Effect of XRCC2 gene expression in colorectal cancer cells on damage response induced by ionizing radiation

WANG Qin; WANG Jing-min; XU Chang; WANG Yan; DU Li-qing; FAN Fei-yue; LIU Qiang

Abstract：Objective To establish a colorectal cancer cell line with silenced XRCC2 gene expression and de-scribe the damage response of these cells induced by ionizing radiation.Methods XRCC2 protein expression in various human tumor cell lines including colorectal cancer cell lines ( T84, HT29, Lovo), esophageal carcinoma cell line (EC9706) and breast cancer cell line (MCF-7) and human embryo kidney cell line (HEK293)was determined by west-ern blotting.XRCC2 protein and mRNA expression in T84 cells irradiated with 0 Gy, 2 Gy, 4 Gy, 8 Gy, 12 Gy X-ray and at 0 h, 6 h, 24 h, 48 h after exposure to 8 Gy radiation was determined by western blot and real-time quantitative PCR analyses.T84 cells were transfected with the vector-based shRNA plasmid (shRNA-XRCC2) and selected with puromycin.The efficiency of XRCC2 gene silencing was determined by western blotting and real-time PCR.DNA dam-age repair of T84 cells transfected with shRNA-XRCC2 plasmid after exposure to X-ray radiation was determined by single cell gel electrophoresis.Results XRCC2 protein expression in various tumor cell lines was at different high levels compared with normal HEK293 cells and XRCC2 protein expression in colorectal cancer T84 cells was the highest.XRCC2 protein expression in T84 cells increased with increasing dosage of X-ray exposure and with increasing duration within 48 h after exposure to 8 Gy radiation.XRCC2 mRNA expression of T84 cells also increased with increasing radiation dose and time after radiation.XRCC2 protein and mRNA expression in T84 cells transfected with shRNA-XRCC2 showed signifi-cant decline, down by 70%and 60%, respectively, compared with control cells.The value of TDNA%, TM and OTM in T84 cells irradiated with 8 Gy of the shRNA-XRCC2 group were significantly higher than that of the control group and shRNA-SC group (t=15.12,11.36 and 13.15, P<0.01).Conclusion Colorectal cancer T84 cell line with silenced XRCC2 expression was established successfully.The capability of DNA damage repair induced by ionizing radiation was decreased in T84 cells with silenced XRCC2 gene.