Targeting a Novel Epigenetic Signaling Nexus ACK1-pY88H4-AR/AR-V7 in Drug Resistant Metastatic Prostate Cancer

摘要 半个多世纪以来，前列腺癌的研究一直集中在雄激素受体(AR)， 它在疾病的发生和发展到高度转移阶段--去势阶段中的作用 耐药前列腺癌(CRPC)。而AR拮抗剂，如苯扎鲁胺或雄激素- 合成抑制剂阿比特龙抑制AR的功能活性，这些通常是无效的长时间 长期，因为顽固性疾病在2-3年内复发。CRPC不仅在低或低的情况下茁壮成长 去势后的雄激素水平，还会小心翼翼地维持功能性AR。因此，反 雄激素抵抗已成为前列腺癌治疗中最棘手的问题之一。 尽管进行了密集的努力，但靶向调节AR及其剪接变异体AR-V7的辅助因素 用小分子抑制剂直接和有效地转录还没有得到 已实现。我们发现AR招募癌基因AcK1，这是一种非受体酪氨酸激酶， 调节自身表达--在雄激素体内建立病理性正反馈环 被剥夺的条件。机制上，激活的AcK1通过磷酸化改变染色质 组蛋白H4位于一个新的位置，酪氨酸88(pY88-H4)，位于AR基因上游的三个位置 AREM1-3，促进转录。相反，pY88-H4组蛋白修饰的逆转 通过用新型AcK1抑制剂(R)-9bMS处理或过表达H4Y88F突变体 显著抑制全长AR以及AR-V7剪接变异体的转录， 从而下调AR靶基因的表达，如PSA。此外，我们 证明WDR5/MLL2组蛋白-赖氨酸N-甲基转移酶复合体与 PY88-H4表观遗传标记，将转录激活的H3K4三甲基标记存放在 从而揭示了AR基因座的一种新的表观遗传调控模式。基于这些 广泛的初步数据，我们假设抑制AcK1表观遗传调节活性 抑制AR转录和阻断AR剪接变异体的产生将是关键 对抗对苯扎鲁胺和阿比特龙耐药的CRPC。为了解决这一假设，我们将 追求以下目标： 目的1.评估pY88-H4沉积位点AREM1-3在AR/AR-V7中的功能作用 CRPC中的转录。 目的2.检测全基因组mll2/wdr5/ash2L和pY88-H4的协同作用及其在 推动AR/AR-V7表达和CRPC进展。 目的3.AcK1抑制剂(R)-9bMS克服苯扎鲁胺的详细表征 阿比特龙耐药及ADME/DMPK研究

Abstract For over half a century, prostate cancer research has focused on the Androgen receptor (AR), its role in the initiation of the disease and progression to the highly metastatic stage, castration resistant prostate cancer (CRPC). While AR antagonists such as enzalutamide or androgen- synthesis inhibitor abiraterone dampen AR functional activity, these are often ineffective long term, as the recalcitrant disease recurs within 2-3 years. CRPCs not only thrive under low or castrate levels of androgen, but also fastidiously maintain functional AR. Consequently, anti- androgen-resistance has become one of the most vexing problems in prostate cancer therapy. Despite intensive efforts, targeting co-factors that regulate AR and its splice variant, AR-V7 transcription, directly and efficaciously, with small molecule inhibitors has not yet been achieved. We uncovered that AR recruits the oncogene ACK1, a non-receptor tyrosine kinase, to regulate its own expression- setting up a pathological positive feedback loop in androgen deprived condition. Mechanistically, activated ACK1 modifies chromatin via phosphorylation of the histone H4 at a novel site, tyrosine 88 (pY88-H4), upstream of the AR gene at three sites AREM1-3, to promote transcription. Conversely, reversal of this pY88-H4 histone modification by treatment with a novel ACK1 inhibitor, (R)-9bMS, or overexpression of the H4Y88F mutant significantly suppressed transcription of the full length AR as well as AR-V7 splice variant, consequently downregulating expression of AR-target genes, such as PSA. Moreover, we demonstrate that WDR5/MLL2 histone-Lysine N-Methyltransferase complex, interact with the pY88-H4 epigenetic marks, deposit the transcriptionally activating H3K4 tri-methyl marks in trans, thus uncovering a novel mode of epigenetic regulation at the AR locus. Based on these extensive preliminary data, we hypothesize that inhibition of ACK1 epigenetic regulator activity that suppresses AR transcription and block production of AR splice variants will be critical to combat enzalutamide- and abiraterone-resistant CRPCs. To address this hypothesis, we will pursue the following aims: Aim 1. Assess the functional role of pY88-H4 deposition sites AREM1-3 on AR/AR-V7 transcription in CRPCs. Aim 2. Examine genome wide MLL2/WDR5/ASH2L and pY88-H4 co-association and its role in driving AR/AR-V7 expression and CRPC progression. Aim 3. Detail characterization of ACK1 inhibitor (R)-9bMS to overcome enzalutamide & abiraterone-resistance and ADME/DMPK studies.