Oncogenesis Of Gastric Cancer Research Articles

The Roles of Innate Lymphoid Cells in the Gastric Mucosal Immunology and Oncogenesis of Gastric Cancer

Innate lymphoid cells (ILCs) are a group of innate immune cells that have garnered considerable attention due to their critical roles in regulating immunity and tissue homeostasis. They are particularly abundant in the gastrointestinal tract, where they have been shown to interact with commensal bacteria, pathogens, and other components of the local microenvironment to influence host immune responses to infection and oncogenesis. Their tissue-residency properties enable gastric ILCs a localized and rapid response to alert and stress, which indicates their key potential in regulating immunosurveillance. In this review, we discuss the current understanding of the role of ILCs in the gastric mucosa, with a focus on their interactions with the gastric microbiota and Helicobacter pylori and their contributions to tissue homeostasis and inflammation. We also highlight recent findings on the involvement of ILCs in the pathogenesis of gastric cancer and the implications of targeting ILCs as a therapeutic approach. Overall, this review provides an overview of the diverse functions of ILCs in gastric mucosa and highlights their potential as targets for future therapies for gastric cancer.

Molecular characteristics, oncogenic roles, and relevant immune and pharmacogenomic features of NEK2 in gastric cancer

Gastric cancer (GC) is the most common form of gastrointestinal cancer, with a high mortality rate and limited treatment options. High levels of NEK2 are associated with malignant progression and a poor prognosis in several tumors; however, the role of NEK2 in GC remains unclear. We aimed to explore the potential role of NEK2 in the oncogenesis of GC and in the shaping of the tumor microenvironment (TME). The expression levels of NEK2 were analyzed using immunohistochemistry and real-time quantitative polymerase chain reaction. We found that NEK2 expression was upregulated in GC and was a predictor of a poor prognosis. Based on Kyoto Encyclopedia of Genes and Genomes pathway enrichment and gene set enrichment analyses, multiple tumor pathways were hyperactivated in patients with high NEK2 mRNA expression. Immunological characteristics indicated that NEK2 upregulation might lead to decreased immune cell infiltration and weakened immune activity in the cancer immunity cycle. Additionally, higher frequencies of amplifications and deletions were observed in the high NEK2 expression subpopulation. Based on the TME classification, patients with high expression of NEK2 were more susceptible to targeted therapy with drugs targeting the cell cycle and DNA replication. Following verification, a NEK2-derived genomic model reliably predicted the patient prognosis; A nomogram (radiation therapy, tumor/node/metastasis staging, and the NEK2-derived risk score) was used to better estimate an individual’s survival probability. In summary, our findings indicate that NEK2 plays a vital role in the tumorigenesis of GC.

Helicobacter pylori-induced NAT10 stabilizes MDM2 mRNA via RNA acetylation to facilitate gastric cancer progression

BackgroundN4-acetylcytidine (ac4C), a widespread modification in human mRNAs that is catalyzed by the N-acetyltransferase 10 (NAT10) enzyme, plays an important role in promoting mRNA stability and translation. However, the biological functions and regulatory mechanisms of NAT10-mediated ac4C were poorly defined.Methodsac4C mRNA modification status and NAT10 expression levels were analyzed in gastric cancer (GC) samples and compared with the corresponding normal tissues. The biological role of NAT10-mediated ac4C and its upstream and downstream regulatory mechanisms were determined in vitro and in vivo. The therapeutic potential of targeting NAT10 in GC was further explored.ResultsHere, we demonstrated that both ac4C mRNA modification and its acetyltransferase NAT10 were increased in GC, and increased NAT10 expression was associated with disease progression and poor patient prognosis. Functionally, we found that NAT10 promoted cellular G2/M phase progression, proliferation and tumorigenicity of GC in an ac4C-depedent manner. Mechanistic analyses demonstrated that NAT10 mediated ac4C acetylation of MDM2 transcript and subsequently stabilized MDM2 mRNA, leading to its upregulation and p53 downregulation and thereby facilitating gastric carcinogenesis. In addition, Helicobacter pylori (Hp) infection contributed to NAT10 induction, causing MDM2 overexpression and subsequent p53 degradation. Further investigations revealed that targeting NAT10 with Remodelin showed anti-cancer activity in GC and augmented the anti-tumor activity of MDM2 inhibitors in p53 wild-type GC.ConclusionsThese results suggest the critical role of NAT10-mediated ac4C modification in GC oncogenesis and reveal a previously unrecognized signaling cascade involving the Hp-NAT10-MDM2-p53 axis during GC development.

