NKX2-1 and adenocarcinoma: Nkx2-1 (also called Titf1 or Ttf-1), which is essential for lung epithelial lineage determination, is frequently up- or downregulated in poorly differentiated lung adenocarcinomas.50, 51 Winslow et al.52 noticed that Nkx2-1 is frequently silenced in malignant adenocarcinomas in a KrasLSL-G12D;p53−/− mouse cancer model.