In Vitro Mammalian Cell Gene Mutation Test (HPRT Gene)

The in vitro mammalian cell gene mutation test is used to detect mutations of the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene in Chinese hamster ovary (CHO) or lung (V79) fibroblasts.

Screening and Regulatory Support

  • Cultures are incubated with several concentrations of the test compound for three to four hours in the presence and absence of metabolic activation (S9).
  • Cells are subcultured for seven to eight days after treatment to allow expression of the mutant phenotype, and then plated in media with and without 6-thioguanine (TG) to select for mutants and determine cloning efficiency.
  • A positive outcome is characterized by a statistically significant, dose-dependent increase in mutant frequency that exceeds historical negative control limits.

When To Perform

  • Screening
    • Reduced volume and/or abbreviated formats available
  • REACH requirement
    • As part of Annex VIII testing
  • Mutagenicity
    • To confirm presumed mutagenic activity arising from limited/small genetic damage (e.g., positive Ames or large colony MLA)
    • To assess mutagenicity when the Ames assay may not be appropriate (e.g., antibiotics, nanomaterials)