Gastrokine 1 inhibits gastrin-induced cell proliferation

miR-548d-3p inhibits the invasion and migration of gastric cancer cells by targeting GKN1

Background

The aim of this study was to explore the function and mechanism of GKN1 in gastric cancer (GC) progression.

Methods

Firstly, we used GEO2R to perform differential gene analysis on GSE26942 and GSE79973 and constructed the protein–protein interaction network of differential genes by STRING. Next, the cytoHubba, Mcode plugins, and GEPIA were used to obtain our follow‐up research object GKN1. Then, the function of GKN1 in GC was verified by scratch and transwell assay in GC cells. We further analyzed the genes related to GKN1 through LinkedOmics, and exported top 100 genes positively or negatively correlated with GKN1. Meanwhile, Metascape was performed on these genes. Finally, we analyzed the miRNAs that bind to GKN1 through the miRDB and verified the correlation between miR‐548d‐3p and GKN1 using dual‐fluorescence and quantitative PCR experiments.

Results

Bioinformatics analysis showed that there were 52 differential genes on GSE26942 and GSE79973. In addition, the results of functional assays indicated that overexpressed GKN1 can inhibit GC cell migration and invasion, while GKN1 knockdown demonstrated the opposite effect. Additionally, Metascape analysis results showed that the 3′‐UTR region of mRNA is rich in AU sequences, based on which we infer that mRNA may be regulated by miRNA. Dual‐fluorescence and quantitative PCR assays clarified that miR‐548d‐3p may be one of the target miRNAs of GKN1, which was up‐regulated in GC tissues.

Conclusions

In summary, we clarified that miR‐548d‐3p regulates GKN1 to participate in GC cell migration and invasion, and provides a possible target for the prognostic diagnosis and treatment of GC.

Gastrin/CCK-B Receptor Signaling Promotes Cell Invasion and Metastasis by Upregulating MMP-2 and VEGF Expression in Gastric Cancer

Accumulated evidence suggests that a functional loop composed of gastrin and cholecystokinin B receptor (CCK-BR) may exist in gastric carcinogenesis. However, this suggestion is not completely supported due to a lack of direct evidence, and the underlying mechanism is not completely understood. Here, we evaluated the effects of gastrin/CCK-BR signaling on the cell growth, invasion, and expression of MMP-2 and VEGF, as well as xenograft growth in vivo. Furthermore, we detected gastrin mRNA content in human gastric cancer tissues, metastatic lymph nodes, and adjacent nontumor tissues. We found that the forced gastrin could promote the proliferation, migration, and invasion of gastric cancer cells by upregulating the expression of MMP-2 and VEGF. Blocking gastrin/CCK-BR signal using either Proglumide, a CCK-BR antagonist, or shRNA against GASTRIN significantly inhibited the gastrin-promoting effects. In vivo study revealed that the tumor growth in nude mice inoculated with gastrin-overexpressed cells was significantly faster than control cells. The gastrin mRNA content in metastatic lymph nodes was higher in patients with gastric cancer than in primary gastric cancer and adjacent nontumor tissues. In conclusion, we provided direct evidence and possible mechanism of gastrin/CCK-BR signaling in the initiation and progression of gastric cancer.

Whole genome transcriptome analysis of the stomach resected in human vertical sleeve gastrectomy: cutting more than calories

Vertical sleeve gastrectomy (VSG) is a surgical weight loss procedure that resects 80% of the stomach, creating a tube linking the esophagus to the duodenum. Because of the efficacy and relative simplicity of VSG, it is preferred in the United States, with VSG currently at >61% of bariatric surgeries performed. Surprisingly, there has never been a complete molecular characterization of the human stomach greater curvature's fundus and corpus. Here we compare and contrast the molecular makeup of these regions. We performed a prospective cohort study to obtain gastric tissue samples from patients undergoing elective VSG. Paired fundus and corpus samples were obtained. Whole genome transcriptome analysis was performed by RNA sequencing (N = 10), with key findings validated by qPCR (N = 24). Participants were primarily female (95.8%) and White (79.15%). Mean body mass index, body weight, and age were 46.1 kg/m², 121.6 kg, and 43.29 yr, respectively. Overall, 432 gene transcripts were significantly different between the fundus and the corpus (P < 0.05). A significant correlation was found between the RNA sequencing dataset and qPCR validation, demonstrating robust gene expression differences between the fundus and the corpus. Significant genes included progastricsin, acidic chitinase, and gastokine 1 and 2 in both the fundus and the corpus. Of the very highly expressed genes in both regions, 87% were present in both the stomach's fundus and corpus, indicating substantial overlap. Despite significant overlap in the greater curvature gene signature, regional differences exist within the fundus and the corpus. Given that the mechanism of VSG is partly unresolved, the potential that the resected tissue may express genes that influence long-term body weight regulation is unknown and could influence VSG outcomes.

Helicobacter pylori inhibits GKN1 expression via the CagA/p-ERK/AUF1 pathway

BACKGROUND

Recent studies have shown that gastrokine 1 (GKN1), an important tumor suppressor gene, is downregulated in Helicobacter pylori (H. pylori) infected gastric mucosa and gastric cancer. However, the underlying mechanism is poorly understood. Herein, we investigated the potential mechanism of H. pylori-induced GKN1 downregulation.

