ARHGEF39通过与STRAP相互作用激活TGF-β/Smad信号通路而促进肝癌侵袭转移的机制研究

Hepatic carcinoma is a common malignant tumor and recurrence and metastasis are the main reasons for the failure of treatment of hepatic carcinoma. Our primary data showed that ARHGEF39 was highly expressed in hepatoma tissues compared to tumor-adjacent tissues. Overexpression of ARHGEF39 signifcantly promoted the migration and invasion of hepatoma carcinoma cell (HCC). Moreover, STRAP was identified and demonstrated to be interacted with ARHGEF39 by Mass spectrum and co-immunoprecipitation. Knockdown of STRAP markedly decreased the promoting migration and invasion of ARHGEF39. In addition, our primary data also showed that the target genes of TGF-β/Smad signaling pathway can be upregulated by ARHGEF39. And it has been known that STRAP is an inhibitor of TGF-β/Smad signaling pathway. Therefore, we speculate that ARHGEF39 could activate TGF-β/Smad signaling pathway by decreasing the inhibition of STRAP through the interaction between ARHGEF39 and STRAP, thus promote the invasion and metastasis of hepatic carcinoma. We will test this hypothesis by performing experiments using cell and animal models as well as clinical samples. Results of this project will not expand our understanding of the roles of ARHGEF39, but also provide a novel target for the prevention and treatment of hepatic carcinoma metastasis.

肝癌是严重危害人类健康的常见恶性肿瘤之一。复发与转移是导致肝癌治疗失败的主要原因。本课题组最近的研究发现：ARHGEF39在肝癌组织中的表达显著高于癌旁组织，且过表达ARHGEF39显著促进肝癌细胞的迁移和侵袭；联用质谱和免疫共沉淀证明STRAP和ARHGEF39存在相互作用；敲低STRAP表达可以削弱ARHGEF39的促迁移侵袭作用；ARHGEF39可上调TGF-β/Smad信号通路靶基因的表达。由于STRAP是TGF-β/Smad信号通路的抑制子，我们推测：ARHGEF39通过和STRAP相互作用而降低其对TGF-β/Smad通路的抑制，从而激活TGF-β/Smad通路，进而促进肝癌的侵袭转移。本项目将从细胞水平、动物水平和临床水平设计实验对此假说进行验证。本项目的研究结果不仅可以进一步丰富对ARHGEF39蛋白功能的认识，而且可以为肝癌转移的预防和治疗提供新的靶点。

大量研究表明，TGF-β/Smad信号通路在调控肝癌细胞侵袭、凋亡和粘附等过程中发挥重要作用。本课题通过翔实的实验数据揭示了ARHGEF39在肝癌发展中的重要生物学功能及其在TGF-β/Smad信号通路中的作用机制。在肝癌样本中，我们发现ARHGEF39在肝癌中显著高表达，并且与肝癌病灶大小、肝内转移灶的数量及是否合并癌栓成正相关，与总生存率负相关。细胞功能实验发现ARHGEF39能够促进肝癌细胞的迁移和侵袭能力。利用质谱分析和免疫共沉淀相结合的方法，筛选并鉴定出与ARHGEF39相互作用的蛋白STRAP。通过截短质粒构建和免疫共沉淀技术确定ARHGEF39蛋白中与STRAP相互作用的结构域PH domain。利用免疫共沉淀技术、GST pulldown等技术证实ARHGEF39可通过和STRAP相互作用而降低其对TGF-β/Smad通路的抑制，促进Smad3的磷酸化和入核，进而激活TGF-β/Smad通路，促进肝癌的迁移侵袭。本研究一方面丰富了对于ARHGEF39这个重要鸟嘌呤核苷酸交换因子功能的认识，另一方面为肝癌转移的预防和治疗提供新的有效靶点。