The E-cadherin gene (CDH1) variants T340A and L599V in gastric and colorectal cancer patients in Korea

Colonoscopy findings in CDH1 carriers from a multicenter international study

Germline (likely-)pathogenic variants (PV) in CDH1 predispose carriers to hereditary diffuse gastric cancer and lobular breast cancer. Previous studies from the United States suggest CDH1 variant carriers have an increased risk for adenomas or sessile serrated lesions (SSL), yet data linking CDH1 PVs and colorectal neoplasia are scarce. We aimed to investigate colonoscopy findings in CDH1 PVs. Adults carrying a PV/LPV in CDH1 with ≥ 1 colonoscopy between 01/01/2004-12/31/2023 were included. Patients were sourced from the David G. Jagelman Inherited Colorectal Cancer Registries at Cleveland Clinic and the German Consortium for Familial Intestinal Cancer. 103 CDH1 PV carriers were included. Most were female (66%) and white (93.1%). The median age at first colonoscopy was 47 years. The adenoma detection rate (ADR) was 29.4% (95% CI:19.9-41.1%) in the German cohort and 48.6% (95% CI: 33.0-64.4%) in the Cleveland cohort (p = 0.055) and significantly correlated with age (< 45 years, 13.6% (95% CI: 6.40-26.7%); 45-49 years, 52.4% (95% CI: 32.4-71.7%); ≥50 years, 52.6% (95% CI: 37.3-67.5%); p < 0.001). The ADR in Cleveland was higher than the U.S. average ADR but the difference was not statistically significant (48.6% vs. 35.6%, p = 0.08), and the ADR in the German cohort (29.4%) was similar to the national German average risk screening cohort (31.3% in men, p = 0.84; 20.1% in women, p = 0.08). In our screening cohort with CDH1 PV carriers, we demonstrated an ADR of 13.5% in individuals under 45 years, similar to the ADR in patients aged 25-40 years with a family history of CRC. Overall, SSL detection rate was 9.7%. Colorectal cancer was diagnosed in 3 patients (3.2%), 2/3 with an early age of onset before the age of 50 years. This first international study provides preliminary evidence of a higher ADR in U.S. CDH1 PV carriers compared to the general population, with a high number of adenomas detected before the age of 50. This may indicate an increased CRC risk that should be explored in larger studies.

Association of CDH1 Germline Variants and Colon Polyp Phenotypes in Patients with Hereditary Diffuse Gastric Cancer

Background and Aims

Germline CDH1 variants resulting in E-cadherin loss of function result in an increased risk of diffuse type gastric cancer and lobular type breast cancer. However, the risk of developing other epithelial neoplasms, specifically colorectal cancer, is unknown.

Methods

Patients enrolled in a prospective natural history study of hereditary gastric cancer who underwent at least one colonoscopy were evaluated.

Results

Out of 300 patients with CDH1 pathogenic or likely pathogenic variants, 85 underwent colonoscopy. More than half of patients (56%, 48/85) had at least one colorectal polyp. Most of those patients (83%, 40/48) had at least one precancerous polyp (adenoma or sessile serrated lesion). More than half (56%) of patients younger than age 45 had a colorectal polyp. Of those with polyps, the most frequent CDH1 variant type was canonical splice site (27%, 13/48) followed by nonsense (21%, 10/48). There was no association between CDH1 variant type and increased likelihood of colorectal polyps.

Conclusions

In summary, a majority of CDH1 variant carriers who underwent colonoscopy had colorectal polyps detected, and most subjects were less than 45 years old. This study of colorectal cancer risk based on the prevalence of colorectal polyps in the CDH1 population requires further investigation to appropriately counsel patients on colorectal cancer screening. Clinical trial registry website: https://clinicaltrials.gov/. Clinical trial number: NCT03030404.

CDH1 germline mutations in a Chinese cohort with hereditary diffuse gastric cancer

PURPOSE

Germline mutations in CDH1 are associated with hereditary diffuse gastric cancer (HDGC) and have been identified in multiple ethnicities. However, CDH1 germline mutations have seldom been documented in Chinese patients with HDGC, and their frequency remains unclear. Here, we aimed to examine the frequency of CDH1 germline mutations in Chinese patients with HDGC. In total, 285 patients who met the International Gastric Cancer Linkage Consortium 2015 testing criteria of HDGC for CDH1 germline mutations were recruited.

METHODS

All 16 CDH1 exons, including neighboring intronic sequences, were amplified using polymerase chain reaction and screened using Sanger sequencing. Variants were analyzed using Mutation Surveyor V4.0, SIFT, and PolyPhen-2 software.

RESULTS

Three nonsense and nine missense CDH1 germline mutations were identified in 21 of 285 index cases (7.4%). Two CDH1 germline mutations, N405Y (Asn405Tyr) and W409X (Trp409Ter), were identified as new variants. In addition, up to 28.6% of CDH1 mutations in the 21 indicated patients were identified as c.1775G>C (E551Q). The frequency of CDH1 mutations was 6.5% (7/108) in HDGC and 7.9% (14/177) in early onset diffuse gastric cancer (EODGC). The mutation detection rates of CDH1 in males and females were 6.7% (4/60) and 8.5% (10/117) in EODGC and 4.6% (3/65) and 9.3% (4/43) in HDGC, respectively.

CONCLUSION

These data reveal, for the first time, the type and frequency of CDH1 germline mutations in Chinese HDGC and demonstrate that germline CDH1 mutations are a noteworthy contributor to the high frequency of HDGC in Chinese.

Germline CDH1 G212E Missense Variant: Combining Clinical, In Vitro and In Vivo Strategies to Unravel Disease Burden

E-cadherin, encoded by CDH1, is an essential molecule for epithelial homeostasis, whose loss or aberrant expression results in disturbed cell-cell adhesion, increased cell invasion and metastasis. Carriers of CDH1 germline mutations have a high risk of developing diffuse gastric cancer and lobular breast cancer, associated with the cancer syndrome Hereditary Diffuse Gastric Cancer (HDGC). The ubiquitous availability of cancer panels has led to the identification of an increasing amount of "incidental" CDH1 genetic variants that pose a serious clinical challenge. This has sparked intensive research aiming at an accurate classification of the variants and consequent validation of their clinical relevance. The present study addressed the significance of a novel CDH1 variant, G212E, identified in an unusually large pedigree displaying strong aggregation of diffuse gastric cancer. We undertook a comprehensive pipeline encompassing family data, in silico predictions, in vitro assays and in vivo strategies, which validated the deleterious phenotype induced by this genetic alteration. In particular, we demonstrated that the G212E variant affects the stability and localization, as well as the adhesive and anti-invasive functions of E-cadherin, triggering epithelial disruption and disorganization. Our findings illustrate the clinical implication of a complementary approach for effective variant categorization and patient management.