MATERIALS AND METHODS

GKN1 and AU-rich element RNA-binding factor 1 (AUF1) expressions were assessed by quantitative real-time PCR, Western blot, or immunohistochemistry in H. pylori-infected tissues and H. pylori co-cultured cell lines. The regulation of AUF1 on GKN1 was determined by RNA pulldown assay, RNA immunoprecipitation, mRNA turnover, and luciferase activity assays. The involvement of phosphorylated extra-cellular signal-regulated kinase (p-ERK) or CagA in H. pylori-induced AUF1 expression was verified using p-ERK inhibitor or CagA knockout H. pylori. In addition, the cell proliferation and migration capacities of AUF1-knockdown cells were investigated.

RESULTS

GKN1 expression progressively decreased from H. pylori-infected gastritis to gastric cancer tissues. H. pylori co-culture also induced significant GKN1 reduction in GES-1 and BGC-823 cells. Besides, the mRNA level of GKN1 and AUF1 in human gastric mucosa showed negative correlation significantly. AUF1 knockdown resulted in upregulation of GKN1 expression and promoted GKN1 mRNA decay by binding the 3' untranslated region of GKN1 mRNA H. pylori-induced AUF1 expression was associated with p-ERK activation and CagA. Furthermore, knockdown of AUF1 significantly inhibited cell viability, migration ability, and arrested fewer cells in S-phase.

CONCLUSION

Our data demonstrated that H. pylori infection downregulated GKN1 expression via the CagA/p-ERK/AUF1 pathway. AUF1 promoted gastric cancer at least partly through downregulating GKN1, which presented a novel potential target for the treatment of gastric cancer.

Regulation of GKN1 expression in gastric carcinogenesis: A problem to resolve (Review)

Gastrokine 1 (GKN1) is a protein expressed on the surface mucosa cells of the gastric antrum and fundus, which contributes to maintaining gastric homeostasis, inhibits inflammation and is a tumor suppressor. The expression of GKN1 decreases in mucosa that are either inflamed or infected by Helicobacter pylori, and is absent in gastric cancer. The measurement of circulating GKN1 concentration, the protein itself, or the mRNA in gastric tissue may be of use for the early diagnosis of cancer. The mechanisms that modulate the deregulation or silencing of GKN1 expression have not been completely described. The modification of histones, methylation of the GKN1 promoter, or proteasomal degradation of the protein have been detected in some patients; however, these mechanisms do not completely explain the absence of GKN1 or the reduction in GKN1 levels. Only NKX6.3 transcription factor has been shown to be a positive modulator of GKN1 transcription, although others also have an affinity with sequences in the promoter of this gene. While microRNAs (miRNAs) are able to directly or indirectly regulate the expression of genes at the post‑transcriptional level, the involvement of miRNAs in the regulation of GKN1 has not been reported. The present review analyzes the information reported on the determination of GKN1 expression and the regulation of its expression at the transcriptional, post‑transcriptional and post‑translational levels; it proposes an integrated model that incorporates the regulation of GKN1 expression via transcription factors and miRNAs in H. pylori infection.

Gastrin promotes angiogenesis by activating HIF-1α/β-catenin/VEGF signaling in gastric cancer

Angiogenesis is recognized as a sign of cancer and facilitates cancer progression and metastasis. Suppression of angiogenesis is a desirable strategy for gastric cancer (GC) management. In this study, we showed a novel role of gastrin in angiogenesis of GC. We observed that treatment with gastrin 17 (G17) increased the proliferation of AGS cells and enhanced tube formation during normoxia and hypoxia. The expression level of VEGF were increased by G17 treatment as well. Experiments on the mechanism showed that G17 promoted HIF-1α expression, which subsequently enhanced β-catenin nuclear localization and activation of TCF3 and LEF1 and finally resulted in angiogenesis by upregulating VEGF. An in vivo experiment confirmed that G17 enhanced GC cell proliferation and angiogenesis in the resultant tumor. In conclusion, our findings indicate that gastrin promotes angiogenesis via activating HIF-1α/β-catenin/VEGF axis in GC.

Functional genomics of the digestive tract in broilers

Background

The sustainability of poultry farming relies on the development of more efficient and autonomous production systems in terms of feed supply. This implies a better integration of adaptive traits in breeding programs, including digestive efficiency, in order to favor the use of a wider variety of feedstuffs. The aim of the project was to improve the understanding of genes involved in digestive functions by characterizing the transcriptome of different sections of the digestive tract: the junction between the proventriculus and the gizzard, the gizzard, the gastroduodenal junction, and the jejunum.

Results

Total RNA from the four tissues were sequenced on a HiSeq2500 for six 23-day-old chickens from a second generation (F2) cross between two lines that were divergent for their digestive efficiency (D+/D-). Bioinformatics and biostatistics analyses of the RNA-seq data showed a total of 11,040 differentially expressed transcripts between the four tissues. In total, seven clusters of genes with markedly different expression profiles were identified. Functional analysis on gene groups was performed using “Gene Ontology” and semantic similarity. It showed a significant enrichment of body immune defenses in the jejunum, and an enrichment of transcriptional activity in the gizzard. Moreover, an interesting enrichment for neurohormonal control of muscle contraction was found for the two gizzard’s junctions.

