The common 18-base pair deletion at codons 418-423 of the E-cadherin gene in differentiated-type adenocarcinomas and intramucosal precancerous lesions of the stomach with the features of gastric foveolar epithelium

The role of gastric mucins and mucin-related glycans in gastric cancers

Gastric mucins serve as a protective barrier on the stomach's surface, protecting from external stimuli including gastric acid and gut microbiota. Their composition typically changes in response to the metaplastic sequence triggered by Helicobacter pylori infection. This alteration in gastric mucins is also observed in cases of gastric cancer, although the precise connection between mucin expressions and gastric carcinogenesis remains uncertain. This review first introduces the relationship between mucin expressions and gastric metaplasia or cancer observed in humans and mice. Additionally, we discuss potential pathogenic mechanisms of how aberrant mucins and their glycans affect gastric carcinogenesis. Finally, we summarize challenges to target tumor-specific glycans by utilizing lectin-drug conjugates that can bind to specific glycans. Understanding the correlation and mechanism between these mucin expressions and gastric carcinogenesis could pave the way for new strategies in gastric cancer treatment.

Correlation of Claudin18.2 expression with clinicopathological characteristics and prognosis in gastric cancer

OBJECTIVES

Claudin18.2 (Cldn18.2) is a tight junction protein expressed in gastric epithelial cells and is an emerging target for gastric cancer (GC). This study aimed to analyze the correlation between Cldn18.2 and clinicopathological parameters in GC patients undergoing radical surgery.

METHODS AND RESULTS

This study included 426 GC patients who underwent radical gastrectomy. The expression of Cldn18.2 was analyzed by immunohistochemical staining and grading. The statistical results indicated that the expression of Cldn18.2 was correlated with T stage, TNM stage, Lauren classification, and the expression level of Mucin-2 (MUC2), Mucin-5AC (MUC5AC), Mucin-6 (MUC6), human epidermal growth factor receptor 2 (HER2), P53 and trefoil factor 2 (TFF2). In addition, through data mining of the Cancer Genome Atlas (TCGA) database, it is suggested that Cldn18.2 expression level is significantly correlated with the expression level of MUC5AC, MUC6, and TFF2. Besides, Cldn18.2 is related to tumor immune infiltration, programmed cell death protein 1 (PD 1) pathway, cell cycle and Wnt signaling pathway.

CONCLUSIONS

The expression of Cldn18.2 was closely related to gastric-type GC, so gastric-type GC patients may benefit more from targeted drugs targeting Cldn18.2. In GC cells, depletion of Cldn18.2 may influence cell cycle and immune response by affecting Wnt signaling pathway and PD 1 pathway.

Differences in clinical features and morphology between differentiated and undifferentiated gastric cancer after Helicobacter pylori eradication

BACKGROUND/AIMS

Although undifferentiated gastric cancer (UGC) diagnosed after Helicobacter pylori eradication (HPE) carries a poor prognosis, characteristics of post-HPE UGC have not been evaluated in detail because of its low incidence. Therefore, we compared the clinicopathologic characteristics of UGC and differentiated gastric cancers (DGC) diagnosed after successful HPE.

METHODS

GC lesions from patients who had successfully completed HPE and who had undergone upper gastrointestinal endoscopy between January 2004 and March 2016 were analyzed. Tumors were divided into DGC and UGC groups. Clinicopathologic factors of background and tumor characteristics were compared using univariate and multiple logistic analyses.

RESULTS

A total of 129 tumors from 115 patients were evaluated; 113 tumors were in the DGC group and 16 in the UGC group. Depressed-type tumors (P = 0.024) and sub-submucosal invasion (P<0.001) were significantly higher in the UGC group. The UGC group had larger tumor diameters (25.9±7.3 mm) than the DGC group (13.2±10.2 mm) (P<0.001). Multivariate analysis showed that female sex (odds ratio [OR] 3.24, 95%CI:1.02-10.37; P = 0.047) and absent follow-up (OR 4.99, 95%CI:1.60-15.57; P = 0.006) were significant independent risk factors for UGC. The DGC group showed a gradually decreasing temporal trend by trend test (P = 0.015), while the UGC group showed a relatively constant incidence over time, although the number of cases was small.

CONCLUSION

UGC was diagnosed even after long time spans following HPE, although the number of cases was small. Female sex, and especially absent follow-up, were risks for post-HPE UGC, suggesting that diligent long-term follow-up after HPE is essential.

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

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

Clinicopathologic and molecular characteristics of gastric cancer showing gastric and intestinal mucin phenotype

Gastric cancer (GC), one of the most common human cancers, can be classified into gastric or intestinal phenotype according to mucin expression. TP53 mutation, allelic deletion of the APC gene and nuclear staining of β-catenin are frequently detected in the intestinal phenotype of GC, whereas CDH1 gene mutation, microsatellite instability and DNA hypermethylation of MLH1 are common events in the gastric phenotype of GC. Our Serial Analysis of Gene Expression (SAGE) and Escherichia coli ampicillin secretion trap (CAST) analyses revealed that CDH17, REG4, OLFM4, HOXA10, DSC2, TSPAN8 and TM9SF3 are upregulated in GC and that CLDN18 is downregulated in GC. Expression of CDH17, REG4, HOXA10 and DSC2 and downregulation of CLDN18 are observed in the intestinal phenotype of GC. In contrast, OLFM4 is expressed in the gastric phenotype of GC. Expression of TSPAN8, TM9SF3 and HER2 are not associated with either gastric or intestinal phenotypes. Ectopic CDX2 expression plays a key function in the GC intestinal phenotype. MUC2, CDH17, REG4, DSC2 and ABCB1 are direct targets of CDX2. Importantly, these genes encode transmembrane/secretory proteins, indicating that the microenvironment as well as cancer cells are also different between gastric and intestinal phenotypes of GC.

