Radiosensitizing effects of misonidazole and SR 2508 on a human melanoma transplanted in nude mice: influence on repair of potentially lethal damage.

The radiosensitizing effects of misonidazole and SR 2508 (1 mg/g) were compared on a human melanoma (Na11) containing 85% hypoxic cells transplanted into nude mice. For both drugs, the enhancement ratios (ER) were 1.7 after immediate plating and 2.1 after delayed plating. This difference in ERs is related to a lack of PLD repair in tumors in the presence of the sensitizer. The effect of misonidazole was also investigated in another human melanoma (Be11) containing 40% hypoxic cells. After immediate plating, the ER was similar to that observed with the Na11 tumor (1.7), but PLD repair was not reduced. A comparative analysis of the influence of misonidazole on the response (survival curve - PLD repair) of Na11 melanoma to different ionizing radiations was attempted.