Publications by authors named "Robert J Turesky"

113 Publications

Cytotoxicity and genotoxicity of the carcinogen aristolochic acid I (AA-I) in human bladder RT4 cells.

Arch Toxicol 2021 May 3. Epub 2021 May 3.

Masonic Cancer Center and Department of Medicinal Chemistry, Cancer and Cardiovascular Research Building, University of Minnesota, 2231 6th Street, Minneapolis, MN, 55455, USA.

Aristolochic acid (AA-I) induces upper urothelial tract cancer (UUTC) and bladder cancer (BC) in humans. AA-I forms the 7-(2'-deoxyadenosin-N-yl)aristolactam I (dA-AL-I) adduct, which induces multiple A:T-to-T:A transversion mutations in TP53 of AA-I exposed UTUC patients. This mutation is rarely reported in TP53 of other transitional cell carcinomas and thus recognized as an AA-I mutational signature. A:T-to-T:A transversion mutations were recently detected in bladder tumors of patients in Asia with known AA-I-exposure, implying that AA-I contributes to BC. Mechanistic studies on AA-I genotoxicity have not been reported in human bladder. In this study, we examined AA-I DNA adduct formation and mechanisms of toxicity in the human RT4 bladder cell line. The biological potencies of AA-I were compared to 4-aminobiphenyl, a recognized human bladder carcinogen, and several structurally related carcinogenic heterocyclic aromatic amines (HAA), which are present in urine of smokers and omnivores. AA-I (0.05-10 µM) induced a concentration- and time-dependent cytotoxicity. AA-I (100 nM) DNA adduct formation occurred at over a thousand higher levels than the principal DNA adducts formed with 4-ABP or HAAs (1 µM). dA-AL-I adduct formation was detected down to a 1 nM concentration. Studies with selective chemical inhibitors provided evidence that NQO1 is the major enzyme involved in AA-I bio-activation in RT4 cells, whereas CYP1A1, another enzyme implicated in AA-I toxicity, had a lesser role in bio-activation or detoxification of AA-I. AA-I DNA damage also induced genotoxic stress leading to p53-dependent apoptosis. These biochemical data support the human mutation data and a role for AA-I in BC.
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http://dx.doi.org/10.1007/s00204-021-03059-3DOI Listing
May 2021

Comprehensive Analysis of DNA Adducts Using Data-Independent wSIM/MS Acquisition and wSIM-City.

Anal Chem 2021 04 12;93(16):6491-6500. Epub 2021 Apr 12.

Masonic Cancer Center, University of Minnesota, Minneapolis 55455, Minnesota, United States.

A novel software has been created to comprehensively characterize covalent modifications of DNA through mass spectral analysis of enzymatically hydrolyzed DNA using the neutral loss of 2'-deoxyribose, a nearly universal MS fragmentation process of protonated 2'-deoxyribonucleosides. These covalent modifications termed DNA adducts form through xenobiotic exposures or by reaction with endogenous electrophiles and can induce mutations during cell division and initiate carcinogenesis. DNA adducts are typically present at trace levels in the human genome, requiring a very sensitive and comprehensive data acquisition and analysis method. Our software, wSIM-City, was created to process mass spectral data acquired by a wide selected ion monitoring (wSIM) with gas-phase fractionation and coupled to wide MS fragmentation. This untargeted approach can detect DNA adducts at trace levels as low as 1.5 adducts per 10 nucleotides. This level of sensitivity is sufficient for comprehensive analysis and characterization of DNA modifications in human specimens.
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http://dx.doi.org/10.1021/acs.analchem.1c00362DOI Listing
April 2021

Risk of two common glandular cell-type cancers (breast and colorectal cancers) in Chinese occupational chefs: a nationwide ecological study in Taiwan.

Int Arch Occup Environ Health 2021 Feb 28. Epub 2021 Feb 28.

Research Center for Environmental Medicine, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Room 721, CS Building, Kaohsiung, Taiwan.

Objectives: Cooking oil fumes (COFs) contain many carcinogens. We investigated the association between COFs and incidence risk of colorectal cancer and female breast in chefs.

Methods: We identified Chinese food chefs and non-Chinese food chefs from Taiwan's national database of certified chefs in 1984-2007. In total, 379,275 overall and 259,450 females had not been diagnosed as having any cancer before chef certification. We followed these chefs in Taiwan's Cancer Registry Database (1979-2010) and Taiwan's National Death Statistics Database (1985-2011) for newly diagnosed colorectal cancer and female breast cancer.

Results: A total of 4,218,135 and 2,873,515 person-years were included in our analysis of colorectal cancer and female breast cancer incidence, respectively. Compared to non-Chinese food chefs, the Chinese food chefs had an adjusted IRR for colorectal cancer of 1.65 (95% CI  1.17-2.33). The risk of colorectal cancer was even higher among female Chinese food chefs certified for more than 5 years (adjusted incident rate ratio (IRR) = 2.39, 95% CI   1.38-4.12). For female breast cancer, the risk was also significant (adjusted IRR = 1.40, 95% CI 1.10-1.78) and the risks were even higher in female Chinese food chefs certified for more than 5 years (adjusted IRR = 1.74, 95% CI 1.37-2.22).

Conclusions: This study found that Chinese food chefs had an increased risk of colorectal cancer and female breast cancer, particularly female chefs who had worked for more than 5 years. Future human and animal studies are necessary to re-confirm these findings.
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http://dx.doi.org/10.1007/s00420-021-01673-3DOI Listing
February 2021

Additive Effects of Arsenic and Aristolochic Acid in Chemical Carcinogenesis of Upper Urinary Tract Urothelium.

Cancer Epidemiol Biomarkers Prev 2021 Feb 4;30(2):317-325. Epub 2020 Dec 4.

Department of Urology, National Taiwan University Hospital, Taipei, Taiwan.

Background: Aristolochic acids (AA) and arsenic are chemical carcinogens associated with urothelial carcinogenesis. Here we investigate the combined effects of AA and arsenic toward the risk of developing upper tract urothelial carcinoma (UTUC).

