Cannabinoids reduce ErbB2-driven breast cancer progression through Akt inhibition.

BACKGROUND ErbB2-positive breast cancer is characterized by highly aggressive phenotypes and reduced responsiveness to standard therapies. Although specific ErbB2-targeted therapies have been designed, only a small percentage of patients respond to these treatments and most of them eventually relapse. The existence of this population of particularly aggressive and non-responding or relapsing patients urges the search for novel therapies. The purpose of this study was to determine whether cannabinoids might constitute a new therapeutic tool for the treatment of ErbB2-positive breast tumors. We analyzed their antitumor potential in a well established and clinically relevant model of ErbB2-driven metastatic breast cancer: the MMTV-neu mouse. We also analyzed the expression of cannabinoid targets in a series of 87 human breast tumors. RESULTS Our results show that both Delta9-tetrahydrocannabinol, the most abundant and potent cannabinoid in marijuana, and JWH-133, a non-psychotropic CB2 receptor-selective agonist, reduce tumor growth, tumor number, and the amount/severity of lung metastases in MMTV-neu mice. Histological analyses of the tumors revealed that cannabinoids inhibit cancer cell proliferation, induce cancer cell apoptosis, and impair tumor angiogenesis. Cannabinoid antitumoral action relies, at least partially, on the inhibition of the pro-tumorigenic Akt pathway. We also found that 91% of ErbB2-positive tumors express the non-psychotropic cannabinoid receptor CB2. CONCLUSIONS Taken together, these results provide a strong preclinical evidence for the use of cannabinoid-based therapies for the management of ErbB2-positive breast cancer.

Journal Article; Research Support, Non-U.S. Gov't;

This study was supported by grants from Fondo de Investigaciones Sanitarias (PI080253 to CS and PI086080971 to JP), Ministerio de Ciencia e Innovación (SAF2006-00918 to MG, SAF2007-63075 to GMB and SAF2008-00649 to SM), RETICS (RD06/0020/0013 to JP), Fundación Mutua Madrileña (to CS and to GMB), Consejería de Innovación Junta de Andalucía (to JP), the Marató TV3 Foundation (053132 to SM) and GW Pharmaceuticals/Otsuka Pharmaceuticals (to CS).