Association of XRCC1, XRCC3, and NAT2 polymorphisms with the risk of oral submucous fibrosis among eastern Indian population Sanjit Mukherjee 1 , Aneek Das Bhowmik 2 , Paromita Roychoudhury 2 , Kanchan Mukhopadhyay 2 , Jay Gopal Ray 3 , Keya Chaudhuri 1 1 Molecular & Human Genetics Division, Indian Institute of Chemical Biology (A Unit of CSIR), Kolkata, India; 2 Manovikas Biomedical Research and Diagnostic Centre, Manovikas Kendra, Kolkata, India; 3 Department of Oral Pathology, Dr. R. Ahmed Dental College & Hospital, Kolkata, India BACKGROUND: Arecanut and smokeless tobacco usage is a major cause for oral submucous fibrosis (OSF) and its subsequent development to oral squamous cell carci- noma in South-east Asian population. Polymorphisms at N-acetyltransferase 2 locus, coding for an enzyme cata- lyzing acetylation of aromatic amines, might cause DNA adduct formation because of improper acetylation of these polyaromatic hydrocarbons. DNA repair enzymes remove these adduct to prevent malignancy. METHODS: In this hospital-based study, 100 controls and 88 OSF patients were genotyped at four polymorphic sites on NAT2 481 (C > T; silent), 590 (G > A; Arg197 > Gln), 803 (A > G; Lys268 > Arg), 857 (G > A; Gly286 > Glu) and two on XRCC1 18067 (C > T Arg 194 > Trp), 28152 (G > A Arg 399 > Gln), and one of XRCC3 26304 (C > T Thr 241 > Met) loci by PCR-RFLP to determine the risk of the disease. RESULTS: Heterozygous XRCC3 codon 241 [OR 2.07 (1.05–4.06)], homozygous variant of NAT C481T [OR 2.81 (1.09–7.21)], and both heterozygous and homozy- gous variants of NAT codon 268 and 286 [OR 2.31 (1.20– 4.45) and 4.98 (1.87–13.14), and 6.12 (2.75–13.62) and 2.65 (1.04–6.72)] individually influenced susceptibility to OSF in the population. CONCLUSION: Gene–gene interaction analysis by mul- tifactor dimensionality reduction (MDR) revealed that XRCC3 Thr 241 Met had the largest univariate effect followed by XRCC3 Thr 241 Met – NAT2 A857G in men that presents a highly synergistic interaction as one of the potential combinations of single nucleotide polymor- phisms (SNPs) to increase the risk of OSF in men if ex- posed to arecanut or smokeless tobacco usage. These observations can speculate the impact of the studied SNPs on the etiology of OSF. J Oral Pathol Med (2012) 41: 292–302 Keywords: areca; NAT; oral submucous fibrosis; single nucleo- tide polymorphism; XRCC Abbreviations: AP, apurinic ⁄ apyrimidinic site; BER, base exci- sion repair; DSB, double-strand breaks; HRR, homologous recombination repair; MDR, multifactor dimensionality reduction; NAT, N-acetyl transferase; NHEJ, non-homologous end joining; OSF, oral submucous fibrosis; SNP, single nucleotide polymor- phism; SSB, single-strand breaks; SSBR, single-strand break repair; XRCC, X-ray cross-complementing group Introduction Oral submucous fibrosis (OSF) is an insidious chronic progressive pre-cancerous condition of the oral cavity and oropharynx, a large proportion of which is con- verted into squamous cell carcinoma and the malignant potency being in the order of 7–14% if not detected on time (1). The disease is mainly prevalent in the Indian subcontinent and in many South-east Asian countries in all age groups and across all socioeconomic strata although it has been reported in many parts of the world including United Kingdom and South Africa (2, 3). Oral submucous fibrosis is characterized by bilateral collagenous deposition of fibrous tissues in the submu- cosal layer of the palate, faces, cheek, lips, pharynx, and esophagus, leading to restricted mouth opening, local- ized burning sensation, and intolerance to spicy food, followed by ulceration and blanching of the mucosa (4). Its etiology, although elusive, is thought to be caused by arecoline, an alkaloid of areca nut released during chewing betelquid preparation popularly known as ÔGutkha’ (combination of arecanut, tobacco leaf, lime, Correspondence: Keya Chaudhuri, Molecular & Human Genetics Division, Indian Institute of Chemical Biology, A Unit of CSIR, 4 Raja S C Mullick Road, Kolkata-700032, India. Tel: +91 33 2499 5762, Fax: +91 33 2473 5197, E-mail: kchaudhuri@iicb.res.in; keya.chaudhuri@gmail.com Accepted for publication October 14, 2011 J Oral Pathol Med (2012) 41: 292–302 ª 2011 John Wiley & Sons A/S Æ All rights reserved wileyonlinelibrary.com/journal/jop doi: 10.1111/j.1600-0714.2011.01097.x