Yu Ching-Han, Kan Shu-Fen, Pu Hsiao-Fung, Jea Chien Eileen, Wang Paulus S
Department of Physiology, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan.
Cancer Sci. 2008 Dec;99(12):2467-76. doi: 10.1111/j.1349-7006.2008.00966.x. Epub 2008 Nov 26.
Prostate cancer has its highest incidence in the USA and is becoming a major concern in Asian countries. Bufadienolides are extracts of toxic glands from toads and are used as anticancer agents, mainly on leukemia cells. In the present study, the antiproliferative and apoptotic mechanisms of bufalin and cinobufagin on prostate cancer cells were investigated. Proliferation of LNCaP, DU145, and PC3 cells was measured by 3-(4,5-dimethylthiazol-2-yle)-2,5-diphenyltetrazolium bromide assay and the doubling time (tD) was calculated. Bufalin and cinobufagin caused changes in the tD of three prostate cancer cell lines, which were more significant than that of human mesangial cells. In addition, bufadienolides induced prostate cancer cell apoptosis more significantly than that in breast epithelial cell lines. After treatment, the caspase-3 activity and protein expression of caspase-3, -8, and -9 were elevated. The expression of other apoptotic modulators, including mitochondrial Bax and cytosolic cytochrome c, were also increased. However, expression of p53 was only enhanced in LNCaP cells. Downregulation of p53 by antisense TP53 restored the cell viability suppressed by bufalienolides. Furthermore, the increased expression of Fas was more significant in DU145 and PC3 cells with mutant p53 than in LNCaP cells. Transfection of Fas small interfering RNA restored cell viability in the bufadienolide-treated cells. These results suggest that bufalin and cinobufagin suppress cell proliferation and cause apoptosis in prostate cancer cells via a sequence of apoptotic modulators, including Bax, cytochrome c, and caspases. The upstream mediators might be p53 and Fas in androgen-dependent LNCaP cells and Fas in androgen-independent DU145 and PC3 cells.
前列腺癌在美国的发病率最高，并且在亚洲国家正成为一个主要问题。蟾毒配基是蟾蜍毒腺的提取物，用作抗癌剂，主要作用于白血病细胞。在本研究中，研究了蟾毒灵和华蟾酥毒基对前列腺癌细胞的抗增殖和凋亡机制。通过3-(4,5-二甲基噻唑-2-基)-2,5-二苯基四氮唑溴盐法测定LNCaP、DU145和PC3细胞的增殖，并计算倍增时间（tD）。蟾毒灵和华蟾酥毒基导致三种前列腺癌细胞系的tD发生变化，这比人肾小球系膜细胞的变化更显著。此外，蟾毒配基诱导前列腺癌细胞凋亡比在乳腺上皮细胞系中更显著。处理后，半胱天冬酶-3活性以及半胱天冬酶-3、-8和-9的蛋白表达升高。其他凋亡调节因子的表达，包括线粒体Bax和胞质细胞色素c也增加。然而，p53的表达仅在LNCaP细胞中增强。用反义TP53下调p53可恢复被蟾毒配基抑制的细胞活力。此外，Fas表达增加在p53突变的DU145和PC3细胞中比在LNCaP细胞中更显著。转染Fas小干扰RNA可恢复蟾毒配基处理细胞的细胞活力。这些结果表明，蟾毒灵和华蟾酥毒基通过一系列凋亡调节因子，包括Bax、细胞色素c和半胱天冬酶，抑制前列腺癌细胞的增殖并导致其凋亡。上游介质可能是雄激素依赖的LNCaP细胞中的p53和Fas以及雄激素非依赖的DU145和PC3细胞中的Fas。