E-cadherin (CDH1) gene -160C/A polymorphism and the risk of colorectal cancer: A meta-analysis involving 17,291 subjects

BACKGROUND

The E-cadherin (CDH1) polymorphism has been implicated in the susceptibility to colorectal cancer (CRC). However, the results remain inconclusive. The present meta-analysis aimed to investigate the association between the CDH1-160C/A polymorphism and CRC risk.

METHODS

Relevant studies were retrieved by searching PubMed, Web of Science, Google Scholar, the Cochrane Library, Embase, CNKI and Wanfang databases up to 11 March 2021. Pooled odds ratio and 95% confidence interval were calculated using either the fixed- or random-effects model. Quality evaluation was carried out using Newcastle-Ottawa Scale (NOS). A trial sequential analysis (TSA) was conducted to reduce the risk of type I error.

RESULTS

In total, 16 studies from 14 articles with 8699 patients and 8592 controls were included. In general, all studies were of high quality (NOS score higher than 6). Overall, no significant associations between the CDH1 -160C/A polymorphism and CRC risk were detected. In subgroup analysis by ethnicity, source of control, genotyping method and location, significant associations were found between the CDH1-160C/A polymorphism and the risk of CRC in the Caucasians and the hospital-based subgroup. Furthermore, 10 studies with 8019 subjects reported the association between the polymorphism and clinical characteristics in CRC patients, and we found that the CDH1-160C/A polymorphism might show a protective role in the distal CRC subgroup. By TSA, the findings in the present study were based on sufficient evidence in Caucasians, but not in Asians.

CONCLUSIONS

This meta-analysis suggests that the CDH1-160C/A polymorphism may be an important protective factor for CRC in Caucasians and a hospital-based subgroup. Moreover, the polymorphism show a protective role in the distal CRC group. However, large and well-designed studies are warranted to validate our findings, especially for Asians.

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.

Hereditary Diffuse Gastric Cancer: Approaches to Screening, Surveillance, and Treatment

Hereditary diffuse gastric cancer (HDGC) is a cancer syndrome associated with a significant lifetime risk of diffuse gastric cancer (DGC), a malignancy characterized by late clinical presentation and poor prognosis, as well as lobular breast cancer. HDGC is linked to germline pathogenic variants in the E-cadherin gene (CDH1) that are inherited in an autosomal dominant pattern; however, in many families with DGC clustering, no genetic cause has been identified. This review discusses key elements that allow risk assessment of potential inherited DGC susceptibility. We provide a practical overview of the recommendations for surveillance and treatment of individuals at risk and patients with early disease. The review also outlines future research avenues to improve our understanding of the genetic background and natural history of the disease, the endoscopic detection of early lesions, and the outcome of prophylactic surgery in young individuals.

Case series of three patients with hereditary diffuse gastric cancer in a single family: Three case reports and review of literature

BACKGROUND

Hereditary diffuse gastric cancer (HDGC) is a familial cancer syndrome often associated with germline mutations in the CDH1 gene. However, the frequency of CDH1 mutations is low in patients with HDGC in East Asian countries. Herein, we report three cases of HDGC harboring a missense CDH1 variant, c.1679C>G, from a single Japanese family.

CASE SUMMARY

A 26-year-old female (Case 1) and a 51-year-old male (father of Case 1), who had a strong family history of gastric cancer, were diagnosed with advanced diffuse gastric cancer. After genetic counselling, a 25-year-old younger brother of Case 1 underwent surveillance esophagogastroduodenoscopy that detected small signet ring cell carcinoma foci as multiple pale lesions in the gastric mucosa. Genetic analysis revealed a CDH1 c.1679C>G variant in all three patients.

CONCLUSION

It is important for individuals suspected of having HDGC to be actively offered genetics evaluation. This report will contribute to an increased awareness of HDGC.

Genome-wide association meta-analyses combining multiple risk phenotypes provide insights into the genetic architecture of cutaneous melanoma susceptibility

Most genetic susceptibility to cutaneous melanoma remains to be discovered. Meta-analysis genome-wide association study (GWAS) of 36,760 cases of melanoma (67% newly genotyped) and 375,188 controls identified 54 significant (P < 5 × 10-8) loci with 68 independent single nucleotide polymorphisms. Analysis of risk estimates across geographical regions and host factors suggests the acral melanoma subtype is uniquely unrelated to pigmentation. Combining this meta-analysis with GWAS of nevus count and hair color, and transcriptome association approaches, uncovered 31 potential secondary loci for a total of 85 cutaneous melanoma susceptibility loci. These findings provide insights into cutaneous melanoma genetic architecture, reinforcing the importance of nevogenesis, pigmentation and telomere maintenance, together with identifying potential new pathways for cutaneous melanoma pathogenesis.

Synchronous multiple primary gastrointestinal cancers with CDH1 mutations: A case report

BACKGROUND

Synchronous multiple primary cancers (SMPC) mean two or more malignant tumors occurring simultaneously and with different origins no matter what types they are or where they are located. The carcinogenesis of SMPC often involves variations of some specific genes. However, the correlation between CDH1 mutations and synchronous multiple primary gastrointestinal cancers is largely unknown.

CASE SUMMARY

A 62-year-old woman had sustained abdominal pain for one week and visited our hospital. Gastrointestinal endoscopy revealed multiple small polypoid lesions in both the stomach and colorectum. Computed tomography and laboratory results were within normal limits. Pathological evaluation confirmed signet ring cell carcinoma without obvious metastatic evidence. Malignant cells showed negativity for E-cadherin and positivity for β-catenin in the cytoplasm and nucleus. DNA sequencing performed on paraffin-embedded tissue revealed two exactly coincident alterations in CDH1, C.57T>G and C.1418A>T.

CONCLUSION

This case suggests that the combination of CDH1 mutations and WNT/β-catenin signaling activation contributes to the carcinogenesis of gastrointestinal SMPC.

Clinical spectrum and pleiotropic nature of CDH1 germline mutations

CDH1 encodes E-cadherin, a key protein in adherens junctions. Given that E-cadherin is involved in major cellular processes such as embryogenesis and maintenance of tissue architecture, it is no surprise that deleterious effects arise from its loss of function. E-cadherin is recognised as a tumour suppressor gene, and it is well established that CDH1 genetic alterations cause diffuse gastric cancer and lobular breast cancer—the foremost manifestations of the hereditary diffuse gastric cancer syndrome. However, in the last decade, evidence has emerged demonstrating that CDH1 mutations can be associated with lobular breast cancer and/or several congenital abnormalities, without any personal or family history of diffuse gastric cancer. To date, no genotype–phenotype correlations have been observed. Remarkably, there are reports of mutations affecting the same nucleotide but inducing distinct clinical outcomes. In this review, we bring together a comprehensive analysis of CDH1-associated disorders and germline alterations found in each trait, providing important insights into the biological mechanisms underlying E-cadherin’s pleiotropic effects. Ultimately, this knowledge will impact genetic counselling and will be relevant to the assessment of risk of cancer development or congenital malformations in CDH1 mutation carriers.

