A large-scale meta-analysis to refine colorectal cancer risk estimates associated with MUTYH variants

Phenotype correlations with pathogenic DNA variants in the MUTYH gene

MUTYH -associated polyposis (MAP) is an autosomal recessive disorder where the inheritance of constitutional biallelic pathogenic MUTYH variants predisposes a person to the development of adenomas and colorectal cancer (CRC). It is also associated with extracolonic and extraintestinal manifestations that may overlap with the phenotype of familial adenomatous polyposis (FAP). Currently, there are discrepancies in the literature regarding whether certain phenotypes are truly associated with MAP. This narrative review aims to explore the phenotypic spectrum of MAP to better characterise the MAP phenotype. A literature search was conducted to identify articles reporting on MAP-specific phenotypes. Clinical data from 2109 MAP patients identified from the literature showed that 1123 patients (53.2%) had CRC. Some patients with CRC had no associated adenomas, suggesting that adenomas are not an obligatory component of MAP. Carriers of the two missense founder variants, and possibly truncating variants, had an increased cancer risk when compared to those who carry other pathogenic variants. It has been suggested that somatic G:C>T:A transversions are a mutational signature of MAP, and could be used as a biomarker in screening and identifying patients with atypical MAP, or in associating certain phenotypes with MAP. The extracolonic and extraintestinal manifestations that have been associated with MAP include duodenal adenomas, duodenal cancer, fundic gland polyps, gastric cancer, ovarian cancer, bladder cancer and skin cancer. The association of breast cancer and endometrial cancer with MAP remains disputed. Desmoids and Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPEs) are rarely reported in MAP, but have long been seen in FAP patients, and thus could act as a distinguishing feature between the two. This collection of MAP phenotypes will assist in the assessment of pathogenic MUTYH variants using the American College of Medical Genetics and the Association for Molecular Pathology (ACMG/AMP) Variant Interpretation Guidelines, and ultimately improve patient care.

Case report: Efficacy of immunotherapy as conversion therapy in dMMR/MSI-H colorectal cancer: a case series and review of the literature

Immunotherapy has demonstrated a role in the therapeutic landscape of a small subset of patients with colorectal carcinoma (CRC) that harbor a microsatellite instability (MSI-H) status due to a deficient DNA mismatch repair (dMMR) system. The remarkable responses to immune checkpoint inhibitors (ICIs) are now being tested in the neoadjuvant setting in localized CRC, where the dMMR/MSI-H status can be found in up to 15% of patients, with remarkable results obtained in NICHE2 and 3 trials, among others. This case series aims to report our experience at a tertiary center and provide a comprehensive analysis of the possible questions and challenges to overcome if ICIs were established as standard of care in a neoadjuvant setting, as well as the potential role they may have as conversion therapy not only in locoregional advanced CRC but also in oligometastatic disease.

[Results of Endoscopic Screening and Therapy of the Duodenum in MUTYH-associated Polyposis]

MUTYH-associated polyposis (MAP) is a very rare autosomal recessive polyposis syndrome. It is caused by a homozygous or compound heterozygous germline mutation in the MUTYH gene. MAP is characterised by numerous colorectal adenomas; furthermore there is an increased risk for colorectal cancer (CRC). However, the phenotype can be highly variable; for example, affected individuals also have an increased risk of polyps of the upper gastrointestinal tract and development of duodenal carcinomas.This study included 15 patients with evidence of a pathogenic MUTYH variant, who were screened at the National Center for Hereditary Tumor Syndromes. Oesophagogastroduodenoscopy (EGD) results were prospectively recorded in a database from 2012 to 2023.At least one EGD (median 4, range 1-15) was performed in 15 patients, seven of whom carried a homozygous and 8 a compound heterozygous pathogenic MUTYH variant. The median surveillance period was 115 months (range, 3-215 months). The median age at baseline was 44 (range 17-65) years. A total of 72 EGDs were performed (median 4; range 1-15). Five patients had duodenal adenomas; histology showed tubular adenomas with low grade intraepithelial dysplasia (LGIEN) in all of these cases. The total number of duodenal adenomas detected was 48, and the median number was 3 (range, 1-37). Neither high grade intraepithelial neoplasia (HGIEN) nor duodenal cancer was detected during the surveillance period.Patients with MUTYH-associated polyposis should be managed in a multidisciplinary centre for hereditary tumour disease. Our cohort showed more patients with duodenal adenomas than in previously published data. However, no progression to HGIEN or duodenal carcinomas was observed as a result of the endoscopic therapy performed.

Monoallelic deleterious MUTYH mutations generate colorectal cancer: A case report

Here we reported a particular case of MUTYH-associated polyposis (MAP) that had only one rare heterozygous variant, but some particular clinical manifestations contributed to occur in this male patient by only one defective MUTYH allele were worth of further investigation. We reported a case of MAP. It is about a 33-year-old man with chief complaints of hematochezia who had multiple polyps that were found in his colon via colonoscopy. He followed his doctor's advice and performed a genetic analysis examination. Germline test was positive for a major heterozygous variant: chr1:45800165 on the MUTYH gene. MUTYH gene sequence analysis confirmed the following heterozygous variant: c.55CT (p.R19X) in exon 2 (ClinVar NM_001128425). Unfortunately, his mother and daughter have the ILK variant according to genetic analysis. However, this variant at the site was not detected in his father. Various types of polyps were found on repeated colonoscopy, which tended to become latent cancerous in the future. This case indicated that awareness of the risk of carcinogenesis of polyps in carriers of monoallelic variants might accordingly increase, and our understanding of the type of genetically related disease will be enhanced by us.

The prevalence of germline pathogenic variants in Estonian colorectal cancer patients: results from routine clinical setting 2016-2021

Background: Colorectal cancer (CRC) is the third most common cancer in Estonia in both women and men. According to the Estonian National Institute for Health Development, in 2017, there were 357 new colon cancer only cases in women and 282 in men. For colorectal cancer, the number for men and women altogether was 1040 in the same year. In 2018, there were over 1.8 million new cases worldwide. The Mayo Clinic found in a prospective, two-year multi-site study of CRC patients that 15.5% of patients carried pathogenic germline variants (PGV), using an >80 gene Next Generation Sequencing (NGS) panel. Material and methods: This retrospective study aimed to analyse the estimated prevalence of pathogenic/likely pathogenic germline variants in Estonian colorectal cancer patients using NGS in a routine clinical setting. We gathered five-year data (July 2016-July 2021) of colorectal cancer patients (mostly not selected for age or family history) tested with either Illumina TruSight Cancer (94 genes) or TruSight Hereditary Cancer (113 genes) NGS panels. Results: Three hundred and fourteen NGS analyses were performed due to either CRC or polyposis in anamnesis and/or family anamnesis, including 126 CRC cases and 44 colorectal polyposis cases, while 144 were either healthy family members or had other types of cancers. While a known disease-causing variant was identified in 16.4% of all cancer patients tested, we found that 21.4% of CRC patients had such a variant. Among the 44 colorectal polyps cases MLH1, gene was the most affected one (25%), the second and third most affected genes were MSH2 and CHEK2. Other genes with disease-causing variants found in CRC patients included APC, BLM, BMPR1A, BRCA1, FANCM, MSH6, MUTYH, PMS2, SMAD4, SPINK1 and VHL. Conclusion: Our result give an overview of genetic testing of CRC patients, the prevalence of disease-causing variants and their landscape in Estonia. According to Estonian data, only 2.7-6.1% of CRC patients are genetically tested, which is around ten times less frequently than breast cancer patients and their family members. The diagnostic yield of CRC patients is 21.4%, suggesting that genetic testing will likely improve timely diagnosis and outcomes.

