Intestinal Metaplastic Mucosa Research Articles

Molecular alterations in gastric cancer and the surrounding intestinal metaplastic mucosa: an analysis of isolated glands.

Intestinal metaplasias (IMs) are generally regarded as pre-neoplastic gastric lesions. However, molecular alterations including genetic and epigenetic changes occurring in individual IM glands are not well defined. We sought to identify DNA methylation status, microsatellite instability (MSI) and allelic imbalance (AI) occurring in individual IM glands and non-IM glands within the same mucosa. We divided examined isolated gland obtained from GC into 4 components: isolated cancer, antral isolated intestinal metaplastic tissue, antral isolated non-metaplastic gland and isolated non-metaplastic gland derived from the greater curvature of the most distant gastric body without mucosal atrophy. We examined AI and microsatellite instability statuses using PCR-based microsatellite analysis. Next, the DNA methylation status (high methylation epigenome [HME], intermediate methylation epigenome [IME], and low methylation epigenome [LME]) was investigated. DNA methylation analysis of CDKN2A, mir34-b/c and MLHI genes was also performed. Although antral isolated IM glands were characterized by IME, isolated non-IM glands showed LME. In isolated cancer glands, HME was frequently found, compared with isolated non-IM glands. DNA methylation of mir34-b/c was common in isolated cancer and IM glands, whereas DNA methylation of CDKN2A was a rare event in isolated samples. The MLH1 gene was not methylated in isolated non-IM glands. Although multiple AIs were frequently found in isolated cancer glands, a few AIs were detected in isolated IM glands. We suggest that the DNA methylation status and the status of the mir34-b/c gene among isolated samples of IMs and isolated non-IM glands have an impact on IM development.

Comparative analysis of gastrointestinal microbiota between normal and caudal-related homeobox 2 (cdx2) transgenic mice.

Background/AimsCaudal-related homeobox 2 (Cdx2) is expressed in the human intestinal metaplastic mucosa and induces intestinal metaplastic mucosa in the Cdx2 transgenic mouse stomach. Atrophic gastritis and intestinal metaplasia commonly lead to gastric achlorhydria, which predisposes the stomach to bacterial overgrowth. In the present study, we determined the differences in gut microbiota between normal and Cdx2 transgenic mice, using quantitative reverse transcription-polymerase chain reaction (qRT-PCR).MethodsTwelve normal (control) and 12 Cdx2 transgenic mice were sacrificed, and the gastric, jejunal, ileac, cecal and colonic mucosa, and feces were collected. To quantitate bacterial microbiota, we used real-time qRTPCR with 16S rRNA gene-targeted, species-specific primers.ResultsThe total numbers of bacteria in the gastric, jejunal, ileac, cecal, and colonic mucosa of the Cdx2 transgenic mice were significantly higher than those of the normal mice. The Bacteroides fragilis group and also Prevotella were not detected in the stomach of the normal mice, although they were detected in the Cdx2 transgenic mice. Moreover, the Clostridium coccoides group, Clostridium leptum subgroup, Bacteroides fragilis group, and Prevotella were not detected in the jejunum or ileum of the normal mice, although they were detected in the Cdx2 transgenic mice. The fecal microbiota of the normal mice was similar to that of the Cdx2 transgenic mice.ConclusionsOur results showed the differences in composition of gut microbiota between normal and Cdx2 transgenic mice, which may be caused by the development of gastric achlorhydria and intestinal metaplasia in Cdx2 transgenic mice.

