Role of trefoil factor 1 in gastric cancer and relationship between trefoil factor 1 and gastrokine 1

Identification of stage-specific differentially expressed genes and SNPs in gastric cancer employing RNA-Seq based transcriptome profiling

We analysed over 400 million reads obtained from Illumina sequencing of six pairs of libraries representing two each of stage I, II, and III gastric tumors and corresponding normal tissues to identify differentially expressed genes (DEGs), single nucleotide polymorphisms (SNPs), and transcription factors (TFs). In total, 2207 DEGs including 972 upregulated genes and 1235 downregulated genes were detected. Of these, several stage-specific signature genes were identified. The protein-protein interaction networks involving DEGs and TFs were constructed. The KEGG pathway analysis of SNP harbouring genes revealed their involvement in different cancer related pathways like apoptosis, mTOR pathway, and MAPK signaling pathway. The SNP analysis showed implication of host genes in GO categories like immune system process, regulation of signaling, response to stress, and transport. A biased chromosomal distribution of DEGs and SNP harbouring genes was observed. Our study would provide further insights into the complex regulatory mechanisms operating during gastric tumorigenesis.

Immunoexpression of Trefoil Factor 1 in Non-Neoplastic and Neoplastic Canine Gastric Tissues

Simple Summary

Gastric carcinoma (GC) is the second leading cause of death in humans and the most frequent malignancy in the stomach of dogs. As in humans, the prognosis of canine gastric cancer is generally poor owing to the advanced stage at the time of diagnosis, resulting in limited treatment options. In dogs, the molecular mechanisms involved in the growth and progression of gastric cancer remain largely unknown. Trefoil factor 1 (TFF1) protein is a mucin-associated secretory molecule that plays an important role in the maintenance and protection of epithelial surface integrity. Some human studies showed that TFF1 can protect mucosa against damage and suppress carcinogenesis, while other studies showed that TFF1 can restrict cell adhesion, promote tumor cell invasion, and block necrosis of tumor cells. In human gastric cancer, TFF1 has been found to decrease, and it has been proposed that it might act as a tumor suppressor factor. The present study was carried out to investigate whether there is a relationship between TFF1 and canine gastric carcinogenesis. We found an association between reduced expression of TFF1 and the development and progression of gastric cancer in dogs. The pathological and behavioral similarities between spontaneous canine GC and human counterparts make it logical to assume that dogs may be a useful model for human gastric cancer.

Abstract

TFF1 expression is markedly reduced in human GCs, suggesting that TFF1 is a tumor suppressor for human gastric cancer. The present study evaluated the expression and distribution pattern of TFF1 in paraffin-embedded canine gastric tissue samples, including normal mucosa (n = 3), polyps (n = 8), carcinomas (n = 31) and their adjacent non-neoplastic mucosa (n = 30), neoplastic emboli (n = 14), and metastatic lesions (n = 9), by immunohistochemistry (IHC). All normal gastric tissues expressed TFF1 in the superficial foveolar epithelium and mucopeptic cells of the neck region. Most gastric polyps (GPs) displayed immunoreactivity for TFF1 in >75% of the epithelial component. In GCs, the expression of TFF1 was found reduced in 74.2% of the cases. The level of TFF1 expression had a decreased tendency from normal gastric mucosa to GPs and GCs (p < 0.05). No significant differences in the expression of TFF1 were found in GCs, according to age, sex, histological type based on World Health Organization (WHO) and Lauren classification, tumor location, depth of tumor invasion, presence of neoplastic emboli or metastatic lesions. The median survival time of GC patients with preserved and reduced TFF1 immunoexpression were 30 and 12 days, respectively. Kaplan–Meier analysis revealed no significant survival differences between the two groups (p > 0.05). These findings suggest that TFF1 protein may play a role in canine gastric carcinogenesis, and further studies are necessary to define its usefulness as a prognostic indicator in canine gastric carcinoma.

The protein-protein interaction network of intestinal gastric cancer patients reveals hub proteins with potential prognostic value

BACKGROUND

Gastric cancer (GC) is the third leading cause of cancer worldwide. According to the Lauren classification, gastric adenocarcinoma is divided into two subtypes: diffuse and intestinal. The development of intestinal gastric cancer (IGC) can take years and involves multiple factors.

OBJECTIVE

To investigate the protein profile of tumor samples from patients with IGC in comparison with adjacent nontumor tissue samples.

METHODS

We used label-free nano-LC-MS/MS to identify proteins from the tissues samples. The results were analyzed using MetaCore™ software to access functional enrichment information. Protein-protein interactions (PPI) were predicted using STRING analysis. Hub proteins were determined using the Cytoscape plugin, CytoHubba. Survival analysis was performed using KM plotter. We identified 429 differentially expressed proteins whose pathways and processes were related to protein folding, apoptosis, and immune response.

RESULTS

The PPI network of these proteins showed enrichment modules related to the regulation of cell death, immune system, neutrophil degranulation, metabolism of RNA and chromatin DNA binding. From the PPI network, we identified 20 differentially expressed hub proteins, and assessed the prognostic value of the expression of genes that encode them. Among them, the expression of four hub genes was significantly associated with the overall survival of IGC patients.

