microRNA-375与食管鳞癌顺铂化疗敏感性的关系及机制研究

Esophageal cancer is the eighth most common cancer and the sixth leading cause of cancer related deaths worldwide. The incidence of esophageal squamous cell carcinoma (ESCC) is more frequent in China. Nonetheless, the 5-year survival rate remains relatively modest at less than 40%. To improve the survival rate of patients with ESCC, multimodal treatment, including chemotherapy plus surgery has been developed. In fact, some clinical trials have shown that neoadjuvent chemotherapy prolonged survival of esophageal cancer patients . The most commonly used chemotherapeutic regimen in esophageal cancers is cisplatin-based chemotherapy. However, the reported response rate to chemotherapy including cisplatin is only 19% to 40%, and about half of these patients do not achieve a good response to chemotherapy. Thus, chemoresistance is a major obstacle in the treatment of esophageal cancers. A better understanding of the mechanism of chemoresistance in esophageal cancer is needed to improve prognosis. In our previous study, miR-375 expression was found to be correlated significantly with response to chemotherapy in ESCC. In this study, we will repeat our previous result in another group of ESCC tissues to identify miR-375 as a biomarker for response to chemotherapy in ESCC. We will also show significantly decreased miR-375 expression in cisplatin-resistant cells compared with their parent cells. We will certify miR-375 expression confer chemosensitivity to cisplatin and apoptosis after exposure to cisplatin in ESCC cell lines. The machanism that decreased expression of miR-375 induce cisplatin resistance in ESCC cells will also be explored in this study. At last, we will explore that if upregulation of miR-375 could increased chemosensitivity of chemoresistant ESCC in vitro and in vivo.

我国是世界上食管癌发病率和死亡率最高的国家，病理类型以食管鳞癌为主。食管鳞癌总生存率几十年来一直无显著提高。新辅助化疗在食管鳞癌治疗中的作用日益被重视，但是化疗抵抗严重制约了其在食管癌综合治疗中的作用。寻找与食管癌化疗敏感性相关的分子标志物，开发新的治疗靶点迫在眉睫。我们前期研究发现miR-375的表达水平与食管鳞癌对顺铂化疗的敏感性显著相关。在本研究中，我们将进一步验证miR-375表达与食管鳞癌对顺铂化疗敏感性的关系；并在食管鳞癌细胞系中进一步证实miR-375高表达增加食管鳞癌对顺铂化疗的敏感性，miR-375低表达导致食管鳞癌对顺铂化疗抵抗；同时通过对其下游靶基因的研究，探讨其可能的分子机制；最后，通过体内体外实验，探索miR-375高表达对食管鳞癌顺铂化疗的增敏作用，为解决食管鳞癌的化疗抵抗提供新的潜在途径。

我国是世界上食管癌发病率和死亡率最高的国家，病理类型以食管鳞癌为主。食管鳞癌总生存率几十年来一直无显著提高。新辅助化疗在食管鳞癌治疗中的作用日益被重视，但是化疗抵抗严重制约了其在食管癌综合治疗中的作用。寻找与食管癌化疗敏感性相关的分子标志物，开发新的治疗靶点迫在眉睫。在本研究中，我们通过qRT-PCR检测食管癌化疗前及部分化疗后组织中miR-375的表达水平；在食管癌细胞系中通过western blot及报告基因探讨miR-375在食管癌中可能的靶基因及参与食管癌对顺铂敏感性的可能机制。我们的结果显示：食管鳞癌对顺铂化疗敏感组miR-375表达水平较食管鳞癌对顺铂化疗抵抗组明显增加(p＜0.001)；在对化疗部分敏感（PR组）中，化疗前肿瘤组织miR-375水平明显高于化疗后残留癌组织(p＜0.001)。在食管鳞癌细胞系中，上调miR-375表达水平，可引起细胞增殖抑制及细胞凋亡增加。过表达miR-375，可以引起PDK1, AEG1, IGF1R及JAK2蛋白水平下降，YAP1蛋白水平无明显变化。报告基因显示，在ESCC细胞中，miR-375是直接结合到靶基因mRNA的3＇-UTR而调控其蛋白水平改变。上调miR-375后，Akt总蛋白水平无变化，而pAkt蛋白水平下降，即其磷酸化水平降低，PI3K/Akt通路活性降低，显示miR-375可能通过靶基因影响PI3K/Akt通路活性参与食管癌细胞对化疗敏感性的调节。综上，我们的研究结果提示，miR-375可以作为判断食管鳞癌对顺铂化疗敏感性的潜在分子标志物，同时作为食管癌治疗的潜在靶点。