Germline E-cadherin mutations in hereditary diffuse gastric cancer: assessment of 42 new families and review of genetic screening criteria

Germline mutations of the E-cadherin gene in families with inherited invasive lobular breast carcinoma but no diffuse gastric cancer

BACKGROUND

Present data are highly suggestive but do not unequivocally prove the cosegregation of germ-line CDH1 mutations with inherited invasive lobular breast cancer (ILBC).

METHODS

Two Caucasian families with 6 pathologically confirmed ILBC cases but no diffuse gastric cancer (DGC) were identified in our oncogenetics consultations. Screening for mutations of CDH1, BRCA1, and BRCA2 genes was performed on blood samples. When available, loss of heterozygosity (LOH) and immunohistochemistry (IHC) analyses were performed on tumor samples.

RESULTS

No BRCA1 or BRCA2 mutation was found. Deleterious CDH1 germ-line mutations c.283C>T and c.1582del were found in all the 4 living women with ILBC in family 1 and family 2, respectively. The mutation c.283C>T was also present in a healthy 71-year-old male and 2 obligate carriers in family 1. No DGC was observed in the 2 families. Loss of the wild-type CDH1 allele in 1 of the breast tumors was confirmed by LOH and IHC studies, in accordance with the "2-hit" model of tumor suppressor genes.

CONCLUSIONS

Germline CDH1 mutation can be cosegregated with ILBC in the absence of DGC. Present data do not support recommendation of prophylactic gastrectomy in CDH1 germline mutation carriers with ILBC. Cancer 2011. © 2011 American Cancer Society.

Germline mutations in cancer susceptibility genes: an overview for nurses

OBJECTIVE

To provide an overview of hereditary cancer susceptibility genes and associated cancer risks.

DATA SOURCES

Peer reviewed published research studies and review articles.

CONCLUSIONS

Identifying deleterious mutations in cancer susceptibility genes allows for clarification of cancer risk in individual family members and risk-level appropriate screening, and risk management recommendations. Evolving knowledge of the role of germline mutations provides an unprecedented opportunity to reduce cancer incidence, morbidity, and morality.

IMPLICATIONS FOR NURSING PRACTICE

To provide individuals/families with accurate cancer risk management information and guidance, oncology nurses must be familiar with scientific discoveries related to cancer susceptibility genes.

Germline mutations in CDH1 are infrequent in women with early-onset or familial lobular breast cancers

BACKGROUND

Germline mutations in CDH1 are associated with hereditary diffuse gastric cancer; lobular breast cancer also occurs excessively in families with such condition.

METHOD

To determine if CDH1 is a susceptibility gene for lobular breast cancer in women without a family history of diffuse gastric cancer, germline DNA was analysed for the presence of CDH1 mutations in 318 women with lobular breast cancer who were diagnosed before the age of 45 years or had a family history of breast cancer and were not known, or known not, to be carriers of germline mutations in BRCA1 or BRCA2. Cases were ascertained through breast cancer registries and high-risk cancer genetic clinics (Breast Cancer Family Registry, the kConFab and a consortium of breast cancer genetics clinics in the United States and Spain). Additionally, Multiplex Ligation-dependent Probe Amplification was performed for 134 cases to detect large deletions.

RESULTS

No truncating mutations and no large deletions were detected. Six non-synonymous variants were found in seven families. Four (4/318 or 1.3%) are considered to be potentially pathogenic through in vitro and in silico analysis.

CONCLUSION

Potentially pathogenic germline CDH1 mutations in women with early-onset or familial lobular breast cancer are at most infrequent.

Gastric cancer: prevention, risk factors and treatment

Cancer starts with a change in one single cell. This change may be initiated by external agents and genetic factors. Cancer is a leading cause of death worldwide and accounts for 7.6 million deaths (around 13% of all deaths) in 2008. Lung, stomach, liver, colon and breast cancer cause the most cancer deaths each year. In this review, different aspects of gastric cancer; including clinical, pathological characteristic of gastric cancer, etiology, incidence, risk factors, prevention and treatment are studied.

SATB1 and colorectal cancer in Wnt/β-catenin signaling: Is there a functional link?

Colorectal cancer is the third most common malignant cancer worldwide and molecular mechanisms of cancer metastasis are poorly understood. Researches suggested that the canonical Wnt/β-catenin signaling pathway plays a critical role in development and cancer. β-catenin acts as a component of the Wnt signaling in addition to being an integral component of adherens junctions. The traditional notion that β-catenin dysregulation caused by inactivating mutation of APC cannot completely elucidate the role of β-catenin in invasion and metastasis. Recently, the important roles of SATB1in T-cell development and differentiation and in promotion of breast tumor growth and metastasis were reported. The hypothesis we proposed is that SATB1 may be involved in the development and progression of colorectal cancer in a Wnt/β-catenin signaling-dependent manner.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Biomarkers and molecular diagnosis of gastrointestinal and pancreatic neoplasms

Standard protocols for the diagnosis of neoplasms in the gastrointestinal tract are based on histopathologic analysis in combination with clinical information. With the completion of the Human Genome Project in 2003, our understanding of the contribution of genetics to human disease has increased exponentially. This knowledge is gradually being incorporated into clinical decision-making. However, the rate at which molecular biomarkers are validated for use in mainstream clinical applications has lagged far behind that of biomarker discovery. Nevertheless, a number of molecular biomarkers are available for use in the diagnosis and management of gastrointestinal tract neoplasms. This article reviews the most common molecular biomarkers currently available for neoplasms of the luminal gastrointestinal tract and pancreas. In neoplasms of the esophagus, for which no biomarkers are currently used in routine clinical practice, those that have shown the most promise in early clinical validation studies are discussed.

