Cantharidin induces DNA damage and inhibits DNA repair-associated protein expressions in TSGH8301 human bladder cancer cell.

Cantharidin is an active component of mylabris, which has been used as a traditional Chinese medicine. Cantharidin has been shown to have antitumor activity against several types of human cancers in vitro and in animal models in vivo. We investigated whether cantharidin induces DNA damage and affects DNA damage repair-associated protein levels in TSGH8301 human bladder cancer cells. Using flow cytometry to measure viable cells, cantharidin was found to reduce the number of viable cells in a dose-dependent manner. Comet assay, 4',6-diamidino-2-phenylindole (DAPI) staining and DNA gel electrophoresis were used to measure DNA damage and condensation; the results indicated that cantharidin induced DNA damage (comet tail), DNA condensation (white DAPI staining) and DNA damage (DNA smear). Results from western blotting showed that cantharidin inhibited the expression of DNA-dependent serine/threonine protein kinase, poly-ADP ribose polymerase, phosphate-ataxia-telangiectasia and RAD3-related, O-6-methylguanine-DNA methyltransferase, breast cancer susceptibility protein 1, mediator of DNA damage checkpoint protein 1, phospho-histone H2A.X, but increased that of phosphorylated p53 following 6 and 24 h treatment. Confocal laser microscopy was used to examine the protein translocation; cantharidin suppressed the levels of p-H2A.X and MDC1 but increased the levels of p-p53 in TSGH8301 cells. In conclusion, we found that cantharidin-induced cell death may occur through the induction of DNA damage and suppression of DNA repair-associated protein expression in TSGH8301 cells.