CDH1/E-cadherin germline mutations in early-onset gastric cancer

Early-Onset Gastrointestinal Malignancies: An Investigation into a Rising Concern

There is growing recognition of early-onset gastrointestinal (GI) malignancies in young adults < 50 years of age. While much of the literature has emphasized colorectal cancer, these also include esophageal, gastric, liver, pancreatic, and biliary tract malignancies. Various factors, including lifestyle, hereditary, and environmental elements, have been proposed to explain the rising incidence of GI malignancies in the younger population. This review aims to provide an overview of the recent literature, including global trends and information regarding genetic and environmental risk factors.

Current advances in understanding the molecular profile of hereditary diffuse gastric cancer and its clinical implications

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant cancer syndrome attributed to germline CDH1 mutations that carries a high risk for early onset DGC. HDGC raises a significant health issue due to its high penetrance and mortality unless diagnosed early. The definitive treatment is to undergo prophylactic total gastrectomy which is associated with significant morbidity., highlighting the urgent need for alternative treatment methods. However, there is limited literature examining potential therapeutic strategies building on emerging insights into the molecular basis of progressive lesions in the context of HDGC. The aim of this review is to summarise the current understanding of HDGC in the context of CDH1 pathogenic variants followed by a review of the proposed mechanisms for progression. In addition, we discuss the development of novel therapeutic approaches and highlight pertinent areas for further research. A literature search was therefore performed for relevant studies examining CDH1 germline variants, second-hit mechanisms of CDH1, pathogenesis of HDGC and potential therapeutic strategies in databases, including PubMed, ScienceDirect and Scopus. Germline mutations are mostly truncating CDH1 variants affecting extracellular domains of E-cadherin, generally due to frameshift, single nucleotide variants or splice site mutations. A second somatic hit of CDH1 most commonly occurs via promoter methylation as shown in 3 studies, but studies are limited with a small sample size. The multi-focal development of indolent lesions in HDGC provide a unique opportunity to understand genetic events that drive the transition to the invasive phenotype. To date, a few signalling pathways have been shown to facilitate the progression of HDGC, including Notch and Wnt. In in-vitro studies, the ability to inhibit Notch signalling was lost in cells transfected with mutant forms of E-cadherin, and increased Notch-1 activity correlated with apoptosis resistance. Furthermore, in patient samples, overexpression of Wnt-2 was associated with cytoplasmic and nuclear β-catenin accumulation and increased metastatic potential. As loss-of-function mutations are challenging to target therapeutically, these findings pave the way towards a synthetic lethal approach in CDH1-deficient cells with some promising results in-vitro. In future, if we could better understand the molecular vulnerabilities in HDGC, there may be opportunities to offer alternative treatment pathways to avoid gastrectomy.

Is early-onset cancer an emerging global epidemic? Current evidence and future implications

Over the past several decades, the incidence of early-onset cancers, often defined as cancers diagnosed in adults <50 years of age, in the breast, colorectum, endometrium, oesophagus, extrahepatic bile duct, gallbladder, head and neck, kidney, liver, bone marrow, pancreas, prostate, stomach and thyroid has increased in multiple countries. Increased use of screening programmes has contributed to this phenomenon to a certain extent, although a genuine increase in the incidence of early-onset forms of several cancer types also seems to have emerged. Evidence suggests an aetiological role of risk factor exposures in early life and young adulthood. Since the mid-20th century, substantial multigenerational changes in the exposome have occurred (including changes in diet, lifestyle, obesity, environment and the microbiome, all of which might interact with genomic and/or genetic susceptibilities). However, the effects of individual exposures remain largely unknown. To study early-life exposures and their implications for multiple cancer types will require prospective cohort studies with dedicated biobanking and data collection technologies. Raising awareness among both the public and health-care professionals will also be critical. In this Review, we describe changes in the incidence of early-onset cancers globally and suggest measures that are likely to reduce the burden of cancers and other chronic non-communicable diseases.

