Abstract
Experiments on the effect of transplacental initiation with 7,12-dimethylbenz(a)anthracene (DMBA) and postnatal promotion with teleocidin were carried out in mice. The percentage of tumor-bearing mice among females treated with DMBA transplacentally on day 17 of gestation and postnatally by topical application of teleocidin to the skin of the back was 73.3% in week 30, whereas that among females treated with DMBA on day 10 of gestation and postnatally by topical application of teleocidin was 20.0%. This indicates that teleocidin shows potent tumor promoting activity on mouse skin in a transplacental initiation and postnatal promotion protocol. Furthermore, in the males treated with DMBA transplacentally on day 17 of gestation and given diet containing 0.01% teleocidin postnatally five tumors of the forestomach were found in 5 of 19 effective mice (26.3%) in week 52. One of these five tumors was a squamous cell carcinoma, and the others were papillomas. This indicates that teleocidin also has tumor promoting activity in the forestomach of mice.