Pratap Uday P, Sareddy Gangadhara R, Liu Zexuan, Venkata Prabhakar Pitta, Liu Junhao, Tang Weiwei, Altwegg Kristin A, Ebrahimi Behnam, Li Xiaonan, Tekmal Rajeshwar R, Viswanadhapalli Suryavathi, McHardy Stanton, Brenner Andrew J, Vadlamudi Ratna K
Department of Obstetrics and Gynecology, University of Texas Health San Antonio, San Antonio, Texas, USA.
Mays Cancer Center, University of Texas Health San Antonio, San Antonio, Texas, USA.
Neurooncol Adv. 2021 Jul 17;3(1):vdab099. doi: 10.1093/noajnl/vdab099. eCollection 2021 Jan-Dec.
Glioblastomas (GBMs) are the most lethal primary brain tumors. Estrogen receptor β (ERβ) function as a tumor suppressor in GBM, however, ERβ expression is commonly suppressed during glioma progression. In this study, we examined whether drugs that reverse epigenetic modifications will enhance ERβ expression and augment ERβ agonist-mediated tumor suppression.
We tested the utility of epigenetic drugs which act as an inhibitor of histone deacetylases (HDACs), histone methylases, and BET enzymes. Mechanistic studies utilized RT-qPCR, chromatin immunoprecipitation (ChIP), and western blotting. Cell viability, apoptosis, colony formation, and invasion were measured using in vitro assays. An orthotopic GBM model was used to test the efficacy of in vivo.
Of all inhibitors tested, HDACi (panobinostat and romidepsin) showed the potential to increase the expression of ERβ in GBM cells. Treatment with HDACi uniquely upregulated ERβ isoform 1 expression that functions as a tumor suppressor but not ERβ isoform 5 that drives oncogenic functions. Further, combination therapy of HDACi with the ERβ agonist, LY500307, potently reduced cell viability, invasion, colony formation, and enhanced apoptosis. Mechanistic studies showed that HDACi induced ERβ is functional, as it enhanced ERβ reporter activities and ERβ target genes expression. ChIP analysis confirmed alterations in the histone acetylation at the ERβ and its target gene promoters. In orthotopic GBM model, combination therapy of panobinostat and LY500307 enhanced survival of tumor-bearing mice.
Our results suggest that the combination therapy of HDACi and LY500307 provides therapeutic utility in overcoming the suppression of ERβ expression that commonly occurs in GBM progression.
胶质母细胞瘤（GBM）是最致命的原发性脑肿瘤。雌激素受体β（ERβ）在GBM中发挥肿瘤抑制作用，然而，在胶质瘤进展过程中ERβ表达通常受到抑制。在本研究中，我们研究了逆转表观遗传修饰的药物是否会增强ERβ表达并增强ERβ激动剂介导的肿瘤抑制作用。
我们测试了作为组蛋白脱乙酰酶（HDAC）、组蛋白甲基酶和BET酶抑制剂的表观遗传药物的效用。机制研究采用逆转录定量聚合酶链反应（RT-qPCR）、染色质免疫沉淀（ChIP）和蛋白质免疫印迹法。使用体外试验测量细胞活力、细胞凋亡、集落形成和侵袭。使用原位GBM模型测试体内疗效。
在所有测试的抑制剂中，HDAC抑制剂（帕比司他和罗米地辛）显示出增加GBM细胞中ERβ表达的潜力。HDAC抑制剂处理独特地上调了作为肿瘤抑制因子的ERβ亚型1的表达，但未上调具有致癌功能的ERβ亚型5的表达。此外，HDAC抑制剂与ERβ激动剂LY500307联合治疗可有效降低细胞活力、侵袭、集落形成，并增强细胞凋亡。机制研究表明，HDAC抑制剂诱导的ERβ具有功能，因为它增强了ERβ报告基因活性和ERβ靶基因表达。ChIP分析证实了ERβ及其靶基因启动子处组蛋白乙酰化的改变。在原位GBM模型中，帕比司他和LY500307联合治疗提高了荷瘤小鼠的存活率。
我们的结果表明，HDAC抑制剂和LY500307联合治疗在克服GBM进展过程中常见的ERβ表达抑制方面具有治疗效用。
