Accelerated Development of Spontaneous Mammary Tumors in Mice Pretreated with Mammary Tumor Tissue and Adjuvant* HERBERT M . HIRSCH~ AND IVER IVERSEN~ WITH THE TECHNICAL ASSISTANCE OF GERTRUD OSTREM AND GEORGEANNE DELAHANTY

C3H and C3H backcross mice were given repeated injections of preparations from strain-specific or strain-related mammary tumors of recent spontaneous origin together with Freund's adjuvant. The effect of the course of injections on spontaneous mammary tumor development was studied. Pre t rea tment with mammary tumor tissue did not lead to a significant reduction in spontaneous mammary tumor incidence, did not delay age of tumor onset or prolong survival time following onset of tumors. On the contrary, administration of tumor tissue led to a significant reduction in the age at which spontaneous mammary tumors occurred and to a reduced survival time of the tumorous animals. Frennd's adjuvant alone was without effect on either cancer incidence, cancer age, survival time, or survival time following onset of tumors. The data are discussed in the light of the possibility tha t auto-immune or enhancement phenomena may contribute significantly to tumor development.