Neoplastic progression of human and rat intestinal cell lines after transfer of the ras and polyoma middle T oncogenes

Progression of familial adenomatous polyposis (FAP) colonic cells after transfer of the src or polyoma middle T oncogenes: cooperation between src and HGF/Met in invasion

“…Detailed differences shown by exponentially growing PCm-src cells consisted in the appearance of pseudopod-like structures and ruffling at the cellular membrane, suggesting decreased cell-cell or cell-matrix adhesion properties (data not shown). Transmission electron microscopy showed that the transformation of the highly differentiated PC cell line by src, Py-MT alone or combined with PyLT and small T did not result in loss of epithelial organization or morphological phenotype contrary to our previous observations on ras-and Py-MT-transformed Caco-2 enterocytes (Chastre et al, 1993;Baron-Delage, 1996). Oncogene-transfected PC cells exhibited typical apical tight junctions and retention of the epithelial polarization.…”

“…The Py-MT antigen (Mr 55 000) was found to be phosphorylated and associated with pp6Osrc in src immunoprecipitates Status of p21 ras, cell proliferation and differentiation As the p21ras protein is another downstream effector of src and Py-MT, we analysed the GDP/GTP ratio on ras in the parental PC cells and their derivatives. We observed that PC cells exhibited a high proportion of GTP bound to p2lras (49%), because this cell line harbours a substitution of the Gly-12 residue for a valine in one allele of the Ki-ras gene (Farr et al, 1988;Chastre et al, 1993). This constitutive activation of mutated Ki-ras in PC cells was not further increased after the insertion of the oncogenes (data not shown), and compares with the proportion of GTP bound to p2 lras (45-48%) observed in Caco-2 cells transfected by oncogenic ras (Baron-Delage et al, 1994).…”

“…The Py virus early region encodes the small, middle and large T oncoproteins. The control vector, Homer 6, and the corresponding pHO6MTl vector recombined with the Py middle T oncogene were a generous gift from Dr D Spandidos (Chastre et al, 1993). Transfections were performed using the lipofection method (Lipofectin Reagent, Gibco BRL).…”

“…Monolayers of PC cells were processed for electron microscopy, as previously described (Chastre et al, 1993). The histology of the tumours in nude mice and liver or lung was analysed after fixation in 4% formaldehyde, paraffin embedding and staining with haemoxylin phloxin safran or periodic acid-Schiff.…”

“…Some of the oncogenic effects related to the activation of the pp6Oc-src kinase pathway are mimicked by the polyoma middle T antigen (Py-MT), the main transforming protein of polyomavirus. We demonstrated that Py-MT induced the tumorigenic conversion of the SV40 large Timmortalized rat intestinal cell line SLC-44 and enhanced the tumorigenicity of human colonic Caco-2 cells (Chastre et al, 1993). In polyomavirus (Py)-transformed cells, pp6Oc-src kinase activity in enhanced by the binding of Py-MT to pp60-src (Courtneidge and Heber, 1987).…”