MACC1在Beclin 1非自噬依赖性抗卵巢癌中的作用

Beclin 1 is an important link point between autophagy and apoptosis. As a haploinsufficient tumor suppressor, the mechanisms by which Beclin 1 suppresses tumor largely remain unclarified. Previously we reported that Beclin 1 possesses anti-ovarian cancer activity in an autophagy-independent pattern. To uncover the mechanisms by which Beclin 1 induces autophagy-independent cytotoxicity of ovarian cancer cells, genechip was performed and found that Beclin 1 was inversely correlated with MACC1 expression. MACC1 is a novel gene identified in 2009, which plays a critical role in the regulation of HGF/c-MET signal transduciton as a coactivator of c-MET. Moreover, MACC1 is reported to play important role in epithelial-mesenchymal transition （EMT）and invasion of cancer cells. EMT is a process by which epithelial cells acquire mesenchymal phenotype, and become migratory and invasive. At present EMT is considered as a critical step for invasion of epithelia-derived tumors. For the first time we found that Beclin 1 regulated MACC1 expression at the transcriptional level, while autophagy activators or inhibitors demonstrated no obvious effects on MACC1 expression, indicating that MACC1 might involve in autophagy-independent anti-ovarian cancer activity of Beclin 1. In addtion, Beclin 1 altered expression of marker proteins during EMT process (such as E-cadherin，N-cadherin，Vimentin et al).The MACC1 promoter contains one JunD potential binding site, in addition, we found that JunD and its upstream effectors MAP3K1 and MAP3K8 were increased in shBeclin 1-OVCAR3 cells.These indicates that Beclin 1 might regulate MACC1 expression via MAP3K-JNK-JunD pathway, thus regulate EMT and invasiveness of ovarian cancer cells. Based on our previous data, the current project aims to clarify the mechanisms by which Beclin 1 regulates MACC1 and the role of MACC1 in autophagy-independent antitumoral activity of Beclin 1 in ovarian cancer cells.

2012年我们在《BMC cancer》报道了自噬基因Beclin 1通过非自噬途径增强蛋白酶体抑制剂抗卵巢癌细胞的作用，但其分子机制不明。前期，我们还首次发现Beclin 1在转录水平非自噬依赖性下调卵巢癌细胞MACC1的表达，并改变上皮-间质转化（EMT）过程标志蛋白E-cadherin等的表达。MACC1是2009年新鉴定的c-MET辅助激活因子，能调节肝细胞生长因子/受体（HGF/c-MET）信号通路，调控EMT和肿瘤细胞侵袭。我们发现MACC1基因启动子存在转录因子JunD的潜在结合位点，沉默Beclin 1细胞中JunD及其上游效应分子MAP3K1和MAP3K8明显增加。提示Beclin 1可能通过MAP3K-JNK-JunD信号通路负调控MACC1基因启动子的活性，调节卵巢癌细胞的EMT和侵袭。本项目拟在前期工作基础上阐明Beclin 1调控MACC1表达的分子机制及其意义。