PADI2介导的瓜氨酸化作用在CRPC中的功能及机制研究

Castration-resistant prostate cancer (CRPC) has an extremely poor prognosis and remains a significant clinical challenge as the underlying mechanisms are largely unknown. Previously, our group has reported that TXNDC5 could promote CRPC progression through activating the androgen receptor pathway, but the mechanism regulating its expression and activity is still obscure. Peptidylarginine deiminase 2 (PADI2) could promote tumor progression through post-translationally modifying arginine into citrulline. However, to date, no detailed study has been reported between PADI2 and PCa. Recently, we found that 1) TXNDC5 protein was citrullinated by PADI2 and its expression could be regulated by PADI2 as well; 2) the PADI2 expression increased significantly in both CRPC tissues and PCa cells when placed under long-term androgen-deprivation condition; 3) TXNDC5 could bind with PADI2. Based on the above data, we hypothesized that “PADI2 could regulate the expression and function of TXNDC5 through citrullination and promote the progression of CRPC ”. Our subject is intended to: (1) elucidate the regulation and mechanism of PADI2 on the expression and function of TXNDC5; (2) determine the biological functions of PADI2 in CRPC and interactions between PADI2 and androgen-AR signaling pathway in vitro and in vivo; (3) study the effect of TXNDC5 on the biological activity of PADI2; (4) characterize the clinico-pathological features of PADI2. This study may reveal a novel regulative mechanism regarding CRPC and provide credible evidence to search for new treatment medicine.

去势抵抗性前列腺癌（CRPC）是前列腺癌（PCa）治疗的难点。我们首次发现TXNDC5可促进CRPC的转变，但尚未明确调控其表达及功能的机制。PADI2通过将蛋白的精氨酸催化为瓜氨酸，参与肿瘤病变，但至今没有与PCa的研究报道。最近我们发现PADI2可瓜氨酸修饰TXNDC5蛋白并调控其表达；PADI2的表达在CRPC组织和长期雄激素剥夺培养后的PCa细胞中均显著升高；TXNDC5可与PADI2蛋白结合。在此基础上我们提出“PADI2通过瓜氨酸作用调控TXNDC5，并促进CRPC转变”的科学假说。本课题拟阐明PADI2对TXNDC5表达和功能的调控作用及其机制；探讨PADI2在CRPC病变中的功能及与雄激素受体通路的关系；研究TXNDC5对PADI2活性的影响；明确PADI2在PCa中表达的病理学特征。本课题的开展可望揭示新的CRPC调控机制，为寻找新的CRPC治疗药物提供理论及实验依据。

雄激素剥夺治疗仍是进展期 PCa 的首选治疗方案，但治疗 12～18 个月后，几乎所有患者最终转为 CRPC，预后极差。本课题分别就PADI2和TXNDC9等分子在前列腺癌的作用和致病机制进行了研究，并发现它们可以促进前列腺癌进展并可作为潜在治疗靶点。还发现Oldhamianoside II具有治疗前列腺癌的潜力。.本项目发现PADI2是雄激素抑制性基因并在CRPC中表达上调。体内外实验证实PADI2在雄激素剥夺情况下可促进前列腺癌细胞增殖。胞质中的PADI2可以保护雄激素受体免受蛋白酶体途径的降解，核迁移后瓜氨酸化修饰组蛋白H3的R26氨基酸残基从而促进雄激素受体结合到其下游靶基因上。加入PADI2抑制剂Cl-Amidine和雄激素受体信号通路抑制剂enzalutamide可以协同抑制CRPC细胞的增殖活性和去势条件下的成瘤性。.活性氧和活性氧诱导的氧化压力可以通过激活AR信号通路促进前列腺癌的进展，但具体机制有待进一步研究。 本项目发现TXNDC9受活性氧调控，且在活性氧激活的AR信号通路中发挥重要作用，同时TXNDC9在前列腺癌组织中的表达水平明显升高并能促进CRPC发生。活性氧能促进TXNDC9与PRDX1解离并且增强TXNDC9与MDM2的结合，这种结合的改变不仅促进了MDM2的降解同时增强了PRDX1与AR的结合，进一步活化AR通路。重要的是，PRDX1抑制剂能明显抑制因TXNDC9水平升高所诱导的肿瘤进展，而且这一作用在去势条件下更为明显。.Oldhamianoside II是一种新型三萜皂苷，体外和体内实验表明在各种类型肿瘤，它可以抑制肿瘤生长和转移；但是，确切的机制尚未充分阐明。在本研究中， Oldhamianoside II可起到前列腺癌抑制细胞增殖和侵袭的作用。Oldhamianoside II可以逆转上皮-间质转化，这可以通过在mRNA和蛋白质水平上E-cadherin的诱导作用和Vimentin和N-cadherin的抑制作用来证明。此外，Oldhamianoside II治疗通过上调Wnt拮抗剂的表达并促进蛋白酶体介导的β‑catenin的降解来抑制β‑catenin的信号传导活性。Oldhamianoside II通过调节上皮-间质转化和β‑catenin的功能发挥其抗肿瘤作用，并进一步支持其在临床治疗中的潜在作用。