Molecular diagnosis of gastric cancer: present and future

Histopathological Gastric Cancer Detection on GasHisSDB Dataset Using Deep Ensemble Learning

Gastric cancer is a leading cause of cancer-related deaths worldwide, underscoring the need for early detection to improve patient survival rates. The current clinical gold standard for detection is histopathological image analysis, but this process is manual, laborious, and time-consuming. As a result, there has been growing interest in developing computer-aided diagnosis to assist pathologists. Deep learning has shown promise in this regard, but each model can only extract a limited number of image features for classification. To overcome this limitation and improve classification performance, this study proposes ensemble models that combine the decisions of several deep learning models. To evaluate the effectiveness of the proposed models, we tested their performance on the publicly available gastric cancer dataset, Gastric Histopathology Sub-size Image Database. Our experimental results showed that the top 5 ensemble model achieved state-of-the-art detection accuracy in all sub-databases, with the highest detection accuracy of 99.20% in the 160 × 160 pixels sub-database. These results demonstrated that ensemble models could extract important features from smaller patch sizes and achieve promising performance. Overall, our proposed work could assist pathologists in detecting gastric cancer through histopathological image analysis and contribute to early gastric cancer detection to improve patient survival rates.

Quantification of the Landscape for Revealing the Underlying Mechanism of Intestinal-Type Gastric Cancer

Gastric cancer is a daunting disease with a tragic impact on global health. It is the fourth most common cancer and has become the second most frequent cause of cancer death in recent times. According to the Lauren classification, gastric cancer can be classified into two types: intestinal and diffuse. Intestinal-type gastric cancer (IGC) is more common in elderly people, and atrophic gastritis (AG) and intestinal metaplasia (IM) have been proven to be the main premalignant causes of intestinal-type gastric cancer. In turn, Helicobacter pylori infection has been identified as the most significant cause of AG and IM. In this study, we determine the mechanism of IGC progression and how H. pylori infection induces IGC. Through researching the relevant literature, we identified the key genes associated with gastric cancer and the specific genes associated with IGC. We then use hese genes to build up a gene regulatory network for IGC. Based on this gene regulatory network, we quantify the IGC landscape. Within this landscape, there are three stable states, which are classified as the normal, AG, and gastric cancer states. Through landscape topography, we can determine the biological features and progression process of IGC. To investigate the influence of H. pylori infection on IGC, we simulated different degrees of H. pylori infection. As the H. pylori infection becomes more serious, the landscape topography changes accordingly. A fourth state, named the intestinal metaplasia (IM) state, emerges on the landscape and is associated with a very high risk of developing gastric cancer. The emergence of this state is due to the interactions/regulations among genes. Through variations in the landscape topography, we can determine the influence of H. pylori infection on IGC. Finally, we use global sensitivity analysis to research the regulations most sensitive to IGC prevention or therapies. This study presents a new approach and a novel model with which to explore the mechanism of IGC. The simulations of different degrees of H. pylori infection can provide us with a systematic view of IGC progression. The key regulations found can give us some insight and guidance for clinical trials and experimental studies.

Anticancer Effects of Helminthostachys zeylanica Ethyl acetate Extracts on Human Gastric Cancer Cells through Downregulation of the TNF-α-activated COX-2-cPLA2-PGE2 Pathway

Background: Gastric cancer (GC) is the second most prevalent cancer worldwide and the eighth most common cause of tumor-related death in Taiwan. Helminthostachys zeylanica, a flavonoid compound, has anti-inflammatory, immunomodulatory, and anticancer effects. We examined whether an extract of H. zeylanica (E1 and E2) has potential as a treatment for GC. Methods: We investigated the effects (pro-apoptosis, pro-autophagy, and antiproliferation ability) of H. zeylanica-E2 on cell viability in healthy gastric epithelial (GES-1) and GC cells (AGS and BGC823). H. zeylanica-E2 was toxic to GC cells but had little or no toxicity to normal cells. Results: In this study, H. zeylanica-E2 induced apoptosis through caspase 3/7, Bcl-2, Bax, cyclooxygenase-2 (COX-2), and cleaved poly (ADP-ribose) polymerase pathways in GC cells. In addition, it increased autophagy by stimulating autophagy-related protein (ATG)5, ATG7, LC3-I/LC3-II, and inhibiting COX-2 activity in GC cells. We also found that H. zeylanica-E2 exhibited antiproliferation ability through cell cycle arrest in G0/G1 and G2/M and suppressed the migration of GC cells. The anticancer effects of H. zeylanica-E2 in GC cells might be mediated partly through inhibition of tumor necrosis factor-α (TNF-α)-activated proinflammatory cytosolic phospholipase A2 (cPLA2)-COX-2-prostaglandin E₂ (PGE₂) pathway. Conclusions: Our results suggest that H. zeylanica-E2 has potential as a novel adjunctive agent for the treatment of GC.

Long Non-Coding RNA GRIK1-AS1 Inhibits the Proliferation and Invasion of Gastric Cancer Cells by Regulating the miR-375/IFIT2 Axis

Long non-coding RNAs (lncRNAs) play important roles in various biological processes and human diseases, including cancer. In this study, we demonstrated a regulatory relationship between lncRNA GRIK1-AS1 and miR-375/IFIT2 axis in gastric cancer. Our results show a decreased expression of GRIK1-AS1 in gastric cancer tissues compared to adjacent normal gastric tissues. Gastric cell lines also have reduced levels of GRIK1-AS1 compared to gastric epithelial cell line GES-1. Ectopic expression of GRIK1-AS1 in gastric cancer cell lines significantly inhibits cellular viability, migration, and invasion. RNA-pull down and the luciferase activity assays show that GRIK1-AS1 mainly interacts specifically with miR-375. We further demonstrate a negatively regulatory relationship between lncRNA GRIK1-AS1 and miR-375. We discovered that IFIT2 was one of the direct key downstream target genes of miR-375, and established the important role of the GRIK1-AS1/miR-375/IFIT2 axis in the progression of gastric cancer. Taken together, our results revealed a novel mechanism of GRIK1-AS1 as a sponge to miR-375 that impacts gastric cancer progression via modulating target mRNA IFIT2 translation, and as a result, opens a new strategy to future GRIK1-AS1 based therapeutic development.

Second-order multi-instance learning model for whole slide image classification

Whole slide histopathology images (WSIs) play a crucial role in diagnosing lymph node metastasis of breast cancer, which usually lack fine-grade annotations of tumor regions and have large resolutions (typically 10⁵ × 10⁵pixels). Multi-instance learning has gradually become a dominant weakly supervised learning framework for WSI classification when only slide-level labels are available. In this paper, we develop a novel second-order multiple instances learning method (SoMIL) with an adaptive aggregator stacked by the attention mechanism and recurrent neural network (RNN) for histopathological image classification. To be specific, the proposed method applies a second-order pooling module (matrix power normalization covariance) for instance-level feature extraction of weakly supervised learning framework, attempting to explore second-order statistics of deep features for histopathological images. Additionally, we utilize an efficient channel attention mechanism to adaptively highlight the most discriminative instance features, followed by an RNN to update the final bag-level representation for the slide classification. Experimental results on the lymph node metastasis dataset of 2016 Camelyon grand challenge demonstrate the significant improvement of our proposed SoMIL framework compared with other state-of-the-art multi-instance learning methods. Moreover, in the external validation on 130 WSIs, SoMIL also achieves an impressive area under the curve performance that competitive to the fully-supervised framework.

