Familial Adenomatous Polyposis (FAP)

Overview

Familial Adenomatous Polyposis (FAP) is a genetic condition characterized by multiple (>100) adenomatous polyps in the colon and rectum typically developing after the first decade of life. FAP is also known as familial polyposis coli, adenomatous polyposis coli (APC), or Gardner Syndrome. Individuals with FAP have an increased risk of colorectal cancer and other tumours (see risks below).

Most cases of FAP are caused by mutations of the APC gene on chromosome 5q21. FAP is an autosomal dominant condition - this means that affected persons are genetically heterozygous (having both a good and a mutated copy of the APC gene), each offspring of a patient with FAP has a 50% chance of inheriting FAP. Males and females are equally likely to be affected. A diverse range of different mutations APC have been reported in FAP including insertions, deletions, and nonsense mutations that lead to frameshifts and/or premature stop codons in transcription.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 10 March, 2017 using data from PubMed, MeSH and CancerIndex

Mutated Genes and Abnormal Protein Expression (9)

How to use this data tableClicking on the Gene or Topic will take you to a separate more detailed page. Sort this list by clicking on a column heading e.g. 'Gene' or 'Topic'.

GeneLocationAliasesNotesTopicPapers
APC 5q21-q22 GS, DP2, DP3, BTPS2, DP2.5, PPP1R46 -APC and Adenomatous Polyposis Coli
1198
MUTYH 1p34.1 MYH -MUTYH and Adenomatous Polyposis Coli
107
SMAD4 18q21.1 JIP, DPC4, MADH4, MYHRS -SMAD4 and Adenomatous Polyposis Coli
49
BMPR1A 10q22.3 ALK3, SKR5, CD292, ACVRLK3, 10q23del -BMPR1A and Adenomatous Polyposis Coli
30
MCC 5q21 MCC1 -MCC and Adenomatous Polyposis Coli
28
AXIN2 17q24.1 AXIL, ODCRCS -AXIN2 and Adenomatous Polyposis Coli
10
PLA2G2A 1p35 MOM1, PLA2, PLA2B, PLA2L, PLA2S, PLAS1, sPLA2 -PLA2G2A and Adenomatous Polyposis Coli
6
POLD1 19q13.3 CDC2, MDPL, POLD, CRCS10 -POLD1 and Adenomatous Polyposis Coli
3
CTBP1 4p16 BARS -CTBP1 and Adenomatous Polyposis Coli
3

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Risk of Cancer in FAP

People who inherit a mutant APC gene have over 90% likelihood of developing colonic adenomas. Age at onset of adenomas in the colon varies: 15% by age 10, 75% by age 20, and 90% by 30. Without intervention, most individuals with FAP will develop colon or rectal cancer by the fourth decade of life. APC gene mutation carriers are monitored, typically with regular sigmoidoscopy beginning around puberty.

In addition to increased risk of colorectal cancer, individuals with FAP have increased risk of:

MalignancyRelative RiskAbsolute Lifetime Risk (%)
Desmoid852.015.0
Duodenum330.85.0-12.0
Thyroid7.62.0
Brain7.02.0
Ampullary123.71.7
Pancreas4.51.7
Hepatoblastoma847.01.6
Gastric-0.6

Source: Genetics of Colorectal Cancer, National Cancer Institute (accessed 31/12/14).

Latest Publications (FAP genetics)

Kazubskaya TP, Kozlova VM, Filippova MG, et al.
[Rare hereditary syndromes associated with polyposis and the development of malignant tumors].
Arkh Patol. 2016 Mar-Apr; 78(2):10-8 [PubMed] Related Publications
UNLABELLED: Familial adenomatous polyposis (FAP) and Peutz-Jeghers syndrome are genetic diseases characterized by gastrointestinal polyps, extraintestinal manifestations, and autosomal dominant inheritance. The carriers of these diseases from early childhood are at risk for neoplasias at different sites, which are symptomatic at various ages.
AIM: to study the clinical organ-specific manifestations in patients with FAP and Peutz-Jeghers, genetics update and possibilities of diagnosis, monitoring, and treatment of these diseases.
MATERIAL AND METHODS: The authors give the results of their examination and follow-up of children with FAP and Peutz-Jeghers hamartoma-polypous syndrome. In addition, current data from PubMed, Medline (including reviews, original articles and case reports) were used.
RESULTS: The main clinical organ-specific signs of multiple tumors in FAP and Peutz-Jeghers syndrome are shown. Data on the assessment of a risk for malignant tumors at various sites in the affected patients and their family members at different ages are provided. Each of these syndromes has a dissimilar genetic foundation. FAP is caused by the germline mutations in the APC gene, Peutz-Jeghers syndrome is by the STK11 gene, which predispose individuals to specifically associated neoplasias and require different follow-up strategies. Information on a phenotype-genotype correlation may serve as a reference point for the possible severity and various manifestations of a disease. An update on the molecular pathogenesis of these diseases is considered.
CONCLUSION: Molecular genetic testing of the genes associated with FAP and Peutz-Jeghers syndromes makes it possible to timely recognize family members at high risk, to plan therapeutic strategy and to affect the course of a disease. The joint participation of pediatricians, proctologists, oncologists, morphologists, geneticists, and molecular biologists is essential to timely recognize the carriers of the syndromes and a better prognosis in these patients.

Liu Q, Li X, Li S, et al.
Three novel mutations of APC gene in Chinese patients with familial adenomatous polyposis.
Tumour Biol. 2016; 37(8):11421-7 [PubMed] Free Access to Full Article Related Publications
Familial adenomatous polyposis (FAP) is an autosomal dominant disorder characterized by the development of hundreds to thousands of colonic adenomas and an increased risk of colorectal cancer. Adenomatous polyposis coli (APC), encoding a large multidomain protein involved in antagonizing the Wnt signaling pathway, has been identified as the main causative gene responsible for FAP. In this study, we identified three novel mutations as well as two recurrent mutations in the APC in five Chinese FAP families by sequencing. Immunohistochemical analysis revealed that among these mutations, a nonsense mutation (c.2510C>G) and two small deletions (c.2016_2047del, c.3180_3184del) led to the truncation of the APC protein and the cytoplasmic and nuclear accumulation of β-catenin in the colorectal samples from affected individuals, respectively. Our study expands the database on mutations of APC and provides evidence to understand the function of APC in FAP.

