alpha-catenin expression is decreased in human gastric cancers and in the gastric mucosa of first degree relatives

The Role of CTNNA1 in Malignancies: An Updated Review

Catenin alpha 1 (CTNNA1), encoding α-catenin, is involved in several physiological activities, such as adherens junction synthesis and signal transduction. Recent studies have suggested additional functions for CTNNA1 malignancies. This review systematically summarizes the varying functions of CTNNA1 in different tumors and briefly describes the diverse pathways and mechanisms involved in different types of tumors. CTNNA1 is abnormally expressed in leukemia and solid tumor such as cancers of digestive system, genitourinary system and breast, and it's related to the occurrence, development, and prognosis of tumors. In addition, the possible physiological processes involving CTNNA1, such as methylation, miRNA interference, or regulatory axes, similar to those of CDH1, SETD2, and hsa-miR-30d-5p/GJA1 are also summarized here. The precise mechanism of CTNNA1 in most cancers remains uncertain; hence, additional pre-clinical studies of CTNNA1 are warranted for potential early tumor diagnosis, prognosis, and treatment.

H. pylori slyD, a novel virulence factor, is associated with Wnt pathway protein expression during gastric disease progression

We have previously reported that the virulence factor HpslyD is related to the occurrence of gastric diseases. However, its mechanism of pathogenesis is still unclear. It is commonly believed that the Wnt/β-catenin pathway is indispensable for the development of gastric cancer, but it is unclear whether HpslyD and Wnt/β-catenin interact during the development of gastric diseases. Therefore, we measured the expression of E-cadherin, β-catenin, TCF4, and CDX2 proteins by IHC in gastric mucosa specimens from patients with different gastric diseases and compared the differences in protein expression to H. pylori-infection status. The results indicated that the expression of these proteins was associated with HpslyD infection. HpslyD subtype infection, rather than common H. pylori infection, may have a greater effect on the expression of Wnt proteins in atrophic gastritis and gastric cancer. Additionally, HpslyD strain infection promoted the expression of Wnt pathway-related proteins with the progression of gastric disease. This study provides insight into the pathogenesis of H. pylori-related gastric diseases and "type-based treatment" for H. pylori infection.

The Chemical Potential of Plasma Membrane Cholesterol: Implications for Cell Biology

Cholesterol is abundant in plasma membranes and exhibits a variety of interactions throughout the membrane. Chemical potential accounts for thermodynamic consequences of molecular interactions, and quantifies the effective concentration (i.e., activity) of any substance participating in a process. We have developed, to our knowledge, the first method to measure cholesterol chemical potential in plasma membranes. This was accomplished by complexing methyl-β-cyclodextrin with cholesterol in an aqueous solution and equilibrating it with an organic solvent containing dissolved cholesterol. The chemical potential of cholesterol was thereby equalized in the two phases. Because cholesterol is dilute in the organic phase, here activity and concentration were equivalent. This equivalence allowed the amount of cholesterol bound to methyl-β-cyclodextrin to be converted to cholesterol chemical potential. Our method was used to determine the chemical potential of cholesterol in erythrocytes and in plasma membranes of nucleated cells in culture. For erythrocytes, the chemical potential did not vary when the concentration was below a critical value. Above this value, the chemical potential progressively increased with concentration. We used standard cancer lines to characterize cholesterol chemical potential in plasma membranes of nucleated cells. This chemical potential was significantly greater for highly metastatic breast cancer cells than for nonmetastatic breast cancer cells. Chemical potential depended on density of the cancer cells. A method to alter and fix the cholesterol chemical potential to any value (i.e., a cholesterol chemical potential clamp) was also developed. Cholesterol content did not change when cells were clamped for 24-48 h. It was found that the level of activation of the transcription factor STAT3 increased with increasing cholesterol chemical potential. The cholesterol chemical potential may regulate signaling pathways.

Exploiting the Gastric Epithelial Barrier: Helicobacter pylori's Attack on Tight and Adherens Junctions

Highly organized intercellular tight and adherens junctions are crucial structural components for establishing and maintenance of epithelial barrier functions, which control the microbiota and protect against intruding pathogens in humans. Alterations in these complexes represent key events in the development and progression of multiple infectious diseases as well as various cancers. The gastric pathogen Helicobacter pylori exerts an amazing set of strategies to manipulate these epithelial cell-to-cell junctions, which are implicated in changing cell polarity, migration and invasive growth as well as pro-inflammatory and proliferative responses. This chapter focuses on the H. pylori pathogenicity factors VacA, CagA, HtrA and urease, and how they can induce host cell signaling involved in altering cell-to-cell permeability. We propose a stepwise model for how H. pylori targets components of tight and adherens junctions in order to disrupt the gastric epithelial cell layer, giving fresh insights into the pathogenesis of this important bacterium.

Genetic predisposition to gastric cancer

Gastric cancer ranks as the third leading cause of cancer mortality worldwide and confers a 5-year survival of 20%. While most gastric cancers are sporadic, ~1%-3% can be attributed to inherited cancer predisposition syndromes. Germline E-cadherin/CDH1 mutations have been identified in families with an autosomal dominant inherited predisposition to diffuse gastric cancer. The cumulative risk of gastric cancer for CDH1 mutation carriers by age 80 years is reportedly 70% for men and 56% for women. Female mutation carriers also have an estimated 42% risk for developing lobular breast cancer by age 80 years. However, most individuals meeting clinical criteria for hereditary diffuse gastric cancer syndrome (HDGC) do not have a germline CDH1 mutation, and germline CDH1 mutation carriers do not all exhibit similar clinical outcomes in terms of age of diagnosis or cancer types. E-cadherin (CDH1) as the one known causative gene for HDGC accounts for only 40% of cases, leaving 60% with an unknown genetic diagnosis. In addition to HDGC, we will review other genetic syndromes with elevated gastric cancer risk, as well as newly implicated alterations in other genes (CTNNA1, DOT1L, FBXO24, PRSS1, MAP3K6, MSR1, and INSR) that may affect gastric cancer susceptibility and age-specific penetrance.

