Received for publication June 25, 2007.
Revised March 14, 2008.
Accepted for publication March 14, 2008.

COMPARISON OF TWO IMMORTALIZED HUMAN CELL LINES TO STUDY NUCLEAR RECEPTOR MEDIATED CYP3A4 INDUCTION

Abstract

Since cytochrome P450 3A4 (CYP3A4) is responsible for the biotransformation of over 50% of all clinically used drugs, induction results in an increased clearance of many concomitantly administered drugs, thereby decreasing treatment efficacy or, in the case of pro-drugs, lead to severe intoxications. CYP3A4 induction is regulated by the pregnane X receptor, constitutive androstane receptor, and vitamin D receptor. Since these nuclear receptors show large interspecies differences, accurate prediction of nuclear receptor mediated CYP3A4 induction in humans requires the use of human systems. As primary cultures of human hepatocytes or enterocytes have major drawbacks like poor availability and poor reproducibility, human cell lines are a good alternative. In this study, the widely used HepG2 cell line was compared the LS180 cell line to serve as a model to study CYP3A4 induction. There was a clear difference between the cell lines with respect to CYP3A enzyme expression and induction. In LS180 CYP3A4 was expressed and was found to be induced by prototypical nuclear receptor agonists, while in HepG2 CYP3A4 was non-responsive to treatment with rifampicin, CITCO or calcitriol. We subsequently evaluated if these host-cell differences also have an effect on CYP3A4 reporter gene activity. We clearly show that there are differences in CYP3A4 reporter activity between the cell lines, and based on these results and those found on mRNA and protein level, we conclude that LS180 is a more suitable cell line to study CYP3A4 induction than the widely used HepG2.

Key words: anticancer agents, bioavailability, CAR, CYP3A, cytochrome P450 regulation, drug-drug interactions, first-pass metabolism, induction, nuclear receptors, PXR

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