Effect Of X-Ray On Relative Expression Levels Of DNA Repair Gene XRCC1, XRCC2 And XRCC3 In Lung Cancer Cells

Objective To study the impact of X-ray on relative expression levels of X-ray repair cross-complementing genel(XRCC1),XRCC2 and XRCC3 in lung cancer cells,and explore the effect of DNA base-excision repair mechanism and homologous recombination repair mechanism in the radiation resistance of lung cancer cells.Methods Inhibition rate of lung cancer cell A549 with treatment of the different doses of X-ray was measured by MTT assay.Relative expression levels of XRCC1,XRCC2 and XRCC3 mRNA in lung cancer cell A549 after exposed to different doses of X-ray were measured by real time fluorescent quantitative reverse-transcription polymerase chain reaction(real time RT-PCR) in different time.Results A lot of the time,the rate of proliferation inhibiting of lung cancer cells is increased in line with the prolong radiation time of X-ray(P＜0.05) and the increase radiation dose(P＜0.05),except for comparion between the group of 16Gy and the group of 32Gy(P=0.211).The relative expression levels of XRCC1,XRCC2 and XRCC3 mRNA in the lung cancer cells are increased significantly after treatment with X-ray,and then decreased.The relative expression levels of XRCC1 mRNA of 4Gy group and 8Gy group are the highest at 72h(P＜0.05) after treatment with X-ray,however,the 16Gy group and 32Gy group are the highest at 48h(P＜0.05).The relative expression levels of XRCC2 and XRCC3 mRNA are the highest at 48h after treated with X-ray(P＜0.05),and they are increased markedly with the increase of radiation dose (P＜0.05).Conclusions X-ray has a fairly obvious function to decreases proliferation of lung cancer cell,and it could induce the increase of the relative expression levels of XRCC1,XRCC2 and XRCC3 mRNA in lung cancer cells.The results indicated that DNA base-excision repair mechanism and homologous recombination repair mechanism may play an important role for resistance to radiotherapy in lung cancer cell.