ATF3 and breast cancer: ▪Reduced proliferation (Ki‐67) and increased apoptosis and cell cycle arrest in a caspase 3 and 7 and treatment time‐dependent manner▪Toxicity varied between different BC cell lines▪DNA damage response induced (ATF3, EGR1, ID2)▪Histone RNA oxidation proposed to mediate gas plasma toxicity▪DNA damage is not the primary mode of BC cell death by gas plasma exposure