Increased MUTYH mutation frequency among Dutch families with breast cancer and colorectal cancer

Four pathogenic variants co-occurring in a MINAS early-onset breast cancer

INTRODUCTION

Multilocus Inherited Neoplasia Allele Syndrome (MINAS) is a condition defined by the presence of germline pathogenic variants in more than one Cancer Susceptibility Gene (CSG). MINAS is still underreported in the literature and public databases. Since MINAS-related phenotypes are difficult to predict, case descriptions may contribute to risk assessment, treatment, and personalized surveillance for proband and relatives.

CASE DESCRIPTION

Here we report a unique case of early onset, bifocal, non-Triple Negative breast cancer in a 31-year-old woman. Fast metastatic dissemination involving the brain caused the death of the patient in a few months. Her multigene panel testing showed the co-occurrence of pathogenic variants in PALB2 (c.1221del; p.Thr408fs*40), ATM (c.8545C>T; p.Arg2849*), PMS2 (c.1919C>A; p.Ser640*), and MUTYH (c.1103G>A; p.Gly368Asp). The patient inherited the ATM and MUTYH variants from the mother, and PALB2 and PMS2 variants from the father. The brother inherited the maternal ATM and paternal PMS2 variants. A baseline imaging-based family screening excluded malignancies in both parents and in the brother. Tailored monitoring is ongoing based on the risk predicted by pathogenic variants identified in family members.

CONCLUSIONS

Currently, there are no predictive tools available to determine organ-specific cancer risk in MINAS patients. Given the uncertainty in predicting the phenotypic effect of multiple variants in CSGs, ongoing clinical surveillance and sharing data from complex cases are crucial for improving risk stratification in this condition.

A comprehensive characterization of the spectrum of MUTYH germline pathogenic variants in Latin America

MUTYH-Associated Polyposis (MAP) is caused by biallelic pathogenic germline variants in the MUTYH gene. However, individuals harboring monoallelic MUTYH pathogenic variants in the presence of a positive family history have been reported to have a twofold increased risk of colorectal cancer (CRC) and extra colonic cancers. Our aim was to characterize the spectrum of monoallelic and biallelic germline MUTYH pathogenic variants in Latin American patients and to describe their clinical and genetic characteristics. Patients were identified from eight high-risk genetic cancer centers of five Latin American countries. Statistical analysis was performed using the two-sided P test using the Vassarstats statistical tools. Statistical significance was set at a p value ≤ 0.05. Of the 105 unrelated patients with cancer or colorectal polyposis, 84.8% and 15.2% carried pathogenic monoallelic and biallelic MUTYH variants, respectively. The most common pathogenic variants were p.Gly396Asp and p.Tyr179Cys (55% and 23%, respectively). The mean age at first diagnosis was 48.29 years (range 31-71) and 49.90 years (range 27-87) in biallelic and monoallelic MUTYH patients, respectively. CRC was the only cancer diagnosed in patients with biallelic MUTYH pathogenic variants (75%), while breast cancer (46.1%) was more common than CRC (24.7%) in individuals with monoallelic MUTYH pathogenic variants. We reported a high frequency of European founder variants in our diverse population. Some phenotypic differences from current studies were identified, such as a higher breast cancer burden in monoallelic carriers and a complete absence of extra-colon tumors in biallelic patients.

Novel Pathogenic Variants in Hereditary Cancer Syndromes in a Highly Heterogeneous Cohort of Patients: Insights from Multigene Analysis

Cancer is a major global public health challenge, affecting both quality of life and mortality. Recent advances in genetic research have uncovered hereditary cancer syndromes (HCS) that predispose individuals to malignant neoplasms. While traditional single-gene testing has focused on high-penetrance genes, the past decade has seen a shift toward multigene panels, which facilitate the analysis of multiple genes associated with specific HCS. This approach reveals variants in less-studied gene regions and improves our understanding of cancer predisposition. In a study composed of Russian patients with clinical signs of HCS, we used a multigene hereditary cancer panel and revealed 21.6% individuals with pathogenic or likely pathogenic genetic variants. BRCA1/BRCA2 mutations predominated, followed by the CHEK2 and ATM variants. Of note, 16 previously undescribed variants were identified in the MUTYH, GALNT12, MSH2, MLH1, MLH3, EPCAM, and POLE genes. The implications of the study extend to personalized cancer prevention and treatment strategies, especially in populations lacking extensive epidemiological data, such as Russia. Overall, our research provides valuable genetic insights that give the way for further investigation and advances in the understanding and management of hereditary cancer syndromes.