Methods: Hospital-based ( = 89) and population-based (2,921 cases and 11,684 controls) Taiwanese UTUC cohorts were used to investigate the association between exposure to AA and/or arsenic and the risk of developing UTUC. In the hospital cohort, AA exposure was evaluated by measuring aristolactam-DNA adducts in the renal cortex and by identifying A>T mutations in tumors. In the population cohort, AA exposure was determined from prescription health insurance records. Arsenic levels were graded from 0 to 3 based on concentrations in well water and the presence of arseniasis-related diseases.

Results: In the hospital cohort, 43, 26, and 20 patients resided in grade 0, 1+2, and 3 arseniasis-endemic areas, respectively. Aristolactam-DNA adducts were present in >90% of these patients, indicating widespread AA exposure. A>T mutations in were detected in 28%, 44%, and 22% of patients residing in grade 0, 1+2, and 3 arseniasis-endemic areas, respectively. Population studies revealed that individuals who consumed more AA-containing herbs had a higher risk of developing UTUC in both arseniasis-endemic and nonendemic areas. Logistic regression showed an additive effect of AA and arsenic exposure on the risk of developing UTUC.

Conclusions: Exposure to both AA and arsenic acts additively to increase the UTUC risk in Taiwan.

Impact: This is the first study to investigate the combined effect of AA and arsenic exposure on UTUC.
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http://dx.doi.org/10.1158/1055-9965.EPI-20-1090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8083126PMC
February 2021

Mutagenicity of 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-OH-PhIP) in human TP53 knock-in (Hupki) mouse embryo fibroblasts.

Food Chem Toxicol 2021 Jan 12;147:111855. Epub 2020 Nov 12.

Department of Analytical, Environmental and Forensic Sciences, MRC-PHE Centre for Environment and Health, King's College London, London, SE1 9NH, UK.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a possible human carcinogen formed in cooked fish and meat. PhIP is bioactivated by cytochrome P450 enzymes to form 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-OH-PhIP), a genotoxic metabolite that reacts with DNA leading to the mutation-prone DNA adduct N-(deoxyguanosin-8-yl)-PhIP (dG-C8-PhIP). Here, we studied N-OH-PhIP-induced whole genome mutagenesis in human TP53 knock-in (Hupki) mouse embryo fibroblasts (HUFs) immortalised and subjected to whole genome sequencing (WGS). In addition, mutagenicity of N-OH-PhIP in TP53 and the lacZ reporter gene were assessed. TP53 mutant frequency in HUF cultures treated with N-OH-PhIP (2.5 μM for 24 h, n = 90) was 10% while no TP53 mutations were found in untreated controls (DMSO for 24 h, n = 6). All N-OH-PhIP-induced TP53 mutations occurred at G:C base pairs with G > T/C > A transversions accounting for 58% of them. TP53 mutations characteristic of those induced by N-OH-PhIP have been found in human tumours including breast and colorectal, which are cancer types that have been associated with PhIP exposure. LacZ mutant frequency increased 25-fold at 5 μM N-OH-PHIP and up to ~350 dG-C8-PhIP adducts/10 nucleosides were detected by ultra-performance liquid chromatography-electrospray ionisation multistage scan mass spectrometry (UPLC-ESI-MS) at this concentration. In addition, a WGS mutational signature defined by G > T/C > A transversions was present in N-OH-PhIP-treated immortalised clones, which showed similarity to COSMIC SBS4, 18 and 29 signatures found in human tumours.
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http://dx.doi.org/10.1016/j.fct.2020.111855DOI Listing
January 2021

Mass Spectrometric Quantitation of Apurinic/Apyrimidinic Sites in Tissue DNA of Rats Exposed to Tobacco-Specific Nitrosamines and in Lung and Leukocyte DNA of Cigarette Smokers and Nonsmokers.

Chem Res Toxicol 2020 09 9;33(9):2475-2486. Epub 2020 Sep 9.

Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455, United States.

Metabolic activation of the carcinogenic tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and '-nitrosonornicotine (NNN) results in formation of reactive electrophiles that modify DNA to produce a variety of products including methyl, 4-(3-pyridyl)-4-oxobutyl (POB)-, and 4-(3-pyridyl)-4-hydroxybutyl adducts. Among these are adducts such as 7-POB-deoxyguanosine (NPOBdG) which can lead to apurinic/apyrimidinic (AP) sites by facile hydrolysis of the base-deoxyribonucleoside bond. In this study, we used a recently developed highly sensitive mass spectrometric method to quantitate AP sites by derivatization with -(pyridin-3-yl-methyl)hydroxylamine (PMOA) (detection limit, 2 AP sites per 10 nucleotides). AP sites were quantified in DNA isolated from tissues of rats treated with NNN and NNK and from human lung tissue and leukocytes of cigarette smokers and nonsmokers. Rats treated with 5 or 21 mg/kg bw NNK for 4 days by s.c. injection had 2-6 and 2-17 times more AP sites than controls in liver and lung DNA ( < 0.05). Increases in AP sites were also found in liver DNA of rats exposed for 10 and 30 weeks ( < 0.05) but not for 50 and 70 weeks to 5 ppm of NNK in their drinking water. Levels of NPOBG were significantly correlated with AP sites in rats treated with NNK. In rats treated with 14 ppm ()-NNN in their drinking water for 10 weeks, increased AP site formation compared to controls was observed in oral and nasal respiratory mucosa DNA ( < 0.05). No significant increase in AP sites was found in human lung and leukocyte DNA of cigarette smokers compared to nonsmokers, although AP sites in leukocyte DNA were significantly correlated with urinary levels of the NNK metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). This is the first study to use mass spectrometry based methods to examine AP site formation by carcinogenic tobacco-specific nitrosamines in laboratory animals and to evaluate AP sites in DNA of smokers and nonsmokers.
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http://dx.doi.org/10.1021/acs.chemrestox.0c00265DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7574376PMC
September 2020

Biomarkers of Environmental Toxicants: Exposure and Biological Effects.

Toxics 2020 May 22;8(2). Epub 2020 May 22.

Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.

Biomarkers of environmental toxicants are measures of exposures and effects, some of which can serve to assess disease risk and interindividual susceptibilities.[...].
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http://dx.doi.org/10.3390/toxics8020037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7356252PMC
May 2020

Development of a DNA Adductome Mass Spectral Database.

Chem Res Toxicol 2020 04 30;33(4):852-854. Epub 2020 Mar 30.

Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455, United States.

