Clinical and molecular features of the hereditary mixed polyposis syndrome

Preventive strategies in familial and hereditary colorectal cancer

Colorectal cancer is a leading cause of cancer-related deaths worldwide. While most cases are sporadic, a significant proportion of cases are associated with familial and hereditary syndromes. Individuals with a family history of colorectal cancer have an increased risk of developing the disease, and those with hereditary syndromes such as Lynch syndrome or familial adenomatous polyposis have a significantly higher risk. In these populations, preventive strategies are critical for reducing the incidence and mortality of colorectal cancer. This review provides an overview of current preventive strategies for individuals at increased risk of colorectal cancer due to familial or hereditary factors. The manuscript includes a discussion of risk assessment and genetic testing, highlighting the importance of identifying at-risk individuals and families. This review describes various preventive measures, including surveillance colonoscopy, chemoprevention, and prophylactic surgery, and their respective benefits and limitations. Together, this work highlights the importance of preventive strategies in familial and hereditary colorectal cancer.

Clinical Spectrum and Science Behind the Hamartomatous Polyposis Syndromes

The hamartomatous polyposis syndromes are a set of clinically distinct disorders characterized by the occurrence of hamartomatous polyps in the gastrointestinal tract. These syndromes include juvenile polyposis syndrome, Peutz-Jeghers syndrome, and PTEN hamartoma tumor syndrome. Although each of the syndromes has distinct phenotypes, the hamartomatous polyps can be challenging to differentiate histologically. Additionally, each of these syndromes is associated with increased lifetime risks of gene-specific and organ-specific cancers, including those outside of the gastrointestinal tract. Germline pathogenic variants can be identified in a subset of individuals with these syndromes, which facilitates molecular diagnosis and subsequent gene-enabled management in the setting of genetic counseling. Although the malignant potential of hamartomatous polyps remains elusive, timely recognition of these syndromes is important and enables presymptomatic cancer surveillance and management before symptom exacerbation. Presently, there are no standard agents to prevent the development of polyps and cancers in the hamartomatous polyposis syndromes.

Re-recognition of BMPR1A-related polyposis: beyond juvenile polyposis and hereditary mixed polyposis syndrome

Background

Bone morphogenetic protein receptor type 1A (BMPR1A) is responsible for two individual Mendelian diseases: juvenile polyposis syndrome and hereditary mixed polyposis syndrome 2, which have overlapping phenotypes. This study aimed to elucidate whether these two syndromes are just two subtypes of a single syndrome rather than two isolated syndromes.

Methods

We sequenced the BMPR1A gene in 186 patients with polyposis and colorectal cancer, and evaluated the clinicopathological features and phenotypes of the probands and their available relatives with BMPR1A mutations.

Results

BMPR1A germline mutations were found in six probands and their three available relatives. The numbers of frameshift, nonsense, splice-site, and missense mutations were one, one, two, and two, respectively; two of the six mutations were novel. Typical juvenile polyps were found in only three patients. Two patients had colorectal cancer rather than any polyps.

Conclusions

Diseases in BMPR1A germline mutation carriers vary from mixed polyposis to sole colorectal cancer, and typical juvenile polyps do not always occur in these carriers. The variety of phenotypes reflected the features of BMPR1A-mutation carriers, which should be recognized as a spectrum of one syndrome. Genetic testing may be a good approach to identifying BMPR1A-related syndromes.

Discovery of ginisortamab, a potent and novel anti-gremlin-1 antibody in clinical development for the treatment of cancer

Gremlin-1, a high-affinity antagonist of bone morphogenetic proteins (BMP)-2, -4, and -7, is implicated in tumor initiation and progression. Increased gremlin-1 expression, and therefore suppressed BMP signaling, correlates with poor prognosis in a range of cancer types. A lack of published work using therapeutic modalities has precluded the testing of the hypothesis that blocking the gremlin-1/BMP interaction will provide benefits to patients. To address this shortfall, we developed ginisortamab (UCB6114), a first-in-class clinical anti-human gremlin-1 antibody, currently in clinical development for the treatment of cancer, along with its murine analog antibody Ab7326 mouse immunoglobulin G1 (mIgG1). Surface plasmon resonance assays revealed that ginisortamab and Ab7326 mIgG1 had similar affinities for human and mouse gremlin-1, with mean equilibrium dissociation constants of 87 pM and 61 pM, respectively. The gremlin-1/Ab7326 antigen-binding fragment (Fab) crystal structure revealed a gremlin-1 dimer with a Fab molecule bound to each monomer that blocked BMP binding. In cell culture experiments, ginisortamab fully blocked the activity of recombinant human gremlin-1, and restored BMP signaling pathways in human colorectal cancer (CRC) cell lines. Furthermore, in a human CRC - fibroblast co-culture system where gremlin-1 is produced by the fibroblasts, ginisortamab restored BMP signaling in both the CRC cells and fibroblasts, demonstrating its activity in a relevant human tumor microenvironment model. The safety and efficacy of ginisortamab are currently being evaluated in a Phase 1/2 clinical trial in patients with advanced solid tumors (NCT04393298).

Diagnosis and Management of Cancer Risk in the Gastrointestinal Hamartomatous Polyposis Syndromes: Recommendations From the US Multi-Society Task Force on Colorectal Cancer

