Molecular characterization of undifferentiated-type gastric carcinoma

Optimal Surveillance of Metachronous Gastric Lesion after Endoscopic Resection of Early Gastric Cancer

Endoscopic resection (ER)-a minimal invasive procedure, compared to surgical gastrectomy, with the advantage of preserving the entire stomach and maintaining the patient's quality of life-is a widely used curative treatment for early gastric cancers (EGCs). Despite its advantages, such as the preservation of the whole stomach, a large area of the gastric mucosa with histologic changes such as atrophy and intestinal metaplasia remains after ER, and so does the risk of metachronous gastric cancers (MGCs). Therefore, regular surveillance endoscopy after curative ER of EGCs is important so that MGCs are detected early and so minimally invasive ER remains a treatment option. To date, the optimal interval for surveillance endoscopy after curative ER of EGCs has not been established. Therefore, this review summarizes the results of the published studies on this topic with the aim of establishing the optimal surveillance interval for early identification of MGCs. Based on my review, the median timing of MGC occurrence is within 3 years, and reports suggest biannual endoscopy during the first 3 years; however, the evidence suggests that individual patient characteristics may influence the risk of MGCs. Therefore, stratified endoscopic strategies for surveillance based on patient characteristics, such as age, family history of gastric cancer, synchronous gastric lesions, and corpus intestinal metaplasia, should be applied.

Epigenetic reprogramming in gastrointestinal cancer: biology and translational perspectives

Gastrointestinal tumors, the second leading cause of human mortality, are characterized by their association with inflammation. Currently, progress in the early diagnosis and effective treatment of gastrointestinal tumors is limited. Recent whole-genome analyses have underscored their profound heterogeneity and extensive genetic and epigenetic reprogramming. Epigenetic reprogramming pertains to dynamic and hereditable alterations in epigenetic patterns, devoid of concurrent modifications in the underlying DNA sequence. Common epigenetic modifications encompass DNA methylation, histone modifications, noncoding RNA, RNA modifications, and chromatin remodeling. These modifications possess the potential to invoke or suppress a multitude of genes associated with cancer, thereby governing the establishment of chromatin configurations characterized by diverse levels of accessibility. This intricate interplay assumes a pivotal and indispensable role in governing the commencement and advancement of gastrointestinal cancer. This article focuses on the impact of epigenetic reprogramming in the initiation and progression of gastric cancer, esophageal cancer, and colorectal cancer, as well as other uncommon gastrointestinal tumors. We elucidate the epigenetic landscape of gastrointestinal tumors, encompassing DNA methylation, histone modifications, chromatin remodeling, and their interrelationships. Besides, this review summarizes the potential diagnostic, therapeutic, and prognostic targets in epigenetic reprogramming, with the aim of assisting clinical treatment strategies.

Histogenetic insights and genetic landscape of fibromatosis-like undifferentiated gastric carcinoma: a focused study

BACKGROUND

The aim of this study was to elucidate the histogenesis and genetic underpinnings of fibromatosis-like undifferentiated gastric carcinoma (FLUGC), a rare pathological entity.

METHOD

Through a detailed analysis of seven cases, including histopathological evaluation, CTNNB1 gene mutation screening, human epidermal growth factor receptor 2 (HER2) protein level quantification, and HER2 gene amplification assessment to identify the pathological and molecular characteristics of FLUGC.

RESULTS

Of the seven patients in this study, five were male and two were female (age: 39-73 years). Four patients presented with lesions in the gastric antrum and three had lesions in the lateral curvature of the stomach. Histopathologically, over 90% of the tumor consisted of aggressive fibromatosis-like tissue, including proliferating spindle fibroblasts and myofibroblasts and varying amounts of collagenous fibrous tissues. Undifferentiated cancer cells, accounting for less than 10%, were dispersed among the aggressive fibromatosis-like tissues. These cells were characterized by their small size and were relatively sparse without glandular ducts or nested mass-like structures. Immunophenotyping results showed positive expression of CKpan, CDX2, villin, and p53 in undifferentiated cancer cells; positive expression of vimentin in aggressive fibromatosis-like tissue; positive cytoplasmic expression of β-catenin; and focal cytoplasmic positive expression of smooth muscle actin (SMA). Genetic analysis did not reveal any mutations in the CTNNB1 gene test, nor was there amplification in the HER2 gene fluorescence in situ hybridization (FISH) test. Additionally, the Epstein-Barr encoding region (EBER) of in situ hybridization was negative; and the mismatch repair (MMR) protein was positive. Programmed cell death-1 (PD-1) was < 1-5%; programmed cell death ligand 1 (PD-L1): TPS = 1-4%, CPS = 3-8.

CONCLUSION

The study highlights the significance of CTNNB1, HER2, EBER, and MMR as pivotal genetic markers in FLUGC, underscoring their relevance for diagnosis and clinical management. The rarity and distinct pathological features of FLUGC emphasize the importance of accurate diagnosis to prevent underdiagnosis or misdiagnosis and to raise awareness within the medical community.

Signet ring cell cancer of stomach and gastro-esophageal junction: molecular alterations, stage-stratified treatment approaches, and future challenges

Purpose

There has been an increase in the incidence of signet ring cell cancer (SRCC) of the stomach and gastro-esophageal junction (GEJ). The multistage carcinogenesis involving genetic and epigenetic aberrations may have a major role in the increasing incidence of SRCC. Although there are numerous studies on the prognostic value of SRCC, they are markedly inconsistent in their results, making it impossible to draw any meaningful conclusions. We aimed to examine the available evidences on molecular alterations and stage-stratified treatment approaches in SRCC of the stomach and GEJ.

Methods

A systematic search was carried out in PubMed. Studies available in English related to SRCC of stomach and gastro-esophageal junction were identified and evaluated.

Results

This study reviewed the current evidence and provided an insight into the molecular alterations, stage-stratified treatment approaches, and future challenges in the management of SRCC of the stomach and GEJ. Specific therapeutic strategies and personalized multimodal treatment have been recommended based on the tumor characteristics of SRCC.

Conclusion

Multistage carcinogenesis involving genetic and epigenetic aberrations in SRCC is interlinked with stage-dependent prognosis. Specific therapeutic strategy and personalized multimodal treatment should be followed based on the tumor characteristics of SRCC. Endoscopic resection, radical surgery, and perioperative chemotherapy should be offered in carefully selected patients based on stage and prognostic stratification. Future studies in genetic and molecular analysis, histopathological classification, and options of multimodality treatment will improve the prognosis and oncological outcomes in SRCC of gastric and GEJ.

Clinicopathological features and differential diagnosis of gastrofibromatosis-like undifferentiated carcinoma

Objective

To study the clinicopathological features and differential diagnosis of gastrofibromatosis-like undifferentiated carcinoma (GFLUC).

Methods

Three patients with GFLUC underwent histological and immunophenotypic analyses and fluorescence in situ hybridization to detect human epidermal growth factor receptor (HER2) gene amplification.

Results

Among the three patients (2 male [36 and 44 years old], 1 female [58 years old]), two had lesions in the gastric body and one had lesions in the gastric antrum. Histological analysis revealed mixtures of aggressive fibromatosis and undifferentiated carcinoma in all three cases. Highly invasive fibromatous tissue, consisting of fibroblasts, proliferating myofibroblasts, and collagenous fibrous tissues, accounted for >90% of the tumor, with undifferentiated cancerous tissue accounting for <10% scattered in the gaps within the invasive fibromatous tissue, with no glandular ducts or nests. Immunophenotypic analysis showed that the undifferentiated cancerous cells were positive for pan-cytokeratin, CDX2, villin, and p53, while the cytoplasm of invasive fibromatous cells was positive for vimentin, β-catenin, and smooth muscle actin. No HER2 gene amplification was detected.

Conclusions

Unlike other gastric carcinomas, GFLUC shows specific histological, biological, and immunophenotypic characteristics.