Concurrent Pathogenic Variants of BRCA1, MUTYH and CHEK2 in a Hereditary Cancer Family

Concurrent pathogenic variants (PVs) in cancer predisposition genes have been reported in 0.1-2% of hereditary cancer (HC) patients. Determining concurrent PVs is crucial for the diagnosis, treatment, and risk assessment of unaffected family members. Next generation sequencing based diagnostic tests, which are widely used in HCs, enable the evaluation of multiple genes in parallel. We have screened the family members of a patient with bilateral breast cancer who was found to have concurrent PVs in BRCA1 (NM_007294.3;c.5102_5103del, p.Leu1701Glnfs*14) and MUTYH (NM_001128425.1;c.884C>T, p.Pro295Leu). Further analysis revealed concurrent PVs in CHEK2 (NM_007194.4;c.1427C>T, p.Thr476Met) and MUTYH (NM_001128425.1;c.884C>T, p.Pro295Leu) in the maternal uncle of the index case. Eight additional family members were found to have PVs in BRCA1 and MUTYH among 26 tested relatives. The sister and the brother of the index case who were diagnosed with breast and colon cancers, respectively, presented with the same genotype as the index case. Each family member was evaluated individually for clinical care and surveillance. This is the first report describing a family with BRCA1, MUTYH and CHEK2 concurrent PVs. Our findings provide valuable information for the assessment and management considerations for families with concurrent PVs.

Multi-gene panel testing increases germline predisposing mutations’ detection in a cohort of breast/ovarian cancer patients from Southern Italy

Breast cancer is the most common neoplasia in females worldwide, about 10% being hereditary/familial and due to DNA variants in cancer-predisposing genes, such as the highly penetrant BRCA1/BRCA2 genes. However, their variants explain up to 25% of the suspected hereditary/familial cases. The availability of NGS methodologies has prompted research in this field. With the aim to improve the diagnostic sensitivity of molecular testing, a custom designed panel of 44 genes, including also non-coding regions and 5’ and 3’ UTR regions, was set up. Here, are reported the results obtained in a cohort of 64 patients, including also few males, from Southern Italy. All patients had a positive personal and/or familial history for breast and other cancers, but tested negative to routine BRCA analysis. After obtaining their written informed consent, a genomic DNA sample/patient was used to obtain an enriched DNA library, then analyzed by NGS. Sequencing data analysis allowed the identification of pathogenic variants in 12 of tested patients (19%). Interestingly, MUTYH was the most frequently altered gene, followed by RNASEL, ATM, MSH6, MRE11A, and PALB2 genes. The reported resultsreinforce the need for enlarged molecular testing beyond BRCA genes, at least in patients with a personal and familial history, strongly suggestive for a hereditary/familial form. This gives also a hint to pursue more specific precision oncology therapy.

Human Variation in DNA Repair, Immune Function, and Cancer Risk

DNA damage constantly threatens genome integrity, and DNA repair deficiency is associated with increased cancer risk. An intuitive and widely accepted explanation for this relationship is that unrepaired DNA damage leads to carcinogenesis due to the accumulation of mutations in somatic cells. But DNA repair also plays key roles in the function of immune cells, and immunodeficiency is an important risk factor for many cancers. Thus, it is possible that emerging links between inter-individual variation in DNA repair capacity and cancer risk are driven, at least in part, by variation in immune function, but this idea is underexplored. In this review we present an overview of the current understanding of the links between cancer risk and both inter-individual variation in DNA repair capacity and inter-individual variation in immune function. We discuss factors that play a role in both types of variability, including age, lifestyle, and environmental exposures. In conclusion, we propose a research paradigm that incorporates functional studies of both genome integrity and the immune system to predict cancer risk and lay the groundwork for personalized prevention.

Inherited MUTYH mutations cause elevated somatic mutation rates and distinctive mutational signatures in normal human cells

Cellular DNA damage caused by reactive oxygen species is repaired by the base excision repair (BER) pathway which includes the DNA glycosylase MUTYH. Inherited biallelic MUTYH mutations cause predisposition to colorectal adenomas and carcinoma. However, the mechanistic progression from germline MUTYH mutations to MUTYH-Associated Polyposis (MAP) is incompletely understood. Here, we sequence normal tissue DNAs from 10 individuals with MAP. Somatic base substitution mutation rates in intestinal epithelial cells were elevated 2 to 4-fold in all individuals, except for one showing a 31-fold increase, and were also increased in other tissues. The increased mutation burdens were of multiple mutational signatures characterised by C > A changes. Different mutation rates and signatures between individuals are likely due to different MUTYH mutations or additional inherited mutations in other BER pathway genes. The elevated base substitution rate in normal cells likely accounts for the predisposition to neoplasia in MAP. Despite ubiquitously elevated mutation rates, individuals with MAP do not display overt evidence of premature ageing. Thus, accumulation of somatic mutations may not be sufficient to cause the global organismal functional decline of ageing.

Germline Pathogenic Variant Prevalence Among Latin American and US Hispanic Individuals Undergoing Testing for Hereditary Breast and Ovarian Cancer: A Cross-Sectional Study

PURPOSE

To report on pathogenic germline variants detected among individuals undergoing genetic testing for hereditary breast and/or ovarian cancer (HBOC) from Latin America and compare them with self-reported Hispanic individuals from the United States.

METHODS

In this cross-sectional study, unrelated individuals with a personal/family history suggestive of HBOC who received clinician-ordered germline multigene sequencing were grouped according to the location of the ordering physician: group A, Mexico, Central America, and the Caribbean; group B, South America; and group C, United States with individuals who self-reported Hispanic ethnicity. Relatives who underwent cascade testing were analyzed separately.

RESULTS

Among 24,075 unrelated probands across all regions, most were female (94.9%) and reported a personal history suggestive of HBOC (range, 65.0%-80.6%); the mean age at testing was 49.1 ± 13.1 years. The average number of genes analyzed per patient was highest in group A (A 63 ± 28, B 56 ± 29, and C 40 ± 28). Between 9.1% and 18.7% of patients had pathogenic germline variants in HBOC genes (highest yield in group A), with the majority associated with high HBOC risk. Compared with US Hispanics individuals the overall yield was significantly higher in both Latin American regions (A v C P = 1.64×10-9, B v C P < 2.2×10-16). Rates of variants of uncertain significance were similar across all three regions (33.7%-42.6%). Cascade testing uptake was low in all regions (A 6.6%, B 4.5%, and C 1.9%).

CONCLUSION

This study highlights the importance of multigene panel testing in Latin American individuals with newly diagnosed or history of HBOC, who can benefit from medical management changes including targeted therapies, eligibility to clinical trials, risk-reducing surgeries, surveillance and prevention of secondary malignancy, and genetic counseling and subsequent cascade testing of at-risk relatives.

