sPD-1/sPD-L1 proteins in non-small cell lung cancer and esophageal squamous cell carcinoma

Background. Implementation of immunotherapy in clinical oncological practice has significantly improved the results of cancer treatment. It resulted in the need for seeking new markers to assess the effectiveness of therapy and the disease prognosis. Aim. To analyze the content of soluble forms of PD-1 and PD-L1 immune checkpoint proteins in the blood serum of patients with non-small cell lung cancer and esophageal squamous cell carcinoma and their association with clinical and morphological characteristics of the disease and the disease prognosis. Materials and methods. The study included tumor samples obtained from 43 patients with non-small cell lung cancer and 21 patients with esophageal squamous cell carcinoma. The concentration of sPD-L1 and sPD-1 in the blood serum was determined using enzyme-linked immunosorbent assay (ELISA). The Mann - Whitney test was used to determine statistically significant differences in independent groups. A correlation analysis was performed using the Spearman's rank correlation coefficient. Overall survival was analyzed by constructing survival curves using the Kaplan - Meier method and a Cox proportional hazards model. The differences were considered statistically significant at p < 0.05. Results. The study showed that sPD-1 and sPD-L1 were found in the blood serum of both cancer patients and healthy donors, and their concentrations did not differ significantly. It was shown that the high concentration of sPD-L1 in the blood serum of patients with non-small cell lung cancer was significantly associated with the late stage of the disease and was an independent unfavorable prognostic factor. It should be noted that for patients with esophageal cancer, an unfavorable prognostic marker was the high concentration of the soluble form of PD-1 protein, and not PD-L1 ligand, as in case of lung cancer. Conclusion. The content of sPD-1 and sPD-L1 in the blood serum can have different prognostic significance for various types of cancer, and further studies are required to confirm their clinical usability.