DNA hypermethylation at the pS2 promoter region is associated with early stage of stomach carcinogenesis

Self-Renewal and Cancers of the Gastric Epithelium: An Update and the Role of the Lectin TFF1 as an Antral Tumor Suppressor

In 2020, gastric cancer was the fourth leading cause of cancer deaths globally. About 90% of gastric cancers are sporadic and the vast majority are correlated with Helicobacter pylori infection; whereas familial clustering is observed in about 10% of cases. Gastric cancer is now considered to be a disease originating from dysregulated self-renewal of the gastric glands in the setting of an inflammatory environment. The human stomach contains two types of gastric units, which show bi-directional self-renewal from a complex variety of stem cells. This review focuses on recent progress concerning the characterization of the different stem cell populations and the mainly mesenchymal signals triggering their stepwise differentiation as well as the genesis of pre-cancerous lesions and carcinogenesis. Furthermore, a model is presented (Lectin-triggered Receptor Blocking Hypothesis) explaining the role of the lectin TFF1 as an antral tumor suppressor possibly regulating Lgr5⁺ antral stem cells in a paracrine or maybe autocrine fashion, with neighboring antral gland cells having a role as niche cells.

TFF-1 Functions to Suppress Multiple Phenotypes Associated with Lung Cancer Progression

Introduction

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.

TFF1 Promotes EMT-Like Changes through an Auto-Induction Mechanism

Trefoil factor 1 (TFF1) is a small secreted protein expressed in the gastrointestinal tract where, together with the other two members of its family, it plays an essential role in mucosal protection and repair against injury. The molecular mechanisms involved in the protective function of all three TFF proteins are not fully elucidated. In this paper, we investigated the role of TFF1 in epithelial to mesenchymal transition (EMT) events. The effects of TFF1 on cellular models in normoxia and/or hypoxia were evaluated by western blot, immunofluorescence, qRT-PCR and trans-well invasion assays. Luciferase reporter assays were used to assess the existence of an auto-regulatory mechanism of TFF1. The methylation status of TFF1 promoter was measured by high-resolution melting (HRM) analysis. We demonstrate a TFF1 auto-induction mechanism with the identification of a specific responsive element located between −583 and −212 bp of its promoter. Our results suggest that TFF1 can regulate its own expression in normoxic, as well as in hypoxic, conditions acting synergistically with the hypoxia-inducible factor 1 (HIF-1α) pathway. Functionally, this auto-induction mechanism seems to promote cell invasion and EMT-like modifications in vitro. Additionally, exogenously added human recombinant TFF1 protein was sufficient to observe similar effects. Together, these findings suggest that the hypoxic conditions, which can be induced by gastric injury, promote TFF1 up-regulation, strengthened by an auto-induction mechanism, and that the trefoil peptide takes part in the epithelial-mesenchymal transition events eventually triggered to repair the damage.

Prognostic Significance of Cytosolic pS2 Protein Content in Gastric Cancer

pS2, a 60-amino-acid chain peptide which is the most widespread estrogen-induced RNA messenger in MCF-7 breast cancer cells, is normally detected in the epithelium of gastric mucosa. The aims of this work were to evaluate the cytosolic pS2 content and its clinical significance in gastric carcinomas. Cytosolic pS2 levels were examined by immunoradiometric methods in 108 patients with primary gastric adenocarcinomas. The mean follow-up period was 23.3 months. The cytosolic pS2 levels of the tumors ranged widely, i.e., from 0.1 to 3217 ng/mg protein. There were no significant differences in pS2 content between tumors (mean ± standard error: 137.2±31.4 ng/mg protein) and paired adjacent mucosa samples (n=84; mean ± standard error: 249.6±32.6 ng/mg protein), nor were there any significant differences in tumoral pS2 levels with respect to clinicopathologic parameters such as patient age and sex or tumor location, stage, histologic type or grade. However, the results indicated that high intratumoral pS2 levels were significantly and independently associated with an unfavorable outcome in the overall group of patients (p=0.0266) and in patients with resectable gastric cancer (p=0.003). In conclusion, pS2 may represent a useful biological marker in gastric cancer.

Heterodimeric interaction between GKN2 and TFF1 entails synergistic antiproliferative and pro-apoptotic effects on gastric cancer cells

BACKGROUND

GKN2 and TFF1 form a heterodimer that is only generated in the mucus-secreting cells of the normal stomach. The formation of this heterodimer is frequently disrupted in gastric cancer. However, the precise roles of GKN2 alone and in the heterodimer with TFF1 as well as the contributions of GKN2 and the heterodimer to gastric carcinogenesis are poorly understood.

METHODS

Cell viability, proliferation, and apoptosis were analyzed in AGS, MKN1, MKN28, and MKN45 gastric cancer cells transfected with GKN2 and/or TFF1 using MTT, BrdU incorporation, and apoptosis assays, respectively. In addition, cell viability was examined in HFE-145 non-neoplastic gastric epithelial cells after GKN2 and/or TFF1 silencing. Furthermore, the cell cycle and the expression of cell cycle and apoptosis related proteins were assessed. The interaction between GKN2 and TFF1 was confirmed by co-immunoprecipitation. Immunohistochemistry was employed to explore TFF1 expression in 169 gastric cancer tissues.

RESULTS

Co-transfection with GKN2 and TFF1 significantly inhibited cell viability and proliferation by inducing G1/S cell cycle arrest and suppressing positive cell cycle regulators. Simultaneous knockdown of GKN2 and TFF1 in HFE-145 cells resulted in markedly increased cell viability. Moreover, the interaction of GKN2 and TFF1 promoted cell death by enhancing caspase-3/7 activity and upregulating pro-apoptotic proteins. At the mRNA level, GKN2 and TFF1 were found to be positively correlated in non-tumor and tumor samples. Immunohistochemistry revealed loss of TFF1 expression in 128 (75.73%) of 169 gastric cancers. There was a borderline-significant association between GKN2 and TFF1 protein expression in gastric cancers (P = 0.0598).

CONCLUSION

Collectively, our data demonstrated that the interaction between GKN2 and TFF1 can have synergistic antiproliferative and pro-apoptotic effects on gastric cancer.

Mouse models for gastric cancer: Matching models to biological questions

Gastric cancer is the third leading cause of cancer-related mortality worldwide. This is in part due to the asymptomatic nature of the disease, which often results in late-stage diagnosis, at which point there are limited treatment options. Even when treated successfully, gastric cancer patients have a high risk of tumor recurrence and acquired drug resistance. It is vital to gain a better understanding of the molecular mechanisms underlying gastric cancer pathogenesis to facilitate the design of new-targeted therapies that may improve patient survival. A number of chemically and genetically engineered mouse models of gastric cancer have provided significant insight into the contribution of genetic and environmental factors to disease onset and progression. This review outlines the strengths and limitations of current mouse models of gastric cancer and their relevance to the pre-clinical development of new therapeutics.