Management of familial adenomatous polyposis and MUTYH-associated polyposis; new insights

Familial adenomatous polyposis (FAP) and MUTYH-associated polyposis (MAP) are rare inherited polyposis syndromes with a high colorectal cancer (CRC) risk. Therefore, frequent endoscopic surveillance including polypectomy of relevant premalignant lesions from a young age is warranted in patients. In FAP and less often in MAP, prophylactic colectomy is indicated followed by lifelong endoscopic surveillance of the retained rectum after (sub)total colectomy and ileal pouch after proctocolectomy to prevent CRC. No consensus is reached on the right type and timing of colectomy. As patients with FAP and MAP nowadays have an almost normal life-expectancy due to adequate treatment of colorectal polyposis, challenges in the management of FAP and MAP have shifted towards the treatment of duodenal and gastric adenomas as well as desmoid treatment in FAP. Whereas up until recently upper gastrointestinal surveillance was mostly diagnostic and patients were referred for surgery once duodenal or gastric polyposis was advanced, nowadays endoscopic treatment of premalignant lesions is widely performed. Aiming to reduce polyp burden in the colorectum as well as in the upper gastrointestinal tract, several chemopreventive agents are currently being studied.

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.

Survey of germline variants in cancer-associated genes in young adults with colorectal cancer

Colorectal cancer (CRC) incidence in young adults is rising. Identifying genetic risk factors is fundamental for the clinical management of patients and their families. This study aimed to identify clinically significant germline variants among young adults with CRC. Whole-exome sequencing data of blood-derived DNA from 133 unrelated young CRC patients (<55 years of age) underwent a comprehensive analysis of 133 cancer-predisposition/implicated genes. All patient tumors were evaluated for mismatch repair deficiency (dMMR). Among 133 patients (aged 16-54 years), 15% (20/133) had clinically actionable pathogenic or likely pathogenic (P/LP) variants in at least 1 well established cancer-predisposing gene: dMMR genes (6), MUTYH [bi-allelic (2), mono-allelic (3)], RNF43 (1), BMPR1A (1), BRCA2 (4), ATM (1), RAD51C (1), and BRIP1 (1). Five patients (4%) had variants in genes implicated in cancer but where the significance of germline variants in CRC risk is uncertain: GATA2 (1), ERCC2 (mono-allelic) (1), ERCC4 (mono-allelic) (1), CFTR (2). Fourteen (11%) had dMMR tumors. Eighteen (14%) reported a first-degree relative with CRC, but only three of these carried P/LP variants. Three patients with variants in polyposis-associated genes showed no polyposis (one each in MUTYH [bi-allelic], RNF43, and BMPR1A). Approximately one in five young adults in our series carried at least one P/LP variant in a cancer-predisposing/implicated gene; 80% of these variants are currently considered clinically actionable in a familial cancer setting. Family history and phenotype have limitations for genetic risk prediction; therefore multigene panel testing and genetic counseling are warranted for all young adults with CRC regardless of those two factors.

Forty-eight-year-old female MUTYH carrier presenting with five concurrent primary cancers

Background

MUTYH‐associated polyposis is a rare disorder resulting from mutations involved in DNA mismatch repair. This results in an increased susceptibility to colonic adenomatosis and other cancers. Studies have examined the resulting frequency of extracolonic manifestations; however, these typically occur alone, concurrently, or temporally separate from an already diagnosed colorectal cancer in individuals with a biallelic mutation.

Case

Reported here is a case of five distinct primary neoplasms presenting simultaneously in a patient monoallelic for an MYH mutation. These neoplasms included squamous cell carcinoma of the vulva, rectal adenocarcinoma, synchronous anal adenocarcinoma, papillary thyroid carcinoma, and ovarian serous psammocarcinoma. Throughout her course, she underwent multiple surgical procedures, neoadjuvant chemoradiation, with further adjuvant therapy, and treatment ongoing. Due to her unique presentation, she underwent genetic testing that demonstrated she was monoallelic for an MYH mutation.

Conclusion

The patient had a positive response to her treatment and surgical procedures with ongoing adjuvant therapy. She will continue to undergo further genetic testing, and testing for her children is being considered. This case demonstrates a unique presentation associated with a monoallelic MYH mutation that is not described in the current literature and warrants further investigation.

Hereditary cancer syndrome-associated pathogenic variants are common in patients with hematologic malignancies subsequent to primary solid cancer

Background: As the number of long-term survivors of solid cancers keeps increasing, risk assessment of secondary hematologic malignancies is important for the prognosis of the patient. Germline genetic predisposition to secondary hematologic malignancy has been studied widely in myeloid neoplasms and rarely in lymphoid neoplasms. This study aimed to profile the mutational spectrums of patients with subsequent lymphoid tissue neoplasm to shed some light on the understudied area. Methods: In total, 39 patients who had primary solid cancer and subsequent hematologic malignancies were enrolled. We performed two next-generation sequencing (NGS) panel tests encompassing hereditary cancer predisposition genes and genes related to clonal hematopoiesis of indeterminate potential (CHIP). All statistical analyses were performed using R 3.5.1. Results: We found 8 of 39 patients with germline mutations in cancer predisposition genes; 4 of 18 patients had therapy-related myeloid neoplasms (22.2%); and 4 of 15 patients had secondary lymphoid malignancies (26.7%). Notably, of 14 patients who initially suffered from thyroid cancer, 5 patients (35.7%) had germline mutations. Malignancy of lymphoid tissue showed no association with radioactive iodine therapy but was observed to a greater extent in germline mutation-positive thyroid cancer patients regardless of their history of treatment. We observed that 24 of 39 patients (61.5%) were CHIP carriers. Patients who had secondary lymphoid malignancy were less likely to have CHIP than those who had myeloid malignancy. Conclusions: In patients with primary solid cancer who are planning to undergo cytotoxic chemotherapy, radiotherapy, or radioactive iodine therapy, an initial assessment with germline mutation testing using an expanded NGS panel, including low, moderate, and high-risk cancer-associated genes, and somatic CHIP mutation testing can screen the patients who are at risk of developing therapy-related myeloid and lymphoid malignancies. Through careful screening and monitoring throughout the treatment process, patients can benefit from the early detection of secondary malignancies and receive proper treatment.

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.

National recommendations of the French Genetics and Cancer Group - Unicancer on the modalities of multi-genes panel analyses in hereditary predispositions to tumors of the digestive tract

In case of suspected hereditary predisposition to digestive cancers, next-generation sequencing can analyze simultaneously several genes associated with an increased risk of developing these tumors. Thus, "Gastro Intestinal" (GI) gene panels are commonly used in French molecular genetic laboratories. Lack of international recommendations led to disparities in the composition of these panels and in the management of patients. To harmonize practices, the Genetics and Cancer Group (GGC)-Unicancer set up a working group who carried out a review of the literature for 31 genes of interest in this context and established a list of genes for which the estimated risks associated with pathogenic variant seemed sufficiently reliable and high for clinical use. Pancreatic cancer susceptibility genes have been excluded. This expertise defined a panel of 14 genes of confirmed clinical interest and relevant for genetic counseling: APC, BMPR1A, CDH1, EPCAM, MLH1, MSH2, MSH6, MUTYH, PMS2, POLD1, POLE, PTEN, SMAD4 and STK11. The reasons for the exclusion of the others 23 genes have been discussed. The paucity of estimates of the associated tumor risks led to the exclusion of genes, in particular CTNNA1, MSH3 and NTHL1, despite their implication in the molecular pathways involved in the pathophysiology of GI cancers. A regular update of the literature is planned to up-grade this panel of genes in case of new data on candidate genes. Genetic and epidemiological studies and international collaborations are needed to better estimate the risks associated with the pathogenic variants of these genes either selected or not in the current panel.

