Initial and crucial genetic events in intestinal-type gastric intramucosal neoplasia

Gastric cancer (GC) is one of the most common and life-threatening malignancies. The course of disease and tumor aggressiveness vary among GCs, although how early fate is determined and by what factors remains elusive. To solve this question, we collected 43 gastric intramucosal neoplasias (GINs), comprising dysplasia/intraepithelial neoplasia (D/IEN; a premalignant lesion) and minute GC (miGC; ≤10 mm) of intestinal histotype and performed targeted deep DNA sequencing of 67 GC-related genes derived from large-scale data. Gastric D/IEN was classified into low or high grade (LG-D/IEN or HG-D/IEN). The most frequent mutations in D/IENs included APC (19/25; 76%), ARID2 (6/25; 24%) and MUC6 (5/25; 20%). All LG-D/IENs had APC mutation (12/12) and APC hotspot mutations affecting R1450 and E1554 were noted in both LG-D/IEN and HG-D/IEN. ARID2 mutation always co-occurred with APC mutation, whose tumor variant allele frequency (TVAF) was higher than that of ARID2 in D/IEN. APC and TP53 mutations were mutually exclusive in D/IEN (p = 0.031 [main cohort], p = 0.025 [expanding cohort]) and TP53-mutated D/IEN was exclusively HG-D/IEN (4/4). TP53 mutations were highly recurrent (11/14; 79%) in MLH1-positive miGCs and were detected even in two microscopic lesions measuring 1 and 3 mm, respectively. Furthermore, TVAF analyses suggested that TP53 mutation is the initial event in the TP53-mutated miGCs. In contrast, TP53 mutation was absent (0/4) in MLH1-negative small intramucosal carcinoma (8-24 mm). Advanced GC data suggested that early mutations (APC and TP53) may affect the potential of cancerous progression from D/IEN. This study revealed somatic mutational landscape and initial mutations of GINs, and we report for the first time that TP53 mutations precede other mutations in intestinal-type GC. Our results also indicate that molecular subtyping based on APC/TP53 mutations would be a high-priority approach for determining and predicting the malignant potential of GIN, including D/IEN. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Effects of long-term aspirin use on molecular alterations in precancerous gastric mucosa in patients with and without gastric cancer

The risk of gastric cancer (GC) remains even after H. pylori eradication; thus, other combination treatments, such as chemopreventive drugs, are needed. We evaluated the effects of aspirin on genetic/epigenetic alterations in precancerous conditions, i.e., atrophic mucosa (AM) and intestinal metaplasia (IM), in patients with chronic gastritis who had taken aspirin for more than 3 years. A total of 221 biopsy specimens from 74 patients, including atrophic gastritis (AG) cases without aspirin use (control), AG cases with aspirin use (AG group), and GC cases with aspirin use (GC group), were analyzed. Aspirin use was associated with a significant reduction of CDH1 methylation in AM (OR: 0.15, 95% CI: 0.06-0.41, p = 0.0002), but was less effective in reversing the methylation that occurred in IM. Frequent hypermethylation including that of CDH1 in AM increased in the GC group compared to the AG group, and CDH1 methylation was an independent predictive marker of GC (OR: 8.50, 95% CI: 2.64-25.33, p = 0.0003). In patients with long-term aspirin use, the changes of molecular events in AM but not IM may be an important factor in the reduction of cancer incidence. In addition, methylation of the CDH1 gene in AM may be a surrogate of GC.

