Effect of cigarette smoke inhalation on benzo[a]pyrene-induced lung carcinogenesis in vitamin A deficiency in the rat.

Vitamin A deficiency caused a significant increase (P less than 0.05) in benzo[a]pyrene (BP)-induced lung tumor incidence and tumor burden in male Wistar rats. Inhalation of cigarette smoke during initiation and post-initiation phases of carcinogenesis resulted in higher tumor burden as compared to the same observed in the animals exposed to cigarette smoke during the post-initiation phase only. Stimulation in tumor burden by cigarette smoke was increased further by vitamin A deficiency.