Ziai J, Matloff E, Choi J, et al.
Defining the polyposis/colorectal cancer phenotype associated with the Ashkenazi GREM1 duplication: counselling and management recommendations.
Genet Res (Camb). 2016; 98:e5 [PubMed] Related Publications
Hereditary mixed polyposis is a genetically heterogeneous, autosomal dominant condition with adenomatous, hyperplastic and juvenile polyps. We conducted a comprehensive clinical evaluation of a large Ashkenazi Jewish family with this phenotype and performed extensive genetic testing. As seen in one previous report, a 40 kb duplication upstream of GREM1 segregated with the polyposis/colon cancer phenotype in this kindred. Our study confirms the association of GREM1 with mixed polyposis and further defines the phenotype seen with this mutation. This gene should be included in the test panel for all Jewish patients with mixed polyposis and may be considered in any Ashkenazi patient with unexplained hereditary colon cancer when mutations in other hereditary colon cancer genes have been ruled out.

Dorman A, Baer D, Tomlinson I, et al.
Genetic analysis of intestinal polyp development in Collaborative Cross mice carrying the Apc (Min/+) mutation.
BMC Genet. 2016; 17:46 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Colorectal cancer is an abnormal tissue development in the colon or rectum. Most of CRCs develop due to somatic mutations, while only a small proportion is caused by inherited mutations. Familial adenomatous polyposis is an inherited genetic disease, which is characterized by colorectal polyps. It is caused by inactivating mutations in the Adenomatous polyposis coli gene. Mice carrying and non-sense mutation in Adenomatous polyposis coli gene at site R850, which designated Apc (R850X/+) (Min), develop intestinal adenomas, while the bulk of the disease is in the small intestine. A number of genetic modifier loci of Min have been mapped, but so far most of the underlying genes have not been identified. In our previous studies, we have shown that Collaborative Cross mice are a powerful tool for mapping loci responsible for phenotypic variation. As a first step towards identification of novel modifiers of Min, we assessed the phenotypic variation between 27 F1 crosses between different Collaborative cross mice and C57BL/6-Min lines.
RESULTS: Here, C57BL/6-Min male mice were mated with females from 27 Collaborative cross lines. F1 offspring were terminated at 23 weeks old and multiple phenotypes were collected: polyp counts, intestine length, intestine weight, packed cell volume and spleen weight. Additionally, in eight selected F1 Collaborative cross-C57BL/6-Min lines, body weight was monitored and compared to control mice carry wildtype Adenomatous polyposis coli gene. We found significant (p < 0.05) phenotypic variation between the 27 F1 Collaborative cross-C57BL/6-Min lines for all the tested phenotypes, and sex differences with traits; Colon, body weight and intestine length phenotypes, only. Heritability calculation showed that these phenotypes are mainly controlled by genetic factors.
CONCLUSIONS: Variation in polyp development is controlled, an appreciable extent, by genetic factors segregating in the Collaborative cross population and suggests that it is suited for identifying modifier genes associated with Apc (Min/+) mutation, after assessing sufficient number of lines for quantitative trait loci analysis.

Mur P, Sánchez-Cuartielles E, Aussó S, et al.
Scarce evidence of the causal role of germline mutations in UNC5C in hereditary colorectal cancer and polyposis.
Sci Rep. 2016; 6:20697 [PubMed] Free Access to Full Article Related Publications
Germline mutations in UNC5C have been suggested to increase colorectal cancer (CRC) risk, thus causing hereditary CRC. However, the evidence gathered thus far is insufficient to include the study of the UNC5C gene in the routine genetic testing of familial CRC. Here we aim at providing a more conclusive answer about the contribution of germline UNC5C mutations to genetically unexplained hereditary CRC and/or polyposis cases. To achieve this goal we sequenced the coding region and exon-intron boundaries of UNC5C in 544 familial CRC or polyposis patients (529 families), using a technique that combines pooled DNA amplification and massively parallel sequencing. A total of eight novel or rare variants, all missense, were identified in eight families. Co-segregation data in the families and association results in case-control series are not consistent with a causal effect for 7 of the 8 identified variants, including c.1882_1883delinsAA (p.A628K), previously described as a disease-causing mutation. One variant, c.2210G > A (p.S737N), remained unclassified. In conclusion, our results suggest that the contribution of germline mutations in UNC5C to hereditary colorectal cancer and to polyposis cases is negligible.

Ponti G, Tomasi A, Manfredini M, Pellacani G
Oral mucosal stigmata in hereditary-cancer syndromes: From germline mutations to distinctive clinical phenotypes and tailored therapies.
Gene. 2016; 582(1):23-32 [PubMed] Related Publications
Numerous familial tumor syndromes are associated with distinctive oral mucosal findings, which may make possible an early diagnosis as an efficacious marker for the risk of developing visceral malignancies. In detail, Familial Adenomatous Polyposis (FAP), Gardner syndrome, Peutz-Jeghers syndrome, Cowden Syndrome, Gorlin Syndrome, Lynch/Muir-Torre Syndrome and Multiple Endocrine Neoplasia show specific lesions of the oral mucosa and other distinct clinical and molecular features. The common genetic background of the above mentioned syndromes involve germline mutations in tumor suppressor genes, such as APC, PTEN, PTCH1, STK11, RET, clearly implied in both ectodermal and mesodermal differentiation, being the oral mucosal and dental stigmata frequently associated in the specific clinical phenotypes. The oral and maxillofacial manifestations of these syndromes may become visible several years before the intestinal lesions, constituting a clinical marker that is predictive for the development of intestinal polyps and/or other visceral malignancies. A multidisciplinary approach is therefore necessary for both clinical diagnosis and management of the gene-carriers probands and their family members who have to be referred for genetic testing or have to be investigated for the presence of visceral cancers.