Development of Epstein-Barr virus-associated gastric cancer: Infection, inflammation, and oncogenesis

Epstein-Barr virus (EBV)-associated gastric cancer (EBVaGC) cells originate from a single-cell clone infected with EBV. However, more than 95% of patients with gastric cancer have a history of Helicobacter pylori (H. pylori) infection, and H. pylori is a major causative agent of gastric cancer. Therefore, it has long been argued that H. pylori infection may affect the development of EBVaGC, a subtype of gastric cancer. Atrophic gastrointestinal inflammation, a symptom of H. pylori infection, is observed in the gastric mucosa of EBVaGC. Therefore, it remains unclear whether H. pylori infection is a cofactor for gastric carcinogenesis caused by EBV infection or whether H. pylori and EBV infections act independently on gastric cancer formation. It has been reported that EBV infection assists in the onco-genesis of gastric cancer caused by H. pylori infection. In contrast, several studies have reported that H. pylori infection accelerates tumorigenesis initiated by EBV infection. By reviewing both clinical epidemiological and experimental data, we reorganized the role of H. pylori and EBV infections in gastric cancer formation.

Synaptotagmin 11 scaffolds MKK7–JNK signaling process to promote stem-like molecular subtype gastric cancer oncogenesis

BackgroundIdentifying biomarkers related to the diagnosis and treatment of gastric cancer (GC) has not made significant progress due to the heterogeneity of tumors. Genes involved in histological classification and genetic correlation studies are essential to develop an appropriate treatment for GC.MethodsIn vitro and in vivo lentiviral shRNA library screening was performed. The expression of Synaptotagmin (SYT11) in the tumor tissues of patients with GC was confirmed by performing Immunohistochemistry, and the correlation between the expression level and the patient’s survival rate was analyzed. Phospho-kinase array was performed to detect Jun N-terminal kinase (JNK) phosphorylation. SYT11, JNK, and MKK7 complex formation was confirmed by western blot and immunoprecipitation assays. We studied the effects of SYT11 on GC proliferation and metastasis, real-time cell image analysis, adhesion assay, invasion assay, spheroid formation, mouse xenograft assay, and liver metastasis.ResultsSYT11 is highly expressed in the stem-like molecular subtype of GC in transcriptome analysis of 527 patients with GC. Moreover, SYT11 is a potential prognostic biomarker for histologically classified diffuse-type GC. SYT11 functions as a scaffold protein, binding both MKK7 and JNK1 signaling molecules that play a role in JNK1 phosphorylation. In turn, JNK activation leads to a signaling cascade resulting in cJun activation and expression of downstream genes angiopoietin-like 2 (ANGPTL2), thrombospondin 4 (THBS4), Vimentin, and junctional adhesion molecule 3 (JAM3), which play a role in epithelial-mesenchymal transition (EMT). SNU484 cells infected with SYT11 shRNA (shSYT11) exhibited reduced spheroid formation, mouse tumor formation, and liver metastasis, suggesting a pro-oncogenic role of SYT11. Furthermore, SYT11-antisense oligonucleotide (ASO) displayed antitumor activity in our mouse xenograft model and was conferred an anti-proliferative effect in SNU484 and MKN1 cells.ConclusionSYT11 could be a potential therapeutic target as well as a prognostic biomarker in patients with diffuse-type GC, and SYT11-ASO could be used in therapeutic agent development for stem-like molecular subtype diffuse GC.

244 MICROBIOME ANALYSIS OF UPPER DIGESTIVE TRACT BIOPSY SAMPLES FROM INDIVIDUALS ALONG THE METAPLASIA-DYSPLASIA-ADENOCARCINOMA SEQUENCE.