Investigation of germline variants in Bahraini women with breast cancer using next-generation sequencing based-multigene panel

Germline variants in BRCA1 and BRCA2 (BRCA1/2) genes are the most common cause of hereditary breast cancer. However, a significant number of cases are not linked to these two genes and additional high-, moderate- and low-penetrance genes have been identified in breast cancer. The advent of next-generation sequencing (NGS) allowed simultaneous sequencing of multiple cancer-susceptibility genes and prompted research in this field. So far, cancer-predisposition genes other than BRCA1/2 have not been studied in the population of Bahrain. We performed a targeted NGS using a multi-panel covering 180 genes associated with cancer predisposition to investigate the spectrum and frequency of germline variants in 54 women with a positive personal and/or family history of breast cancer. Sequencing analysis revealed germline variants in 29 (53.7%) patients. Five pathogenic/likely pathogenic variants in four DNA repair pathway-related genes were identified in five unrelated patients (9.3%). Two BRCA1 variants, namely the missense variant c.287A>G (p.Asp96Gly) and the truncating variant c.1066C>T (p.Gln356Ter), were detected in two patients (3.7%). Three variants in non-BRCA1/2 genes were detected in three patients (1.85% each) with a strong family history of breast cancer. These included a monoallelic missense variant c.1187G>A (p.Gly396Asp) in MUTYH gene, and two truncating variants namely c.3343C>T (p.Arg1115Ter) in MLH3 gene and c.1826G>A (p.Trp609Ter) in PMS1 gene. Other variants of uncertain significance (VUS) were also detected, and some of them were found together with the deleterious variants. In this first application of NGS-based multigene testing in Bahraini women with breast cancer, we show that multigene testing can yield additional genomic information on low-penetrance genes, although the clinical significance of these genes has not been fully appreciated yet. Our findings also provide valuable epidemiological information for future studies and highlight the importance of genetic testing, and an NGS-based multigene analysis may be applied supplementary to traditional genetic counseling.

Hereditary Breast Cancer in Romania-Molecular Particularities and Genetic Counseling Challenges in an Eastern European Country

In Romania, breast cancer (BC) is the most common malignancy in women. However, there is limited data on the prevalence of predisposing germline mutations in the population in the era of precision medicine, where molecular testing has become an indispensable tool in cancer diagnosis, prognosis, and therapeutics. Therefore, we conducted a retrospective study to determine the prevalence, mutational spectrum, and histopathological prediction factors for hereditary breast cancer (HBC) in Romania. A cohort of 411 women diagnosed with BC selected upon NCCN v.1.2020 guidelines underwent an 84-gene NGS-based panel testing for breast cancer risk assessment during 2018-2022 in the Department of Oncogenetics of the Oncological Institute of Cluj-Napoca, Romania. A total of 135 (33%) patients presented pathogenic mutations in 19 genes. The prevalence of genetic variants was determined, and demographic and clinicopathological characteristics were analyzed. We observed differences among BRCA and non-BRCA carriers regarding family history of cancer, age of onset, and histopathological subtypes. Triple-negative (TN) tumors were more often BRCA1 positive, unlike BRCA2 positive tumors, which were more often the Luminal B subtype. The most frequent non-BRCA mutations were found in CHEK2, ATM, and PALB2, and several recurrent variants were identified for each gene. Unlike other European countries, germline testing for HBC is still limited due to the high costs and is not covered by the National Health System (NSH), thus leading to significant discrepancies related to the screening and prophylaxis of cancer.

The Unique Spectrum of MUTYH Germline Mutations in Colombian Patients with Extracolonic Carcinomas

Background

Protein MUTYH, encoded by the gene MUTYH, is an important mismatch repair enzyme in the base-excision repair pathway of DNA repair. When genetically altered, different neoplastic conditions can arise. One of the widely known syndromes associated with MUTYH mutations is MUTYH-associated polyposis, a form of familial colorectal cancer syndrome. MUTYH may also be a driver in other familial cancer syndromes, as well as breast cancer and spontaneous cancer cases. However, some controversies about the role of these alterations in oncogenesis remain, especially when affected in a heterozygous way. Most available data on MUTYH mutations are on Caucasian patients.

Material and Methods

We analyzed a small cohort of non-Caucasian, Colombian cancer patients with MUTYH germline heterozygous mutations, clinical features suggestive of familial cancer, and extensive genetic studies with no other mutations and without MUTYH-associated polyposis.

Conclusion

With this case series, we intended to provide important data for the understanding of MUTYH as a possible driver of familial cancer, even when only heterozygous mutations are found.

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.