Overexpression of PLXDC2 in Stromal Cell-Associated M2 Macrophages Is Related to EMT and the Progression of Gastric Cancer

The tumor microenvironment (TME) comprises distinct cell types, including stromal types such as fibroblast cells and macrophage cells, which have recently become a critical factor in tumor development and progression. Here, we identified the TME-related gene, plexin domain containing 2 (PLXDC2), in a high-stromal-score population. And we revealed that this gene was related to poor survival and advanced (tumor-node-metastasis) stage in gastric cancer (GC) patients from The Cancer Genome Atlas database. An integrated gene profile and functional analysis of the proportions of tumor-infiltrating immune cells revealed that the expression of the M2 macrophages cell marker CD163 was positively correlated with PLXDC2 expression. In addition, the M2 macrophages gene signature and high PLXDC2 expression were associated with the inflammatory signaling pathway and the epithelial-to-mesenchymal transition (EMT)-related gene signature. Single-cell study of GC identified PLXDC2 was enriched specifically in fibroblasts and monocytes/macrophages populations, which supported its important role in the stroma. Furthermore, according to a tissue microarray immunohistochemistry analysis, the expression of PLXDC2 elevated in human GC stromal specimens compared to tumor tissue specimens. Moreover, PLXDC2 overexpression in the stromal compartment was associated with CD163-positive regulatory M2 macrophages, and its functions were related to the pathogenesis of GC. Multiplexed immunohistochemistry verified PLXDC2's correlation with EMT markers. Our data suggested that PLXDC2 was expressed in stromal cells and that its crosstalk with tumor-associated macrophages could contribute to cancer biology by inducing the EMT process.

Expression of p27 and p16 and their clinical significance in gastric cancer

BACKGROUND

Deregulated expression of cell cycle regulators p27 and p16 is associated with cancer progression. p27^kip1 and p16^INKa are a cyclin dependent kinase inhibitor whose major target is the cyclinE/CDK2 and cyclinD/CDK4/6 complex, respectively, that governs cell cycle transition from late G1 to S phase.

METHODS

We recruited biopsies of a total of 84 subjects including 72 primary tumor biopsies from histopathologically proven gastric carcinoma, 8 adjacent controls and 12 independent controls. We used gastric cancer cell line, AGS, for validation of our data. Expression profiling at transcript level was done by semi-quantitative RT-PCR and at proteome level by immunohistochemistry and immunofluorescence. Receiver operator characteristics analysis was done for determining the diagnostic utility of p27 and p16 with respect to the sensitivity and specificity.

RESULTS

We demonstrate that p27 and p16 are frequently over expressed in early stages of gastric carcinoma. Our semi-quantitative data show a significant upregulation of p27 (Mean ± SEM, 0.4771 ± 0.0895; p = 0.0001) and p16 (Mean ± SEM, 0.4676 ± 0.04305; p = 0.0001) at mRNA level. Concordant to semi-quantitative data, immunohistochemistry data also showed a significant upregulation of p27 (Mean ± SEM, 196.4 ± 10.84; p < 0.0001) and p16 (Mean ± SEM, 100.4 ± 23.71; p < 0.0001) at protein level.

CONCLUSIONS

The present study showed that the significant upregulation of p27 and p16 were associated with early events in gastric carcinogenesis. Our data suggests that clinical correlation of these differentially expressed genes may be useful as diagnostic biomarkers for early detection of gastric carcinoma and promising therapeutics target for GC patients.

High-speed, multi-modal, label-free imaging of pathological slices with a Bessel beam

Optical imaging of stained pathological slices has become the gold standard for disease diagnosis. However, the procedure of sample preparation is complex and time-consuming. Multiphoton microscopy (MPM) is promising for label-free imaging, but the imaging speed is limited, especially for whole slice imaging. Here we propose a high-speed, multi-modal, label-free MPM by Bessel scan-based strip mosaicking. With a Bessel beam for excitation, the extended depth-of-focus not only enables full axial information acquisition at once, but also alleviates the demanding requirement of sample alignment. With the strip mosaicking protocol, we can save the time of frequent sample transferring. Besides, we add a closely-attached reflection mirror under the sample for enhancing epi-detection signals, and employ circularly polarized beams for recording comprehensive information. We demonstrate its application in multi-modal, label-free imaging of human gastric cancer slices and liver cancer slices, and show its potential in rapid disease diagnosis.

PAK1 silencing is synthetic lethal with CDK4/6 inhibition in gastric cancer cells via regulating PDK1 expression

Gastric cancer (GC) is one of the most common malignancies worldwide. The prognosis of GC is unsatisfied owning to widespread metastasis. P21-activated kinase 1 (PAK1), a member of serine/threonine kinases, is associated with the progression of multiple types of human cancers. Here, we demonstrated that CDK4/6 inhibitor reduced GC cell viability and decreased PAK1 expression. Consistently, PAK1 ablation increased GC cell sensitivity exposed to CDK4/6 inhibitor and promoted DNA damage. We also revealed PAK1 depletion notably affected PDK1-AKT pathway, and PDK1 overexpression totally abrogated the effect of PAK1 deletion on DNA damage in GC cells. Additionally, PDK1 overexpression also rescued the increased GC cell sensitivity towards CDK4/6 inhibitor and the cell cycle arrest caused by PAK1 depletion. Our findings, therefore, suggested that PAK1 silencing increased sensitivity to CDK4/6 inhibition in gastric cancer cells via PDK1-AKT pathway. We, therefore, thought PAK1 as a promising therapeutic target for the treatment of CDK4/6 inhibitor-resistant gastric cancer.

MiR-135b-5p promotes viability, proliferation, migration and invasion of gastric cancer cells by targeting Krüppel-like factor 4 (KLF4)

INTRODUCTION

The expression of MiR-135b-5p was up-regulated while Krüppel-like factor 4 (KLF4) expression was extremely low in human gastric carcinoma (GC) tissues. This study aimed to explore the role of miR-135b-5p in GC cells and its influence on various cell capacity and viability by targeting KLF4.

MATERIAL AND METHODS

The dual-luciferase reporter assay was first performed and the target relationship between miR-135b-5p and KLF4 was confirmed. Then three GC cell lines and the human normal gastric epithelial cell line (GES1) were analyzed for the expression level of miR-135b-5p and KLF4 mRNA by RT-qPCR. The BGC-823 GC cell line was chosen for subsequent assays.

RESULTS

The expression of miR-135b-5p and KLF4 was manipulated via transfection. The changes of proliferation, invasion, migration, viability, cycle and apoptosis of GC cells were evaluated by MTS, colony formation assay, transwell assay, wound healing assay and flow cytometry assay, respectively. Overexpression of MiR-135b-5p enhanced viability, proliferation, invasion and migration of GC cells, increased cell viability and reduced cell apoptosis. Replenishing of KLF4 functioned oppositely.

CONCLUSIONS

The inhibitory effects of ectopic KLF4 could be attenuated by co-transfection of miR-135b-5p. Collective data suggested that miR-135b-5p has a tumor-promoting role in GC cells via downregulating KLF4. Hence, inhibition of miR-135b-5p could be valuable for treatment of gastric cancer.

RMDL: Recalibrated multi-instance deep learning for whole slide gastric image classification

The whole slide histopathology images (WSIs) play a critical role in gastric cancer diagnosis. However, due to the large scale of WSIs and various sizes of the abnormal area, how to select informative regions and analyze them are quite challenging during the automatic diagnosis process. The multi-instance learning based on the most discriminative instances can be of great benefit for whole slide gastric image diagnosis. In this paper, we design a recalibrated multi-instance deep learning method (RMDL) to address this challenging problem. We first select the discriminative instances, and then utilize these instances to diagnose diseases based on the proposed RMDL approach. The designed RMDL network is capable of capturing instance-wise dependencies and recalibrating instance features according to the importance coefficient learned from the fused features. Furthermore, we build a large whole-slide gastric histopathology image dataset with detailed pixel-level annotations. Experimental results on the constructed gastric dataset demonstrate the significant improvement on the accuracy of our proposed framework compared with other state-of-the-art multi-instance learning methods. Moreover, our method is general and can be extended to other diagnosis tasks of different cancer types based on WSIs.

Current and future molecular diagnostics of gastric cancer

Introduction: Gastric cancer (GC) is the fifth most common cancer and confers the second-highest mortality among other cancers. Improving the survival rates of GC patients requires prompt and accurate diagnosis and effective treatment which is often preceded by the poorly understood pathogenic mechanisms. Area covered: This literature review aims to summarize current understanding of genetic and molecular alterations that promote carcinogenesis including (1) activation of oncogenes, (2) overexpression of growth factors, receptors and matrix metalloproteinases, (3) inactivation of tumor suppressor genes, DNA repair genes, and cell adhesion molecules and (4) alterations of cell-cycle regulators that regulate biological characteristics of cancer cells. Moreover, the significance of molecular biomarkers such as micro-RNAs (miRNAs) and long non-coding RNAs (lncRNAs) and advanced molecular techniques including droplet digital polymerase chain reaction (ddPCR), quantitative PCR (qPCR) and next-generation sequencing (NGS) are also discussed. Expert opinion: A GC-specific panel of biomarkers based on the NGS or ddPCR has the potential for diagnosis, prognosis, and monitoring treatment response in GC patients. Despite the requirements for validation in larger population in clinical studies, race-specific differences in the gene panel have also to be examined by performing the clinical trials in subjects with different races.

