UHRF1和AR联合调节癌基因CDC6及抑癌基因P16和MST1促进去势抵抗前列腺癌发展新机理

Androgen/AR play critical roles in the progression of prostate cancer (PCa), and androgen-deprivation therapy (ADT) is an effective modality. However, patients develop the castration-resistant prostate cancer (CRPC) within 6-12 months. UHRF1, as an important epigenetic regulator over-expressing in PCa tissues, promotes the malignancy of PCa. The molecular mechanism is still elusive. In the preliminary studies, we found that AR regulated UHRF1, and UHRF1 enhanced the ability of AR to activate CDC6 gene expression. Meanwhile, tumor suppressor genes p16 and MST1, which are at the status of hypermethylation and expression silence in PCa, were re-activated when AR was knock-down. Therefore, we hypothesize that UHRF1 is a novel co-activator of AR in the regulation of CDC6 gene transcription, and AR plays a critical role in maintaining hypermethylation and expression silence of p16 and MST1, by regulating UHRF1 and PCNA and keeping the stability of epigenetic complex UHRF1/PCNA/DNMT1. In the proposed project, by using the tools of molecular biology and biochemistry in cells, animal models and patient’s specimens, we will explore how UHRF1 and AR regulate reciprocally, how UHRF1 enhances AR ability to regulate CDC6 and DNA replication, and how AR maintains the hypermethylation and expression silence of p16 and MST1 through epigenetic regulation. The project will clarify a novel mechanism of CRPC, and identify UHRF1 as a novel biomarker for CRPC diagnosis and therapy.

雄激素/AR在前列腺癌发展中起关键作用，去势治疗是主流疗法，但疾病很快发展成去势抵抗状态。表观遗传因子UHRF1促进前列腺癌发展，但机理不清。我们前期研究表明，AR调节UHRF1表达，UHRF1与AR蛋白质交联，并促进了AR调节癌基因CDC6表达。此外，敲低AR重新激活了原本在前列腺癌中处于高甲基化与沉默状态的抑癌基因p16和MST1。 据此，我们提出科学假说： 在去势抵抗前列腺癌细胞，UHRF1是新的AR联合转录激动子调节CDC6表达，同时AR通过调节UHRF1和PCNA影响UHRF1/PCNA/DNMT1表观遗传途径，维持p16和MST1高甲基化和基因沉默。本课题拟应用分子生物学和生化手段，通过细胞，动物模型和临床样本，揭示表观遗传因子UHRF1与AR联合参与癌基因转录与抑癌基因表观遗传调控的新机理。本课题将揭示去势抵抗前列腺癌发展新机制，明确UHRF1作为去势抵抗前列腺癌诊疗新靶标。

前列腺癌已经成为中国男性发病率和致死率高的癌症类型。抗雄激素/雄激素受体抑制剂已经成为一线治疗药物，但是经过一段时间治疗后，癌症将产生药物抵抗，发生转移。细胞增殖和DNA复制受雄激素和雄激素受体调控。CDC6是一个DNA复制的执照因子，和CDT1分子协同启动DNA复制，保证一个细胞周期中DNA只复制一次。在以前的研究中，我们发现CDC6基因转录受雄激素/雄激素受体调控，雄激素受体被雄激素激活后结合到CDC6基因启动子上的ARE结合位点，调节DNA复制启动。UHRF1是一个非常重要的表观遗传调节因子，参与肿瘤抑制基因的转录抑制。在本课题中，我们发现UHRF1和AR协同调控CDC6的基因转录，UHRF1特异性结合到CDC6基因启动子上离ARE结合位点很近的CCAAT结合序列，通过招募KDM4c，一个H3K9me3特异性的去甲基化转移酶，从而改变了CDC6基因启动子附近的组蛋白的结构状态，从而发挥和经典UHRF1作用不一致的结果，打开而不是关闭组蛋白的状态，更加有利于AR转录因子与DNA的结合。此外，我们还发现，TIP60，另一个已经报道的AR共转录激活因子，能够导致AR乙酰化，促进AR从胞质向核内转位，从而加强AR的转录效率。总之，本课题研究揭示了UHRF1是一个新的AR共转录因子，协同性和AR共同调节CDC6基因转录和DNA复制，共同靶向AR和UHRF1将显著增强前列腺癌的治疗效果。