Hereditary Diffuse Gastric Cancer Cases Research Articles

Identification of New Pathogenic Variants of Hereditary Diffuse Gastric Cancer.

Hereditary diffuse gastric cancer (HDGC) presents a significant genetic predisposition, notably linked to mutations in the CDH1 and CTNNA1. However, the genetic basis for over half of HDGC cases remains unidentified. The aim of this study is to identify novel pathogenic variants in HDGC and evaluate their protein expression. Among 20 qualifying families, two were selected based on available pedigree and DNA. Whole genome sequencing (WGS) on DNA extracted from blood and whole exome sequencing on DNA from formalin-fixed paraffin-embedded tissues were performed to find potential pathogenic variants in HDGC. After selection of a candidate variant, functional validation, and enrichment analysis were performed. As a result of WGS, three candidate germline mutations (EPHA5, MCOA2, and RHOA) were identified in one family. After literature review and in-silico analyses, the RHOA mutation (R129W) was selected as a candidate. This mutation was found in two gastric cancer patients within the family. In functional validation, it showed RhoA overexpression and a higher GTP-bound state in the RhoaR129W mutant. Decreased phosphorylation at Ser127/397 suggested altered YAP1 regulation in the Rho-ROCK pathway. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses linked RhoaR129W overexpression to changed migration/adhesion in MKN1 cell line. However, this RHOA mutation (R129W) was not found in index patients in other families. The RHOA mutation (R129W) emerges as a potential causative gene for HDGC, but only in one family, indicating a need for further studies to understand its role in HDGC pathogenesis fully.

Whole-Exome Sequencing Among Chinese Patients With Hereditary Diffuse Gastric Cancer

The E-cadherin gene, CDH1, and the α-E-catenin gene, CTNNA1, were previously identified as hereditary diffuse gastric cancer (HDGC) susceptibility genes, explaining 25% to 50% of HDGC cases. The genetic basis underlying disease susceptibility in the remaining 50% to 75% of patients with HDGC is still unknown. To assess the incidence rate of CDH1 germline alterations in HDGC, identify new susceptibility genes that can be used for screening of HDGC, and provide a genetic landscape for HDGC. This cohort study conducted retrospective whole-exome and targeted sequencing of 284 leukocyte samples and 186 paired tumor samples from Chinese patients with HDGC over a long follow-up period (median, 21.7 [range, 0.6-185.9] months). Among 10 431 patients diagnosed with gastric cancer between January 1, 2002, and August 31, 2018, 284 patients who met the criteria for HDGC were included. Data were analyzed from August 1 to 30, 2020. Incidence rate of CDH1 germline alterations, identification of new HDGC susceptibility genes, and genetic landscape of HDGC. Among 284 Chinese patients, 161 (56.7%) were female, and the median age was 35 (range, 20-75) years. The frequency of CDH1 germline alterations was 2.8%, whereas the frequency of CDH1 somatic alterations was 25.3%. The genes with the highest incidence (>10%) of private germline alterations (including insertions and deletions) in the HDGC cohort were MUC4, ABCA13, ZNF469, FCGBP, IGFN1, RNF213, and SSPO, whereas previously reported germline alterations of CTNNA1, BRCA2, STK11, PRSS1, ATM, MSR1, PALB2, BRCA1, and RAD51C were observed at low frequencies (median, 4 [range, 1-12] cases). Furthermore, enrichment of the somatic variant signature of exposure to aflatoxin suggested potential interaction between genetics and environment in HDGC. Double-hit events in genes such as CACNA1D were observed, which suggested that these events might serve as important mechanisms for HDGC tumorigenesis. In addition, germline variants of FSIP2, HSPG2, and NCKAP5 and somatic alterations of FGFR3, ASPSCR1, CIC, DGCR8, and LZTR1 were associated with poor overall survival among patients with HDGC. This study provided a genetic landscape for HDGC. The study's findings challenged the previously reported high germline alteration rate of CDH1 in HDGC and identified new potential susceptibility genes. Analyses of variant signatures and double-hit events revealed potentially important mechanisms for HDGC tumorigenesis. Findings from the present study may provide helpful information for further investigations of HDGC.

The CDH1 c.1901C>T Variant: A Founder Variant in the Portuguese Population with Severe Impact in mRNA Splicing.