Screening E-Cadherin Germline Mutations in Italian Patients with Familial Diffuse Gastric Cancer: An Analysis in the District of Urbino, Region Marche, Central Italy

Aims & Background

Hereditary diffuse gastric cancer is a recently defined cancer syndrome caused by inactivating, heterozygous germline mutations in the E-cadherin gene (CDH1). To date, 16 truncating germline CDH1 mutations have been described in hereditary diffuse gastric cancer families in different ethnic groups, but so far, no investigation has been addressed to Italian patients. In the District of Urbino, Region Marche, Central Italy, gastric cancer is the most common tumor in men and it is the second in women after breast cancer. In this area, we investigated CDH1 mutations in patients who fulfilled the hereditary diffuse gastric cancer criteria.

Material and Methods

Consecutive patients with diffuse gastric cancer were considered eligible for the study. After pedigree analysis, patients who met the International Gastric Cancer Linkage Consortium criteria were studied for CDH1 mutations. After blood samples collection and DNA extraction, standard polymerase chain reaction and sequencing techniques were used for CDH1 analysis.

Results

In a study population of 98 patients with diffuse gastric cancer, 11 patients (11%) showed familial clustering and 3 of them met the International Gastric Cancer Linkage Consortium criteria for hereditary diffuse gastric cancer. None of the 3 patients showed inactivating germline mutation in CDH1.

Conclusions

According to recent studies, the frequency of CDH1 inactivating germline mutations in patients who fulfil the hereditary diffuse gastric cancer criteria may be lower than that reported in early investigations. The results of the present study in a population of Italian patients seem to confirm these data. It is likely that unidentified mutations in CDH1 or other involved genes contribute to diffuse gastric cancer susceptibility.

NRAS germline variant G138R and multiple rare somatic mutations on APC in colorectal cancer patients in Taiwan by next generation sequencing

Colorectal cancer (CRC) arises from mutations in a subset of genes. We investigated the germline and somatic mutation spectrum of patients with CRC in Taiwan by using the AmpliSeq Cancer Hotspot Panel V2. Fifty paired freshly frozen stage 0–IV CRC tumors and adjacent normal tissue were collected. Blood DNA from 20 healthy donors were used for comparison of germline mutations. Variants were identified using an ion-torrent personal genomic machine and subsequently confirmed by Sanger sequencing or pyrosequencing. Five nonsynonymous germline variants on 4 cancer susceptible genes, CDH1, APC, MLH1, and NRAS, were observed in 6 patients with CRC (12%). Among them, oncogene NRAS G138R variant was identified as having a predicted damaging effect on protein function, which has never been reported by other laboratories. CDH1 T340A variants were presented in 3 patients. The germline variants in the cancer patients differed completely from those found in asymptomatic controls. Furthermore, a total of 56 COSMIC and 21 novel somatic variants distributed in 20 genes were detected in 44 (88%) of the CRC samples. High inter- and intra-tumor heterogeneity levels were observed. Nine rare variants located in the β-catenin binding region of the APC gene were discovered, 7 of which could cause amino acid frameshift and might have a pathogenic effect. In conclusion, panel-based mutation detection by using a high-throughput sequencing platform can elucidate race-dependent cancer genomes. This approach facilitates identifying individuals at high risk and aiding the recognition of novel mutations as targets for drug development.

Germline mutations in hereditary diffuse gastric cancer

Gastric cancer is one of the leading causes of cancer-related deaths worldwide. Among which, about 1%-3% of gastric cancer patients were characterized by inherited gastric cancer predisposition syndromes, knowing as hereditary diffuse gastric cancer (HDGC). Studies reported that CDH1 germline mutations are the main cause of HDGC. With the help of rapid development of genetic testing technologies and data analysis tools, more and more researchers focus on seeking candidate susceptibility genes for hereditary cancer syndromes. In addition, National Comprehensive Cancer Network (NCCN) guidelines recommend that the patients of HDGC carrying CDH1 mutations should undergo prophylactic gastrectomy or routine endoscopic surveillances. Therefore, genetic counseling plays a key role in helping individuals with pathogenic mutations make appropriate risk management plans. Moreover, experienced and professional genetic counselors as well as a systematic multidisciplinary team (MDT) are also required to facilitate the development of genetic counseling and benefit pathogenic mutation carriers who are in need of regular and standardized risk management solutions. In this review, we provided an overview about the germline mutations of several genes identified in HDGC, suggesting that these genes may potentially act as susceptibility genes for this malignant cancer syndrome. Furthermore, we introduced information for prevention, diagnosis and risk management of HDGC. Investigations on key factors that may have effect on risk management decision-making and genetic data collection of more cancer syndrome family pedigrees are required for the development of HDGC therapeutic strategies.

Accuracy of Hereditary Diffuse Gastric Cancer Testing Criteria and Outcomes in Patients With a Germline Mutation in CDH1

BACKGROUND & AIMS

Germline mutations in the cadherin 1, type 1, E-cadherin gene (CDH1) cause a predisposition to gastric cancer. We evaluated the ability of the internationally accepted hereditary diffuse gastric cancer (HDGC) criteria to identify individuals with pathogenic mutations in CDH1, and assessed their outcomes. The criteria were as follows: families with 2 or more cases of gastric cancer, with at least 1 patient diagnosed with diffuse gastric cancer (DGC) before age 50; families with 3 or more cases of DGC; families with 1 DGC before the age of 40; and families with a history of DGC and lobular breast cancer, with 1 diagnosis before the age of 50.

METHODS

We collected results of a CDH1 mutation analysis of 578 individuals from 499 families tested in The Netherlands between 1999 and 2014 (118 families met the HDGC criteria for testing and 236 did not; there were 145 families with incomplete data and/or availability of only first-degree relatives). Data were linked with family histories and findings from clinical and pathology analyses. The Kaplan-Meier method and Cox regression analysis were used to evaluate the overall survival of patients with and without CDH1 mutations.

