Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0009402 (colorectal cancer)
 53,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The MUTYH DNA glycosylase specifically removes adenine misincorporated by replicative polymerases opposite the oxidized purine 8-oxo-7,8-dihydroguanine (8-oxoG). A defective protein activity results in the accumulation of G>T transversions because of unrepaired 8-oxoG:A mismatches. In humans, MUTYH germline mutations are associated with a recessive form of familial adenomatous polyposis and colorectal cancer predisposition (MUTYH-associated polyposis, MAP). Here we studied the repair capacity of the MUTYH variants R171W, E466del, 137insIW, Y165C and G382D, identified in MAP patients. Following expression and purification of human proteins from a bacterial system, we investigated MUTYH incision capacity on an 8-oxoG:A substrate by standard glycosylase assays. For the first time, we employed the surface plasmon resonance (SPR) technology for real-time recording of the association/dissociation of wild-type and MUTYH variants from an 8-oxoG:A DNA substrate. When compared to the wild-type protein, R171W, E466del and Y165C variants showed a severe reduction in the binding affinity towards the substrate, while 137insIW and G382D mutants manifested only a slight decrease mainly due to a slower rate of association. This reduced binding was always associated with impairment of glycosylase activity, with adenine removal being totally abrogated in R171W, E466del and Y165C and only partially reduced in 137insIW and G382D. Our findings demonstrate that SPR analysis is suitable to identify defective enzymatic behaviour even when mutant proteins display minor alterations in substrate recognition.
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PMID:Functional analysis of MUTYH mutated proteins associated with familial adenomatous polyposis. 2041 87

Germline mutations within the adenomatous polyposis coli (APC) gene are associated with familial adenomatous polyposis (FAP), an autosomal dominant disease predisposing individuals to colorectal cancer. Identification of APC mutations has important implications for genetic counseling and management of FAP patients. We examined the APC mutation status of 10 Korean FAP patients by polymerase chain reaction-direct sequencing method and found six APC mutations, including three novel mutations. Testing for MUTYH mutation was done for FAP patients in whom no mutation in the APC gene was identified. Three novel mutations (c.1654_1663delTCTTGGCGAG, c.3709C>T, and c.6092_6094delinsTT) and three previously reported mutations (c.3631_3632delAT, c.4438C>T, and c.4612_4613delGA) were detected. The MUTYH mutation was not detected in any of the four FAP patients without an APC mutation. This finding of three novel mutations in a group of Korean FAP patients broadens the spectrum of APC mutations.
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PMID:Three novel mutations of the APC gene in Korean patients with familial adenomatous polyposis. 2051 32

MUTYH-associated polyposis (MAP) is a colorectal cancer predisposition syndrome that is caused by inherited biallelic mutations in the base excision repair (BER) gene, MUTYH. MUTYH is a DNA glycosylase that removes adenine (A) misinserted opposite 8-oxo-7,8-dihydro-2'-deoxyguanosine (OG). In this work, wild type (WT) MUTYH overexpressed using a baculovirus-driven insect cell expression system (BEVS) provided significantly higher levels of enzyme compared to bacterial overexpression. The isolated MUTYH enzyme was analyzed for potential post-translational modifications using mass spectrometry. An in vivo phosphorylation site was validated at Serine 524, which is located in the C-terminal OG recognition domain within the proliferating cell nuclear antigen (PCNA) binding region. Characterization of the phosphomimetic (S524D) and phosphoablating (S524A) mutants together with the observation that Ser 524 can be phosphorylated suggest that this residue may play an important regulatory role in vivo by altering stability and OG:A mismatch affinity.
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PMID:Ser 524 is a phosphorylation site in MUTYH and Ser 524 mutations alter 8-oxoguanine (OG): a mismatch recognition. 2072 27

