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

Downregulation of the Tumor Suppressor TFF1 Is Required during Induction of Colon Cancer Progression by L1

Simple Summary

Aberrant activation of Wnt/β-catenin signaling and the subsequent induction of downstream target genes is a hallmark of colorectal cancer (CRC) development. Previously, we found that overexpression of the immunoglobulin-like cell adhesion receptor L1CAM (L1), a target of the Wnt/β-catenin pathway, confers enhanced proliferation, motility, tumorigenesis, and liver metastasis in CRC cells. Transcriptomic and proteomic analyses revealed changes in both pro-tumorigenic and potential tumor-suppressor genes in L1-overexpressing CRC cells. We wished to identify such tumor suppressor/s, and found that trefoil family factor 1 (TFF1) was involved in L1-mediated CRC progression. TFF1 overexpression suppressed the growth, motility and tumorigenesis of L1-expressing CRC cells by inhibiting the NF-κB pathway. In human CRC tissue, TFF1-positive staining was evident in goblet cells of the normal mucosa, while in CRC tissue, TFF1 expression was lost in >50% of the tumor samples. Our results support a tumor-suppressor role of TFF1 in human CRC, and we suggest that TFF1 could be used for CRC detection and as a novel therapeutic target in L1-mediated CRC.

Abstract

The immunoglobulin family cell adhesion receptor L1 is induced in CRC cells at the invasive front of the tumor tissue, and confers enhanced proliferation, motility, tumorigenesis, and liver metastasis. To identify putative tumor suppressors whose expression is downregulated in L1-expressing CRC cells, we blocked the L1–ezrin–NF-κB signaling pathway and searched for genes induced under these conditions. We found that TFF1, a protein involved in protecting the mucus epithelial layer of the colon, is downregulated in L1-expressing cells and displays characteristics of a tumor suppressor. Overexpression of TFF1 in L1-transfected human CRC cells blocks the pro-tumorigenic and metastatic properties conferred by L1 by suppressing NF-κB signaling. Immunohistochemical analyses revealed that human CRC tissue samples often lose the expression of TFF1, while the normal mucosa displays TFF1 in goblet cells. Identifying TFF1 as a tumor suppressor in CRC cells could provide a novel marker for L1-mediated CRC development and a potential target for therapy.

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.

NF-kB-dependent activation of STAT3 by H. pylori is suppressed by TFF1

BACKGROUND

H. pylori infection is the main risk factor for gastric cancer. In this study, we investigated H. pylori-mediated activation of STAT3 and NF-κB in gastric cancer, using in vitro and in vivo models.

METHODS

To investigate the activation of NF-κB and STAT3 by H. pylori strains we used in vitro and in vivo mouse models, western blots, immunofluorescence, ChIP Assay, luciferase and quantitative real-time PCR assays.

RESULTS

Following infection with H. pylori in vitro, we found an earlier phosphorylation of NF-kB-p65 (S536), followed by STAT3 (Y705). Immunofluorescence, using in vitro and in vivo models, demonstrated nuclear localization of NF-kB and STAT3, following H. pylori infection. NF-kB and STAT3 luciferase reporter assays confirmed earlier activation of NF-kB followed by STAT3. In vitro and in vivo models demonstrated induction of mRNA expression of IL-6 (p < 0.001), VEGF-α (p < 0.05), IL-17 (p < 0.001), and IL-23 (p < 0.001). Using ChIP, we confirmed co-binding of both NF-kB-p65 and STAT3 on the IL6 promoter. The reconstitution of Trefoil Factor 1 (TFF1) suppressed activation of NF-kB with reduction in IL6 levels and STAT3 activity, in response to H. pylori infection. Using pharmacologic (BAY11-7082) and genetic (IκB super repressor (IκBSR)) inhibitors of NF-kB-p65, we confirmed the requirement of NF-kB-p65 for activation of STAT3, as measured by phosphorylation, transcription activity, and nuclear localization of STAT3 in in vitro and in vivo models.

CONCLUSION

Our findings suggest the presence of an early autocrine NF-kB-dependent activation of STAT3 in response to H. pylori infection. TFF1 acts as an anti-inflammatory guard against H. pylori-mediated activation of pro-inflammatory networks.

