Cell Lines: A Tool for In Vitro Drug Metabolism Studies

Abstract

Primary cultured hepatocytes are a valuable in vitro model for drug metabolism studies. However, their widespread use is greatly hindered by the scarcity of suitable human liver samples. Moreover, the well-known in vitro phenotypic instability of hepatocytes, the irregular availability of fresh human liver for cell harvesting purposes, and the high batch-to-batch functional variability of hepatocyte preparations obtained from different human liver donors, seriously complicate their use in routine testing. To overcome these limitations, different cell line models have been proposed for drug metabolism screening. Human liver-derived cell lines would be ideal models for this purpose given their availability, unlimited life-span, stable phenotype, and the fact that they are easy to handle. However, the human hepatoma cells currently used (i.e. HepG2, Mz-Hep-1) show negligible levels of drug-metabolizing and do not constitute a real alternative to primary hepatocytes. Different strategies have been proposed to generate metabolically competent immortalized hepatocytes (transformation of human hepatocytes with plasmids encoding immortalizing genes, hepatocyte-like cells derived from stem cells, cell lines generated from transgenic animals, hepatocyte/hepatoma hydrid cells). Moreover, recombinant models heterologously expressing P450 enzymes in different host cells have been developed and successfully used in drug metabolism testing. In addition, new strategies have recently been explored to upregulate the expression of drug-metabolizing enzymes in cell lines of a human origin (i.e. transfection with expression vectors encoding key hepatic transcription factors). Among metabolic-based drug-drug interactions, P450 inhibition seems to be the most important. A major application of recombinant models expressing a single P450 is the screening of potential enzyme inhibitors. Therefore, pharmaceutical companies increasingly make use of cell lines to speed up the selection of new drugs with favourable pharmacokinetic and metabolic properties.

Present state and future perspectives of using pluripotent stem cells in toxicology research

“…As an alternative to primary hepatocytes, human hepatocellular carcinoma cell lines that exhibit partial liver cell characteristics have been frequently used for the investigation of certain aspects of liver metabolism and toxicity (reviewed in Donato et al 2008), but their use is limited due to low expression of crucial hepatocyte-specific genes and no or only low enzyme activities of the CYP450 family members that are critical for phase I metabolism.…”

In Vitro Analysis of the Interaction between Atovaquone and Proguanil against Liver Stage Malaria Parasites

“…In hepatocytes, proguanil is partially metabolized by host cytochrome P450 enzymes into cycloguanil (6), which potently inhibits the development of liver stage Plasmodium infection (7). To address this confounding factor, we used HepG2-CD81 human hepatoma cells that retain many liver-specific properties and can be infected by some Plasmodium species (8) while displaying impaired cytochrome P450 activity (9).…”

Evidence-based absorption, distribution, metabolism, excretion (ADME) and its interplay with alternative toxicity methods

“…A broad variety of cellular and subcellular models of metabolism of xenobiotics are available (Costa et al, 2014;Donato et al, 2008;Gómez-Lechón et al 2003;Gordon et al, 2015;Vermeir et al, 2005;Williams, 2014). Many focus on liver metabolism because of the extensive metabolic capacity of that organ, its central role in blood circulation, and as an important elimination/ detoxification organ.…”