A novel diffuse gastric cancer susceptibility variant in E-cadherin (CDH1) intron 2: a case control study in an Italian population

The Identification of Large Rearrangements Involving Intron 2 of the CDH1 Gene in BRCA1/2 Negative and Breast Cancer Susceptibility

E-cadherin, a CDH1 gene product, is a calcium-dependent cell-cell adhesion molecule playing a critical role in the establishment of epithelial architecture, maintenance of cell polarity, and differentiation. Germline pathogenic variants in the CDH1 gene are associated with hereditary diffuse gastric cancer (HDGC), and large rearrangements in the CDH1 gene are now being reported as well. Because CDH1 pathogenic variants could be associated with breast cancer (BC) susceptibility, CDH1 rearrangements could also impact it. The aim of our study is to identify rearrangements in the CDH1 gene in 148 BC cases with no BRCA1 and BRCA2 pathogenic variants. To do so, a zoom-in CGH array, covering the exonic, intronic, and flanking regions of the CDH1 gene, was used to screen our cohort. Intron 2 of the CDH1 gene was specifically targeted because it is largely reported to include several regulatory regions. As results, we detected one large rearrangement causing a premature stop in exon 3 of the CDH1 gene in a proband with a bilateral lobular breast carcinoma and a gastric carcinoma (GC). Two large rearrangements in the intron 2, a deletion and a duplication, were also reported only with BC cases without any familial history of GC. No germline rearrangements in the CDH1 coding region were detected in those families without GC and with a broad range of BC susceptibility. This study confirms the diversity of large rearrangements in the CDH1 gene. The rearrangements identified in intron 2 highlight the putative role of this intron in CDH1 regulation and alternative transcripts. Recurrent duplication copy number variations (CNV) are found in this region, and the deletion encompasses an alternative CDH1 transcript. Screening for large rearrangements in the CDH1 gene could be important for genetic testing of BC.

Overview on new progress of hereditary diffuse gastric cancer with CDH1 variants

Hereditary diffuse gastric cancer (HDGC), comprising 1%-3% of gastric malignances, has been associated with CDH1 variants. Accumulating evidence has demonstrated more than 100 germline CDH1 variant types. E-cadherin encoded by the CDH1 gene serves as a tumor suppressor protein. CDH1 promoter hypermethylation and other molecular mechanisms resulting in E-cadherin dysfunction are involved in the tumorigenesis of HDGC. Histopathology exhibits characteristic signet ring cells, and immunohistochemical staining may show negativity for E-cadherin and other signaling proteins. Early HDGC is difficult to detect by endoscopy due to the development of lesions beneath the mucosa. Prophylactic gastrectomy is the most recommended treatment for pathogenic CDH1 variant carriers. Recent studies have promoted the progression of promising molecular-targeted therapies and management strategies. This review summarizes recent advances in CDH1 variant types, tumorigenesis mechanisms, diagnosis, and therapy, as well as clinical implications for future gene therapies.

Nuclear factor one transcription factors as epigenetic regulators in cancer

Tumour heterogeneity poses a distinct obstacle to therapeutic intervention. While the initiation of tumours across various physiological systems is frequently associated with signature mutations in genes that drive proliferation and bypass senescence, increasing evidence suggests that tumour progression and clonal diversity is driven at an epigenetic level. The tumour microenvironment plays a key role in driving diversity as cells adapt to demands imposed during tumour growth, and is thought to drive certain subpopulations back to a stem cell-like state. This stem cell-like phenotype primes tumour cells to react to external cues via the use of developmental pathways that facilitate changes in proliferation, migration and invasion. Because the dynamism of this stem cell-like state requires constant chromatin remodelling and rapid alterations at regulatory elements, it is of great therapeutic interest to identify the cell-intrinsic factors that confer these epigenetic changes that drive tumour progression. The nuclear factor one (NFI) family are transcription factors that play an important role in the development of many mammalian organ systems. While all four family members have been shown to act as either oncogenes or tumour suppressors across various cancer models, evidence has emerged implicating them as key epigenetic regulators during development and within tumours. Notably, NFIs have also been shown to regulate chromatin accessibility at distal regulatory elements that drive tumour cell dissemination and metastasis. Here we summarize the role of the NFIs in cancer, focusing largely on the potential mechanisms associated with chromatin remodelling and epigenetic modulation of gene expression.

