{ "items": [ "\n\n
The molecular processes that underlie addiction are beginning to unfold. Genetically determined variations in dopaminergic neurotransmission predispose to nicotine dependence. In addition, tobacco use is likely to be governed by the rate at which smokers metabolize nicotine. Functional polymorphisms in CYTOCHROME P450 monooxygenases that metabolize nicotine have now been defined and it should soon be possible to identify fast nicotine metabolizers by DNA analysis. Here, we review the key neurotransmitter receptors and metabolic enzymes implicated in tobacco dependence. We explore the potential benefits of classifying smokers according to the molecular aetiology of their habit. One major benefit will be in planning effective strategies for smoking cessation. Methods of typing for alleles related to smoking behavior that might be suitable for use in clinical practice in the future will also be discussed
\n \n\n \n \nLarge-scale genetic studies are reliably identifying many risk factors for disease in the general population. Several of these genetic risk factors encode potential drug targets, and genetics has already helped to introduce targeted agents for some diseases, an example being lipid-lowering drugs to reduce the incidence of cardiovascular disease. Multiple drugs have been developed to treat cancers based on somatic mutations and genomics, but in stark contrast, there seems to be a reluctance to use germline genetic data to develop drugs to prevent malignancy, despite the large numbers of people who could benefit, the potential for lowering cancer rates, and the widespread current use of non-pharmaceutical measures to reduce cancer risk factors such as tobacco, alcohol, and infectious diseases. We argue that concerted efforts for cancer prevention based on genetics, including genes influenced by common polymorphisms that modulate cancer risk, are urgently needed. There are enormous, yet underutilized, opportunities to develop novel targeted agents for chemoprevention of cancer based on human germline genetics. Such efforts are likely to require the support of a dedicated funding program by national and international agencies. See related commentary by Winham and Sherman, p. 13.
\n \n\n \n \nINTRODUCTION: Stopping smoking results in weight gain. Avoidance of alcohol is often advocated to reduce cues to smoking, but the effect of alcohol consumption on body weight is unclear. METHODS: We used regression models to examine weight change by baseline alcohol consumption in quitting and continuing smokers. Weight was measured at baseline and at 8 years, and weekly alcohol consumption was reported at baseline in participants from the Oxfordshire general practices nicotine patch/placebo trial. Of 698 smokers attempting to stop smoking, 85 were abstinent for 8 years and 613 continued to smoke. RESULTS: The association between baseline alcohol consumption and weight change depended upon smoking status (p for interaction = .019). In smokers, there was no association with weight change, 0.005 (95% CI: -0.037 to 0.056) kg per UK unit (U) (8 g of ethanol) consumed each week. This was unmodified by gender and baseline body mass index (BMI). In quitters, there was a negative association with weight change, -0.174 (95% CI: -0.315 to -0.034) kg per U consumed each week (unmodified by gender and baseline BMI). Quitters who consumed 14 U (112 g ethanol) a week weighed a mean 2.4 kg less than quitters who did not drink. CONCLUSIONS: Quitting smokers who drink more alcohol appear to gain less weight after quitting than those who do not drink. This is consistent across studies, it may be accounted for by unmeasured confounders or it may be that alcohol reduces weight gain. If alcohol reduces weight gain, the advice for quitting smokers must balance the benefits and hazards of alcohol consumption. However, there is currently insufficient evidence to advise quitters who drink little or no alcohol to increase consumption.
\n \n\n \n \nIn the UK, approximately one-third of the population currently smoke. It is estimated that up to 70% of these smokers want to stop smoking but smoking cessation rates currently only stand at 20-30%. In order to reduce the health burden associated with smoking in the short-term we need to increase cessation rates. This will stem from deeper understanding of the processes involved in nicotine addiction, targeted therapy and the development of new pharmacological cessation agents. This article is not intended to be an exhaustive examination of nicotine addiction but rather an overview of some of the genetic aspects and how we can go on to use this knowledge in order to develop a genetic test to aid smoking cessation.
\n \n\n \n \nRelatively few studies have investigated the role of the 5HTT gene in intermediate phenotypes such as alcohol consumption in non-alcohol dependent populations. A recent study reported an association with alcohol consumption in a student population. We attempted to replicate these findings and extend on this work in a representative, ethnically homogenous, non-alcohol dependent sample of social drinkers in the United Kingdom. The short allele of the 5HTT gene was significantly associated with increased alcohol consumption (P = 0.03). There was suggestive evidence of a genotype-sex interaction (P = 0.04). Post-hoc tests indicated higher alcohol consumption in men with one or more copies of the short allele, while in women consumption was highest among heterozygotes compared to both homozygote groups. Age at time of data collection and cigarette consumption were entered as covariates. These results replicate recent previous findings and suggest a possibility that this association may differ in men and women.
