Kinetics of induction of reactive oxygen species during the post-irradiation expression of neoplastic transformation in vitro

Purpose : To examine whether the delayed expression of cell death and neoplastic foci in irradiated HeLa ×human skin fibroblast human hybrid cells correlates with the presence of reactive oxygen species (ROS) in the progeny of the irradiated cells. Material and methods : HeLa ×human skin fibroblast human hybrid cells were irradiated and plated as for assay of neoplastic transformation. At regular time intervals during the post-irradiation expression period of 21 days, samples were harvested and assessed for the presence of oxyradical activity by measuring the oxidation of dichlorohydrofluorescein (DCFH) to dichlorofluorescein (DCF) using flow cytometry. This reagent principally detects hydrogen peroxide. The kinetics of production of ROS were compared with those previously measured using the identical experimental protocol for the expression of both cell death and neoplastic foci. Results : The kinetics of production of ROS closely matched those for the onset of delayed cell death and delayed expression of neoplastic transformation. Conclusions : The induction of ROS is associated with delayed cell death and delayed neoplastic transformation in irradiated HeLa ×human skin fibroblast human hybrid cells.