Abstract The human microbiota, the collection of microbes that inhabit the human body, is increasingly being appreciated as playing a role in human health. A seminal example of this relationship is Helicobacter pylori and gastric cancer oncogenesis. The drop in H.pylori infections and non-cardia gastric cancer incidences has coincided with the rise in oesophageal adenocarcinoma (OAC) incidences. We sought to explore the relationship between the upper digestive tract microbiome and OAC oncogenesis. Methods Pinch biopsies were taken from individual’s oesophagus and stomach who were along the metaplasia-dysplasia-adenocarcinoma sequence (GERD, Barrett's oesophagus, dysplasia, OAC, metastatic OAC) as well as healthy controls. We carried out 16 s rRNA gene DNA sequencing protocols on these samples. DNA extraction and library preparation was performed with consideration to the low mass nature of oesophageal biopsies. Raw reads were processed and amplicon sequence variants (ASVs) were generated using the DADA2. We dissected ecological differences between sample site and clinical classification using a variety of approaches including examining differentially abundant taxa and inferred metabolic pathways, alpha diversity and beta-diversity. Results The upper digestive tract was found to be dominated by the genera Streptococcus, Prevotella, and Haemophilus. There was no statistically significant shift in beta diversity with respect to biopsy location. Alpha diversity was reduced in gastric biopsies compare to oesophageal biopsies. A slight yet significant shift was seen in beta diversity (Bray–Curtis Dissimilarity) with respect to clinical classification in biopsies derived from the gastroesophageal junction (GEJ) and stomach. Various taxa were found to be differentially abundant between biopsy site and with regard to clinical classification. Conclusion OAC primarily occurs at the GEJ. Community structure was shifted in samples derived from the GEJ and the stomach. Fusobacterium nucleatum was overrepresented in oesophageal biopsies from individuals with diseased oesophagus compared to individuals with a histologically normal oesophagus. This bacterium has been implicated in oncogenesis of various cancers most notably colorectal cancer. Serval ASVs assigned to the genus Prevotella were depleted in stomachs of individuals with metastatic OAC compared to all other groups.

A global and physical mechanism of gastric cancer formation and progression

Gastric cancer is regarded as a major health issue for human being nowadays. The Helicobacter pylori (H. pylori) infection has been found to accelerate the development of gastritis and gastric cancer. Significant efforts have been made towards the understanding of the biology of gastric cancer on both genetic and epigenetic levels. However the physical mechanism behind the gastric cancer formation is still elusive. In this study, we constructed a model for investigating gastric cancer formation by explored the gastric cancer landscape and the flow flux. We uncovered three stable state attractors on the landscape: normal, gastritis and gastric cancer. The definition of each attractor is based on the biological function and gene expression levels. The global stabilities and the switching processes were quantified through the barrier heights and dominant kinetic paths. To investigate the underlying mechanism of the process from normal through the gastritis to the gastric cancer caused by genetic or epigenetic factors, we simulate the oncogenesis of gastric cancer through changes of several gene regulation strengths and H. pylori infection. The simulated results can illustrate the developmental and metastasis process of gastric cancer. Different H. pylori infection degrees accelerating the process from gastritis to gastric cancer can be quantified. Then we applied global sensitivity analysis, one key gene and four key regulations were found. These results are consist with the experimental results and can be used to design the polygenic anti-cancer agents through multiple key genes or regulations. The landscape approach provides a physical and simple strategy for analyzing gastric cancer in a systematic and quantitative way. It also offers new insight into treatment strategy for gastric cancer by adjusting relevant polygenic genes and regulations.

EZH2-mediated epigenetic suppression of lncRNA PCAT18 predicts a poor prognosis and regulates the expression of p16 by interacting with miR-570a-3p in gastric cancer.

It was recently demonstrated that long noncoding RNAs (lncRNAs) have key regulation functions in the biology of human cancer. The current study aimed to determine the expression, clinicopathological characteristics and functional roles of lncRNA PCAT18 in gastric cancer (GC).By analysis of (Gene Expression Omnibus) GEO and TCGA data, following experimental verification, we identified the function role and molecular mechanism of PCAT18 in tumorigenesis of GC. We discovered that PCAT18 is significantly decreased in paired GC tissues and correlates with a poor outcome. Mechanistic studies found that suppression of the expression of EZH2 could prevent its binding to the PCAT18's promoter region and decrease H3K27's trimethylation modification. In addition, PCAT18 could adjust cell proliferation of GC in vitro as well as in vivo. Further mechanism research revealed that PCAT18 could regulate the expression of p16 by interacting with miR-570a-3p, thus inhibiting cell proliferation of GC. Our results have shown that the histone modification-mediated epigenetic suppression of PCAT18 and its essential role of PCAT18 in GC oncogenesis, which could provide a theoretical basis for GC therapy.

