NDRG1调控结直肠癌转移相关膜蛋白内吞与转运的机制研究

Colorectal cancer metastasis indicates poor prognosis and poses significant challenges on the clinical management of this disease. Tumor cell migration and invasion through extracellular matrix is a key step during cancer metastasis. This process, as reported, could be modulated by cytoskeleton based-endocytosis and vesicle trafficking of key membrane proteins including receptors and adhesion molecules. Recent years, our group published successive articles on the function of a metastatic suppressor, NDRG1, against colorectal cancer invasion and migration while further studies implicate a potential role of actin skeleton dynamics in this function. We therefore raise the hypothesis that NDRG1 can inhibit colorectal cancer metastasis by modulating the endocytosis and vesicle trafficking of EGFR and Integrin through its impact on actin skeleton dynamics. This study will focused on the process of NDRG1 activating the actin skeleton assembly at specific sites, and form endosome by pulling the auxiliary membrane sag, as well as the interaction between the NDRG1 regulated actin skeleton assembly and specific small G protein family members, a crosstalk determining the final destination of the endosome. Importantly, this study will elucidate the novel mechanism of NDRG1 in inhibiting colorectal cancer metastasis in an endocytosis and vesicle trafficking pattern.

结直肠癌转移严重影响该病患者的预后，也是临床治疗难题。肿瘤细胞在基质中的侵袭迁移是肿瘤转移的重要步骤。以actin细胞骨架为结构基础的内吞和囊泡转运通过调控受体、黏附分子等关键膜蛋白的数量和分布而影响肿瘤细胞的侵袭迁移行为。我们近年连续研究并报道了NDRG1基因能抑制结直肠癌细胞的侵袭迁移，而该过程可能是通过调控actin细胞骨架来实现的。通过进一步的研究，我们提出假说，认为NDRG1可通过抑制actin细胞骨架重构调控EGFR和Integrin的内吞和转运进而抑制结直肠癌细胞的侵袭迁移。本研究将探索NDRG1通过激活actin骨架在特定位点的组装并牵拉辅助质膜凹陷形成内体，以及NDRG1调控的actin骨架组装与特异小G蛋白家族成员相互作用从而决定内体最终去路的过程。本研究立足膜蛋白内吞转运这一新的角度，为阐释NDRG1抑制结直肠癌转移提供了新机制与新思路。

结直肠癌转移严重影响该病患者的预后，也是临床治疗难题。肿瘤细胞在基质中的侵袭迁移是肿瘤转移的重要步骤。我们近年连续研究并报道 了NDRG1基因能抑制结直肠癌细胞的侵袭迁移，该作用可能是通过影响细胞骨架重构、内吞蛋白的转运机制以及调控细胞周期实现的，本课题对这一理论进行了深入研究与验证。我们首先探索NDRG1对于内吞蛋白Caveolin-1的影响，发现NDRG1的水平在体外实验和临床样本均与Caveolin-1表达显著相关，随后进一步证实了NDRG1与Caveolin-1存在的直接相互作用：NDRG1通过蛋白水解酶途径促进Caveolin-1泛素化降解，进而影响结直肠癌的EMT通路及转移过程；同时我们发现NDRG1通过促进凋亡抑制蛋白Bcl-2泛素化降低其表达水平，增强结直肠癌细胞凋亡，其中的机制可能是由NDRG1与蛋白激酶PKCα直接作用并促进Bcl-2蛋白多聚泛素化降低其表达水平引起的；此后我们发现NDRG1与细胞周期相关蛋白p21的相关性，并结合数据分析、通过体内、外实验验证了NDRG1可抑制p21与NEDD4的结合，进而抑制其泛素化，发挥抑制肿瘤的作用。