Incidence of metachronous cancer after endoscopic submucosal dissection: a comparison between undifferentiated-type and differentiated-type early gastric cancer

BACKGROUND AND AIMS

Endoscopic submucosal dissection (ESD) has become an important and minimally invasive treatment for early gastric cancer (EGC) with a negligible risk of metastasis not only for differentiated-type (D-type) cancer but also for undifferentiated-type (UD-type) cancer. We aimed to investigate the incidence and characteristics of metachronous cancer after ESD for UD-type cancer, which has not yet been elucidated.

METHODS

In total, 175 patients who underwent ESD for UD-type EGC were enrolled. For comparison, 350 patients who underwent ESD for D-type EGC during the same period were randomly selected. These patients underwent a follow-up EGD annually. The median observation period was 6.0 years and 5.4 years, respectively.

RESULTS

The annual incidence of metachronous cancer after ESD for UD-type and D-type cancer was .9% and 5.3%, respectively. Among the patients who underwent ESD for UD-type cancer, 30.9% of patients were uninfected with Helicobacter pylori, whereas all patients who underwent ESD for D-type cancer were infected with H pylori. All patients who developed metachronous cancer were infected with H pylori. UD-type metachronous cancer developed more frequently in patients after ESD for UD-type cancer than after ESD for D-type cancer, and the curative resection rate of ESD was significantly lower in these cases.

CONCLUSIONS

Metachronous cancers developed only in H pylori-infected patients in this cohort. Although metachronous cancer incidence was significantly less frequent in patients after ESD for UD-type cancer, the curative resection rate of ESD was significantly lower. Routine surveillance should be conducted more carefully after ESD for UD-type cancer, especially in H pylori-infected patients.

Integrated clinicopathological and immunohistochemical analysis of gastric adenocarcinoma with hepatoid differentiation: an exploration of histogenesis, molecular characteristics, and prognostic markers

In addition to hepatoid adenocarcinoma (HAC), gastric adenocarcinoma with enteroblastic differentiation (GAED) and common adenocarcinoma (COM) could also show hepatoid differentiation, which presents a poor prognosis. To elucidate the histogenesis and development of gastric cancer with hepatoid differentiation, we identified 55 cases by histological morphology and a panel of markers, including α-fetoprotein (AFP), Glypican 3 (GPC3) and SALL4, then clinicopathological parameters, pathomorphological characteristics, mucin phenotypes, molecular features, Immunoscore and survival analysis were assessed. A mixture of three types (COM + GAED + HAC) was most commonly observed in the same case, and typical transitions between each histological subtype were frequently seen. Hyaline globule and pink amorphous substance were often present. HER2 was amplified in 21.8% of cases. All the tumors showed intestinal phenotype (69.1%) and mixed gastric/intestinal phenotype (30.9%) and were all defined to chromosomal instable (CIN)/genomically stable (GS) group. Considering that 83.6% cases presented TP53 gene mutation phenotype and 61.8% cases showed ≥10% aberrant E-cadherin expression, the precise molecule classification is ambiguous. Survival analysis showed that patients with high SALL4 expression, high preoperative serum AFP level, or low Immunoscore had a significantly poor overall survival (OS). Moreover, SALL4, HER2, and Immunoscore had an independent influence on OS. In conclusion, we suggest that the development of gastric adenocarcinoma with hepatoid differentiation might a continuously progressive profile: from intestinal-type COM adenocarcinoma to GAED and then HAC. CIN/GS subtypes might be where they belonged. SALL4, HER2, and Immunoscore may be potential therapeutic targets.

Association of APC gene promoter methylation and the risk of gastric cancer: A meta-analysis and bioinformatics study

BACKGROUND

The methylation status of the adenomatous polyposis coli (APC) promoter has been shown to be associated with the occurrence of gastric cancer, but this finding remains controversial. The aim of this study was to investigate the relationship between methylation of the APC gene promoter and gastric cancer.

METHODS

We searched the Web of Science, EMBASE, Medline, and Cochrane Central Register of Controlled Trials (CENTRAL) databases from the date of creation until August 1, 2019. According to the inclusion criteria, the relationship between the methylation status of the APC gene promoter and gastric cancer was investigated. The incidence of APC promoter methylation in the tissues or blood of patients with and without gastric cancer was compared. The results are expressed as the odds ratio (OR) and 95% confidence interval (CI). The pooled OR of each study was estimated using a fixed effects model or a random effects model to generate forest plots. We further validated the results using the MethHC database.

RESULTS

Eight studies (985 samples) were included. Our meta-analysis showed that the incidence of APC promoter methylation in patients with gastric cancer was higher than that of patients without gastric cancer (OR = 3.86, 95% CI 1.71-8.74, P = .001). Methylation of the APC promoter is associated with the incidence of gastric cancer, and it increases the risk of gastric cancer.

CONCLUSION

This study provides a new strategic direction for research on gastric cancer. Methylation of the APC promoter may be a potential biomarker for the diagnosis of gastric cancer, but the results of this work require further confirmation.

Deficiency of mismatch repair genes is less frequently observed in signet ring cell compared with non-signet ring cell gastric cancer

Signet ring cell (SRC) gastric cancer at advanced stage has poor prognosis. While a recent study reported nearly one-third of SRC cases contain tumors with deficient mismatch repair (MMR) genes, other studies in SRC have been inconclusive. To re-analyze the results, we performed immunohistochemical staining of MLH1, MSH2, MSH6 and PMS2 proteins in 38 SRC gastric tumors compared with 109 non-SRC (NSRC) tumors from 94 patients. In contrast to the previous study, all SRC gastric tumors normally expressed MMR proteins, whereas 22 of 109 of NSRC (20%) showed deficient MMR proteins. To reinforce our results, we referred to the Cancer Genome Atlas (TCGA) genomic database and found that only 6 (6%) of 99 samples with diffuse gastric tumors showed deficient MMR, whereas 64 (21%) of 304 in intestinal gastric tumors showed deficient MMR. Our results as well as the TCGA database indicated that MMR genes are infrequently inactivated in SRC gastric cancer. These findings indicate that SRC patients may not be the best candidates for immuno-oncology therapy.

Diagnostic and prognostic value of circulating tumor DNA in gastric cancer: a meta-analysis

BACKGROUND

Circulating tumor DNA (ctDNA) has offered a minimally invasive approach for detection and measurement of gastric cancer (GC). However, its diagnostic and prognostic value in gastric cancer still remains unclear.

RESULTS

A total of 16 studies comprising 1193 GC patients met our inclusion criteria. The pooled sensitivity and specificity were 0.62 (95% confidence intervals (CI) 0.59-0.65) and 0.95 (95% CI 0.93-0.96), respectively. The AUSROC (area under SROC) curve was 0.94 (95% CI 0.89-0.98). The results showed that the presence of certain ctDNA markers was associated with larger tumor size (OR: 0.26, 95% CI 0.11-0.61, p = 0.002), TNM stage (I + II/III + IV, OR: 0.11, 95% CI 0.07-0.17, p = 0.000), as well as H. pylori infection. (H.p negative/H.p positive, OR: 0.57, 95% CI 0.36-0.91, p = 0.018). Moreover, there was also a significant association between the presence of ctDNA and worse overall survival (HR 1.77, 95% CI 1.38-2.28, p < 0.001), as well as disease-free survival (HR 4.36, 95% CI 3.08-6.16, p < 0.001).

MATERIALS AND METHODS

Pubmed, Embase, Cochrane Library and Web of Science databases were searched for relating literature published up until November 30, 2016. Diagnostic accuracy variables were pooled by the Meta-Disc software. Engauge Digitizer and Stata software were applied for prognostic data extraction and analysis.

CONCLUSIONS

Our meta-analysis indicates the detection of certain ctDNA targets is significantly associated with poor prognosis of GC patients, with high specificity and relatively moderate sensitivity.

