Eight mammary carcinomas were induced by either 3-methylcholanthrene or 7,12-dimethylbenz(a)anthracene in a nonviral- and noncarcinogen-induced preneoplastic (premalignant) alveolar nodule which had arisen in a hormonally stimulated BALB/c female mouse. The preneoplastic mammary nodule outgrowth was found to be nonantigenic when tested in the strain of origin. Seven of the eight carcinogen-induced carcinomas were also found to exhibit no clear-cut evidence of antigenicity. The eighth tumor, however, was shown to produce tumor-specific immunity in BALB/c mice.

The results suggest that carcinogens may not directly induce the appearance of new antigens in the tumors they produce. Furthermore, carcinogens may act in a different manner when inducing a preneoplastic change than when inducing a tumor from a preexisting preneoplastic lesion.

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This work was supported by NIH Grants CA-5388 and CA-5045, by Grant PRA-37 from the American Cancer Society, and by cancer research funds of the University of California, Berkeley, Calif. 94720.

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