Classification of gastric carcinomas

Histological and mutational profile of diffuse gastric cancer: current knowledge and future challenges

Gastric cancer (GC) pathogenesis is complex and heterogeneous, reflecting morphological, molecular and genetic diversity. Diffuse gastric cancer (DGC) and intestinal gastric cancer (IGC) are the major histological types. GC may be sporadic or hereditary; sporadic GC is related to environmental and genetic low-risk factors and hereditary GC is caused by inherited high-risk mutations, so far identified only for the diffuse histotype. DGC phenotypic heterogeneity challenges the current understanding of molecular mechanisms underlying carcinogenesis. The definition of a DGC-specific mutational profile remains controversial, possibly reflecting the heterogeneity of DGC-related histological subtypes [signet-ring cell carcinoma (SRCC) and poorly cohesive carcinoma not otherwise specified (PCC-NOS)]. Indeed, DGC and DGC-related subtypes may present specific mutational profiles underlying the particularly aggressive behaviour and dismal prognosis of DGC vs IGC and PCC-NOS vs SRCC. In this systematic review, we revised the histological presentations, molecular classifications and approved therapies for gastric cancer, with a focus on DGC. We then analysed results from the most relevant studies, reporting mutational analysis data specifying mutational frequencies, and their relationship with DGC and IGC histological types, and with specific DGC subtypes (SRCC and PCC-NOS). We aimed at identifying histology-associated mutational profiles with an emphasis in DGC and its subtypes (DGC vs IGC; sporadic vs hereditary DGC; and SRCC vs PCC-NOS). We further used these mutational profiles to identify the most commonly affected molecular pathways and biological functions, and explored the clinical trials directed specifically to patients with DGC. This systematic analysis is expected to expose a DGC-specific molecular profile and shed light into potential targets for therapeutic intervention, which are currently missing.

[Update on gastric cancer. New molecular classifications]

Gastric cancer (GC) is an aggressive tumor, which is usually diagnosed at an advanced stage and shows high mortality rates. Several GC classifications have been published, based on features such as tumor location, endoscopic features or microscopic architecture. However, TNM stage remains the mainstay of GC management and treatment. In the last years, technical advances have allowed us to investigate the biological heterogeneity of GC and develop new molecular classifications. This knowledge may enhance current classifications, and has the potential to refine GC management and aid in the identification of new molecular targets. In this literature review we have summarized the main findings in epidemiology, screening, classification systems and treatment of GC, focusing on the molecular alterations and new molecular classifications published in the last years.

Precancerous lesions of the stomach, gastric cancer and hereditary gastric cancer syndromes

Gastric cancer accounts for about 6% of cancers worldwide, being the fifth most frequently diagnosed malignancy and the third leading cause of cancer related death. Gastric carcinogenesis is a multistep and multifactorial process and is the result of the complex interplay between genetic susceptibility and environmental factors. The identification of predisposing conditions and of precancerous lesions is the basis for screening programs and early stage treatment. Furthermore, although most gastric cancers are sporadic, familial clustering is observed in up to 10% of patients. Among them, hereditary cases, related to known cancer susceptibility syndromes and/or genetic causes are thought to account for 1-3% of all gastric cancers. The pathology report of gastric resections specimens therefore requires a standardized approach as well as in depth knowledge of prognostic and treatment associated factors.

Assessing molecular subtypes of gastric cancer: microsatellite unstable and Epstein-Barr virus subtypes. Methods for detection and clinical and pathological implications

Background

The molecular classification of gastric cancer recognises two subtypes prone to immune checkpoint blockade: the microsatellite unstable and the Epstein-Barr virus (EBV)-related tumours. We aim to assess the concordance between immunohistochemistry and PCR for microsatellite status evaluation, and explore the value of microsatellite instability (MSI) and EBV as predictive survival factors.

Material and methods

We collected 246 consecutively diagnosed gastric cancer cases in all stages and evaluated the microsatellite status using immunohistochemistry for mismatched repair (MMR) proteins and PCR. EBV expression was studied through in situ hybridisation.

Results

Forty-five (18%) cases presented MSI and 13 (6%) were positive for EBV. MSI was associated with female sex, older age, distal location and distal non-diffuse type of the modified Lauren classification. EBV expression was most frequent in proximal location and proximal non-diffuse type. The sensitivity, specificity, positive predictive value and negative predictive value of immunohistochemistry for the microsatellite study were 91%, 98%, 91% and 98%, respectively. In the multivariate analysis, MSI was an independent predictor of favourable tumour-specific survival (TSS) in stages I–III (MSI: HR: 0.37, 95% CI 0.12 to 0.95, p=0.04).

