Pathogenesis of Gastric Cancer

Oleanolic acid regulates the Treg/Th17 imbalance in gastric cancer by targeting IL-6 with miR-98-5p

BACKGROUND

Gastric cancer (GC) was a type of malignant tumor with a very high fatality rate. Oleanolic acid (OA) was a class of pentacyclic triterpenes which was proved to have anti-cancer activity. While the specific molecular mechanism of OA's role in inhibiting GC was not fully understood. This study aimed to explore how OA played an anti-cancer role in GC.

METHODS

Expression of miR-98-5p was examined using qPCR, and expression levels of Treg/Th17-related factors were evaluated using qPCR and western blot. Flow cytometry was conducted to assess the proportion of Treg cells and Th17 cells. Besides, dual luciferase reporter assay was performed to verify that IL-6 was a target of miR-98-5p.

RESULTS

Downregulation of miR-98-5p and upregulation of Treg/Th17-related factors were observed in GC tissues. What's more, the Treg/Th17 imbalance was found in PBMCs of GC patients. Overexpression of miR-98-5p promoted balance of Treg/Th17 cells via directly targeting IL-6 to downregulate expression of IL-6. Finally, OA could promote balance of Treg/Th17 cells by upregulating expression of miR-98-5p.

DISCUSSION

All our results proved that OA could promote balance of Treg/Th17 cells in GC by targeting IL-6 with miR-98-5p, indicating a potential drug for treatment of GC.

Knockdown of Circ_0000144 Suppresses Cell Proliferation, Migration and Invasion in Gastric Cancer Via Sponging MiR-217

Previous studies have uncovered the role of circ_0000144 in various tumors. Here, we investigated the function and mechanism of circ_0000144 in gastric cancer (GC) progression. The expression of circ_0000144 in GC tissues and cells was detected through quantitative real-time polymerase chain reaction (qRT-PCR) method. Gain- and loss-of-function experiments including colony formation, wound healing and transwell assays were performed to examine the role of circ_0000144 in GC cells. Furthermore, western blot was conducted to determine the expressions of epithelial mesenchymal transition (EMT)-related proteins. The interaction between circ_0000144 and miR-217 was analyzed by bioinformatic analysis and luciferase reporter assays. The circ_0000144 expression was obviously upregulated in GC tissues and cells. Silencing of circ_0000144 inhibited cell proliferation, migration and invasion of GC cells, but ectopic expression of circ_0000144 showed the opposite results. Moreover, circ_0000144 sponged miR-217, and rescue assays revealed that silencing miR-217 expression reversed the inhibitory effect of circ_0000144 knockdown on the progress of GC. Our findings reveal that circ_0000144 inhibition suppresses GC cell proliferation, migration and invasion via absorbing miR-217, providing a new biomarker and potential therapeutic target for treatment of GC.

The Multifaceted Role of Long Non-Coding RNA in Gastric Cancer: Current Status and Future Perspectives

Gastric cancer (GC) is one of the major public health concerns. Long non-coding RNAs (lncRNAs) have been increasingly demonstrated to possess a strong correlation with GC and play a critical role in GC occurrence, progression, metastasis and drug resistance. Many studies have shed light on the understanding of the underlying mechanisms of lncRNAs in GC. In this review, we summarized the updated research about lncRNAs in GC, focusing on their roles in Helicobacter pylori infection, GC metastasis, tumor microenvironment regulation, drug resistance and associated signaling pathways. LncRNAs may serve as novel biomarkers for diagnosis and prognosis of GC and potential therapeutic targets. The research gaps and future directions were also discussed.

Long Noncoding RNAs: New Regulators of Resistance to Systemic Therapies for Gastric Cancer

Gastric cancer (GC) is the second leading cause of cancer mortality and the fourth most commonly diagnosed malignant disease, with approximately 951,000 new cases diagnosed and approximately 723,000 cases of mortality each year. The highest mortality rate of GC is in East Asia, and the lowest is in North America. A large number of studies have demonstrated that GC patients are characterized by higher morbidity, metastasis rates, and mortality and lower early diagnosis rates, radical resection rates, and 5-year survival rates. All cases of GC can be divided into two important stages, namely, early- and advanced-stage GC, and the stage mainly determines the treatment strategy for and the therapeutic effect in GC patients. Patients with early-stage GC undergo radical surgery followed by chemotherapy, and the 5-year survival rate can be as high as 90%. However, patients with advanced-stage GC cannot undergo radical surgery because they are at risk for metastasis; therefore, they can choose only radiotherapy or chemotherapy and have a poor prognosis. Based on the lack of specific clinical manifestations and detection methods, most GC patients (>70%) are diagnosed in the advanced stage; therefore, continued efforts toward developing treatments have been focused on advanced-stage GC patients and include molecular targeted therapy, immunotherapy, and small molecular therapy. Nevertheless, in recent years, accumulating evidence has indicated that small molecules, especially long noncoding RNAs (lncRNAs), are involved in the occurrence, development, and progression of GC, and their abundantly dysregulated expression has been identified in GC tissues and cell lines. Therefore, lncRNAs are considered easily detectable molecules and ideal biomarkers or target-specific agents for the future diagnosis or treatment of GC. In this review, we primarily discuss the status of GC, the role of lncRNAs in GC, and the emerging systemic treatments for GC.

