New Toke on Treating Skin Cancer

The active components in marijuana inhibit the growth of nonmelanoma skin tumors in mice, with no inhalation necessary, suggesting that cannabinoids may be a potential therapy for one of the most common malignancies in humans.

The vast majority of nonmelanoma skin tumors arise in the basal or squamous cells, and these tumors account for ∼95% of all skin malignancies. Risk factors for nonmelanoma skin cancers include fair skin and excessive sun exposure.

Having already shown that cannabinoids inhibit the growth of malignant gliomas—a highly fatal form of brain cancer—Manuel Guzmán at Complutense University (Madrid, Spain) and a team of Spanish and American colleagues sought to determine if these compounds would have the same effect on skin tumors (J. Clin. Invest., January). Using western blot analysis and immunohistochemistry, Guzmán's group first determined that normal skin and skin tumors in both mice and humans express cannabinoid receptors (CB₁ and CB₂). They then inoculated nude mice with epidermal tumor cells to induce tumors. Local administration of a CB₁/CB₂ agonist was associated with an inhibition of tumor growth, an increase in the number of apoptotic cells, and impaired tumor vascularization.

Guzmán tells Lab Animal that the group's next step in this project is to “elucidate the molecular mechanism involved in cannabinoid anti-tumoral action” to determine whether these effects derive primarily from “direct apoptotic action on tumor cells or inhibition of tumor angiogenesis.”