Effect of 41.5°C or 42.5°C thermal treatments on unirradiated or irradiated human U-1 melanoma cells. (A) Clonogenic survival of cells after heating for 0.5, 1, 2, 4, 6, or 15 h at 41.5° C or 42.5° C. (B) Comparison of cell survival after irradiation with various doses of X-rays (0–8 Gy) and thermal treatment at 41.5°C for 2 h or at 42.5°C for 2 h (C). Surviving fractions of cells that were heated for 2 h at 41.5°C or 42.5°C (shown in panel A) were normalized to the surviving fraction of unheated, unirradiated cells (shown in panels B and C). Standard error of the mean for 2-3 experiments is denoted by error bars.