Gene expression and epigenetic alterations in human hepatocytes treated with low doses of chemical carcinogens

The increasing number of man-made chemicals in the environment that may pose a carcinogenic risk emphasizes the need for the development of reliable time- and cost-effective approaches for carcinogen detection. To address this issue, we have investigated the utility of human hepatocytes for the in vitro identification of genotoxic and non-genotoxic carcinogens. Induced pluripotent stem cell (iPSC)-derived human hepatocytes were treated with the genotoxic carcinogens aflatoxin B1 (AFB1) and benzo[a]pyrene (B[a]P) and with the non-genotoxic liver carcinogen methapyrilene at non-cytotoxic concentrations for 7 days, and transcriptomic profile was examined. 1569 (892 protein-coding and 677 non-coding), 1693 (922 protein-coding and 771 non-coding), and 2061 (1462 protein-coding and 599 non-coding) differentially expressed genes were detected in cells treated with AFB1, B[a]P, and methapyrilene, respectively. Additionally, we examined the toxicogenomics response to AFB1, B[a]P, and methapyrilene exposure in human HepaRG cells and demonstrated that carcinogens had a less prominent effect on the cellular transcriptome as compared to that in human iPSC-derived hepatocytes. Overall, the results demonstrate that the prime non-genotoxic effect of exposure to carcinogens, regardless of their mode of action, in short-term in vitro testing is a profound global transcriptome response, indicating a greater value of toxicogenomics for rapid carcinogen screening in vitro. iPSC-derived human hepatocytes (on the 4th day after seeding) were treated with 0.2 µM AFB1 or AFB2, 1 µM B[a]P or B[e]P, or 20 µM methapyrilene for 7 consecutive days.