RESULTS

In a cohort study in The Netherlands, the HDGC criteria identified individuals with a germline CDH1 mutation with a positive predictive value of 14% and 89% sensitivity. There were 18 pathogenic CDH1 mutations in 499 families (4%); 16 of these mutations were detected in the 118 families who met the HDGC criteria for testing. One pathogenic CDH1 mutation was detected in the 236 families who did not meet HDGC criteria and 1 in the 145 families with incomplete data and/or availability of only first-degree relatives. No CDH1 mutations were found in the 67 families whose members developed intestinal-type gastric cancer, or in the 22 families whose families developed lobular breast cancer. Among patients who fulfilled the HDGC criteria and had pathogenic CDH1 mutations, 36% survived for 1 year and 4% survived for 5 years; among patients who fulfilled the HDGC criteria but did not carry pathogenic CDH1 mutations, 48% survived for 1 year and 13% survived for 5 years (P = .014 for comparative survival analysis between patients with and without a CDH1 mutation).

CONCLUSIONS

All individuals with a CDH1 mutation had a personal or family history of diffuse gastric cancer. Patients with gastric cancer and germline CDH1 mutations had shorter survival times than patients who met the HDGC criteria but did not have CDH1 mutations.

Hereditary diffuse gastric cancer in a Japanese family with a large deletion involving CDH1

Hereditary diffuse gastric cancer (HDGC), characterized by susceptibility to gastric signet ring cell carcinomas (SRCCs) and caused by CDH1 germline mutations, is rare in the Japanese. We present here a Japanese family with HDGC identified by comparative genomic hybridization (CGH) analysis. A 55-year-old woman was treated with completion gastrectomy for multiple SRCCs, and pathological examination revealed approximately 200 foci of SRCC with loss of E-cadherin expression. Her 30-year-old son had surveillance endoscopy and was found to have multiple SRCCs. He underwent total gastrectomy, and 32 foci of SRCC with loss of E-cadherin expression were histologically found. Although no point mutations were detected in CDH1 by sequencing, CGH revealed a 275-kb deletion involving exons 7-16 of CDH1 in both patients. While only a few HDGCs have been reported in East Asia, patients with multiple SRCC may need to be offered appropriate genetic counseling and testing in this area.

Presymptomatic identification of CDH1 germline mutation in a healthy korean individual with family history of gastric cancer

Gastric cancer (GC) is one of the most common cancers with high morbidity and mortality. Familial GC is seen in 10% of cases, and approximately 3% of familial GC cases arise owing to hereditary diffuse gastric cancer (HDGC). CDH1, which encodes the protein E-cadherin, is the only gene whose mutations are associated with HDGC. Screening for the familial GC-predisposing gene has been neglected in high-risk countries such as Korea, China, and Japan, where all the cases have been attributed to Helicobacter pylori or other carcinogens. Screening for the GC-causing CDH1 mutation may provide valuable information for genetic counseling, testing, and risk-reduction management for the as-yet unaffected family members. An asymptomatic 44-yr-old Korean male visited our genetic clinic for consultation owing to his family history of GC. Eventually, c.1018A>G in CDH1, a known disease-causing mutation, was found. As of the publication time, the individual is alive without the evidence of GC, and is on surveillance. To our knowledge, this is the first Korean case of presymptomatic detection of CDH1 mutation, and it highlights the importance of genetic screening for individuals with a family history of GC, especially in high-risk geographical areas.

Searching for E-cadherin gene mutations in early onset diffuse gastric cancer and hereditary diffuse gastric cancer in Korean patients

The impact of CDH1 gene mutations and large deletions on hereditary diffuse gastric cancer (HDGC) and early onset diffuse gastric cancer (EODGC) has not been determined in Asians. We investigated the mutation status of the CDH1 gene in 25 Korean EODGC patients younger than 50 years and 23 HDGC patients who met the clinical criteria for HDGC. Polymerase chain reaction-direct sequencing was performed, and multiplex ligation-dependent probe amplification (MLPA) was used to evaluate the patients with negative sequencing results. We determined that 2 of 25 (8 %) EODGC patients had CDH1 germline mutations. One was a nonsense mutation (c.1003C>T, p.Arg335*, exon 7) in a 41-year-old female with no family history of cancer. The other was a missense mutation (c.715G>A, p.Gly239Arg, exon 6) in a 28-year-old male with no family history of cancer. One of 23 (4.3 %) HDGC patients had a CDH1 germline mutation (c.1003C>T). The patient's brother and sister died of stomach cancer. The MLPA results revealed no deletion or duplication in any patient. More research is needed to determine additional genetic targets that trigger HDGC. More comprehensive methods such as next-generation sequencing might be a good approach that can be used to identify the genetic causes of pathogenetically unexplained disorders.

Genomic profile analysis of diffuse-type gastric cancers

BACKGROUND

Stomach cancer is the third deadliest among all cancers worldwide. Although incidence of the intestinal-type gastric cancer has decreased, the incidence of diffuse-type is still increasing and its progression is notoriously aggressive. There is insufficient information on genome variations of diffuse-type gastric cancer because its cells are usually mixed with normal cells, and this low cellularity has made it difficult to analyze the genome.

RESULTS

We analyze whole genomes and corresponding exomes of diffuse-type gastric cancer, using matched tumor and normal samples from 14 diffuse-type and five intestinal-type gastric cancer patients. Somatic variations found in the diffuse-type gastric cancer are compared to those of the intestinal-type and to previously reported variants. We determine the average exonic somatic mutation rate of the two types. We find associated candidate driver genes, and identify seven novel somatic mutations in CDH1, which is a well-known gastric cancer-associated gene. Three-dimensional structure analysis of the mutated E-cadherin protein suggests that these new somatic mutations could cause significant functional perturbations of critical calcium-binding sites in the EC1-2 junction. Chromosomal instability analysis shows that the MDM2 gene is amplified. After thorough structural analysis, a novel fusion gene TSC2-RNF216 is identified, which may simultaneously disrupt tumor-suppressive pathways and activate tumorigenesis.

CONCLUSIONS

We report the genomic profile of diffuse-type gastric cancers including new somatic variations, a novel fusion gene, and amplification and deletion of certain chromosomal regions that contain oncogenes and tumor suppressors.

Synchronous appendiceal and intramucosal gastric signet ring cell carcinomas in an individual with CDH1-associated hereditary diffuse gastric carcinoma: a case report of a novel association and review of the literature

Background

Hereditary diffuse gastric carcinoma is an autosomal dominant cancer syndrome associated with mutations of the E-cadherin gene (CDH1). E-cadherin is normally involved in cell-cell adhesion, so it not surprising that individuals with this syndrome are predisposed to develop malignancies with dyshesive morphologies at a young age, such as diffuse (signet ring cell) gastric carcinoma and lobular breast carcinoma. Herein we describe the first reported case of primary appendiceal signet ring cell carcinoma arising in a CDH1-associated hereditary diffuse gastric carcinoma kindred with synchronous primary diffuse gastric carcinoma.

Case presentation

A 51- year old woman, with known CDH1 mutation carrier status and a prior history of lobular breast carcinoma underwent prophylactic total gastrectomy which revealed multifocal intramucosal signet ring cell carcinoma. An appendectomy was performed at the same time due to a prior episode of presumed appendicitis, with pathologic examination significant for a primary signet ring cell carcinoma of the appendix.

