Activation of the AhR target genes by leflunomide.

<p>Hepa1 and HepG2 cells were treated with vehicle (V, 0.1% DMSO), TCDD (T, 1 nM), or leflunomide (L20, 20 µM; L10, 10 µM; L1, 1 µM) for 18 hours. RNA was isolated and semi quantitative RT-PCR was performed for the AhR target genes Cytochrome P450 1A1 (CYP1A1), Cytochrome P450 1A2 (CYP1A2), UDP glucuronosyltransferase 1A1 (UGT1A1), and NAD(P)H dehydrogenase [quinone 1] (NQO1), as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013128#s2" target="_blank">methods</a> section. Expression analysis of GAPDH (Glyceraldehyde-3-phosphate dehydrogenase) was performed as a control. Cycle numbers during which PCR reactions were sampled are indicated. PCR products were visualized on a 2% TAE agarose gel stained with ethidium bromide. Leflunomide activated the selected panel of AhR target genes in WT Hepa1 (A) and HepG2 cells (B).