Clinicopathological significant and prognostic influence of cadherin-17 expression in gastric cancer

Cadherin-17 (CDH17), also called liver–intestine cadherin, is a structurally unique member of the cadherin superfamily. Our serial analysis of gene expression demonstrated that CDH17 was one of the most up-regulated genes in advanced gastric carcinomas. CDH17 expression is known to be regulated by Cdx2. In the present study, we examined the expression of CDH17 in primary gastric carcinoma tissues by immunohistochemistry, and analyzed the correlation of CDH17 expression with clinicopathological characteristics and patients prognosis. CDH17 expression was detected in 63/94 (67%) of gastric adenocarcinomas in addition to intestinal metaplasia. The expression of CDH17 tended to be associated with intestinal type carcinoma, and carcinomas with CDH17 expression was significantly more frequent in advanced stage cases (80%) than in early stage (53%). The prognosis of patients with positive CDH17 expression was significantly poorer than that of the negative cases (P=0.0314). However, multivariate analysis revealed that CDH17 was not an independent prognostic factor. Six of seven cases that showed positive expression of Cdx2 simultaneously expressed CDH17 protein. These results suggested that the expression of CDH17 was characteristic of the advanced gastric carcinoma that is associated with poor prognosis.     

Distinct promoter hypermethylation of p16INK4a,CDH1, and RAR-beta in intestinal,diffuse-adherent,and diffuse-scattered type gastric carcinomas

Hypermethylation of CpG islands in gene promoters is associated with silencing of various tumour suppressor genes. Recent studies of colorectal and gastric carcinomas have defined a CpG island methylator phenotype (CIMP), which involves the targeting of multiple genes by promoter hypermethylation. In this study, methylation-specific polymerase chain reaction (PCR) was performed to study methylation of CpG islands in the promoters of the p16(INK4a), cadherin 1 (CDH1), and retinoic acid receptor-beta (RAR-beta) genes in 45 gastric carcinomas and to investigate whether CDH1 and RAR-beta promoter hypermethylation is associated with CIMP-positive gastric carcinoma. CpG island hypermethylation of the p16(INK4a), CDH1, and RAR-beta promoters was detected in 12 (27%), 26 (58%), and 24 (53%) of the 45 gastric carcinomas, respectively. Hypermethylation of the p16(INK4a) promoter was more common in intestinal type than in diffuse type gastric carcinomas (p = 0.0023; Fisher's exact test) and was inversely associated with p53 mutations (p = 0.0225; Fisher's exact test). However, CDH1 and RAR-beta promoter hypermethylation was observed more frequently in diffuse-scattered type gastric carcinoma than in other types (intestinal and diffuse-adherent types) (p = 0.0175 and p = 0.0335, respectively; Fisher's exact test) and was not associated with p53 mutation status. Moreover, hypermethylation of the CDH1 and RAR-beta promoters occurred concordantly (p < 0.0001; Fisher's exact test). These results suggest that at least two types of promoter methylation status are involved in the development of the intestinal (p16(INK4a) promoter hypermethylation) and diffuse-scattered types (CDH1 and RAR-beta promoter hypermethylation) of gastric carcinoma.     

Promoter hypermethylation of multiple genes in early gastric adenocarcinoma and precancerous lesions

