| Objective:Renal cell carcinoma is one of the most common malignant tumors in the urinary system.However,kidney cancer is resisted to radiotherapy and chemotherapy,and there are individual differences in the effects of targeted drug therapy.For renal cancer with venous tumor thrombus and distant metastatic renal cell carcinoma the treatment is limited and further research is still required.The aim of this study was to explore the genetic mutation characteristics of renal cell caecinoma by whole-genome second-generation sequencing and explore new therapeutic targets.2.On the basis of sequencing results demonstrating the existence of BRCAness in renal cancer,we investigate the effect of PARP inhibitors on renal cancer.3.To investigate the underlying mechanism of the renal cancer cells' resistance to PARP inhibitors.Methods:1.Whole-genome sequencing and mutation signature analysis have been conducted in 5 cases of renal cell carcinoma with venous tumor thrombus.2.The whole-genome sequencing information was acquired and mutation signature has been analyzed of 537 cases of renal clear cell carcinoma in TCGA database.2.MTT proliferation assay was used to test the sensitivity of kidney cancer cell lines(786-O,RCC4,Caki-1,Caki-2,A498,ACHN)to the PARP inhibitors-Talazoparib and Olaparib,and the combined therapy of PARP inhibitors with hemotherapeutic drug carboplatin,HDAC inhibitor SAHA(vorinostat),and ATM inhibitor KU55933,respectively.3.The Capan-1 cell line of pancreatic cancer with BRCA2 mutation was set as the control group.The expression of 53BP1-RIF1 axis proteins were detected by western-blot.4.Immunofluorescence was used to detect the DNA damage and the expression of 53BP1-RIF1 axis proteins in renal cancer cells treated with PARP inhibitor combined with carboplatin.5.Overexpression plasmid of 53BP1 was transfected to the renal cancer cell line.Sensitivity of kidney cancer cell to the PARP inhibitor was tested after transfection.6.Immunohistochemistry was used to investigate the expression of 53BP1 in renal cancer patients in tissue microarrays of 500 patients.The relationship between 53BP1 expression and clinic-pathological parameters as well as prognostic parameters was analyzed.Results:1.Five cases of renal cell carcinoma with venous tumor thrombus were sequenced by next generation whole genome sequencing.The analyze of mutational signature revealed the of high AC3 value and BRCAness in both the primary tumors and the tumor thrombus.The analyzing of the TCGA database of 537 cases of kidney cancer also give a clue of widespread AC3 mutational signature and BRCAness in renal cancer.2.Renal cancer cell lines are not sensitive to PARP inhibitors.The combination treatment of chemotherapy drug carboplatin or ATM inhibitor or SAHA cannot resensitize renal cancer cells to PARP inhibitors.3.The 53BP1-RIF1 axis is disrupted in the renal cancer cell line,and 53BP1 is loss or low expressed in the renal cancer cell lines.4.PARP inhibitors combined with carboplatin can induce DNA damage in renal cancer cell lines but cannot induce cell death.5.Overexpression of 53BP1 can resensitize renal cancer cells to PARP inhibitors and carboplatin combined treatment.6.53BP1 is absent in 7%of patients with renal cell carcinoma and is low in 14%of patients with renal cell carcinoma.There is no significant difference in the prognosis between the groups with different 53BP1-expression-level.Conclusion:The AC3 mutation signature and BRCAness is notable in renal cancer.Despite the BRCAness,renal cancer cell lines are resistant to PARP inhibitors,which are mediated by deletion or low expression of 53BP1.Over expression of 53BP1 resensitize renal cancer cells to PARP inhibitors.Although the expression of 53BP1 has no statistically significant difference in the prognosis of patients with renal cell carcinoma.it may be a marker for the application of PARP inhibitors in renal cell carcinoma.For the presence of BRCAness and the simultaneous expression of 53BP1 cases,the potential of PARP inhibitors' application is worth exploring. |
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