Blockage of ETS homologous factor inhibits the proliferation and invasion of gastric cancer cells through the c-Met pathway

BACKGROUNDGastric cancer (GC) is one of the most common and deadliest types of cancer worldwide due to its delayed diagnosis and high metastatic frequency, but its exact pathogenesis has not been fully elucidated. ETS homologous factor (EHF) is an important member of the ETS family and contributes to the pathogenesis of multiple malignant tumors. To date, whether EHF participates in the development of GC via the c-Met signaling pathway remains unclear.AIMTo investigate the role and mechanism of EHF in the occurrence and development of GC.METHODSThe expression of EHF mRNA in GC tissues and cell lines was measured by quantitative PCR. Western blotting was performed to determine the protein expression of EHF, c-Met, and its downstream signal molecules. The EHF expression in GC tissues was further detected by immunohistochemical staining. To investigate the role of EHF in GC oncogenesis, small interfering RNA (siRNA) against EHF was transfected into GC cells. The cell proliferation of GC cells was determined by Cell Counting Kit-8 and colony formation assays. Flow cytometry was performed following Annexin V/propidium iodide (PI) to identify apoptotic cells and PI staining to analyze the cell cycle. Cell migration and invasion were assessed by transwell assays.RESULTSThe data showed that EHF was upregulated in GC tissues and cell lines in which increased expression of c-Met was also observed. Silencing of EHF by siRNA reduced the proliferation of GC cells. Inhibition of EHF induced significant apoptosis and cell cycle arrest in GC cells. Cell migration and invasion were significantly inhibited. EHF silencing led to c-Met downregulation and further blocked the Ras/c-Raf/extracellular signal-related kinase 1/2 (Erk1/2) pathway. Additionally, phosphatase and tensin homolog was upregulated and glycogen synthase kinase 3 beta was deactivated. Moreover, inactivation of signal transducer and activator of transcription 3 was detected following EHF inhibition, leading to inhibition of the epithelial-to-mesenchymal transition (EMT).CONCLUSIONThese results suggest that EHF plays a key role in cell proliferation, invasion, apoptosis, the cell cycle and EMT via the c-Met pathway. Therefore, EHF may serve as an antineoplastic target for the diagnosis and treatment of GC.

Epstein-Barr virus-associated gastric cancer: A distinct subtype.

Epstein-Barr virus (EBV)-associated gastric cancer (EBVaGC) is a common malignant tumor associated with EBV infection. The molecular classification of gastric carcinoma indicates that EBVaGC is a distinct subtype in terms of oncogenesis and molecular features. Viral proteins, Bam-HI-A rightward transcripts (BART) miRNAs, and Bam-HI A rightward frame 1 (BARF1) promote oncogenesis after EBV infection via the induction of methylation, regulation of host gene expression, and malignant transformation. Together with abnormal mutations and amplification of the host genome as driving factors, interactions between the EBV genome and host genome accelerate carcinogenesis. The molecular profile of EBVaGC is that of EBV driving DNA hypermethylation, frequent phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) mutations, and the overexpression of Janus kinase 2 (JAK2), programmed death ligand-1 (PD-L1), and PD-L2. Clinically, the frequency of lymph node metastasis is lower, and the prognosis is better for EBVaGC than EBV-negative gastric cancer (EBVnGC). Pathologically, EBVaGC is a gastric adenocarcinoma with lymphoid stroma. This review interprets how the EBV genome is involved in the oncogenesis of gastric cancer and describes the molecular and clinicopathological features of EBVaGC.

