To see whether H1299RASSF1A tumours are well‐differentiated, we measured levels of TTF‐1 (thyroid transcription factor 1) and Mucin 5B, characterized markers for terminal lung differentiation (Li et al, 2012) for which expression in tumours is correlated with better prognosis and survival in lung cancer patients (Saad et al, 2004; Boggaram, 2009; Nass et al, 2018). Here, MUC5B is linked to lung cancer.