辛伐他汀通过调控RhoB放疗增敏作用及机制研究

Radiation resistance exists in almost all kinds of tumor and could reduce the effects of radiotherapy. It is urgent to find sensitizing agent with efficiency but low toxicity for patients with cancer. Statin lipid-lowering drugs other than play pleiotropic effects through inhibit Rho family of isoprenylation. Statins can improve the effect of radiotherapy for patients with cancer, but the mechanism is not clear. RhoB is an important signal molecule in the DNA damage pathway, may induce apoptosis or DNA repair. Various lipid modification (also exist isoprene and palmitoylated) may be the reason. We recently discovered, simvastatin could enhance the radiation sensitivity of gastric cancer cells by up regulating RhoB protein. We put forward the hypothesis as follow. Statins may regulate histone acetylation, inhibition of isoprenoid synthesis and then change the RhoB protein lipid modification, thus affecting the protein function to induce cell apoptosis. To test this hypothesis, we designed this study, intends to reveal the mechanism of depth. First through the in vitro and in vivo experiments to confirm the radiation sensitization effect of simvastatin. Then study in vitro will be performed to explore whether simvastatin regulate RhoB gene promoter histone acetylation to upregulate the expression of RhoB protein. Lastly, after simvastatin treatment and X ray radiation, palmitoylated RhoB would be detected and be studied whether promoting cancer cell apoptosis. Its molecular mechanism to promote apoptosis would be also explored. This project will undoubtedly promote statins as radiosensitizer in clinical application, rich our kownlege of RhoB molecular, and to promote more radiotherapy sensitizing agents targeting RhoB being development.

放射线抵抗普遍存在于各类肿瘤，阻碍放疗疗效，寻找高效低毒的增敏剂是研究热点。他汀通过抑制Rho家族异戊二烯化发挥降脂以外的药物多效性。他汀可提高肿瘤患者放疗效果，但机制不清。RhoB是DNA损伤通路重要信号分子，具有促进凋亡/DNA修复双重作用，多样的脂类修饰（同时存在异戊二烯化及棕榈酰化）可能是原因。我们研究发现，辛伐他汀通过上调RhoB增强胃癌细胞放射敏感性。因此提出假说：他汀通过调控组蛋白乙酰化促进RhoB蛋白表达，抑制异戊二烯改变RhoB脂类修饰，发挥其促凋亡作用。本课题首先通过体内体外实验验证辛伐他汀放疗增敏作用；研究辛伐他汀能否调控启动子组蛋白乙酰化促进RhoB表达；检测辛伐他汀作用后RhoB是否存在棕榈酰化修饰，放射后棕榈酰化RhoB-P是否促进细胞凋亡及其分子机制。本课题的实施将推动他汀作为放疗增敏剂临床应用，丰富对RhoB分子的认知，促进以RhoB为靶点新增敏剂研发。

甲羟戊酸途径是一条重要的细胞代谢途径，参与多种代谢产物如胆固醇、法尼基焦磷酸（farnesyl pyrophosphate，FPP）及牻牛儿基牻牛儿基焦磷酸（geranylgeranyl pyrophosphate，GGPP）等的合成。这些代谢产物在维持细胞膜的完整性，细胞内信号传导，糖蛋白的合成及细胞周期进展等方面发挥重要作用。他汀类药物作为甲羟戊酸途径限速酶3-羟基-3-甲基戊二酸辅酶A还原酶（3-hydroxy-3-methylglutaryl-coenzyme A reductase, HMGCR）的竞争性抑制剂，能阻碍这些产物的合成。越来越多的研究提示他汀药物有抗肿瘤作用，其在胃癌的作用及分子机制尚不清楚。本课题中我们发现辛伐他汀可以抑制胃癌细胞增殖、迁移和侵袭能力，促进胃癌细胞凋亡，并且可以增强化疗药物对胃癌细胞的杀伤作用。通过我们的课题，明确了辛伐他汀是通过抑制RhoA活性进而抑制YAP蛋白以及β-Catenin蛋白实现对Hippo和Wnt通路的调节到达其抗癌作用。我们进行了另一项课题也证实辛伐他汀可抑制结肠癌细胞中YAP蛋白活性，而YAP表达越高，结肠癌细胞对西妥昔单抗越抵抗，敲除YAP蛋白的结直肠癌细胞对西妥昔单抗敏感性增强。体内体外研究证实辛伐他汀增强西妥昔单抗对结肠癌的抗癌作用，因此，两药联用双靶点治疗有望成为潜在可行的增强抗EGFR治疗结直肠癌患者疗效的新策略。