CDH1 Germline Variants in a Tunisian Cohort with Hereditary Diffuse Gastric Carcinoma

Mutational screening of the CDH1 gene is a standard treatment for patients who fulfill Hereditary Diffuse Gastric Cancer (HDGC) testing criteria. In this framework, the classification of variants found in this gene is a crucial step for the clinical management of patients at high risk for HDGC. The aim of our study was to identify CDH1 as well as CTNNA1 mutational profiles predisposing to HDGC in Tunisia. Thirty-four cases were included for this purpose. We performed Sanger sequencing for the entire coding region of both genes and MLPA (Multiplex Ligation Probe Amplification) assays to investigate large rearrangements of the CDH1 gene. As a result, three cases, all with the HDGC inclusion criteria (8.82% of the entire cohort), carried pathogenic and likely pathogenic variants of the CDH1 gene. These variants involve a novel splicing alteration, a missense c.2281G > A detected by Sanger sequencing, and a large rearrangement detected by MLPA. No pathogenic CTNNA1 variants were found. The large rearrangement is clearly pathogenic, implicating a large deletion of two exons. The novel splicing variant creates a cryptic site. The missense variant is a VUS (Variant with Uncertain Significance). With ACMG (American College of Medical Genetics and Genomics) classification and the evidence available, we thus suggest a revision of its status to likely pathogenic. Further functional studies or cosegregation analysis should be performed to confirm its pathogenicity. In addition, molecular exploration will be needed to understand the etiology of the other CDH1- and CTNNA1-negative cases fulfilling the HDGC inclusion criteria.

Association of CDH1 -160 C → A and -347 G→ GA polymorphisms and expression of E-cadherin and gastric cancer: A case-control study

Objectives

The loss of function of the E-cadherin (CDH1) gene with -160 C→A and -347 G→GA polymorphisms is regarded as a critical step for gastric cancer. It was aimed to investigate possible association of these polymorphisms and immunoexpression of E-cadherin with gastric cancer.

Material and Methods

Gastric adenocarcinoma patients and individuals with benign gastric pathologies were included in this case-control study. Demographic data and pathological findings were recorded. Immunohistochemical staining of E-cadherin expression and analysis of -160 C→A and -347 G→GA polymorphisms were done. Differences between allele frequencies of -160 C→A and -347 G→GA polymorphisms and expression of E-cadherin were the primary outcomes.

Results

There were 78 gastric cancer patients (Group A) and 113 individuals with benign gastric pathologies (Group B). The number of male patients and mean age were higher in Group A (p <0.001). -160 C→A and 347 G→GA polymorphisms and their allelic distributions showed no difference between the groups (p> 0.05 for all). There was a significant association between -160 C→A polymorphism and grade of E-cadherin expression (p= 0.013). There were no significant differences between survival rates with -160 C→A, 347 G→GA and intensity of E-cadherin expression (p> 0.05 for all). There was no significant association between -160 C→A and -347 G→GA polymorphisms and gastric cancer.

Conclusion

There was no impact of E-cadherin expression on tumoral features and survival in gastric cancer. -160 C→A polymorphism may influence the expression of E-cadherin in gastric cancer.

A Distinct Clinicopathological Feature and Prognosis of Young Gastric Cancer Patients Aged ≤ 45 Years Old

Purpose

The aim of this retrospective study was to probe into clinicopathological features and prognosis of early-onset gastric cancer (EOGC) patients aged ≤ 45 years old.

Methods

This study selected 154 young gastric cancer patients aged ≤ 45 years old and 158 elderly gastric cancer patients aged > 50 years old admitted to West China Hospital of Sichuan University in 2009-2019 as the research object. These patients were further divided into two groups according to whether tumor can be resected radically. The following parameters were analyzed: age, gender, helicobacter pylori (HP) infection status, Her-2 status, pathological type and stage, chemotherapy, tumor differentiation degree, overall survival (OS).

Results

More than 3,000 patients with gastric carcinoma were screened, and 154 young gastric cancer patients aged ≤ 45 years old were identified as EOGC. Among them, the number of female patients in EOGC group was significantly higher than that of males, accounting for 63.6%. In addition, EOGC were associated with diffuse Laur´en type and poorly differentiated tumors. Interestingly, the Kaplan-Meier method showed that the OS of unresectable EOGC group was significantly lower than that of unresectable LOGC group (P = 0.0005) and chemotherapy containing paclitaxel tended to be more effective in the young people (P = 0.0511). Nevertheless, there was no significant difference in OS between young and elderly patients with gastric cancer in the radical resection group (P = 0.3881).

Conclusion

EOGC patients have a worse prognosis than late-onset gastric cancer (LOGC) patients with advanced unresectable gastric cancer. Palliative surgery or chemotherapy containing paclitaxel may improve the OS of unresectable young individuals with gastric cancer. Additional randomized controlled trials are required for guiding clinical practice.

