TTF1 and lung adenocarcinoma: The cells were positive for cytokeratin (CK) 7, CEA, and TTF-1, the biomarkers for epithelial-derived tissue and non-small-cell lung cancer (Figures 1(b)–1(d)), while 3T3-J2 cells or SPCA-1 (a lung adenocarcinoma cell line) cells were negative or positive for all these three biomarkers.