ERCC1 Overexpression Increases Radioresistance in Colorectal Cancer Cells.

Preoperative concurrent chemoradiotherapy (CCRT) is a standard treatment for locally advanced rectal cancer patients, but 20-30% do not benefit from the desired therapeutic effects. Previous reports indicate that high levels of ERCC1 reduce the effectiveness of cisplatin-based CCRT; however, it remains unclear as to whether ERCC1 overexpression increases radiation resistance. To clarify the correlation between ERCC1 levels and radiation (RT) resistance, we established two cell lines (HCT116-Tet-on and COLO205-Tet-on), induced them to overexpress ERCC1, detected cell survival following exposure to radiation, established HCT116-Tet-on and COLO205-Tet-on heterotopic cancer animal models, and detected tumor volume following exposure to radiation. We found that ERCC1 overexpression increased radiation resistance. After regulating ERCC1 levels and radiation exposure to verify the correlation, we noted that increased radiation resistance was dependent on ERCC1 upregulation in both cell lines. For further verification, we exposed HCT116-Tet-on and COLO205-Tet-on heterotopic cancer animal models to radiation and observed that ERCC1 overexpression increased colorectal cancer tumor radioresistance in both. Combined, our results suggest that ERCC1 overexpression may serve as a suitable CCRT prognostic marker for colorectal cancer patients.