Association of genetic variants in and promoter hypermethylation of CDH1 with gastric cancer: a meta-analysis

Gastric cancer (GC) is a common cause of cancer-related death. The etiology and pathogenesis of GC remain unclear, with genetic and epigenetic factors playing an important role. Previous studies investigated the association of GC with many genetic variants in and promoter hypermethylation of E-cadherin gene (CDH1), with conflicting results reported.To clarify this inconsistency, we conducted updated meta-analyses to assess the association of genetic variants in and the promoter hypermethylation of CDH1 with GC, including C-160A (rs16260) and other less-studied genetic variants,Data sources were PubMed, Cochrane Library, Google Scholar, Web of Knowledge, and HuGE, a navigator for human genome epidemiology.Study eligibility criteria and participant details are as follows: studies were conducted on human subjects; outcomes of interest include GC; report of genotype data of individual genetic variants in (or methylation status of) CDH1 in participants with and without GC (or providing odds ratios [OR] and their variances).Study appraisal and synthesis methods included the use of OR as a measure of the association, calculated from random effects models in meta-analyses. We used I for the assessment of between-study heterogeneity, and publication bias was assessed using funnel plot and Egger test.A total of 33 studies from 30 published articles met the eligibility criteria and were included in our analyses. We found no association between C-160A and GC (OR = 0.88; 95% confidence interval [CI], 0.71-1.08; P = 0.215), assuming an additive model (reference allele C). C-160A was associated with cardia (OR = 0.21; 95% CI, 0.11-0.41; P = 2.60 × 10), intestinal (OR = 0.66; 95% CI, 0.49-0.90; P = 0.008), and diffuse GC (OR = 0.57; 95% CI, 0.40-0.82; P = 0.002). The association of C-160A with noncardia GC is of bottom line significance (OR = 0.65; 95% CI, 0.42-1.01; P = 0.054). Multiple other less-studied genetic variants in CDH1 also exhibited association with GC. Gene-based analysis indicated a significant cumulative association of genetic variants in CDH1 with GC (all Ps <10). Sensitivity analysis excluding studies not meeting Hardy-Weinberg equilibrium (HWE) yielded similar results. Analysis by ethnic groups revealed significant association of C-160A with cardia GC in both Asian and whites, significant association with noncardia GC only in Asians, and no significant association with intestinal GC in both ethnic groups. There was significant association of C160-A with diffuse GC in Asians (P = 0.011) but not in whites (P = 0.081). However, after excluding studies that violate HWE, this observed association is no longer significant (P = 0.126). We observed strong association of promoter hypermethylation of CDH1 with GC (OR = 12.23; 95% CI, 8.80-17.00; P = 1.42 × 10), suggesting that epigenetic regulation of CDH1 could play a critical role in the etiology of GC.Limitations of this study are as follows: we could not adjust for confounding factors; some meta-analyses were based on a small number of studies; sensitivity analysis was limited due to unavailability of data; we could not test publication bias for some meta-analyses due to small number of included studies.We found no significant association of the widely studied genetic variant C-160A, but identified some other genetic variants showing significant association with GC. Future studies with large sample sizes that control for confounding risk factors and/or intensively interrogate CpG sites in CDH1 are needed to validate the results found in this study and to explore additional epigenetic loci that affect GC risk.

Beyond the stomach: An updated view of Helicobacter pylori pathogenesis, diagnosis, and treatment

Helicobacter pylori (H. pylori) is an extremely common, yet underappreciated, pathogen that is able to alter host physiology and subvert the host immune response, allowing it to persist for the life of the host. H. pylori is the primary cause of peptic ulcers and gastric cancer. In the United States, the annual cost associated with peptic ulcer disease is estimated to be $6 billion and gastric cancer kills over 700000 people per year globally. The prevalence of H. pylori infection remains high (> 50%) in much of the world, although the infection rates are dropping in some developed nations. The drop in H. pylori prevalence could be a double-edged sword, reducing the incidence of gastric diseases while increasing the risk of allergies and esophageal diseases. The list of diseases potentially caused by H. pylori continues to grow; however, mechanistic explanations of how H. pylori could contribute to extragastric diseases lag far behind clinical studies. A number of host factors and H. pylori virulence factors act in concert to determine which individuals are at the highest risk of disease. These include bacterial cytotoxins and polymorphisms in host genes responsible for directing the immune response. This review discusses the latest advances in H. pylori pathogenesis, diagnosis, and treatment. Up-to-date information on correlations between H. pylori and extragastric diseases is also provided.