Recapitulating Human Gastric Cancer Pathogenesis: Experimental Models of Gastric Cancer

This review focuses on the various experimental models to study gastric cancer pathogenesis, with the role of genetically engineered mouse models (GEMMs) used as the major examples. We review differences in human stomach anatomy compared to the stomachs of the experimental models, including the mouse and invertebrate models such as Drosophila and C. elegans. The contribution of major signaling pathways, e.g., Notch, Hedgehog, AKT/PI3K is discussed in the context of their potential contribution to foregut tumorigenesis. We critically examine the rationale behind specific GEMMs, chemical carcinogens, dietary promoters, Helicobacter infection, and direct mutagenesis of relevant oncogenes and tumor suppressor that have been developed to study gastric cancer pathogenesis. Despite species differences, more efficient and effective models to test specific genes and pathways disrupted in human gastric carcinogenesis have yet to emerge. As we better understand these species differences, "humanized" versions of mouse models will more closely approximate human gastric cancer pathogenesis. Towards that end, epigenetic marks on chromatin, the gut microbiota, and ways of manipulating the immune system will likely move center stage, permitting greater overlap between rodent and human cancer phenotypes thus providing a unified progression model.

Promoter hypermethylation and downregulation of trefoil factor 2 in human gastric cancer

Trefoil factor 2 (TFF2) plays a protective role in gastric mucosa and may be involved in the progression of gastric cancer, but the detailed functions and underlying molecular mechanisms are not clear. The present study used a combination of clinical observations and molecular methods to investigate the correlation between abnormal expression of TFF2 and gastric cancer progression. TFF2 expression was evaluated by reverse transcription polymerase chain reaction (RT-PCR), quantitative PCR (qPCR), and western blot and immunohistochemistry analyses. TFF2 methylation levels were analyzed by genomic bisulfite sequencing method. The results showed that TFF2 mRNA and protein expression were decreased in gastric cancer tissues compared with the matched non-cancerous mucosa, and the decreased level was associated with the differentiation and invasion of gastric cancer. Moreover, the average TFF2 methylation level of CpG sites in the promoter region was 70.4% in three gastric cancer tissues, while the level in associated non-neoplastic tissues was 41.0%. Furthermore, the promoter hypermethylation of TFF2 was also found in gastric cancer cell lines, AGS and N87, and gene expression was significantly increased following treatment with a demethylating agent, 5-Aza-2′-deoxycytidine. In conclusion, TFF2 expression was markedly decreased in gastric cancer and promoter hypermethylation was found to regulate the downregulation of TFF2. TFF2 has been suggested as a tumor suppressor in gastric carcinogenesis and metastasis.

miRNA423-5p regulates cell proliferation and invasion by targeting trefoil factor 1 in gastric cancer cells

TFF1 is a small, secreted protein in the TFF family that has a pivotal role as a motogenic factor in epithelial restitution and cell motility, and as a tumor suppressor gene in the stomach. In this study, we identified TFF1 as a novel target gene of miRNA-423-5p. miRNA-423-5p negatively regulated the expression of TFF1 by binding to its 3'UTR and participated in proliferation/invasion-related processes via a TFF1-dependent manner in gastric cancer cells. Our findings suggested that miR-423-5p may be a novel target for the future development of specific therapeutic interventions for gastric cancer.

DNA methylation of trefoil factor 1 (TFF1) is associated with the tumorigenesis of gastric carcinoma

Trefoil factor 1 (TFF1) is a tumor suppressor gene that encodes a peptide belonging to the trefoil factor family of protease‑resistant peptides. Although TFF1 expression is frequently lost in gastric carcinomas (GCs), the tumorigenic pathways that are affected have yet to be determined. The aim of the current study was to identify the mechanism(s) by which the TFF1 gene is regulated in gastric carcinogenesis. In this study, TFF1 was shown to be silenced or downregulated in gastric tumor tissue compared with matched non‑cancerous tissue. In addition, human gastric cells weakly expressed TFF1. The hypermethylation status in the promoter CpG islands appeared to be correlated with TFF1 expression levels in gastric cell lines or specimen tissue. Further molecular analysis indicated that the CpG islands play a role in the promoter activity of the TFF1 gene. The expression of TFF1 and DNA methylation of its promoter affected cell proliferation and apoptosis. The expression of TFF1 in gastric cell lines was restored with a demethylating agent, 5‑azacytidine. Low expression of TFF1 in gastric cell lines and cancer tissue is associated with TP 53. In conclusion, the current study demonstrates that DNA methylation is a key mechanism of silencing TFF1 expression in human gastric cells and TFF1 gene hypermethylation of the CpG islands is a potential biomarker for GC.

Activation of the NF-kB pathway downregulates TFF-1 in gastric carcinogenesis

Trefoil factor 1 (TFF1) is expressed in the normal superficial epithelium of the stomach and is implicated in the maintenance of gastric epithelial structure and function. During gastric carcinogenesis, in which pro-inflammatory cytokines play a crucial role, its expression level decreases suggesting a role as tumor suppressor factor. We have compared expression of TFF1 in gastric mucosa from cancer patients, in which several degrees of inflammatory infiltrate are present, with that in normal mucosa from non-cancer patients without infiltrating inflammatory cells. TFF1 is less expressed in the superficial gastric epithelium from cancer patients than in that from normal individuals in which the nuclear factor (NF)-κB pathway is not activated. We analyzed TFF1 expression in ex vivo samples of gastric mucosa from cancer patients, and in MKN45 gastric cancer cell line after exposure to proinflammatory cytokines interleukin (IL)-1β or tumor necrosis factor (TNF)-α, that activate the NF-κB pathway. We found that IL-1β and TNF-α activate the NF-κB pathway, as reflected in the nuclear expression of p65 and the activation of p-IκBα, and downregulate TFF1 expression after 1 or 2 h of exposure. Moreover, cells in the superficial gastric epithelium in ex vivo samples co-expressed TFF1/p65 at cellular level, whereas tumor cells did not. In summary, downregulation of TFF1 expression during gastric neoplastic transformation is associated with activation of the NF-κB pathway through IL-1β or TNF-α, but other regulatory mechanisms might also be involved.

Mouse models of gastric cancer

Animal models have greatly enriched our understanding of the molecular mechanisms of numerous types of cancers. Gastric cancer is one of the most common cancers worldwide, with a poor prognosis and high incidence of drug-resistance. However, most inbred strains of mice have proven resistant to gastric carcinogenesis. To establish useful models which mimic human gastric cancer phenotypes, investigators have utilized animals infected with Helicobacter species and treated with carcinogens. In addition, by exploiting genetic engineering, a variety of transgenic and knockout mouse models of gastric cancer have emerged, such as INS-GAS mice and TFF1 knockout mice. Investigators have used the combination of carcinogens and gene alteration to accelerate gastric cancer development, but rarely do mouse models show an aggressive and metastatic gastric cancer phenotype that could be relevant to preclinical studies, which may require more specific targeting of gastric progenitor cells. Here, we review current gastric carcinogenesis mouse models and provide our future perspectives on this field.