Promoter hypermethylation is an alternative mechanism of gene silencing in human cancers including gastric cancer. To date, several reports on methylation of various genes in gastric cancer have been published. However, most of these studies have focused on cancer tissues or only a single gene. In this study, we determined the methylation frequency of 5 genes, including p16, Runx3, MGMT, DAPK, and RASSF1A, by methylation-specific polymerase chain reaction, in a series of formalin-fixed paraffin-embedded tissues including normal gastric mucosa (n = 20), intestinal metaplasia (n = 14), gastric epithelial dysplasia (n = 27), and early gastric adenocarcinoma (n = 16). Immunohistochemistry was used to determine expression of MGMT and RASSF1A protein. All 20 histologically normal gastric biopsy specimens were methylation-free for all 5 genes. Aberrant hypermethylation of RASSF1A was not detected in any case from intestinal metaplasia to early gastric adenocarcinoma. The methylation rate of the other 4 genes increased with the histological progression from intestinal metaplasia to gastric epithelial dysplasia, to early gastric adenocarcinoma. Methylation was detected in 28.6% of intestinal metaplasia (4/14), in 77.8% of gastric epithelial dysplasia (21/27), and in 87.5% of early gastric adenocarcinoma (14/16). The average number of methylated genes in intestinal metaplasia, gastric epithelial dysplasia, and early gastric adenocarcinoma was 0.43, 1.3, and 1.8, respectively. Concurrent methylation in 3 or more genes was found in 7.1% of intestinal metaplasia, 11.1% of gastric epithelial dysplasia, and 31.3% of early gastric adenocarcinoma. No correlation was found between hypermethylation and other clinicopathologic parameters such as age, sex, Helicobacter pylori infection, and location of lesions. However, we observed a significant association between hypermethylation of p16 and MGMT and elevated serum carcinoembryonic antigen level. No reduction or loss of RASSF1A expression was observed in our study. Weak or loss of MGMT expression was found in 20 lesions and was significantly associated with promoter hypermethylation (P < .01). Our results suggest that promoter hypermethylation of the p16, Runx3, MGMT, and DAPK genes may play an important role in the pathogenesis of gastric precancerous lesions and early gastric adenocarcinoma. Hypermethylation and inactivation of RASSF1A, however, could be a later event in malignant transformation. Further studies are warranted to determine whether the presence of promoter hypermethylation in gastric precancerous lesions is associated with higher risk of subsequent cancer development and how to interrupt the malignant transition from intestinal metaplasia and gastric epithelial dysplasia to early gastric adenocarcinoma by developing some gene-targeting therapies that may reverse aberrant methylation.     

Increased expression of sonic hedgehog and altered methylation of its promoter region in gastric cancer and its related lesions.

The hedgehog (Hh) signaling pathway plays an important role in foregut development, and its activity is increased in various tumors, including those of the digestive tract. Our objective in the present study was to determine the pattern and extent of Sonic hedgehog (Shh) expression in gastric cancer and related lesions as well as the methylation status of its promoter region, in an attempt to clarify the regulatory mechanism of Shh expression. A total of 237 gastric cancers and related lesions (89 carcinomas, 22 high-grade dysplasia, 21 low-grade dysplasia, 47 intestinal metaplasia, 38 chronic gastritis, and 20 normal epithelia) were subjected to immunohistochemical analysis with the Shh monoclonal antibody. The methylation status of Shh was determined by methylation-specific PCR (MS PCR), involving bisulfate treatment of DNA from 150 tissues followed by amplification using specific primer pairs designed by our group. Shh was completely absent in the upper part of normal gastric epithelia (gastric pit cells), and no significant differences were observed among the lower parts of normal epithelia, chronic gastritis, and intestinal metaplasia. However, Shh expression was significantly elevated in neoplastic lesions, such as carcinoma and high low-grade dysplasia, compared to non-neoplastic lesions. In carcinomas, Shh expression was associated with clinical stage, direct tumor invasion, and differentiation of tumor cells. Methylation of the Shh promoter region was frequent in normal gastric pit cells (11/18, 61.1%), but very rare in gastritis (0/18), intestinal metaplasia (0/19), dysplasia (0/10), and carcinoma (1/63, 1.6%), and correlated significantly with expression (P<0.001). Our results suggested that the increased and constitutive Shh expression is implicated in gastric carcinogenesis, and that promoter methylation may be an important regulatory mechanism of Shh expression.     

