Figure 1

ATM is critical for both resistance and sensitivity responses of chemorefractory cells following genotoxic stress. (a) Percent viability of different cancer cells treated with dose range of genotoxic drugs, cisplatin, doxorubicin and etoposide, was scored by using trypan blue dye exclusion assay. (b) Genotoxic stress-induced apoptosis in resistant cancer cells was determined by quantifying the 7-AAD/Annexin-V-FITC-positive cells (regarded as apoptotic cells) flow cytometrically at low dose (10 μM) and high dose (60 μM) cisplatin (left panel) and represented graphically (right panel). (c) A549 and (d) H460 cells, treated with increasing dose of different drugs, were subjected to western blotting to determine the expression levels of p-ATM, ATM and γH2AX. α-Actin was used as internal loading control. Percent apoptosis in the ATM-siRNA transfected or KU55933 pre-exposed (c) A549 and (d) H460 cells was scored following drug treatment. The efficiencies of both genetic and pharmacological ATM depletion in (c) A549 and (d) H460 were determined by examining the expression status of p-ATM, ATM and p-Chk2. (e) Specificity of ATM knockdown was determined by scoring the percent apoptosis of siRNA-resistant ATM-cDNA- and siRNA-sensitive ATM-cDNA-expressing A549 cells transfected with ATM-siRNA following drug treatment. Values are mean±S.E.M. of five independent experiments in each case. *P<0.01 when compared with respective control sets