Histological localization of 4-S-cysteinylphenol in melanoma-bearing mice

4-S-cysteinylphenol (4-S-CP), the S-homologue of tyrosine, has been recently synthesized as a selective chemotherapeutic agent against malignant melanoma and has been shown to be a specific substrate for tyrosinase in vitro. In vivo incorporation of 4-S-CP into the B16 and Harding Passey (HP) melanomas and the systemic organs have been evaluated by the autoradiographic method. The distribution of the silver grains indicated that 4-S-CP was selectively incorporated into both the B16 and HP melanomas. 4-S-CP was excreted mainly from the kidneys and there was an accumulation of 4-S-CP in the reticulo-endothelial system. These results seemed to contribute to the utilization of 4-S-CP and other related compounds as chemotherapeutic agents against malignant melanoma.