Hereditary diffuse gastric cancer: updated consensus guidelines for clinical management and directions for future research

25–30% of families fulfilling the criteria for hereditary diffuse gastric cancer have germline mutations of the CDH1 (E-cadherin) gene. In light of new data and advancement of technologies, a multidisciplinary workshop was convened to discuss genetic testing, surgery, endoscopy and pathology reporting. The updated recommendations include broadening of CDH1 testing criteria such that: histological confirmation of diffuse gastric criteria is only required for one family member; inclusion of individuals with diffuse gastric cancer before the age of 40 years without a family history; and inclusion of individuals and families with diagnoses of both diffuse gastric cancer (including one before the age of 50 years) and lobular breast cancer. Testing is considered appropriate from the age of consent following counselling and discussion with a multidisciplinary team. In addition to direct sequencing, large genomic rearrangements should be sought. Annual mammography and breast MRI from the age of 35 years is recommended for women due to the increased risk for lobular breast cancer. In mutation positive individuals prophylactic total gastrectomy at a centre of excellence should be strongly considered. Protocolised endoscopic surveillance in centres with endoscopists and pathologists experienced with these patients is recommended for: those opting not to have gastrectomy, those with mutations of undetermined significance, and in those families for whom no germline mutation is yet identified. The systematic histological study of prophylactic gastrectomies almost universally shows pre-invasive lesions including in situ signet ring carcinoma with pagetoid spread of signet ring cells. Expert histopathological confirmation of these early lesions is recommended.

Gastric cancer, Helicobacter pylori infection and other risk factors

Gastric cancer incidence is declining. However, it is too early to consider this neoplastic disease as rare and the worldwide mortality rate still remains high. Several risk factors have been identified for non-cardia gastric cancer and primary prevention is feasible since most of the risk factors can be removed. Helicobacter pylori eradication treatment reduces but does not abolish gastric cancer risk. Indeed, gastric cancer is a multifactorial disease and removing one factor does not therefore prevent all cases. Endoscopic surveillance is still needed, especially in subjects at higher risk. The definition of high-risk patients will be the future challenge as well as identifying the best surveillance strategy for such patients.

Helicobacter pylori infection and gastric histology in first-degree relatives of gastric cancer patients: a meta-analysis

OBJECTIVES

Helicobacter pylori (H. pylori) is believed to predispose to gastric cancer by inducing the precancerous changes, that is, atrophy and intestinal metaplasia (IM). First-degree relatives of patients with gastric cancer might be at an increased risk of developing gastric cancer. However, this evidence is based on the scattered individual studies. The aim of this study was to examine the risk of first-degree relatives developing gastric cancer, in comparison with controls that have no family history of gastric cancer, by meta-analyzing all relevant studies.

METHODS

Extensive English language medical literature searches for human studies were performed up to the end of November 2009, using suitable keywords. Inclusion and exclusion criteria were identified and in eligible studies data on three parameters, that is, H. pylori prevalence, atrophy and IM, were extracted. Pooled estimates (odds ratio with 95% confidence intervals) were obtained using either the fixed or random-effects model as appropriate. Heterogeneity between studies was evaluated with the Cochran Q test, whereas the likelihood of publication bias was assessed by constructing funnel plots. Their symmetry was estimated by the Egger's regression asymmetry test.

RESULTS

Out of 155 initially identified studies, 11 studies, from various countries, fulfilling the inclusion criteria, examined the risk of first-degree relatives developing gastric cancer (n=1500) in comparison with controls (n=2638). For H. pylori prevalence, the pooled odds ratio with 95% confidence interval was 1.925 (1.419-2.611) and the test for overall effect Z was 4.211 (P=0.000). The respective values for atrophy and IM were 2.200 (1.266-3.824), Z=2.797, (P=0.005) and 1.982 (1.363-2.881), Z=3.582 (P=0.000) respectively.

CONCLUSION

The results of this meta-analysis showed that first-degree relatives of patients with gastric cancer might be at an increased risk of developing gastric cancer, as judged by significantly higher prevalence of H. pylori, gastric atrophy and IM, in comparison with controls. Consequently, H. pylori detection and prophylactic eradication of the infection should be offered to such individuals. However, follow-up studies are required to prove the above.