Trefoil Factor 1 Suppresses Epithelial-mesenchymal Transition through Inhibition of TGF-beta Signaling in Gastric Cancer Cells

Gastric cancer is a malignancy with high incidence and mortality worldwide. In gastric cancer, epithelial-mesenchymal transition (EMT) and metastasis further increase the mortality rate. Trefoil factor 1 (TFF1) has been reported as a protective factor in the gastric mucosa. In this study, TFF1 inhibited the migration and invasive capability of gastric cancer cells. Elevated TFF1 levels induced the expression of E-cadherin, the epithelial marker, and reduced the expression of N-cadherin, vimentin, Snail, Twist, Zinc finger E-box binding homeobox (ZEB) 1 and ZEB2, well-known repressors of E-cadherin expression. In addition, the expression of matrix metalloproteinase (MMP)-2, MMP-7 and MMP-9, which are major markers of cancer metastasis, was suppressed by TFF1. Upregulation of TFF1 inhibited TGF-β, a major signaling for EMT induction, and the phosphorylation of Smad2/3 activated by TGF-β in AGS cells. In conclusion, TFF1 inhibits EMT through suppression of TGF-β signaling in AGS cells, which might be used in therapeutic strategies for reducing metastatic potential and invasiveness of these cells.

Helicobacter pylori induced gastric carcinogenesis - The best molecular model we have?

Gastric carcinogenesis can be described as a consequence of multilevel molecular alterations that is triggered by a cascade of events. Historically, diet and environmental factors have been identified to substantially contribute to carcinogenesis before the discovery of Helicobacter pylori (H. pylori). But H. pylori infection has revolutionized the understanding of gastric carcinogenesis. Although the model of H. pylori-driven carcinogenesis remains valid, there is a continuous effort to precisely delineate the molecular pathways involved and to understand the interplay with additional risk factors including recent relevant knowledge on the stomach microbiota. In this review, we provide an updated view on the models of gastric carcinogenesis. This includes historically appreciated H. pylori-induced models and expands these taking recent molecular data into consideration. Based on the data provided, we conclude that indeed H. pylori-carcinogenesis remains one of the best-established models at least for a subset of gastric cancers. Implementation of the recently identified molecular subtypes in novel genetic animal models is required to expand our knowledge on H. pylori-independent carcinogenesis.

Trefoil Factor Family (TFF) Peptides and Their Diverse Molecular Functions in Mucus Barrier Protection and More: Changing the Paradigm

Trefoil factor family peptides (TFF1, TFF2, TFF3) are typically co-secreted together with mucins. Tff1 represents a gastric tumor suppressor gene in mice. TFFs are also synthesized in minute amounts in the immune and central nervous systems. In mucous epithelia, they support rapid repair by enhancing cell migration ("restitution") via their weak chemotactic and anti-apoptotic effects. For a long time, as a paradigm, this was considered as their major biological function. Within recent years, the formation of disulfide-linked heterodimers was documented for TFF1 and TFF3, e.g., with gastrokine-2 and IgG Fc binding protein (FCGBP). Furthermore, lectin activities were recognized as enabling binding to a lipopolysaccharide of Helicobacter pylori (TFF1, TFF3) or to a carbohydrate moiety of the mucin MUC6 (TFF2). Only recently, gastric TFF1 was demonstrated to occur predominantly in monomeric forms with an unusual free thiol group. Thus, a new picture emerged, pointing to diverse molecular functions for TFFs. Monomeric TFF1 might protect the gastric mucosa as a scavenger for extracellular reactive oxygen/nitrogen species. Whereas, the TFF2/MUC6 complex stabilizes the inner layer of the gastric mucus. In contrast, the TFF3-FCGBP heterodimer (and also TFF1-FCGBP) are likely part of the innate immune defense of mucous epithelia, preventing the infiltration of microorganisms.