Geographical Distribution of E-cadherin Germline Mutations in the Context of Diffuse Gastric Cancer: A Systematic Review

Simple Summary

E-cadherin (CDH1 gene) germline mutations are associated with the development of the autosomal cancer syndrome known as hereditary diffuse gastric cancer. About 30% of families fulfilling the clinical criteria established by the International Gastric Cancer Linkage Consortium have constitutional alterations of the CDH1 gene. Different patterns of CDH1 germline mutations have described as truncating, deletion, insertion, splice site, non sense, silence, and at last, missense alterations. The frequency of the different E-cadherin germline mutations in countries with different incidence rates for gastric carcinoma has reported extremely variable. In this study we aimed to assess the worldwide frequency of CDH1 germline mutations in gastric cancers coming from different geographical areas, using a systematic approach.

Abstract

Hereditary diffuse gastric cancer (HDGC) is a complex and multifactorial inherited cancer predisposition syndrome caused by CDH1 germline mutations. Nevertheless, current CDH1 genetic screening recommendations disregard an unbalanced worldwide distribution of CDH1 variants, impacting testing efficacy and patient management. In this systematic review, we collected and analyzed all studies describing CDH1 variants in gastric cancer patients originating from both high- and low-prevalence countries. Selected studies were categorized as family study, series study, and unknown study, according to the implementation of HDGC clinical criteria for genetic testing. Our results indicate that CDH1 mutations are more frequently identified in gastric cancer low-incidence countries, and in the family study group that encompasses cases fulfilling criteria. Considering the type of CDH1 alterations, we verified that the relative frequency of mutation types varies within study groups and geographical areas. In the series study, the missense variant frequency is higher in high-incidence areas of gastric cancer, when compared with non-missense mutations. However, application of variant scoring for putative relevance led to a strong reduction of CDH1 variants conferring increased risk of gastric cancer. Herein, we demonstrate that criteria for CDH1 genetic screening are critical for identification of individuals carrying mutations with clinical significance. Further, we propose that future guidelines for testing should consider GC incidence across geographical regions for improved surveillance programs and early diagnosis of disease.

Hispanic/Latino Patients with Gastric Adenocarcinoma Have Distinct Molecular Profiles Including a High Rate of Germline CDH1 Variants

Hispanic/Latino patients have a higher incidence of gastric cancer and worse cancer-related outcomes compared with patients of other backgrounds. Whether there is a molecular basis for these disparities is unknown, as very few Hispanic/Latino patients have been included in previous studies. To determine the genomic landscape of gastric cancer in Hispanic/Latino patients, we performed whole-exome sequencing (WES) and RNA sequencing on tumor samples from 57 patients; germline analysis was conducted on 83 patients. The results were compared with data from Asian and White patients published by The Cancer Genome Atlas. Hispanic/Latino patients had a significantly larger proportion of genomically stable subtype tumors compared with Asian and White patients (65% vs. 21% vs. 20%, P < 0.001). Transcriptomic analysis identified molecular signatures that were prognostic. Of the 43 Hispanic/Latino patients with diffuse-type cancer, 7 (16%) had germline variants in CDH1. Variant carriers were significantly younger than noncarriers (41 vs. 50 years, P < 0.05). In silico algorithms predicted five variants to be deleterious. For two variants that were predicted to be benign, in vitro modeling demonstrated that these mutations conferred increased migratory capability, suggesting pathogenicity. Hispanic/Latino patients with gastric cancer possess unique genomic landscapes, including a high rate of CDH1 germline variants that may partially explain their aggressive clinical phenotypes. Individualized screening, genetic counseling, and treatment protocols based on patient ethnicity and race may be necessary. SIGNIFICANCE: Gastric cancer in Hispanic/Latino patients has unique genomic profiles that may contribute to the aggressive clinical phenotypes seen in these patients.

Sporadic Early-Onset Diffuse Gastric Cancers Have High Frequency of Somatic CDH1 Alterations, but Low Frequency of Somatic RHOA Mutations Compared With Late-Onset Cancers

BACKGROUND & AIMS

Early-onset gastric cancer, which develops in patients younger than most gastric cancers, is usually detected at advanced stages, has diffuse histologic features, and occurs more frequently in women. We investigated somatic genomic alterations associated with the unique characteristics of sporadic diffuse gastric cancers (DGCs) from younger patients.

