"The aim of this study was to identify natural cannabinoids with anti-tumor activities at least similar to those of THC, and devoid of the potential central effects of this compound. Given that the efficacy of cannabinoids as antitumoral agents appears to be strictly correlated to the cell type under investigation, we screened a panel of plant-cannabinoids in a wide range of tumoral cell lines distinct in origin and typology. We found that, surprisingly, cannabidiol acted as a more potent inhibitor of cancer cell growth than THC, and that cannabigerol and cannabichromene usually followed cannabidiol in the rank of potency. ... These results suggest the use in cancer therapy for cannabidiol, a compound lacking the psychotropic effects typical of THC."

"In conclusion, our data indicate that cannabidiol, and possibly Cannabis extracts enriched in this natural cannabinoid, represent a promising non-psychoactive antineoplastic strategy. In particular, for a highly malignant human breast carcinoma cell line we have shown here that cannabidiol and a cannabidiol-rich extract counteract cell growth both in vivo and in vitro as well as tumor metastasis in vivo."

Published May 25, 2006 in the Journal of Pharmacology and Experimental Therapeutics. Full text available for free download here: http://jpet.aspetjournals.org/cgi/reprint/jpet.106.105247v1