Conclusion

As appendiceal signet ring cell carcinoma is exceedingly rare, the occurrence of this neoplasm in this patient, with this particular morphology, provides credence for it being part of the hereditary diffuse gastric carcinoma spectrum of malignancies.

A systematic review of the indications for genetic testing and prophylactic gastrectomy among patients with hereditary diffuse gastric cancer

BACKGROUND

Hereditary diffuse gastric cancer (HDGC) is a familial cancer syndrome specifically associated with germline mutations to the E-cadherin (CDH1) gene. HDGC is characterized by autosomal dominance and high penetrance and a high cumulative risk for advanced gastric cancer. Our purpose in this study was to identify and synthesize findings from all articles on: (1) current recommendations for CDH1 screening and prophylactic gastrectomy; (2) CDH1 testing results in HDGC patients; and (3) prophylactic gastrectomy results in HDGC patients.

METHODS

Systematic electronic literature searches were conducted using Medline, Embase, and the Cochrane Central Register of Controlled Trials from 1985 to 2009.

RESULTS

Seventy articles were included in this review. Among patients with a positive family history of gastric cancer, 1085 were screened from 454 families, and 38.4% tested positive. Mutation-positive families also had a considerable family history of breast and colon cancer. Of the 322 patients screened for CDH1 mutations by current HDGC screening criteria, 29.2% tested positive. Among the 76.8% of patients who underwent prophylactic gastrectomy following positive CDH1 test results, 87.0% had positive final histopathology results and 64.6% had signet ring cells identified. Some of the patients with negative final histopathology results had opted to undergo prophylactic gastrectomy prior to CDH1 testing, and were ultimately found to be negative for CDH1 mutations.

CONCLUSION

CDH1 mutation testing in families with a history of gastric cancer and prophylactic gastrectomy in mutation-positive patients are recommended for the management of HDGC.

SEQCHIP: a powerful method to integrate sequence and genotype data for the detection of rare variant associations

MOTIVATION

Next-generation sequencing greatly increases the capacity to detect rare-variant complex-trait associations. However, it is still expensive to sequence a large number of samples and therefore often small datasets are used. Given cost constraints, a potentially more powerful two-step strategy is to sequence a subset of the sample to discover variants, and genotype the identified variants in the remaining sample. If only cases are sequenced, directly combining sequence and genotype data will lead to inflated type-I errors in rare-variant association analysis. Although several methods have been developed to correct for the bias, they are either underpowered or theoretically invalid. We proposed a new method SEQCHIP to integrate genotype and sequence data, which can be used with most existing rare-variant tests.

RESULTS

It is demonstrated using both simulated and real datasets that the SEQCHIP method has controlled type-I errors, and is substantially more powerful than all other currently available methods.

AVAILABILITY

SEQCHIP is implemented in an R-Package and is available at http://linkage.rockefeller.edu/suzanne/seqchip/Seqchip.html.

E-cadherin destabilization accounts for the pathogenicity of missense mutations in hereditary diffuse gastric cancer

E-cadherin is critical for the maintenance of tissue architecture due to its role in cell-cell adhesion. E-cadherin mutations are the genetic cause of Hereditary Diffuse Gastric Cancer (HDGC) and missense mutations represent a clinical burden, due to the uncertainty of their pathogenic role. In vitro and in vivo, most mutations lead to loss-of-function, although the causal factor is unknown for the majority. We hypothesized that destabilization could account for the pathogenicity of E-cadherin missense mutations in HDGC, and tested our hypothesis using in silico and in vitro tools. FoldX algorithm was used to calculate the impact of each mutation in E-cadherin native-state stability, and the analysis was complemented with evolutionary conservation, by SIFT. Interestingly, HDGC patients harbouring germline E-cadherin destabilizing mutants present a younger age at diagnosis or death, suggesting that the loss of native-state stability of E-cadherin accounts for the disease phenotype. To elucidate the biological relevance of E-cadherin destabilization in HDGC, we investigated a group of newly identified HDGC-associated mutations (E185V, S232C and L583R), of which L583R is predicted to be destabilizing. We show that this mutation is not functional in vitro, exhibits shorter half-life and is unable to mature, due to premature proteasome-dependent degradation, a phenotype reverted by stabilization with the artificial mutation L583I (structurally tolerated). Herein we report E-cadherin structural models suitable to predict the impact of the majority of cancer-associated missense mutations and we show that E-cadherin destabilization leads to loss-of-function in vitro and increased pathogenicity in vivo.

Genotype frequencies of the Val384Asp missense mutation in the hMLH1 gene in patients with familial gastric cancer

AIM: To investigate the etiological role of the missense mutation, Val384Asp, in the human mutL homolog 1 (hMLH1) gene in familial gastric cancer (FGC) based on a Chinese population in Jiangsu Province.

METHODS: A case-control study was conducted. One hundred newly diagnosed or suspected FGC patients and 180 healthy controls were included in the study. Peripheral white blood cells were obtained from all subjects for DNA extraction. The Val384Asp missense mutation was detected using PCR-based denaturing high-performance liquid chromatography (DHPLC) and verified by DNA sequencing. Bioinformatic software was then used to analyze the etiological mechanism of the Val384Asp missense mutation.

RESULTS: About 5% healthy individuals were Val384Asp carriers. Significant differences were noted for the following comparisons: patients with newly diagnosed or suspected FGC vs healthy controls (OR = 2.84, 95%CI: 1.07-7.81, P < 0.05), patients with an onset age ≥ 50 vs healthy controls (P < 0.05), patients with precancerous disease history vs healthy controls (P < 0.01), and patients having a high-risk family history of GC vs healthy controls (P < 0.05). Bioinformatic analysis showed that the Val384Asp missense mutation might destroy the structure of hMLH1 protein and impair its function. Besides, the conversion of T→A may disrupt pre-mRNA splicing.

CONCLUSION: The Val384Asp missense mutation may be associated with genetic susceptibility to FGC. Detection of the Val384Asp missense mutation may be able to help identify individuals with increased risk of FGC.

