Utilization of Nitrosamine-Induced Tumors as Models for Cancer Chemotherapy

Abstract

Chemotherapeutic studies on transplanted tumors have only little relevance for the cancer in man. The reason for this is first the biological differences between transplanted tumors and autochthonous tumours, and second, that the malignant tumors in man are of autochthonous character. It is not surprising, therefore, that positive chemotherapy findings in rats on transplanted tumors (2) first carried out in the 1950’s, were later proved to be unsuccessful when used as therapy for human cancer. It is well known that in rats and mice a great number of transplanted tumors can be cured today by various chemotherapeutic agents, whereas malignant tumors in man are mostly resistant to chemotherapy or are only partially responding. Therefore, for the last few years we have tried to use chemically-induced autochthonous tumors (predominantly in rats) in chemotherapeutic studies (1, 4, 7–12). These tumors appear to be ideal test models because most of the human tumors are also considered to be induced by chemical carcinogens (12). The following essentials are required for the use of autochthonous animal tumors in chemotherapeutic studies: a) the tumor must be reproducible in high yield and if possible should be developed in only one organ (unilocular occurrence); b) the tumors must occur at almost the same time in all animals (use of inbred strains); c) the tumors must be diagnosable in time; d) a chemotherapeutically untreated control, as large as possible, is particularly important.