MIIP通过PP1/Akt/mTOR和miR-129-5p/Beclin1调控细胞自噬和前列腺癌化疗敏感性

Chemotherapy is the main treatment for metastatic prostate cancer (PCa), but there exists different chemosensitivity between individuals. Cell autophagy is involved in regulation of PCa chemosensivity through its two-sided regulation of cell survival and death., but the exact effect and the mechanism of the upstream regulation is still not clear. MIIP is a newly identified tumor suppressor. Our recent RNA-seq data indicated that MIIP influences the process of cell autophagy. MIIP-overexpressing PCa cells exhibited more obvious autophagy-marker alterations induced by starvation and were more sensitive to chemodrug taxanes than did the control cells. Moreover, we found that MIIP interacts with phosphatase PP1 and inhibits Akt/mTOR pathway. Meanwhile, MIIP downregulates miR-129-5p but upregualtes its target gene BECN1, which encodes well-known autophagy molecule Beclin-1. This suggested that MIIP can regulates cell autophagy through PP1/Akt/mTOR and miR-129-5p/Beclin-1, thereby influencing PCa chemosensitivity. In this project, by taking advantage of PCa cell lines, xenograft in nude mouse and MIIPKO mouse, as well as PCa samples, we will clarify the role of MIIP in cell autophagy, uncover the underlying mechanism through which MIIP regulates cell autophagy, elucidate the functional effect of such regulation in PCa chemosensitivity and finally, evaluate its clinical relevance. This study will enrich the theroy about autophagy regulation, reveal the novel MIIP function and may provide the evidence for autophagy-based treatment for PCa.

化疗是晚期前列腺癌（PCa）的主要治疗手段，但药物敏感性存在个体差异。细胞自噬通过对细胞存亡的双向调控作用，参与调节PCa化疗敏感性，但具体效应及上游调控机制不清。MIIP是新抑癌基因，我们新近转录组测序表明MIIP影响细胞自噬过程。MIIP过表达PCa细胞中饥饿诱导的自噬标志分子变化更明显，且细胞对紫杉醇类药物更敏感。进一步，我们发现MIIP通过结合磷酸酶PP1并抑制 Akt/mTOR通路；并且MIIP下调miR-129-5p而上调其靶基因BECN1。这些强烈提示MIIP可能通过此两种方式调控细胞自噬，影响PCa化疗敏感性。据此，本项目拟利用PCa细胞系、裸鼠移植瘤和MIIPKO小鼠及临床组织样本，明确MIIP在细胞自噬中的作用，揭示MIIP调控自噬的分子机制，解析该调控在PCa化疗敏感性中的作用。本研究将丰富自噬调控理论，揭示MIIP新功能，并可能为基于自噬干预的PCa治疗提供依据。

化疗是晚期前列腺癌（PCa）的主要治疗手段，但药物敏感性存在个体差异。细胞自噬通过对细胞存亡的双向调控作用，参与调节PCa化疗敏感性，但具体效应及上游调控机制不清。我们根据转录组测序和进一步实验结果，提出新抑癌基因MIIP影响细胞自噬过程和促进紫杉醇类药物敏感性，并可能通过Akt/mTOR通路和miR-129-5p/Beclin-1实现。本项目利用PCa细胞系、裸鼠移植瘤及临床组织样本，明确MIIP在细胞自噬中的作用，揭示MIIP调控自噬的分子机制，解析该调控在PCa化疗敏感性中的作用。主要发现如下：①MIIP可促进前列腺癌细胞自噬和增强Docetaxel和Cabazitaxel的敏感性，且对DTX的作用依赖于细胞自噬。②MIIP依赖其C端与PP1α结合从而抑制Akt-mTOR信号通路的活化与细胞活力；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 抑制miR-129-5p/ BECN1并可能借此促进细胞自噬。MIIP能够下调miR-129-5p，miR-129-5p可抑制细胞基础自噬和DTX诱导的自噬及化疗敏感性，并证实BECN1是miR-129-5p的靶基因。④MIIP通过181a/b-5p-KLF17轴抑制EMT而抑制前列腺癌转移，是前列腺癌EMT的抑制因子。⑤MIIP通过HIF-2α-CYR61轴抑制肾癌血管生成，是血管生成的负调节因子。这些研究从新的角度阐明了抑癌分子MIIP在调控PCa自噬和紫杉醇类化疗敏感性中的生物学功能，揭示了MIIP调控肾癌血管生成的分子机制及其临床意义。