NFKB1 and neoplasm: In summary, we demonstrate that ROS‐lipid peroxidation–ER stress under cytotoxic therapy establishes an AREG‐ and bFGF‐based extracellular microenvironment of dying tumour cells, which activates KAT6B‐dependent NF‐κB signalling by disrupting the balance between miR‐22 and lncRNAs in live tumour cells to promote tumour cell repopulation.