Brief communication: Tumor suppression by Mycobacterium bovis (Strain BCG) enhanced by vitamin A

Tumor suppression mediated by Mycobacterium bovis (strain BCG) was enhanced in vitamin A-treated mice. A significant decrease in tumor incidence was observed with a transplantable, syngeneic, 3-methylcholanthrene-induced sarcoma when tumor cells were mixed with 6×10⁴ colony-forming units of BCG and injected intradermally into vitamin A-treated animals. This level of tumor suppression required 100-fold higher concentrations of BCG in untreated animals. Vitamin A treatment without BCG had no effect on tumor incidence or growth.