The DNA glycosylase MutY homologue (MYH or MUTYH) removes adenines misincorporated opposite 8-oxoguanine as part of the base excision repair pathway. Importantly, defects in human MYH (hMYH) activity cause the inherited colorectal cancer syndrome MYH-associated polyposis. A key feature of MYH activity is its coordination with cell cycle checkpoint via interaction with the Rad9-Rad1-Hus1 (9-1-1) complex. The 9-1-1 complex facilitates cell cycle checkpoint activity and coordinates this activity with ongoing DNA repair. The interdomain connector (IDC, residues 295-350) between the catalytic domain and the 8-oxoguanine recognition domain of hMYH is a critical element that maintains interactions with the 9-1-1 complex. We report the first crystal structure of a eukaryotic MutY protein, a fragment of hMYH (residues 65-350) that consists of the catalytic domain and the IDC. Our structure reveals that the IDC adopts a stabilized conformation projecting away from the catalytic domain to form a docking scaffold for 9-1-1. We further examined the role of the IDC using Schizosaccharomyces pombe MYH as model system. In vitro studies of S. pombe MYH identified residues I261 and E262 of the IDC (equivalent to V315 and E316 of the hMYH IDC) as critical for maintaining the MYH/9-1-1 interaction. We determined that the eukaryotic IDC is also required for DNA damage selection and robust enzymatic activity. Our studies also provide the first evidence that disruption of the MYH/9-1-1 interaction diminishes the repair of oxidative DNA damage in vivo. Thus, preserving the MYH/9-1-1 interaction contributes significantly to minimizing the mutagenic potential of oxidative DNA damage.
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PMID:A structural hinge in eukaryotic MutY homologues mediates catalytic activity and Rad9-Rad1-Hus1 checkpoint complex interactions. 2081 84

Whether people who inherit a mutation in MUTYH from only one parent (monoallelic mutation) are at increased risk of colorectal cancer (CRC) remains controversial. Most previous studies and meta-analyses have not found statistically significant associations but, given carriers are relatively rare, may be underpowered to detect small increased risks. We have conducted a systematic review and meta-regression analysis of previously published case-control studies to estimate the strength of association for monoallelic MUTYH mutation and CRC risk. Potential sources of heterogeneity were evaluated. We have compared the carrier frequency in cases with a family history of CRC to that of controls, as a novel and powerful design, to measure statistical evidence of an association but not the strength of association. The magnitude of the genotype-disease association, estimated from a pooled odds ratio comparing cases unselected for family history with controls, was 1.15 (95% CI = 0.98-1.36) and not substantially altered by adjustment for potential sources of heterogeneity. Monoallelic mutation carrier frequency was greater for cases ascertained due to a family history (3.3%; SE 0.9%) than for controls (1.4%; SE 0.3%) (P = 0.02). Monoallelic MUTYH mutation carriers are at increased risk of CRC but the average increase is small.
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PMID:Association between monoallelic MUTYH mutation and colorectal cancer risk: a meta-regression analysis. 2106 Nov 73

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.
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PMID:Cancer risks for monoallelic MUTYH mutation carriers with a family history of colorectal cancer. 2117 Oct 15

Advances in molecular biology have defined the molecular basis for colorectal cancer (CRC). Though only a fraction of CRC has been determined to have a hereditary component, the discovery of genetic alterations in these clinical syndromes has permitted definition of similar discoveries in sporadic CRC. Here we will delineate the molecular basis for the most common of these defined syndromes, including familial adenomatous polyposis, hereditary non-polyposis colon cancer, MUTYH associated polyposis, Juvenile polyposis, Peutz-Jeghers syndrome, and Cowden's syndrome. The newest paradigm with implications for the pathogenesis of sporadic CRC is called the cancer stem cell hypothesis. As this paradigm also implicates aberrations in molecular pathways, a brief discussion of this hypothesis is included.
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PMID:MOLECULAR BASIS OF HEREDITARY COLORECTAL CANCER. 2177 43