Histone deacetylase 3 inhibits expression of PUMA in gastric cancer cells

During cancer development, tumor suppressor genes were silenced by promoter methylation or histone deacetylation. Histone deacetylases (HDACs) are important to maintain histone deacetylation. HDAC inhibitors (HDACis) were thus proposed as a new therapeutic approach to cancer. The current study aims to understand the effect and molecular mechanisms of HDACis on gastric cancer cells. Trichostatin A (TSA) significantly inhibited the growth of gastric cancer cells by inducing apoptosis. Gene profiling results showed PUMA (p53 upregulated modulator of apoptosis) as one of 122 genes upregulated in TSA-treated gastric cancer cells. PUMA was downregulated in gastric cancer cell lines and primary gastric carcinoma tissues. Patients with low PUMA expression had significant decreases in overall survival (HR, 2.04; p?=?0.047). Ectopic PUMA expression inhibited the growth of gastric cancer cells while PUMA depletion promoted cellular growth. The knockdown of HDAC3 but not other HDACs upregulated PUMA expression. HDAC3 could bind to PUMA promoter, which was abrogated after TSA treatment. In contrast to TSA and SB, HDAC3 siRNA failed to upregulate p53 expression but promoted the interaction of p53 with PUMA promoter. In summary, proapoptotic PUMA was downregulated in gastric cancer and its mRNA expression level is a valuable prognosis factor for gastric cancer. HDAC3 is important to downregulate PUMA expression in gastric cancer and HDACis, like TSA, promoted PUMA expression through stabilizing p53 in addition to HDAC3 inhibition. In combination with chemotherapy, targeting HDAC3 might be a promising strategy to induce apoptosis of gastric cancer cells.     

Prognostic significance of E-cadherin/catenin complex expression in gastric cancer

Abnormal expression of E-cadherin/catenin complex in cancer has been associated with poor differentiation and acquisition of invasiveness, suggesting a possible role of this protein as an invasion suppressor. In this study, we conducted an immunohistochemical investigation of all components of the E-cadherin/catenin complex in 65 gastric cancer patients. Abnormal expression of E-cadherin and, alpha- and gamma-catenin occurred more frequently in diffuse than in intestinal type of gastric cancer, and correlated with poor differentiation. Abnormal expression of E-cadherin and beta-catenin correlated with poor survival. Abnormal expression of all four components of the complex was associated with poorly differentiated and diffuse-type carcinoma, and poor survival. In the multivariate analysis, abnormal expression of the E-cadherin/catenin complex was not an independent prognostic factor. These results suggest that the E-cadherin/catenin complex may be a useful marker of differentiation and prognosis in gastric cancer. Further studies are warranted to clarify the impact of the E-cadherin/catenin complex on prognostic factor of gastric cancer.     

Molecular analysis of primary gastric cancer, corresponding xenografts, and 2 novel gastric carcinoma cell lines reveals novel alterations in gastric carcinogenesis

We report the molecular characterization of 8 primary gastric carcinomas, corresponding xenografts, and 2 novel gastric carcinoma cell lines. We compared the tumors and cell lines, with respect to histology, immunohistochemistry, copy number, and hypermethylation of up to 38 genes using methylation-specific multiplex ligation-dependent probe amplification, and TP53 and CDH1 mutation analysis where relevant. The primary tumors and xenografts were histologically comparable and shared expression of 11 of 14 immunohistochemical markers (E-cadherin, beta-catenin, COX-2, p53, p16, TFF1, cyclin E, MLH1, SMAD4, p27, KLK3, CASR, CHFR, and DAPK1). Gains of CASR, DAPK1, and KLK3--not yet described in gastric cancer--were present in the primary tumors, xenografts, and cell lines. The most prominent losses occurred at CDKN2A (p16), CDKN2B (p15), CDKN1B (p27/KIP1), and ATM. Except for ATM, these losses were found only in the cell line or xenograft, suggesting an association with tumor progression. However, examination of p16 and p27 in 174 gastric cancers using tissue microarrays revealed no significant correlation with tumor stage or lymph node status. Further losses and hypermethylation were detected for MLH1, CHFR, RASSF1, and ESR, and were also seen in primary tumors. Loss of CHFR expression correlated significantly with the diffuse phenotype. Interestingly, we found the highest rate of methylation in primary tumors which gave rise to cell lines. In addition, both cell lines harbored mutations in CDH1, encoding E-cadherin. Xenografts and gastric cancer cell lines remain an invaluable research tool in the uncovering of the multistep progression of cancer. The frequent gains, losses, and hypermethylation reported in this study indicate that the involved genes or chromosomal regions may be relevant to gastric carcinogenesis.     