Conclusions

The MSI status and the EBV expression should be incorporated in routine pathological report for two reasons. First, MSI defines a different pathological entity with a better outcome. Second, MSI and EBV may be useful biomarkers to identify patients who will respond to immune checkpoint blockade inhibitors. For this purpose, immunohistochemical study for MMR proteins and in situ hybridisation study for EBV evaluation are feasible and cost-effective methods.

Helicobacter pylori Infection, the Gastric Microbiome and Gastric Cancer

After a long period during which the stomach was considered as an organ where microorganisms could not thrive, Helicobacter pylori was isolated in vitro from gastric biopsies, revolutionising the fields of Microbiology and Gastroenterology. Since then, and with the introduction of high-throughput sequencing technologies that allowed deep characterization of microbial communities, a growing body of knowledge has shown that the stomach contains a diverse microbial community, which is different from that of the oral cavity and of the intestine. Gastric cancer is a heterogeneous disease that is the end result of a cascade of events arising in a small fraction of patients colonized with H. pylori. In addition to H. pylori infection and to multiple host and environmental factors that influence disease development, alterations to the composition and function of the normal gastric microbiome, also known as dysbiosis, may also contribute to malignancy. Chronic inflammation of the mucosa in response to H. pylori may alter the gastric environment, paving the way to the growth of a dysbiotic gastric bacterial community. This dysbiotic microbiome may promote the development of gastric cancer by sustaining inflammation and/or inducing genotoxicity. This chapter summarizes what is known about the gastric microbiome in the context of H. pylori-associated gastric cancer, introducing the emerging dimension of the microbiome into the pathogenesis of this highly incident and deadly disease.

Gastric cancer

Gastric cancer is one of the leading causes of cancer-related death worldwide. Many patients have inoperable disease at diagnosis or have recurrent disease after resection with curative intent. Gastric cancer is separated anatomically into true gastric adenocarcinomas and gastro-oesophageal-junction adenocarcinomas, and histologically into diffuse and intestinal types. Gastric cancer should be treated by teams of experts from different disciplines. Surgery is the only curative treatment. For locally advanced disease, adjuvant or neoadjuvant therapy is usually implemented in combination with surgery. In metastatic disease, outcomes are poor, with median survival being around 1 year. Targeted therapies, such as trastuzumab, an antibody against HER2 (also known as ERBB2), and the VEGFR-2 antibody ramucirumab, have been introduced. In this Seminar, we present an update of the causes, classification, diagnosis, and treatment of gastric cancer.

Diffuse Gastric Carcinoma Undergoes Characteristic Phenotypic Changes in the Intravascular Environment: Evidence for a Reversal of the Epithelial-Mesenchymal Transition in Lymphovascular Metastasis

This article reports differences between the properties of extravascular carcinoma, which generally forms the vast bulk of a tumor, and those of intravascular carcinoma, at both primary and metastatic lymph node sites. In a morphological and immunohistochemical study of 19 diffuse gastric adenocarcinomas, we report that in comparison to extravascular carcinoma, the intravascular tumor compartment showed frequent and profound phenotypic change, including increased tumor cell cohesion, differentiation and cadherin/catenin expression. For example, greatest cohesion was seen at the intravascular site in 78% ( P = .00006) of primary cancers and in 84% ( P = .000015) of their lymph node metastases. Pan cadherin showed a statistically significant increase at the intravascular metastatic site ( P = .031). We suggest that this change from an extravascular isolated cell phenotype to an intravascular cohesive phenotype represents reversal of the epithelial to mesenchymal transition. Since this proposed reversal of epithelial to mesenchymal transition in intravascular carcinoma is frequently conspicuous in routine histological sections of many types of cancer, as our previous publications have indicated, this process is likely to have widespread significance for the biology of metastasis.