The Czech Republic has one of the highest incidences of colorectal cancer (CRC) in Europe. To evaluate whether sporadic CRCs in Czech patients have specific mutational profiles we analysed somatic genetic changes in known CRC genes (APC, KRAS, TP53, CTNNB1, MUTYH and BRAF, loss of heterozygosity (LOH) at the APC locus, microsatellite instability (MSI), and methylation of the MLH1 promoter) in 103 tumours from 102 individuals. The most frequently mutated gene was APC (68.9% of tumours), followed by KRAS (31.1%), TP53 (27.2%), BRAF (8.7%) and CTNNB1 (1.9%). Heterozygous germline MUTYH mutations in 2 patients were unlikely to contribute to the development of their CRCs. LOH at the APC locus was found in 34.3% of tumours, MSI in 24.3% and MLH1 methylation in 12.7%. Seven tumours (6.9%) were without any changes in the genes tested. The analysis yielded several findings possibly specific for the Czech cohort. Somatic APC mutations did not cluster in the mutation cluster region (MCR). Tumours with MSI but no MLH1 methylation showed earlier onset and more severe mutational profiles compared to MSI tumours with MLH1 methylation. TP53 mutations were predominantly located outside the hot spots, and transitions were underrepresented. Our analysis supports the observation that germline MUTYH mutations are rare in Czech individuals with sporadic CRCs. Our findings suggest the influence of specific ethnic genetic factors and/or lifestyle and dietary habits typical for the Czech population on the development of these cancers.
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PMID:Molecular genetic analysis of 103 sporadic colorectal tumours in Czech patients. 2190 Nov 62

FAP is characterized by 100-1000s of adenomatous polyps in colon and rectum, and is in 70% of the patients associated with extracolonic manifestations. Attenuated FAP (AFAP) is a less severe form of FAP, marked by the presence of < 100 polyps and a later onset of colorectal cancer (CRC). (A)FAP is caused by autosomal dominantly inherited mutations in the APC (Adenomatous polyposis coli) gene, a tumour suppressor gene that controls beta-catenin turnover in the Wnt pathway. De novo occurrence is reported in 30-40% of the patients. Mutations are detected in 85% of classical FAP families, while only 20%-30% of AFAP cases will exhibit a germline APC mutation. MUTYH is the second (A)FAP-related gene and is involved with base-excision repair of DNA damaged by oxidative stress. MUTYH mutations are inherited in an autosomal recessive way and account for 10%-20% of classical FAP cases without an APC mutation and for 30% of AFAP cases. Genotype-phenotype correlations exist for mutations in the APC gene, however, contradictions in the literature caution against the sole use of the genotype for decisions regarding clinical management. Once the family's specific APC mutation is identified in the proband, predictive testing for first degree relatives is possible from the age of 10 to 12 years on. For AFAP, relatives are tested at age 18 and older. Opinions about the appropriate ages at which to initiate genetic testing may vary. Physicians must have a discussion about prenatal testing with patients in childbearing age. They may either opt for conventional prenatal diagnosis (amniocentesis or chorionic villous sampling) or for preimplantation genetic diagnosis (PGD).
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PMID:The genetics of familial adenomatous polyposis (FAP) and MutYH-associated polyposis (MAP). 2210 48

Methylation of the MLH1 gene promoter region is an underlying cause of colorectal cancer (CRC) with high microsatellite instability (MSI-H) diagnosed in persons without a germ line mutation in a mismatch repair (MMR) gene (non-Lynch Syndrome CRC). It is unclear whether relatives of CRC cases with MLH1 methylation have an increased risk of colorectal or other cancers. In this retrospective cohort study, we assessed risk of CRC and other cancers for the first- and second-degree relatives of CRC cases with a methylated MLH1 gene, by comparing observed numbers of cases with those expected on the basis of age-, sex-, and country-specific cancer incidences (standardized incidence ratios). The cohort consisted of 3,128 first- and second-degree relatives of the 233 MLH1-methylated CRC cases with no MMR or MUTYH gene mutations. The standardized incidence ratio (SIR) for CRC was 1.60 [95% confidence interval (CI), 1.22-2.16] for first-degree relatives and 1.08 (0.74-1.60) for second-degree relatives. The SIR for gastric cancer was 2.58 (1.52-4.71) for first-degree relatives and 4.52 (2.23-10.61) for second-degree relatives and, for ovarian cancer, it was 2.16 (1.29-3.86) for first-degree relatives. The risk of liver cancer was also increased significantly in first-degree relatives but the estimate was on the basis of only two cases. These data imply that relatives of CRC cases with MLH1 methylation may be at increased risk of CRC and stomach cancer and possibly ovarian and liver cancer, suggesting that there may be a heritable factor for CRC and other cancers associated with MLH1 methylation in non-Lynch syndrome CRCs.
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PMID:Cancer risks for the relatives of colorectal cancer cases with a methylated MLH1 promoter region: data from the Colorectal Cancer Family Registry. 2214 22


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