DNA double-strand break induced by ionizing radiation (DSB (when referring to "double-strand break"); no standard abbreviation for the full process)

A DNA double-strand break induced by ionizing radiation (IR) refers to one of the most severe forms of genetic damage where both strands in the DNA helix are broken simultaneously. Ionizing radiation—including X-rays, gamma rays, protons, alpha particles—can cause these lesions either directly through energy deposition into the DNA backbone or indirectly via generation of reactive oxygen species that attack nucleotides and sugar moieties within DNA molecules[2]. Double-strand breaks can result in loss or rearrangement of genetic information if improperly repaired; this underlies their central role both as drivers for mutagenesis/cancer development and as mediators for cell killing during radiotherapy treatments. Upon occurrence, cells activate complex DNA damage response pathways, including phosphorylation events like γH2AX formation at break sites and recruitment/activation of proteins suchs as p53BP1. These responses lead either toward successful repair—primarily through homologous recombination or non-homologous end joining—or toward programmed cell death/senescence if repair fails. The efficiency with which different types/doses/qualities ("LET") of IR induce clustered versus isolated lesions influences biological outcomes ranging from effective tumor control during radiotherapy to risk for late-onset secondary cancers due to misrepair events[5][7]. While not itself a druggable target, understanding how cells respond mechanistically has led researchers to develop combination therapies exploiting differences between tumor and normal tissue repair capacity—for example using PARP inhibitors alongside IR when tumors have defective homologous recombination machinery.[6] Biomarkers like γH2AX remain essential tools both experimentally and clinically for quantifying exposure/effectiveness/safety margins related to IR-induced genotoxicity.[3]

Other names

Radiation-induced DNA double-strand breakIR-induced DSBIonizing radiation–induced DSB

Drugs do not act on the break per se but may: - Inhibit repair pathways such as homologous recombination or non-homologous end joining to increase cell death after irradiation. - Enhance formation of reactive oxygen species leading to more breaks during radiotherapy.