Weak carcinogenic effect of masheri, a pyrolysed tobacco product, in mouse skin tumor models.

Two commonly used varieties of masheri, pyrolysed tobacco products, were tested for their skin carcinogenicity in Swiss mice and the more sensitive strain of Swiss bare mice. In Swiss mice, painting of brown and black varieties of masheri extract did not show any tumorgenic effect; however, a marginal synergistic effect of 7,12-dimethylbenz[a]anthracene (DMBA) and black masheri extract was observed when DMBA was used as an initiator. In Swiss bare mice, black masheri extract induced tumors in 20%-35% animals at both the doses tested. In an initiation/promotion protocol with DMBA as an initiator, induction of tumors in 50%-52% Swiss bare mice and a slight synergistic effect of black masheri extract were observed with a low dose of DMBA, suggesting a synergistic effect.