Expression of programmed cell death protein 1 (PD-1) and its ligand PD-L1 in High-Grade serous ovarian cancer

Recently, the immunotherapeutic treatment of ovarian cancer is of much concern. This is due to the discovery of the signaling pathway of the PD-1/PD-L1 immune checkpoints, which are capable of controlling autoimmune response severity and duration. The aim of the study is to determine the dependence of PD-1/PD-L1 expression on the proliferative activity of high-grade serous ovarian cancer cells. Materials and Methods. The study was performed at Central Research Laboratory, Pacific State Medical University, Ministry of Health of the Russian Federation. The material was collected at Primorsky Regional Oncological Dispensary, 2016-2021. The pathological and anatomical samples were analyzed by immuno-histochemistry using p53, Ki-67, PD-L1, and Anti-Hu CD279 (PD-1). The main group included 74 patients with high-grade serous ovarian cancer, the comparative group consisted of 26 patients with benign ovarian tumors. Results. PD-1/PD-L1 expression was observed in tumor tissues in ovarian cancer. There was also an increase in the positive reaction to Ki-67 and p53 according to grading and staging of cancer. Conclusion. Despite the claimed immunomodulatory function, high PD-1/PD-L1 levels are favorable prognostic indicators in ovarian cancer. The obtained data show that PD-1/PD-L1 molecules are biologically significant regulators of the immune response in high-grade serous ovarian cancer, which is an argument in favor of immune checkpoint inhibitors. Thus, PD-L1 in the immune cells infiltrating the tumor is a favorable prognostic factor. A statistically significant direct correlation between Ki-67 and PD-L1 proves a direct dependence of PD-L1 expression on proliferative activity of the ovarian tumor. A statistically significant inverse correlation between p53 and PD-1 shows the dependence of PD-1 expression on apoptotic changes in the ovarian tumor.