Mutational analysis of driver genes with tumor suppressive and oncogenic roles in gastric cancer

Gastric cancer (GC) is a complex disease with heterogeneous genetic mechanisms. Genomic mutational profiling of gastric cancer not only expands our knowledge about cancer progression at a fundamental genetic level, but also could provide guidance on new treatment decisions, currently based on tumor histology. The fact that precise medicine-based treatment is successful in a subset of tumors indicates the need for better identification of clinically related molecular tumor phenotypes, especially with regard to those driver mutations on tumor suppressor genes (TSGs) and oncogenes (ONGs). We surveyed 313 TSGs and 160 ONGs associated with 48 protein coding and 19 miRNA genes with both TSG and ONG roles. Using public cancer mutational profiles, we confirmed the dual roles of CDKN1A and CDKN1B. In addition to the widely recognized alterations, we identified another 82 frequently mutated genes in public gastric cancer cohort. In summary, these driver mutation profiles of individual GC will form the basis of personalized treatment of gastric cancer, leading to substantial therapeutic improvements.

Lymph Node Metastasis in Mucosal Gastric Cancer: Reappraisal of Expanded Indication of Endoscopic Submucosal Dissection

OBJECTIVE

To evaluate risk factors for lymph node (LN) metastasis in mucosal gastric cancer, particularly the effect of cellular differentiation, and implications for the indication of endoscopic submucosal dissection (ESD).

SUMMARY BACKGROUND DATA

The indication of ESD has been expanded to undifferentiated-type (UD-type) gastric cancer despite risk of LN metastasis.

METHODS

Patients who underwent radical gastrectomy for pT1a stage primary gastric adenocarcinoma between 2008 and 2012 were retrospectively analyzed. We evaluated risk factors of LN metastasis using univariate and multivariate analyses. Pathologic slides of primary tumor and metastatic LNs from LN positive patients were reviewed.

RESULTS

A total of 1003 mucosal gastric cancer patients were enrolled, and mean number of retrieved LNs was 35.5. Eighteen (1.8%) among them had LN metastasis: 2 of the 502 differentiated-type (D-type) patients and 16 of the 501 UD-type patients (0.4% vs 3.2%, P < 0.001). Type of cellular differentiation was a significant risk factor for LN metastasis in univariate and multivariate analyses. Of 216 UD-type patients satisfying the expanded indication of ESD, 5 patients (2.3%) showed LN metastasis. Despite more aggressive clinical features such as larger size of tumor and more LN metastasis, the UD-type cancer showed a less invasion into the muscularis mucosae layer than the D-type cancer.

CONCLUSIONS

Because UD-type cancer is a risk factor for LN metastasis in mucosal gastric cancer, ESD cannot be concluded to be a better option than surgery in all UD-type cancer patients. Redefinition of the expanded indication of ESD is required.

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.

Prognostic role of APC and RASSF1A promoter methylation status in cell free circulating DNA of operable gastric cancer patients

Gastric carcinogenesis is a multistep process including not only genetic mutations but also epigenetic alterations. The best known and more frequent epigenetic alteration is DNA methylation affecting tumor suppressor genes that may be involved in various carcinogenetic pathways. The aim of the present study was to investigate the methylation status of APC promoter 1A and RASSF1A promoter in cell free DNA of operable gastric cancer patients. Using methylation specific PCR, we examined the methylation status of APC promoter 1A and RASSF1A promoter in 73 blood samples obtained from patients with gastric cancer. APC and RASSF1A promoters were found to be methylated in 61 (83.6%) and 50 (68.5%) of the 73 gastric cancer samples examined, but in none of the healthy control samples (p < 0.001). A significant association between methylated RASSF1A promoter status and lymph node positivity was observed (p = 0.005). Additionally, a significant correlation between a methylated APC promoter and elevated CEA (p = 0.033) as well as CA-19.9 (p = 0.032) levels, was noticed. The Kaplan-Meier estimates of survival, significantly favored patients with a non-methylated APC promoter status (p = 0.008). No other significant correlations between APC and RASSF1A methylation status and different tumor variables examined was observed. Serum RASSF1A and APC promoter hypermethylation is a frequent epigenetic event in patients with early operable gastric cancer. The observed correlations between APC promoter methylation status and survival as well as between a hypermethylated RASSF1A promoter and nodal positivity may be indicative of a prognostic role for those genes in early operable gastric cancer. Additional studies, in a larger cohort of patients are required to further explore whether these findings could serve as potential molecular biomarkers of survival and/or response to specific treatments.

Methylation-mediated gene silencing as biomarkers of gastric cancer: A review

Despite a decline in the overall incidence of gastric cancer (GC), the disease remains the second most common cause of cancer-related death worldwide and is thus a significant global health problem. The best means of improving the survival of GC patients is to screen for and treat early lesions. However, GC is often diagnosed at an advanced stage and is associated with a poor prognosis. Current diagnostic and therapeutic strategies have not been successful in decreasing the global burden of the disease; therefore, the identification of reliable biomarkers for an early diagnosis, predictive markers of recurrence and survival and markers of drug sensitivity and/or resistance is urgently needed. The initiation and progression of GC depends not only on genetic alterations but also epigenetic changes, such as DNA methylation and histone modification. Aberrant DNA methylation is the most well-defined epigenetic change in human cancers and is associated with inappropriate gene silencing. Therefore, an increasing number of genes methylated at the promoter region have been targeted as possible biomarkers for different purposes, including early detection, classification, the assessment of the tumor prognosis, the development of therapeutic strategies and patient follow-up. This review article summarizes the current understanding and recent evidence regarding DNA methylation markers in GC with a focus on the clinical potential of these markers.

"Crawling-type" adenocarcinoma of the stomach: a distinct entity preceding poorly differentiated adenocarcinoma

BACKGROUND

Gastric "crawling-type" adenocarcinoma (CTAC) is a neoplasm histologically comprising irregularly fused glands with low-grade cellular atypia that tends to spread laterally in the mucosa. It is necessary to elucidate the clinicopathological characteristics of CTAC.

METHODS

We evaluated 25 CTACs-16 intramucosal (M-) and 9 submucosal invasive (SM-) cancers-clinicopathologically and immunohistochemically.

RESULTS

CTAC was most frequently located in the lesser curvature of the middle-third of the stomach. Macroscopically, 21 lesions were superficial-depressed and 4 were superficial-flat type. Histologically, all CTACs had cystic dilated glands and 16 lesions had focal signet-ring cells. All invasive areas of the SM-CTACs were occupied by poorly differentiated adenocarcinoma with an infiltrative growth pattern and abundant stroma. Fifteen CTACs were surrounded by mucosa with partial or no intestinal metaplasia. In the intramucosal area, 24 lesions were mixed phenotype with mucin and brush border immunoexpression. SM-CTAC was frequent in lesions with an intramucosal poorly differentiated component (PDC) greater than 10 mm in size (P = 0.041), and lymph node metastasis (LNM) was frequent in lesions with a PDC greater than 20 mm (P = 0.039). The frequency of an expanded pattern (Ki-67-positive cells occupying > 50 % of the mucosa) was higher in SM-CTAC than in M-CTAC (P = 0.027). p53 overexpression was not detected in the intramucosal areas of any of the lesions.

CONCLUSION

CTAC is a distinct subgroup of gastric adenocarcinoma in the early phase. A larger PDC and a Ki-67 expanded pattern were predictive of submucosal invasion or LNM.

The combined expression of metaplasia biomarkers predicts the prognosis of gastric cancer

BACKGROUND

Our previous study indicated that gene expression profiling of intestinal metaplasia (IM) or spasmolytic polypeptide-expressing metaplasia (SPEM) can identify useful prognostic markers of early-stage gastric cancer, and seven metaplasia biomarkers (MUC13, CDH17, OLFM4, KRT20, LGALS4, MUC5AC, and REG4) were selectively expressed in 17-50% of gastric cancer tissues. We investigated whether the combined expression of these metaplasia biomarkers could predict the prognosis of advanced stage gastric cancer.

METHODS

The expression of seven metaplasia biomarkers was evaluated immunohistochemically using tissue microarrays comprised of 450 gastric cancer patients. The clinicopathologic correlations and the prognostic impact were analyzed according to the expression of multiple biomarkers.