Simple SummaryAn unexpectedly high number of early-onset diffuse gastric and lobular breast cancer in apparently unrelated families carrying the same CDH1 c.1901C>T variant (formerly known as missense p.A634V) in Northern Portugal suggested a founder effect in this region. We demonstrated that c.1901C>T is a truncating variant triggered by cryptic splicing, calculated its mutational age, and characterized the tumour spectrum and age of onset in affected families.Hereditary diffuse gastric cancer (HDGC) caused by CDH1 variants predisposes to early-onset diffuse gastric (DGC) and lobular breast cancer (LBC). In Northern Portugal, the unusually high number of HDGC cases in unrelated families carrying the c.1901C>T variant (formerly known as p.A634V) suggested this as a CDH1-founder variant. We aimed to demonstrate that c.1901C>T is a bona fide truncating variant inducing cryptic splicing, to calculate the timing of a potential founder effect, and to characterize tumour spectrum and age of onset in carrying families. The impact in splicing was proven by using carriers’ RNA for PCR-cloning sequencing and allelic expression imbalance analysis with SNaPshot. Carriers and noncarriers were haplotyped for 12 polymorphic markers, and the decay of haplotype sharing (DHS) method was used to estimate the time to the most common ancestor of c.1901C>T. Clinical information from 58 carriers was collected and analysed. We validated the cryptic splice site within CDH1-exon 12, which was preferred over the canonical one in 100% of sequenced clones. Cryptic splicing induced an out-of-frame 37bp deletion in exon 12, premature truncation (p.Ala634ProfsTer7), and consequently RNA mediated decay. The haplotypes carrying the c.1901C>T variant were found to share a common ancestral estimated at 490 years (95% Confidence Interval 445–10,900). Among 58 carriers (27 males (M)–31 females (F); 13–83 years), DGC occurred in 11 (18.9%; 4M–7F; average age 33 ± 12) and LBC in 6 females (19.4%; average age 50 ± 8). Herein, we demonstrated that the c.1901C>T variant is a loss-of-function splice-site variant that underlies the first CDH1-founder effect in Portugal. Knowledge on this founder effect will drive genetic testing of this specific variant in HDGC families in this geographical region and allow intrafamilial penetrance analysis and better estimation of variant-associated tumour risks, disease age of onset, and spectrum.

Abstract 800: A germline CTNNA1 variant in a large Chilean family with hereditary diffuse gastric cancer

Abstract The purpose of this study is to describe a large Chilean family having a Hereditary Diffuse Gastric Cancer and a possible causative mutation of cancer in this family. Gastric cancer is the leading cause of cancer-related death in Chile. Worldwide, only ten percent of gastric cancer have a familial aggregation and in Hereditary Diffuse Gastric Cancer (HDGC), E-Cadherine 1 gene (CDH1) is the most commonly mutated gene (30%). To our knowledge, only one HDGC Chilean family with a pathogenic CDH1 mutation has been reported, suggesting a low frequency of CDH1 mutations in this population. CTNNA1 mutations (alpha-1 catenin gene), also have been found in HDGC cases. E-cadherine 1 and alpha-1 catenin are part of adherens junction complex. In this family, there are eleven members affected with gastric cancer and two with breast cancer, in two following generations. The index patient was diagnosed with a diffuse gastric tumor at 51 years of age and one affected relative (a deceased brother of the index case) at 38 years of age. The index patient´s gastric tumor histology type is diffuse, but the tumor of the affected sister is papillary. Cancer gene panel sequencing was performed in index patient DNA and cascade genotyping in family members was performed using Kompetitive allele-specific PCR. A germline variant c.293G>A (p.R98Q, rs746832629) in the CTNNA1 gene was found in the index patient. This variant has been reported two times in ClinVar and is classified as an uncertain significance variant. In TCGA, CTNNA1 c.293G>A variant has been reported four times in gastric, colon, and uterine tumor samples. This variant maps to the beta-catenin binding domain of the protein, and the mutated residue is conserved from fish to primates. The variant population frequency in the Genome Aggregation Database is in Latinos is 0.0049 and worldwide is 0.000076. We searched the variant in other members of the family and carried out a co-segregation analysis, that indicates an incomplete penetrance of the variant because two non-affected brothers do have it. Based on our data, we think that this variant could be pathogenic and causative of the HDGC observed in this family, but showing an incomplete penetrance. Additionally, the variant was not found in sixty-two other early-onset Chilean cancer gastric patients, thus we are going to search the variant in a sample of the general population of the family´s region. Also, we will do a whole-exome sequence in the samples of all available affected relatives looking for other variants to explain the incomplete penetrance, search for the second hit in an index patient´s tumor sample and perform a functional analysis of the variant during this semester. Beca Chile Postdoctorado 74190063, CONICYT-FONDAP 15130011-2 (NIH). Citation Format: Graciela Molina, Ana Estrada, Alma Poceros, Carol Parra, Osvaldo Torres, Natalia Landeros, Andrés Rodríguez, Alejandro Corvalán, Luis Carvajal-Carmona. A germline CTNNA1 variant in a large Chilean family with hereditary diffuse gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 800.

