Antitumor effects of a variety of non-viable bacteria against the murine EL-4 lymphoma

Summary Suppression of growth of the EL-4 murine lymphoma was achieved in syngeneic animals by the simultaneous injection of EL-4 cells and a variety of non-viable bacteria. Heat-killed Staphylococcus aureus, Mycobacterium bovis, Propionibacterium acnes, Streptococcus mutans, and Escherichia coli injected together with viable EL-4 cells resulted in significant tumor suppression. The antitumor effects observed were dependent upon the numbers of bacteria injected. Heat-killed Listeria monocytogenes caused no significant tumor suppression. Injections of S. aureus, M. bovis, P. acnes, and S. mutans into sites previously injected with EL-4 cells also produced significant antitumor effects, while L. monocytogenes and E. coli did not.