[摘要] 目的:探讨miR-503 通过调控人切除修复交叉互补基因1（ERCC1）介导食管鳞状细胞癌（ESCC）放疗抵抗作用的分子机制。方法：采用qPCR法检测在放疗抵抗的ESCC肿瘤组织及KYSE140、KYSE140R细胞中miR-503 的表达水平。将miR-503模拟物、miR-503 抑制物或si-ERCC1 转染至KYSE140 和KYSE140R细胞中，经射线照射后，克隆形成实验和CCK-8 实验检测KYSE140R细胞的增殖活力，流式细胞仪检测KYSE140R细胞的凋亡情况，WB实验检测ERCC1 蛋白表达水平的变化。双荧光素酶报告基因验证miR-503 与ERCC1 的靶向关系。结果：miR-503 在ESCC放疗抵抗组织和细胞中均低表达（均P<0.01）。过表达miR-503 可显著抑制KYSE140R细胞增殖并诱导细胞凋亡（均P<0.01）。双荧光素酶报告基因实验证实ERCC1 是miR-503 的靶基因，且miR-503 负调控ERCC1 的表达。过表达miR-503 显著下调KYSE140、KYSE140R 细胞中ERCC1 表达水平（均P<0.01），并显著抑制细胞增殖活力（均P<0.01）、显著提高细胞凋亡率（均P<0.01）；敲降ERCC1 有类似作用，而同时敲降ERCC1 和miR-503 则逆转以上影响。结论：过表达miR-503 通过靶向ERCC1 调控KYSE140R细胞对放疗的敏感性。

[Abstract] Objective: To investigate the mechanism of miR-503 modulates radio-resistance of esophageal squamous cell carcinoma (ESCC) by targeting excision-repair cross-complementing 1 (ERCC1). Methods: The expression level of miR-503 in radio-resistant ESCC tumor tissues and KYSE140 and KYSE140R cells was detected by qPCR. The miR-503 mimic, miR-503 inhibitor or si-ERCC1 was transfected into KYSE140 and KYSE140R cells. After radiation treatment, the colony formation assay and CCK-8 assay were used to detect the proliferation of KYSE140R cells. Flow cytometry was used to detect apoptosis of KYSE140R cells. WB was used to detect changes in protein expression of ERCC1. Dual luciferase reporter gene assay was used to validate the targeting relationship between miR-503 and ERCC1. Results: The expression level of miR-503 was down-regulated in radio-resistant tissues and ESCC cell lines (all P<0.01). Over-expression of miR-503 significantly inhibited cell proliferation and promoted apoptosis of KYSE140R cells (all P<0.01). Dual-luciferase reporter assay validated that ERCC1 was a target gene of miR-503, and miR-503 negatively regulated the expression of ERCC1. Over-expression of miR-503 significantly down-regulated the expression of ERCC1 in KYSE140 and KYSE140R cells (both P<0.01), inhibited cell proliferation (both P<0.01), but significantly increased apoptosis rate (all P<0.01); knockdown of ERCC1 exhibited a similar effect, while knockdown of both ERCC1 and miR-503 reversed the above effects. Conclusion: Over-expression of miR-503 up-regulated the radio-sensitivity of KYSE140R cells by targeting ERCC1.