microRNA-31调控整合素α5β1介导膀胱癌化疗抵抗的机理研究

Chemoresistance plays an important role in the treatment failure of bladder cancer. In our previous studies, it has been found that chemoresistance of bladder cancer is mainly mediated via extracellular matrix (ECM) fibronectin-integrin signal pathway in which integrin β1 acts as a crucial factor. In addition, we also found that microRNA-31 (miR-31) could target integrin α5β1, which is composed of β1 and α5 subunit. Further studies should be performed to investigate the influence on chemosensitivity and the mechanism of chemoresistance resulting from miR-31 targeting integrin α5β1 in bladder cancer. This project includes: (1) in vitro: to study the influence of different miR-31 expression levels on biological behavior and chemosensitivity of common and chemoresistant bladder cancer cell lines, and detect the changes in downstream signaling pathways of integrin α5β1; (2) in vivo: to study miR-31's influence on growth, metastasis and chemosensitivity of bladder cancer in immunodeficient mice with bladder cancer and genetically engineered mice with orthotopic bladder cancer; (3) clinical: to analyze the relationship of varying expressions of miR-31 and integrin α5β1 with the prognosis and chemosensitivity in patients with bladder cancer. Based on these researches, we will reveal the molecular mechanism of chemoresistance resulting from miR-31 targeting integrin α5β1 in bladder cancer.

膀胱癌化疗抵抗是治疗失败的重要原因。申请者发现，细胞外基质纤维连接蛋白-整合素信号通路介导了膀胱癌化疗抵抗，整合素β1亚基为关键位点；还发现microRNA-31（miR-31）可调控整合素α5β1（由β1与α5亚基组合而成）。miR-31调控整合素α5β1，介导膀胱癌化疗抵抗的机理有待研究。 本申请课题拟：（1）体外研究：不同miR-31表达水平，对膀胱癌普通及耐药细胞系生物学行为和化疗敏感性的影响，检测整合素α5β1下游信号通路的变化；（2）体内研究：利用人膀胱癌免疫缺陷小鼠和原位膀胱癌基因工程小鼠模型，研究miR-31对膀胱肿瘤生长、转移和化疗敏感性的影响，检测整合素α5β1下游信号通路分子；（3）临床研究：测定膀胱癌组织miR-31、整合素α5β1的差异表达，比较分析上述差异与化疗抵抗、疾病预后的关系。拟揭示miR-31调控整合素，影响膀胱癌化疗敏感性、产生化疗抵抗的分子机制。

膀胱癌化疗抵抗是治疗失败的重要原因。申请者发现，细胞外基质纤维连接蛋白-整合素信号通路介导了膀胱癌化疗抵抗，整合素β1 亚基为关键位点；还发现 microRNA-31（miR-31）可调控整合素α5β1（由β1 与α5 亚基组合而成）。miR-31 调控整合素α5β1，介导膀胱癌化疗抵抗的机理有待研究。本课题拟揭示 miR-31 调控整合素，影响膀胱癌化疗敏感性、产生化疗抵抗的分子机制。本课题利用两种膀胱尿路上皮癌细胞系（T24、5637），成功构建了稳定过表达miR-31的T24膀胱癌细胞系，并建立了原位膀胱癌动物模型及活体检测体系。体外研究发现，miR-31在膀胱癌细胞中发挥负调控作用，可显著抑制增殖、迁移和侵袭等肿瘤细胞的经典生物学行为，提高膀胱癌对丝裂霉素C（MMC）化疗敏感性；luciferase基因报告实验和western blot实验证实integrin α5为miR-31的靶基因。本课题组在体实验结果发现miR-31在体外和体内均可提高膀胱癌对丝裂霉素C（MMC）化疗敏感性；其机制为：miR-31通过抑制其靶基因ITGA5蛋白表达，削弱了细胞内Akt和Erk信号通路的活化，提高膀胱癌的化疗敏感性。我们还利用膀胱癌标本，对miR-31表达进行检测，结果显示膀胱癌组织中miR-31表达降低，而浸润性癌组织表达水平更低，与miR-31抑癌作用相符。本课题深入研究阐明了 miR-31 靶向调控整合素 α5β1，影响膀胱癌对化疗的敏感性，出现化疗抵抗的分子机制。为减少膀胱癌化疗抵抗提供了科学依据。