Computational identification and structural analysis of deleterious functional SNPs in MLL gene causing acute leukemia

A promising application of the huge amounts of data from the Human Genome Project currently available offers new opportunities for identifying the genetic predisposition and developing a better understanding of complex diseases such as cancers. The main focus of cancer genetics is the study of mutations that are causally implicated in tumorigenesis. The identification of such causal mutations does not only provide insight into cancer biology but also presents anticancer therapeutic targets and diagnostic markers. In this study, we evaluated the Single Nucleotide Polymorphisms (SNPs) that can alter the expression and the function in MLL gene through computational methods. We applied an evolutionary perspective to screen the SNPs using a sequence homologybased SIFT tool, suggested that 10 non-synonymous SNPs (nsSNPs) (50%) were found to be deleterious. Structure based approach PolyPhen server suggested that 5 nsSNPS (25%) may disrupt protein function and structure. PupaSuite tool predicted the phenotypic effect of SNPs on the structure and function of the affected protein. Structure analysis was carried out with the major mutations that occurred in the native protein coded by MLL gene is at amino acid positions Q1198P and K1203Q. The solvent accessibility results showed that 7 residues changed from exposed state in the native type protein to buried state in Q1198P mutant protein and remained unchanged in the case of K1203Q. From the overall results obtained, nsSNP with id (rs1784246) at the amino acid position Q1198P could be considered as deleterious mutation in the acute leukemia caused by MLL gene.

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.

Hedgehog signaling and gastrointestinal cancer

Hedgehog (Hh) signaling is critical for embryonic development and in differentiation, proliferation, and maintenance of multiple adult tissues. De-regulation of the Hh pathway is associated with birth defects and cancer. In the gastrointestinal tract, Hh ligands Sonic (Shh) and Indian (Ihh), as well as the receptor Patched (Ptch1), and transcription factors of Glioblastoma family (Gli) are all expressed during development. In the adult, Shh expression is restricted to the stomach and colon, while Ihh expression occurs throughout the luminal gastrointestinal tract, its expression being highest in the proximal duodenum. Several studies have demonstrated a requirement for Hh signaling during gastrointestinal tract development. However to date, the specific role of the Hh pathway in the adult stomach and intestine is not completely understood. The current review will place into context the implications of recent published data related to the biochemistry and cell biology of Hh signaling on the luminal gastrointestinal tract during development, normal physiology and subsequently carcinogenesis.

Genetic variation in carboxylesterase genes and susceptibility to isoniazid-induced hepatotoxicity

Treatment of latent tuberculosis infection (LTBI) generally includes isoniazid (INH), a drug that can cause serious hepatotoxicity. Carboxylesterases (CES) are important in the metabolism of a variety of substrates, including xenobiotics. We hypothesized that genetic variation in CES genes expressed in the liver could affect INH-induced hepatotoxicity. Three CES genes are known to be expressed in human liver: CES1, CES2 and CES4. Our aim was to systematically characterize genetic variation in these novel candidate genes and test whether it is associated with this adverse drug reaction. As part of a pilot study, 170 subjects with LTBI who received only INH were recruited, including 23 cases with hepatotoxicity and 147 controls. All exons and the promoters of CES1, CES2 and CES4 were bidirectionally sequenced. A large polymorphic deletion was found to encompass exons 2 to 6 of CES4. No significant association was found. Eleven single-nucleotide polymorphisms (SNPs) in CES1 were in high linkage disequilibrium with each other. One of these SNPs, C(-2)G, alters the translation initiation sequence of CES1 and represents a candidate functional polymorphism. Replication of this possible association in a larger sample set and functional studies will be necessary to determine if this CES1 variant has a role in INH-induced hepatotoxicity.

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

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

Germline mutation of the E-cadherin gene in three sibling cases with advanced gastric cancer: clinical consequences for the other family members

BACKGROUND AND AIMS

Germline mutations in the E-cadherin (CDH1) gene have been found in families with hereditary diffuse gastric cancer (HDGC). These families are characterized by a highly penetrant susceptibility to diffuse gastric cancer with an autosomal dominant pattern of inheritance. We describe the clinical presentation of three sibling cases with advanced gastric cancer, the way of confirming the suspicion of underlying HDGC and the clinical management of the other healthy family members.

METHODS

Screening for CDH1 germline mutation was carried out by denaturing high-performance liquid chromatography and automated DNA sequencing. The clinical suspicion of HDGC has been confirmed by identifying a frameshift mutation in exon 9 (1302_1303insA, 1306_1307delTT) of the E-cadherin gene.

RESULTS

Eight of nine tested family members were positive for the CDH1 germline mutation. Prophylactic laparoscopic gastrectomies were performed in five mutation carriers. After pathological examination, we could identify intramucosal malignant signet-ring cell carcinoma in all resected stomachs.

CONCLUSION

This report underlines that prophylactic gastrectomy remains the only option to eliminate the high risk for gastric cancer in CDH1 mutation carriers.

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 diffuse gastric cancer

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

Involvement of members of the cadherin superfamily in cancer

We review the role of cadherins and cadherin-related proteins in human cancer. Cellular and animal models for human cancer are also dealt with whenever appropriate. E-cadherin is the prototype of the large cadherin superfamily and is renowned for its potent malignancy suppressing activity. Different mechanisms for inactivating E-cadherin/CDH1 have been identified in human cancers: inherited and somatic mutations, aberrant protein processing, increased promoter methylation, and induction of transcriptional repressors such as Snail and ZEB family members. The latter induce epithelial mesenchymal transition, which is also associated with induction of "mesenchymal" cadherins, a hallmark of tumor progression. VE-cadherin/CDH5 plays a role in tumor-associated angiogenesis. The atypical T-cadherin/CDH13 is often silenced in cancer cells but up-regulated in tumor vasculature. The review also covers the status of protocadherins and several other cadherin-related molecules in human cancer. Perspectives for emerging cadherin-related anticancer therapies are given.