METHODS

We conducted whole exome and RNA sequence analyses of 80 resected DGC samples from patients 45 years old or younger in Korea. Patients with pathogenic germline mutations in CDH1, TP53, and ATM were excluded from the onset of this analysis, given our focus on somatic alterations. We used MutSig2CV to evaluate the significance of mutated genes. We recruited 29 additional early-onset Korean DGC samples and performed SNP6.0 array and targeted sequencing analyses of these 109 early-onset DGC samples (54.1% female, median age, 38 years). We compared the SNP6.0 array and targeted sequencing data of the 109 early-onset DGC samples with those from diffuse-type stomach tumor samples collected from 115 patients in Korea who were 46 years or older (late onset) at the time of diagnosis (controls; 29.6% female, median age, 67 years). We compared patient survival times among tumors from different subgroups and with different somatic mutations. We performed gene silencing of RHOA or CDH1 in DGC cells with small interfering RNAs for cell-based assays.

RESULTS

We identified somatic mutations in the following genes in a significant number of early-onset DGCs: the cadherin 1 gene (CDH1), TP53, ARID1A, KRAS, PIK3CA, ERBB3, TGFBR1, FBXW7, RHOA, and MAP2K1. None of 109 early-onset DGC cases had pathogenic germline CDH1 mutations. A higher proportion of early-onset DGCs had mutations in CDH1 (42.2%) or TGFBR1 (7.3%) compared with control DGCs (17.4% and 0.9%, respectively) (P < .001 and P = .014 for CDH1 and TGFBR1, respectively). In contrast, a smaller proportion of early-onset DGCs contained mutations in RHOA (9.2%) than control DGCs (19.1%) (P = .033). Late-onset DGCs in The Cancer Genome Atlas also contained less frequent mutations in CDH1 and TGFBR1 and more frequent RHOA mutations, compared with early-onset DGCs. Early-onset DGCs from women contained significantly more mutations in CDH1 or TGFBR1 than early-onset DGCs from men. CDH1 alterations, but not RHOA mutations, were associated with shorter survival times in patients with early-onset DGCs (hazard ratio, 3.4; 95% confidence interval, 1.5-7.7). RHOA activity was reduced by an R5W substitution-the RHOA mutation most frequently detected in early-onset DGCs. Silencing of CDH1, but not RHOA, increased migratory activity of DGC cells.

CONCLUSIONS

In an integrative genomic analysis, we found higher proportions of early-onset DGCs to contain somatic mutations in CDH1 or TGFBR1 compared with late-onset DGCs. However, a smaller proportion of early-onset DGCs contained somatic mutations in RHOA than late-onset DGCs. CDH1 alterations, but not RHOA mutations, were associated with shorter survival times of patients, which might account for the aggressive clinical course of early-onset gastric cancer. Female predominance in early-onset gastric cancer may be related to relatively high rates of somatic CDH1 and TGFBR1 mutations in this population.

Future Directions in Improving Outcomes for Patients with Gastric and Esophageal Cancer

"This issue of Hematology/Oncology Clinics of North America provides an update to the current understanding of the physiology of gastric and esophageal cancers and the state-of-the-art management of disease. Over the past 10 years, we have witnessed dramatic changes in both our understanding of the disease and its management. We have 2 new biological agents approved to treat advanced disease, with several more prospects under development. In this article, the author looks to the future, attempting to answer the question of which advancements will play the biggest role in improving patient outcomes in this still-devastating disease.

Lauren classification and individualized chemotherapy in gastric cancer

Gastric cancer is one of the most common malignancies worldwide. During the last 50 years, the histological classification of gastric carcinoma has been largely based on Lauren's criteria, in which gastric cancer is classified into two major histological subtypes, namely intestinal type and diffuse type adenocarcinoma. This classification was introduced in 1965, and remains currently widely accepted and employed, since it constitutes a simple and robust classification approach. The two histological subtypes of gastric cancer proposed by the Lauren classification exhibit a number of distinct clinical and molecular characteristics, including histogenesis, cell differentiation, epidemiology, etiology, carcinogenesis, biological behaviors and prognosis. Gastric cancer exhibits varied sensitivity to chemotherapy drugs and significant heterogeneity; therefore, the disease may be a target for individualized therapy. The Lauren classification may provide the basis for individualized treatment for advanced gastric cancer, which is increasingly gaining attention in the scientific field. However, few studies have investigated individualized treatment that is guided by pathological classification. The aim of the current review is to analyze the two major histological subtypes of gastric cancer, as proposed by the Lauren classification, and to discuss the implications of this for personalized chemotherapy.

