RADIATION-INDUCED APOPTOSIS IN HUMAN OVARIAN-CARCINOMA CELLS GROWING AS A MONOLAYER AND AS MULTICELL SPHEROIDS

Response to external gamma irradiation was studied in a human ovarian carcinoma cell line (OVCAR 3) growing as a monolayer and as multicell spheroids. Necrosis and apoptosis were documented using Trypan-blue up take and acridine-orange staining, respectively, and apoptosis was qua ntified using a terminal deoxynucleotidyl transferase assay, Exposure of OVCAR 3 cells growing as a monolayer to Cs-137 gamma radiation at a dose of 10 Gy produced 30-40% apoptosis 72 hr after irradiation, Cell -cycle analysis of irradiated cells showed an accumulation of cells in G(2)/M phase 24 hr after irradiation and then a decline at 48 hr in c onjunction with apoptosis onset. The loss of G(0)/G(1) cells in irradi ated cultures suggested a preferential entry into apoptosis. No increa se in apoptotic cell number was observed in OVCAR 3 spheroids after ir radiation, and the cells probably died as a result of necrosis, When s pheroids were disrupted immediately after irradiation to obtain a cell suspension, minor apoptosis was observed in association with a marked increase in TB-positive cell number after 96 hr of incubation followi ng irradiation. Thus, a relationship was found between radiation-induc ed apoptosis and the cell cycle, Results with spheroids suggested the possible involvement of cell-to-cell interactions in apoptosis regulat ion. (C) 1997 Wiley-Liss, Inc.