Synbindin in Extracellular Signal-Regulated Protein Kinase Spatial Regulation and Gastric Cancer Aggressiveness

The molecular mechanisms that control the aggressiveness of gastric cancer (GC) remain poorly defined. Here we show that synbindin contributes to the aggressiveness of GC by activating extracellular signal-regulated protein kinase (ERK) signaling on the Golgi apparatus. Expression of synbindin was examined in normal gastric mucosa (n = 44), intestinal metaplastic gastric mucosa (n = 66), and GC tissues (n=52), and the biological effects of synbindin on tumor growth and ERK signaling were detected in cultured cells, nude mice, and human tissue samples. The interaction between synbindin and mitogen-activated protein kinase kinase (MEK1)/ERK was determined by immunofluorescence and fluorescence resonance energy transfer assays. The transactivation of synbindin by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) was detected using luciferase reporter assay and chromatin immunoprecipitation. High expression of synbindin was associated with larger tumor size (120.8 vs 44.8 cm(3); P = .01), advanced tumor node metastasis (TNM) stage (P = .003), and shorter patient survival (hazard ratio = 1.51; 95% confidence interval [CI] = 1.01 to 2.27; P = .046). Synbindin promotes cell proliferation and invasion by activating ERK2 on the Golgi apparatus, and synbindin is directly transactivated by NF-κB. Synbindin expression level was statistically significantly higher in human GCs with activated ERK2 than those with low ERK2 activity (intensity score of 11.5, 95% CI = 10.4 to 12.4 vs intensity score of 4.6, 95% CI 3.9 to 5.3; P < .001). Targeting synbindin in xenograft tumors decreased ERK2 phosphorylation and statistically significantly reduced tumor volume (451.2mm(3), 95% CI = 328.3 to 574.1 vs 726.1mm(3), 95% CI = 544.2 to 908.2; P = .01). Synbindin contributes to malignant phenotypes of GC by activating ERK on the Golgi, and synbindin is a potential biomarker and therapeutic target for GC.

Premalignant conditions of gastric cancer

Premalignant lesions of gastric cancer encompass a variety of conditions such as chronic gastritis, intestinal metaplasia and dysplasia, in which elevated risk of developing gastric cancer have been documented. Among them, intestinal metaplasia is frequently encountered in our daily endoscopic examination, yet its clinical significance is often underestimated despite of a number of reports demonstrating genetic and epigenetic alterations in the intestinal metaplastic mucosa. In this review, I will describe the molecular mechanisms of phenotypic changes from gastric mucosa to intestinal metaplasia based on our analysis of mouse model of intestinal metaplasia generated by ectopic expression of CDX2 in conjunction with the studies with human intestinal metaplasia.

Cdx2 expression and its promoter methylation during metaplasia-dysplasia-carcinoma sequence in Barrett's esophagus

To examine how the expression of caudal type homebox transcription factor 2 (Cdx2) is regulated in the development of malignancy in Barrett's esophagus. Cdx2, mucin (MUC) series (MUC2, MUC5AC and MUC6), p53 and E-cadherin expression in Barrett's esophagus and adenocarcinoma specimens were examined by immunostaining. Isolated clusters of cells from (1) MUC2 and Cdx2-positive intestinal metaplastic mucosa; (2) MUC5AC and MUC6-positive, and MUC2 and Cdx2-negative high-grade dysplasia (HD), or intramucosal adenocarcinoma (IMC); and (3) MUC5AC, MUC6 and Cdx2-positive poorly-differentiated invasive adenocarcinoma (PDA) were analyzed by methylation-specific polymerase chain reaction using sets of primers for detecting methylation status of the Cdx2 gene. Most of the non-neoplastic Barrett's esophageal mucosa showing intestinal-type metaplasia with or without low-grade dysplasia was positive for E-cadherin, MUC series and Cdx2, but negative for p53. A portion of the low-grade to HD was positive for E-cadherin, MUC5AC, MUC6 and p53, but negative for MUC2 and Cdx2. The definite IMC area was strongly positive for MUC5AC, MUC6 and p53, but negative for MUC2 and Cdx2. Methylation of the Cdx2 promoter was not observed in intestinal metaplasia, while hypermethylation of part of its promoter was observed in hot dipped and IMC. Hypermethylation of a large fraction of the Cdx2 promoter was observed in PDA. Cdx2 expression is restored irrespective of the methylation status of its promoter. Apparent positive immunohistochemical results can be a molecular mark for gene silencing memory.