RESULTS

MUC13, CDH17, LGALS4, and REG4 were significant prognostic biomarkers in univariate analysis. No expression of four markers was found in 56 cases (14.2%); 1 marker was seen in 67 cases (17%), 2 in 106 cases (27%), 3 in 101 cases (25.7%), and 4 in 63 cases (16%). Patients in which two or fewer proteins were expressed (group B) showed younger age, undifferentiated or diffuse type cancer, larger tumor size, larger number of metastatic lymph nodes, and more advanced stage than those in which three or more proteins were expressed (group A). In undifferentiated or stage II/III gastric cancer, the prognosis of group B was significantly poorer than that of group A by multivariate analysis.

CONCLUSIONS

The combined loss of expression of multiple metaplasia biomarkers is considered an independent prognostic indicator in undifferentiated or stage II/III gastric cancer.

Epigenetic regulation of cellular adhesion in cancer

Epigenetics describes the development and maintenance of stable heritable gene expression patterns, which allow cells to show different phenotypes despite of a commonly shared genetic code. The increasing knowledge in this field during the last decades reveals its importance for many physiological processes like differentiation, embryogenesis and parental imprinting, but also for some diseases such as cancer. Recent data have shown that the complexity of carcinogenesis can no longer be explained solely on the basis of genetic changes, but epigenomic alterations such as changes of the DNA methylation pattern and/or post-translational histone modifications and changes of microRNA expression need to be equally considered. Such epigenetic alterations may cause permanent changes in gene expression patterns and may therefore essentially contribute to some of the known phenotypic characteristics of cancer cells like the loss of growth control, altered intercellular communication and enhanced motility. The two latter may essentially be associated with the downregulation of cellular adhesion molecules, which may therefore be relevant in the context of cancer invasiveness and prognosis. The targeted modification of the epigenome may therefore open new horizons within the increasingly important field of epigenetic therapeutics-particularly in view of the regulation of cellular adhesion with particular attention to tumor cell invasion and metastasis.

Expression and significance of p53 and mdm2 in atypical intestinal metaplasia and gastric carcinoma

Subtypes of intestinal metaplasia may have different manifestations in the carcinogenesis of gastric mucosa. The present study aimed to investigate expression of murine double minute gene 2 (mdm2) in atypical intestinal metaplasia (AIM) and its relationship to gastric carcinoma. Intestinal metaplasia (IM) specimens were obtained from 58 cases. Using a novel classification of IM, the specimens were classified according to morphological changes exhibited in the gastric mucosa; specifically, atypical intestinal metaplasia (AIM) and simple intestinal metaplasia (SIM). The gatric carcinoma specimens were then compared with types I, II and III IM based on different substances present in the mucous. Envision immunohistochemical technique was applied to the detection of the expression of p53 and mdm2 in 58 IM and 30 gastric carcinoma cases. Expression of both p53 and mdm2 proteins was found to be higher in gastric carcinomas (p53, 56.67%, 17/30 and mdm2, 53.33%, 16/30) and AIM (p53, 51.85%, 14/27 and mdm2, 51.85%, 14/27) as compared to SIM (p53, 25.81%, 8/31 and mdm2, 19.35%, 6/31) (P<0.05). A similar pattern of expression of mdm2 protein was found in type I (36.84%, 7/19), type II (38.46%, 10/26) and type III (23.08%, 3/13) IM and gastric carcinoma (53.33%, 16/30). p53 expression was higher in gastric carcinoma (56.67%) compared to type I IM (26.32%) (P<0.05). However, no differences were evident among type II (42.31%, 11/26), type III (46.15%, 6/13) IM and gastric carcinoma. AIM may reveal the precancerous nature of gastric carcinoma more clearly than SIM or the conventional IM subtypes. Additionally, AIM may be involved as a preneoplastic lesion and therefore be an effective indicator in the clinical follow-up of gastric carcinoma patients.

Clinicopathological Features of Upper Third Gastric Cancer during a 21-Year Period (Single Center Analysis)

Purpose

The aim of this study was to determine proportions of upper third gastric cancer (UTG) among all gastric cancers and analyze clinicopathological features of the disease.

Materials and Methods

The medical records of 12,300 patients who underwent gastric surgery between 1986 and 2006 at Seoul National University Hospital (SNUH) were retrospectively reviewed. Clinicopathological features of 1,260 patients with UTG and 9,929 patients with middle or lower third gastric cancer (MLG) were compared, and annual proportions of UTG were evaluated.

Results

The proportion of patients with UTG rapidly increased from 2.6% in 1986 to 12.5% in 1992. However, linear regression analysis showed that the rate of increase was reduced (0.21%/year) after 1992 (12.5% to 14.2% from 1992 to 2006). Compared with the MLG group, the UTG group had a lower proportion of (22.3% vs. 39.7%, P<0.001) and a greater proportion of stage III/IV disease (39.4% vs. 31.7%, P<0.001). The UTG group also had larger tumors than the MLG group in stages I/II and III (3.5 cm/5.3 cm/6.5 cm vs. 3.2 cm/5.0 cm/5.8 cm, P=0.020/0.028 /<0.001), a higher proportion of undifferentiated cancer (63.1% vs. 53.7%, P<0.001), and less intestinal Lauren's type (38.8% vs. 47.4%, P<0.001). The 5-year survival rate of the UTG group was significantly lower than that of the MLG group in stages I/II and III (85.6%/63.1%/34.2% vs. 91.6%/ 69.2%/44.7%, P<0.001/0.028/0.006).

Conclusions

The proportion of UTGs has increased over the last two decades at SNUH, but the rate of increase has been greatly reduced since 1992. The UTG group showed a poorer prognosis compared with the MLG group in stages I/II and III.

Application of a novel method of double APAAP staining with subsequent quantitative image analysis to the examination of integrin expression in undifferentiated-type gastric carcinomas

In undifferentiated-type gastric carcinoma (UGC), recognition of cancer cells is not easy, which has hampered its precise phenotypic analysis. To examine alterations of the integrin phenotype during the progression of UGC, we used double alkaline phosphatase anti-alkaline phosphatase staining and computer-aided image analyses for the expression of alpha1, alpha2, alpha3, alpha5, alpha6, alphaV, beta1, and beta4 integrin subunits and alphaVbeta3, alphaVbeta5, and alphaVbeta6 integrins in cytokeratin-positive cells in the mucosal, the submucosal, and the deeper parts of 10 early and 17 advanced UGCs, their non-neoplastic counterparts, and 9 lymph node (LN) metastases. We revealed declining expression of epithelial integrin subunits (alpha2, alpha3, alpha6, beta4) and increasing expression of mesenchymal integrin subunits (alpha1, alpha5) as the tumor invaded deeper, reflecting gradual epithelial-to-mesenchymal transition of the integrin phenotype during tumor invasion. Enhanced expression of the alphaV integrin subunit and alphaVbeta3 and alphaVbeta5 integrins correlated with tumor invasion, and that of alphaVbeta6 integrins with LN metastasis. Our results have demonstrated that the method we introduced is suitable for analysis of dynamic alterations of the integrin repertoire in UGC progression.

Roles of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 expression and beta-catenin activation in gastric carcinogenesis in N-methyl-N-nitrosourea-treated K19-C2mE transgenic mice

K19-C2mE transgenic (Tg) mice, simultaneously expressing cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) in the gastric mucosa under the cytokeratin 19 gene promoter, were here treated with N-methyl-N-nitrosourea (MNU) and inoculated with Helicobacter pylori (H. pylori) to investigate gastric carcinogenesis. Wild-type (WT) and Tg mice undergoing MNU treatment frequently developed tumors in the pyloric region (100% and 94.7%, respectively); multiplicity in Tg was higher than that in WT (P < 0.05) with H. pylori infection. Larger pyloric tumors were more frequently observed in Tg than in WT (P < 0.05). In addition, Tg developed fundic tumors, where WT did not. No gastric tumors were observed without MNU treatment. Transcripts of TNF-alpha, iNOS, IL-1beta, and CXCL14 were up-regulated with H. pylori infection in both genotypes and were also increased more in Tg than in WT within H. pylori-inoculated animals. Immunohistochemical analysis demonstrated significantly greater beta-catenin accumulation in pyloric tumors, compared with those in the fundus (P < 0.01) with mutations of exon 3; 18.2% and 31.6% in MNU-alone and MNU + H. pylori-treated WT, whereas 21.4% and 62.5% was observed in the Tg, respectively; the latter significantly higher (P < 0.05), suggesting the role of H. pylori in Wnt activation. In conclusion, K19-C2mE mice promoted gastric cancer in both fundic and pyloric regions. Furthermore beta-catenin activation may play the important role of pyloric carcinogenesis especially in H. pylori-infected Tg. Induction of various inflammatory cytokines in addition to overexpression of COX-2/mPGES-1 could be risk factors of gastric carcinogenesis and may serve as a better gastric carcinogenesis model.

