E3泛素连接酶Fbxw7通过抑制细胞自噬从而调控胃癌侵袭转移的分子机制研究

The recurrence and metastasis of gastric cancer (GC) are the most important factors which influence on the prognosis of GC patients and the treatment of GC is still a tough problem. We have proved that E3 ubiquitin ligase Fbxw7 could regulate the recurrence and metastasis of gastric cancer, however, the mechanism is basically unknown. To explore the downstream signaling pathway and intervention targets, we could find a new idea on preventing the recurrence and metastasis of gastric cancer. Our previous studies found that Fbxw7 had a down-regulation expression in GC, and the expression of ULK1, LC3 were decreased, the expression of p-AMPK, p-RhoA after Fbxw7 overexpression. Based on these previous researches, we speculate that Fbxw7 could control the autophagy by regulating the expression of ULK1,and then regulate the recurrence and metastasis of gastric cancer through AMPK-RhoA signaling pathway. To test this hypothesis, we plan to investigate the relationship between Fbxw7 and ULK1 and the prognosis value of Fbxw7 in more collected clinical samples. Next, we investigate whether Fbxw7 could regulate the expression of ULK1 through establishing Fbxw7 overexpression or knock-down in vivo and in vitro models. Then, we discuss the impact of autophagy on the recurrence and metastasis of gastric cancer, and confirm whether ULK1 could regulate the recurrence and metastasis of gastric cancer through AMPK-RhoA signaling pathway. This study will attempt to illuminate the molecular mechanism of Fbxw7 in GC invasion and metastasis and to establish the Fbxw7-ULK1-AMPK-RhoA signaling pathway which should supply some new therapeutic strategies and treatment targets in prevention of GC invasion and metastasis.

胃癌转移复发是影响胃癌预后的重要因素和难题。E3泛素连接酶Fbxw7在胃癌的转移复发过程中起着重要作用，但其具体分子机制尚不明确。前期研究结果表明：Fbxw7在胃癌中表达下调，过表达Fbxw7后ULK1，LC3的表达水平下降,而p-AMPK、p-RhoA的表达水平提高，RhoA活性降低。因此，我们推测Fbxw7能够通过泛素蛋白酶体途径调控自噬启动蛋白ULK1从而影响细胞自噬，进而通过调控AMPK-RhoA信号通路影响胃癌的侵袭转移过程。本项目拟在此基础上分析Fbxw7与ULK1的表达相关性及预后判断价值；证实Fbxw7能够调控ULK1的表达；观察细胞自噬作用对胃癌侵袭转移的影响，同时探讨其是否通过下游AMPK-RhoA信号通路调控胃癌侵袭转移。本项目将阐述Fbxw7-ULK1-AMPK-RhoA调控胃癌侵袭转移的分子机制，为预防胃癌的复发转移提供新的思路。

胃癌（Gastric cancer，GC）是世界范围内最常见的恶性肿瘤之一，也是威胁人类健康的主要疾病之一。胃癌患者根治术后5年生存率不超过40%，导致该疾病临床治疗失败和患者短期内死亡的首要原因是肿瘤原发灶侵袭和转移。因此，深入探讨胃癌侵袭转移的分子机制，同时寻找胃癌侵袭转移的标志物及相关干预靶点则成为目前研究的重点和关键。Fbxw7，作为SKIP-CUL-F框蛋白（SCF）E3泛素连接酶复合体的重要组成部分能够通过特异性识别和结合靶蛋白从而导致多种癌基因蛋白降解，我们的前期研究结果表明：Fbxw7在胃癌中表达下调，并且其表达水平对胃癌的生物学特性方面体现出十分重要的影响。因此，Fbxw7通过何种具体分子机制对胃癌发生发展及侵袭转移过程进行调控的则是本课题研究的一个重要目标。根据课题组前期的研究成果我们大胆假设Fbxw7可能通过泛素蛋白酶体途径调控自噬启动蛋白ULK1从而影响细胞自噬作用，进一步调控AMPK-RhoA信号通路从而影响胃癌的发生发展及侵袭转移过程。通过本项研究，我们验证发现Fbxw7在胃癌组织及多种胃癌细胞中低表达，且其在胃癌伴有转移组织中表达更是显著降低；自噬相关标记物、自噬启动蛋白ULK1在胃癌组织及多种胃癌细胞中具有相反的表达趋势并且Fbxw7与ULK1在胃癌组织及细胞中表达呈负相关。Fbxw7能调控自噬启动蛋白ULK1的表达从而影响细胞自噬进而调控胃癌的侵袭迁移。RhoA是AMPK的下游靶基因，Fbxw7-ULK1轴能够通过调控AMPK-RhoA信号通路从而影响胃癌侵袭转移。本项目的展开，期望能够深入探讨E3泛素连接酶Fbxw7在胃癌发生发展中的调控作用，有力的证明了Fbxw7调控胃癌侵袭转移的具体分子机制，为预防胃癌的复发转移提供了新的治疗靶点，为胃癌治疗提供一条新的思路。