ENHANCEMENT OF CELL-KILLING OF HL-60 CELLS BY ULTRASOUND IN THE PRESENCE OF THE PHOTOSENSITIZING DRUG PHOTOFRIN-II

Enhancement of acute cell killing of HL-60 cells by low-level ultrasound in the presence of the photosensitizing drug Photofrin II was examined. HL-60 cells were exposed to ultrasound (270 kHz) at intensities of 150, 300 and 450 mW/cm2 for 60 s in the presence of Photofrin II (200 mug/ml). Cell survival after treatment was 49.6 +/- 5.1%, 34.5 +/- 3.1% and 27.4 +/- 3.9%, respectively. Ultrasound exposure alone at 150, 300 and 450 mW/cm2 resulted in a decrease in cell survival to 92.9 +/- 1.5%, 82.3 +/- 2.2% and 77.9 +/- 7.2%, respectively. The cell survival rate after the addition of Photofrin II alone showed no significant cell killing. These results indicate that Photofrin II was sensitized by low-level, non-thermal ultrasound to enhance the cell killing of HL-60 cells.