Three Molecular Subtypes of Gastric Adenocarcinoma Have Distinct Histochemical Features Reflecting Epstein-Barr Virus Infection Status and Neuroendocrine Differentiation

Current histopathologic classification schemes for gastric adenocarcinoma have limited clinical utility and are difficult to apply due to tumor heterogeneity. Elucidation of molecular subtypes of gastric cancer may contribute to our understanding of gastric cancer biology and to the development of new molecular markers that may lead to improved diagnosis, therapy, or prognosis. We previously demonstrated that Epstein-Barr virus (EBV)-infected gastric cancers have a distinct human gene expression profile compared with uninfected cancers. We now examine the histopathologic features characterizing infected (n=14) and uninfected (n=89) cancers; the latter of which are now further divided into 2 major molecular subtypes based on expression patterns of 93 RNAs. One uninfected gastric cancer subtype was distinguished by upregulation of 3 genes with neuroendocrine (NE) function (CHGA, GAST, and REG4 encoding chromogranin, gastrin, and the secreted peptide REG4 involved in epithelial cell regeneration), implicating hormonal factors in the pathogenesis of a major class of gastric adenocarcinomas. Evidence of NE differentiation (molecular, immunohistochemical, or morphologic) was mutually exclusive of EBV infection. EBV-infected tumors tended to have solid-type morphology with lymphoid stroma. This study reveals novel molecular subtypes of gastric cancer and their associated morphologies that demonstrate divergent NE features.

Risk of lymph node metastasis in differentiated type mucosal early gastric cancer mixed with minor undifferentiated type histology

BACKGROUND

The possibility of lymph node metastasis is critical to the assessment of the indication for endoscopic submucosal dissection. The differentiation of tumors is an important predicting factor for lymph node metastasis. Even though gastric cancers frequently show intratumoral heterogeneity, most studies have not considered the effects of the minor histologic components. The purpose of this study was to investigate the relationship between the presence of undifferentiated type histology (UD-min) within differentiated type tumors and lymph node metastases in early gastric cancer confined to the mucosal layer.

METHODS

A retrospective study of 847 patients who underwent surgery for differentiated early gastric cancer, confined to mucosa, was conducted. We analyzed the proportion of the undifferentiated type components of the tumor and their relationship with lymph node metastasis.

RESULTS

The overall rate of lymph node metastasis was 1.7 % (14/847 patients) and 215 differentiated tumors (25.4 %) have UD-min. UD-min was associated with female sex, younger age, larger tumor size, and the presence of ulcer. Lymph node metastasis rate with or without UD-min was 5.1 % (11/215) versus 0.5 % (3/632), respectively (p < 0.001). UD-min was found to be associated with lymph node metastasis in the multivariate analyses (odds ratio [OR] = 4.39, CI 1.08-17.89). When three risk factors (tumor size >2 cm, ulcer, and UD-min) were present concurrently, the rate of lymph node metastasis was high (10 %).

CONCLUSIONS

The presence of an UD-min component should be considered when assessing curative resection status of endoscopic submucosal dissection for differentiated type mucosal cancer.

[Ways to personalized medicine for gastric cancer]

Gastric cancer is the fourth most common tumor and the second most common cause of cancer-related deaths in the world. Approximately 70 % of the patients already have lymph node metastases at the time of the diagnosis leading to a median overall survival time of 16.7 months. Complete resection of the primary tumor with D2 lymphadenectomy offers the only chance of cure in the early stages of the disease. Survival of more locally advanced gastric cancer was improved by the introduction of perioperative, adjuvant and palliative chemotherapy of gastric cancer; however, the identification of novel predictive and diagnostic targets is urgently needed. Our own studies on gastric cancer biology identified several putative tumor biologically relevant G-protein-coupled receptors (e.g. AT1R, AT2R, CXCR4, FZD7, LGR4, LGR5, LGR6). Some of these receptors are also putative stem cell markers and may serve as future targets of an individualized therapy of gastric cancer.

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

Background

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

Methods

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

Results

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

Conclusions

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

[Molecular pathology of gastric cancer]

Gastric cancer is one of the most common cancers worldwide. In recent decades, major advancements in the understanding of the epidemiology, pathology and pathogenesis of gastric cancer have been witnessed. Infections with Helicobacter pylori or Epstein-Barr virus, dietary and lifestyle factors contribute to the risk of developing gastric cancer. With respect to pathogenesis at least three distinct types of gastric cancer exist, (1) proximal, (2) distal diffuse and (3) distal non-diffuse types. Genetic and epigenetic alterations are related to oncogene mutations and tumor suppressor gene inactivation. Canonical oncogenic pathways such as the WNT/β-catenin signaling pathway are de-regulated in gastric cancer. Hereditary and familial type gastric cancers are currently linked to CDH1 gene mutations and various genetic polymorphisms determining disease susceptibility. Molecular subtypes of gastric cancer have been identified which separate diffuse from intestinal type gastric cancer and are not entirely congruent with the histopathological phenotype according to Laurén but may influence chemosensitivity. Putative cancer stem cell markers of gastric cancer have been found (e.g. ADAM17, CD133, FZD7, LGR5) and correlate with patient prognosis. Thus, molecular phenotyping of gastric cancer is still in its infancy and the search for novel diagnostic, prognostic and predictive biomarkers continues.

