Phenomenon and mechanism of ionizing radiation-induced bystander effects

Abstract

The bystander effect is the phenomenon whereby ionizing radiation induces biological effects in non-irradiated bystander cells having received signals from directly irradiated cells. Bystander cells manifest genetic changes (e.g., chromosome aberrations, mutagenesis and micronucleation), epigenetic changes, alterations in gene expression, activation of signaling pathways, and delayed effects in their progeny. Proposed mechanisms mediating the bystander effect involve gap-junctional intercellular communication, reactive oxygen/nitrogen species, secreted soluble factors, lipid rafts, and calcium fluxes. Here we briefly overview the current knowledge of the bystander effect, particularly focusing on the observed phenomenon and its proposed mechanisms.