Yamaguchi T, Ishida H, Ueno H, et al.
Upper gastrointestinal tumours in Japanese familial adenomatous polyposis patients.
Jpn J Clin Oncol. 2016; 46(4):310-5 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
OBJECTIVE: The upper gastrointestinal characteristics in Japanese familial adenomatous polyposis patients have not yet been clarified. The aim of the present study was to elucidate these characteristics in Japanese familial adenomatous polyposis patients.
METHODS: This study was conducted by the study group for familial adenomatous polyposis in the Japanese Society for Cancer of the Colon and Rectum. Familial adenomatous polyposis patients who underwent surgical resection from 2000 to 2012 were included in the study.
RESULTS: In total, 303 familial adenomatous polyposis patients were enrolled, with 265 cases of classical familial adenomatous polyposis (≥100 adenomas) and 38 cases of attenuated familial adenomatous polyposis (<100 adenomas). Fundic gland polyps were significantly more common in classical familial adenomatous polyposis than in attenuated familial adenomatous polyposis; however, gastric cancer was significantly less common in classical familial adenomatous polyposis than in attenuated familial adenomatous polyposis. Gastric cancer and duodenal adenoma were significantly more common in familial adenomatous polyposis patients with gastric adenoma than in those without gastric adenoma. Duodenal cancer was detected in 7 of 72 familial adenomatous polyposis patients with duodenal adenoma. The median tumour risk in 50-year-old familial adenomatous polyposis patients was 55.3, 21.8, 3.8, 39.2 and 7.7% for fundic gland polyp, gastric adenoma, gastric cancer, duodenal adenoma and duodenal cancer, respectively.
CONCLUSIONS: Upper gastrointestinal tumours/polyps were frequently found in familial adenomatous polyposis patients, and their incidences were correlated; however, the frequency of gastric cancer in Japanese familial adenomatous polyposis patients was similar to that in the general population.

Clark CR, Starr TK
Mouse models for the discovery of colorectal cancer driver genes.
World J Gastroenterol. 2016; 22(2):815-22 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Colorectal cancer (CRC) constitutes a major public health problem as the third most commonly diagnosed and third most lethal malignancy worldwide. The prevalence and the physical accessibility to colorectal tumors have made CRC an ideal model for the study of tumor genetics. Early research efforts using patient derived CRC samples led to the discovery of several highly penetrant mutations (e.g., APC, KRAS, MMR genes) in both hereditary and sporadic CRC tumors. This knowledge has enabled researchers to develop genetically engineered and chemically induced tumor models of CRC, both of which have had a substantial impact on our understanding of the molecular basis of CRC. Despite these advances, the morbidity and mortality of CRC remains a cause for concern and highlight the need to uncover novel genetic drivers of CRC. This review focuses on mouse models of CRC with particular emphasis on a newly developed cancer gene discovery tool, the Sleeping Beauty transposon-based mutagenesis model of CRC.

Goldberg Y, Halpern N, Hubert A, et al.
Mutated MCM9 is associated with predisposition to hereditary mixed polyposis and colorectal cancer in addition to primary ovarian failure.
Cancer Genet. 2015; 208(12):621-4 [PubMed] Related Publications
Mutations in MCM9, which encodes DNA helicase, were recently shown to cause a clinical phenotype of primary ovarian failure and chromosomal instability. MCM9 plays an essential role in homologous recombination-mediated double-strand break repair. We describe a multiplex family with early colorectal carcinoma and mixed polyposis associated with primary hypergonadotropic hypogonadism. A combination of whole genome homozygosity mapping as well as exome sequencing and targeted gene sequencing identified a homozygous c.672_673delGGinsC mutation that predicts a truncated protein, p.Glu225Lysfs*4. Our data expand the phenotypic spectrum of MCM9 mutations and suggest a link between MCM9 and inherited predisposition to mixed polyposis and early-onset colorectal cancer.

Buecher B
Colorectal adenomatous polyposis syndromes: Genetic determinism, clinical presentation and recommendations for care.
Bull Cancer. 2016; 103(2):199-209 [PubMed] Related Publications
Colorectal adenomatous polyposis constitutes a diverse group of disorders with different modes of inheritance. Molecular diagnosis of this condition has become more complex. In fact, somatic mosaicism for APC mutations now appears to be more frequent than previously thought and rare germline alterations of this gene may be implicated in patients tested negative for "classical" APC mutations (point mutations and large genomic rearrangements). Moreover, the knowledge concerning several aspects of the MUTYH-associated polyposis has improved since its first description in 2002 and germline mutations in new genes have recently been implicated in some cases of unexplained adenomatous polyposis. Genetic testing in probands and their relatives should be conducted in the context of pre- and post-test genetic counseling. The recent advent of New Generation Sequencing (NGS) techniques affords the opportunity to rapidly screen patients for a comprehensive panel of colorectal cancer susceptibility genes in a cost-effective fashion. This type of approach will probably replace the classical sequential approach based on clinical presumptive diagnoses in the near future. The risk of colorectal cancer is very high in affected patients in the absence of appropriate care. Clinical management is complex and should be provided in centers with special expertise in these diseases. This review focuses on the various colorectal adenomatous polyposis syndromes with special attention to more innovative and important aspects.

Suzuki O, Chika N, Fukuchi M, et al.
[A Case of Colon Cancer with Familial Adenomatous Polyposis Showing MSI-H and Deletion of MSH2/MSH6 Protein].
Gan To Kagaku Ryoho. 2015; 42(12):2208-10 [PubMed] Related Publications
A 31-year-old woman with familial adenomatous polyposis (FAP) was diagnosed with colon cancer. Genetic testing showed a germ cell line mutation of APC (a frame-shift mutation). Moreover, deletion of MSH2/MSH6 protein and high microsatellite instability (MSI-H) was detected. Therefore, Lynch syndrome (LS) associated with FAP was suspected. Additional analysis showed no pathogenic mutation of MSH2 and no change in the number of copies or methylation in the promoter region. Therefore, this was not a case of LS caused by a genetic germ cell line mutation. The chromosome instability had been caused by a malfunction of APC, and it produced a structural change in a gene in the somatic cells. This case is very interesting.

