In vitro effect of hyperthermia on chemoenhancement and uptake of cisplatin in human pharyngeal carcinoma KB cells.

The purpose of this study was to assess the efficacy of hyperthermia (42 or 44 degrees C) as a modifier of cis-diamminedichloroplatinum (II) (CDDP) cytotoxicity and platinum incorporation in human pharyngeal carcinoma KB cells. To maximize the interactive effect, we examined the time sequence of high (above 43 degrees C) or low (below 43 degrees C) hyperthermia and CDDP. Within the dose range of CDDP studied, there was a marked synergism between the effects of heating at 44 degrees C and subsequent CDDP exposure for 5 h. Pretreatment at 44 degrees C for 30 min or at 42 degrees C for 4 h enhanced CDDP cytotoxicity more than posttreatment at 44 degrees C for 30 min or at 42 degrees C for 4 h. However, the chemoenhancement ratio of pretreatment at 44 degrees C for 30 min was higher then that of pretreatment at 42 degrees C for 4 h, although the thermal isotoxic dose decreased the cell count to 60% under both conditions. There was a significant increase in CDDP uptake after hyperthermia at 44 degrees C. These results indicate that high hyperthermia effectively enhances subsequent CDDP cytotoxicity in human pharyngeal carcinoma KB cells.