Altered response to growth factors in rat epithelial liver cells overexpressing human c-Fos protein

Human c-fos cDNA was transfected into normal rat liver epithelial (REL) cells to identify cellular modifications associated with high expression of c-Fos protein. Responses to EGF and TGFβ were examined in the different cell lines, under anchorage-dependent and -independent conditions. Sensitivity to both factors was modified in transfected cells. While parental cells in monolayer did not respond to EGF, c-fos containing cells growth was stimulated by this factor. Overexpression of c-Fos protein led to an enhanced TGFβ-induced growth inhibition under anchorage dependent conditions, and TGFβ abolished spontaneous growth in soft agar of the cell lines containing c-fos oncogene. The mechanisms underlying, the increased sensitivity to TGFβ in c-fos transfected cells are still to be determined.