Gastric cancer: basic aspects

Gastric cancer (GC) is a world health burden, ranging as the second cause of cancer death worldwide. Etiologically, GC arises not only from the combined effects of environmental factors and susceptible genetic variants but also from the accumulation of genetic and epigenetic alterations. In the last years, molecular oncobiology studies brought to light a number of genes that are implicated in gastric carcinogenesis. This review is intended to focus on the recently described basic aspects that play key roles in the process of gastric carcinogenesis. Genetic variants of the genes IL-10, IL-17, MUC1, MUC6, DNMT3B, SMAD4, and SERPINE1 have been reported to modify the risk of developing GC. Several genes have been newly associated with gastric carcinogenesis, both through oncogenic activation (GSK3β, CD133, DSC2, P-Cadherin, CDH17, CD168, CD44, metalloproteinases MMP7 and MMP11, and a subset of miRNAs) and through tumor suppressor gene inactivation mechanisms (TFF1, PDX1, BCL2L10, XRCC, psiTPTE-HERV, HAI-2, GRIK2, and RUNX3). It also addressed the role of the inflammatory mediator cyclooxygenase-2 (COX-2) in the process of gastric carcinogenesis and its importance as a potential molecular target for therapy.

Loss of TFF1 is associated with activation of NF-κB-mediated inflammation and gastric neoplasia in mice and humans

Trefoil factor 1 (TFF1) is a tumor suppressor gene that encodes a peptide belonging to the trefoil factor family of protease-resistant peptides. Although TFF1 expression is frequently lost in gastric carcinomas, the tumorigenic pathways this affects have not been determined. Here we show that Tff1-knockout mice exhibit age-dependent carcinogenic histological changes in the pyloric antrum of the gastric mucosa, progressing from gastritis to hyperplasia, low-grade dysplasia, high-grade dysplasia, and ultimately malignant adenocarcinoma. The histology and molecular signatures of gastric lesions in the Tff1-knockout mice were consistent with an inflammatory phenotype. In vivo, ex-vivo, and in vitro studies showed that TFF1 expression suppressed TNF-α-mediated NF-κB activation through the TNF receptor 1 (TNFR1)/IκB kinase (IKK) pathway. Consistent with these mouse data, human gastric tissue samples displayed a progressive decrease in TFF1 expression and an increase in NF-κB activation along the multi-step carcinogenesis cascade. Collectively, these results provide evidence that loss of TFF1 leads to activation of IKK complex-regulated NF-κB transcription factors and is an important event in shaping the NF-κB-mediated inflammatory response during the progression to gastric tumorigenesis.

The trefoil factor interacting protein TFIZ1 binds the trefoil protein TFF1 preferentially in normal gastric mucosal cells but the co-expression of these proteins is deregulated in gastric cancer

The gastric tumour suppressor trefoil protein TFF1 is present as a covalently bound heterodimer with a previously uncharacterised protein, TFIZ1, in normal human gastric mucosa. The purpose of this research was firstly to examine the molecular forms of TFIZ1 present, secondly to determine if TFIZ1 binds other proteins apart form TFF1 in vivo, thirdly to investigate if TFIZ1 and TFF1 are co-regulated in normal gastric mucosa and fourthly to determine if their co-regulation is maintained or disrupted in gastric cancer. We demonstrate that almost all human TFIZ1 is present as a heterodimer with TFF1 and that TFIZ1 is not bound to either of the other two trefoil proteins, TFF2 and TFF3. TFIZ1 and TFF1 are co-expressed by the surface mucus secretory cells throughout the stomach and the molecular forms of each protein are affected by the relative abundance of the other. TFIZ1 expression is lost consistently, early and permanently in gastric tumour cells. In contrast, TFF1 is sometimes expressed in the absence of TFIZ1 in gastric cancer cells and this expression is associated with metastasis (lymph node involvement: p = 0.007). In conclusion, formation of the heterodimer between TFIZ1 and TFF1 is a specific interaction that occurs uniquely in the mucus secretory cells of the stomach, co-expression of the two proteins is disrupted in gastric cancer and expression of TFF1 in the absence of TFIZ1 is associated with a more invasive and metastatic phenotype. This indicates that TFF1 expression in the absence of TFIZ1 expression has potentially deleterious consequences in gastric cancer.

Decreased expression of gastrokine 1 and the trefoil factor interacting protein TFIZ1/GKN2 in gastric cancer: influence of tumor histology and relationship to prognosis

PURPOSE

Transcriptional profiling showed decreased expression of gastrokine 1 (GKN1) and the related trefoil factor interacting protein (TFIZ1/GKN2) in Helicobacter pylori infection. Decreased GKN1 and GKN2 mRNA expression has been reported in gastric adenocarcinoma. We have examined GKN1 and GKN2 protein expression in a large gastric cancer series, correlated expression with tumor subtype, and evaluated their utility as prognostic biomarkers.

EXPERIMENTAL DESIGN

GKN1, GKN2, and the trefoil factors TFF1 and TFF3 were examined in tissue microarrays from 155 distal gastric adenocarcinomas. Immunohistochemical expression was correlated with clinical outcome. GKN1 and GKN2 expression was measured by real-time PCR and Western analysis in samples of gastric cancer and adjacent nonneoplastic mucosa.

RESULTS

GKN1 was lost in 78% of diffuse and 42% of intestinal cancers (P < 0.0001, diffuse versus intestinal). GKN2 expression was lost in 85% of diffuse and 54% of intestinal type cancers (P < 0.002). GKN1 and GKN2 down-regulation were confirmed by Western and real-time PCR analysis. Loss of either protein was associated with significantly worse outcome in intestinal-type tumors by univariate analysis; and GKN2 loss remained a predictor of poor outcome in multivariate analysis (P < 0.033). TFF1 was lost in >70%, and TFF3 was expressed in approximately 50% of gastric cancers.

CONCLUSIONS

Loss of GKN1 and GKN2 expression occurs frequently in gastric adenocarcinomas, especially in the diffuse subtype. GKN1 and GKN2 loss are associated with shorter overall survival in the intestinal subtype.

Epigenetic modification and gastrointestinal tumor

Carcinogenesis springs from the combined forces of both genetic and epigenetic events. The role of epigenetic modification in the progression of carcinoma has been suggested by a lot of evidences in recent years. An epigenetic event alters the activity of genes without changing their structure. Gastrointestinal tumor is the most common cancer in China, and the investigation of epigenetic modification is significant in cell immunity, phylaxis, cell differentiation and preventive therapy.

Trefoil factor family-1 mutations enhance gastric cancer cell invasion through distinct signaling pathways

BACKGROUND & AIMS

Trefoil factor family-1 (TFF1) is a key gastric tumor-suppressor gene. TFF1 knockout mice develop multiple gastric adenomas and carcinomas, and human gastric cancers typically lack TFF1 expression. Recently, TFF1 mutations have been found in human gastric cancer. The purpose of this study was to determine the functionality of these mutants.

METHODS

Recombinant wild-type TFF1 and the gastric cancer-associated TFF1 mutants (A10D and E13K) were produced and tested for their effect on gastric cancer cell proliferation, apoptosis, and invasion. Molecular modeling was used to guide the choice of mutants and to evaluate structure-function relationships.

RESULTS

Molecular modeling suggested that A10D and E13K altered the surface charge of the loop 1 region of TFF1 without disturbing protein stability. Recombinant wild-type TFF1 significantly inhibited cell growth; A10D and E13K lost this tumor-suppressive property along with the ability to block etoposide-induced apoptosis. Although wild-type TFF1 promoted cell invasion, A10D and E13K were even more pro-invasive. Invasion induced by both mutants was blocked by inhibiting PI3-kinase or phospholipase-C, but inhibiting Rho-associated kinase (ROCK) blocked only E13K-induced invasion.

