Metabolism of NNK Among African Americans

Lung cancer is the most common cause of cancer death in the United States, with the annual
number of cases estimated at 162,460 deaths per year. It is more prevalent in African
Americans as compared to European Americans. Cigarette smoking causes up to 90% of lung
cancer, being the major risk factor in both African Americans and European Americans.

Tobacco-specific nitrosamines (TSNA) are among the most significant carcinogens in tobacco
products. Multiple international studies clearly document the occurrence of substantial
amounts of these carcinogens in both unburned tobacco and tobacco smoke. One of the most
prevalent of these compounds, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), is
present in both unburned tobacco and cigarette smoke, and is a remarkably effective lung
carcinogen in laboratory animals, inducing lung tumors in rodents independent of the route
of administration. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolite of
NNK, is also a pulmonary carcinogen. NNK has been classified by the International Agency for
Research on Cancer as a Group 1 carcinogen (carcinogenic to humans). Consistent with this, 2
recent studies by our group have demonstrated that levels of NNAL in serum or urine are
related to lung cancer in smokers.

Our primary aim is to conduct a comprehensive analysis of urinary biomarkers of NNK
metabolic activation and detoxification in African American and European American smokers.
We hypothesize that, after adjustment for smoking level, the relative contribution of the
biomarkers of NNK metabolic activation to the total amount of NNK metabolites will be higher
in African Americans as compared to European Americans. Our secondary aim is to measure in
exfoliated oral mucosa cells of African American and European American smokers DNA adducts
formed as a result of NNK metabolic activation. The results of these measurements will offer
a direct measure of NNK-induced DNA damage in smokers, and will be critical to an
understanding of the balance between the urinary excretion of NNK metabolites and the extent
of NNK DNA binding. We hypothesize that African Americans will have in the DNA of their oral
mucosa cells higher levels of NNK-derived DNA adducts as compared to European Americans.
Finally, we will investigate the relationship between levels of NNK-derived DNA adducts
measured in oral mucosa cells and the rates of repair of these adducts in cultured
lymphocytes from our subjects. These measurements will allow us to evaluate more fully the
role of variations in NNK metabolism in the observed differences in lung cancer risk between
European American and African American smokers. We expect that that African Americans will
have lower capacity to repair NNK-induced DNA damage as compared to European Americans, and
this will correlate with higher levels of NNK-derived buccal DNA adducts.

Inclusion Criteria:

1. Male or female subjects with a smoking history of at least 10 cigarettes daily for at
least 1 year;

2. Subjects report themselves, biological parents and both sets of biological
grandparents as

- African American or African descent or

- European American or European descent

3. Subjects are in apparently good physical health (no unstable medical condition)

4. Subjects are in stable, good mental health (e.g. not currently, within the past 6
months, experiencing unstable or untreated psychiatric diagnosis, including substance
abuse, as determined by the PRIME-MD);

5. Subjects have provided written informed consent to participate in the study.

Exclusion Criteria:

1. Unstable medical conditions including cancer, coronary heart disease and arrhythmia

2. Cannot or unwilling to identify ethnic/racial ancestry

3. Women who are currently pregnant or breast feeding

4. Currently using any other tobacco or nicotine-containing product

5. Currently taking any medications that affect relevant metabolic enzymes.