Genetic ancestry as an effect modifier of naltrexone in smoking cessation among African Americans: an analysis of a randomized controlled trial

A scoping review of smoking cessation pharmacogenetic studies to advance future research across racial, ethnic, and ancestral populations

Abstinence rates among smokers attempting to quit remain low despite the wide availability and accessibility of pharmacological smoking cessation treatments. In addition, the prevalence of cessation attempts and abstinence differs by individual-level social factors such as race and ethnicity. Clinical treatment of nicotine dependence also continues to be challenged by individual-level variability in effectiveness to promote abstinence. The use of tailored smoking cessation strategies that incorporate information on individual-level social and genetic factors hold promise, although additional pharmacogenomic knowledge is still needed. In particular, genetic variants associated with pharmacological responses to smoking cessation treatment have generally been conducted in populations with participants that self-identify as White race or who are determined to be of European genetic ancestry. These results may not adequately capture the variability across all smokers as a result of understudied differences in allele frequencies across genetic ancestry populations. This suggests that much of the current pharmacogenetic study results for smoking cessation may not apply to all populations. Therefore, clinical application of pharmacogenetic results may exacerbate health inequities by racial and ethnic groups. This scoping review examines the extent to which racial, ethnic, and ancestral groups that experience differences in smoking rates and smoking cessation are represented in the existing body of published pharmacogenetic studies of smoking cessation. We will summarize results by race, ethnicity, and ancestry across pharmacological treatments and study designs. We will also explore current opportunities and challenges in conducting pharmacogenomic research on smoking cessation that encourages greater participant diversity, including practical barriers to clinical utilization of pharmacological smoking cessation treatment and clinical implementation of pharmacogenetic knowledge.

Effect of extended-release naltrexone on alcohol consumption: a systematic review and meta-analysis

AIMS

The aims of this study were to (1) estimate the effect of extended-release naltrexone compared with placebo on alcohol consumption in patients with alcohol use disorder (AUD) and (2) conduct pre-planned subgroup analyses to test whether being abstinent when initiating treatment (lead-in abstinence) or the duration of treatment improves treatment efficacy.

DESIGN

Systematic review and random-effects meta-analysis of blinded randomized placebo-controlled trials reporting the effect extended-release naltrexone on alcohol consumption.

SETTING

Outpatient clinics.

PARTICIPANTS

Seven trials evaluating a total of 1500 adults with AUD receiving monthly injections of either placebo or extended-release naltrexone at doses of 150-400 mg for 2-6 months and some form of behavioral therapy.

MEASUREMENTS

Pooled weighted mean difference (WMD) in drinking days per month and heavy drinking days per month.

FINDINGS

The WMD was -2.0 [95% confidence interval (CI) = -3.4, -0.6; P = 0.03] in favor of extended-release naltrexone for drinking days per month and -1.2 (95% CI = -0.2, -2.1; P = 0.02) for heavy drinking days per month, indicating that treatment resulted in two fewer drinking days per month and 1.2 fewer heavy drinking days per month compared with placebo. Trials not requiring lead-in abstinence and those lasting longer than 3 months reported larger reductions in heavy drinking days per month; WMD -2.0 (95% CI = -3.52, -0.48; P = 0.01) and -1.9 (95% CI = -3.2, -0.5; P = 0.01), respectively. In all cases, the I² statistics (0-7.2%) did not suggest substantial heterogeneity.

CONCLUSIONS

Extended-release naltrexone reduces drinking days and heavy drinking days per month compared with placebo. Reductions are larger with a longer duration of treatment.

Leveraging genetic ancestry to study health disparities

Research to understand human genomic variation and its implications in health has great potential to contribute in the reduction of health disparities. Biological anthropology can play important roles in genomics and health disparities research using a biocultural approach. This paper argues that racial/ethnic categories should not be used as a surrogate for sociocultural factors or global genomic clusters in biomedical research or clinical settings, because of the high genetic heterogeneity that exists within traditional racial/ethnic groups. Genetic ancestry is used to show variation in ancestral genomic contributions to recently admixed populations in the United States, such as African Americans and Hispanic/Latino Americans. Genetic ancestry estimates are also used to examine the relationship between ancestry-related biological and sociocultural factors affecting health disparities. To localize areas of genomes that contribute to health disparities, admixture mapping and genome-wide association studies (GWAS) are often used. Recent GWAS have identified many genetic variants that are highly differentiated among human populations that are associated with disease risk. Some of these are population-specific variants. Many of these variants may impact disease risk and help explain a portion of the difference in disease burden among racial/ethnic groups. Genetic ancestry is also of particular interest in precision medicine and disparities in drug efficacy and outcomes. By using genetic ancestry, we can learn about potential biological differences that may contribute to the heterogeneity observed across self-reported racial groups.