Cytogenetic and molecular aspects of gastric cancer: clinical implications

Gastric cancer is of major importance world-wide being the second most common cause of cancer-related death in the world. According to Lauren's histological classification gastric cancer is divided in two groups, the better differentiated intestinal carcinomas and the poorly differentiated diffuse-type cancers. The genetic changes underlying the initiation and progression of gastric cancer are not well defined. Gastric carcinogenesis is a multistep process involving a number of genetic and epigenetic factors. Although it has been proposed that different genetic pathways exist for differentiated and undifferentiated carcinomas, the two histological subtypes of gastric cancer share some common genetic alterations. Currently, tumor histology and pathologic stage are the major prognostic variables used in the clinical practice for gastric cancer patients. However, it is known that tumors with similar morphology may differ in biological aggressiveness, prognosis and response to treatment. Molecular genetic analysis of gastric cancer revealed a number of associations of certain genetic changes with pathological features, tumor biological behavior and prognosis of gastric cancer patients, suggesting that these genetic abnormalities might play an important role in gastric tumorigenesis. Increasing evidence suggests that the molecular genetic changes could be helpful in the clinical setting, contributing to prognosis and management of patients. Regarding epigenetic events in gastric tumorigenesis, a number of methylating markers have been proposed for risk assessment, prognostic evaluation and as therapeutic targets. However, further research is required in order to systematically investigate the genetic changes in gastric cancer estimating also their usefulness in the clinical practice. A good understanding of the genetic changes underlying gastric carcinogenesis may provide new perspectives for prognosis and screening of high risk individuals. Some of the genetic alterations could definitely improve tumor classification and management of gastric cancer patients. Also, based on molecular data identified in gastric cancer novel therapeutics might help to improve the treatment of this disease.

Carcinogenic hypergastrinemia: signet-ring cell carcinoma in a patient with multiple endocrine neoplasia type 1 with Zollinger-Ellison's syndrome

CONTEXT

Gastric neuroendocrine tumors are rare neoplasms that originate from gastric enterochromaffin-like (ECL) cells in the oxyntic mucosa. Gastrin and its derivates have been reported to regulate epithelial cell proliferation, migration, and differentiation. Mutations in the epithelial cadherin (E-cadherin) gene have been shown to be associated with the occurrence of diffuse gastric carcinomas in affected families.

OBJECTIVE

In this study we investigated the histopathological and molecular findings in the gastrointestinal wall of a patient with multiple endocrine neoplasia type 1 with malignant duodenal gastrinoma and multiple gastric ECL cell tumors, who additionally developed a signet-ring cell carcinoma of the stomach.

DESIGN AND PATIENT

Biopsies from the gastrointestinal tract of a patient with multiple endocrine neoplasia type 1 were immunostained for vesicular monoamine transporter-2 and E-cadherin. Nonamidated gastrin products were measured in the serum of the patient using antibodies that react with progastrin, Gly-extended, and amidated gastrins. Genetic analyses were performed to exclude germ-line mutations within the E-cadherin gene.

RESULTS

Immunohistochemical studies of gastric ECL cell tumors showed a largely diminished E-cadherin expression in comparison to gastric surface mucosa cells and a loss of E-cadherin expression in the cells of the signet-ring carcinoma. Detailed biochemical measurements revealed progastrin concentrations that were approximately 20%, and Gly-gastrin concentrations that were approximately 10% the amidated gastrin concentrations in plasma. Molecular analyses revealed no E-cadherin germ-line mutation.

CONCLUSION

Our immunohistochemical studies might suggest that the gastrinoma-associated excessive progastrin tissue concentrations led to diminished expression of E-cadherin within the gastric mucosa and promoted tumor development of a signet-ring cell carcinoma.

Aberrant methylation of multiple genes in gastric carcinomas

In this study, we examined aberrant methylation of the E-cadherin, estrogen receptor, RB1 , p16, p15, p14, and MGMT genes by the methylation-specific polymerase chain reaction method in 101 gastric carcinomas. Hypermethylation was detected in E-cadherin, estrogen receptor, RB1, p16, p14, p15, and MGMT at the rates of 27.7%, 44.6%, 44.6%, 30.7%, 19.2%, 7.7%, and 6.9%, respectively. A total of 82.2% cases had methylation in at least 1 of these genes, and 44.6% had methylation in 2 or more of these genes. Methylation of RB1 was associated with absence of lymph node metastasis. Methylation of estrogen receptor was associated with age and tumor location. Methylation of E-cadherin coincided with methylation of p16 or estrogen receptor. Moreover, loss of p16 protein was strongly associated with its gene methylation. This study indicates that aberrant methylation of multiple genes is involved in gastric carcinogenesis.

High-resolution fluorescent analysis of microsatellite instability in gastric cancer

BACKGROUND

Microsatellite instability (MSI) is associated with various human malignancies and regarded as reflecting cellular deficiency in DNA mismatch repair (MMR). Analysis of MSI has been prevalent in the field of oncology, and numerous data have accumulated in the literature. It has been reported that the MSI+ phenotype is relatively frequent in gastric cancer. The reported frequencies of MSI+ gastric tumors, however, are diverse.

AIM AND METHODS

To determine the frequencies of the MSI+ phenotype and defective MMR in gastric cancer, we examined tumors derived from 167 patients with sporadic gastric cancer, using our unique fluorescent technique, 'high-resolution fluorescent microsatellite analysis'.

RESULTS

High-resolution fluorescent microsatellite analysis allowed us the unequivocal designation of MSI. The frequencies of MSI-H and MSI-L were 11 and 9.6%, respectively. In addition to the distinction based on the frequency of microsatellite changes, MSI was classifiable into two distinct categories, type A and type B, according to the mode of length changes in the dinucleotide microsatellites. Type A and type B MSI were observed in 14 and 6.6%, respectively. The overall frequency of MSI was 21%. Intriguingly, MSI did not correlate with any of commonly used clinicopathological variables. In addition, neither MSI-H nor MSI-L correlated with family history of malignancies or patient history of multiple cancers. Instead, type B MSI was significantly more frequent in patients with family history of gastric cancer. Type A MSI appeared to occur more frequently in tumors of patients with a history of double cancer, which, however, was not statistically significant.

CONCLUSION

In gastric cancer, contribution of defective MMR to the risk of multiple cancer or familial predisposition appears more limited than has been expected. The relationship between MSI and high risk of cancer may have been oversimplified, at least in gastric cancer.

Clinicopathological significance of loss of heterozygosity in intestinal- and solid-type gastric carcinomas: a comprehensive study using the crypt isolation technique

The clinicopathological significance of loss of heterozygosity (LOH) in gastric carcinoma remains poorly understood. We and other researchers have previously demonstrated that LOH is fairly common in intestinal- and solid-type gastric carcinomas, but rare in diffuse-type tumors. In this study, we investigated the relationship between clinicopathological variables and LOH status in intestinal- and solid-type gastric carcinomas. The crypt isolation technique was utilized to analyze LOH at 1p36, 3p14, 4p15, 5q21-22, 8p11-12, 9p21, 13q22, 17p13.1 18q21 and 22q13.31 in 113 intestinal- and solid-type gastric carcinomas using a polymerase chain reaction assay. Immunostaining with D2-40 and Elastica van Gieson staining were used to detect lymphatic invasion and vessel invasion, respectively. High LOH rates (49-71%) were observed in all chromosomal regions tested. 1p36 loss was significantly associated with advanced tumors and lymph node metastasis. 8p11-12 loss was significantly associated with lymph node metastasis, lymphatic invasion, and vessel invasion. 17p13.1 (TP53) loss was significantly associated with vessel invasion. 22q13.31 loss was significantly associated with advanced tumors, lymph node metastasis, lymphatic invasion, vessel invasion and late TNM stage. No significant associations were observed between LOH at other chromosomal regions and aggressive behaviors. In addition, significantly higher LOH rates at 1p36, 9p21, 18q21 and 22q13.31 were observed in cardiac tumors compared with noncardiac tumors. These results suggest that in intestinal- and solid-type gastric carcinomas, LOH on 3p14, 4p15, 5q21-22, 9p21, 13q22 and 18q21 is associated with carcinogenesis, while LOH on 1p36, 8p11-12, 17p31.1 and 22q13.31 is associated with tumor progression.

