1. To clarify the therapeutic efficacy of anticancer combination chemotherapy, we analyzed intracellular active metabolites of drugs, and effects of these drugs on nucleic acid metabolism with high performance liquid chromatography. After treatment with methotrexate, reduction of intracelluar ATP, GTP, dTTP and dCTP levels were observed. Ara-C had significant effects on the growth of cells at the higher level of ara-CTP than of dCTP. So the dCTP/ara-CTP ratio is one of very important factors in ara-C cytotoxicity. The increased production of intracellular fluoro-UTP(FUTP) and ara-CTP by pretreatment with MTX were recognized. These enhanced effects were based on biochemical modulation in each grugs. VP16 and Ara-C combination chemotherapy showed similar modulation effects. 6TG was metabolized to 6-thioGMP, GDP, GTP. Major products of 6MP, however, was 6-thioIMP. Small quantity of 6-thioGMP was detected, but no 6-thioGDP, GTP were produced. The intracellular levels of ATP and GTP pools decreased after treatment with 6TG and 6MP. Intracellular dCTP, and dTTP pools have declined after exposure to 6TG, whereas not decline with 6MP. These results suggested that cytotoxic mechanism of 6TG include inhibition of both purine pathway and DNA synthesis and 6MP only inhibits purine pathway.
2. Protein kinase C and phorbor diester receptor were related with pleiotropic drug resistance. Phorbor esters, also, were linked to the glucocorticoid-induced growth inhibition.