HGF- clones. Immunostaining of tumor sections for proliferating cell nuclear antigen revealed only a modest increase in the proportion of cycling cells in HGF+ versus HGF- tumors (70% versus 60%, respectively). The terminal deoxytransferase-labeling index was equally low (approximately 1%) in HGF+ and HGF- tumors, suggesting that apoptosis was not responsible for the slower growth of HGF- tumors. However, HGF+ tumors had significantly higher tumor microvessel densities than HGF- tumors (p < 0.001). Moreover, there were much higher titers of chemotactic activity for microvascular endothelial cells in cell-conditioned media and primary tumor extracts from HGF+ clones as compared with HGF- clones. As demonstrated using the rat cornea assay, there was more angiogenic activity in HGF+ tumor extracts than in HGF- extracts. The increased chemotactic and angiogenic activities in HGF+ tumor extracts were not explained by secondary alterations in the content of the angiogenic mediator, vascular endothelial growth factor, or the antiangiogenic glycoprotein, thrombospondin-1; and those activities were neutralized using an anti-HGF monoclonal antibody (Lamszus K. et al., 1997).

- Prostaglandins produced by mouse mammary tumor cells were shown to induce HGF production by human fibroblasts. HGF was able to enhance uPA, but not MMP9 activity, in mouse mammary cells and to increase their invasion through Matrigel (Matsumoto-Taniura N. et al., 1999).

- Following c-met activation by HGF in tumour cells, phosphorylation of beta-catenin occurs, together with loss of intercellular adhesion and a gain in the motile and invasive nature of the cell. It was shown that c-met is co-localised with beta-catenin and E-cadherin at regions of cell-cell contact in MCF7 and MDA MB 231 BCC lines. Immunoprecipitation studies demonstrated an association between c-met and members of the cadherin adhesion complex in these epithelial tumour cells, along with the membrane tyrosine protein phophatase, PTPmu (Hiscox S. and Jiang W.G., 1999).

- T47D BCC were transfected with human HGF. The HGF-positive clones exhibited different levels of biologically functional HGF expression and up-regulation of endogenous Met (HGF receptor) expression. In addition, a constitutive phosphorylation of the receptor on tyrosine residues was detected, establishing a Met-HGF autocrine loop. The autocrine activation of Met caused marked inhibition in cell growth accompanied by cell accumulation at G₀/G₁. These cells underwent terminal cell differentiation as determined by morphological changes, synthesis of milk proteins such as beta-casein and alpha-lactalbumin, and production of lipid vesicles (Ronen D. et al., 1999).

Tumors: - In malignant breast epithelium, HGF expression was seen in 15 of 21 cases of in situ and invasive breast cancer. In some cases of invasive ductal carcinoma stronger labeling appeared to be associated with areas of tubule formation compared with areas of infiltrating growth, although this was not a universal finding. In contrast, two examples each of in situ comedo carcinoma and invasive lobular carcinoma were completely negative (Wang Y. et al., 1994).

- The expression of HGF is elevated in mammary carcinomas, in comparison with findings in benign hyperplasia (Tuck A.B. et al., 1996; Jin L. et al., 1997).

- It has been shown that HGF and c-met are overexpressed in breast carcinoma as compared with benign breast tissue, and that they tend to be coexpressed in cancerous tissue. These findings are consistent with the idea that the HGF:c-met ligand:receptor pair may have a role in breast carcinoma progression (Jin L. et al., 1997).

- HGF levels in breast cancer tissue are a strong a strong predictor of a recurrence in breast cancer patients (Yamashita J. et al., 1994; Nagy J. et al., 1996; Yao Y. et al., 1996).

- In a series of 166 breast cancer, there was no significant correlation between HGF content and other parameters, including estrogen receptor, progesterone receptor, DNA ploidy, S phase, or Scarff-Bloom-Richardson score. In the same study, HGF content showed a strong positive correlation with von Willebrand factor (a marker of blood vessels) content (P < 0.001), but did not appear to be correlated with interleukin-1 beta (Yao Y. et al., 1996).

