Thermochemotherapy: synergism between hyperthermia (42-43 degrees) and adriamycin (of bleomycin) in mammalian cell inactivation.

The sensitivity of cells exposed in vitro to the antibiotics bleomycin or adriamycin is only mildly increased at 41 degrees over that seen at 37 degrees. However, at 43 degrees a marked synergism between the effects of hyperthermia and drug is observed. This synergism can also be demonstrated to occur in solid tumors in vivo. Cells after bleomycin exposure at 37 degrees repair potentially lethal damage, and 43 degrees inhibits this repair. This inhibition may in part account also for the observed sensitization of the cells to bleomycin, but not to adriamycin, since for the latter no repair can be demonstrated. However, fluorescence measurements show that at 43 degrees much more adriamycin is able to enter the cells than at 37 degrees. The possible implications of the results for cancer treatment are discussed.