The gastrointestinal hamartomatous polyposis syndromes are rare, autosomal dominant disorders associated with an increased risk of benign and malignant intestinal and extraintestinal tumors. They include Peutz-Jeghers syndrome, juvenile polyposis syndrome, the PTEN hamartoma tumor syndrome (including Cowden's syndrome and Bannayan-Riley-Ruvalcaba syndrome), and hereditary mixed polyposis syndrome. Diagnoses are based on clinical criteria and, in some cases, confirmed by demonstrating the presence of a germline pathogenic variant. The best understood hamartomatous polyposis syndrome is Peutz-Jeghers syndrome, caused by germline pathogenic variants in the STK11 gene. The management is focused on prevention of bleeding and mechanical obstruction of the small bowel by polyps and surveillance of organs at increased risk for cancer. Juvenile polyposis syndrome is caused by a germline pathogenic variant in either the SMAD4 or BMPR1A genes, with differing clinical courses. Patients with SMAD4 pathogenic variants may have massive gastric polyposis, which can result in gastrointestinal bleeding and/or protein-losing gastropathy. Patients with SMAD4 mutations usually have the simultaneous occurrence of hereditary hemorrhagic telangiectasia (juvenile polyposis syndrome-hereditary hemorrhagic telangiectasia overlap syndrome) that can result in epistaxis, gastrointestinal bleeding from mucocutaneous telangiectasias, and arteriovenous malformations. Germline pathogenic variants in the PTEN gene cause overlapping clinical phenotypes (known as the PTEN hamartoma tumor syndromes), including Cowden's syndrome and related disorders that are associated with an increased risk of gastrointestinal and colonic polyposis, colon cancer, and other extraintestinal manifestations and cancers. Due to the relative rarity of the hamartomatous polyposis syndromes, recommendations for management are based on few studies. This U.S Multi-Society Task Force on Colorectal Cancer consensus statement summarizes the clinical features, assesses the current literature, and provides guidance for diagnosis, assessment, and management of patients with the hamartomatous polyposis syndromes, with a focus on endoscopic management.

Diagnosis and management of cancer risk in the gastrointestinal hamartomatous polyposis syndromes: recommendations from the U.S. Multi-Society Task Force on Colorectal Cancer

The gastrointestinal hamartomatous polyposis syndromes are rare, autosomal dominant disorders associated with an increased risk of benign and malignant intestinal and extraintestinal tumors. They include Peutz-Jeghers syndrome, juvenile polyposis syndrome, the PTEN hamartoma tumor syndrome (including Cowden's syndrome and Bannayan-Riley-Ruvalcaba syndrome), and hereditary mixed polyposis syndrome. Diagnoses are based on clinical criteria and, in some cases, confirmed by demonstrating the presence of a germline pathogenic variant. The best understood hamartomatous polyposis syndrome is Peutz-Jeghers syndrome, caused by germline pathogenic variants in the STK11 gene. The management is focused on prevention of bleeding and mechanical obstruction of the small bowel by polyps and surveillance of organs at increased risk for cancer. Juvenile polyposis syndrome is caused by a germline pathogenic variant in either the SMAD4 or BMPR1A genes, with differing clinical courses. Patients with SMAD4 pathogenic variants may have massive gastric polyposis, which can result in gastrointestinal bleeding and/or protein-losing gastropathy. Patients with SMAD4 mutations usually have the simultaneous occurrence of hereditary hemorrhagic telangiectasia (juvenile polyposis syndrome-hereditary hemorrhagic telangiectasia overlap syndrome) that can result in epistaxis, gastrointestinal bleeding from mucocutaneous telangiectasias, and arteriovenous malformations. Germline pathogenic variants in the PTEN gene cause overlapping clinical phenotypes (known as the PTEN hamartoma tumor syndromes), including Cowden's syndrome and related disorders that are associated with an increased risk of gastrointestinal and colonic polyposis, colon cancer, and other extraintestinal manifestations and cancers. Due to the relative rarity of the hamartomatous polyposis syndromes, recommendations for management are based on few studies. This U.S. Multi-Society Task Force on Colorectal Cancer consensus statement summarizes the clinical features, assesses the current literature, and provides guidance for diagnosis, assessment, and management of patients with the hamartomatous polyposis syndromes, with a focus on endoscopic management.

Diagnosis and Management of Cancer Risk in the Gastrointestinal Hamartomatous Polyposis Syndromes: Recommendations From the US Multi-Society Task Force on Colorectal Cancer

The gastrointestinal hamartomatous polyposis syndromes are rare, autosomal dominant disorders associated with an increased risk of benign and malignant intestinal and extraintestinal tumors. They include Peutz-Jeghers syndrome, juvenile polyposis syndrome, the PTEN hamartoma tumor syndrome (including Cowden's syndrome and Bannayan-Riley-Ruvalcaba syndrome), and hereditary mixed polyposis syndrome. Diagnoses are based on clinical criteria and, in some cases, confirmed by demonstrating the presence of a germline pathogenic variant. The best understood hamartomatous polyposis syndrome is Peutz-Jeghers syndrome, caused by germline pathogenic variants in the STK11 gene. The management is focused on prevention of bleeding and mechanical obstruction of the small bowel by polyps and surveillance of organs at increased risk for cancer. Juvenile polyposis syndrome is caused by a germline pathogenic variant in either the SMAD4 or BMPR1A genes, with differing clinical courses. Patients with SMAD4 pathogenic variants may have massive gastric polyposis, which can result in gastrointestinal bleeding and/or protein-losing gastropathy. Patients with SMAD4 mutations usually have the simultaneous occurrence of hereditary hemorrhagic telangiectasia (juvenile polyposis syndrome-hereditary hemorrhagic telangiectasia overlap syndrome) that can result in epistaxis, gastrointestinal bleeding from mucocutaneous telangiectasias, and arteriovenous malformations. Germline pathogenic variants in the PTEN gene cause overlapping clinical phenotypes (known as the PTEN hamartoma tumor syndromes), including Cowden's syndrome and related disorders that are associated with an increased risk of gastrointestinal and colonic polyposis, colon cancer, and other extraintestinal manifestations and cancers. Due to the relative rarity of the hamartomatous polyposis syndromes, recommendations for management are based on few studies. This US Multi-Society Task Force on Colorectal Cancer consensus statement summarizes the clinical features, assesses the current literature, and provides guidance for diagnosis, assessment, and management of patients with the hamartomatous polyposis syndromes, with a focus on endoscopic management.

Evaluation of Classic, Attenuated, and Oligopolyposis of the Colon

The goal of this review is to provide an overview of evaluating patients with adenomatous polyposis of the colon, including elements such as generating a differential diagnosis, referral considerations for genetic testing, genetic testing options, and expected outcomes from genetic testing in these individuals. In more recent years, adenomatous colonic polyposis has evolved beyond the more robustly characterized familial adenomatous polyposis (FAP) and MUTYH-associated polyposis (MAP) now encompassing more newly described genes and associated syndromes. Technological innovation, from whole-exome sequencing to multigene panel testing, has dramatically increased the amount of genotypic and phenotypic data amassed in adenomatous polyposis cohorts, which has contributed greatly to informing diagnosis and clinical management of affected individuals and their families.

