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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. (J Histochem Cytochem 58:1129–1134, 2010)

The presence of CB1 and CB2 cannabinoid receptors and their physiological role in the kidney has been described in animal models but not in humans. Our aim in this study was to evaluate the presence of these receptors in human kidney, adult and fetal. For this purpose, RT-PCR, western-blot and immunohisto-chemical assays were performed. RT-PCR confirmed the presence of CB1 receptor mRNA receptor and the absence of the CB2 receptor mRNA in adult and fetal kidney. Western-blot and immunohistochemical assays revealed the presence of the CB1 cannabinoid receptor protein, which displayed a similar distribution in fetal and adult kidneys. Proximal and distal convoluted tubule cells and intercalated cells in the collecting ducts showed marked positivity. Conversely, the CB2 cannabinoid receptor protein was consistently negative in all cases. Our data suggest a possible implication of the endocannabinoid system in the physiology and development of the human kidney.