CONCLUSIONS

The loss of tumor-suppressor activity and gain of invasiveness from single point mutations constitute evidence for a functional role of TFF1 mutations in gastric cancer. These site-directed mutagenesis experiments provide the tools for continued probing of signal transduction mechanisms and structural elements responsible for TFF1 functions.

Cofactor of BRCA1: A Novel Transcription Factor Regulator in Upper Gastrointestinal Adenocarcinomas

Cofactor of BRCA1 (COBRA1) is a newly characterized member of the negative elongation factor (NELF) complex. In this work, we show that COBRA1 is overexpressed in the majority of primary upper gastrointestinal adenocarcinomas (UGC), and its overexpression correlates with down-regulation of TFF1. We have detected overexpression of COBRA1 mRNA using quantitative real-time reverse transcription-PCR in 28 (79%) primary UGCs. Immunohistochemical analysis of UGC tissue arrays that contained 70 tumor samples showed moderate-strong staining for COBRA1 in 60 (84%) tumors. Interestingly, the tumor samples showed absent-weak staining for TFF1 in 45 (65%) of the tumors. Simultaneous loss of TFF1 expression and overexpression of COBRA1 was observed in 42 of 70 (60%) tumors. Using small interfering RNA technology with gastric cancer cells, we have shown that COBRA1 inhibition leads to increased TFF1 promoter activity and gene expression. Promoter analysis of TFF1 indicated that regulation of TFF1 by COBRA1 is estrogen independent in contrast to breast cancer. Moreover, COBRA1 regulation of TFF1 in gastric cancer cells was independent of NELF-E. Using several truncated mutants and site mutants of the TFF1 promoter, we have shown that COBRA1 can negatively regulate the activator protein-1 (AP-1) complex at the TFF1 promoter and thus down-regulate TFF1 expression in gastric cancer cell lines. Electrophoretic mobility shift assay showed that COBRA1 attenuates AP-1 binding to DNA. Our results suggest COBRA1 as a novel oncogene in UGCs that regulate AP-1 binding and the expression of TFF1 in upper gastric epithelia.

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Altered expression of TFF-1 and CES-2 in Barrett's Esophagus and associated adenocarcinomas

Identification of biomarkers to recognize individuals with Barrett's esophagus (BE) predisposed to develop malignancy is currently a pressing issue. We utilized gene expression profiling to compare molecular signatures of normal esophagus and stomach, BE, and adenocarcinoma (AC) to identify such potential biomarkers. Over 22,000 genes were analyzed by oligonucleotide microarrays on 38 unique RNA Unsupervised and supervised clusterings were performed on a subset of 2849 genes that varied most significantly across the specimens. Immunohistochemistry (IHC) for two of the significantly differentially expressed gene products was performed on tissue microarrays. Unsupervised clustering identified two discernable molecular BE profiles, one of which was similar to normal gastric tissue ("BE1"), and another that was shared by several of the AC specimens ("BE2"). The BE1 profile included expression of several genes that have been described as tumor-suppressor genes, most notably trefoil factor 1 (TFF-1). The BE2 profile included expression of genes previously found overexpressed in cancers, such as carboxylesterase-2 (CES-2). IHC demonstrated the loss of TFF-1 late in the progression of BE to AC. It also revealed CES-2 as being upregulated in AC documented to have arisen in the presence of BE. These potential biomarkers, as well as the relative expression of genes from BE1 versus those from BE2, may be validated in the future to aid in risk stratification and guide treatment protocols in patients with BE and associated AC.

Persistent trefoil factor 1 expression imprinted on mouse vaginal epithelium by neonatal estrogenization

Exposure of female mice to estrogenic substances during the neonatal period induces developmental defects in the reproductive tract such as estrogen-independent persistent proliferation of the vaginal epithelium, which often leads to carcinogenesis in adulthood. In this study, several estrogen-regulated genes have been identified in the neonatal mouse vagina by DNA microarray hybridization analysis. Among the genes up-regulated in the developing vagina by a high dose of estrogen, trefoil factor 1 (TFF1), a mucin-associated gastrointestinal growth factor, showed a unique expression pattern in accordance with the irreversible changes induced by neonatal estrogenization in the vagina. Vaginal expression of TFF1 mRNA was markedly increased by estrogen in neonatal mice but not in adults, and pronouncedly intensified expression of the gastrointestinal gene was observed in the vagina of neonatally estrogenized mice even at adulthood. The specific localization of TFF1 protein in the epithelium of neonatally estrogenized vagina was confirmed by immunohistochemistry. Moreover, without any obvious alteration in the expression of gel-forming mucin genes, the lumen of the neonatally estrogenized vagina became filled with periodic-acid-Schiff-stained mucinous gel, which was possibly caused by the overexpression of TFF1. Thus, estrogen acts directly on the developing vagina in the permanent induction of TFF1 gene expression, and the gene induction does not appear to be related to hypermethylation of the cis-promoter of the TFF1 gene. TFF1 may be a useful marker for developmental estrogenization syndrome of the mouse vagina.

Gene Expression Profiling to Identify Oncogenic Determinants of Autocrine Human Growth Hormone in Human Mammary Carcinoma

We have exploited a discrepancy in the oncogenic potential of autocrine and exogenous human growth hormone (hGH) in an attempt to identify molecules that could potentially be involved in oncogenic transformation of the human mammary epithelial cell. Microarray analysis of 19,000 human genes identified a subset of 305 genes in a human mammary carcinoma cell line that were remarkably different in their response to autocrine and exogenous hGH. Autocrine and exogenous hGH also regulated 167 common genes. Semiquantitative reverse transcription-PCR confirmed differential regulation of genes by either autocrine or exogenous hGH. Functional analysis of one of the identified autocrine hGH-regulated genes, TFF3, determined that its expression is sufficient to support anchorage-independent growth of human mammary carcinoma cells. Small interfering RNA-mediated knockdown of TFF3 concordantly abrogated anchorage-independent growth of mammary carcinoma cells and abrogated the ability of autocrine hGH to stimulate oncogenic transformation of immortalized human mammary epithelial cells. Further functional characterization of the identified subset of specifically autocrine hGH regulated genes will delineate additional novel oncogenes for the human mammary epithelial cell.

Transcriptional repression of TFF1 in gastric epithelial cells by CCAAT/enhancer binding protein-beta

TFF1 is a member of a unique family of gastrointestinal peptides. Loss of TFF1 expression has been observed in the majority of human gastric cancers and the biological significance of this loss has been demonstrated in a Tff1 knockout mouse model. However, few TFF1 gene mutations or allelic loss have also been documented. To understand the molecular mechanism repressing the TFF1 gene expression, the 5'-flanking region of the human TFF1 gene was characterized. We found a repressor region (-241 to -84), which is active in MKN45 and IMGE5 cells expressing endogenous TFF1 gene. A consensus binding site for C/EBPbeta was identified and EMSA analysis demonstrated specific binding of CEBPbeta. Mutation of this C/EBPbeta element potentiated the transactivation of TFF1 by 50% and 145% for MKN45 and IMGE5 cells respectively. Furthermore, co-transfection of C/EBPbeta isoforms specifically decreased TFF1 promoter activity. These findings suggest that C/EBPbeta is involved in the down-regulating of TFF1 gene expression and this mode of repression may account at least in part for the loss of TFF1 gene expression in transformed human and mice gastric epithelial cells.