Pathology of gastric cancer and its precursor lesions

Gastric cancers are a histologically heterogenous group of neoplasms arising from unique epidemiologic and molecular backgrounds. There is accumulating evidence that the intestinal type of gastric adenocarcinoma develops through a multistep process beginning with chronic gastritis triggered primarily by Helicobacter pylori and progressing through atrophy, intestinal metaplasia, and dysplasia (intraepithelial neoplasia) to carcinoma. Loss of E-cadherin expression resulting from CDH1 gene alterations is the primary carcinogenetic event in hereditary diffuse gastric cancer. Proximal gastric adenocarcinomas likely result from either gastroesophageal reflux or H pylori gastritis. This article provides an update of the histologic, immunohistochemical, and molecular pathways of gastric cancer and its precursors.

Lineage analysis of early and advanced tubular adenocarcinomas of the stomach: continuous or discontinuous?

BACKGROUND

Eradication of early gastric carcinoma (GC) is thought to contribute to reduction in the mortality of GC, given that most of the early GCs progress to the advanced GCs. However, early GC is alternatively considered a dormant variant of GC, and it infrequently progresses to advanced GC. The aim of this study was to clarify the extent of overlap of genetic lineages between early and advanced tubular adenocarcinomas (TUBs) of the stomach.

METHODS

Immunohistochemical staining for p53 was performed using 28 surgically resected stomachs with 13 intramucosal and 15 invasive TUBs. By chromosome- and array-based comparative genomic hybridization (CGH), genomic copy number constitution was compared between the mucosal and invasive parts of the invasive TUBs and between the mucosal parts of the invasive and intramucosal TUBs, using 25 and 22 TUBs, respectively. TP53 mutation in exons 5-8 was examined in 20 TUBs.

RESULTS

Chromosomal CGH revealed that 4q+ and 11q+ were more common in advanced and early TUBs, respectively, whereas copy number changes in 8q and 17p showed no significant differences between early and advanced TUBs. However, array CGH revealed that, of the 13 intramucosal TUBs examined, loss of MYC (MYC-) and gain of TP53 (TP53+) was detected in 9 TUBs and MYC+ and/or TP53- was detected in 3 TUBs. Of the mucosal samples of 9 invasive TUBs, 7 showed MYC-/TP53+ and none showed MYC+ and/or TP53-. Of the 9 samples from the invasive parts, 1 (from submucosal cancers) showed MYC-/TP53+ and 6 (1 from submucosal and 5 from advanced cancers) showed MYC+ and/or TP53-. The latter 6 tumours commonly showed a mutant pattern (diffuse or null) in p53 immunohistochemistry, and 4 of the 6 tumours assessable for TP53 sequence analysis revealed mutations. The overall array CGH pattern indicated that, between the mucosal and invasive parts, genetic lineage was found discontinuous in 5 advanced cancers and continuous in 3 submucosal cancers.

CONCLUSIONS

Genetic lineages often differed between early and advanced TUBs. MYC-/TP53+ and MYC + and/or TP53- may be the signatures of dormant and aggressive TUBs, respectively, in the stomach.

Hereditary gastric cancer

Gastric cancer is a heterogeneous and highly prevalent disease, being the fourth most common cancer and the second leading cause of cancer associated death worldwide. Most cases are sporadic and familial clustering is observed in about 10% of the cases. Hereditary gastric cancer accounts for a very low percentage of cases (1-3%) and a single hereditary syndrome - Hereditary Diffuse Gastric Cancer (HDGC) - has been characterised. Among families that fulfil the clinical criteria for HDGC, about 40% carry CDH1 germline mutations, the genetic cause of the others being unknown. The management options for CDH1 asymptomatic germline carriers are intensive endoscopic surveillance and prophylactic gastrectomy. In this chapter we review the pathophysiology and clinicopathological features of HDGC and discuss issues related with genetic testing and management of family members.

Intratumoural heterogeneity of intestinal expression reflects environmental induction and progression-related loss of induction in undifferentiated-type gastric carcinomas

AIMS

Gene expression in tumours is regulated by environmental as well as genetic/epigenetic factors. This study assessed the environmental factors in intestinal expression of gastric cancers.