A protein and mRNA expression-based classification of gastric cancer

The overall survival of gastric carcinoma patients remains poor despite improved control over known risk factors and surveillance. This highlights the need for new classifications, driven towards identification of potential therapeutic targets. Using sophisticated molecular technologies and analysis, three groups recently provided genetic and epigenetic molecular classifications of gastric cancer (The Cancer Genome Atlas, 'Singapore-Duke' study, and Asian Cancer Research Group). Suggested by these classifications, here, we examined the expression of 14 biomarkers in a cohort of 146 gastric adenocarcinomas and performed unsupervised hierarchical clustering analysis using less expensive and widely available immunohistochemistry and in situ hybridization. Ultimately, we identified five groups of gastric cancers based on Epstein-Barr virus (EBV) positivity, microsatellite instability, aberrant E-cadherin, and p53 expression; the remaining cases constituted a group characterized by normal p53 expression. In addition, the five categories correspond to the reported molecular subgroups by virtue of clinicopathologic features. Furthermore, evaluation between these clusters and survival using the Cox proportional hazards model showed a trend for superior survival in the EBV and microsatellite-instable related adenocarcinomas. In conclusion, we offer as a proposal a simplified algorithm that is able to reproduce the recently proposed molecular subgroups of gastric adenocarcinoma, using immunohistochemical and in situ hybridization techniques.

Eleven metachronous early gastric cancers in an elderly woman

We report on a patient with 11 metachronous multiple early gastric cancers treated by gastrectomy after endoscopic resection. An 87-year-old Japanese woman was admitted to our hospital for treatment of four synchronous multiple early gastric cancers detected by endoscopic examination. The patient had a history of two endoscopic treatments for four metachronous early gastric cancers. The pathological findings of four lesions resected by endoscopic resection and four biopsy specimens showed well-differentiated carcinoma. In March 2012, we performed a distal gastrectomy for four lesions. The surgical specimen revealed 3 minute lesions after surgery in addition to these four lesions. Histologically, all seven lesions were intramucosal well-differentiated adenocarcinomas without vascular invasion. Although the incidence of synchronous and metachronous early gastric cancer is reportedly 11-14.5 % and 8.5-14 %, respectively, only two or three lesions are generally present. Moreover, multiple early gastric cancers usually originate as differentiated adenocarcinoma in male elderly patients with intestinal metaplasia. In the present case, there were multiple early gastric cancers, whose origin may be correlated with the background of intestinal metaplasia, in excess of the number generally expected.

Histopathological phenotypes of early gastric cancer and its background mucosa

Recent advances in endoscopic submucosal dissection (ESD) techniques contribute to endoscopic treatment of early gastric cancer (EGC). Recognition of chronic atrophic gastritis as the background is important for high-quality detection and diagnosis of EGC. But, relationships between EGC and atrophy of the background gastric mucosa caused by Helicobacter pylori are not well understood. The present study demonstrated histopathological phenotypes of EGC, as well as chronic atrophic gastritis as background mucosa of EGC. We evaluated mucosal heights, number of glands, and degree of intestinal metaplasia (IM) of the background gastric mucosa, using 81 cases of EGC resected by ESD. Gastric phenotype cancer cases showed IM of the background gastric mucosa less frequently, compared with intestinal phenotype cancer cases (score of IM, 1.15 vs. 1.65, P = 0.012). The average mucosal heights around EGC were lower in moderately to poorly differentiated adenocarcinoma cases than well differentiated adenocarcinoma cases (442.6 µm vs. 500.2 µm, P = 0.011). The mucosal atrophy indicated by average heights of background mucosa was low in the gastric phenotype cancer cases, compared with the intestinal phenotype cancercases (452.8 µm vs. 505.6 µm, P = 0.018). In the fundic gland area, the mucosal heights were low in the gastric phenotype cancer cases, compared with the intestinal phenotype cancer cases (413.2 µm vs. 495.5 µm, P = 0.015). Our results using EGC specimens indicated that gastric phenotype cancer and moderately to poorly differentiated adenocarcinoma had atrophic background mucosa with lower mucosal heights and less IM. The atrophic gastric mucosa with less IM is thought to play an important role in gastric carcinogenesis, especially tumoriogenesis of gastricphenotype cancer.

