Isabel Claro

Hereditary Diffuse Gastric Cancer Syndrome: CDH1 Mutations and Beyond

IMPORTANCE E-cadherin (CDH1) is a cancer predisposition gene mutated in families meeting clinically defined hereditary diffuse gastric cancer (HDGC). Reliable estimates of cancer risk and spectrum in germline mutation carriers are essential for management. For families without CDH1 mutations, genetic-based risk stratification has not been possible, resulting in limited clinical options. OBJECTIVES To derive accurate estimates of gastric and breast cancer risks in CDH1 mutation carriers and determine if germline mutations in other genes are associated with HDGC. DESIGN, SETTING, AND PARTICIPANTS Testing for CDH1 germline mutations was performed on 183 index cases meeting clinical criteria for HDGC. Penetrance was derived from 75 mutation-positive families from within this and other cohorts, comprising 3858 probands (353 with gastric cancer and 89 with breast cancer). Germline DNA from 144 HDGC probands lacking CDH1 mutations was screened using multiplexed targeted sequencing for 55 cancer-associated genes. MAIN OUTCOMES AND MEASURES Accurate estimates of gastric and breast cancer risks in CDH1 mutation carriers and the relative contribution of other cancer predisposition genes in familial gastric cancers. RESULTS Thirty-one distinct pathogenic CDH1 mutations (14 novel) were identified in 34 of 183 index cases (19%). By the age of 80 years, the cumulative incidence of gastric cancer was 70% (95% CI, 59%-80%) for males and 56% (95% CI, 44%-69%) for females, and the risk of breast cancer for females was 42% (95% CI, 23%-68%). In CDH1 mutation-negative index cases, candidate mutations were identified in 16 of 144 probands (11%), including mutations within genes of high and moderate penetrance: CTNNA1, BRCA2, STK11, SDHB, PRSS1, ATM, MSR1, and PALB2. CONCLUSIONS AND RELEVANCE This is the largest reported series of CDH1 mutation carriers, providing more precise estimates of age-associated risks of gastric and breast cancer that will improve counseling of unaffected carriers. In HDGC families lacking CDH1 mutations, testing of CTNNA1 and other tumor suppressor genes should be considered. Clinically defined HDGC families can harbor mutations in genes (ie, BRCA2) with different clinical ramifications from CDH1. Therefore, we propose that HDGC syndrome may be best defined by mutations in CDH1 and closely related genes, rather than through clinical criteria that capture families with heterogeneous susceptibility profiles.

Immunohistochemical detection of mismatch repair gene proteins as a useful tool for the identification of colorectal carcinoma with the mutator phenotype

There are two well‐defined pathways for colorectal carcinogenesis, the suppressor and the mutator pathways. The latter is characteristic of hereditary non‐polyposis colorectal cancer (HNPCC), but can also be found in a subset of sporadic colorectal cancer (SCC) possessing distinctive clinical and pathological features, namely early age of onset, location in the right colon, poor differentiation, and a predominant mucinous component. This mutator pathway results from inactivation of mismatch repair (MMR) genes, namely MSH2 and MLH1. The aim of this study was to ascertain if abnormal MMR protein gene expression is a good indicator for identifying tumours from the mutator pathway. Seventy‐six cases of SCC were studied by immunohistochemistry using two monoclonal mouse antibodies that react against MSH2 and MLH1 protein gene products. Immunoexpression was assessed both in tumour and in non‐neoplastic, adjacent and distant mucosa. Microsatellite instability (MSI) was detected by evaluating the length of poly(CA) repeated sequences at seven loci, or by the detection of small unstable alleles in a poly(A) repeat – BAT‐26. Except for BAT‐26, in which only tumour DNA was used, MSI analysis was performed in both tumour and normal mucosal DNA. MSI was classified as high (MSI‐H), low (MSI‐L) or stable (MSS). Abnormal protein expression was found in 9/76 (12%) tumours. Immunohistochemistry for hmlh1 and hmsh2 detected 75% of MSI‐H. There was also a highly significant correlation between the observed immunoexpression and several clinical and pathological characteristics described as the phenotypic profile of the mutator pathway, such as right‐sided location (p=0.003), mucin production (p=0.008), and a peritumoural lymphoid infiltrate (p=0.009). Non‐neoplastic adjacent mucosa showed normal hMSH2 expression in all cases, but in ten cases there was no hMLH1 expression in this transitional mucosa, which is known to display an alterated mucin pattern and a high proliferative rate. These results demonstrated a good correlation between hMLH1 and hMSH2 gene immunoexpression and the clinico‐pathological features characteristic of the mutator phenotype and support the use of this method as a rapid and efficient way to detect tumours arising from this pathway. Copyright

BAT-26 identifies sporadic colorectal cancers with mutator phenotype: a correlative study with clinico-pathological features and mutations in mismatch repair genes