A novel stop codon mutation in exon 5 (c.639G>A) of the cadherin-1 gene in a Vietnamese man with hereditary diffuse gastric cancer: a case report

BackgroundGermline pathogenic variants in the cadherin-1 (CDH1) gene cause a predisposition to hereditary diffuse gastric cancer (HDGC). We report an HDGC case in Vietnam and identify a novel mutation in the CDH1 gene.Case presentationA 28-year-old Vietnamese man was diagnosed with HDGC and a novel mutation at c.639G>A. All exons of CDH1 were sequenced in his pedigree, which revealed the c.639G>A mutation in the proband, his father, and uncle. The patient refused treatment and died 4 months after diagnosis. Endoscopic surveillance of the father and the uncle showed structural abnormalities in the father.ConclusionIn cases of HDGC, identification of the CDH1 gene mutation is very important for better counseling and more effective strategies to prevent the development of diseases, such as prophylactic gastrectomy for family members with genetic mutations.

Abstract 2523: Loss of expression of wild-type transcript of CDH1 gene is associated with overexpression of microRNA-20 in diffuse-type of gastric cancer

Abstract Background: Gastric cancer (GC) is the third cause of cancer death in the world. In Latin America, GC is one of the leading causes of death, particularly in Chile. E-cadherin has been classified as a tumor suppressor gene that participates in cell adhesion. Reduction or loss of E-cadherin expression could promote tumor progression particularly in the sporadic diffuse subtype of GC (SDGC). In addition, inactivation germline mutations of CDH1 (E-cadherin gene) have been linked to the hereditary diffuse gastric cancer (HDGC) syndrome. Methods: We evaluated the expression of E-cadherin by Immunohistochemistry (IHC) in SDGC (n=27) and HDGC (n=22) cohorts. We also analyzed, by Sanger sequencing the full coding region of CDH1 in both cohorts. To identified miRNA-CDH1 interactions, an in silico analysis by mirWalk 2.0 software (5 or more algorithms) was performed. To validated in silico findings, 10 paired tumor and normal matched fresh gastric tissues were analyzed by miQ-PCR (miRNA) and qRT-PCR assay (CDH1 transcript) were performed. Results: The expression analysis of E-cadherin showed loss of expression in 13/27 (48%) SDGC and in 19/22 (90%) HDGC cases, respectively. The decrease of E-cadherin expression was significantly higher in the hereditary cohort (p=0.002, χ2: 9.12, 95%CI:13.0-63.3). Exome sequence analysis of the full coding region of CDH1 identified 3 and 9 mutations in SDGC and HDGC, respectively. Correlation between loss of protein expression by IHC and mutations was not found. Next, we explore the role of miRNA, as an alternative mechanism of the loss of E-cadherin protein expression. In silico analysis identified 417 miRNAs candidates with predicted binding sites. Among these candidates, all members of the polycistronic cluster miR-17/92 have seed regions against the 3'-UTR of the CDH1 transcript. Levels of expression of all 6 members of the polycistronic cluster were validated against CDH1 expression in paired normal and tumor fresh tissues of SDGC. A strong inverse correlation between the overexpression of miR-20a and downregulation of CDH1 transcript was found exclusively in tumor tissue (p= 0.0267) but not in normal counterparts. These results were validated in the STAD-TCGA cohort. Conclusions: Our results might explain the loss of expression of CDH1 in GC due to overexpression miR-20, a member of the polycistronic cluster miR-17/92. Future experimental validation of the predicted seed region will be necessary to confirm these findings. Grant support: CONICYT-FONDAP-15130011, Fondecyt-1191928 Citation Format: Natalia Landeros, Maria A. Alarcon, Graciela Molina, Pablo Santoro, Keila Torres, Wilda Olivares, Ignacio Wichmann, Franz Villarroel-Espindola, Iva Polakovicova, Enrique Norero, Alejandro H. Corvalan. Loss of expression of wild-type transcript of CDH1 gene is associated with overexpression of microRNA-20 in diffuse-type of gastric cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2523.