Comparison of site-specific gene expression levels in primary tumors and synchronous lymph node metastases in advanced gastric cancer

BACKGROUND

Many malignant tumors consist of heterogeneous subpopulations of cells. This heterogeneity is associated with genetic characteristics. However, it remains unclear whether gene expression levels differ among specific sites of tumors in gastric cancer.

METHODS

We studied differences in gene expression levels among specific sites of primary tumors and synchronous lymph node metastases, using formalin-fixed, paraffin-embedded specimens resected surgically from 48 patients with previously untreated advanced gastric cancer. Specimens were obtained by laser-captured microdissection from five regions: (1) nonneoplastic mucosa, (2) surface layer (mucosa) of the primary tumor (surface sections), (3) middle layer (submucosa) of the primary tumor (middle sections), (4) the deepest layer of the primary tumor (muscularis propria or deeper) at the site of deepest invasion (deep sections), and (5) level 1 synchronous lymph node metastasis (lymph node metastases). Expression levels of the following target genes were determined by quantitative real-time polymerase chain reaction: thymidylate synthase (TS), thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD), epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), and hypoxia-inducible factor-1α (HIF1α).

RESULTS

TP, DPD, EGFR, and HIF1α gene expression levels were significantly higher in deep sections than in surface sections. TP, EGFR, VEGF, and HIF1α gene expression levels were significantly higher in lymph node metastases than in surface sections. TP, DPD, EGFR, VEGF, and HIF1α gene expression levels were positively correlated with the specific samples harvested from the tumors.

CONCLUSIONS

Our results show that the expression levels of some genes in tumor cells can change in specific sites of tumors and can become higher in association with tumor progression.

Overexpression of Lysophosphatidylcholine Acyltransferase 1 and Concomitant Lipid Alterations in Gastric Cancer

BACKGROUND

The involvement of lipids in carcinogenic and developmental processes has been reported in some malignancies, but their roles in gastric cancer remain to be analyzed. In this study, we compared the lipid content of gastric cancer tissue and adjacent nonneoplastic mucosa using imaging mass spectrometry.

METHODS

Mass spectra were acquired from 12 sections of human gastric cancer tissue and adjacent nonneoplastic mucosa using a matrix-assisted laser desorption-ionization time-of-flight tandem mass spectrometry type mass spectrometer equipped with a 355 nm Nd:YAG laser. Protein expression of lysophosphatidylcholine acyltransferase 1 (LPCAT1), which converts lysophosphatidylcholine (LPC) to phosphatidylcholine (PC) in the presence of acyl-CoA in Lands' cycle, was immunohistochemically analyzed in 182 gastric cancer specimens.

RESULTS

The averaged mass spectra from the cancer tissue and nonneoplastic mucosa were identical. Most of the signals that differed between cancer tissue and nonneoplastic mucosa corresponded to phospholipids, the majority of which were PC and LPC. Two signals, m/z 798.5 and 496.3, were higher and lower, respectively, in cancer tissues, predominantly in differentiated adenocarcinoma. A database search enabled identification of the ions at m/z 798.5 and m/z 496.3 as potassium-adducted PC (16:0/18:1) and proton-adducted LPC (16:0), respectively. Immunohistochemical analysis revealed that LPCAT1 was highly expressed in cancer lesions compared to nonneoplastic mucosa, predominantly in differentiated adenocarcinoma. LPCAT1 expression levels correlated positively with tumor differentiation and negatively with tumor depth, lymph node metastasis, and tumor stage.

CONCLUSIONS

Overexpressed LPCAT1 protein in gastric mucosa appears to play important roles in the tumorigenic process of gastric cancer by converting LPC to PC.

Magnifying narrow-band imaging of surface maturation in early differentiated-type gastric cancers after Helicobacter pylori eradication

BACKGROUND

Even after successful Helicobacter pylori eradication, primary or metachronous gastric cancers are sometimes discovered. The endoscopic features of these cancers may be modified by controlling inflammation. Characteristic findings for such lesions in terms of narrow-band imaging with magnifying endoscopy (NBI-ME) and histopathology need to be clarified to allow accurate diagnosis.

METHODS

Distinctive NBI-ME characteristics were examined retrospectively in intramucosal or minimally submucosal and differentiated-type adenocarcinomas from a successful eradication group (42 patients, 50 lesions) and a non-eradicated control group (44 patients, 50 lesions) matched in age and sex. A "gastritis-like" appearance under NBI-ME was characterized by uniform papillae and/or tubular pits with a whitish border, regular or faint microvessels and unclear demarcation, resembling the adjacent noncancerous mucosa. Histological differentiation at the luminal surface of the cancer was evaluated according to Ki-67 immunoreactivity restricted at the middle or lower portion of the tubules. NBI-ME alteration was prospectively confirmed in 29 patients (30 lesions) after eradication therapy.

RESULTS

The frequency of a "gastritis-like" appearance was 44% (22/50) for the eradication group, which was significantly higher than the 4% (2/50) for the control group (p < 0.001). In the eradication group, the "gastritis-like" appearance was significantly correlated with histological surface differentiation (p < 0.001). In the prospective study, NBI-ME showed changes to heterogeneous papillary microstructures in 43% (10/23) of the lesions after successful eradication at short-term follow-up.

CONCLUSIONS

Identification of surface maturation under NBI-ME offers a promising approach for accurate diagnosis of early gastric cancers after successful eradication.

Genetic lineages of undifferentiated-type gastric carcinomas analysed by unsupervised clustering of genomic DNA microarray data

Background

It is suspected that early gastric carcinoma (GC) is a dormant variant that rarely progresses to advanced GC. We demonstrated that the dormant and aggressive variants of tubular adenocarcinomas (TUBs) of the stomach are characterized by loss of MYC and gain of TP53 and gain of MYC and/or loss of TP53, respectively. The aim of this study is to determine whether this is also the case in undifferentiated-type GCs (UGCs) of different genetic lineages: one with a layered structure (LS+), derived from early signet ring cell carcinomas (SIGs), and the other, mostly poorly differentiated adenocarcinomas, without LS but with a minor tubular component (TC), dedifferentiated from TUBs (LS−/TC+).

