Zhang Chengyue, Su Zheng-Yuan, Wang Ling, Shu Limin, Yang Yuqing, Guo Yue, Pung Douglas, Bountra Chas, Kong Ah-Ng
Center for Phytochemical Epigenome Studies, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, USA; Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, USA.
Department of Clinical Pharmacy and Pharmacy Administration, West China School of Pharmacy, Sichuan University, China.
Biochem Pharmacol. 2016 Oct 1;117:35-45. doi: 10.1016/j.bcp.2016.08.009. Epub 2016 Aug 9.
The neoplastic transformation of cells and inflammation are processes that contribute to tumor initiation. Recently, emerging evidence has suggested that epigenetic alterations are also implicated in the early stages of carcinogenesis. Therefore, potent small molecules targeting epigenetic regulators have been developed as novel cancer therapeutic and preventive strategies. Bromodomain and extraterminal domain (BET) proteins are epigenetic readers that play key roles at the interface between chromatin modification and transcriptional regulation. In this study, we investigated the effect of the BET inhibitor JQ-1 on malignant transformation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse skin epidermal JB6 P+ cells. Treatment with JQ-1 effectively impaired TPA-induced colony formation in vitro. At the molecular level, the expression of several key TPA-induced pro-survival and pro-proliferative genes (Bcl2, Cyclin D1, and c-Myc) decreased rapidly after BET inhibition. In addition, JQ-1 treatment attenuated the activation of inflammatory NF-κB signaling triggered by TPA. Luciferase reporter assays using plasmids carrying different elements from the COX2 or IL6 promoters demonstrated that JQ-1 does not directly inhibit interactions between NF-κB and its binding sequence; rather, it affects CRE-element-associated transcriptional enhancement. Through siRNA gene silencing, we found that JQ-1 inhibits the p300-dependent transcriptional activation of COX2, which correlates with the results of the luciferase assay. Chromatin immunoprecipitation assays showed that TPA elevated H3K27Ac enrichment in the COX2 promoter region, which is mediated by p300, and Brd4. JQ-1 treatment did not change H3K27Ac levels but decreased the recruitment of Brd4 and RNA Polymerase II. Collectively, our study reveals that the BET inhibitor JQ-1 exerts potent anti-cancer and anti-inflammatory effects by interfering with the core transcriptional program of neoplastic transformation.
细胞的肿瘤转化和炎症是促成肿瘤起始的过程。最近，新出现的证据表明表观遗传改变也与癌症发生的早期阶段有关。因此，靶向表观遗传调节因子的强效小分子已被开发为新型癌症治疗和预防策略。溴结构域和额外末端结构域（BET）蛋白是表观遗传阅读器，在染色质修饰和转录调控之间的界面发挥关键作用。在本研究中，我们研究了BET抑制剂JQ-1对12-氧代十四烷酰佛波醇-13-乙酸酯（TPA）诱导的小鼠皮肤表皮JB6 P+细胞恶性转化的影响。用JQ-1处理可有效损害TPA诱导的体外集落形成。在分子水平上，几种关键的TPA诱导的促生存和促增殖基因（Bcl2、细胞周期蛋白D1和c-Myc）的表达在BET抑制后迅速下降。此外，JQ-1处理减弱了TPA触发的炎症性NF-κB信号通路的激活。使用携带来自COX2或IL6启动子不同元件的质粒进行的荧光素酶报告基因测定表明，JQ-1不会直接抑制NF-κB与其结合序列之间的相互作用；相反，它影响与CRE元件相关的转录增强。通过siRNA基因沉默，我们发现JQ-1抑制COX2的p300依赖性转录激活，这与荧光素酶测定结果相关。染色质免疫沉淀测定表明，TPA提高了COX2启动子区域中由p300和Brd4介导的H3K27Ac富集。JQ-1处理并未改变H3K27Ac水平，但减少了Brd4和RNA聚合酶II的募集。总体而言，我们的研究表明，BET抑制剂JQ-1通过干扰肿瘤转化的核心转录程序发挥强效抗癌和抗炎作用。
