Prostate-specific membrane antigen expression in hepatocellular carcinoma, cholangiocarcinoma, and liver cirrhosis

Primary liver cancer includes three subtypes: Hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (CCA), and combined hepatocellular carcinoma. Patients with primary liver cancer experienced poor prognosis and high mortality, so early detection of liver cancer and improved management of metastases are both key strategies to reduce the death toll from liver cancer. Prostate-specific membrane antigen (PSMA) expression in the tumor-associated neovasculature of nonprostate malignancies including liver cancer has been reported recently, but conclusive evidence of PSMA expression based on the pathological type of liver cancer remains limited.

To study the expression of PSMA in HCC, CCA, and liver cirrhosis.

A total of 446 formalin-fixed paraffin-embedded (FFPE) liver tumor and liver cirrhosis tissue samples were obtained retrospectively from the Pathology Department of Tongji Hospital. Immunohistochemistry was used to detect PSMA expression in these 446 FFPE liver biopsy specimens (213 HCC, 203 CCA, and 30 liver cirrhosis). The tumor compartment and the associated neovascular endothelium were separately analyzed. PSMA expression was examined by two certified pathologists, and the final results were presented in a 4-point scoring system (0-3 points). Correlation between PSMA expression and clinicopathological information was also assessed.

PSMA was expressed primarily in the neovascular endothelium associated with tumors. The positive rate of PSMA staining in HCC was significantly higher than that in CCA (86.8% vs 79.3%; P = 0.001) but was only 6.6% in liver cirrhosis (P = 0.000). HCC cases had more 3-score PSMA staining than CCA had (89/213, 41.8% vs 35/203, 17.2%; P = 0.001). PSMA expression correlated positively with the stage and grade of HCC and CCA. In both liver cancer subtypes, there were more PSMA⁺ cases in stages III-V diseases than in stages I and II. High staining intensity of PSMA was more frequently observed in liver cancers at high grade and advanced stage. There was no significant association of PSMA expression with sex, age, region, α-fetoprotein, hepatitis B surface antigen, or tumor size in both tumor subtypes.

Neovascular PSMA may be a promising marker to differentiate HCC from liver cirrhosis and a prognostic marker for anti-tumor angiogenesis therapy for HCC.