Mass spectrometry-based DNA adductomics is an emerging approach for the human biomonitoring of hazardous chemicals. A mass spectral database of DNA adducts will be created for the scientific community to investigate the associations between chemical exposures, DNA damage, and disease risk.
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http://dx.doi.org/10.1021/acs.chemrestox.0c00031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7197645PMC
April 2020

Kinetics of DNA Adducts and Abasic Site Formation in Tissues of Mice Treated with a Nitrogen Mustard.

Chem Res Toxicol 2020 04 2;33(4):988-998. Epub 2020 Apr 2.

Departments of Chemistry and Biochemistry, and Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37067, United States.

Nitrogen mustards (NM) are an important class of chemotherapeutic drugs used in the treatment of malignant tumors. The accepted mechanism of action of NM is through the alkylation of DNA bases. NM-adducts block DNA replication in cancer cells by forming cytotoxic DNA interstrand cross-links. We previously characterized several adducts formed by reaction of bis(2-chloroethyl)ethylamine (NM) with calf thymus (CT) DNA and the MDA-MB-231 mammary tumor cell line. The monoalkylated N7-guanine (NM-G) adduct and its cross-link (G-NM-G) were major lesions. The cationic NM-G undergoes a secondary reaction through depurination to form an apurinic (AP) site or reacts with hydroxide to yield the stable ring-opened -substituted formamidopyrimidine (NM-Fapy-G) adduct. Both of these lesions are mutagenic and may contribute to secondary tumor development, a major clinical limitation of NM chemotherapy. We established a kinetic model with NM-treated female mice and measured the rates of formation and removal of NM-DNA adducts and AP sites. We employed liquid chromatography-mass spectrometry (LC-MS) to measure NM-G, G-NM-G, and NM-Fapy-G adducts in liver, lung, and spleen over 168 h. NM-G reached a maximum level within 6 h in all organs and then rapidly declined. The G-NM-G cross-link and NM-FapyG were more persistent with half-lives over three-times longer than NM-G. We quantified AP site lesions in the liver and showed that NM treatment increased AP site levels by 3.7-fold over the basal levels at 6 h. The kinetics of AP site repair closely followed the rate of removal of NM-G; however, AP sites remained 1.3-fold above basal levels 168 h post-treatment with NM. Our data provide new insights into NM-induced DNA damage and biological processing . The quantitative measurement of the spectrum of NM adducts and AP sites can serve as biomarkers in the design and assessment of the efficacy of novel chemotherapeutic regimens.
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http://dx.doi.org/10.1021/acs.chemrestox.0c00012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7266082PMC
April 2020

Applying Tobacco, Environmental, and Dietary-Related Biomarkers to Understand Cancer Etiology and Evaluate Prevention Strategies.

Cancer Epidemiol Biomarkers Prev 2020 10 12;29(10):1904-1919. Epub 2020 Feb 12.

Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota.

Many human cancers are caused by environmental and lifestyle factors. Biomarkers of exposure and risk developed by our team have provided critical data on internal exposure to toxic and genotoxic chemicals and their connection to cancer in humans. This review highlights our research using biomarkers to identify key factors influencing cancer risk as well as their application to assess the effectiveness of exposure intervention and chemoprevention protocols. The use of these biomarkers to understand individual susceptibility to the harmful effects of tobacco products is a powerful example of the value of this type of research and has provided key data confirming the link between tobacco smoke exposure and cancer risk. Furthermore, this information has led to policy changes that have reduced tobacco use and consequently, the tobacco-related cancer burden. Recent technological advances in mass spectrometry led to the ability to detect DNA damage in human tissues as well as the development of adductomic approaches. These new methods allowed for the detection of DNA adducts in tissues from patients with cancer, providing key evidence that exposure to carcinogens leads to DNA damage in the target tissue. These advances will provide valuable insights into the etiologic causes of cancer that are not tobacco-related.
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http://dx.doi.org/10.1158/1055-9965.EPI-19-1356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423750PMC
October 2020

Dietary Carcinogens and DNA Adducts in Prostate Cancer.

Adv Exp Med Biol 2019 ;1210:29-55

Department of Medicinal Chemistry, Cancer and Cardiovascular Research Building, University of Minnesota, Minneapolis, MN, USA.

Prostate cancer (PC) is the most commonly diagnosed non-cutaneous cancer and the second leading cause of cancer-related to death in men. The major risk factors for PC are age, family history, and African American ethnicity. Epidemiological studies have reported large geographical variations in PC incidence and mortality, and thus lifestyle and dietary factors influence PC risk. High fat diet, dairy products, alcohol and red meats, are considered as risk factors for PC. This book chapter provides a comprehensive, literature-based review on dietary factors and their molecular mechanisms of prostate carcinogenesis. A large portion of our knowledge is based on epidemiological studies where dietary factors such as cancer promoting agents, including high-fat, dairy products, alcohol, and cancer-initiating genotoxicants formed in cooked meats have been evaluated for PC risk. However, the precise mechanisms in the etiology of PC development remain uncertain. Additional animal and human cell-based studies are required to further our understandings of risk factors involved in PC etiology. Specific biomarkers of chemical exposures and DNA damage in the prostate can provide evidence of cancer-causing agents in the prostate. Collectively, these studies can improve public health research, nutritional education and chemoprevention strategies.
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http://dx.doi.org/10.1007/978-3-030-32656-2_2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7203629PMC
February 2020

Neuromelanin Modulates Heterocyclic Aromatic Amine-Induced Dopaminergic Neurotoxicity.

Toxicol Sci 2020 01;173(1):171-188

School of Health Sciences.

