It has recently been reported that ATM-null mouse thymocytes have mitochondrial DNA damage and enhanced levels of reactive oxygen species (ROS)69 and a recent report has shown that olaparib induces ROS in bladder cancer cells.43 However, we did not see evidence of elevated ROS in either ATM-deficient cells or A549 control cells treated with olaparib, suggesting that ROS do not contribute to olaparib induced toxicity in A549 cells. Here, ATM is linked to urinary bladder carcinoma.