Genetic and epigenetic changes in stomach cancer

Molecular evolution of intestinal-type early gastric cancer according to Correa cascade

Early screening is crucial for the prevention of intestinal-type gastric cancer. The objective of the current study was to ascertain molecular evolution of intestinal-type gastric cancer according to the Correa cascade for the precise gastric cancer screening. We collected sequential lesions of the Correa cascade in the formalin-fixed and paraffin-embedded endoscopic submucosal dissection-resected specimens from 14 Chinese patients by microdissection, and subsequently determined the profiles of somatic aberrations during gastric carcinogenesis using the whole exome sequencing, identifying multiple variants at different Correa stages. The results showed that TP53, PCLO, and PRKDC were the most frequently mutated genes in the early gastric cancer (EGC). A high frequency of TP53 alterations was found in low-grade intraepithelial neoplasia (LGIN), which further increased in high-grade intraepithelial neoplasia (HGIN) and EGC. Intestinal metaplasia (IM) had no significant correlation with EGC in terms of mutational spectra, whereas both LGIN and HGIN showed higher genomic similarities to EGC, compared with IM. Based on Jaccard similarity coefficients, three evolutionary models were further constructed, and most patients showed linear progression from LGIN to HGIN, ultimately resulting in EGC. The ECM-receptor interaction pathway was revealed to be involved in the linear evolution. Additionally, the retrospective validation study of 39 patients diagnosed with LGIN indicated that PRKDC mutations, in addition to TP53 mutations, may drive LGIN progression to HGIN or EGC. In conclusion, the current study unveils the genomic evolution across the Correa cascade of intestinal-type gastric cancer, elucidates the underlying molecular mechanisms of gastric carcinogenesis, and provides some evidence for potential personalized gastric cancer surveillance.

miR-188-5p Suppresses Gastric Cancer Cell Proliferation and Invasion via Targeting ZFP91

MicroRNAs (miRNAs) have been demonstrated to be essential regulators in the development and progression of various cancers. The role of miR-188-5p in gastric cancer (GC) has not been determined. In this study, we found that the expression of miR-188-5p was downregulated in GC tissues compared with adjacent normal tissues. The lowly expressed miR-188-5p was significantly associated with lymph node metastasis and advanced TNM stage. Moreover, overexpression of miR-188-5p significantly inhibited GC cell proliferation, migration, and invasion but promoted cellular apoptosis. Mechanistically, we identified transcription factor ZFP91 as a target gene of miR-188-5p in GC. We found that miR-188-5p overexpression significantly inhibited the expression of ZFP91 in GC cell lines. There was an inverse correlation between the expression of miR-188-5p and ZFP91 in GC tissues. We found that restoration of ZFP91 in miR-188-5p-overexpressed MGC-803 and SGC-7901 cells promoted cell proliferation, migration, and invasion. Finally, we also showed that overexpression of miR-188-5p inhibited tumor growth in vivo. Taken together, our findings indicated that miR-188-5p serves as a tumor suppressor in human GC by targeting ZFP91, suggesting that miR-188-5p might be a promising therapeutic target for GC treatment.

C-Met as a potential target for the treatment of gastrointestinal cancer: Current status and future perspectives

Aberrant activation of the HGF/c-Met signalling pathways is shown to be related with cell proliferation, progression, metastasis, and worse prognosis in several tumor types, including gastrointestinal cancers, suggesting its value as a stimulating-target for cancer-therapy. Several approaches have been developed for targeting HGF and/or c-Met, and one of them, crizotinib (dual c-Met/ALK inhibitor), is recently been approved by FDA for lung-cancers with ALK-rearrangement. The main aim of current review is to give an overview on the role of c-Met/HGF pathway in gastrointestinal cancer, in preclinical and clinical trials. Although several important matters is still remained to be elucidated on the molecular pathways underlying the antitumor effects of this therapy in gastrointestinal-cancers. Further investigations are warranted to recognize the main determinants of the activity of c-Met inhibitors, for parallel targeting signalling pathway associated/activated via MET/HGF pathway or in response to the cell resistance to anti-c-Met agents. Additionally, identification of patients that might benefit from therapy could help to increase the selectivity and efficacy of the therapy.

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.

Advances of Molecular Targeted Therapy in Gastric Cancer

BACKGROUND

Gastric cancer is the second most common cause of cancer-related death in the world, and its prognosis remains poor with a median overall survival of 12 months for advanced disease. Advances in the understanding of molecular genetics have led to the development of directed molecular targeted therapy in gastric cancer, leading to improve patient outcomes and quality of life.

DISCUSSION

In the treatment of human epidermal growth factor receptor 2 (HER2)-positive gastric cancer, the addition of trastuzumab significantly improves survival in the first-line setting of therapy. Ramucirumab, an antibody directed against vascular endothelial growth factor receptor 2, significantly improved progression-free and overall survival and has been approved for second-line treatment of gastric cancer. Anti-mesenchymal-epithelial transition (c-MET), mammalian target of rapamycin inhibitors, and polo-like kinase 1 inhibitors are under investigation as a novel therapeutic option for the treatment of gastric cancer. The novel therapies target the key immune checkpoint interaction between a T cell co-inhibitory receptor called programmed death 1 (PD-1) and one of its immunosuppressive ligands, PD-L1. This article reviews molecular targeted therapies in gastric cancer, in light of recent advances.

Identification of key genes associated with gastric cancer based on DNA microarray data

The present study aimed to identify genes with a differential pattern of expression in gastric cancer (GC), and to find novel molecular biomarkers for GC diagnosis and therapeutic treatment. The gene expression profile of GSE19826, including 12 GC samples and 15 normal controls, was downloaded from the Gene Expression Omnibus database. Differentially-expressed genes (DEGs) were screened in the GC samples compared with the normal controls. Two-way hierarchical clustering of DEGs was performed to distinguish the normal controls from the GC samples. The co-expression coefficient was analyzed among the DEGs using the data from COXPRESdb. The gene co-expression network was constructed based on the DEGs using Cytoscape software, and modules in the network were analyzed by ClusterOne and Bingo. Furthermore, enrichment analysis of the DEGs in the modules was performed using the Database for Annotation, Visualization and Integrated Discovery. In total, 596 DEGs in the GC samples and 57 co-expression gene pairs were identified. A total of 7 genes were enriched in the same module, for which the function was phosphate transport and which was annotated to participate in the extracellular matrix-receptor interaction pathway. These genes were collagen, type VI, α3 (COL6A3), COL1A2, COL1A1, COL5A2, thrombospondin 2, COL11A1 and COL5A1. Overall, the present study identified several biomarkers for GC using the gene expression profiling of human GC samples. The COL family is a promising prognostic marker for GC. Gene expression products represent candidate biomarkers endowed with great potential for the early screening and therapy of GC patients.

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.

