Arl13b在胃癌中的作用及其机理研究

The occurrence and development of gastric cancer are processes affected by multi-factors and multi-steps, the precise mechanism is yet to be defined. It has been shown that Hedgehog was abnormally activated in gastric cancer, suggesting that Hedgehog signals might play a pivotal role in gastric cancer. Our preliminary results found that the transmembrane protein Smoothened (Smo) in the Hedgehog signals could bind to Arl13b by using the yeast two-hybrid system. The protein level of Arl13b in human gastric cancer specimens was significantly stronger than that in normal tissues; and there was also higher content of Arl13b in gastric cancer cell lines, compared with normal gastric cells. These results indicate that Arl13b might regulate Hedgehog signals by binding to Smo and promote gastric cancer progression. Therefore, we will test this hypothesis by the following approaches: (1) we will employ Immunohistochemistry, immunocytochemistry, and western blotting to investigate whether the protein levels of Arl13b, Smo and Gli2 were significantly higher in gastric cancer specimens and in gastric cancer cell lines, (2) Co-Immunoprecipitation (Co-IP) will be used to assess binding of Arl13b to Smo in these cells and (3), we will determine whether Arl13b promotes gastric cancer progression by binding to Smo of the Hedgehog signals. The present study will provide a novel insight into the mechanism of gastric cancer.

胃癌的发生发展是一个多因素、多步骤的过程，其发病机理非常复杂，到目前为止其确切发病机理尚未完全清楚。研究显示，Hedgehog（Hh）信号通路在胃癌组织中异常活化。我们前期通过酵母双杂交实验发现，Hh信号通路中的Smo蛋白可与Arl13b相互结合，而且Arl13b在人胃癌组织及胃癌细胞系中高表达，提示Arl13b可能通过与Smo蛋白相互作用而促进胃癌的发生发展。本课题通过免疫组织化学、免疫细胞化学和western blot等方法确定Arl13b和Hh信号通路中Smo和Gli2蛋白在胃癌和胃癌细胞系中高表达，然后用免疫共沉淀等方法确定Arl13b与Smo相互结合，并最终确定Arl13b通过Smo蛋白而促进胃癌的发生。本课题的研究可为胃癌的发病机理提供新的理论基础和实验依据。

胃癌是当前危害人类生命健康最严重的恶性肿瘤之一，并呈逐年上升趋势，其发病率较高，预后较差。研究显示，Hedgehog（Hh）信号通路在胃癌组织中高表达。Hedgehog(Hh)通路抑制剂（Smo）已被批准用于癌症治疗，但Smo突变通常会导致肿瘤耐药，目前Smo的调控机制仍尚不明确。在这项研究中，我们发现小的GTPaseArl13b是Smo的新的相互作用蛋白，并能调节Smo的活性。Arl13b的GTP binding domain(1-150aa)与Smo的胞内C端(550-787aa)相互作用，调控Smo的稳定性、转运和定位，激活Hh信号通路。在胃癌细胞中，Arl13b在体外和体内均能促进细胞的增殖、迁移和侵袭。Arl13b、Smo在胃癌组织中表达高于癌旁组织；Arl13b与肿瘤大小、浸润深度正相关，Smo与肿瘤大小，浸润深度，淋巴结转移，神经侵犯，血管侵犯，临床分期呈正相关。Arl13b、Smo的高表达是胃癌患者总生存期及无病生存期的不良预后因素。Arl13b在胃癌中的表达为胃癌的临床诊断和治疗提供了一个新的生物标识，为药物靶向治疗提供了新的方向。