Smoking Cessation Pharmacotherapy Based on Genetically-Informed Biomarkers: What is the Evidence?

INTRODUCTION

Pharmacogenomic studies have used genetic variants to identify smokers likely to respond to pharmacological treatments for smoking cessation.

METHODS

We performed a systematic review and meta-analysis of primary and secondary analyses of trials of smoking cessation pharmacotherapies. Eligible were trials with data on a priori selected single nucleotide polymorphisms, replicated non-single nucleotide polymorphisms, and/or the nicotine metabolite ratio. We estimated the genotype × treatment interaction as the ratio of risk ratios (RRR) for treatment effects across genotype groups.

RESULTS

We identified 18 trials (N = 9017 participants), including 40 active (bupropion, nicotine replacement therapy [NRT], varenicline, or combination therapies) versus placebo comparisons and 16 active versus active comparisons. There was statistical evidence of heterogeneity across rs16969968 genotypes in CHRNA5 with regard to both 6-month abstinence and end-of-treatment abstinence in non-Hispanic black smokers and end-of-treatment abstinence in non-Hispanic white smokers. There was also heterogeneity across rs1051730 genotypes in CHRNA3 with regard to end-of-treatment abstinence in non-Hispanic white smokers. There was no clear statistical evidence for other genotype-by-treatment combinations. Compared with placebo, NRT was more effective among non-Hispanic black smokers with rs16969968-GG with regard to both 6-month abstinence (RRR for GG vs. GA or AA, 3.51; 95% confidence interval [CI] = 1.19 to 10.30) and end-of-treatment abstinence (RRR for GG vs. GA or AA, 5.84; 95% CI = 1.89 to 18.10). Among non-Hispanic white smokers, NRT effectiveness relative to placebo was comparable across rs1051730 and rs169969960 genotypes.

CONCLUSIONS

We did not identify widespread differential effects of smoking cessation pharmacotherapies based on genotype. The quality of the evidence is generally moderate.

IMPLICATIONS

Although we identified some evidence of genotype × treatment interactions, the vast majority of analyses did not provide evidence of differential treatment response by genotype. Where we find some evidence, these results should be considered preliminary and interpreted with caution because of the small number of contributing trials per genotype comparison, the wide confidence intervals, and the moderate quality of evidence. Prospective trials and individual-patient data meta-analyses accounting for heterogeneity of treatment effects through modeling are needed to assess the clinical utility of genetically informed biomarkers to guide pharmacotherapy choice for smoking cessation.

Lack of Association between Opioid-Receptor Genotypes and Smoking Cessation Outcomes in a Randomized, Controlled Naltrexone Trial

AIMS

The present study examined how variation in mu- (OPRM1), kappa- (OPRK), and delta- (OPRD) opioid receptor genes may influence the efficacy of naltrexone in the context of a smoking cessation trial.

METHODS

The study's primary objective was to examine the association of the Asn40Asp OPRM1 single nucleotide polymorphism (SNP) with naltrexone's effects on smoking quit rate, weight gain, and heavy drinking behavior during a double-blind, randomized clinical trial in 280 adult DSM-IV nicotine-dependent participants. The secondary goal of the study was to examine the relationship of 20 additional SNPs of OPRM1, OPRK, and OPRD with the aforementioned outcomes.

RESULTS

Results indicated a null association between any opioid-receptor gene SNP and naltrexone's effects on smoking quit rate, weight gain, and heavy drinking behavior in this sample of nicotine dependent participants.

CONCLUSIONS

In sum, these results do not suggest that genetic variation in opioid-receptors is related to treatment responses to naltrexone in a smoking cessation trial.

Relationship between West African ancestry with lung cancer risk and survival in African Americans

PURPOSE

African Americans, especially men, have a higher incidence of lung cancer compared with all other racial and ethnic groups in the US. Self-reported race is frequently used in genomic research studies to capture an individual's race or ethnicity. However, it is clear from studies of genetic admixture that human genetic variation does not segregate into the same biologically discrete categories as socially defined categories of race. Previous studies have suggested that the degree of West African ancestry among African Americans can contribute to cancer risk in this population, though few studies have addressed this question in lung cancer.