METHODS AND RESULTS

We immunohistochemically examined intratumoural heterogeneity in the expression of Cdx2, MUC2, MUC5AC and MUC6 in 39 intramucosal and 49 extramucosally invasive undifferentiated-type gastric carcinomas (UGCs), consisting of signet ring cell carcinomas showing a layered structure (LS) in the mucosa and dedifferentiated tubular adenocarcinomas without LS and with minor tubular components (TC). The LS retains mucosal vertical polarity with superficial MUC5AC expression. Loss of this polarity was independent of intestinal expression and associated with extramucosal invasion. In LS(+) UGCs, intestinal expression was enhanced as the size of mucosal spread increased and was significantly reduced with deeper extramucosal invasion, whereas, in LS(-)/TC(+) UGCs, intestinal expression was frequent and predominant in the mucosa and was insignificantly reduced with deeper extramucosal invasion.

CONCLUSIONS

In LS(+) UGCs, intestinal expression showed dynamic alteration probably by environmental induction and progression-related loss of induction, whereas it was relatively stable in LS(-)/TC(+) UGCs. Thus, intestinal expression in UGCs is not useful as a marker of tumour progression because it is also affected by environmental factors and genetic lineage.

Association of ERBB2 gene status with histopathological parameters and disease-specific survival in gastric carcinoma patients

The clinical significance of ERBB2 amplification/overexpression in gastric cancer remains unclear. In this study, we evaluated the ERBB2 status in 463 gastric carcinomas using immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH), and compared the findings with histopathological characteristics and with disease-specific survival. ERBB2 overexpression (2+ and 3+) and amplification (ratio ERBB2/CEP17⩾2) were found in 43 (9.3%) and 38 (8.2%) gastric carcinomas, respectively. Perfect IHC/FISH correlation was found for the 19 cases scored as 0 (all negative by FISH), and also for the 25 cases scored as 3+ (all positive by FISH). One out of six carcinomas scored as 1+ and 12 out of 18 carcinomas scored as 2+ were positive by FISH. ERBB2 amplification was associated with gastric carcinomas of intestinal type (P=0.007) and with an expansive growth pattern (P=0.021). ERBB2 amplification was detected in both histological components of two mixed carcinomas, indicating a common clonal origin. A statistically significant association was found between ERBB2 amplification and worse survival in patients with expansive gastric carcinomas (P=0.011). We conclude that ERBB2 status may have clinical significance in subsets of gastric cancer patients, and that further studies are warranted to evaluate whether patients whose gastric carcinomas present ERBB2 amplification/overexpression may benefit from therapy targeting this surface receptor.

Molecular targets and biological modifiers in gastric cancer

The overall survival of gastric cancer patients remains poor despite efforts and advances in its prevention, diagnosis, and treatment. The development of new therapies is crucial for the effective control of this disease. An increasing number of genetic and epigenetic alterations have been associated with distinct histological types of gastric cancer. In this review, we will discuss the involvement of E-cadherin, EGFR, ERBB2, MMR genes, KRAS, and PIK3CA in the development and progression of gastric cancer and their role as biomarkers or as novel putative targets for therapy.

Fruit and vegetable consumption and gastric cancer by location and histological type: case-control and meta-analysis

The available information favours a greater impact of environmental exposures on intestinal type gastric cancer, and risk factors for the cardia and distal stomach cancers also appear to be different. We aimed to estimate the association between fruit and vegetable intake and gastric cancer, by location and histological type. We performed a population-based case-control study and a meta-analysis of studies addressing this issue. Incident cases (n=305) were identified in two large teaching hospitals (Porto, Portugal), and controls were randomly sampled among city dwellers (n=1129). Published studies were searched through PubMed, and effects were combined with random effects meta-analysis. In our case-control study, the odds ratio (OR) for the comparison of the highest vs. lowest tertile of fruit consumption was 0.47 [95% confidence interval (CI): 0.21-1.05] for cardia, 0.53 (95% CI: 0.35-0.80) for non-cardia cancer, 0.36 (95% CI: 0.20-0.62) for intestinal, and 1.00 (95% CI: 0.53-1.90) for the diffuse histological type. For vegetables, the corresponding OR was 0.59 (95% CI: 0.26-1.35), 0.85 (95% CI: 0.58-1.26), 0.95 (95% CI: 0.57-1.57), and 0.60 (95% CI: 0.32-1.14). In meta-analysis, considering fruit consumption (highest vs. lowest category), the combined OR was 0.58 (95% CI: 0.38-0.89) for cardia, 0.61 (95% CI: 0.44-0.84) for non-cardia, 0.49 (95% CI: 0.33-0.72) for intestinal type, and 0.82 (95% CI: 0.57-1.20) for diffuse type. Vegetables also decreased the risk of cardia (OR=0.63, 95% CI: 0.50-0.79), non-cardia (OR=0.75, 95% CI: 0.59-0.95), intestinal (OR=0.61, 95% CI: 0.44-0.86), and diffuse type (OR=0.67, 95% CI: 0.44-1.01). Fruit or vegetable intake was associated with a decreased risk of gastric cancer regardless of the anatomical location and the histological type, although dietary intake had a more clear-cut protective effect on intestinal type cancers.