MUTYH: Not just polyposis

MUTYH is a base excision repair enzyme, it plays a crucial role in the correction of DNA errors from guanine oxidation and may be considered a cell protective factor. In humans it is an adenine DNA glycosylase that removes adenine misincorporated in 7,8-dihydro-8-oxoguanine (8-oxoG) pairs, inducing G:C to T:A transversions. MUTYH functionally cooperates with OGG1 that eliminates 8-oxodG derived from excessive reactive oxygen species production. MUTYH mutations have been linked to MUTYH associated polyposis syndrome (MAP), an autosomal recessive disorder characterized by multiple colorectal adenomas. MAP patients show a greatly increased lifetime risk for gastrointestinal cancers. The cancer risk in mono-allelic carriers associated with one MUTYH mutant allele is controversial and it remains to be clarified whether the altered functions of this protein may have a pathophysiological involvement in other diseases besides familial gastrointestinal diseases. This review evaluates the role of MUTYH, focusing on current studies of human neoplastic and non-neoplastic diseases different to colon polyposis and colorectal cancer. This will provide novel insights into the understanding of the molecular basis underlying MUTYH-related pathogenesis. Furthermore, we describe the association between MUTYH single nucleotide polymorphisms (SNPs) and different cancer and non-cancer diseases. We address the utility to increase our knowledge regarding MUTYH in the light of recent advances in the literature with the aim of a better understanding of the potential for identifying new therapeutic targets. Considering the multiple functions and interactions of MUTYH protein, its involvement in pathologies based on oxidative stress damage could be hypothesized. Although the development of extraintestinal cancer in MUTYH heterozygotes is not completely defined, the risk for malignancies of the duodenum, ovary, and bladder is also increased as well as the onset of benign and malignant endocrine tumors. The presence of MUTYH pathogenic variants is an independent predictor of poor prognosis in sporadic gastric cancer and in salivary gland secretory carcinoma, while its inhibition has been shown to reduce the survival of pancreatic ductal adenocarcinoma cells. Furthermore, some MUTYH SNPs have been associated with lung, hepatocellular and cervical cancer risk. An additional role of MUTYH seems to contribute to the prevention of numerous other disorders with an inflammatory/degenerative basis, including neurological and ocular diseases. Finally, it is interesting to note that MUTYH could be a new therapeutic target and future studies will shed light on its specific functions in the prevention of diseases and in the improvement of the chemo-sensitivity of cancer cells.

Validation of a Semiautomated Natural Language Processing-Based Procedure for Meta-Analysis of Cancer Susceptibility Gene Penetrance

PURPOSE

Quantifying the risk of cancer associated with pathogenic mutations in germline cancer susceptibility genes-that is, penetrance-enables the personalization of preventive management strategies. Conducting a meta-analysis is the best way to obtain robust risk estimates. We have previously developed a natural language processing (NLP) -based abstract classifier which classifies abstracts as relevant to penetrance, prevalence of mutations, both, or neither. In this work, we evaluate the performance of this NLP-based procedure.

MATERIALS AND METHODS

We compared the semiautomated NLP-based procedure, which involves automated abstract classification and text mining, followed by human review of identified studies, with the traditional procedure that requires human review of all studies. Ten high-quality gene-cancer penetrance meta-analyses spanning 16 gene-cancer associations were used as the gold standard by which to evaluate the performance of our procedure. For each meta-analysis, we evaluated the number of abstracts that required human review (workload) and the ability to identify the studies that were included by the authors in their quantitative analysis (coverage).

RESULTS

Compared with the traditional procedure, the semiautomated NLP-based procedure led to a lower workload across all 10 meta-analyses, with an overall 84% reduction (2,774 abstracts v 16,941 abstracts) in the amount of human review required. Overall coverage was 93%-we are able to identify 132 of 142 studies-before reviewing references of identified studies. Reasons for the 10 missed studies included blank and poorly written abstracts. After reviewing references, nine of the previously missed studies were identified and coverage improved to 99% (141 of 142 studies).

CONCLUSION

We demonstrated that an NLP-based procedure can significantly reduce the review workload without compromising the ability to identify relevant studies. NLP algorithms have promising potential for reducing human efforts in the literature review process.

[MUTYH-associated polyposis: Review and update of the French recommendations established in 2012 under the auspices of the National Cancer Institute (INCa)]

MUTYH-associated polyposis (MUTYH-associated polyposis, MAP) is an autosomal recessive inheritance disorder related to bi-allelic constitutional pathogenic variants of the MUTYH gene which was first described in 2002. In 2011, a group of French experts composed of clinicians and biologists, performed a summary of the available data on this condition and drew up recommendations concerning the indications and the modalities of molecular analysis of the MUTYH gene in index cases and their relatives, as well as the management of affected individuals. In view of recent developments, some recommendations have become obsolete, in particular with regard to the molecular analysis strategy since MUTYH gene has been recently included in a consensus panel of 14 genes predisposing to colorectal cancer. This led us to revise all the points of the previous expertise. We report here the revised version of this work which successively considers the phenotype and the tumor risks associated with this genotype, the differential diagnoses, the indication criteria and the strategy of the molecular analysis and the recommendations for the management of affected individuals. We also discuss the phenotype and the tumor risks associated with mono-allelic pathogenic variants of MUTYH gene.

Diagnostic yield of a custom-designed multi-gene cancer panel in Irish patients with breast cancer

BACKGROUND

Breast cancer is genetically heterogeneous, and parellel multi-gene sequencing is the most cost- and time-efficient manner to investigate breast cancer predisposition. Numerous multi-gene panels (MGPs) are commercially available, but many include genes with weak/unproven associaton with breast cancer, or with predisposition to cancer of other types. This study investigates the utility of a custom-designed multi-gene panel in an Irish cohort with breast cancer.

METHODS

A custom panel comprising 83 genes offered by 19 clinical "breast cancer predisposition" MGPs was designed and applied to germline DNA from 91 patients with breast cancer and 77 unaffected ethnicially matched controls. Variants were identified and classified using a custom pipeline.

RESULTS

Nineteen loss-of-function (LOF) and 334 missense variants were identified. After removing common and/or benign variants, 15 LOF and 30 missense variants were analysed. Variants in known breast cancer susceptibility genes were identified, including in BRCA1 and ATM in cases, and in NF1 and CHEK2 in controls. Most variants identified were in genes associated with predisposition to cancers other than breast cancer (BRIP1, RAD50, MUTYH, and mismatch repair genes), or in genes with unknown or unproven association with cancer.

CONCLUSION

Using multi-gene panels enables rapid, cost-effective identification of individuals with high-risk cancer predisposition syndromes. However, this approach also leads to an increased amount of uncertain results. Clinical management of individuals with particular genetic variants in the absence of a matching phenotype/family history is challenging. Further population and functional evidence is required to fully elucidate the clinical relevance of variants in genes of uncertain significance.

Implication of DNA repair genes in Lynch-like syndrome

Many colorectal cancers (CRCs) that exhibit microsatellite instability (MSI) are not explained by MLH1 promoter methylation or germline mutations in mismatch repair (MMR) genes, which cause Lynch syndrome (LS). Instead, these Lynch-like syndrome (LLS) patients have somatic mutations in MMR genes. However, many of these patients are young and have relatives with cancer, suggesting a hereditary entity. We performed germline sequence analysis in LLS patients and determined their tumor's mutational profiles using FFPE DNA. Six hundred and fifty-four consecutive CRC patients were screened for suspected LS using MSI and absence of MLH1 methylation. Suspected LS cases were exome sequenced to identify germline and somatic mutations. Single nucleotide variants were used to characterize mutational signatures. We identified 23 suspected LS cases. Germline sequence analysis of 16 available samples identified five cases with LS mutations and 11 cases without LS mutations, LLS. Most LLS tumors had a combination of somatic MMR gene mutation and loss of heterozygosity. LLS patients were relatively young and had excess first-degree relatives with cancer. Four of the 11 LLS patients had rare likely pathogenic variants in genes that maintain genome integrity. Moreover, tumors from this group had a distinct mutational signature compared to tumors from LLS patients lacking germline mutations in these genes. In summary, more than a third of the LLS patients studied had germline mutations in genes that maintain genome integrity and their tumors had a distinct mutational signature. The possibility of hereditary factors in LLS warrants further studies so counseling can be properly informed.

Germline variants in cancer genes in high-risk non-BRCA patients from Puerto Rico

Inherited pathogenic variants in genes that confer moderate to high risk of breast cancer may explain up to 50% of familial breast cancer. This study aimed at identifying inherited pathogenic variants in breast cancer cases from Puerto Rico that were not linked to BRCA1 or BRCA2. Forty-eight breast cancer patients that met the clinical criteria for BRCA testing but had received a negative BRCA1/2 result were recruited. Fifty-three genes previously implicated in hereditary cancer predisposition were captured using the BROCA Agilent cancer risk panel followed by massively parallel sequencing. Missense variants of uncertain clinical significance in CHEK2 were evaluated using an in vitro kinase assays to determine their impact on function. Pathogenic variants were identified in CHEK2, MUTYH, and RAD51B in four breast cancer patients, which represented 8.3% of the cohort. We identified three rare missense variants of uncertain significance in CHEK2 and two variants (p.Pro484Leu and p.Glu239Lys) showed markedly decreased kinase activity in vitro comparable to a known pathogenic variant. Interestingly, the local ancestry at the RAD51B locus in the carrier of p.Arg47* was predicted to be of African origin. In this cohort, 12.5% of the BRCA-negative breast cancer patients were found to carry a known pathogenic variant or a variant affecting protein activity. This study reveals an unmet clinical need of genetic testing that could benefit a significant proportion of at-risk Latinas. It also highlights the complexity of Hispanic populations as pathogenic factors may originate from any of the ancestral populations that make up their genetic backgrounds.

Monoallelic MUTYH carrier status is not associated with increased breast cancer risk in a multigene panel cohort

Whether monoallelic MUTYH mutations increase female breast cancer risk remains controversial. This study aimed to determine if monoallelic MUTYH mutations are associated with increased breast cancer risk in women undergoing multigene panel testing (MGPT). The prevalence of monoallelic MUTYH mutations was compared between Non-Hispanic white female breast cancer cases (n = 30,456) and cancer-free controls (n = 12,289), all of whom underwent MGPT that included MUTYH. We tested breast cancer associations with MUTYH alleles using Fisher's exact test, followed by multivariate logistic regression adjusted for age at testing and MGPT type ordered. Frequencies of the two most common MUTYH founder mutations, p.G396D and p.Y179C, were compared independently between the breast cancer cases and MGPT controls, as well as the healthy UK10K control population (n = 2640). Comparing cases to MGPT controls, no association was observed between female breast cancer and any monoallelic MUTYH carrier status (OR 0.86-1.36, p = 0.21-0.96). Similarly, comparisons to UK10K controls revealed no significant increase in breast cancer risk associated with p.G396D (OR 1.20, p = 0.44) or p.Y179C (OR 1.71, p = 0.24). This study did not find a significant increase in breast cancer risk associated with monoallelic MUTYH mutations.

Multi-Gene Panel Testing of 23,179 Individuals for Hereditary Cancer Risk Identifies Pathogenic Variant Carriers Missed by Current Genetic Testing Guidelines

Recent advancements in next-generation sequencing have greatly expanded the use of multi-gene panel testing for hereditary cancer risk. Although genetic testing helps guide clinical diagnosis and management, testing recommendations are based on personal and family history of cancer and ethnicity, and many carriers are being missed. Herein, we report the results from 23,179 individuals who were referred for 30-gene next-generation sequencing panel testing for hereditary cancer risk, independent of current testing guidelines-38.7% of individuals would not have met National Comprehensive Cancer Network criteria for genetic testing. We identified a total of 2811 pathogenic variants in 2698 individuals for an overall pathogenic frequency of 11.6% (9.1%, excluding common low-penetrance alleles). Among individuals of Ashkenazi Jewish descent, three-quarters of pathogenic variants were outside of the three common BRCA1 and BRCA2 founder alleles. Across all ethnic groups, pathogenic variants in BRCA1 and BRCA2 occurred most frequently, but the contribution of pathogenic variants in other genes on the panel varied. Finally, we found that 21.7% of individuals with pathogenic variants in genes with well-established genetic testing recommendations did not meet corresponding National Comprehensive Cancer Network criteria. Taken together, the results indicate that more individuals are at genetic risk for hereditary cancer than are identified by current testing guidelines and/or use of single-gene or single-site testing.

When you're strange: Unusual features of the MUTYH glycosylase and implications in cancer

MUTYH is a base-excision repair glycosylase that removes adenine opposite 8-oxoguanine (OG). Variants of MUTYH defective in functional activity lead to MUTYH-associated polyposis (MAP), which progresses to cancer with very high penetrance. Whole genome and whole exome sequencing studies have found MUTYH deficiencies in an increasing number of cancer types. While the canonical OG:A repair activity of MUTYH is well characterized and similar to bacterial MutY, here we review more recent evidence that MUTYH has activities independent of OG:A repair and appear centered on the interdomain connector (IDC) region of MUTYH. We summarize evidence that MUTYH is involved in rapid DNA damage response (DDR) signaling, including PARP activation, 9-1-1 and ATR signaling, and SIRT6 activity. MUTYH alters survival and DDR to a wide variety of DNA damaging agents in a time course that is not consistent with the formation of OG:A mispairs. Studies that suggest MUTYH inhibits the repair of alkyl-DNA damage and cyclopyrimidine dimers (CPDs) is reviewed, and evidence of a synthetic lethal interaction with mismatch repair (MMR) is summarized. Based on these studies we suggest that MUTYH has evolved from an OG:A mispair glycosylase to a multifunctional scaffold for DNA damage response signaling.