496 THE INFLAMMATORY-METAPLASIA-DYSPLASIA-OESOPHAGEAL ADENOCARCINOMA SEQUENCE: THE ROLE OF THE MICROBIOME

Abstract The human microbiota, the collection of microbes that inhabit the human body, is increasingly recognized as playing a role in human health. A seminal example of this relationship is Helicobacter pylori and gastric cancer oncogenesis. The decline in H.pylori prevalence and non-cardia gastric cancer incidence have coincided with the rise in oesophageal adenocarcinoma (OAC) incidence. We sought to explore the relationship between the gastric and oesophageal microbiome and OAC oncogenesis. Methods This study aimed to explore changes in the microbiome associated with oesophageal adenocarcinoma and its precancerous and inflammatory states by performing 16S rRNA gene amplicon sequencing on DNA extracted from oesophago-gastric biopsies from patients with normal oesophageal mucosa, reflux oesophagitis, Barrett’s oesophagus with and without dysplasia, locally advanced but resectable oesophageal adenocarcinoma, and incurable metatstatic oesophageal adenocarcinoma (See Table 1). We dissected ecological differences between sample site and clinical classification using a variety of approaches including examining differentially abundant taxa and inferred metabolic pathways, alpha diversity and beta-diversity. Results There was no statistically significant difference in beta diversity with respect to biopsy location. Alpha diversity was reduced in gastric biopsies compare to oesophageal biopsies. A small but significant shift was noted in beta diversity (Bray–Curtis Dissimilarity) with respect to clinical classification in biopsies derived from the gastroesophageal junction (GEJ) and stomach. Fusobacterium nucleatum was found to overrepresented in oesophageal biopsies derived from diseased groups relative to the healthy controls. Several taxa assigned to the genus Prevotella were depleted in biopsies of individuals with metastatic OAC compared to all other groups. Conclusion Community structure was shifted in samples derived from the GEJ, the epicentre of OAC oncogenesis. Fusobacterium plays a role in cancer development and progression through a number of mechanisms including increasing cell proliferation, immune cell infiltration and chemoresistance. Fusobacterium can cause upregulation of MicroRNA-21, a microRNA upregulated in OAC.

151P - Gene expression profiling for a better understanding of gastric cancer: From the perspective of metabolic rearrangement

BackgroundMetabolic rearrangement has been shown to be an important characteristic for stomach adenocarcinomas. Here we aimed to improve our understanding of the tumorigenesis of gastric cancer by means of gene and protein expression profile analysis with a focus on metabolic genes and pathways. MethodsArray-based gene expression profiling of fresh frozen cancer tissues and adjacent normal tissues were obtained from 8 patients with gastric cancer at early stage by using Affymetrix oligonucleotide microarray. Assays targeted 179 unique genes related to cancer metabolism. The raw expression data were normalized using nSolver Analysis Software 3.0 and a dataset of gene expression ratios for GC vs. controls was generated. The p values were calculated using a paired t-test, and the threshold for up- and down-regulated genes was set at p value < 0.05. The protein expression of the dysregualted genes were detected by immunohistochemistry (IHC) in the formalin fixed paraffin embedded tissue blocks. The signal was quantified by the Allred score system which represented the estimated intensity and proportion of positive-staining cells. ResultsOur microarray results showed increased expression of 20 metabolic genes and decreased expression of 6 metabolic genes in all cases of gastric cancer at early stage. Besides of the undetected NOX4, the protein levels of all the others dysregualted genes, detected by IHC, showed consistently results. Half of all dysregulated genes (AKT2, EGLN3, G6PD, GLS, HIF1A, HK2, HRAS, MAP2K1, NTRK3, PGK1, PLCG1, RET and RPS6KB1) are implicated in Carbon Metabolism, a pivotal metabolic approach involving in nucleic acid biosynthesis. Five genes (ARNT, EGLN1, EGLN3, HIF1A and NOX4) are molecules implicated in hypoxia signaling. Besides, the upregulated HIF1A is a cancer metabolism driver, which means that HIF1A may induce the oncogenesis of gastric cancer. ConclusionsThe gastric mucosa in gastric cancer at early stage is characterized by dysregulated expression of a limited repertoire of metabolic genes. The nature of the corresponding metabolic rearrangement and pathways may help guide further investigations into its etiology. Legal entity responsible for the studyFudan University Shanghai Cancer Center. FundingNational Human Genetic Resources Sharing Service Platform (2005DKA21300), National Natural Science Foundation of China (81602078),. DisclosureAll authors have declared no conflicts of interest.