Methods

Using 29 surgically resected stomachs with 9 intramucosal and 20 invasive UGCs (11 LS+ and 9 LS−/TC+), 63 genomic DNA samples of mucosal and invasive parts and corresponding reference DNAs were prepared from formalin-fixed, paraffin-embedded tissues with laser microdissection, and were subjected to array-based comparative genomic hybridization (aCGH), using 60K microarrays, and subsequent unsupervised, hierarchical clustering. Of 979 cancer-related genes assessed, we selected genes with mean copy numbers significantly different between the two major clusters.

Results

Based on similarity in genomic copy-number profile, the 63 samples were classified into two major clusters. Clusters A and B, which were rich in LS+ UGC and LS−/TC+ UGC, respectively, were discriminated on the basis of 40 genes. The aggressive pattern was more frequently detected in LS−/TC+ UGCs, (20/26; 77%), than in LS+UGCs (17/37; 46%; P = 0.0195), whereas no dormant pattern was detected in any of the UGC samples.

Conclusions

In contrast to TUBs, copy number alterations of MYC and TP53 exhibited an aggressive pattern in LS+ SIG at early and advanced stages, indicating that early LS+ UGCs inevitably progress to an advanced GC. Cluster B (enriched in LS−/TC+) exhibited more frequent gain of driver genes and a more frequent aggressive pattern than cluster A, suggesting potentially worse prognosis in UGCs of cluster B.

Mucin phenotype and narrow-band imaging with magnifying endoscopy for differentiated-type mucosal gastric cancer

BACKGROUND

Several studies have described the surface glandular structure in differentiated early gastric cancer observed by narrow-band imaging with magnifying endoscopy (NBI-ME) in two main patterns, i.e., a papillary or granular structure in an intralobular loop pattern (ILL) and a pit structure in a fine network pattern (FNP). However, it is uncertain why the NBI-ME findings of differentiated-type carcinomas are divided into two main patterns. We investigated the significance of the mucin phenotype in the morphogenetic difference between ILL and FNP.

METHODS

We evaluated 120 intramucosal, well- or predominantly well-differentiated tubular adenocarcinomas. In each lesion, one area that showed the predominant pattern of microsurface structures and microvessels was selected and marked by electrocoagulation for a strict comparative study by NBI-ME and pathological investigation. NBI-ME findings were classified into three patterns: ILL, FNP, and intermediate. Mucin phenotypes were judged as gastric, intestinal, or gastrointestinal type by immunohistochemistry.

RESULTS

The mucin phenotype was gastric or gastrointestinal type in 24 (92.3%) of 26 ILL lesions. Intestinal phenotype was observed in 22 (84.6%) of 26 FNP lesions. The gastrointestinal phenotype was observed in 50 (73.5%) of 68 intermediate pattern lesions. The mucin phenotype and NBI-ME results were significantly correlated (P < 0.001).

CONCLUSIONS

The mucin phenotype of differentiated early gastric cancer might be involved in morphogenetic differences between the papillary and pit structures visualized by NBI-ME.

Gastric and intestinal phenotypic marker expression in early differentiated-type tumors of the stomach: clinicopathologic significance and genetic background

PURPOSE

Gastric and intestinal phenotypic cell markers are expressed in gastric carcinomas, irrespective of their histologic type. In the present study, we determined the clinicopathologic significance of phenotypic marker expression in early-stage gastric differentiated-type tumors and the association between marker expression and genetic alterations.

EXPERIMENTAL DESIGN

Phenotypic marker expression was determined by examining the expressions of human gastric mucin (HGM), MUC6, MUC2, and CD10 in 63 gastric adenomas, 133 early differentiated-type carcinomas, and 24 follow-up cases with gastric adenoma. Tumors were classified into gastric, gastric and intestinal mixed, or intestinal phenotypes according to the immunopositivity of the above markers. The presence of mutations in APC, K-ras, and p53 and the microsatellite instability status were also determined in all tumors.

RESULTS

The expressions of HGM and MUC6, representing gastric or gastric and intestinal mixed phenotypes, were significantly associated with high-grade atypia in the 63 gastric adenomas. Among the 133 early differentiated-type carcinomas, HGM expression was significantly associated with mixed-type (with an undifferentiated-type component) tumors and lymph node metastasis. MUC2 expression was inversely associated with submucosal invasion. A multivariate analysis revealed that gastric adenomas were significantly associated with the intestinal phenotype and were inversely associated with p53 mutation compared with early differentiated-type carcinomas. Among all 196 tumors, APC mutation was significantly associated with CD10 expression and the intestinal phenotype and was inversely associated with the expressions of HGM and MUC6. The microsatellite instability status was significantly associated with MUC6 expression. Malignant transformation from gastric adenoma to carcinoma was shown in 5 of the 24 follow-up cases of gastric adenoma. The malignant transformation was significantly associated with the gastric and intestinal mixed phenotype and was inversely associated with APC mutation. No malignant transformation was found in intestinal phenotype gastric adenomas with APC mutation.

CONCLUSIONS

Our present findings show that phenotypic marker expression is associated with tumor aggressiveness during the early stage of gastric differentiated-type tumors. Differences in the biological behavior of tumors with different phenotypes may result from differences in the genetic backgrounds during the incipient phase of gastric tumorigenesis.