Interaction between TFF1, a Gastric Tumor Suppressor Trefoil Protein, and TFIZ1, a Brichos Domain-Containing Protein with Homology to SP-C

TFF1 is a gastric tumor suppressor that protects gastric epithelial cells from damage but can promote invasive properties of tumor cells. Antibodies were raised against correctly folded TFF1 protein. These showed that the 6.67 kDa secreted trefoil protein is present as an approximately 25 kDa complex in normal human gastric mucosa. The TFF1 complex was immunopurified from human gastric mucosa and shown to comprise two proteins joined by a disulfide bond. Both were identified by amino-terminal sequencing and MALDI TOF mass spectrometry. The TFF1 protein partner is a previously unknown protein that we have called TFIZ1 for trefoil factor interactions(z) 1. TFIZ1 is expressed and secreted in normal gastric mucosa. TFIZ1 mRNA was cloned from gastric mucosa and sequenced. TFIZ1 is an 18.31 kDa protein and contains an approximately 100 amino acid brichos domain and homology with smart00019.10, SF_P. This is the first demonstration that a member of the trefoil factor family of proteins is bound covalently to a brichos domain-containing protein. The apparent molecular mass of the TFF1:TFIZ1 heterodimer is remarkably close to the theoretical molecular mass of 24.98 kDa. In conclusion, the heterodimer comprises one molecule each of TFF1 and TFIZ1, and the disulfide bond between TFF1 and TFIZ1 is the most important factor stabilizing the heterodimer.

Anti-sense trefoil factor family-3 (intestinal trefoil factor) inhibits cell growth and induces chemosensitivity to adriamycin in human gastric cancer cells

Intestinal trefoil factor (ITF), which is normally absent in gastric mucosa, is over-expressed in gastric cancer. However, the functional significance of ITF in gastric cancer is unknown. We examined the effects of blocking ITF expression on the growth of gastric cancer cells and their responses to chemotherapeutic agents. Anti-sense ITF cDNA was cloned into mammalian expression vector pcDNA3 and was transfected into an ITF-expressing gastric cancer cell line SNU-1. We assessed the doubling time and anchorage dependent growth of the transfected cells using growth curve and soft agar assay respectively. Cell cycle analysis and apoptosis were determined by flow cytometry and cell death ELISA. The response to chemotherapeutic agents after transfecting anti-sense ITF was also examined. Anti-sense ITF transfectant (3A-5) had a significantly longer doubling time as compared to control cells which were transfected with empty vector (32.4 hr vs 26.9 hr, p < 0.05). In the soft agar assay, 3A-5 formed fewer colonies than control (3.5 colonies vs 23.5 colonies, p < 0.05). Although there was no significant difference in the cell cycle distribution between 3A-5 and control, anti-sense ITF resulted in marked increase in adriamycin-induced apoptosis. Our results demonstrated that blocking the expression of ITF inhibits growth of gastric cancer cells and enhances the response to chemotherapy.

Trefoil factor family-3 is associated with aggressive behavior of colon cancer cells

BACKGROUND AND AIM

Trefoil factor family 3 (TFF3) is expressed by intestinal epithelial cells and it mainly functions to protect the mucosa from injury. Expression of TFF3 has been correlated with a poor prognosis in patients with cancer, but little is known about whether TFF3 directly contributes to the malignant behavior of cancer cells. The present study was conducted to determine whether TFF3 expression contributes to the malignant behavior of cancer cells in vitro and in vivo.

METHODS

Two subclones of a metastatic rat colorectal cancer cell line, demonstrated previously to manifest aggressive (LN cells) and non-aggressive (LP cells) growth in vivo, were analyzed for expression of TFF3 and tested in assays of cancer cell migration, invasion, and apoptosis in vitro, and mortality in vivo.

RESULTS

The aggressive LN cell line endogenously expressed TFF3 and supported the transcription of a TFF3 promoter-driven reporter construct, whereas the non-aggressive LP cell line did not express TFF3. LN cells demonstrated enhanced migration, invasion, and less apoptosis compared to LP cells. Transfecting TFF3 into LP cells enhanced their ability to migrate, invade, block apoptosis, and behave more aggressively in vivo, thereby resembling the phenotype of LN cells.

CONCLUSIONS

In rat colon cancer cells, both endogenous and constitutive expression of TFF3 correlates with an aggressive phenotype. These data provide direct evidence that TFF3 contributes to the malignant behavior of cancer cells.

Frequent CpG island methylation in precursor lesions and early gastric adenocarcinomas

Gastric carcinogenesis involves multiple genetic and epigenetic alterations. Epigenetic silencing of tumor-related genes due to CpG island methylation (CIM) has been recently reported in gastric cancer, but the role in precursor lesions is not well understood. We analysed the methylation status of the tumor suppressor gene p16, the DNA mismatch repair gene hMLH1, and four CpG islands (MINT1, MINT2, MINT25, and MINT31) using methylation-specific polymerase chain reaction in 35 polypoid adenomas and 46 flat dysplasias unassociated with carcinoma, 34 early adenocarcinomas (T1N0M0) and associated adenomas/dysplasias, and corresponding adjacent non-neoplastic mucosa. The extent of CIM was defined by the fraction of methylated loci (methylation index), and compared with previously characterized genetic alterations (microsatellite instability (MSI) and APC gene mutation). We found that methylation of p16 was more frequent in adenocarcinoma-associated dysplasias/adenomas (29%) and adenocarcinomas (44%) as compared to flat dysplasias (4%) and adenomas (18%) unassociated with adenocarcinoma (P=0.001). The mean methylation index increased from normal/chronic gastritis (CG) mucosa (0.09) to intestinal metaplasia (IM) (0.16), flat dysplasias (0.40) or polypoid adenomas (0.41) unassociated with carcinoma, dysplasias/adenomas associated with carcinoma (0.44), and adenocarcinomas (0.44). There was no difference in frequencies of high-level CpG island methylation (CIM-H, methylation index > or =0.5) among flat dysplasias (50%) and polypoid adenomas (51%) unassociated with carcinoma, dysplasias/adenomas associated with adenocarcinoma (47%), and adenocarcinoma (47%). CIM-H was present in 15% of IM, but not in normal/CG mucosa. There was a significant correlation between methylation of hMLH1 and high-level of microsatellite instability (MSI-H): methylation of hMLH1 was present in 71% of MSI-H tumors, but only 8% of MSI-low tumors and 13% of microsatellite-stable tumors (P=0.0001). There was no statistical difference between methylation index and APC mutation. Our results indicate that concurrent promoter methylation is an early and frequent event in gastric tumorigenesis, including both MSI-H and microsatellite-stable neoplasms. Methylation of the p16 gene may contribute to the malignant transformation of gastric precursor lesions.