Mechanisms and sequelae of E-cadherin silencing in hereditary diffuse gastric cancer

Around 25-40% of cases of hereditary diffuse gastric cancer (HDGC) are caused by heterozygous E-cadherin (CDH1) germline mutations. The mechanisms for loss of the second allele still remain unclear. The aims of this study were to elucidate mechanisms for somatic inactivation of the wild-type CDH1 allele and to seek evidence for cadherin switching. Archival tumour material was analysed from 16 patients with CDH1 germline mutations and seven patients fulfilling HDGC criteria without CDH1 germline mutations. The 16 CDH1 exons were sequenced. E-cadherin promoter methylation was analysed by bisulphite sequencing and pyrosequencing and allele specificity was determined using polymorphic loci. Loss of heterozygosity was analysed using microsatellite markers. Cadherin expression levels were determined by real-time RT-PCR and immunohistochemistry. Six of 16 individuals with germline mutations had at least one second hit mechanism. Two exonic mutations (exon 9 truncating, exon 3 missense) and four intronic mutations which may affect splicing were identified. Tumours from 4/16 individuals had promoter hypermethylation that was restricted to the A allele haplotype in three cases. E-cadherin loss (mRNA and protein) generally correlated with identification of a second hit. In cases without germline E-cadherin mutations there was no evidence for somatic mutation or significant promoter methylation. P-cadherin (>25% cells) was expressed in 7/13 (54%) and 4/5 (80%) with and without germline CDH1 mutations, respectively, independent of complete E-cadherin loss. Overall, inactivation of the second CDH1 allele occurs by mutation and methylation events. Methylation is commonly allele-specific and is uncommon without germline mutations. P-cadherin over-expression commonly occurs in individuals with diffuse type gastric cancer.     

p53 mutations and microsatellite instabilities in the subtype of intestinal metaplasia of the stomach

To investigate the potential implication of the subtype of intestinal metaplasia in the progression to the gastric carcinoma, we analyzed the mutations of the p53 gene and microsatellite instability (MSI) both in the complete type (type I) and in the sulphomucin-secreting incomplete type (type III) intestinal metaplasia located adjacent to the gastric carcinoma. p53 mutations were observed in 13.3% of type I, in 6.6% of type III intestinal metaplasia, and in 40% of gastric carcinoma. The difference between p53 mutations observed in type I and type III intestinal metaplasia was not statistically significant. No identical mutation of the p53 gene was found in the intestinal metaplasia and carcinoma specimens from the patients. There was no case of intestinal metaplasia showing MSI. In gastric carcinomas, MSI was observed in six cases (40%). The cases harboring BAT-26 instability did not have the mutation of the p53 gene. These data suggest that intestinal metaplasia adjacent to gastric carcinoma, irrespective of its subtype, do not have the genetic alterations as showing in their carcinoma tissues.     

