TRANSFORMATION OF MOUSE FIBROBLASTS WITH THE ONCOGENES H-RAS OR TRK IS ASSOCIATED WITH PRONOUNCED CHANGES IN DRUG SENSITIVITY AND METABOLISM

Malignant activation of oncogenes ras or trk is implicated in a number of solid tumors and leukemias. We determined the chemosensitivity pro file of wild-type mouse NIH-3T3 fibroblasts, and that of NIH-3T3 lines transformed by the H-ras (S2-72 1) and trk (106-632) oncogenes, again st 11 different drugs from various classes. Differences in sensitivity were related to drug accumulation and metabolism. Both ras- and trk-t ransformed cell lines were less sensitive to cisplatin (CDDP) and doxo rubicin (DXR) than the wild type. NIH-3T3 transformants expressing H-r as were less sensitive than those expressing trk or the wild type to t he indoloquinone EO9, methotrexate and arabino-furanosylcytosine. No c lear difference in sensitivity was observed for vincristine, VP-16, or the new cytidine analog 2',2'-difluoro-deoxycytidine. In both ras- an d trk-transformed cell lines sensitivity to 5FU was increased moderate ly, but sensitivity to 5'deoxy-5-fluorouridine (5'dFUR) was increased markedly. Only the trk-transformed line NIH-3T3 was more sensitive to 2'deoxy-5-fluorouridine. Expression of P-glycoprotein was not differen t between the 3 cell lines but DXR accumulation in both mutants was de creased, indicating a non-P-glycoprotein-associated difference in sens itivity. Conversion of 5'dFUR to 5FU (catalyzed by pyrimidine nucleosi de phosphorylases) was 5-10 times higher in both mutants than in the w ild type. The activity of the phosphoribosyl-transferase (direct conve rsion of 5FU to FUMP) was comparable, but the rate of conversion of 5F U to fluorouridine (FUR) was lower in the wild type, as well as that o f 5FU to FUMP via FUR. In contrast, the activity of thymidylate syntha se, the target enzyme for fluoropyrimidines, was higher in the wild-ty pe cells. The concentrations of both purine and pyrimidine nucleotides were lower in cells expressing trk. In conclusion, transformation of cells with the H-ras or trk oncogenes can markedly influence sensitivi ty to several drugs and affect normal metabolism and that of several a nti-cancer agents.