Spier I, Kerick M, Drichel D, et al.
Exome sequencing identifies potential novel candidate genes in patients with unexplained colorectal adenomatous polyposis.
Fam Cancer. 2016; 15(2):281-8 [PubMed] Related Publications
In up to 30% of patients with colorectal adenomatous polyposis, no germline mutation in the known genes APC, causing familial adenomatous polyposis, MUTYH, causing MUTYH-associated polyposis, and POLE or POLD1, causing Polymerase-Proofreading-associated polyposis can be identified, although a hereditary etiology is likely. To uncover new causative genes, exome sequencing was performed using DNA from leukocytes and a total of 12 colorectal adenomas from seven unrelated patients with unexplained sporadic adenomatous polyposis. For data analysis and variant filtering, an established bioinformatics pipeline including in-house tools was applied. Variants were filtered for rare truncating point mutations and copy-number variants assuming a dominant, recessive, or tumor suppressor model of inheritance. Subsequently, targeted sequence analysis of the most promising candidate genes was performed in a validation cohort of 191 unrelated patients. All relevant variants were validated by Sanger sequencing. The analysis of exome sequencing data resulted in the identification of rare loss-of-function germline mutations in three promising candidate genes (DSC2, PIEZO1, ZSWIM7). In the validation cohort, further variants predicted to be pathogenic were identified in DSC2 and PIEZO1. According to the somatic mutation spectra, the adenomas in this patient cohort follow the classical pathways of colorectal tumorigenesis. The present study identified three candidate genes which might represent rare causes for a predisposition to colorectal adenoma formation. Especially PIEZO1 (FAM38A) and ZSWIM7 (SWS1) warrant further exploration. To evaluate the clinical relevance of these genes, investigation of larger patient cohorts and functional studies are required.

Taki K, Sato Y, Nomura S, et al.
Mutation analysis of MUTYH in Japanese colorectal adenomatous polyposis patients.
Fam Cancer. 2016; 15(2):261-5 [PubMed] Related Publications
Germline MUTYH mutations were investigated in 14 Japanese colorectal polyposis patients without germ line adenomatous polyposis coli (APC) gene mutations. Three patients had a heterozygous IVS10-2A>G MUTYH mutation. The onset of MUTYH-associated polyposis (MAP) occurs later than that of familial adenomatous polyposis with germline APC mutation. Thus, we compared the carrier frequency of MUTYH IVS10-2A>G heterozygote in the APC mutation negative cases with that in 115 controls over 70 years of age who showed no apparent clinical manifestations of cancer and claimed that they had no history of cancer at the time of enrollment. The frequency of IVS10-2A>G heterozygote in APC germline mutation negative polyposis patients was significantly higher than control subject (p = 0.012, Chi square test). Although the sample size is still too small to conclude, the IVS10-2A>G MUTYH heterozygote might add to the risk of developing germline APC mutation negative polyposis.

Feng H, Zhang Z, Qing X, et al.
Promoter methylation of APC and RAR-β genes as prognostic markers in non-small cell lung cancer (NSCLC).
Exp Mol Pathol. 2016; 100(1):109-13 [PubMed] Related Publications
Aberrant promoter hypermethylations of tumor suppressor genes are promising markers for lung cancer diagnosis and prognosis. The purpose of this study was to determine methylation status at APC and RAR-β promoters in primary NSCLC, and whether they have any relationship with survival. APC and RAR-β promoter methylation status were determined in 41 NSCLC patients using methylation specific PCR. APC promoter methylation was detectable in 9 (22.0%) tumor samples and 6 (14.6%) corresponding non-tumor samples (P=0.391). RAR-β promoter methylation was detectable in 13 (31.7%) tumor samples and 4 (9.8%) corresponding non-tumor samples (P=0.049) in the NSCLC patients. APC promoter methylation was found to be associated with T stage (P=0.046) and nodal status (P=0.019) in non-tumor samples, and with smoking (P=0.004) in tumor samples. RAR-β promoter methylation was found associated with age (P=0.031) in non-tumor samples and with primary tumor site in tumor samples. Patients with APC promoter methylation in tumor samples showed significantly longer survival than patients without it (Log-rank P=0.014). In a multivariate analysis of prognostic factors, APC methylation in tumor samples was an independent prognostic factor (P=0.012), as were N1 positive lymph node number (P=0.025) and N2 positive lymph node number (P=0.06). Our study shows that RAR-β methylation detected in lung tissue may be used as a predictive marker for NSCLC diagnosis and that APC methylation in tumor sample may be a useful marker for superior survival in NSCLC patients.

Hata K, Yamamoto Y, Kiyomatsu T, et al.
Hereditary gastrointestinal cancer.
Surg Today. 2016; 46(10):1115-22 [PubMed] Related Publications
Gastrointestinal (GI) cancer, including gastric and colorectal cancer, is a major cause of death worldwide. A substantial proportion of patients with GI cancer have a familial history, and several causative genes have been identified. Gene carriers with these hereditary GI syndromes often harbor several kinds of cancer at an early age, and genetic testing and specific surveillance may save their lives through early detection. Gastroenterologists and GI surgeons should be familiar with these syndromes, even though they are not always associated with a high penetrance of GI cancer. In this review, we provide an overview and discuss the diagnosis, genetic testing, and management of four major hereditary GI cancers: familial adenomatous polyposis, Lynch syndrome, hereditary diffuse gastric cancer, and Li-Fraumeni syndrome.

