[Experimental multiple primary malignant tumors induced by chemical carcinogen]

Experimental induction of multiple primary malignant tumors has been observed in laboratory animals exposed to various carcinogens or irradiation. The development of the tumor by chemical carcinogens is usually multiple. In order to explain different susceptibilities of animals to carcinogenic effect of chemicals, several factors such as different genetic background, aging, dose of drugs and so on have to be taken into consideration. The tumorigenicity of DMBA, MNNG, and 3'-Me-DAB was studied in five strain rats, that is Wistar, Sprague-Dawley, inbred Fischer, inbred Lewis, and inbred Brown-Norway rats. The relationship between multiple tumor, dose of carcinogen, age of animals, and species (strain) of animals is discussed.