Pathology findings and validation of gastric and esophageal cancer cases in a European cohort (EPIC/EUR-GAST)

OBJECTIVE

Cardia, non-cardia and intestinal and diffuse subtypes of gastric cancer may have different trends and etiological factors. However, the available information is not always collected in population cancer registries, and heterogeneous criteria have been applied for the histopathological classification of tumors. We describe the pathological features of incident gastric and esophageal cancers identified within the European Prospective Investigation into Cancer and Nutrition (EPIC).

MATERIAL AND METHODS

In an investigation on gastric and esophageal cancer (EUR-GAST) in the EPIC project, a validation study of diagnoses reported by EPIC centers was conducted by a European panel of pathologists. Original pathology reports, stained slides of tumors and the respective paraffin blocks were requested from the centers.

RESULTS

The whole series encompassed 467 cancer cases (gastric and esophageal cancers). Material was available for histopathological validation in 263 cases (56%); in the remaining cases, information was retrieved from the original reports (n=110; 24%) or codes provided by the EPIC centers (n=94; 20%). Among cases submitted to histopathological validation reported originally as unknown histotype or unknown site, a specific diagnosis was made in 95% and 74% of the cases, respectively. In cases for which only the original reports were available, the respective percentages were 46% and 67%. Gastric adenocarcinomas were classified according to site (cardia (29.4%), non-cardia (48.2%) and unknown (22.4%)) and histological type (intestinal (33.4%), diffuse (33.7%) and mixed, unclassified or unknown (32.9%)). Frequency of cardia was higher in Northern countries (35%) than in Mediterranean countries (18%).

CONCLUSIONS

In addition to providing epidemiological data within the EPIC cohort on gastric and esophageal adenocarcinomas, the results reported here confirm the relevance of a validation study, notably for multicenter studies.

beta-catenin (CTNNB1) gene amplification: a new mechanism of protein overexpression in cancer

beta-Catenin nuclear translocation is frequently observed in different types of malignancies, including gastric cancer. In gastric cancer, however, the molecular mechanisms leading to accumulation of this protein in the nucleus remain unknown. In this setting, beta-catenin (CTNNB1) mutations have been reported, but studies of mutation frequency have yielded conflicting results. Mutations or silencing of other partners of beta-catenin (i.e., APC and AXIN) are also considered rare genetic events in gastric tumorigenesis. Gene amplification is a common mechanism of activation and/or overexpression of oncogenes in gastric and other cancers. In this study, we investigated whether gene amplification is a possible mechanism of beta-catenin activation in gastric cancer by determining its presence in 49 patients with gastric cancer and two gastric-derived cell lines (KATO III and ST2957). Using fluorescence in situ hybridization, we identified beta-catenin amplification in one of the tumor samples as well as in KATO III cells. beta-Catenin immunostaining revealed nuclear translocation of the protein in both cases. In the KATO III cells, beta-catenin overexpression was confirmed by quantitative real-time PCR and Western blot analyses and beta-catenin gene amplification by Southern blot analysis and multiplex ligation probe amplification. In the KATO III cell line, no correlation was found between beta-catenin nuclear translocation and increased expression of the WNT1 target gene CCND1 (cyclin D1). Our data suggest that gene amplification is a possible mechanism of beta-catenin overexpression in cancer.

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.

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.

Hereditary cancer syndromes of the gastrointestinal system

Gastrointestinal (GI) malignancies account for a large percentage of the cancer burden in the United States. Although the majority of cancer cases are sporadic, approximately 5% to 10% of cancer results from inherited genetic mutations. There are several hereditary cancer syndromes of the GI tract that have been identified. To date, the genetics of colorectal cancer and its associated hereditary cancer syndromes have been characterized in detail, and effective screening modalities and recommendations have been incorporated into standards of care. Today, scientists are beginning to understand the genetic basis of pancreatic and gastric cancer, and in some cases have identified a number of their associated inherited cancer syndromes. Information about cancer genetics and hereditary cancer syndromes not only will provide advanced practice nurses with knowledge of these diseases but also, more importantly, will provide opportunities to improve patient care by providing patients with treatment options and opportunities for the early detection and prevention of cancer.