Elevated limb-bud and heart development (LBH) expression indicates poor prognosis and promotes gastric cancer cell proliferation and invasion via upregulating Integrin/FAK/Akt pathway

The limb-bud and heart development (LBH) gene is a highly conserved, tissue-specific transcription cofactor in vertebrates that regulates multiple key genes in embryonic development. The role of LBH in various cancer types is still controversial, and its specific role and molecular mechanism in the oncogenesis of gastric cancer (GC) remains largely unexplored. In the present study, the prognostic significance and clinicopathological characteristics of LBH in GC was determined. The LBH mRNA expression was first investigated in four independent public datasets (TCGA-STAD, GSE15459, GSE29272, and GSE62254) and then validated with our samples at the protein level. LBH was overexpressed at both the mRNA and protein levels in cancer compared with normal tissues. High LBH expression was correlated with advanced T, N, and M stages. Kaplan–Meier analysis and log-rank test indicated that higher LBH expression was statistically correlated with shorter overall survival (OS) in the public datasets and our study samples. Univariate and multivariate Cox regression analysis showed that LBH was an independent prognostic biomarker for survival in TCGA-STAD, GSE15459, GSE62254 cohorts, and our GC patients. In vitro experiments showed that knockdown of LBH can significantly inhibit the proliferation and invasion of HGC-27 cells, while overexpression of LBH can significantly enhance the proliferation and invasion of BGC-823 cells. Gene Set Enrichment Analysis (GSEA), Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomics (KEGG) indicated that high LBH expression is associated with the PI3K-Akt pathway, focal adhesion, and extracellular matrix (ECM)-receptor interaction. Western blot analysis showed that knockdown of LBH significantly inhibited the expression of integrin α5, integrin β1, p-FAK, and p-Akt. Therefore, results from the present study indicate that LBH is a potential independent prognostic biomarker and promotes proliferation and invasion of GC cells by activating the integrin/FAK/Akt pathway.

A novel long noncoding RNA HOXC-AS3 mediates tumorigenesis of gastric cancer by binding to YBX1

BackgroundRecently, increasing evidence shows that long noncoding RNAs (lncRNAs) play a significant role in human tumorigenesis. However, the function of lncRNAs in human gastric cancer remains largely unknown.ResultsBy using publicly available expression profiling data from gastric cancer and integrating bioinformatics analyses, we screen and identify a novel lncRNA, HOXC-AS3. HOXC-AS3 is significantly increased in gastric cancer tissues and is correlated with clinical outcomes of gastric cancer. In addition, HOXC-AS3 regulates cell proliferation and migration both in vitro and in vivo. RNA-seq analysis reveals that HOXC-AS3 knockdown preferentially affects genes that are linked to proliferation and migration. Mechanistically, we find that HOXC-AS3 is obviously activated by gain of H3K4me3 and H3K27ac, both in cells and in tissues. RNA pull-down mass spectrometry analysis identifies that YBX1 interacts with HOXC-AS3, and RNA-seq analysis finds a marked overlap in genes differentially expressed after YBX1 knockdown and those transcriptionally regulated by HOXC-AS3, suggesting that YBX1 participates in HOXC-AS3-mediated gene transcriptional regulation in the tumorigenesis of gastric cancer.ConclusionsTogether, our data demonstrate that abnormal histone modification-activated HOXC-AS3 may play important roles in gastric cancer oncogenesis and may serve as a target for gastric cancer diagnosis and therapy.

CCAT1 expressed in malignant and pre-malignant human gastric tissues

CCAT1 has been reported to implicate in various human malignancies. However, its expression in the oncogenesis of gastric cancer (GC) remains unknown. Quantitative reverse transcription (RT)-qPCR assay was performed to detect the expression of CCAT1 in 68cases of GC tissues,paired tumor-proximal gastric mucosa and normal gastric mucosa, 19 cases of gastric intraepithelial neoplasia (GIN), and the sera of these 68 GC patients and 22 healthy volunteers. And the relationship between CCAT1 and clinicopathologic features of GC patients were analyzed. Inthe present study, we found that CCAT1 expression was significantly abnormally deregulated in GC tissues (185.43 ± 21.37), GIN tissues (121.30 ± 43.61), tumor-proximal mucosa (8.9 ± 1.21), and normal mucosa (1.5 ± 0.55). CCAT1 wasalso overexpressed in the sera of GC patients (47.40 ± 6.60) compared with healthy controls (0.62 ± 0.06; p &lt; 0.001). And high CCAT1 expression in GC tissues was associated with high tumor burden, including larger tumor size, lymphatic metastasis and advanced TNM stage (all p &lt; 0.05). These results reveal that CCAT1 is a detectable biomarkerforgastric cancertumorigenesis and may be utilized as adiagnosticand prognosticindicator.

