Leof E B, Lyons R M, Cunningham M R, O'Sullivan D
Department of Cell Biology, Vanderbilt University, Nashville, Tennessee 37232.
Cancer Res. 1989 May 1;49(9):2356-61.
Transfection of C3H/10T1/2 cells with either a c-myc or an activated c-Ha-ras gene decreased the cellular dependence for serum-derived factors to proliferate in monolayer. The c-myc-transfected cells did, however, require a high plasma concentration for significant growth, while the ras transfectants grew extremely well in either low or high concentrations of either plasma or serum. Stimulation of quiescent cultures with purified growth factors demonstrated that c-myc transfection did not alter qualitatively or quantitatively the requirement for both epidermal growth factor (EGF) and insulin to progress to DNA synthesis. Cells transfected with either a ras gene alone or a combination of ras plus c-myc lost their dependence on EGF for DNA synthesis; cultures became committed to S phase in serum-free medium supplemented with insulin alone. The ras transfectants arrested in mid-G1, 6 h prior to S phase. The EGF independence of the ras transfectants is consistent with the mid-G1 arrest of these cells at a point(s) distal to the primary action of EGF in early G0-G1.
用c-myc或激活的c-Ha-ras基因转染C3H/10T1/2细胞，可降低细胞在单层培养中对血清衍生因子增殖的依赖性。然而，c-myc转染的细胞确实需要高血浆浓度才能显著生长，而ras转染细胞在低浓度或高浓度的血浆或血清中生长都非常良好。用纯化的生长因子刺激静止培养物表明，c-myc转染在质量或数量上都没有改变对表皮生长因子（EGF）和胰岛素进入DNA合成的需求。单独用ras基因或ras加c-myc组合转染的细胞失去了对EGF进行DNA合成的依赖性；培养物在仅添加胰岛素的无血清培养基中进入S期。ras转染细胞在S期前6小时停滞在G1中期。ras转染细胞对EGF的不依赖性与这些细胞在G0-G1早期EGF主要作用的远端点停滞在G1中期一致。
