ATR and breast cancer: To test this hypothesis, we inhibited DNA2 with the specific DNA2 inhibitor C5 (Liu et al, 2016) and/or blocked ATR activation with the ATR inhibitor VE‐821 in several commonly used aggressive cancers cell lines such as MCF7 (breast cancer; Fig 7A–C), and HCT‐116 (colorectal cancer) and H460 (non‐small‐cell lung cancer; Fig 7D and E).