Genetic variations of NAT2 and CYP2E1 and isoniazid hepatotoxicity in a diverse population

AIMS

TB is a serious global public health problem. Isoniazid, a key drug used to treat latent TB, can cause hepatotoxicity in some patients. This pilot study investigated the effects of genetic variation in NAT2 and CYP2E1 on isoniazid-induced hepatotoxicity in TB contacts in British Columbia, Canada.

MATERIALS & METHODS

DNA re-sequencing was used to establish the spectrum of genetic variation in the exons, promoter and conserved regions of NAT2 in all subjects. For CYP2E1, the CYP2E1*1C polymorphism was genotyped by PCR-RFLP. Association tests of NAT2 variants and haplotypes, as well acetylator types were performed.

RESULTS

We enrolled 170 subjects on isoniazid treatment (23 cases and 147 controls). Systematic re-sequencing of NAT2 revealed 18 known and 10 novel variants.

CONCLUSION

No single genetic variant of NAT2 and CYP2E1 showed a significant association with isoniazid-induced hepatotoxicity in this highly heterogeneous population. There was evidence of a trend for increasing hepatotoxicity risk across the rapid, intermediate and slow acetylator groups (p = 0.08).

Genetic variation in the NBS1, MRE11, RAD50 and BLM genes and susceptibility to non-Hodgkin lymphoma

BACKGROUND

Translocations are hallmarks of non-Hodgkin lymphoma (NHL) genomes. Because lymphoid cell development processes require the creation and repair of double stranded breaks, it is not surprising that disruption of this type of DNA repair can cause cancer. The members of the MRE11-RAD50-NBS1 (MRN) complex and BLM have central roles in maintenance of DNA integrity. Severe mutations in any of these genes cause genetic disorders, some of which are characterized by increased risk of lymphoma.

METHODS

We surveyed the genetic variation in these genes in constitutional DNA of NHL patients by means of gene re-sequencing, then conducted genetic association tests for susceptibility to NHL in a population-based collection of 797 NHL cases and 793 controls.

RESULTS

114 SNPs were discovered in our sequenced samples, 61% of which were novel and not previously reported in dbSNP. Although four variants, two in RAD50 and two in NBS1, showed association results suggestive of an effect on NHL, they were not significant after correction for multiple tests.

CONCLUSION

These results suggest an influence of RAD50 and NBS1 on susceptibility to diffuse large B-cell lymphoma and marginal zone lymphoma. Larger association and functional studies could confirm such a role.

Preemptive surgery for premalignant foregut lesions

INTRODUCTION

Preemptive surgery is the prophylactic removal of an organ at high risk for malignant transformation or the resection of a precancerous or "early" malignant neoplasm in an individual with a hereditary predisposition to cancer. Recent advances in molecular diagnostic techniques have improved our understanding of the biologic behavior of these conditions. Predictive testing is an emerging field that attempts to assess the potential risk of cancer development in predisposed individuals. Despite substantial improvement in these forms of testing, all results are imperfect. This information often becomes an important tool that is used by healthcare providers to evaluate the risk-benefit ratio of various risk modifying strategies (i.e., intensive surveillance or preemptive surgery).

METHODS

A systematic literature review was performed using Medline and the bibliographies of all referenced publications to identify articles relating to preemptive surgery for premalignant foregut lesions.

RESULTS AND DISCUSSION

In this review, we outline the controversies surrounding predictive risk assessment, surveillance strategies, and preemptive surgery in the management of high-grade dysplasia (HGD) in Barrett's esophagus (BE), hereditary diffuse gastric cancer (HDGC), bile duct cysts, primary sclerosing cholangitis (PSC), and pancreatic cystic neoplasms. Resection of BE is supported by the progressive nature of the disease, the risk of occult carcinoma, and the lethality of esophageal cancer. Prophylactic total gastrectomy for HDGC appears reasonable in the absence of accurate screening tests but must be balanced by the impact of surgical complications and altered quality of life. Surgical resection of biliary cysts theoretically eliminates the exposed epithelium to decrease the lifetime risk of cholangiocarcinoma. Liver transplantation for PSC remains controversial given the scarcity of donor organs and inability to accurately identify high-risk individuals. Given the uncertain natural history of pancreatic cystic neoplasms, the merits of selective versus obligatory resection will continue to be debated.

CONCLUSIONS

Preemptive operations require optimal judgment and surgical precision to maximize function and enhance survival. Ultimately, balancing the risk of surgical intervention with less invasive interventions or observation must be individualized on a case-by-case basis.

