Construction and characterization of hepatocyte nuclear factor HNF4alpha1 over-expressing cell line derived from human hepatoma HepG2 cells.

Cancer cell lines derived from hepatocytes have an altered phenotype and they lack hepatocyte-specific functions. It is at least partly due to the under-expression of transcription factors such as hepatocyte nuclear factor 4α (HNF4α), steroid receptor co-activator 1 (SRC1) etc. Recently, a strategy of transient transfection of human hepatic cells with HNF4α revealed improved hepatospecific functions, including the expression of drug-metabolizing enzymes. In the current study we established a human cell line derived from HepG2 cells stably transfected with human HNF4α, and we examined this line for hepatospecific markers. Of the 9 clones analyzed, we found an increased secretion of fibrinogen (9 clones), albumin (5 clones) and plasminogen (3 clones), while secretion of alpha1-antitrypsin was not changed. The expression of pregnane X receptor (PXR) and aryl hydrocarbon receptor (AhR) proteins but not mRNAs was slightly increased. TCDD-dependent induction of CYP1A1 mRNA and protein was augmented in 50% of clones, but there was no correlation between the CYP1A1 inducibility and expression levels of AhR and HNF4α. Induction of CYP3A4 mRNA by rifampicin was about 1.5-2.5 fold (clones 2, 4, 6, 7) and it was not significantly different from CYP3A4 mRNA induction in parent HepG2. The basal expression of CYP3A4 protein was increased in all clones, but rifampicin-induced expression of CYP3A4 protein was in all clones lower than in parent HepG2. Overall, the stable over-expression of HNF4α in HepG2 cells restores some of the hepatospecific functions, but it has a minor effect on the expression of xenobiotic-metabolizing enzymes and their regulators.