Tamgue Ousman, Lei Ming
University of Cape Town, Institute of Infectious Diseases and Molecular Medicine (IDM), Division of Immunology, Faculty of Health Sciences, University of Cape Town, Cape Town 7925, South Africa.
College of Life Science, Northwest A&F University, 3 Taicheng Road, Yangling, 712100, China. Email:
Asian Pac J Cancer Prev. 2017 Sep 27;18(9):2519-2526. doi: 10.22034/APJCP.2017.18.9.2519.
Background: Triptolide is a medicinal herb-derived diterpene triepoxide with potent anti-tumor activity, mainly ,correlated with its ability to inhibit and inactivate subunits of RNA polymerase II, thereby suppressing global gene transcription. Epigenetic imbalance including histone methylation are well known to play important roles in prostate cancer (PCa) onset and progression. The goal of this study was to investigate whether triptolide might exert anti-PCa influence by reshaping the histone methylation landscape. Methods: Triptolide-treated PCa cell lines were analyzed by RT-qPCR and western blotting for expression of histone demethylases and associated markers. Detection of senescence was achieved using senescence associated β-galactosidase staining and analyses of apoptosis and cell cycle were performed by flow cytometry. Senescence–associated heterochromatin foci were detected by immunofluorescence while chromatin immunoprecipitation associated with qPCR (CHIP-qPCR) was applied to assess accumulation of histone markers on promoters of target genes. Cell viability was determined using the CCK-8 assay. Results: We found triptolide to enhance H3K27me3 levels by down-regulating JMJD3 and UTX and also H3K9me3 through up-regulation of SUV39H1. Furthermore, it up-regulated expression of HP1α. Thereby, heterochromatin formation and deposition on promoters of E2F1-target genes was promoted, correlating with suppression of gene transcription, decreased cell viability and induction of a senescence-like phenotype in PCa cells. Conclusions: Our results indicate that triptolide exerts anti-tumor effects including PCa cell senescence at least partially through increasing the levels of repressive histone H3 methylation and formation of a repressive chromatin state in PCa cells. Further studies of its potential as an epigenetic anti-PCa drug appear warranted.
雷公藤甲素是一种从药用植物中提取的二萜类三环氧物，具有强大的抗肿瘤活性，主要与其抑制和失活RNA聚合酶II亚基的能力相关，从而抑制整体基因转录。众所周知，包括组蛋白甲基化在内的表观遗传失衡在前列腺癌（PCa）的发生和发展中起重要作用。本研究的目的是调查雷公藤甲素是否可能通过重塑组蛋白甲基化格局发挥抗PCa作用。方法：通过RT-qPCR和蛋白质印迹法分析雷公藤甲素处理的PCa细胞系中组蛋白去甲基化酶及相关标志物的表达。使用衰老相关β-半乳糖苷酶染色检测衰老，通过流式细胞术分析细胞凋亡和细胞周期。通过免疫荧光检测衰老相关异染色质灶，同时应用与qPCR相关的染色质免疫沉淀（CHIP-qPCR）评估组蛋白标志物在靶基因启动子上的积累。使用CCK-8法测定细胞活力。结果：我们发现雷公藤甲素通过下调JMJD3和UTX来提高H3K27me3水平，还通过上调SUV39H1提高H3K9me3水平。此外，它上调了HP1α的表达。从而促进了异染色质在E2F1靶基因启动子上的形成和沉积，这与基因转录的抑制、细胞活力的降低以及PCa细胞中衰老样表型的诱导相关。结论：我们的结果表明，雷公藤甲素至少部分通过增加抑制性组蛋白H3甲基化水平和在PCa细胞中形成抑制性染色质状态来发挥包括PCa细胞衰老在内的抗肿瘤作用。对其作为表观遗传抗PCa药物的潜力进行进一步研究似乎是有必要的。