Genetic variation in healthy oldest-old

Individuals who live to 85 and beyond without developing major age-related diseases may achieve this, in part, by lacking disease susceptibility factors, or by possessing resistance factors that enhance their ability to avoid disease and prolong lifespan. Healthy aging is a complex phenotype likely to be affected by both genetic and environmental factors. We sequenced 24 candidate healthy aging genes in DNA samples from 47 healthy individuals aged eighty-five years or older (the 'oldest-old'), to characterize genetic variation that is present in this exceptional group. These healthy seniors were never diagnosed with cancer, cardiovascular disease, pulmonary disease, diabetes, or Alzheimer disease. We re-sequenced all exons, intron-exon boundaries and selected conserved non-coding sequences of candidate genes involved in aging-related processes, including dietary restriction (PPARG, PPARGC1A, SIRT1, SIRT3, UCP2, UCP3), metabolism (IGF1R, APOB, SCD), autophagy (BECN1, FRAP1), stem cell activation (NOTCH1, DLL1), tumor suppression (TP53, CDKN2A, ING1), DNA methylation (TRDMT1, DNMT3A, DNMT3B) Progeria syndromes (LMNA, ZMPSTE24, KL) and stress response (CRYAB, HSPB2). We detected 935 variants, including 848 single nucleotide polymorphisms (SNPs) and 87 insertion or deletions; 41% (385) were not recorded in dbSNP. This study is the first to present a comprehensive analysis of genetic variation in aging-related candidate genes in healthy oldest-old. These variants and especially our novel polymorphisms are valuable resources to test for genetic association in models of disease susceptibility or resistance. In addition, we propose an innovative tagSNP selection strategy that combines variants identified through gene re-sequencing- and HapMap-derived SNPs.

Absence of germline mono-allelic promoter hypermethylation of the CDH1 gene in gastric cancer patients

BACKGROUND

Germline mono-allelic promoter hypermethylation of the MLH1 or MSH2 gene in families with hereditary nonpolyposis colorectal cancer has recently been reported. The purpose of this study was to evaluate if germline promoter hypermethylation of the tumor suppressor gene CDH1 (E-cadherin) might cause predisposition to gastric cancer.

METHODS

We prepared two groups of samples, a group of blood samples from 22 patients with familial gastric cancer or early-onset gastric cancer selected from among 39 patients, and a group of non-cancerous gastric tissue samples from 18 patients with sporadic gastric cancer showing loss of CDH1 expression selected from among 159 patients. We then investigated the allele-specific methylation status of the CDH1 promoter by bisulfite sequencing of multiple clones.

RESULTS

Although there was a difference between the methylation level of the two alleles in some samples, there was no mono-allelic promoter hypermethylation in any of the samples.

CONCLUSION

These results suggest that germline mono-allelic hypermethylation of the CDH1 promoter is not a major predisposing factor for gastric cancer.

Gastric cancer

Gastric cancer is the second most frequent cause of cancer death worldwide, although much geographical variation in incidence exists. Prevention and personalised treatment are regarded as the best options to reduce gastric cancer mortality rates. Prevention strategies should be based on specific risk profiles, including Helicobacter pylori genotype, host gene polymorphisms, presence of precursor lesions, and environmental factors. Although adequate surgery remains the cornerstone of gastric cancer treatment, this single modality treatment seems to have reached its maximum achievable effect for local control and survival. Minimally invasive techniques can be used for treatment of early gastric cancers. Achievement of locoregional control for advanced disease remains very difficult. Extended resections that are standard practice in some Asian countries have not been shown to be as effective in other developed countries. We present an update of the incidence, causes, pathology, and treatment of gastric cancer, consisting of surgery, new strategies with neoadjuvant and adjuvant chemotherapy or radiotherapy, or both, novel treatment strategies using gene signatures, and the effect of caseload on patient outcomes.

Gastric cancer

Gastric cancer is the second most frequent cause of cancer death worldwide, although much geographical variation in incidence exists. Prevention and personalised treatment are regarded as the best options to reduce gastric cancer mortality rates. Prevention strategies should be based on specific risk profiles, including Helicobacter pylori genotype, host gene polymorphisms, presence of precursor lesions, and environmental factors. Although adequate surgery remains the cornerstone of gastric cancer treatment, this single modality treatment seems to have reached its maximum achievable effect for local control and survival. Minimally invasive techniques can be used for treatment of early gastric cancers. Achievement of locoregional control for advanced disease remains very difficult. Extended resections that are standard practice in some Asian countries have not been shown to be as effective in other developed countries. We present an update of the incidence, causes, pathology, and treatment of gastric cancer, consisting of surgery, new strategies with neoadjuvant and adjuvant chemotherapy or radiotherapy, or both, novel treatment strategies using gene signatures, and the effect of caseload on patient outcomes.

Quantification of epigenetic and genetic 2nd hits in CDH1 during hereditary diffuse gastric cancer syndrome progression

BACKGROUND & AIMS

Hereditary diffuse gastric cancer (HDGC) families carry CDH1 heterozygous germline mutations; their tumors acquire complete CDH1 inactivation through "2nd-hit" mechanisms. Most frequently, this occurs via promoter hypermethylation (epigenetic modification), and less frequently via CDH1 mutations and loss of heterozygosity (LOH). We quantified the different 2nd hits in CDH1 occurring in neoplastic lesions from HDGC patients.

