IN-VIVO SHORT-TERM ASSAYS FOR TUMOR INITIATION AND PROMOTION IN THE GLANDULAR STOMACH OF FISCHER RATS

Here we summarize the data on 55 compounds tested in in vivo short-ter m assays for tumor-initiating and tumor-promoting activity in the glan dular stomach of male Fischer (F344) rats. Most of the data has been p reviously published. Tumor-initiating activity was assayed by measurin g the induction of unscheduled DNA synthesis (UDS) and DNA single stra nd scission; tumor-promoting activity was assayed by measuring the ind uction of ornithine decarboxylase (ODC) activity, increased replicativ e DNA synthesis (RDS), and of c-fos and c-myc oncogene expression. The compounds were orally administered. Twenty-nine compounds were tested for UDS. Eight were positive, including 5 glandular stomach carcinoge ns; 16 were negative, including 5 liver carcinogens; and 5 were equivo cal. Twenty compounds were tested for DNA single strand scission. Twel ve were positive, including 6 glandular stomach carcinogens; 7 negativ e, including 2 liver carcinogens; and 1 was equivocal. Thirty-two comp ounds were tested for RDS. Twenty-six were positive, including 8 gland ular stomach carcinogens and 6 glandular stomach tumor-promoters; 4 we re negative, including 3 liver carcinogens and a stomach irritant; and 2 were equivocal. Forty-five compounds were tested for ODC. Thirty-se ven were positive, including 8 glandular stomach carcinogens and 6 gla ndular stomach tumor promoters; 7 were negative, including 3 liver car cinogens; and one was equivocal. All glandular stomach carcinogens and tumor-promoters examined were positive in both RDS and ODC. Two compo unds were tested for c-fos and c-myc expression; one was a glandular s tomach carcinogen and one was a glandular stomach tumor promoter, and both were positive. In addition, 2 compounds inhibited the increase in RDS induced by the tumor promoter NaCl, suggesting anti-tumor-promote r activity. Thus these assays are useful for assessing potential tumor -initiating and tumor-promoting activity in the rat glandular stomach.