Böger C, Haag J, Egberts JH, Röcken C
Complex APC germline mutation associated metaplasia and intraepithelial neoplasia (CAM-IEN) of the gallbladder.
Pathol Res Pract. 2016; 212(1):54-8 [PubMed] Related Publications
Preneoplasic and neoplastic changes of the gallbladder of patients with a familial adenomatous polyposis (FAP) are rare, and very little is known about their incidence in patients with an attenuated FAP. We herein report on a unique case of a woman with an attenuated FAP who shows eight distinct, partially preneoplastic differentiation patterns within the gallbladder mucosa, which are: (1) regular gallbladder epithelium, (2) low grade biliary intraepithelial neoplasia, (3) papillary adenoma, (4) Paneth cell metaplasia, (5) goblet cell metaplasia, (6) pancreatic metaplasia, (7) pseudopyloric metaplasia, and (8) neuroendocrine differentiation. Moreover, this is the first case of a KRAS mutation in a gallbladder adenoma of a patient with an APC germline mutation, which is highly suggestive of an early event of malignant transformation. As a consequence of our findings, clinicians should draw special attention to the gallbladder of FAP patients, and a simultaneous protective cholecystectomy of FAP patients, which undergo colectomy and show conspicuous changes of the gallbladder mucosa, should be performed in these patients in order to eliminate the risk of a synchronous or metachronous gallbladder neoplasia.

Zhang S, Qin H, Lv W, et al.
Novel and reported APC germline mutations in Chinese patients with familial adenomatous polyposis.
Gene. 2016; 577(2):187-92 [PubMed] Related Publications
OBJECTIVE: Familial adenomatous polyposis (FAP) is mainly caused by germline mutations in the adenomatous polyposis coli (APC) gene. This study aimed to detect pathogenic variants in five Chinese FAP families and review all previously reported pathogenic variants of APC gene in Chinese population.
METHODS: Five non-consanguineous FAP families and 100 unrelated ethnicity-matched controls were included in the study. Sanger sequencing was performed to screen for APC coding and splicing variants. Chinese and English literature on APC germline mutations were reviewed to compile the mutation spectrum of APC gene in Chinese FAP patients.
RESULTS: One pathogenic variant was detected in each family for the five pedigrees we tested. Three variants (c.3183_3187delACAAA, c.2626C>T and c.1312+1G>A) were previously reported as pathogenic. The other two variants were novel: c.794_795insG/p.Val266SerfsTer11 and c.2142_2143insG/p.His715AlafsTer19. They are absent from public databases (1000 Genomes, dbSNP, ESP and ExAC) and 100 normal controls, and are classified as pathogenic based on the new ACMG/AMP variant classification guidelines. Literature review and current study revealed a total of 82 different pathogenic variants from 127 Chinese FAP families. Among these families, 83 families had frameshift variants (65.35%), 26 with nonsense variants (20.47%), six with splice site variants (4.72%), three with missense variants (2.36%) and nine with large deletion or duplication variants (7.09%). Apart from the two previously reported mutation hotspots c.3927_3931delAAAGA (20.47%) and c.3183_3187delACAAA (7.09%), c.847C>T/p.Arg283Ter variant occurred with a frequency of 3.15% (4 out of 127) in Chinese FAP patients.
CONCLUSIONS: We reported two novel pathogenic variants. The comprehensive compilation of variants and comparison revealed largely similar mutation spectrum between Chinese and Western patient populations. Some unique features noticed in Chinese patient population may help to better understand the pathogenesis of FAP.

Spier I, Drichel D, Kerick M, et al.
Low-level APC mutational mosaicism is the underlying cause in a substantial fraction of unexplained colorectal adenomatous polyposis cases.
J Med Genet. 2016; 53(3):172-9 [PubMed] Related Publications
BACKGROUND: In 30-50% of patients with colorectal adenomatous polyposis, no germline mutation in the known genes APC, causing familial adenomatous polyposis, MUTYH, causing MUTYH-associated polyposis, or POLE or POLD1, causing polymerase-proofreading-associated polyposis can be identified, although a hereditary aetiology is likely. This study aimed to explore the impact of APC mutational mosaicism in unexplained polyposis.
METHODS: To comprehensively screen for somatic low-level APC mosaicism, high-coverage next-generation sequencing of the APC gene was performed using DNA from leucocytes and a total of 53 colorectal tumours from 20 unrelated patients with unexplained sporadic adenomatous polyposis. APC mosaicism was assumed if the same loss-of-function APC mutation was present in ≥ 2 anatomically separated colorectal adenomas/carcinomas per patient. All mutations were validated using diverse methods.
RESULTS: In 25% (5/20) of patients, somatic mosaicism of a pathogenic APC mutation was identified as underlying cause of the disease. In 2/5 cases, the mosaic level in leucocyte DNA was slightly below the sensitivity threshold of Sanger sequencing; while in 3/5 cases, the allelic fraction was either very low (0.1-1%) or no mutations were detectable. The majority of mosaic mutations were located outside the somatic mutation cluster region of the gene.
CONCLUSIONS: The present data indicate a high prevalence of pathogenic mosaic APC mutations below the detection thresholds of routine diagnostics in adenomatous polyposis, even if high-coverage sequencing of leucocyte DNA alone is taken into account. This has important implications for both routine work-up and strategies to identify new causative genes in this patient group.

