The Relationship Between Ovarian Cancer Gene Methylation, PD-L1 Protein Expression And Clinical Characteristics, And The Efficacy Of Chemotherapy Combined With PD-L1 MAb

Malignant tumor threats people's physical and mental health seriously.With the development of economy and the improvement of living standards,the incidence of cancer is rising,up to now,ovarian cancer(OC)is one of the most prevalent malignant tumors in women.The 5-year survival rate for early stage disease is over 70%with current therapies but less than 30%for those with late stage.The standard and first-line treatment strategy for OC is cytoreductive surgery in combination with platinum/taxane-based chemotherapy.The majority of patients who initially achieve remission following the end of treatment eventually relapse within 16-18 months and die from the disease.The death rate for OC still remains at a high level.Therefore,innovative and effective therapeutic practice need to be integrated into OC treatment strategies to achieve durable clinical prognosis.Studies demonstrated that BRCA1 mutation was common in the hereditary breast cancer or OC,it is unexpected that BRCA1 mutation can be rarely found in sporadic OC.Despite sporadic OC patients do not have germline alternation of genes,they often share similar histological characteristics and clinical outcomes with BRCA1-mutation carriers.Herein,it was postulated that BRCA1 inactivation might also have a role in sporadic OCs.Previoue studies also showed that RASSF1A was one of the most frequently hypermethylated genes in the formation and development of OC.Epigenetic alterations are now well recognized as another mean to silence tumor suppressor genes independent of mutation or deletion.Besides,DNA methyltransferase inhibitions(DNMTis)increased immune-related molecules in tumor site;DNMTis in combination with various immune-based therapies improved the prognosis of malignancies.In contrast to genetic mutations,epigenetic changes are potentially reversible,which makes them promising targets for combating OC.In this study,we aimed to assess the relationship between genes hypermethylation and PD-L1 protein expression and their links to clinicopathological features of OC.Monoclonal antibodies that block programmed death-ligand 1(PD-L1)signaling pathway hold great potential as a novel cancer immunotherapy for various malignancies including melanoma,renal cell cancer and non-small cell lung cancer.However,the antitumor effect of single PD-L1 pathway mAb seems to be unobvious in advanced or some poorly immunogenic tumor.In this study,we evaluated the therapeutic effect and underlying anti-tumor mechanisms of single and combined carboplatin/PD-L1 mAb treatments with ID8 OC in mice.The contents of this study are divided into two parts as followed:Part 1:Bisulfite pyrosequencing and immunohistochemistry were used to detect BRCA1?RASSF1A genes methylation and PD-L1 protein expression in tumor tissues from sporadic OC patients,respectively.The study aimed to investigate the correlation of genes methylation to clinicopathological features,prognosis and PD-L1 protein expression which indicated the roles of hypermethylation in early detection and individualized treatment for OC and also indicated the possibility of the combined treatment of DNMTis with PD-L1 blockades for OC.Our study showed that the frequency of BRCA1 hypermethylation was significantly higher in serous OC(P<0.05).RASSF1A hypermethylation was significantly related with early FIGO stage(P<0.05)which implied the predictive role for early detection in OC.RASSF1A hypermethylation was also related with nonserous subtype,nonrecurrent OC(P<0.05).No significant relation was observed between PD-L1 expression and clinicopathological characteristics,prognosis of OC.The expression of PD-L1 also had no relationship with the BRCA1 and RASSF1A hypermethylation.We firstly reported the relationship between BRCA1?RASSF1A methylations and the PD-L1 expression in OC.Future researches based on this study are expected to elevate the integrative level of personalized treatment and to promote the development of precision medicine for OC.Part 2:C57BL/6 mice(6-8 weeks)with established peritoneal ID8 ovarian cancer were intraperitoneally injected with PBS,single or combined carboplatin and PD-L1 monoclonal antibody.The formation time of ascites and their overall survival were recorded;the compositions of tumor-associated immune cells:CD4+?CD8+?Treg?myeloid suppressor cells(MDSC)were analyzed by flow cytometry.Study revealed that the single treatment of carboplatin and combined carboplatin/PD-L1 mAb induced a strong anti-ascites response which presented the longer overall survival than the control and single carboplatin treatment(P<0.05).Mechanistic investigation on tumor microenvironment revealed that the carboplatin and carboplatin/PD-L1 mAb increased anti-tumor effector CD4+,CD8+ T cells while decreased Treg and MDSC(P<0.05),giving rise to remarkably higher ratios of both effector CD4+,CD8+ T cells to Treg and MDSC in peritoneal cavity.This study may aid reference to future preclinical experiments or clinical trials.