Epidemiologic studies have shown that tobacco smoking is a risk factor for colorectal cancer, but the chemicals associated with this risk are unknown. We reported that the heterocyclic aromatic amine, 2-amino-9H-pyrido- [2,3-b]indole (AaC), a rodent carcinogen, is present at high frequency in urine of male subjects of the Shanghai Cohort Study. The urinary concentration of AaC was strongly related to the frequency of cigarette smoking. We hypothesize that the high exposure to AaC through cigarettes, and the propensity of AaC to undergo bioactivation by enzymes expressed in liver and colorectum, provides a biochemical mechanism for the development of colorectal cancer in smokers. Our long-term goal is to determine if AaC in tobacco smoke is causally related to colorectal cancer in smokers, and to elucidate the mechanistic pathways underlying this exposure-cancer relationship. There are three objectives of this application.
In Aim 1, the extent of exposure to AaC will be determined, by measuring the levels of AaC in urine and stool of tobacco smokers participating in a smoking cessation study, under a clinical trial setting.
In Aim 2, the genotoxicity of AaC in the colorectum of C57BL/6N mice will be determined, by measurement of DNA adducts and aberrant crypt foci, as early biomarkers of neoplasia. This study will provide us with a clearer idea about the carcinogenic potential of AaC in this mouse strain. The demonstration of an organ-specific genotoxic effect of AaC in the colorectum of mice is critical for our hypothesis of a causal role for AaC in tobacco-induced colorectal cancer.
In Aim 3, the major pathways of AaC metabolism will be characterized in mice and humans, especially as they relate to DNA adduct formation at the target tissue. These studies will be done with hepatocytes, colorectal cytosols, and in a mouse model where the NADPH- cytochrome P450 reductase gene has been selectively deleted in either the liver or in the small and large intestines. Dosing will be done orally or by inhalation to assess the impact of dose routes on DNA damage in the colon. These studies will reveal the capacities of enzymes across species to bioactivate AaC and the relative roles of P450s in liver and colon to induce DNA damage in the colon. This proposed research is relevant to NIH's mission on public health and highlighted by the Genes, Environment, and Health Initiative, which is designed to address the very questions raised in this application. Our hypothesis of the contribution of an HAA from a non-dietary source to human colorectal cancer risk is highly novel and innovative. The proposed research will fill critical gaps on exposure and the biochemical toxicology of AaC and advance our understanding of the genotoxicity of the most abundant aromatic amine present in mainstream tobacco smoke that is a potential risk factor of colorectal cancer.

Public Health Relevance

2-Amino-9H-pyrido[2,3-b]indole (AaC) is the most abundant of the heterocyclic amine/aromatic amine carcinogens formed in tobacco smoke and may be a causal agent of colorectal cancer in smokers. Mechanistic studies on AaC genotoxicity in the colon of an animal model and characterization of the metabolic pathways involved in bioactivation and detoxication of AaC in humans are warranted to clarify the potential role of this genotoxicant in human colorectal cancer.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA134700-06
Application #
8629539
Study Section
Cancer Etiology Study Section (CE)
Program Officer
Johnson, Ronald L
Project Start
2010-01-20
Project End
2014-12-31
Budget Start
2014-01-01
Budget End
2014-12-31
Support Year
6
Fiscal Year
2014
Total Cost
$248,894
Indirect Cost
$76,254
Name
University of Minnesota Twin Cities
Department
Pharmacology
Type
Schools of Pharmacy
DUNS #
555917996
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
Yun, Byeong Hwa; Bellamri, Medjda; Rosenquist, Thomas A et al. (2018) Method for Biomonitoring DNA Adducts in Exfoliated Urinary Cells by Mass Spectrometry. Anal Chem 90:9943-9950
Turesky, Robert J (2018) Mechanistic Evidence for Red Meat and Processed Meat Intake and Cancer Risk: A Follow-up on the International Agency for Research on Cancer Evaluation of 2015. Chimia (Aarau) 72:718-724
Sabbioni, Gabriele; Turesky, Robert J (2017) Biomonitoring Human Albumin Adducts: The Past, the Present, and the Future. Chem Res Toxicol 30:332-366
Cai, Tingting; Bellamri, Medjda; Ming, Xun et al. (2017) Quantification of Hemoglobin and White Blood Cell DNA Adducts of the Tobacco Carcinogens 2-Amino-9H-pyrido[2,3-b]indole and 4-Aminobiphenyl Formed in Humans by Nanoflow Liquid Chromatography/Ion Trap Multistage Mass Spectrometry. Chem Res Toxicol 30:1333-1343
Bellamri, Medjda; Le Hegarat, Ludovic; Turesky, Robert J et al. (2017) Metabolism of the Tobacco Carcinogen 2-Amino-9H-pyrido[2,3-b]indole (A?C) in Primary Human Hepatocytes. Chem Res Toxicol 30:657-668
Cai, Tingting; Yao, Lihua; Turesky, Robert J (2016) Bioactivation of Heterocyclic Aromatic Amines by UDP Glucuronosyltransferases. Chem Res Toxicol 29:879-91
Pathak, Khyatiben V; Chiu, Ting-Lan; Amin, Elizabeth Ambrose et al. (2016) Methemoglobin Formation and Characterization of Hemoglobin Adducts of Carcinogenic Aromatic Amines and Heterocyclic Aromatic Amines. Chem Res Toxicol 29:255-69
Bellamri, Medjda; Le Hegarat, Ludovic; Vernhet, Laurent et al. (2016) Human T lymphocytes bioactivate heterocyclic aromatic amines by forming DNA adducts. Environ Mol Mutagen 57:656-667
Kim, Sangyub; Guo, Jingshu; O'Sullivan, M Gerald et al. (2016) Comparative DNA adduct formation and induction of colonic aberrant crypt foci in mice exposed to 2-amino-9H-pyrido[2,3-b]indole, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, and azoxymethane. Environ Mol Mutagen 57:125-36
Turesky, Robert J; Konorev, Dmitri; Fan, Xiaoyu et al. (2015) Effect of Cytochrome P450 Reductase Deficiency on 2-Amino-9H-pyrido[2,3-b]indole Metabolism and DNA Adduct Formation in Liver and Extrahepatic Tissues of Mice. Chem Res Toxicol 28:2400-10

Showing the most recent 10 out of 17 publications