SOX9 is expressed in normal stomach, intestinal metaplasia, and gastric carcinoma in humans

SOX9 is a marker for stem cells in the intestine and overexpression of SOX9 is found in some types of cancer. However, the expression of SOX9 in normal stomach, precancerous intestinal metaplasia, and gastric carcinoma has not yet been clarified. This study aimed to investigate SOX9 expression in the corpus and pyloric regions of the normal human stomach, premalignant intestinal metaplasia, and gastric carcinoma by using immunohistochemistry. We evaluated SOX9 expression in 46 clinical samples (early gastric well-differentiated adenocarcinoma including surrounding intestinal metaplasia) resected under esophagogastroduodenoscopy. A small amount of SOX9 was expressed in the neck/isthmus of the corpus region and SOX9 expression was predominantly restricted to the neck/isthmus of the pyloric region in normal human stomach. In the intestinal metaplastic mucosa, SOX9- and PCNA-positive cells were located at the base of the intestinal metaplastic mucosa. Almost all of the gastric carcinoma cells expressed SOX9. SOX9 is expressed in intestinal metaplasia and gastric carcinoma in humans.

Sox2 expression is maintained while gastric phenotype is completely lost in Cdx2-induced intestinal metaplastic mucosa

Sox2 is closely related to the gastric phenotype. Sox2 plays a pivotal role in gastric epithelial differentiation in the adult. Sox2 expression is reduced in Helicobacter pylori-associated intestinal metaplastic change of the gastric epithelium. The gastric mucosa is replaced by intestinal metaplastic mucosa in the stomach of caudal type homeobox 2 (Cdx2)-transgenic mice. The aim of this study was to use Cdx2-transgenic mice to investigate: (i) Sox2 expression in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach; and (ii) the relationship between Sox2 and Cdx2. Quantitative real-time PCR was performed to determine Sox2, Cdx2, Muc5Ac, and alkaline phosphatase mRNA expression levels and single- or double-label immunohistochemistry was used to evaluate the localization of Sox2, Cdx2, gastric mucin and alkaline phosphatase activity. We determined that Sox2 mRNA in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach was expressed 3.5-fold compared to the normal mouse stomach. Immunohistochemical analysis showed that the same cells in the intestinal metaplastic mucosa expressed both Cdx2 and Sox2. Gastric mucin was not expressed while alkaline phosphatase activity was recognized in the intestinal metaplastic mucosa in spite of the Sox2 expression. Cdx2 increased the transcriptional activity of the Sox2 gene, and Sox2 increased the transcriptional activity of the Muc5Ac gene, which was reduced by cotransfecion of Cdx2 together with Sox2 in the human gastric carcinoma cell line AGS. In conclusion, Sox2 expression is maintained while gastric phenotype is completely lost in the intestinal metaplastic mucosa of Cdx2-transgenic mouse stomach.

Monocyte chemoattractant protein‐1 is generated via TGF‐β by myofibroblasts in gastric intestinal metaplasia and carcinoma without H. pylori infection

Helicobacter pylori (H. pylori) stimulates secretion of monocyte chemoattractant protein 1 (MCP-1) from gastric mucosa. Monocyte chemoattractant protein-1 (MCP-1) expression and macrophage infiltration are recognized in human gastric carcinoma. We have previously generated Cdx2-transgenic mice as model mice for intestinal metaplasia. Both chronic H. pylori-associated gastritis and Cdx2-transgenic mouse stomach develop intestinal metaplasia and finally gastric carcinoma. In this study we have directed our attention to MCP-1 expression in the intestinal metaplastic mucosa and the gastric carcinoma of Cdx2-transgenic mouse stomach. Quantitative real-time PCR was performed to determine MCP-1 and transforming growth factor-beta1 (TGF-beta1) mRNA expression levels and single- or double-label immunohistochemistry was used to evaluate the localization of MCP-1, TGF-beta type I receptor, and alpha-smooth muscle actin (alphaSMA). We determined that MCP-1 mRNA dramatically increased in the intestinal metaplastic mucosa and the gastric carcinoma of Cdx2-transgenic mouse stomach, compared with normal mouse stomach. Both MCP-1 and TGF-beta type I receptor were co-expressed in the alphaSMA-positive myofibroblasts of intestinal metaplastic mucosa and gastric carcinoma. Exogenous application of TGF-beta1 increased MCP-1 mRNA expression levels in the intestinal metaplastic tissue. Furthermore, TGF-beta1 was overexpressed and macrophage was strongly infiltrated in the gastric carcinoma. In conclusion, MCP-1 expression, which was stimulated by TGF-beta1, was recognized in the TGF-beta type I receptor-expressing myofibroblasts of the intestinal metaplastic mucosa and the gastric carcinoma of Cdx2-transgenic mouse stomach. The present results suggest that intestinal metaplasia and gastric carcinoma themselves induce MCP-1 expression independently of H. pylori infection.