Monoallelic MUTYH pathogenic variants ascertained via multi-gene hereditary cancer panels are not associated with colorectal, endometrial, or breast cancer

We aimed to determine whether monoallelic MUTYH pathogenic and likely pathogenic variants (PVs) are associated with colorectal, breast, and endometrial cancer. Cases were individuals with colorectal, female breast, or endometrial cancer who reported European ancestry alone and underwent a multi-gene hereditary cancer panel at a large reference laboratory. Controls were individuals of European (non-Finnish) descent from GnomAD with cancer cohorts removed. We performed a Fisher's exact test to generate odds ratios (ORs) with 95% confidence intervals (CI). Prevalence of single MUTYH PVs in cancer cohorts versus controls, respectively, was: colorectal cancer, 2.1% vs. 1.8% (OR 1.2, 95% CI 0.99-1.5, p = 0.064); breast cancer 1.9% vs. 1.7% (OR 1.1, 95% CI 0.96-1.3, p = 0.15); and endometrial cancer, 1.7% vs. 1.7% (OR 0.98; 95% CI 0.70-1.3, p = 0.94). Using the largest colorectal and endometrial cancer cohorts and one of the largest breast cancer cohorts from a single case-control study, we did not observe a significant difference in the prevalence of monoallelic MUTYH PVs in these cohorts compared to controls. Additionally, frequencies among cancer cohorts were consistent with the published MUTYH carrier frequency of 1-2%. These findings suggest there is no association between colorectal, endometrial, or breast cancer and MUTYH heterozygosity in individuals of European ancestry.

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.

Multi-Gene Mutation Profiling by Targeted Next-Generation Sequencing in Premenopausal Breast Cancer

Breast cancer has distinct etiology, prognoses, and clinical outcomes at premenopausal ages. Determination of the frequency of germline and somatic mutations will refine our understanding of the genetic contribution to premenopausal breast cancer susceptibility. We applied a comprehensive next generation sequencing-based approach to analyze blood and/or tissue samples of 54 premenopausal breast cancer patients treated in our clinic. Genetic testing results were descriptively analyzed in correlation with clinicopathological data. In the present study, 42.5% of premenopausal breast cancer patients tested carried pathogenic mutations in cancer predisposition genes (CHEK2, BRCA1, TP53, and MUTYH). Germline variants of unknown/uncertain significance (VUSs) in eight different cancer susceptibility genes, namely BRCA1, BRCA2, CHEK2, RAD51C, RAD51D, ATM, BRIP1, and PMS2, were also identified in 14 premenopausal patients (35%). Of the breast tumors tested, 61.8% harbored pathogenic somatic variants in tumor suppressor genes (TP53, NF1, RB), genes involved in DNA repair (BRCA1, BRCA2, ATM, RAD50), cell proliferation (PTEN, PIK3C FGFR3, AKT1, ROS1, ERBB2, NOTCH1), and cell adhesion (CTNNB1). This descriptive study employs the powerful NGS technology to highlight the high frequency of premenopausal cases attributable to genetic predisposition. Mutation identification in a larger cohort may further ensure that these patients receive tailored treatment according to their menopausal status.

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.

Genetic Variants and Tumor Immune Microenvironment: Clues for Targeted Therapies in Inflammatory Breast Cancer (IBC)

To better understand the etiology of inflammatory breast cancer (IBC) and identify potential therapies, we studied genomic alterations in IBC patients. Targeted, next-generation sequencing (NGS) was performed on cell-free DNA (cfDNA) (n = 33) and paired DNA from tumor tissues (n = 29) from 32 IBC patients. We confirmed complementarity between cfDNA and tumor tissue genetic profiles. We found a high incidence of germline variants in IBC patients that could be associated with an increased risk of developing the disease. Furthermore, 31% of IBC patients showed deficiencies in the homologous recombination repair (HRR) pathway (BRCA1, BRCA2, PALB2, RAD51C, ATM, BARD1) making them sensitive to poly (ADP-ribose) polymerase (PARP) inhibitors. We also characterized the tumor-infiltrating lymphocytes (TILs) in tumor tissue biopsies by studying several markers (CD4, CD8, FoxP3, CD20, PD-1, and PD-L1) through immunohistochemistry (IHC) staining. In 7 of 24 (29%) patients, tumor biopsies were positive for PD-L1 and PD-1 expression on TILs, making them sensitive to PD-1/PD-L1 blocking therapies. Our results provide a rationale for considering PARP inhibitors and PD-1/PDL1 blocking immunotherapy in qualifying IBC patients.

Impact of deleterious variants in other genes beyond BRCA1/2 detected in breast/ovarian and pancreatic cancer patients by NGS-based multi-gene panel testing: looking over the hedge

BACKGROUND

Hereditary breast cancer (BC), ovarian cancer (OC), and pancreatic cancer (PC) are the major BRCA-associated tumours. However, some BRCA1/2-wild-type (wt) patients with a strong personal and/or family history of cancer need a further genetic testing through a multi-gene panel containing other high- and moderate-risk susceptibility genes.

PATIENTS AND METHODS

Our study was aimed to assess if some BC, OC, or PC patients should be offered multi-gene panel testing, based on well-defined criteria concerning their personal and/or family history of cancer, such as earliness of cancer onset, occurrence of multiple tumours, or presence of at least two or more affected first-degree relatives. For this purpose, 205 out of 915 BC, OC, or PC patients, resulted negative for BRCA1/2 and with significant personal and/or family history of cancer, were genetically tested for germline pathogenic or likely pathogenic variants (PVs/LPVs) in genes different from BRCA1/2.

