RADIATION-INDUCED DNA-DAMAGE IN TUMORS AND NORMAL-TISSUES .4. INFLUENCE OF PROLIFERATION STATUS AND CELL-TYPE ON THE FORMATION OF OXYGEN-DEPENDENT DNA-DAMAGE IN CULTURED-CELLS

Using a variety of techniques, several laboratories have recently demo nstrated the feasibility of using radiation-induced DNA strand breaks and/or DNA-protein crosslinks (DPCs) to detect and/or quantify hypoxic cells in tumors and normal tissues. However, if strand breaks and/or DPCs are to be used to estimate the hypoxic fraction or the fractional hypoxic volume of tumors and normal tissues, their formation as a fun ction of the oxygen concentration near the DNA must be relatively inde pendent of the biological properties of these cells. In the present st udy, the shape of the oxygen dependence curves and the K-m values for radiation-induced strand breaks and DPCs were measured by alkaline elu tion for proliferative (P) and quiescent (Q) cells of the mouse mammar y adenocarcinoma, line 66. The sigmoidal shape of the oxygen dependenc e curves, the K-m for strand breaks (approximate to 0.027 mM) and the K-m for the formation of DPCs (approximate to 0.020 mM) were identical for the P and Q cells of line 66. Consequently, the proliferative sta tus of these tumor cells had no measurable influence on the oxygen-dep endent formation of radiation-induced strand breaks and DPCs. In addit ion, the percentage of the DNA retained on the filters after approxima te to 24 ml of elution without proteinase K in the lysis solution, a p arameter equal to the sum of the strand breaks and DPCs that has been shown to be proportional to the percentage of hypoxic cells in the sam ple, was not significantly different for fully oxygenated or fully hyp oxic populations from five tumor cell lines that varled in species, si te of origin, proliferative status and/or properties of the proteins w hich are intimately associated with their DNA. These data indicate tha t the formation of radiation-induced strand breaks and DPCs depends pr edominantly on the oxygen concentration in the microenvironment around the DNA, and only minimally on the biological properties of the cells . (C) 1997 by Radiation Research Society.