“Several studies in cell cultures and in animal models have demonstrated that cannabinoids have important antitumoral properties… many of these effects are mediated through cannabinoid (CB) receptors CB1 and CB2…

The obtained data suggest a possible implication of the endocannabinoid system in renal carcinogenesis.”

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2989249/