Expression of Claudin-2 in intestinal metaplastic mucosa of Cdx2-transgenic mouse stomach

Objective. Cdx2 is expressed in human intestinal metaplastic mucosa and induces intestinal metaplastic mucosa in Cdx2-transgenic mouse stomach. Claudin-2 is a structural component of tight junctions in the intestine and Cdx2 activates the Claudin-2 promoter in the human intestinal epithelial cell line Caco-2. Our aim is to evaluate the expression of Claudin-2 in intestinal metaplastic mucosa of Cdx2-transgenic mouse stomach. Material and methods. The Claudin-2 expression in the normal gastric mucosa and normal intestinal mucosa of wild type mice and the intestinal metaplastic mucosa of Cdx2-transgenic mice was analyzed by immunohistochemistry, Western blotting and quantitative real-time PCR (qRT-PCR). Results. Claudin-2 was expressed in the base of the glands in intestine and intestinal metaplasia while it was not expressed in the body of stomach. Claudin-2 expression was found in the antrum of stomach, while it was weaker than that in the intestine and the intestinal metaplasia. Claudin-2 was also detected in intestinal metaplasia, colon and ileum by both Western blotting and qRT-PCR while it was not detected in gastric body. Conclusion. These results suggest that Cdx2 plays an important role in the expression of Claudin-2 in vivo.

Direct repression of Sonic Hedgehog expression in the stomach by Cdx2 leads to intestinal transformation

Shh (Sonic Hedgehog) is a morphogen involved in gastric fundic gland differentiation in the adult. Shh expression is reduced in Helicobacter pylori-associated intestinal metaplastic change of the gastric epithelium and mice that lack Shh show intestinal transformation of the gastric mucosa. Similarly, in the stomach of Cdx2 (caudal-type homeobox 2)-transgenic mice, the gastric mucosa is replaced by intestinal metaplastic mucosa. The aim of the present study was to use Cdx2-transgenic mice to investigate: (i) Shh expression in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach; and (ii) the relationship between Shh and Cdx2. We determined that Shh mRNA levels were dramatically reduced in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach compared with the normal (wild-type) mouse stomach. This was not due to hypermethylation of the Shh promoter, but instead we showed that Cdx2 directly bound to the TATA box region of the Shh promoter. Cdx2 also down-regulated transcription of the Shh gene in the human gastric carcinoma cell lines AGS, MKN45 and MKN74. In conclusion, Cdx2 reduced Shh expression by binding to the unmethylated Shh promoter in the intestinal metaplastic mucosa of Cdx2-transgenic mouse stomach.

