Rahimi N, Hung W, Tremblay E, Saulnier R, Elliott B
Department of Pathology, Cancer Research Laboratories, Queen's University, Kingston, Ontario K7L 3N6, Canada.
J Biol Chem. 1998 Dec 11;273(50):33714-21. doi: 10.1074/jbc.273.50.33714.
Overexpression and amplification of hepatocyte growth factor (HGF) receptor (Met) have been detected in many types of human cancers, suggesting a critical role for Met in growth and development of malignant cells. However, the molecular mechanism by which Met contributes to tumorigenesis is not well known. The tyrosine kinase c-Src has been implicated as a modulator of cell proliferation, spreading, and migration; these functions are also regulated by Met. To explore whether c-Src kinase is involved in HGF-induced cell growth, a mouse mammary carcinoma cell line (SP1) that co-expresses HGF and Met and a nonmalignant epithelial cell line (Mv1Lu) that expresses Met but not HGF were used. In this study, we have shown that c-Src kinase activity is constitutively elevated in SP1 cells and is induced in response to HGF in Mv1Lu cells. In addition, c-Src kinase associates with Met following stimulation with HGF. The enhanced activity of c-Src kinase also correlates with its ability to associate with Met. Expression of a dominant negative double mutant of c-Src (SRC-RF), lacking both kinase activity (K295R) and a regulatory tyrosine residue (Y527F), in SP1 cells significantly reduced c-Src kinase activity and strongly blocked HGF-induced motility and colony growth in soft agar. In contrast, expression of the dominant negative c-Src mutant had no effect on HGF-induced cell proliferation on plastic. Taken together, our data strongly suggest that HGF-induced association of c-Src with Met and c-Src activation play a critical role in HGF-induced cell motility and anchorage-independent growth of mammary carcinomas and further support the notion that the presence of paracrine and autocrine HGF loops contributes significantly to the transformed phenotype of carcinoma cells.
在多种人类癌症中均检测到肝细胞生长因子（HGF）受体（Met）的过表达和扩增，这表明Met在恶性细胞的生长和发育中起关键作用。然而，Met促进肿瘤发生的分子机制尚不清楚。酪氨酸激酶c-Src被认为是细胞增殖、扩散和迁移的调节因子；这些功能也受Met调控。为了探究c-Src激酶是否参与HGF诱导的细胞生长，我们使用了共表达HGF和Met的小鼠乳腺癌细胞系（SP1）以及表达Met但不表达HGF的非恶性上皮细胞系（Mv1Lu）。在本研究中，我们发现c-Src激酶活性在SP1细胞中组成性升高，在Mv1Lu细胞中则对HGF产生应答而被诱导。此外，HGF刺激后c-Src激酶与Met结合。c-Src激酶活性的增强也与其与Met结合的能力相关。在SP1细胞中表达缺乏激酶活性（K295R）和调节性酪氨酸残基（Y527F）的c-Src显性负性双突变体（SRC-RF），显著降低了c-Src激酶活性，并强烈阻断了HGF诱导的软琼脂中细胞的运动性和集落生长。相反，显性负性c-Src突变体的表达对塑料培养皿上HGF诱导的细胞增殖没有影响。综上所述，我们的数据强烈表明，HGF诱导的c-Src与Met结合以及c-Src激活在HGF诱导的乳腺癌细胞运动性和非锚定依赖性生长中起关键作用，并进一步支持旁分泌和自分泌HGF环的存在对癌细胞转化表型有显著贡献这一观点。
