Novel phenotype of C3H 10T1/2 fibroblasts cotransfected with the c‐Ha‐ ras and adenovirus 5 E1A oncogenes

C3H 10T1/2 fibroblasts are converted to fully transformed phenotype following coexpression of an activated c‐Ha‐ ras gene and either a constitutively expressed viral or cellular myc gene. In this report, we examined whether the early region 1A (E1A) of adenovirus 5, which synergizes with ras to convert primary embryonic cells to a transformed phenotype, can synergize with ras to transform the established mouse embryonic cell line, C3H 10T1/2. We demonstrate that coexpression of ras and E1A generated a transformed phenotype that could be scored by colony assays and by soft agarose assays but not by standard focus assays. The ras ‐E1A‐transformed phenotype relies on sequences present in conserved regions 1 and 2 of the E1A proteins and, in part, on information encoded by the extreme carboxy terminus of E1A. The contrast between the transformed phenotypes generated following the transfection of C3H 10T1/2 cells with either ras and myc or ras and E1A suggests that myc and E1A cooperate with ras to transform C3H 10T1/2 cells by mechanisms that can be distinguished using this established cell line as a model system.