Molecular characterization of undifferentiated-type gastric carcinoma

As the great majority of gastric cancers develop histologically differentiated, and a significant proportion of differentiated-type carcinomas progress to become undifferentiated, both histological types are likely to share several common genetic abnormalities, such as p53 mutations at advanced stages. However, a subset of gastric cancers develop as undifferentiated carcinomas, including signet-ring cell carcinoma and poorly differentiated adenocarcinoma, and the molecular pathogenesis of this tumor type remains largely unknown. To characterize the molecular features of undifferentiated-type gastric carcinomas that developed as undifferentiated-type, we examined for p53, APC, and epithelial (E)-cadherin gene mutations, microsatellite alterations including loss of heterozygosity (LOH) and microsatellite instability (MSI), and hypermethylation of the E-cadherin gene promoter in 26 early undifferentiated gastric carcinomas, consisting of 14 signet-ring cell carcinomas and 12 poorly differentiated adenocarcinomas. E-cadherin expression was evaluated immunohistochemically. p53 mutations were detected in only one poorly differentiated adenocarcinoma sample (3.8%; 1/26), whereas no APC or E-cadherin mutations were found. LOH was present only at D8S261 on the short arm of chromosome 8 in 2 of 14 (14%) informative tumors, both of which were poorly differentiated adenocarcinomas, and MSI was not observed in any of the tumors. No signet-ring cell carcinomas have been found to carry gene mutations or microsatellite alterations. In contrast, hypermethylation of the E-cadherin promoter occurred in 69% (18/26) of the tumors; 57% (8/14) of signet-ring cell carcinomas, and 83% (10/12) of poorly differentiated adenocarcinomas, and was significantly associated with loss or reduced expression of E-cadherin. Thus, whereas tumor suppressor gene mutation, LOH, and MSI were less common in undifferentiated-type early gastric carcinomas, epigenetic inactivation of E-cadherin via promoter hypermethylation may be an early critical event in the development of undifferentiated tumors.     

Expression of Lewis antigens and their precursors in gastric mucosa: relationship with Helicobacter pylori infection and gastric carcinogenesis

Lewis (Le)-associated antigens are carbohydrates that are related biochemically to the ABO blood groups, and may have a role in Helicobacter pylori adherence. To evaluate their relationship to clinicopathological outcomes, gastric Le expression, including type 1 precursor, type 1 H, Le(a), Le(b), Le(x), Le(y) and sialylated Le(a) (CA19-9), was evaluated immunohistochemically in 233 gastric biopsy specimens obtained at routine gastroscopy. Expression was also investigated in gastric tissues showing chronic gastritis, intestinal metaplasia, and carcinoma from 42 patients with gastric cancer. A polymerase chain reaction was performed for H. pylori and the bacterial babA2 gene. We identified type 1 precursor expression in 34.3%, type 1 H in 55.8%, Le(a) in 44.2%, Le(b) in 82.0%, Le(x) in 44.2%, Le(y) 56.7%, and CA19-9 in 16.3% of the 233 gastric biopsy specimens. Expression of type 1 H, Le(b), and CA19-9 was significantly associated with H. pylori infection and histological features (p < 0.05), and expression of type 1 H was an independent predictive factor for H. pylori infection by multivariate logistic regression (p = 0.020). Positivity for the babA2 genotype correlated significantly with H. pylori infection and type 1 H expression in gastric biopsy specimens (p < 0.05). The babA2 genotype was more frequent in gastric mucosa from the gastric cancer patients than in gastric biopsy specimens from routine gastroscopy (p = 0.009). In the 42 gastric cancer patients, the frequency of type 1 precursor, Le(a), and Le(x) expression was significantly higher in intestinal metaplasia and carcinoma than in chronic gastritis (p < 0.05), but the frequency of type 1 H and Le(b) expression was significantly lower in intestinal metaplasia and carcinoma (p < 0.05). In conclusion, Le expression, especially that of type 1 H, was significantly associated with clinicopathological features. In gastric cancer patients, Le expression was altered in intestinal metaplasia and carcinoma in comparison with chronic gastritis.     