Contribution of MUTYH Variants to Male Breast Cancer Risk: Results From a Multicenter Study in Italy

Inherited mutations in BRCA1, and, mainly, BRCA2 genes are associated with increased risk of male breast cancer (MBC). Mutations in PALB2 and CHEK2 genes may also increase MBC risk. Overall, these genes are functionally linked to DNA repair pathways, highlighting the central role of genome maintenance in MBC genetic predisposition. MUTYH is a DNA repair gene whose biallelic germline variants cause MUTYH-associated polyposis (MAP) syndrome. Monoallelic MUTYH variants have been reported in families with both colorectal and breast cancer and there is some evidence on increased breast cancer risk in women with monoallelic variants. In this study, we aimed to investigate whether MUTYH germline variants may contribute to MBC susceptibility. To this aim, we screened the entire coding region of MUTYH in 503 BRCA1/2 mutation negative MBC cases by multigene panel analysis. Moreover, we genotyped selected variants, including p.Tyr179Cys, p.Gly396Asp, p.Arg245His, p.Gly264Trpfs^*7, and p.Gln338His, in a total of 560 MBC cases and 1,540 male controls. Biallelic MUTYH pathogenic variants (p.Tyr179Cys/p.Arg241Trp) were identified in one MBC patient with phenotypic manifestation of adenomatous polyposis. Monoallelic pathogenic variants were identified in 14 (2.5%) MBC patients, in particular, p.Tyr179Cys was detected in seven cases, p.Gly396Asp in five cases, p.Arg245His and p.Gly264Trpfs^*7 in one case each. The majority of MBC cases with MUTYH pathogenic variants had family history of cancer including breast, colorectal, and gastric cancers. In the case-control study, an association between the variant p.Tyr179Cys and increased MBC risk emerged by multivariate analysis [odds ratio (OR) = 4.54; 95% confidence interval (CI): 1.17-17.58; p = 0.028]. Overall, our study suggests that MUTYH pathogenic variants may have a role in MBC and, in particular, the p.Tyr179Cys variant may be a low/moderate penetrance risk allele for MBC. Moreover, our results suggest that MBC may be part of the tumor spectrum associated with MAP syndrome, with implication in the clinical management of patients and their relatives. Large-scale collaborative studies are needed to validate these findings.

A Clinical Decision Support Tool to Predict Cancer Risk for Commonly Tested Cancer-Related Germline Mutations

The rapid drop in the cost of DNA sequencing led to the availability of multi-gene panels, which test 25 or more cancer susceptibility genes for a low cost. Clinicians and genetic counselors need a tool to interpret results, understand risk of various cancers, and advise on a management strategy. This is challenging as there are multiple studies regarding each gene, and it is not possible for clinicians and genetic counselors to be aware of all publications, nor to appreciate the relative accuracy and importance of each. Through an extensive literature review, we have identified reliable studies and derived estimates of absolute risk. We have also developed a systematic mechanism and informatics tools for (1) data curation, (2) the evaluation of quality of studies, and (3) the statistical analysis necessary to obtain risk. We produced the risk prediction clinical decision support tool ASK2ME (All Syndromes Known to Man Evaluator). It provides absolute cancer risk predictions for various hereditary cancer susceptibility genes. These predictions are specific to patients' gene carrier status, age, and history of relevant prophylactic surgery. By allowing clinicians to enter patient information and receive patient-specific cancer risks, this tool aims to have a significant impact on the quality of precision cancer prevention and disease management activities relying on panel testing. It is important to note that this tool is dynamic and constantly being updated, and currently, some of its limitations include (1) for many gene-cancer associations risk estimates are based on one study rather than meta-analysis, (2) strong assumptions on prior cancers, (3) lack of uncertainty measures, and (4) risk estimates for a growing set of gene-cancer associations which are not always variant specific. All of these concerns are being addressed on an ongoing basis, aiming to make the tool even more accurate.

Recent progress in Lynch syndrome and other familial colorectal cancer syndromes

The current understanding of familial colorectal cancer was limited to descriptions of affected pedigrees until the early 1990s. A series of landscape-altering discoveries revealed that there were distinct forms of familial cancer, and most were related to genes previously not known to be involved in human disease. This review largely focuses on advances in our understanding of Lynch syndrome because of the unique relationship of this disease to defective DNA mismatch repair and the clinical implications this has for diagnostics, prevention, and therapy. Recent advances have occurred in our understanding of the epidemiology of this disease, and the advent of broad genetic panels has altered the approach to germline and somatic diagnoses for all of the familial colorectal cancer syndromes. Important advances have been made toward a more complete mechanistic understanding of the pathogenesis of neoplasia in the setting of Lynch syndrome, and these advances have important implications for prevention. Finally, paradigm-shifting approaches to treatment of Lynch-syndrome and related tumors have occurred through the development of immune checkpoint therapies for hypermutated cancers. CA Cancer J Clin 2018;68:217-231. © 2018 American Cancer Society.

Microsatellite instability in colorectal cancer

Colorectal cancer (CRC) is a heterogeneous disease that is caused by the interaction of genetic and environmental factors. Although it is one of the most common cancers worldwide, CRC would be one of the most curable cancers if it is detected in the early stages. Molecular changes that occur in colorectal cancer may be categorized into three main groups: 1) Chromosomal Instability (CIN), 2) Microsatellite Instability (MSI), and 3) CpG Island Methylator phenotype (CIMP). Microsatellites, also known as Short Tandem Repeats (STRs) are small (1-6 base pairs) repeating stretches of DNA scattered throughout the entire genome and account for approximately 3 % of the human genome. Due to their repeated structure, microsatellites are prone to high mutation rate. Microsatellite instability (MSI) is a unique molecular alteration and hyper-mutable phenotype, which is the result of a defective DNA mismatch repair (MMR) system, and can be defined as the presence of alternate sized repetitive DNA sequences which are not present in the corresponding germ line DNA. The presence of MSI is found in sporadic colon, gastric, sporadic endometrial and the majority of other cancers. Approximately, 15-20 % of colorectal cancers display MSI. Determination of MSI status in CRC has prognostic and therapeutic implications. As well, detecting MSI is used diagnostically for tumor detection and classification. For these reasons, microsatellite instability analysis is becoming more and more important in colorectal cancer patients. The objective of this review is to provide the comprehensive summary of the update knowledge of colorectal cancer classification and diagnostic features of microsatellite instability.

Characteristics of MUTYH variants in Japanese colorectal polyposis patients

BACKGROUND

The base excision repair gene MUTYH is the causative gene of colorectal polyposis syndrome, which is an autosomal recessive disorder associated with a high risk of colorectal cancer. Since few studies have investigated the genotype-phenotype association in Japanese patients with MUTYH variants, the aim of this study was to clarify the clinicopathological findings in Japanese patients with MUTYH gene variants who were detected by screening causative genes associated with hereditary colorectal polyposis.

METHODS

After obtaining informed consent, genetic testing was performed using target enrichment sequencing of 26 genes, including MUTYH.

RESULTS

Of the 31 Japanese patients with suspected hereditary colorectal polyposis, eight MUTYH variants were detected in five patients. MUTYH hotspot variants known for Caucasians, namely p.G396D and p.Y179D, were not among the detected variants.Of five patients, two with biallelic MUTYH variants were diagnosed with MUTYH-associated polyposis, while two others had monoallelic MUTYH variants. One patient had the p.P18L and p.G25D variants on the same allele; however, supportive data for considering these two variants 'pathogenic' were lacking.