Trefoil factor family (TFF) peptides and cancer progression

TFF peptides are involved in mucosal maintenance and repair through motogenic and antiapoptotic activities. These peptides are overexpressed during inflammatory processes and cancer progression. They also function as scatter factors, proinvasive and angiogenic agents. Such a divergence is related to the pathophysiological state of tissues submitted to persistent aggressive situations during digestive processes in the normal gastrointestinal tract, inflammatory and neoplastic diseases. In agreement with this model, TFF peptides are connected with multiple oncogenic pathways. As a consequence, the TFF signaling pathways may serve as potential targets in the control of chronic inflammation and progression of human solid tumors.

Expression of trefoil peptides in the subtypes of intestinal metaplasia

We studied the expression of trefoil peptides in the different types of intestinal metaplasia of the stomach. Endoscopic biopsy was performed in 132 patients with dyspepsia. Intestinal metaplasia subtype was classified according to the pattern of alcian blue/PAS staining and high iron diamine staining. Expression of trefoil peptides was measured by immunohistochemistry. TFF1 and TFF3 were mainly expressed in goblet cells and TFF2 in columnar cells in all the types of intestinal metaplasia. There was a gradual decrease of TFF1 and TFF3, and increase of TFF2, during the progression of intestinal metaplasia from type I to type III via the type II intermediate.

Urinary pS2/TFF1 levels in the management of hormonodependent breast carcinomas

pS2/TFF1 overexpression in breast carcinomas correlates with response to hormonotherapy. We evaluated the clinical relevance of urinary pS2/TFF1 in breast cancer patients. In healthy controls (100 cases), it represents an individual and relatively stable parameter. Although 24 out 83 pre-operative breast cancer patients showed elevated levels, both the sensitivity and specificity of the test were too low for breast cancer screening. However, neoadjuvant hormonotherapy decreased pS2/TFF1 levels in nine out of 20 patients. Furthermore, among 22 patients receiving long-term adjuvant hormonotherapy, four exhibited elevated levels, two of them at the time of relapse. Thus, urinary pS2/TFF1 quantification might be suitable as an in vivo diagnosis for tumor hormonodependency, and disease follow-up during hormonotherapy.

GATA-4 and GATA-5 transcription factor genes and potential downstream antitumor target genes are epigenetically silenced in colorectal and gastric cancer

The GATA family of transcription factors participates in gastrointestinal (GI) development. Increases in GATA-4 and -5 expression occur in differentiation and GATA-6 expression in proliferation in embryonic and adult settings. We now show that in colorectal cancer (CRC) and gastric cancer promoter hypermethylation and transcriptional silencing are frequent for GATA-4 and -5 but are never seen for GATA-6. Potential antitumor target genes upregulated by GATA-4 and -5, the trefoil factors, inhibinalpha, and disabled-2 (Dab2) are also silenced, in GI cancers, with associated methylation of the promoters. Drug or genetically induced demethylation simultaneously leads to expression, in CRC cells, of all of the GATA-4, -5, and downstream genes. Expression of exogenous GATA-5 overrides methylation at the downstream promoters to activate the target genes. Selection for silencing of both upstream transcription factors and their target genes in GI cancers could indicate that epigenetic silencing of the involved genes provides a summated contribution to tumor progression.

Decreased abundance of trefoil factor 1 transcript in the majority of gastric carcinomas

BACKGROUND

Gastric carcinoma is one of the leading causes of cancer-related death worldwide, but the mechanisms underlying its development and progression still remain largely uncharacterized. As loss of trefoil factor 1 (TFF1) expression leads to neoplastic growth in the antropyloric mucosa of mice, the authors sought to comprehensively study the human TFF1 gene in primary gastric carcinomas.

METHODS

The authors studied the human TFF1 gene in primary gastric carcinomas and normal gastric mucosa at the DNA, RNA, and protein levels through DNA sequencing, quantitative real-time reverse transcriptase-polymerase chain reaction, and immunohistochemistry.

RESULTS

Strikingly, TFF1 mRNA expression was significantly decreased in all 37 gastric carcinomas studied compared with normal gastric mucosa. Furthermore, six tumor/normal pairs with available histologic samples demonstrated a marked decrease in protein expression in tumor samples. Screening of the entire TFF1 coding region in a panel of 42 human gastric tumors did not reveal any somatic mutations, although a few rare germline sequence variants were identified.

CONCLUSIONS

These findings demonstrated a significant decrease in the TFF1 transcript in the majority of human gastric carcinomas along with a corresponding reduction in protein expression, both of which occurred in the absence of gene mutation. Dysregulation of TFF1 expression at the transcript level was a critical event in the development of most gastric carcinomas.

Trefoil factors: initiators of mucosal healing

Maintaining the integrity of the gastrointestinal tract, despite the continual presence of microbial flora and injurious agents, is essential. Epithelial continuity depends on a family of small, yet abundant, secreted proteins--the trefoil factors (TFFs). TFFs protect mucous epithelia from a range of insults and contribute to mucosal repair, although the signalling events that mediate these responses are only partially understood.

Aberrant expression of trefoil factor family 1 in biliary epithelium in hepatolithiasis and cholangiocarcinoma

Stepwise progression of intrahepatic cholangiocarcinoma (ICC) has been proposed in hepatolithiasis. We examined the participation of trefoil factor family 1 (TFF1), which is critical for mucosal protection and tumor suppression in the stomach, in the development and progression of ICC. We used 16 livers of ICC with hepatolithiasis, 11 of biliary epithelial dysplasia with hepatolithiasis, 16 of hepatolithiasis without dysplasia or carcinoma, 18 of ICC without hepatolithiasis, and 39 control livers. TFF1 expression in the biliary epithelium was increased in hepatolithiasis compared with control livers (p < 0.01). In biliary epithelial dysplasia and noninvasive ICC with hepatolithiasis, TFF1 was extensively expressed and MUC5AC gastric mucin was usually colocalized with TFF1. However, TFF1 expression was significantly decreased in invasive ICC despite preserved expression of MUC5AC. A total of four missense mutations were detected: three in two noninvasive ICC with hepatolithiasis (28.6%) and one in invasive ICC (11%). Loss of heterozygosity of the TFF1 gene was not detectable. The decreased expression of TFF1 in invasive ICC may be explained by the methylation of the TFF1 promoter region. Up-regulation of TFF1 coupled with MUC5AC in biliary epithelium in hepatolithiasis, biliary epithelial dysplasia, and noninvasive ICC may reflect the gastric metaplasia and early neoplastic lesion. Under such conditions, decreased TFF1 expression may lead to increased cell proliferation and then to the invasive character of ICC.

Expression of estrogen inducing gene PS2/TFF1 in gastric cancer and precancerous lesions

AIM

To determine the significance of PS2/TFF1 protein expression in chronic superficial gastritis (CSG), gastric ulcer (GU),gastric mucosal intestinal metaplasia (IM), gastric mucosal dysplasia and gastric cancer(GC).

METHODS

Pathologic specimens of 121 patients with gastric mucosal diseases and 20 healthy volunteers were immunostained for PS2/TFF1.

RESULTS

Positive PS2/TFF1 staining was seen throughout all epithelia with normal gastric mucosas, CSG, GU and in complete type of intestinal metaplasia (20/21). On the contrary, 11 of 20 incomplete type of intestinal metaplasia had positive staining (P <0.01). The expressions of PS2/TFF1 protein in CSG and GU were significantly higher than that in control group (P <0.01), while the expressions of PS2/TFF1 protein in IM,gastric mucosal dysplasia and GC were obviously lower than that in control group (P <0.01).

