Skin transplantation in the study of chemical carcinogenesis. III. Reduced papilloma-formation after initiation during epidermal hyperplasia induced by skin grafting or by a single application of the cocarcinogen TPA.

Skin autografting or a single painting with the cocarcinogen TPA was used to induce epidermal hyperplasia in the back skin of C3H mice. Initiation by intragastric application of the carcinogen DMBA during this state of hyperplasia and subsequent promotion by repeated application of the cocarcinogen TPA led to decreased papilloma-formation, as compared to mice of a control group which had not been pretreated before initiation. Reports by others referring to increased susceptibility of replicating epidermal cells to the effect of initiation thus cannot be confirmed. The reduction of papilloma-formation can most probably be ascribed to effects of local inflammation, either preferentially but unspecifically damaging initiated cells, or facilitating a specific immune response against tumor-associated transplantation antigens of prospective tumor cells.