A combined cell killing effect in vitro of photoradiation and hyperthermia (second report)

Abstract

The combined effect has been investigated using KK-47 cells and colony forming assay system. From the heat-response curve at 43°C hyperthermia, 20% growth inhibition time (IT20) was calculated, and the IT20 was combined with the following photoradiations. In combination of hyperthermia and photoradiation, a pronounced cell killing effect was obtained when hyperthermia was carried out after one hour of photoradiation. Damage repair from the photoradiation was observed when hyperthermia was performed 3 or 5 hours after photoradiation. The reverse sequence of hyperthermia and photoradiation, no combination effect was obtained. In addition, the uptake of HpD was investigated with measuring of the fluorescence intensity of HpD bound to KK-47 cells at various temperatures. It was shown that the fluorescence peak appeared at 614 nm at 7 and 37°C, and its peak appeared at 635 nm at 41°C, respectively. It was considered that the former spectra were assigned to the weak binding mode and the latter one stable binding mode, respectively.