The association between miR-146a gene rs2910164 polymorphism and gastric cancer risk: a meta-analysis

PURPOSE

Studies have demonstrated that single nucleotide polymorphisms (SNPs) in miRNAs may lead to varying functional outcomes by altering miRNAs expression, even leading to the development of cancers. The association between a single nucleotide polymorphism (SNP) in miR-146a rs2910164 and susceptibility to gastric cancer has been studied during the recent years, but the results are still inconclusive and inconsistent. We performed a meta-analysis to evaluate the relationship between miR-146a rs2910164 polymorphism and the risk of gastric cancer.

MATERIALS AND METHODS

The databases of PubMed, MEDLINE and Web of Science were searched for suitable studies. A total of 8 published case-control studies on miR-146a rs2910164 polymorphism and gastric cancer risk including 4308 cases and 6370 controls were included.

RESULTS

Overall, significant association was observed between rs2910164 and gastric cancer risk in allele model (OR=1.11, 95% CI=1.02-1.21); homozygote model (OR=1.26, 95% CI=1.10-1.43) and dominant model (OR=1.21, 95% CI=1.09-1.34). Stratified analysis by ethnicity showed significant association between rs2910164 polymorphism and gastric cancer susceptibility in Asians (OR=1.10, 95% CI=1.00-1.23 for G vs. C; OR=1.25, 95% CI=1.09-1.43 for GG vs. CC; OR=1.19, 95% CI=1.07-1.33 for GG vs. GC+CC, respectively). When stratified by genotyping methods and sample size, increased gastric cancer risk was only observed with the method by TaqMan and the sample size more than 1000.

CONCLUSION

In summary, this meta-analysis indicated that miR-146a rs2910164 polymorphism was associated with the susceptibility to gastric cancer, especially in Asian population.

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.

MTHFR C677T polymorphism contributes to the risk for gastric cancer

Methylenetetrahydrofolate reductase (MTHFR) has been demonstrated to be involved in carcinogenesis. Increasing individual studies have investigated the role of MTHFR C677T polymorphism in gastric cancer pathogenesis, but with inconsistent findings. The aim of this study was to clarify the potential association of the MTHFR C677T polymorphism with gastric cancer risk by pooling all available data from published case-control studies. We searched the PubMed, Embase, Web of Science, and Wanfang databases for all relevant publications to date. The pooled odds ratio (OR) with corresponding 95 % confidence interval (95% CI) was calculated. Stratified analysis and sensitivity analysis were also carried out to estimate the strength of this association. A total of 25 case-control studies with 6,572 cases and 9,584 controls were retrieved. Overall, the ORs under five contrast models indicated that the MTHFR C677T variant was positively associated with gastric cancer risk (ORT vs. C = 1.21, 95% CI 1.10–1.34, P(OR) < 0.001; OR(TT vs. CC) = 1.47, 95% CI 1.22–1.76, P(OR) < 0.001; OR(TC vs. CC) = 1.20, 95% CI 1.03-1.40, P(OR) = 0.022; OR(TT + TC vs. CC) = 1.27, 95% CI 1.10-1.47, P(OR) = 0.001; OR(TT vs. CC + TC) = 1.29, 95% CI 1.15-1.46, P(OR) < 0.001). Stratified analyses according to ethnicity and source of controls further confirmed the significant correlations. The current meta-analysis provides strong evidence that the MTHFR C677T polymorphism may be a risk factor for gastric cancer among Asians and Caucasians.

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.

A c-Met inhibitor increases the chemosensitivity of cancer stem cells to the irinotecan in gastric carcinoma

Background:

Cancer stem cells (CSCs) may be postulated mediators of the chemoresistance. This study aimed to determine an effective signal inhibitor with effects on the proliferation of CSCs in combination with anticancer drugs.

Methods:

We used three gastric cancer cell lines and three side population (SP)-enriched CSC cell lines. We examined the combined effects of inhibitors against stemness signals, including c-Met inhibitor SU11274, and five anticancer drugs on the CSC proliferation and mRNA expression of chemoresistance-associated genes.

Results:

The IC₅₀ of irinotecan in SP-enriched CSC was 10.5 times higher than parent OCUM-2M cells, whereas that of oxaliplatin, taxol, gemcitabine, and 5-fluorouracil was 2.0, 2.8, 2.0, and 1.2, respectively. The SP cell lines had higher expression levels of UGT1A1, ABCG2, and ABCB1 than their parent cell lines. There was a synergistic antiproliferative effect with a combination of SU11274 and SN38 in SP cells, but not other inhibitors. The SU11274 significantly decreased the expression of UGT1A1, but not ABCG2 and ABCB1. The SN38 plus SU11274 group more effectively suppressed in vivo tumour growth by OCUM-2M/SP cells than either group alone.

Conclusion:

Cancer stem cells have chemoresistance to irinotecan. The c-Met inhibitor may be a promising target molecule for irinotecan-based chemotherapy of gastric cancer.

Identification of molecular subtypes of gastric cancer with different responses to PI3-kinase inhibitors and 5-fluorouracil

BACKGROUND & AIMS

Almost all gastric cancers are adenocarcinomas, which have considerable heterogeneity among patients. We sought to identify subtypes of gastric adenocarcinomas with particular biological properties and responses to chemotherapy and targeted agents.

METHODS

We compared gene expression patterns among 248 gastric tumors; using a robust method of unsupervised clustering, consensus hierarchical clustering with iterative feature selection, we identified 3 major subtypes. We developed a classifier for these subtypes and validated it in 70 tumors from a different population. We identified distinct genomic and epigenomic properties of the subtypes. We determined drug sensitivities of the subtypes in primary tumors using clinical survival data, and in cell lines through high-throughput drug screening.

RESULTS

We identified 3 subtypes of gastric adenocarcinoma: proliferative, metabolic, and mesenchymal. Tumors of the proliferative subtype had high levels of genomic instability, TP53 mutations, and DNA hypomethylation. Cancer cells of the metabolic subtype were more sensitive to 5-fluorouracil than the other subtypes. Furthermore, in 2 independent groups of patients, those with tumors of the metabolic subtype appeared to have greater benefits with 5-fluorouracil treatment. Tumors of the mesenchymal subtype contain cells with features of cancer stem cells, and cell lines of this subtype are particularly sensitive to phosphatidylinositol 3-kinase-AKT-mTOR inhibitors in vitro.

CONCLUSIONS

Based on gene expression patterns, we classified gastric cancers into 3 subtypes, and validated these in an independent set of tumors. The subgroups have differences in molecular and genetic features and response to therapy; this information might be used to select specific treatment approaches for patients with gastric cancer.