Heterocyclic aromatic amines (HAAs) are mutagens and potential human carcinogens. Our group and others have demonstrated that HAAs may also produce selective dopaminergic neurotoxicity, potentially relevant to Parkinson's disease (PD). The goal of this study was to elucidate mechanisms of HAA-induced neurotoxicity through examining a translational biochemical weakness of common PD models. Neuromelanin is a pigmented byproduct of dopamine metabolism that has been debated as being both neurotoxic and neuroprotective in PD. Importantly, neuromelanin is known to bind and potentially release dopaminergic neurotoxicants, including HAAs (eg, β-carbolines such as harmane). Binding of other HAA subclasses (ie, aminoimidazoaazarenes) to neuromelanin has not been investigated, nor has a specific role for neuromelanin in mediating HAA-induced neurotoxicity been examined. Thus, we investigated the role of neuromelanin in modulating HAA-induced neurotoxicity. We characterized melanin from Sepia officinalis and synthetic dopamine melanin, proposed neuromelanin analogs with similar biophysical properties. Using a cell-free assay, we demonstrated strong binding of harmane and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) to neuromelanin analogs. To increase cellular neuromelanin, we transfected SH-SY5Y neuroblastoma cells with tyrosinase. Relative to controls, tyrosinase-expressing cells exhibited increased neuromelanin levels, cellular HAA uptake, cell toxicity, and oxidative damage. Given that typical cellular and rodent PD models form far lower neuromelanin levels than humans, there is a critical translational weakness in assessing HAA-neurotoxicity. The primary impacts of these results are identification of a potential mechanism by which HAAs accumulate in catecholaminergic neurons and support for the need to conduct neurotoxicity studies in systems forming neuromelanin.
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http://dx.doi.org/10.1093/toxsci/kfz210DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6944224PMC
January 2020

Methods and Challenges for Computational Data Analysis for DNA Adductomics.

Chem Res Toxicol 2019 11 6;32(11):2156-2168. Epub 2019 Nov 6.

Masonic Cancer Center , University of Minnesota , Minneapolis , Minnesota 55455 , United States.

Frequent exposure to chemicals in the environment, diet, and endogenous electrophiles leads to chemical modification of DNA and the formation of DNA adducts. Some DNA adducts can induce mutations during cell division and, when occurring in critical regions of the genome, can lead to the onset of disease, including cancer. The targeted analysis of DNA adducts over the past 30 years has revealed that the human genome contains many types of DNA damages. However, a long-standing limitation in conducting DNA adduct measurements has been the inability to screen for the total complement of DNA adducts derived from a wide range of chemicals in a single assay. With the advancement of high-resolution mass spectrometry (MS) instrumentation and new scanning technologies, nontargeted "omics" approaches employing data-dependent acquisition and data-independent acquisition methods have been established to simultaneously screen for multiple DNA adducts, a technique known as DNA adductomics. However, notable challenges in data processing must be overcome for DNA adductomics to become a mature technology. DNA adducts occur at low abundance in humans, and current softwares do not reliably detect them when using common MS data acquisition methods. In this perspective, we discuss contemporary computational tools developed for feature finding of MS data widely utilized in the disciplines of proteomics and metabolomics and highlight their limitations for conducting nontargeted DNA-adduct biomarker discovery. Improvements to existing MS data processing software and new algorithms for adduct detection are needed to develop DNA adductomics into a powerful tool for the nontargeted identification of potential cancer-causing agents.
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http://dx.doi.org/10.1021/acs.chemrestox.9b00196DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7127864PMC
November 2019

Quantitation of Lipid Peroxidation Product DNA Adducts in Human Prostate by Tandem Mass Spectrometry: A Method That Mitigates Artifacts.

Chem Res Toxicol 2019 09 16;32(9):1850-1862. Epub 2019 Aug 16.

Reactive oxygen species (ROS) and chronic inflammation contribute to DNA damage of many organs, including the prostate. ROS cause oxidative damage to biomolecules, such as lipids, proteins, and nucleic acids, resulting in the formation of toxic and mutagenic intermediates. Lipid peroxidation (LPO) products covalently adduct to DNA and can lead to mutations. The levels of LPO DNA adducts reported in humans range widely. However, a large proportion of the DNA adducts may be attributed to artifact formation during the steps of isolation and nuclease digestion of DNA. We established a method that mitigates artifacts for most LPO adducts during the processing of DNA. We have applied this methodology to measure LPO DNA adducts in the genome of prostate cancer patients, employing ultrahigh-performance liquid chromatography electrospray ionization ion trap multistage mass spectrometry. Our preliminary data show that DNA adducts of acrolein, 6-hydroxy-1,-propano-2'-deoxyguanosine (6-OH-PdG) and 8-hydroxy-1,-propano-2'-deoxyguanosine (8-OH-PdG) (4-20 adducts per 10 nucleotides) are more prominent than etheno (ε) adducts (<0.5 adducts per 10 nucleotides). This analytical methodology will be used to examine the correlation between oxidative stress, inflammation, and LPO adduct levels in patients with benign prostatic hyperplasia and prostate cancer.
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http://dx.doi.org/10.1021/acs.chemrestox.9b00181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746595PMC
September 2019

Bioactivation of the tobacco carcinogens 4-aminobiphenyl (4-ABP) and 2-amino-9H-pyrido[2,3-b]indole (AαC) in human bladder RT4 cells.

Arch Toxicol 2019 07 15;93(7):1893-1902. Epub 2019 Jun 15.

Masonic Cancer Center and Department of Medicinal Chemistry, Cancer and Cardiovascular Research Building, University of Minnesota, 2231 6th Street, Minneapolis, MN, 55455, USA.

Occupational and tobacco exposure to aromatic amines (AAs) including 4-aminobiphenyl (4-ABP) and 2-naphthylamine (2-NA) are associated with bladder cancer (BC) risk. Several epidemiological studies have also reported a possible role for structurally related heterocyclic aromatic amines (HAAs) formed in tobacco smoke or cooked meats with BC risk. We had screened for DNA adducts of 4-ABP, 2-NA, and several prominent HAAs formed in tobacco smoke or grilled meats including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylmidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-9H-pyrido[2,3-b]indole (AαC) in the bladder DNA of BC patients, using liquid chromatography/mass spectrometry. We detected DNA adducts of 4-ABP, but not adducts of the other carcinogens. In this study, we have examined the capacity of RT4 cells, an epithelial human bladder cell line, to bioactivate AAs and HAAs to DNA damaging agents, which may contribute to BC. 4-ABP and AαC formed DNA adducts, but DNA adducts of 2-NA, PhIP, and MeIQx were not detected. 4-ABP DNA adducts were formed at tenfold higher levels than AαC adducts. Pretreatment of RT4 cells with α-naphthoflavone (1-10 µM), a specific cytochrome P450 1 (CYP1) inhibitor, decreased AαC adduct formation by 50% but did not affect the level of 4-ABP adducts. However, cell pretreatment with 8-methoxypsoralen (0.1-1 µM), a potent inhibitor of CYP2A, resulted in a 90% decrease of 4-ABP DNA adducts levels. These data signify that CYP2A and CYP1A isoforms expressed in the target urothelium bioactivate 4-ABP and AαC, respectively, and may be a critical feature of aromatic amine-induced urinary bladder carcinogenesis. The bioactivation of other tobacco and environmental AAs by bladder CYPs and their ensuing bladder DNA damage warrants further study.
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http://dx.doi.org/10.1007/s00204-019-02486-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6714057PMC
July 2019

Emerging Technologies in Mass Spectrometry-Based DNA Adductomics.

