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.