CDX2 expression is increased in gastric cancers with less invasiveness and intestinal mucin phenotype

OBJECTIVE

CDX2 is an intestinal transcription factor that might be involved in the regulation of proliferation and differentiation of intestinal epithelial cells. It is well known that both gastric and intestinal phenotypic cell markers are expressed in gastric cancers. The aims of this study were to analyze the CDX2 expression and its relationship with the patients' clinicopathological characteristics and the mucin phenotypes by performing immunohistochemistry.

MATERIAL AND METHODS

A total of 259 gastric cancer cases (122 early and 137 advanced cancers) were evaluated histologically and phenotypically. CDX2 expression was assessed by immunohistochemistry.

RESULTS

Increased CDX2 expression correlated with a higher proportion of intestinal-type cancers of Lauren and early gastric cancers (p<0.001 and p<0.001, respectively) and a lower proportion of perineural invasion and lymph node metastasis (p<0.001 and p=0.003, respectively). Increased expressions of intestinal mucin (MUC-2, CD10) and decreased gastric mucin (MUC5AC) were associated with an increased CDX2 expression (p<0.001, p=0.045 and p=0.004, respectively). MUC6 expression was not associated with CDX2 expression. There was a significantly increased CDX2 expression in the intestinal phenotype compared with the other phenotypes (p<0.001).

CONCLUSIONS

These results suggest that CDX2 might be a useful marker in predicting the clinical outcome for patients with gastric cancers.

Hedgehog signal activation in gastric pit cell and in diffuse-type gastric cancer

BACKGROUND & AIMS

Sonic hedgehog (SHH) and Indian hedgehog (IHH) have cell-specific actions in some organs. Only SHH has been shown to regulate parietal cell differentiation. This study examined whether SHH, 2 other ligands IHH and Desert hedgehog, and receptors or downstream targets are expressed in normal gastric epithelium or in intestinal and diffuse-type gastric cancers. The effects of a Hedgehog (Hh) inhibitor, cyclopamine, were assessed in primary gastric epithelium cultures and gastric cancer cell lines.

METHODS

Reverse-transcription polymerase chain reaction and immunostaining compared expression and localization of Hh signaling molecules and phenotypic markers of pit, neck, and gland cells in situ and in cultured cells treated with cyclopamine. Bromodeoxyuridine staining assessed the effects of cyclopamine on proliferation.

RESULTS

Hh signaling molecules were expressed differentially in pit, neck, and gland cells. IHH co-expressed with most downstream targets in the pit. IHH, SHH, Patched (PTCH), Smoothened (SMO), and downstream targets were expressed more frequently and highly in the diffuse as compared with intestinal type cancers. In diffuse cancers, IHH was expressed in cells with an epithelial phenotype and SHH in cells with a mesenchymal phenotype. Cyclopamine reduced the number of cells with a pit phenotype but not a gland phenotype in primary cultures. Cyclopamine had particularly potent effects of inhibiting the growth of cell lines that expressed high levels of SMO.

CONCLUSIONS

Expression of IHH and downstream targets correlates with pit cells. IHH and SMO may be useful biomarkers of diffuse cancers that may show growth inhibition with Hh antagonists such as cyclopamine.

Tumor differentiation phenotype in gastric differentiated-type tumors and its relation to tumor invasion and genetic alterations

AIM: To clarify the relations between tumor differentiation phenotype and tumor invasion or genetic alterations in gastric differentiated-type tumors.

METHODS: We examined the tumor differentiation phenotype, the presence of mutations in APC and p53, and the microsatellite instability (MSI) status in 48 gastric adenomas and 171 differentiated-type carcinomas. The tumor differentiation phenotype was determined by examining the expression of human gastric mucin (HGM), MUC6, MUC2 and CD10. The tumors were then classified into gastric- (G-), gastric and intestinal mixed- (GI-), or intestinal- (I-) phenotypes, according to the immunopositivity of the above markers. The presence of mutations in APC and p53 and the MSI status were also investigated in all the tumors.

RESULTS: Gastric adenomas were significantly associated with CD10 expression, I-phenotype tumors and the presence of APC mutations, compared with carcinomas (66.7% vs 25.1%, P < 0.0001; 56.3% vs 14.6%, P < 0.0001; 39.6% vs 14.0%, P < 0.0001, respectively) and inversely associated with expressions of HGM and MUC6 and the presence of p53 mutations (10.4% vs 62.6%, P < 0.0001; 39.6% vs 64.3%, P = 0.003; 2.0% vs 26.3%, P = 0.001, respectively). The frequency of APC mutations was significantly higher in HGM-negative tumors, MUC6-negative tumors, CD10-positive tumors and I-phenotype tumors than in HGM-positive tumors, MUC6-positive tumors, CD10-negative tumors and G-phenotype tumors (32.7% vs 7.1%, P < 0.0001; 27.8% vs 14.0%, P = 0.0182; 37.3% vs 10.4%, P < 0.0001; and 38.5% vs 9.5%, P = 0.0017, respectively). The frequency of MSI was significantly higher in MUC6-positive tumors, CD10-negative tumors and G-phenotype tumors than in MUC6-negative tumors, CD10-positive tumors and I-phenotype tumors (24.8% vs 6.7%, P = 0.0009; 22.2% vs 8.0%, P = 0.0143; and 28.6% vs 9.6%, P = 0.0353, respectively).

CONCLUSION: The tumor differentiation phenotype is closely related to tumor invasion and genetic alterations in gastric differentiated-type tumors.

