Influence of the Cyp1B1 L432V gene polymorphism and exposure to tobacco smoke on Cyp1B1 mRNA expression in human leucocytes

PCB Polychlorinated biphenyls PAH Polycyclic aromatic hydrocarbons TCDD Tetrachlorodibenzo-p-dioxin DMOS Dimethyl sulfoxide [Tm; dF; dT; T] Fluorescence data were converted to derivative melting curves by plotting the negative derivative of the fluorescence with respect to temperature vs. temperature [-(dF/dT) vs. T] and show two different melting maxima (Tm), one for each allele. PCR Polymerase Chain Reaction AhR Aromatic hydrocarbon receptor Cyp1B1 Cytochrome P450 1B1 This article has not been copyedited and formatted. The final version may differ from this version. Abstract Cytochrome P450 1B1 (CYP1B1), a phase I enzyme, is involved in the activation of a broad spectrum of procarcinogens. An association of the Cyp1B1 Leu432Val polymorphism with diverse types of cancer as well as an impact on the catalytic activity of the enzyme have been described. To demonstrate the functional impact of the allelic variant Cyp1B1*3 we investigated the quantitative Cyp1B1 mRNA expression in a population of smokers non-smokers and ex-smokers and determined their genotypes. Detection of the Leu432Val polymorphism in exon 3 of the Cyp1B1 gene was performed by rapid capillary PCR with melting curve analysis. For quantitative comparison of Cyp1B1 mRNA levels real-time PCR was performed using SYBR-green fluorescence in a LightCycler ® System. Calculations of expression were made with the 2 −ΔΔCT method. In comparing relative Cyp1B1 mRNA expression, highly significant differences between the two homozygote genotypes *1/*1 and *3/*3 between the genotypes were also detected within the subgroup smokers, non-smokers and ex-smokers. No significant differences were determined in comparing the relative Cyp1B1 mRNA expression with regards to tobacco smoke exposure. Our results suggest that genotypes carrying the C-allele (*1/*1 and *1/*3) at Cyp1B1 Leu432Val polymorphism have a significantly higher Cyp1B1 mRNA expression compared to the genotype without the C-allele (*3/*3). Gene expression of Cyp1B1 mRNA cannot be used as a biomarker for exposure of tobacco smoke.