HoxC6 Functions as an Oncogene and Isoform HoxC6-2 May Play the Primary Role in Gastric Carcinogenesis

PURPOSE

Based on previous researches of HoxC6, this study aims to investigate the expression levels of isoforms HoxC6-1 and HoxC6-2 and to explore their roles in gastric carcinogenesis as well as the possible molecular mechanism.

METHODS

We investigated expression levels of HoxC6, HoxC6-1, and HoxC6-2 in gastric cancer tissues, coupled with relevant data in TCGA dataset. In vitro, HoxC6, HoxC6-1, and HoxC6-2 knockdown by small interference RNA was carried for evaluating the changes of malignant biological behaviors of gastric cancer cells, such as proliferation, migration, invasion, apoptosis, and cell cycle alternation. Metastasis-related nucleotide lncRNA HOTAIR was selected by bioinformatics, and verification was carried out by in vitro researches.

RESULTS

Data suggested HoxC6-1 and HoxC6-2 were considerably over-expressed with different folds in gastric cancerous tissues. Decreased expression of HoxC6-2 was detected in well-differentiated type of gastric cancer. In vitro, the conclusion that HoxC6 functions as a tumor oncogene illuminated by previous studies was verified again. Additionally, down-regulating of HoxC6-2 significantly inhibited SGC-7901 and BGC-823 cells from proliferation, migration, invasion, apoptosis, while quite slight results or none statistically significant results were observed when HoxC6-1 was knockdown. Besides, over-expression of HOTAIR, which is relevant with HoxC6 during gastric carcinogenesis, was detected in gastric cancerous tissues. Restored expression of HoxC6 partially reversed the decreased migration caused by down-regulating HOTAIR in gastric cancer cells.

CONCLUSION

HoxC6 acts as an oncogene in gastric carcinogenesis and might be a promising therapeutic target. Isoform HoxC6-2 plays a primary carcinogenic role in gastric carcinogenesis. HOTAIR, over-expressed in gastric cancer, might regulate HoxC6 on the protein level in promoting migration of gastric cells.

Limb-bud and heart as a novel biomarker for gastric intestinal type adenocarcinoma

The present study compared the expression levels of limb-bud and heart (LBH) between gastric intestinal-type adenocarcinoma (GITA) and healthy gastric tissues; with the aim of investigating the possible effect of LBH on the prognosis of patients with GITA and to analyze the associated signaling pathways in GITA. Three Oncomine gastric datasets were utilized for the preliminary prediction of the expression levels of LBH mRNA in GITA and healthy gastric tissues. Gene expression and corresponding clinical data of 163 patients with GITA were downloaded from The Cancer Genome Atlas. Wilcoxon signed rank-sum test was used to distinguish the clinical value of LBH expression in the various clinicopathological features. Subsequently, Kaplan-Meier univariate and Cox multivariate survival analyses were performed to determine the prognostic significance of LBH expression in patients with GITA. Function enrichment analysis was conducted for the co-expression gene of LBH, defined as correlation coefficient r>0.06 and P<0.05 using Pearson's χ2 test. Bioinformatics data demonstrated that compared with that in the normal gastric mucosa, LBH mRNA expression was dramatically higher in GITA tissues (P<0.05). There were significant relationships between the differential expression levels of LBH and clinicopathological parameters in GITA patients (all p<0.05), including pathological stage T (T3-4 vs. T1-2), lymph node metastasis (no vs. yes), distant metastasis (no vs. yes), histological grade (grade 3 vs. grades 1-2) and tumor stage (stages 3-4 vs. stages 1-2). Additionally, the overall survival and disease-free survival (DFS) of patients in the high expression group were poorer compared with those in the low expression group (P<0.05). Cox multivariate survival analysis indicated that increased LBH expression was an independent predictor of poor DFS prognosis in patients with GITA (P=0.045). In summary, LBH is highly expressed in GITA, which can be used as an independent predictor of poor prognosis in patients with GITA. LBH co-expressed genes are closely associated with GITA tumor migration and metastasis.

Cytomegalovirus Infection Is a Risk Factor in Gastrointestinal Cancer: A Cross-Sectional and Meta-Analysis Study

BACKGROUND

This study was planned to investigate the association betweenhuman cytomegalovirus (HCMV) infection and gastrointestinal cancer (GIC) risk, by undertaking a meta-analysis and case-control cross-sectional study.

SUMMARY

A cross-sectional study analysis of 160 GIC patients and 100 control subjects indicated significantly higher HCMV prevalence in GIC patients based on the HCMV IgM test. However, a similar analysis based on an IgG test revealed no significant relationship. Further meta-analysis of 11 studies, including 1,044 patients and 991 healthy subjects, displayed HCMV infection as an important risk factor for not only colorectal cancer occurrence and development based on a HCMV DNA test, but also for GIC based on a HCMV IgM test. However, the IgG test again displayed no significant relationship between HCMV infection and GIC occurrence. Key Message: Overall, our study revealed that HCMV infection is associated with an increased GIC risk. However, additional studies are warranted to elucidate the molecular mechanism underlying this association.