Vinculin promotes gastric cancer proliferation and migration and predicts poor prognosis in patients with gastric cancer

Vinculin is a highly conserved protein involved in cell proliferation, migration, and adhesion. However, the effects of vinculin on gastric cancer (GC) remain unclear. Therefore, we aimed to explore the functional role of vinculin in GC, as well as its underlying mechanism. Expression of vinculin in patients with GC was analyzed by real-time polymerase chain reaction, Western blot analysis, and immunohistochemistry. Overall survival was evaluated by the Kaplan-Meier method with the log-rank test. The relationship between vinculin and clinicopathological characteristics of patients with GC was further identified. In addition, we assessed the expression of vinculin in GC cell lines. Besides, vinculin was suppressed or overexpressed by transfection with small interfering (si-vinculin) or pcDNA-vinculin and then cell viability, cell apoptosis, and/or migration was respectively examined by the 3-(4, 5-dimethylthiazole-2-yl)-2, 5-biphenyl tetrazolium bromide assay, flow cytometer, and scratch assay, respectively. Moreover, the cell cycle- and apoptosis-related proteins were detected by Western blot analysis. The expression of vinculin was significantly increased in the GC tissues and cells compared with the nontumor tissues or cells. Vinculin protein positive staining was mainly located in the cell membrane and cytoplasm. Moreover, vinculin was significantly associated with Tumor Node Metastasis (TNM) and poor differentiation. Patients with high vinculin levels had significantly worse overall survival than those with low levels. Suppression of vinculin significantly decreased cell viability and migration and promoted cell apoptosis. However, overexpression of vinculin statistically increased cell viability but had no effects on cell apoptosis. Vinculin promotes GC proliferation and migration and predicts poor prognosis in patients with GC.

Molecular carcinogenesis of gastric cancer: Lauren classification, mucin phenotype expression, and cancer stem cells

Gastric cancer (GC), one of the most common human cancers, is a heterogeneous disease with different phenotypes, prognoses, and responses to treatment. Understanding the pathogenesis of GC at the molecular level is important for prognosis prediction and determining treatments. Microsatellite instability (MSI), silencing of MLH1, MGMT, and CDKN2A genes by DNA hypermethylation, KRAS mutation, APC mutation, and ERBB2 amplification are frequently found in intestinal type GC. Inactivation of CDH1 and RARB by DNA hypermethylation, and amplification of FGFR and MET, are frequently detected in diffuse type GC. In addition, BST2 and PCDHB9 genes are overexpressed in intestinal type GC. Both genes are associated with GC progression. GC can be divided into gastric/intestinal mucin phenotypes according to mucin expression. MSI, alterations of TP73, CDH1 mutation, and DNA methylation of MLH are detected frequently in the gastric mucin phenotype. TP53 mutation, deletion of APC, and DNA methylation of MGMT are detected frequently in the intestinal mucin phenotype. FKTN is overexpressed in the intestinal mucin phenotype, and IQGAP3 is overexpressed in the gastric mucin phenotype. These genes are involved in GC progression. To characterize cancer stem cells, a useful method is spheroid colony formation. KIFC1 and KIF11 genes show more than twofold higher expression in spheroid-forming cells than that in parental cells. Both KIF genes are overexpressed in GC, and knockdown of these genes inhibits spheroid formation. Alterations of these molecules may be useful to understand gastric carcinogenesis. Specific inhibitors of these molecules may also be promising anticancer drugs.

MicroRNA-26b inhibits tumor metastasis by targeting the KPNA2/c-jun pathway in human gastric cancer

MicroRNAs (miRNA) play an important role in carcinogenesis. Previously, we identified miR-26b as a significantly downregulated miRNA in gastric cancer (GC) tissues (n = 106) based on differential quantitative RT-PCR (RT-qPCR) miRNA expression profiles. In the current study, we aimed to clarify the potential role of miR-26b and related target genes in GC progression. Downregulation of miR-26b was associated with advanced tumor-node-metastasis stage (TNM stage) and poor 5-year survival rate. Forced expression of miR-26b led to inhibition of GC cell migration and invasion in vitro and lung metastasis formation in vivo. Conversely, depletion of miR-26b had stimulatory effects. Additionally, miR-26b affected GC cell behavior through negative regulation of the metastasis promoter, karyopherin alpha 2 (KPNA2). Ectopic expression of miR-26b induced a reduction in KPNA2 protein levels, confirmed by luciferase assay data showing that miR-26b directly binds to the 3' untranslated regions (UTR) of KPNA2 mRNA. Furthermore, miR-26b and KPNA2 mRNA/protein expression patterns were inversely correlated in GC tissues. Cag A of Helicobacter pylori (Hp) enhanced miR-26b levels through regulation of the KPNA2/c-jun pathway. Taken together, our data indicate that miR-26b plays an anti-metastatic role and is downregulated in GC tissues via the KPNA2/c-jun pathway. Based on the study findings, we propose that miR-26b overexpression or KPNA2/c-jun suppression may have therapeutic potential in inhibiting GC metastasis.

Effect of Helicobacter pylori Eradication and ABO Genotype on Gastric Cancer Development

BACKGROUND

Evidence is lacking regarding how Helicobacter pylori infection status, eradication history, and ABO blood type affect the development of gastric cancer (GC) given the multifactorial and distinctive etiology according to cancer location (noncardia vs cardia) and histologic type (intestinal vs diffuse-type). We evaluated the effect of H. pylori infection status incorporated with H. pylori eradication history and ABO genotype on GC development according to cancer location and histologic type.

METHODS

A case-control study of 997 patients with noncardia GC (NCGC) and 1147 control subjects was performed using risk analyses with 14 factors including H. pylori infection with eradication history and ABO genotype. As final analyses, multivariable logistic regression models were fitted. Additionally, H. pylori infection status with eradication history was tested for its association with age, atrophic gastritis (AG), and intestinal metaplasia (IM).

RESULTS

The ABO genotype with the B allele was associated with a significantly lower risk of NCGC of both histologic types. The reduction in risk for NCGC by adding the B allele was more prominent in diffuse-type than that in the intestinal-type. H. pylori infection with eradication history was associated with a significantly lower risk of NCGC of both histologic types, compared with those without eradication history (odds ratio (OR), 0.22; 95% confidence interval (CI), 0.14-0.34) approaching that of uninfected subjects. Past infection status without an eradication history was associated with older age, AG, and IM.

CONCLUSIONS

H. pylori eradication and the B allele decreased the risks of the intestinal and diffuse-types of NCGC. H. pylori eradication revealed a strong association against developing NCGC. Therefore, it should be considered as a primary measure in NCGC prevention.

Long non-coding RNA XIST regulates gastric cancer progression by acting as a molecular sponge of miR-101 to modulate EZH2 expression

BACKGROUND

Long non-coding RNAs (lncRNAs) have emerged as critical regulators of tumor progression. However, the role and molecular mechanism of lncRNA XIST in gastric cancer is still unknown.

METHODS

Real-time PCR analysis was performed to measure the expression levels of lncRNA XIST in gastric cancer tissues and cell lines, the correlation between lncRNA XIST expression and clinicopathological characteristics and prognosis was analyzed in gastric cancer patients. The biological function of lncRNA XIST on gastric cancer cells were determined both in vitro and in vivo. The regulating relationship between lncRNA XIST and miR-101 was investigated in gastric cancer cells.