Association of RASSF1A promoter methylation with gastric cancer risk: a meta-analysis

Ras-association domain family 1A (RASSF1A), a candidate tumor suppressor gene, is frequently silenced and inactivated by hypermethylation of its promoter region in several human tumors. However, the association between RASSF1A promoter methylation and gastric cancer risk remains conflicting. The aim of this study was to assess the association of RASSF1A promoter methylation with gastric cancer risk by a comprehensive meta-analysis. Relevant studies were identified by searches of PubMed and Web of Science databases with no restrictions. Combined odds ratio (OR) and 95 % confidence interval (CI) were used to assess the strength of the association between RASSF1A promoter methylation and gastric cancer risk. A chi-square-based Q test and sensitivity analyses were performed to test the between-study heterogeneity and the contributions of single studies to the final results, respectively. Funnel plots were carried out to evaluate publication bias. Overall, a significant association was observed between RASSF1A promoter methylation and gastric cancer risk (OR, 12.67; 95 % CI, 8.12-19.78; p < 0.001) with no between-study heterogeneity. Subgroup analyses further revealed that gastric cancer risk was increased for individuals carrying the methylated RASSF1A compared with those with unmethylated RASSF1A. In addition, no publication bias was detected in the overall and subgroup analyses. This study identified a strong association between RASSF1A promoter methylation and risk of gastric cancer and highlighted a promising potential for RASSF1A promoter methylation in gastric cancer risk prediction.

Correlation between global genome methylation and mutation at CpG codons of p53 gene

OBJECTIVE

Hypomethylation within the body of the p53 gene, which is normally methylated, has been found in neoplasms. Also, the CG → TA transition was not detected in the CpG codons of the p53 gene in gastritis lesions in Iranian patients. Therefore, an evaluation of the probable correlation between global genome methylation and alteration at CpG codons of p53 gene was needed.

METHODS

For defining the genotypes of CpG codons, DNA sequencing was performed on 90 paired samples of gastritis and normal tissues. To measure global genome methylation status, the extracted DNA was digested with HpaII (methylation sensitive) and MspI (insensitive). Then, enzymatic digestion was quantitated using Pyrosequencing as peak height. By calculating the HpaII/ MspI peak ratio it is possible to evaluate the methylation level of normal and gastritis tissues.

RESULTS

Codons 9, 245 and 248 underwent a CG → AT transversion but not a CG → TA transition. In addition, the mean methylation level was significantly different between the patients with GG and GT genotypes at codon 245 (P = 0.019).

CONCLUSIONS

As CG → AT transversion at codon 245 is associated with global genome methylation, GG hypomethylation may induce different pattern of mutations, for example, C → A instead of C → T at the CpG codons of the p53 gene during gastritis development in Iranian patients.

Bioinformatics analysis with graph-based clustering to detect gastric cancer-related pathways

Despite a dramatic reduction in incidence and mortality rates, gastric cancer still remains one of the most common malignant tumors worldwide, especially in China. We sought to identify a set of discriminating genes that could be used for characterization and prediction of response to gastric cancer. Using bioinformatics analysis, two gastric cancer datasets, GSE19826 and GSE2685, were merged to find novel target genes and domains to explain pathogenesis; we selected differentially expressed genes in these two datasets and analyzed their correlation in order to construct a network. This network was examined to find graph clusters and related significant pathways. We found that ALDH2 and CCNB1 were associated with gastric cancer. We also mined for the underlying molecular mechanisms involving these differently expressed genes. We found that ECM-receptor interaction, focal adhesion, and cell cycle were among the significantly associated pathways. We were able to detect genes and pathways that were not considered in previous research on gastric cancer, indicating that this approach could be an improvement on the investigative mechanisms for finding genetic associations with disease.

Identification of differentially expressed genes in gastric cancer by high density cDNA microarray

The identification of molecular markers for diagnosis, treatment, and prognosis is a significant issue in the management of patients with gastric cancer. We compared the expression profiles of 23 gastric cancers and 22 normal gastric tissues using cDNA microarrays. We divided the samples into two sets, 11 pairs as a training set and 12 unpaired gastric cancer and 11 unpaired normal gastric tissues as a test set. We selected significant genes in the training set and validated the significance of the genes in the test set. We obtained 238 classifier genes that showed a maximum cross-validation probability and clear hierarchical clustering pattern in the training set, and showed excellent class prediction probability in the independent test set. The classifier genes consisted of known genes related to the biological features of cancer and 28% unknown genes. We obtained genome-wide molecular signatures of gastric cancer, which provides preliminary exploration data for the pathophysiology of gastric cancer.

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.

c-Met upregulates aquaporin 3 expression in human gastric carcinoma cells via the ERK signalling pathway

Aquaporin 3 (AQP3) and c-Met are both overexpressed in human gastric carcinoma and highly associated with its metastasis and invasion. However, it still remains unknown whether c-Met and AQP3 correlate with each other. Herein, we demonstrated that c-Met expression in gastric cancer tissues significantly correlated with differentiation, lymph node metastasis and lymphovascular invasion, and c-Met exhibited marked association with AQP3 expression. Immunoblotting assays showed that hHGF phosphorylated c-Met in SGC7901 and AGS cells and upregulated AQP3 expression in a dose- or time-dependent way. RNAi against c-Met reduced total c-Met levels by about two thirds in both AGS and SGC7901 cells and attenuated hHGF-induced AQP3 expression significantly. In vitro migration and proliferation assays showed that siRNA against AQP3 noticeably restrained HGF-promoted migration and proliferation of these cells. Furthermore, Immunoblotting studies revealed that HGF induced phosphorylation of ERK, and pre-treatment with U0126, a MAPK/ERK inhibitor, partially inhibited hHGF-induced increase in AQP3 expression. Together, these data provide initial evidence that c-Met regulates the expression of AQP3 via the ERK signalling pathway in gastric carcinoma. These findings assist in understanding the mechanism of growth and invasion of gastric carcinoma, and provide a possible strategy for the inhibition of gastric tumor metastasis.

Identification of proteins differentially expressed in gastric cancer cells with high metastatic potential for invasion to lymph nodes

In a search for proteins involved in cancer metastasis, we analyzed proteomes of the human gastric cancer cell OCUM-2M and its metastatic subline OCUM-2MLN. We observed that aspartate aminotransferase (AAT), D-site binding protein (DBP), and anterior gradient protein 2 (AGR2) are differentially expressed in metastatic OCUM-2MLN cells. Measurement of protein expression in clinical samples indicated that DBP and AAT are also down-regulated in metastatic adenocarcinoma. Additionally, urokinase-type tissue plasminogen activator is up-regulated in OCUM-2MLN cells and also in metastatic gastric cancer samples. Collectively, these results raise a possibility that AAT, DBP and AGR2 are functionally implicated in the invasiveness of gastric cancer cells.