RESULTS

Our investigation revealed that 31 (15.1%) out of 205 patients harboured germline PVs/LPVs in no-BRCA genes, including PALB2, CHEK2, ATM, MUTYH, MSH2, and RAD51C. Interestingly, in the absence of an analysis conducted through multi-gene panel, a considerable percentage (15.1%) of PVs/LPVs would have been lost.

CONCLUSIONS

Providing a multi-gene panel testing to BRCA1/2-wt BC/OC/PC patients with a strong personal and/or family history of cancer could significantly increase the detection rates of germline PVs/LPVs in other cancer predisposition genes beyond BRCA1/2. The use of a multi-gene panel testing could improve the inherited cancer risk estimation and clinical management of patients and unaffected family members.

Heritable Susceptibility to Breast Cancer among African-American Women in the Detroit Research on Cancer Survivors Study

BACKGROUND

African-American women have high rates of breast cancer associated with hereditary features. However, no studies have reported the prevalence of inherited variation across all genes known to be breast cancer risk factors among African-American patients with breast cancer not selected for high-risk characteristics.

METHODS

We evaluated 182 African-American women diagnosed with invasive breast cancer in metropolitan Detroit via targeted capture and multiplex sequencing of 13 well-established breast cancer risk genes and five suggested breast cancer risk genes.

RESULTS

We identified 24 pathogenic variants in 23 women [12.6%; 95% confidence interval (CI), 8.2%-18.4%] and five genes (BRCA2, BRCA1, ATM, RAD50, CDH1). BRCA1 and BRCA2 accounted for 58.3% of all pathogenic variants. An additional six pathogenic variants were found in suggested breast cancer risk genes (MSH6, MUTYH, NF1, BRIP1).

CONCLUSIONS

The prevalence of germline pathogenic variants is relatively high among African-American patients with breast cancer unselected for high-risk characteristics across a broad spectrum of genes.

IMPACT

This study helps to define the genomic landscape of breast cancer susceptibility in African-American women who could benefit from enhanced surveillance and screening.

Multiple cancer susceptible genes sequencing in BRCA-negative breast cancer with high hereditary risk

Background

Hereditary factors contributed to breast cancer susceptibility. Low BRCA mutation prevalence was demonstrated in previous BRCA mutation screening in Chinese breast cancer patients. Multiple-gene sequencing may assist in discovering detrimental germline mutation in

BRCA

negative breast cancers.

Methods

A total of 384 Chinese subjects with any two of high-risk factors were recruited and screened by next-generation sequencing (NGS) for 30 cancer susceptible genes. Variants with a truncating, initiation codon or splice donor/acceptor effect, or with pathogenicity demonstrated in published literature were classified into pathogenic/likely-pathogenic mutations.

Results

In total, we acquired 39 (10.2%) patients with pathogenic/likely-pathogenic germline mutations, including one carrying two distinct mutations. Major mutant non-BRCA genes were MUTYH (n=11, 2.9%), PTCH1 (n=7, 1.8%), RET (n=6, 1.6%) and PALB2 (n=5, 1.3%). Other mutant genes included TP53 (n=3, 0.8%), RAD51D (n=2, 0.5%), CHEK2 (n=1, 0.3%), BRIP1 (n=1, 0.3%), CDH1 (n=1, 0.3%), MRE11 (n=1, 0.3%), RAD50 (n=1, 0.3%) and PALLD (n=1, 0.3%). A splicing germline mutation, MUTYH c.934-2A>G, was a hotspot (9/384, 2.3%) in Chinese breast cancer.

Conclusions

Among BRCA-negative breast cancer patients with high hereditary risk in China, 10.2% carried mutations in cancer associated susceptibility genes. MUTYH and PTCH1 had relatively high mutation rates (2.9% and 1.8%). Multigene testing contributes to understand genetic background of BRCA-negative breast cancer patients with high hereditary risk.

Exon splicing analysis of intronic variants in multigene cancer panel testing for hereditary breast/ovarian cancer

The use of multigene panel testing for patients with a predisposition to breast/ovarian cancer is increasing as the identification of variants is useful for diagnosis and disease management. We identified pathogenic and likely pathogenic (P/LP) variants of high-and moderate-risk genes using a 23-gene germline cancer panel in 518 patients with hereditary breast and ovarian cancers (HBOC). The frequency of P/LP variants was 12.4% (64/518) for high- and moderate-penetrant genes, namely, BRCA2 (5.6%), BRCA1 (3.3%), CHEK2 (1.2%), MUTYH (0.8%), PALB2 (0.8%), MLH1 (0.4%), ATM (0.4%), BRIP1 (0.4%), TP53 (0.2%), and PMS2 (0.2%). Five patients possessed two P/LP variants in BRCA1/2 and other genes. We also compared the results from in silico splicing predictive tools and exon splicing patterns from patient samples by analyzing RT-PCR product sequences in six P/LP intronic variants and two intronic variants of unknown significance (VUS). Altered transcriptional fragments were detected for P/LP intronic variants in BRCA1, BRIP1, CHEK2, PARB2, and PMS2. Notably, we identified an in-frame deletion of the BRCA1 C-terminal (BRCT) domain by exon skipping in BRCA1 c.5152+6T>C-as known VUS-indicating a risk for HBOC. Thus, exon splicing analysis can improve the identification of veiled intronic variants that would aid decision making and determination of hereditary cancer risk.