Aberrant activation-induced cytidine deaminase expression is associated with mucosal intestinalization in the early stage of gastric cancer

Although Helicobacter pylori is a risk factor for gastric cancer (GC), its detailed carcinogenesis remains unclear. Recently, aberrant expression of activation-induced cytidine deaminase (AID) was demonstrated in gastric epithelium with H. pylori infection and seems to cause the accumulation of mutation. This investigation aims to elucidate whether or not AID expression plays an important role in the carcinogenesis of early GC. We examined the correlation between immunohistochemical AID expression and histological characteristics, including pre-existing chronic gastritis and cellular mucin phenotype in 138 cases of intramucosal GC. Furthermore, we investigated the relationship between AID, p53 protein, and β-catenin. The low degree of polymorphonuclear neutrophil activity, and the high degree of glandular atrophy and intestinal metaplasia were significantly correlated with the high levels of AID expression in non-neoplastic mucosa (P = 0.007, P ≤ 0.001, and P = 0.003). With regard to mucin phenotype of carcinoma, the intestinal phenotype tended to have the higher AID expression levels (P = 0.052). AID showed close correlations with Cdx2 and nuclear staining of β-catenin (P = 0.003, P = 0.034). As for p53 protein, no correlation was found with AID expression. Our findings suggest that aberrant AID expression is correlated with persistent inflammatory condition induced by H. pylori infection and may contribute to the development of GC through an inflammatory condition and intestinalization.

Analysis of cell cycle-related proteins in gastric intramucosal differentiated-type cancers based on mucin phenotypes: a novel hypothesis of early gastric carcinogenesis based on mucin phenotype

Background

Abnormalities of cell cycle regulators are common features in human cancers, and several of these factors are associated with the early development of gastric cancers. However, recent studies have shown that gastric cancer tumorigenesis was characterized by mucin expression. Thus, expression patterns of cell cycle-related proteins were investigated in the early phase of differentiated-type gastric cancers to ascertain any mechanistic relationships with mucin phenotypes.

Methods

Immunostaining for Cyclins D1, A, E, and p21, p27, p53 and β-catenin was used to examine impairments of the cell cycle in 190 gastric intramucosal differentiated-type cancers. Mucin phenotypes were determined by the expressions of MUC5AC, MUC6, MUC2 and CD10. A Ki-67 positive rate (PR) was also examined.

Results

Overexpressions of p53, cyclin D1 and cyclin A were significantly more frequent in a gastric phenotype than an intestinal phenotype. Cyclin A was overexpressed in a mixed phenotype compared with an intestinal phenotype, while p27 overexpression was more frequent in an intestinal phenotype than in a mixed phenotype. Reduction of p21 was a common feature of the gastric intramucosal differentiated-type cancers examined.

Conclusions

Our results suggest that the levels of some cell cycle regulators appear to be associated with mucin phenotypes of early gastric differentiated-type cancers.

Gastric adenocarcinoma of fundic gland type (chief cell predominant type): proposal for a new entity of gastric adenocarcinoma

Only a few cases of gastric adenocarcinoma of fundic gland type have been reported. Gastric adenocarcinoma with chief cell differentiation (GA-CCD) has been recently reported as a new variant of gastric adenocarcinoma. However, its clinicopathologic features are uncertain. To elucidate them, GA-CCDs exhibiting pepsinogen-I expression (10 lesions: Group A) and randomly selected gastric adenocarcinomas of differentiated type (111 lesions: Group B) were evaluated in this study. Cell differentiation by MUC2, MUC5AC, MUC6, CD10, pepsinogen-I, H+/K+-ATPase and chromogranin A, cell proliferation by Ki-67, and overexpression of p53 protein were evaluated immunohistochemically. In Group A, all GA-CCDs were located in the upper third of the stomach. Tumors were small, with the average maximum diameter ranging from 4 to 20 (average, 8.6) mm. Histologically, GA-CCDs were well-differentiated adenocarcinomas composed of pale gray-blue, basophilic columnar cells with mild nuclear atypia, resembling chief cells. Immunohistochemically, scattered positivity for H+/K+-ATPase was observed in addition to expression of pepsinogen-I and MUC6, indicating focal differentiation toward parietal cells. In Group B, pepsinogen-I was very focally expressed in 2 cases. As these 2 cases exhibited different clinicopathological and histologic features, they cannot be categorized as GA-CCD. Mild atypism, no lymphovascular invasion, low proliferative activity, no overexpression of p53, and no recurrence indicated less aggressiveness of GA-CCD. GA-CCD is rare, but it has distinct clinicopathological characteristics, especially in terms of tumor location, histologic features, phenotypic expression, and low-grade malignancy. We propose gastric adenocarcinoma of fundic gland type (chief cell predominant type) as a new entity of gastric adenocarcinoma.