Genetic mutations of p53 and k-ras in gastric carcinoma patients from Hunan, China

This case-control study investigated the mutations in p53 and k-ras genes of 123 gastric carcinoma patients and 129 normal individuals from Hunan, China. By isolating genomic DNA from peripheral blood and employing polymerase chain reaction-single strand conformation polymorphism and DNA sequencing, the mutations of p53 exons-5, 6, 7, and 8 and k-ras were detected. The overall mutation frequency of p53 was 29.3%, and mutation was found in all four exons studied. The point mutations were predominant and among them, G:C→A:T was the highest (41.7%), followed by A:T→G:C (25%), G:C→C:G (11.1%), G:C→T:A (8.3%), and A:T→T:A (2.8%). The frameshift mutation was 11.1%. Mutations were detected in codons-131, 132, 133, 135, 149, 151, 162, 167, 173, 174, and 175 of exon 5, codons-193, 197, 213, and 215 of exon 6, codons-245, 246, 248, 249, and 270 of exon 7, and codons-271, 272, 273, and 282 of exon 8 of p53. The overall frequency of mutation in k-ras was 9.8%, mostly in codon-12 (91.7%) and in codon-13 (8.3%). There was no significant relationship between p53 and k-ras gene mutation in gastric carcinoma patients. Also, the relationships between p53 mutation and age, sex, smoking or drinking, and tumor metastasis were not significant. However, the patients with high/high-middle differentiated gastric carcinoma had a higher association with of p53 mutations. This study identified some novel p53 mutations in gastric cancer and showed mutation pattern and frequency of p53 and k-ras in the population of the central southern region of China.

EGFR(s) in aging and carcinogenesis of the gastrointestinal tract

Cells of the gastrointestinal (GI) mucosa are subject to a constant process of renewal which, in normal adults, reflects a balance between the rates of cell production and cell loss. Detailed knowledge of these events is, therefore, essential for a better understanding of the normal aging processes as well as many GI diseases, particularly malignancy, that represent disorders of tissue growth. In general, many GI dysfunctions, including malignancy, increase with advancing age, and aging itself is associated with alterations in structural and functional integrity of the GI tract. Although the regulatory mechanisms for age-related increase in the incidence of GI-cancers are yet to be fully delineated, recent evidence suggests a role for epidermal growth family receptors and its family members {referred to as EGFR(s)} in the development and progression of carcinogenesis during aging. The present communication discusses the involvement of EGFR(s) in regulating events of GI cancers during advancing age and summarizes the current available therapeutics targeting these receptors. The current review also describes the effectiveness of ErbB inhibitors as well as combination therapies. Additionally, the involvement of GI stem cells in the development of the age-related rise in GI cancers is emphasized.

NAT2 polymorphism and gastric cancer susceptibility: a meta-analysis

BACKGROUND AND AIMS

N-acetyltransferase 2 (NAT2) is a polymorphic enzyme that plays an important role in the metabolism of various potential carcinogens. NAT2 can be subdivided into rapid and slow acetylation phenotype according to the different genotypes. Studies investigating the association between NAT2 polymorphisms and gastric cancer risk in humans showed conflicting results. The aim of this study was to conduct a meta-analysis assessing the association of NAT2 acetylation phenotype with risk of gastric cancer.

METHODS

Relevant studies were identified through a search of Embase, ISI Web of Knowledge, Medline and Chinese Biomedicine Database until January 2010. A meta-analysis was conducted to quantitatively summarize association of NAT2 acetylation phenotype with GC susceptibility.

RESULTS

Thirteen studies were included in the present meta-analysis, which described a total of 2,391 gastric cancer cases and 3,237 controls. The combined ORs for NAT2 slow or rapid acetylator and gastric cancer risk were 1.05 (95% CI 0.810-1.35) and 0.96 (95% CI 0.74-1.23), respectively. When stratifying for race and Lauren's classification, results also showed no significant association in genotype distribution between gastric cancer and control.

CONCLUSIONS

No association is found between NAT2 acetylation status and gastric cancer risk in this meta-analysis.

Role of methylation of the hMLH1 gene promoter in the development of gastric and colorectal carcinoma in the elderly

The occurrence of malignant neoplasms increases with advancing age. Although aging and carcinogenesis are basically different processes, they share phenomena such as the accumulation of DNA damage and abnormal proteins. Recent advances in molecular biology have shown an accumulation of genetic and epigenetic changes in both aging and carcinogenesis, as well as the alteration of metabolism, immunosenescence and shortened telomeres. DNA methylation is a representative epigenetic phenomenon and is frequently involved in controlling gene functions during development and tumorigenesis. We herein focused on methylation of genes in the development of gastrointestinal carcinomas in the elderly. The proportion of gastric and colorectal carcinomas with hypermethylation of the hMLH1 promoter increases with age, reaching 25-30% of all carcinomas of the stomach and large intestine in elderly patients. These tumors have clinicopathological and molecular characteristics such as loss of hMLH1 expression, microsatellite instability, poorly differentiated histology, peritumoral inflammatory cell infiltration, low incidence of lymph node metastasis and favorable prognosis. However, methylation-related carcinogenesis accounts for up to approximately one-third of tumors, and other mechanisms; for example chromosomal instability as a result of telomere dysfunction, are responsible for the development of most carcinomas in the elderly.

Clinical significance of detection of hMLH1 and hPMS2 mRNA expression in gastric cancer by real-time fluorescent quantitative RT-PCR

AIM: To investigate the expression of DNA mismatch repair genes hMLH1/hPMS2 and to analyze their clinical significance in gastric cancer.

METHODS: The expression of hMLH1/hPMS2 mRNAs in 40 specimens of gastric cancer and cancer-adjacent mucosa tissue and 21 specimens of chronic gastritis tissue was detected by real-time fluorescent quantitative reverse transcription-polymerase chain reaction (RT-PCR). The human glyceraldehydes-3-phosphate dehydrogenase (hGAPDH) gene was used for normalization of gene expression levels.

RESULTS: The level of hMLH1 mRNA in gastric cancer was significantly higher than those in cancer-adjacent mucosa tissue and chronic gastritis tissue (7.23 ± 11.91 vs 3.80 ± 5.13 and 2.01 ± 1.25, respectively; both P < 0.05). The level of hMLH1 mRNA was significantly higher in cancer-adjacent mucosa tissue than in chronic gastritis tissue (P < 0.05). The level of hPMS2 mRNA was significantly higher in gastric cancer and cancer-adjacent mucosa tissue than in chronic gastritis tissue (0.43 ± 0.35 and 0.55 ± 0.39 vs 0.32 ± 0.15, respectively; both P < 0.05). No significant difference was noted in the level of hPMS2 mRNA between gastric cancer and cancer-adjacent mucosa tissue. The expression levels of hMLH1/hPMS2 mRNAs in gastric cancer showed no significant correlation with tumor size, infiltration degree, and lymph node metastasis. However, the expression level of hMLH1 mRNA was significantly higher in gastric cancer with lymph node metastasis than in that without lymph node metastasis (all P < 0.05).