Lost expression of AT-rich interaction domain 1A in the gastric mucosa—A constituent of field cancerization in the stomach

Abnormalities of the AT-rich interaction domain 1A (ARID1A) occur in cancer tissues and precursors or premalignant lesions in various organs. To investigate the significance of ARID1A abnormalities in the early phase of cancer development in the stomach, we screened for ARID1A loss and p53 overexpression in glands in non-neoplastic gastric mucosa using immunohistochemistry. We tested 230 tissue blocks of 77 patients with gastric carcinoma, and in 10% of non-neoplastic mucosa we detected ARID1A-lost and in 3.7% p53-overexpressed foci. Loss of ARID1A expression occurred in the scales of several glands, which were morphologically characterized as authentic, pseudo-pyloric, or intestinal metaplastic glands devoid of dysplastic changes. In contrast, p53-overexpressed foci were detected in dysplastic intestinal metaplasia. In early gastric cancer cases (n = 46), ARID1A-lost foci were frequent in samples of patients with Epstein–Barr virus-associated gastric carcinoma (p = 0.037). Ultra-deep DNA sequencing of ARID1A-lost foci revealed frameshift and nonsense mutations in ARID1A. Mapping abnormal glands in the entire resected stomach of the three selected patients demonstrated that ARID1A-lost foci clustered with p53 abnormal glands. ARID1A-lost epithelial cells may develop clonal growth through the pathway, different from p53-abnormal intestinal metaplasia, and require one or more events to develop into an overt carcinoma, such as EBV infection.     

CDX2 expression is progressively decreased in human gastric intestinal metaplasia, dysplasia and cancer.

Intestinal metaplasia is a key event in multistep gastric carcinogenesis. CDX2, a master regulator of intestinal phenotype, was shown to play a tumor-suppressive role in colon cancer. However, it was reported to be expressed in nearly all gastric intestinal metaplasia and many gastric cancers. As CDX2 is differentially expressed in normal stomach and intestine, we sought to relate the CDX2 expression to gastrointestinal differentiation along gastric carcinogenesis. The expression of CDX2 protein in gastric intestinal metaplasia, dysplasia and cancer was examined and related to their gastrointestinal differentiation. CDX2 expression was significantly decreased in incomplete intestinal metaplasia, which expresses both gastric mucins (MUC5AC and MUC6) and intestinal mucin (MUC2), compared with complete intestinal metaplasia, which expresses intestinal mucin (MUC2) only. Although incomplete intestinal metaplasia morphologically resembles colon, its CDX2 expression was apparently lower than that in the normal colon. Moreover, CDX2 expression was progressively reduced in gastric dysplasia and cancer. The CDX2 expression in gastric cancer was also inversely correlated with the expression of gastric mucins. As incomplete intestinal metaplasia is associated with higher risk of gastric cancer, its lower CDX2 expression compared with that in complete intestinal metaplasia and normal colon epithelium resolved the current contradiction between the tumor-suppressive role of CDX2 in the colon and the high prevalence of CDX2 in intestinal metaplasia. Further decrease of CDX2 expression in gastric dysplasia and cancer suggests that CDX2 plays a similar anticarcinogenic role in intestinal metaplasia as it does in colon. Intestinal metaplasia or dysplasia with low expression of CDX2 may serve as predictive markers for gastric cancer.     

CDH1基因启动子甲基化在上皮性卵巢癌转移方面的研究

目的探讨CDH1基因启动子甲基化对上皮性卵巢癌转移的影响。方法采用免疫组织化学方法检测38例正常卵巢上皮和80例上皮性卵巢癌组织中E-钙黏附素（E-cadherin）表达;应用甲基化特异的PCR（MSP）检测上述组织中CDH1基因启动子区甲基化;应用5-氮-2＇-脱氧胞苷（5-aza-CdR）使SKOV3细胞去甲基化,观察SKOV3细胞体外侵袭性的改变,并通过RT-PCR检测CDH1基因的改变。结果E-cadherin在正常卵巢组织中表达明显高于上皮性卵巢癌（P〈0．05）。34例CDH1基因启动子区甲基化全部出现在卵巢癌组织中,有淋巴结转移组织中甲基化明显高于无淋巴结转移者（P〈0．05）,而CDH1基因启动子区有甲基化的卵巢癌组织中E-cadherin表达明显降低（P〈0．05）。经5-Aza-CdR处理后的SKOV3细胞体外侵袭性降低（P〈0．01）,CDH1基因的表达明显上调（P〈0．01）。结论E-cadherin表达降低与上皮性卵巢癌转移关系密切,CDH1基因启动子区甲基化可能是导致E-cadherin蛋白表达减低的重要原因之一,因此启动子区甲基化与上皮性卵巢癌转移有关。     

