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

Background

Gastric cancer remains a leading cause of cancer deaths worldwide. Genetic factors, including germline mutations in E‐cadherin (CDH1, MIM#192090) in hereditary diffuse gastric cancer (HDGC, MIM#137215), are implicated in this disease. Family studies have reported CDH1 germline mutations in HDGC but the role of CDH1 germline mutations in the general population remains unclear.

Aims

To examine the frequency of CDH1 germline mutations in a population‐based series of early‐onset gastric cancer (EOGC <50 years old).

Methods

211 cases of EOGC were identified in Central‐East Ontario region from 1989 to 1993, with archival material and histological confirmation of non‐intestinal type gastric cancer available for 81 subjects. Eligible cases were analysed for CDH1 germline mutations by single‐strand conformation polymorphism, variants were sequenced, and tumours from cases with functional mutations were stained for E‐cadherin (HECD‐1) using immunohistochemistry.

Results

1155 (89%) of 1296 polymerase chain reactions amplified successfully. One new germline deletion (nt41delT) was identified in a 30‐year‐old patient with isolated cell gastric cancer. The overall frequency of germline CDH1 mutations was 1.3% (1/81) for EOGC and 2.8% (1/36) for early‐onset isolated cell gastric cancer.

Conclusion

This is the first population‐based study, in a low‐incidence region, of genetic predisposition to gastric cancer. Combined with our previous report of germline hMLH1 mutations in two other subjects from this series, it is suggested that 2–3% of EOCG cases in North Americans may be owing to high‐risk genetic mutations. These data should inform cancer geneticists on the utility of searching for specific genetic mutations in EOGC.Gastric cancer is the second most common cause of cancer deaths worldwide.¹ Despite an overall decline in the incidence of gastric cancer in older people, the incidence of early‐onset (⩽50 years old) gastric cancer (EOGC) and familial clustering of gastric cancer remains stable in frequency.² Genetic predisposition to gastric cancer caused by known genes such as CDH1 and the mismatch repair genes may have an important role in the development of gastric cancer in these cases.³ Autosomal dominant gastric cancer is estimated to account for about 1–3% of all cases.⁴ We have previously reported two new germline mutations (2 of 139 cases) in the hMLH1 gene in our population‐based series of EOGC.⁵In 1998, Guildford et al⁶ first described inactivating germline mutations in E‐cadherin (CDH1 gene) responsible for the development of diffuse‐type gastric cancer (DGC) in three families of Maori origin. Additional family studies have shown that E‐cadherin is responsible for some families presenting with DGC, according to the Lauren classification.⁷ In 1999, the International Gastric Cancer Linkage Consortium (IGCLC) provided the first clinical management guidelines for this autosomal dominant hereditary predisposition syndrome, hereditary diffuse gastric cancer (HDGC, MIM#137215), as defined by Guildford et al earlier that year.^8,9 HDGC is caused by germline inactivating mutations in E‐cadherin (CDH1, MIM# 192090). However, other genes are likely to cause HDGC, as only 30% of families with HDGC meeting the primary criteria for HDGC have been found to have CDH1 germline mutations. To date, 57 distinct functional CDH1 germline mutations have been reported. Of these, 50 are listed in the Human Gene Mutation Database (http://www.hgmd.cf.ac.uk/ac/gene.php?gene = CDH1), an additional five functional mutations were reported by Suriano et al,¹⁰ and a further two splice mutations associated with cleft lip/palate and HDGC were more recently reported by Frebourg et al.¹¹ Most of these mutations result in a truncated, non‐functional protein. Although primary criteria are fairly well established for screening of CDH1 germline mutations in kindreds with gastric cancer, the IGCLC recognise the need for large population‐based studies of genetic predisposition to gastric cancer to determine the role of germline mutations in sporadic EOGC. Here, we report the first population‐based study of EOGC to determine the frequency of CDH1 germline mutations in a population at a low risk for gastric cancer.

Keypoints

• This is the first and largest population‐based study of genetic predisposition to gastric cancer in a low‐incidence region reporting a new germline CDH1 mutation.
• 2–3% of cases of early‐onset gastric cancer (EOGC) in North America may be owing to high‐risk genetic mutations.
• Informs geneticists on the use of searching for genetic mutations in EOGC.