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.

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.

Germline investigation in male breast cancer of DNA repair genes by next-generation sequencing

PURPOSE

In order to better define the breast cancer (BC) genetic risk factors in men, a germline investigation was carried out on 81 Male BC cases by screening the 24 genes involved in BC predisposition, genome stability maintenance and DNA repair mechanisms by next-generation sequencing.

METHODS

Germline DNAs were tested in a custom multi-gene panel focused on all coding exons and exon-intron boundaries of 24 selected genes using two amplicon-based assays on PGM-Ion Torrent (ThermoFisher Scientific) and MiSeq (Illumina) platforms. All variants were recorded and classified by using a custom pipeline.

RESULTS

Clinical pathological data and the family history of 81 Male BC cases were gathered and analysed, revealing the average age of onset to be 61.3 years old and that in 35 cases there was a family history of BC. Our genetic screening allowed us to identify a germline mutation in 22 patients (23%) in 4 genes: BRCA2, BRIP1, MUTYH and PMS2. Moreover, 12 variants of unknown clinical significance (VUS) in 9 genes (BARD1, BRCA1, BRIP1, CHEK2, ERCC1, NBN, PALB2, PMS1, RAD50) were predicted as potentially pathogenic by in silico analysis bringing the mutation detection rate up to 40%.

CONCLUSION

As expected, a positive family history is a strong predictor of germline BRCA2 mutations in male BC. Understanding the potential pathogenicity of VUS represents an extremely urgent need for the management of BC risk in Male BC cases and their own families.

Base excision repair deficiency signatures implicate germline and somatic MUTYH aberrations in pancreatic ductal adenocarcinoma and breast cancer oncogenesis

We report a case of early-onset pancreatic ductal adenocarcinoma in a patient harboring biallelic MUTYH germline mutations, whose tumor featured somatic mutational signatures consistent with defective MUTYH-mediated base excision repair and the associated driver KRAS transversion mutation p.Gly12Cys. Analysis of an additional 730 advanced cancer cases (N = 731) was undertaken to determine whether the mutational signatures were also present in tumors from germline MUTYH heterozygote carriers or if instead the signatures were only seen in those with biallelic loss of function. We identified two patients with breast cancer each carrying a pathogenic germline MUTYH variant with a somatic MUTYH copy loss leading to the germline variant being homozygous in the tumor and demonstrating the same somatic signatures. Our results suggest that monoallelic inactivation of MUTYH is not sufficient for C:G>A:T transversion signatures previously linked to MUTYH deficiency to arise (N = 9), but that biallelic complete loss of MUTYH function can cause such signatures to arise even in tumors not classically seen in MUTYH-associated polyposis (N = 3). Although defective MUTYH is not the only determinant of these signatures, MUTYH germline variants may be present in a subset of patients with tumors demonstrating elevated somatic signatures possibly suggestive of MUTYH deficiency (e.g., COSMIC Signature 18, SigProfiler SBS18/SBS36, SignatureAnalyzer SBS18/SBS36).

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.

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.

Not breathing is not an option: How to deal with oxidative DNA damage

Oxidative DNA damage constitutes a major threat to genetic integrity, and has thus been implicated in the pathogenesis of a wide variety of diseases, including cancer and neurodegeneration. 7,8-dihydro-8oxo-deoxyGuanine (8-oxo-G) is one of the best characterised oxidative DNA lesions, and it can give rise to point mutations due to its miscoding potential that instructs most DNA polymerases (Pols) to preferentially insert Adenine (A) opposite 8-oxo-G instead of the correct Cytosine (C). If uncorrected, A:8-oxo-G mispairs can give rise to C:G→A:T transversion mutations. Cells have evolved a variety of pathways to mitigate the mutational potential of 8-oxo-G that include i) mechanisms to avoid incorporation of oxidized nucleotides into DNA through nucleotide pool sanitisation enzymes (by MTH1, MTH2, MTH3 and NUDT5), ii) base excision repair (BER) of 8-oxo-G in DNA (involving MUTYH, OGG1, Pol λ, and other components of the BER machinery), and iii) faithful bypass of 8-oxo-G lesions during replication (using a switch between replicative Pols and Pol λ). In the following, the fate of 8-oxo-G in mammalian cells is reviewed in detail. The differential origins of 8-oxo-G in DNA and its consequences for genetic stability will be covered. This will be followed by a thorough discussion of the different mechanisms in place to cope with 8-oxo-G with an emphasis on Pol λ-mediated correct bypass of 8-oxo-G during MUTYH-initiated BER as well as replication across 8-oxo-G. Furthermore, the multitude of mechanisms in place to regulate key proteins involved in 8-oxo-G repair will be reviewed. Novel functions of 8-oxo-G as an epigenetic-like regulator and insights into the repair of 8-oxo-G within the cellular context will be touched upon. Finally, a discussion will outline the relevance of 8-oxo-G and the proteins involved in dealing with 8-oxo-G to human diseases with a special emphasis on cancer.