RESULTS

lncRNA XIST was significantly up-regulated in gastric cancer tissues and cell lines. Overexpression of lncRNA XIST was markedly associated with larger tumor size, lymph node invasion, distant metastasis and TNM stage in gastric cancer patients. Functionally, knockdown of lncRNA XIST exerted tumor-suppressive effects by inhibiting cell proliferation, migration and invasion in vitro and tumor growth and metastasis in vivo. Furthermore, an inverse relationship between lncRNA XIST and miR-101 was found. Polycomb group protein enhancer of zeste homolog 2 (EZH2), a direct target of miR-101, could mediated the biological effects that lncRNA XIST exerted.

CONCLUSIONS

lncRNA XIST is up-regulated and is associated with aggressive tumor phenotypes and patient survival in gastric cancer, and the newly identified lncRNA XIST/miR-101/EZH2 axis could be a potential biomarkers or therapeutic targets for gastric cancer patients.

Molecular classification of gastric cancer: Towards a pathway-driven targeted therapy

Gastric cancer (GC) is the third leading cause of cancer mortality worldwide. Although surgical resection is a potentially curative approach for localized cases of GC, most cases of GC are diagnosed in an advanced, non-curable stage and the response to traditional chemotherapy is limited. Fortunately, recent advances in our understanding of the molecular mechanisms that mediate GC hold great promise for the development of more effective treatment strategies. In this review, an overview of the morphological classification, current treatment approaches, and molecular alterations that have been characterized for GC are provided. In particular, the most recent molecular classification of GC and alterations identified in relevant signaling pathways, including ErbB, VEGF, PI3K/AKT/mTOR, and HGF/MET signaling pathways, are described, as well as inhibitors of these pathways. An overview of the completed and active clinical trials related to these signaling pathways are also summarized. Finally, insights regarding emerging stem cell pathways are described, and may provide additional novel markers for the development of therapeutic agents against GC. The development of more effective agents and the identification of biomarkers that can be used for the diagnosis, prognosis, and individualized therapy for GC patients, have the potential to improve the efficacy, safety, and cost-effectiveness for GC treatments.

Molecular Pathobiology of Gastric Cancer

Gastric carcinogenesis is a multistep process, during which numerous genetic and epigenetic alterations accumulate: there are abnormalities of growth factors/receptors, angiogenic factors, cell cycle regulators, DNA mismatch repair genes etc. These abnormalities define, at the same time, the biological character of the cancer cell and may thus serve as therapeutic targets. Genetic instability may cause accumulation of genetic abnormalities. The most important epigenetic alterations are DNA methylation, histone modification and chromatin remodeling. Some of these changes are common in gastric cancer, regardless of subtype, and some differ by histological type or (gastric or intestinal) mucin phenotype. Genetic polymorphism is a crucial endogenous cause and fundamental aspect of cancer risk. Importantly, genetic polymorphisms are also associated with the therapeutic efficacy and toxicity of anti-cancer drugs. Genomic science and technology such as Serial Analysis of Gene Expression (SAGE) allows the identification of novel genes and molecules specifically up-regulated or down-regulated in gastric cancer, e.g., RegIV and claudin-18 can be identified. Advances in our understanding of the genetic and molecular bases lead to improved diagnosis, personalised medicine and prevention of gastric cancer.

Y-box binding protein 1 is correlated with lymph node metastasis in intestinal-type gastric cancer

AIMS

Y-box binding protein-1 (YB-1) is known to modulate gene transcription and protein translation, as well as cellular response to drug treatment. The aim of this study is to correlate YB-1 protein expression levels with clinicopathological parameters in intestinal-type gastric cancer tissue samples (as categorized by the Lauren classification) and substantiate the findings with in vitro experimentation.

METHODS AND RESULTS

Paraffin-embedded samples from 167 patients with intestinal-type gastric cancer were used for the construction of tissue microarrays (TMAs). TMA slides were immunostained and YB-1 immunoreactivity score was based on the weighted average intensity score. Univariate analysis revealed that YB-1 immunohistochemical expression was correlated significantly with lymph node status (P = 0.054, borderline significance) and perforation (P = 0.043). YB-1 expression was also found to be an independent predictor of lymph node spread by multivariate analysis. Furthermore, siRNA-mediated YB-1 gene knockdown in MKN7 gastric cancer cells (which is known to originate from an intestinal-type gastric cancer tissue) inhibited cell migration (P = 0.0002) and invasion in vitro (P = 0.0129) significantly.

CONCLUSION

YB-1 expression is associated with lymph node spread in intestinal-type gastric cancer and is a potential prognostic biomarker in this subtype of gastric cancer.

Gastric cancer review

Gastric cancer is an aggressive disease that continues to have a daunting impact on global health. Despite an overall decline in incidence over the last several decades, gastric cancer remains the fourth most common type of cancer and is the second leading cause of cancer-related death worldwide. This review aims to discuss the global distribution of the disease and the trend of decreasing incidence of disease, delineate the different pathologic subtypes and their immunohistochemical (IHC) staining patterns and molecular signatures and mutations, explore the role of the pathogen H. pylori in tumorgenesis, discuss the increasing incidence of the disease in the young, western populations and define the role of biologic agents in the treatment of the disease.

MicroRNA-542-3p suppresses cell growth of gastric cancer cells via targeting oncogene astrocyte-elevated gene-1

MicroRNAs (miRNAs) have been suggested to play critical roles in tumorigenesis as well as in the development of therapies for the treatment of cancers. However, the tumor-associated miRNAs in gastric cancers remain poorly understood. Here, we report on miR-542-3p in gastric cancers, which has been widely studied in other cancers as a tumor suppressor. Real-time quantitative PCR analysis demonstrated that miR-542-3p was significantly down-regulated in gastric cancer tissues (p < 0.0001) and cell lines (p < 0.001). Overexpression of miR-542-3p significantly inhibited cell growth of gastric cancer cells both in vitro (p < 0.01) and in vivo (p < 0.01). Notably, overexpression of miR-542-3p apparently reduced the protein expression of astrocyte-elevated gene-1 (AEG-1) (p < 0.01). The dual-luciferase reporter assay validated that miR-542-3p directly bound the 3'-untranslated region (UTR) of AEG-1, which could be abolished by mutation of the predicted miR-542-3p binding site. Furthermore, overexpression of miR-542-3p markedly inhibited the activation of oncogenic signaling pathways including the Akt, β-catenin and nuclear factor-κB pathways. Additionally, overexpression of AEG-1 without the 3'-UTR partially reversed the cell growth arrest induced by miR-542-3p overexpression in gastric cancer cells (p < 0.05). Taken together, these data suggest that miR-542-3p might function as a tumor suppressor in gastric cancer, potentially by targeting the oncogene AEG-1, implying a potential role for miR-542-3p in the development of therapeutic methods for gastric cancer.

Potential prognostic, diagnostic and therapeutic markers for human gastric cancer

The high incidence of gastric cancer (GC) and its consequent mortality rate severely threaten human health. GC is frequently not diagnosed until a relatively advanced stage. Surgery is the only potentially curative treatment. Thus, early screening and diagnosis are critical for improving prognoses in patients with GC. Gastroscopy with biopsy is an appropriate method capable of aiding the diagnosis of specific early GC tumor types; however, the stress caused by this method together with it being excessively expensive makes it difficult to use it as a routine method for screening for GC on a population basis. The currently used tumor marker assays for detecting GC are simple and rapid, but their use is limited by their low sensitivity and specificity. In recent years, several markers have been identified and tested for their clinical relevance in the management of GC. Here, we review the serum-based tumor markers for GC and their clinical significance, focusing on discoveries from microarray/proteomics research. We also review tissue-based GC tumor markers and their clinical application, focusing on discoveries from immunohistochemical research. This review provides a brief description of various tumor markers for the purposes of diagnosis, prognosis and therapeutics, and we include markers already in clinical practice and various forthcoming biomarkers.

Concomitant PIK3CA amplification and RASSF1A or PAX6 hypermethylation predict worse survival in gastric cancer

OBJECTIVES

A large number of genetic and epigenetic alterations have been found in gastric cancer, but there is remarkably little consensus on the value of individual biomarker in diagnosis and prognosis of this cancer. This study was designed to illustrate the value of PIK3CA amplification in combination with promoter methylation of RASSF1A and PAX6 genes in early diagnosis and prognosis of gastric cancer.

