Clonogenic assay

Clonogenic assays were performed as described previously [42]. NCI-H460 and NCI-H1299 cells were seeded in 60 mm dishes in triplicate at densities estimated to yield 20-100 colonies/dish (100, 200, 400, 600 and 1000 cells/dish). After 24 h incubation, cells were pre-incubated with or without 10 or 30 μM AMRI-59 for 16 h and exposed to different doses of IR (1, 3, 5, 7 Grey [Gy]) using ¹³⁷Cs as the radiation source (Atomic Energy of Canada, Ltd., Ontario, Canada). Treated and control cells were cultured for 10-14 days, and colonies >200 μm in diameter counted using a colony counter (Imaging Products, VA, USA). Dose enhancement ratio (DER) values were calculated with Excel program (Microsoft Co. USA) as describe in Table ​Table11.