METHODS

Samples were collected from 16 primary tumors and 12 metastases from 17 patients among 15 HDGC families; CDH1 mutations, LOH, and promoter hypermethylation were analyzed. E-cadherin protein expression and localization were determined by immunohistochemistry.

RESULTS

Somatic CDH1 epigenetic and genetic alterations were detected in lesions from 80% of HDGC families and in 75% of all lesions analyzed (21/28). Of the 28 neoplastic lesions analyzed, promoter hypermethylation was found in 32.1%, LOH in 25%, both alterations in 17.9%, and no alterations in 25%. Half of the CDH1 2nd hits in primary tumors were epigenetic modifications, whereas a significantly greater percentage of 2nd hits in metastases were LOH (58.3%; P = .0274). Different neoplastic lesions from the same patient frequently displayed distinct 2nd-hit mechanisms. Different 2nd-hit mechanisms were also detected in the same tumor sample.

CONCLUSION

The 2nd hit in CDH1 frequently occurs via epigenetic changes in HDGC primary tumors and LOH in metastases. Because of the concomitance and heterogeneity of these alterations in neoplastic lesions and the plasticity of hypermethylated promoters during tumor initiation and progression, drugs targeting only epigenetic alterations might not be effective, particularly in patients with metastatic HDGC.

Prophylactic total gastrectomy (PTG) for hereditary diffuse gastric cancer (HDGC): the Newfoundland experience with 23 patients

BACKGROUND

Hereditary diffuse gastric cancer (HDGC) results from truncating mutations of the CDH1 (E-cadherin) gene. It is an autosomal dominant cancer susceptibility syndrome with a lifetime risk of diffuse gastric cancer (DGC) of 60-80%, with a mean age of onset of 37 years. There exists no adequate screening test for DGC. Early intramucosal diffuse/signet-ring cell carcinomas have been found in prophylactic total gastrectomy (PTG) specimens following normal preoperative endoscopy. Total gastrectomy has been advocated on a prophylactic basis. The aim of this study was to report our experience with PTG in 23 patients from the Canadian province of Newfoundland and Labrador. This is the largest series worldwide.

METHODS

A retrospective study of consecutive patients undergoing PTG for HDGC was performed. All patients were confirmed to have a truncating mutation of the CDH1 gene.

RESULTS

Twenty-three patients underwent PTG between February 2006 and November 2008. Major complications were found in 4/23 patients (17%), with no mortality. Two of 23 patients (9%) had positive mucosal biopsies on preoperative EGD. Twenty-two of 23 patients (96%) had evidence of diffuse/signet-ring carcinoma on final standardized pathological evaluation. Therefore, 21/23 (91%) were not picked up by preoperative EGD screening.

CONCLUSIONS

PTG can be performed in patients with HDGC with a low rate of serious complications. Methods of reconstruction incorporating a pouch reservoir and preservation of the postgastric branches of the vagus nerves need to be explored. More refined penetrance estimates, effective screening protocols, and long-term psychological and functional outcomes following PTG require organized multicenter collaborative efforts.

Investigation on the role of nsSNPs in HNPCC genes--a bioinformatics approach

BACKGROUND

A central focus of cancer genetics is the study of mutations that are causally implicated in tumorigenesis. The identification of such causal mutations not only provides insight into cancer biology but also presents anticancer therapeutic targets and diagnostic markers. Missense mutations are nucleotide substitutions that change an amino acid in a protein, the deleterious effects of these mutations are commonly attributed to their impact on primary amino acid sequence and protein structure.

METHODS

The method to identify functional SNPs from a pool, containing both functional and neutral SNPs is challenging by experimental protocols. To explore possible relationships between genetic mutation and phenotypic variation, we employed different bioinformatics algorithms like Sorting Intolerant from Tolerant (SIFT), Polymorphism Phenotyping (PolyPhen), and PupaSuite to predict the impact of these amino acid substitutions on protein activity of mismatch repair (MMR) genes causing hereditary nonpolyposis colorectal cancer (HNPCC).

RESULTS

SIFT classified 22 of 125 variants (18%) as 'Intolerant." PolyPhen classified 40 of 125 amino acid substitutions (32%) as "Probably or possibly damaging". The PupaSuite predicted the phenotypic effect of SNPs on the structure and function of the affected protein. Based on the PolyPhen scores and availability of three-dimensional structures, structure analysis was carried out with the major mutations that occurred in the native protein coded by MSH2 and MSH6 genes. The amino acid residues in the native and mutant model protein were further analyzed for solvent accessibility and secondary structure to check the stability of the proteins.

CONCLUSION

Based on this approach, we have shown that four nsSNPs, which were predicted to have functional consequences (MSH2-Y43C, MSH6-Y538S, MSH6-S580L, and MSH6-K854M), were already found to be associated with cancer risk. Our study demonstrates the presence of other deleterious mutations and also endorses with in vivo experimental studies.