Novel Genetic Causes of Gastrointestinal Polyposis Syndromes

Hereditary polyposis syndromes are characterized by a large number and/or histopathologically specific polyps in the gastrointestinal tract and a high risk of both colorectal cancer and extracolonic cancer at an early age. While the genes responsible for some of the syndromes, eg, APC in familial adenomatous polyposis and STK11 in Peutz-Jeghers syndrome, have been known for decades, novel genetic causes have recently been detected that have shed light on the broader clinical spectrum of syndromes. Genetic diagnoses are important because they can facilitate a personalized surveillance program. Furthermore, at-risk members of the patient's family can be tested and enrolled in surveillance as needed. In some cases, prenatal diagnostics should be offered. In this paper, we describe the development in germline genetics of the hereditary polyposis syndromes over the last 10-12 years, their clinical characteristics, as well as how to implement genetic analyses in the diagnostic pipeline.

Danish guidelines for management of non-APC-associated hereditary polyposis syndromes

Hereditary Polyposis Syndromes are a group of rare, inherited syndromes characterized by the presence of histopathologically specific or numerous intestinal polyps and an increased risk of cancer. Some polyposis syndromes have been known for decades, but the development in genetic technologies has allowed the identification of new syndromes.. The diagnosis entails surveillance from an early age, but universal guideline on how to manage and surveille these new syndromes are lacking. This paper represents a condensed version of the recent guideline (2020) from a working group appointed by the Danish Society of Medical Genetics and the Danish Society of Surgery on recommendations for the surveillance of patients with hereditary polyposis syndromes, including rare polyposis syndromes.

Hamartomatous polyposis syndrome associated malignancies: Risk, pathogenesis and endoscopic surveillance

Hamartomatous polyposis syndromes (HPS) are a heterogeneous spectrum of diseases that are characterized by diffuse hamartomatous polyps lining the gastrointestinal (GI) tract together with extra-GI manifestations. Classical HPS includes juvenile polyposis syndrome, Peutz-Jeghers syndrome, PTEN hamartoma tumor syndrome and hereditary mixed polyposis syndrome. Patients with HPS have a higher risk of GI and extra-GI malignancies than the general population, although the underlying mechanisms remain unclear and are obviously different from the carcinogenesis of classical adenocarcinoma and colitis-associated malignancy. In this review we aimed to clarify the risks, possible mechanism and endoscopic surveillance of HPS-associated GI malignancies.

The Inherited and Familial Component of Early-Onset Colorectal Cancer

Early-onset colorectal cancer (EOCRC), defined as that diagnosed before the age of 50, accounts for 10–12% of all new colorectal cancer (CRC) diagnoses. Epidemiological data indicate that EOCRC incidence is increasing, despite the observed heterogeneity among countries. Although the cause for such increase remains obscure, ≈13% (range: 9–26%) of EOCRC patients carry pathogenic germline variants in known cancer predisposition genes, including 2.5% of patients with germline pathogenic variants in hereditary cancer genes traditionally not associated with CRC predisposition. Approximately 28% of EOCRC patients have family history of the disease. This article recapitulates current evidence on the inherited syndromes that predispose to EOCRC and its familial component. The evidence gathered support that all patients diagnosed with an EOCRC should be referred to a specialized genetic counseling service and offered somatic and germline pancancer multigene panel testing. The identification of a germline pathogenic variant in a known hereditary cancer gene has relevant implications for the clinical management of the patient and his/her relatives, and it may guide surgical and therapeutic decisions. The relative high prevalence of hereditary cancer syndromes and familial component among EOCRC patients supports further research that helps understand the genetic background, either monogenic or polygenic, behind this increasingly common disease.

A novel germline BMPR1A variant (c.72_73delGA) in a Japanese family with hereditary mixed polyposis syndrome

Hereditary mixed polyposis syndrome (HMPS) is a rare autosomal dominant disorder characterized by a mixture of typical and/or atypical juvenile polyps, adenomas and hyperplastic polyps, resulting in an increased risk of colorectal cancer. In HMPS, four different germline BMPR1A variants from five unrelated families have been reported. This study is the first to report HMPS within a Japanese family. The proband underwent repeated colonoscopic polypectomies over a 5-year period, since the age of 67. Histological examination of these resected polyps revealed adenomas, juvenile-like polyps and hyperplastic changes. Genetic testing was conducted to identify the causative genes for hereditary gastrointestinal cancer syndromes, including BMPR1A. We detected a germline variant, c.72_73delGA, in BMPR1A. The proband’s elder brother, younger sister and nephew have also undergone repeated colonoscopic polypectomies at other clinics. His sister and nephew underwent genetic testing, and the same BMPR1A variant was identified.

Current status of the genetic susceptibility in attenuated adenomatous polyposis

Adenomatous polyposis (AP) is classified according to cumulative adenoma number in classical AP (CAP) and attenuated AP (AAP). Genetic susceptibility is the major risk factor in CAP due to mutations in the known high predisposition genes APC and MUTYH. However, the contribution of genetic susceptibility to AAP is lower and less understood. New predisposition genes have been recently proposed, and some of them have been validated, but their scarcity hinders accurate risk estimations and prevalence calculations. AAP is a heterogeneous condition in terms of severity, clinical features and heritability. Therefore, clinicians do not have strong discriminating criteria for the recommendation of the genetic study of known predisposition genes, and the detection rate is low. Elucidation and knowledge of new AAP high predisposition genes are of great importance to offer accurate genetic counseling to the patient and family members. This review aims to update the genetic knowledge of AAP, and to expound the difficulties involved in the genetic analysis of a highly heterogeneous condition such as AAP.

