Gene-level expression analysis of selected liver-specific categories in human hepatocyte donors and hepatoma-derived cell lines using microarray profiling. Distribution of fold change from the liver in 10 hepatocyte donors is shown for genes encoding select transcription factors (A) and drug-metabolizing enzymes (C). For comparison, the fold change for the same genes in HepG2 and Huh7 hepatoma cells are presented in panels B and D. Differential expression is defined as greater than 4-fold change from the human liver (dotted lines). * indicates the measured probe set is detected as absent in at least one human hepatocyte donor (PPARA: absent in two donors; TCF1: absent two donors; CYP1A2: absent in one donor). ** indicates the probe set is detected as absent in Huh7 cells (NR1I2, NR1I3, CYP1A2, CYP2B6, CYP2C9, CYP2D6, CYP3A4). *** indicates the probe set is detected as absent in HepG2 (CYP1A2, CYP286, CYP2C9, CYP2D6, CYP2E1). Reproduced from Toxicology and Applied Pharmacology (88) 2007, with permission from Elsevier.