Loss of Tff1 Promotes Pro-Inflammatory Phenotype with Increase in the Levels of RORγt+ T Lymphocytes and Il-17 in Mouse Gastric Neoplasia

Background: TFF1 deficiency induces a mucosal pro-inflammatory phenotype that contributes to gastric tumorigenesis in mouse and human. Methods: We utilized the Tff1-KO mouse model to assess the impact of TFF1 loss on immune cells infiltration in the stomach. We used single cell suspension, flow cytometry, immunohistochemistry, and quantitative PCR (qPCR) assays. Results: The Tff1-KO gastric mucosa demonstrated high chronic inflammatory scores (score: 3-4) at age 2 months, which exacerbated at age 8 months (score: 4-6). We next used single-cell suspensions for flow cytometry analysis of total leukocytes (CD45+ cells), total T lymphocytes (CD45+CD3+cells), T cell subsets (CD4+, CD8+, and CD3+CD4-CD8-cells), and monocytes/macrophages (CD45+F4/80+cells). The results demonstrated an age-dependent (2 → 8 month age) significant increase of leukocytes (p<0.05), T cells (p<0.05), and monocytes/macrophages (p<0.001) in the gastric mucosa of the Tff1-KO mice, as compared to Tff1-WT. A similar increase was observed in blood samples (p<0.05). Using ionomycin to activate CD4⁺ splenocytes, the results indicated that Tff1-KO CD4⁺ splenocytes secreted higher levels of IL-17A (p<0.05 at 2 and p<0.001 at 8 months) and IL-17F (p<0.05 at 2 and 8 months) than Tff1-WT splenocytes. Conversely, Tff1-KO CD8⁺-cells secreted less IL-17F, but comparable levels of IL-17A. In addition, we detected a significant upregulation of Il-17 mRNA expression in gastric tissues in the Tff1-KO, as compared to Tff1-WT (p<0.001). Conclusions: The results identify TFF1 loss as a major pro-inflammatory step that modulates the tumor microenvironment and immune cell infiltration in the stomach. Furthermore, the data suggest that the increase of IL-17A and IL-17F in Th17 cells, derived from CD4⁺ T cells, reflects the chronic inflammation in gastric mucosa, whereas the absence of change of IL-17A and decrease of IL-17F in CD8⁺Tc17 cells suggest loss of cytotoxic function of CD8⁺Tc17 cells during gastric tumorigenesis of the Tff1-KO mice.

Transgenic and gene knockout mice in gastric cancer research

Mouse models are useful tool for carcinogenic study. They will greatly enrich the understanding of pathogenesis and molecular mechanisms for gastric cancer. However, only few of mice could develop gastric cancer spontaneously. With the development and improvement of gene transfer technology, investigators created a variety of transgenic and knockout/knockin mouse models of gastric cancer, such as INS-GAS mice and gastrin knockout mice. Combined with helicobacter infection and carcinogens treatment, these transgenic/knockout/knockin mice developed precancerous or cancerous lesions, which are proper for gene function study or experimental therapy. Here we review the progression of genetically engineered mouse models on gastric cancer research, and emphasize the effects of chemical carcinogens or infectious factors on carcinogenesis of genetically modified mouse. We also emphasize the histological examination on mouse stomach. We expect to provide researchers with some inspirations on this field.

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.

Trefoil factor 1 expression suppresses Helicobacter pylori-induced inflammation in gastric carcinogenesis

BACKGROUND

Infection with Helicobacter pylori, a high-risk factor for gastric cancer, is frequently associated with chronic inflammation through activation of nuclear factor κB (NF-κB). Trefoil factor 1 (TFF1) is a constitutively expressed protein in the stomach that has tumor-suppressor functions and plays a critical role in maintaining mucosal integrity. This study investigated the role of TFF1 in regulating the proinflammatory response to H. pylori infections.

METHODS

For in vitro studies, immunofluorescence, luciferase reporter assays, Western blots, and quantitative real-time polymerase chain reaction were performed to investigate the activation of NF-κB and its target genes in response to infections with H. pylori strains J166 and 7.13. In addition, Tff1-knockout (KO) and Tff1-wild-type mice were used for infections with the H. pylori strain called premouse Sydney strain 1.