Implication of Reprimo and hMLH1 gene methylation in early diagnosis of gastric carcinoma

DNA methylation has been recently recognized as a novel tumor marker. This study investigated the methylation status of Reprimo and hMLH1 gene in both plasma and tissue samples from gastric cancer patients, in an attempt to investigate their diagnostic implications in gastric cancer. A total of 180 tissue and plasma samples (including 50 cases of gastric cancer, 50 dysplasia, 50 chronic atrophic gastritis with intestinal metaplasia and 30 normal controls) were collected for detecting DNA methylation status of Reprimo and hMLH1 genes using MSP method. Tissue protein expression levels were further tested by immunohistochemical (IHC) staining. The positive rate of DNA methylation rate was, in ascending sequence, gastritis tissue, dysplasia tissue and gastric carcinoma tissue. All those tissues had significantly elevated DNA methylation level compared to normal group (P < 0.05). Expression level of Reprimo and hMLH1 proteins were, however, decreased in pathological tissues compared to normal ones (P < 0.05). A significantly negative relationship existed between protein level and promoter region methylation level. The DNA methylation occurred in promoter regions of both Reprimo and hMLH1 genes depressed the protein expression, and may participate in the occurrence and progression and gastric cancer. The combined assay of serum Reprimo and hMLH1 DNA methylation levels thus had critical importance in the early diagnosis and gastric cancer.     

Molecular characteristics of eight gastric cancer cell lines established in Japan

Molecular characterization of eight gastric cancer cell lines established in Japan are summarized according to the genetic and epigenetic alterations and growth factor status. TMK-1 poorly differentiated adenocarcinoma cell line harbors mutant p53 tumor suppressor gene and rearrangement of p15MTS2. MKN-1 adenosquamous carcinoma line with mutant p53 reveals silencing of E-cadherin by promoter CpG hypermethylation. MKN-7 well-differentiated adenocarcinoma cell line has amplification of c-erbB2 oncogene and cyclin E gene. MKN-28 well-differentiated adenocarcinoma cell line reveals mutations in p53 and APC tumor suppressor genes and silencing of CD44. The MKN-45 poorly differentiated adenocarcinoma cell line with wild-type p53 is characterized by homozygous deletion of p16CDKN2/MTS1/INK4A and p15MTS2, amplification of c-met oncogene and promoter mutation of E-cadherin. MKN-74 derived from moderately differentiated tubular adenocarcinoma has wild-type p53. KATO-III signet ring cell carcinoma line has genomic deletion of p53, amplification of K-sam and c-met oncogene and mutation of E-cadherin. HSC-39 signet ring cell carcinoma cell line harboring p53 missense mutation has homozygous deletion of p16CDKN2/MTS1/INK4A and p15MTS2, amplifications of c-myc, c-met, K-sam and CD44 gene and mutation in beta-catenin gene.     

