Human Hep G2 cells as a model to examine induction of quinone reductase

The use of cultured human hepatoma Hep G2 cells as a model to identify inducers of the phase II enzyme quinone reductase is examined. Cells were transiently transfected with a plasmid (pWNQO₁tkCAT4.61kb) containing functional sequences in the 5'-flanking region of the human quinone reductase (NQO₁) gene. In this plasmid, the nucleotides -587 to -379, containing a functional ARE, are linked to a CAT reporter. Benzylisothiocyanate, a known inducer of quinone reductase in animal models and in hepa1c1c7 cells, increased expression of the reporter gene after transient transfection into Hep G2 cells by up to 5.5-fold (at 1 μM benzylisothiocyanate). In untransfected cells, this concentration of benzylisothiocyanate gave a small and not significant induction of quinone reductase activity (1.3-fold). The specific activity of quinone reductase in uninduced Hep G2 cells is 10-fold higher than found in the uninduced mouse hepatoma Hepa1c1c7 cell line. These preliminary results suggest that transfection of pWNQO₁tkCAT4.61kb into Hep G2 cells may be a suitable method to determine which compounds have the potential to induce QR transcription in humans.