Characterization of soluble PD-L1 in pleural effusions of mesothelioma patients: potential implications in the immune response and prognosis

Programmed death-ligand 1 (PD-L1) protein plays a central role in the antitumor immune response, and appears to be a predictor of prognosis and efficacy for PD-L1 and programmed death 1 (PD-1) blockade therapy. The immunoregulatory role and prognostic impact of PD-L1 soluble form (sPD-L1) have been investigated in biological fluids of patients with different tumors. In malignant pleural mesothelioma (MPM), circulating sPD-L1 has been recently reported in patients' sera, but no data are available in pleural effusions (PE). In our study, we evaluated the baseline expression levels of sPD-L1 in PE from 84 MPM patients and correlated them with PD-L1-status in matched tumors and patients' overall survival (OS)