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pubmed:abstractText |
The rationale for melanoma specific antitumor agents containing phenolic amines is based in part upon the ability of the enzyme tyrosinase to oxidize these prodrugs to toxic intermediates. Two phenolic amine compounds, N-acetyl-4-S-cysteaminylphenol (N-Ac-4-S-CAP) and 4-S-cysteaminylphenol (4-S-CAP), demonstrated growth inhibitory activity with a variety of melanoma cell lines and were essentially non-toxic to non-melanoma cell lines. Theophylline, an inhibitor of cyclic nucleotide phosphodiesterase, increased in situ tyrosinase activity and enhanced the antimelanoma effects of 4-S-CAP and N-Ac-4-S-CAP in pigmented melanoma cell lines. Phenylthiourea, a specific inhibitor of tyrosinase activity, partially blocked the growth inhibitory activity of N-Ac-4-S-CAP in human pigmented melanoma cells. Buthionine sulfoximine, an inhibitor of the synthesis of the cellular antioxidant glutathione, potentiated the growth inhibitory activity of N-Ac-4-S-CAP in pigmented melanoma cells.
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