DESIGN AND METHODS

Using real-time quantitative PCR, quantitative methylation-specific PCR (Q-MSP), and methylation-specific PCR (MSP) assays, we examined PIK3CA amplification and promoter methylation of RASSF1A and PAX6 genes in a cohort of gastric cancers, and explored the association of various (epi)genotypes with clinical outcomes of gastric cancer patients.

RESULTS

We demonstrated that PIK3CA gene was specifically amplified in gastric cancers, but not in normal gastric tissues. Moreover, frequent methylation of RASSF1A and PAX6 was also found in gastric cancers. Given the patients harboring diverse (epi)genotypes, we thus investigated the effect of various (epi)genotypes on poor prognosis in gastric cancer. The data showed that concomitant PIK3CA amplification and RASSF1A or PAX6 methylation were closely associated with poor clinical outcomes, particularly survival, as compared to other (epi)genotypes in gastric cancer.

CONCLUSIONS

We found frequent PIK3CA amplification and promoter methylation of RASSF1A and PAX6 genes in gastric cancers, and demonstrated that concomitant PIK3CA amplification and promoter methylation in any one of these two genes were significantly associated with worse survival in gastric cancer. Collectively, such (epi)genotypes may be strong and independent poor prognostic factors for gastric cancer patients.

MicroRNA-196a/-196b promote cell metastasis via negative regulation of radixin in human gastric cancer

MicroRNAs (miRNAs) play an important role to contribute carcinogenesis. The aim of the current study was to identify useful biomarkers from miRNAs. Differential miRNA profiles were analyzed using the miRNA qRT-PCR-based assay. Two of the most upregulated miRNAs were selected and validated. The miR-196a/-196b levels were significantly increased in gastric cancer (GC) tissues (n=109). Overexpression of miR-196a/-196b was significantly associated with tumor progression and poorer 5-year survival outcomes. Overexpression of miR-196a/-196b enhances GC cell migration and invasion. Further, radixin was identified as a target gene of miR-196a/-196b. Elevated miR-196a/-196b expression in GC cells led to reduced radixin protein levels and vice versa. Notably, an inverse correlation between miR-196a/-196b and radixin mRNA and protein expression was observed in GC tissues with in situ hybridization and immunohistochemistry analyses. Together, miR-196a/-196b inhibitory oligonucleotides or overexpression of the radixin may thus have therapeutic potential in suppressing GC metastasis.

Variable copy number of mitochondrial DNA (mtDNA) predicts worse prognosis in advanced gastric cancer patients

BACKGROUND

Change of mitochondrial DNA (mtDNA) copy number is widely reported in various human cancers, including gastric cancer, and is considered to be an important hallmark of cancers. However, there is remarkably little consensus on the value of variable mtDNA content in the prognostic evaluation of this cancer.

METHODS

Using real-time quantitative PCR approach, we examined mtDNA copy number in a cohort of gastric cancers and normal gastric tissues, and explored the association of variable mtDNA content with clinical outcomes of gastric cancer patients.

RESULTS

Our data showed that the majority of gastric cancer patients had low mtDNA content as compared to control subjects although the relative mean mtDNA content was higher in the former than the latter. Moreover, we found that variable mtDNA content was strongly associated with lymph node metastasis and cancer-related death of the patients with late-stage tumors. Notably, variable mtDNA content did not affect overall survival of gastric cancer patients, however, we found that increased mtDNA content was associated with poor survival in the patients with late-stage tumors.

CONCLUSION

In this study, we demonstrated that variable mtDNA content markedly increased the risk of lymph node metastasis and high mortality of the patients with late-stage tumors. Additionally, we found a strong link between increased mtDNA content and worse survival of the patients with late-stage tumors. Taken together, variable mtDNA content may be a valuable poor prognostic factor for advanced gastric cancer patients.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1344721463103353.

Prognostic significance of overexpression of EZH2 and H3k27me3 proteins in gastric cancer

The enhancer of zeste homolog 2 (EZH2) methyl transferase and histone 3 lysine 27 (H3K27me3) protein can repress gene transcription, and their aberrant expression has been observed in various human cancers. This study determined their expression levels in gastric cancer tissues with reference to clinicopathological features and patient survival. We collected 117 gastric cancer and corresponding normal tissues for immunohistochemistry analysis. In gastric cancers, 82/117 (70.1%) were positive for EZH2 and 66/117 (56.4%) for H3K27me3 proteins in contrast to only 5.41% and 7.25% of normal gastric mucosa specimens, respectively. Kaplan-Meier survival data showed the average overall and disease-free survival of EZH2 high expression patients was 25.2 and 20.2 months, respectively, shorter than that with EZH2 low expression (40.5 and 35.9 months). The average overall survival and disease-free survival of high H3K27me3 expression patients was 23.4 and 17.4 months, shorter than without H3K27me3 expression (37.6 and 34.5 months). The average overall survival and disease-free survival of patients with both EZH2 and H3K27me3 expression was 18.8 and 12.9 months, respectively, shorter than that with either alone (34.7 and 31.2 months) or with low levels of both (43.9 and 39.9 months). Multivariate Cox regression analysis showed that H3K27me3 and EZH2 expression, tumor size differentiation and clinical stage were all independent prognostic factors for predicting patient survival. This study demonstrated that detection of both EZH2 and H3K27me3 proteins can predict poor survival of gastric cancer patients, superior to single protein detection. In addition, H3K27me3 and EZH2 protein expression could predict lymph node metastasis.

Metastasis-associated factors facilitating the progression of colorectal cancer

Tumor metastasis remains the principal cause of treatment failure and poor prognosis in patients with colorectal cancer. It is a multistage process which includes proteolysis, motility and migration of cells, proliferation in a new site, and neoangiogenesis. A crucial step in the process of intra- and extra-vasation is the activation of proteolytic enzymes capable of degrading the extracellular matrix (ECM). In this stage, urokinase plasminogen activator receptor (uPAR) and matrix metalloproteinases (MMPs) are necessary. Micrometastases need the presence of growth factor and vascular growth factor so that they can form macrometastasis. In addition, cell adhesion molecules (CAMs) and guanine nucleotide exchange factors (GEFs) play important roles in the progression of colorectal cancer and metastatic migration. Further elucidation of the mechanisms of how these molecules contribute will aid in the identification of diagnostic and prognostic markers as well as therapeutic targets for patients with colorectal metastasis.

Vascular endothelial growth factor and survivin immunostaining in gastric adenocarcinoma

Two molecules - vascular endothelial growth factor involved in new vessels formation and survivin - antiapoptotic protein, reported to be associated with worse prognosis in various malignancies have been chosen for the study. Both are potential target for novel therapies.

THE AIM OF THE STUDY

Was to determine the immunostaining of VEGF and survivin in gastric carcinoma and to analyse their relationship to the selected clinicopathological features and survival.

MATERIAL AND METHODS

Formalin-fixed, paraffin-embedded sections from 41 gastric adenocarcinomas were used for immunohistochemical reaction with monoclonal antibodies against vascular endothelial growth factor and survivin. The results were compared with selected clinicopathological features and survival.

RESULTS

Positive immunohistochemical reaction for vascular endothelial growth factor and survivin was revealed in 24 (58,53%) and 30 (73,17%), gastric carcinomas respectively. Vascular endothelial growth factor-negative gastric carcinomas were significantly more common in cases without metastases to regional lymph nodes and distant organs and in less advanced cases. Similar, distant metastases were also statistically less common in survivin-negative carcinomas. The differences in immunohistochemical reactions for survivin between less and more advanced cases almost reach statistical significance. The only factors significantly influenced 1, 2 and 3-year survival were vascular endothelial growth factor and survivin status. Statistically significant higher percentage of survival was noted in patients with vascular endothelial growth factor- and survivin-negative tumors.

CONCLUSIONS

It seems that vascular endothelial growth factor and survivin play role in local invasion and spread of gastric adenocarcinoma and negatively influences survival. However, further studies are required to assess their true usefulness in the clinical practice.

Meta-analysis of the association between P53 codon 72 polymorphisms and gastric cancer

PURPOSE

This meta-analysis aims to examine whether the P53 codon 72 polymorphisms is associated with gastric cancer risk.