Bifidobacterium bifidum PRL2010 modulates the host innate immune response

Here, we describe data obtained from transcriptome profiling of human cell lines and intestinal cells of a murine model upon exposure and colonization, respectively, with Bifidobacterium bifidum PRL2010. Significant changes were detected in the transcription of genes that are known to be involved in innate immunity. Furthermore, results from enzyme-linked immunosorbent assays (ELISAs) showed that exposure to B. bifidum PRL2010 causes enhanced production of interleukin 6 (IL-6) and IL-8 cytokines, presumably through NF-κB activation. The obtained global transcription profiles strongly suggest that Bifidobacterium bifidum PRL2010 modulates the innate immune response of the host.

Construction of a eukaryotic expression vector expressing FOXQ1 and its expression in colorectal cancer cell line Colo-320

AIM: To construct a eukaryotic expression vector expressing FOXQ1 (pAcGFP1-N1-FOXQ1) and investigate its transient expression in colorectal cancer cell line Colo-320.

METHODS: The full-length FOXQ1 cDNA sequence was amplified from the plasmid containing full-length FOXQ1 cDNA (NM_033260) and inserted into eukaryotic expression vector pAcGFP1-N1. The resulting pAcGFP1-N1-FOXQ1 plasmid was identified by PCR, double digestion and DNA sequencing. The constructed plasmid was then transfected into colorectal cancer cell line Colo-320 using Lipofectamine 2000, and transfection efficiency was assessed by fluorescence microscopy. The expression level of FOXQ1 protein was detected by Western blot.

RESULTS: Eukaryotic expression vector pAcGFP1-N1-FOXQ1 was constructed successfully and verified by PCR, double digestion and DNA sequencing. The constructed vector could express mature FOXQ1 protein correctly in colorectal cancer cell line Colo-320.

CONCLUSION: Successful construction of the eukaryotic expression vector pAcGFP1-N1-FOXQ1 provides an experimental basis for further study of functions of the FOXQ1 gene in tumorigenesis.

Loss of alpha-catenin decreases the strength of single E-cadherin bonds between human cancer cells

The progression of several human cancers correlates with the loss of cytoplasmic protein alpha-catenin from E-cadherin-rich intercellular junctions and loss of adhesion. However, the potential role of alpha-catenin in directly modulating the adhesive function of individual E-cadherin molecules in human cancer is unknown. Here we use single-molecule force spectroscopy to probe the tensile strength, unstressed bond lifetime, and interaction energy between E-cadherins expressed on the surface of live human parental breast cancer cells lacking alpha-catenin and these cells where alpha-catenin is re-expressed. We find that the tensile strength and the lifetime of single E-cadherin/E-cadherin bonds between parental cells are significantly lower over a wide range of loading rates. Statistical analysis of the force displacement spectra reveals that single cadherin bonds between cancer cells feature an exceedingly low energy barrier against tensile forces and low molecular stiffness. Disassembly of filamentous actin using latrunculin B has no significant effect on the strength of single intercellular E-cadherin bonds. The absence of alpha-catenin causes a dominant negative effect on both global cell-cell adhesion and single E-cadherin bond strength. These results suggest that the loss of alpha-catenin alone drastically reduces the adhesive force between individual cadherin pairs on adjoining cells, explain the global loss of cell adhesion in human breast cancer cells, and show that the forced expression of alpha-catenin in cancer cells can restore both higher intercellular avidity and intercellular E-cadherin bond strength.

Analysis of APC, alpha-, beta-catenins, and N-cadherin protein expression in aggressive fibromatosis (desmoid tumor)

The aims of this study were to analyze the cadherin/catenin adhesion complex in cells from abdominal and extra-abdominal aggressive fibromatosis tumors, and to estimate the correlation between the expression of the tested proteins and the clinical data of the desmoid patients. Immunohistochemistry was used to examine the expression of the cadherin/catenin adhesion complex: APC protein, alpha-, beta-catenin, and N-cadherin in archival material derived from 15 cases of extra-abdominal desmoid tumor (E-AD) and 20 cases of abdominal (AD) desmoid tumor. The tested proteins demonstrated cytoplasmic (c) staining. Furthermore, nuclear (n) or cytoplasmic and nuclear (c+n) staining was observed for beta-catenin. The mean values of the percentage of positive cells for the tested proteins between E-AD vs. AD did not demonstrate any statistically significant difference except for alpha-catenin. In the E-AD group, in both cases of recurrent tumors, no alpha-catenin expression was observed but the expression of this protein was detected in primary tumors. In the groups investigated, no statistically significant correlation was found between alpha-catenin, beta-catenin (c), (n) and (c+n) expression, and tumor size (p>0.1). The results regarding beta-catenin expression obtained in our study confirm the previous findings that nuclear accumulation of this protein plays a crucial role in the pathogenesis of aggressive fibromatosis.

Bench to bedside and back again: molecular mechanisms of alpha-catenin function and roles in tumorigenesis

The cadherin/catenin complex, comprised of E-cadherin, beta-catenin and alpha-catenin, is essential for initiating cell-cell adhesion, establishing cellular polarity and maintaining tissue organization. Disruption or loss of the cadherin/catenin complex is common in cancer. As the primary cell-cell adhesion protein in epithelial cells, E-cadherin has long been studied in cancer progression. Similarly, additional roles for beta-catenin in the Wnt signaling pathway has led to many studies of the role of beta-catenin in cancer. Alpha-catenin, in contrast, has received less attention. However, recent data demonstrate novel functions for alpha-catenin in regulating the actin cytoskeleton and cell-cell adhesion, which when perturbed could contribute to cancer progression. In this review, we use cancer data to evaluate molecular models of alpha-catenin function, from the canonical role of alpha-catenin in cell-cell adhesion to non-canonical roles identified following conditional alpha-catenin deletion. This analysis identifies alpha-catenin as a prognostic factor in cancer progression.

Syndrome differentiation in traditional Chinese medicine and E-cadherin/ICAM-1 gene protein expression in gastric carcinoma

AIM

To explore the syndrome differentiation in traditional Chinese medicine (TCM) and gene protein expression in gastric carcinoma.