RASSF2, a potential tumour suppressor, is silenced by CpG island hypermethylation in gastric cancer

RASSF2, a member of the RASSF1 family, has recently been identified as a potential tumour suppressor. We examined methylation status in multiple regions which included the CpG island and spanned the transcription start site of RASSF2 in 10 gastric cancer cell lines, as well as 78 primary gastric cancers and corresponding non-neoplastic gastric epithelia. Hypermethylation of RASSF2 in at least one of the regions examined was detected in seven (70%) of the 10 cell lines; two (20%) exhibited hypermethylation in all the regions examined including the transcription start site and lost expression of RASSF2 mRNA, which could, however, be restored by 5-aza-2′ deoxycytidine treatment, while the other five (50%) cell lines exhibited hypermethylation at the 5′- and/or 3′- edge, with four of them expressing RASSF2 mRNA. In primary gastric cancers and corresponding non-neoplastic gastric epithelia, frequencies of RASSF2 methylation ranged from 29% (23 out of 78) to 79% (62 out of 78) and 3% (two out of 78) to 60% (47 out of 78), respectively, at different CpG sites examined. Methylation was frequently observed at the 5′- and 3′- edges, and became less frequent near the transcription start site in both the primary gastric cancers and corresponding non-neoplastic gastric epithelia. Hypermethylation near the transcription start site was mostly cancer-specific. We thus showed that RASSF2 is silenced by hypermethylation near the transcription start site in gastric cancer. Hypermethylation was found initially to occur at the 5′- and 3′- furthest regions of the CpG island in non-neoplastic gastric epithelia, to gradually spreads near the transcription start site to shut down RASSF2 expression, and ultimately to constitute a field-defect placing tissue increased risk for development of gastric cancer.

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

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

Pathology and molecular biology of gastric cancer

Several attempts to classify gastric cancer (GCA) have been made over the past decades. Most successful, and widely used, is the classification by Laurén, which distinguishes, by microscopical morphology alone, two main cancer pathogeneses, diffuse (DGCA) and intestinal (IGCA) subtypes, which appear clearly as dissimilar clinical and epidemiological entities. Here we review the main differences in epidemiology, histopathology, and molecular pathology of the two main subtypes of gastric carcinomas based on Laurén classification. In clinical practice, however, clinical staging, particularly in predicting the survival, still remains superior to all classifications of gastric cancer independent of cancer type. The existence of local precursor lesions or conditions of IGCA tumours, i.e. Helicobacter pylori gastritis, atrophic gastritis (AG), intestinal metaplasia (IM), adenoma, dysplasia, and intramucosal neoplasia, is firmly established. The links of DGCA with intestinal-type epithelium, AG or IM are poor, or do not exist. So far, H. pylori gastritis is the only universal precursor condition for DGCA. It implies that AG and achlorhydria are of minor significance and infrequent in the development of DGCA but are important steps in that of IGCA. Despite an increasing body of data, the overall view on molecular pathology of GCA remains fragmentary. No consistent differences in the molecular pathology of GCA subtypes to meet the Laurén classification have been established. With the exception of TP53, no gene mutation occurring regularly in both histological types of GCA has been reported. Chromosomal aberrations and loss of heterozygosity seem to be non-specific and do not follow any consistent route in the progression of GCA. Microsatellite instability is more commonly found in IGCA than in DGCA. The present epigenetic data suggest that most of the decrease (or loss) of gene expression may be explained by promoter hypermethylation which is more often found in IGCA. In DGCA specific genes such as CDH1 are more often hypermethylated. Compared with GCA, in premalignant condition lesions gene mutations and chromosomal aberrations are infrequent. Epigenetic dysregulation might also represent a major mechanism for altered gene expression in premalignant stages in gastric carcinogenesis.

Expression of tumor suppressor and tumor-related proteins in differentiated carcinoma, undifferentiated carcinoma with tubular component and pure undifferentiated carcinoma of the stomach

BACKGROUND

The recent development of tissue microarray (TMA) technology allows high-throughput protein expression profiling of cancer tissues by immunohistochemistry. We attempted to clarify the derivation of undifferentiated-type gastric carcinoma with tubular component by using TMA.

METHODS

We constructed a TMA system composed of six paraffin blocks in which 274 samples of formalin-fixed gastric carcinoma tissue from 274 patients were embedded. Using this system, we performed immunohistochemical stains for five tumor suppressor and tumor-related proteins, i.e. p53, p16, hMLH1, c-erbB-2 and carcinoembryonic antigen (CEA). The 274 gastric carcinomas were histopathologically divided into the following three groups according to the degree of differentiation: differentiated-type (D-type), undifferentiated-type with tubular component (UT-type) and pure undifferentiated-type (UP-type). Immunohistochemical results were then compared with histological types.

RESULTS

The percentages of abnormal expression of each protein in D-type, UT-type and UP-type carcinomas were as follows: 27% (38/143), 17% (17/98) and 15% (5/33) for p53; 27% (39/143), 19% (19/98) and 18% (6/33) for p16; 38% (54/143), 44% (43/98) and 24% (8/33) for hMLH1; 15% (22/143), 5% (5/98) and 0% (0/33) for c-erbB-2; and 22% (31/143), 35% (34/98) and 70% (23/33) for CEA. UP-type carcinomas exhibited the lowest frequencies of abnormal expression for p53, p16, hMLH1 and c-erbB-2, but the highest frequencies for CEA. UT-type carcinomas generally showed intermediate frequencies between those of D-type and UP-type carcinomas. Differences between D-type and UP-type for c-erbB-2 (P < 0.05) and CEA (P < 0.001) were significant, as were differences between D-type and UT-type for c-erbB-2 (P < 0.05) and CEA (P < 0.05), and differences between UT-type and UP-type for hMLH1 (P < 0.05) and CEA (P < 0.001).

CONCLUSIONS

These findings reveal that gastric carcinomas have distinct expression profiles for tumor suppressor and tumor-related proteins depending on histological types, and support the hypothesis that UT-type carcinomas are derived not only from D-type but also from UP-type carcinomas. We also found significant differences between abnormal protein expression and other clinicopathological parameters such as gender, age and status of tumor and nodes.

Tonsillar metastasis revealing signet-ring cell carcinoma of the rectum

A 45-year-old man presented with a tonsillar tumor and rectal syndrome. Histology specimens revealed signet-cell adenocarcinoma of both the tonsils and rectum. The clinical course was rapidly degenerated with multiple metastases in the skin and bones. Tonsil metastasis is rare and generally develops from primary gastric or colorectal cancer, predominantly poorly-differentiated or signet-ring cell adenocarcinomas.