\n \n\n \n \nImmune checkpoint blockade (ICB) provides effective and durable responses for several tumour types by unleashing an immune response directed against cancer cells. However, a substantial number of patients treated with ICB develop relapse or do not respond, which has been partly attributed to the immune-suppressive effect of tumour hypoxia. We have previously demonstrated that the mitochondrial complex III inhibitor atovaquone alleviates tumour hypoxia both in human xenografts and in cancer patients by decreasing oxygen consumption and consequently increasing oxygen availability in the tumour. Here, we show that atovaquone alleviates hypoxia and synergises with the ICB antibody anti-PD-L1, significantly improving the rates of tumour eradication in the syngeneic CT26 model of colorectal cancer. The synergistic effect between atovaquone and anti-PD-L1 relied on CD8+ T cells, resulted in the establishment of a tumour-specific memory immune response, and was not associated with any toxicity. We also tested atovaquone in combination with anti-PD-L1 in the LLC (lung) and MC38 (colorectal) cancer syngeneic models but, despite causing a considerable reduction in tumour hypoxia, atovaquone did not add any therapeutic benefit to ICB in these models. These results suggest that atovaquone has the potential to improve the outcomes of patients treated with ICB, but predictive biomarkers are required to identify individuals likely to benefit from this intervention.
\n \n\n \n \nRichter transformation (RT) represents an aggressive histological transformation from chronic lymphocytic leukaemia, most often to a large B cell lymphoma. It is characterised by chemo-resistance and subsequent short survival. Drug development has struggled over recent years in light of the aggressive kinetics of the disease, lack of pivotal registrational trials and relative rarity of the phenomenon. In this review we will highlight the diagnostic and therapeutic challenges of managing patients with RT as well as taking a look to the future therapeutic landscape. Highly active therapies developed across B cell malignancies are starting to impact this field, with T-cell activation therapies (CAR-T, bispecific antibodies), antibody-drug conjugates, and novel small molecule inhibitor combinations (e.g. BTKi-BCL2i) being actively studied. We will highlight the data supporting these developments and look to the studies to come to provide hope for patients suffering from this devastating disease.
\n \n\n \n \nBACKGROUND: Cytochrome P450 2B6 (CYP2B6) has a role in the metabolism of many clinically important substances, but the variation within the CYP2B6 gene has not been fully characterized. The aim of the present study was to develop a reliable and robust assay for determining genotypic variants. METHODS: We used a two-stage procedure. An initial multiplex PCR reaction amplified the relevant gene fragments in exonic and regulatory regions to ensure isolation of CYP2B6 from its similar pseudogene (CYP2B7). This product was then genotyped by allele-specific PCR. RESULTS: The assay detected the following published single-nucleotide polymorphisms: C64T (Arg22Cys), C78T, G216C, G516T (Gln172His), C777A (Ser259Arg), A785G (Lys262Arg), and C1459T (Arg487Cys), as well as additional loci found within the single-nucleotide polymorphism (SNP) databases: A1190G, C1268A, C1330T, A1382G, A1402T, and an A/T SNP in intron 2 (A12917T). This approach detected all common, previously reported alleles and identified a new allele (CYP2B6*4C) present in 2.2% of a Caucasian population. Genotypic frequencies obtained were consistent with previously published results. CONCLUSIONS: This method is simple, reliable, rapid, and amenable to automation and could facilitate the large-scale genotypic analysis of CYP2B6.
\n \n\n \n \nDopaminergic transmission in the central nervous system is thought to underlie addictive behaviours, including smoking. One effective smoking cessation drug, bupropion, enhances dopaminergic transmission; conversely, antipsychotic drugs, which are dopamine antagonists, are associated with increased smoking. Thus we hypothesized that subfertile women treated with the potent dopamine agonist bromocriptine might smoke less as a consequence of their treatment. Among 4,608 subfertile women those conceiving on bromocriptine were half as likely to smoke as those taking other drugs or those conceiving without medication (p < 0.0001). This observation supports the role of dopamine in nicotine addiction, and suggests that bromocriptine-like drugs could be used effectively by pregnant women to aid cessation.
\n \n\n \n \nNicotine stimulates dopamine release and activates dopaminergic reward neurones in central pathways giving rise to dependence. Catechol O-methyl transferase (COMT) inactivates extraneuronally released dopamine and is present in dopaminergic brain regions. A functional polymorphism (COMT 1947A>G) resulting in increased enzyme activity has been associated with alcoholism and polysubstance abuse. We examined the relationship between the COMT 1947A>G polymorphism and smoking initiation, smoking persistence and smoking cessation. We genotyped 266 current smokers, 270 ex-smokers and 265 lifetime non-smokers (never smokers), matched for age and gender, for the COMT 1947A>G polymorphism. Smoking status was ascertained by self-report. There was no difference in genotype frequencies between never smokers and ever smokers (current + ex-smokers); between non-smokers (never + ex-smokers) and current smokers; or between current smokers and ex-smokers. These data suggest that the COMT 1947A>G polymorphism is not associated with smoking initiation, smoking persistence or smoking cessation.