Gastric and intestinal phenotypic cell marker expressions in gastric differentiated-type carcinomas: association with E-cadherin expression and chromosomal changes

Gastric and intestinal phenotypic cell markers are widely expressed in gastric carcinomas, irrespective of their histological type. In the present study, the relations between the phenotypic marker expression of the tumour, histological findings, expression of cell adhesion molecules, and the chromosomal changes in gastric differentiated-type carcinomas were examined. The phenotypic marker expression of the tumour was determined by the combination of the expression of the human gastric mucin (HGM), MUC6, MUC2 and CD10, and was evaluated in comparison with the expression of cell adhesion molecules, such as E-cadherin and beta-catenin, and chromosomal changes by comparative genomic hybridization (CGH) in 34 gastric differentiated-type carcinomas. Tumours were classified into the gastric- (G-), gastric and intestinal mixed- (GI-), intestinal- (I-), or unclassified- (UC-) phenotype according to the immunopositivity of staining for HGM, MUC6, MUC2, and CD10. G-phenotype tumours were significantly associated with a higher incidence of differentiated-type tumours mixed with undifferentiated-type component, compared with GI- and I-phenotype tumours (88.9 vs 33.3%, P=0.0498 and 88.9 vs 42.9%, P=0.0397; respectively). HGM-positive tumours were significantly associated with a higher incidence of tumours with abnormal expression of E-cadherin, compared with HGM-negative tumours (66.7 vs 21.1%, P=0.0135). GI-phenotype tumours were significantly associated with a higher incidence of tumours with abnormal expression of E-cadherin, compared with I-phenotype tumours (77.8 vs 21.4%, P=0.0131). HGM-negative tumours were significantly associated with higher frequencies of the gains of 19q13.2 and 19q13.3, compared with HGM-positive tumours (57.9 vs 20.0%, P=0.0382 and 63.2 vs 13.3%, P=0.0051; respectively). MUC6-positive tumours were significantly associated with higher frequencies of the gains of 20q13.2, compared with MUC6-negative tumours (71.4 vs 30.0%, P=0.0349). MUC2-positive tumours were significantly associated with the gain of 19p13.3, compared with MUC2-negative tumours (41.2 vs 5.9%, P=0.0391). I-phenotype tumours were significantly associated with higher frequencies of gains of 5p15.2 and 13q33-34, compared with G-phenotype tumours (66.7 vs 0%, P=0.0481, each) and also associated with higher frequencies of gain of 7p21, compared with GI-phenotype tumours (66.7 vs 0%, P=0.0481). Our present results show that gastric differentiated-type carcinomas have different characteristics according to the phenotypic marker expression of the tumour in terms of histological findings, E-cadherin expression and pattern of chromosomal changes.

Microsatellite instability is linked to loss of hMLH1 expression in advanced gastric cancers: lack of a relationship with the histological type and phenotype

BACKGROUND

It has been suggested that the prevalence of microsatellite instability (MSI) is high in intramucosal differentiated gastric cancers with gastric foveolar phenotypic expression, and that these tumors are prone to lose their glandular structures and progress to undifferentiated-type lesions. To test this hypothesis, we examined the relationships among human MutL homologue 1 (hMLH1) expression (which is linked to MSI), the phenotype, and the histological type in patients with advanced and intramucosal gastric cancer.

METHODS

We analyzed hMLH1 expression by immunohistochemistry in 70 advanced and 30 intramucosal gastric cancers with histological evaluation and assessment of the phenotype, and Cdx2 expression determined by immunohistochemistry. The MSI status was also examined in 20 cases.

RESULTS

Thirteen (18.6%) advanced and 5 (16.7%) intramucosal gastric cancers were judged to be hMLH1-negative. In the advanced cases, no association was observed between the histological type and the phenotype and loss of hMLH1. In the intramucosal cases, MUC5AC expression was observed in all 5 hMLH1-negative differentiated-type cancers. However, no hMLH1-negative lesions were detected in the intramucosal undifferentiated cancers (0/14; P < 0.05 vs differentiated types). In the advanced cases, MSI-positivity (MSI +) and loss of hMLH1 expression did correlate (P < 0.0001), while no association was observed between MSI +, histological type, and phenotype.

CONCLUSION

Our data support the hypothesis that, phenotypically, some MSI-positive differentiated gastric cancers of gastric foveolar phenotypic expression may easily change, from gastric to intestinal phenotypic expression, also changing, histologically, from differentiated to undifferentiated type with progression.

Loss of phenotypic expression is related to tumour progression in early gastric differentiated adenocarcinoma

AIMS

To evaluate the relationship between phenotypic expression and tumour progression as represented by macroscopic features, submucosal invasion and lymph node metastasis in early differentiated gastric adenocarcinoma.

METHODS

One hundred and fifty-five cases of early gastric differentiated adenocarcinoma without any poorly differentiated components were studied. The mucosal and submucosal components of carcinomas and lymph node metastatic lesions were classified into four categories, gastric type (G-type), incomplete intestinal type (I-type), complete intestinal type (C-type) and unclassified type (U-type), based on the combination of the phenotypic expression of HGM (gastric foveolar epithelium), MUC 6 (gastric pyloric glands), MUC 2 (intestinal goblet cells) and CD 10 (small intestinal brush border). In addition, a new classification representing a phenotypic shift from mucosa to submucosa or from primary lesion to lymph node metastasis was established with the categories of preserved group (P-group), loss group (L-group) and acquired group (A-group).

RESULTS

(1) In submucosal carcinoma, U-type was more common in the submucosa (39%) than in the mucosa (9%). (2) U-type was more common in the metastatic lesions (42%) than in the primary lesions (5%). (3) The submucosal component and lymph node metastatic lesions were classified as P-group in 48% and 43% of cases, respectively, and as L-group in 50% and 52% of cases, respectively. (4) Lymph node metastatic lesions comprising undifferentiated carcinoma were classified as L-group in 100% of cases.

CONCLUSION

During the course of tumour progression, early differentiated adenocarcinoma at first tends to lose its phenotypic expression despite preserving its morphology, but subsequently morphological dedifferentiation occurs.

Clinicopathologic significance of gastric and intestinal phenotypic marker expression in gastric carcinomas

BACKGROUND

It is well known that both gastric and intestinal phenotypic cell markers are expressed in gastric cancers. This study was aimed at investigating the correlation between gastric and intestinal phenotypic marker expression patterns of tumors and the clinicopathologic characteristics of gastric carcinomas.