CONCLUSIONS

Two patients with biallelic MUTYH variants and two others with monoallelic MUTYH variants were identified among Japanese colorectal polyposis patients. Hotspot variants of the MUTYH gene for Caucasians were not hotspots for Japanese patients.

Association of monoallelic MUTYH mutation among Egyptian patients with colorectal cancer

Colorectal cancer (CRC) is a heterogeneous triat that involves both environmental and genetic factors. Genetic mutations of MUTYH (p.Y179C and p.G396D) have been reported to be associated with increased risk of CRC among several ethnic populations. The aim of this work is to assess the association of the monoallelic MUTYH mutations (p.Y179C and p.G396D) with increased risk of CRC among Egyptian patients. This study included 120 unrelated CRC Egyptian patients who were compared with 100 healthy controls from the same locality. For all individuals, DNA was genotyped for MUTYH p.Y179C and MUTYH p.G396D mutations using the T-ARMS-PCR technique. The frequencies of monoallelic MUTYH mutations showed a strong association with the increased risk of CRC among Egyptian patients compared with controls (12.5 vs. 4.0 %, OR = 3.49, 95 % CI = 1.12-10.90, P = 0.03). Moreover, the frequency of MUTYH p.Y179C mutation was noted to be significantly higher among CRC patients compared to controls rather than MUTYH p.G396D mutation. Interestingly, CRC patients with tumors in the right side colon showed an evidence for association with the MUTYH p.Y179C mutation compared with tumors in the left side colon (p = 0.01). MUTYH p.Y179C mutation was associated with an increased risk of CRC among Egyptian patients rather than MUTYH p.G396D mutation.

BERing the burden of damage: Pathway crosstalk and posttranslational modification of base excision repair proteins regulate DNA damage management

DNA base damage and non-coding apurinic/apyrimidinic (AP) sites are ubiquitous types of damage that must be efficiently repaired to prevent mutations. These damages can occur in both the nuclear and mitochondrial genomes. Base excision repair (BER) is the frontline pathway for identifying and excising damaged DNA bases in both of these cellular compartments. Recent advances demonstrate that BER does not operate as an isolated pathway but rather dynamically interacts with components of other DNA repair pathways to modulate and coordinate BER functions. We define the coordination and interaction between DNA repair pathways as pathway crosstalk. Numerous BER proteins are modified and regulated by post-translational modifications (PTMs), and PTMs could influence pathway crosstalk. Here, we present recent advances on BER/DNA repair pathway crosstalk describing specific examples and also highlight regulation of BER components through PTMs. We have organized and reported functional interactions and documented PTMs for BER proteins into a consolidated summary table. We further propose the concept of DNA repair hubs that coordinate DNA repair pathway crosstalk to identify central protein targets that could play a role in designing future drug targets.

Numtogenesis as a mechanism for development of cancer

Transfer of genetic material from cytoplasmic organelles to the nucleus, an ongoing process, has implications in evolution, aging, and human pathologies such as cancer. The transferred mitochondrial DNA (mtDNA) fragments in the nuclear genome are called nuclear mtDNA or NUMTs. We have named the process numtogenesis, defining the term as the transfer of mtDNA into the nuclear genome, or, less specifically, the transfer of mitochondria or mitochondrial components into the nucleus. There is increasing evidence of the involvement of NUMTs in human biology and pathology. Although information pertaining to NUMTs and numtogenesis is sparse, the role of this aspect of mitochondrial biology to human cancers is apparent. In this review, we present available knowledge about the origin and mechanisms of numtogenesis, with special emphasis on the role of NUMTs in human malignancies. We describe studies undertaken in our laboratory and in others and discuss the influence of NUMTs in tumor initiation and progression and in survival of cancer patients. We describe suppressors of numtogenesis and evolutionary conserved mechanisms underlying numtogenesis in cancer. An understanding the emerging field of numtogenesis should allow comprehension of this process in various malignancies and other diseases and, more generally, in human health.

Colorectal Adenomatous Polyposis: Heterogeneity of Susceptibility Gene Mutations and Phenotypes in a Cohort of Italian Patients

AIMS

Colorectal adenomatous polyposis entailing cancer predisposition is caused by constitutional mutations in different genes. APC is associated with the familial adenomatous polyposis (FAP/AFAP) and MUTYH with the MUTYH-associated polyposis (MAP), while POLE and POLD1 mutations cause the polymerase proofreading-associated polyposis (PPAP).

METHODS

We screened for mutations in patients with multiple adenomas/FAP: 121 patients were analyzed for APC and MUTYH mutations, and 36 patients were also evaluated for POLE and POLD1 gene mutations.

RESULTS

We found 20 FAP/AFAP, 15 MAP, and no PPAP subjects: pathogenic mutations proved to be heterogeneous, and included 5 APC and 1 MUTYH novel mutations. The mutation detection rate was significantly different between patients with 5-100 polyps and those with >100 polyps (p = 8.154 × 10^-7), with APC mutations being associated with an aggressive phenotype (p = 1.279 × 10^-9). Mean age at diagnosis was lower in FAP/AFAP compared to MAP (p = 3.055 × 10^-4). Mutation-negative probands showed a mean age at diagnosis that was significantly higher than FAP/AFAP (p = 3.46986 × 10^-7) and included 45.3% of patients with <30 polyps and 70.9% of patients with no family history.

CONCLUSIONS

This study enlarges the APC and MUTYH mutational spectra, and also evaluated variants of uncertain significance, including the MUTYH p.Gln338His mutation. Moreover this study underscores the phenotypic heterogeneity and genotype-phenotype correlations in a cohort of Italian patients.

Risk of extracolonic cancers for people with biallelic and monoallelic mutations in MUTYH

Germline mutations in the DNA base excision repair gene MUTYH are known to increase a carrier's risk of colorectal cancer. However, the risks of other (extracolonic) cancers for MUTYH mutation carriers are not well defined. We identified 266 probands (91% Caucasians) with a MUTYH mutation (41 biallelic and 225 monoallelic) from the Colon Cancer Family Registry. Mutation status, sex, age and histories of cancer from their 1,903 first- and 3,255 second-degree relatives were analyzed using modified segregation analysis conditioned on the ascertainment criteria. Compared with incidences for the general population, hazard ratios (HRs) (95% confidence intervals [CIs]) for biallelic MUTYH mutation carriers were: urinary bladder cancer 19 (3.7-97) and ovarian cancer 17 (2.4-115). The HRs (95% CI) for monoallelic MUTYH mutation carriers were: gastric cancer 9.3 (6.7-13); hepatobiliary cancer 4.5 (2.7-7.5); endometrial cancer 2.1 (1.1-3.9) and breast cancer 1.4 (1.0-2.0). There was no evidence for an increased risk of cancers at the other sites examined (brain, pancreas, kidney or prostate). Based on the USA population incidences, the estimated cumulative risks (95% CI) to age 70 years for biallelic mutation carriers were: bladder cancer 25% (5-77%) for males and 8% (2-33%) for females and ovarian cancer 14% (2-65%). The cumulative risks (95% CI) for monoallelic mutation carriers were: gastric cancer 5% (4-7%) for males and 2.3% (1.7-3.3%) for females; hepatobiliary cancer 3% (2-5%) for males and 1.4% (0.8-2.3%) for females; endometrial cancer 3% (2%-6%) and breast cancer 11% (8-16%). These unbiased estimates of both relative and absolute risks of extracolonic cancers for people, mostly Caucasians, with MUTYH mutations will be important for their clinical management.

