Tobacco-specific nitrosamines, NNK and NNN, are carcinogenic in laboratory and are potential human carcinogens. NNN is metabolized to a DNA pyridyloxobutylating agent whereas NNK is metabolized to both DNA pyridyloxobutylating and methylating intermediates. Pyridyloxobutylation of DNA results in the formation of a variety of DNA adducts, one of which is O6-[4-oxo-4-(3-pyridyl)butyl]guanine (O6-pobG). Our previous studies indicate that this mutagenic adduct is repaired by O6-alkylguanine-DNA alkyltransferase (AGT). Human AGT variants differ substantially in their ability to repair O6-pobG, suggesting that individuals with reduced repair capacity may be at increased risk of tobacco-related cancers. However, it is unclear what the overall role O6-pobG makes in the mutagenic and carcinogenic properties of pyridyloxobutylating nitrosamines. The central hypothesis under investigation in this grant is that O6-pobG contributes significantly to the mutagenic and carcinogenic activity of the tobacco-specific nitrosamines, NNK and NNN, when not repaired. We plan to test our central hypothesis by pursuing the following specific aims: 1) Determine if O6-pobG formation and persistence are linked to the pulmonary carcinogenic properties of NNN and NNKOAc in A/J mice. 2) Phenotype human livers for their ability to repair bulky O6-alkylguanine adducts relative to O6-mG adducts by AGT. 3) Determine the involvement of other repair pathways in the overall repair of the mutagenic O6-pobG and determine whether these pathways affect the mutagenic properties of pyridyloxobutylating agents. Collectively, these aims will establish the importance of formation and repair of O6-pobG in the mutagenic and carcinogenic properties of pyridyloxobutylating nitrosamines. These studies will set the stage for a molecular epidemiological study to determine whether individuals who are unable to repair this mutagenic adduct are at increased risk of tobacco-related cancers. ? ?

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA115309-02
Application #
7060517
Study Section
Cancer Etiology Study Section (CE)
Program Officer
Poland, Alan P
Project Start
2005-05-01
Project End
2010-04-30
Budget Start
2006-05-01
Budget End
2007-04-30
Support Year
2
Fiscal Year
2006
Total Cost
$253,866
Indirect Cost
Name
University of Minnesota Twin Cities
Department
Public Health & Prev Medicine
Type
Schools of Public Health
DUNS #
555917996
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
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