Genes involved in the regulation of intestinal permeability and their role in ulcerative colitis

OBJECTIVE

Genome-wide association studies have identified single nucleotide polymorphisms in genes that might influence intestinal barrier function (HNF4A, ECM1, CDH1 and LAMB1) to increase the risk for ulcerative colitis (UC). The aim of our study was to detect causative sequence alterations and provide a functional link to a disturbed intestinal permeability (IP) in UC.

METHODS

A total of 19 UC patients with increased IP (lactulose/mannitol ratio measured by sugar drink test) were identified from a large database, and exon/intron boundaries, coding and promoter regions of HNF4A, ECM1, CDH1 and LAMB1 were sequenced. Variants with putative protein alterations were studied for an association with IP in 82 UC patients. A case-control analysis including a genotype phenotype correlation was performed in 743 patients with inflammatory bowel disease (IBD) and 473 healthy controls.

RESULTS

In UC patients, we identified 11 missense-mutations, 12 synonymous mutations, one putative promoter variant and three variants in introns close to the intron/exon boundaries (CDH1, HNF4A). For several variants prediction tools revealed damaging protein alterations. None of the studied variants, however, showed an association with an increased IP in UC. In the case-control analysis, the frequency of all investigated variants did not differ between UC or Crohn's disease and healthy controls. Furthermore, no significant association was found to a distinct phenotype.

CONCLUSIONS

Despite our large sequencing approach, we could not identify protein altering variants in the genes HNF4A, ECM1, CDH1 and LAMB1 which could explain an impaired intestinal barrier function in UC. The functional relevance of these genes in IBD remains unknown.

Identification and characterization of CDH1 germline variants in sporadic gastric cancer patients and in individuals at risk of gastric cancer

Objective

To screen and characterize germline variants for E-cadherin (CDH1) in non-hereditary gastric cancer (GC) patients and in subjects at risk of GC.

Methods

59 GCs, 59 first degree relatives (FDRs) of GC, 20 autoimmune metaplastic atrophic gastritis (AMAGs) and 52 blood donors (BDs) were analyzed for CDH1 by direct sequencing, structural modelling and bioinformatics. Functional impact on splicing was assessed for intronic mutations. E-cadherin/β-catenin immunohistochemical staining and E-cadherin mRNA quantification using RT-PCR were performed.

Results

In GCs, 4 missense variants (p.G274S; p.A298T; p.T470I; p.A592T), 1 mutation in the 5′UTR (−71C>G) and 1 mutation in the intronic IVS12 (c.1937-13T>C) region were found. First pathogenic effect of p.A298T mutation was predicted by protein 3D modelling. The novel p.G274S mutation showed a no clear functional significance. Moreover, first, intronic IVS12 (c.1937-13T>C) mutation was demonstrated to lead to an aberrant CDH1 transcript with exon 11 deletion. This mutation was found in 2 GCs and in 1 BD. In FDRs, we identified 4 variants: the polymorphic (p.A592T) and 3 mutations in untranslated regions with unidentified functional role except for the 5′UTR (−54G>C) that had been found to decrease CDH1 transcription. In AMAGs, we detected 2 alterations: 1 missense (p.A592T) and 1 novel variant (IVS1 (c.48+7C>T)) without effect on CDH1 splicing. Several silent and polymorphic substitutions were found in all the groups studied.

Conclusions

Overall our study improves upon the current characterization of CDH1 mutations and their functional role in GC and in individuals at risk of GC. Mutations found in untranslated regions and data on splicing effects deserve a particular attention like associated with a reduced E-cadherin amount. The utility of CDH1 screening, in addition to the identification of other risk factors, could be useful for the early detection of GC in subjects at risk (i.e. FDRs and AMAGs), and warrants further study.

