ATM and breast carcinoma: We did not find evidence for ATM activation downstream of mitochondrial H2O2 release in RPE1-hTERT-DAAOTOM20 cells regardless of p53 status (Fig. 3), nor in MCF7-DAAOTOM20 breast cancer cells (Supplementary Fig. 9), at levels of H2O2 production in the physiological range and far above.