Re-evaluation of histogenesis of gastric carcinomas: a comparative histopathological study between Helicobacter pylori-negative and H. pylori-positive cases

We histopathologically re-evaluated the histogenesis of gastric carcinomas from comparative studies between Helicobacter pylori-positive and H. pylori-negative cases using the gastritis score from the Updated Sydney System. The incidence of H. pylori-negative gastric carcinomas was 3.11% (12/386); they are likely to develop in the fundic gland mucosa, and show a gastric phenotype by mucin immunohistochemistry. Even in cases of completely gastric and predominantly gastric phenotypes, CDX2 protein was expressed in most cases (90.9% of pT1 and 100% of pT2-3), indicating a possibility that intestinalization of carcinoma cells occurs independently of the background mucosa. Regarding the degree of gastritis of background mucosa surrounding 143 H. pylori-positive differentiated-type adenocarcinomas, the mean score ranged from 1.497 to 1.713. Our data support the hypothesis that intestinal metaplasia is not a precancerous but a paracancerous lesion, and most gastric adenocarcinomas develop in mildly to moderately atrophic mucosa with H. pylori-infection, i.e., ongoing atrophy.

Clinicopathological and prognostic significance of mucin phenotype in gastric cancer

BACKGROUND AND OBJECTIVES

Gastric and intestinal mucin phenotype cell markers are widely expressed in gastric carcinoma cells, irrespective of their tumor histological type. In the present study, we tried to reveal the clinicopathological significance of mucin phenotype in human gastric carcinomas. Moreover, we investigated the clinical significance of RUNX3 in association with mucin phenotype.

METHODS

The mucin expression of MUC5AC, MUC6, MUC2, and CD10 was evaluated in 97 gastric carcinomas by immunohistochemistry. Tumors were classified into gastric (G), gastric and intestinal mixed (GI), intestinal (I), and null (N) phenotype according to combination of mucin expression.

RESULTS

The rate of G, GI, I, and N phenotype was 40.0%, 38.1%, 10.3%, and 19.6%, respectively. Mucin phenotype was also significantly correlated with several clinicopathological findings. Patients with I phenotype had a significantly poorer prognosis than those with any other phenotypes. They also had a higher rate of postoperative liver metastasis. Multivariate analysis revealed that mucin phenotype was a significant independent prognostic factor. We suggested that Loss of RUNX3 expression might correlate with intestinal phenotype and postoperative outcome.

CONCLUSIONS

Mucin phenotype has a significant prognostic value and may be a useful marker for the treatment of human gastric carcinoma.

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.

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.

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.

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.

Absence of either gastric or intestinal phenotype in microscopic differentiated gastric carcinomas

Differentiated gastric carcinoma (DGC) corresponds roughly to the intestinal type of gastric carcinoma described by Laurén. It has been suggested that DGCs arise from intestinalized gastric mucosa, but recent findings regarding their mucin expression do not support this hypothesis. To evaluate the histogenetic relationship between DGCs and intestinal metaplasia, lesions that are as small as possible should be examined. Twenty-five DGCs, ranging in their greatest dimension from 0.4 to 2.7 mm, were collected and divided into two groups by size. Group A consisted of 13 lesions less than 1.4 mm across, and group B of 12 lesions 1.4 mm or more. The presence of mucin and a brush border was assessed by immunostaining with antibodies against human gastric mucin, pyloric-gland-type mucin, Muc-2 glycoprotein, and CD10 antigen, and the lesions were classified as having the gastric phenotype (G-type), intestinal phenotype (I-type), mixed gastric and intestinal phenotype (M-type), or null phenotype (N-type). Thirteen (52%) of the 25 lesions were N-type, 5 (20%) lesions were G-type, 5 (20%) were I-type, and 2 (8%) were M-type. Group A had a larger proportion of N-type lesions than B (10/13, or 77%, vs. 3/12, or 25%; p = 0.027, chi-square test for proportions). Group B had a larger proportion of G-type lesions than A (5/12, or 42%, vs. 0/13, or 0%; p = 0.033). The phenotypes of the carcinomas and their surrounding mucosa were unrelated. Therefore, DGCs may arise from gastric mucosa affected by intestinal metaplasia or not, without having either the gastric or intestinal phenotype.

TP53 and gastric carcinoma: a review

In this article, we survey the major p53 (TP53) alterations identified in gastric carcinomas and their precursors. These include p53 expression, mutations, and loss of heterozygosity (LOH). Not only are the various abnormalities summarized, but in addition there is a survey of the literature with respect to the impact of these changes on patient prognosis and treatment response. The majority of published studies involve the immunohistochemical detection of the protein. These use different antibodies, different detection techniques, and different methods of interpretation. Therefore not surprisingly, the results of many of the studies are contradictory with one another. Overall, however, it appears that p53 alterations occur early in the development of gastric carcinoma, being present even in the nonneoplastic mucosa and they increase in frequency as one progresses along the pathway of gastric carcinoma development. p53 immunoreactivity is seen in 17%-90.7% of invasive gastric carcinomas. p53 alterations occur much more commonly in proximal lesions than in distal ones, suggesting that the molecular events leading to the development of gastric carcinoma may be very different in proximal vs. distal tumors. p53 mutations occur in 0%-77% of gastric carcinomas. The mutations are distributed widely across the gene from exons 4-11 with hot spots of mutation at codons 175, 248, 273, 282, 245, and 213. G:C>A:T transitions at CpG sites are the commonest type of mutation. At least 60% of carcinomas with mutations also exhibit p53 LOH.

Cell kinetics and genetic instabilities in differentiated type early gastric cancers with different mucin phenotype

To clarify the biological impact and molecular pathogenesis of cellular phenotype in differentiated-type gastric cancers (DGCs), we investigated cell kinetics and genetic instabilities in early stage of DGCs. A total of 43 early gastric cancers (EGCs) were studied. EGCs were divided into 3 phenotypic categories: gastric (G type, n = 11), ordinary (O type, n = 20), and complete intestinal (CI type, n = 12) based on the combination of HGM, ConA, MUC2, and CD10. Proliferative index (PI), apoptotic index (AI), and p53 overexpression were investigated by immunohistochemical staining with anti-Ki-67, the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method, and p53 antibody, respectively. Using a high-resolution fluorescent microsatellite analysis system, microsatellite instability (MSI) and loss of heterozygosity (LOH) were examined. Frameshift mutation analysis of transforming growth factor-beta type II receptor (TGF-betaRII) and bcl-2-associated X (BAX) in cancers with MSI was also performed. The mean AI/PI ratio values were 0.04 for G-type, 0.10 for O-type, and 0.13 for CI-type cancers--significantly lower in G type than in O and CI types (P = 0.02 and P = 0.001, respectively). No difference in the incidence of MSI and LOH was seen among the 3 cellular phenotypes. However, the major pattern of MSI, which showed drastic and widely dispersed changes and is related to an increased risk for cancer, was significantly higher in G and O types than in CI type (P <0.005). No frame shift mutations of TGF-betaRII or BAX were found in CI-type cancers. These results indicate that G-type cancers are likely to show more aggressive behaviors than CI-type cancers, and that O-type cancers show the intermediate characteristics of both types. However, the molecular pathogenesis of each phenotypic cancer is not associated with microsatellite alterations.

