title: Loss of trefoil factor 1 is regulated by DNA methylation and is an independent             predictive factor for poor survival in advanced gastric cancer.
abstract: Trefoil factor 1 (TFF1) is considered to be a tumor suppressor gene in gastric cancer. However, the role of TFF1 expression and its regulation in gastric cancer patients remain unclear. The aims of this study were to clarify the clinical significance of TFF1 and to determine its regulatory mechanisms. We assessed the immunohistochemical expression of TFF1 in 182 gastric cancer patients and examined whether or not TFF1 is associated with the clinicopathological factors and patient survival. In vitro study using TFF1 knockdown gastric cancer cells evaluated the role of TFF1 in cancer invasion. Bisulfite sequencing was performed to assess DNA methylation of TFF1 in cells and resected tissues. Patients with low expression of TFF1 showed a significantly deeper invasion of the tumor than those with high expression (p=0.037). Low expression of TFF1 was also associated with a poor survival (p=0.029) in 108 patients who were treated by surgery alone. Both TFF1 expression and lymph node metastasis are independent predictive factors for disease-specific survival in a multivariate analysis. In an in vitro study, invasive power of the cells was significantly increased in the TFF1‑deficient cells compared with the control cells. Bisulfate sequencing showed that TFF1 expression is strongly dependent on DNA methylation in both gastric cancer cells and tissues. Interestingly, methylation status of two specific CpG sites, which are located close to a TATA box and hypoxia response element (HRE), determined the TFF1 expression in the resected tissues. TFF1 expression is silenced by DNA methylation and is associated with tumor invasion and a poor survival in gastric cancer patients. The expression and̸or methylation status of TFF1 may, therefore, serve as a useful biomarker for predicting survival in patients with advanced gastric cancer.
authors.affiliation: Department of Surgery, Saga University Faculty of Medicine, Saga                     849-8501, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Tanaka
authors.forename: Jun
authors.initials: J
authors.lastname: Nakamura
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kitajima
authors.forename: Keita
authors.initials: K
authors.lastname: Kai
authors.forename: Shuusuke
authors.initials: S
authors.lastname: Miyake
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Hiraki
authors.forename: Takao
authors.initials: T
authors.lastname: Ide
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Koga
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Noshiro
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000235:genetics; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000235:genetics; D011379:Prognosis; D011401:Promoter Regions, Genetic / Q000235:genetics; D034622:RNA Interference; D034741:RNA, Small Interfering; D017422:Sequence Analysis, DNA; D013274:Stomach Neoplasms / Q000235:genetics* / Q000401:mortality* / Q000601:surgery; D013534:Survival; D016385:TATA Box / Q000235:genetics; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor; D034741:RNA, Small Interfering; C051838:TFF1 protein, human; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins