Genome-Wide Meta-Analysis of Cotinine Levels in Cigarette Smokers Identifies Locus at 4q13.2

Genome-wide association studies (GWAS) of complex behavioural phenotypes such as cigarette smoking typically employ self-report phenotypes. However, precise biomarker phenotypes may afford greater statistical power and identify novel variants. Here we report the results of a GWAS meta-analysis of levels of cotinine, the primary metabolite of nicotine, in 4,548 daily smokers of European ancestry. We identified a locus close to UGT2B10 at 4q13.2 (minimum p = 5.89 x 10(-10) for rs114612145), which was consequently replicated. This variant is in high linkage disequilibrium with a known functional variant in the UGT2B10 gene which is associated with reduced nicotine and cotinine glucuronidation activity, but intriguingly is not associated with nicotine intake. Additionally, we observed association between multiple variants within the 15q25.1 region and cotinine levels, all located within the CHRNA5-A3-B4 gene cluster or adjacent genes, consistent with previous much larger GWAS using self-report measures of smoking quantity. These results clearly illustrate the increase in power afforded by using precise biomarker measures in GWAS. Perhaps more importantly however, they also highlight that biomarkers do not always mark the phenotype of interest. The use of metabolite data as a proxy for environmental exposures should be carefully considered in the context of individual differences in metabolic pathways.Peer reviewe

Genetic Relationship between Schizophrenia and Nicotine Dependence

It is well known that most schizophrenia patients smoke cigarettes. There are different hypotheses postulating the underlying mechanisms of this comorbidity. We used summary statistics from large meta-analyses of plasma cotinine concentration (COT), Fagerstrom test for nicotine dependence (FTND) and schizophrenia to examine the genetic relationship between these traits. We found that schizophrenia risk scores calculated at P-value thresholds of 5 x 10(-3) and larger predicted FTND and cigarettes smoked per day (CPD), suggesting that genes most significantly associated with schizophrenia were not associated with FTND/CPD, consistent with the self-medication hypothesis. The COT risk scores predicted schizophrenia diagnosis at P-values of 5 x 10(-3) and smaller, implying that genes most significantly associated with COT were associated with schizophrenia. These results implicated that schizophrenia and FTND/CPD/COT shared some genetic liability. Based on this shared liability, we identified multiple long non-coding RNAs and RNA binding protein genes (DA376252, BX089737, LOC101927273, LINC01029, LOC101928622, HY157071, DA902558, RBFOX1 and TINCR), protein modification genes (MANBA, UBE2D3, and RANGAP1) and energy production genes (XYLB, MTRF1 and ENOX1) that were associated with both conditions. Further analyses revealed that these shared genes were enriched in calcium signaling, long-term potentiation and neuroactive ligand-receptor interaction pathways that played a critical role in cognitive functions and neuronal plasticity.Peer reviewe

www.mdpi.com/journal/ijms Pilot Study of CYP2B6 Genetic Variation to Explore the Contribution of Nitrosamine Activation to Lung Carcinogenesis

Abstract: We explored the contribution of nitrosamine metabolism to lung cancer in a pilot investigation of genetic variation in CYP2B6, a high-affinity enzymatic activator of tobacco-specific nitrosamines with a negligible role in nicotine metabolism. Previously we found that variation in CYP2A6 and CHRNA5-CHRNA3-CHRNB4 combined to increase lung cancer risk in a case-control study in European American ever-smokers (n = 860). However, these genes are involved in the pharmacology of both nicotine, through which they alter smoking behaviours, and carcinogenic nitrosamines. Herein, we separated participants by CYP2B6 genotype into a high- vs. low-risk group (*1/*1 + *1/*6 vs. *6/*6). Odds ratios estimated through logistic regression modeling were 1.25 (95 % CI 0.68–2.30), 1.27 (95 % CI 0.89–1.79) and 1.56 (95 % CI 1.04–2.31) for CYP2B6, CYP2A6 and CHRNA5-CHRNA3-CHRNB4, respectively, with negligible differences when all genes were evaluated concurrently. Modeling the combined impact of high-risk genotypesInt. J. Mol. Sci. 2013, 14 838

Pilot Study of CYP2B6 Genetic Variation to Explore the Contribution of Nitrosamine Activation to Lung Carcinogenesis

We explored the contribution of nitrosamine metabolism to lung cancer in a pilot investigation of genetic variation in <i>CYP2B6</i>, a high-affinity enzymatic activator of tobacco-specific nitrosamines with a negligible role in nicotine metabolism. Previously we found that variation in <i>CYP2A6</i> and <i>CHRNA5-CHRNA3-CHRNB4</i> combined to increase lung cancer risk in a case-control study in European American ever-smokers (<i>n</i> = 860). However, these genes are involved in the pharmacology of both nicotine, through which they alter smoking behaviours, and carcinogenic nitrosamines. Herein, we separated participants by <i>CYP2B6</i> genotype into a high- <i>vs.</i> low-risk group (<i>*1/*1</i> + <i>*1/*6</i> <i>vs.</i> <i>*6/*6</i>). Odds ratios estimated through logistic regression modeling were 1.25 (95% CI 0.68–2.30), 1.27 (95% CI 0.89–1.79) and 1.56 (95% CI 1.04–2.31) for <i>CYP2B6</i>, <i>CYP2A6</i> and <i>CHRNA5-CHRNA3-CHRNB4</i>, respectively, with negligible differences when all genes were evaluated concurrently. Modeling the combined impact of high-risk genotypes yielded odds ratios that rose from 2.05 (95% CI 0.39–10.9) to 2.43 (95% CI 0.47–12.7) to 3.94 (95% CI 0.72–21.5) for those with 1, 2 and 3 <i>vs.</i> 0 high-risk genotypes, respectively. Findings from this pilot point to genetic variation in <i>CYP2B6</i> as a lung cancer risk factor supporting a role for nitrosamine metabolic activation in the molecular mechanism of lung carcinogenesi