Gastrointestinal Polyposis in Pediatric Patients

Gastrointestinal polyps are mucosal overgrowths that, if unchecked, can undergo malignant transformation. Although relatively uncommon in the pediatric age group, they can be the harbingers of multiorgan cancer risk and require close management and follow-up. Additionally, as many polyposis syndromes are inherited, appropriate genetic testing and management of relatives is vital for the health of the entire family. In this review, we discuss both common and uncommon childhood gastrointestinal polyposis syndromes in terms of clinical presentation, management, and surveillance. We also detail any additional malignancy risk and surveillance required in the pediatric age group (<21 years old). Through this review, we provide a framework for gastroenterologists to manage the multifaceted nature of pediatric polyposis syndromes.

Update on genetic predisposition to colorectal cancer and polyposis

The present article summarizes recent developments in the characterization of genetic predisposition to colorectal cancer (CRC). The main themes covered include new hereditary CRC and polyposis syndromes, non-CRC hereditary cancer genes found mutated in CRC patients, strategies used to identify novel causal genes, and review of candidate genes that have been proposed to predispose to CRC and/or colonic polyposis. We provide an overview of newly described genes and syndromes associated with predisposition to CRC and polyposis, including: polymerase proofreading-associated polyposis, NTHL1-associated polyposis, mismatch repair gene biallelic inactivation-related adenomatous polyposis (including MSH3- and MLH3-associated polyposes), GREM1-associated mixed polyposis, RNF43-associated serrated polyposis, and RPS20 mutations as a rare cause of hereditary nonpolyposis CRC. The implementation of next generation sequencing approaches for genetic testing has exposed the presence of pathogenic germline variants in genes associated with hereditary cancer syndromes not traditionally linked to CRC, which may have an impact on genetic testing, counseling and surveillance. The identification of new hereditary CRC and polyposis genes has not deemed an easy endeavor, even though known CRC-related genes explain a small proportion of the estimated familial risk. Whole-genome sequencing may offer a technology for increasing this proportion, particularly if applied on pedigree data allowing linkage type of analysis. The final section critically surveys the large number of candidate genes that have been recently proposed for CRC predisposition.

Identification of a novel GREM1 duplication in a patient with multiple colon polyps

Hereditary mixed polyposis syndrome (HMPS) is a hereditary syndrome that is characterized by multiple colon polyps of mixed pathologic subtypes and an increased risk for colorectal cancer. A 40 kb duplication in the 5' regulatory region of the GREM1 gene was recently found to be the causal mutation in a subset of Ashkenazi Jewish families with HMPS. Given this discovery, the GREM1 5' regulatory region is now analyzed on many different multi-gene cancer panels, however the data on duplications distinct from the 40 kb duplication remains minimal. Herein we report a novel 24 kb tandem duplication of the 5' regulatory region of GREM1 in a patient without Ashkenazi Jewish heritage, who had a family history that was concerning for Lynch syndrome and satisfied Amsterdam II criteria. This is only the third reported GREM1 duplication separate from the 40 kb Ashkenazi Jewish duplication, and is the only reported duplication to selectively involve exon 1 of GREM1. This finding supports comprehensive testing of the GREM1 regulatory region in families of all ethnicities with multiple colon polyps or colon cancer, and when Lynch syndrome is suspected.

Update on Hereditary Colorectal Cancer: Improving the Clinical Utility of Multigene Panel Testing

Colorectal cancer (CRC), one of the most common cancers, is a major public health issue globally, especially in Westernized countries. Up to 35% of CRCs are thought to be due to heritable factors, but currently only 5% to 10% of CRCs are attributable to high-risk mutations in known CRC susceptibility genes, predominantly the mismatch repair genes (Lynch syndrome) and adenomatous polyposis coli gene (APC; familial adenomatous polyposis). In this era of precision medicine, high-risk mutation carriers, when identified, can be offered various risk management options that prevent cancers and improve survival, including risk-reducing medication, screening for early detection, and surgery. The practice of clinical genetics is currently transitioning from phenotype-directed single gene testing to multigene panels, now offered by numerous providers. For CRC, the genes included across these panels vary, ranging from well established, clinically actionable susceptibility genes with quantified magnitude of risk, to genes that lack extensive validation or have less evidence of association with CRC and, therefore, have minimal clinical utility. The current lack of consensus regarding inclusion of genes in CRC panels presents challenges in patient counseling and management, particularly when a variant in a less validated gene is identified. Furthermore, there remain considerable challenges regarding variant interpretation even for the well established CRC susceptibility genes. Ironically though, only through more widespread testing and the accumulation of large international data sets will sufficient information be generated to (i) enable well powered studies to determine if a gene is associated with CRC susceptibility, (ii) to develop better models for variant interpretation and (iii) to facilitate clinical translation.

Expanding the genotype-phenotype spectrum in hereditary colorectal cancer by gene panel testing

Hereditary syndromes causing colorectal cancer include both polyposis and non-polyposis syndromes. Overlapping phenotypes between the syndromes have been recognized and this make targeted molecular testing for single genes less favorable, instead there is a gaining interest for multi-gene panel-based approaches detecting both SNVs, indels and CNVs in the same assay. We applied a panel including 19 CRC susceptibility genes to 91 individuals of six phenotypic subgroups. Targeted NGS-based sequencing of the whole gene regions including introns of the 19 genes was used. The individuals had a family history of CRC or had a phenotype consistent with a known CRC syndrome. The purpose of the study was to demonstrate the diagnostic difficulties linked to genotype-phenotype diversity and the benefits of using a gene panel. Pathogenicity classification was carried out on 46 detected variants. In total we detected sixteen pathogenic or likely pathogenic variants and 30 variants of unknown clinical significance. Four of the pathogenic or likely pathogenic variants were found in BMPR1A in patients with unexplained familial adenomatous polyposis or atypical adenomatous polyposis, which extends the genotype-phenotype spectrum for this gene. Nine patients had more than one variant remaining after the filtration, including three with truncating mutations in BMPR1A, PMS2 and AXIN2. CNVs were found in three patients, in upstream regions of SMAD4, MSH3 and CTNNB1, and one additional individual harbored a 24.2 kb duplication in CDH1 intron1.