CONCLUSION

Our results indicate that PS2/TFF1 may play an important role in gastric mucosal protection,and loss of PS2/TFF1 expression may occur as an early event in the malignant transformation process of intestinal-type tumors.

The development of CpG island methylation biomarkers using restriction landmark genomic scanning

CpG island hypermethylation is a common occurrence in cancer. Because this is a stable molecular alteration of the DNA, which can be detected easily from very small amounts, DNA methylation is an attractive candidate to use as a molecular biomarker. Recent studies have used DNA methylation of genes known to be targets of genetic disruption in cancer as biomarkers for early detection of cancer, classification of malignancies, response to drug treatment, and as markers predictive of outcome. Since many of the currently used targets of methylation are methylated at rather low frequencies in various cancer types even though the gene may be frequently disrupted by other mechanisms, it would be useful to develop additional markers that are methylated at high frequency in the cancer being studied. Restriction landmark genomic scanning has been used for the identification of frequent targets of methylation in multiple malignancies. These markers, which can be either cancer type-specific or nonspecific, may prove to be effective biomarkers for diagnostic or prognostic purposes, or for midpoint analysis of intervention strategies.

DNA methylation markers in patients with gastrointestinal cancers. Current understanding, potential applications for disease management and development of diagnostic tools

DNA methylation, the modification of a cytosine nucleotide immediately preceding a guanine base in a stretch of DNA, is rapidly gaining strength in the diagnostic field as a powerful tool to be utilized for the discrimination of neoplastic tissue from its healthy counterpart. This epigenetic modification occurs often in the promoter region of genes and is associated with transcriptional silencing of tumor suppressors or other genes important for normal cellular function. These changes have been found to occur at very early stages in the progression of healthy to malignant phenotype in many cancer types. We are taking a targeted approach to finding methylation-based markers that can be used not only for the early detection of cancer but also for determining risk, monitoring patient response to therapy and even determining the degree of aggressiveness of a tumor. In this paper, we review the progress in our understanding of methylation in gastrointestinal tumors, the potential clinical applications of methylation-based markers and our process for the discovery and validation of highly specific and sensitive markers for the use in these applications.

Loss of heterozygosity and promoter methylation, but not mutation, may underlie loss of TFF1 in gastric carcinoma

It has been advanced that the trefoil factor (TFF) 1 gene is a candidate tumor-suppressor gene and may be involved in the development and/or progression of human gastric cancer. We aimed to clarify the putative role of TFF1 in gastric carcinogenesis. Ninety gastric carcinomas and eight gastric carcinoma-derived cell lines were screened for TFF1 mutations; subsets of the primary tumors and of the cell lines were subjected to loss of heterozygosity (LOH), immunohistochemistry, and promoter methylation analyses. TFF1 mutations were not detected in any of 90 gastric carcinomas. Eight (28%) of 28 informative cases displayed LOH at the TFF1 locus and absence of TFF1 staining by immunohistochemistry. These results indicate a frequent loss of TFF1 expression in gastric carcinomas through a mutation-independent mechanism. Extensive TFF1 promoter methylation was observed in nonexpressing gastric carcinoma-derived cell lines and tissues. Expressing cell lines, as well as normal gastric mucosa, presented little or no methylation of the promoter. Gastric carcinoma DNA presented de novo methylation of the promoter. These results point to the involvement of promoter methylation in the shutting down of TFF1. We conclude that TFF1 point mutations seem to be a rare event in gastric carcinogenesis. The loss of expression of TFF1 in a proportion of gastric carcinomas may be explained by LOH and methylation of the TFF1 promoter region. Our results further support the role of TFF1 inactivation in gastric carcinogenesis, in agreement with the results obtained in the Tff1-knockout mice model.

The study of aberrant methylation in cancer via restriction landmark genomic scanning

Restriction landmark genomic scanning (RLGS) has been used to study DNA methylation in cancer for nearly a decade. The strong bias of RLGS for assessing the methylation state of CpG islands genome wide makes this an attractive technique to study both hypo- and hypermethylation of regions of the genome likely to harbor genes. RLGS has been used successfully to identify regions of hypomethylation, candidate tumor suppressor genes, correlations between hypermethylation events and clinical factors, and quantification of hypermethylation in a multitude of malignancies. This review will examine the major uses of RLGS in the study of aberrant methylation in cancer and discuss the significance of some of the findings.

Expression of trefoil peptides (TFF1, TFF2, and TFF3) in gastric carcinomas, intestinal metaplasia, and non-neoplastic gastric tissues

Trefoil factor family (TFF) domain peptides consist of three members that play a role in intestinal mucosal defence and repair, and in tumourigenesis. The role of the three TFF members in the gastric carcinogenesis cascade remains poorly defined. This study examined seven gastric cell lines, 50 gastric cancers and their adjacent non-cancer tissues, and tissues from 40 non-cancer patients, in order to elucidate the chronology of TFF expression in various stages of gastric carcinogenesis. TFF expression was determined by RT-PCR, immunohistochemistry, and western blot. Aberrant expression of TFF1, TFF2, and TFF3 was frequently detected in gastric cell lines. Specifically, TFF1 was detected in all non-cancer patients, but was detected in only 50% of gastric cancer and 66% of adjacent normal tissues. TFF2 expression was demonstrated in 87.5% of non-cancer patients, 34% of gastric carcinomas, and 58% of adjacent non-cancer tissues. There was a significant correlation between TFF1 and TFF2 expression in gastric cancer and adjacent non-cancer tissues (p<0.001). By contrast, TFF3 was detected in 25% of non-cancer patients and showed a predilection for areas with intestinal metaplasia (p=0.005). Sixty-two per cent of gastric cancers and 24% of neighbouring non-cancer tissues showed TFF3 expression. Immunoreactivity against TFF3 was demonstrated in goblet cells of intestinal metaplasia and within the cytoplasm and nuclei of tumour cells. Progressive loss of TFF1 and TFF2, together with the induction of TFF3, is likely to be involved in the early stage of the multi-step gastric carcinogenesis pathway.

Cell type specific expression of secretory TFF peptides: colocalization with mucins and synthesis in the brain

The "TFF domain" is an ancient cysteine-rich shuffled module forming the basic unit for the family of secretory TFF peptides (formerly P-domain peptides and trefoil factors). It is also an integral component of mosaic proteins associated with mucous surfaces. Three mammalian TFF peptides are known (i.e., TFF1-TFF3); however, in Xenopus laevis the pattern is more complex (xP1, xP4.1, xP4.2, and xP2). TFF peptides are typical secretory products of a variety of mucin-producing epithelial cells (e.g., the conjunctiva, the salivary glands, the gastrointestinal tract, the respiratory tract, and the uterus). Each TFF peptide shows an unique expression pattern and different mucin-producing cells are characterized by their specific TFF peptide/secretory mucin combinations. TFF peptides have a pivotal role in maintaining the surface integrity of mucous epithelia in vivo. They are typical constituents of mucus gels, they modulate rapid mucosal repair ("restitution") by their motogenic and their cell scattering activity, they have antiapoptotic effects, and they probably modulate inflammatory processes. Pathological expression of TFF peptides occurs as a result of chronic inflammatory diseases or certain tumors. TFF peptides are also found in the central nervous system, at least in mammals. In particular, TFF3 is synthesized from oxytocinergic neurons of the hypothalamus and is released from the posterior pituitary into the bloodstream.

