Genetic Variants in Nicotine Addiction and Alcohol Metabolism Genes, Oral Cancer Risk and the Propensity to Smoke and Drink Alcohol: A Replication Study in India Devasena Anantharaman 1 , Ame ´ lie Chabrier 2 , Vale ´ rie Gaborieau 1 , Silvia Franceschi 3 , Rolando Herrero 4 , Thangarajan Rajkumar 5 , Tanuja Samant 6 , Manoj B. Mahimkar 6 , Paul Brennan 1 , James D. McKay 2 * 1 Genetic Epidemiology Group, International Agency for Research on Cancer, Lyon, France, 2 Genetic Cancer Susceptibility Group, International Agency for Research on Cancer, Lyon, France, 3 Infections and Cancer Epidemiology Group, International Agency for Research on Cancer, Lyon, France, 4 Prevention and Implementation Group, International Agency for Research on Cancer, Lyon, France, 5 Department of Molecular Oncology, Cancer Institute, Chennai, India, 6 Mahimkar Lab, Advanced Center for Treatment Research and Education in Cancer, Tata Memorial Center, Navi Mumbai, India Abstract Background: Genetic variants in nicotinic acetylcholine receptor and alcohol metabolism genes have been associated with propensity to smoke tobacco and drink alcohol, respectively, and also implicated in genetic susceptibility to head and neck cancer. In addition to smoking and alcohol, tobacco chewing is an important oral cancer risk factor in India. It is not known if these genetic variants influence propensity or oral cancer susceptibility in the context of this distinct etiology. Methods: We examined 639 oral and pharyngeal cancer cases and 791 controls from two case-control studies conducted in India. We investigated six variants known to influence nicotine addiction or alcohol metabolism, including rs16969968 (CHRNA5), rs578776 (CHRNA3), rs1229984 (ADH1B), rs698 (ADH1C), rs1573496 (ADH7), and rs4767364 (ALDH2). Results: The CHRN variants were associated with the number of chewing events per day, including in those who chewed tobacco but never smoked (P = 0.003, P = 0.01 for rs16969968 and rs578776 respectively). Presence of the variant allele contributed to approximately 13% difference in chewing frequency compared to non-carriers. While no association was observed between rs16969968 and oral cancer risk (OR = 1.01, 95% CI = 0.83– 1.22), rs578776 was modestly associated with a 16% decreased risk of oral cancer (OR = 0.84, 95% CI = 0.72– 0.98). There was little evidence for association between polymorphisms in genes encoding alcohol metabolism and oral cancer in this population. Conclusion: The association between rs16969968 and number of chewing events implies that the effect on smoking propensity conferred by this gene variant extends to the use of smokeless tobacco. Citation: Anantharaman D, Chabrier A, Gaborieau V, Franceschi S, Herrero R, et al. (2014) Genetic Variants in Nicotine Addiction and Alcohol Metabolism Genes, Oral Cancer Risk and the Propensity to Smoke and Drink Alcohol: A Replication Study in India. PLoS ONE 9(2): e88240. doi:10.1371/journal.pone.0088240 Editor: Qing-Yi Wei, Duke Cancer Institute, United States of America Received October 7, 2013; Accepted January 8, 2014; Published February 5, 2014 Copyright: ß 2014 Anantharaman et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The International oral cancer study was funded by the International Agency for Research on Cancer. The Mumbai study was supported by the Department of Biotechnology, Government of India (BT/PR 2277/09/333/2000). The National Institute of Dental and Craniofacial Research grant funded the laboratory analyses for this study (R03 DE020116). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of this manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: gcs@iarc.fr Introduction Cancers of the oral cavity and pharynx contribute to nearly 400,000 new cases each year worldwide, more than half of which occur in India. Each year over 200,000 die of the disease, and over a third of these deaths occur in India [1]. Tobacco use and alcohol consumption are the key established risk factors for oral cancer, with the use of smokeless tobacco being particularly important in the Indian population [2]. Exposure to human papillomavirus is becoming increasingly important to cancers of the oropharynx [3,4]. Genome-wide association studies (GWAS) have successfully identified disease susceptibility loci to various complex diseases [5]. Lung cancer GWAS and nicotine addiction studies have identified the 15q25 locus harbouring the nicotinic acetylcholine receptor (CHRN) gene cluster [6–8]. These genes code for receptors expressed in neuronal and other epithelial cells that bind to nicotine and nicotine derivatives [9,10]. Two CHRN receptor subunit variants, rs16969968 and rs578776 have been consistently associated with lung cancer risk and smoking behavior in several populations [11–15]. Homozygous carriers of the rs1669968 rare allele have been reported to smoke approximately 1.2 cigarettes more per day [13]. Further, this variant has also been associated with increased risk of Upper Aero-Digestive Tract (UADT) cancer. UADT cancer GWAS and candidate gene association studies have identified genetic variants in the 4q (rs1229984, rs698, rs1573496) and 12q (rs4767364) loci containing genes involved in alcohol metabolism [16,17]. The balance between alcohol dehydrogenase and aldehyde dehydrogenase activities has been suggested to regulate blood acetaldehyde concentrations that PLOS ONE | www.plosone.org 1 February 2014 | Volume 9 | Issue 2 | e88240