NKX2-1 and lung adenocarcinoma: Consistent with this, IGFIR-driven tumors expressed established markers of human lung adenocarcinoma [44] including Nkx2-1 and Napsa while the expression levels of marker genes associated with lung squamous cell carcinoma (Trp63 and Krt5) or mucinous adenocarcinoma (Muc5ac, Muc5b) were either lower than normal lung tissue or unchanged (Fig 1F).