Serum induces a transcriptional activation of CYP1A1 gene in HepG2 independently of the AhR pathway

CYP1A1 is largely implicated in carcinogenesis. To date, it is known that t his gene is induced by xenobiotics such as polycyclic aromatic hydrocarbons . In this study, we evaluated the effect of serum in the regulation of CYP1 A1 gene expression. CYP1A1 mRNA level is induced 1) in HepG2 and HT29-D4 ce lls by 3-methylcholanthrene 2) only in HepG2 after treatment by serum. The CYP1A1 mRNA induction in HepG2 is the consequence at least in part of a tra nscriptional activation as was demonstrated by evaluation of the hnRNA leve l. HepG2 cells were transfected by a plasmid containing the 7.5 Kb of the C YP1A1 promoter and the CAT reporter gene. No CAT stimulation was observed a fter serum treatment. These results demonstrated that CYP1A1 is induced at a transcriptional level by a physiological compound contained in serum inde pendently of the Ah receptor and the 7.5 Kb promoter region. (C) 2001 Elsev ier Science Inc. All rights reserved.