CONCLUSION: The expression levels of hMLH1 /hPMS2 gene in gastric cancer and cancer-adjacent mucosa tissue are abnormal when compared with that in chronic gastritis. Abnormal transcription of hMLH1/hPMS2 may be related with the genesis of gastric cancer, but not involved in the progression of the disease.

Correlation between intensity of ultrasonographic contrast enhancement and microvessel density in gastric cancer

AIM: To investigate the correlation between the enhanced intensity (EI) revealed by contrast-enhanced ultrasonography (CEUS) and microvessel density (MVD) in gastric cancer.

METHODS: Thirty-seven patients who had pathologically confirmed gastric cancer and underwent CEUS were enrolled in this study. Parameters of the time-intensity curve (TIC), including peak intensity (PI) and basic intensity (BI) of gastric cancer and normal gastric wall, were analyzed. EI (EI = PI - BI) was then calculated. Immunohistochemical staining for CD34 was performed to evaluate MVD. The correlation between EI and MVD was then analyzed.

RESULTS: The EI in gastric cancer lesions was significantly higher than that in normal gastric wall (19.46 ± 5.97 vs 14.25 ± 2.55, P < 0.01). The MVD in gastric cancer lesions was also significantly higher than that in normal gastric wall (84.68 ± 37.99 vs 21.09 ± 5.49, P < 0.01). There was a positive linear correlation between EI and MVD in gastric cancer lesions (r = 0.77, P < 0.01).

CONCLUSION: EI is positively correlated with MVD in patients with gastric cancer. CEUS may be used for assessing the angiogenesis, biological behavior and prognosis of gastric cancer.

Correlation of trefoil factor 3 expression in gastric carcinoma, precancerous lesions, gastric adenoma with angiogenesis

AIM: To investigate the expression of trefoil factor 3 (TFF3) in gastric carcinoma, precancerous lesions, gastric adenoma and explore its correlation with microvessel density (MVD) in gastric carcinogenesis.

METHODS: The expression of TFF3 was detected by the immunohistochemical PV-6000 method in 120 gastric mucosal specimens, including 20 cases of normal gastric mucosa (NGM), 20 cases of gastric adenoma (GA), 20 cases of chronic atrophic gastritis with intestinal metaplasia (IM), 20 cases of dysplasia (DYS), and 40 cases of gastric carcinoma (GC). MVD was examined by immunohistochemistry using anti-CD34 antibody.

RESULTS: The positive rates of TFF3 expression were significantly higher in GA, IM, DYS and GC than in NGM (50.0%, 65.0%, 70.0% and 57.5% vs 5.0%, respectively; all P < 0.01). MVD was significantly higher in GC than in NGM, GA, IM and DYS (30.65 ± 6.04 vs 14.87 ± 3.06, 22.33 ± 3.78, 23.16 ± 3.20 and 25.22 ± 4.66, respectively; all P < 0.01). MVD was also significantly higher in GA, IM, DYS and GC than in NGM (all P < 0.01). TFF3 expression and MVD were correlated with lymph node metastasis and tumor stage in GC (all P < 0.05). MVD was also correlated with depth of invasion in GC (P < 0.05). MVD in specimens showing positive expression of TFF3 was higher than that in specimens showing negative expression (34.53 ± 4.45 vs 25.39 ± 3.25, P < 0.01).

CONCLUSION: TFF3 may be involved in an early event in gastric carcinogenesis and play an important role in gastric carcinogenesis. Detection of TFF3 expression may be of great significance for early diagnosis and prediction of metastasis in gastric carcinoma.

Differences in genetic instability and cellular phenotype among Barrett's, cardiac, and gastric intestinal metaplasia in a Japanese population with Helicobacter pylori

AIMS

Intestinal metaplasia is considered to be a precursor lesion in both Barrett's and intestinal-type gastric cancer. The aim was to clarify the differences in molecular pathology between specialized intestinal metaplasia (SIM) in Barrett's oesophagus (BO), cardiac (CIM) and gastric intestinal metaplasia (GIM).

METHODS AND RESULTS

Eighty-eight SIM cases with BO, 30 CIM cases and 52 GIM cases in patients with or without Helicobacter pylori infectionwere analysed for genetic instability and Das-1. Microsatellite instability and a loss of heterozygosity were evaluated at five microsatellite loci. The incidence of genetic instability was 55.7% in SIM, 40.0% in CIM and 23.1% in GIM, revealing a significant difference between SIM and GIM (P < 0.0005). For each microsatellite marker analysed, there were obvious differences in frequency among the three conditions. Das-1 reactivity was significantly higher in SIM than in CIM or GIM (P < 0.0001, both). Interestingly, both genetic instability and Das-1 reactivity in SIM showed a significantly higher incidence in patients with H. pylori infection than in those without (P < 0.005 and P < 0.01, respectively).

CONCLUSIONS

SIM is distinct from CIM and GIM, and the pathogenesis of SIM, like that of GIM, is associated to some degree with H. pylori infection in a Japanese population.

Generation of expression clone set for functional proteomics of human gastric and liver cancers

Two thousand sixty-eight multi-purpose expression clones for the 326 candidate genes related to gastric or liver cancers were constructed using the Gateway system. These clones can be expressed as His, Glutathione-S-transferase (GST) or Enhanced version of the green fluorescent protein (EGFP) fusion proteins in E. coli, insect cells or mammalian cells. For the 246 E. coli expression clones, the GST fusion proteins had greater expression efficiency and solubility than the His fusion proteins. Approximately 20% of the expressed proteins had unexpected molecular weights. A detailed sequence analysis of these clones revealed frameshift mutations resulting from insertion, deletion or substitution of nucleotides. The results indicate that these changes in the candidate genes may affect the occurrence of gastric or liver cancers. In addition, when 105 proteins, which were expressed in E. coli at very low or undetectable levels, were expressed in insect cells, 76% of the proteins were expressed very well and most were soluble. We also found that most of the 30 proteins prepared using EGFP mammalian expression clones were localized to cellular compartments expected by Gene ontology (GO) and this localization was unaffected if the EGFP-fusion was at the N-terminal or C-terminal region of the protein. Antibody production and subcellular localization analysis of the candidate genes as well as a screen of genes involved in carcinogenesis pathways are currently in progress using these expression clones. These studies provide a valuable resource for developing a better understanding of the molecular mechanism of carcinogenesis in both gastric and liver cancer and would be very helpful in diagnosis and therapeutic predictions.