RESULTS

The reconstitution of TFF1 expression in gastric cancer cells significantly suppressed H. pylori-mediated increases in NF-κB-p65 nuclear staining, transcriptional activity, and expression of proinflammatory cytokine genes (tumor necrosis factor α, interleukin 1β, chemokine [C-X-C motif] ligand 5, and interleukin 4 receptor) that were associated with reductions in the expression and phosphorylation of NF-κB-p65 and IκB kinase α/β proteins. The in vivo studies using the Tff1-KO mouse model of gastric neoplasia confirmed the in vitro findings. Furthermore, they demonstrated increases in chronic inflammation scores and in the frequency of invasive gastric adenocarcinoma in the Tff1-KO mice infected with H. pylori versus the uninfected Tff1-KO mice.

CONCLUSIONS

These findings underscore an important protective role of TFF1 in abrogating H. pylori-mediated inflammation, a crucial hallmark of gastric tumorigenesis. Therefore, loss of TFF1 expression could be an important step in H. pylori-mediated gastric carcinogenesis.

Trefoil Factor 1 is involved in gastric cell copper homeostasis

Trefoil Factor 1 belongs to a group of small secreted proteins (the Trefoil Factor Family proteins), that are localized within the mucous granules and are expressed and secreted by epithelial cells that line mucous membranes. Trefoil factors are mainly expressed in the gastrointestinal tract, where they normally contribute to maintain the integrity of the mucosa. We recently demonstrated a selective binding ability of Trefoil Factor 1 for copper ions, through its carboxy-terminal tail, and we also observed that copper levels influence the equilibrium between the monomeric and homodimeric forms of Trefoil Factor 1, thus modulating its biological activity. Here we report that transcriptional regulation of Trefoil Factor 1 is also affected by copper levels, through the modulated binding of the copper-sensing transcription factor Sp1 onto the responsive elements present in the regulatory region of the gene. In addition we demonstrate that copper overload causes an accumulation of the trefoil protein in the Trans-Golgi Network and that Trefoil Factor 1 levels can influence copper excretion and copper related toxicity. These findings suggest that the protein might play a role in the overall complex mechanisms of copper homeostasis in the gastrointestinal tissues.

Trefoil factor 1 gene alternations and expression in colorectal carcinomas

Aims and background

Aberrant expression of the trefoil factor family (TFF) has been recognized to be involved in the development and/or progression of various solid tumors. Increased trefoil factor 1 (TFF1) expression is found associated with tumor progression in some tumors, and TFF1 missense mutations have been detected in gastric cancer. The aim of the study was to analyze TFF1 alternations and expression in colorectal carcinoma and their correlation with cancer progression and pathological aspects.

Methods

TFF1 mutations were detected in colorectal carcinomas by DNA sequencing. TFF1mRNA and protein levels in subsets of the primary tumors were determined using quantitative reverse transcription polymerase chain reaction and immunohistochemistry analyses. The serum level of TFF1 was also detected by enzyme-linked immunosorbent assay for patients with colorectal carcinoma.

Results

Five variants were detected in the 5'-untranslation region and intron 1 of TFF1. TFF1 expression was increased in colorectal carcinoma compared to paired distal colonic mucosa. Immunohistochemistry in primary colorectal carcinoma showed no significant differences in tumor TFF1 levels with respect to clinicopathological parameters such as the patient's sex, cancer differentiation, stage and lymph node metastasis. However, serum TFF1 levels were significantly elevated in patients with colorectal carcinoma compared to healthy individuals.

Conclusions

The results indicate that TFF1 missense mutations seem to be a rare event in colorectal carcinogenesis. Serum TFF1 may be a potential useful marker for patients with colorectal carcinoma.

Genetics/genomics/proteomics of gastric adenocarcinoma

Hereditary diffuse gastric cancer can be caused by epithelial cadherin mutations for which genetic testing is available. Inherited cancer predisposition syndromes including Lynch, Li-Fraumeni, and Peutz-Jeghers syndromes, can be associated with gastric cancer. Chromosomal and microsatellite instability occur in gastric cancers. Several consistent genetic and molecular alterations including chromosomal instability, microsatellite instability, and epigenetic alterations have been identified in gastric cancers. Biomarkers and molecular profiles are being discovered with potential for diagnostic, prognostic, and treatment guidance implications.

