MCF7-ATMi cells are more sensitive than MCF7-ctr cells to iniparib. (A) Quantitative analyses of colony formation. The numbers of DMSO-resistant colonies in MCF7-ATMi and MCF7-ctr cells were set to 100, while iniparib treated cel1s were presented as mean ± SD. (B) Flow cytometry analysis of cell-cycle distribution of MCF7-ATMi and MCF7-ctr cells treated with the indicated concentrations of iniparib for 48 hrs. (C) DNA synthesis was measured by BrdU incorporation assay 48 hrs after iniparib treatment. Data are represented as mean ± SD. Asterisks indicate statistical significant difference (*P < 0.1; **P < 0.05).