Effects of Helicobacter pylori infection on genetic instability, the aberrant CpG island methylation status and the cellular phenotype in Barrett's esophagus in a Japanese population

Genetic or epigenetic alterations in Barrett's esophagus (BE) with/without Helicobacter pylori (H. pylori) infection remain unclear. We examined the effects of H. pylori infection on genetic instability (GIN), the CpG island methylation status and a biomarker related to BE carcinogenesis. We analyzed 113 Japanese individuals with endoscopically suspected BE. The patients included, Group CLE (n = 25): no specialized intestinal metaplasia (SIM) in a columnar lined epithelium (control); Group BE (n = 88): all had SIM. Microsatellite instability and a loss of heterozygosity as GIN, the methylation status at hMLH1, E-cadherin, p16 and APC, and immunoreactivity using a monoclonal antibody (mAb) Das-1, which specifically reacts with BE, were evaluated. Nine additional patients with BE were prospectively followed up for 2 years after successful H. pylori eradication. The frequency of GIN, methylation at E-cadherin and APC, and mAb Das-1 reactivity in Group BE was significantly higher than that in Group CLE (p < 0.0001, p < 0.0001 and p < 0.005, and p < 0.0001, respectively). Furthermore, GIN, E-cadherin methylation and mAb Das-1 reactivity showed a significantly higher incidence in patients with H.pylori infection than in those without H. pylori infection (p < 0.01, p < 0.005, and p < 0.01, respectively). Interestingly, the patients from Group BE were observed to change to a stable state of molecular alterations in 60% for GIN, 42.9% for E-cadherin methylation and 55.6% for APC methylation, or a reduction of mAb Das-1 reactivity was noted in 25% following eradication. H. pylori infection may therefore affect these molecular alterations associated with the pathogenesis of BE, to some degree, in the Japanese population.

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 microRNA-34a overexpression with proliferation is cell type-dependent

Recently Welch et al. reported that microRNA (miRNA)-34a functions as a potential tumor suppressor in neuroblastoma cells (Oncogene 26: 5017-22, 2007). Here, we conversely show that miRNA-34a supports cell proliferation in rat oxidative stress-induced renal carcinogenesis and is overexpressed in various types of human cancers. While searching for genetically unstable chromosomal areas in rat renal carcinogenesis, we found the miRNA-34 family reciprocally overexpressed in chromosomal areas with frequent allelic loss. By in situ hybridization and reverse transcription-polymerase chain reaction, cerebral neurons and Purkinje cells showed the highest expression of a major type, miRNA-34a, followed by a variety of endocrine cells and proliferating cells including germinal center lymphocytes and mouse embryonic fibroblasts and stem cells. In contrast, normal renal tubules, hepatocytes and myocardial cells showed faint expression. After 3 weeks of ferric nitrilotriacetate (Fe-NTA)-induced oxidative stress, regenerating renal proximal tubular cells showed high miRNA-34a expression. All of the Fe-NTA-induced rat renal carcinomas and an array of human cancers (151 positive cases of 177) showed high expression of miRNA-34a. Furthermore, knockdown of miRNA-34a with small interfering RNA significantly suppressed proliferation not only of renal carcinoma cells but also of HeLa and MCF7 cells. These results indicate that miRNA-34a overexpression, an acquired trait during carcinogenesis, supports cell proliferation in the majority of cancers suggesting an unexpected link in the cellular metabolism between cancer and neuronal and/or endocrine cells, which warrants further investigation.

Clinicopathological and molecular characteristics of gastric and colorectal carcinomas in the elderly

The occurrence of malignant neoplasms increases with advancing age. Although aging and carcinogenesis are basically different processes, there are phenomena common to each such as accumulation of DNA damage and abnormal proteins. Gastric and colorectal carcinomas are representative tumors in which the prevalence and the number of patients increase significantly with age. Compared with gastric and colorectal cancers occurring in younger patients, those occurring in older patients have clinicopathological differences in tumor location, gender distribution, histological type, histological diversity, multiplicity, incidence of lymph node metastasis, and prognosis. In the elderly there are peculiar types of carcinoma such as medullary-type poorly differentiated colorectal adenocarcinoma and solid-type poorly differentiated gastric adenocarcinoma, both of which occur in older women. Methylation, apoptosis, and telomere dysfunction play important roles in the development of gastric and colorectal cancers in the elderly.

Missense mutation with/without nonsense mutation of the p53 gene is associated with large cell morphology in human malignant lymphoma

Mutations in p53 gene exons 5-9 were studied in 44 non-Hodgkin's lymphomas (NHL) consisting of 35 B-NHL and 9 T-NHL. Missense mutations were found in two diffuse large B-cell lymphomas (DLBL) and one peripheral T-cell lymphoma (unspecified). Double transversion missense and nonsense mutations were detected in one DLBL and one adult T-cell leukemia/lymphoma. Silent mutations were found in two DLBL. Detailed histomorphological study showed that cases harboring p53 missense mutation with/without nonsense mutation tended to have larger nuclei with much more prominent nucleoli. Cytomorphometric analysis was therefore conducted by measuring the gross area of 100 lymphoma cell nuclei in 44 cases and the results were compared between lymphomas harboring p53 missense mutation with/without nonsense mutation and lymphomas harboring p53 silent mutation or lacking mutation. It was found that the lymphomas harboring p53 missense mutation with/without nonsense mutation had a highly significantly larger nuclear gross area than lymphomas with silent p53 mutation or lacking mutation (two-sample t-test, P < 0.00001; Exact Wilcoxon rank-sum test, P < 0.00001). This result suggests that p53 mutation might induce enlargement of neoplastic cell nuclei by some molecular mechanism.

High PRL-3 expression in human gastric cancer is a marker of metastasis and grades of malignancies: an in situ hybridization study

Phosphatase of regenerating liver (PRL)-3, encoding a 22-kD low molecular weight tyrosine phosphatase, has been reported to be associated with metastasis of colorectal carcinoma. We assessed the levels of PRL-3 mRNA expression to know whether its up-regulation was involved in progression and metastasis of gastric carcinoma. Levels of PRL-3 expression in 94 human gastric adenocarcinomas and 54 matched lymph node metastases were detected by in situ hybridization and compared with clinicopathological characteristics including prognosis. High PRL-3 expression was detected in 36.2% of primary gastric carcinoma (with nodal metastasis, 55.6%; without nodal metastasis, 10%; P < 0.001) and in 74.1% of lymph node metastases. The incidence of high PRL-3 expression in lymph node metastasis was significantly higher than in primary tumors (P < 0.044). Moreover, high expression of PRL-3 was closely associated with tumor size, lymphatic invasion, venous invasion, extent of lymph node metastasis, and tumor stage. These results suggest that high PRL-3 expression may participate in the progression and metastasis of gastric carcinoma. PRL-3 might be a novel molecular marker for aggressive gastric cancer.

