We have demonstrated that activation of the Hippo pathway in H1299RASSF1A positively correlates with upregulation of TTF‐1 and Mucin 5B in vivo and in vitro, suggesting that RASSF1A promotes differentiation of lung cancer cells, thus impairing tumour growth, metastatic progression and invasion in vivo and in vitro. The gene discussed is TTF1; the disease is lung cancer.