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.

The role of base excision repair in pathogenesis of breast cancer in the Polish population

Breast cancer (BC) is leading type of cancer among group of women, which determines almost 23% of invasive cancers. It has been reported repeatedly that the level of oxidative stress is higher for BC in comparison to cancer-free woman. The goal of the present study was to evaluate the role of base excision repair (BER) pathway in the development of BC. One-hundred seventy-one women with confirmed BC and 222 healthy controls were enrolled in presented study. The level of oxidative DNA damage and the kinetic of their repair were analyzed by the modified alkaline comet assay. The efficiency of BER pathway was evaluated by BER assay. The presence of the 326Cys/Cys genotype and 326Cys allele of OGG1 gene and the 324His/His of MUTYH gene are associated with increased risk of BC development. Moreover, correlation between clinical parameter with selected genes has shown increased risk of BC progression. The survival analysis has shown a significant lower DFS for individuals with the 762Ala/Ala genotype compared to 762Val/Vla carriers and the 762Val/Ala genotype in relation to concomitant chemotherapy and radiotherapy. In subgroup of patients with alone chemotherapy and alone radiotherapy, the 762Val/Val genotype was significantly associated with lower overall survival. Furthermore, we also elevated the level of basal and oxidative DNA damage in a group of patients with BC in relation to healthy controls. We also observed the difference in effectiveness of DNA damage repair. The results of present studies suggested the important role of BER pathway in BC development. © 2015 Wiley Periodicals, Inc.

Germline MUTYH gene mutations are not frequently found in unselected patients with papillary breast carcinoma

MUTYH-associated polyposis (MAP) is an autosomal recessive disease, which predisposes to polyposis and colorectal cancer. There is a trend towards an increased risk of breast cancer in MAP patients, with a remarkable proportion of papillary breast cancers. To determine whether MUTYH mutations are associated with this specific and rare type of breast cancer, 53 unselected patients with papillary breast cancer were analyzed for founder mutations in the MUTYH gene. No germline mutations were identified, indicating that biallelic MUTYH mutations are not a frequent underlying cause for the development of papillary carcinomas of the breast.

Biallelic MUTYH mutations can mimic Lynch syndrome

The hallmarks of Lynch syndrome (LS) include a positive family history of colorectal cancer (CRC), germline mutations in the DNA mismatch repair (MMR) genes, tumours with high microsatellite instability (MSI-H) and loss of MMR protein expression. However, in ∼10-15% of clinically suspected LS cases, MMR mutation analyses cannot explain MSI-H and abnormal immunohistochemistry (IHC) results. The highly variable phenotype of MUTYH-associated polyposis (MAP) can overlap with the LS phenotype, but is inherited recessively. We analysed the MUTYH gene in 85 'unresolved' patients with tumours showing IHC MMR-deficiency without detectable germline mutation. Biallelic p.(Tyr179Cys) MUTYH germline mutations were found in one patient (frequency 1.18%) with CRC, urothelial carcinoma and a sebaceous gland carcinoma. LS was suspected due to a positive family history of CRC and because of MSI-H and MSH2-MSH6 deficiency on IHC in the sebaceous gland carcinoma. Sequencing of this tumour revealed two somatic MSH2 mutations, thus explaining MSI-H and IHC results, and mimicking LS-like histopathology. This is the first report of two somatic MSH2 mutations leading to an MSI-H tumour lacking MSH2-MSH6 protein expression in a patient with MAP. In addition to typical transversion mutations in KRAS and APC, MAP can also induce tumourigenesis via the MSI-pathway.

Role of MUTYH in human cancer

MUTYH, a human ortholog of MutY, is a post-replicative DNA glycosylase, highly conserved throughout evolution, involved in the correction of mismatches resulting from a faulty replication of the oxidized base 8-hydroxyguanine (8-oxodG). In particular removal of adenine from A:8-oxodG mispairs by MUTYH activity is followed by error-free base excision repair (BER) events, leading to the formation of C:8-oxodG base pairs. These are the substrate of another BER enzyme, the OGG1 DNA glycosylase, which then removes 8-oxodG from DNA. Thus the combined action of OGG1 and MUTYH prevents oxidative damage-induced mutations, i.e. GC->TA transversions. Germline mutations in MUTYH are associated with a recessively heritable colorectal polyposis, now referred to as MUTYH-associated polyposis (MAP). Here we will review the phenotype(s) associated with MUTYH inactivation from bacteria to mammals, the structure of the MUTYH protein, the molecular mechanisms of its enzymatic activity and the functional characterization of MUTYH variants. The relevance of these results will be discussed to define the role of specific human mutations in colorectal cancer risk together with the possible role of MUTYH inactivation in sporadic cancer.