High Throughput 2019 May 14;8(2). Epub 2019 May 14.

Masonic Cancer Center and Department of Medicinal Chemistry, University of Minnesota, 2231 6th St. SE, Minneapolis, MI 55455, USA.

The measurement of DNA adducts, the covalent modifications of DNA upon the exposure to the environmental and dietary genotoxicants and endogenously produced electrophiles, provides molecular evidence for DNA damage. With the recent improvements in the sensitivity and scanning speed of mass spectrometry (MS) instrumentation, particularly high-resolution MS, it is now feasible to screen for the totality of DNA damage in the human genome through DNA adductomics approaches. Several MS platforms have been used in DNA adductomic analysis, each of which has its strengths and limitations. The loss of 2'-deoxyribose from the modified nucleoside upon collision-induced dissociation is the main transition feature utilized in the screening of DNA adducts. Several advanced data-dependent and data-independent scanning techniques originated from proteomics and metabolomics have been tailored for DNA adductomics. The field of DNA adductomics is an emerging technology in human exposure assessment. As the analytical technology matures and bioinformatics tools become available for analysis of the MS data, DNA adductomics can advance our understanding about the role of chemical exposures in DNA damage and disease risk.
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http://dx.doi.org/10.3390/ht8020013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6630665PMC
May 2019

Quantitation of Apurinic/Apyrimidinic Sites in Isolated DNA and in Mammalian Tissue with a Reduced Level of Artifacts.

Anal Chem 2019 06 13;91(11):7403-7410. Epub 2019 May 13.

Masonic Cancer Center and Department of Medicinal Chemistry , University of Minnesota , Minneapolis , Minnesota 55455 , United States.

The apurinic/apyrimidinic (AP) site is a common lesion of DNA damage. The levels of AP sites reported in the literature cover a wide range, which is primarily due to the artifactual generation or loss of AP sites during processing of the DNA. Herein, we have developed a method for quantitating AP sites with a largely reduced level of artifacts by derivatizing AP sites before DNA isolation. A rapid digestion of nuclear protein was performed to minimize enzymatic DNA repair, followed by direct derivatization of AP sites in the nuclear lysate with O-(pyridin-3-yl-methyl)hydroxylamine, yielding an oxime derivative that is stable through the subsequent DNA processing steps. Quantitation was done using highly selective and sensitive liquid chromatography-tandem mass spectrometry, with a limit of quantitation at 2.2 lesions per 10 nucleotides (nts, 0.9 fmol on column). The method was applied in vivo to measure AP sites in rats undergoing oxidative stress [liver, 3.31 ± 0.47/10 nts (dosed) vs 0.91 ± 0.06/10 nts (control); kidney, 1.60 ± 0.07/10 nts (dosed) vs 1.13 ± 0.12/10 nts (control)]. The basal AP level was significantly lower than literature values. The method was also used to measure AP sites induced by the chemotherapeutic nitrogen mustard in vitro.
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http://dx.doi.org/10.1021/acs.analchem.9b01351DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6718090PMC
June 2019

Targeted and Untargeted Detection of DNA Adducts of Aromatic Amine Carcinogens in Human Bladder by Ultra-Performance Liquid Chromatography-High-Resolution Mass Spectrometry.

Chem Res Toxicol 2018 12 19;31(12):1382-1397. Epub 2018 Nov 19.

Department of Pharmacological Sciences , Stony Brook University , Stony Brook , New York 11794 , United States.

Epidemiological studies have linked aromatic amines (AAs) from tobacco smoke and some occupational exposures with bladder cancer risk. Several epidemiological studies have also reported a plausible role for structurally related heterocyclic aromatic amines present in tobacco smoke or formed in cooked meats with bladder cancer risk. DNA adduct formation is an initial biochemical event in bladder carcinogenesis. We examined paired fresh-frozen (FR) and formalin-fixed paraffin-embedded (FFPE) nontumor bladder tissues from 41 bladder cancer patients for DNA adducts of 4-aminobiphenyl (4-ABP), a bladder carcinogen present in tobacco smoke, and 2-amino-9 H-pyrido[2,3- b]indole, 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine and 2-amino-3,8-dimethylimidazo[4,5- f]quinoxaline, possible human carcinogens, which occur in tobacco smoke and cooked meats. These chemicals are present in urine of tobacco smokers or omnivores. Targeted DNA adduct measurements were done by ultra-performance liquid chromatography-electrospray ionization multistage hybrid Orbitrap MS. N-(2'-Deoxyguanosin-8-yl)-4-ABP ( N-(dG-C8)-4-ABP) was the sole adduct detected in FR and FFPE bladder tissues. Twelve subjects (29%) had N-(dG-C8)-4-ABP levels above the limit of quantification, ranging from 1.4 to 33.8 adducts per 10 nucleotides (nt). DNA adducts of other human AA bladder carcinogens, including 2-naphthylamine (2-NA), 2-methylaniline (2-MA), 2,6-dimethylaniline (2,6-DMA), and lipid peroxidation (LPO) adducts, were screened for in bladder tissue, by our untargeted data-independent adductomics method, termed wide-selected ion monitoring (wide-SIM)/MS. Wide-SIM/MS successfully detected N-(dG-C8)-4-ABP, N-(2'-deoxyadenosin-8-yl)-4-ABP and the presumed hydrazo linked adduct, N-(2'-deoxyguanosin- N-yl)-4-ABP, and several LPO adducts in bladder DNA. Wide-SIM/MS detected multiple DNA adducts of 2-NA, 2-MA, and, 2,6-DMA, when calf thymus DNA was modified with reactive intermediates of these carcinogens. However, these AA-adducts were below the limit of detection in unspiked human bladder DNA (<1 adduct per 10 nt). Wide-SIM/MS can screen for many types of DNA adducts formed with exogenous and endogenous electrophiles and will be employed to identify DNA adducts of other chemicals that may contribute to the etiology of bladder cancer.
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http://dx.doi.org/10.1021/acs.chemrestox.8b00268DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6424598PMC
December 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.