METHODS

We evaluated phenotypic marker expression by immunohistochemical staining with monoclonal antibodies. All tumors were classified as gastric (G), gastric and intestinal mixed (GI), intestinal (I), or null (N) phenotype.

RESULTS

The tumors were phenotypically divided into G-phenotype tumors (33.2%), GI-phenotype tumors (25.7%), I-phenotype tumors (26.8%), and N-phenotype tumors (14.3%). N-phenotype tumors were associated with more corporeal location than GI- and I-phenotype tumors (o=0.009 and p=0.007, respectively), a larger size than I-phenotype tumors (0=0.007), a higher proportion of advanced gastric cancers than G-, GI-, and I-phenotype tumors (0=0.003, p<0.001, and p<0.001, respectively), more perineural invasion than G-, GI-, and I-phenotype tumors (p=0.076, p=0.003, and p=0.003, respectively), and more lymph node metastasis than GI-phenotype tumors (p=0.017). I-phenotype tumors were associated with a higher proportion of intestinal-type tumors than G-, GI-, and N-phenotype tumors (p<0.001, p=0.011, and p<0.001, respectively).

CONCLUSION

Our results indicate that the gastric and intestinal phenotypic marker expression pattern of tumors is prognostically useful for patients with gastric carcinoma.

Re-evaluation of mucin phenotypes of gastric minute well-differentiated-type adenocarcinomas using a series of HGM, MUC5AC, MUC6, M-GGMC, MUC2 and CD10 stains

We examined which, and how many, mucin markers are necessary to define the phenotypes of gastric cancers, and re-evaluated the incidence of their mucin phenotypes and whether minute gastric carcinomas arise as unclassified type. Well-differentiated-type minute gastric carcinomas (n = 33) measuring <or=5 mm were examined using human gastric mucin (HGM) and MUC5AC, MUC6 and M-GGMC-1 (or paradoxical concanavalin A type III mucin (Con A)), MUC2 and CD10 stains, and a new method to separate the previous intestinal type into intestinal type and small intestinal type. The phenotypes of carcinomas were classified into gastric, gastrointestinal, intestinal, small intestinal, and unclassified types. MUC5AC or HGM, MUC6, MUC2, and CD10 stains were all necessary to define gastric cancer phenotypes. The incidence of gastric, gastrointestinal, intestinal, small intestinal, and unclassified type was 6%, 49%, 0%, 45%, and 0%, respectively, when the percentage of positive mucin phenotype was set at >0%, and was 33%, 33%, 3%, 30%, and 0%, respectively, when the percentage of positive mucin phenotype was set at >or=10%. Thus, a panel of MUC5AC (or HGM), MUC6, MUC2 and CD10 stains is indispensable for accurately determining the mucin phenotypes of gastric carcinomas, and the above-mentioned classification is important for studying changes in the histological types of well-differentiated-type adenocarcinomas during change to the poorly differentiated type, as well as corresponding genetic abnormalities.

Gastric and intestinal phenotypic marker expression in gastric carcinomas and recurrence pattern after surgery-immunohistochemical analysis of 213 lesions

Both gastric and intestinal phenotypic markers are known to be expressed in gastric carcinomas, irrespective of their histologic type. In the present study, the relation between gastric and intestinal phenotypic marker expression in gastric carcinomas and the recurrence pattern after surgery was examined. The phenotypic marker expression of the tumour was determined by examining the expression of human gastric mucin (HGM), MUC6, MUC2 and CD10 in 213 advanced gastric carcinomas in 213 patients who had undergone a curative resection (97 died from recurrent gastric carcinoma and 116 were alive without recurrence at the end of the follow-up period). Tumours were classified into gastric (G), gastric and intestinal mixed (GI), intestinal (I) or unclassified (UC) phenotypes according to the immunopositivity of HGM, MUC6, MUC2 and CD10 stainings. The incidence of HGM-positive tumours and MUC2-negative tumours was significantly higher in tumours with peritoneal recurrence than in tumours without recurrence (73.3%, 44 out of 60 cases vs 54.3%, 63 out of 116 (P=0.022); and 70.0%, 42 out of 60 vs 38.8%, 45 out of 116 (P=0.0002), respectively). The incidence of G-phenotype tumours was also significantly higher in tumours with peritoneal recurrence than in tumours without recurrence (58.3%, 35 out of 60 cases vs 28.4%, 33 out of 116 (P=0.0002)). The incidence of MUC2-negative tumours and CD10-positive tumours was significantly higher in tumours with haematogenous recurrence than in tumours without recurrence (62.5%, 20 out of 32 cases vs 38.8%, 45 out of 116 (P=0.028); and 43.8%, 14 out of 32 vs 23.3%, 27 out of 116 (P=0.039); respectively). Our present findings show that the gastric and intestinal phenotypic marker expression of the tumour, determined by immunohistochemical staining for HGM, MUC6, MUC2 and CD10, can be used to predict the pattern of gastric carcinoma recurrence after curative resection.

