Performance of high-throughput CometChip assay using primary human hepatocytes: a comparison of DNA damage responses with in vitro human hepatoma cell lines

Primary human hepatocytes (PHHs) are considered the "gold standard" for evaluating hepatic metabolism and toxicity of xenobiotics. In the present study, we evaluated the genotoxic potential of four indirect-acting (requiring metabolic activation) and six direct-acting genotoxic carcinogens, one aneugen, and five non-carcinogens that are negative or equivocal for genotoxicity in vivo in cryopreserved PHHs derived from three individual donors. DNA damage was determined over a wide range of concentrations using the CometChip technology and the resulting dose-responses were quantified using benchmark dose (BMD) modeling. Following a 24-h treatment, nine out of ten genotoxic carcinogens produced positive responses in PHHs, while negative responses were found for hydroquinone, aneugen colchicine and five non-carcinogens. Overall, PHHs demonstrated a higher sensitivity (90%) for detecting DNA damage from genotoxic carcinogens than the sensitivities previously reported for HepG2 (60%) and HepaRG (70%) cells. Quantitative analysis revealed that most of the compounds produced comparable BMD10 values among the three types of hepatocytes, while PHHs and HepaRG cells produced similar BMD1SD values. Evidence of sex- and ethnicity-related interindividual variation in DNA damage responses was also observed in the PHHs. A literature search for in vivo Comet assay data conducted in rodent liver tissues demonstrated consistent positive/negative calls for the compounds tested between in vitro PHHs and in vivo animal models. These results demonstrate that CometChip technology can be applied using PHHs for human risk assessment and that PHHs had higher sensitivity than HepaRG cells for detecting genotoxic carcinogens in the CometChip assay.