OBJECTIVE:O6-methylguanine-DNA methyltransferase (MGMT) removes mutagenic adducts from the O6-position of guanine in DNA. Unrepaired O6-methylguanines result in G:C to A:T transitions in mutated K-ras and p53 in colorectal tumors. Two non-synonymous MGMT coding region variants, Leu84Phe and Ile143Val, lie in close proximity to the reactive 145Cys residue and to a conserved estrogen receptor interacting helix. METHODS: We assessed the association between the MGMT Leu84Phe and Ile143Val polymorphisms and risk of colorectal cancer in two nested case-control studies: one each in the Nurses' Health Study (NHS) and the Physicians' Health Study (PHS) cohorts. RESULTS: Among 197 female cases and 2,500 controls from the NHS, the variant 143Val allele was significantly associated with reduced risk of colorectal cancer [odds ratio (OR) = 0.52, 95% confidence interval (CI) 0.33-0.80]. In women, statistically significant gene-environment interactions were found between the Leu84Phe polymorphism and alcohol intake (P = 0.03), BMI (P = 0.04) and postmenopausal hormone use (P = 0.03). The Leu84Phe and Ile143Val polymorphisms were not significantly associated with risk of colorectal cancer among 271 male cases and 451 controls from the PHS. CONCLUSIONS: Our results suggest that the common Leu84Phe and Ile143Val polymorphisms in MGMT influence risk of colorectal cancer in women possibly through modulating estrogen receptor-dependent transcriptional activation, which has previously been shown to occur in response to DNA alkylation damage.
RCT Entities:
OBJECTIVE:O6-methylguanine-DNA methyltransferase (MGMT) removes mutagenic adducts from the O6-position of guanine in DNA. Unrepaired O6-methylguanines result in G:C to A:T transitions in mutated K-ras and p53 in colorectal tumors. Two non-synonymous MGMT coding region variants, Leu84Phe and Ile143Val, lie in close proximity to the reactive 145Cys residue and to a conserved estrogen receptor interacting helix. METHODS: We assessed the association between the MGMT Leu84Phe and Ile143Val polymorphisms and risk of colorectal cancer in two nested case-control studies: one each in the Nurses' Health Study (NHS) and the Physicians' Health Study (PHS) cohorts. RESULTS: Among 197 female cases and 2,500 controls from the NHS, the variant 143Val allele was significantly associated with reduced risk of colorectal cancer [odds ratio (OR) = 0.52, 95% confidence interval (CI) 0.33-0.80]. In women, statistically significant gene-environment interactions were found between the Leu84Phe polymorphism and alcohol intake (P = 0.03), BMI (P = 0.04) and postmenopausal hormone use (P = 0.03). The Leu84Phe and Ile143Val polymorphisms were not significantly associated with risk of colorectal cancer among 271 male cases and 451 controls from the PHS. CONCLUSIONS: Our results suggest that the common Leu84Phe and Ile143Val polymorphisms in MGMT influence risk of colorectal cancer in women possibly through modulating estrogen receptor-dependent transcriptional activation, which has previously been shown to occur in response to DNA alkylation damage.
Authors: Yanhong Liu; Michael E Scheurer; Randa El-Zein; Yumei Cao; Kim-Anh Do; Mark Gilbert; Kenneth D Aldape; Qingyi Wei; Carol Etzel; Melissa L Bondy Journal: Cancer Epidemiol Biomarkers Prev Date: 2009-01 Impact factor: 4.254
Authors: Aditi Hazra; Charles S Fuchs; Takako Kawasaki; Gregory J Kirkner; David J Hunter; Shuji Ogino Journal: Cancer Causes Control Date: 2010-03 Impact factor: 2.506
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