Molecular analysis of single isolated glands in gastric cancers and their surrounding gastric intestinal metaplastic mucosa

The biological properties and underlying genetics of gastric cancer and gastric intestinal metaplasia evolve with neoplastic progression from the genetics of the original gland cell. PCR assay with crypt isolation was used in tumors from 20 patients to examine microsatellite alterations (allelic imbalance at 17p, 5q, 18q, 3p, 4p, and 9p, and microsatellite instability) in glands from each tumor and from intestinal metaplastic lesions. Tumor specimens were processed as either pooled-gland samples or single-gland samples. Pooled gland sample was composed of 10-20 tumor glands, intestinal metaplastic glands, or nonmetaplastic glands. Single gland sample was 10 tumor glands from tumor and single gland sample was 5 gastric intestinal metaplastic and 5 nonmetaplastic glands from its surrounding metaplastic mucosa. Multiple genetic alterations were found in individual tumor glands, with various subclonal expansions seen within the same tumor. Although microsatellite instability was found in 2 of 20 tumor single-gland samples, none was detected in metaplastic single-gland samples. Most cancers appear to have a heterogeneous composition. On the other hand, microsatellite alterations were also detected within the nonmetaplastic as well as intestinal metaplastic single-gland samples. In conclusion, the present data on tumor and corresponding intestinal metaplastic and nonmetaplastic glands suggest that genetic alterations already occur within the surrounding of the noncancerous mucosa.

Transgenic Cdx2 induces endogenous Cdx1 in intestinal metaplasia of Cdx2‐transgenic mouse stomach

Cdx1 and Cdx2, which are transcription factors regulating normal intestinal development, have been studied as potential key molecules in the pathogenesis of the precancerous intestinal metaplasia of the human stomach. However, the regulation of Cdx1 expression in the intestinal metaplasia is poorly understood. Cdx2-expressing gastric mucosa of Cdx2-transgenic mouse stomach was replaced by intestinal metaplastic mucosa. The aim of this study was to investigate the following: (a) Cdx1 expression in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach; and (b) the relationship between Cdx1 and Cdx2. A mouse model of intestinal metaplasia, the Cdx2-transgenic mouse, was used to investigate Cdx1 gene expression by RT-PCR. DNA methylation profile analysis was performed by bisulfite sequencing, and the interaction of Cdx2 with the Cdx1 promoter was examined by chromatin immunoprecipitation assay, electrophoretic mobility shift assay, and luciferase reporter assays. Cdx2 mRNA was expressed in the Cdx2-transgenic mouse stomach. However, endogenous Cdx2 mRNA was not expressed in the intestinal metaplasia of the Cdx2-transgenic mouse stomach. On the other hand, endogenous Cdx1 mRNA and protein were expressed in the intestinal metaplasia of the Cdx2-transgenic mouse stomach. The Cdx1 promoter was unmethylated in the intestinal metaplasia of the Cdx2-transgenic mouse stomach. Chromatin immunoprecipitation assay and electrophoretic mobility shift assay showed that Cdx2 was bound to the Cdx1 promoter region in the intestinal metaplasia and the normal intestine. Cdx2 upregulated and siRNA-Cdx2 downregulated the transcriptional activity of the Cdx1 gene in the human gastric carcinoma cell lines AGS, MKN45, and MKN74. In conclusion, transgenic Cdx2 induced endogenous Cdx1 through the binding of Cdx2 to the unmethylated Cdx1 promoter region in the intestinal metaplasia of the Cdx2-transgenic mouse stomach.

Molecular defense mechanisms of Barrett’s metaplasia estimated by an integrative genomics

Barrett's esophagus is characterized by the replacement of squamous epithelium with specialized intestinal metaplastic mucosa. The exact mechanisms of initiation and development of Barrett's metaplasia remain unknown, but a hypothesis of "successful adaptation" against noxious reflux components has been proposed. To search for the repertoire of adaptation mechanisms of Barrett's metaplasia, we employed high-throughput functional genomic and proteomic methods that defined the molecular background of metaplastic mucosa resistance to reflux. Transcriptional profiling was established for 23 pairs of esophageal squamous epithelium and Barrett's metaplasia tissue samples using Affymetrix U133A 2.0 GeneChips and validated by quantitative real-time polymerase chain reaction. Differences in protein composition were assessed by electrophoretic and mass-spectrometry-based methods. Among 2,822 genes differentially expressed between Barrett's metaplasia and squamous epithelium, we observed significantly overexpressed metaplastic mucosa genes that encode cytokines and growth factors, constituents of extracellular matrix, basement membrane and tight junctions, and proteins involved in prostaglandin and phosphoinositol metabolism, nitric oxide production, and bioenergetics. Their expression likely reflects defense and repair responses of metaplastic mucosa, whereas overexpression of genes encoding heat shock proteins and several protein kinases in squamous epithelium may reflect lower resistance of normal esophageal epithelium than Barrett's metaplasia to reflux components. Despite the methodological and interpretative difficulties in data analyses discussed in this paper, our studies confirm that Barrett's metaplasia may be regarded as a specific microevolution allowing for accumulation of mucosal morphological and physiological changes that better protect against reflux injury.