Selmin OI, Fang C, Lyon AM, et al.
Inactivation of Adenomatous Polyposis Coli Reduces Bile Acid/Farnesoid X Receptor Expression through Fxr gene CpG Methylation in Mouse Colon Tumors and Human Colon Cancer Cells.
J Nutr. 2016; 146(2):236-42 [PubMed] Related Publications
BACKGROUND: The farnesoid X receptor (FXR) regulates bile acid (BA) metabolism and possesses tumor suppressor functions. FXR expression is reduced in colorectal tumors of subjects carrying inactivated adenomatous polyposis coli (APC). Identifying the mechanisms responsible for this reduction may offer new molecular targets for colon cancer prevention.
OBJECTIVE: We investigated how APC inactivation influences the regulation of FXR expression in colonic mucosal cells. We hypothesized that APC inactivation would epigenetically repress nuclear receptor subfamily 1, group H, member 4 (FXR gene name) expression through increased CpG methylation.
METHODS: Normal proximal colonic mucosa and normal-appearing adjacent colonic mucosa and colon tumors were collected from wild-type C57BL/6J and Apc-deficient (Apc(Min) (/+)) male mice, respectively. The expression of Fxr, ileal bile acid-binding protein (Ibabp), small heterodimer partner (Shp), and cyclooxygenase-2 (Cox-2) were determined by real-time polymerase chain reaction. In both normal and adjacent colonic mucosa and colon tumors, we measured CpG methylation of Fxr in bisulfonated genomic DNA. In vitro, we measured the impact of APC inactivation and deoxycholic acid (DCA) treatment on FXR expression in human colon cancer HCT-116 cells transfected with silencing RNA for APC and HT-29 cells carrying inactivated APC.
RESULTS: In Apc(Min) (/+) mice, constitutive CpG methylation of the Fxrα3/4 promoter was linked to reduced (60-90%) baseline Fxr, Ibabp, and Shp and increased Cox-2 expression in apparently normal adjacent mucosa and colon tumors. Apc knockdown in HCT-116 cells increased cellular myelocytomatosis (c-MYC) and lowered (∼50%) FXR expression, which was further reduced (∼80%) by DCA. In human HCT-116 but not HT-29 colon cancer cells, DCA induced FXR expression and lowered CpG methylation of FXR.
CONCLUSIONS: We conclude that the loss of APC function favors the silencing of FXR expression through CpG hypermethylation in mouse colonic mucosa and human colon cells, leading to reduced expression of downstream targets (SHP, IBABP) involved in BA homeostasis while increasing the expression of factors (COX-2, c-MYC) that contribute to inflammation and colon cancer.

Aceto GM, Fantini F, De Iure S, et al.
Correlation between mutations and mRNA expression of APC and MUTYH genes: new insight into hereditary colorectal polyposis predisposition.
J Exp Clin Cancer Res. 2015; 34:131 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
BACKGROUND: Transcript dosage imbalance may influence the transcriptome. To gain insight into the role of altered gene expression in hereditary colorectal polyposis predisposition, in the present study we analyzed absolute and allele-specific expression (ASE) of adenomatous polyposis coli (APC) and mutY Homolog (MUTYH) genes.
METHODS: We analyzed DNA and RNA extracted from peripheral blood mononuclear cells (PBMC) of 49 familial polyposis patients and 42 healthy blood donors selected according similar gender and age. Patients were studied for germline alterations in both genes using dHPLC, MLPA and automated sequencing. APC and MUTYH mRNA expression levels were investigated by quantitative Real-Time PCR (qRT-PCR) analysis using TaqMan assay and by ASE assays using dHPLC-based primer extension.
RESULTS: Twenty out of 49 patients showed germline mutations: 14 in APC gene and six in MUTYH gene. Twenty-nine patients did not show mutations in both genes. Results from qRT-PCR indicated that gene expression of both APC and MUTYH was reduced in patients analyzed. In particular, a significant reduction in APC expression was observed in patients without APC germline mutation vs control group (P < 0.05) while APC expression in the mutation carrier patients, although lower compared to control individuals, did not show statistical significance. On the other hand a significant reduced MUTYH expression was detected in patients with MUTYH mutations vs control group (P < 0.05). Altered ASE of APC was detected in four out of eight APC mutation carriers. In particular one case showed a complete loss of one allele. Among APC mutation negative cases, 4 out of 13 showed a moderate ASE. ASE of MUTYH did not show any altered expression in the cases analyzed. Spearman's Rho Test analysis showed a positive and significant correlation between APC and MUTYH genes both in cases and in controls (P = 0.020 and P < 0.001).
CONCLUSIONS: APC and MUTYH showed a reduced germline expression, not always corresponding to gene mutation. Expression of APC is decreased in mutation negative cases and this appears to be a promising indicator of FAP predisposition, while for MUTYH gene, mutation is associated to reduced mRNA expression. This study could improve the predictive genetic diagnosis of at-risk individuals belonging to families with reduced mRNA expression regardless of presence of mutation.

Rohlin A, Eiengård F, Lundstam U, et al.
GREM1 and POLE variants in hereditary colorectal cancer syndromes.
Genes Chromosomes Cancer. 2016; 55(1):95-106 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Hereditary factors are thought to play a role in at least one third of patients with colorectal cancer (CRC) but only a limited proportion of these have mutations in known high-penetrant genes. In a relatively large part of patients with a few or multiple colorectal polyps the underlying genetic cause of the disease is still unknown. Using exome sequencing in combination with linkage analyses together with detection of copy-number variations (CNV), we have identified a duplication in the regulatory region of the GREM1 gene in a family with an attenuated/atypical polyposis syndrome. In addition, 107 patients with colorectal cancer and/or polyposis were analyzed for mutations in the candidate genes identified. We also performed screening of the exonuclease domain of the POLE gene in a subset of these patients. The duplication of 16 kb in the regulatory region of GREM1 was found to be disease-causing in the family. Functional analyses revealed a higher expression of the GREM1 gene in colorectal tissue in duplication carriers. Screening of the exonuclease domain of POLE in additional CRC patients identified a probable causative novel variant c.1274A>G, p.Lys425Arg. In conclusion a high penetrant duplication in the regulatory region of GREM1, predisposing to CRC, was identified in a family with attenuated/atypical polyposis. A POLE variant was identified in a patient with early onset CRC and a microsatellite stable (MSS) tumor. Mutations leading to increased expression of genes can constitute disease-causing mutations in hereditary CRC syndromes.