Genetic lineage of poorly differentiated gastric carcinoma with a tubular component analysed by comparative genomic hybridization

Analysis of cell lineage is based on the use of genetic markers inherent to the lineage to be analysed. The breakpoints of unbalanced translocations, and the pattern of chromosomal loss/gain determined by comparative genomic hybridization (CGH), have been previously used to demonstrate lineages in diffuse-type gastric carcinoma. Signet ring cell carcinoma was shown to progress to poorly differentiated adenocarcinoma, and early diffuse-type gastric carcinoma to advanced diffuse-type gastric carcinoma. The present study focuses on poorly differentiated adenocarcinoma with a tubular component to clarify its derivation. CGH and array CGH were applied to DNA extracted from multiple portions of individual tumours and amplified by degenerate oligonucleotide-primed (DOP) PCR and the changes common to the samples in each tumour (stemline changes) were compared between the tumours with and those without a tubular component. Within individual tumours, the samples from the tubular component and those from the other components had common stemline changes and a very similar frequency pattern of chromosomal changes, indicating their common derivation. Frequent stemline changes were 8q+, 7p+, 3q+, 20q+, and 10p+, and these were different from those in the tumours without a tubular component. It was noticed that there were two subgroups in the tumours with a tubular component: one with 5p+, 6p+, 7p+, and 10p+, and the other without these changes. The latter had cytogenetic and clinicopathological features similar to those of the tumours without a tubular component. Analysis of the clonal evolution process by constructing dendrograms for each tumour gave results consistent with the notion that the latter subgroup may derive from signet ring cell carcinoma and the former from tubular adenocarcinoma.

Mucin Phenotype and Background Mucosa of Intramucosal Differentiated-Type Adenocarcinoma of the Stomach

<i>Objectives:</i> Gastric carcinomas have been divided into differentiated (intestinal) and undifferentiated (diffuse) types. Recently, classification studies based on mucin expression have revealed that some differentiated-type carcinomas are of a gastric phenotype. In this study, we investigated the clinicopathological features of differentiated-type adenocarcinomas and evaluated the background mucosa of the stomach based on mucin expression by the tumors. <i>Methods:</i> Seventy-six intramucosal differentiated-type adenocarcinomas of the stomach were evaluated macroscopically and histologically. The mucin expression of tumor cells was examined by immunohistochemical staining with monoclonal antibodies against human gastric mucin (45M1), class III mucin (HIK1083), small intestinal mucinous antigen (SIMA-4D3), and MUC2 (Ccp58). Tumors were classified by phenotype as gastric (G-type), intestinal (I-type), mixed (M-type), or null (N-type). Not only the clinicopathological features but also the background mucosa of the stomach of G-type and I-type carcinomas were compared histologically and serologically. <i>Results:</i> Seventeen tumors (22.4%) were classified as G-type, 31 (40.8%) as I-type, 22 (28.9%) as M-type, and 6 (7.9%) as N-type. The frequencies of elevated type tumors and papillary adenocarcinomas and the ratio of moderately/well-differentiated adenocarcinomas were higher in G-type than in I-type carcinomas. The scores for glandular atrophy and intestinal metaplasia were higher and the scores for chronic inflammation, polymorphonuclear neutrophil activity, and the density of <i>Helicobacter pylori</i> were lower in G-type than in I-type tumors. The serum level of pepsinogen I and the pepsinogen I/II ratio were significantly lower in G-type than in I-type tumors. <i>Conclusions:</i> G-type carcinoma is the predominant phenotype of papillary adenocarcinoma. The background mucosa of G-type carcinoma is associated with glandular atrophy and intestinal metaplasia, whereas that of I-type carcinoma is associated with active and chronic inflammation induced by <i>H. pylori</i> infection.

Association of gastric and intestinal phenotypic marker expression of gastric carcinomas with tumor thymidylate synthase expression and response to postoperative chemotherapy with 5-fluorouracil

PURPOSE

It is well known that both gastric and intestinal phenotypic markers are expressed in gastric carcinomas, irrespective of their histological type. In the present study, the associations among phenotypic marker expression of gastric carcinomas, tumor thymidylate synthase (TS) expression, and the chemotherapeutic response to 5-fluorouracil (5-FU) were examined.

METHODS

The gastric and intestinal phenotypic marker expression of the tumor was determined by the combination of the expression of human gastric mucin (HGM), MUC6, MUC2, and CD10, and was evaluated in comparison with tumor TS expression in 137 advanced gastric carcinomas in 137 patients (75 with postoperative chemotherapy with 5-FU and 62 without postoperative chemotherapy). Tumors were classified into the gastric- (G-), gastric and intestinal mixed- (GI-), intestinal- (I-), or unclassified- (UC-) phenotype according to the immunopositivity of HGM, MUC6, MUC2, and CD10 stainings. The associations among the gastric and intestinal phenotypic marker expression of the tumor, tumor TS expression, effect of postoperative chemotherapy with 5-FU, and the patient's prognosis were examined.

RESULTS

Of the 137 gastric carcinomas, 48 (35.0%), 58 (42.3%), 23 (16.8%), and 8 (5.8%)were classified as the G-, GI-, I- and UC-phenotype, respectively. The high TS expression of more than 25% tumor cell positivity was found in 25 (52.1%) of the 48 G-phenotype tumors, 39 (67.2%) of the 58 GI-phenotype tumors, 18 (78.3%) of the 23 I-phenotype tumors, and 4 (50.0%) of the 8 UC-phenotype tumors. The I-phenotype tumors were significantly correlated with the higher rate of the high TS expression as compared with the G-phenotype tumors (P<0.05). Among 48 patients with the G-phenotype tumor, the 5-year survival rate in patients with and without postoperative chemotherapy was 39.7 and 27.8%, respectively. The patients with postoperative chemotherapy had a significantly better prognosis than those without postoperative chemotherapy (P<0.05). Conversely, there were no significant correlations between the presence of postoperative chemotherapy and the patient's prognosis among patients with GI-, I-, and UC-phenotype tumors.

CONCLUSIONS

These results indicate that postoperative chemotherapy with 5-FU could be effective for patients with the G-phenotype tumor, since the incidence of intratumoral expression of TS, the target enzyme of 5-FU, is significantly low in G-phenotype tumors.

Gastric and intestinal phenotypic marker expression in gastric carcinomas and its prognostic significance: immunohistochemical analysis of 136 lesions

OBJECTIVE

It is well known that both gastric and intestinal phenotypic cell markers are expressed in gastric carcinomas, irrespective of their histologic type. However, the clinicopathologic significance of these expressions has not yet been clarified.

