Therapeutic Targeting of BET Bromodomain Proteins in Castration-Resistant Prostate Cancer (ChIP-Seq). Homo sapiens

Men who develop metastatic castration-resistant prostate cancer (CRPC) invariably succumb to the disease. The development and progression to CRPC following androgen ablation therapy is predominantly driven by unregulated androgen receptor (AR) signaling1-3. Despite the success of recently approved therapies targeting AR signaling such as abiraterone4-6 and second generation anti-androgens MDV3100 (enzalutamide)7,8, durable responses are limited, presumably due to acquired resistance. Recently JQ1 and I-BET, two selective small molecule inhibitors that target the amino-terminal bromodomains of BRD4, have been shown to exhibit antiproliferative effects in a range of malignancies9-12. Here we show that AR signaling-competent CRPC cell lines are preferentially sensitive to BET bromodomain inhibition. BRD4 physically interacts with the N-terminal domain of AR and can be disrupted by JQ111,13. Like the direct AR antagonist, MDV3100, JQ1 disrupted AR recruitment to target gene loci. In contrast to MDV3100, JQ1 functions downstream of AR, and more potently abrogated BRD4 localization to AR target loci and AR mediated gene transcription including induction of TMPRSS2-ERG and its oncogenic activity. In vivo, BET bromodomain inhibition was more efficacious than direct AR antagonism in CRPC xenograft models. Taken together, these studies provide a novel epigenetic approach for the concerted blockade of oncogenic drivers in advanced prostate cancer. Overall design: Examination of AR, BRD2, BRD3, BRD4, ERG, RNA Pol II and H3K27ac in prostate cancer cells with respect to BET inhibitors

罹患转移性去势抵抗性前列腺癌（metastatic castration-resistant prostate cancer, CRPC）的男性患者最终均会因该病离世。经雄激素剥夺疗法后进展为CRPC的过程，主要由不受调控的雄激素受体（androgen receptor, AR）信号通路驱动1-3。尽管近期获批的靶向AR信号通路疗法（如阿比特龙4-6）与第二代抗雄激素药物MDV3100（恩扎卢胺）7,8已取得一定临床进展，但持久应答仍较为有限，推测其根源为获得性耐药。此前研究表明，JQ1与I-BET这两种靶向BRD4氨基端溴结构域的选择性小分子抑制剂，可在多种恶性肿瘤中发挥抗增殖活性9-12。本研究证实，保留AR信号通路活性的CRPC细胞系对BET溴结构域抑制剂具有优先敏感性。BRD4可与AR的N端结构域发生物理相互作用，且该相互作用可被JQ1阻断11,13。与直接AR拮抗剂MDV3100类似，JQ1可阻断AR向靶基因位点的招募。与MDV3100不同的是，JQ1作用于AR信号通路下游，可更高效地阻断BRD4定位至AR靶基因位点，并抑制AR介导的基因转录，包括TMPRSS2-ERG融合基因的诱导及其致癌活性。体内实验显示，在CRPC异种移植模型中，BET溴结构域抑制剂的治疗效果优于直接AR拮抗疗法。综上，本研究为晚期前列腺癌中协同阻断致癌驱动因子提供了一种全新的表观遗传学策略。整体实验设计：针对经BET抑制剂处理的前列腺癌细胞，检测AR、BRD2、BRD3、BRD4、ERG、RNA聚合酶II（RNA Pol II）及H3K27ac的相关表达与结合情况。