Genetic progression in sporadic endometrial and gastrointestinal cancers with high microsatellite instability

This study selected a series of 136 MSI-H (microsatellite instability at high frequency) gastric, colorectal, and endometrial carcinomas combining immunohistochemical analysis for hMLH1 or hMSH2 gene products and microsatellite study. The clinico-pathological profile of all tumours was correlated with the overall instability rates at coding and non-coding repeats, in order to clarify the role and the mutation timing of seven target genes (TGFbetaRII, IGFIIR, BAX, hMSH3, hMSH6, CHK1, and BRCA2) in the progression of an MSI-H neoplasm. Regardless of the primary site, the results confirm a model of oncogenesis in which inactivation of hMLH1, or less frequently hMSH2, may initiate a pathway culminating in a progressive accumulation of frameshifts in coding region (CDR) microsatellites. Comparing gastrointestinal and endometrial tumours, significantly lower levels of microsatellite instability at both coding and non-coding repeats were observed. Among gastric and colorectal tumours, the detection of small shortening within Bat-26 and Bat-25 markers defines a subgroup of MSI-H gastrointestinal tumours invariably characterized by early stage at diagnosis. In these tumours, mutations of TGFbetaRII or BAX genes precede frameshifts in the other tested genes. The analysis of correlations between the mutational and clinico-pathological profiles of advanced gastrointestinal tumours revealed that the higher levels of microsatellite instability at both coding and non-coding repeats were not associated with a more advanced clinico-pathological stage or a less favourable outcome. A significant association was observed between a low number of CDR frameshifts and the presence of lymph-node metastasis in advanced gastrointestinal tumours. The existence of advanced MSI-H tumours with more aggressive behaviour and a 'mild mutator phenotype' could be explained by hypothesizing an overlapping of different mechanisms of tumourigenesis, including both the mutator and the suppressor pathways; this should be tested by further studies.

Relationship between phenotypes of cell-function differentiation and pathobiological behavior of gastric carcinomas

AIM

To reveal the correlation between the functional differentiation phenotypes of gastric carcinoma cells and the invasion and metastasis by a new way of cell-function classification.

METHODS

Surgically resected specimens of 361 gastric carcinomas(GC) were investigated with enzyme-, mucin-, and tumor-related marker immunohistochemistry. According to the direction of cell-function differentiation, stomach carcinomas were divided into five functionally differentiated types.

RESULTS

(1) Absorptive function differentiation type (AFDT): there were 82 (22.7%) patients including 76 (92.7%) aged 45 years. Sixty-nine (84.1%) cases belonged to the intestinal type. Thirty-eight (46.3%) expressed CD44v6 and 9 (13.6%) of 66 male patients developed liver metastasis. The 5-year survival rate of patients in this group (58.5%) was higher than those with the other types (P<0.01). (2) Mucin secreting function differentiation type (MSFDT): 54 (15%) cases. Fifty-three (98.1%) tumors had penetrated the serosa, 12 (22.2%) expressed ER and 22 (40.7%) expressed CD44v6. The postoperative 5-year survival rate was 28.6%. (3) Absorptive and mucin-producing function differentiation type (AMPFDT): there were 180 (49.9%) cases, including 31 (17.2%) aged younger than 45 years. The tumor was more common in women (62, 34.4%,) and expressed more frequently estrogen receptors (ER) (129, 81.7%) than other types (P<0.01). Ovary metastasis was found in 12 (19.4%) out of 62 female subjects. The patients with this type GC had the lowest 5-year survival rate (24.7%) among all types. (4) Specific function differentiation type (SFDT): 13 (3.6%) cases. Nine (69.2%) tumors of this type derived from APUD system, the other 4 (30.7%) were of different histological differentiation. Sixty per cent of the patients survived at least five years. (5) Non-function differentiation type (NFDT): 32 (8.9%) cases. Nineteen (59.4%) cases had lymph node metastases but no one with liver or ovary metastasis. The 5-year survival rate was 28.1%.