     

Screening E-cadherin in gastric cancer families reveals germline mutations only in hereditary diffuse gastric cancer kindred

The International Gastric Cancer Linkage Consortium (IGCLC) predicted that up to 25% of families fulfilling the criteria for hereditary diffuse gastric cancer (HDGC) would harbor CDH1 germline mutations. This was based on observations from the low number of diffuse gastric cancer families described at the time, and its validation would require analysis of larger numbers. Here we report the results of germline CDH1 mutation screening in 39 kindred with familial aggregation of gastric cancer, a subset of which fulfills the criteria defined by the IGCLC for HDGC. CDH1 germline mutations were detected in four of 11 (36.4%) HDGC families. No mutations were identified in 63.6% of HDGC families or in kindred with familial aggregation of gastric cancer not fulfilling criteria for HDGC. These results add support to the evidence that only HDGC families harbor germline mutations in CDH1 and that genes other than CDH1 remain to be identified.     

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.     

A rare tumor and an ethical dilemma in a family with a germline TP53 mutation

We describe a family with a history of cancer suggestive of the Li-Fraumeni syndrome (LFS). A 27-year-old woman suffered at 17 years of age from phyllodes breast tumor and was shown to carry a germline mutation in the TP53 gene. Two years after testing, she became pregnant and was offered prenatal diagnosis by her gynecologist. The patient expressed her commitment to deliver the baby regardless of its mutation status, but with a strong interest in having the child tested soon after the birth. When she was informed that testing of children is usually postponed until after they reach 18 years of age, she consulted several geneticists, who repeatedly discouraged her from the intent to test the newborn. In the end, the patient decided for prenatal genetic testing only to learn the mutation status of the child. This scenario being unacceptable, she was offered early postnatal testing of the child, and this analysis showed that the newborn boy carried the mutation. Based on this finding, the family was enrolled into a preventive screening program for childhood cancer. The case illustrates ethical problems associated with early predisposition testing in LFS, and the lack of consensus on this issue in the literature.     

A novel CDH1 germline missense mutation in a sporadic gastric cancer patient in north-east of Italy

It is well documented that germline mutations in the E-cadherin (CDH1) gene are linked to hereditary diffuse gastric cancer (HDGC). Despite the known molecular genetic causes, most gastric cancers are sporadic and poorly investigated for susceptibility genes. We report the finding of a novel germline missense mutation in exon 6, c. 820 G > A (p.G274S) in one sporadic gastric cancer patient. This new variant does not affect cryptic splicing of CDH1 as demonstrated by molecular assay. Immunohistochemical analysis shows a mixed pattern of E-cadherin staining (membranous and cytoplasmic) in the intestinal component, while in the diffuse counterpart, the membranous staining was prevalent and a reduced membranous expression of ß-catenin was observed. In vitro assays suggest that the mutant G274S does not affect the E-cadherin protein function, its expression pattern or subcellular localization. This new variant is present in EC2 extracellular domain of the protein (p.G120S in mature protein). The molecular modelling shows that this point mutation is not dramatic for local structure. However, p.S120 is located on the surface of the protein close to the functional calcium sites and in the region of interaction with EC1 domain of another E-cadherin molecule involved in the formation of the intercellular junction. Moreover, p.S120 residue could be involved in posttranslational modifications, such as phosphorylation or glycosylation, with possible effects on stability and integrity of adhesive properties of E-cadherin. In conclusion, the pathogenicity of this mutation is unlikely; probably we found a new germline CDH1 missense mutation with potential impact, however, of uncertain significance.     