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.

Loss of trefoil factor 1 is regulated by DNA methylation and is an independent predictive factor for poor survival in advanced gastric cancer

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.

Expression of MUC5AC and Trefoil Peptide 1 (TFF1) in the Subtypes of Intestinal Metaplasia

Background/Aims

Alterations of the expression pattern of mucins and trefoil peptides have been described in gastric adenocarcinomas and in their precursor lesions. The aim of this study was to determine the progression patterns of intestinal metaplasia (IM) subtypes by analyzing the expression patterns of TFF1 and MUC5AC in different subtypes of IM of the stomach.

Methods

Endoscopic gastric biopsies of the antrum and body were obtained from patients with dyspepsia and endoscopic IM. Alcian blue/periodic acid-Schiff staining and the high iron diamine technique were used to classify the subtypes of IM. Immunoreactivity for MUC5AC and TFF1 was estimated in different types of IM.

Results

IM was detected in 128 samples from 80 patients; type I was found in 48 samples, type II was found in 37 samples, and type III was found in 43 samples. There was a gradual decrease in MUC5AC and TFF1 expression during the progression of IM from type I to type III via the type II intermediate.

Conclusions

This downregulation of MUC5AC and TFF1 expression may challenge the sequential progression of IM from type I to type III via the type II intermediate, and it might be associated with gastric carcinogenesis.

[Trefoil factor: from laboratory to clinic]

Trefoil factor (TFF) family is a group of peptides with one or several trefoil factor domains in their structure, which are highly conserved in evolution, and are characterized by heat and enzymatic digestion resistance. The mammalian TFFs have three members (TFF1-3), and the gastrointestinal tract and the airway system are major organs of their expression and secretion. At certain physiological conditions, with a tissue-specific distribution, TFF plays an important role in mucosal protection and wound healing. But in the malignant tissues, TFF is widely expressed, correlated strongly with the genesis, metastasis and invasion of tumor cells. These phenomena indicated that TFF may be a possible common mediator of oncogenic responses to different stimuli. The biological functions of TFF involve complex regulatory processes. Single chain TFF may activate cell membrane receptors and induce specific signaling transduction. On the other hand, TFF can form a complex with other proteins to exert its biological effects. In clinical medicine, TFF is primarily applied as drugs in the mucosal protection, in the prevention and the treatment of mucosal damage-related diseases and as pathological biomarkers of tumors. At present the first hand actions and the molecular mechanisms related to TFFs are still the major challenges in TFF research. Furthermore, the discovery of the naturally occurring complex of TFF and crystallins is highly valuable to the understanding of the biological functions and action mechanisms of TFF.

Amplification and invasiveness of epithelial progenitors during gastric carcinogenesis in trefoil factor 1 knockout mice

OBJECTIVE

It is not known whether or not epithelial progenitors of the pyloric antrum are involved in gastric carcinogenesis. Normally, these progenitors give rise to two main cell lineages: pit and gland mucous cells. This study was designed to examine the changes that occur in pyloric antral mucous cell lineages and their progenitors during development of gastric adenoma and carcinoma in trefoil factor 1 (TFF1) knockout mice.

MATERIALS AND METHODS

Pyloric antral mucosal tissues of TFF1 knockout mice at ages from 3 days to 17 months were processed for histochemical analysis using Ulex europaeus and Grifforia simplifolica lectins as markers for pit and gland mucous cells, respectively. The dividing epithelial progenitors were identified by using immunohistochemical and electron microscopy techniques.

RESULTS

TFF1 loss was associated with amplification of both mucus-secreting pit and gland cells. Both lectins examined bound not only to mature mucous cells, but also to most of epithelial progenitors which gradually amplified with age and frequently were seen in mitosis. Analysis of 12- to 17-month-old TFF1-deficient stomachs revealed occasional groups of poorly differentiated mucosal cells with features similar to those of epithelial progenitors (or stem cells), in the basal portion of the antral mucosa. These cells eventually invaded the muscularis mucosa while maintaining some capacity to differentiate.

