[Resistance to anticancer drugs in NIH3T3 cells transfected with c-myc and/or c-H-ras genes].

NIH3T3 cells transfected with c-H-ras and/or c-myc genes were examined for differences in drug sensitivity. The two transfectants used were NIH3T3-nm-1 (nm-1), pT22-3-nm-2. They were transfected with c-myc, c-myc plus activated c-H-ras, respectively. The relative resistances (IC50 values of transfectants/those of NIH3T3 cells) to cisplatin, adriamycin, 4-hydroperoxycyclophosphamide, melphalan, and CPT-11 were 2.1, 1.6, 4.7, 4.9, 1.6, respectively for nm-1 and 1.6, 2.2, 3.3, 9.1 and 2.2, respectively for nm-2. These results strongly suggest that the expression of the c-myc gene plays a role for the acquisition of drug resistance. The c-myc gene is believed to provide us an important clue for determining the mechanism of drug resistance.