A novel STK11 germline mutation in two siblings with Peutz-Jeghers syndrome complicated by primary gastric cancer

Patients with Peutz-Jeghers syndrome (PJS) are known to be at risk of gastric cancer (GC), and the STK11 gene is a susceptibility gene for PJS. However, as no cases of PJS with GC in which a STK11 germline mutation has been identified have ever been reported and other susceptibility genes have also been suggested to be involved in PJS, the relation between STK11 germline mutations and GC in PJS is still unknown. In this study, we used sequencing analysis to investigate the STK11, CDH1, and TP53 loci for a germline mutation in two siblings with PJS with primary GC. A novel type of the STK11 germline mutation, c.890delG, encoding a truncated protein (p.Arg297fsX38) was identified, but no germline mutations of the CDH1 and TP53 genes were detected. No inactivation of the wild-type allele by somatic mutation or chromosomal deletion or hypermethylation at the 5'-CpG site of STK11 was detected in the GC. This is the first report of a STK11 germline mutation in a PJS patient with GC and should contribute to establishing correlations between the STK11 germline mutations and GC in PJS patients.     

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

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

Novel c-KIT germline mutation in a family with gastrointestinal stromal tumors and cutaneous hyperpigmentation

Mutations in the c-KIT gene have been identified in many sporadic and familial cases of gastrointestinal stromal tumor (GIST). We report a familial case of GIST with cutaneous hyperpigmentation associated with a novel germline mutation in the c-KIT gene. Screening for mutations in exon 11 of the c-KIT gene in genomic DNA from tumors and peripheral blood of the members of a family with GISTs was undertaken by direct genomic sequencing. Tumors from GIST patients were analyzed histologically and immunohistochemically. Clinical examination of GIST patients was also performed to detect other systemic diseases associated with c-KIT mutations. Histological study showed that the tumors were GISTs expressing CD34 and c-KIT protein. This GIST-hyperpigmentation disease was associated in the family with a germline mutation in the c-KIT gene. The mutation is a duplication of the sequence CAACTT located in exon 11 of the c-KIT gene, which introduces two extra glutamine and leucine residues in the encoding protein between positions 576 and 577. This Spanish family was affected with GISTs and cutaneous hyperpigmentation associated with a novel germline mutation Leu576_Pro577insGlnLeu in the juxtamembrane domain of the c-KIT receptor. These types of mutation in the c-KIT gene activate the tyrosine kinase activity of the c-KIT receptor and induce constitutive signaling leading to GISTs, in some cases associated with cutaneous hyperpigmentation.     

Identification of CDH1 germline missense mutations associated with functional inactivation of the E-cadherin protein in young gastric cancer probands

E-cadherin is involved in the formation of cell-junctions and the maintenance of epithelial integrity. Direct evidence of E-cadherin mutations triggering tumorigenesis has come from the finding of inactivating germline mutations of the gene (CDH1) in hereditary diffuse gastric cancer (HDGC). We screened a series of 66 young gastric cancer probands for germline CDH1 mutations, and two novel missense alterations together with an intronic variant were identified. We then analysed the functional significance of the two exonic missense variants found here as well as a third germline missense variant that we previously identified in a HGDC family. cDNAs encoding either the wild-type protein or mutant forms of E-cadherin were stably transfected into CHO (Chinese hamster ovary) E-cadherin-negative cells. Transfected cell-lines were characterized in terms of aggregation, motility and invasion. We show that a proportion of apparently sporadic early-onset diffuse gastric carcinomas are associated with germline alterations of the E-cadherin gene. We also demonstrate that a proportion of missense variants are associated with significant functional consequences, suggesting that our cell model can be used as an adjunct in deciding on the potential pathogenic role of identified E-cadherin germline alterations.     

Prospective risk of cancer in CDKN2A germline mutation carriers

Background: The CDKN2A gene is the major known high-risk melanoma susceptibility gene. Susceptibility to other cancers has also been suggested. However, most studies examining the risks of other cancers classified individuals according to the family''s CDKN2A mutation rather than determining individual mutation status. For non-population-based studies, risks could also be biased because of cancer occurrence prior to family ascertainment. Methods: We examined the risk of non-melanoma cancer in 117 mutation-positive and 136 mutation-negative members from 15 families that had at least two first degree relatives with melanoma and CDKN2A mutations restricting the analysis to the period after the families were ascertained (that is, the prospective period) and using individual mutation data. The families have been followed prospectively for 4–26 years starting in the 1970s. Results: Overall, there was no significant association for mutation-negative subjects (Obs/Exp = 0.3, 95% confidence interval (CI) 0.0 to 1.2) although this group had only two observed cancers. In contrast, mutation-positive subjects had a significantly increased risk for all cancers combined (Obs/Exp = 12/5.5 = 2.2, 95% CI 1.1 to 3.8) primarily because of digestive system tumours, particularly pancreatic cancer. No other organ systems or individual tumour sites showed significantly increased risks. Conclusions: Differences in CDKN2A–non-melanoma cancer associations across studies may result from variation in genetic backgrounds, insufficient follow up, misclassification of mutation carriers, or the presence of other genetic and/or environmental risk factors in both CDKN2A mutation carriers and non-carriers. Larger sample sizes, prospective follow up, and individual mutation data will be required to understand these differences.     