E-cadherin and gastric cancer: cause, consequence, and applications

E-cadherin (epithelial-cadherin), encoded by the CDH1 gene, is a transmembrane glycoprotein playing a crucial role in maintaining cell-cell adhesion. E-cadherin has been reported to be a tumor suppressor and to be down regulated in gastric cancer. Besides genetic mutations in CDH1 gene to induce hereditary diffuse gastric cancer (HDGC), epigenetic factors such as DNA hypermethylation also contribute to the reduction of E-cadherin in gastric carcinogenesis. In addition, expression of E-cadherin could be mediated by infectious agents such as H. pylori (Helicobacter pylori). As E-cadherin is vitally involved in signaling pathways modulating cell proliferation, survival, invasion, and migration, dysregulation of E-cadherin leads to dysfunction of gastric epithelial cells and contributes to gastric cancer development. Moreover, changes in its expression could reflect pathological conditions of gastric mucosa, making its role in gastric cancer complicated. In this review, we summarize the functions of E-cadherin and the signaling pathways it regulates. We aim to provide comprehensive perspectives in the molecular mechanism of E-cadherin and its involvement in gastric cancer initiation and progression. We also focus on its applications for early diagnosis, prognosis, and therapy in gastric cancer in order to open new avenues in this field.

Genetic features of familial gastric cancer

Gastric cancer is a common malignant tumor of the gastrointestinal tract worldwide. Although its incidence has declined in recent years, it is still the most prevalent cancer in Asian countries. Familial aggregation has been seen in approximately 10% of the patients, and 1%-3% of cases are hereditary, indicating a genetic basis of familial gastric cancer (FGC). Hereditary diffuse gastric cancer (HDGC), regarded as a subset of FGC, performs germline mutations of the cell to cell adhesion molecule E-cadherin (CDH1) in one-third of the families. Other susceptibility genes include MMR and MET. In this article, we will review the genetic features of FGC.

Hereditary diffuse gastric cancer: translation of CDH1 germline mutations into clinical practice

Hereditary diffuse gastric cancer (HDGC) is the only known cancer syndrome that is dominated by gastric adenocarcinoma. HDGC is caused by germline mutation of the CDH1 gene that encodes the cell adhesion protein E-cadherin. Mutation carriers have a more than 70% lifetime risk of developing DGC and an elevated risk of lobular breast cancer. Intestinal-type gastric cancer is not part of the syndrome. Clinical management of HDGC involves predictive genetic testing beginning at or near 16 years of age. It is recommended that mutation carriers undergo prophylactic gastrectomy after about 20 years of age. Anatomical mapping has demonstrated that mutation carriers develop multifocal stage T1a signet ring cell carcinomas, with up to several hundred foci being observed in single stomachs. These foci develop following the somatic inactivation of the second CDH1 allele by mechanisms that include DNA promoter hypermethylation.

Hereditary diffuse gastric cancer

Gastric cancer is one of the world's leading causes of cancer mortality. A small percentage of cases can be attributed to heritable mutations in highly penetrant cancer susceptibility genes. In this chapter we will focus on the genetic cause of hereditary diffuse gastric cancer (HDGC). Until 10 years ago, individuals from these families lived with the uncertainty of developing lethal gastric cancer. Today, HDGC families can be identified, tested for causative mutations in CDH1, and for those families where a pathogenic mutation can be identified, prophylactic total gastrectomy can be implemented in asymptomatic mutation carriers who elect to virtually eliminate their risk of developing this lethal disease.