Histopathologic Analysis of Signet-ring Cell Carcinoma In Situ in Patients With Hereditary Diffuse Gastric Cancer.

Hereditary diffuse gastric cancer (HDGC) is a rare autosomal dominant syndrome associated with an increased risk of developing Laurén's diffuse-type gastric carcinoma and lobular breast carcinoma. Although signet-ring cell carcinoma (SRCC) in situ (SRCC-pTis) has been reported as a characteristic lesion in HDGC cases with CDH1 germline mutations (CDH1 pathogenic variant), and a precursor of conventional intramucosal SRCC (SRCC-pT1a), its histopathologic features and specificity have not been sufficiently clarified. Here, we examined gastrectomy samples from 6 Japanese HDGC patients with CDH1 germline mutation, belonging to 4 families, and analyzed SRCC lesions histologically and immunohistochemically. Of the 274 foci found in the 6 samples, SRCC-pT1a accounted for 225 lesions (range: 8 to 107, mean 45.7 lesions per patient), while 46 foci were of SRCC-pTis (range: 1 to 15, mean 7.67 foci per patient). All SRCC-pTis foci were observed in the fundic gland area and on the superficial side of the mucosa. Histologically, tumor cells of SRCC-pTis were found between normal foveolar epithelial cells and the basement membrane, following a typical pagetoid spread pattern. Immunohistochemically, E-cadherin expression was lost in SRCC-pTis (27/28, 96.4%) more frequently than in SRCC-pT1a (95/197, 48.2%; P<0.001). To elucidate the specificity of SRCC-pTis for HDGC, 60 samples (range: 0.12 to 1.49 m, total 28.8 m of mucosal length) from gastric cancer cases were analyzed as controls, in which no SRCC-pTis were identified. Our results indicate that SRCC-pTis is a distinct histologic feature with high specificity for HDGC cases with CDH1 germline mutations.

2780 A Case of a 20-Year-Old Female With Hereditary Diffuse Gastric Cancer Syndrome With Synchronous Diffuse Gastric Cancer and a Giant Uterine Tumor

INTRODUCTION: Hereditary Diffuse Gastric Cancer (HDGC) is defined by germline autosomal dominant mutation in the CDH1 gene causing an inherited form of diffuse gastric cancer. There are no reported cases of HDCG presenting with a synchronous giant uterine tumor. CASE DESCRIPTION/METHODS: A 20-year-old female with known pathogenic CDH1 mutation presented with 3 days of pelvic pain and a palpable lower abdominal mass. She underwent a CT abdomen/pelvis which revealed a large uterine tumor measuring 16 cm. The patient’s family history is notable for maternal grandmother and maternal uncle who were diagnosed with and died of gastric cancer at 46 and 55, respectively. Her mother, the proband, was diagnosed with stage IV diffuse gastric cancer at age 46, underwent genetic testing and was found to have a pathogenic mutation in the CDH1 gene. The patient’s 42-year-old maternal aunt, who also tested positive, underwent prophylactic gastrectomy. There was no evidence of gastric adenocarcinoma on pathology. The patient also tested positive for CDH1 mutation and was counselled about prophylactic gastrectomy. Given she had just turned 20, the patient was not offered immediate surgery. She underwent a baseline upper endoscopy prior to planned hysterectomy. Random endoscopic biopsies revealed diffuse poorly differentiated carcinoma with signet ring features. Given poor histology and diffuse nature, the patient received 3 cycles of neoadjuvant chemotherapy before undergoing total gastrectomy with Roux-en-Y reconstruction and uterine myomectomy. She opted for myomectomy to preserve fertility. Pathology revealed diffuse pT1aN0M0 poorly differentiated G3, stage IA gastric adenocarcinomaand a benign leiomyoma. DISCUSSION: HDGC is exceedingly rare, accounting for only 1% of all gastric cancers. The median age to develop gastric cancer in pathogenic CDH1 carrier is 33 to 40. The risk of developing gastric cancer is less than 1% in patients under the age of 20. HDGC has penetrance of up to 80%. Our patient’s 42 year old aunt had a pathogenic CDH1 gene; however, her final pathology following prophylactic gastrectomy did not show any evidence of cancer, highlighting the small possibility of having no disease manifestation. Lastly, our patient had a synchronous, yet separate, primary uterine tumor at the time of presentation. In reviewing the literature, there are no other reported HDGC cases with a concurrent separate primary uterine tumor.

