ATR and cancer: Hypoxia activation of major DDR proteins, particularly ATR and DNA‐PK, has recently been reported in various cancers, including breast cancers.[32, 62, 63] These observations perhaps explains to the failure of most reported HAPs, which predominantly focused on hypoxia release of cytoxic DNA damaging agents,[41, 64] considering that DDR mechanisms in tumor hypoxia are now known to be already activated prior treatment.