METHODS

Pooled odds ratios (ORs) were appropriately derived from random-effects models. Separate analyses were conducted on Asian and Caucasian populations. And a total of 21 studies were eligible (5,867 cases and 7,001 controls); 15 of them were conducted on Asians, others on Caucasians.

RESULTS

The combined results based on all studies showed that there was significant difference in genotype distribution between gastric cancer and non-cancer patients in the allele contrast (Pro vs. Arg); the codominant model (Pro/Pro vs. Arg/Arg) and the recessive model (Pro/Pro vs. Pro/Arg + Arg/Arg). When stratifying for race, patients with gastric cancer had a significantly higher frequency of Pro (OR = 1.136, 95% CI = 1.051-1.229), Pro/Pro (OR = 1.314, 95% CI = 1.110-1.555), Pro/Arg (OR = 1.099, 95% CI = 1.009-1.197), (Pro/Pro + Pro/Arg (OR = 1.153, 95% CI = 1.059-1.255) than non-cancer patients among Asians. There was statistically significant heterogeneity across all included studies with the Q statistic and study population may be the most important factor contributed to the heterogeneity.

CONCLUSIONS

In conclusion, the P53 codon 72 polymorphisms seems to be associated with gastric cancer risk and the analyses suggested that P53 codon 72 polymorphisms may be an important biomarker of gastric cancer susceptibility for Asians.

Review of the molecular profile and modern prognostic markers for gastric lymphoma: how do they affect clinical practice?

Primary gastric lymphoma is a rare cancer of the stomach with an indeterminate prognosis. Recently, a series of molecular prognostic markers has been introduced to better describe this clinical entity. This review describes the clinical importance of several oncogenes, apoptotic genes and chromosomal mutations in the initiation and progress of primary non-Hodgkin gastric lymphoma and their effect on patient survival. We also outline the prognostic clinical importance of certain cellular adhesion molecules, such as ICAM and PECAM-1, in patients with gastric lymphoma, and we analyze the correlation of these molecules with apoptosis, angiogenesis, tumour growth and metastatic potential. We also focus on the host-immune response and the impact of Helicobacter pylori infection on gastric lymphoma development and progression. Finally, we explore the therapeutic methods currently available for gastric lymphoma, comparing the traditional invasive approach with more recent conservative options, and we stress the importance of the application of novel molecular markers in clinical practice.

The influence of transforming growth factor-α, cyclooxygenase-2, matrix metalloproteinase (MMP)-7, MMP-9 and CXCR4 proteins involved in epithelial-mesenchymal transition on overall survival of patients with gastric cancer

AIMS

Determination of prognostic parameters that are predictive of survival of gastric cancer (GC) may allow better identification of patients who could benefit from current chemotherapy regimens. To assess the correlation between tumour progression and epithelial-mesenchymal transition (EMT), we assayed the expression levels of selected molecules involved in EMT [CD44, transforming growth factor (TGF)-α, cyclooxygenase-2 (COX-2), matrix metalloproteinase (MMP)-7, MMP-9 and C-X-C chemokine receptor (CXCR4)], and correlated these with overall patient survival (OS) and disease stage.

METHODS AND RESULTS

Medical records and pathological biopsy results of 137 patients with GC were evaluated retrospectively. Spearman's correlation analysis showed that expression of CXCR4 was correlated significantly with the expression of all other proteins studied. In contrast, COX-2 expression correlated significantly with the expression of only MMP-7 (P = 0.011), MMP-9 (P = 0.015) and CXCR4 (P = 0.013). We observed significant negative correlations between OS and the expression of TGF-α (P = 0.017), COX-2 (P < 0.001), CXCR4 (P = 0.010), MMP-7 (P = 0.020) and MMP-9 (P = 0.015). On multivariate analysis, only COX-2 was an independent prognostic factor for OS [hazard ratio (HR) = 3.34; 95% confidence interval (CI): 1.43-9.75; P = 0.002).

CONCLUSIONS

COX-2, TGF-α, MMP-7, MMP-9 and CXCR4 are associated with poor OS in gastric cancer.

Overexpression of ADP-ribosylation factor 1 in human gastric carcinoma and its clinicopathological significance

Gastric cancer is the sixth leading cause of cancer-related death in Taiwan, and the identification of related factors is essential to increase patient survival. ADP-ribosylation factor 1 (ARF1) was initially identified using 2-D electrophoresis combined with MALDI-time-of-flight mass spectrometry. ADP-ribosylation factor 1 belongs to the Ras superfamily or GTP-binding protein family and has been shown to enhance cell proliferation. In the current study, we evaluated the potential of ARF1 as a biomarker for gastric cancer detection. ADP-ribosylation factor 1 mRNA was upregulated in tumor tissues (compared with adjacent non-tumor tissues, n = 55) in approximately 67.2% of gastric cancer patients. Expression of ARF1 protein was additionally observed using Western blot and immunohistochemistry (IHC) analyses. The clinicopathological correlations of ARF1 were further evaluated. Elevated ARF1 expression was strongly correlated with lymph node metastasis (P = 0.008), serosal invasion (P = 0.046), lymphatic invasion (P = 0.035), and pathological staging (P = 0.010). Moreover, the 5-year survival rate for the lower ARF1 expression group (n = 50; IHC score < 90) was higher than that of the higher expression group (n = 60; IHC score ≥ 90) (P = 0.0228, log-rank test). To establish the specific function of ARF1 in human gastric cancer, isogenic ARF1-overexpressing cell lines were prepared. Our results showed that ARF1-overexpressing clones display enhanced cell proliferation, migration, and invasion. Furthermore, ARF1-overexpression might contribute to poor prognosis of patients. These findings collectively support the utility of ARF1 as a novel prognostic marker for gastric cancer and its role in cell invasion.

Highly frequent PIK3CA amplification is associated with poor prognosis in gastric cancer

Background

The phosphoinositide 3-kinase (PI3K)/Akt pathway plays a fundamental role in cell proliferation and survival in human tumorigenesis, including gastric cancer. PIK3CA mutations and amplification are two major causes of overactivation of this pathway in human cancers. However, until this work, there was no sound investigation on the association of PIK3CA mutations and amplification with clinical outcome in gastric cancer, particularly the latter.

Methods

Using direct sequencing and real-time quantitative PCR, we examined PIK3CA mutations and amplification, and their association with clinicopathological characteristics and clinical outcome of gastric cancer patients.

Results

PIK3CA mutations and amplification were found in 8/113 (7.1%) and 88/131 (67%) gastric cancer patients, respectively. PIK3CA amplification was closely associated with increased phosphorylated Akt (p-Akt) level. No relationship was found between PIK3CA mutations and clinicopathological characteristics and clinical outcome in gastric cancer. PIK3CA amplification was significantly positively associated with cancer-related death. Importantly, Kaplan-Meier survival curves revealed that the patients with PIK3CA amplification had significantly shorter survival times than the patients without PIK3CA amplification.

Conclusions

Our data showed that PIK3CA mutations were not common, but its amplification was very common in gastric cancer and may be a major mechanism in activating the PI3K/Akt pathway in gastric cancer. Importantly, Kaplan-Meier survival curves revealed that PIK3CA amplification was significantly positively associated with poor survival of gastric cancer patients. Collectively, the PI3K/Akt signaling pathway may be an effective therapeutic target in gastric cancer.

Quantitative assessment of gene methylation and their impact on clinical outcome in gastric cancer

BACKGROUND

Promoter methylation is an alternative mechanism of gene silencing in human tumorigenesis. Although a number of methylated genes have been found in gastric cancer, useful methylation markers for early diagnosis and prognostic evaluation of this cancer remain largely unknown.

METHODS

Using quantitative methylation-specific PCR (Q-MSP), we examined promoter methylation of 6 genes, including CALCA, DAPK1, RARbeta, RASSF1A, TIMP3, and PAX6, and explored their association with clinical outcome in gastric cancer.

RESULTS

We found that most of the genes investigated in the present study had significantly higher methylation level in tumor tissues than normal gastric tissues, including CALCA, RARbeta, RASSF1A, TIMP3, and PAX6. With more focus on specificity compared to sensitivity, all genes were hypermethylated in gastric cancer, ranging from 12.8% to 36.9%. Methylation of TIMP3 and PAX6 was strongly associated with differentiation and lymph node metastasis, respectively. Importantly, most of gene methylation, except for DAPK1, was closely associated with poor survival in gastric cancer.

