INCREASED FREQUENCY OF P-GLYCOPROTEIN GENE AMPLIFICATION IN COLCHICINE-RESISTANT RAT-1 CLONES TRANSFORMED BY V-SRC

A rat fibroblast cell line (Rat-1) carrying a temperature-sensitive mu tation of v-src was used to determine whether inducible cellular trans formation altered the ability of cells to amplify the p-glycoprotein g ene in response to colchicine selection. Transformed and nontransforme d Rat-1 fibroblasts selected under 4 times the LD50 generated the same number of colchicine-resistant colonies. We next examined colchicine- resistant colonies derived from transformed cells and compared them to colchicine-resistant colonies derived from nontransformed cells. When Rat-1 cells were selected at 35 degrees C (transforming temperature), 7 out of 7 clones exhibited a 3- to 5-fold p-glycoprotein gene amplif ication. These results contrasted to those found at the nontransformin g temperature (40 degrees C); none of the 8 colchicine-resistant clone s examined had amplified the p-glycoprotein gene. Thus in Rat-1 cells carrying a temperature-sensitive v-src gene, p-glycoprotein gene ampli fication was observed at a high frequency only in transformed clones s elected at the temperature permissive for v-src activity. (C) Elsevier Science Inc., 1997.