XRCC2-Deficient Cells are Highly Sensitive to 5-Fluorouracil in Colorectal Cancer.

BACKGROUND/AIMS: Inhibition of the repair of 5-fluorouracil (5-FU)-induced DNA lesions may improve the responses of tumors to anticancer agents. XRCC2 is a key factor in DNA repair. However, the role of XRCC2 in the chemoresistance of colorectal cancer (CRC) treated with 5-FU remains unclear. The aim of this study is to investigate whether XRCC2 expression affects the chemosensitivity of colorectal cancer.

METHODS: XRCC2 expression in CRC tissues was assessed, and the outcomes were analyzed to determine the clinical importance of XRCC2 expression. Following treatment with 5-FU, the effect of XRCC2 on proliferation was evaluated via a CCK-8 assay, the effects on cell cycle distribution and apoptosis were analyzed using flow cytometry, and γH2AX foci formation assays were performed to examine the influence of 5-FU on DNA Double-strand breaks(DSBs) repair in CRC cells.

RESULTS: XRCC2 expression in CRC tissues was significantly higher than that in normal tissues, and this increased XRCC2 expression was associated with advanced T staging, M staging, TNM staging, Duke's staging, and greater liver and lymph node metastases. XRCC2 expression might be an independent prognostic indicator for CRC patients. Patients with negative XRCC2 expression exhibit greater sensitivity to treatment with 5-FU-based chemotherapy than those with positive XRCC2 expression. Moreover, our observations revealed that the knockdown of XRCC2 in CRC cells increased the sensitivities to 5-FU in terms of cell proliferation, apoptosis and cell cycle arrest. DNA DSBs repair was slower in the XRCC2-deficient cells than in the XRCC2-wild type cells.

CONCLUSION: Our study demonstrated that XRCC2 might play an important role in CRC and function as a novel prognostic indicator and that the down-regulation of XRCC2 may be useful for sensitizing CRC cells during 5-FU chemotherapy.