Hyperthermic radiosensitization of cells from a human melanoma xenograft.
Cells derived directly from a human melanoma xenograft were exposed to radiation and/or hyperthermia under aerobic conditions in vitro. Single cell survival was assayed in soft agar. The activation energies for heat treatment alone were 420 +/- 40 kcal/mole (41.5-42.5 degrees C) and 170 +/- 10 kcal/mole (43.0-45.5 degrees C). Heat doses of 41.5 degrees C (30 min) or 43.5 degrees C (30 min) did not cause a reduction in the shoulder of the X-ray survival curve of the cells, but the D0 value was reduced. The thermal enhancement ratios (the ratio of the D0 values) were in the ranges 1.0-1.3 (41.5 degrees C, 30 min) and 1.1-1.7 (43.5 degrees C, 30 min), depending on the sequence and the time between the treatments. Repair of sublethal radiation damage was not significantly inhibited when treatments with 41.5 degrees C (30 min) or 43.5 degrees C (30 min) preceded irradiation, but was inhibited when 44.5 degrees C (30 min) was given immediately before radiation and when 41.5 degrees C (120 min) was given immediately after radiation. Implications of the results for clinical treatment of malignant melanomas are discussed.
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D003131:Combined Modality Therapy; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D006979:Hyperthermia, Induced; D008297:Male; D008545:Melanoma / Q000532:radiotherapy*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011836:Radiation Tolerance; D013997:Time Factors; D014183:Transplantation, Heterologous