The effect of dacarbazine and vincristine sulfate on human melanoma cell lines. In vitro analysis of interaction on DNA synthesis, RNA synthesis and protein synthesis

The effect of anticancer agents, dacarbazine [DTIC (dimethyl-triazeno-imidazole-carboxamide)] and vincristine sulfate (VCR) on two human melanoma cell lines (G 361 and MeWo) was investigated. First we estimated the growth curve of two cell lines by using an isotope labelling technique with DNA, RNA and protein precursors to find the most appropriate conditions, and then, DTIC and VCR were added at various concentrations. When the drug was added alone, DNA, RNA and protein synthesis were suppressed in a dose-dependent fashion and the pattern of responses was similar between the two. When the two agents were administered in combination, responses were variable depending on the combinations of the concentrations of these agents. It was also observed that the response on DNA synthesis is not similar to that on RNA or protein synthesis, and that unbalanced growth can happen when two anticancer agents, whose mechanisms of action against tumour cells, are different, are administered at the same time. These observations also differed between the two cell lines. It suggests that these diverse responses of melanoma cells against chemotherapeutic agents hinder the establishment of a sensitive combination chemotherapeutic regimen.