The interaction of neoplastic cells with the extracellular matrix is a critical event for the initiation of cancer invasion and metastasis. This study was designed to evaluate the potential implication of stromelysin-3 (ST3), a newly identified member of the matrix-degrading metalloproteinase family, and of BM-40/SPARC, a glycoprotein associated with the extracellular matrix, during the progression of human colorectal cancers. We analyzed the relative abundance of ST3 and BM-40/SPARC transcripts by Northern blot, and their distribution by in situ hybridization, in normal mucosa, benign adenomas, and primary colorectal adenocarcinomas and their liver metastases. The ST3 and BM-40/SPARC transcripts were overexpressed in primary colorectal cancers and their liver metastases compared to non-neoplastic mucosa. These transcripts were localized in stromal fibroblasts adjacent to the neoplastic foci. Overexpression of ST3 correlated with the progression of human colorectal tumors toward local invasion and liver metastasis. Induction of these genes also occurred in diverticulitis and digestive neoplasms such as gastric and esophageal carcinomas.

Summary Little is known about the the signalling pathways driving the adenoma-to-carcinoma sequence in human colonic epithelial cells. Accumulation and activation of the src tyrosine kinase in colon cancer suggest a potential role of this oncogene in this early progression. Therefore, we introduced either activated src (m-src), polyoma-MT alone or combined with normal c-src in the adenoma PC/AA/C1 cell line (PC) to define the function and phenotypic transformations induced by these oncogenes in familial adenomatous polyposis (FAP) colonic epithelial cells. Functional expression of these oncoproteins induced the adenoma-to-carcinoma conversion, overexpression of the hepatocyte growth factor (HGF) receptor Met, but failed to confer invasiveness in vivo and in vitro, or to produce alterations in cell proliferation and differentiation. In contrast, PC-msrc cells became susceptible to the HGF-induced invasion of collagen gels and exhibited sustained activation of the pp6osrctyrosine kinase and Tyr phosphorylation of the 120-kDa E-cadherin, which was further increased by HGF Transcripts of HGF were clearly identified by reverse transcription -polymerase chain reaction (RT-PCR) and Southern blot in the parental and transformed PC cells, suggesting an autocrine mechanism. Taken together, the data indicate that: (1) experimental activation of src and PyMT pathways directly induces tumorigenicity and Met upregulation in a colon adenoma cell line; (2) HGF-activated Met and src cooperate in inducing invasion; (3) in view of the molecular associations between catenins and cadherin or the tumour-suppressor gene product APC, the cell adhesion molecule E-cadherin may constitute a downstream effector of src and Met.

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ShcA and Grb2 are crucial components in signalling by most tyrosine kinase‐associated receptors. How ever, it is not clear whether Grb2 bound directly to the receptor is equivalent to Grb2 associated via ShcA. We have used signalling stimulated by the middle T‐antigen (MT) of polyoma virus to address this question. The two known Grb2‐binding sites from murine ShcA, 313Y and 239/240YY, could functionally replace the MT ShcA‐interacting region in transformation assays using Rat2 fibroblasts. This demonstrates that signal output from membrane‐bound ShcA requires only these two sequences and the ShcA‐binding site in MT does not recruit other signalling molecules. Two standard Grb2‐interacting sequences, either from the EGF receptor or the ShcA 313Y region, could not replace the requirement for ShcA binding to MT, indicating an enhanced role for the ShcA 239/240YY motif. Sos1 and the docking protein Gab1 are brought into the MT complex through Grb2 association and this may be more effective using the 239/240YY sequence.