Overexpression of cannabinoid receptors CB1 and CB2 correlates with improved prognosis of patients with hepatocellular carcinoma.

CB1 and CB2 are multifunctional cannabinoid-specific receptors considered to be involved in inhibition of tumor development. To elucidate their roles in hepatocarcinogenesis, we analyzed the expression of these receptors in tumor and matched nontumorous tissues of human hepatocellular carcinoma (HCC) samples. In situ hybridization analysis showed overexpression of CB1 mRNAs in 8 of 13 (62%) HCC samples, and of CB2 mRNAs in 7 of 13 (54%). Immunohistochemical analysis of 64 HCC samples showed the expression of CB1 and CB2 receptors to increase from normal liver to chronic hepatitis to cirrhosis. Marked expression of CB1 and CB2 receptors was noted in the majority of cirrhotic liver samples (86 and 78%, respectively). In HCC, high expression of CB1 and CB2 receptors was observed in 29 (45%) and 33 (52%) cases, respectively. Clinicopathological evaluation indicated a significant correlation between CB1 and CB2 expression and two clinicopathological parameters such as the histopathological differentiation (P = 0.021 and 0.001, respectively), portal vein invasion (P = 0.015 and 0.004, respectively). Univariate analysis indicated that disease-free survival was significantly better in HCC patients with high versus those with low CB1 and CB2 expression levels (P = 0.010 and 0.037, respectively). Our results indicate that CB1 and CB2 have potential as prognostic indicators and suggest possible beneficial effects of cannabinoids on prognosis of patients with HCC.