Authors:
Robert J Turesky

Chimia (Aarau) 2018 Oct;72(10):718-724

Masonic Cancer Center Department of Medicinal Chemistry College of Pharmacy, University of Minnestoa 2231 6th St SE, Minneapolis, MN, USA;, Email:

The Working Group of the International Agency for Research on Cancer classified the consumption of processed meat as carcinogenic to humans (Group 1), and classified red meat as probably carcinogenic to humans (Group 2A); consumption of both meat types is associated with an increased risk of colorectal cancer. These classifications are based on a compilation of epidemiology data and mechanistic evidence from animal and human studies. The curing of meats with nitrite can produce carcinogenic -nitroso compounds (NOCs), and the smoking of meat produces polycyclic aromatic hydrocarbons (PAHs). The high-temperature cooking of meat also produces carcinogenic heterocyclic aromatic amines (HAAs). The ingestion of heme from meat can catalyze the formation of NOCs and lipid peroxidation products (LPOs) in the digestive tract. Many of these chemicals form DNA adducts, some of which can induce mutations and initiate carcinogenesis. Another recent hypothesis is that -glycolylneuraminic acid, a non-human sialic acid sugar present in red meat, becomes incorporated in the cell membrane, triggering the immune response with associated inflammation and reactive oxygen species, which can contribute to DNA damage, tumor promotion, and cancer. The mechanisms by which these chemicals in meat induce DNA damage, and the impact of dietary and host factors that influence the biological potency of these chemicals are highlighted in this updated report.
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http://dx.doi.org/10.2533/chimia.2018.718DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6294997PMC
October 2018

Biomonitoring an albumin adduct of the cooked meat carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in humans.

Carcinogenesis 2018 12;39(12):1455-1462

Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is formed in cooked meats and may be linked to dietary-associated colorectal, prostate and mammary cancers. Genotoxic N-oxidized metabolites of PhIP react with the Cys34 of albumin (Alb) to form a sulfinamide adduct, a biomarker of the biologically effective dose. We examined the kinetics of PhIP-Alb adduct formation in plasma of volunteers on a 4-week semicontrolled diet of cooked meat containing known quantities of PhIP. The adduct was below the limit of detection (LOD) (10 femtograms PhIP/mg Alb) in most subjects before the meat feeding but increased by up to 560-fold at week 4 in subjects who ate meat containing 8.0 to 11.7 μg of PhIP per 150-200 g serving. In contrast, the adduct remained below the LOD in subjects who ingested 1.2 or 3.0 μg PhIP per serving. Correlations were not seen between PhIP-Alb adduct levels and PhIP intake levels (P = 0.76), the amount of PhIP accrued in hair (P = 0.13), the amounts of N-oxidized urinary metabolites of PhIP (P = 0.66) or caffeine CYP1A2 activity (P = 0.55), a key enzyme involved in the bioactivation of PhIP. The half-life of the PhIP-Alb adduct was <2 weeks, signifying that the adduct was not stable. PhIP-Alb adduct formation is direct evidence of bioactivation of PhIP in vivo. However, the PhIP hair biomarker is a longer lived and more sensitive biomarker to assess exposure to this potential human carcinogen.
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http://dx.doi.org/10.1093/carcin/bgy125DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7191085PMC
December 2018

Method for Biomonitoring DNA Adducts in Exfoliated Urinary Cells by Mass Spectrometry.

Anal Chem 2018 08 30;90(16):9943-9950. Epub 2018 Jul 30.

Masonic Cancer Center and Department of Medicinal Chemistry , University of Minnesota , Minneapolis , Minnesota 55455 , United States.

Tobacco smoking contributes to about 50% of the bladder-cancer (BC) cases in the United States. Some aromatic amines in tobacco smoke are bladder carcinogens; however, other causal agents of BC are uncertain. Exfoliated urinary cells (EUCs) are a promising noninvasive biospecimen to screen for DNA adducts of chemicals that damage the bladder genome, although the analysis of DNA adducts in EUCs is technically challenging because of the low number of EUCs and limiting quantity of cellular DNA. Moreover, EUCs and their DNA adducts must remain viable during the time of collection and storage of urine to develop robust screening methods. We employed RT4 cells, a well-differentiated transitional epithelial bladder cell line, as a cell-model system in urine to investigate cell viability and the chemical stability of DNA adducts of two prototypical bladder carcinogens: 4-aminobiphenyl (4-ABP), an aromatic amine found in tobacco smoke, and aristolochic acid I (AA-I), a nitrophenanthrene found in Aristolochia herbaceous plants used for medicinal purposes worldwide. The cell viability of RT4 cells pretreated with 4-ABP or AA-I in urine exceeded 80%, and the major DNA adducts of 4-ABP and AA-I, quantified by liquid chromatography-mass spectrometry, were stable for 24 h. Thereafter, we successfully screened EUCs of mice treated with AA-I to measure DNA adducts of AA-I, which were still detected 25 days following treatment with the carcinogen. EUCs are promising biospecimens that can be employed for the screening of DNA adducts of environmental and dietary genotoxicants that may contribute to the development of BC.
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http://dx.doi.org/10.1021/acs.analchem.8b02170DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6237078PMC
August 2018

DNA adducts: Formation, biological effects, and new biospecimens for mass spectrometric measurements in humans.

Mass Spectrom Rev 2020 03 11;39(1-2):55-82. Epub 2018 Jun 11.

Masonic Cancer Center and Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN.

Hazardous chemicals in the environment and diet or their electrophilic metabolites can form adducts with genomic DNA, which can lead to mutations and the initiation of cancer. In addition, reactive intermediates can be generated in the body through oxidative stress and damage the genome. The identification and measurement of DNA adducts are required for understanding exposure and the causal role of a genotoxic chemical in cancer risk. Over the past three decades, P-postlabeling, immunoassays, gas chromatography/mass spectrometry, and liquid chromatography/mass spectrometry (LC/MS) methods have been established to assess exposures to chemicals through measurements of DNA adducts. It is now possible to measure some DNA adducts in human biopsy samples, by LC/MS, with as little as several milligrams of tissue. In this review article, we highlight the formation and biological effects of DNA adducts, and highlight our advances in human biomonitoring by mass spectrometric analysis of formalin-fixed paraffin-embedded tissues, untapped biospecimens for carcinogen DNA adduct biomarker research.
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http://dx.doi.org/10.1002/mas.21570DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6289887PMC
March 2020

Formalin-Fixed Paraffin-Embedded Tissues-An Untapped Biospecimen for Biomonitoring DNA Adducts by Mass Spectrometry.

