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Effect of Corynebacterium liquefaciens on a C3Hf Mouse Squamous Cell Carcinoma

Division of Clinical Research, National Institute of Radiological Sciences, 9-1, 4-Chome, Anagawa, Chiba-shi, 280 Japan

The antitumor effect of anaerobic Corynebacterium liquefaciens was compared with that of specific immunization. Experimental tumors were fourth or fifth generation isotransplants of a NR-SI squamous cell carcinoma that arose spontaneously in a C3Hf/He female mouse. Specific immunization failed to exhibit an antitumor effect, whereas a single administration of the bacterium markedly inhibited the growth of the tumor. This growth inhibition was most effective when C. liquefaciens was administered 2 to 4 days before transplantation of tumor cells, but marked inhibition was also observed when this agent was administered after transplantation. The inhibitory effect was independent of dose within a range of 0.1 to 2.0 mg/mouse; a single dose of less than 0.05 mg/mouse did not exhibit antitumor effect. Multiple administrations of large doses, if given with short treatment intervals, were no more effective than one small dose. Multiple doses given at 14-day intervals resulted in marked growth retardation. The dose of cells that produced 50% tumor takes in C. liquefaciens-treated animals was not significantly different from that in nontreated animals, indicating that this bacterium exhibited no lethal effect on the tumor cells studied.

¹ Present address: Section of Experimental Radiotherapy, The University of Texas System Cancer Center, M. D. Anderson Hospital and Tumor Institute, 6723 Bertner Ave. Houston, Texas 77030.

Received 5/20/76. Accepted 6/ 7/77.