To quantify p53‐dependent transcription at individual promoters, we performed smFISH (Bertrand et al, 1998; Raj et al, 2008) in the small cell lung carcinoma cell line A549, which shows characteristic pulses of p53 in response to IR (Finzel et al, 2016; Stewart‐Ornstein & Lahav, 2017) (Appendix Fig S2A and B). This evidence concerns the gene TP53 and small cell lung carcinoma.