Su Chin-Chuan, Liu Shing-Hwa, Lee Kuan-I, Huang Kou-Tong, Lu Tien-Hui, Fang Kai-Min, Wu Chin-Ching, Yen Cheng-Chieh, Lai Chih-Ho, Su Yi-Chang, Huang Chun-Fa
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;43(3):581-600. doi: 10.1142/S0192415X15500366.
Bladder 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.
膀胱癌是全球常见的恶性肿瘤。然而，目前仍没有针对膀胱癌的有效治疗方法。在本研究中，我们研究了斑蝥素[一种由中国斑蝥（南方大斑蝥或黄黑小斑蝥）和西班牙绿蝇（绿芫菁）产生的天然毒素（纯化合物）]对人膀胱癌细胞系（包括：T24和RT4细胞）的细胞毒性作用。用斑蝥素处理人膀胱癌细胞可显著降低细胞活力。在经斑蝥素处理的T24细胞中，caspase-3活性及caspase-9/-7/-3裂解形式的表达也增加。此外，斑蝥素增加了磷酸化eIF2α和Grp78的水平，并降低了procaspase-12的蛋白表达，同时T24细胞中的钙蛋白酶活性增加。斑蝥素能够增加T24细胞内的Ca（2+）及蛋白激酶C（PKC）的磷酸化。添加BAPTA/AM（一种Ca（2+）螯合剂）和RO320432（一种选择性细胞可渗透的PKC抑制剂）可有效逆转斑蝥素诱导的caspase-3和钙蛋白酶活性增加、PKC和eIF2α的磷酸化水平以及Grp78蛋白表达增加，以及procaspase-12表达降低。重要的是，斑蝥素显著减小了接种T24细胞的裸鼠的肿瘤体积（治疗21天后显著减少71%）。综上所述，这些结果表明斑蝥素通过钙/PKC调节的内质网应激途径诱导人膀胱癌细胞凋亡。这些发现提示斑蝥素可能是一种针对膀胱癌细胞的新型潜在抗癌药物。