Recent Discoveries in the Genetics of Familial Colorectal Cancer and Polyposis

The development of genome-wide massively parallel sequencing, ie, whole-genome and whole-exome sequencing, and copy number approaches has raised high expectations for the identification of novel hereditary colorectal cancer genes. Although relatively successful for genes causing adenomatous polyposis syndromes, both autosomal dominant and recessive, the identification of genes associated with hereditary non-polyposis colorectal cancer has proven extremely challenging, mainly because of the absence of major high-penetrance genes and the difficulty in demonstrating the functional impact of the identified variants and their causal association with tumor development. Indeed, most, if not all, novel candidate non-polyposis colorectal cancer genes identified so far lack corroborative data in independent studies. Here we review the novel hereditary colorectal cancer genes and syndromes identified and the candidate genes proposed in recent years as well as discuss the challenges we face.

Features of Patients With Hereditary Mixed Polyposis Syndrome Caused by Duplication of GREM1 and Implications for Screening and Surveillance

Hereditary mixed polyposis syndrome is a rare colon cancer predisposition syndrome caused by a duplication of a noncoding sequence near the gremlin 1, DAN family BMP antagonist gene (GREM1) originally described in Ashkenazi Jews. Few families with GREM1 duplications have been described, so there are many questions about detection and management. We report 4 extended families with the duplication near GREM1 previously found in Ashkenazi Jews; 3 families were identified at cancer genetic clinics in Israel and 1 family was identified in a cohort of patients with familial colorectal cancer. Their clinical features include extracolonic tumors, onset of polyps in adolescence, and rapid progression of some polyps to advanced adenomas. One family met diagnostic criteria for Lynch syndrome. Expansion of the hereditary mixed polyposis syndrome phenotype can inform surveillance strategies for carriers of GREM1 duplications.

Gastric Hamartomatous Polyps-Review and Update

Gastric polyps are frequently encountered on endoscopic examinations. While many of these represent true epithelial lesions, some of the polyps may result from underlying stromal or lymphoid proliferations or even heterotopic tissue. Histologic examination is essential for accurate typing of the polyps to predict malignant potential and underlying possible genetic abnormalities. The focus of this review is on gastric hamartomatous polyps, which are relatively rare and diagnostically challenging. Though most of the gastric hamartomatous polyps are benign, certain types are associated with increased malignant potential. These include certain polyps associated with specific genetic familial polyposis syndromes and gastric inverted hamartomatous polyps. Identification of these polyps can result in the prevention or early diagnosis of gastric carcinoma and also help in the identification of family members with polyposis syndromes. The aim of this review is to categorize gastric hamartomatous polyps and aid in the identification of high-risk categories.

Defining the polyposis/colorectal cancer phenotype associated with the Ashkenazi GREM1 duplication: counselling and management recommendations

Hereditary mixed polyposis is a genetically heterogeneous, autosomal dominant condition with adenomatous, hyperplastic and juvenile polyps. We conducted a comprehensive clinical evaluation of a large Ashkenazi Jewish family with this phenotype and performed extensive genetic testing. As seen in one previous report, a 40 kb duplication upstream of GREM1 segregated with the polyposis/colon cancer phenotype in this kindred. Our study confirms the association of GREM1 with mixed polyposis and further defines the phenotype seen with this mutation. This gene should be included in the test panel for all Jewish patients with mixed polyposis and may be considered in any Ashkenazi patient with unexplained hereditary colon cancer when mutations in other hereditary colon cancer genes have been ruled out.

The Genetics of Colorectal Cancer

The hereditary colorectal cancer syndromes comprise a heterogeneous group of conditions with varying cancer risks, gastrointestinal polyp types, nonmalignant findings, and inheritance patterns. Although each one is unique in its own right, these syndromes often have overlapping features, making diagnoses difficult in select cases. Obtaining accurate polyp history (histologic type, number, location, and age of onset), cancer history (location, type, and age of onset), and other nonmalignant features is imperative in determining the likely disease diagnosis and thereby the appropriate genetic tests for precise diagnosis in a timely fashion. This process often necessitates collaboration among surgical oncology team members and genetic counselors.

The molecular basis of rectal cancer

The majority of rectal carcinomas are sporadic in nature, and relevant testing for driver mutations to guide therapy is important. A thorough family history is necessary and helpful in elucidating a potential hereditary predilection for a patient's carcinoma. The adequate diagnosis of a heritable tendency toward colorectal carcinoma alters the management of a patient disease and permits the implementation of various surveillance algorithms as preventive measures.

Aberrant epithelial GREM1 expression initiates colonic tumorigenesis from cells outside the stem cell niche

Hereditary mixed polyposis syndrome (HMPS) is characterized by the development of mixed-morphology colorectal tumors and is caused by a 40-kb genetic duplication that results in aberrant epithelial expression of the gene encoding mesenchymal bone morphogenetic protein antagonist, GREM1. Here we use HMPS tissue and a mouse model of the disease to show that epithelial GREM1 disrupts homeostatic intestinal morphogen gradients, altering cell fate that is normally determined by position along the vertical epithelial axis. This promotes the persistence and/or reacquisition of stem cell properties in Lgr5-negative progenitor cells that have exited the stem cell niche. These cells form ectopic crypts, proliferate, accumulate somatic mutations and can initiate intestinal neoplasia, indicating that the crypt base stem cell is not the sole cell of origin of colorectal cancer. Furthermore, we show that epithelial expression of GREM1 also occurs in traditional serrated adenomas, sporadic premalignant lesions with a hitherto unknown pathogenesis, and these lesions can be considered the sporadic equivalents of HMPS polyps.

Genetic predisposition to colorectal cancer: Where we stand and future perspectives

The development of colorectal cancer (CRC) can be influenced by genetic factors in both familial cases and sporadic cases. Familial CRC has been associated with genetic changes in high-, moderate- and low-penetrance susceptibility genes. However, despite the availability of current gene-identification techniques, the genetic causes of a considerable proportion of hereditary cases remain unknown. Genome-wide association studies of CRC have identified a number of common low-penetrance alleles associated with a slightly increased or decreased risk of CRC. The accumulation of low-risk variants may partly explain the familial risk of CRC, and some of these variants may modify the risk of cancer in patients with mutations in high-penetrance genes. Understanding the predisposition to develop CRC will require investigators to address the following challenges: the identification of genes that cause uncharacterized hereditary cases of CRC such as familial CRC type X and serrated polyposis; the classification of variants of unknown significance in known CRC-predisposing genes; and the identification of additional cancer risk modifiers that can be used to perform risk assessments for individual mutation carriers. We performed a comprehensive review of the genetically characterized and uncharacterized hereditary CRC syndromes and of low- and moderate-penetrance loci and variants identified through genome-wide association studies and candidate-gene approaches. Current challenges and future perspectives in the field of CRC predisposition are also discussed.