Thrombospondin-4 expression is activated during the stromal response to invasive breast cancer

The thromobospondins are a family of extracellular glycoproteins that are activated during tissue remodeling processes such as embryogenesis, wound healing and cancer. Thrombospondin-4 (THBS4) is known to have roles in cellular migration, adhesion and attachment, as well as proliferation in different contexts. Data to support a role in cancer biology is increasing, including for gastrointestinal and prostate tumours. Here, using a combination of immunohistochemistry, immunofluorescence and analysis of publicly available genomic and expression data, we present the first study describing the pattern of expression of THBS4 in normal breast and breast cancer. THBS4 was located to the basement membrane of large ducts and vessels in normal breast tissue, but was absent from epithelium and extracellular matrix. There was a significant induction in expression in cancer-associated stroma relative to normal stroma (P = 0.0033), neoplastic epithelium (P < 0.0001) and normal epithelium (P < 0.0001). There was no difference in stromal expression of THBS4 between invasive ductal carcinomas (IDC) and invasive lobular carcinomas (ILC). The THBS4 mRNA levels were variable yet were generally highest in tumours typically rich in stromal content (ILC, ER positive low grade IDC; luminal A and normal-like subtypes). Genomic alterations of the THBS4 gene (somatic mutations and gene copy number) are rare suggesting this dramatic activation in expression is most likely dynamically regulated through the interaction between invading tumour cells and stromal fibroblasts in the local microenvironment. In summary, THBS4 expression in breast cancer-associated extracellular matrix contributes to the activated stromal response exhibited during tumour progression and this may facilitate invasion of tumour cells.

Novel CDH1 germline mutations identified in Chinese gastric cancer patients

AIM: To give a comprehensive report of E-cadherin gene (CDH1) variations in a population at a high risk for gastric cancer (GC).

METHODS: The samples consisted of 178 men and 58 women with a mean age of 62.3 ± 9.4 years and an age range of 30-84 years. A total of 240 cancer-free controls were recruited (mean age of 61.8 ± 10.1 years, age range of 26-82 years). Samples were screened for CDH1 germline mutations by high-resolution melting analysis or directly sequencing. Luciferase reporter assay, RNA splicing assay and bioinformatic analysis were used to evaluate the effect of mutations.

RESULTS: Four novel CDH1 sequence alterations were identified in GC patients including a G>T transition 49 bp before the start codon; a three-nucleotide deletion, c.44_46del TGC; one missense mutation, c.604G>A (V202I); and one variation in the intron, c.1320+7A>G. In addition, polymorphism frequencies were observed for CDH1-164delT, -161C>A, -73A>C, c.48+6C>T, c.48+62_48+63delinsCGTGCCCCAGCCC, c.894C>T (A298A), c.1224G>A (A408A), c.1888C>G (L630V), c.2076T>C (A692A), and c.2253C>T (N751N) which is similar to the data reported in http://www.ncbi.nlm.nih.gov/projects/SNP/. RNA splicing analysis suggested that the c.1320+7A>G and c.1224G>A variations did not affect exon splicing ability. Luciferase reporter assay demonstrated that the c.-49T variation might be helpful for E-cadherin transcription, though the increase in transcription activity is limited (only 33%). SIFT score and PolyPhen analysis both demonstrated that the L630V missense mutation probably damages protein function, while the V202I variant does not.

CONCLUSION: This study reveals novel mutations in sporadic GC patients which had been poorly investigated for susceptibility genes.

Hereditary diffuse gastric cancer: a family diagnosis and treatment

Hereditary diffuse gastric cancer (HDGC) is a rare cancer representing approximately 2% of all gastric cancers. It is caused by CDHI gene mutations, inherited in an autosomal dominant fashion, that affect the function of E-cadherin. Approximately 38% of HDGC families have a CDHI gene mutation. With an estimated 75% penetrance rate, carriers are at high risk for HDGC. We describe the case of a Caucasian male of German-Russian ancestry, carrying a CDHI gene mutation, who survived for 18 months after being diagnosed with HDGC. The results of genetic testing undergone by his family members are also reported, along with a review of the current literature. Since surveillance methods for HDGC are ineffective and unreliable, total prophylactic gastrectomy is advised for individuals with the gene mutation. Additionally, a diagnosis of HDGC should lead to genetic evaluation of family members followed by preventative measures.