Allele-specific CDH1 downregulation and hereditary diffuse gastric cancer

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant cancer susceptibility syndrome characterized by early-onset diffuse gastric cancer (DGC) and lobular breast cancer. E-cadherin (CDH1) heterozygous germline mutations and deletions are found in 40% of families. Independent of CDH1 alterations, most HDGC tumours display mislocalized or absent E-cadherin immunoexpression, therefore undetected defects at the CDH1 locus may still be involved. We aimed at determining whether CDH1 mutation-negative probands display germline CDH1 allele-specific expression (ASE) imbalance, using a single-nucleotide primer extension-based procedure and tried to uncover the underlying molecular defect. CDH1 ASE analysis was performed using three intragenic SNPs in RNA extracted from the blood of 21 cancer-free individuals and 22 HDGC probands (5 CDH1 mutation carriers and 17 CDH1 negative). Germline promoter methylation, deletions and haplotype-related susceptibility at the CDH1 locus were analysed. Both CDH1 alleles from cancer-free individuals displayed equivalent expression levels, whereas monoallelic CDH1 expression or high allelic expression imbalance (AI) was present in 80% of CDH1 mutant and 70.6% (n = 12) of CDH1-negative HDGC probands. Germline deletions and promoter hypermethylation were found in 25% of probands displaying high CDH1 AI. No particular haplotype was found to be associated with CDH1 high AI. Germline CDH1 AI is highly frequent among CDH1 mutation-negative probands but was not seen in cancer-free individuals. This implicates the CDH1 locus in the majority of mutation-negative HDGC families.

E-cadherin polymorphisms and breast cancer susceptibility: a report from the Shanghai Breast Cancer Study

The epithelial transmembrane glycoprotein E-cadherin (CDH1) is necessary for intercellular adhesion, cell signaling, and maintenance of cellular differentiation; reduced expression contributes to cell proliferation, invasion, and cancer progression. Functional or potentially functional single nucleotide polymorphisms (SNPs) in E-cadherin have been previously identified and evaluated in relation to cancer risk; however, studies on breast cancer have been sparse. Forty-six SNPs were genotyped to capture genetic variation of the CDH1 gene among 2,290 Phase 1 and 1,944 Phase 2 participants of the Shanghai Breast Cancer Study (SBCS), a large, population-based, case-control study. No overall associations between E-cadherin SNPs and breast cancer risk were observed. When stratified by menopausal status, associations that were consistent between Phases 1 and 2 and significant when data from both phases were combined were observed for several SNPs. Although none of these associations retained statistical significance after correcting for the total number of polymorphisms evaluated, this study suggests that genetic variation in CDH1 may be associated with breast cancer risk, and that this relationship may vary by menopausal status.

Hereditary diffuse gastric cancer: a manifestation of lost cell polarity

Hereditary diffuse gastric cancer is a cancer syndrome caused by germline mutations in the gene for the cell adhesion protein E-cadherin (CDH1). E-cadherin plays a central role in the maintenance of cell polarity and its loss during tumorigenesis is associated with poorly differentiated cancers and a poor prognosis. Hereditary diffuse gastric cancer is dominated by diffuse-type gastric adenocarcinoma, often with signet ring cell morphology. Large numbers of stage T1a signet ring cell carcinomas exist in the stomachs of CDH1 mutation carriers from a young age, and these foci sometimes show enrichment to the transition zone between the body and antrum. Generally these signet ring cell carcinomas are hypoproliferative, lack Wnt pathway activation, and are relatively indolent. However, a small proportion of the T1a foci contain cells that are poorly differentiated, display mesenchymal features, and express activated c-Src and its downstream targets. These same features are observed in more advanced stages of hereditary diffuse gastric cancer progression, suggesting that an epithelial-mesenchymal transition is required for tumor invasion beyond the muscularis mucosae. Hereditary diffuse gastric cancer initiation requires somatic down-regulation of the second CDH1 allele, which in most cases is caused by DNA promoter hypermethylation. Subsequent to CDH1 down-regulation, lost polarity in gastric stem or progenitor cells would be predicted to interfere with mitotic spindle orientation and the segregation of cell fate determinants. We predict that this disruption of cell division results in daughter cells being deposited in the lamina propria where their population expands and partially differentiates, resulting in the formation of foci of signet ring cells.