Functional role of autophagy in gastric cancer.

Autophagy is a highly regulated catabolic pathway responsible for the degradation of long-lived proteins and damaged intracellular organelles. Perturbations in autophagy are found in gastric cancer. In host gastric cells, autophagy can be induced by Helicobacter pylori (or H. pylori) infection, which is associated with the oncogenesis of gastric cancer. In gastric cancer cells, autophagy has both pro-survival and pro-death functions in determining cell fate. Besides, autophagy modulates gastric cancer metastasis by affecting a wide range of pathological events, including extracellular matrix (ECM) degradation, epithelial-to-mesenchymal transition (EMT), tumor angiogenesis, and tumor microenvironment. In addition, some of the autophagy-related proteins, such as Beclin 1, microtubule-associated protein 1 light chain 3 (MAP1-LC3), and p62/sequestosome 1 (SQSTM1) have certain prognostic values for gastric cancer. In this article, we review the recent studies regarding the functional role of autophagy in gastric cancer.

3,3'-Diindolylmethane potentiates paclitaxel-induced antitumor effects on gastric cancer cells through the Akt/FOXM1 signaling cascade.

Gastric cancer is the fourth most common cancer and is one of the leading causes of cancer-related mortality worldwide. Forkhead boxM1 (FOXM1) is overexpressed in gastric cancer, suggesting that it is important in gastric cancer oncogenesis. However, no studies have investigated the role of 3,3'-diindolylmethane (DIM), a component of cruciferous vegetables, in the regulation of FOXM1 and its signaling pathway in gastric cancer. Here, we report for the first time that DIM effectively downregulated Akt/FOXM1 in gastric cancer cells. Combination treatment with DIM and paclitaxel significantly and dose-dependently inhibited the proliferation of SNU638 cells when compared to treatment with DIM or paclitaxel alone. Colony formation of SNU638 cells was significantly attenuated by treatment with DIM and paclitaxel, and DIM potentiated the inhibition of colony formation in SNU638 cells by paclitaxel when compared to treatment with a single agent. Treatment with DIM plus paclitaxel substantially increased apoptosis as indicated by increased levels of cleaved polyADP-ribose polymerase (PARP) and cleaved caspase-9 protein. DIM dose-dependently sensitized gastric cancer cells through downregulation of FOXM1 and potentiated the effects of paclitaxel. FOXM1 effector genes such as CDK4, p53 and cyclinD1 were downregulated in gastric cancer cells by combination treatment with DIM and paclitaxel. In addition, DIM significantly and dose-dependently inhibited phosphorylation of Akt and potentiated paclitaxel-induced inhibition of Akt function in gastric cancer cells. Therefore, our results indicate that DIM effectively potentiates the efficacy of chemotherapeutic agents such as paclitaxel by downregulation of the Akt/FOXM1 signaling cascade in gastric cancer cells. Our findings suggest that DIM enhances the therapeutic efficacy of paclitaxel in gastric cancer and is a potential clinical anticancer agent for the prevention and/or treatment of gastric cancer.