METHODS

Preoperative data of gastric cancer cases were collected from the General Surgery Department and classified according to the criteria for syndrome differentiation in TCM. E-cadherin (E-cad) and ICAM-1 gene protein expressions were detected in postoperative specimens from these cases by the immunohistochemical EnVision two-step method.

RESULTS

The E-cad positive expression rate was 90% in 100 cases of gastric carcinoma. The difference in E-cad expression was significant between the different syndrome differentiation types in TCM (P < 0.01). Further group-group comparison showed that there was a significant difference in E-cad expression between the stagnation of phlegm-damp type and the deficiency in both qi and blood and the deficiency-cold of stomach and spleen types, where E-cad expression was high. There was no significant difference between the internal obstruction of stagnant toxin type and the in-coordination between liver and stomach type, where E-cad expression was relatively low. The ICAM-1 positive expression rate was 58%, and there was no statistically significant difference between the two groups (c2 = 8.999, P > 0.05).

CONCLUSION

E-cad expression is relatively low in the internal obstruction of stagnant toxin type and the in-coordination between liver and stomach type, where tumor development and metastasis may be associated with low E-cad expression, or with low homogeneous adhesiveness between tumor cells.

Elevated risk for gastric adenocarcinoma can be predicted from histomorphology

The number of patients with gastric cancer has more than doubled since 1985 in developing countries. Thus, the questions of whether it can be predicted from gastritis morphology, who is at risk and who has a lower risk of developing gastric carcinoma are raised. H pylori-infection leads to erosions, ulcerations, carcinoma, mucosa associated lymphoid tissue (MALT)-lymphoma and extragastric diseases only in some individuals. The frequency of ulcerations among H pylori-infected individuals is estimated to be 13%, gastric cancer about 1% and MALT lymphoma around 0.1%. In the literature a multistep model from chronic active H pylori-infection through multifocal atrophy, intestinal metaplasia, dysplasia (intraepithelial neoplasia) and carcinoma has been described. But this model cannot be applied to all routine cases. Since risk factors such as metaplasia and atrophy are paracancerous rather than precancerous conditions, this raises the question whether there is a better morphological marker. Differences in topography, grade and activity of Helicobacter gastritis in the antrum and corpus might be good markers for identifying those who are at risk of developing gastric cancer. It is known that the so-called corpus dominant

H pylori gastritis is found more frequently among individuals with early and advanced gastric cancer and within high risk populations. This is valid both for first-degree relatives of gastric cancer patients and for patients with gastric adenoma and hyperplastic polyps. In conclusion, corpus-dominant H pylori gastritis is significantly more common in patients with advanced and early gastric cancer, first-degree relatives of patients with gastric cancer, patients with gastric adenoma and gastric hyperplastic polyps. Therefore, all these patients are at risk of developing gastric cancer. Next, the question of who is at risk of developing corpus-dominant gastritis is raised. It appears that patients with a low acid output more frequently develop gastric cancer. Eradication therapy is never performed too early but probably sometimes too late after the patients pass a “point of no return”. Large prospective long term studies are necessary to prove this and identify new reliable markers for gastric cancer development.

Eradication of H pylori for the prevention of gastric cancer

Infection with H pylori is the most important known etiological factor associated with gastric cancer. While colonization of the gastric mucosa with H pylori results in active and chronic gastritis in virtually all individuals infected, the likelihood of developing gastric cancer depends on environmental, bacterial virulence and host specific factors. The majority of all gastric cancer cases are attributable to H pylori infection and therefore theoretically preventable. There is evidence from animal models that eradication of H pylori at an early time point can prevent gastric cancer development. However, randomized clinical trials exploring the prophylactic effect of H pylori eradication on the incidence of gastric cancer in humans remain sparse and have yielded conflicting results. Better markers for the identification of patients at risk for H pylori induced gastric malignancy are needed to allow the development of a more efficient public eradication strategy. Meanwhile, screening and treatment of H pylori in first-degree relatives of gastric cancer patients as well as certain high-risk populations might be beneficial.

Risk assessment in relatives of gastric cancer patients: hyperproliferation, genetics, and Helicobacter pylori infection

Approximately 10% of cases of gastric cancer present with some kind of familial aggregation, but only 1-3% of gastric carcinomas arise as a result of clearly defined genetic syndromes that require genetic counselling and aggressive preventative measures. In the remaining families, no specific abnormalities, either genetic, biochemical or histological, responsible for the increased risk have been identified. However, several lines of evidence suggest that the increased cancer risk in first-degree relatives of gastric cancer probands is mostly dependent on Helicobacter pylori infection clustering.

Molecular screening of gastric cancer by proteome analysis

Gastric cancer affects annually more than 800,000 individuals worldwide and remains a challenge for clinicians and oncologists. Most patients with gastric cancer are diagnosed in advanced stages, when a curative resection is impossible, which leads to an overall poor prognosis. Finding new diagnostic and treatment procedures is of paramount importance to improve patient prognosis, which will be improved most dramatically by techniques that allow the detection of gastric cancer in its early stages. So far the value of conventional tumour markers such as Ca72-4 or carcinoembryonic antigen is limited, and even markers developed from molecular biological studies on the carcinogenesis of gastric cancer, such as E-cadherin and others, have not proved to be of adequate sensitivity and specificity to allow the early detection of gastric cancer. With the development of innovative diagnostic tools, such as proteome analysis, new biomarkers may be identified that may allow early diagnosis and thus screening for gastric cancer, particularly in at-risk patient populations. Recent studies have indicated that these biomarkers may be derived from the tumour itself or reflect a specific metabolic or immunological response to cancer that can be used to find gastric cancer patients at an early and putatively curative stage of the disease.

Correlation between Helicobacter pylori infection and distribution of gastric premalignant lesions

AIM: To determine the distribution and prevalence of premaligant lesions (gastric atrophy, intestinal metaplasia and desplasia) in the stomach of H. pylori infected patients.

METHODS: Outpatients with the symptoms of dyspepsia were enrolled in this study and received a ¹⁴C-urea breath test for the diagnosis of H. pylori infection. Endoscopic examination with antral and corporal biopsy was performed, and gastritis, atrophy, and metaplasia were classified.