Molecular pathology of gastric carcinoma

Gastric carcinoma (GC) is a biologically heterogeneous disease involving numerous genetic and epigenetic alterations. A very small proportion of GCs can be caused by a specific germ-line mutation of the E-cadherin gene (CDH1). Sporadic GC is developed through multistep processes that begin with Helicobacter pylori-induced atrophic gastritis. Epstein-Barr virus is another infectious cause of GC, and the above two infection-associated GCs are characterized by global CpG island methylation in the promoter region of cancer-related genes. Mutations of tumor protein p53 (TP53) and β-catenin (CTNNB1) genes occur early in the development of GC and contribute to gastric carcinogenesis. Furthermore, significant numbers of GCs show loss of Runx3 due to hemizygous deletion and hypermethylation of the promoter region. Aberrant Cdx2 expression has been shown in precancerous lesions as well as GC. However, it remains unclear whether Cdx2 plays an oncogenic role in gastric carcinogenesis. GC with microsatellite instability is also a well-defined subset exhibiting distinctive clinicopathologic features. Targeted therapy against GC with ERBB2 amplification recently improved the prognosis of patients with advanced GC. In addition, epigenetic changes in GC could be attractive targets for cancer treatment with modulators. A genome-wide search has been undertaken to identify novel methylation-silenced genes in GC, which will help us understand the overall molecular features of GC and further provide novel opportunities in the treatment of GC.     

Loss of E-cadherin expression in early gastric cancer

AIMS: Reduction or loss of E-cadherin expression was examined in early gastric carcinomas and precursor lesions with the following aims: (1) to assess overall E-cadherin expression in various stages of gastric carcinogenesis; (2) to correlate E-cadherin expression with the Lauren type, the grade of differentiation and the type of growth pattern of the tumours; and (3) to correlate E-cadherin expression with lymph node metastasis and overall prognosis. METHODS AND RESULTS: Forty-five paraffin-embedded gastrectomy specimens from early carcinomas were examined for the presence of various precursor lesions. The Lauren type, the grade of differentiation and the type of growth pattern were reassessed for all early carcinomas. E-cadherin expression was examined using antibody HECD-1. Whereas E-cadherin was strongly and evenly expressed in the gastric foveolar epithelium, intestinal metaplasia and early gastric carcinomas showed a lower expression. A significant difference in E-cadherin expression was found between the Lauren types (P < 0.0001). Moreover, an inverse correlation was found between E-cadherin expression and histological grade (P < 0.0001). Neither a difference in E-cadherin expression between the various growth types nor an association with lymph node metastasis and overall prognosis was found. CONCLUSIONS: The Lauren types differ in E-cadherin expression, although reduced E-cadherin expression in all probability rather reflects poor differentiation than a diffuse growth pattern 'genotype'. Moreover, E-cadherin expression does not underlie the difference in biological behaviour of early carcinomas with different types of growth pattern. Finally, E-cadherin expression is not associated with lymph node status and 5-year survival rate, at least not in early gastric carcinomas.     

Diagnostic p53 expression in gastric endoscopic mucosal resection.

Endoscopic mucosal resection (EMR) has been standardized for the treatment of intestinal type of intramucosal gastric carcinomas, and careful histological examination of the resected specimen is important for further treatment. To evaluate the diagnostic utility of p53 expression in gastric EMR samples, using immunohistochemical staining, we examined 24 gastric carcinomas (22 intestinal types and two diffuse types) and 20 adenomas removed by EMR. Intestinal type of adenocarcinomas revealed strong p53 expression in 13 cases (59%), weak in four cases (18%), and negative in five cases (23%). Resection margins of 11 carcinomas were involved in the carcinoma cells, which showed the same p53 expression pattern with main carcinoma cells. Squeezed carcinoma cells, remaining in resection margins, were definitely identified by strong p53 expression in seven cases of which the main tumor strongly expressed p53. Microscopic in situ carcinoma could be easily detected in p53 immunostaining. Multifocal involvement and submucosal invasion of carcinomas could be demarcated easily and definitely by strong p53 expression of carcinoma cells. All adenomas showed diffuse weak p53 expression. The difference of p53 expression (p< 0.001) could be used as a differential diagnosis between adenomas and carcinomas. According to these results, we propose that for careful histological examination in hospital diagnosis, both histological evaluation and p53 immunostaining are important diagnostic parameters in EMR samples of the intestinal type of gastric carcinomas.