Molecular and cellular phenotypic profiles of gastric noninvasive neoplasia

According to the Padova international classification, 52 gastric noninvasive neoplasias (NIN) were classified as follows: 20 low-grade NIN (L-NIN); 9 high-grade NIN including suspicion for carcinoma without invasion (H-NIN); and 23 high-grade NIN including carcinoma without invasion (Ca-NIN). The molecular and cellular phenotypic profiles were investigated and compared. The APC gene was mutated in seven (35%) L-NIN, two (22%) H-NIN, and two (9%) Ca-NIN tumors; APC mutations were significantly more frequent in L-NIN compared with Ca-NIN tumors (p < 0.05). Mutations of the p53 gene were found in five (22%) Ca-NIN tumors but were not observed in L-NIN or H-NIN tumors (p < 0.05). Loss of heterozygosity involving at least one chromosomal locus was detected in 14 (61%) Ca-NIN tumors but was not detected in L-NIN or H-NIN tumors. High-frequency microsatellite instability (MSI-H) was detected in one (5%) L-NIN tumor and in six (26%) Ca-NIN tumors. The frequencies of loss of heterozygosity and MSI-H were significantly higher in Ca-NIN than in L-NIN or H-NIN tumors (p < 0.05). Nuclear accumulation of p53 protein was detected in no L-NIN tumors, 1 (11%) H-NIN tumor, and 10 (44%) Ca-NIN tumors (p < 0.01). All tumors with loss of hMLH1 expression exhibited MSI-H (p < 0.01). Cellular phenotypic analysis revealed that seven (35%) L-NIN tumors and one (4%) Ca-NIN tumor had complete-type intestinal metaplastic phenotype and that one (5%) L-NIN tumor and one (4%) Ca-NIN tumor had a gastric foveolar epithelial phenotype, whereas the remaining tumors exhibited an ordinary phenotype. Thus, the complete-type intestinal metaplastic phenotype was more characteristic of L-NIN tumors than of H-NIN or Ca-NIN tumors (p < 0.01). In summary, the Padova international classification correlated with both the molecular and cellular phenotypic profiles. In practice, p53 and hMLH1 immunohistochemistry discriminated Ca-NIN from L-NIN and H-NIN tumors.

Usefulness of p53 and Ki-67 immunohistochemical analysis for preoperative diagnosis of extremely well-differentiated gastric adenocarcinoma

Of 987 cases of gastric adenocarcinoma seen at Nagoya University School of Medicine, we found 6 rare, extremely well-differentiated advanced gastric adenocarcinomas that could not be diagnosed as malignant tumors with only H&E staining, even with repeated biopsies under preoperative endoscopy. The aim of this study was to determine whether an immunohistochemical method using p53 and Ki-67 antibody would be helpfulfor preoperative pathologic diagnosis. The cancer control cases were 16 cases of ordinary well-differentiated advanced gastric adenocarcinoma, while the gastritis control cases were 22 cases of Helicobacter pylori-positive chronic gastritis. The p53 labeling index and the localization of Ki-67+ cells showed that the special adenocarcinomas in biopsy specimens were distinct from the surrounding normal mucosa and chronic gastritis, but not from the cancer control cases. These methods are useful markers for preoperative pathologic diagnosis of extremely well-differentiated gastric adenocarcinoma, which sometimes is confused with regenerative atypical glands before operation.

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.

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).

Clinicopathological study of early adenocarcinoma of the gastric cardia: comparison with early adenocarcinoma of the distal stomach and esophagus

