Drug-Metabolizing Gene Expression Identity: Comparison Across Liver Tissues and Model Cell Lines

<b>Background:</b> Human cell lines underpin modern biomedical research, offering reproducibility, standardisation, and unrestricted access to biological material. Among the 1206 human lines documented in the Human Protein Atlas, in vitro systems overcome the ethical and technical constraints of primary tissues. The liver is an organ of intricate structure, diverse physiological roles, and limited in vitro viability. Liver-derived cell lines are increasingly used to address the growing burden of liver disease and to accelerate pharmaceutical development, yet their capacity to replicate native hepatic functions remains uncertain. The mutational profiles and expression patterns of hepatocyte-characteristic genes provide critical benchmarks for their suitability for pharmacology and toxicology. <b>Methods:</b> Here, we systematically compare ten widely used hepatic cell lines (HepG2, Huh7, Hep3B, LX-2, HepaRG, HLF, HLE, MHCC97H, SK-Hep1, PLC/PRF/5) with primary hepatocytes and liver tissue, focusing on drug-metabolizing enzyme (DME) gene expression. Beyond literature synthesis, we analysed pre-processed RNA-seq expression data. <b>Results:</b> Overall, among the models examined, the HepaRG cell line shows the greatest similarity to liver and primary hepatocytes, most faithfully reproducing the expression patterns of DME genes. HepG2, Hep3B, and Huh7 form a cluster that retains only a subset of hepatic characteristics. Other models display more pronounced deviations from the reference profile and are generally used for specialized applications. Thus, no universal cell line exists that can fully substitute for the liver. Each model has its own limitations and biases in the expression profile of DME genes, which must be carefully considered when selecting an appropriate system for specific research objectives.