Hyperthermia: biological studies at the cellular level.

Tissue culture techniques were used to study the effect of hyperthermia on several cell types, including normal liver and hepatoma cells, as well as cell lines that have been established in culture for many years. Short exposures (less than 30 min.) at 45 degrees C readily kill a large proportion of cells. The response to heat was strikingly similar in all cells tested, and no preferential killing of neoplastic cells could be demonstrated. By contrast, hypoxic cells were found to be dramatically more susceptible to killing by heat than aerated cells. This is the reverse of the situation for x irradiation. The effectiveness of x irradiation was potentiated by treating the irradiated cells for 20 min. at 43 degrees C, which did not kill a detectable number of cells.