METHODS

Using a genetic ancestry panel of 100 SNPs, we estimated West African, European, and Native American ancestry in 1,407 self-described African Americans and 2,413 European Americans.

RESULTS

We found that increasing West African ancestry was associated with increased risk of lung cancer among African American men (ORQ5 vs Q1 = 2.55 (1.45-4.48), p = 0.001), while no association was observed in African American women (ORQ5 vs Q1 = 0.90 (0.51-1.59), p = 0.56). This relationship diminished following adjustment for income and education.

CONCLUSIONS

Genetic ancestry is not a major contributor to lung cancer risk or survival disparities.

Reduction in Drinking was Associated With Improved Clinical Outcomes in Women With HIV Infection and Unhealthy Alcohol Use: Results From a Randomized Clinical Trial of Oral Naltrexone Versus Placebo

BACKGROUND

Alcohol consumption is associated with poor health outcomes in women living with HIV (WLWH), but whether medication can help to reduce drinking in non-treatment-seeking women or whether reduction in drinking improves HIV outcomes is unclear. We conducted a randomized clinical trial (RCT) of daily oral naltrexone (50 mg) versus placebo in WLWH who met criteria for current unhealthy alcohol use.

METHODS

WLWH with current unhealthy alcohol use (>7 drinks/wk or >3 drinks/occasion) were randomly assigned to daily oral naltrexone 50 mg (n = 96) or placebo (n = 98) for 4 months. Drinking outcomes, including the proportion of women who reduced (

RESULTS

The participants' mean age was 48 years, 86% were African American, and 94% were receiving HIV antiretroviral therapy. Among all participants, 89% and 85% completed the 4-month and 7-month follow-ups, respectively. Participants in both groups substantially reduced drinking over time. At 1 and 3 months, naltrexone was associated with a greater reduction in drinking (p < 0.05), but the proportion who reduced/quit drinking at 4 months (52% vs. 45%, p = 0.36) or 7 months (64% in both groups) was not different. HIV viral suppression at follow-up was significantly better in participants who reduced/quit drinking versus those continuing unhealthy alcohol use at 4 months (72% vs. 53%, p = 0.02) and 7 months (74% vs. 54%, p = 0.02).

CONCLUSIONS

Participating in an RCT to reduce drinking was associated with significant drinking reduction regardless of medication assignment, suggesting that nonmedication aspects of research study participation (e.g., repeated assessments and support from research staff) could be important interventions to help reduce drinking outside of research studies. Drinking reduction was associated with improved HIV viral suppression, providing evidence to support recommendations to avoid unhealthy alcohol use among WLWH.

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Key Words

• Alcohol Consumption
• HIV Infection
• Pharmacotherapy
• Randomized Clinical Trial
• Women

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MESH Headings

• Alcohol Deterrents/therapeutic use
• Alcohol Drinking/drug therapy
• Alcohol-Related Disorders/complications
• Alcohol-Related Disorders/drug therapy
• Anti-Retroviral Agents/therapeutic use
• CD4 Lymphocyte Count/statistics & numerical data
• Female
• HIV Infections/complications
• HIV Infections/drug therapy
• Humans
• Middle Aged
• Naltrexone/therapeutic use
• Treatment Outcome
• Viral Load/statistics & numerical data

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Grants

• U24 AA022002 NIAAA NIH HHS
• U01 AA020797 NIAAA NIH HHS
• U24 AA022003 NIAAA NIH HHS
• UL1 TR000460 NCATS NIH HHS
• P01 AA029543 NIAAA NIH HHS

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Affiliation(s)

Robert L. Cook Department of Epidemiology, (RLC, ZZ), University of Florida, Gainesville
Zhi Zhou Department of Epidemiology, (RLC, ZZ), University of Florida, Gainesville
Maria Jose Miguez Florida, School of Integrated Science and Humanity, (MJM, CQ), Florida International University, Miami, Florida
Clery Quiros Florida, School of Integrated Science and Humanity, (MJM, CQ), Florida International University, Miami, Florida
Luis Espinoza Public Health & Medical Affairs, (LE), Gilead Sciences Inc., Miami, Florida
John E. Lewis Psychiatry & Behavioral Sciences, (JEL), University of Miami School of Medicine, Miami, Florida
Babette Brumback Biostatistics, (BB), University of Florida, Gainesville, Florida
Kendall Bryant Alcohol and HIV/AIDS Research, (KB), National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland

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Genetic Ancestry Analysis Reveals Misclassification of Commonly Used Cancer Cell Lines

BACKGROUND

Given the scarcity of cell lines from underrepresented populations, it is imperative that genetic ancestry for these cell lines is characterized. Consequences of cell line mischaracterization include squandered resources and publication retractions.

