Human colorectal mucosal O6-alkylguanine DNA-alkyltransferase activity and DNA-N7-methylguanine levels in colorectal adenoma cases and matched referents.

2.50
Hdl Handle:
http://hdl.handle.net/10541/73077
Title:
Human colorectal mucosal O6-alkylguanine DNA-alkyltransferase activity and DNA-N7-methylguanine levels in colorectal adenoma cases and matched referents.
Authors:
Lees, Nicholas P; Harrison, Kathryn L; Hall, C Nicholas; Margison, Geoffrey P; Povey, Andrew C
Abstract:
BACKGROUND AND AIMS: O(6)-alkylguanine DNA-alkyltransferase (MGMT) provides protection against alkylating agent-induced GC-->AT transition mutations. Such mutations are frequently seen in the KRAS oncogene of large colorectal adenomas, but whether adenoma or mutational risk in humans is influenced by MGMT activity and alkylating agent exposure is unclear. Hence, MGMT activity and, as an indicator of alkylating agent exposure, DNA-N7-methylguanine (N7-MeG) levels were determined in the normal tissue of patients with and without adenomas. METHODS: Biopsy specimens of normal colorectal mucosa were collected during colonoscopy from 85 patients with histologically proved colorectal adenomas (cases) and from 85 patients free of gastrointestinal neoplasia (referents) matched by age, sex and biopsy location. MGMT activity and N7-MeG levels were measured in colorectal tissue extracts and DNA, respectively. RESULTS: MGMT activity was higher in the normal mucosa of cases than in referents (6.65+/-3.03 vs 5.61+/-2.74 fmol/micro g DNA, p = 0.01). On stratification of cases, MGMT activity was found to be considerably greater in the normal mucosa of cases with large adenomas (p = 0.003) and slightly higher in cases with a GC-->AT transition mutation in the K-ras gene (p = 0.03). Elevated MGMT levels were associated with an increased risk of adenoma (OR 1.17, 95% CI 1.03 to 1.33 per unit increase in activity). Detectable levels of N7-MeG were found in DNA from 89% of cases and 93% of referents, with levels ranging from <0.1 to 7.7 micro mol/mol dG. Cases and referents had similar DNA-N7-MeG levels. CONCLUSIONS: Human exposure to methylating agents is widespread. MGMT activity is increased in the normal mucosa of patients with adenomas.
Affiliation:
Cancer Research UK Carcinogenesis Group, Paterson Institute for Cancer Research, Christie Hospital, Manchester, UK.
Citation:
Human colorectal mucosal O6-alkylguanine DNA-alkyltransferase activity and DNA-N7-methylguanine levels in colorectal adenoma cases and matched referents. 2007, 56 (3):380-4 Gut
Journal:
Gut
Issue Date:
Mar-2007
URI:
http://hdl.handle.net/10541/73077
DOI:
10.1136/gut.2006.097899
PubMed ID:
16891355
Type:
Article
Language:
en
ISSN:
0017-5749
Appears in Collections:
All Paterson Institute for Cancer Research

Full metadata record

DC FieldValue Language
dc.contributor.authorLees, Nicholas P-
dc.contributor.authorHarrison, Kathryn L-
dc.contributor.authorHall, C Nicholas-
dc.contributor.authorMargison, Geoffrey P-
dc.contributor.authorPovey, Andrew C-
dc.date.accessioned2009-07-09T12:13:33Z-
dc.date.available2009-07-09T12:13:33Z-
dc.date.issued2007-03-
dc.identifier.citationHuman colorectal mucosal O6-alkylguanine DNA-alkyltransferase activity and DNA-N7-methylguanine levels in colorectal adenoma cases and matched referents. 2007, 56 (3):380-4 Guten
dc.identifier.issn0017-5749-
dc.identifier.pmid16891355-
dc.identifier.doi10.1136/gut.2006.097899-
dc.identifier.urihttp://hdl.handle.net/10541/73077-
dc.description.abstractBACKGROUND AND AIMS: O(6)-alkylguanine DNA-alkyltransferase (MGMT) provides protection against alkylating agent-induced GC-->AT transition mutations. Such mutations are frequently seen in the KRAS oncogene of large colorectal adenomas, but whether adenoma or mutational risk in humans is influenced by MGMT activity and alkylating agent exposure is unclear. Hence, MGMT activity and, as an indicator of alkylating agent exposure, DNA-N7-methylguanine (N7-MeG) levels were determined in the normal tissue of patients with and without adenomas. METHODS: Biopsy specimens of normal colorectal mucosa were collected during colonoscopy from 85 patients with histologically proved colorectal adenomas (cases) and from 85 patients free of gastrointestinal neoplasia (referents) matched by age, sex and biopsy location. MGMT activity and N7-MeG levels were measured in colorectal tissue extracts and DNA, respectively. RESULTS: MGMT activity was higher in the normal mucosa of cases than in referents (6.65+/-3.03 vs 5.61+/-2.74 fmol/micro g DNA, p = 0.01). On stratification of cases, MGMT activity was found to be considerably greater in the normal mucosa of cases with large adenomas (p = 0.003) and slightly higher in cases with a GC-->AT transition mutation in the K-ras gene (p = 0.03). Elevated MGMT levels were associated with an increased risk of adenoma (OR 1.17, 95% CI 1.03 to 1.33 per unit increase in activity). Detectable levels of N7-MeG were found in DNA from 89% of cases and 93% of referents, with levels ranging from <0.1 to 7.7 micro mol/mol dG. Cases and referents had similar DNA-N7-MeG levels. CONCLUSIONS: Human exposure to methylating agents is widespread. MGMT activity is increased in the normal mucosa of patients with adenomas.en
dc.language.isoenen
dc.subjectColorectal Canceren
dc.subjectCancer DNAen
dc.subjectCancer Proteinsen
dc.subject.meshAdenoma-
dc.subject.meshAged-
dc.subject.meshAged, 80 and over-
dc.subject.meshCarrier Proteins-
dc.subject.meshCase-Control Studies-
dc.subject.meshColonic Polyps-
dc.subject.meshColonoscopy-
dc.subject.meshColorectal Neoplasms-
dc.subject.meshDNA Mutational Analysis-
dc.subject.meshDNA Repair-
dc.subject.meshDNA, Neoplasm-
dc.subject.meshFemale-
dc.subject.meshGuanine-
dc.subject.meshHumans-
dc.subject.meshIntestinal Mucosa-
dc.subject.meshMale-
dc.subject.meshMembrane Proteins-
dc.subject.meshMiddle Aged-
dc.subject.meshNeoplasm Proteins-
dc.subject.meshO(6)-Methylguanine-DNA Methyltransferase-
dc.titleHuman colorectal mucosal O6-alkylguanine DNA-alkyltransferase activity and DNA-N7-methylguanine levels in colorectal adenoma cases and matched referents.en
dc.typeArticleen
dc.contributor.departmentCancer Research UK Carcinogenesis Group, Paterson Institute for Cancer Research, Christie Hospital, Manchester, UK.en
dc.identifier.journalGuten

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