Characterization of a CCAAT-enhancer element of trefoil factor family 2 (TFF2) promoter in MCF-7 cells

Odyssey of trefoil factors in cancer: Diagnostic and therapeutic implications

Trefoil factors 1, 2, and 3 (TFFs) are a family of small secretory molecules involved in the protection and repair of the gastrointestinal tract (GI). TFFs maintain and restore epithelial structural integrity via transducing key signaling pathways for epithelial cell migration, proliferation, and invasion. In recent years, TFFs have emerged as key players in the pathogenesis of multiple diseases, especially cancer. Initially recognized as tumor suppressors, emerging evidence demonstrates their key role in tumor progression and metastasis, extending their actions beyond protection. However, to date, a comprehensive understanding of TFFs' mechanism of action in tumor initiation, progression and metastasis remains obscure. The present review discusses the structural, functional and mechanistic implications of all three TFF family members in tumor progression and metastasis. Also, we have garnered information from studies on their structure and expression status in different organs, along with lessons from their specific knockout in mouse models. In addition, we highlight the emerging potential of using TFFs as a biomarker to stratify tumors for better therapeutic intervention.

Differential Expression of TFF Genes and Proteins in Breast Tumors

SUMMARY – The objective of this study was to determine differential expression of TFF1, TFF2 and TFF3 genes and proteins in breast tumor subtypes. In addition, we investigated the correlation between TFF genes within tumor subgroups, and TFF genes with clinical and pathologic characteristics of the tumor. Study group included 122 patients with surgically removed breast tumors. Samples were investigated using qRT-PCR and immunohistochemistry. TFF1 and TFF3 genes and proteins were expressed in breast tumors, while the levels of TFF2 gene and protein expression were very low or undetectable. TFF1 was significantly more expressed in benign tumors, while TFF3 was more expressed in malignant tumors. Gene and protein expression of both TFF1 and TFF3 was greater in lymph node-negative tumors, hormone positive tumors, tumors with moderate levels of Ki67 expression, and in grade II tumors. A strong positive correlation was found between TFF1 and TFF3 genes, and the expression of both negatively correlated with Ki67 and the level of tumor histologic differentiation. Our results suggest that TFF1 and TFF3, but not TFF2, may have a role in breast tumor pathogenesis and could be used in the assessment of tumor differentiation and malignancy.

Trefoil factors: Gastrointestinal-specific proteins associated with gastric cancer

Trefoil factor family (TFF), composed of TFF1, TFF2, and TFF3, is a cluster of secreted peptides characterized by trefoil domain (s) and C-terminal dimerization domain. TFF1, a gastric tumor suppressor, is a single trefoil peptide originally detected in breast cancer cell lines but expressed mainly in the stomach; TFF2, a candidate of gastric cancer suppressor with two trefoil domains, is abundant in the stomach and duodenal Brunner's glands; and TFF3 is another single trefoil peptide expressed throughout the intestine which can promote the development of gastric carcinoma. According to multiple studies, TFFs play a regulatory function in the mammals' digestive system, namely in mucosal protection and epithelial cell reconstruction, tumor suppression or promotion, signal transduction and the regulation of proliferation and apoptosis. Action mechanisms of TFFs remain unresolved, but the recent demonstration of a GKN (gastrokine) 2-TFF1 heterodimer implicates structural and functional interplay with gastrokines. This review aims to encapsulate the structural and biological characteristics of TFF.

Correlation between TFF 2 expression and tumor angiogenesis in gastric carcinoma, adjacent carcinoma and normal gastric mucosa

AIM: To investigate the correlation among the expression of trefoil factor 2 (TFF2) and vascular endothelial growth factor (VEGF) and microvessel density (MVD) in gastric carcinoma.

METHODS: The expression of TFF2 and VEGF and MVD were determined by immunohistochemistry in 50 gastric carcinoma specimens, 50 tumor-adjacent gastric mucosal specimens, and 30 normal gastric mucosa specimens.

RESULTS: The expression level of TFF2 was highest in normal gastric mucosa, followed by tumor-adjacent gastric mucosa and gastric carcinoma (165.80 ± 16.42, 184.44 ± 19.02, 206.79 ± 17.62, all P < 0.01). The expression of TFF2 in gastric cancer was significantly associated with the degree of tumor differentiation and lymph node metastasis (both P < 0.01). The expression level of VEGF and MVD were lowest in normal gastric mucosa, followed by tumor-adjacent gastric mucosa and gastric carcinoma (36.7%, 42.0%, 72.6%; 26.35 ± 4.54, 30.78 ± 5.64, 40.13 ± 6.92, all P < 0.01). The expression of VEGF and MVD in gastric cancer were associated with tumor differentiation, invasion and lymph node metastasis (all P < 0.01). There is a negative correlation between the expression of TFF2 and MVD (r = -0.781, P < 0.01).