Long Non-Coding RNA BLACAT1 Promotes the Tumorigenesis of Gastric Cancer by Sponging microRNA-149-5p and Targeting KIF2A

Objective

Gastric cancer (GC) is a gastrointestinal tumor. This study is aimed to explore the regulatory mechanism of long non-coding RNA BLACAT1 (BLACAT1)/microRNA-149-5p (miR-149-5p)/KIF2A cascade on GC.

Methods

The expression of BLACAT1, miR-149-5p and KIF2A in GC was detected by qRT-PCR. The proliferation, migration and invasion of GC cells in vitro were analyzed by MTT, wound-healing and transwell assay, respectively. The xenograft tumor model was constructed in nude mice to confirm the inhibition effect of BLACAT1 knockdown on GC in vivo. Then, dual-luciferase reporter assay was used to detect the interactions among BLACAT1, miR-149-5p and KIF2A. Western blot assay was performed to determine the protein expression of KIF2A.

Results

The expression of BLACAT1 and KIF2A was up-regulated in GC, but miR-149-5p expression was down-regulated. Silencing of BLACAT1 retarded the proliferation, migration and invasion of GC cells in vitro and the growth of tumor xenograft in vivo. Moreover, BLACAT1 acted as the molecular sponge of miR-149-5p to up-regulate KIF2A expression. At last, feedback experiments suggested that BLACAT1 accelerated the proliferation, migration and invasion of GC cells by regulating miR-149-5p/KIF2A axis.

Conclusion

BLACAT1 facilitated the tumorigenesis of GC through regulating miR-149-5p/KIF2A axis, which indicated BLACAT1/miR-149-5p/KIF2A cascade may be a new therapeutic target.

Molecular profiling of gastric cancer in a population with high HIV prevalence reveals a shift to MLH1 loss but not the EBV subtype

The human immunodeficiency virus (HIV) pandemic heavily affects sub-Saharan Africa. It is associated with persistently active Epstein-Barr virus (EBV) infection. To determine if this translates into increased frequency of EBV-associated gastric cancer (EBVaGC), we evaluated molecular profiles of gastric cancer (GC) in Zambia. Patients with GC or premalignant gastric lesions were enrolled in Lusaka, Zambia. We used patients without any of these lesions as a control group. Chromogenic in situ hybridization (CISH) on tumor tissue was used to identify EBVaGC. To identify the microsatellite unstable subtype, immunofluorescence staining for MutL homolog 1 (MLH1) was used. Exposure to EBV and HIV was assessed serologically. We enrolled 369 patients (median age 52 years [IQR 41-65]; 198 (54%) female). Of these, 72 (20%) had GC and 35 (9%) had gastric premalignant lesions (PL). CISH identified EBVaGC in 5/44 (11%) of those with adequate tissue, while MLH1 loss was identified in 29/45 (64%). Both GC and PL were associated with the highest titers of antibodies to Early antigen-diffuse (OR 2.5, 95% CI 1.0-6.1, P = .048 and OR 3.9, 95% CI 1.1-12.9, P = .03, respectively) at high concentrations. Human immunodeficiency virus infection was associated with a range of antibodies to EBV, but not with any cancer subtype. Despite the association of HIV with persistent EBV, the proportion of EBVaGC in Zambia is similar to populations with a low prevalence of HIV infection. The proportion of microsatellite unstable tumors may be higher than other populations.

Mechanisms of the Epithelial-Mesenchymal Transition and Tumor Microenvironment in Helicobacter pylori-Induced Gastric Cancer

Helicobacter pylori (H. pylori) is one of the most common human pathogens, affecting half of the world's population. Approximately 20% of the infected patients develop gastric ulcers or neoplastic changes in the gastric stroma. An infection also leads to the progression of epithelial-mesenchymal transition within gastric tissue, increasing the probability of gastric cancer development. This paper aims to review the role of H. pylori and its virulence factors in epithelial-mesenchymal transition associated with malignant transformation within the gastric stroma. The reviewed factors included: CagA (cytotoxin-associated gene A) along with induction of cancer stem-cell properties and interaction with YAP (Yes-associated protein pathway), tumor necrosis factor α-inducing protein, Lpp20 lipoprotein, Afadin protein, penicillin-binding protein 1A, microRNA-29a-3p, programmed cell death protein 4, lysosomal-associated protein transmembrane 4β, cancer-associated fibroblasts, heparin-binding epidermal growth factor (HB-EGF), matrix metalloproteinase-7 (MMP-7), and cancer stem cells (CSCs). The review summarizes the most recent findings, providing insight into potential molecular targets and new treatment strategies for gastric cancer.

CircDUSP16 promotes the tumorigenesis and invasion of gastric cancer by sponging miR-145-5p

BACKGROUND

Circular RNAs (circRNAs) as a novel subgroup of non-coding RNAs act a critical role in the pathogenesis of gastric cancer (GC). However, the underlying mechanisms by which hsa_circ_0003855 (circDUSP16) contributes to GC are still undocumented.

MATERIALS

The differentially expressed circRNAs were identified by GEO database. The association of circDUSP16 or miR-145-5p expression with clinicopathological features and prognosis in GC patients was analyzed by FISH and TCGA-seq data set. Loss- and gain-of-function experiments as well as a xenograft tumor model were performed to assess the role of circDUSP16 in GC cells. circDUSP16-specific binding with miR-145-5p was confirmed by bioinformatic analysis, luciferase reporter, and RNA immunoprecipitation assays.

