Cannabinoid CB1 receptor is expressed in chromophobe renal cell carcinoma and renal oncocytoma.

OBJECTIVE: To analyze the mRNA and protein expression of cannabinoid receptors CB1 and CB2 in chromophobe renal cell carcinoma (ChRCC) and renal oncocytoma (RO). DESIGN AND METHODS: Fresh and formalin-fixed tissue samples of ChRCC and RO were analyzed by using real-time quantitative RT-PCR and immunohistochemical techniques (n=40). RESULTS: Quantitative RT-PCR analysis showed that CB1 mRNA was underexpressed by 12-fold in ChRCC and had a variable expression in RO. CB1 protein showed intense positive immunostaining in both neoplasms. Both CB2 mRNA and protein were not expressed in tumor and non tumor renal tissue. CONCLUSION: This distinct immunoprofile may eventually be used as an additional tool with practical interest in the differential diagnosis of renal tumors.

Cannabinoid CB1 receptor is downregulated in clear cell renal cell carcinoma.

Several studies in cell cultures and in animal models have demonstrated that cannabinoids have important antitumoral properties. Because many of these effects are mediated through cannabinoid (CB) receptors CB1 and CB2, the study of their expression in human neoplasms has become of great interest in recent years. Fresh and formalin-fixed tissue samples of 20 consecutive clear cell renal cell carcinomas (CCRCCs) were collected prospectively and analyzed for the expression of both CB receptors by using RT-PCR, Western blot (WB), and immunohistochemical techniques. RT-PCR assays demonstrated the expression of mRNA encoding the CB1 in tumor tissue and in adjacent non-neoplastic kidney. Conversely, WB and IHC revealed a marked downregulation of CB1 protein in tumor tissue; CB2 was not expressed. The obtained data suggest a possible implication of the endocannabinoid system in renal carcinogenesis. A posttranscriptional downregulation of CB1 and the absence of expression of CB2 characterize CCRCC.