\n \n\n \n \nPolymorphisms in the dopamine D2 receptor (DRD2 C/T and DRD2 A/G) and in dopamine beta hydroxylase (DBH A/G) have been implicated in modulation of smoking and other reward-seeking behaviours. We hypothesized that these alleles would predict the outcome of nicotine patch therapy for smoking cessation. In 1991-93, we performed a randomized controlled trial of the nicotine patch on 1686 heavy smokers (> or = 15 cigarettes/day). In 1999-2000, we contacted 1532 of the 1612 subjects still available; 767 (50%) completed a questionnaire and gave a blood sample. In the 755 cases in which DNA was successfully genotyped, we examined associations between the polymorphisms in DRD2 and DBH, and smoking cessation. At 1 week, the patch was more effective for smokers with DRD2 CT/TT genotype [patch/placebo odds ratio (OR) 2.8, 95% confidence interval (CI) 1.7-4.6] than with CC (OR 1.4, 0.9-2.1; P for difference in ORs 0.04). Smokers with both DRD2 CT/TT and DBH GA/AA genotypes had an OR of 3.6 (2.0-6.5) compared to 1.4 (1.0-2.1) for others (P = 0.01). At 12 weeks, the ORs for these genotypic groups were 3.6 (1.7-7.8) and 1.4 (0.9-2.3), respectively (P = 0.04). There was no association between patch effectiveness and DRD2 exon 8. Short-term effectiveness of the nicotine patch may be related to dopamine beta-hydroxylase and dopamine D2 receptor genotype. Our results support the need for further investigation into personalized therapies for smoking cessation based on individual genotype.
\n \n\n \n \nThe naked mole rat (NMR), Heterocephalus glaber, the longest-living rodent, provides a unique opportunity to explore how evolution has shaped adult stem cell (ASC) activity and tissue function with increasing lifespan. Using cumulative BrdU labelling and a quantitative imaging approach to track intestinal ASCs (Lgr5+) in their native in vivo state, we find an expanded pool of Lgr5+ cells in NMRs, and these cells specifically at the crypt base (Lgr5+CBC) exhibit slower division rates compared to those in short-lived mice but have a similar turnover as human LGR5+CBC cells. Instead of entering quiescence (G0), NMR Lgr5+CBC cells reduce their division rates by prolonging arrest in the G1 and/or G2 phases of the cell cycle. Moreover, we also observe a higher proportion of differentiated cells in NMRs that confer enhanced protection and function to the intestinal mucosa which is able to detect any chemical imbalance in the luminal environment efficiently, triggering a robust pro-apoptotic, anti-proliferative response within the stem/progenitor cell zone.
\n \n\n \n \nClopidogrel is an oral antiplatelet agent used in the treatment of acute coronary syndrome (ACS), myocardial infarction (MI), cerebrovascular disease and peripheral arterial disease. It is also indicated in combination with aspirin in patients undergoing percutaneous coronary intervention (PCI). Clopidogrel is a pro-drug which is converted into its active metabolite by several hepatic enzymes, especially CYP2C19. There is wide variability among patients in response to clopidogrel therapy, which is attributable to genetic variations at several locations of the CYP2C19 gene leading to either loss or gain of function of the enzyme. Here, we report a simple and fast multiplexed allele-specific PCR-based method to detect the clinically important variants of CYP2C19. CYP2C19*1 is the wild-type form of the gene that encodes an enzyme encodes with normal activity. Other variants such as, CYP2C19*2, CYP2C19*3, CYP2C19*4 result in loss of function, whereas CYP2C19*17 imparts gain of function. This multiplexed method does not call for high-end and expensive laboratory equipment, but can reliably detect clinically important CYP2C19 variants. This method was further validated by direct sequencing of the target variants. We applied this method to determine the genotypes of 673 Bangladeshi individuals. Our study showed that the CYP2C19*2 and CYP2C19*17 variants are present at high frequencies in Bangladeshi population. This method may be applied in routine genotyping of patients under clopidogrel regimen.