- The serum concentration of HGF was examined in 34 patients with metastatic breast cancer. Although no significant difference was observed between HGF concentration and the site of metastasis, serum HGF levels were slightly higher in patients with liver metastasis and in patients with multiple metastatic sites than in patients with other lesions. Significantly higher levels of serum HGF were observed in patients with progressive metastasis of breast cancer compared with those with stable metastasis. The patients with high HGF levels exhibited a significantly shorter survival rate than those with low HGF levels (Maemura M. et al., 1998).

- The prognostic value of the circulating HGF level determined by enzymatic immunoassay was investigated in 200 primary breast cancer patients. 54 (27.0%) showed an increase of serum HGF level according to the age-matched cutoff values. The prognosis of the patients with the increased HGF level was statistically worse than that of the patients with normal HGF level. Multivariate analysis confirmed that the increase in HGF level was an independent prognostic indicator in primary breast cancer patients. In the background analysis, the increase in serum HGF level was significantly associated with tumor size, nodal status, and histological evidence of venous invasion (Toi M. et al., 1998).

Fukuyama R. et al. (1991) Assignment of hepatocyte growth factor (HGF) gene to chromosome 7q21.1. (Abstract) Cytogenet. Cell Genet. 58, 1921.
Gherardi E. and Stoker M. (1990) Hepatocytes and scatter factor. Nature 346, 228.
Hiscox S. and Jiang W.G. (1999) Association of the HGF/SF receptor, c-met, with the cell-surface adhesion molecule, E-cadherin, and catenins in human tumor cells. Biochem. Biophys. Res. Commun. 261, 406-411.
Jin L. et al. (1997) Expression of scatter factor and c-met receptor in benign and malignant breast tissue. Cancer 79, 749-760.
Lamszus K. et al. (1996) Scatter factor binds to thrombospondin and other extracellular matrix components. Am. J. Pathol. 149, 805-819.
Lamszus K. et al. (1997) Scatter factor stimulates tumor growth and angiogenesis in human breast cancers in the mammary fat pads of nude mice. Lab. Invest. 76, 339-353.
Maemura M. et al. (1998) Serum concentration of hepatocyte growth factor in patients with metastatic breast cancer. Cancer Lett. 126, 215-220.
Matsumoto-Taniura N. et al. (1999) Prostaglandin production in mouse mammary tumour cells confers invasive growth potential by inducing hepatocyte growth factor in stromal fibroblasts. Br. J. Cancer 81, 194-202.
Miyazawa K. et al. (1989) Molecular cloning and sequence analysis of cDNA for human hepatocyte growth factor. Biochem. Biophys. Res. Commun. 163, 967-973.
Nagy J. et al. (1996) Hepatocyte growth factor/scatter factor expression and c-met in primary breast cancer. Surg. Oncol. 5, 15-21.
Nakamura T. et al. (1989) Molecular cloning and expression of human hepatocyte growth factor. Nature 342, 440-443.
Ronen D. et al. (1999) Met-HGF/SF mediates growth arrest and differentiation in T47D breast cancer cells. Cell Growth Differ. 10, 131-140.
Seslar S. et al. (1993) Regulation of fibroblast hepatocyte growth factor/scatter factor expression by human carcinoma cell lines and peptide growth factors. Cancer Res. 53, 1233-1238.
Toi M. et al. (1998) Significance of circulating hepatocyte growth factor level as a prognostic indicator in primary breast cancer. Clin. Cancer Res. 4, 659-664.
Tuck A.B. et al. (1996) Coexpression of hepatocyte growth factor and receptor (Met) in human breast carcinoma. Am. J. Pathol. 148, 225-232.
Wang Y. et al. (1994) Hepatocyte growth factor/scatter factor expression in human mammary epithelium. Am. J. Pathol. 144, 675-682.
Weidner K.M. et al. (1991) Evidence for the identity of human scatter factor and human hepatocyte growth factor. Proc. Nat. Acad. Sci. USA 88, 7001-7005.
Yamashita J. et al. (1994) Immunoreactive hepatocyte growth factor is a strong and independent predictor of recurrence and survival in human breast cancer. Cancer Res. 54, 1630-1633.
Yao Y. et al. (1996) Scatter factor protein levels in human breast cancers: clinicopathological and biological correlations. Am. J. Pathol. 149, 1707-1717.