Gupta S, Ahmad N, Nieminen A L, Mukhtar H
Department of Dermatology, Department of Anatomy, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, Ohio 44106, USA.
Toxicol Appl Pharmacol. 2000 Apr 1;164(1):82-90. doi: 10.1006/taap.1999.8885.
Prostate cancer (PCA) is the most prevalent cancer diagnosed and the second leading cause of cancer-related deaths among men in the United States. Descriptive epidemiological data suggest that androgens and environmental exposures play a key role in prostatic carcinogenesis. Since androgen action is intimately associated with proliferation and differentiation, at the time of clinical diagnosis in humans most PCA represent themselves as a mixture of androgen-sensitive and androgen-insensitive cells. Androgen-sensitive cells undergo rapid apoptosis upon androgen withdrawal. On the other hand, the androgen-insensitive cells do not undergo apoptosis upon androgen blocking, but maintain the molecular machinery of apoptosis. Thus, agents capable of inhibiting growth and/or inducing apoptosis in both androgen-sensitive and androgen-insensitive cells will be useful for the management of PCA. In the present study, we show that (-)-epigallocatechin-3-gallate (EGCG), the major polyphenolic constituent present in green tea, imparts antiproliferative effects against both androgen-sensitive and androgen-insensitive human PCA cells, and this effect is mediated by deregulation in cell cycle and induction of apoptosis. EGCG treatment was found to result in a dose-dependent inhibition of cell growth in both androgen-insensitive DU145 and androgen-sensitive LNCaP cells. In both the cell types, EGCG treatment also resulted in a dose-dependent G(0)/G(1)-phase arrest of the cell cycle as observed by DNA cell-cycle analysis. As evident by DNA ladder assay, confocal microscopy, and flow cytometry, the treatment of both DU145 and LNCaP cells with EGCG resulted in a dose-dependent apoptosis. Western blot analysis revealed that EGCG treatment resulted in (i) a dose-dependent increase of p53 in LNCaP cells (carrying wild-type p53), but not in DU145 cells (carrying mutant p53), and (ii) induction of cyclin kinase inhibitor WAF1/p21 in both cell types. These results suggest that EGCG negatively modulates PCA cell growth, by affecting mitogenesis as well as inducing apoptosis, in cell-type-specific manner which may be mediated by WAF1/p21-caused G(0)/G(1)-phase cell-cycle arrest, irrespective of the androgen association or p53 status of the cells.
前列腺癌（PCA）是美国男性中诊断出的最常见癌症，也是癌症相关死亡的第二大主要原因。描述性流行病学数据表明，雄激素和环境暴露在前列腺癌发生过程中起关键作用。由于雄激素作用与增殖和分化密切相关，在人类临床诊断时，大多数PCA表现为雄激素敏感细胞和雄激素不敏感细胞的混合物。雄激素敏感细胞在雄激素撤除后会迅速凋亡。另一方面，雄激素不敏感细胞在雄激素阻断后不会发生凋亡，但维持凋亡的分子机制。因此，能够抑制雄激素敏感和雄激素不敏感细胞生长和/或诱导其凋亡的药物将有助于PCA的治疗。在本研究中，我们表明绿茶中的主要多酚成分（-）-表没食子儿茶素-3-没食子酸酯（EGCG）对雄激素敏感和雄激素不敏感的人PCA细胞均具有抗增殖作用，且这种作用是通过细胞周期失调和凋亡诱导介导的。发现EGCG处理导致雄激素不敏感的DU145细胞和雄激素敏感的LNCaP细胞的细胞生长呈剂量依赖性抑制。在这两种细胞类型中，通过DNA细胞周期分析观察到，EGCG处理还导致细胞周期呈剂量依赖性的G(0)/G(1)期阻滞。如DNA梯状分析、共聚焦显微镜和流式细胞术所示明显，用EGCG处理DU145和LNCaP细胞均导致剂量依赖性凋亡。蛋白质印迹分析表明，EGCG处理导致（i）LNCaP细胞（携带野生型p53）中p53呈剂量依赖性增加，但在DU145细胞（携带突变型p53）中未增加，以及（ii）两种细胞类型中细胞周期蛋白激酶抑制剂WAF1/p21的诱导。这些结果表明，EGCG以细胞类型特异性方式通过影响有丝分裂以及诱导凋亡来负向调节PCA细胞生长，这可能由WAF1/p21引起的G(0)/G(1)期细胞周期阻滞介导，而与细胞的雄激素相关性或p53状态无关。