METHODS

We analyzed the correlations among gastric and intestinal phenotypic marker expression patterns of the tumor, clinicopathologic findings and the patient's outcome in 136 advanced gastric carcinomas.

RESULTS

Phenotypic marker expression was immunohistochemically evaluated using the monoclonal antibodies 45M1 (anti-human gastric mucin; HGM), CLH5 (anti-MUC6), Ccp58 (anti-MUC2) and 56C6 (anti-CD10). All tumors were classified as gastric (G), gastric and intestinal mixed (GI), intestinal (I) or unclassified (UC) phenotype. Of the 136 gastric carcinomas, 50 (36.8%), 56 (41.2%), 21 (15.4%) and 9 (6.6%) were classified as G, GI, I and UC phenotype, respectively. The G-phenotype tumors were associated with a higher rate of undifferentiated-type and infiltrative histology as compared with the I-phenotype tumors (p < 0.05 and p < 0.001, respectively). Furthermore, both univariate and multivariate analysis of survival revealed the G-phenotype tumor to be associated with a significantly poorer outcome than the I-phenotype tumor (p < 0.05).

CONCLUSION

Our present results indicate that the gastric and intestinal phenotypic marker expression pattern of tumors, determined by the combination of HGM, MUC6, MUC2 and CD10 expression, is prognostically useful for patients with gastric carcinoma.

Frequent loss of expression without sequence mutations of the DCC gene in primary gastric cancer

Loss of heterozygosity (LOH) on chromosome 18q21 is frequently found in various human cancers, suggesting the presence of tumour suppressor gene(s) in this chromosomal region. DCC is the most likely target of LOH because loss or reduction of DCC expression has been found in many types of cancers. However, few reports have focused on sequence mutations of this gene. We investigated sequence mutations and expression of DCC in primary gastric cancers. We studied mutations in 25 of the 29 DCC exons by PCR-SSCP in 17 primary gastric cancers exhibiting LOH on 18q21. No mutations of DCC were found in any of the tumours, although 78% (47/60) of the primary tumours showed apparent loss or reduction of DCC expression by immunohistochemistry. Analysis of methylation status of DCC revealed that methylation frequently occurred in both primary tumours (75%; 45/60) and corresponding non-cancerous gastric mucosae (72%; 43/60). Methylated status of DCC was significantly correlated with the loss of DCC expression in primary tumours (P< 0.01). These results indicate that DCC is frequently silenced, probably by epigenetic mechanisms instead of sequence mutations in gastric cancer.

Frequent hypermethylation of the hMLH1 gene promoter in differentiated-type tumors of the stomach with the gastric foveolar phenotype

Hypermethylation of the hMLH1 mismatch repair gene promoter has been revealed to lead to microsatellite instability (MSI). Previously, we demonstrated a high prevalence of MSI in differentiated-type gastric tumors showing distinct features of gastric foveolar epithelium (foveolar type). To clarify the significance of hMLH1 promoter hypermethylation in the development of this tumor type, we studied promoter methylation status and expression of hMLH1 in foveolar-type tumors and their surrounding non-neoplastic mucosae, as well as in tumors with other cellular phenotypes. The results were compared to MSI status. After phenotypical analyses using mucin histochemistry and immunohistochemistry, 41 differentiated-type tumors with distinct cellular phenotypes were classified into three categories: foveolar type, intestinal type (tumors with the distinct cellular phenotype of the intestine), and combined type (tumors with both foveolar and intestinal phenotypes). Methylation-specific polymerase chain reaction (MSP) was performed to determine the methylation status of hMLH1 promoter. hMLH1 protein expression was immunohistochemically examined. MSI was detected in 57% of the foveolar type, 8% of the intestinal type, and 67% of the combined-type tumors. Hypermethylation of hMLH1 promoter was found in 74% of the foveolar type, 33% of the intestinal type, and 83% of the combined-type tumors. Of 18 MSI-positive tumors, all but one were hypermethylated. Methylation status of hMLH1 promoter correlated well with protein expression in foveolar-type tumors. Moreover, hypermethylation was also detected frequently (71%) in the non-neoplastic surrounding mucosa of the hypermethylated tumors. Hypermethylation of hMLH1 promoter is an initial, vital event in the development of foveolar-type tumors of the stomach.

Cellular phenotypes of differentiated-type adenocarcinomas and precancerous lesions of the stomach are dependent on the genetic pathways

To elucidate the relationship between genetic alterations and cellular phenotypes in differentiated-type carcinomas and precancerous lesions of the stomach, mutations of p53, APC and K-ras genes were examined, as well as microsatellite instability (MSI), in 52 tumours of the stomach. Tumours were selected with the following phenotypical features, using mucin histochemical and immunohistochemical analyses, in addition to their morphological features: (1) tumours with an extremely well-preserved gastric foveolar phenotype (foveolar-type); (2) tumours with an extremely well-preserved complete-type intestinal metaplastic phenotype (CIM-type); and (3) ordinary tumours without extreme phenotypes (ordinary-type). MSI occurred in 45% of foveolar-type, 24% of ordinary-type, and 0% of CIM-type tumours. p53 gene alterations occurred in 5% of foveolar-type, 18% of ordinary-type, and 31% of CIM-type. APC gene alterations were detected in 9% of foveolar-type, 6% of ordinary-type, and 0% of CIM-type. No K-ras gene mutation was detected in any of the three types. These results indicate that the genetic pathways are quite different among the phenotypes of tumours of the stomach. The 'mutator pathway', characterized by MSI, plays an important role in the tumourigenesis of foveolar-type, but not CIM-type tumours. The 'suppressor pathway', represented by p53 alteration, could participate in the tumourigenesis of the CIM-type, but is rare in foveolar-type tumours.