In contrast, many other cell lines used in toxicology, and in particular non-hepatic cells, have not been extensively characterized for their metabolic competency. The deficiencies in the metabolic

capabilities of cell lines could lead to inaccurate evaluation of test compounds ( Kirkland et al., 2007). This is the case for benzo[a]pyrene (B[a]P), a well-known tobacco smoke chemical that is ultimately metabolized to a diol-epoxide carcinogen by the inducible lung CYPs, CYP1A1/1B1. The formation of B[a]P DNA adducts has been reported in vitro using lung carcinoma-derived A549 cells ( Feldman et al., 1978) but the role of CYP1A1/1B1 in the formation of such adducts ABT-199 cell line in A549 was not demonstrated at the time. In 2000, Hukkanen and colleagues reported the expression and inducibility of CYP1A1/1B1 in the A549 cell line but activity was not verified. In 2008, Quinn established that CYP1A1 was not required in A549 for the oxidation of B[a]P to its reactive form and that this reaction could be catalyzed by AKR1B10 ( Quinn et al.,

2008). However CYP1A1 activity was reported the same year by EROD assay after A549 induction ( Billet et al., 2008). In contrast, in a comparison between CYP1A1/1B1 activity in A549 and HBECS Newland et al. showed that the CYP1A1 activity in A549 was limited when compared to a culture of human primary lung epithelial cells when incubated with a luminogenic probe substrate. Thus the mechanism of adduct formation in A549 can potentially follow multiple metabolic routes Selleck ABT 888 different than what would be expected in a normal lung epithelium. CYP2B6 activity has also been reported in A549 together Dehydratase with mRNA expression of CYP2D6, 2E1, 3A5, and CYP3A7, the latest is not expected to be present in normal adult tissue. Other key lung epithelium CYPs such as CYP2A6, CYP2A13, and

CYP2F1 involved in the bioactivation of toxicants such as nitrosamines were not detected in this cell line. This example highlights the importance of characterizing the metabolic enzyme profile in cell lines used for toxicological evaluation, with the possibility to restrict such study to enzymes relevant to the metabolic pathway of specific toxicants. However, to date, there is no standard approach to metabolic characterization. Where some researchers focus on gene expression only ( Jennen et al., 2010) others may combine gene expression with enzyme activity ( Westerink and Schoonen, 2007). The aim of our investigation was to describe an experimental strategy combining quantitative real time PCR (qPCR) and functional enzymatic assays applied to the lung-derived BEAS-2B cell line. Initially, we profiled the gene expression of a panel of oxidative and conjugative metabolism-related genes involved in xenobiotics metabolism, more specifically related to the toxicity of cigarette smoke to human lung (Hecht, 2006).