Highly selective suppression of melanoma cells by inducible DNA cross-linking agents: bis(catechol) derivatives.

A series of bis(catechol) quaternary ammonium derivatives were designed and synthesized. We investigated their ability to cross-link DNA induced by tyrosinase and found that the o-quinone is key intermediate in the process by using the nucleophile 3-methyl-2-benzothiazolinone hydrazone (MBTH) in the tyrosinase assay. Their cytotoxicities to B16F1, Hela, and CHO cells were tested by MTT assays. The specific and potent abilities to kill the tyrosinase-efficient melanoma cells kindled our interest in exploring the relationship between their abilities of cross-linking DNA and their selective cytotoxicities to cells. Through an integrated approach including intracellular imaging for detection of the dihydroxyphenyl groups, alkaline comet assays, and γ-H2AX immunofluorescence assays, the speculation was confirmed. The bis(catechol) quaternary ammonium derivatives showed notable cell selectivity because they displayed cytotoxicities after being oxidized by tyrosinase, and they were able to target the DNA efficiently in the tyrosinase-efficient melanoma cells, forming both alkylated and cross-linked species.