MUTYH-associated polyposis (MAP): evidence for the origin of the common European mutations p.Tyr179Cys and p.Gly396Asp by founder events

MUTYH-associated polyposis (MAP) is an autosomal recessive adenomatous polyposis caused by biallelic germline mutations of the base-excision-repair gene MUTYH. In MAP patients of European origin, the combined allele frequency of the mutations p.Tyr179Cys and p.Gly396Asp ranges between 50 and 82%, while these mutations have not been identified in Far Eastern Asian populations, supporting the hypothesis that a founder effect has occurred at some point in European history. To investigate the natural history of the two common European MUTYH alleles, we genotyped six gene-flanking microsatellite markers in 80 unrelated Italian and German MAP patients segregating one or both mutations and calculated their age in generations (g) by using DMLE+2.2 software. Three distinct common haplotypes, one for p.Tyr179Cys and two for p.Gly396Asp, were identified. Estimated mutation ages were 305 g (95% CS: 271-418) for p.Tyr179Cys and 350 g (95% CS: 313-435) for p.Gly396Asp. These results provide evidence for strong founder effects and suggest that the p.Tyr179Cys and p.Gly396Asp mutations derive from ancestors who lived between 5-8 thousand years and 6-9 thousand years B.C., respectively.

MUTYH gene variants and breast cancer in a Dutch case–control study

The MUTYH gene is involved in base excision repair. MUTYH mutations predispose to recessively inherited colorectal polyposis and cancer. Here, we evaluate an association with breast cancer (BC), following up our previous finding of an elevated BC frequency among Dutch bi-allelic MUTYH mutation carriers. A case–control study was performed comparing 1,469 incident BC patients (ORIGO cohort), 471 individuals displaying features suggesting a genetic predisposition for BC, but without a detectable BRCA1 or BRCA2 mutation (BRCAx cohort), and 1,666 controls. First, for 303 consecutive patients diagnosed before age 55 years and/or with multiple primary breast tumors, the MUTYH coding region and flanking introns were sequenced. The remaining subjects were genotyped for five coding variants, p.Tyr179Cys, p.Arg309Cys, p.Gly396Asp, p.Pro405Leu, and p.Ser515Phe, and four tagging SNPs, c.37-2487G>T, p.Val22Met, c.504+35G>A, and p.Gln338His. No bi-allelic pathogenic MUTYH mutations were identified. The pathogenic variant p.Gly396Asp and the variant of uncertain significance p.Arg309Cys occurred twice as frequently in BRCAx subjects as compared to incident BC patients and controls (p = 0.13 and p = 0.15, respectively). The likely benign variant p.Val22Met occurred less frequently in patients from the incident BC (p = 0.03) and BRCAx groups (p = 0.11), respectively, as compared to the controls. Minor allele genotypes of several MUTYH variants showed trends towards association with lobular BC histology. This extensive case–control study could not confirm previously reported associations of MUTYH variants with BC, although it was too small to exclude subtle effects on BC susceptibility.

MutYH mutation carriers have increased breast cancer risk

BACKGROUND

Variants of the mutY homolog gene MutYH, a DNA repair gene, are associated with increased risk of colorectal cancer; however, it remains unclear whether these variants also are associated with the risk of other cancers. The authors studied the risk of breast cancer associated with MutYH variants in a unique ethnic group of Sephardi Jews in Israel with a high prevalence of MutYH mutations.

METHODS

The study participants were 930 Sephardi Jewish women of North African origin who were recruited into the population-based case-control Breast Cancer in Northern Israel Study (BCINIS) either as breast cancer cases or as healthy controls. All participants contributed a blood sample and completed an interview. Two MutYH variants, a glycine-to-aspartic acid substitution at codon 396 (G396D) and a tyrosine-to-cysteine substitution at codon 179 (Y179C), were studied.

RESULTS

In the Sephardi Jews, among the healthy controls, 20 women (3.7%) were homozygote or heterozygote carriers of the G396D variant, and 4 women (0.7%) were heterozygote carriers of the Y179C variant. Breast cancer cases had a 6.7% prevalence of G396D, yielding a significantly elevated risk estimate for breast cancer (odds ratio, 1.86; 95% confidence interval, 1.02-3.39; P = .039). The tumors detected in carriers with MutYH variants were similar in characteristics to those without MutYH variants, as was the age at diagnosis.

CONCLUSIONS

Carriers of variants in MutYH, although not very common, may have an increased risk of breast cancer in Jews of North African origin. Identification of such carriers and special surveillance protocols may be warranted.

