Local tumor regression after intralesional injection of croton oil

Intralesional administration of emulsified croton oil into established syngeneic transplants of murine firosarcoma no. 1023 caused complete regression of the injected tumors in C3H mice without recurrence during the period of observation. In Sewall Wright strain 2 guinea pigs, in contrast to BCG cell wall vaccine which eradicated regional lymph node metastasis as well as dermal transplants, croton oil treatment only delayed the development of metastatic disease despite the fact that the injected skin tumors did not recur. 12-O-Tetradecanoylphorbol 13-acetate (TPA), the active principle of croton oil, incorporated in mineral oil droplets in aqueous suspension, caused regression of murine tumors when injected intralesionally. Aqueous suspensions of TPA failed to eliminate the tumors. Our results suggest that tumor regression induced by croton oil of TPA emulsions was due to indiscriminate destruction of the injected tissue.