Cytokinins and
cytokinin nucleosides are
purine derivatives with potential anticancer activity. N(6)-furfuryladenosine (FAdo,
kinetin-riboside) displays anti-proliferative and apoptogenic activity against various human
cancer cell lines, and FAdo has recently been shown to suppress
tumor growth in murine xenograft models of human
leukemia and
melanoma. In this study, FAdo-induced genotoxicity, stress response gene expression, and cellular
ATP depletion were examined as early molecular consequences of FAdo exposure in MiaPaCa-2 pancreas
carcinoma, A375
melanoma, and other human
cancer cell lines. FAdo, but not
adenosine or N(6)-furfuryladenine (FA), displayed potent anti-proliferative activity that was also observed in human primary fibroblasts and keratinocytes. Remarkably, massive
ATP depletion and induction of genotoxic stress as assessed by the alkaline comet assay occurred within 60-180min of exposure to low micromolar concentrations of FAdo. This was followed by rapid upregulation of CDKN1A and other DNA damage/stress response genes (HMOX1, DDIT3, and GADD45A) as revealed by expression array and Western analysis. Pharmacological and
siRNA-based genetic inhibition of
adenosine kinase (ADK) suppressed FAdo cytotoxicity and also prevented
ATP depletion and p21 upregulation suggesting the importance of bioconversion of FAdo into the
nucleotide form required for
drug action. Taken together our data suggest that early induction of genotoxicity and energy crisis are important causative factors involved in FAdo cytotoxicity.