CONCLUSION

We found that a panel of genes was specifically methylated in gastric cancer, and demonstrated the effect of promoter methylation of some genes on clinical outcome in gastric cancer, indicating these methylated genes may be useful biomarkers for prognostic evaluation in this cancer.

Molecular pathology of gastric cancer: research and practice

Recent advances in the understanding of molecular stomach carcinogenesis are reviewed. As to molecular events in individual mucin phenotypes of gastric cancer, the CDX2-Reg IV-SOX9 pathway is associated with the intestinal mucin phenotype, while OLFM4 and CLDN18 are novel markers for the gastric phenotype. microRNAs play an important role in epigenetic deregulation in gastric cancer. Many microRNAs are up-regulated and down-regulated, and some of these are associated with histological differentiation and cancer progression. Reduced miR-200 may participate in the genesis of diffuse type gastric cancer by reducing E-cadherin expression. Genetic polymorphism is a crucial endogenous cause and a fundamental factor of cancer risk. PSCA polymorphism alters the susceptibility to diffuse type gastric cancer through modulation of cell proliferation activity. Cancer stem cells possess the capacity for self-renewal and cause the heterogeneous lineages of cancer cells. Cancer stem cells also show resistance to anti-tumor chemotherapy. Only a minor population of gastric cancer cells reveals the properties of cancer stem cells, and CD44 is one of the markers for gastric cancer stem cells. The origin of gastric cancer stem cells remains to be elucidated.

A novel molecular marker for early detection and evaluating prognosis of gastric cancer: N-myc downstream regulated gene-1 (NDRG1)

OBJECTIVE

N-myc downstream regulated gene-1 (NDRG1) is known as a differentiation-related gene that plays important roles in cell differentiation, organ formation, and embryonic development. NDRG1 was recently found to significantly down regulate in a variety of different neoplasms. Its significance in gastric cancer has not been studied.

MATERIALS AND METHODS

NDRG1 was detected at its protein level by immunohistochemistry in formalin-fixed and paraffin-embedded sections with a total of 110 pair gastric cancer specimens including tumor and corresponding paraneoplastic tissues; NDRG1 mRNA was detected by real time-polymerase chain reaction. Meanwhile, the correlations between NDRG1 and clinicopathological factors were observed. Overexpression of NDRG1 has influence on the biological behavior of gastric cancer cell, which was detected by cell growth assay, apoptosis assay, and in vitro motility and invasion assay.

RESULTS

NDRG1 protein was down regulated in gastric cancer tissues, and the NDRG1 low expression rate was 73.6% (79/110). Moreover, NDRG1 expression has a significant inverse correlation with tumor stromal invasion, lymph node metastasis, pathological stage, but not with distant metastasis. The patients with low NDRG1 expression had a significantly shorter survival opportunity than those with high NDRG1 expression. In addition, overexpression of NDRG1 induced early apoptosis and inhibited SGC7901 cell proliferation and its motility and invasion capability.

CONCLUSIONS

NDRG1 plays a significant role in carcinogenesis and preventing the metastasis and invasion of gastric cancer cells. NDRG1 could be developed as a marker contributing to diagnosis and evaluating prognosis in gastric cancer, as well as a potential therapeutic target of gastric cancer.

Gastric adenocarcinoma and Helicobacter pylori: correlation with p53 mutation and p27 immunoexpression

INTRODUCTION

Helicobacter pylori infection is an established risk factor for gastric cancer development, but the exact underlying mechanism still remains obscure. The inactivation of tumor suppressor genes such as p53 and p27(KIP1) is a hypothesized mechanism, although there is no consensus regarding the influence of H. pylori cagA(+) in the development of these genetic alterations.

GOALS

To verify the relationship among H. pylori infection, p53 mutations and p27(Kip1) Protein (p27) expression in gastric adenocarcinomas (GA) seventy-four tissues were assayed by PCR for H. pylori and cagA presence. Mutational analysis of p53 gene was performed by single-strand conformation polymorphism (SSCP). Seventy tissues were analyzed by an immunohistochemical method for p27 expression.

RESULTS

From the samples examined, 95% (70/74) were H. pylori positive, 63% cagA(+). Altered p53 electrophoretic mobility was found in 72% of cases and significantly more frequent in the presence of cagA. Considerable reduction in p27 expression (19%) was found with a tendency for association between cagA(+) and p27(-), although the results were not statistically significant. Concomitant alterations of both suppressor genes were detected in 60% of cases. In the cases cagA(+), 66.7% of them had these concomitant alterations.

CONCLUSIONS

The data suggest that H. pylori cagA(+) contributes to p53 alteration and indicate that concomitant gene inactivation, with reduced p27 expression, may be a mechanism in which H. pylori can promote the development and progression of gastric cancer.

Glutamate receptor, ionotropic, kainate 2 silencing by DNA hypermethylation possesses tumor suppressor function in gastric cancer

Aberrant DNA methylation is considered a major mechanism for silencing tumor suppressor genes in gastric cancer. We used CpG microarray and differential methylation hybridization strategies to identify potential tumor suppressor genes and recovered glutamate receptor, ionotropic, kainate 2 (GRIK2) as a novel epigenetic target in gastric cancer. Additional experiments showed that the promoter region of GRIK2 was hypermethylated in 3 of the 4 tested gastric cancer cell lines, and its expression was restored by treatment of cells with the DNA methylation inhibitor, 5'-aza-dC. In clinical samples, the GRIK2 promoter was differentially hypermethylated in tumor tissues compared with adjacent normal tissues (p < 0.001), and this methylation was inversely correlated with the expression level of GRIK2 mRNA (r = -0.44). Functional studies further showed that GRIK2-expressing gastric cancer cell lines showed decreased colony formation and cell migration. Taken together, these results suggest that GRIK2 may play a tumor-suppressor role in gastric cancer. Future studies are warranted to examine whether DNA hypermethylation of the GRIK2 promoter can be used as a potential tumor marker for gastric cancer.

Clinicopathologic significance of KIAA1199 overexpression in human gastric cancer

BACKGROUND

KIAA1199 is an inner-ear-specific gene which encodes KIAA1199 protein, the function of which is unknown. KIAA1199 might be a novel, positively regulated target of Wnt signaling. The aim of this study was to examine the expression of KIAA1199 in surgical specimens of gastric cancer to evaluate the clinical outcome.

METHODS

The expression of KIAA1199 mRNA was studied by semiquantitative reverse-transcription polymerase chain reaction (RT-PCR), and the expression status was analyzed from the viewpoint of clinical and pathological factors. Univariate and multivariate analyses were performed. In addition, an immunohistochemical study was performed in the selected samples.

RESULTS

A significantly higher expression of KIAA1199 messenger RNA (mRNA) was recognized in tumor tissue compared with that of paired normal tissues (P < 0.01). The cases were divided into high- (n = 39) and low-expression (n = 71) groups according to KIAA1199 expression status in the tumor. The overall 5-year survival rate was significantly better in the KIAA1199 low-expression group (61.2%) than in the high-expression group (29.6%) (P < 0.05). Clinicopathological factors such as well and moderately tumor differentiation, positive lymph node metastasis, positive distant metastases, and positive peritoneal dissemination were more frequently observed in the high-expression group than in the low-expression group (P = 0.02, 0.08, 0.01, and 0.03, respectively). KIAA1199 expression was an independent prognostic factor (P = 0.03).

CONCLUSIONS

KIAA1199 was highly expressed in gastric cancer, and was associated with prognosis and lymph node metastasis in multivariate analyses. Taken together, KIAA1199 may be a novel gene that plays an important role in progression of gastric cancer.