Dynamic alteration of the E-cadherin/catenin complex during cell differentiation and invasion of undifferentiated-type gastric carcinomas

To examine qualitative alterations of the E-cadherin/catenin complex (CCC) during cell differentiation and invasion of undifferentiated-type gastric carcinoma, immunoreactivity for the intracytoplasmic domain and the extracellular domain (ECD) of E-cadherin, and that of beta-catenin, was analysed in the mucosal, submucosal, and deepest invasive parts of 20 early and 20 advanced cancers that had a component of intramucosal signet ring cell carcinoma. Histological subtype affected the mode of E-CCC alteration. The tumours with a tubular component and without organized differentiation of signet ring cells in a layered structure were associated with nuclear expression of beta-catenin and may derive from tubular adenocarcinomas through de-differentiation and de-regulation of the Wnt pathway. These tumours were characterized by relatively stable ECD expression throughout the course of tumour progression. On the other hand, the tumours with a layered structure, which may derive from signet ring cell carcinoma by de novo abnormality of E-cadherin, were characterized by dynamic alteration of ECD expression during cell differentiation and tumour progression; intramucosal spread (with a layered structure) as well as deep invasion (beyond the submucosa) commonly showed cellular dissociation with downregulation of ECD, whereas submucosal invasion and lymph node metastasis often showed cellular cohesion and retention (or 'reappearance') of ECD. Thus, cellular dissociation did not always reflect enhanced invasive activity but may be reversibly regulated during tumour progression.

Mutations in the hMLH1 gene in Slovenian patients with gastric carcinoma

Alterations of multiple oncogenes and tumor suppressor genes, together with genetic instability, are responsible for carcinogenesis in gastric cancer. The microsatellite mutator phenotype is the cause of many somatic frameshift and point mutations in non-coding repetitive sequences and in coding regions associated with cell proliferation and apoptosis. Genetic mutations in hMLH1 and transcriptional silencing of its promoter by hypermethylation lead to the inactivation of the mismatch repair system. In our study, we screened for mutations the hMLH1 gene in patients expressing the microsatellite instability genotype by using single-strand conformational polymorphism analysis and direct sequencing. Seven changes were identified; of these, three (A92P, E433Q, and K618A) were germline mutations and the other four (IVS5 453 + 79 A > G, I219V, 1039 - 7 del (T)(n), and IVS15 1668 - 19 A > G) germline polymorphisms. A92P and E433Q are novel, previously unidentified mutations. In addition, we found a rather complex distribution of mutations and polymorphisms in individual patients and in two cases also a methylated hMLH1 promoter.

E-cadherin expression as predictive marker of proximal resection line involvement for advanced carcinoma of the gastric cardia

AIMS

Total gastrectomy for gastric cardia tumours harbours a high risk of proximal resection line (PRL) involvement. The adhesion markers CD44v6 and E-cadherin were evaluated as predictive factors for PRL involvement independent of tumour stage.

METHODS

Forty-nine gastrectomy specimens for gastric cardia carcinoma (type II) were evaluated for stage, resection margins, and CD44v6 and E-cadherin immunohistochemistry.

RESULTS

PRL involvement was microscopically recognized in 49% of specimens. CD44v6 expression was found in 84% of intestinal tumours, and in 56% of diffuse/mixed tumours (p=0.045). In the group of resections performed with curative intent, the proximal extension of the resection (margin) was significantly shorter in E-cadherin negative tumours than in E-cadherin positive tumours (p=0.029). Histological type and stage of the tumour, lymph node metastases, and absence of E-cadherin expression, but not the presence of CD44v6 correlated with PRL involvement. Only the absence of E-cadherin expression appeared to be a significant predictor of PRL involvement, independent of tumour stage. Survival for patients with PRL involvement was shorter than that for patients after R0 resection (p=0.07). Stage was the only independent prognostic factor emerging from multivariate survival analysis (p=0.002).

CONCLUSIONS

When curative resection is intended in type II cardiac cancer patients, an oesophageal resection and gastric tube reconstruction should be considered, especially for a tumour without E-cadherin expression.

Hypermethylation of Chfr and hMLH1 in gastric noninvasive and early invasive neoplasias

Human tumors are genetically unstable, and the instability exists at two distinct levels-the chromosomal level and the nucleotide level. Chfr and hMLH1 hypermethylation, which may lead to chromosomal instability (CIN) and microsatellite instability (MSI), respectively, was analyzed in gastric noninvasive neoplasias (NIN, Padova international classification) and submucosal invasive adenocarcinomas and in their corresponding non-neoplastic gastric epithelia. Results were compared with microsatellite status, p53 immunoreactivity, and cellular phenotype. Hypermethylation of Chfr and hMLH1 was observed in: 10% (1/10) and 0% (0/10) of low-grade NIN (L-NIN); 63% (5/8) and 63% (5/8) of high-grade NIN, including suspicion for carcinoma without invasion (H-NIN); 36% (5/14) and 57% (8/14) of high-grade NIN, including carcinoma without invasion; and 35% (7/20) and 25% (5/20) of submucosal invasive adenocarcinomas, respectively. Hypermethylation was less frequent in L-NIN than H-NIN (P<0.05) for Chfr and was also less frequent in L-NIN than the others (P<0.05) for hMLH1. We failed to find a significant correlation between Chfr hypermethylation and chromosomal loss of heterozygosity, although hypermethylation of hMLH1 was significantly associated with high-frequency MSI (P<0.01). Expression of p53 was not associated with Chfr or hMLH1 methylation. As for cellular phenotype, hypermethylation of Chfr and hMLH1 was frequent in tumors exhibiting the foveolar epithelial phenotype (50%, 2/4 and 75%, 3/4, respectively) and the ordinary phenotype (40%, 16/40 and 38%, 15/40, respectively), but never in those with the complete-type intestinal metaplastic phenotype (0%, 0/8 for both). In addition, hypermethylation of Chfr and hMLH1 occurred concurrently (P<0.01); methylation was more frequent in patients over 70 years of age (P<0.01), and it was also present in some samples of non-neoplastic gastric epithelia from elderly patients. Thus, some gastric tumors with the foveolar or ordinary phenotype may develop as a result of age-related methylation of Chfr and hMLH1, although Chfr methylation was not associated with CIN.

Development of gastric carcinoma from intestinal metaplasia in Cdx2-transgenic mice

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

Microsatellite instability in dysplasia mucosa and gastric cancer

AIM: Gastric mucosa dysplasia has been regarded as a precancerous lesion of the stomach. Abnormal gene alterations in the mucosa dysplasia of the stomach, which may lead to cell transformation, are probably of great importance in the development of gastric cancer (GC). Microsatellite instability (MSI) is a good marker of genome instability. Investigation of MSI in the cancer and precancerous lesion of the stomach will help us to search into the carcinogenesis of stomach and the potential role of MSI in the development of gastric cancer.

METHODS: Silver staining single strand conformation polymorphis-polymerease chain reaction (PCR-SSCP) was used to screen MSI markers at 5 loci in formalin-fixed,paraffin-embeded tissues of GC (n = 30), dysplasia (n = 30) and corresponding normal gastric tissues.

RESULTS: The abnormal shifting of the single-strand DNA was identified in 7 (23.3%) out of GC, in 9 (30%) out of dysplasia samples respectively. Three (10%) tumors and two (6.7%) dysplasia displayed a high-level of MSI (two or more loci altered). Low-level MSI (one loci altered) was detected in 13.3% of the tumors and in 23.3% dysplasia samples. GC with MSI was associated with distal location of the tumors (P = 0.044). No association was detected between MSI and the grade of dysplasia.

CONCLUSION: The accumulation of MSI in the dysplasia of gastric mucosa may be an early molecular event in the development of gastric cancer. It contributes probably to the multistep gastric carcinogenesis.

Mitochondrial microsatellite instability in gastric cancer and its precancerous lesions

AIM: To evaluate the role of mitochondrial microsatellite instability (mtMSI) in gastric carcinogenesis.

METHODS: MtMSI was measured with PCR-single strand conformation polymophism (PCR-SSCP) in 68 cases of advanced gastric cancer, 40 cases of chronic gastritis, 30 cases of intestinal metaplasia and 20 cases of dysplasia.

RESULTS: MtMSI was observed in 12.5% (5 of 40) of chronic gastritis, 20.0% (6 of 30) of intestinal metaplasia, 25.0% (5 of 20) of dysplasia and 38.2% (26 of 68) of gastric cancer. These findings showed a sequential accumulation of mtMSI in the histological progression from chonic gastritis to gastric cancer. An association of mtMSI with intestinal histological type and distal location was found (P = 0.001 and P = 0.002), whereas no significant correlation was found between mtMSI and age at diagnosis, sex, tumor size, depth of invasion, lymph node spread and clinical stages (P > 0.05).

