CELL-DEATH INDUCED BY A I-131-LABELED MONOCLONAL-ANTIBODY IN OVARIAN-CANCER MULTICELL SPHEROIDS

Treatment of OVCAR-3 spheroids with I-131-OC125 monoclonal antibody pr oduced a decrease in spheroid volume and a concomitant rise in necroti c cell number. No increase in apoptotic cell number was observed durin g incubation of spheroids with the labeled antibody. Necrosis began ea rly, reaching a maximum after 3 Gy of accumulated dose delivered at a dose rate of 1.8 cGy/h. Higher accumulated doses induced necrosis for longer incubation times. Thus, dose rate and time are both determinant s of ultimate radiation effects when spheroids are incubated with labe led antibodies, although dose rate is the most important factor.