Molecular characteristics of differentiated-type gastric carcinoma with distinct mucin phenotype: LI-cadherin is associated with intestinal phenotype

Gastric carcinomas (GC) are classified into four phenotypes on the basis of the mucin expression profile: G type (gastric or foveolar phenotype), I type (intestinal phenotype), GI type (intestinal and gastric mixed phenotype) and N type (neither gastric nor intestinal phenotype). Immunohistochemistry was used to examine the expression of epidermal growth factor receptor (EGFR), E-cadherin, liver-intestine (LI)-cadherin, CD44v9 and p53 and correlation of these molecules with mucin phenotype and tumor stage was evaluated. Overexpression of EGFR and LI-cadherin, reduced expression of E-cadherin and abnormal expression of p53 were observed more frequently in advanced GC than in early GC. Among I-type GC, overexpression of EGFR and reduced expression of E-cadherin were observed more frequently in advanced tumors than in early tumors. Among G-type GC, reduced expression of E-cadherin was significantly associated with advanced tumors. With respect to the relationship between mucin phenotype and expression of cancer-related molecules, overexpression of LI-cadherin was observed more frequently in I-type (12/25, 48.0%) than in G-type (1/14, 7.1%) GC. I-type GC tended to express LI-cadherin more frequently than GI-type GC. These results provide insights into the molecular characteristics of the distinct mucin phenotype of differentiated-type GC and suggest that LI-cadherin may contribute to the biological behavior of I-type GC.

Prediction of peritoneal metastasis in advanced gastric cancer by gene expression profiling of the primary site

Peritoneal metastasis is the most common cause of tumour progression in advanced gastric cancer. Clinicopathological findings including cytologic examination of peritoneal lavage have been applied to assess the risk of peritoneal metastasis, but are sometimes inadequate for predicting peritoneal metastasis in individuals. Hence, we tried to construct a new prediction system for peritoneal metastasis by using a PCR-based high throughput array with 2304 genes. The prediction system, constructed from the learning set comprised of 30 patients with the most informative 18 genes, classified each case into a 'good signature group' or 'poor signature group'. Then, we confirmed the predictive performance in an additional validation set comprised of 24 patients, and the prediction accuracy for peritoneal metastasis was 75%. Kaplan-Meier analysis with peritoneal metastasis revealed significant difference between these two groups (P=0.0225). By combining our system with conventional clinicopathological factors, we can identify high risk cases for peritoneal metastasis more accurately.

Expression of DNA mismatch repair gene hMLH1 and its significance in gastric cancer and premalignant lesions

AIM: To investigate the expression of DNA mismatch repair gene hMLH1 and its clinical significances in gastric cancer and premalignant lesions.

METHODS: Immunohistochemical technique was used to detect the expression of hMLH1 protein in 20 cases of chronic superficial gastritis, 20 cases of chronic atrophic gastritis complicated with intestinal metaplasia, 8 cases of adenomatous polyp, 58 cases of gastric cancer and the corresponding cancer-adjacent mucosa.

RESULTS: The hMLH1 protein was expressed mostly in epithelial cytoplasm and a little in cell nucleus. The positive rate of hMLH1 expression in chronic superficial gastritis and chronic atrophic gastritis with intestinal metaplasia were all 90%, which were significantly higher (χ² = 9.741, P = 0.02) than those in adenomatous polyp (62.5%) and the corresponding cancer-adjacent mucosa (62.1%). The positive rate of hMLH1 expression was not significantly different between gastric cancer (72.4%) and the others (P > 0.05). Of 58 cases of cancer-adjacent mucosa, 21 (36.2%) were with chronic superficial gastritis, and 37 (63.8%) with chronic atrophic gastritis and intestinal metaplasia. The positive rates of hMLH1 expression were similar between the 21 and 37 cases, but they were both markedly lower than those in the nonneoplastic mucosa (χ² = 9.885, P = 0.02).

CONCLUSION: Absence of hMLH1 expression may be one of the early molecular events in the carcinogenesis of gastric cancer. Timely visiting and monitoring chronic gastric patients with absence of hMLH1 protein expression may help to achieve early diagnosis of gastric cancer.

Expression of the enhancer of zeste homolog 2 is correlated with poor prognosis in human gastric cancer

Overexpression of the enhancer of zeste homolog 2 (EZH2) protein, a known repressor of gene transcription, has been reported to be associated with biological malignancy of prostate cancer and several other cancers. The purpose of this study was to examine the expression of EZH2 and analyze its relationship with the clinicopathological features of human gastric cancers. Expression levels of EZH2 mRNA and protein were examined in 13 gastric cancer cell lines and in 83 surgically removed human gastric cancer tissues. Immunohistochemical analysis of the 83 tissue samples and corresponding non-cancerous gastric mucosa showed that EZH2 was more highly expressed in the cancerous than in the non-cancerous tissues, and the expression levels of EZH2 were highly correlated with tumor size, depth of invasion, vessel invasion, lymph node metastasis and clinical stages. Univariate analysis of survival rate calculated by the Kaplan-Meier method revealed that gastric cancer patients with high-level EZH2 expression had poorer prognosis than those expressing no or low levels of EZH2 (P = 0.0271). These findings suggest that overexpression of EZH2 may contribute to the progression and oncogenesis of human gastric cancers, and thus immunohistochemical study of EZH2 expression may serve as a new biomarker for predicting the prognosis of gastric cancers.

CpG island hypermethylation in progression of esophageal and gastric cancer

The upper gastrointestinal (GI) cancers have various carcinogenic pathways and precursor lesions, such as dysplasia for esophageal squamous cell carcinoma, Barrett esophagus for esophageal adenocarcinoma, and intestinal metaplasia for the intestinal-type of gastric cancer. Recently, many epigenetic events in carcinogenic pathways have been revealed, along with genomic and genetic alterations. This information has provided deeper insight into an understanding of the mechanisms of upper GI carcinogenesis. Moreover, detection methods of aberrant methylation have been applied to clinical fields to stratify high-risk groups, detect early cancer, and to predict clinical outcomes. In this review, a variety of information is summarized regarding gene hypermethylation in esophageal and gastric cancer.

Warthin Tumors Do Not Have Microsatellite Instability and Express Normal DNA Mismatch Repair Proteins

Context.—Warthin tumors are controversial entities with a poorly understood etiology. Although some investigators have suggested a neoplastic origin, others have supported a developmental anomaly. A recent study described the absence of staining for hMLH1 and hMSH2 proteins in the epithelial component of Warthin tumors, suggesting that they arise secondary to defects in the DNA mismatch repair system.

Objective.—To determine if Warthin tumors exhibit evidence of DNA mismatch repair defects.

Design.—Immunostains for hMLH1 and hMSH2 were performed using a standard approach. Microdissection of the epithelial component was followed by DNA extraction from the tissue fragments. Polymerase chain reaction and capillary electrophoresis analyses were performed for the following 5 National Cancer Institute–recommended microsatellites: D2s123, D5s346, D17s250, BAT25, and BAT26.

Patients.—Twelve patients with Warthin tumors were included.

Results.—The immunostains for hMLH1 and hMSH2 showed preserved expression in the nuclei of the epithelial component of all Warthin tumors. No microsatellite instability was detected, and no loss of heterozygosity was seen.

