肾癌细胞中MAGI3表达对MAS介导的细胞增殖和迁移的影响

Renal cell carcinoma (RCC) is one of the most common and lethal cancer in urologic system carcinomas. Recent studies have found that renin - angiotensin system (RAS) plays an important role in the proliferation and invasion of renal cell carcinoma.There are two branches of the RAS including the classic angiotensin II-AT1R receptor axis, and a new important angiotensin (1-7)-MAS axis.angiotensin (1-7)-MAS receptor axis is being the new target of anti-RCC research but functions mediated by MAS and its molecular mechanism remain to be investigated. As a new member of G protein-coupled receptor, MAS has a PDZ binding motif in its carboxy terminus but there is no PDZ protein reported to interact with MAS and affect functions mediated by MAS in kidney. We found that mRNA expression of MAGI3 decreased in renal clear cell carcinoma from results of human genome U133 plus 2.0 array. MAGI3 is one of the typical PDZ scaffold protein. Our preliminary results showed that MAGI3 could inhibit activation of ERK pathway mediated by MAS, and MAS could interact with MAGI3 directly. On these basis, we will confirm the interaction between the MAS and MAGI3 in renal cancer cell, and study the impacts of MAGI3 expression on the roles induced by MAS in proliferation and invasion of renal cancer cell. Moreover, we will explore its mechanism whether it is induced by activation of ERK pathway mediated by MAS directly or interaction between MAS and AT1 receptor. This study will be helpful to understand the functions and its molecular mechanisms mediated by MAS, and enrich new targets in RAS as the aim of anti-cancer drugs research. This will be helpful to provide supports of the theoretical basis for personalized treatment of renal cancer.

肾细胞癌是最常见和致命的泌尿生殖系统肿瘤之一。近年研究发现肾素-血管紧张素系统（RAS）在肾癌的增殖和侵袭中扮演着重要角色，RAS的两大分支包括经典的血管紧张素II-AT1R轴，还有新的血管紧张素（1-7）-MAS轴，但对MAS轴所介导的功能及分子机制仍有待研究。MAS作为有PDZ结合域的G蛋白偶联受体家族的新成员，肾组织中尚无与其相互作用的PDZ蛋白报道。我们通过基因表达芯片结果查询发现与正常肾组织比较，肾透明细胞癌肿瘤组织中PDZ支架蛋白MAGI3表达下降。我们的前期结果表明MAGI3可以抑制MAS介导的ERK通路激活，且初步鉴定MAS可以和MAGI3直接相互作用。在此基础上，将继续研究在肾癌细胞中二者的相互作用，及MAGI3表达对MAS轴在肾癌细胞增殖和侵袭中的作用及其机制的影响。本研究将有助于阐述MAS介导的功能及其分子机制，为肾癌的个性化药物治疗提供理论基础。

肾癌主要指肾细胞癌，其中肾透明细胞癌是最常见的类型，也是最常见和致命的泌尿生殖系统肿瘤之一。肾素-血管紧张素系统（RAS）不仅在心血管系统中扮演着重要的角色，而且发现在肾脏肿瘤增殖和侵袭生长过程中扮演重要的角色。血管紧张素(1-7) -MAS受体轴作为肾素-血管紧张素系统中一个新的重要分支，为抗肾癌药物的研发提供了新的靶标。MAS作为G蛋白偶联受体家族的新成员，羧基端具有PDZ结合域。我们发现一个典型的PDZ蛋白MAGI3可以和MAS羧基端直接相互作用，此相互作用不仅是组成性的，而且可以在MAS内源性激动剂血管紧张素(1-7)激动下，相互作用增加。当MAS羧基端突变会消除与MAGI3的相互作用，说明二者相互作用的特异性。进而我们证实MAGI3可以抑制血管紧张素(1-7)激动引起的ERK通路激活，且此作用可以被MAS拮抗剂A779抑制。同时，MAGI3在肾癌组织中低表达，并且与肾癌进展及预后相关。在此基础上，发现MAGI3表达可以影响肾癌细胞的增殖和凋亡。我们发现加入AT1R拮抗剂氯沙坦对MAS介导的细胞增殖等恶性表型没有显著性影响，说明无论血管紧张素II-AT1R通路抑制与否，血管紧张素(1-7)刺激均可引起肾癌细胞增殖增加。动物荷瘤实验进一步证实了MAGI3高表达使肿瘤细胞增殖减少。本研究表明MAGI3可以抑制MAS介导的ERK信号通路和肿瘤细胞增殖，肾癌中MAGI3低表达会减少对MAS的信号通路抑制作用，增强了MAS介导的ERK信号通路。本课题丰富RAS作为抗肿瘤药物研发靶标的新靶点的开发，为肾癌的个性化药物治疗提供理论基础。