A new familial gastric cancer-related gene polymorphism: T1151A in the mismatch repair gene hMLH1

We designed to understand the effects of the T1151A gene polymorphism in the hMLH1 gene on the pathogenesis of familial gastric cancer. Peripheral blood DNA from 113 patients with familial gastric cancer or suspected familial gastric cancer that were newly identified in the same year, along with 180 healthy subjects, was subjected to polymerase chain reaction-denaturing high-performance liquid chromatography (PCR-DHPLC) and DNA sequencing of exon 12 in the hMLH1 gene. Our results as following, the T1151A detection rate was remarkably higher in patients with familial gastric cancer or suspected familial gastric cancer compared to normal control patients (P < 0.05). Stratified analysis showed that there was a significant difference in the detection rate between the control group and elderly patients whose age of onset was greater than 50 years old (P < 0.05). The detection rate of patients from high-risk families were relatively high (P < 0.05). An especially significant distribution was observed in patients who had suffered precancerous diseases related to gastric cancer (P < 0.01). In conclusion, familial gastric carcinoma families in China carrying the T1151A polymorphism may have a higher risk of suffering from gastric cancer. This gene polymorphism can be used as a candidate screening index for high-risk populations.

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.

E-cadherin mutations and cell motility: a genotype-phenotype correlation

E-cadherin has a determinant role in tumour progression, acting as an invasion and metastasis suppressor. Germline mutations of E-cadherin gene (CDH1) occur in 30% of families with Hereditary Diffuse Gastric Cancer (HDGC); of these 23% are missense mutations. The CDH1 missense mutations described to date span the entire gene and some lead to significant functional consequences. In this study, we explored the hypothesis that mutations affecting different E-cadherin protein domains have distinct effects on cell motility. To accomplish our objective we characterized the effect of eleven HDGC CDH1 germline missense mutations (T118R, L214P, G239R, A298T, T340A, P373L, R749W, E757K, E781D, P799R and V832M) on cell motility. Further, we studied their effect on the activation of signalling pathways known to be relevant for cell motility such as the EGFR, Src kinase and MAPKs. CDH1 mutations localized on the extracellular and juxtamembrane domains, both affecting the integrity of the extracellular domain, led to increased cell motility accompanied by increased EGFR activation. Moreover, we observed that cells expressing extracellular mutants exhibit increased activation of Src kinase and p38 MAPK. Our results allowed the identification of the E-cadherin domains pivotal for cell motility, further demonstrated a genotype-phenotype correlation, and defined a subset of HDGC cases which may benefit from EGFR inhibitors.

Association of familial colorectal cancer with variants in the E-cadherin (CDH1) and cyclin D1 (CCND1) genes

INTRODUCTION

About 20% of colorectal cancer (CRC) patients show some kind of familiarity, which might be caused by yet unknown combinations of low penetrance susceptibility genes. We aimed to identify genetic factors for familial CRC (fCRC) in a unique study design that includes phenotypic extremes as represented by fCRC cases and 'hyper-normal' controls without CRC history and no adenomatous polyps on colonoscopy.

MATERIALS AND METHODS

Candidate gene variants were determined by allele-specific amplification (SLC10A2 c.169C>T and c.171G>T) and restriction fragment length polymorphism assays (CCND1 c.870A>G; CDH1 -160C>A; TP53 R72P; VDR T2M). In total, 98 patients with fCRC, 96 patients with sporadic CRC, and 220 hyper-normal controls were included.

RESULTS

The minor allele of the CDH1 -160C>A polymorphism occurred significantly more often in controls compared to fCRC cases (OR = 0.664; p = 0.042). Homozygosity of the minor allele was significantly associated with affiliation to the control group (OR = 0.577; p = 0.029), indicating that both heterozygous and homozygous carriers of the common allele are at-risk for CRC. With respect to the CCND1 c.870A>G mutation, comparison of fCRC and sporadic CRC cases showed that A/A homozygosity was more common than G/G homozygosity among fCRC patients compared to controls (OR = 2.119; p = 0.045). However, no differences in allele or genotype frequencies were detected between sporadic CRC cases and controls, and no associations were observed for SLC10A2, TP53, and VDR polymorphisms.

CONCLUSIONS

We report a potential association of variants in the CCND1 and CDH1 genes with fCRC using a unique study design with phenotypic extremes.

Tumor specificity and in vivo targeting of an antibody against exon 9 deleted E-cadherin in gastric cancer

PURPOSE

The aim of this study was to evaluate the possibility of using a monoclonal antibody against exon 9 deleted E-cadherin (E-cad delta 9-1) for immunotherapy of gastric cancer.

METHODS

Among nine human diffuse-type gastric cancer cell lines, we selected a cell line expressing exon 9 deleted E-cadherin (HSC-45M2) by direct sequencing. Tumor specificity and tumor specific in vivo targeting of E-cad delta 9-1 were evaluated in nude mouse bearing a tumor derived from HSC-45M2 cell line by immunohistochemical staining. The expression rate of E-cad delta 9-1 was evaluated in 299 gastric cancer patients, and in positive cases, the mutational status of E-cadherin exon 9 was examined.

RESULTS

Immunohistochemical staining of various tissues from nude mice showed that only tumor tissue reacted with E-cad delta 9-1. However, immunohistochemical staining of the same tissues after systemic injection of E-cad delta 9-1 showed that reticuloendothelial and hypervascular organs reacted with E-cad delta 9-1, but tumor tissue showed only a slight reaction. Evaluation of the reactivity of 299 gastric cancer patients to E-cad delta 9-1 showed that 4.8% (9/187) of patients, who all had diffuse- or mixed-type gastric cancers, reacted positively, but none of the 112 intestinal-type gastric cancer patients reacted positively. Two of 9 patients (22%) with positive staining to E-cad delta 9-1 were confirmed to have mutant forms of E-cadherin exon 9.

CONCLUSION

Considering that E-cad delta 9-1 showed good tumor specificity and that some diffuse-type gastric cancers were immunopositive to it, this antibody could be a candidate therapeutic antibody against gastric cancers that express mutant E-cadherin.

A model to infer the pathogenic significance of CDH1 germline missense variants

Germline mutations of the E-cadherin gene (CDH1) are involved in the tumorigenesis of hereditary diffuse gastric cancer (HDGC). Recent studies have highlighted the lifesaving potential of total prophylactic gastrectomy for CDH1 germline mutation carriers. In this regard, CDH1 germline mutations of the missense type represent a clinical burden in genetic counseling, as their pathogenic relevance is not straightforward. In this work, we have outlined a possible multivariate approach to infer the significance of such variants. We reviewed all HDGC-associated E-cadherin germline missense mutations reported to date. The information collected included: co-segregation of the mutation within pedigrees, frequency in healthy population control, recurrence in independent families, and functional in vitro and in silico data. We used the neighbor-joining method to group mutations according to the collected information and assessed the robustness of mutation clusters with a bootstrap test. CDH1 germline missense variants were classified according to the parameters defined in the multivariate analysis. This analysis allowed the distribution of the variants into two distinct groups: neutral variants vs mutations. The model described in this study provides an important tool that can ultimately improve the genetic counseling offered to the carriers of the germline CDH1 missense variants.