Expression of the Na+/l-symporter (NIS) is markedly decreased or absent in gastric cancer and intestinal metaplastic mucosa of Barrett esophagus

BackgroundThe sodium/iodide symporter (NIS) is a plasma membrane glycoprotein that mediates iodide (I-) transport in the thyroid, lactating breast, salivary glands, and stomach. Whereas NIS expression and regulation have been extensively investigated in healthy and neoplastic thyroid and breast tissues, little is known about NIS expression and function along the healthy and diseased gastrointestinal tract.MethodsThus, we investigated NIS expression by immunohistochemical analysis in 155 gastrointestinal tissue samples and by immunoblot analysis in 17 gastric tumors from 83 patients.ResultsRegarding the healthy Gl tract, we observed NIS expression exclusively in the basolateral region of the gastric mucin-producing epithelial cells. In gastritis, positive NIS staining was observed in these cells both in the presence and absence of Helicobacter pylori. Significantly, NIS expression was absent in gastric cancer, independently of its histological type. Only focal faint NIS expression was detected in the direct vicinity of gastric tumors, i.e., in the histologically intact mucosa, the expression becoming gradually stronger and linear farther away from the tumor. Barrett mucosa with junctional and fundic-type columnar metaplasia displayed positive NIS staining, whereas Barrett mucosa with intestinal metaplasia was negative. NIS staining was also absent in intestinalized gastric polyps.ConclusionThat NIS expression is markedly decreased or absent in case of intestinalization or malignant transformation of the gastric mucosa suggests that NIS may prove to be a significant tumor marker in the diagnosis and prognosis of gastric malignancies and also precancerous lesions such as Barrett mucosa, thus extending the medical significance of NIS beyond thyroid disease.

A close relationship between intestinal metaplasia and Cdx2 expression in human gallbladders with cholelithiasis

We previously reported a case of a human gallbladder with cholelithiasis consisting of intestinal metaplasia with the expression of caudal-related homeobox transcription factor (Cdx2). However, it is unclear how often intestinal metaplasia and Cdx2 expression occur in human, nontumorous gallbladders with cholelithiasis. We studied the incidence of intestinal metaplasia and Cdx2 expression in human gallbladders with cholelithiasis. Gallbladders were resected under laparoscopy from 103 patients with cholelithiasis between September 2003 and March 2005. The mean age of the patients was 59.6 +/- 15.0 years (range, 22-92 years). We retrospectively reviewed these cases to look for the presence of intestinal metaplasia and the expression of Cdx2. In addition, the characteristics of intestinal metaplasia were examined by immunostaining for Muc2, chromogranin A, and serotonin. Intestinal metaplasia was found in 11.7% (12/103) of the gallbladders with cholelithiasis. The mean ages of patients with and without intestinal metaplasia were 60.8 +/- 15.4 and 59.4 +/- 14.9 years, respectively. Cdx2, Muc2, chromogranin A, and serotonin were expressed in 91.7% (11/12), 91.7% (11/12), 83.3% (10/12), and 50.0% (6/12) in intestinal metaplastic mucosa, respectively. Only one case (1.1%) that expressed Cdx2 without intestinal metaplasia did not express Muc2, chromogranin A, and serotonin. We found that 10.7% (11/103) of nontumorous gallbladders resected because of cholelithiasis under laparoscopy revealed intestinal metaplasia with Cdx2 expression.

