Expression of PSMA in Tumor-Associated Vasculature Predicts Poorer Survival in Patients With Hepatocellular Carcinoma and Is Likely Associated With PD-L1

Abstract

Background PSMA (prostate-specific membrane antigen) is a type II transmembrane glycoprotein recently found to be expressed in hepatocellular carcinoma (HCC). We aimed to characterize the expression pattern of PSMA in HCC and its association with clinicopathologic parameters and other biomarkers. Methods Immunohistochemical studies for PSMA were performed on a previously established tissue microarray of 103 surgically resected HCC. Results Conceivable PSMA expression in ≥5% tumor-associated vasculature (TAV) was considered positive, and was identified in 56 (54.4%) tumors. Eight (7.8%) tumors also showed membranous/cytoplasmic and/or canalicular staining in tumor cells. By chi-square tests, only PSMA-positive TAV was associated with moderate-to-poorly differentiated HCC and the modified higher tumor stage ( P < .05). PSMA-positive TAV was not associated with age, sex, or expression of glypican-3, keratin 7, CD3, CD8, HHLA-2, but marginally correlated with programmed death-ligand 1 (PD-L1) expression ( P = .052). Kaplan-Meier survival analysis revealed PSMA-positive TAV as an independent risk factor for poorer disease-specific survival ( P = .008). Co-expression of PD-L1 did not ameliorate the adverse prognostication of PSMA-positive TAV. Membranous/cytoplasmic/canalicular expression of PSMA alone was not prognostically significant. Conclusions Our study confirmed that PSMA-positive TAV is a prospective diagnostic and prognostic biomarker for HCC. Co-expression of PSMA with PD-L1 may suggest potential crosstalk between the 2 proteins, likely regulating the tumor microenvironment.