Identification of a novel CTR9 germline mutation in a family with Wilms tumor

Germline mutations in the WT1 gene have been identified in some families with Wilms tumor. Recently, the CTR9 gene was found to be mutated in three families with Wilms tumor, thus representing a novel predisposition gene for this disease. We identified a family with a history of Wilms tumor characterized by three affected siblings, one of them presenting an aggressive bilateral tumor.Here we investigated the involvement of WT1 and CTR9 genes in this family with Wilms tumor. The involvement of WT1 was first evaluated by Next generation sequencing in leukocytes DNA from one affected family member. Subsequently, the CTR9 gene was analyzed by Sanger sequencing in DNA and RNA from patients’ leukocytes and/or tumor. No mutations were detected in WT1. However, we identified a novel CTR9 germline variant, located in a consensus splice acceptor site, which was found to segregate with Wilms tumor in this family. We found that this variant leads to the skipping of the entire exon 9 in the mRNA, which is predicted to encode a truncated CTR9 protein, strongly suggesting that it is pathogenic. Additionally, we also detected loss of heterozygosity in the index case tumor, which is consistent with CTR9 being a tumor suppressor gene, confirming also its contribution to familial Wilms tumor etiology.The identification of a novel CTR9 germline mutation will improve the present knowledge on the molecular basis of familial Wilms tumor. Importantly, it will help in the genetic counselling and may also lead to earlier diagnosis in other family members and future generations.     

Cytogenetic instability in a family with gastric cancer recurrence

An index case with a congenital malformation syndrome enabled detection of a family that had a previous history of spontaneous abortuses and recurrence of neoplasia through three generations. Cytogenetic analysis performed on lymphocytes from 11 subjects in the second and third generation showed karyotypic alterations in both tumor bearers and apparently normal subjects. Chromosome variations consisted of: spontaneous chromosome fragility; chromosome translocations; polymorphisms in the heterochromatic regions in chromosomes Y, #1, #16, #22. The inheritance pattern of all chromosome rearrangements and heteromorphisms observed was established starting with the second generation, and the contribution of specific individuals was identified. Although the relationship between chromosomal instability and predisposition to gastric cancer does not appear to be coincidental, no specific chromosome alteration in normal somatic cells was shared by all members of the family who developed or are at risk of developing tumors.     

Phenotypic findings of Cowden syndrome and Bannayan-Zonana syndrome in a family associated with a single germline mutation in PTEN

Cowden syndrome (CS) and Bannayan-Zonana syndrome (BZS) are two hamartoma syndromes with distinct phenotypic features. Although partial clinical overlap exists between CS and BZS, they are considered to be separate entities. PTEN has been identified as the susceptibility gene for both disorders, suggesting allelism. We have identified a germline mutation, R335X, in PTEN in a family consisting of two female members with the phenotypic findings of CS and two male members with the phenotypic findings of BZS. To our knowledge, this is the first report that shows the presence of separate subjects with CS and with BZS in a single family associated with a single germline PTEN mutation.     

