西咪替丁促进STUB1依赖性的胃癌细胞内FOXP3蛋白泛素化降解的研究

Basic and clinical study has confirmed the anti-tumor effect of cimetidine, but its targets and regulatory mechanism remain fully elusive. Our group has recently reported that FOXP3 in gastric cancer cells play a pro-tumoral role. And preliminary study indicated that cimetidine promoted the ubiquitination/degradation of FOXP3 in gastric cancer cells. Moreover, the protein level of FOXP3 was associated with the sensitivity to cimetidine treatment, suggesting that FOXP3 may be a sensitive target of cimetidine in the treatment of gastric cancer. In addition, we also found that cimetidine promoted STUB1 expression by activating PI3K/Akt pathway, and the down-regulation of STUB1 can reverse the degradation of FOXP3 induced by cimetidine. Thus, we propose the hypothesis"Cimetidine can promote STUB1-dependent ubiquitination/degradation of FOXP3 in gastric cancer cells by activating PI3K/Akt pathway". In the current study, we will further validate whether STUB1 is the key enzyme of cimetidine-induced FOXP3 ubiquitination/degradation, and identify the regulatory mechanism by regulating STUB1 protein level and PI3K/Akt pathway. Then gastric cancer organoid is used to determine whether FOXP3 can be taken as the genetic feature associated with the sensitivity to cimetidine treatment. This study will reveal the target and regulatory mechanism of cimetidine in the treatment of gastric cancer from a novel perspective, to guide the development of individualized and accurate treatment for gastric cancer.

基础和临床研究证实西咪替丁具有抗肿瘤作用，但抑癌靶点和机制尚不明确。本课题组近期报道胃癌细胞表达的FOXP3具有促癌作用。另外，预实验结果证实西咪替丁能够促进胃癌细胞内FOXP3发生泛素化降解，其蛋白水平影响治疗的敏感性，提示FOXP3是西咪替丁治疗胃癌的敏感靶点。研究还发现西咪替丁通过激活PI3K/Akt通路促进STUB1表达，而下调STUB1能够逆转西咪替丁对FOXP3的降解作用。因此，我们提出假说“西咪替丁通过激活PI3K/Akt通路促进STUB1依赖性的胃癌细胞内FOXP3泛素化降解”。本项目拟通过调控STUB1蛋白水平和PI3K/Akt通路，验证STUB1是否是西咪替丁促进FOXP3泛素化降解的关键酶，明确其调控机制。并利用胃癌类器官模型明确FOXP3能否作为与西咪替丁治疗敏感性相关的遗传特征。本项目从全新角度揭示西咪替丁治疗胃癌的靶点和调控机制，以指导胃癌个体化精准治疗的开展。

胃癌是威胁人类生命健康最常见的恶性肿瘤之一，肿瘤的复发和转移是影响进展期胃癌患者临床预后的主要因素。然而，目前尚缺乏胃癌有效的治疗靶点。本课题组前期工作中发现西咪替丁具有抗肿瘤作用。本项目进一步揭示了西咪替丁的抑制胃癌的靶点和机制。本研究主要完成以下研究内容：(1) 西咪替丁对胃癌细胞恶性生物学行为的影响。(2) 西咪替丁对胃癌细胞内 FOXP3 蛋白的调控作用和调控方式。(3) 揭示西咪替丁调控胃癌细胞内 FOXP3 蛋白的分子机制。(4) 分析 FOXP3 能否作为与西咪替丁治疗胃癌敏感性相关的遗传特征。研究结果显示：(1) 西咪替丁能够有效抑制胃癌细胞的增殖、迁移和侵袭能力。(2) 西咪替丁能够促进胃癌细胞内 FOXP3 蛋白的泛素化降解。(3) STUB1 是西咪替丁促进 FOXP3 泛素化的E3连接酶。(4) 西咪替丁通过PI3K-Akt信号通路上调 STUB1 促进FOXP3 的泛素化降解。(5) 胃癌细胞FOXP3 的蛋白水平影响西咪替丁治疗的敏感性，有希望作为与西咪替丁治疗胃癌敏感性相关的遗传特征。本研究从全新的角度揭示西咪替丁在胃癌中的治疗靶点和调控机制，为胃癌治疗提供新的药物靶点和临床干预手段。对指导临床开展胃癌的个体化精准治疗，提高胃癌的临床疗效和患者生活质量具有极积的临床意义和社会价值。