DNA Repair Protein XPF Affects Cisplatin Resistance Of Renal Cancer Cells

According to the data from the Ministry of Health of the People’s Republic of China,the incidence of renal cancer is among the top ten of malignant tumors of the male, raisingyear by year. Among the tumors of the urogenital system, the incidence of renal cancerranks second only to bladder cancer. The early stage or intermediate stage renal cancer istreated the same as other cancers, mainly by surgical operation. However, since renal canceris resistant to traditional chemotherapeutic drugs such as cisplatin, the treatment foradvanced renal cancer is totally different from other cancers which are treated mainly bychemotherapy. Immunotherapy and targeted therapy are applied to renal cancer, whoseeffectiveness is far from satisfying.Different with renal cancer, testicular cancer is quite sensitive to chemotherapy basedon cisplatin. The cure rate of testicular cancer can exceed90%. It is proved that the highsensitivity to cisplatin is correlated with the low expression of DNA repair protein XPF.XPF is an important DNA repair factor, which mainly take part in the nucleotide excisionrepair (NER) pathway. Decreasing the level of XPF expression can impair the DNA repairability, leading to higher sensitivity to DNA damage agents. This phenomenon indicatesthat the resistance to chemotherapeutic drugs of renal cancer is related with its XPFexpression. If so, we can elevate its sensitivity to chemotherapy by decreasing its XPFexpression.Immunohistochemistry staining is used to detect the XPF expression in cancer tissuesand the adjacent normal tissues. Among cancer tissues, the positive expression rate of renalcancer tissues is the highest, then the bladder cancer tissues while the rate of testicularcancer tissues is the lowest. The same order goes for the adjacent normal tissues. WesternBlot is used to detect the XPF expression in cancer cell lines. Renal cancer cells expresshigher level of XPF than bladder cancer cells. Colony formation assay is used to detect thecisplatin sensitivity of cancer cells. The cisplatin sensitivity of renal cancer cells is lowerthan bladder cancer cells. Short hairpin RNA interfering technique is used to knock down XPF expression in ACHN cells. ACHN-shXPF cells are acquired which expresses low levelof XPF stably and shows higer sensitivity to cisplatin. Nude mouse subcutaneoustransplanted tumor model is used to detect the cisplatin sensitivity of ACHN-shXPF cells invivo. ACHN-shXPF cells show higher cisplatin sensitivity in vivo. Host cell reactivationassay, cell cycle arrest analysis and cell apoptosis analysis are used to detect DNA repairability, cisplatin induced cell cycle arrest and cisplatin induced cell apoptosis respectively.The DNA repair ability of ACHN-shXPF cells is lower. Cells induced by cisplatin arearrested in S phase abnormally. Cell apoptosis induced by cisplatin is higher. In addition,β-galactosidase staining assay was used to detect cell senescence. The proportion ofsenescent cells among ACHN-shXPF cells is higher.All in all, the more XPF cancer tissues and cancer cells express, the less sensitive tocisplatin they are, which means the XPF level is correlated with cisplatin sensitivitynegatively. Both in vitro and in vivo work proves that knocking down XPF sensitize renalcancer cells to cisplatin. By knocking down XPF, the DNA repair ability is decreased, thecell cycle arrest induced by cisplatin is disturbed, cell apoptosis induced by cisplatin isincreased, leading to the increase of cisplatin sensitivity. The increase of senescent cellsmay also contribute to the higher cisplatin sensitivity. Our wok indicates that the resistanceto cisplatin of renal cancer can be overcome by using small molecular to interfere the XPFexpression, making cisplatin applicable for renal cancer.