RESULTS

The expression levels of circDUSP16 were markedly increased in GC tissue samples and acted as an independent prognostic factor of poor survival in patients with GC. Knockdown of circDUSP16 repressed the cell viability, colony formation, and invasive potential in vitro and in vivo, but ectopic expression of circDUSP16 reversed these effects. Moreover, circDUSP16 possessed a co-localization with miR-145-5p in the cytoplasm, and acted as a sponge of miR-145-5p, which attenuated circDUSP16-induced tumor-promoting effects and IVNS1ABP expression in GC cells. MiR-145-5p had a negative correlation with circDUSP16 expression and its low expression was associated with poor survival in GC patients.

CONCLUSIONS

CircDUSP16 facilitates the tumorigenesis and invasion of GC cells by sponging miR-145-5p, and may provide a novel therapeutic target for GC.

LncRNA LINC00974 Upregulates CDK6 to Promote Cell Cycle Progression in Gastric Carcinoma

Background: It is known that LINC00974 is an oncogenic long noncoding RNA in liver cancer. Results: The authors observed in this study that LINC00974 was upregulated in gastric cancer (GC) and positively correlated with CDK6. Survival analysis showed that high levels of LINC00974 and CDK6 predicted poor survival. In GC tissues, LINC00974 and CDK6 were positively correlated. In GC cells, LINC00974 overexpression led to upregulated, whereas LINC00974 siRNA silencing led to downregulated CDK6. Analysis of cell cycle progression and proliferation showed that LINC00974 and CDK6 overexpression promoted and siRNA silencing inhibited G1-S transition and cell proliferation. Conclusion: Therefore, LINC00974 upregulates CDK6 to promote cell cycle progression in GC.

EZH2 promotes gastric cancer cells proliferation by repressing p21 expression

EZH2 is a core component of the polycomb repressive complex 2 (PRC2), which catalyzes trimethylation of histone H3 lysine 27 (H3K27me3) and promotes carcinogenesis by epigenetically silencing many tumor suppressor genes. Increased EZH2 expression is a marker of advanced and metastatic in many cancers, including lung, prostate and breast cancer, and it has been considered as a potential novel therapeutic target. However, the clinical significance and molecular mechanisms of EZH2 controlling gastric cancer cell proliferation and invasion are not well documented. In this study, immunohistochemical analysis was conducted to investigate the EZH2 expression in gastric cancer. We found that EZH2 levels were increased in gastric cancer tissues compared with adjacent normal tissues. Moreover, patients with high levels of EZH2 expression had a relatively poor prognosis. Furthermore, knockdown of EZH2 expression by siRNA could impair cell proliferation and invasion both in vitro and vivo. Finally, we found that EZH2 influences gastric cancer cells proliferation partly through regulating p21 expression. Our findings present that EZH2 over-expression can be identified as a poor prognostic biomarker in gastric cancer.

Increased musashi 2 expression indicates a poor prognosis and promotes malignant phenotypes in gastric cancer

Musashi 2 (MSI2), a marker of stem and progenitor cells, has been identified as an oncogene. Various investigations have revealed that MSI2 is differently expressed in several types of blood cancer and solid cancers. However, its expression and biological functions in gastric cancer (GC) remain unclear. In the present study, MSI2 mRNA and protein expression were assessed in GC tissue samples. The associations between MSI2 mRNA expression and the clinicopathological characteristics of patients with GC were analyzed, and the effect of MSI2 on the prognosis of patients with GC was verified. The biological functions of MSI2 in GC cells were assessed using gain-of-function assays in vitro. The results revealed that MSI2 was overexpressed in the majority of GC tissue samples, although this difference was not significant. MSI2 mRNA expression levels were associated with invasion depth, tumor-node-metastasis stage, degree of differentiation and tumor size (P<0.05), but were not associated with sex, age, tumor location or human epidermal growth factor receptor 2 expression. Increased MSI2 expression resulted in a poorer prognosis in patients with GC (χ²=4.221; P=0.040). In vitro assays revealed that MSI2 promoted MKN-28 cell proliferation, migration and invasion, and promoted tube formation in HUVECs. Although no significance of MSI2 expression was found, its oncogenic functions in the GC cell line indicated that MSI2 may be a potential oncogene that may serve as a biomarker for GC diagnosis and prognosis with verification from a larger sample and more GC cell lines.

Systematic literature review of IL-6 as a biomarker or treatment target in patients with gastric, bile duct, pancreatic and colorectal cancer

Gastrointestinal cancer (GI) is a major health problem. Patients with gastric, pancreatic, colorectal, bile duct and gall bladder cancer often have advanced disease at the time of diagnosis and are generally difficult to cure, resulting in a dismal prognosis for most patients. Inflammation plays an important role in the development and growth of cancer, which has led to a growing interest in the pro-inflammatory cytokine interleukin 6 (IL-6). The aim of the present review was to evaluate the clinical use of IL-6 as a biomarker or therapeutic target in patients with GI cancer. We did a systematic review of studies (1993-2018), to assess the clinical use of IL-6 as a diagnostic, prognostic or predictive tumor biomarker or as a potential therapeutic target. This review includes 48 studies and 5316 patients. Circulating IL-6 levels appear to be an independent prognostic biomarker in patients with GI cancer, with high IL-6 levels associated with short overall survival (OS). The results for colorectal cancer were too ambiguous to give conclusive results. IL-6 seemed to be a marker for some of the clinical characteristics of GI cancer, and may have a role in the diagnostic workup in general practice. No published studies have examined the use of IL-6 as a therapeutic target in pancreatic, gastric, bile duct or colorectal cancer. In conclusion, high circulating IL-6 was associated with short OS in most studies in GI cancer patients. Whether inhibition of IL-6 would decrease GI cancer symptoms and increase quality of life is unknown.

