<i>In vitro</i> Enhancement of Antitumor Activity of a Water‐soluble Duocarmycin Derivative, KW‐2189, by Caffeine‐mediated DNA‐repair Inhibition in Human Lung Cancer Cells

Abstract

Duocarmycins, including KW-2189, bind in the minor groove of double-stranded DNA at A-T-rich sequences, followed by covalent bonding with N-3 of adenine in preferred sequences. We examined the effect of DNA-repair modulators, such as caffeine and aphidicolin, on the cytotoxicity of duocarmycins towards human lung cancer cells, as determined by dye formation assay. Caffeine (0.5 or 1 mM), but not aphidicolin, enhanced the growth-inhibitory activity of KW-2189, DU-86, and duocarmycin SA. Caffeine inhibited repair of DNA strand breaks induced by KW-2189, as assayed by the alkaline elution technique. This suggests that duocarmycin-induced DNA strand breaks, which are potentially lethal to cells, are repaired through a caffeine-sensitive pathway.