Upgrading HepG2 cells with adenoviral vectors that encode drug-metabolizing enzymes: application for drug hepatotoxicity testing

ABSTRACT

Introduction: Drug attrition rates due to hepatotoxicity are an important safety issue considered in drug development. The HepG2 hepatoma cell line is currently being used for drug-induced hepatotoxicity evaluations, but its expression of drug-metabolizing enzymes is poor compared with hepatocytes. Different approaches have been proposed to upgrade HepG2 cells for more reliable drug-induced liver injury predictions.

Areas covered: We describe the advantages and limitations of HepG2 cells transduced with adenoviral vectors that encode drug-metabolizing enzymes for safety risk assessments of bioactivable compounds. Adenoviral transduction facilitates efficient and controlled delivery of multiple drug-metabolizing activities to HepG2 cells at comparable levels to primary human hepatocytes by generating an ‘artificial hepatocyte’. Furthermore, adenoviral transduction enables the design of tailored cells expressing particular metabolic capacities.

Expert opinion: Upgraded HepG2 cells that recreate known inter-individual variations in hepatic CYP and conjugating activities due to both genetic (e.g., polymorphisms) or environmental (e.g., induction, inhibition) factors seems a suitable model to identify bioactivable drug and conduct hepatotoxicity risk assessments. This strategy should enable the generation of customized cells by reproducing human pheno- and genotypic CYP variability to represent a valuable human hepatic cell model to develop new safer drugs and to improve existing predictive toxicity assays.

KEYWORDS:

• CYP-engineered cell line
• HepG2 cells
• adenoviral vectors
• CYP
• drug metabolism
• hepatotoxicity

Article highlights

• Metabolic bioactivation of drugs is of major concern and is considered an initiation mechanism for idiosyncratic DILI. Reducing the bioactivation risk early in drug discovery may help diminish compound attrition and provide safer drug therapies.

• Hepatoma cell lines, although metabolically poor compared to hepatocytes, offer key advantages, such as unlimited life span, reproducibility, high availability and easy handling, which make them useful in vitro systems for screening purposes.

• Recombinant adenoviruses that encode drug-metabolising enzymes (CYPs and conjugating enzymes) allow the rapid, high-efficient and controlled infection of hepatic cell lines without cytotoxic effects.

• HepG2 cells engineered for the individual expression of CYPs allow the screening of metabolism-related hepatotoxicity and to identify the role of specific enzymes in drug metabolism and toxicity, which help safety risk assessments of bioactivable compounds and lead to prioritisation.

• The generation of tailored HepG2 cells that co-express particular drug-metabolising enzyme patterns and reproduce pheno and genotypic variability in humans is a valuable hepatic cell model for developing new safer drugs to improve existing predictive toxicity assays.

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Declaration of interest

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Additional information

Funding

The authors acknowledge the support from the ALIVE Foundation, the Instituto de Salud Carlos III (Spanish Ministry of Economy and Competitiveness) and FEDER (EU) funds (grant number PI13/00986).