CONCLUSIONS

This study reveals important findings that affect IGC development based on specific biological alterations in IGC patients. Bioinformatics analysis showed that the pathogenesis of IGC patients is complex and involves different interconnected biological processes. These findings may be useful in research on new targets to develop novel therapies to improve the overall survival of patients with IGC.

Long-chain fatty acid-induced intracellular signaling in GPR120-expressing brush cells at the limiting ridge of the murine stomach

Brush cells at the gastric groove have been proposed to operate as sensory cells capable of sensing constituents of ingested food. Recent studies have indicated that these cells express GPR120 (also known as FFAR4), the G protein-coupled receptor for long-chain fatty acids (LCFAs). However, functional implications of this receptor in brush cells have remained elusive. Here, we show that a great proportion of brush cells express GPR120. We used phosphorylation of the extracellular signal-regulated kinases 1/2 (ERK1/2) as a readout to monitor brush cell responses to the LCFAs oleic acid and α-linolenic acid. Our results demonstrate that ERK1/2 phosphorylation is increased upon exposure to both fatty acids. Increased ERK1/2 phosphorylation is accompanied by upregulated mRNA and protein levels of cyclooxygenase 2 (COX-2), a key enzyme for prostaglandin biosynthesis. Immunohistochemical experiments confirmed that oleic acid caused ERK1/2 phosphorylation and induced COX-2 expression in brush cells. Our results indicate that LCFA sensing elicits a signaling process in brush cells that may be relevant for a local regulation of gastric functions.

Gastric cancer biomarkers; A systems biology approach

Gastric cancer is one of the most fatal cancers in the world. Many efforts in recent years have attempted to find effective proteins in gastric cancer. By using a comprehensive list of proteins involved in gastric cancer, scientists were able to retrieve interaction information. The study of protein-protein interaction networks through systems biology based analysis provides appropriate strategies to discover candidate proteins and key biological pathways.

In this study, we investigated dominant functional themes and centrality parameters including betweenness as well as the degree of each topological clusters and expressionally active sub-networks in the resulted network. The results of functional analysis on gene sets showed that neurotrophin signaling pathway, cell cycle and nucleotide excision possess the strongest enrichment signals. According to the computed centrality parameters, HNF4A, TAF1 and TP53 manifested as the most significant nodes in the interaction network of the engaged proteins in gastric cancer. This study also demonstrates pathways and proteins that are applicable as diagnostic markers and therapeutic targets for future attempts to overcome gastric cancer.

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A systematic study of protein-protein interaction networks through comprehensive extracted list of proteins involved in gastric cancer.

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Dominant functional theme and pathways of each topological clusters and expressionally active subnetworks were reported.

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The most effective proteins in gastric cancer formation were proposed according to the computed centrality parameters.

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HNF4A, TAF1and TP53 were mentioned as the key proteins in gastric cancer.

EBNA1 binding and epigenetic regulation of gastrokine tumor suppressor genes in gastric carcinoma cells

BACKGROUND

Epstein-Barr Virus (EBV) latently infects ~10% of gastric carcinomas (GC). Epstein-Barr Nuclear Antigen 1 (EBNA1) is expressed in EBV-associated GC, and can bind host DNA, where it may impact cellular gene regulation. Here, we show that EBNA1 binds directly to DNA upstream of the divergently transcribed GC-specific tumor suppressor genes gastrokine 1 (GKN1) and gastrokine 2 (GKN2).

METHODS

We use ChIP-Seq, ChIP-qPCR, and EMSA to demonstrate that EBNA1 binds directly to the GKN1 and GKN2 promoter locus. We generate AGS-EBV, and AGS-EBNA1 cell lines to study the effects of EBNA1 on GKN1 and GKN2 mRNA expression with or without 5' azacytidine treatment.

RESULTS

We show that gastrokine genes are transcriptionally silenced by DNA methylation. We also show that latent EBV infection further reduces GKN1 and GKN2 expression in AGS gastric carcinoma cells, and that siRNA depletion of EBNA1 partially alleviates this repression. However, ectopic expression of EBNA1 slightly increased GKN1 and GKN2 basal mRNA levels, but reduced their responsiveness to demethylating agent.

CONCLUSIONS

These findings demonstrate that EBNA1 binds to the divergent promoter of the GKN1 and GKN2 genes in GC cells, and suggest that EBNA1 contributes to the complex transcriptional and epigenetic deregulation of the GKN1 and GKN2 tumor suppressor genes in EBV positive GC.

Gastrokines: stomach-specific proteins with putative homeostatic and tumor suppressor roles

During the past decade, a new family of stomach-specific proteins has been recognized. Known as "gastrokines" (GKNs), these secreted proteins are products of gastric mucus-producing cell lineages. GKNs are highly conserved in physical structure, and emerging data point to convergent functions in the modulation of gastric mucosal homeostasis and inflammation. While GKNs are highly prevalent in the normal stomach, frequent loss of GKN expression in gastric cancers, coupled with established antiproliferative activity, suggests putative tumor suppressor roles. Conversely, ectopic expression of GKNs in reparative lesions of Crohn's disease alludes to additional activity in epithelial wound healing and/or repair. Modes of action remain unsolved, but the recent demonstration of a GKN2-trefoil factor 1 heterodimer implicates functional interplay with trefoil factors. This review aims to provide a historical account of GKN biology and encapsulate the rapidly accumulating evidence supporting roles in gastric epithelial homeostasis and tumor suppression.