METHODS

We calculated genetic ancestry proportions for 15 cell lines to assess the accuracy of previous race/ethnicity classification and determine previously unknown estimates. DNA was extracted from cell lines and genotyped for ancestry informative markers representing West African (WA), Native American (NA), and European (EUR) ancestry.

RESULTS

Of the cell lines tested, all previously classified as White/Caucasian were accurately described with mean EUR ancestry proportions of 97%. Cell lines previously classified as Black/African American were not always accurately described. For instance, the 22Rv1 prostate cancer cell line was recently found to carry mixed genetic ancestry using a much smaller panel of markers. However, our more comprehensive analysis determined the 22Rv1 cell line carries 99% EUR ancestry. Most notably, the E006AA-hT prostate cancer cell line, classified as African American, was found to carry 92% EUR ancestry. We also determined the MDA-MB-468 breast cancer cell line carries 23% NA ancestry, suggesting possible Afro-Hispanic/Latina ancestry.

CONCLUSIONS

Our results suggest predominantly EUR ancestry for the White/Caucasian-designated cell lines, yet high variance in ancestry for the Black/African American-designated cell lines. In addition, we revealed an extreme misclassification of the E006AA-hT cell line.

IMPACT

Genetic ancestry estimates offer more sophisticated characterization leading to better contextualization of findings. Ancestry estimates should be provided for all cell lines to avoid erroneous conclusions in disparities literature.

West African Ancestry and Nocturnal Blood Pressure in African Americans: The Jackson Heart Study

BACKGROUND

African Americans have a higher prevalence of nocturnal hypertension and nondipping blood pressure than European Americans, but the genetic contribution to these racial differences remains unclear. We assessed the association of the percentage West African genetic ancestry with nocturnal hypertension and nondipping blood pressure in 932 African Americans from the Jackson Heart Study.

METHODS

Using percentage West African ancestry determined from 389 ancestry informative markers, participants were categorized into tertiles (tertile 1 [low]: <79.3%, tertile 2: ≥79.3-86.3%, and tertile 3 [high]: >86.3%). Nocturnal hypertension was defined as mean nighttime (midnight-6 am) systolic (SBP)/diastolic blood pressure ≥120/70 mm Hg. Nondipping blood pressure was defined as mean nighttime-to-daytime (10 am-8 pm) SBP ratio >0.90.

RESULTS

Nocturnal hypertension was present in 57.9% of participants; 66.6% had nondipping blood pressure. The mean age was 59.4 years, 32.8% were male, and 56.0% were taking antihypertensive medication. The prevalence ratios (95% confidence interval) adjusted for age, sex, cardiovascular disease risk factors, and socioeconomic and psychosocial factors comparing participants with moderate and high to those with low percentage West African ancestry for nocturnal hypertension were 0.98 (0.87-1.10) and 0.95 (0.84-1.08), respectively, and for nondipping blood pressure was 0.96 (0.86-1.07) and 0.98 (0.88-1.09), respectively.

CONCLUSIONS

West African ancestry was not associated with nocturnal hypertension and nondipping blood pressure among African Americans. While rare genetic variants cannot be ruled out, these data highlight the need to better understand how environmental and behavioral factors contribute to differences in nocturnal blood pressure among African Americans compared with European Americans.

Pharmacotherapy for smoking cessation: effects by subgroup defined by genetically informed biomarkers

BACKGROUND

Smoking cessation therapies are not effective for all smokers, and researchers are interested in identifying those subgroups of individuals (e.g. based on genotype) who respond best to specific treatments.