Microsatellite instability (MSI) is present in most colorectal cancers (CRC) associated with hereditary nonpolyposis colorectal cancer (HNPCC). MSI testing in so‐called sporadic forms of CRC may become a useful tool in identifying new HNPCC kindred. The aim of this study was to analyse the utility of BAT‐26 as a marker to identify CRCs with MSI and to investigate whether sporadic CRCs with MSI have a phenotypic expression similar to HNPCC cases. MSI was detected using two methods, an association of 7 poly(CA) repeats and a poly(A) repeat alone, BAT‐26, in a series of 62 patients with apparently sporadic forms of CRC. Germ‐line and somatic mutations in the hMSH2, hMLH1, and hMSH6 genes were analysed in patients with MSI+ tumours. Patients with MSI+ at poly(CA) loci and at BAT‐26 were younger (p = 0·024 and p = 0·002), had tumours more frequently right sided (p = 0·017 and p = 0·0001) and more often mucinous (p = 0·037 and p = 0·005, respectively) than patients with MSI negative tumours. Mutation analysis allowed the identification of two patients carrying germ‐line mutations in the hMLH1 gene (both were BAT‐26+) and two other patients who had somatic mutation in the hMSH2 and in hMLH1 genes. In conclusion, the detection of MSI using poly(CA) repeats or BAT‐26 alone allowed the identification of a subset of patients with clinico‐pathological characteristics similar to those associated to HNPCC. BAT‐26 has the advantage of being a simple and less expensive method that might be used as a screening procedure before mutation analysis. Copyright

APC or MUTYH mutations account for the majority of clinically well-characterized families with FAP and AFAP phenotype and patients with more than 30 adenomas

Patients presenting familial adenomatous polyposis (FAP), attenuated familial adenomatous polyposis (AFAP) or multiple colorectal adenomas (MCRAs) phenotype are clinically difficult to distinguish. We aimed to genetically characterize 107 clinically well‐characterized patients with FAP‐like phenotype, and stratified according to the recent guidelines for the clinical management of FAP: FAP, AFAP, MCRA (10–99 colorectal adenomas) without family history of colorectal cancer or few adenomas (FH), MCRA (10–99) with FH, MCRA (3–9) with FH. Overall, APC or MUTYH mutations were detected in 42/48 (88%), 14/20 (70%) and 10/38 (26%) of FAP, AFAP and MCRA patients, respectively. APC and MUTYH mutations accounted for 81% and 7% of FAP patients and for 30% and 40% of AFAP patients, respectively. Notably, MCRA patients did not present APC mutations. In 26% of these patients, an MUTYH mutation was identified and the detection rate increased with the number of adenomas, irrespectively of family history, being significantly higher in MCRA patients presenting more than 30 adenomas [7/12 (58%) vs 2/14 (14%), p = 0.023]. We validate the recently proposed guidelines in our patients cohort and show that APC or MUTYH germline defects are responsible for the majority of clinically well‐characterized patients with FAP and AFAP phenotype, and patients with more than 30 colorectal adenomas. The different mutation frequencies according to family history and to the number of adenomas underscore the importance of an adequate familial characterization, both clinically and by colonoscopy, in the management of FAP‐like phenotypes. The phenotypes of the mutation‐negative patients suggest distinct etiologies in these cases.

Colorectal cancers show distinct mutation spectra in members of the canonical WNT signaling pathway according to their anatomical location and type of genetic instability.

It is unclear whether the mutation spectra in WNT genes vary among distinct types of colorectal tumors. We have analyzed mutations in specific WNT genes in a cohort of 52 colorectal tumors and performed a meta‐analysis of previous studies. Notably, significant differences were found among the mutation spectra. We have previously shown that in familial adenomatous polyposis, APC somatic mutations are selected to provide the “just‐right” level of WNT signaling for tumor formation. Here, we found that APC mutations encompassing at least two β‐catenin down‐regulating motifs (20 a.a. repeats) are significantly more frequent in microsatellite unstable (MSI‐H) than in microsatellite stable (MSS) tumors where truncations retaining less than two repeats are more frequent (P = 0.0009). Moreover, in cases where both APC hits are detected, selection for mutations retaining a cumulative number of two 20 a.a. repeats became apparent in MSI‐H tumors (P = 0.001). This type of mutations were also more frequent in proximal versus distal colonic tumors, regardless of MSI status (P = 0.0008). Among MSI‐H tumors, CTNNB1 mutations were significantly more frequent in HNPCC than in sporadic lesions (28% versus 6%, P < 10‐6) and were preferentially detected in the proximal colon, independently of MSI status (P = 0.017). In conclusion, the observed spectra of WNT gene mutations in colorectal tumors are likely the result from selection of specific levels of β‐catenin signaling, optimal for tumor formation in the context of specific anatomical locations and forms of genetic instability. We suggest that this may underlie the preferential location of MMR deficient tumors in the proximal colon.