Papp J, Kovacs ME, Matrai Z, et al.
Contribution of APC and MUTYH mutations to familial adenomatous polyposis susceptibility in Hungary.
Fam Cancer. 2016; 15(1):85-97 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Familial adenomatous polyposis (FAP) is a colorectal cancer predisposition syndrome with considerable genetic and phenotypic heterogeneity, defined by the development of multiple adenomas throughout the colorectum. FAP is caused either by monoallelic mutations in the adenomatous polyposis coli gene APC, or by biallelic germline mutations of MUTYH, this latter usually presenting with milder phenotype. The aim of the present study was to characterize the genotype and phenotype of Hungarian FAP patients. Mutation screening of 87 unrelated probands from FAP families (21 of them presented as the attenuated variant of the disease, showing <100 polyps) was performed using DNA sequencing and multiplex ligation-dependent probe amplification. Twenty-four different pathogenic mutations in APC were identified in 65 patients (75 %), including nine cases (37.5 %) with large genomic alterations. Twelve of the point mutations were novel. In addition, APC-negative samples were also tested for MUTYH mutations and we were able to identify biallelic pathogenic mutations in 23 % of these cases (5/22). Correlations between the localization of APC mutations and the clinical manifestations of the disease were observed, cases with a mutation in the codon 1200-1400 region showing earlier age of disease onset (p < 0.003). There were only a few, but definitive dissimilarities between APC- and MUTYH-associated FAP in our cohort: the age at onset of polyposis was significantly delayed for biallelic MUTYH mutation carriers as compared to patients with an APC mutation. Our data represent the first comprehensive study delineating the mutation spectra of both APC and MUTYH in Hungarian FAP families, and underscore the overlap between the clinical characteristics of APC- and MUTYH-associated phenotypes, necessitating a more appropriate clinical characterization of FAP families.

Kasap E, Gerceker E, Boyacıoglu SÖ, et al.
The potential role of the NEK6, AURKA, AURKB, and PAK1 genes in adenomatous colorectal polyps and colorectal adenocarcinoma.
Tumour Biol. 2016; 37(3):3071-80 [PubMed] Related Publications
Colorectal adenomatous polyp (CRAP) is a major risk factor for the development of sporadic colorectal cancer (CRC). Histone modifications are one of the epigenetic mechanisms that may have key roles in the carcinogenesis of CRC. The objective of the present study is to investigate the alternations in the defined histone modification gene expression profiles in patients with CRAP and CRC. Histone modification enzyme key gene expressions of the CRC, CRAP, and control groups were evaluated and compared using the reverse transcription PCR (RT-PCR) array method. Gene expression analysis was performed in the CRAP group after dividing the patients into subgroups according to the polyp diameter, pathological results, and morphological parameters which are risk factors for developing CRC in patients with CRAP. PAK1, NEK6, AURKA, AURKB, HDAC1, and HDAC7 were significantly more overexpressed in CRC subjects compared to the controls (p < 0.05). PAK1, NEK6, AURKA, AURKB, and HDAC1 were significantly more overexpressed in the CRAP group compared to the controls (p < 0.005). There were no significant differences between the CRAP and CRC groups with regards to PAK1, NEK6, AURKA, or AURKB gene overexpression. PAK1, NEK6, AURKA, and AURKB were significantly in correlation with the polyp diameter as they were more overexpressed in polyps with larger diameters. In conclusion, overexpressions of NEK6, AURKA, AURKB, and PAK1 genes can be used as predictive markers to decide the colonoscopic surveillance intervals after the polypectomy procedure especially in polyps with larger diameters.

Lozynska MR, Pospishil YO, Varyvoda OY, et al.
Rare case of intraintestinal stromal tumors in the patient with familial adenomatous polyposis.
Exp Oncol. 2015; 37(3):227-30 [PubMed] Related Publications
AIM: To describe the case of metachronous gastrointestinal stromal tumors in a proband with familial adenomatous polyposis (FAP), carrier of APC gene mutation in codon 1309.
MATERIAL AND METHODS: The physical examination, genealogical analysis and molecular genetic analysis of peripheral blood in 15-years-old girl with FAP and her sister, were carried out. Macroscopic, standard histological and immunohistochemical study of surgical specimens - intraintestinal tumors of the small intestine in proband was performed.
RESULTS: Extraintestinal manifestations, including congenital abnormalities of facial skeleton, typical for Gardner's syndrome, were observed in the sisters with FAP as the addition symptoms of the disease. Frameshift mutation in codon 1309 in the APC gene was detected in these patients. A rare neoplasia - metachronous gastrointestinal stromal tumor was found in proband 15 months after total colectomy for FAP. This is the third case described in the accessible medical literature.
CONCLUSION: The possible role of APC gene mutation in the development of mesenchymal neoplasms is discussed. The study of stromal tumors is important for understanding of their pathogenesis that will enable to develop effective targeted therapy.

Rashid M, Fischer A, Wilson CH, et al.
Adenoma development in familial adenomatous polyposis and MUTYH-associated polyposis: somatic landscape and driver genes.
J Pathol. 2016; 238(1):98-108 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Familial adenomatous polyposis (FAP) and MUTYH-associated polyposis (MAP) are inherited disorders associated with multiple colorectal adenomas that lead to a very high risk of colorectal cancer. The somatic mutations that drive adenoma development in these conditions have not been investigated comprehensively. In this study we performed analysis of paired colorectal adenoma and normal tissue DNA from individuals with FAP or MAP, sequencing 14 adenoma whole exomes (eight MAP, six FAP), 55 adenoma targeted exomes (33 MAP, 22 FAP) and germline DNA from each patient, and a further 63 adenomas by capillary sequencing (41 FAP, 22 MAP). With these data we examined the profile of mutated genes, the mutational signatures and the somatic mutation rates, observing significant diversity in the constellations of mutated driver genes in different adenomas, and loss-of-function mutations in WTX (9%; p < 9.99e-06), a gene implicated in regulation of the WNT pathway and p53 acetylation. These data extend our understanding of the early events in colorectal tumourigenesis in the polyposis syndromes.