RESULTS: Premaligant lesions were identified in 55.47% (71/128) of H. pylori infected patients, but only in 31.25% (71/128) of H. pylori negative patients (P < 0.05). The incidence rate of gastric premalignant lesions noted in H. pylori positive patients was 58.46% in the lesser curvature of the antrum, 36.92% in the greater curvature of the antrum, 23.85% in the lesser curvature of the body and 14.62% in the greater curvature of the body. The differences between any two of the above different areas were significant (P< 0.05). However, the difference was not found in H. pylori negative patients (P > 0.05).

CONCLUSION: H. pylori infection is closely associated with gastric premalignant lesions, which mostly present in the lesser curvature of gastric antrum, and then in the greater curvature of the antrum.

Effects of Helicobacter pylori on the cadherin-catenin complex

BACKGROUND

The cadherin-catenin complex is the key component of the adherens junction in epithelial cells, and changes in this complex are implicated in gastric adenocarcinoma. Germline mutations in E-cadherin have been described in diffuse-type gastric adenocarcinoma. Helicobacter pylori infection is the first stage in gastric carcinogenesis.

AIMS

To determine whether H pylori was associated with changes in the complex, and whether this was affected by virulence of the strain.

METHODS

Epithelial cell lines were cultured with H pylori using the wild-type pathogenic and non-pathogenic strains and CagE null and VacA null isogenic mutants. Gastric biopsy specimens at endoscopy were obtained from patients with (n = 17) and without (n = 15) H pylori infection, and E-cadherin and beta-catenin expression was assessed by immunohistochemistry. H pylori was typed by polymerase chain reaction from these patients for CagE and VacA.

RESULTS

In vitro studies showed that coculture with a pathogenic strain of H pylori led to disruption of epithelial junctional beta-catenin expression, but without evidence of nuclear translocation or signalling. This effect was independent of a functional Cag pathogenicity island and vacuolating activity, but dependent on live bacteria. No marked differences in beta-catenin or E-cadherin expression were seen in gastric biopsy specimens in patients with and without H pylori infection.

CONCLUSION

Acute H pylori infection disrupts junctional beta-catenin in vitro, but chronic infection by H pylori has no effect on E-cadherin and beta-catenin expression, as seen in gastric biopsy specimens at the initial gastritis stage of the proposed Correa pathway of gastric carcinogenesis. A later effect at the later stages of atrophy or intestinal metaplasia cannot be ruled out.

Mechanisms inactivating the gene for E-cadherin in sporadic gastric carcinomas

AIM: To study the role of CDH1/E-cadherin (E-cad) gene alteration profiles including mutation, loss of heterozygosity (LOH), promoter polymorphism and hypermethylation in mechanisms of CDH1 inactivation in gastric carcinoma (GC).

METHODS: Specimens were collected surgically from 70 patients with GC. Allelotyping PCR and detection of LOH, denaturing high pressure liquid chromatography and DNA sequencing, restriction fragment length polymorphism analysis, methylation specific PCR, and immunohistochemical staining were used.

RESULTS: Promoter polymorphism was not a major mechanism of E-cad inactivation. Only one truncating mutation was found in a diffuse type tumor (3%). Both LOH and promoter hypermethylation were major mechanisms of E-cad inactivation, but interestingly, there was a negative association between the fraction of allelic loss (LOH) in tumors and hypermethylation of CDH1. Therefore LOH and hypermethylation were two different tumorigenic pathways involved in GC.

CONCLUSION: Given the findings that somatic mutation was extremely low and the relationship between LOH and hypermethylation was inverse, any two combinations of these three factors cannot fulfill the classical two-hit hypothesis of CDH1 inactivation. Thus, other mechanisms operating at the transcriptional level or at the post-translational level might be required to induce E-cadherin inactivation.

Increased expression of cyclooxygenase-2 in first-degree relatives of gastric cancer patients

AIM: To study the expression of cyclooxygenase-2 (COX-2) in human gastric cancer tissues and their paired adjacent mucosa, as well as mucosa from gastric antrum and corpus of the first-degree relatives of the recruited cancer patients.

METHODS: The expression of COX-2 mRNA in 38 patients with gastric cancer and their 29 first-degree relatives and 18 healthy controls was assessed by the real time RT-PCR. The expression of COX-2 protein was determined by Western blot.

RESULTS: A marked increase in COX-2 mRNA expression was found in 20 of 37 (54%) cancerous tissues compared to their respective paired normal mucosa (P<0.001). Interestingly, increased COX-2 mRNA expression was also found in mucosa of the corpus (6/29) and antrum (13/29) of their first-degree relatives. Increased COX-2 mRNA expression was more frequently observed in the antrum biopsies from cancer patients than in the antrum biopsies from healthy controls (P<0.05). In addition, 3 of 23 (13%) patients with atrophic mucosa and 6 of 35 (17%) patients with intestinal metaplasia showed increased COX-2 mRNA expression. Furthermore, COX-2 expression increased in H pylori-positive tissues, especially in antrum mucosa.

CONCLUSION: Increased COX-2 expression is involved in gastric carcinogenesis, and may be necessary for maintenance of the malignant phenotype and contribute to Helicobacter pylori-associated malignant transformation.

α-catenin expression is decreased in patients with gastric carcinoma

AIM: To assess the expression of α-catenin in gastric carcinoma and to determine the role of α-catenin expression in gastric carcinogenesis.

METHODS: α-catenin expression was assessed by semi-quantitative reverse transcriptase-polymerase chain reaction and immunohistochemical staining in 49 gastric carcinomas, 26 adjacent non-cancerous mucosae, and gastric biopsy specimens from 11 healthy controls.