OBJECTIVES

To assess whether quit rates vary by genetically informed biomarkers within pharmacotherapy treatment arms and as compared with placebo. To assess the effects of pharmacotherapies for smoking cessation in subgroups of smokers defined by genotype for identified genome-wide significant polymorphisms.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group specialised register, clinical trial registries, and genetics databases for trials of pharmacotherapies for smoking cessation from inception until 16 August 2016.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that recruited adult smokers and reported pharmacogenomic analyses from trials of smoking cessation pharmacotherapies versus controls. Eligible trials included those with data on a priori genome-wide significant (P < 5 × 10-8) single-nucleotide polymorphisms (SNPs), replicated non-SNPs, and/or the nicotine metabolite ratio (NMR), hereafter collectively described as biomarkers.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. The primary outcome was smoking abstinence at six months after treatment. The secondary outcome was abstinence at end of treatment (EOT). We conducted two types of meta-analyses- one in which we assessed smoking cessation of active treatment versus placebo within genotype groups, and another in which we compared smoking cessation across genotype groups within treatment arms. We carried out analyses separately in non-Hispanic whites (NHWs) and non-Hispanic blacks (NHBs). We assessed heterogeneity between genotype groups using T², I², and Cochrane Q statistics.

MAIN RESULTS

Analyses included 18 trials including 9017 participants, of whom 6924 were NHW and 2093 NHB participants. Data were available for the following biomarkers: nine SNPs (rs1051730 (CHRNA3); rs16969968, rs588765, and rs2036527 (CHRNA5); rs3733829 and rs7937 (in EGLN2, near CYP2A6); rs1329650 and rs1028936 (LOC100188947); and rs215605 (PDE1C)), two variable number tandem repeats (VNTRs; DRD4 and SLC6A4), and the NMR. Included data produced a total of 40 active versus placebo comparisons, 16 active versus active comparisons, and 64 between-genotype comparisons within treatment arms.For those meta-analyses showing statistically significant heterogeneity between genotype groups, we found the quality of evidence (GRADE) to be generally moderate. We downgraded quality most often because of imprecision or risk of bias due to potential selection bias in genotyping trial participants. Comparisons of relative treatment effects by genotypeFor six-month abstinence, we found statistically significant heterogeneity between genotypes (rs16969968) for nicotine replacement therapy (NRT) versus placebo at six months for NHB participants (P = 0.03; n = 2 trials), but not for other biomarkers or treatment comparisons. Six-month abstinence was increased in the active NRT group as compared to placebo among participants with a GG genotype (risk ratio (RR) 1.47, 95% confidence interval (CI) 1.07 to 2.03), but not in the combined group of participants with a GA or AA genotype (RR 0.43, 95% CI 0.15 to 1.26; ratio of risk ratios (RRR) GG vs GA or AA of 3.51, 95% CI 1.19 to 10.3). Comparisons of treatment effects between genotype groups within pharmacotherapy randomisation armsFor those receiving active NRT, treatment was more effective in achieving six-month abstinence among individuals with a slow NMR than among those with a normal NMR among NHW and NHB combined participants (normal NMR vs slow NMR: RR 0.54, 95% CI 0.37 to 0.78; n = 2 trials). We found no such differences in treatment effects between genotypes at six months for any of the other biomarkers among individuals who received pharmacotherapy or placebo.

AUTHORS' CONCLUSIONS

We did not identify widespread differential treatment effects of pharmacotherapy based on genotype. Some genotype groups within certain ethnic groups may benefit more from NRT or may benefit less from the combination of bupropion with NRT. The reader should interpret these results with caution because none of the statistically significant meta-analyses included more than two trials per genotype comparison, many confidence intervals were wide, and the quality of this evidence (GRADE) was generally moderate. Although we found evidence of superior NRT efficacy for NMR slow versus normal metabolisers, because of the lack of heterogeneity between NMR groups, we cannot conclude that NRT is more effective for slow metabolisers. Access to additional data from multiple trials is needed, particularly for comparisons of different pharmacotherapies.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Disparities in Treatment Uptake and Outcomes of Patients with Obesity in the USA

There are clear and persistent disparities in obesity prevalence within the USA. Some of these disparities fall along racial/ethnic lines; however, there are a number of other social and demographic constructs where obesity disparities are present. In addition to differing rates of obesity across groups, there is growing evidence that subgroups of patients both seek out and respond to obesity treatment differently. This review article explores the epidemiology of obesity disparities, as well as the existing evidence around how different groups may respond to behavioral, medical, and surgical therapies, and potential reasons for differential uptake and response, from culture, to access, to physiology. We find that the vast majority of evidence in this area has focused on the observation that African Americans tend to lose less weight in clinical trials compared to non-Hispanic whites and mainly pertains to behavioral interventions. Moving forward, there will be a need for studies that broaden the notion of health disparity beyond just comparing African Americans and non-Hispanic whites. Additionally, a more thorough examination of the potential for disparate outcomes after medical and surgical treatments of obesity is needed, coupled with the careful study of possible physiologic drivers of differential treatment response.