Toxics 2018 Jun 1;6(2). Epub 2018 Jun 1.

Masonic Cancer Center and Department of Medicinal Chemistry, University of Minnesota, 2231 6th St. SE, Minneapolis, MN 55455, USA.

The measurement of DNA adducts provides important information about human exposure to genotoxic chemicals and can be employed to elucidate mechanisms of DNA damage and repair. DNA adducts can serve as biomarkers for interspecies comparisons of the biologically effective dose of procarcinogens and permit extrapolation of genotoxicity data from animal studies for human risk assessment. One major challenge in DNA adduct biomarker research is the paucity of fresh frozen biopsy samples available for study. However, archived formalin-fixed paraffin-embedded (FFPE) tissues with clinical diagnosis of disease are often available. We have established robust methods to recover DNA free of crosslinks from FFPE tissues under mild conditions which permit quantitative measurements of DNA adducts by liquid chromatography-mass spectrometry. The technology is versatile and can be employed to screen for DNA adducts formed with a wide range of environmental and dietary carcinogens, some of which were retrieved from section-cuts of FFPE blocks stored at ambient temperature for up to nine years. The ability to retrospectively analyze FFPE tissues for DNA adducts for which there is clinical diagnosis of disease opens a previously untapped source of biospecimens for molecular epidemiology studies that seek to assess the causal role of environmental chemicals in cancer etiology.
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http://dx.doi.org/10.3390/toxics6020030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6027047PMC
June 2018

Metabolic Activation of the Cooked Meat Carcinogen 2-Amino-1-Methyl-6-Phenylimidazo[4,5-b]Pyridine in Human Prostate.

Toxicol Sci 2018 06;163(2):543-556

Masonic Cancer Center and Department of Medicinal Chemistry, Cancer and Cardiovascular Research Building.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), an heterocyclic aromatic amine (HAA) formed in cooked meat, is a rodent and possible human prostate carcinogen. Recently, we identified DNA adducts of PhIP in the genome of prostate cancer patients, but adducts of 2-amino-3, 8-dimethylmidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-9 H-pyrido[2,3-b]indole (AαC), other prominent HAAs formed in cooked meats, were not detected. We have investigated the bioactivation of HAAs by Phase I and II enzymes in the human prostate (LNCaP) cell line using cytotoxicity and DNA adducts as endpoints. PhIP, MeIQx, and 2-amino-3-methylimidazo[4,5-f]quinoline, another HAA found in cooked meats, were poorly bioactivated and not toxic. The synthetic genotoxic N-hydroxylated-HAAs were also assayed in LNCaP cells with Phase II enzyme inhibitors. Notably, 2-hydroxy-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (HONH-PhIP), but not other HONH-HAAs, induced cytotoxicity. Moreover, PhIP-DNA adduct formation was 20-fold greater than adducts formed with other HONH-HAAs. Pretreatment of LNCaP cells with mefenamic acid, a specific inhibitor of sulfotransferase (SULT1A1), decreased PhIP-DNA adducts by 25%, whereas (Z)-5-(2'-hydroxybenzylidene)-2-thioxothiazolidin-4-one and pentachlorophenol, inhibitors of SULTs and N-acetyltransferases (NATs), decreased the PhIP-DNA adduct levels by 75%. NATs in cytosolic fractions of LNCaP cells and human prostate catalyzed DNA binding of HONH-PhIP by up to 100-fold greater levels than for SULT and kinase activities. Recombinant NAT2 is catalytically superior to recombinant NAT1 in the bioactivation of HONH-PhIP; however, the extremely low levels of NAT2 activity in prostate suggest that NAT1 may be the major isoform involved in PhIP-DNA damage. Thus, the high susceptibility of LNCaP cells recapitulates the DNA-damaging effect of HONH-PhIP in rodent and human prostate.
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http://dx.doi.org/10.1093/toxsci/kfy060DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5974788PMC
June 2018

Non-invasive detection of urothelial cancer through the analysis of driver gene mutations and aneuploidy.

Elife 2018 03 20;7. Epub 2018 Mar 20.

Masonic Cancer Center, University of Minnesota, Minneapolis, United States.

Current non-invasive approaches for detection of urothelial cancers are suboptimal. We developed a test to detect urothelial neoplasms using DNA recovered from cells shed into urine. UroSEEK incorporates massive parallel sequencing assays for mutations in 11 genes and copy number changes on 39 chromosome arms. In 570 patients at risk for bladder cancer (BC), UroSEEK was positive in 83% of those who developed BC. Combined with cytology, UroSEEK detected 95% of patients who developed BC. Of 56 patients with upper tract urothelial cancer, 75% tested positive by UroSEEK, including 79% of those with non-invasive tumors. UroSEEK detected genetic abnormalities in 68% of urines obtained from BC patients under surveillance who demonstrated clinical evidence of recurrence. The advantages of UroSEEK over cytology were evident in low-grade BCs; UroSEEK detected 67% of cases whereas cytology detected none. These results establish the foundation for a new non-invasive approach for detection of urothelial cancer.
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http://dx.doi.org/10.7554/eLife.32143DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5860864PMC
March 2018

A Rapid Throughput Method To Extract DNA from Formalin-Fixed Paraffin-Embedded Tissues for Biomonitoring Carcinogenic DNA Adducts.

Chem Res Toxicol 2017 12 27;30(12):2130-2139. Epub 2017 Nov 27.

Masonic Cancer Center, Division of Carcinogenesis and Chemoprevention and Department of Medicinal Chemistry, ‡Department of Laboratory Medicine and Pathology, and §Department of Urology, University of Minnesota , Minneapolis, Minnesota 55455, United States.