Diffuse large B-cell lymphoma: reduced CD20 expression is associated with an inferior survival

CD19 and CD20 are B cell-specific antigens whose expression is heterogeneous when analyzed by flow cytometry (FCM). We determined the association between CD20 expression and clinical outcome in patients with diffuse large B-cell lymphoma (DLBCL). The mean fluorescence intensity of CD20 and CD19 was determined by FCM, and the cytoplasmic expression of CD20 was determined by immunohistochemistry (IHC) on 272 diagnostic DLBCL samples. Exon 5 of the MS4A1 gene coding for the extracellular component of the CD20 antigen was sequenced in 15 samples. A total of 43 of 272 (16%) samples had reduced CD20 expression by FCM; of these, 35 (13%) had bright CD19 expression. The latter had a markedly inferior survival when treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or rituximab-CHOP (R-CHOP; median survival of 1.2 and 3.0 years vs not reached for the others, P < .001 and P = .001), independent of the International Prognostic Index. A total of 41 of 43 samples with reduced CD20 expression by FCM had strong staining for CD20 by IHC. There were no mutations in exon 5 of the MS4A1 gene to explain the discrepancy between FCM and IHC. CD20 and CD19 expression by FCM should be determined on all biopsies of patients with DLBCL because reduced CD20 expression cannot be reliably detected by IHC.

Nuclear accumulation of e-cadherin correlates with loss of cytoplasmic membrane staining and invasion in pituitary adenomas

CONTEXT

Loss of the cell adhesion protein E-cadherin is associated with invasion and metastasis in a number of malignancies. Recent studies have highlighted that loss of E-cadherin cell membrane expression may be accompanied by its detection in the nucleus, suggesting cellular redistribution during neoplasia. Pituitary tumors, although typically benign, may be locally invasive, and loss of membranous E-cadherin has been reported as a marker of invasion in prolactinomas.

OBJECTIVE

Our objective was to study E-cadherin expression in pituitary adenomas, specifically whether nuclear redistribution occurs in this setting.

METHODS

Immunohistochemistry, RT-PCR, and direct sequencing were performed.

RESULTS

Strong cytoplasmic membrane staining was present in all eight normal samples but completely absent in 21 of 44 adenomas (48%) with weak staining in an additional 11 adenomas using an antibody against the extracellular domain of E-cadherin. To identify nuclear translocation of the protein, immunohistochemistry was performed using an antibody against the cytoplasmic domain. Nuclear staining was present in 38 of 44 adenomas (86%) and absent in normal tissue. Nuclear E-cadherin inversely correlated with loss of E-cadherin cytoplasmic membrane staining and was associated with tumor invasion (P = 0.009). To investigate the mechanism of nuclear redistribution of E-cadherin, we performed RT-PCR of mRNA and sequenced tumor DNA. E-cadherin mRNA expression was reduced in only one of 30 samples (3%). No mutations were detected.

CONCLUSIONS

E-cadherin was frequently lost at the cytoplasmic membrane but detected in the nucleus, suggesting that cleavage of the extracellular domain and nuclear translocation of E-cadherin is a common event that may determine local invasion in pituitary adenomas.

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.

CD20 mutations involving the rituximab epitope are rare in diffuse large B-cell lymphomas and are not a significant cause of R-CHOP failure

Rituximab binds an epitope on the CD20 antigen, encompassed in exon 5 of the MS4A1 gene. We sequenced this region and correlated the presence of mutations with CD20 protein expression and response to R-CHOP in patients with diffuse large B-cell lymphoma: 264 diagnostic biopsies and 15 biopsies taken at the time of relapse were successfully sequenced. CD20 mutations involving the rituximab epitope were detected in only 1/264 (0.4%) and 1/15 (6%) of the biopsies taken at diagnosis and relapse, respectively. No polymorphic sequence variants were detected in this region. Three patients had malignant cells that were CD20 protein-positive at diagnosis but CD20-negative at relapse. Thus, CD20 mutations involving the rituximab epitope are rare in both de novo and relapsed diffuse large B-cell lymphoma, and do not represent a significant cause of R-CHOP resistance. CD20 protein-negative relapses occur after R-CHOP therapy but their clinical relevance is unknown.

Germline CDH1 deletions in hereditary diffuse gastric cancer families

Germline CDH1 point or small frameshift mutations can be identified in 30-50% of hereditary diffuse gastric cancer (HDGC) families. We hypothesized that CDH1 genomic rearrangements would be found in HDGC and identified 160 families with either two gastric cancers in first-degree relatives and with at least one diffuse gastric cancer (DGC) diagnosed before age 50, or three or more DGC in close relatives diagnosed at any age. Sixty-seven carried germline CDH1 point or small frameshift mutations. We screened germline DNA from the 93 mutation negative probands for large genomic rearrangements by Multiplex Ligation-Dependent Probe Amplification. Potential deletions were validated by RT-PCR and breakpoints cloned using a combination of oligo-CGH-arrays and long-range-PCR. In-silico analysis of the CDH1 locus was used to determine a potential mechanism for these rearrangements. Six of 93 (6.5%) previously described mutation negative HDGC probands, from low GC incidence populations (UK and North America), carried genomic deletions (UK and North America). Two families carried an identical deletion spanning 193 593 bp, encompassing the full CDH3 sequence and CDH1 exons 1 and 2. Other deletions affecting exons 1, 2, 15 and/or 16 were identified. The statistically significant over-representation of Alus around breakpoints indicates it as a likely mechanism for these deletions. When all mutations and deletions are considered, the overall frequency of CDH1 alterations in HDGC is approximately 46% (73/160). CDH1 large deletions occur in 4% of HDGC families by mechanisms involving mainly non-allelic homologous recombination in Alu repeat sequences. As the finding of pathogenic CDH1 mutations is useful for management of HDGC families, screening for deletions should be offered to at-risk families.

