Effect of Heterologous Antithymocyte Serum on Mouse Skin Tumorigenesis

Summary

The effect of transient immune impairment on the initiating and promoting phase of skin tumorigenesis, as expressed by tumor incidence, latency, number of papillomas per mouse, papilloma regression, and rate of malignant transformation, was evaluated. Heterologous antithymocyte serum (ATS) was used as the immunosuppressive agent, a single skin painting of 7,12-dimethylbenz[a]anthracene (DMBA) for skin-tumor initiation, and repeated croton oil skin paintings for promotion. ATS treatment before the initiating phase did not change the tumorigenic potency of DMBA. ATS injections administered concurrently for several weeks with croton oil paintings, early or late during the promoting phase, did not enhance or diminish croton oil activity, but prevented tumor regression after termination of the croton oil treatment. Immunosuppression could not replace or enhance the effect of croton oil on papilloma development. ATS given after termination of the croton oil treatment (when papilloma regression is enhanced) did not prevent the regression phenomenon. The incidence of progression from benign tumors to malignancies was enhanced in the ATS-treated groups.