The intestine-specific homeobox gene Cdx2 induces expression of the basic helix–loop–helix transcription factor Math1

The basic helix–loop–helix transcription factor Math1, which is transiently expressed in proliferating neural precursors in multiple domains of the developing nervous system, is also related to the cell fate decision of enteroendocrine, goblet, and Paneth cells in the intestine. On the other hand, the transcription factor Cdx2, which is normally confined to intestinal epithelial cells, is related to the differentiation of these cells. Therefore, we investigated the relationship between Math1 and Cdx2 in intestinal epithelial cells. The Math1 and Cdx2 expressions in normal intestinal mucosa and intestinal metaplastic mucosa from mouse and human stomachs, as well as an intestinal crypt-derived cell line, were analyzed by immunohistochemistry, reverse transcription-polymerase chain reaction and Northern blotting, and Math1 enhancer element was analyzed by luciferase reporter assays. Math1-positive epithelial cells co-expressing Cdx2 were found in normal intestinal mucosa from humans and mice. Furthermore, Math1-producing epithelial cells that showed positive immunostaining for Cdx2 were also observed in intestinal metaplastic mucosa from human and Cdx2 transgenic mouse stomachs, although they were not detected in normal gastric mucosa of humans and mice. Expression of Cdx2 stimulated endogenous Math1 mRNA expression in the intestinal crypt-derived cell line IEC-6, corroborating observations in Cdx2-expressing intestinal metaplastic mucosa. Furthermore, expression of Cdx2 in IEC-6 cells conferred the ability to express a Math1 reporter gene containing a Math1 enhancer. Based on these results, we hypothesize that Cdx2 is involved in activating Math1 expression in intestinal epithelial cells.

Alterations of tumor suppressor and tumor-related genes in the development and progression of gastric cancer

The development and progression of gastric cancer involves a number of genetic and epigenetic alterations of tumor suppressor and tumor-related genes. The majority of differentiated carcinomas arise from intestinal metaplastic mucosa and exhibit structurally altered tumor suppressor genes, typified by p53, which is inactivated via the classic two-hit mechanism, i.e. loss of heterozygosity (LOH) and mutation of the remaining allele. LOH at certain chromosomal loci accumulates during tumor progression. Approximately 20% of differentiated carcinomas show evidence of mutator pathway tumorigenesis due to hMLH1 inactivation via hypermethylation of promoter CpG islands, and exhibit high-frequency microsatellite instability. In contrast, undifferentiated carcinomas rarely exhibit structurally altered tumor suppressor genes. For instance, while methylation of E-cadherin is often observed in undifferentiated carcinomas, mutation of this gene is generally associated with the progression from differentiated to undifferentiated carcinomas. Hypermethylation of tumor suppressor and tumor-related genes, including APC, CHFR, DAP-kinase, DCC, E-cadherin, GSTP1, hMLH1, p16, PTEN, RASSF1A, RUNX3, and TSLC1, can be detected in both differentiated and undifferentiated carcinomas at varying frequencies. However, the significance of the hypermethylation varies according to the analyzed genomic region, and hypermethylation of these genes can also be present in non-neoplastic gastric epithelia. Promoter demethylation of specific genes, such as MAGE and synuclein Y, can occur during the progressive stages of both histological types, and is associated with patient prognosis. Thus, while the molecular pathways of gastric carcinogenesis are dependent on histological background, specific genetic alterations can still be used for risk assessment, diagnosis, and prognosis.