Validation and simplification of Bethesda guidelines for identifying apparently sporadic forms of colorectal carcinoma with microsatellite instability.

Colorectal tumors with microsatellite instability (MSI) that do not comply with previously defined clinical criteria may be found in recently diagnosed hereditary nonpolyposis colorectal carcinoma families. Until recently, the indications for MSI testing were not clearly established. The objective of the current study was to validate the recently published Bethesda guidelines for MSI testing in a series of patients with apparently sporadic forms of colorectal carcinoma (CRC).

High Rate of Percutaneous Endoscopic Gastrostomy Site Infections Due to Oropharyngeal Colonization

We prospectively analyzed peristomal infection agents during the first week following percutaneous endoscopic gastrostomy (PEG) placement by the pull technique in patients with head and neck cancer. Nasal and pharyngeal swabs were obtained from a consecutive series of cancer patients prior to PEG placement. All patients underwent antibiotic prophylaxis with cefotaxime and oral disinfection. PEG site infection was prospectively evaluated at days 2, 3, and 7 after insertion. Twenty-eight patients (25 males; mean age, 58 years) were included. Oropharyngeal or nasal colonization were observed in 68% (19/28) and 19% (5/28) of patients, respectively. Early infections occurred in 36% (10/28) of the patients, all with oropharyngeal colonization and concordance between agents (P=0.01). Three patients required hospital admission and 1 required surgery. Head and neck cancer patients with oropharyngeal colonization have a high risk of early PEG site infection with substantial morbidity owing to oral–stomal spread.

Double-balloon enteroscopy in the management of patients with Peutz-Jeghers syndrome: A retrospective cohort multicenter study

BACKGROUND AND OBJECTIVE Little is known about the clinical impact of double-balloon enteroscopy (DBE) in patients with Peutz- Jeghers syndrome (PJS).The aim of this study was to assess the efficacy and safety of DBE in the management of small-bowel polyps in PJS patients. PATIENTS AND METHODS We conducted a multicentre, retrospective cohort study, which included all consecutive patients diagnosed with PJS who underwent DBE for polypectomy between January 2006 and August 2012. In all cases, previous videocapsule enteroscopy had shown at least one polyp ≥ 10 mm in size. RESULTS Twenty-five patients (13 men; median age 36 years; 14 with prior laparotomy) underwent 46 DBE procedures (1 to 5 per patient, 44 via oral route). Polypectomy was performed in 39/46 DBEs. A total of 214 polyps were removed (median-size 30 mm), with a median number of polypectomies per procedure of 5.0 (range 1-18). The estimated maximum-sizes of resected polyps significantly decreased at each session: 30.0, 25.0, 20.0, 15.0, and 17.5 mm (p = 0.02). In 7 DBEs no polypectomy was performed (4-only minor polyps detected; 3-endoscopic irresecability). Complications occurred in 3/39 of therapeutic procedures (2-minor delayed bleeding; 1-mucosal tear), all of them dealt with conservative or endoscopic therapy. Six patients underwent elective surgery post DBE due to polyps not amenable for endoscopic resection. There were no small-bowel polyp related complications during a median follow-up of 56.5 months. CONCLUSION DBE showed to be a safe and effective technique in the management of small-bowel polyps in PJS patients, allowing a presymptomatic and non-surgical approach.

Association of colonic and endometrial carcinomas in portuguese families with hereditary nonpolyposis colorectal carcinoma significantly increases the probability of detecting a pathogenic mutation in mismatch repair genes, primarily the MSH2 gene

Hereditary nonpolyposis colorectal carcinoma (HNPCC) significantly raises the risk of developing colorectal carcinoma (CRC) and other extracolonic tumors. It is defined by the Amsterdam Criteria and is associated with germline mutations in mismatch repair genes, primarily MLH1 and MSH2. The objectives of the current study were to evaluate the presence of CRC (Type I) and other extracolonic tumors (Type II) in families with HNPCC and to analyze the findings for correlations with germline mutations in the MLH1 and MSH2 genes.

A case of multiple gastrointestinal stromal tumors caused by a germline KIT gene mutation (p.Leu576Pro)

Multiple gastrointestinal stromal tumors (GISTs) caused by germline KIT gene mutations are an extremely rare autosomal dominant disorder. We report a case of a 21-year-old woman who presented to the emergency department with a 2-week history of asthenia, palpitations and upper gastrointestinal bleeding. After further clinical evaluation one gastric and two small bowel GISTs were diagnosed, which were surgically resected after neoadjuvant therapy with Imatinib. Diffuse hyperplasia of the interstitial cells of Cajal was also seen in the background gastric and small intestinal walls. Somatic mutational analysis of the KIT gene revealed a substitution at codon 576 in exon 11 (p.Leu576Pro) in all tumors and normal ileal mucosa. The germline nature of this mutation was confirmed by mutation analysis in peripheral blood leukocytes. However, she had no familial history of GISTs and her parents did not carry the respective germline mutation.