Mechanisms Of PARP Inhibitor Resistance And Survival Analysis Of Lymph Node Resection In Ovarian Cancer

PART ?:Mechanisms of PARP Inhibitor Resistance in Ovarian Cancer CellObject:Poly-(ADP)-ribose polymerase inhibition(PARPi)has shown great promise in the clinic,but rates of pre-existing and acquired resistance are high.The development of predictive biomarkers and the ability to identify mechanisms of PARPi resistance are vital for optimization of its clinical utility.The purpose of this study is to explore the mechanisms of both primary and secondary resistance to PARPi by multi-omics analysis.Material and methods:We firstly identified PARPi resistance profile of 41 ovarian cancer cell lines by public databases and performed multi-omics analysis as corroborative evidence for the following research.Secondly,we cultured six types of human ovarian cancer cell lines and constructed three of Olaparib resistance cell lines.Then genomic DNA of resistant cell lines and parental cell lines was extracted for whole-exome sequencing(WES).Additionally,the nine cell lines were treated with 10uM Olaparib for 24 hours and 72 hours respectively.And RNAs of the nine cell lines treated with Olaparib were extracted for transcriptome sequencing for analysis drug response between cells of different sensitivity.Result:Forty-one kinds of ovarian epithelial cell lines from public databases were included and performed bioinformatics analysis.Cells sensitive to PARPi have a higher mutation load,a higher proportion of microsatellite variables,a higher mutation frequency of DNA damage repair genes;and the DNA damage repair pathways were more activated.Conversely,the DNA damage repair pathways of cells resistant to PARPi were under-expressed,while the pathways related to drug metabolism and transport,detoxification,and exogenous stimuli were highly expressed.At the transcriptome and proteome levels,the expression of BRCA1 or BRCA2 was weakly correlated with the sensitivity of the cell lines to PARPi;while the expression of PARP1 and HPF1 is significantly positively correlated with the sensitivity of the cell line to PARPi.Olaparib acquired resistant cell lines were significantly up-regulated in DNA damage repair,cell cycle arrest,histone modification,and other pathways,while the extracellular matrix was down-regulated and showed different characteristics from the parent cell lines.Analysis of whole-exome sequencing(WES)revealed that high mutations were found in acquired resistant cells.The functional mutations mainly affected DNA damage repair,tumor sternness,cell adhesion and migration,and histone modified expression.Additionally,a functional mutation of homozygous PARP1 was found in the resistant cell line of A2780.Conclusion:Ovarian epithelial cancer cells have different mechanisms for primary resistance and acquired resistance to PARPi.Long-term PARPi induction mediated the accumulation of a large number of new mutations in the cell genome.At the transcriptome level,pathways related to DNA damage repair,cell cycle,and histone modification of acquired resistant cells are up-regulated,extracellular matrix is down-regulated,and cells are de-epithelialized.Changes in the transcriptome of acquired drug-resistant cell was correlated with changes induced by drugs in parental cell.PART ?:Survival Analysis of Lymph Node Resection in Ovarian CancerObjective:This study aimed at comprehensively investigating the survival impact of lymphadenectomy during primary surgery in ovarian cancer.Methods:Based on the surveillance,epidemiology,and end results registry(SEER)database,we included ovarian cancer patients with detailed information between 2010 to 2016.Cox regression was performed to select prognostic factors.We conducted propensity score-weighted survival analysis to balance baseline variables,and series of stratified analyses to control main confounding factors.Results:A total of 8,652 patients was ultimately identified.Among 3,266(75%)patients with the apparent early-stage disease received lymphadenectomy,7.75%of whom were reported isolated lymph nodes metastasis,and have a poorer survival(p<0.05).Among 4,360 patients with advanced disease,lymphadenectomy did not show a significant survival benefit in general(median overall survival 44 months in non-lymphadenectomy versus 49 months in lymphadenectomy group,p=0.055).In subgroup analysis on patients received optimal debulking,lymphadenectomy did not significantly benefit the survival outcome(median overall survival 51,47,60,and 58 months in the non-lymphadenectomy,1-9 lymph nodes,1-19 lymph nodes,?20 lymph nodes groups respectively,p=0.287).Consistent results were observed in further stratification analyses.In optimal debulking subgroup,lymph node metastasis indicated worse survival.However,when limited the number of removed lymph nodes to more than 15,there was a marginal statistical difference in overall survival(p=0.0498)while no significant difference presented in cause-specific survival(p=0.129)between non-lymphadenectomy,pathological negative lymph node group and positive lymph node group.And the regions of lymph metastasis were also not significantly associated with survival(p=0.123).Conclusions:In primary debulking for patients with advanced ovarian cancer,lymphadenectomy was not associated with more favorable outcomes when compared to no lymphadenectomy.The value of lymphadenectomy lies more in staging for apparent earlv disease rather than a therapeutic benefit.