\n \n\n \n \nThe dopamine D2 receptor has been extensively studied in relation to alcoholism, substance abuse, and nicotine dependence. The most frequently examined polymorphism linked to this gene is the Taq1A restriction fragment length polymorphism (RFLP) (dbSNP rs1800497; g.32806C>T in GenBank AF050737.1), which has been associated with a reduction in D2 receptor density, although this is not universally accepted. The Taq1A RFLP lies 10 kB downstream of DRD2 and may therefore fall within a different coding region than the DRD2 gene or within a regulatory region. Within this downstream region, we have identified a novel kinase gene, named ankyrin repeat and kinase domain containing 1 (ANKK1), which contains a single serine/threonine kinase domain and is expressed at low levels in placenta and whole spinal cord RNA. This gene is a member of an extensive family of proteins involved in signal transduction pathways. The DRD2 Taq1A RFLP is a single nucleotide polymorphism (SNP) that causes an amino acid substitution within the 11th ankyrin repeat of ANKK1 (p.Glu713Lys), which, while unlikely to affect structural integrity, may affect substrate-binding specificity. If this is the case, then changes in ANKK1 activity may provide an alternative explanation for previously described associations between the DRD2 Taq1A RFLP and neuropsychiatric disorders such as addiction.
\n \n\n \n \nThe mu1 opioid receptor gene, OPRM1, has long been a high-priority candidate for human genetic studies of addiction. Because of its potential functional significance, the non-synonymous variant rs1799971 (A118G, Asn40Asp) in OPRM1 has been extensively studied, yet its role in addiction has remained unclear, with conflicting association findings. To resolve the question of what effect, if any, rs1799971 has on substance dependence risk, we conducted collaborative meta-analyses of 25 datasets with over 28,000 European-ancestry subjects. We investigated non-specific risk for \"general\" substance dependence, comparing cases dependent on any substance to controls who were non-dependent on all assessed substances. We also examined five specific substance dependence diagnoses: DSM-IV alcohol, opioid, cannabis, and cocaine dependence, and nicotine dependence defined by the proxy of heavy/light smoking (cigarettes-per-day >20 vs. \u2264 10). The G allele showed a modest protective effect on general substance dependence (OR = 0.90, 95% C.I. [0.83-0.97], p value = 0.0095, N = 16,908). We observed similar effects for each individual substance, although these were not statistically significant, likely because of reduced sample sizes. We conclude that rs1799971 contributes to mechanisms of addiction liability that are shared across different addictive substances. This project highlights the benefits of examining addictive behaviors collectively and the power of collaborative data sharing and meta-analyses.
\n \n\n \n \nWe investigated change in body mass index following long-term smoking cessation in a representative cohort of treatment-seeking heavy smokers in the United Kingdom, to determine the extent of long-term weight gain in successful quitters versus continuing smokers. We further investigated whether DRD4 genotype moderated any weight gain in either group. Smoking cessation was associated with an increase in BMI, and persisted up to 8 years after smoking cessation. Ex-smokers at 8-year follow-up weighed over 2.5 kg/m(3) more on average than they did at baseline, while participants who were smokers at both baseline and 8-year follow-up did not demonstrate any change in BMI. We did not observe an interaction between smoking status and DRD4 genotype. However, independently of the weight gain among those who stopped smoking during the course of the study, DRD4 genotype was significantly associated with BMI, with possession of the -521 C-allele associated with increased BMI. The magnitude of increase in BMI following smoking cessation, and the persistence of this change at 8-year follow-up, suggests that health benefits associated with smoking cessation may to some extent be negated by the detrimental effects on health of associated weight gain. Smoking cessation programmes should therefore consider incorporating follow-up support to promote weight loss among those who successfully stop smoking.
\n \n\n \n \nIn this issue of Molecular Cell, Bao et\u00a0al.1 set out to elucidate \"functional lysines\" in the genome using adenine base editors. The study reveals several cases of alteration of functions that previous canonical CRISPR-Cas9 screens were unable to detect.
\n \n\n \n \nActivation of oncogenic gene expression from long-range enhancers is initiated by the assembly of DNA-binding transcription factors (TF), leading to recruitment of co-activators such as CBP/p300 to modify the local genomic context and facilitate RNA-Polymerase 2 (Pol2) binding. Yet, most TF-to-coactivator recruitment relationships remain unmapped. Here, studying the oncogenic fusion TF PAX3-FOXO1 (P3F) from alveolar rhabdomyosarcoma (aRMS), we show that a single cysteine in the activation domain (AD) of P3F is important for a small alpha helical coil that recruits CBP/p300 to chromatin. P3F driven transcription requires both this single cysteine and CBP/p300. Mutants of the cysteine reduce aRMS cell proliferation and induce cellular differentiation. Furthermore, we discover a profound dependence on CBP/p300 for clustering of Pol2 loops that connect P3F to its target genes. In the absence of CBP/p300, Pol2 long range enhancer loops collapse, Pol2 accumulates in CpG islands and fails to exit the gene body. These results reveal a potential novel axis for therapeutic interference with P3F in aRMS and clarify the molecular relationship of P3F and CBP/p300 in sustaining active Pol2 clusters essential for oncogenic transcription.
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