CONCLUSION

This study shows that the progenitors of pit and gland mucous cells contribute to gastric carcinogenesis in the pyloric antrum of TFF1 knockout mice, strongly supporting the concept of stem cell origin of cancer.

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.

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.

Early-onset gastric cancers have a different molecular expression profile than conventional gastric cancers

Many studies examine the molecular genetics of gastric cancer, but few look at young patients in particular and there is no comparison of molecular expression between early-onset gastric cancer (< or = 45 years old) and conventional gastric cancers. Expression of cycloxygenase-2 (COX-2) is elevated in gastric adenocarcinomas compared to non-neoplastic mucosa, and in light of studies showing reduced risk of gastric cancer in nonsteroidal anti-inflammatory drug users, we have chosen to investigate the expression of COX-2 and related molecules in 113 early-onset gastric cancers and compare it with 91 conventional gastric cancers, using tissue microarrays. These markers include molecules known to be important in conventional gastric carcinogenesis, such as E-Cadherin, p53, COX-2, Trefoil Factor-1 (TFF1), beta-catenin, p16 and c-myc; as well as molecules not yet described as being important in gastric cancer, such as the transcription factor c-jun, the COX-2 mRNA stabilizer HuR, and C/EBP-beta, a transcription factor for COX-2. All markers showed a statistically significant difference between early-onset gastric cancers and conventional gastric cancers, using a chi2 test. In particular, early-onset gastric cancers displayed a COX-2 Low, TFF1-expressing phenotype, whereas COX-2 overexpression and loss of TFF1 was found in conventional cancers, and this difference between early-onset gastric cancers and conventional cancers remained statistically significant when adjusted for location and histology (P<0.0001 and P = 0.002 respectively). We found that COX-2 overexpression correlates significantly with loss of TFF1 (P = 0.001), overexpression of C/EBP-beta (P<0.001) and cytoplasmic HuR (P = 0.016). COX-2 was significantly associated with p53 positivity (P = 0.003). Abnormalities in E-Cadherin correlated significantly with diffuse phenotype, whereas high expression of COX-2, loss of TFF1 and overexpression of C/EBP-beta correlated with the intestinal phenotype. Our results provide further evidence that early-onset gastric cancer exhibits a distinctive expression profile that may have practical implications.

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Overexpression of CEBPbeta correlates with decreased TFF1 in gastric cancer

CCAAT element binding protein beta (C/EBPbeta) is an important regulator of cell growth, differentiation and in promoting tumor invasiveness. C/EBPbeta is located on chromosome 20q, which is amplified in many solid tumors including gastric cancers (GC). We sought to characterize the status of C/EBPbeta expression in GCs, which was recently found to repres TFF1 gene. Microarray analysis revealed overexpression of C/EBPbeta in 25 of 27 (93%) GC when compared to 12 normal gastric tissue samples. RT-PCR analysis confirmed the overexpression of C/EBPbeta transcripts in 54 of 59 (91%) GC. In total, 15 of 18 gastric tumors exhibited at least fivefold higher C/EBPbeta transcript levels compared to their corresponding adjacent normal gastric tissue samples. Moreover, immunohistochemistry analysis demonstrated increased nuclear staining of C/EBPbeta in 10 of 13 GC and at least fourfold overexpression of C/EBPbeta in three primary GC compared to adjacent normal gastric tissue. Furthermore, a striking correlation of decreased TFF1 expression with increased C/EBPbeta was observed in the gastric tumors studied. Microarray analysis demonstrated a loss of TFF1 expression in all 27 GC cases examined, of which 25 exhibited high C/EBPbeta expression compared to normal gastric tissue. RT-PCR analysis revealed loss of TFF1 expression in 56 of 59 gastric tumors in which 54 of these tumors exhibited overexpression of C/EBPbeta. Immunohistochemical analysis revealed overexpression of C/EBPbeta in 10 of 13 gastric tumors that exhibited low expression of TFF1 at the protein level. Thus, overexpression of the transcription factor C/EBPbeta in the majority of GCs is a novel finding.