E-cadherin alterations in hereditary disorders with emphasis on hereditary diffuse gastric cancer

The only gastric cancer (GC) syndrome with a proven inherited defect is designated as hereditary diffuse gastric cancer (HDGC) and is caused by germline E-cadherin/CDH1 alterations. Other E-cadherin-associated hereditary disorders have been identified, encompassing HDGC families with or without cleft-lip/palate involvement, isolated early-onset diffuse GCs, and lobular breast cancer families without GC. To date, 141 probands harboring more than 100 different germline CDH1 alterations, mainly point mutations and large deletions, have been described in these different settings. A third of all HDGC families described so far carry recurrent CDH1 alterations. Full screening of CDH1 is recommended in patients fulfilling the HDGC criteria and total prophylactic gastrectomy is the only reliable intervention for carriers of pathogenic alterations. In this chapter, we discuss CDH1-associated syndromes, frequency and type of CDH1 germline alterations, clinical criteria, and guidelines for genetic counseling, molecular pathology, and available animal/cell line models of the disease.

Familial gastric cancer: genetics, diagnosis, and management

This article focuses on the diagnosis and management of familial gastric cancer, particularly hereditary diffuse gastric cancer (HDGC). First, existing consensus guidelines are discussed and then the pathology and genetics of HDGC are reviewed. Second, patient management is covered, including surveillance gastroscopy, prophylactic total gastrectomy, and management of the risk of breast cancer.

Frequency of CDH1 germline mutations in gastric carcinoma coming from high- and low-risk areas: metanalysis and systematic review of the literature

Background

The frequency of E-cadherin germline mutations in countries with different incidence rates for gastric carcinoma has not been well established. The goal of this study was to assess the worldwide frequency of CDH1 germline mutations in gastric cancers coming from low- and high-risk areas.

Methods

English articles using MEDLINE access (from 1998 to 2011). Search terms included CDH1, E-cadherin, germline mutation, gastric cancer, hereditary, familial and diffuse histotype.

The study included all E-cadherin germline mutations identified in gastric cancer patients; somatic mutations and germline mutations reported in other tumors were excluded.

The method of this study was scheduled in accordance with the "PRISMA statement for reporting systematic reviews and meta-analyses". Countries were classified as low- or middle/high risk-areas for gastric carcinoma incidence. Statistical analysis was performed to correlate the CDH1 mutation frequency with gastric cancer incidence areas.

Results

A total of 122 E-cadherin germline mutations have been identified; the majority (87.5%) occurred in gastric cancers coming from low-risk areas. In high-risk areas, we identified 16 mutations in which missense mutations were predominant. (68.8%). We verified a significant association between the mutation frequency and the gastric cancer risk area (p < 0.001: overall identified mutations in low- vs. middle/high-risk areas).

Conclusions

E-cadherin genetic screenings performed in low-risk areas for gastric cancer identified a higher frequency of CDH1 germline mutations. This data could open new approaches in the gastric cancer prevention test; before proposing a proband candidate for the CDH1 genetic screening, geographic variability, alongside the family history should be considered.

De novo CDH1 mutation in a family presenting with early-onset diffuse gastric cancer

In this report, we describe the first concluded case of a de novo germline mutation in CDH1 in a hereditary diffuse gastric cancer (HDGC) kindred. The incident case was a woman with a personal history of Hodgkin's lymphoma and diffuse gastric cancer, who was then confirmed to have a CDH1 mutation (c.1792 C>T (R598X)). The patient's mother was found to have the same CDH1 germline mutation; however, neither maternal grandparent was found to carry the mutation, thus leading to a conclusion that the proband's mother's mutation is of de novo origin. This case highlights the importance of recognition of the HDGC syndrome and of testing for CDH1 germline mutations in young individuals with diffuse gastric cancer without a family history of the disease.

E-cadherin genetic screening and clinico-pathologic characteristics of early onset gastric cancer

AIM

CDH1 germline alterations occur in about 40% of hereditary diffuse gastric cancer (HDGC) families. CDH1 germline mutations are also documented in few early onset diffuse gastric cancer patients (EODGC) without family history, but the real frequency in this setting in unknown. In these patients, the advanced stage at the time of diagnosis remains a clinical burden due to the poor long term survival.

METHODS

The entire coding region and exon flanking sequences of the CDH1 gene was analysed by direct sequencing in 21 EODGC patients aged ≤50 years. The potential deleterious nature for a new CDH1 missense variant was assessed by cell-cell aggregation and invasion assays. Somatic CDH1 mutation, loss of heterozygosity (LOH) and promoter hypermethylation was explored in the tumour from one CDH1 germline mutation carrier.