Genetics of hereditary diffuse gastric cancer: progress and future challenges

Hereditary diffuse gastric cancer (HDGC) is a rare cancer susceptibility syndrome. One third of HDGC syndrome families carry germline mutations of the E-cadherin gene. Owing to the limitation of the current endoscopic screening techniques and since no chemoprevention is yet available, total prophylactic gastrectomy is the only option offered to carriers of inactivating mutations in genetic counseling. In this regard, 30% of the E-cadherin germline mutations reported to date are of the missense type, and since their pathogenic significance is not straightforward, the management of carriers of such mutations is suboptimal. In the absence of definitive clinical evidence, functional in vitro studies together with in silico analysis have been used to infer the pathogenic significance of germline missense mutations. Since most of the HDGC families reported to date are negative for E-cadherin germline mutations, the identification of alternative genes underlying the tumorigenesis of diffuse gastric has become an important target for research.

Genetics, pathology, and clinics of familial gastric cancer

Gastric cancer is relatively common worldwide, mainly in its sporadic form, but familial aggregation of the disease may be seen in approximately 10% of the cases. This suggests a genetic cause for the cancer in those families that has not been identified in most cases. Despite all efforts to determine its genetic basis, a single syndrome has been characterized-the hereditary diffuse gastric cancer (HDGC)-which is specifically associated with CDH1 (E-cadherin) germline mutations in one third of the families. The other two thirds and all the gastric cancer families not fulfilling the HDGC criteria remain without molecular diagnosis. In this article we review the state of the art of familial gastric cancer regarding the molecular aspects, the clinical criteria, the pathology features, and the management recommendations described so far to be associated with this cancer disease.

Increased Epithelial Cadherin Expression among Japanese Intestinal-Type Gastric Cancers Compared with Specimens from American Patients of European Descent

The different patterns of gastric cancer in the Far East and West have evolved to the extent that it has been suggested that the disease in Japan is biologically less aggressive than in the West. We studied paraffin-embedded, formalin-fixed tissue blocks from Japanese patients and American patients of European descent who had undergone gastrectomy for gastric cancer not involving the gastroesophageal junction. Specimens were staged (T stage), graded (Lauren classification), and biomarker expression (epithelial cadherin [E-cadherin], c-erbB2, Ki67, and p53) was quantified using immunohistochemistry without knowledge of the country of origin. E-cadherin was expressed in 49 per cent of malignant cells from Japanese specimens compared with 27 per cent of malignant cells from American specimens (P = 0.04). The expression of E-cadherin on diffuse cancers from the two countries was similar (34.4 in Japanese vs 41.5 in American, P = 0.92). E-cadherin expression, however, was significantly higher among intestinal cancers from the two countries: 56.3 per cent of cells from intestinal or mixed cancers from Japan (n = 32) expressed E-cadherin compared with 22.2 per cent of American specimens (n = 12; P = 0.008). c-erbB2 was expressed on a higher proportion of malignant cells from American specimens (30% vs 22%; P = 0.20). E-cadherin expression, a favorable prognostic factor, is more common in Japanese intestinal-type gastric cancer not involving the gastroesophageal junction. If the biology of gastric cancer in the Far East is less aggressive than that in the United States, it is likely that treatments need to be individualized.

Familial gastric cancer - aetiology and pathogenesis

Gastric cancer is the second most common cause of cancer death worldwide. It is estimated that 5-10% of gastric cancer cases have a familial association; however, knowledge concerning the genetic predisposition to familial gastric cancer is currently limited. In this chapter we discuss what is known about the aetiology and pathogenesis of both the diffuse and intestinal forms of familial gastric cancer. We focus particularly on hereditary diffuse gastric cancer because the discovery of germ-line E-cadherin mutations in a number of affected families has opened the prospect of identifying gene carriers, with implications for clinical management. The interplay of other conventional risk factors, such as Helicobacter pylori infection, with genetic factors is also discussed. It is hoped that understanding the genetic basis for familial gastric cancer will facilitate the development of clinically useful screening and preventative procedures.

Multiple rare variants in different genes account for multifactorial inherited susceptibility to colorectal adenomas

Clear-cut inherited Mendelian traits, such as familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer, account for <4% of colorectal cancers. Another 20% of all colorectal cancers are thought to occur in individuals with a significant inherited multifactorial susceptibility to colorectal cancer that is not obviously familial. Incompletely penetrant, comparatively rare missense variants in the adenomatous polyposis coli gene, which is responsible for familial adenomatous polyposis, have been described in patients with multiple colorectal adenomas. These variants represent a category of variation that has been suggested, quite generally, to account for a substantial fraction of such multifactorial inherited susceptibility. The aim of this study was to explore this rare variant hypothesis for multifactorial inheritance by using multiple colorectal adenomas as the model. Patients with multiple adenomas were screened for germ-line variants in a panel of candidate genes. Germ-line DNA was obtained from 124 patients with between 3 and 100 histologically proven synchronous or metachronous adenomatous polyps. All patients were tested for the adenomatous polyposis coli variants I1307K and E1317Q, and variants were also sought in AXIN1 (axin), CTNNB1 (beta-catenin), and the mismatch repair genes hMLH1 and hMSH2. The control group consisted of 483 random controls. Thirty of 124 (24.9%) patients carried potentially pathogenic germ-line variants as compared with 55 ( approximately 12%) of the controls. This overall difference is highly significant, suggesting that many rare variants collectively contribute to the inherited susceptibility to colorectal adenomas.

A TP53-truncating germline mutation (E287X) in a family with characteristics of both hereditary diffuse gastric cancer and Li-Fraumeni syndrome

Mutations in CDH1, which encodes E-cadherin, have been associated with hereditary diffuse gastric cancer (HDGC) in Western populations but have not been shown to play a major role in Asians. Recently, a patient with familial gastric cancer (FGC) was shown to harbor a germline mutation in the TP53 gene, which encodes p53 and has been previously associated with Li-Fraumeni Syndrome (LFS). To determine whether mutations in TP53 are associated with FGC in Asians, we screened the entire coding region of TP53 in probands from 23 Korean FGC families. We identified a nonsense (E287X) TP53 germline mutation in a family whose history is compatible with both HDGC and LFS. Two members of this family (SNU-G2) were afflicted with brain tumors, seven with gastric cancers, two with sarcomas, and one with both gastric cancer and a sarcoma. The E287X TP53 mutation segregated with the cancer phenotype in the family members from whom DNA samples were available. To our knowledge, this is the first report of a large family with both HDGC and LFS. Our results suggest that TP53 mutational screening in FGC families should be interpreted with caution because additional TP53 mutation-carrying HDGC families may also show LFS-related phenotypes.

