Toxic tides.

4-Hydroxyanisole (4-OHA) was administered to C57Bl/lOJ mice in which B16 melanoma or Lewis lung carcinoma had been implanted s.c. or i.m. The drug had the largest antitumour effect against B16 melanoma growing s.c. and a smaller antitumour effect against B16 melanoma or Lewis lung carcinoma growing i.m. In the treatment regimens where drug was administered only after tumour implantation, a significant reduction in number of spontaneous metastases and their incidence was observed. Again, the largest antimetastatic effect was observed for s.c. B16 melanoma with smaller effects observed for i.m. B16 melanoma or Lewis lung carcinoma. Experiments in which 4-OHA treatment was initiated after amputation of the primary tumour implanted in the tail confirmed that 4-OHA did have antitumour activity against disseminated tumour cells. The drug regimens studied to date produced significant delays in the appearance of spontaneous metastases in the lungs and significant increases in the life spans of the treated animals. The discovery of melanocytotoxic activity of certain phenolic depigmenting agents due to their oxidation by tyrosinase, the 'clue' enzyme in cellular pigment formation, appeared to offer a therapeutic potential in the treatment of melanotic melanoma. Animal studies on experimental melanomas have given variable results as regards the therapeutic efficacy of these agents Several other phenolic compounds with antioxidant properties were tested more recently for antitumour activity against murine melanomas (Demopoulos et