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 ultrasou nd in the presence of the photosensitizing drug Photofrin II was exami ned. HL-60 cells were exposed to ultrasound (270 kHz) at intensities o f 150, 300 and 450 mW/cm2 for 60 s in the presence of Photofrin II (20 0 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 surviv al 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 H L-60 cells.