Improved tumour yields by means of a TPA-DMBA-TPA variation of the Berenrlum-Mottram experiment on the back skin of NMRI mice. : The effect of stationary hyperplasia without inflammation

Abstract

Application of the phorbol ester TPA to the back skin of NMRI mice 14 times within a period of 7 weeks causes a stationary hyperplasia, with a corresponding increase in the labelling index of the basal cells from 1% to 14%. By initiation of skin, which has been pretreated with TPA in this way, with the carcinogen DMBA, followed by continued treatment with TPA (initiation-promotion corresponding to the classical Berenblum-Mottram experiment) the tumour yield (papillomas, carcinomas) is very much higher than that obtained using the scheme of the normal Berenblum-Mottram experiment. The preliminary induction of a stationary hyperplasia with high rates of nucleic acid synthesis must be considered an important co-factor in epidermal carcinogenesis.