RESULTS: mRNA levels of α-catenin were reduced or absent in 34 of 49 (69%) gastric carcinoma tissues and in 5 of 26 (19%) tumor-free gastric mucosae of carcinoma patients, respectively. Of the carcinoma samples with altered α-catenin mRNA levels, α-catenin expression was negative in 20 and decreased in 14 cases. Up to 69% of tumors were stained abnormally for α-catenin. Of the 34 cases whose mRNA expression of α-catenin was reduced, 32 (94%) showed abnormal immunostaining patterns, while only 2 showed a normal α-catenin expression. The frequency of reduced expression of α-catenin mRNA was 14% in well-differentiated carcinomas, higher than that in poorly differentiated carcinomas (86%). A significant correlation was not shown between α-catenin expression and both depth of invasion and lymph node metastasis. Moreover, there was no statistical difference between loss or down-regulation of α-catenin mRNA and Helicobacter pylori (H pylori) infection.

CONCLUSION: Downregulation of α-catenin expression is common in gastric carcinoma, and α-catenin expression may be used as a differentiation marker. Downregulation of α-catenin expression may be an early event in tumorigenesis. Reduced α-catenin expression is not correlated with H pylori infection.

Molecular markers in Helicobacter pylori-associated gastric carcinogenesis

Helicobacter pylori infection is a known risk factor of gastric carcino-genesis. This article presents early molecular alterations associated with H. pylori chronic gastritis and advances in the molecular characterization of preneoplastic intestinal metaplasia (IM) and premalignant gastric mucosal lesions. H. pylori infection induces changes in gene expression, genomic instability and accumulation of gene mutations in the stomach epithelium. Mutations, including LOH and microsatellite instability, and gene hypermethylation are seen not only in gastric cancer, but are already detectable in IM and gastric dysplasia/adenoma. Recent reports using microarray expression analysis identified several gastric epithelial genes that are regulated by H. pylori. Among the many genes showing altered epithelial expression in response to H. pylori, some might be useful as markers to assess gastric cancer risk. Profiles of mutagenesis and gene expression in IM and dysplasia/adenoma have been characterized and represent potential markers of preneoplastic and premalignant lesions during gastric carcinogenesis.

Beta-catenin gene alteration in glandular stomach adenocarcinomas in N-methyl-N-nitrosourea-treated and Helicobacter pylori-infected Mongolian gerbils

The goal of this study was to elucidate whether beta-catenin gene mutations might contribute to glandular stomach carcinogenesis in Helicobacter pylori (H.pylori)-infected Mongolian gerbils. Firstly, exon 3 of gerbil beta-catenin cDNA, a mutation hot spot, was cloned and sequenced and found to have 89.3% homology with the human form and 95.5% with the rat and mouse forms. Peptide sequence in this region was shown to be 100% conserved in these mammals. Then, 45 stomach adenocarcinomas induced with N-methyl-N-nitrosourea (MNU) plus H. pylori infection and 7 induced with MNU alone were examined for beta-catenin expression by immunohistochemistry and for DNA mutations using a combination of microdissection and PCR-single strand conformation polymorphism analysis. One gastric cancer in the MNU + H. pylori group (2.2%) displayed nuclear (N) beta-catenin localization, 3 (6.7%) showed cytoplasmic (C) distribution in local regions, and 41 (91.1%) demonstrated cell membrane (M) localization. Tumors induced by MNU alone showed only membranous beta-catenin localization (7/7). Analysis of exon 3 of the beta-catenin gene dem-onstrated all tumors with membrane or cytoplasmic staining as well as surrounding normal mucosa (S) to feature wild-type beta-catenin. In contrast, the lesion with nuclear staining had a missense mutation at codon 34 [GAC (Gly) --> GAA (Glu)] in exon 3 (1/1 = 100%, N vs. M, P < 0.05; and N vs. S, P < 0.05). In conclusion, these results suggest that beta-catenin may not be a frequent target for mutation in stomach carcinogenesis in MNU + H. pylori-treated gerbils.

Effects of c9,t11-conjugated linoleic acid on adhesion of human gastric carcinoma cell line SGC-7901

AIM

To investigate the effect of c9,t11-conjugated linoleic acid (c9,t11-CLA) on the adhesion of human gastric carcinoma cell line (SGC-7901).

METHODS

SGC-7901 cells were at first treated with different concentrations (25, 50, 100, 200 micromol/L) of c9,t11-CLA and 1 mL/L ethanol (as a negative control) for 24 h. Using adhesion assay and Western blot, we investigated the ability of SGC-7901 cells to adhere to intracellular matrix and examined the expression of E-cadherin (ECD), alpha-catenin, intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) in these cells.

RESULTS

The attachment rate to laminin of SGC-7901 cells treated with different concentrations of c9,t11-CLA (0, 25, 50, 100, and 200 micromol/L) was 100.0+/-3.3, 95.7+/-4.0, 89.2+/-4.6, 87.9+/-6.1, and 65.9+/-5.8, respectively. The attachment rate to fibronectin was 100.0+/-4.7, 96.8+/-3.8, 94.5+/-4.1, 76.5+/-4.3, and 61.8+/-4.8, respectively. The attachment rate to Matrigel was 99.9+/-6.6, 91.4+/-6.8, 85.5+/-7.4, 79.3+/-5.6, and 69.6+/-5.1, respectively. Besides, c9,t11-CLA could increase the level of ECD and alpha-catenin, and decrease the level of ICAM-1 and VCAM-1 in SGC-7901 cells.

CONCLUSION

c9,t11-CLA can reduce the adhesion of human gastric carcinoma cells to laminin, fibronectin and Matrigel. c9,t11-CLA can increase the level of ECD and alpha-catenin, and decrease the level of ICAM-1 and VCAM-1 in human gastric carcinoma cells.

Relationship between abnormal expression of α-catenin and biological behaviors of gastric carcinoma

AIM

To assess the expression of α-catenin in gastric carcinoma and to determine its relation with tumor clinicopathological features and patient survival.

METHODS

Immunohistochemical staining of α-catenin was performed for 163 cases of gastric carcinomas,44 cases of gastric dysplasia and 25 cases of intestinal metaplasia,and 28 cases of atrophic gastritis.

