STEPDOWN HYPERTHERMIA IN HUMAN-MELANOMA CELLS - EFFECTS ON PROTRACTEDMILD HYPERTHERMIA FOR SURVIVAL AND DNA-POLYMERASE INACTIVATION

Human melanoma cells have been used to evaluate whether stepdown heati ng (SDH) could increase the effectiveness of long-duration mild hypert hermia (LDMH). The effects of these treatments were also evaluated on cell survival and DNA polymerase inactivation. Short treatments (30 mi n) at 43 degrees C did not result in much SDH effect for subsequent pr otracted heating at 40 degrees C. The effect on DNA polymerases was al so very small. However, heating at 44 degrees C for 30 min had a large SDH heating effect on subsequent heating at 40 degrees C and 41 degre es C. The SDH effect occurred mainly in the first 5-10 h of subsequent LDMH and, at longer heating times, the rate of cell killing was reduc ed. The 44 degrees C SDH effect was also observed on DNA polymerase in activation. Comparing the degree of cell killing and polymerase inacti vation showed a good correlation for the various SDH protocols.