RESULTS

Two novel CDH1 germline variants were identified in 21 EODGC cases, c.670C>T and -63C>A. Functional analysis of the c.670C>T missense variant classified this mutation as non-pathogenic. The analysis of CDH1 somatic second hits failed to demonstrate E-cadherin structural and epigenetic alterations in the tumour sample.

CONCLUSION

Data from the present work and a systematic review of the literature revealed that CDH1 germline mutations occurred in 7.2% of EOGC patients invariably with diffuse of mixed histology. From these, proved CDH1 mutation pathogenicity has been assigned only to 2.3% of the cases who were recurrently diagnosed before 35 years old. Germline CDH1 mutation remain the only germline genetic defect described in this type of patients and CDH1 mutation screening should be recommended for patients with these characteristics.

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.

Early-onset gastric cancer: Learning lessons from the young

There is by no means a clear-cut pattern of mutations contributing to gastric cancers, and gastric cancer research can be hampered by the diversity of factors that can induce gastric cancer, such as Helicobacter pylori infection, diet, ageing and other environmental factors. Tumours are unquestionably riddled with genetic changes yet we are faced with an unsolvable puzzle with respect to a temporal relationship. It is postulated that inherited genetic factors may be more important in early-onset gastric cancer (EOGC) than in gastric cancers found in older patients as they have less exposure to environmental carcinogens. EOGC, therefore, could provide a key to unravelling the genetic changes in gastric carcinogenesis. Gastric cancers occurring in young patients provide an ideal background on which to try and uncover the initiating stages of gastric carcinogenesis. This review summarizes the literature regarding EOGC and also presents evidence that these cancers have a unique molecular-genetic phenotype, distinct from conventional gastric cancer.

Hereditary diffuse gastric cancer: prophylactic surgical oncology implications

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominantly inherited syndrome attributed to mutations of the E-cadherin gene, CDH1. There is no proven effective screening for early HDGC, and symptomatic disease is almost universally fatal. The only available effective option for CDH1 carriers is prophylactic total gastrectomy, but the variable age of onset of HDGC and the reduced penetrance (about 70%) of the CDHI gene further complicate patients' decision making.

Hereditary diffuse gastric cancer: diagnosis, genetic counseling, and prophylactic total gastrectomy

BACKGROUND

A subset of patients with diffuse gastric cancer harbor deleterious cancer-causing germline mutations in the type 1 E-cadherin (epithelial) gene (CDH1), which predisposes to the autosomal dominantly inherited hereditary diffuse gastric cancer (HDGC) syndrome. These mutations are associated with a 70% life-time risk for diffuse gastric cancer (DGC) and an additional 40% risk for lobular breast cancer in women. Management options for unaffected mutation carriers include prophylactic total gastrectomy.

METHODS

Four HDGC pedigrees from a cohort of 56 CDH1 mutation-positive families were subjected to further analysis. Cancer diagnoses, whenever possible, were verified with pathology reports and/or slides/tissue block review. Genetic counseling for family members covered the natural history of HDGC, the pros and cons of mutation testing, the lack of effective screening procedures available to CDH1 mutation-positive individuals, and the option for them of prophylactic total gastrectomy.

RESULTS

Within the 4 families, carrier testing for mutations in the CDH1 gene was carried out on 52 individuals, including 25 individuals who were positive for mutation. Prophylactic gastrectomies were performed on a total of 17 individuals from 3 of the families, including 11 first cousins from 1 of the families. Occult DGC was diagnosed in gastrectomy specimens from 13 of 17 individuals (76.5%). During follow-up questioning, each of the 11 cousins stated that the decision for the prophylactic procedure was the "right one" for them.

CONCLUSIONS

Unaffected mutation carriers from HDGC families face difficult decisions and can be assisted best through education and interactions with counseling by an informed multidisciplinary team.

A short guide to hereditary diffuse gastric cancer

Hereditary diffuse gastric cancer (HDGC) is the only known predisposition syndrome dominated by carcinoma of the stomach and with a recognised genetic cause. Germline mutations in the E-cadherin gene (CDH1) co-segregate with the disease in about half of the families with multiple diffuse gastric cancer. In these families, identification of the CDH1 mutation allows for clinical measures to be taken. Importantly, clinical intervention is likely to be therapeutic and associated with tolerable morbidity. This review is thus aimed at providing a current overview of the clinical management and the underlying biology of HDGC.