MIIP与泛素-蛋白酶体系统（UPS）的交互调控在前列腺癌去势抵抗中的作用与机制

Castration-resistant prostate cancer (CRPC) is the inevitable outcome of the prostate cancer after androgen-deprivation therapy. The underlying mechanism involves the re-activation of AR and the activation of other by-pass pathways. According to the literatures, ubiquitin-proteasome system (UPS) is involved in CRPC through regulating the transcriptional activity of AR and AR-independent signaling pathways. Howerver, the upstream regulation of UPS in CRPC is still unknown. Our group firstly reported MIIP as a tumor suppressor gene. Most recently, we found that the expression of MIIP is downregulated in CRPC cell lines and some PCa tumor samples. Moreover,The forced expression of MIIP can inhibit the malignant behaviors in CRPC cell lines. Particularly, MIIP interacts with the proteasome subunit, PSMB5, and inhibits the activity of UPS, whereas the E3 ubiquitin ligase E6AP promotes the degradation of MIIP by the proteasome. This strongly suggests that there is a reciprocal regulation between MIIP and UPS and it is involved in CRPC. In this project, we plan to carry out the experimental study with cellular and molecular techniques, xenograft and MIIP-ko/TRAMP mouse CRPC model, as well as PCa samples analysis. We will confirm the role of MIIP in CRPC, clarify the underlying mechanism through which MIIP regulates the function of UPS, elucidate the functional effect of MIIP degradation by UPS and finally, evaluate the clinical relevance of such reciprocal regulation. This study will enrich the theroy about UPS regulation, reveal the novel function of MIIP and may provide the new throught for the prevention and treatment for CRPC.

去势抵抗性前列腺癌（CRPC）是前列腺癌（PCa）去势治疗后的必然转归，其机制主要涉及AR再度激活及其它旁路活化。文献表明，泛素-蛋白酶体系统（UPS）通过调控AR转录活性和非AR信号通路，参与CRPC，但上游调节机制尚不清楚。MIIP是项目组早期报道的抑癌基因，我们新近研究表明：CRPC细胞系和部分PCa 患者癌组织MIIP表达降低；过表达MIIP可抑制细胞恶性行为；特别是，MIIP与蛋白酶体亚基结合并抑制UPS活性；而MIIP含量又受UPS降解调控。这些强烈提示MIIP与UPS之间存在交互调控并参与CRPC。基于此，本项目拟从细胞、分子、CRPC小鼠模型和PCa临床样本多层面，确认MIIP在CRPC中的作用；阐明MIIP调控UPS的分子机制；解析UPS 降解MIIP的功能效应；并评估上述交互调控的临床意义。本研究将丰富UPS调控理论，揭示MIIP新功能，并可能为CRPC防治提供新思路。

去势抵抗性前列腺癌（CRPC）是前列腺癌（PCa）去势治疗后的必然转归，其机制主要涉及AR再度激活及其它旁路活化。泛素-蛋白酶体系统（UPS）可通过调控AR转录活性和非AR信号通路，参与CRPC，但上游调节机制尚不清楚。MIIP是项目组早期报道的抑癌基因，我们发现PCa 患者癌组织中MIIP表达降低；过表达MIIP可抑制细胞恶性行为；MIIP与UPS之间存在交互调控。但MIIP在PCa中的具体的作用及分子机制均未报道。本项目利用细胞、分子、CRPC小鼠模型和PCa临床样本，确认了MIIP在PCa特别是CRPC中的作用， 阐明了MIIP调控UPS、EMT等细胞内过程的分子机制，对上述调控作用的生物学效应及其临床意义进行了评估。主要发现如下：①MIIP可抑制PCa细胞内蛋白酶体活性及蛋白质降解功能，该作用通过MIIP与蛋白酶体的催化亚单位PSMB5结合而实现，MIIP亦可能籍此影响CRPC对药物的反应性。②MIIP在体外和皮下荷瘤鼠模型中均具有明显抑制激素敏感PCa和CRPC细胞增殖的作用。MIIP并不影响AR信号通路，但明显抑制 AKT-mTOR信号通路的活化，该作用通过MIIP借助其C端结构与Ser/Thr磷酸酶PP1α结合而实现。 临床PCa组织标本中MIIP水平明显低于正常组织，且其表达水平与PCa的Gleason评分负相关。③MIIP具有明显抑制CRPC细胞上皮-间质转化（EMT）和侵袭转移的作用。MIIP可抑制181a/b-5p，使其对靶分子--EMT的关键负调控因子KLF17--的负调控作用解除，从而抑制EMT和细胞侵袭。MIIP表达降低导致181a/b-5p升高，KLF17下调，增强EMT和癌细胞的侵袭能力，从而参与前列腺癌进展。这些研究从新的视角阐明了抑癌基因MIIP在PCa增殖和侵袭中的生物学功能，揭示了MIIP调控UPS和EMT的分子机制及其临床意义。项目研究期间在 Cell Commun Signal、Prostate、Am J Cancer Res等期刊发表标注本基金的论文8篇（1篇影响因子大于5.0，中文核心期刊论文2篇），申请国家发明专利1项。培养研究生3人，其中博士生2人，硕士生1人。