An Analytical Method for Quantifying the Yields of DNA Double-Strand Breaks Coupled with Strand Breaks by γ-H2AX...

Area of Science:

• Radiation Biology
• Molecular Biology
• Biophysics

Background:

• Complex DNA double-strand breaks (DSBs) are critical, potentially lethal radiation-induced DNA damage.
• The γ-H2AX focus formation assay is used to detect DSBs, but accurately assessing DSB complexity via focus size remains challenging.

Purpose of the Study:

• To develop an analytical method for quantifying complex DNA double-strand break (DSB) complexity induced by photon irradiation.
• To establish a relationship between γ-H2AX foci size and the underlying DSB complexity at the DNA scale.

Main Methods:

• Utilized Monte Carlo (MC) track-structure simulation codes (WLTrack and PHITS) to score ionization and excitation events along electron tracks.
• Established an experimental correlation between the number of simulated events and experimentally measured γ-H2AX foci size.
• Applied the developed method to evaluate DSB complexity across various X-ray spectra.

Main Results:

• A direct proportionality was found between the number of events in a nanometer-scale water cube and γ-H2AX foci size.
• The number of events serves as a reliable indicator of DSB complexity at the DNA level.
• The method demonstrated applicability to diverse X-ray spectra, including diagnostic and therapeutic ranges.

Conclusions:

• The developed analytical method accurately quantifies complex DSB formation induced by photon irradiation using γ-H2AX foci size.
• This approach enhances the precision of the γ-H2AX focus formation assay for assessing early biological impacts of radiation.
• The findings contribute to a more accurate understanding of DNA damage induced by various X-ray sources.