Long noncoding RNA ZFAS1 promotes gastric cancer cells proliferation by epigenetically repressing KLF2 and NKD2 expression

Recently, long noncoding RNAs have been emerged as critical regulators of human disease and prognostic markers in several cancers, including gastric cancer. In this study, we globally assessed the transcriptomic differences of lncRNAs in gastric cancer using publicly available microarray data from Gene Expression Omnibus (GEO) and identified an oncogenetic lncRNA ZFAS1, which may promote gastric tumorigenesis. ZFAS1 has been found to be upregulated and function as oncogene in colorectal cancer and hepatocellular carcinoma, but its expression pattern, biological function and underlying mechanism in gastric cancer is still undetermined. Here, we reported that ZFAS1 expression is also overexpressed in gastric cancer, and its increased level is associated with poor prognosis and shorter survival. Knockdown of ZFAS1 impaired gastric cancer cells proliferation and induced apoptosis in vitro, and inhibited tumorigenicity of gastric cancer cells in vivo. Mechanistically, RNA immunoprecipitation and RNA pull-down experiment showed that ZFAS1 could simultaneously interact with EZH2 and LSD1/CoREST to repress underlying targets KLF2 and NKD2 transcription. In addition, rescue experiments determined that ZFAS1 oncogenic function is partly dependent on repressing KLF2 and NKD2. Taken together, our findings illuminate how ZFAS1 over-expression confers an oncogenic function in gastric cancer.

Inverse expression of survivin and reprimo correlates with poor patient prognosis in gastric cancer

BACKGROUND

The objective of the study was to determine the relationship between Survivin and Reprimo transcript/protein expression levels, and gastric cancer outcome.

METHODS

In silico correlations between an agnostic set of twelve p53-dependent apoptosis and cell-cycle genes were explored in the gastric adenocarcinoma TCGA database, using cBioPortal. Findings were validated by regression analysis of RNAseq data. Separate regression analyses were performed to assess the impact of p53 status on Survivin and Reprimo. Quantitative reverse-transcription PCR (RT-qPCR) and immunohistochemistry confirmed in silico findings on fresh-frozen and paraffin-embedded gastric cancer tissues, respectively. Wild-type (AGS, SNU-1) and mutated p53 (NCI-N87) cell lines transfected with pEGFP-Survivin or pCMV6-Reprimo were evaluated by RT-qPCR and Western blotting. Kaplan-Meier method and Long-Rank test were used to assess differences in patient outcome.

RESULTS

cBioPortal analysis revealed an inverse correlation between Survivin and Reprimo expression (Pearson's r= -0.3, Spearman's ρ= -0.55). RNAseq analyses confirmed these findings (Spearman's ρ= -0.37, p<4.2e-09) and revealed p53 dependence in linear regression models (p<0.05). mRNA and protein levels validated these observations in clinical samples (p<0.001). In vitro analysis in cell lines demonstrated that increasing Survivin reduced Reprimo, while increasing Reprimo reduced Survivin expression, but only did so in p53 wild-type gastric cells (p<0.05). Survivin-positive but Reprimo-negative patients displayed shorter overall survival rates (p=0.047, Long Rank Test) (HR=0.32; 95%IC: 0.11-0.97; p=0.044).

CONCLUSIONS

TCGA RNAseq data analysis, evaluation of clinical samples and studies in cell lines identified an inverse relationship between Survivin and Reprimo. Elevated Survivin and reduced Reprimo protein expression correlated with poor patient prognosis in gastric cancer.

Over-expression of oncigenic pesudogene DUXAP10 promotes cell proliferation and invasion by regulating LATS1 and β-catenin in gastric cancer

BACKGROUND

Recently, the pesudogenes have emerged as critical regulators in human cancers tumorigenesis and progression, and been identified as a key revelation in post-genomic biology. However, the expression pattern, biological function and mechanisms responsible for these molecules in human gastric cancer (GC) are not fully understood.

METHODS

In this study, we globally assessed the transcriptomic differences of pesudogenes in gastric cancer using publicly available microarray data. DUXAP10 expression levels in GC tissues and cells was detected using quantitative real-time PCR (qPCR). DUXAP10 siRNAs and over-expression vector were transfected into GC cells to down-regulate or up-regulate DUXAP10 expression. Loss- and gain-of function assays were performed to investigate the role of DUXAP10 in GC cells cell proliferation, and invasion. RIP, RNA pulldown, and ChIP assays were used to determine the mechanism of DUXAP10's regulation of underlying targets.

