Quantitative comparison of in vitro genotoxicity between metabolically competent HepaRG cells and HepG2 cells using the high-throughput high-content CometChip assay

In vitro genotoxicity testing that employs metabolically active human cells may be better suited for evaluating human in vivo genotoxicity than current bacterial or non-metabolically active mammalian cell systems. In the current study, 28 compounds, known to have different genotoxicity and carcinogenicity modes of action (MoAs), were evaluated over a wide range of concentrations for the ability to induce DNA damage in human HepG2 and HepaRG cells. DNA damage dose–responses in both cell lines were quantified using a combination of high-throughput high-content (HTHC) CometChip technology and benchmark dose (BMD) quantitative approaches. Assays of metabolic activity indicated that differentiated HepaRG cells had much higher levels of cytochromes P450 activity than did HepG2 cells. DNA damage was observed for four and two out of five indirect-acting genotoxic carcinogens in HepaRG and HepG2 cells, respectively. Four out of seven direct-acting carcinogens were positive in both cell lines, with two of the three negatives being genotoxic mainly through aneugenicity. The four chemicals positive in both cell lines generated HTHC Comet data in HepaRG and HepG2 cells with comparable BMD values. All the non-genotoxic compounds, including six non-genotoxic carcinogens, were negative in HepaRG cells; five genotoxic non-carcinogens also were negative. Our results indicate that the HTHC CometChip assay detects a greater proportion of genotoxic carcinogens requiring metabolic activation (i.e., indirect carcinogens) when conducted with HepaRG cells than with HepG2 cells. In addition, BMD genotoxicity potency estimate is useful for quantitatively evaluating CometChip assay data in a scientifically rigorous manner.