赖氨酸特异性去甲基化酶1对曲古抑菌素A诱导卵巢癌细胞凋亡的作用

LSD1 acetylation mediates TSA-induced apoptosis of ovarian cancer cells

目的赖氨酸特异性去甲基化酶1(LSD1)是黄素腺嘌呤二核苷酸依赖的胺氧化酶,其参与细胞的增殖、分化以及介导基因激活和抑制等多种生物学过程。文中旨在探讨组蛋白去乙酰化酶抑制剂曲古抑菌素A(TSA)对LSD1的乙酰化,以及LSD1在TSA诱导卵巢癌细胞凋亡中的作用。方法利用RNA干扰方法建立诱导型稳定敲低LSD1基因表达的卵巢癌HO8910和SKOV3细胞株;实验设置p LKO对照组(感染空载体慢病毒)、p LKO+Dox(100 ng/m L)组、LSD1-KD组(感染LSD1-shRNA慢病毒)和LSD1-KD+Dox(100 ng/m L)组。用免疫沉淀(IP)和Western blot检测LSD1乙酰化程度,及其底物组蛋白H3第4位赖氨酸的二甲基化(H3K4me2)水平;AnnexinⅤ/PI和流式细胞术分析细胞凋亡的变化;RT-PCR检测凋亡相关基因Bax和p21 mRNA表达水平;染色质免疫沉淀(Ch IP)分析Bax和p21基因启动子区H3K4me2程度。实验设置methanol对照组(2 mg/m L)、TSA组(200 nmol/L)、TCP组(抑制LSD1活性;100μmol/L)和TSA+TCP组,处理细胞48 h。在RNA干扰LSD1表达实验中,设置溶剂对照组(2 mg/m L methanol)、TSA处理组(200 nmol/L)、Dox组(干扰LSD1表达;100 ng/m L)和联合处理组(200 nmol/L TSA与100ng/m L Dox)联合处理细胞48h。结果免疫沉淀结合Western blot检测结果显示,200nmol/L TSA处理后LSD1蛋白的乙酰化和H3K9的乙酰化水平较methanol溶剂处理显著增加(P<0.01)。与methanol溶剂对照处理比较,200nmol/L TSA处理HO8910和SKOV3细胞后H3K4me2水平明显升高(P<0.01)。AnnexinⅤ/PI结果显示,与methanol对照组比较,TSA组、TCP组和TSA+TCP组HO8910和SKOV3细胞的总凋亡率均显著升高(P<0.05);且TSA+TCP组较TSA组和TCP组细胞凋亡率明显升高(P<0.05)。LSD1-KD+Dox组细胞中LSD1蛋白水平(HO8910:0.21±0.16;SKOV3:0.26±0.11)较p LKO对照组(HO8910:1.15±0.16;SKOV3:0.97±0.31)和LSD1-KD组(HO8910:1.07±0.19;SKOV3:0.98±0.21)显著减少(P<0.01)。与溶剂对照组比较,TSA处理组、Dox组和联合处理组细胞的总凋亡率均显著增高(P<0.05);其中联合处理组较TSA或Dox组亦显著增高(P<0.05)。RT-PCR结果表明,在HO8910细胞中,与溶剂对照组Bax和p21 mRNA水平比较,TSA处理组、Dox组及联合处理组均显著上调(P<0.05);且联合处理组较TSA处理组或Dox组亦显著上调(P<0.05)。TSA处理组细胞中Bax和p21基因启动子区H3K4me2水平较methanol对照组显著升高(Bax:2.92±0.26 vs 0.86±0.19;p21:3.07±0.29 vs 0.93±0.17,P<0.01)。结论 TSA诱导了LSD1蛋白的乙酰化,抑制LSD1表达或活性可增强TSA对卵巢癌细胞的杀伤作用。

Objective Lysine-specific demethylase 1 （LSD1） is a flavin adenine dinucleotide-dependent oxidase, which participates in many biological processes , such as cell proliferation and differentiation and gene activation and repression .The aim of this study was to investigate LSD1 acetylation by histone deacetylase inhib -itor trichostatin A （ TSA） and its effect on TSA-induced apoptosis of ovarian cancer cells . Methods LSD1 shRNA was synthesized and implanted into the pLKO-Tet-On lentiviral vector , which was transfected into HO8910 and SKOV3 ovarian cancer cell lines , and then the transfected cells were screened with 1.5μg/mL puromycin for one week until stable clones were established .The cells were treated for 48 hours with methanol （2 mg/mL, control）, TSA （200 nmol/L）, TCP （100μmol/L）, or TSA＋TCP.And in the experiment of RNA interfering the LSD1 expression, the cells were also treated for 48 hours with methanol （2 mg/mL, control）, TSA （200 nmol/L）, Dox （100 ng/mL）, or TSA ＋Dox.The levels of LSD1 acetylation and its substrate histone H3 lysine 4 dimethylation （H3K4me2） were de-tected by immunoprecipitation （IP） and Western blot.The apoptosis of the cells was determined by Annexin Ⅴ/PI staining and flow cytometry, the transcription levels of the Bax and p21 genes detected by real-time quantitative PCR, and the H3K4me2levels in the promoter regions of Bax and p21 measured by chromatin immunoprecipitation （ ChIP ） .Results In comparison with the methanol control, the TSA group showed significantly increased levels of LSD 1 acetylation in the HO8910（1.00±0.29 vs 5.83±0.46, P〈0.01） and SKOV3 cells （ 1.00±0.24 vs 5.07±0.35, P〈0.01） as well as that of H3K4me2 （ P〈0.01）;the total apoptosis rates of HO 8910 and SKOV3 cells were remarkably increased in the TSA, TCP, and TSA＋TCP groups （P〈0.05）, even more significantly in the TSA＋TCP than in the TSA and TCP groups （ P〈0.05） .The mRNA expressions of Bax and p21 in the HO8910 cells were markedly upregulated in the TSA, Dox, and TSA＋Dox groups （P〈0.05）, even more significantly in the latter than in the former two groups （P〈0.05）.The TSA group exhibited a higher level of H 3K4me2 than the methanol control in the promoters of Bax（2 .92±0.26 vs 0.68±0.19, P〈0.01） and p21 （3.07±0.29 vs 0.93±0.17, P〈0.01）. Conclusion TSA induces the LSD1 acetylation, while suppression of LSD1 expres-sion and activity may enhance the antitumor activity of TSA .