RESULTS

The pesudogene DUXAP10 is the only pseudogene that significantly over-expressed in all four GEO datasets, and frequently over-expressed in many other cancers including Liver Hepatocellular carcinoma, Bladder cancer, and Esophageal Cancer. High DUXAP10 expression is associated with GC patients poor prognosis, and knockdown of DUXAP10 significantly inhibits cells proliferation, migration and invasion in GC. Mechanistic investigation shows that DUXAP10 can interact with PRC2 and LSD1 to repress LATS1 expression at transcriptional level, and bind with HuR to maintain the stability of β-catenin mRNA and increase its protein levels at post-transcriptional level.

CONCLUSIONS

Overall, our findings illuminate how increased DUXAP10 confers an oncogenic function in GC development and progression that may serve as a candidate prognostic biomarker and target for clinical management of GC.

Reduction of gastric cancer proliferation and invasion by miR-15a mediated suppression of Bmi-1 translation

B-cell specific moloney leukemia virus insertion site 1 (Bmi-1) gene plays important roles in gastric cancer, but the epigenetic regulatory mechanism by microRNA (miRNA) and the functional significance of Bmi-1 inhibition in gastric cancer remains elusive. In this study, we systematically investigated the functional roles of miRNA mediated Bmi-1 suppression in gastric cancer. Our results show that the expression of miR-15a is significantly reduced in gastric cancer and the protein expression levels of Bmi-1 are inversely correlated with miR-15a (P = 0.034) in gastric cancer patient samples. Functional studies revealed that ectopic expression of miR-15a decreased Bmi-1 in gastric cancer cell lines with reduced proliferation and tumor invasion. High levels of Bmi-1 in gastric cancer patients are significantly associated with better overall survival (P = 0.024) based on the Kaplan-Meier survival analysis.

Effect and mechanism of long noncoding RNAs HOTAIR on occurrence and development of gastric cancer

OBJECTIVE

In this study, we aimed at looking for the long noncoding RNA (lncRNA) abnormally expressed in gastric cancer (GC) tissues and analyzing the association of its expression level with the clinicopathological feature and patient prognosis. The biological function of this lncRNA in occurrence and development of GC was studied in vivo and in vitro. The underlying molecular mechanism was further discussed.

METHODS

We investigated the lncRNA expression level in GC tissues and normal gastric mucosa tissues by lncRNA chips analysis. The expression of lncRNA HOTAIR was detected by quantitative real time polymerase chain reaction (qRT-PCR). The relationship between HOTAIR expression level and prognosis was investigated by analyzing clinical samples. The influence of HOTAIR downregulation on GC cell proliferation, chemosensitivity, apoptosis, and invasion were determined by bromodeoxyuridine (BrdU) incorporation assay, flow cytometry analysis, and transwell assay. Tumor xenograft model was developed to study the influence of downregulated HOTAIR on tumor growth and metastasis.

RESULTS

lncRNA HOTAIR had an extremely high expression level in GC cells, and predicted poor prognosis in patients. Downregulation of HOTAIR could promote chemosensitivity, induce apoptosis of GC cells, and significantly inhibit GC cell proliferation, invasion, and metastasis in vivo and in vitro.

CONCLUSION

It was proved that HOTAIR played a positive role in GC occurrence and development according to the study in its mechanism, function, and clinical manifestation so that it could be expected to become a new target in GC prevention and treatment.

Over-expressed long noncoding RNA HOXA11-AS promotes cell cycle progression and metastasis in gastric cancer

Background

Long noncoding RNAs (lncRNAs) have emerged as critical regulators in a variety of human cancers, including gastric cancer (GC). However, the function and mechanisms responsible for these molecules in GC are not fully understood. In our previous study, we found that GC associated lncRNA HOXA11-AS is significantly upregulated in GC tissues. Over-expressed HOXA11-AS promotes GC cells proliferation and invasion through scaffolding the chromatin modification factors PRC2, LSD1 and DNMT1.

Methods

HOXA11-AS expression levels in GC cells was detected by quantitative real-time PCR (qPCR). HOXA11-AS siRNAs and overexpression vector were transfected into GC cells to down-regulate or up-regulate HOXA11-AS expression. In vitro and in vivo assays were performed to investigate the functional role of HOXA11-AS in GC cells cell cycle progression, invasion and metastasis. RIP and ChIP assays were used to determine the mechanism of HOXA11-AS’s regulation of underlying targets.

Results

We found that knockdown of HOXA11-AS induced GC cells G0/G1 phase arrest and suppressed GC cells migration, invasion and metastasis in vivo. Moreover, mechanistic investigation showed that HOXA11-AS could interact with WDR5 and promote β-catenin transcription, bind with EZH2 and repress P21 transcription, and induce KLF2 mRNA degradation via interacting with STAU1.

Conclusions

Taken together, these findings show that HOXA11-AS not only could promote GC cells migration and invasion in vitro, but also promotes GC cells metastasis in vivo, at least in part, by regulating β-catenin and KLF2.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0651-6) contains supplementary material, which is available to authorized users.