RESULTS

Normal membranous staining was observed in intestinal metaplasia and control biopsy specimens for α-catenin. 76% of tumors and 43% of gastric dysplasia were stained abnormally for α-catenin. Only one of atrophic gastritis showed abnormal staining. Abnormal α-catenin expression occurred more significantly in Borrmann III/IV type than in Borrmann I/II type (P <0.01) A significantly higher proportion of signet-ring (91%), mucinous(79%) and tubular adenocarcinomas (78%) showed abnormal α-catenin expression compared with papillary adenocarcinomas (47%) (P <0.01) Morever, abnormal α-catenin staining occurred more frequently in diffuse type(95%, 38/40) than in intestinal type tumors (68%, 73/108) (P <0.01). No association was found between abnormal α-catenin and tumour invasive depth, lymph node metastasis and distance metastasis (P >0.05, respectively). A survival advantage was not noted in the tumors retaining normal staining of α-catenin.

CONCLUSION

Abnormal expression of α-catenin occurs frequently in gastric carcinoma, and is closely related to its poor differentiation. Abnormal expression of α-catenin in gastric dysplasia may be an early event in tumorigenesis.

Loss of beta-catenin expression in metastatic gastric cancer

PURPOSE

Beta-catenin (beta-catenin) participates in intercellular adhesion and is an integral part of the Wnt signaling pathway. The role of beta-catenin in the pathogenesis of gastric cancer and its metastasis is largely unknown.

PATIENTS AND METHODS

Immunohistochemistry and Western blot analysis were used to analyze the expression of beta-catenin in 87 human gastric cancers, in metastasis and cancer cell lines. The beta-catenin and the adenomatous polyposis coli (APC) genes were analyzed for gene mutations. Furthermore, methylation of the beta-catenin promoter in cell lines was assessed by treatment with 5'-azadeoxycytidine and sodium bisulfite genomic sequencing.

RESULTS

beta-Catenin expression was present at either the cell membrane or the cytoplasm in 34 of 75 primary gastric cancers. Expression of beta-catenin was significantly more frequent in intestinal-type (P =.0049) and well-differentiated gastric cancers (P <.001). There were no quantitative differences between gastric cancers and the nonmalignant gastric tissues, as determined by Western blot analysis. One of 18 metastatic cancer lesions and four of five gastric cancer cell lines expressed beta-catenin protein. N87 cells, derived from the liver metastasis of a gastric cancer, did not express beta-catenin. Treatment with 5'-azadeoxycytidine restored beta-catenin protein levels in this cell line, which exhibited significantly more 5-methylcytosines in the beta-catenin promoter compared with the other cell lines.

CONCLUSION

beta-Catenin expression is lost in a subgroup of primary gastric cancers, is frequently absent in metastases, and exhibits nuclear localization in cancers with either beta-catenin or APC gene mutations. Interestingly, the loss of beta-catenin expression in metastatic gastric cancers may result from hypermethylation of the beta-catenin promoter.

Prognostic use of growth characteristics of early gastric cancer and expression patterns of apoptotic, cell proliferation, and cell adhesion proteins

BACKGROUND AND OBJECTIVES

Selection of suitable treatment for early gastric cancers, such as endoscopic mucosal resection or the major surgical option of resection of the cancer together with a radical lymph node dissection, may be assisted by comparing the growth characteristics of the cancer with selected molecular characteristics. The results could be used to predict those cases that have a higher risk of developing secondary metastases.

METHODS

A total of 1,196 Japanese patients with early gastric cancers (648 mucosal cancers and 548 submucosal) were included in the selection of two groups: a metastatic group made up 57 cancers with lymph node metastasis (9 mucosal, 48 submucosal), and a nonmetastatic group of 61 cases (6 mucosal, 55 submucosal) without lymph node metastasis. Growth characteristics of the cancers (superficially spreading, penetrating or invasive, lymph node metastasis) were compared with immunohistochemical expression of single-stranded DNA (ssDNA) protein (apoptosis indicator), bcl-2 and p53 (apoptosis-associated), Ki-67 (cell proliferation), and E-cadherin (cell adhesion) proteins.

RESULTS

The lesions in the nonmetastatic group had higher levels of apoptosis and lower expression of bcl-2 than in the metastatic group, indicating an inhibitory role for apoptosis in malignant progression. Apoptosis was also higher in the superficial compared with the invasive lesions of both groups. The lesions in the metastatic group had higher p53 expression than that of the nonmetastatic group, whereas apoptosis in the metastatic group was lower than in the nonmetastatic group. An unproved explanation for this finding may be that, although increased, p53 was mutated and ineffective in promoting apoptotic control of metastatic progression. E-cadherin was decreased in the invasive lesions of both groups, indicating a greater ability of these cells to lose adhesion, to invade the submucosa, and to metastasize. Cell proliferation was highest in the superficial lesions of both metastatic and nonmetastatic groups.

CONCLUSIONS

Early gastric cancers with low levels of apoptosis, increased bcl-2, and high levels of p53 expression are more likely to invade and metastasize.

Expression of E-cadherin and β-catenin in gastric carcinoma and its correlation with the clinicopathological features and patient survival

AIM: The E-cadherin-catenin complex is important for cell-cell adhesion of epithelial cells. Impairment of one or more components of this complex is associated with poor differentiation and increased invasiveness of carcinomas. We evaluated the expression pattern of E-cadherin and β-catenin in gastric carcinoma and dysplasia and analyzed their relationship with tumor clinicopathological features and patient survival.

METHODS: Immunohistochemical staining of E-cadherin and β-catenin was performed from paraffin specimens of 163 gastric carcinomas, 44 gastric mucosal dysplasia, and 25 intestinal metaplasia, 28 atrophic gastritis and 12 healthy controls.

RESULTS: Normal membrane staining was observed in intestinal metaplasia, atrophic gastritis and control biopsy specimens for E-cadherin and β-catenin. 36% and 16% of gastric dysplasia were stained abnormally for E-cadherin and β-catenin respectively. Abnormal expression of E-cadherin and β-catenin was demonstrated in 46% and 44% of gastric carcinoma respectively. Abnormal expression of E-cadherin and β- catenin occurred more significantly in Borrmann III/IV than in Borrmann I/II type (P < 0.005, respectively). A significantly higher proportion of signet-ring, mucinous and tubular adenocarcinomas were abnormally expressed for E-cadherin and β-catenin as compared with papillary adenocarcinomas (χ² = 8.47, P < 0.005, and χ² = 7.05, P < 0.01, respectively). Morever, abnormal E-cadherin and β-catenin staining occurred more frequently in diffuse than in intestinal type of tumor (χ² = 18.18 and 17.79, P < 0.005, respectively). There was a significant correlation between abnormal β-catenin expression and positive lymph node metastasis. A survival advantage was noted in tumors retaining normal membranous expression of β-catenin, independent of type, grade, or stage of the disease (P < 0.0005).