Frequency of the common germline MUTYH mutations p.G396D and p.Y179C in patients diagnosed with colorectal cancer in Southern Brazil

INTRODUCTION

MUTYH-associated polyposis (MAP) is an autosomal recessive cancer predisposition syndrome associated with the development of colorectal tumors and colonic polyps at an early age. MAP syndrome is associated to germline biallelic mutations in the MUTYH gene which lead to deficient DNA repair through the base-excision repair system and accumulation of G:C→T:A transversions. Occurrence of such mutations in oncogenes and tumor suppressor genes drives colorectal carcinogenesis and is associated with the development of colonic polyps. Two common mutations, p.Y179C and p.G396D, are present in approximately 70-80% of MAP in European families with identified MUTYH germline mutations. The aim of this study was to assess the frequency of the germline MUTYH mutations p.Y179C and p.G396D in Brazilian patients with MAP and other hereditary colorectal cancer (CRC) phenotypes, as well as in sporadic CRC cases.

MATERIALS AND METHODS

A total of 75 patients were included. Samples were screened for the MUTYH germline mutations p.Y179C and p.G396D by allelic discrimination assays using allele-specific TaqMan® probes. In all mutation-positive cases, results were confirmed by sequencing.

RESULTS AND CONCLUSIONS

Biallelic germline MUTYH mutations were identified in 4 of 60 (6.6%) patients with a phenotype of hereditary colorectal cancer. Germline MUTYH mutation screening should be considered in the differential diagnosis of hereditary colorectal syndromes, and not only in MAP, but also in familial adenomatous polyposis and Bethesda criteria-positive families. Additional mutation screening studies of the MUTYH gene in a larger number of Brazilian patients will be necessary to confirm these results and determine the validity and applicability of MUTYH mutation screening in our population.

Cancer risks for monoallelic MUTYH mutation carriers with a family history of colorectal cancer

Cancer risks for a person who has inherited a MUTYH mutation from only one parent (monoallelic mutation carrier) are uncertain. Using the Colon Cancer Family Registry and Newfoundland Familial Colon Cancer Registry, we identified 2,179 first- and second-degree relatives of 144 incident colorectal cancer (CRC) cases who were monoallelic or biallelic mutation carriers ascertained by sampling population complete cancer registries in the United States, Canada and Australia. Using Cox regression weighted to adjust for sampling on family history, we estimated that the country-, age- and sex-specific standardized incidence ratios (SIRs) for monoallelic mutation carriers, compared to the general population, were: 2.04 (95% confidence interval, CI 1.56-2.70; p < 0.001) for CRC, 3.24 (95%CI 2.18-4.98; p < 0.001) for gastric cancer, 3.09 (95%CI 1.07-12.25; p = 0.07) for liver cancer and 2.33 (95%CI 1.18-5.08; p = 0.02) for endometrial cancer. Age-specific cumulative risks to age 70 years, estimated using the SIRs and US population incidences, were: for CRC, 6% (95%CI 5-8%) for men and 4% (95%CI 3-6%) for women; for gastric cancer, 2% (95%CI 1-3%) for men and 0.7% (95%CI 0.5-1%) for women; for liver cancer, 1% (95%CI 0.3-3%) for men and 0.3% (95%CI 0.1-1%) for women and for endometrial cancer, 4% (95%CI 2-8%). There was no evidence of increased risks for cancers of the brain, pancreas, kidney, lung, breast or prostate. Monoallelic MUTYH mutation carriers with a family history of CRC, such as those identified from screening multiple-case CRC families, are at increased risk of colorectal, gastric, endometrial and possibly liver cancers.

MUTYH-associated polyposis - variability of the clinical phenotype in patients with biallelic and monoallelic MUTYH mutations and report on novel mutations

To further characterize 215 APC mutation-negative patients with colorectal neoplasias classified in classical, attenuated, or atypical familial adenomatous polyposis (FAP) coli we performed mutation screening in the Mut Y homologue (MUTYH) gene. The incidence was 15% for biallelic and 3.7% for monoallelic MUTYH mutations. We describe six novel MUTYH mutations in biallelic constellation and two novel monoallelic missense mutations. Of 33 MUTYH-associated polyposis coli (MAP) patients 57% were attenuated familial adenomatous polyposis (AFAP) patients, 10% display early-onset classical FAP and 18% had only few adenomas at higher age. Biallelic cases had a high incidence of extracolonic polyposis in 32% and colorectal cancer (CRC) in 33% of the cases. The clinical picture of MAP ranged from classical FAP or synchronous CRC at age 30 years to few adenomas at age 54 years without evidence of CRC, initially suspected for hereditary non-polyposis colorectal cancer (HNPCC). The mean age of onset was 43 years, with 11 (33%) patients being younger than 40 years of age, indicating that the clinical manifestation can be earlier than so far reported. Monoallelic MUTYH mutation carriers had a positive family history in seven of eight cases allowing the hypothesis of a disease-causing synergism of MUTYH mutations with other genes.