Indian Journal of Biochemistry & Biophysics Vol. 48, August 2011, pp. 283-289 Modulatory effect of plasma folate and polymorphisms in one-carbon metabolism on catecholamine methyltransferase (COMT) H108L associated oxidative DNA damage and breast cancer risk Shaik Mohammad Naushad 1 , Addepalli Pavani 1 , Yedluri Rupasree 1 , Deepti Sripurna 1 , Suryanarayana Raju Gottumukkala 2 , Raghunadha Rao Digumarti 3 and Vijay Kumar Kutala 1* 1 Departments of Clinical Pharmacology & Therapeutics, 2 Surgical Oncology, 3 Medical Oncology; Nizam’s Institute of Medical Sciences (NIMS), Panjagutta, Hyderabad 500082, AP, India Received 24 January 2011; revised 13 June 2011 The present study was aimed to investigate the modulatory role of plasma folate and eight putatively functional polymorphisms of one-carbon metabolism on catecholamine methyltransferase (COMT)-mediated oxidative DNA damage and breast cancer risk. Plasma folate and 8-oxo-2’-deoxyguanosine (8-oxodG) were estimated by commercially available kits, while polymorphisms were screened by PCR-RFLP and PCR-AFLP methods. COMT H108L polymorphism showed independent association with breast cancer (OR: 1.73, 95% CI: 1.31-2.30). No significant interaction was observed between folate status and COMT genotype. Multifactor dimensionality reduction (MDR) analysis gave evidence for the significant epistatic (gene-gene) interactions (p<0.0001) of COMT H108L with reduced folate carrier 1 (RFC1) G80A, thymidylate synthase (TYMS) 5’-UTR 3R2R, TYMS 3’-UTR ins6/del6. Increased plasma 8-oxodG were observed in cases compared to controls (mean ± SE: 5.59 ± 0.60 vs. 3.50 ± 0.40 ng/ml, p<0.004). Plasma folate deficiency alone was not a significant predictor of 8-oxodG elevation. The genotype combinations namely, RFC1 G80A/methionine synthase reductase (MTRR) A66G, RFC1 G80A/SHMT C1420T/TYMS 3R2R and serine hydroxymethyltransferase (SHMT) C1420T/TYMS 3R2R/methionine synthase (MTR) A2756G/COMT H108L were strong predictors of 8-oxodG elevation in the order of risk. To conclude, the current study provides substantial evidence for a cross talk between one-carbon metabolism and COMT catalysis that might influence oxidative DNA damage and breast cancer risk. Keywords: Catechol-O-methyltransferase (COMT), 8-Oxo-2’-deoxyguanosine (8-oxodG), One-carbon metabolism, Oxidative DNA damage, Breast cancer, Polymorphism, Plasma folate. The etiology of breast cancer is complex involving genetic, nutritional, environmental and epigenetic factors. Most of the established risk factors, including age at menarche and menopause, age at first full-time pregnancy as well as the number of parturitions indicate association between cumulative estrogen exposure and breast cancer. Estrogens can potentially induce carcinogenesis i) by stimulating the transcription of genes necessary for cell proliferation via the estrogen receptor, and ii) by causing oxidative DNA damage via their catechol estrogen metabolites 1,2 . This later pathway popularly known as xenobiotic pathway has two phases i.e. phase I and II that catalyze the generation of electrophiles and their detoxification, respectively (Fig. 1). Phase I enzymes namely cytochrome P450 (CYP) 1A1 and CYP1B1 catalyze the oxidation of 17β-estradiol (E2) and estrone (E1) to the 2- and 4-catechol estrogens and 16-α hydroxyestrogen 3,4 , which on further oxidation generate highly reactive semiquinones and quinones 5,6 . They interact with DNA to form adducts, leading to oxidative DNA damage, an important event in the molecular pathophysiology of human cancers 7,8 . On the other hand, phase II enzymes catecholamine methyltransferase (COMT) and glutathione S-transferase (GST) inactivate the toxic effects of phase I ————— *Author for correspondence Tel: +91-9395532288 E-mail: vijaykutala@gmail.com Abbreviations: AFLP, amplified fragment length polymorphism; COMT, catechol-O-methyltransferase; cSHMT, cytosolic serine hydroxymethyltransferase; GCPII, glutamate carboxypeptidase II; MDR, multifactor dimensionality reduction analysis; MTHF, methylene tetrahydrofolate; MTHFR, methylenetetrahydrofolate reductase; MTR, methionine synthase; MTRR, methionine synthase reductase; 8-oxodG, 8-Oxo-2’-deoxyguanosine; PCR, polymerase chain reaction; RFC1, reduced folate carrier 1; RFLP, restriction fragment length polymorphism; SNP, single nucleotide polymorphism; tHcy, total plasma homocysteine; THF, tetrahydrofolate; TYMS, thymidylate synthase.