CONCLUSION: Abnormal expression of the E-cadherin-catenin complex occurs frequently in gatric carcinoma, closely related to its histogenesis. Abnormal expression of the E-cadherin- catenin complex in gastric dysplasia may be an early event in the tumorigenesis. The close correlation with poor survival suggests that abnormal β-catenin may be a useful prognostic marker.

Increased expression of survivin in gastric cancer patients and in first degree relatives

Survivin was recently described as an apoptosis inhibitor. Its pathogenic role in gastric cancer is largely unknown. Expression of survivin in gastric cancer and non-cancer first-degree relatives, and its association with apoptosis and cyclo-oxygenase-2 expression was investigated. Fifty gastric cancer, 30 non-cancer first-degree relatives, 20 normal controls and five gastric cancer cell lines were studied. Survivin and cyclo-oxygenase-2 were evaluated by reverse transcriptase-polymerase chain reaction, immunohistochemistry and Western blot. Survivin expression was absent from normal gastric mucosa. All five cancer cell lines and 34 out of 50 (68%) human gastric cancer tissues expressed survivin mRNA. Survivin expression was less frequent (22%; P<0.001) in adjacent non-tumour gastric tissues. Immunohistochemistry and Western blot obtained similar findings. Gastric cancers with survivin expression displayed significantly reduced apoptosis (P=0.02), and associated with cyclo-oxygenase-2 overexpression at both mRNA (P=0.001) and protein levels (P=0.041). Moreover, survivin mRNA was detected in the gastric mucosa of eight (27%) non-cancer relatives. Expression in non-cancer patients showed positive correlation with H. pylori infection (P=0.004). This demonstrates the frequent expression of survivin in gastric cancer and in first-degree relatives. Co-expression of survivin and cyclo-oxygenase-2 may suggest multiple pathways contributing to the inhibition of apoptosis in gastric cancer.

Role of Helicobacter pylori in gastric carcinogenesis

Peptic ulcers and gastric malignancies are the two major complication of the course of Helicobacter pylori-associated chronic gastritis. Both gastric adenocarcinomas and MALT lymphomas occur in association with H. pylori infection, and studies support an etiological association. This article discusses the natural history of H. pylori-related gastric carcinogenesis and criteria to identify people susceptible to H. pylori infection-associated gastric cancer. It then reviews the molecular and genetic mechanisms underlying the malignant transformation of the gastric mucosa associated with H. pylori.

Expression of G1 phase cyclins in human gastric cancer and gastric mucosa of first-degree relatives

The aim of this study was to investigate the expression of D-type cyclins and cyclin E in gastric cancer patients (N = 34), in healthy first-degree relatives of gastric cancer patients (N = 29), and in control subjects (N = 18). Expression of cyclins D1, D2, D3, and E was determined by RT-PCR. Localization of cyclin expression was determined by immunohistochemistry. Expression of cyclins D2, D3, and E was more frequently detected in tumor tissue compared with tumor-free gastric mucosa (P < 0.05) and was associated with the presence of intestinal metaplasia. In contrast, cyclin D1 was frequently expressed in both tumor- and tumor-free tissue. Cyclin D3 expression was more frequently detected in the antrum mucosa of first-degree relatives compared to controls (P < 0.01) and was associated with the presence of Helicobacter pylori. Our data suggest that deregulation of G1 phase cyclins may play a role in gastric carcinogenesis, and may point to the presence of molecular alterations in individuals at an increased risk for gastric cancer.

Multifocal atrophic gastritis and gastric carcinoma

Gastric carcinoma remains a major cause of morbidity and mortality worldwide despite its significant decline in recent years. H. pylori infection begins with nonatrophic gastritis, and most individuals continue to have nonatrophic H. pylori gastritis throughout their lifetime. A minority of those with severe antral inflammation will develop a duodenal ulcer, and a few, for unknown reasons, may develop gastric MALT lymphoma. Others, who acquired the H. pylori infection in early childhood, develop progressive multifocal atrophic gastritis with loss of gastric glands. A small proportion of these individuals develop extensive, incomplete (type III) intestinal metaplasia, and an even smaller proportion will progress to dysplasia and intestinal-type gastric carcinoma. H. pylori-associated gastritis is also a risk factor for diffuse-type gastric carcinoma, which is not preceded by atrophy, intestinal metaplasia, or dysplasia. Appropriate screening and preventive measures should be considered in high-risk groups. It is also crucial to identify cofactors such as genetic susceptibility and environmental factors that might interact with H. pylori infection to increase gastric cancer risk. To make an impact on gastric cancer incidence and mortality, serious consideration should be given to early H. pylori eradication in high-risk groups and endoscopic surveillance according to the updated Sydney system in some patients with high-risk preneoplastic lesions, whereas dysplastic lesions should be removed without delay. Studies currently in progress may tell us whether H. pylori eradication can prevent later development of gastric carcinoma and thus eliminate a major cause of mortality worldwide.

Review article: Pathogenesis of sporadic and familial gastric cancer--implications for clinical management and cancer prevention

Gastric cancer remains a great clinical challenge despite its decreasing incidence. While major progress has been achieved in the understanding of the pathogenesis and molecular biology of sporadic gastric cancer, only recently has the role of familial aggregation of gastric cancers been rediscovered. The genetic changes underlying sporadic and familial gastric cancer have been revealed, and recent studies indicate that this familial aggregation combines genetic and microbiological aspects. Thus, for the prevention of gastric cancers these findings might be helpful for the early diagnosis and for the screening of risk groups and family members.

