• Chin-Chuan Su, Shing-Hwa Liu, Kuan-I Lee, Kou-Tong Huang, Tien-Hui Lu, Kai-Min Fang, Chin-Ching Wu, Cheng-Chieh Yen, Chih-Ho Lai, Yi-Chang Su, and Chun-Fa Huang.
• Graduate Institute of Basic Medical Science, China Medical University, Taichung, Taiwan , Department of Otorhinolaryngology, Head and Neck Surgery, Changhua Christian Hospital, Changhua County, Taiwan.
• Am. J. Chin. Med. 2015 Jan 1; 43 (3): 581-600.

AbstractBladder cancer is a common malignancy worldwide. However, there is still no effective therapy for bladder cancer. In this study, we investigated the cytotoxic effects of cantharidin [a natural toxin produced (pure compound) from Chinese blister beetles (Mylabrisphalerata or Mylabriscichorii) and Spanish flies (Cantharis vesicatoria)] in human bladder cancer cell lines (including: T24 and RT4 cells). Treatment of human bladder cancer cells with cantharidin significantly decreased cell viability. The increase in the expressions of caspase-3 activity and cleaved form of caspase-9/-7/-3 were also increased in cantharidin-treated T24 cells. Furthermore, cantharidin increased the levels of phospho-eIF2α and Grp78 and decreased the protein expression of procaspase-12, which was accompanied by the increase in calpain activity in T24 cells. Cantharidin was capable of increasing the intracellular Ca (2+) and the phosphorylation of protein kinase C (PKC) in T24 cells. The addition of BAPTA/AM (a Ca (2+) chelator) and RO320432 (a selective cell-permeable PKC inhibitor) effectively reversed the increase in caspase-3 and calpain activity, the phosphorylation levels of PKC and eIF2α and Grp78 protein expression, and the decrease in procaspase-12 expression induced by cantharidin. Importantly, cantharidin significantly decreased the tumor volume (a dramatic 71% reduction after 21 days of treatment) in nude mice xenografted with T24 cells. Taken together, these results indicate cantharidin induced human bladder cancer cell apoptosis through a calcium/PKC-regulated ER stress pathway. These findings suggest that cantharidin may be a novel and potential anticancer agent targeting on bladder cancer cells.

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