Increased risk of cancer in patients with fumarate hydratase germline mutation

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a tumour predisposition syndrome caused by heterozygous germline mutations in the fumarate hydratase (FH) gene. The condition is characterised by predisposition to benign leiomyomas of the skin and the uterus, renal cell carcinoma (RCC), and uterine leiomyosarcoma (ULMS). To comprehensively examine the cancer risk and tumour spectrum in Finnish FH mutation positive families, genealogical and cancer data were obtained from 868 individuals. The cohort analysis of the standardised incidence ratios (SIR) was analysed from 256 individuals. FH mutation status was analysed from all available individuals (n=98). To study tumour spectrum in FH mutation carriers, loss of the wild type allele was analysed from all available tumours (n=22). The SIR was 6.5 for RCC and 71 for ULMS. The overall cancer risk was statistically significantly increased in the age group of 15–29 years, consistent with features of cancer predisposition families in general. FH germline mutation was found in 55% of studied individuals. Most RCC and ULMS tumours displayed biallelic inactivation of FH, as did breast and bladder cancers. In addition, several benign tumours including atypical uterine leiomyomas, kidney cysts, and adrenal gland adenomas were observed. The present study confirms with calculated risk ratios the association of early onset RCC and ULMS with FH germline mutations in Finns. Some evidence for association of breast and bladder carcinoma with HLRCC was obtained. The data enlighten the organ specific malignant potential of HLRCC.     

BRCA2 mutation in a family with hereditary prostate cancer

Hereditary prostate cancer is a genetically heterogeneous disease, and so far four different susceptibility loci have been identified. Reports of associated cancers are few, and it is generally considered a site-specific disease. However, some reports have shown an elevated risk for prostate cancer among BRCA2 mutation carriers. In this report, we present a family in which the father and four of his sons were diagnosed with prostate cancer at exceptionally early ages (51, 52, 56, 58, and 63 years, respectively). In addition, three daughters were diagnosed with breast cancer between the ages of 47 and 61. In this family, a truncating mutation in exon 11, 6051delA of the BRCA2 gene, leading to an early termination of the protein (codon 1962), was identified. Although BRCA2 is probably responsible only for a very small fraction of hereditary prostate cancers, this finding supports previous reports of an increased risk of prostate cancer in BRCA2 mutation carriers.     

A germline variant N375S in MET and gastric cancer susceptibility in a Chinese population

MET tyrosine kinase and its ligand,hepatocyte growth factor(HGF),play a pivotal role in the activties of tumor cells.A germline missense variant in exon 2 of the MET gene,N375S(rs33917957 A>G),may alter the binding affinity of MET for HGF and thus modify the risk of tumorigenesis.In this study,we performed a case-control study to assess the association between N375S and gastric cancer risk in 1,681 gastric cancer cases and 1,858 cancer-free controls.Logistic regression analysis was applied to estimate crude and adjusted odds ratios(ORs) and 95% confidence intervals(CIs) for the associations between genotypes and gastric cancer risk.We found that MET N375S variant genotypes(NS/SS) were associated with a significantly decreased risk of gastric cancer(OR = 0.78,95% CI = 0.63-0.96,P = 0.021) compared with the wildtype homozygote(NN).The finding indicates that this germline variant in MET may decrease gastric cancer susceptibility in Han Chinese.     

Analysis of a cytoskeleton-associated kinase PEAK1 and E-cadherin in gastric cancer

The expression of pseudopodium-enriched atypical kinase 1(PEAK1) has been studied in human cancers. However, their roles in gastric cancer are still unknown. In this study, gastric cancer tissue microarrays were constructed with 159 gastric cancer tissue samples, 150 non-neoplastic gastric epithelium specimens and 152 lymph node samples. Immunohistochemical staining for PEAK1 and E-cadherin was performed. Our study found negative expression of PEAK1 in 113 of 159 (71.1%) gastric cancers, in 46 of 150 (30.7%) non-neoplastic gastric epithelium tissues and in 69 of 94 (73.4%) metastatic lymph nodes. Negative expression of PEAK1 and E-cadherin associated with tumor grading, depth of invasion, lymph node metastases, pTNM stage and macroscopic type. Patients with either positive PEAK1 or E-cadherin expression had a significantly higher survival than those with negative expression. When combined, PEAK1⁻/E-cadherin⁻ had a significantly poor prognosis than the rest of the patients. The expression of PEAK1 protein was positively correlated with E-cadherin in cancer tissues. Cox regression analyses showed that PEAK1, E-cadherin and PEAK1⁻/E-cadherin⁻ were independent predictors of overall survival. In conclusion, our findings suggest that loss of PEAK1 may play an important role in carcinogenesis and development of gastric cancer through activating epithelial to mesenchymal transition.