"Why Don't You Go Into Suburbs? Why Are You Targeting Us?": Trust and Mistrust in HIV Vaccine Trials in South Africa

Trust is a key element of high-quality stakeholder relations, which are themselves essential for the success of HIV vaccine trials. Where trust is absent, community stakeholders might not volunteer to become involved in key trial activities, and potential participants might not volunteer for enrollment. We explored site staff and Community Advisory Board (CAB) members' experiences of trust/mistrust among community members and potential participants. We analyzed 10 focus group discussions with site staff and CAB members at two active South African HIV vaccine trial sites. We report on key characteristics perceived to contribute to the trustworthiness of communicators, as well as factors associated with mistrust. Attributes associated with trustworthy communicators included shared racial identity, competence, and independence (not being "captured"). Key foci for mistrust included explanations about site selection, stored samples, vaccination, and Vaccine Induced Sero-Positivity (VISP). Our findings suggest that community members' trust is not necessarily global, in which trials are trusted or not; rather, it appears fairly nuanced and is impacted by various perceived attributes of communicators and the information they provide. We make recommendations for clinical trial site stakeholders invested in building trust and for future research into trust at these sites.This study was made possible by funds from the Canadian Institutes of Health Research (CIHR) Canadian HIV Vaccine Initiative (CHVI) (THA-118570; PI: Newman)

". . . I've Gone Through This My Own Self, So I Practice What I Preach . . . ": Strategies to Enhance Understanding and Other Valued Outcomes in HIV Vaccine Trials in South Africa

This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License (http://www.creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage).There has not been enough study of the processes by which site staff help participating community members and potential participants to understand complicated concepts for HIV vaccine trials. This article describes strategies reported in six focus group discussions with Community Advisory Board members, educators, and consent counselors at an active HIV vaccine trial site in South Africa. Thematic analysis identified a considerable range of strategies, and findings suggest that such staff do not only try to promote understanding of critical information but also try to build trust in communicated information, to respect cultural differences, and to promote voluntariness. Findings also suggest occasional tensions between these implicit goals. Actual engagement and consent encounters at HIV vaccine trial sites should be observed, recorded, and analyzed; and the relationship between practices and valued outcomes should be assessed. These efforts may help to make consent-related encounters as "potent" as possible given finite resources.This study was made possible by funds from the Canadian Institutes of Health Research (CIHR) and Canadian HIV Vaccine Initiative (CHVI) (THA-118570; Principal Investigator [PI]: Newman)

UGT1A and UGT2B genetic variation alters nicotine and nitrosamine glucuronidation in european and african american smokers.

BackgroundIdentifying sources of variation in the nicotine and nitrosamine metabolic inactivation pathways is important to understanding the relationship between smoking and cancer risk. Numerous UGT1A and UGT2B enzymes are implicated in nicotine and nitrosamine metabolism in vitro; however, little is known about their roles in vivo.MethodsWithin UGT1A1, UGT1A4, UGT1A9, UGT2B7, UGT2B10, and UGT2B17, 47 variants were genotyped, including UGT2B10*2 and UGT2B17*2. The association between variation in these UGTs and glucuronidation activity within European and African American current smokers (n = 128), quantified as urinary ratios of the glucuronide over unconjugated compound for nicotine, cotinine, trans-3'-hydroxycotinine, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), was investigated in regression models assuming a dominant effect of variant alleles.ResultsCorrecting for multiple testing, three UGT2B10 variants were associated with cotinine glucuronidation, rs2331559 and rs11726322 in European Americans and rs835309 in African Americans (P ≤ 0.0002). Additional variants predominantly in UGT2B10 were nominally associated with nicotine (P = 0.008-0.04) and cotinine (P = &lt;0.001-0.02) glucuronidation in both ethnicities in addition to UGT2B10*2 in European Americans (P = 0.01, P &lt; 0.001). UGT2B17*2 (P = 0.03) in European Americans and UGT2B7 variants (P = 0.02-0.04) in African Americans were nominally associated with 3HC glucuronidation. UGT1A (P = 0.007-0.01), UGT2B10 (P = 0.02), and UGT2B7 (P = 0.02-0.03) variants in African Americans were nominally associated with NNAL glucuronidation.ConclusionsFindings from this initial in vivo study support a role for multiple UGTs in the glucuronidation of tobacco-related compounds in vivo, in particular UGT2B10 and cotinine glucuronidation.ImpactFindings also provide insight into ethnic differences in glucuronidation activity, which could be contributing to ethnic disparities in the risk for smoking-related cancers. Cancer Epidemiol Biomarkers Prev; 24(1); 94-104. ©2014 AACR