INHIBITION OF DNA-SYNTHESIS IN METH-A CELLS BY CHLORPROMAZINE

We examined the influence of chlorpromazine, a phenothiazine derivativ e, on DNA synthesis in Meth A cells. Pulse-labelling experiments with [H-3]thymidine showed that chlorpromazine inhibited DNA synthesis in c ells cultured in vitro. The drug also inhibited DNA synthesis in isola ted nuclei. Observation by fluorescence microscopy of fibroblastic cel ls stained with chlorpromazine indicated that the drug was localized i n the cytoplasm and nuclear membranes. suggesting that it inhibited DN A synthesis in a manner dependent on the interaction of replication pr oteins with nuclear membranes. Meth A sarcomas growing in the endoderm of BALB/c mice regressed on intra-tumor injection of chlorpromazine, indicating that the drug has an anticancer action.