Transcriptional regulation of miR-196b by ETS2 in gastric cancer cells

E26 transformation-specific sequence (ETS)-2 is a transcriptional modulator located on chromosome 21, alterations in its expression have been implicated with a reduced incidence of solid tumors in Down syndrome patients. MicroRNAs (miRNAs) are thought to participate in diverse biological functions; however, the regulation of miRNAs is not well characterized. Recently, we reported that miR-196b is highly expressed in gastric cancers. Herein, we demonstrate that miR-196b expression was significantly repressed by ETS2 during gastric cancer oncogenesis. We demonstrate that knockdown of endogenous ETS2 expression increases miR-196b expression. A genomic region between −751 and −824 bp upstream of the miR-196b transcriptional start site was found to be critical for the repression activity. This putative regulatory promoter region contains three potential ETS2-binding motifs. Mutations within the ETS2 binding sites blocked the repression activity of ETS2. Furthermore, knockdown of ETS2 or overexpression of miR-196b significantly induced migration and invasion in gastric cancer cells. In addition, alterations in ETS2 and miR-196b expression in gastric cancer cell lines affected the expression of epithelial–mesenchymal transition-related genes. The levels of vimentin, matrix metalloproteinase (MMP)-2 and MMP9 were drastically induced, but levels of E-cadherin were decreased in shETS2- or miR-196b-transfected cells. Our data indicate that ETS2 plays a key role in controlling the expression of miR-196b, and miR-196b may mediate the tumor suppressor effects of ETS2. We demonstrated that miR-196b was transcriptionally regulated by ETS2 and there was an inverse expression profile between miR-196b and ETS2 in clinical samples. This finding could be beneficial for the development of effective cancer diagnostic and alternative therapeutic strategies.

Suppressor of Cytokine Signaling 4 Detected as a Novel Gastric Cancer Suppressor Gene using Double Combination Array Analysis

Molecular mechanisms behind the oncogenesis of gastric cancer (GC) have yet to be identified. A novel candidate tumor-suppressor gene, which is also associated with inhibition of epidermal growth factor (EGF), was sought by means of double combination array analysis for use as a prognostic marker of GC. This consisted of expression array and single nucleotide polymorphism array analysis, along with a literature search. Cancerous and noncancerous tissues from an 82-year-old man with GC were analyzed simultaneously. The expression array and literature search identified that the suppressor of cytokine signaling 4 (SOCS4), a negative feedback regulator of EGF signaling, had significantly attenuated expression in tumor tissue. Although chromosomal deletion was not found at 14q22 where SOCS4 is located, numerous CpG sites were observed in the promoter region of the SOCS4 gene. Several GC cell lines showed reactivation of SOCS4 mRNA expression after treatment with 5-aza-2'-deoxycytidine. Using surgically resected specimens, we found that 40 of 50 (80%) tumor tissues exhibited promoter hypermethylation of the SOCS4 gene. Consequently, SOCS4 expression in tumor tissues was significantly weaker than in noncancerous counterparts (P < 0.0001). In the survival analysis, SOCS4 hypermethylation was associated with a poor prognosis of GC patients (P = 0.0320). Double combination array analysis suggested that SOCS4 could be a novel candidate for further exploration as a tumor-suppressor gene in GC. Hypermethylation was the mechanism by which SOCS4 was silenced and was implicated in the development of GC. SOCS4 methylation might be an informative marker in predicting the prognosis.

Expression profile of EFNB1, EFNB2, two ligands of EPHB2 in human gastric cancer.

We have previously reported that EPHB2 is overexpressed in gastric cancer; however, the expression profiles of its ligands, EFNB1 and EFNB2, are unknown. This study was designed to investigate the expression of EPHB2 and its ligands, EFNB1 and EFNB2, in human gastric cancer. Semi-quantitative RT-PCR using (32)P was performed on human gastric cancer tissues and corresponding normal tissues (29 gastric cancer patients). EPHB2 was more highly expressed in tumor tissues than in normal tissues in 21 out of 29 (72.4%), in gastric cancer patients ( P = 0.01); EFNB1 and EFNB2 were highly expressed in 21 out of 29 (72.4%) ( P = 0.037) and 14 out of 29 (48.3%) patients, respectively. The overexpression of EPHB2 was frequently detected in both well-differentiated adenocarcinoma and poorly differentiated adenocarcinoma [10/13 (76.9%) and 9/14 (64.3%), respectively]. On the other hand, the overexpression of EFNB1 was more frequently detected in poorly differentiated adenocarcinoma than in well-differentiated adenocarcinoma [12/14 (85.7%) and 7/13 (53.8%), respectively. P =0.027]. Elevated levels of EPHB2 and EFNB1 were detected in substantial subsets of early gastric cancers. Genomic alterations to these three genes in gastric cancer specimens were either not found or rarely found except for several rare variations of EPHB2. These findings suggest that not only the expression of EPHB2, but the expression of its ligand EFNB1 may have some relation with the oncogenesis of gastric cancer.