title: Suitable top concentration for tests with mammalian cells: mouse lymphoma assay workgroup.
abstract: The Mouse Lymphoma Expert Workgroup of the International Workshop for Genotoxicity Tests (IWGT) met in Basel, Switzerland in August of 2009. The Workgroup (WG) was tasked with discussing the appropriate top concentration for non-pharmaceuticals that would be required for the conduct of the mouse lymphoma assay (MLA) when sufficient cytotoxicity [to between 10 and 20% relative total growth (RTG)] has not been attained. The WG approached this task by (1) enumerating the various regulatory decisions/use for MLA data, (2) discussing the appropriate assays to which MLA data and assay performance should be compared and (3) discussing all the proposals put forth concerning the top concentration for non-pharmaceuticals. In addition, one of the members presented a summary of a re-evaluation of the National Toxicology Program MLA data using the IWGT harmonized guidance that was underway as a separate (non IWGT) activity, being conducted by two members of the Expert WG. The WG was asked to vote on each of the various proposals for top concentration for when cytotoxicity is not concentration limiting. While there was general agreement that the top concentration for non-pharmaceuticals should be re-evaluated and likely lowered from the current recommended levels, there was no agreement on a specific new recommendation.
authors.affiliation: Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U. S. Food and Drug Administration, HFT-120, 3900 NCTR Rd., Jefferson, AR, USA. Martha.Moore@fda.hhs.gov
authors.forename: Martha M
authors.initials: MM
authors.lastname: Moore
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Honma
authors.forename: Julie
authors.initials: J
authors.lastname: Clements
authors.forename: Takumi
authors.initials: T
authors.lastname: Awogi
authors.forename: George R
authors.initials: GR
authors.lastname: Douglas
authors.forename: Freddy
authors.initials: F
authors.lastname: van Goethem
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Gollapudi
authors.forename: Aoi
authors.initials: A
authors.lastname: Kimura
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Muster
authors.forename: Mike
authors.initials: M
authors.lastname: O'Donovan
authors.forename: Rita
authors.initials: R
authors.lastname: Schoeny
authors.forename: Shinobu
authors.initials: S
authors.lastname: Wakuri
mesh_terms: D000818:Animals; D008223:Lymphoma; D051379:Mice; D009152:Mutagenicity Tests / Q000592:standards*; D017009:Professional Autonomy