Dynamic recognition and repair of DNA complex damage

Area of Science:

• Molecular Biology
• Cancer Research
• Radiation Oncology

Background:

• Irradiation (IR) induces DNA damage for cancer treatment, but its molecular mechanisms remain unclear.
• Understanding DNA damage complexity is crucial for optimizing radiotherapy efficacy.

Purpose of the Study:

• To investigate the molecular mechanisms of DNA damage induced by X-ray and carbon ion irradiation combined with bleomycin (BLM) in A549 non-small-cell lung cancer cells.
• To correlate DNA damage markers with treatment outcomes.

Main Methods:

• A549 cells were treated with X-ray or carbon ion IR + BLM.
• Assessed cell survival, DNA double-strand breaks (DSBs), γH2AX/53BP1 foci, and protein expression (Ku70, Rad51, XRCC1) using clone formation assay, gel electrophoresis, immunofluorescence, and western blot.

Main Results:

• Carbon ion IR + BLM induced the most complex DSBs.
• X-ray IR + BLM showed the highest γH2AX and 53BP1 foci at 0.5 hr (p < 0.001).
• γH2AX foci translocated from nucleus to cytoplasm by 6 hr in carbon ion IR + BLM group; Ku70 increased, XRCC1 decreased.

Conclusions:

• Clustered DNA damage resulted in a DNA damage frequency of 13.4/Mbp.
• γH2AX, 53BP1, and XRCC1 levels correlate with the extent of DNA damage.
• Findings offer insights into DNA damage recognition and support radiotherapy clinical applications.