Prophylactic Gastrectomy in Hereditary Diffuse Gastric Cancer

Gastric cancer (GC) is one of the leading causes of cancer-related deaths worldwide. It is classified as intestinal and diffuse. Only 1-3% of all cases are inherited and include hereditary diffuse gastric cancer (HDGC). It has an autosomal dominant inheritance with poor prognosis. The risk for developing gastric cancer in people with E. cadherin1 encoding gene (CDH1) mutations is estimated to be 70% for men and 83% for women at an average age of 38. We present a case of a patient with HDGC, who underwent prophylactic gastrectomy with a prior negative EGD. A 38-year-old woman with CDH1 mutation and a family history of colon, gastric, and breast malignancies in first and second-degree relatives, presented for endoscopic surveillance of gastric cancer. EGD was unremarkable and she was scheduled for a 1-year follow-up. One year later, after further evaluation, she was recommended to undergo prophylactic gastrectomy. She underwent an exploratory laparotomy with subtotal gastrectomy and jejunal pouch creation. Biopsy revealed poorly differentiated adenocarcinoma of the stomach, penetrating the serosa, stage T4aN1M0. Due to family history, CDH1 mutation and a personal history of gastric cancer, the patient was diagnosed with HDGC. She was started on chemotherapy with future plans for radiation. Patients with GC are usually asymptomatic or have nonspecific symptoms. Breast cancer might be the only presenting pathology because of its association with CDH1. A gastric tumor may be the initial presentation of HDGC syndrome in CDH1 positive individuals without a positive family history. CDH1 gene is found in only 30-50% of all HDGC cases, suggesting a potential for additional gene involvement. Current guidelines recommend prophylactic total gastrectomy without D2 node dissection in all confirmed CDH1 mutation carriers between ages 18-40 years. A baseline endoscopy is indicated prior to gastrectomy to map gastric margins, identify any macroscopic tumors, and to rule out Barrett's esophagus. EGD with mapping biopsies can detect 9% of patients with microscopic foci of adenocarcinoma with one study showing 65%. Women with CDH1 mutations should undergo annual mammogram and should consider breast MRI at age 30, or 5-10 years earlier than the youngest diagnosis in the family. Patients with an incidental finding of CDH1 mutations during multi-genetic testing or those without a family history of HDGC should at least undergo screening EGD and be referred to HDGC specialist.2718_A Figure 1. CK7 stain highlighting tumor cells.2718_B Figure 2. Tumor cells at serosal edge.

Histologic and immunohistochemical differences between hereditary and sporadic diffuse gastric carcinoma

We aimed to identify histopathologic features unique in hereditary diffuse gastric cancer (HDGC) by comparing with its sporadic counterpart (SDGC). 11 patients with confirmed CDH1 mutation who were found to have HDGC in a prophylactic total gastrectomy were collected. Median age of HDGC patients was 39 years (range 24-57). All HDGC cases had intramucosal signet ring cell carcinoma. Twenty-three invasive tumor foci from 7 patients with HDGC were available for ancillary studies, and we evaluated each focus separately. Almost all foci (20/23) showed two distinct tumor cell populations, namely, large signet ring cells and small signet ring cells. The large cells were located just beneath the surface epithelium and were positive for mucicarmine and pCEA, while the small cells were found in the deeper lamina propria and were mostly negative for mucicarmine and pCEA. A subset of small cells (6 foci from two resected stomachs) showed poorly differentiated morphology with p16 positivity. All other tumor cells with well-differentiated signet ring cell morphology were negative for p16. In contrast, 18 of 20 SDGCs were positive for p16. In addition, all HDGCs were negative for CDX2, while 19 of 20 SDGCs were positive. We propose that there are three distinct tumor cell populations in HDGC: well-differentiated large cells, well-differentiated small cells, and poorly differentiated small cells, and that the latter group with aberrant p16 expression may represents a more aggressive phenotype. The absence of CDX2 in HDGC suggests that it may develop along a carcinogenetic pathway different from that of SDGC.