Reduced PTEN expression in gastric cancer and in the gastric mucosa of gastric cancer relatives

OBJECTIVES

Gastric cancer is a leading cause of cancer-related deaths worldwide, and the genetic and molecular alterations underlying its pathogenesis are largely unknown. PTEN, a tyrosine phosphatase, is frequently mutated in brain and breast cancers but not in gastric cancers. In order to assess the role of PTEN in gastric carcinogenesis, we analysed the expression of PTEN in human gastric cancer and in the gastric mucosa of cancer relatives.

METHODS

Gastric cancer tissues were obtained from 26 patients with gastric cancer undergoing upper-gastrointestinal endoscopy or resection for gastric cancer. Furthermore, 21 first-degree relatives of gastric cancer patients and 12 healthy individuals agreed to undergo upper-gastrointestinal endoscopy. In all cases, biopsies were taken from the antrum and corpus. PTEN expression was assessed by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis and immunohistochemistry.

RESULTS

PTEN expression was reduced or absent in 21/26 gastric cancers compared with the matched non-malignant gastric biopsy (P < 0.001). Furthermore, PTEN expression was reduced significantly in the antrum biopsy of first-degree relatives compared with healthy controls (P < 0.05).

CONCLUSIONS

Reduced expression of PTEN in gastric cancer points to another mechanism apart from PTEN mutation that may be involved in the pathogenesis of gastric cancer. The reduction of PTEN expression was also observed in first-degree relatives.

Helicobacter pylori infection and molecular changes in gastric carcinogenesis

In recent years there has been much progress in understanding the pathogenesis of gastric cancer. The role of individual factors in gastric carcinogenesis continues to be debated and is also subject to further analysis. In addition to the activation of oncogenes and the inactivation of tumor suppressor genes, alteration of adhesion molecules seems to be critical for the development of gastric cancer. Helicobacter pylori has been linked to an increased risk of developing gastric cancer, and the molecular changes induced by H. pylori are currently being investigated. Recent studies indicate that H. pylori induces cell proliferation and apoptosis during the early phase of chronic inflammation of the gastric mucosa, whereas in the malignant transformation of the gastric mucosa apoptosis is inhibited and adhesion of gastric epithelial cells is impaired. This review focuses on the role of H. pylori in the development of molecular changes in gastric cancer and its preneoplastic lesions.

Atrophy-metaplasia-dysplasia-carcinoma sequence in the stomach: a reality or merely an hypothesis?

The results of recent investigations have suggested that the old hypothesis of an atrophy-metaplasia-dysplasia-carcinoma sequence in the stomach needs to be qualified. The most common cause of intestinal metaplasia is Helicobacter pylori gastritis. The consequence of this intestinal metaplasia is focal atrophy. Helicobacter pylori infection may also trigger an autoimmune gastritis of the corpus mucosa, with atrophy and intestinal metaplasia. Most intestinal metaplasias are only 'paracancerous' but not 'precancerous' lesions. Diffuse gastric carcinomas, such as the signet ring cell carcinoma, arise independently of intestinal metaplasia. Histogenetically, numerous carcinomas of the stomach are primarily of the gastric type, and may secondarily change into the intestinal type.High-grade intra-epithelial neoplasias (dysplasias) detected during the biopsy-based diagnostic work-up appear to be a marker for carcinoma and must, therefore, be removed endoscopically. The detection of intestinal metaplasia in routinely obtained biopsy material is subject to sampling error and is, therefore, not a suitable marker for an increased risk of a gastric carcinoma developing. As an alternative, the concept of gastritis of the carcinoma phenotype, which is more frequently found in early gastric carcinomas and in the relatives of gastric carcinoma patients, has been developed. In this concept, the diffuse parameters of grade and activity of the gastritis in the antrum and corpus, which are independent of sampling error, are subjected to a comparative analysis. A risk gastritis of the carcinoma phenotype is diagnosed when the grade and activity of the gastritis in the corpus are at least equally as pronounced as in the antrum. Currently, this concept is being tested in a prospective ongoing study. Future studies must show whether, and if so which, immunohistochemical or molecular-genetically detectable changes can be applied as risk markers in the diagnostic work-up. Helicobacter pylori eradication probably does not lead to complete regression of the intestinal metaplasia and ensuing focal atrophy. However, eradication of H. pylori does lead to the normalization of changes that can lead to mutations of the stem cells of the gastric mucosa (free radicals, nitric oxide, cell proliferation and vitamin C secretion).

Inactivation of the E-cadherin gene in sporadic diffuse-type gastric cancer

Loss of the cell adhesion molecule E-cadherin has been observed in a variety of human carcinomas, and germline E-cadherin mutations have been found in several familial cases of diffuse gastric cancer. We sought to determine the prevalence and nature of E-cadherin alterations in "sporadic" gastric carcinomas. We performed comprehensive sequencing of the coding region, loss of heterozygosity (LOH) analysis, and immunohistochemical protein expression determination on 40 sporadic gastric adenocarcinomas. In total, 7 of 25 diffuse-type cancers harbored genetic alterations in the E-cadherin gene. Novel mutations predicted to significantly compromise protein function were found within 4 of these cancers, 2 of which harbored alterations resulting in biallelic inactivation of the gene product. Three diffuse cancers failed to amplify Exon 8 of E-cadherin, suggesting the presence of a homozygous abnormality. Notably, one germline E-cadherin mutation was also identified within these "sporadic" diffuse cancers. Significant gene mutations were not found in the 14 intestinal-type or histologically mixed cancer. Immunohistochemistry revealed aberrant or negative protein expression in seven diffuse-type tumors, four of which correlated with the genetic alterations. Both diffuse and intestinal-type tumors exhibited low rates of LOH, suggesting that allelic loss at the locus is not a common mechanism for E-cadherin inactivation during gastric tumorigenesis. Our observations suggest that inactivation of the E-cadherin gene occurs only in a subset of diffuse-type gastric cancers, as the majority of cases did not contain genetic alterations or identifiable protein abnormalities. Germline E-cadherin alterations, although rare, may underlie some diffuse gastric cancer cases that have important biologic and practical implications