Formalin-fixed paraffin-embedded (FFPE) tissues are rarely used for screening DNA adducts of carcinogens because the harsh conditions required to reverse the formaldehyde-mediated DNA cross-links can destroy DNA adducts. We recently adapted a commercial silica-based column kit used in genomics to manually isolate DNA under mild conditions from FFPE tissues of rodents and humans and successfully measured DNA adducts of several carcinogens including aristolochic acid I (AA-I), 4-aminobiphenyl (4-ABP), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) (Yun et al. (2013) Anal. Chem. 85, 4251-8, and Guo et al. (2016) Anal. Chem. 88, 4780-7). The DNA retrieval methodology is robust; however, the procedure is time-consuming and labor intensive, and not amenable to rapid throughput processing. In this study, we have employed the Promega Maxwell 16 MDx system, which is commonly used in large scale genomics studies, for the rapid throughput extraction of DNA. This system streamlines the DNA isolation procedure and increases the sample processing rate by about 8-fold over the manual method (32 samples versus 4 samples processed per hour). High purity DNA is obtained in satisfactory yield for the measurements of DNA adducts by ultra performance liquid chromatography-electrospray-ionization-ion trap-multistage scan mass spectrometry. The measurements show that the levels of DNA adducts of AA-I, 4-ABP, and PhIP in FFPE rodent and human tissues are comparable to those levels measured in DNA from matching tissues isolated by the commercial silica-based column kits and in DNA from fresh frozen tissues isolated by the conventional phenol-chloroform extraction method. The isolation of DNA from tissues is one major bottleneck in the analysis of DNA adducts. This rapid throughput methodology greatly decreases the time required to process DNA and can be employed in large-scale epidemiology studies designed to assess the role of chemical exposures and DNA adducts in cancer risk.
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http://dx.doi.org/10.1021/acs.chemrestox.7b00218DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5822421PMC
December 2017

Data-Independent Mass Spectrometry Approach for Screening and Identification of DNA Adducts.

Anal Chem 2017 11 18;89(21):11728-11736. Epub 2017 Oct 18.

Masonic Cancer Center and ∥Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota , 2231 Sixth Street SE, Minneapolis, Minnesota 55455, United States.

Long-term exposures to environmental toxicants and endogenous electrophiles are causative factors for human diseases including cancer. DNA adducts reflect the internal exposure to genotoxicants and can serve as biomarkers for risk assessment. Liquid chromatography-multistage mass spectrometry (LC-MS) is the most common method for biomonitoring DNA adducts, generally targeting single exposures and measuring up to several adducts. However, the data often provide limited evidence for a role of a chemical in the etiology of cancer. An "untargeted" method is required that captures global exposures to chemicals, by simultaneously detecting their DNA adducts in the genome; some of which may induce cancer-causing mutations. We established a wide selected ion monitoring tandem mass spectrometry (wide-SIM/MS) screening method utilizing ultraperformance-LC nanoelectrospray ionization Orbitrap MS with online trapping to enrich bulky, nonpolar adducts. Wide-SIM scan events are followed by MS scans to screen for modified nucleosides by coeluting peaks containing precursor and fragment ions differing by -116.0473 Da, attributed to the neutral loss of deoxyribose. Wide-SIM/MS was shown to be superior in sensitivity, specificity, and breadth of adduct coverage to other tested adductomic methods with detection possible at adduct levels as low as 4 per 10 nucleotides. Wide-SIM/MS data can be analyzed in a "targeted" fashion by generation of extracted ion chromatograms or in an "untargeted" fashion where a chromatographic peak-picking algorithm can be used to detect putative DNA adducts. Wide-SIM/MS successfully detected DNA adducts, derived from chemicals in the diet and traditional medicines and from lipid peroxidation products, in human prostate and renal specimens.
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http://dx.doi.org/10.1021/acs.analchem.7b03208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5727898PMC
November 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 2017 06 25;30(6):1333-1343. Epub 2017 May 25.

Retired, Norris Cancer Center and Department of Preventive Medicine, Keck School of Medicine, University of Southern California , Los Angeles, California 90033, United States.

Aromatic amines covalently bound to hemoglobin (Hb) as sulfinamide adducts at the cysteine 93 residue of the Hb β chain have served as biomarkers to assess exposure to this class of human carcinogens for the past 30 years. In this study, we report that 2-amino-9H-pyrido[2,3-b]indole (AαC), an abundant carcinogenic heterocyclic aromatic amine formed in tobacco smoke and charred cooked meats, also reacts with Hb to form a sulfinamide adduct. A novel nanoflow liquid chromatography/ion trap multistage mass spectrometry (nanoLC-IT/MS) method was established to assess exposure to AαC and the tobacco-associated bladder carcinogen 4-aminobiphenyl (4-ABP) through their Hb sulfinamide adducts. Following mild acid hydrolysis of Hb in vitro, the liberated AαC and 4-ABP were derivatized with acetic anhydride to form the N-acetylated amines, which were measured by nanoLC-IT/MS. The limits of quantification (LOQ) for AαC- and 4-ABP-Hb sulfinamide adducts were ≤7.1 pg/g Hb. In a pilot study, the mean level of Hb sulfinamide adducts of AαC and 4-ABP were, respectively, 3.4-fold and 4.8-fold higher in smokers (>20 cigarettes/day) than nonsmokers. In contrast, the major DNA adducts of 4-ABP, N-(2'-deoxyguanosin-8-yl)-4-aminobiphenyl, and AαC, N-(2'-deoxyguanosin-8-yl)-2-amino-9H-pyrido[2,3-b]indole, were below the LOQ (3 adducts per 10 bases) in white blood cell (WBC) DNA of smokers and nonsmokers. These findings reaffirm that tobacco smoke is a major source of exposure to AαC. Hb sulfinamide adducts are suitable biomarkers to biomonitor 4-ABP and AαC; however, neither carcinogen binds to DNA in WBC, even in heavy smokers, at levels sufficient for biomonitoring.
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http://dx.doi.org/10.1021/acs.chemrestox.7b00072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5550894PMC
June 2017

Call for Papers on Mass Spectrometry and Biomarkers in Human Population Studies.

Authors:
Robert J Turesky

Chem Res Toxicol 2017 02;30(2):487

Masonic Cancer Center and Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota , Minneapolis, Minnesota 55455, United States.

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http://dx.doi.org/10.1021/acs.chemrestox.6b00431DOI Listing
February 2017