Hamartomatous polyposis syndromes: a review

Hamartomatous Polyposis Syndromes (HPS) are genetic syndromes, which include Peutz-Jeghers syndrome, Juvenile polyposis syndrome, PTEN hamartoma tumour syndrome (Cowden Syndrom, Bannayan-Riley-Ruvalcaba and Proteus Syndrome) as well as hereditary mixed polyposis syndrome. Other syndromes such as Gorlin Syndrome and multiple endocrine neoplasia syndrome 2B are sometimes referred to as HPS. HPS is characterized by the development of hamartomatous polyps in the gastrointestinal tract as well as several extra-intestinal findings such as dermatological and dysmorphic features or extra-intestinal cancer. The syndromes are rare and inherited in an autosomal dominant manner.

The diagnosis of HPS has traditionally been based on clinical criteria, but can sometimes be difficult as the severity of symptoms range considerably from only a few symptoms to very severe cases - even within the same family. De novo cases are also frequent. However, because of the discovery of several associated germline-mutations as well as the rapid development in genetics it is now possible to use genetic testing more often in the diagnostic process. Management of the syndromes is different for each syndrome as extra-intestinal symptoms and types of cancers differs.

Clinical awareness and early diagnosis of HPS is important, as affected patients and at-risk family members should be offered genetic counselling and surveillance. Surveillance in children with HPS might prevent or detect intestinal or extra-intestinal complications, whereas in adulthood surveillance is recommended due to an increased risk of cancer e.g. intestinal cancer or breast cancer.

What clinicians wish to know about benign colorectal polyps: an operative classification

INTRODUCTION

In recent years we assisted to a real "boom" of colorectal polyps, mainly due to the diffusion of screening procedures and of colonoscopy. This new "Polyp Epidemic" raises a series of problems and challenges. It became clear that many syndromes are defined by the number, histological type and location of polyps, together with extraintestinal manifestations and, in most cases, specific molecular changes. This paper discusses some of the above mentioned points, focusing on the relative role of endoscopists and pathologists. The objective is to reach an operative classification of the most common polyps observed in daily practice which might be of help for the identification of inherited syndromes.

METHODS AND RESULTS

Six main histological types of polyps are defined and underlined: Adenoma, hyperplastic/serrated, hamartoma, ganglioneuroma, mixed, inflammatory. The importance of a brief description, in pathology reports, of each type of polyps is fundamental for a correct diagnosis. Each of the defined polyps is associated with inherited syndromes whose genetic basis has recently been elucidated. Relevant information should be given, and separated from additional (and not strictly necessary) information.

RECOMMENDATIONS

A correct polyp analysis is a valuable element for identifying specific inherited syndromes. Polyps represent a precious tool for planning screening and follow-up in a given individual. In addition, these lesions focus the interest of clinicians toward syndrome which were considered as rare diseases; indeed, the explosion of molecular biology and the diffusion of colonoscopy revealed that these conditions are frequent and amenable of treatment.

The growing complexity of the intestinal polyposis syndromes

Familial adenomatous polyposis has been the first form of inherited intestinal polyposis to be recognized. For a long time it has been considered the main polyposis syndrome, associated with an easily recognizable phenotype, with a marginal role attributed to a few very rare hamartomatous conditions. More recently, it has been gradually demonstrated that the intestinal polyposes encompass a range of conditions within a wide spectrum of disease severity, polyp histology, and extraintestinal manifestations. A growing number of genes and phenotypes has been identified, and heterogeneity of somatic molecular pathways underlying epithelial transformation in different syndromes and associated tumors has been documented. Increasing knowledge on the molecular bases and more widespread use of genetic tests has shown phenotypic overlaps between conditions that were previously considered distinct, highlighting diagnostic difficulties. With the advent of next generation sequencing, the diagnosis and the classification of these syndromes will be progressively based more on genetic testing results. However, the phenotypic variability documented among patients with mutations in the same genes cannot be fully explained by different expressivity, indicating a role for as yet unknown modifying factors. Until the latter will be identified, the management of patients with polyposis syndromes should be guided by both clinical and genetic findings.

Germline Mutations in the Polyposis-Associated Genes BMPR1A, SMAD4, PTEN, MUTYH and GREM1 Are Not Common in Individuals with Serrated Polyposis Syndrome

Background

Recent reports have observed that individuals with serrated polyps, some of whom meet the clinical diagnostic criteria for Serrated Polyposis Syndrome (SPS), are among those who carry germline mutations in genes associated with polyposis syndromes including; (1) genes known to underlie hamartomatous polyposes (SMAD4, BMPR1A, and PTEN), (2) MUTYH-associated polyposis and (3) GREM1 in Hereditary Mixed Polyposis Syndrome (HMPS). The aim of this study was to characterise individuals fulfilling the current WHO criteria for SPS for germline mutations in these polyposis-associated genes.

Methods

A total of 65 individuals with SPS (fulfilling WHO criteria 1 or 3), were recruited to the Genetics of Serrated Neoplasia study between 2000 and 2012, through multiple Genetics or Family Cancer Clinics within Australia, or from the New Zealand Familial Gastrointestinal Cancer Service. Individuals with SPS were tested for coding mutations and large deletions in the PTEN, SMAD4, and BMPR1A genes, for the MUTYH variants in exons 7 (Y179C) and 13 (G396D), and for the duplication upstream of GREM1.

Results

We found no variants that were likely to be deleterious germline mutations in the SPS cases in the PTEN, SMAD4, and BMPR1A genes. A novel variant in intron 2 (c.164+223T>C) of PTEN was identified in one individual and was predicted by in silico analysis to have no functional consequences. One further individual with SPS was found to be mono-allelic for the MUTYH G396D mutation. No individuals carried the recently reported duplication within GREM1.