The histone demethylase lysine-specific demethylase-1-mediated epigenetic silence of KLF2 contributes to gastric cancer cell proliferation, migration, and invasion

Gastric cancer is one of the most common malignancies and leading causes of cancer-related death worldwide. An increasing number of evidence has revealed that gastric tumorigenesis is a multistage pathological state, and epigenetic alterations are considered to play critical roles in the etiology of gastric cancer. Lysine-specific demethylase-1, a histone demethylase, has been linked to malignancy in several human cancers and considered to epigenetically regulate many tumor suppressor genes during tumorigenesis and cancer progression. However, its role and underlying targets in gastric cancer are still unclear. In this study, we detected the lysine-specific demethylase-1 expression level in gastric cancer tissues and cell lines and investigated the function and mechanism of lysine-specific demethylase-1 in the gastric cancer. The in vitro analysis shows that knockdown of lysine-specific demethylase-1 significantly inhibits gastric cancer cell proliferation, migration, and invasion and induces cell cycle G1 phase arrest and cell apoptosis. In vivo assays determine that lysine-specific demethylase-1 downregulation represses gastric cancer cell tumorigenesis. Mechanistic investigation reveals that tumor suppressor KLF2 is a key downstream target of lysine-specific demethylase-1 in gastric cancer. These findings indicate that lysine-specific demethylase-1 is an important oncogene in gastric cancer, and lysine-specific demethylase-1-mediated epigenetic repression of KLF2 plays a critical role in gastric cancer development and progression, which supports lysine-specific demethylase-1 as a potential therapeutic target in this disease.

Long noncoding AGAP2-AS1 is activated by SP1 and promotes cell proliferation and invasion in gastric cancer

BACKGROUND

Long noncoding RNAs (lncRNAs) have emerged as important regulators of tumorigenesis and cancer progression. Recently, the lncRNA AGAP2-AS1 was identified as an oncogenic lncRNA in human non-small cell lung cancer (NSCLC) and its elevated expression was linked to NSCLC development and progression. However, the expression pattern and molecular mechanism of AGAP2-AS1 in gastric cancer (GC) have not been characterized.

METHODS

Bioinformatic analysis was performed to determine AGAP2-AS1 expression levels in the GC and normal tissues using gene profiling data from the Gene Expression Omnibus. Quantitative real-time polymerase chain reaction was used to validate AGAP2-AS1 expression in the GC tissues/cell lines compared with that in the adjacent nontumorous tissues/normal epithelial cells. Loss- and gain-of-function approaches were performed to investigate the effect of AGAP2-AS1 on GC cell phenotypes. The effect of AGAP2-AS1 on cell proliferation was evaluated by MTT, colony formation, flow cytometry, and in vivo tumor formation assays. The effects of AGAP2-AS1 on cell migration and invasion were examined using Transwell assays. Chromatin immunoprecipitation, luciferase reporter assays, RNA pull-down, and RNA immunoprecipitation were used to investigate the factors involved in AGAP2-AS1 dysregulation and the mechanism of action of AGAP2-AS1 in the GC cells.

RESULTS

AGAP2-AS1 was highly expressed in the GC tissues and cell lines, and patients with higher AGAP2-AS1 expression had a poorer prognosis and shorter overall survival. Furthermore, knockdown of AGAP2-AS1 significantly inhibited GC cell proliferation, migration, and invasion in vitro and tumor growth in vivo. AGAP2-AS1 overexpression promoted cell growth and invasion. In addition, the transcription factor SP1 activated AGAP2-AS1 expression in the GC cells. AGAP2-AS1 functions as an oncogenic lncRNA by interacting with LSD1 and EZH2 and suppressing CDKN1A (P21) and E-cadherin transcription.

CONCLUSIONS

Taken together, these findings imply that AGAP2-AS1 upregulated by SP1 plays an important role in GC development and progression by suppressing P21 and E-cadherin, which suggests that AGAP2-AS1 is a potential diagnostic marker and therapeutic target for GC patients.

Human cytomegalovirus detection in gastric cancer and its possible association with lymphatic metastasis

Increasing evidence suggests that human cytomegalovirus (HCMV) is associated with many human malignancies. However, its prevalence in gastric cancer (GC) and clinical association remain unknown. HCMV IgG and IgM antibodies in the sera of 80 GC patients and 80 healthy controls were detected using a microparticle enzyme immunoassay. The prevalence of HCMV UL47, UL55, UL56, and UL77 genes among 102 GC tumor tissues and adjacent normal specimens was measured by polymerase chain reaction (PCR) or nested PCR. Quantitative real-time PCR (Q-PCR) was used to determine viral load. Virus localization in neoplastic tissues was determined by immunohistochemistry. No significant difference of HCMV IgG and IgM seropositivity was found between GC patients and the healthy group. However, the overall HCMV DNA positivity rate was significantly higher in GC cancerous tissue compared with in paired normal tissue (P<0.01). HCMV infection was mainly localized in the tumorous epithelium. Q-PCR in HCMV-positive specimens indicated that the viral copy number was notably higher in GC tissues than in adjacent normal specimens (P<0.001). Clinical statistical analysis indicated that HCMV load in GC tumor tissue was positively associated with lymphatic metastasis (P=0.043), the area under the receiver operating characteristic (ROC) curve was 0.6638. Our data clearly provide the prevalence of HCMV in GC patients. We conclude that HCMV infection in malignant tissues might be associated with carcinogenesis or progression of GC and possibly relates to lymphatic metastasis.

