A 549

Human lung adenocarcinoma epithelial cells A549 and H-1299 were obtained from American Type Culture Collection and grown as recommended. All cell lines were used within 6 months after resuscitation. For γ-H2AX immunofluorescence, H-1299 or A-549 cells were seeded on coverslips in 6-well dishes at a density of 1 × 10⁵ cells/well and allowed to attach for 24 h. These were then treated with the ABT-888, DETA or combined for 4 h and then exposed to a single dose of IR (MDS Nordion Gammacell 40 research irradiator, ON, Canada). Then cells were incubated for 4 h and 24 h post-irradiation. After washing in PBS three times, cells were fixed in 4% formaldehyde for 20 min and permeabilized with 0.2% TritonX-100 in 5% BSA/PBS for 30 min. The coverslips were then incubated in primary antibodies placed on parafilm strips and incubated at RT for 1 h. The coverslips were washed in PBS three times for 5 min each. They were then incubated with secondary antibodies at RT for 1 h. The coverslips were washed with PBS three times for 5 min each, air-dried and then mounted in Fluoroshield mounting medium with DAPI (Abcam) and viewed using a fluorescence microscope.