To clarify the clinicopathological characteristics of adenocarcinoma of the gastric cardia (AGC), including its association with Barrett's esophagus and intestinal metaplasia, 49 surgically resected early AGCs (EAGCs) were examined clinicopathologically, histopathologically, histochemically, and immunohistochemically. The clinicopathological characteristics of the patients with EAGC were compared with those of 293 patients with early adenocarcinoma of the distal stomach (EADS) and 7 patients with early adenocarcinoma of the esophagus (EAE). Histochemical staining with paradoxical concanavalin A (ConA) and immunohistochemical staining with monoclonal antibodies 45M1, Ccp58, and 56C6 were performed to investigate the differentiation phenotype of the tumor. ConA and 45M1 were used for markers of the gastric phenotype, and Ccp58 and 56C6 were used for markers of the intestinal phenotype. EAGC was associated with a higher mean age (p < 0.0001), a higher male-to-female ratio (p < 0.05), a higher incidence of elevated-type tumors (p < 0.0001), a higher incidence of differentiated-type tumors (p < 0.0001), and greater depth of invasion (p < 0.05) compared with EADS. EAE was associated with a higher incidence of elevated-type tumors (p < 0.001), a higher incidence of differentiated-type tumors (p < 0.05), and larger tumor size (p < 0.05) compared with EADS. The prevalence of Barrett's esophagus in patients with EAGC was significantly lower than in patients with EAE (10.2%, 5/49 patients vs. 100%, 7/7; p < 0.0001). The prevalence of intestinal (Barrett's) metaplasia in surrounding non-neoplastic mucosa in patients with EAGC was significantly lower than in patients with EADS or EAE (36.7%, 18/49 patients vs. 72.0%, 211/293 and 85.7%, 6/7; p < 0.0001 and p < 0.05, respectively). EAGC was associated with a higher incidence of tumors that reacted positively for gastric phenotype markers alone than EADS (32.7%, 16/49 cases vs. 17.1%, 50/293; p < 0.05) and a lower incidence of tumors that reacted positively for both gastric and intestinal markers than EADS or EAE (40.8%, 20/49 cases vs. 59.7%, 175/293 and 85.7%, 6/7; p < 0.05, respectively). Our findings indicate that AGC forms a specific category different from both adenocarcinoma of the distal stomach and esophagus in terms of association with Barrett's esophagus or intestinal metaplasia, and the differentiation phenotype of the tumor.

Towards a molecular approach to gastric cancer management

Gastric cancer is a leading cause of cancer death worldwide. Most patients with gastric cancer present with locally advanced and incurable disease, and overall survival is poor. Considerable research efforts towards the epidemiology and pathogenesis of gastric cancer have not been translated into treatment success. We discuss current concepts of the pathogenesis of gastric cancer and how recent research advances, in particular global gene expression strategies, may improve this understanding, and suggest a framework wherein these approaches may be used.

Hypermethylation of the hMLH1 gene promoter is associated with microsatellite instability in early human gastric neoplasia

A significant portion of gastric cancers exhibit defective DNA mismatch repair, manifested as microsatellite instability (MSI). High-frequency MSI (MSI-H) is associated with hypermethylation of the human mut-L homologue 1 (hMLH1) mismatch repair gene promoter and diminished hMLH1 expression in advanced gastric cancers. However, the relationship between MSI and hMLH1 hypermethylation has not been studied in early gastric neoplasms. We therefore investigated hMLH1 hypermethylation, hMLH1 expression and MSI in a group of early gastric cancers and gastric adenomas. Sixty-four early gastric neoplasms were evaluated, comprising 28 adenomas, 18 mucosal carcinomas, and 18 carcinomas with superficial submucosal invasion but clear margins. MSI was evaluated using multiplex fluorescent PCR to amplify loci D2S123, D5S346, D17S250, BAT 25 and BAT 26. Methylation-specific PCR was performed to determine the methylation status of hMLH1. In two hypermethylated MSI-H cancers, hMLH1 protein expression was also evaluated by immunohistochemistry. Six of sixty-four early gastric lesions were MSI-H, comprising 1 adenoma, 4 mucosal carcinomas, and 1 carcinoma with superficial submucosal invasion. Two lesions (one adenoma and one mucosal carcinoma) demonstrated low-frequency MSI (MSI-L). The remaining 56 neoplasms were MSI-stable (MSI-S). Six of six MSI-H, one of two MSI-L, and none of thirty MSI-S lesions showed hMLH1 hypermethylation (P<0.001). Diminished hMLH1 protein expression was demonstrated by immunohistochemistry in two of two MSI-H hypermethylated lesions. hMLH1 promoter hypermethylation is significantly associated with MSI and diminished hMLH1 expression in early gastric neoplasms. MSI and hypermethylation-associated inactivation of hMLH1 are more prevalent in early gastric cancers than in gastric adenomas. Thus, hypermethylation-associated inactivation of the hMLH1 gene can occur early in gastric carcinogenesis.

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.