Although there are some exceptions [e.g., engagement of CB1 and CB2 were found to promote tumor progression in human melanoma cells (CB1), in renal cell carcinoma (CB1), as well as in colon cancer (CB2) (135–137)], most studies agree that their putative beneficial antitumor effects deserves further scrutiny (138, 139). This evidence concerns the gene CNR2 and renal cell carcinoma.