Increased risk for colorectal adenomas and cancer in mono-allelic MUTYH mutation carriers: results from a cohort of North-African Jews

Bi-allelic MUTYH gene mutations are associated with a clinical phenotype of multiple colorectal adenomas and an increased risk for colorectal cancer (CRC). It is unclear whether mono-allelic MUTYH gene carriers (heterozygotes) are also at increased risk for even few adenomas or cancer. In order to clarify an association between MUTYH heterozygotes and adenomas, we evaluated the frequency and types of MUTYH mutations and variants in 72 North-African Jews having few (≥3) colorectal adenomas with or without early onset (<50 years) CRC compared to 29 healthy controls. Germ-line DNA was analyzed for a panel of 6 MUTYH mutations and variants, and Sanger sequencing of the entire MUTYH gene was performed for mono-allelic MUTYH mutation carriers. APC gene mutations and Lynch syndrome were excluded in the relevant cases according to accepted clinical criteria. Twenty-two of the 72 adenoma subjects (30.5%) had MUTYH mutations or variants. Nine were homozygotes or compound heterozygotes: all had >10 adenomas and one had CRC. Thirteen others were mono-allelic carriers (heterozygotes) of a single MUTYH mutation: six had more than ten adenomas and seven had less than ten adenomas; of these 13 mono-allelic carriers, six had a neoplasm: three CRCs and three extra-intestinal tumors. Eleven of the thirteen mono-allelic carriers with adenomas had a family history of cancer in first or second degree relatives. A multivariable model showed positive correlation between G396D, Y179C and 1186 ins GG mutations and number of adenomas (OR 8.6, 10.2 and 14.4, respectively). The Q324H variant was negatively associated with the number of adenomatous polyps (OR -5.23). In conclusion, MUTYH mutations are prevalent among Jews of North-African origin with colorectal adenomas with or without early onset CRC. Mono-allelic MUTYH carriers with a family history of cancer had a clinical phenotype that varied from having only few adenomas to multiple (>10) adenomas. These findings support MUTYH testing in patients with even few adenomas and suggest the consideration of increased surveillance in mono-allelic carriers with a family history of cancer.

Using Genetics to Identify Hereditary Colorectal Polyposis and Cancer Syndromes in Your Patient

The majority of patients with colorectal polyps and cancer do not have a Mendelian cause of the disease. Age, lifestyle, and environmental factors interact with complex genetic traits to contribute to the etiology. However, approximately 5-10 % of patients with colorectal cancer (CRC) and more than 40 % of patients meeting specific clinical features of the hereditary polyposis syndromes have a discoverable, actionable genetic cause which will significantly alter their medical management.

Clinical and molecular features of young-onset colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer related mortality worldwide. Although young-onset CRC raises the possibility of a hereditary component, hereditary CRC syndromes only explain a minority of young-onset CRC cases. There is evidence to suggest that young-onset CRC have a different molecular profile than late-onset CRC. While the pathogenesis of young-onset CRC is well characterized in individuals with an inherited CRC syndrome, knowledge regarding the molecular features of sporadic young-onset CRC is limited. Understanding the molecular mechanisms of young-onset CRC can help us tailor specific screening and management strategies. While the incidence of late-onset CRC has been decreasing, mainly attributed to an increase in CRC screening, the incidence of young-onset CRC is increasing. Differences in the molecular biology of these tumors and low suspicion of CRC in young symptomatic individuals, may be possible explanations. Currently there is no evidence that supports that screening of average risk individuals less than 50 years of age will translate into early detection or increased survival. However, increasing understanding of the underlying molecular mechanisms of young-onset CRC could help us tailor specific screening and management strategies. The purpose of this review is to evaluate the current knowledge about young-onset CRC, its clinicopathologic features, and the newly recognized molecular alterations involved in tumor progression.

Efficiency of Base Excision Repair of Oxidative DNA Damage and Its Impact on the Risk of Colorectal Cancer in the Polish Population

DNA oxidative lesions are widely considered as a potential risk factor for colorectal cancer development. The aim of this work was to determine the role of the efficiency of base excision repair, both in lymphocytes and in epithelial tissue, in patients with CRC and healthy subjects. SNPs were identified within genes responsible for steps following glycosylase action in BER, and patients and healthy subjects were genotyped. A radioisotopic BER assay was used for assessing repair efficiency and TaqMan for genotyping. Decreased BER activity was observed in lymphocyte extract from CRC patients and in cancer tissue extract, compared to healthy subjects. In addition, polymorphisms of EXO1, LIG3, and PolB may modulate the risk of colorectal cancer by decreasing (PolB) or increasing (LIG3 and EXO1) the chance of malignant transformation.

Genetics and Genetic Testing in Hereditary Colorectal Cancer

Colorectal cancer (CRC) remains the third most common cancer affecting men and women in the United States. Approximately one-third of CRCs are diagnosed in individuals who have family members also affected with the disease. Although the vast majority of colorectal neoplasms develop as a consequence of somatic genomic alterations arising in individual cells, approximately 5% of all CRCs arise in the setting of germline mutations in genes involved in key cellular processes. To date, multiple genes have been implicated in single-gene hereditary cancer syndromes, many of which are associated with increased risk for CRC, as well as other tumor types. This review outlines the clinical, pathologic, and genetic features of the hereditary cancer syndromes known to be associated with increased risk for CRC and delineates strategies for implementing genetic risk assessments in clinical settings.

Management of Patients with Hereditary Colorectal Cancer Syndromes

Colorectal cancer (CRC) is one of the most important causes of death in the world. Hereditary CRC is found in 5–10% of CRC patients. In this review, we will focus on the major forms of hereditary CRC and their management according to the most recent literature available.

Colonic polyposis syndromes--an experience from a tertiary centre in South India

BACKGROUND

Several polyposis syndromes of the gastrointestinal tract have been recognized which carry increased risk for cancer and have a genetic predisposition. There is a paucity of literature regarding the occurrence and the burden of colonic polyposis syndromes in the Indian subcontinent. This study attempts to highlight this hitherto unaddressed burden and the associated increased risk for inherited colonic cancer in this geographical location.

METHODS

A retrospective study of various colonic polyposis syndromes encountered at a tertiary centre in South India over a period of 8 years (2005 to 2012) was performed. The diagnosis in each case was made histologically with clinicopathological correlation.

RESULTS

Fifty cases were identified as belonging to a colonic polyposis syndrome, during the study period. There were 27 males and 23 females with a median age of 36.5 years (range 19 months to 78 years). The commonest syndrome was familial adenomatous polyposis (n = 27; 54 %) followed by Peutz-Jeghers syndrome (n = 11), attenuated familial adenomatous polyposis (n = 7), juvenile polyposis syndrome (n = 3), hyperplasic polyposis syndrome (n = 1) and Cronkhite-Canada syndrome (n = 1). Colonic malignancy was documented at first presentation in 22 patients (44 %).

CONCLUSIONS

Our study highlights the various colonic polyposis syndromes encountered in a tertiary care institution in Southern India.