Conclusions.—These results are not concordant with previously reported results showing loss of expression of the hMLH1 and hMSH2 DNA mismatch repair enzymes in the epithelial component of Warthin tumors. Furthermore, no microsatellite instability was detected in the 5 loci tested for each tumor in this series. These data demonstrate that Warthin tumors do not have evidence of DNA mismatch repair defects at the genomic or protein expression level.

Transcriptome analysis of human gastric cancer

To elucidate the genetic events associated with gastric cancer, 124,704 cDNA clones were collected from 37 human gastric cDNA libraries, including 20 full-length enriched cDNA libraries of gastric cancer cell lines and tissues from Korean patients. An analysis of the collected ESTs revealed that 97,930 high-quality ESTs coalesced into 13,001 clusters, of which 11,135 clusters (85.6%) were annotated to known ESTs. The analysis of the full-length cDNAs also revealed that 4862 clusters (51.7%) contained at least one putative full-length cDNA clone with an initiation codon, with the average length of the 5' UTR of 140 bp. A large number appear to have a diverse transcription start site (TSS). An examination of the TSS of some genes, such as TEGT and GAPD, using 5' RACE revealed that the predicted TSSs are actually found in human gastric cancer cells and that several TSSs differ depending on the specific gastric cell line. Furthermore, of the human gastric ESTs, 766 genes (9.5%) were present as putative alternatively spliced variants. Confirmation of the predicted spliced isoforms using RT-PCR showed that the predicted isoforms exist in gastric cancer cells and some isoforms coexist in gastric cell lines. These results provide potentially useful information for elucidating the molecular mechanisms associated with gastric oncogenesis.

The results of the expression array studies correlate and enhance the known genetic basis of gastric and colorectal cancer

Gastric and colorectal cancers belong to the most frequent cancer types in the world today. This fact emphasizes the importance of identification of useful diagnostic and prognostic markers, in the earliest stage of the disease. The examination of gene expression profile in gastric and colorectal cancer may develop the bases of early diagnosis and of individual therapeutic strategies. In the microarray examinations done so far for these types of cancers, the expression of hundreds and thousands of genes were studied, however, both the sample collection and the results showed wide variations. The diversity of expression array methods and data analysis makes the comparison of microarray results difficult. Beside the exposition of the practical aspects of the chip technology, our aims are the systematization of data that are currently available in the international scientific literature and the description of the results in a comprehensive way. Microarray results show that the gene expression pattern, detected in gastric and colon cancers, highly depends on the histological type and heterogeneity of the sample, array type, and softwares, used for data analysis. Recent experiments point out not just the changes of the alterations of tumor suppression, apoptosis, cell-cycle regulation, and signal transduction, but tumor cell metabolism and cell-microenvironment interactions also. Results show connection to and make more complete the already known molecular background of gastric and colorectal cancers. Based on the accumulation of recent and further data, such kind of multifunctional diagnostic microarrays that can be suited for completing the conventional histological diagnostics and subtypization will certainly become available in the near future.

The prognostic significance of p53, p27 kip1, p21 waf1, HER-2/neu, and Ki67 proteins expression in gastric cancer: a clinicopathological and immunohistochemical study of 121 Arab patients

BACKGROUND

The variability of prognosis within a pathological stage of gastric cancer (GC) at presentation, underscores the need for specific biological markers to identify subgroups of patients with aggressive course for intensive treatment. To our knowledge, this is the first study from an Arab population reporting on the relationship of p53, p27 kip1, p21 waf1, HER-2/neu, and Ki67 expression, and clinicopathological features and their prognostic significance.

METHODS

Formalin-fixed paraffin-embedded tumors were studied by immunohistochemistry, using monoclonal antibodies to p53, p27 kip1, p21 waf1, HER-2/neu, and Ki67. The results were correlated with clinicopathological features and survival.

RESULTS

M:F = 80:41; median age = 60 years; stage III and IV = 71%; and median follow-up = 34.4 months. Positive expression rates of p53, p27 kip1, p21 waf1, Ki67, and HER-2/neu were 54%, 40%, 8.3%, 70%, and 12% respectively. p53 expression correlated with age <60 years (P = 0.03), tumor size >5 cm (P = 0.01), p27 kip1 and Ki67 expression (P = 0.0001), and HER-2/neu (P = 0.04). p21 waf1 correlated inversely with T-stage (P = 0.008) and Her-2/neu expression correlated with histological grade (P = 0.04) and T-stage (P = 0.008). Univariate analysis showed that p53 overexpression (P = 0.01), fungating and infiltrative macroscopic appearance (P = 0.02), size >5 cm (P = 0.0001), lymph node metastasis (P = 0.0001), p T3 and T4 disease (P = 0.01), and overall stage III and IV (P = 0.0001) disease were adverse prognostic factors. Patients with tumor profiles p53 (-)/p27 (+) had better survival than those with p53 (+)/p27 kip1 (-)(P = 0.02). On multivariate analysis by Cox regression model, the expression of p53 (P = 0.03) and lymph node involvement (P = 0.01) were significant adverse prognostic factors for overall survival.

CONCLUSIONS

The expression of p53 in Arab patients with GC correlates with aggressive tumor characteristics and is an independent prognostic factor. The combined analysis of p53 and p27 kip1 is of added prognostic value.

Development and biological analysis of peritoneal metastasis mouse models for human scirrhous stomach cancer

The number of published studies on peritoneal dissemination of scirrhous gastric carcinoma is very small as a result of the unavailability of highly reproducible animal models. Orthotopic implantation of HSC-44PE and HSC-58 (scirrhous gastric carcinoma-derived cell lines) cells into nude mice led to dissemination of the tumor cells to the greater omentum, mesenterium, peritoneum and so on, and caused ascites in a small number of animals. Cycles of isolation of the ascitic tumor cells and orthotopic inoculation of these cells were repeated in turn to animals. This was to isolate highly metastatic cell lines with a strong capability of inducing the formation of ascites (44As3 from HSC-44PE; 58As1 and 58As9 from HSC-58). All three cell lines induced tumor formation at the site of orthotopic injection, and caused fatal cancerous peritonitis and bloody ascites in 90-100% of the animals approximately 3-5 weeks after the inoculation. When the parent cells were implanted, the animals became moribund in approximately 12-18 weeks, however, none of the animals developed ascites. Complementary DNA microarray and immunohistochemical analyses revealed differences in the expression levels of genes coding for the matrix proteinase, cell adhesion, motility, angiogenesis and proliferation between the highly metastatic- and parent-cell lines. The usefulness of this model for the evaluation of drugs was assessed by analyzing the stability of the metastatic potential of the cells and the reproducibility. Animals intravenously treated with CPT-11 and GEM showed suppressed tumor growth and significantly prolonged survival. The metastatic cell lines and the in vivo model established in the present study are expected to serve as a model of cancerous peritonitis developing from primary lesions, and as a useful means of clarifying the pathophysiology of peritoneal dissemination of scirrhous gastric carcinoma and the development of drugs for its treatment.