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.

Hormonal influences on cancer progression and prognosis

Cell differentiation, proliferation, apoptosis, and cell motility are induced and regulated by a host of growth factors, vitamins, and hormones. The mode of function of these modifiers of biological response, the signaling pathways that they activate, and the interacting pathways that can influence the biological outcome have been the focus of attention. Especially recognized and discussed in this review is the deregulation of their function, leading to abnormalities in cell proliferation, alteration of intercellular adhesive cohesion, remodeling of the extracellular matrix, and invasive behavior and metastatic deposition that are so characteristic of tumor development and progression, which strongly underscores the concept of molecular progression of cancer constructed on the basis of the relationship between genetic changes and the biological events associated with cancer progression. The molecular changes associated with hormone- and vitamin-driven responses and the deregulation of the expression and function of their target genes seem to correlate with specific biological events linked with cancer invasion and progression, and these findings could lead to the establishment of new markers of progression and to the development of new strategies for patient management. The scope of this work has been restricted by design and is dictated by the field of interest of the author's laboratory, but it is hoped that this field would be regarded adequately to reflect the wide genre of scientific interest in this field of human disease.

Expression of tight-junction protein claudin-7 is an early event in gastric tumorigenesis

Trefoil factor-1 (Tff1) expression is remarkably down-regulated in nearly all human gastric cancers. Therefore, we used the Tff1 knockout mouse model to detect molecular changes in preneoplastic gastric dysplasia. Oligonucleotide microarray gene expression analysis of gastric dysplasia of Tff1-/- mice was compared to that of normal gastric mucosa of wild-type mice. The genes most overexpressed in Tff1-/- mice included claudin-7 (CLDN7), early growth response-1 (EGR1), and epithelial membrane protein-1 (EMP1). Quantitative real-time reverse transcriptase-polymerase chain reaction and immunohistochemistry showed that Cldn7 was overexpressed in all 10 Tff1-/- gastric dysplasia samples. Comparison with our serial analysis of gene expression database of human gastric cancer revealed similar deregulation in human gastric cancers. Quantitative real-time reverse transcriptase-polymerase chain reaction of human gastric adenocarcinoma samples indicated that, of these three genes, CLDN7 was the most frequently up-regulated gene. Using immunohistochemistry, both mouse and human gastric glands overexpressed Cldn7 in dysplastic but not surrounding normal glands. Cldn7 expression was observed in 30% of metaplasia, 80% of dysplasia, and 70% of gastric adenocarcinomas. Interestingly, 82% of human intestinal-type gastric adenocarcinomas expressed Cldn7 whereas diffuse-type gastric adenocarcinomas did not (P < 0.001). These results suggest that Cldn7 expression is an early event in gastric tumorigenesis that is maintained throughout tumor progression.

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.

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.

Gene expression profiling reveals sequential changes in gastric tubular adenoma and carcinoma in situ

AIM: To analyze the expression profiles of premalignant and/or preclinical lesions of gastric cancers.

METHODS: We analyzed the expression profiles of normal gastric pit, tubular adenoma and carcinoma in situ using microdissected cells from routine gastric biopsies. For the DNA microarray analysis of formalin-fixed samples, we developed a simple and reproducible RNA extraction and linear amplification procedure applying two polymerase-binding sites. The amplification procedure took only 8 h and yielded comparable DNA microarray data between formalin-fixed tissues and unfixed controls.

RESULTS: In comparison with normal pit, adenoma/carcinoma showed 504 up-regulated and 29 down-regulated genes at the expected false significance rate 0.15%. The differential expression between adenoma and carcinoma in situ was subtle: 50 and 22 genes were up-, and down-regulated in carcinomas at the expected false significance rate of 0.61%, respectively. Differentially expressed genes were grouped according to patterns of the sequential changes for the the ‘tendency analysis’ in the gastric mucosa-adenoma-carcinoma sequence.

CONCLUSION: Groups of genes are shown to reflect the sequential expression changes in the early carcinogenic steps of stomach cancer. It is suggested that molecular carcinogenic pathways could be analyzed using routinely processed biopsies.