Three or four lines each of L1210 were treated for 10 to 15 transplant generations with 5-(3,3-dimethyl-1-triazeno) imidazole-4-carboxamide, 1-phenyl-3,3-dimethyltriazene, and 1-phenyl-3-monomethyltriazene. With increasing numbers of maintenance generations, there was a marked increase in the survival times of the untreated control mice with all three compounds. In subsequent untreated transfer generations, most of the sublines did not take and the others retained reduced growth rates. X-irradiation, or treatment with the triazenes which severely depressed the white blood cell count, decreased the median survival times of the mice bearing the altered sublines but not to the level of the parent L1210. Transplantation into hamsters showed that all triazene-altered lines had less oncogenic potential than the parent line L1210. The results of the present experiments do not exclude changes in antigenicity but the heterotransplantation experiments show clearly that the altered lines lost oncogenic potential.


Supported in part by Grant CA 08748 from the National Cancer Institute, Grant IC-66N from the American Cancer Society, and by the Elsa U. Pardee Foundation.

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