Trefoil factor 3 as a novel biomarker to distinguish between adenocarcinoma and squamous cell carcinoma

In carcinoma, such as of the lung, the histological subtype is important to select an appropriate therapeutic strategy for patients. However, carcinomas with poor differentiation cannot always be distinguished on the basis of morphology alone nor on clinical findings. Hence, delineation of poorly differentiated adenocarcinoma and squamous cell carcinoma, the 2 most common epithelial-origin carcinomas, is pivotal for selection of optimum therapy. Herein, we explored the potential utility of trefoil factor 3 (TFF3) as a biomarker for primary lung adenocarcinoma and extrapulmonary adenocarcinomas derived from different organs. We observed that 90.9% of lung adenocarcinomas were TFF3-positive, whereas no expression of TFF3 was observed in squamous cell carcinomas. The subtype of lung carcinoma was confirmed by four established biomarkers, cytokeratin 7 and thyroid transcription factor 1 for adenocarcinoma and P63 and cytokeratin 5/6 for squamous cell carcinoma. Furthermore, expression of TFF3 mRNA was observed by quantitative PCR in all of 11 human lung adenocarcinoma cell lines and highly correlated with markers of the adenocarcinomatous lineage. In contrast, little or no expression of TFF3 was observed in 4 lung squamous cell carcinoma cell lines. By use of forced expression, or siRNA-mediated depletion of TFF3, we determined that TFF3 appeared to maintain rather than promote glandular differentiation of lung carcinoma cells. In addition, TFF3 expression was also determined in adenocarcinomas from colorectum, stomach, cervix, esophagus, and larynx. Among all these extrapulmonary carcinomas, 93.7% of adenocarcinomas exhibited TFF3 positivity, whereas only 2.9% of squamous cell carcinomas were TFF3-positive. Totally, 92.9% of both pulmonary and extrapulmonary adenocarcinomas exhibited TFF3 positivity, whereas only 1.5% of squamous cell carcinomas were TFF3-positive. In conclusion, TFF3 is preferentially expressed in adenocarcinoma and may function as an additional biomarker for distinguishing adenocarcinoma from squamous cell carcinoma.