Elevated ROS production is closely associated with radiation-induced genomic instability in cultured human cells

Abstract

We devised a human HT1080 cell line carrying a tandem duplication in a part of HPRT gene (HPRT-dup cells) to address whether the repeat sequence instability (detected by reversion due to loss of the duplication by intrachromosomal recombination) is implicated in forward mutations at unique sequences in ordinary genes in radiation- induced genomic instability. Previously, we found that there were no absolute correlations in the instability between the reversion mutation from HPRT-dup to HPRT+ and the subsequent forward mutation from HPRT+ to HPRT-. In the present study, we found that many of the clones with the repeat-sequence instability showed 2-5 fold increases in production of reactive oxygen species (ROS) and substantial increase in the number of gamma-H2AX foci. Further, the repeat-sequence instability was not suppressed by fusion of the unstable cells with parental cells (instability-negative), indicating that the nature of the instability is genetically dominant. The results suggest that production of cytosolic diffusible factor(s) that causes persistent intracellular inflammation is responsible for the maintenance of the instability.