Current Perspectives on Gastric Cancer

Gastric cancer (GC) is third leading cause of cancer-related death. Only 28.3% of new GC cases survive more than 5 years. Although incidence has declined in the United States, an increase is estimated for 2016. Risk factors include sex (risk is higher in men), Helicobacter pylori infection, heredity, and lifestyle. GC is usually diagnosed between the ages of 60-80 years. Prognosis of GC is largely dependent on the tumor stage at diagnosis and classification as intestinal or diffuse type; diffuse-type GC has worse prognosis. Chemoprevention has been shown to decrease risk, but is currently not used clinically.

Genome-wide analysis of DNA copy number alterations in early and advanced gastric cancers

To better understand progressive changes in gastric cancer (GC), early and advanced GCs (EGC and AGC, respectively) were examined for copy number alterations (CNAs). A crypt isolation method was used to isolate DNA from tumors and normal glands in 20 AGCs, and fresh tumor samples were obtained from 45 EGCs. We assessed CNAs for differentiated-type GCs using an Infinium HumanCytoSNP-12v2.1 BeadChip in EGCs and AGCs. The most frequent aberrations in EGC were gains at 8q23.3 (42.2%) and 8q23.2 (40%), and loss of heterozygosity (LOH) at 3p14.2 (24.2%), suggesting that these CNAs were involved in the development of EGC. On the other hand, the highest frequencies of gains in AGC were found at 8q24.21 (65%) and 8q24.3 (60%). The most frequent LOHs in AGC were at 11q24.3-25, 11q23.2-24.1, 11q14.1, and 12p11.21-13.33, whereas that in EGC was at 3p14.2. In addition, regions of copy-neutral LOHs in AGC were detected at 11q21, 11q13.3-14.3, 11q11, 11p13-15.3, 12q21.1, 12q12-13.3 and 5q33.3-35.1. Comparisons of gains in EGC and AGC showed significant differences at 12q22-q23.2, 12q21.33, 11p12, 11p14.1, 12q21.31-32.32, 3p12.3, 3p14.1, 10p15.1, 1q24.2 and 2q12.1. Copy neutral LOHs were significantly higher in AGC than in EGC at 14q32.11-32.33, 14q21.3, 14q11.2, 5q11.2, 5q 13.3, 14q21.1-23.2, 14q13.2-13.3, 5q12.1-12.3, 5q11.1, and 17p13.3. The total lengths of the CNAs were significantly greater in AGC than in EGC. We found that the pattern of CNAs in AGC was quite different from that in EGC. We suggest that increasing numbers of CNAs are associated with disease progression from EGC to AGC. © 2016 Wiley Periodicals, Inc.

Gastric adenocarcinoma: the role of Helicobacter pylori in pathogenesis and prevention efforts

Gastric cancer is the third most common cause of cancer deaths in the world, prompting high-risk countries like South Korea and Japan to establish nationwide screening programmes. Helicobacter pylori is linked to the majority of gastric adenocarcinoma cases and to the vast majority of non-cardia gastric adenocarcinomas. Several studies have demonstrated the effectiveness of 'test-and-treat' programmes for H. pylori infection to prevent gastric cancer in high-risk populations. While this strategy has gained momentum, providers in low-risk developed countries may be unaware of the risk individual patients face, particularly those who have emigrated from high-risk regions and members of economically disadvantaged minority groups. Rapidly evolving science in recent years has made it difficult for clinicians to keep up with the current best practices. This article reviews the epidemiology of H. pylori and gastric cancer, screening and diagnostic tests and the current treatment regimens for clinicians.

[Unpleasant Journey from Helicobacter pylori-associated Gastritis to Gastric Cancer: Cancer Prevention by Taking a Detour]

As a commensal or a pathogen, Helicobacter pylori can change the balance of a complex interaction that exists among gastric epithelial cells, microbes, and their environment. Therefore, unraveling this complex relationship of these mixtures can be expected to help prevent cancer as well as troublesome unmet medical needs of H. pylori infection. Though gastric carcinogenesis is a multi-step process, precancerous lesion can be reversible in the early phase of mucosal damage before reaching the stage of no return. However, biomarkers to predict rejuvenation of precancerous atrophic gastritis have not been identified yet and gastric cancer prevention is still regarded as an impregnable fortress. However, when we take the journey from H. pylori-associated gastritis to gastric cancer, it provides us with the clue for prevention since there are two main preventive strategies: eradication and anti-inflammation. The evidence supporting the former strategy is now ongoing in Japan through a nation-wide effort to eradicate H. pylori in patients with chronic gastritis, but suboptimal apprehension to increasing H. pylori resistance to antibiotics and patient non-compliance still exists. The latter strategy has been continued in the author'sresearch center under siTRP (short-term intervention to revert premalignant lesion) strategy. By focusing on the role of inflammation in the development of H. pylori-associated gastric carcinogenesis, this review is intended to explain the connection between inflammation and gastric cancer. Strategies on H. pylori eradication, removal of inflammation, and reverting preneoplastic lesion will also be introduced. In the end, we expect to be able to prevent gastric cancer by take a detour from the unpleasant journey, i.e. from H. pylori-associated gastritis to gastric cancer.