Impact of single nucleotide polymorphisms in HBB gene causing haemoglobinopathies: in silico analysis

Single nucleotide polymorphisms (SNPs) are being intensively studied to understand the biological basis of complex traits and diseases. Deleterious mutations of the human beta-globin gene (HBB) are responsible for beta-thalassaemia and other haemoglobinopathies, which are the most common genetic diseases of blood. Single amino acid substitutions in the globin chain are the commonest forms of haemoglobinopathy. Although many haemoglobinopathies present similar structural abnormal points, their functions sometimes are different. Here, using computational methods, we analysed the genetic variations that can alter the expression and function of the HBB gene. We applied an evolutionary perspective to screen the SNPs using a sequence homology-based SIFT tool, which suggested that 210 (90%) non-synonymous (ns)SNPs were found to be deleterious. The structure-based approach PolyPhen server suggested that 134 (57%) nsSNPS may disrupt protein function and structure. The PupaSuite tool predicted the phenotypic effect of SNPs on the structure and function of the affected protein. Structure analysis was carried out with the major mutation that occurred in the native protein coded by the HBB gene in HbC, HbD, HbE and HbS. The amino acid residues in the native and mutant modelled protein were further analysed for solvent accessibility, and secondary structure to check the stability of the proteins. The functional analysis presented here may be a good model for further research.

Mechanisms and sequelae of E-cadherin silencing in hereditary diffuse gastric cancer

Around 25-40% of cases of hereditary diffuse gastric cancer (HDGC) are caused by heterozygous E-cadherin (CDH1) germline mutations. The mechanisms for loss of the second allele still remain unclear. The aims of this study were to elucidate mechanisms for somatic inactivation of the wild-type CDH1 allele and to seek evidence for cadherin switching. Archival tumour material was analysed from 16 patients with CDH1 germline mutations and seven patients fulfilling HDGC criteria without CDH1 germline mutations. The 16 CDH1 exons were sequenced. E-cadherin promoter methylation was analysed by bisulphite sequencing and pyrosequencing and allele specificity was determined using polymorphic loci. Loss of heterozygosity was analysed using microsatellite markers. Cadherin expression levels were determined by real-time RT-PCR and immunohistochemistry. Six of 16 individuals with germline mutations had at least one second hit mechanism. Two exonic mutations (exon 9 truncating, exon 3 missense) and four intronic mutations which may affect splicing were identified. Tumours from 4/16 individuals had promoter hypermethylation that was restricted to the A allele haplotype in three cases. E-cadherin loss (mRNA and protein) generally correlated with identification of a second hit. In cases without germline E-cadherin mutations there was no evidence for somatic mutation or significant promoter methylation. P-cadherin (>25% cells) was expressed in 7/13 (54%) and 4/5 (80%) with and without germline CDH1 mutations, respectively, independent of complete E-cadherin loss. Overall, inactivation of the second CDH1 allele occurs by mutation and methylation events. Methylation is commonly allele-specific and is uncommon without germline mutations. P-cadherin over-expression commonly occurs in individuals with diffuse type gastric cancer.

Histopathological and molecular analysis of gastrectomy specimens from hereditary diffuse gastric cancer patients has implications for endoscopic surveillance of individuals at risk

Hereditary diffuse gastric cancer (HDGC) is caused by germline E-cadherin (CDH1) mutations in 25-40% of tested families. Management options for asymptomatic mutation carriers are fraught, since endoscopic surveillance can miss cancer foci and prophylactic gastrectomy has profound clinical sequelae. The aims of this study were to evaluate the impact of current surveillance practices on pre-operative diagnosis and to characterize the microscopic lesions in gastrectomy specimens to better inform clinical practice. Histological assessment and mapping of endoscopic surveillance and gastrectomy specimens were performed for eight asymptomatic CDH1 mutation carriers. E-cadherin expression and proliferation were analysed and evidence of epithelial-mesenchymal transition (EMT) was sought by immunohistochemistry for vimentin and cytokeratin 8/18. Four of eight patients had lesions detected at endoscopic surveillance. A median of 20.5 (range 0-66) signet ring foci were identified per gastrectomy (including in situ lesions and pagetoid spread). Foci were predominantly identified in the fundus and body (90% endoscopic biopsies and 85% in gastrectomy). The likelihood of detecting foci pre-operatively was positively correlated with the number of biopsies taken and the number of lesions in the gastrectomy specimen. E-cadherin expression in gastrectomy specimens was reduced or absent in all of the foci compared with the intervening gastric tissue, suggesting that these lesions are polyclonal. The foci had a low proliferative index (<2%) and there was no evidence for EMT. Multiple endoscopic biopsy sampling of the gastric mucosa increases the yield of microscopic cancer foci. The low proliferative index and lack of EMT suggests that these foci may represent an indolent stage of HDGC.