Hereditary diffuse gastric cancer in two families: A case report.

Hereditary diffuse gastric cancer (HDGC) is associated with E-cadherin 1 (CDH1) germline mutations. In the present study, two unusual HDGC cases are described. Case 1 was a female with no family history of gastric cancer who developed Hodgkin's lymphoma at 19 years of age, and DGC at 32 years of age. Due to her young age (32 years), the patient was examined for CDH1 abnormalities and a deleterious mutation was identified. Her father and younger sister were identified to be carriers of the mutation. Case 2 was a 36-year-old female diagnosed with lobular breast cancer (LBC); her mother had LBC, and her grandmother had LBC and DGC. The molecular test was wild-type for breast cancer susceptibility genes 1 and 2; however, a large deletion in CDH1 was identified. At prophylactic gastrectomy, early DGC was identified. Early onset of DGC and LBC justifies testing for CDH1. A better knowledge of tumor natural history in carrier subjects is important to aid genetic counseling, in order to assess the surveillance time required prior to carrying out prophylactic surgery.

E-cadherin mediated cellular effects and molecular partners. Gastric cancer as an invasive model

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 most of them are functionally relevant and constitute a invaluable model do study E-cadherin dependent signaling pathways and find new molecular targets for therapy. Recently, we explored the hypothesis that mutations affecting different E-cadherin protein domains have distinct effects on cell motility. To verify this hypothesis 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 signaling pathways known to be relevant for cell motility, such as the EGFR signaling. We found that all cell lines expressing extracellular mutant forms of E-cadherin (T118R, L214P, G239R, A298T and P373L) displayed higher EGFR activation than cells expressing wild-type E-cadherin. This phenotype is similar to what we observed for cells negative for E-cadherin, which also displayed increased EGFR phosphorylation in comparison to the wild-type expressing cells. The same pattern was observed for the cells expressing the intracellular mutations within the juxtamembrane region, R749W and E757K, which is in accordance with the motility analysis results. 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. The role of E-cadherin in tumor development is well established, with many human carcinomas exhibiting E-cadherin loss at the invasive front. In many invasive carcinomas, the mechanisms leading to the loss of E-cadherin remains elusive. We recently hypothesize that trafficking deregulation has a role in the regulation of E-cadherin missense mutations. We first analyzed the intracellular trafficking of two HDGC-associated missense mutations, R749W and E757K, localized in the justamembranar domain of E-cadherin, know to have higher impact in E-cadherin trafficking. We found that these mutations frequently accumulate in the endoplasmic reticulum. Moreover, treatment of the mutant cells with specific chemical chaperones, restored mutant E-cadherin to the cell membrane and rescued its function. The protein-stabilizing power of chemical chaperones has been show to be effective on rescuing different disease-associated mutant proteins, but the mechanism is not understood. In order to understand and further explore the therapeutic power of such organic molecules in the context of HDGC, be believe its crucial to dissect their mode of action in the regulation of E-cadherin mutants. We are now investigating the mechanism by which the chemical chaperone DMSO rescues mutant E-cadherin expression by analyzing its effect on different known E-cadherin trafficking regulators.

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.

Hereditary Diffuse Gastric Cancer: Surveillance Endoscopy is Not Enough to Save Lives

Hereditary Diffuse Gastric Cancer: Surveillance Endoscopy is Not Enough to Save Lives

Evidence that the V832M E-Cadherin Germ-Line Missense Mutation does not Influence the Affinity of α -Catenin for the Cadherin/Catenin Complex

Mutations in E-cadherin are associated with a number of diseases, and have been shown to contribute to disease progression. In particular, 50% of hereditary diffuse gastric cancer cases have inactivating mutations in the E-cadherin gene. An interesting mutation near the beta-catenin-binding site on the cytoplasmic domain of E-cadherin (V832M) was recently reported that produces full-length protein, but exhibits decreased binding of alpha -catenin to the cadherin/catenin complex. The study was done by transfecting mutant E-cadherin into Chinese hamster ovary fibroblast cells. Here we show that the previously reported characteristics of this mutation do not apply to human epithelial cells expressing this mutant protein and suggest that the mechanism whereby the V832M mutation in human E-cadherin promotes gastric cancer is not yet understood.