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γH2AX in Bystander Cells: Not Just a Radiation-Triggered Event, a Cellular Response to Stress Mediated by Intercellular Communication

Mykyta V. Sokolov, Jennifer S. Dickey, William M. Bonner and Olga A. Sedelnikova

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The recent years have witnessed a rapid accumulation of experimental data showing that ionizing radiation elicits a plethora of biological effects in unirradiated cells receiving bystander signals from hit cells. This so-called radiation-induced bystander effect (RIBE) manifests in various ways including changes in gene expression, genetic and epigenetic alterations, as well as increases in cell transformation and cell death. Our group and others found that DNA double-stranded breaks (DSBs), directly measured by the γ-H2AX focus formation assay, accumulate in bystander cells in a number of experimental systems such as human cultured cells, human 3-dimensional tissue models and in mice. In addition, we recently found that various other sources of cell stress, including media from cancerous cells resulted in a DNA damage response (DDR) in normal human cells that is reminiscent of RIBE. These results suggest that the RIBE may be part of a more general stress response, however, the molecular mechanism underpinning the formation of DNA DSBs in bystander cells is still unclear. This extra view points to some possibilities that might explain why DDR in human cells can be observed under bystander conditions.

Authors

Mykyta V. Sokolov

National Cancer Institute; Bethesda, Maryland

Jennifer S. Dickey

National Cancer Institute; Bethesda, Maryland

William M. Bonner

National Cancer Institute, Bethesda, Maryland

Olga A. Sedelnikova

National Cancer Institute, Bethesda, Maryland

This is an open-access article

 Download PDF

If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.