CONCLUSION

This new cell-function classification of GC is helpful in indicating the characteristics of invasion and metastasis of GC with different cell-function differentiation phenotypes. Further study is needed to disclose the correlation between the cell-functional differentiation phenotypes and the relevant genotypes and the biological behavior of gastric carcinoma.

Gastric carcinoma exhibits distinct types of cell differentiation: an immunohistochemical study of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6)

The expression of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6) has previously been described in gastric polyps. In the present study, the expression profile of these trefoil peptides and mucins was characterized in 96 gastric carcinomas, in an attempt to further the understanding of the histogenesis and cell differentiation of gastric carcinoma. Taking together the co-expression of trefoil peptides and mucins, three phenotypes were defined: complete gastric, incomplete gastric, and non-gastric phenotype. Gastric differentiation (complete and incomplete) was observed in 30 out of 33 (90.9%) diffuse carcinomas and in 38 out of 53 (71.7%) intestinal carcinomas. Non-gastric differentiation was observed in only three (9.1%) diffuse carcinomas and in 15 (28.3%) intestinal carcinomas. The phenotypes observed in intestinal carcinomas were similar to those previously observed in adenomatous polyps, whereas most diffuse carcinomas mimicked the phenotype of hyperplastic polyps. The percentage of cases displaying a non-gastric phenotype was higher, though not significantly, in tumours that had invaded the gastric wall than in T1 tumours, regardless of histotype. It is concluded that gastric-type differentiation is retained in the majority of gastric carcinomas, being more prominent in diffuse than in intestinal carcinomas, and in early than in advanced carcinomas.

Gastric carcinoma exhibits distinct types of cell differentiation: an immunohistochemical study of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6)

The expression of trefoil peptides (TFF1 and TFF2) and mucins (MUC1, MUC2, MUC5AC, and MUC6) has previously been described in gastric polyps. In the present study, the expression profile of these trefoil peptides and mucins was characterized in 96 gastric carcinomas, in an attempt to further the understanding of the histogenesis and cell differentiation of gastric carcinoma. Taking together the co-expression of trefoil peptides and mucins, three phenotypes were defined: complete gastric, incomplete gastric, and non-gastric phenotype. Gastric differentiation (complete and incomplete) was observed in 30 out of 33 (90.9%) diffuse carcinomas and in 38 out of 53 (71.7%) intestinal carcinomas. Non-gastric differentiation was observed in only three (9.1%) diffuse carcinomas and in 15 (28.3%) intestinal carcinomas. The phenotypes observed in intestinal carcinomas were similar to those previously observed in adenomatous polyps, whereas most diffuse carcinomas mimicked the phenotype of hyperplastic polyps. The percentage of cases displaying a non-gastric phenotype was higher, though not significantly, in tumours that had invaded the gastric wall than in T1 tumours, regardless of histotype. It is concluded that gastric-type differentiation is retained in the majority of gastric carcinomas, being more prominent in diffuse than in intestinal carcinomas, and in early than in advanced carcinomas.

The clinicopathological features of gastric carcinomas with microsatellite instability may be mediated by mutations of different "target genes": a study of the TGFbeta RII, IGFII R, and BAX genes

Gastric carcinomas with DNA replication errors (RER phenotype) display a particular clinicopathologic profile and carry a putative favorable prognosis. The RER phenotype has been identified as microsatellite instability in noncoding regions, as well as in repeat sequences within exons of several "target genes": TGFbeta RII, IGFII R, and BAX. In an attempt to find out whether the RER status is a significant prognostic factor in gastric carcinoma in a multivariate analysis and whether the clinicopathological features of the RER+ tumors are associated with mutations in the "target genes," we evaluated a series of 152 cases of sporadic gastric carcinoma. Five or six microsatellite loci and/or BAT 26, a poly(A) tract, were analyzed in each case using polymerase chain reaction and electrophoresis. Thirty-five cases (23.0%) were RER+. The RER phenotype was closely associated with a low pTNM stage and carried a significantly better prognosis. The repeat sequences of the target genes were screened for mutations in 28 RER+ and 13 RER-tumors. Mutations in TGFbeta RII occurred in 67.9% of the RER+ tumors and were significantly associated with the glandular histotype. IGFII R and BAX mutations occurred, respectively, in 25.0% and 32.1% of the cases; there was a trend toward an association between mutations in these genes and decreased nodal metastization and wall invasiveness, respectively. We conclude that the RER status is a significant prognostic indicator in gastric carcinoma and that such prognostic influence may be mediated by mutations in TGFbeta RII, IGFII R, and BAX genes.