HepaRG cells, a newly developed human
hepatoma cell line, differentiate into hepatocyte-like morphology by treatment with
dimethyl sulfoxide (
DMSO). The expression of
cytochrome P450 (
P450) enzymes, transporter
proteins, and
transcription factors was stable in differentiated HepaRG cells over a period of 6 weeks when cultured with
DMSO. Compared with human hepatocytes, expression of P450 in HepaRG cells was in general lower with the exception for a considerably higher expression of
CYP3A4 and CYP7A1. The expression of P450s generally decreased when
DMSO was removed from the medium, whereas transporters and liver-specific factors were unaffected. The relative
mRNA content of drug-metabolizing P450s displayed the highest resemblance between human hepatocytes and differentiated HepaRG cells 1 day after removal of
DMSO from the medium. The metabolism of
midazolam,
naloxone, and
clozapine in HepaRG cells was similar to human hepatocytes, indicating the function of
CYP3A4,
CYP1A2, and
UDP-glucuronosyltransferase enzymes. However, the metabolism of
7-ethoxycoumarin and
dextromethorphan was low, confirming low levels of
CYP2E1 and
CYP2D6 in HepaRG cells. The P450 probe substrates indicate a decrease in
CYP1A2,
CYP2B6,
CYP2C9, and
CYP3A4 activities in HepaRG cells 1 day after removal of
DMSO from the medium. The activities were then relatively stable in
DMSO-free medium for up to 14 days. Based on the stable expression of liver-specific functions over a long period in culture, the relative
mRNA content of drug-metabolizing P450s, and metabolic properties, HepaRG cells provide a valuable in vitro model for human drug metabolism studies.