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Minimum datasets to establish a CAR-mediated mode of action for rodent liver tumors

Richard C Peffer1, Matthew J LeBaron2, Michael Battalora3

  • 1Syngenta Crop Protection, LLC, P.O. Box 18300, Greensboro, NC, 27419-8300, United States.

Regulatory Toxicology and Pharmacology : RTP
|April 21, 2018
PubMed

Insights

Investigating rodent liver tumors caused by constitutive androstane receptor (CAR) activation requires measuring key events. These CAR-mediated tumor mechanisms are not operative in humans, supporting the use of newer in vitro methods.

Area of Science:

  • Toxicology
  • Molecular Biology
  • Carcinogenesis

Background:

  • Constitutive androstane receptor (CAR) activation is a known pathway for rodent liver tumors.
  • Regulatory agencies globally provide feedback on investigating this mode of action (MoA).
  • Understanding the CAR MoA is crucial for risk assessment of chemical compounds.

Purpose of the Study:

  • To outline methods for investigating the CAR-mediated MoA of rodent liver tumors.
  • To provide a framework for assessing CAR activation and its downstream effects.
  • To discuss species-specific differences and future approaches for CAR MoA assessment.

Main Methods:

  • Measuring key events (CAR activation, gene expression, cell proliferation, altered foci, tumors) and associative events.
  • Utilizing short-term studies in relevant species/strains for crop protection products.
  • Analyzing case studies involving nitrapyrin (mice) and metofluthrin (rats).

Main Results:

  • The CAR activation MoA involves a cascade from receptor activation to tumor formation.
  • Key and associative events can serve as markers for demonstrating the CAR MoA.
  • Species-specific qualitative differences indicate the CAR MoA in rodents is not operative in humans.

Conclusions:

  • Established methods allow for the investigation of CAR-mediated rodent liver tumors.
  • The CAR MoA pathway differs between rodents and humans.
  • Future approaches like biomarker signatures and in vitro assays may reduce the need for animal studies.
Keywords:
CARConstitutive androstane receptorLiverMetofluthrinMinimal datasetMode of actionNitrapyrinRodentTumor

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