Transcriptome dissection of gastric cancer: identification of novel diagnostic and therapeutic targets from pathology specimens

Gastric cancer is the fourth most common malignancy in the world, and mortality due to gastric cancer is second only to that from lung cancer. 'Transcriptome dissection' is a detailed analysis of the entire expressed transcripts from a cancer, for the purpose of understanding the precise molecular mechanism of pathogenesis. Serial analysis of gene expression (SAGE) is a suitable technique for performing transcriptome dissection. Gastric cancers of different stages and histology were analyzed on SAGE, and one of the largest gastric cancer SAGE libraries in the world was created (GEO accession number GSE 545). Through SAGE, many candidate genes have been identified as potential diagnostic and therapeutic targets for the treatment of gastric cancer. Regenerating islet-derived family, member 4 (Reg IV) participated in 5-fluorouracil (5-FU) resistance and peritoneal metastasis, and its expression was associated with an intestinal phenotype of gastric cancer and with endocrine differentiation. GW112 expression correlated with advanced tumor stage. Measurement of Reg IV and GW112 levels in sera indicated a sensitivity of 57% for detection of cancer. SPC18 participated in tumor growth and invasion through transforming tumor growth factor-alpha upregulation. Palate, lung, and nasal epithelium carcinoma-associated protein (PLUNC) was a useful marker for gastric hepatoid adenocarcinoma. Expression of SOX9, HOXA10, CDH17, and loss of claudin-18 expression were associated with an intestinal phenotype of gastric cancer. Information obtained from transcriptome dissection greatly contributes to diagnosis and treatment of gastric cancer.

Genome-wide analysis of DNA copy number alterations and gene expression in gastric cancer

Genomic copy number aberrations (CNAs) are believed to play a major role in the development and progression of human cancers. Although many CNAs have been reported in gastric cancer, their genome-wide transcriptional consequences are poorly understood. In this study, to reveal the impact of CNAs on genome-wide expression in gastric cancer, we analysed 30 cases of gastric cancers for their CNAs by array comparative genomic hybridization (array CGH) and 24 of these 30 cases for their expression profiles by oligonucleotide-expression microarray. We found that with the application of laser microdissection, most CNAs were detected at higher frequency than in previous studies. Notably, gain at 20q13 was detected in almost all cases (97%), suggesting that this may play an important role in the pathogenesis of gastric cancer. By comparing the array CGH data with expression profiles of the same samples, we showed that both genomic amplification and deletion strongly influence the expression of genes in altered genomic regions. Furthermore, we identified 125 candidate genes, consisting of 114 up-regulated genes located in recurrent regions (>10%) of amplification and 11 down-regulated genes located in recurrent regions of deletion. Up-regulation of several candidate genes, such as CDC6, SEC61G, ANP32E, BYSL and FDFT1, was confirmed by immunohistochemistry. Interestingly, some candidate genes were localized at genomic loci adjacent to well-known genes such as EGFR, ERBB2 and SMAD4, and concordantly deregulated by genomic alterations. Based on these results, we propose that our list of candidate genes may contain novel genes involved in the pathogenesis of advanced gastric cancer.

Cross talk between hedgehog and epithelial-mesenchymal transition pathways in gastric pit cells and in diffuse-type gastric cancers

We previously reported hedgehog (Hh) signal activation in the mucus-secreting pit cell of the stomach and in diffuse-type gastric cancer (GC). Epithelial–mesenchymal transition (EMT) is known to be involved in tumour malignancy. However, little is known about whether and how both signallings cooperatively act in diffuse-type GC. By microarray and reverse transcription–PCR, we investigated the expression of those Hh and EMT signalling molecules in pit cells and in diffuse-type GCs. How both signallings act cooperatively in those cells was also investigated by the treatment of an Hh-signal inhibitor and siRNAs of Hh and EMT transcriptional key regulator genes on a mouse primary culture and on human GC cell lines. Pit cells and diffuse-type GCs co-expressed many Hh and EMT signalling genes. Mesenchymal-related genes (WNT5A, CDH2, PDGFRB, EDNRA, ROBO1, ROR2, and MEF2C) were found to be activated by an EMT regulator, SIP1/ZFHX1B/ZEB2, which was a target of a primary transcriptional regulator GLI1 in Hh signal. Furthermore, we identified two cancer-specific Hh targets, ELK1 and MSX2, which have an essential role in GC cell growth. These findings suggest that the gastric pit cell exhibits mesenchymal-like gene expression, and that diffuse-type GC maintains expression through the Hh–EMT pathway. Our proposed extensive Hh–EMT signal pathway has the potential to an understanding of diffuse-type GC and to the development of new drugs.

Bmi-1 expression predicts prognosis for patients with gastric carcinoma

BACKGROUND AND OBJECTIVE

The Bmi-1 gene is a transcriptional repressor involved in oncogenesis in various human cancers. Here, we examine Bmi-1 expression in gastric carcinoma (GC) and investigates whether its expression correlates with patient prognosis.

METHODS

Immunohistochemistry was performed using an anti-Bmi-1 antibody on primary tumor samples of 146 cases of GC. The association between Bmi-1 expression and the clinicopathological status and prognosis of GC patients was statistically analyzed. Furthermore, reverse transcription-PCR (RT-PCR) and Western blotting were performed to determine the expression levels of Bmi-1 in an additional 8 GC and the adjacent non-cancerous samples.

RESULTS

Using immunohistochemistry, we found that 99 of 146 paraffin-embedded GC samples expressed Bmi-1 extensively. Statistical analysis showed that Bmi-1 overexpression was highly correlated with tumor size, clinical stage, lymph node metastasis and T classification (P < 0.05), Patients with Bmi-1 expression had shorter overall survival time than those without Bmi-1 expression (P < 0.01). Multivariate analysis indicated that Bmi-1 expression is an independent prognostic factor of GC. RT-PCR and Western blotting showed that Bmi-1 was up-regulated at both the transcriptional and translational levels in the GC tissues compared with the adjacent non-cancerous tissues.

CONCLUSIONS

Bmi-1 may serve as a valuable marker for diagnosis and prognosis of GC.

Association of ezrin expression in intestinal and diffuse gastric carcinoma with clinicopathological parameters and tumor type

AIM: To investigate the correlation between ezrin expression and types of gastric carcinoma and clinico-pathological variables.

METHODS: We examined ezrin protein expression in 75 gastric carcinoma (53 intestinal types of adenocarcinoma, 22 diffuse types of carcinoma) tissues by immunohistochemistry. The results were compared with clinicopathological parameters such as tumor type, grade of tumor, clinical stage, presence of metastatic lymph node, and depth of invasion.

RESULTS: Ezrin immunostaining was positive in 43 cases (81.1%) of intestinal type and in 9 (40.9%) cases of diffuse type adenocarcinomas (P < 0.001). In gastric carcinomas, the expression of ezrin protein correlated with the status of H pylori and survival. There was no correlation between expression of ezrin with TNM stage and histological grade of gastric carcinomas (P > 0.05).

CONCLUSION: The low expression of ezrin implicates the loss of adhesion in diffuse carcinomas. Furthermore, overexpression of ezrin in carcinomas with H pylori infection may be a genuine specific pathway in which H pylori may cause/initiate gastric carcinoma.

Molecular basis of the differences between normal and tumor tissues of gastric cancer

To be able to describe the differences between the normal and tumor tissues of gastric cancer at a molecular level would be essential in the study of the disease. We investigated the gene expression pattern in the two types of tissues from gastric cancer by performing expression profiling of 86 tissues on 17K complementary DNA microarrays. To select for the differentially expressed genes, class prediction algorithm was employed. For predictor selection, samples were first divided into a training (n=58), and a test set (n=28). A group of 894 genes was selected by a t-test in a training set, which was used for cross-validation in the training set and class (normal or tumor) prediction in the test set. Smaller groups of 894 genes were individually tested for their ability to correctly predict the normal or tumor samples based on gene expression pattern. The expression ratios of the 5 genes chosen from microarray data can be validated by real time RT-PCR over 6 tissue samples, resulting in a high level of correlation, individually or combined. When a representative predictor set of 92 genes was examined, pathways of 'focal adhesion' (with gene components of THBS2, PDGFD, MAPK1, COL1A2, COL6A3), 'ECM-receptor interaction' pathway (THBS2, COL1A2, COL6A3, FN1) and 'TGF-beta signaling' (THBS2, MAPK1, INHBA) represent some of the main differences between normal and tumor of gastric cancer at a molecular level.