Influence of hypoxia and acidity on thermal radiosensitization and direct heat-induced death of BP-8 sarcoma cells

The response to heat of BP-8 murine sarcoma cells was evaluated with the ¹²⁵I-iododeoxyuridine prelabeling technique. Euoxic and hypoxic BP-8 cells were heated in vitro at pH 7.4 vs. 6.5 at temperatures ranging from 37°C to 44°C. The results indicated that acute hypoxia had no effect on either heat potentiation of radiation damage or direct heat-induced death. However, lowering of media pH increased direct thermal cell death and, to a lesser extent, heat potentiation of radiation lethality. These findings suggest that the enhanced radiosensitization and heat-induced death observed in chronically hypoxic tumor populations may, at least in part, be caused by hypoxia-induced tumor acidification.