Conclusions

Genes involved in the gastrointestinal hamartomatous polyposis, Hereditary Mixed Polyposis Syndrome and MUTYH-associated polyposis syndromes are not commonly altered in individuals with SPS.

Advanced precancerous lesions (APL) in the colonic mucosa

Colorectal cancer is a leading cause of cancer death worldwide. Most colorectal cancers are preventable. Surveillance colonoscopy is used to detect and remove precancerous lesions. Although the majority of precancerous lesions develop sporadically, some have an inherited component. In this review, we summarize the clinical, pathologic, and molecular features of advanced precancerous lesions of the colon. The most common and clinically important intestinal polyposis syndromes, and their genetics, are also discussed. Finally, current recommendations regarding the treatment and surveillance of precancerous lesions, both in the sporadic and in inherited setting, are reviewed.

Serrated polyposis is an underdiagnosed and unclear syndrome: the surgical pathologist has a role in improving detection

Serrated polyposis syndrome (SPS) is poorly defined and patients have an increased but unspecified risk for colorectal carcinoma through the serrated pathway. Despite this association SPS remains relatively obscure and is therefore likely underrecognized. We determined the frequency of SPS among patients with any serrated polyps (SPs) over a 6-month "index" period, and in doing so we assessed the ability of surgical pathologists to improve SPS detection. Particular attention was given to the index procedure to assess the potential predictive value of the findings resulting from a single colonoscopy. A total of 929 patients with at least 1 SP were identified, 17 of whom (1.8%) were determined to meet World Health Organization criteria for SPS. Nine patients met the first criterion (≥ 5 proximal SPs, 2 of which are > 10 mm); 4 met the third criterion (> 20 SPs of any size distributed throughout the colon); and 4 met both criteria. Although no specific SP size or number at the index procedure was clearly superior in its ability to predict SPS, > 50% of cases would be detected if a cutoff of ≥ 3 SPs or a single SP ≥ 15 mm at the index procedure is used. In summary, SPS is rare but more likely underdiagnosed. Additional studies to address the underlying genetic basis for SPS are ongoing in order to shed further light on this syndrome. Surgical pathologists are in a unique position to assist in this endeavor by identifying those patients who either meet or seem to be at high risk of meeting World Health Organization criteria.

Hereditary mixed polyposis syndrome is caused by a 40-kb upstream duplication that leads to increased and ectopic expression of the BMP antagonist GREM1

The hereditary mixed polyposis syndrome (HMPS) was first described about 50 years ago in a large Ashkenazi Jewish family from St Mark’s Hospital, London. The family showed apparent autosomal dominant inheritance of multiple types of colorectal polyp, with colorectal carcinoma in a high proportion of individuals. In the last 15 years, we have mapped the HMPS gene to chromosome 15q13.3 and identified an ancestral haplotype common to all the known HMPS families. Here, we have used genetic mapping, copy number analysis, exclusion of mutations by high-throughput sequencing, gene expression analysis and functional assays to show that HMPS is caused by a large duplication spanning the 3′ end of the SCG5 gene and a region upstream of the GREM1 locus. This mutation has no effect on SCG5 expression, but is associated with greatly increased, allele-specific GREM1 expression. Whilst GREM1 is expressed in intestinal sub-epithelial myofibroblasts in controls, HMPS patients predominantly express GREM1 in the epithelium of the large bowel. The HMPS duplication contains predicted transcriptional enhancer elements; we have shown that some of these interact with the GREM1 promoter and are capable of driving gene expression in vitro. Increased GREM1 expression is predicted to lead to reduced bone morphogenetic protein pathway activity, a mechanism that also underlies tumorigenesis in juvenile polyposis of the large bowel. The pathogenic mechanism in HMPS is extremely unusual in Mendelian cancer syndromes and highlights ectopic gene expression as a mechanism of tumorigenesis.

Small bowel polyposis syndromes

Intestinal polyposis syndromes are relatively rare. However, it is important for clinicians to recognize the potential risks of these syndromes. Based on histology, these syndromes can be classified mainly into hamartomatous polyposis syndromes and familial adenomatous polyposis (FAP), which affects mainly the large intestine. This review discusses the clinical manifestations and underlying genetics of the most common small intestinal polyposis syndromes: Peutz-Jeghers syndrome (PJS), juvenile polyposis (JP), PTEN hamartoma tumor syndrome (PHTS), and the small intestinal implications of familial adenomatous polyposis (FAP).

Diagnosing hereditary colorectal cancer

Although progress in the treatment of patients with colorectal cancer (CRC) has resulted in improved median survival, most patients with metastatic CRC still die of their disease, and essentially all patients with early-stage disease must undergo surgical resection and subsequently face the possibility of adjuvant chemotherapy. As effective screening and prevention strategies for CRC have been developed, identification of individuals with a hereditary predisposition to developing CRC is especially important and provides the opportunity to reduce disease burden in this high-risk population. Increased awareness and improved diagnostic techniques for hereditary CRC syndromes have facilitated more frequent diagnosis and management of a small number of highly penetrant syndromes within families. However, known high-penetrance genetic predisposition syndromes account for a minority of all familial CRC, leaving much of the genetic basis of CRC unexplained. Recent advances in high-throughput genotyping have made possible genome-wide association studies, which have identified novel genetic variants associated with modest increases in CRC risk. While these associations have helped to identify potentially important pathways in CRC carcinogenesis, at the current time, the clinical use of such genetic risk variants in colon cancer risk stratification remains limited.

Germline bone morphogenesis protein receptor 1A mutation causes colorectal tumorigenesis in hereditary mixed polyposis syndrome

OBJECTIVES

Hereditary mixed polyposis syndrome (HMPS) is characterized by polyps of mixed adenomatous/hyperplastic/atypical juvenile histology that are autosomal dominantly inherited and that eventually lead to colorectal cancer (CRC). Although CRC with adenomatous polyps is initiated by inactivating adenomatous polyposis coli (APC), the initiating event of CRC with mixed polyps remains unclear. We aimed to identify the underlying germline defect in HMPS.