Conclusion

This analysis allows us to draw the first molecular portrait of the different sections of the digestive tract, which will serve as a basis for future studies on the genetic and physiological control of the response of the animal to feed variations.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5344-z) contains supplementary material, which is available to authorized users.

Gastrokine 1 protein is a potential theragnostic target for gastric cancer

BACKGROUND

Gastrokine 1 (GKN1) plays important roles in maintaining mucosal homeostasis, and in regulating cell proliferation and differentiation. Here, we determined whether GKN1 is a potential theragnostic marker for gastric cancer.

METHODS

We identified GKN1 binding proteins using the protein microarray assay and investigated whether GKN1 is one of the exosomal cargo proteins by western blot, immunoprecipitation, and immunofluorescent assays. Cell proliferation and apoptosis were analyzed by MTT, BrdU incorporation, flow cytometry, and western blot assays. We further validated the functional relevance of exosomal GKN1 in MKN1-injected xenograft mice. The possibility of serum GKN1 as a diagnostic marker for gastric cancer was determined by ELISA assay.

RESULTS

In protein microarray assay, GKN1 binding to 27 exosomal proteins was clearly observed. GKN1 was expressed in exosomes derived from HFE-145 gastric epithelial cells by western blot and immunofluorescent assays, but not in exosomes from AGS and MKN1 gastric cancer cells. Exosomes carrying GKN1 inhibited cell proliferation and induced apoptosis in both AGS and MKN1 cells, and exosomes carrying GKN1-treated nude mice-bearing MKN1 xenograft tumors exhibited significantly reduced tumor volume and tumor weight. Silencing of clathrin markedly down-regulated the internalization of exosomal GKN1. Interestingly, serum GKN1 concentrations in patients with gastric cancer were significantly lower than those in healthy individuals and patients with colorectal and hepatocellular carcinomas.

CONCLUSIONS

The GKN1 is secreted and internalized in the gastric epithelium by exosome-driven transfer, which inhibits gastric tumorigenesis and supports the clinical application of GKN1 protein in gastric cancer diagnosis and treatment.

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.

Identification of significant biomarkers and pathways associated with gastric carcinogenesis by whole genome-wide expression profiling analysis

The incidence of gastric cancer (GC) is extremely high in East Asia. GC is also one of the most common and lethal forms of cancer from a global perspective. However, to date, we have not been able to determine one or several genes as biomarkers in the diagnosis of GC and have also been unable to identify the genes which are important in the therapy of GC. In this study, we analyzed all genome-wide expression profiling arrays uploaded onto the Gene Expression Omnibus (GEO) database to filtrate the differentially expressed genes (DEGs) between normal stomach tissues and GC tissues. GSE13911, GSE19826 and GSE79973 were based on the GPL570 platform, and GSE29272 was based on the GPL96 platform. We screened out the DEGs from the two platforms and by selecting the intersection of these two platforms, we identified the common DEGs in the sequencing data from different laboratories. Finally, we obtained 3 upregulated and 34 downregulated DEGs in GC from 384 samples. As the number of downregulated DEGs was greater than that of the upregulated DEGs, functional analysis and pathway enrichment analysis were performed on the downregulated DEGs. Through our analysis, we identified the most significant genes associated with GC, such as secreted phosphoprotein 1 (SPP1), sulfatase 1 (SULF1), thrombospondin 2 (THBS2), ATPase H+/K+ transporting beta subunit (ATP4B), gastric intrinsic factor (GIF) and gastrokine 1 (GKN1). The prognostic power of these genes was corroborated in the Oncomine database and by Kaplan-Meier plotter (KM-plotter) analysis. Moreover, gastric acid secretion, collecting duct acid secretion, nitrogen metabolism and drug metabolism were significantly related to GC. Thus, these genes and pathways may be potential targets for improving the diagnosis and clinical effects in patients with GC.

Gastric cancer and gene copy number variation: emerging cancer drivers for targeted therapy

Gastric cancer (GC) is among the most common malignancy in the world with poor prognosis and limited treatment options. It has been established that gastric carcinogenesis is caused by a complex interaction between host and environmental factors. Copy number variation (CNV) refers to a form of genomic structural variation that results in abnormal gene copy numbers, including gene amplification, gain, loss and deletion. DNA CNV is an important influential factor for the expression of both protein-coding and non-coding genes, affecting the activity of various signaling pathways. CNV arises as a result of preferential selection that favors cancer development, and thus, targeting the amplified 'driver genes' in GC may provide novel opportunities for personalized therapy. The detection of CNVs in chromosomal or mitochondrial DNA from tissue or blood samples may assist the diagnosis, prognosis and targeted therapy of GC. In this review, we discuss the recent CNV discoveries that shed light on the molecular pathogenesis of GC, with a specific emphasis on CNVs that display diagnostic, prognostic or therapeutic significances in GC.