Cdx2 specifies the differentiation of morphological as well as functional absorptive enterocytes of the small intestine

Many transcription factors are involved in the molecular control of intestinal epithelial cell differentiation. We report in this study that the transcription factor Cdx2 functions to define absorptive enterocytes during intestinal epithelial differentiation. Cdx2 is expressed in the villi of the normal small intestine. Intestinal metaplasia, which expresses Cdx2, occurs as a pathological condition in gastric mucosa. We have previously established Cdx2 transgenic mice expressing Cdx2 exclusively in the gastric epithelium. In this study using Cdx2 transgenic mice, we show that Cdx2 plays a key role in the differentiation of intestinal absorptive enterocytes. The gastric mucosa of Cdx2 transgenic mice was morphologically completely changed into intestinal metaplastic mucosa. Absorptive enterocytes had microvilli which were observed by electron microscope. The intestinal metaplastic mucosa of Cdx2 transgenic mice expressed sucrase and peptide transporter PepT1. Disaccharidase and leucine aminopeptidase activities were observed in the intestinal metaplastic mucosa. Glucose and amino acids were absorbed from Cdx2 transgenic mouse stomach with intestinal metaplasia. Finally we generated mice whose intestine was extensively excised. Cdx2 transgenic mice with intestinal metaplasia survived even after extensive intestinal excision. We successfully demonstrated that Cdx2 induced not only morphological but also functional absorptive enterocytes in the intestinal metaplastic mucosa in vivo. Our results suggest that Cdx2 is necessary and sufficient by itself to specify the development of intestinal absorptive enterocytes, whereas other factors which are expressed in the small intestine are not always necessary for the differentiation of functional absorptive enterocytes.

Development of Gastric Carcinoma from Intestinal Metaplasia in Cdx2-transgenic Mice

In the progression of chronic gastritis, gastric mucosal cells deviate from the normal pathway of gastric differentiation to an intestinal phenotype. Many epidemiologic studies have found an association between the formation of intestinal metaplasia and the development of gastric carcinoma. However, there is no direct evidence that shows intestinal metaplasia is a precursor lesion of gastric carcinoma, to date. We periodically examined the intestinal metaplastic mucosa of Cdx2-transgenic mice we have previously generated. Gastric polyps developed from intestinal metaplastic mucosa in all stomachs of Cdx2-transgenic mice examined. These gastric polyps consisted of intestinal-type adenocarcinoma that invaded the submucosa and muscularis propria and occasionally spread into the subserosa. p53 and APC gene mutations were recognized in the adenocarcinomas. The participation of APC and p53 gene mutations in gastric carcinogenesis from the intestinal metaplasia was verified by the Cdx2-transgenic mice, carrying Apc(Min) mutation or p53 deficiency, that developed gastric polyps much earlier than Cdx2 alone. We successfully showed that long-term intestinal metaplasia induces invasive gastric carcinoma. These results indicate that intestinal metaplasia itself plays a significant role in the genesis and progression of gastric carcinoma.

CD44v6

Objective Intestinal metaplasia is a well-established risk factor in the development of stomach cancer. However, since the specificity is low it would be of great practical value to find a marker to separate cases of intestinal metaplasia into low and high risk for progression to dysplasia/carcinoma. So far this has not been achieved. CD44 is a cell surface molecule involved in cell–cell and cell–matrix interactions, and the spliced variant 6 has been shown to play a role in the progression of gastric carcinoma. The aim of this study was therefore to evaluate CD44v6 as a marker of increased cancer risk in intestinal metaplasia. Methods The current study investigated immunohistochemical CD44v6 expression in biopsies of normal gastric mucosa (n = 154) and gastric mucosa with intestinal metaplasia (n = 127). A third group consisted of cancer gastrectomies (n = 117) in which both tumour and uninvolved mucosa was studied. Proximal (cardia) and distal (corpus/antrum) locations were noted in all cases. Results There was a significant sequential increase in CD44v6 expression from normal mucosa and mucosa showing intestinal metaplasia to uninvolved mucosa adjacent to cancers without and with intestinal metaplasia to tumour. The most striking increase was from ‘normal’ to intestinal metaplastic mucosa adjacent to cancers. There were no differences between proximal and distal cases in any group. Conclusion These findings strongly suggest that CD44v6 expression is a late phenomenon in the transformation of intestinal metaplasia to dysplasia/cancer. It may therefore be a useful marker of cancer risk in patients with intestinal metaplasia.