Abstract
AIM: Ovarian cancer (OC) is one of the most lethal gynecological malignancies. Recent studies suggest a crucial role of the PD-1/PD-L1 pathway in OC pathogenesis. Therefore, our study aimed at evaluation of the clinical importance of PD-1 expression in ovarian cancer patients. PATIENTS AND METHODS: In this study, we investigated the role of PD-1 in OC patients (n=50) by analyzing its expression on CD4(+) and CD8(+) T cells in three OC environments: peripheral blood (PB), peritoneal fluid (PF), and tumor (TT) as well as soluble PD-1 (sPD-1) in plasma and PF in terms of their clinical and prognostic significance. T cells with PD-1 expression were analyzed using flow cytometry. The concentration of sPD-1 was determined with the use of ELISA. Our research demonstrated differences in PD-1 expression on CD4(+) and CD8(+) T cells in the OC environments. RESULTS: We found an elevated level of CD4(+)PD-1(+) T cells in tumor and PF, compared to PB. Additionally, we found the highest percentage of CD8(+) PD-1(+) in tumor, compared to PB and PF. The levels of sPD-1 were higher (p<0.0001) in plasma than in PF. For the first time, we discovered that the higher level of CD4(+)PD-1(+) T cells in the circulation and the higher sPD-1 level in plasma predict poor survival of OC patients. CONCLUSION: We suggest that PD-1 could be a predictive biomarker for OC patients and successful immunotherapy.