CONCLUSION: MtMSI may play an early and important role in the gastric carcinogenesis pathway, especially in the intestinal type and distal gastric cancer.

Alterations of chromosomal copy number during progression of diffuse-type gastric carcinomas: metaphase- and array-based comparative genomic hybridization analyses of multiple samples from individual tumours

The application of comparative genomic hybridization (CGH) has led to the rapid accumulation of cytogenetic information on gastric carcinoma (GC), but there is little information on the time sequence of cytogenetic changes. In the present study, degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR) and CGH were applied to multiple samples microdissected from 19 diffuse-type GCs including eight early cancers. Recurrent gains were detected at 8q, 3q, 7q, and 8p, and loss at 17p (in more than 50% of the cancers), the frequencies of which were fairly similar between the samples with (SIG) and those without (POR) abundant signet ring cells. Earlier stemline changes (8q+, 8p+, 1q+, 17p-, etc), with breakpoints that were common to all the samples, were discriminated from later sideline changes (2q+, 11q+, 17q-, 21q-, etc) in individual tumours. The changes were generally common to early and advanced cancers, except for 7p+, 15q+, 3p-, and 18q-, which were largely sideline changes and more frequently detected in advanced cancers (p<0.05). Because the samples with 7p+ had a greater number of copy-number changes than those without 7p+ (p<0.01), 7p+ may play a role in tumour progression by acceleration of chromosomal instability. Fifteen different chromosomal loci with amplification were detected in ten cases, mostly as sideline changes in advanced cancers. By microarray-based CGH, KRAS, MDM2, and FGFR2 were confirmed in the amplicons at 12p, 12q, and 10q, and FES at 15q26, for the first time in GC. These results support the notion that SIG and POR are of a genetically single lineage in both early and advanced diffuse-type GC and that the majority of advanced cancers derive from early cancers through the accumulation of various sideline changes in addition to stemline changes.

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.

Cadherins in cancer

The presence of a functional E-cadherin/catenin cell-cell adhesion complex is a prerequisite for normal development and maintenance of epithelial structures in the mammalian body. This implies that the acquisition of molecular abnormalities that disturb the expression or function of this complex is related to the development and progression of most, if not all, epithelial cell-derived tumors, i.e. carcinomas. E-cadherin downregulation is indeed correlated with malignancy parameters such as tumor progression, loss of differentiation, invasion and metastasis, and hence poor prognosis. Moreover, E-cadherin has been shown to be a potent invasion suppressor as well as a tumor suppressor. Disturbed expression profiles of the E-cadherin/catenin complex have been demonstrated in histological sections of many human tumor types. In different kinds of carcinomas, biallelic downregulation of the E-cadherin gene, resulting in tumor-restricted decrease or even complete loss of E-cadherin expression, appears to be caused by a variety of inactivation mechanisms. Gene deletion due to loss of heterozygosity of the CDH1 locus on 16q22.1 frequently occurs in many carcinoma types. However, somatic inactivating mutations resulting in aberrant E-cadherin expression by loss of both wild-type alleles is rare and restricted to only a few cancer types. A majority of carcinomas thus seems to show deregulated E-cadherin expression by other mechanisms. The present evidence proposes transcriptional repression as a powerful and recurrent molecular mechanism for silencing E-cadherin expression. The predominant mechanisms emerging in most carcinomas are hypermethylation of the E-cadherin promoter and expression of transrepressor molecules such as SIP1, Snail, and Slug that bind sequence elements in the proximal E-cadherin promoter. Interestingly, complex differential expression of other cadherins seems to be associated with loss of E-cadherin and to reinforce effects of this loss on tumor progression. Multiple agents can upregulate and stabilize the E-cadherin/catenin complex. Especially for those tumors with transcriptional and thus reversible downregulation of E-cadherin expression, these drug agents offer important therapeutic opportunities.

Effect of P-selectin monoclonal antibody on metastasis of gastric cancer and immune function

AIM: To investigate the effect of cell adhesion molecule P-selectin monoclonal antibody (Mab) on metastasis and immune function of mice orthototopically implanted with human gastric cancer tissue.

METHODS: SCID mice were implanted orthotopically with SGC-7901 human gastric carcinoma tissue. Starting from day 3 after operation, animals were given intravenously PBS or P-selectin Mab (100 μg/injection) (for both normal mice and tumor-implanted mice with tumors), twice weekly for 3 wk. Two animals in each group were sacrificed randomly at the 1st, 2nd, 4th week and 6th week. While T cell and B cell transformation indices were determined with the ³H TdR infiltration method, the NK cell activity was detected by the LDH release method.

RESULTS: The metastatic rate in the P-selectin Mab treated group was lower than that in the PBS treated group (with tumors). The NK activity of normal mice increased over time. The immune functions (T, B cell function, NK activity) of the tumor group in the 6th week were significantly lower than those in the 4th week, but the change was attenuated by P-selectin Mab.

CONCLUSION: P-selectin Mab could suppress the metastasis of gastric cancer with no adverse effect on host immune function.

MeCP2 and promoter methylation cooperatively regulate E-cadherin gene expression in colorectal carcinoma

Reduced expression of E-cadherin (E-cad) owing to aberrant 5'CpG island hypermethylation has been regarded as one of the main molecular events involved in the dysfunction of the cell-cell adhesion system. The molecular mechanisms providing diversity and heterogeneity of E-cad expression in colorectal carcinoma were explored. In 29 cases of colorectal carcinoma in Indonesia, the expression of E-cad was analyzed by immunohistochemical staining, the methylation status of the E-cad promoter was determined by methylation-specific PCR, and the expression of methyl-CpG-binding protein (MeCP) 2 was studied by in situ hybridization. E-cad expression was strong, and no methylation was observed in normal colon mucosa and most of the well-differentiated adenocarcinoma. In contrast, both signet-ring cell carcinoma and mucinous adenocarcinoma showed fully methylated patterns and strong MeCP2 expression. In moderately- and poorly-differentiated adenocarcinomas, however, E-cad expression was rather heterogeneous, especially at the front of invasion and in the dissociated areas, where loss of MeCP2 expression correlated with E-cad reexpression even in the presence of E-cad promoter methylation. We conclude that both CpG methylation of the E-cad promoter and significant MeCP2 expression cooperatively and epigenetically regulate E-cad expression in colorectal cancer.

Mutation and methylation of hMLH1 in gastric carcinomas with microsatellite instability

AIM: To appraise the correlation of mutation and methylation of hMSH1 with microsatellite instability (MSI) in gastric cancers.

METHODS: Mutation of hMLH1 was detected by Two-dimensional electrophoresis (Two-D) and DNA sequencing; Methylation of hMLH1 promoter was measured with methylation-specific PCR; MSI was analyzed by PCR-based methods.

RESULTS: Sixty-eight cases of sporadic gastric carcinoma were studied for mutation and methylation of hMLH1 promoter and MSI. Three mutations were found, two of them were caused by a single bp substitution and one was caused by a 2 bp substitution, which displayed similar Two-D band pattern. Methylation of hMLH1 promoter was detected in 11 (16.2%) gastric cancer. By using five MSI markers, MSI in at least one locus was detected in 17/68 (25%) of the tumors analyzed. Three hMLH1 mutations were all detected in MSI-H (≥ 2 loci, n = 8), but no mutation was found in MSI-L (only one locus, n = 9) or MSS (tumor lacking MSI or stable, n = 51). Methylation frequency of hMLH1 in MSI-H (87.5%, 7/8) was significantly higher than that in MSI-L (11.1%, 1/9) or MSS (5.9%, 3/51) (P < 0.01-0.001), but no difference was found between MSI-L and MSS (P > 0.05).

CONCLUSION: Both mutation and methylation of hMLH1 are involved in the MSI pathway but not related to the LOH pathway in gastric carcinogenesis.

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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.