The Prognostic Value of TTF-1/NKX2-1 in Lung Squamous Cell Carcinoma

Background: TTF-1/NKX2-1 is a lineage-specific transcription factor that is expressed in the thyroid gland, lung, and forehead. It functions as a key component in regulating lung morphogenesis and differentiation. It is mainly expressed in lung adenocarcinoma, while its prognostic value in non-small-cell lung cancer remains controversial. This study evaluates the prognostic value of TTF-1 in different cellular locations in lung squamous cell carcinoma (SCC) and adenocarcinoma (ADC). Materials and Methods: The expression of TTF-1 was analyzed by immunohistochemistry in 492 patients (ADC 340 and SCC 152) who had undergone surgery between June 2004 and June 2012. Disease-free survival (DFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Results: Positive TTF-1 expression was 68.2% in ADC (located in the nucleus) and 29.6% in SCC (cytoplasm staining). The presence of TTF-1 was associated with better OS in SCC and ADC (P=0.000 and P=0.003, respectively). In SCC, an increased level of TTF-1 was associated with a longer disease-free survival (DFS). Positive TTF-1 expression was an independent favorable prognostic factor in SCC (P=0.020, HR: 2.789, 95%CI: 1.172–6.637) and ADC (P=0.025, HR: 1.680, 95%CI: 1.069–2.641). Conclusions: TTF-1 was largely located in the nucleus of ADC, while it always accumulated in the cytoplasm of SCC. The higher level of TTF-1 in the different subcellular locations of ADC and SCC was an independent, favorable prognostic factor, respectively. Increased TTF-1 in the cytoplasm of SCC was associated with a longer OS and DFS.