Genetic susceptibility and gastric cancer risk

The aim of the present paper is to review and evaluate, in a comprehensive manner, the most recent published evidence on the contribution of genetic susceptibility to gastric cancer risk in humans. We have identified all studies available in MEDLINE published up to October 2001. Only studies carried out in humans and comparing gastric cancer cases with at least 1 standard control group were included in the analysis. We were able to find 31 articles based on 25 case-control studies carried out in Caucasian, Asian and African populations. Most of the studies assess the effect of genes involved in detoxifying pathways (n = 12) and inflammatory responses (n = 7). The most widely studied is the GSTM1 null polymorphism. Only a very few studies have evaluated the risk of gastric cancer associated with genes acting on mucosa protection, oxidative damage and DNA repair. The most consistent results are the increased gastric cancer risk associated with IL1B and NAT1 variants, which may account for up to 48% of attributable risk of gastric cancer. Only polymorphisms at HLA-DQ, TNF and CYP2E genes may confer some protective effect against gastric cancer. The most important limitations that preclude definitive conclusions are (i) the lack of appropriate control of potential sources of bias (only 5 population-based studies have been published so far); (ii) the low number of cases analyzed (14 studies included fewer than 99 cases); and (iii) the low number of studies (n = 3) offering concomitant analysis of genetic susceptibility and exposure to relevant cofactors (Helicobacter pylori infection, diet and smoking). We conclude that the scientific data on the role of genetic factors in gastric cancer risk are promising. The lack of association reported so far should be considered with caution due to significant limitations in study design. Cohort studies taking into account simultaneously the different genetic and environmental factors potentially involved in gastric tumorigenesis are needed to ascertain not only the relative contribution of these factors to tumor development but also the contribution of their putative interactions.

The trefoil factor 1 participates in gastrointestinal cell differentiation by delaying G1-S phase transition and reducing apoptosis

Trefoil factor (TFF)1 is synthesized and secreted by the normal stomach mucosa and by the gastrointestinal cells of injured tissues. The link between mouse TFF1 inactivation and the fully penetrant antropyloric tumor phenotype prompted the classification of TFF1 as a gastric tumor suppressor gene. Accordingly, altered expression, deletion, and/or mutations of the TFF1 gene are frequently observed in human gastric carcinomas. The present study was undertaken to address the nature of the cellular and molecular mechanisms targeted by TFF1 signalling. TFF1 effects were investigated in IEC18, HCT116, and AGS gastrointestinal cells treated with recombinant human TFF1, and in stably transfected HCT116 cells synthesizing constitutive or doxycycline-induced human TFF1. We observed that TFF1 triggers two types of cellular responses. On one hand, TFF1 lowers cell proliferation by delaying G1-S cell phase transition. This results from a TFF1-mediated increase in the levels of cyclin-dependent kinase inhibitors of both the INK4 and CIP subfamilies, leading to lower E2F transcriptional activity. On the other hand, TFF1 protects cells from chemical-, anchorage-free-, or Bad-induced apoptosis. In this process, TFF1 signalling targets the active form of caspase-9. Together, these results provide the first evidence of a dual antiproliferative and antiapoptotic role for TFF1. Similar paradoxical functions have been reported for tumor suppressor genes involved in cell differentiation, a function consistent with TFF1.

Trefoil factor 1 (TFF1/pS2) deficiency activates the unfolded protein response

BACKGROUND

The trefoil factor 1 (TFF1/pS2) is a secreted gastrointestinal peptide that is often altered or lost in human gastric cancers. Consistently, mouse TFF1 deficiency leads to antropyloric tumors.

MATERIALS AND METHODS

To investigate the gene expression alterations in response to the lack of TFF1, we performed differential expression analyses of TFF1 null antropyloric tumors using an array containing 588 cDNAs.

RESULTS

Using total and enriched probes, 22 genes were found to be up-regulated. The identification of the genes for endoplasmic reticulum (ER)-resident GRP78, ERp72, and p58IPK proteins connected TFF1 deficiency to the unfolded protein response (UPR). Accordingly, CHOP10, a transcription factor induced early in response to ER stress, and the pleiotropic Clusterin, involved in protein folding, were also overexpressed. Northern blot analyses of 8 weeks and 1 year TFF1 null tumors confirmed that GRP78, ERp72, p58IPK, CHOP10, and Clusterin overexpression is a common and permanent feature shared by all TFF1 null antropyloric tumors. Finally, consistent with UPR, ultrastructural analyses showed that tumor rough ER was enlarged and contained dense material, supporting the hypothesis that TFF1 deficiency leads to the accumulation of misfolded proteins in the ER.

CONCLUSION

Together, our data provide the first evidence of a relationship between a member of the TFF family and the ER machinery. Whereas to date TFF1 is believed to act as an extracellular molecule, our results suggest a possible additional function for TFF1 in protein folding and/or secretion.

[Cytosolic pS2 levels in 154 non-small-cell lung carcinomas. Correlation with other clinical and biological parameters]

INTRODUCTION

pS2 was first identified as an estrogen induced molecule in a breast cancer cell line, but its gene responds to several growth factors and oncogenic proteins. Its main clinical application lies in breast carcinomas, where it is a molecular marker to identify breast cancer patients who will respond to hormone therapy. This study was performed to evaluate the significance of the pS2 cytosolic levels in non small cell lung carcinomas classified according to different clinical and biological parameters. Likewise, the results obtained were correlated with those observed in normal tissues.

MATERIAL AND METHODS

The study group included 154 non small cell lung carcinomas (59 adenocarcinomas and 95 squamous carcinomas) and 54 normal lung samples. Cathepsin D, pS2, neuron specific enolase (NSE) and CA125 cytosolic concentrations were determined, as well as those of epidermal growth factor receptor (EGFR), erbB2 protein, CD44s, CD44v5 and CD44v6 on cell surface membranes. Likewise, clinical stage, histological grade, ploidy and cellular S-phase fraction were also considered as variables of the study.

RESULTS

We observed cytosolic pS2 values greater than 1 ng/mg protein (positive cutoff) in 18/59 adenocarcinomas and in 10/95 squamous carcinomas (p:0.00177). In adenocarcinomas, pS2 positivity was not correlated with any clinical and biological parameters, but positive cases had lower EGFR (p:0.03770) concentrations and higher CA125 (p:0.01902) levels. In squamous carcinomas, pS2 positivity was associated with lower EGFR (p:0.02270) levels and higher erbB2 protein (p:0,00563) concentrations.

CONCLUSIONS

Our results led us to suggest the following: 1) cytosolic pS2 concentrations are higher in tumoral than in normal samples; 2) adenoarcinomas had higher levels than squamous lung carcinomas; 3) in adenocarcinomas, positivity for pS2 is associated with lower EGFR levels and higher CA125 concentrations suggesting a worse outcome, and 4) in squamous lung tumors, positivity for pS2 was associated with lower EGFR and higher erbB2 oncoprotein concentrations, it not being possible to establish its clinical significance, although it may be correlated with a poor prognosis.