CHARACTERIZATION OF RADIATION-INDUCED APOPTOSIS IN RODENT CELL-LINES

For REC:myc(chl), Rat1 and Rat1:myc, cells, we determined the events i n the development of radiation-induced apoptosis to be in the followin g order: cell division followed by chromatin condensation, membrane bl ebbing, loss of adhesion and the uptake of vital dye. Experimental dat a which were obtained using He-4 ions of well-defined energies and whi ch compared the dependence of apoptosis and clonogenic survival on He- 4 range strongly suggested that in our cells both apoptosis and loss o f clonogenic survival resulted from radiation damage to the cell nucle us. Corroboratory evidence was that BrdU incorporation sensitized thes e cells to radiation-induced apoptosis. Comparing the dose response fo r apoptosis and the clonogenic survival curves for Rat1 and Rat1:myc(b ) cells, we concluded that radiation-induced apoptosis contributed to the overall radiation-induced cell inactivation as assayed by clonogen ic survival, and that a modified linear-quadratic model, proposed prev iously, modeled such a contribution effectively. In the same context, the selective increase in radiation-induced apoptosis during late S an d G(2) phases reduced the relative radioresistance observed for clonog enic survival during late S and G(2) phases. (C) 1997 by Radiation Res earch Society.