The role of the E-cadherin gene (CDH1) in diffuse gastric cancer susceptibility: from the laboratory to clinical practice

Loss of function of the E-cadherin gene (CDH1) has been linked with diffuse gastric cancer susceptibility, and germline inactivating mutations in CDH1 characterise the hereditary diffuse gastric cancer (HDGC) syndrome. Hypermethylation in the CDH1 promoter region is a frequent phenomenon in poorly differentiated, diffuse gastric carcinomas and it was identified as the main mechanism for the inactivation of the remaining wild-type allele in HDGC cases. Specific criteria are used to identify patients with suspected HDGC and who should be investigated for CDH1 germline mutations. Accurate screening is mandatory for unaffected carriers of CDH1 mutations and selected high-risk individuals could be considered for prophylactic gastrectomy. Also, germline CDH1 mutations may predispose to lobular breast carcinoma and prostate cancer. Germline CDH1 mutations are not always detectable in patients who meet the HDGC criteria and the aetiological role of this gene is still under investigation. Families without recognised inactivating CDH1 mutations may have undisclosed CDH1 mutations or mutations in its regulatory sequences or germline mutations in unidentified genes that also contribute to the disease. In recent years, several germline missense CDH1 mutations have been identified, some of which showed a marked negative influence on E-cadherin function in experimental models. CDH1 promoter hypermethylation seems a key event in the carcinogenetic process of poorly differentiated, diffuse gastric cancer and it deserves further investigation as a new target for anticancer therapies with demethylating agents.

Ile-Leu substitution (I415L) in germline E-cadherin gene (CDH1) in Japanese familial gastric cancer

BACKGROUND

Germline mutation in the cell adhesion molecule E-cadherin is known to be associated with the development of undifferentiated or diffuse-type familial gastric cancers, but the prevalence of this contribution seems to be low in Japanese familial cases, so far.

METHODS

We screened all exons of the E-cadherin gene for mutations in 101 Japanese patients having an intense family history of gastric cancers.

RESULTS

An abnormal band pattern was found in exon 9 in three patients (Y6, B21, B37) from two families by PCR-SSCP. DNA sequencing analysis of these three patients revealed isoleucine-leucine substitution at codon 415 in exon 9. B21 and B37 are siblings and the other three brothers died of gastric cancer and another brother (B36) has not been affected by gastric cancer to date. This case (B36) did not have this alteration in the exon 9 of E-cadherin.

CONCLUSION

Although the mechanistic basis is not clear, our findings may provide a possibility that this additional missense mutation in germline E-cadherin gene may contribute to gastric cancer predisposition.

Mutation cluster region, association between germline and somatic mutations and genotype-phenotype correlation in upper gastrointestinal familial adenomatous polyposis

Studies of adenomatous polyposis coli (APC) mutations in familial adenomatous polyposis (FAP) have focused on large bowel disease. It has been found that: 1) germline APC mutations around codon 1300 are associated with severe colorectal polyposis; 2) somatic APC mutations in colorectal tumors tend to cluster approximately between codons 1250 and 1450; and 3) patients with germline mutations close to codon 1300 tend to acquire somatic mutations (second hits) in their colorectal polyps by allelic loss, whereas the tumors of other FAP patients have truncating second hits. Using new and published data, we have investigated how germline and somatic APC mutations influence the pathogenesis of upper gastrointestinal polyps in FAP. We have compared the results with those from colorectal disease. We found that somatic mutations in upper gastrointestinal polyps cluster approximately between codons 1400 and 1580. Patients with germline APC mutations after codon 1400 tend to show allelic loss in their upper gastrointestinal polyps; the tumors of other patients have truncating somatic mutations after codon 1400. Finally, patients with germline mutations after codon 1400 tend to have more severe duodenal polyposis (odds ratio, 5.72; 95% confidence interval, 1.13 to 28.89; P = 0.035). Thus, in both upper gastrointestinal and colorectal tumors, a specific region of the APC gene is associated with severe disease, clustering of somatic mutations, and loss of the wild-type allele. However, the region concerned is different in upper gastrointestinal and colorectal disease. The data suggest that loss of all APC SAMP repeats is probably necessary for duodenal and gastric tumorigenesis in FAP, as it is in colonic tumors. Compared with colonic tumors, however, retention of a greater number of beta-catenin binding/degradation repeats is optimal for tumorigenesis in upper gastrointestinal FAP.

Novel germline CDH1 mutations in hereditary diffuse gastric cancer families

Hereditary diffuse gastric cancer (HDGC) is a recently defined cancer syndrome caused by inactivating, heterozygous germline mutations in the gene for the cell-to-cell adhesion protein E-cadherin (CDH1). Here, we describe the search for CDH1 mutations in 10 newly identified gastric cancer families. Seven of 10 families met the clinical criteria for HDGC. Germline mutations were identified in four of these seven families and one family that was borderline for the clinical criteria. Of the mutations identified in the five new families, four were previously unreported and consisted of two frameshift and two donor splice site mutations. One splice site mutation occurred at the 100% conserved +1 position. The second splice site mutation occurred at the +5 position and was shown to lead to abnormal splicing. Additional CDH1 variants detected include the heterozygous -160 C-->A promoter polymorphism, which has previously been reported to be associated with decreased CDH1 transcription. We, however, found this polymorphism to be common in a control population, suggesting that a major role for this polymorphism in gastric cancer susceptibility is unlikely.

Hereditary diffuse gastric cancer

Hereditary diffuse gastric cancer (HDGC) is a cancer predisposition syndrome caused by germline mutation of the gene for the cell-to-cell adhesion protein E-cadherin. The syndrome is dominated by predisposition to the histologically diffuse, poorly differentiated form of gastric cancer. It is not associated with intestinal-type gastric cancer, but families may have an elevated risk of lobular breast cancer. Here, we review the identified families, mutations, and proposed mechanisms by which E-cadherin loss promotes tumorigenesis.

Genetics of colorectal cancer: hereditary aspects and overview of colorectal tumorigenesis

Familial adenomatous polyposis and hereditary non-polyposis colorectal cancer are dominantly inherited conditions with 100% and 80% life-time risk of developing colorectal cancer, respectively. The genetic mutations responsible for these two conditions lie in the adenomatous polyposis coli (APC) and mismatch repair genes. These same genes also play a key role in the formation of sporadic colorectal cancers, which arise on a background of a similar spectrum of mutations to the hereditary cancers. This article examines the genetic mechanisms underlying the hereditary colorectal cancers, as well as genetic predisposition to colorectal cancer in the general population in the absence of a clear-cut genetic syndrome. Colorectal cancer arises as the cumulative effect of multiple mutations within the cell, allowing it to escape growth and regulatory control mechanisms. This step-wise progression of mutations facilitates the histological transition from normal mucosa to adenoma to carcinoma. The latter part of this paper focuses on the key genetic events underlying this process and provides an overview of the genetic mechanisms responsible for colorectal tumorigenesis.