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The Accelerating Effect of Heat-denatured Isogeneic Spontaneous Mammary Tumor Cells on Spontaneous Tumor Incidence in Female C3H Mice and the Effect of Time of Injection¹

Department of Hygiene, Faculty of Medicine, Kyoto University, Kyoto, Japan

Thirty experimental virgin female C3H mice were given one injection s.c. of 0.5 ml tumor cell suspension of spontaneous mammary tumor from a C3H mouse. Thirty control virgin female C3H mice were given one injection s.c. of 0.5 ml 0.9% NaCl solution containing streptomycin and penicillin. Tumor development was observed by inspection and palpation at appropriate intervals until all mice died. All dead mice were dissected. Spontaneous tumors developed in 21 experimental mice and in 13 control mice. The difference in tumor incidence between these 2 groups is statistically significant. The heat-denatured tumor injection was significantly more effective in accelerating spontaneous tumor incidence when injected into mice 199 to 275 days old than it was in other mice 56 to 197 or 286 to 354 days old.

¹ This investigation was aided in part by the Fujiwara Memorial Foundation.

Received 1/31/72. Accepted 5/23/72.