Aldehyde reactive probe assay

The levels of AP sites were determined using the DNA damage assay kit (ab211154, Abcam, Cambridge, UK) according to the manufacturer’s protocol. Cells were seeded in 6-well plates at 3×10⁵/well. After 24 h, the cells were briefly rinsed in phosphate-buffered saline (PBS) and incubated for 1 h in 1 mM MMS dissolved in dimethyl sulfoxide (DMSO); as a control, 0.1% DMSO solution in PBS was used. Then the cells were again rinsed in PBS and incubated for 2 hours in the complete medium. After that, the cells were collected by trypsinization, washed in PBS, and the genomic DNA was extracted using QIAamp DNA mini kit (Qiagen) and used for AP site determination.