Inhibition of the growth of mouse melanoma by chlorpromazine.

The effects of three phenothiazines, chlorpromazine (CPZ), chlorpromazine sulfoxide (CPZ-O), and 74iydroxychlor promazine (7-OH-CPZ), on the growth of B-16 and HardingPassey mouse melanomas were investigated. CPZ and 7-OH-CPZ both inhibited tumor growth, but CPZ-O did not. The melanoma tyrosinase was activated by CPZ both in vivo and in vitro. There was no significant effect of CPZ on the succinic oxidase and reduced nicotinamide adenine dinucleotide oxidase of either the melanoma or liver of these animals. The marked affinity of phenothiazines for melanin might be used to develop more effective melanoma chemotherapeutic agents.