METHODS

We screened for bone morphogenesis protein receptor 1A (BMPR1A) mutation by exonic sequencing, reverse-transcriptase polymerase chain reaction (PCR) followed by cDNA sequencing, and multiplex ligation-dependent probe amplification (MLPA) analysis in eight Singapore Chinese HMPS families.

RESULTS

Germline BMPR1A defects were found in four (50%) families. In two families, it is shown to co-segregate with the disease phenotype in all affected members over three generations, indicating that it is the disease-causing mutation. CRC incidence is 75%. The most defining characteristic is the presence of mixed hyperplastic-adenomatous polyps. Juvenile polyps are rarely reported, and if present, are usually of mixed components. Detailed histology of the polyps from one patient over 11 years distinguishes HMPS from juvenile polyposis syndrome (JPS). We report further the first cases of Wilms' tumor and papillary thyroid carcinoma associated with BMPR1A germline defect.

CONCLUSIONS

Germline BMPR1A defect is the disease-causing mutation in 50% of the HMPS families. If patients present with mixed morphology polyps in the large bowel that are autosomal dominantly inherited and corresponding absence of upper gastrointestinal abnormalities, the gene to begin mutation screening should be BMPR1A rather than APC.

Genetics of the hamartomatous polyposis syndromes: a molecular review

BACKGROUND AND AIMS

Hamartomatous polyposis syndromes are a heterogeneous group of disorders that are inherited in an autosomal dominant fashion. These syndromes only represent a small number of the inherited gastrointestinal cancer predisposition syndromes. However, many of these syndromes carry a substantial risk for developing colorectal cancer, as well as extra-colonic malignancy.

MATERIALS AND METHODS

We searched for articles on inherited hamartomatous polyposis syndromes, including familial juvenile polyposis syndrome, Peutz-Jeghers syndrome, PTEN hamartoma tumor syndrome, multiple endocrine neoplasia syndrome 2B, hereditary mixed polyposis syndrome, Cronkhite-Canada syndrome, basal cell nevus syndrome, and neurofibromatosis 1, in PubMed, Embase, and Elsevier ScienceDirect. In this review, we briefly discuss the diagnosis and clinical features of these disorders and the molecular alterations responsible for these syndromes.

RESULTS AND CONCLUSION

Given the clinical similarities of these hamartomatous syndromes and the autosomal dominant pattern of inheritance, it is sometimes difficult to differentiate hamartomatous polyps, especially with atypical presentation. The molecular analysis and diagnosis make it possible to identify the subtype of these syndromes. In addition, these tests raise an intriguing possibility that surveillance and early medical intervention will allow for the identification of at-risk patients and the reduction of morbidity and mortality.

Recent advances in colorectal cancer genetics and diagnostics

Colorectal cancer (CRC) is one of the most prevalent cancers and leading cause of cancer mortality worldwide. It is also one of the most curable cancers if detected early. This review classifies the diverse disease subtypes using various parameters including phenotypes of the polyps and describes how recent advances in genetics have impacted on disease diagnostics. For familial syndromes, the discovery of initiating mutations in the germline made personalized medicine a reality. A model linking the main tumorigenesis (Wnt/TGF-beta-BMP/LKB-1/PI3K-AKT) pathways and a strategy for gene testing are proposed. For sporadic CRC, high throughput technology has enabled the discovery of susceptibility loci that increased CRC risk. The ramifications of screening the population for susceptibility loci are discussed.

Hamartomatous polyposis syndromes

Since the histologic description of the hamartomatous polyp in 1957 by Horrilleno and colleagues, descriptions have appeared of several different syndromes with the propensity to develop these polyps in the upper and lower gastrointestinal tracts. These syndromes include juvenile polyposis, Peutz-Jeghers syndrome, hereditary mixed polyposis syndrome, and the phosphatase and tensin homolog gene (PTEN) hamartoma tumor syndromes (Cowden and Bannayan-Riley-Ruvalcaba syndromes), which are autosomal-dominantly inherited, and Cronkhite-Canada syndrome, which is acquired. This article reviews the clinical aspects, the molecular pathogenesis, the affected organ systems, the risks of cancer, and the management of these hamartomatous polyposis syndromes. Although the incidence of these syndromes is low, it is important for clinicians to recognize these disorders to prevent morbidity and mortality in these patients, and to perform presymptomatic testing in patients at risk.

[Sporadic colonic juvenile polyps in adults]

Sporadic colonic juvenile polyps are uncommon in adults. We report three cases for which clinical manifestations were presence of occult blood in the stool, rectal bleeding or chronic diarrhea. Two of these polyps occurred in the caecum which is an uncommon localisation. Endoscopic characteristics of these polyps were indistinguishable from adenomas. Endoscopic resection was complicated in one case by bleeding.

Colorectal polyposes: from phenotype to diagnosis

The colorectal polyposes are uncommon and frequently present diagnostic difficulties. Although the final diagnostic arbiter is the demonstration of a germline mutation, this may not always be demonstrable, and some forms of colorectal polyposis have no known genetic basis. Therefore, an accurate description of the phenotype by the pathologist is central to the establishment of a working diagnosis. This can direct the search for the underlying genetic cause (if any) and is also essential for establishing the magnitude of risk of colorectal malignancy for the patient and the patient's relatives. The pathologist may be provided with only a small and selected sample of endoscopically resected polyps or with prodigious numbers of polyps (too many to sample) when receiving a surgical specimen. Each type of polyposis presents its own particular diagnostic problems that may relate to polyp numbers, gross recognition of small or flat polyps, incomplete development of the full phenotype at the stage of investigation, and the histological classification of unusual or mixed polyps. The aim of this review is to highlight the principles and pitfalls in achieving a comprehensive description of the various types of colorectal polyposis, including classical FAP, attenuated FAP, MUTYH- (formerly MYH-) associated polyposis (MAP), other presentations of multiple adenomas, Peutz-Jeghers syndrome (P-JS), juvenile polyposis syndrome (JPS), Cowden syndrome (CS), hereditary mixed polyposis syndrome (HMPS), and hyperplastic polyposis syndrome (HPS).