CONCLUSION: TFF2 may be a negative regulatory factor of gastric carcinogenesis. The expression of TFF2 is down-regulated during the development of gastric cancer, while that of VEGF and MVD are up-regulated during this process.

p53 inhibition of AP1-dependent TFF2 expression induces apoptosis and inhibits cell migration in gastric cancer cells

Overexpression of trefoil factor 2 (TFF2) is associated with increased cell migration, resistance to apoptosis, and possibly increased gastric cancer invasion. Dysregulation of p53 is frequently observed in preneoplastic conditions of the stomach. Here, we investigated the effect of p53 on the expression and function of TFF2 in gastric cancer cell lines. Gene expression was determined by reverse transcription-polymerase chain reaction, and promoter activity was assessed by dual luciferase reporter assays. Apoptosis was detected by flow cytometry, and cell migration was evaluated by the Boyden chamber assay. Exogenous expression of p53 dose dependently inhibited endogenous TFF2 mRNA, protein, and promoter activity and resulted in induction of cell apoptosis and inhibition of cell migration. Downregulation of TFF2 by small interfering RNA sensitized gastric cancer cells to drug-induced p53-dependent apoptosis. Addition of human TFF2 peptide reversed p53-dependent apoptosis and inhibition of cell migration. The p53-responsive element was mapped to an AP-1-like cis-element at -182 bp upstream of the TFF2 transcription start site. Mutation of this AP-1-like element abrogated p53-mediated inhibition of TFF2 promoter activity. Gel shift and chromatin immunoprecipitation assays demonstrated that c-Jun and c-Fos bind to this AP-1-like element. Ectopic expression of c-Jun/c-Fos or p300 or treatment of cells with phorbol 12-myristate 13-acetate (PMA) stimulated endogenous TFF2 mRNA expression and promoter activity, and p53 inhibited the effects of AP-1 and PMA on TFF2. p53 induces cell apoptosis and inhibits cell migration in part by downregulating TFF2 expression through an AP-1-like site, suggesting that TFF2 may be an important downstream target of p53.

Gastrin regulates the TFF2 promoter through gastrin-responsive cis-acting elements and multiple signaling pathways

Trefoil family factor 2 (TFF2) is expressed in gastrointestinal epithelial cells where it serves to maintain mucosal integrity and promote epithelial repair. The peptide hormone, gastrin, stimulates acid secretion but also induces proliferation of the acid-secreting mucosa. Because the relationship between these peptides of overlapping function is not understood, we chose to investigate the regulatory effect of gastrin on TFF2 expression. The expression of mRNA and protein of TFF2 was determined by RT-PCR and immunohistochemical staining, respectively. A series of truncated and mutant murine TFF2 promoter constructs was generated. Promoter activity was assessed using dual luciferase reporter assays. Gastrin-responsive DNA-binding sites in the TFF2 promoter were evaluated by electrophoretic mobility shift assay. Gastrin significantly increased the level of endogenous mRNA of TFF2 in the gastrin receptor-expressing AGS-E gastric cancer cell line in a time- and dose-dependent manner. TFF2 protein expression in the gastric fundus was elevated in hypergastrinemic (INS-GAS) transgenic mice and reduced in gastrin-deficient mice. Gastrin treatment increased TFF2 promoter activity through cis-acting regions, containing CCAATA- and GC-rich enhancers. Pretreatment with Y-F476, a gastrin/CCK(B) receptor antagonist, abolished gastrin-dependent promoter activity. Inhibitors of protein kinase C (PKC), mitogen/extracellular signal-regulated kinase (MEK1), and phosphatidylinositol 3-kinase (PI 3-kinase) reduced gastrin-dependent TFF2 promoter activity, whereas an epithelial growth factor receptor (EGFR) inhibitor had no effect. We found that gastrin regulates TFF2 transcription through a GC-rich DNA-binding site and a PKC-, MEK1- and PI 3-kinase-dependent but EGFR-independent pathway. Regulation of TFF2 by gastrin may play a role in the maintenance and repair of the gastrointestinal mucosa.

N/A

N/A

N/A

N/A

N/A

N/A