Narayan S, Sharma R
Molecular mechanism of adenomatous polyposis coli-induced blockade of base excision repair pathway in colorectal carcinogenesis.
Life Sci. 2015; 139:145-52 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Colorectal cancer (CRC) is the third leading cause of death in both men and women in North America. Despite chemotherapeutic efforts, CRC is associated with a high degree of morbidity and mortality. Thus, to develop effective treatment strategies for CRC, one needs knowledge of the pathogenesis of cancer development and cancer resistance. It is suggested that colonic tumors or cell lines harbor truncated adenomatous polyposis coli (APC) without DNA repair inhibitory (DRI)-domain. It is also thought that the product of the APC gene can modulate base excision repair (BER) pathway through an interaction with DNA polymerase β (Pol-β) and flap endonuclease 1 (Fen-1) to mediate CRC cell apoptosis. The proposed therapy with temozolomide (TMZ) exploits this particular pathway; however, a high percentage of colorectal tumors continue to develop resistance to chemotherapy due to mismatch repair (MMR)-deficiency. In the present communication, we have comprehensively reviewed a critical issue that has not been addressed previously: a novel mechanism by which APC-induced blockage of single nucleotide (SN)- and long-patch (LP)-BER play role in DNA-alkylation damage-induced colorectal carcinogenesis.

Jiang SS, Li JJ, Li Y, et al.
A novel pathogenic germline mutation in the adenomatous polyposis coli gene in a Chinese family with familial adenomatous coli.
Oncotarget. 2015; 6(29):27267-74 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
Familial adenomatous polyposis (FAP) is an autosomal dominant disease manifesting as colorectal cancer in middle-aged patients. Mutations of the adenomatous polyposis coli (APC) gene contribute to both FAP and sporadic or familial colorectal carcinogenesis. Here we describe the identification of the causative APC gene defects associated with FAP in a Chinese pedigree. All patients with FAP were diagnosed by their combination of clinical features, family history, colonoscopy, and pathology examinations. Blood samples were collected and genomic DNA was extracted. Mutation analysis of APC was conducted by targeted next-generation sequencing, long-range PCR and Sanger sequencing. A novel mutation in exon 14-15(c.1936-2148 del) and intron 14 of the APC gene was demonstrated in all FAP patients and was absent in unaffected family members. This novel deletion causing FAP in Chinese kindred expands the germline mutation spectrum of the APC gene in the Chinese population.

Moreira-Nunes CA, Alcântara Dd, Lima-Júnior SF, et al.
Presence of c.3956delC mutation in familial adenomatous polyposis patients from Brazil.
World J Gastroenterol. 2015; 21(31):9413-9 [PubMed] Article available free on PMC after 01/04/2017 Related Publications
AIM: To characterize APC gene mutations and correlate them with patient phenotypes in individuals diagnosed with familial adenomatous polyposis (FAP) in northern Brazil.
METHODS: A total of 15 individuals diagnosed with FAP from 5 different families from the north of Brazil were analyzed in this study. In addition to patients with histopathological diagnosis of FAP, family members who had not developed the disease were also tested in order to identify mutations and for possible genetic counseling. All analyzed patients or their guardians signed a consent form approved by the Research Ethics Committee of the João de Barros Barreto University Hospital (Belem, Brazil). DNA extracted from the peripheral blood of a member of each of the affected families was subjected to direct sequencing. The proband of each family was sequenced to identify germline mutations using the Ion Torrent platform. To validate the detected mutations, Sanger sequencing was also performed. The samples from all patients were also tested for the identification of mutations by real-time quantitative polymerase chain reaction using the amplification refractory mutation system.
RESULTS: Through interviews with relatives and a search of medical records, it was possible to construct genograms for three of the five families included in the study. All 15 patients from the five families with FAP exhibited mutations in the APC gene, and all mutations were detected in exon 15 of the APC gene. In addition to the patients with a histological diagnosis of FAP, family members without disease symptoms showed the mutation in the APC gene. In the present study, we detected two of the three most frequent germline mutations in the literature: the mutation at codon 1309 and the mutation at codon 1061. The presence of c.3956delC mutation was found in all families from this study, and suggests that this mutation was introduced in the population of the State of Pará through ancestor immigration (i.e., a de novo mutation that arose in one member belonging to this state from Brazil).
CONCLUSION: Regardless of its origin, the c.3956delC mutation is a strong candidate biomarker of this hereditary cancer syndrome in families of northern Brazil.

Macaron C, Heald B, Burke CA
Using Genetics to Identify Hereditary Colorectal Polyposis and Cancer Syndromes in Your Patient.
Curr Gastroenterol Rep. 2015; 17(10):463 [PubMed] Related Publications
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.

Li FF, Liu Z, Yan P, et al.
Identification of a novel mutation associated with familial adenomatous polyposis and colorectal cancer.
Int J Mol Med. 2015; 36(4):1049-56 [PubMed] Related Publications
Colorectal cancer (CRC) is among the most fatal forms of solid tumor in men and women. While the majority of diagnosed CRC cases are sporadic, 15‑25% of patients have a family history of adenomatous polyposis and CRC; however, the associated gene mutations remain largely unidentified. The aim of the present study was to investigate the genomes of a four‑generational Chinese Han family with familial adenomatous polyposis and CRC to identify the potential genetic anomalies associated with the disease. Diagnoses were made by physical and enteroscopic examinations of all the family members. Mutational analyses of the potential CRC‑associated genes were carried out by direct gene sequencing, and the statistically significant differences in polymorphisms between normal and diseased populations were determined. Multiple sequence alignment and protein modeling were conducted using the Vector NTI and DNAMAN software tools. Clinical and pathological features of all the examined patients were consistent with typical familial adenomatous polyposis (FAP) syndrome. From the genomes of these family members, a 131564T>C (p.1125Val>Ala) mutation was identified in exon 15 of the APC gene, and a 1126G>C (p.324Gln>His) mutation was identified in exon 12 of the MUTYH gene. The 131564T>C mutation co‑segregated with the affected individuals in the family and was specifically associated with the incidence of CRC (P=0.018<0.05). The 1125Val residue was highly conserved in the APC protein, and the p.1125Val>Ala mutation led to changes in the secondary structure and hydrophilicity of the APC protein. In conclusion, the APC gene mutation 131564T>C is associated with FAP and the pathogenesis of CRC.

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