Effect of cobalt-60 gamma rays and DTIC (5-(3,3 dimethyl-1-triazeno)-imidazole-r-carboxamide) on human malignant melanomas grown in athymic nude mice.

The effects of 60Co gamma rays and DTIC on two human malignant melanomas, inoculated and passed serially in athymic mutant nude mice, were studied in vivo. Dose-response curves determined after single exposures to 60Co gamma radiation indicate that human malignant melanomas remain radioresistant after transplantation in mutant nude mice. A fractionated irradiation régime, used in the treatment of patients suffering from malignant melanomas, had a considerable effect but did not cure. A corresponding treatment régime with DTIC inhibited the tumour growth, but less effectively than 60Co gamma rays. These two treatments combined were more effective than either alone. The results obtained show no disagreement with results from clinical practice regarding treatment of disseminated malignant melanomas. This suggests that human malignant tissue, transplanted to mutant nude mice, retains its properties with respect to response to therapy. The mutant nude mouse may therefore be valuable in developing new treatment régimes for cancer.