Kentaro Minegishi,1 Yoh Dobashi,2,3 Hiroyoshi Tsubochi,1 Koichi Hagiwara,4 Yuko Ishibashi,5,6 Sachiyo Nomura,7 Ritsuko Nakamura,8 Yasukazu Ohmoto,9 Shunsuke Endo1 1Department of Thoracic Surgery, Saitama Medical Center, Jichi Medical University, Saitama, Japan; 2Department of Medicine, Saitama Medical Center, Jichi Medical University, Saitama, Japan; 3Department of Pathology, School of Medicine, International University of Health and Welfare, Tochigi, Japan; 4Division of Pulmonary Medicine, Department of Medicine, Jichi Medical University, Tochigi, Japan; 5Department of Breast and Endocrine Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; 6Division of Breast Surgery, Hospital of the National Center for the Global Health and Medicine, Tokyo, Japan; 7Department of Gastrointestinal Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; 8Department of Molecular and Cellular Pathology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan; 9Tokushima University Industry-University R&D Startup Leading Institute, Tokushima, JapanCorrespondence: Yoh DobashiDepartment of Pathology, School of Medicine, International University of Health and Welfare, 537-3 Iguchi, Nasushiobara, Tochigi, 329-2763, JapanTel +81-287-37-2221Fax +81-287-39-3001Email ydobashi2@iuhw.ac.jpIntroduction: Trefoil Factor (TFF) is a member of a protein family comprised of three isoforms, of which TFF-1 exhibits antithetical functions; promotion or suppression of cell proliferation, survival and invasion, depending on the cancer type. However, the pathobiological function of TFF-1 in lung carcinoma has been still unclear.Methods: We examined the expression and secretion of TFF-1 using cultured human lung carcinoma cells by immunoblotting, immunofluorescence, enzyme-linked immunosorbent assay and quantitative real-time PCR analyses. The effects of TFF-1 on various phenotypes were analyzed in two cell lines, including those transfected with cDNA encoding TFF-1. Cell proliferation and death were examined by hemocytometer cell counting and by colorimetric viability/cytotoxicity assay. Cell cycle profile, migration and invasion were also examined by flow cytometry, wound healing assay and Matrigel Transwell assay, respectively. The effect of TFF-1 overexpression was confirmed by additional transfection of TFF-1-specific siRNA.Results: Endogenous TFF-1 protein expression and secretion into the media were observed exclusively in adenocarcinoma-derived cell lines. Forced overexpression of TFF-1 drove cell cycle transition, while the proliferation decreased by 19% to 25% due to increased cell death. This cell death was predominantly caused by apoptosis, as assessed by the activation of caspase 3/7. Cell migration was also suppressed by 71% to 82% in TFF-1-transfected cells. The suppressive effect of TFF-1 on proliferation and migration was restored by transfection of TFF-1 siRNA. Moreover, invasion was also suppressed to 77% to 83% in TFF-1-transfected cells.Conclusion: These findings reveal that TFF-1 functions as a suppressor of cancer proliferation by induction of apoptosis, cell migration and invasion and thus may provide a synergistic target for potential treatment strategies for human lung carcinoma.Keywords: TFF-1, lung carcinoma cells, growth inhibition, apoptosis, migration, invasion