A role for epidermal growth factor receptor, c-Src and focal adhesion kinase in an in vitro model for the progression of colon cancer

Abstract

We have examined the function of the epidermal growth factor (EGF) receptor, c-Src and focal adhesion kinase (FAK) in the progression of colon cancer using an in vitro progression model. A non-tumorigenic cell line was derived from a premalignant colonic adenoma (PC/AA) from which a clonogenic variant was established (AA/ C1). Following sequential treatment with sodium butyrate and the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine an anchorage-independent line was isolated which, with time in culture, became tumorigenic when injected into athymic nude mice (AA/C1/SB10). We have shown that both EGF receptor and FAK protein levels were elevated in the carcinoma cells as compared to the adenoma cells, while the expression and activity of c-Src were unaltered during the adenoma to carcinoma transition. EGF induced the movement of the carcinoma cells into a reconstituted basement membrane which was not seen with the premalignant adenoma cells. This increased motility was accompanied by an EGF-induced increase in c-Src kinase activity, relocalisation of c-Src to the cell periphery and phosphorylation of FAK in the carcinoma cells but not in the adenoma cells. This suggests that c-Src plays a role in the biological behaviour of colonic carcinoma cells induced by migratory factors such as EGF, perhaps acting in conjunction with FAK to regulate focal adhesion turnover and tumour cell motility. Furthermore, although cSrc has been implicated in colonic tumour progression, we demonstrate here that in the adenoma to carcinoma in vitro model c-Src is not the driving force for this progression but co-operates with other molecules in carcinoma development.

Activation of c-Src by receptor tyrosine kinases in human colon cancer cells with high metastatic potential

“…A 120 kDa protein as well as a 85 kDa protein, whose identities have yet to be determined, are also phosphorylated in c-Src transfectants. A recent report by Brunton et al (1997) corroborates our ®ndings in that they demonstrated an EGF induced increase in c-Src kinase activity in an in vitro, chemically-induced model of colon cancer. Data derived from experiments using v-Src and other mutationally-active forms of c-Src have also provided strong evidence for a role for c-Src and receptor kinases in metastasis.…”

Complex formation between EphB2 and Src requires phosphorylation of tyrosine 611 in the EphB2 juxtamembrane region

“…These are similar to the modi®cations of Src occurring upon activation of the PDGF receptor (Ralston and Bishop, 1985), which reportedly re¯ect phosphorylation of residues in the amino terminus of Src and increased Src kinase activity (Gould and Hunter, 1988;Stover et al, 1996). Interestingly, Src activity has been associated with changes in cytoskeletal organization (Thomas et al, 1995;Parsons and Parsons, 1997;Brunton et al, 1997), such as those that might occur during the migration of cells (Hall et al, 1996;Boyer et al, 1997) and the retraction of neurites (Schindelholz et al, 1997).…”

Src promotes destruction of c-Cbl: Implications for oncogenic synergy between Src and growth factor receptors

“…Within the complex, Src phosphorylates the associated receptor at a site located in the kinase domain (26), a modification known to enhance catalytic activity of growth factor receptors. In line with the possibility that these interactions enable synergy between c-Src and various receptors (4,27), mutational inactivation of the c-Src-specific phosphorylation site on EGFR ablated EGF-induced mitogenicity (5). Thus, by blocking receptor degradation (Fig.…”