title: Different sensitivity of BALB/c 3T3 cell clones in the response to carcinogens.
abstract: Cell transformation assays (CTAs) are currently regarded as the only possible in vitro alternative to animal testing for carcinogenesis studies. CTAs have been proposed as screening tests for the carcinogenic potential of compounds that have no evidence of genotoxicity but present structural alerts for carcinogenicity. We have extensively used the BALB/c 3T3 model based on the A31 cell clone to test single chemicals, complex mixtures and environmental pollutants. In the prevalidation study carried out by ECVAM, the improved protocol is based on BALB/c 3T3 A31-1-1 cells, a clone derived by A31 cells, that is very sensitive to PAH-induced transformation. The present study was performed in the aim to compare the results obtained with the two different clones exposed to different classes of carcinogens. Cells were treated with PAHs (3-methylcholanthrene, benzo(a)pyrene), alkylating agents (melphalan) and aloethanes (1,2-dibromoethane). The induction of cytotoxicity and the onset of chemically transformed foci were evaluated by two experimental protocols, differing for cell seeding density and chemical treatment duration. The A31-1-1 cells showed higher inherent transformation rate after PAHs treatment, but they were insensitive to 1,2-dibromoethane at concentrations that usually induced transformation in A31 cells. As 1,2-dibromoethane is bioactivated to reactive forms able to bind DNA mainly through the conjugation with intracellular glutathione, these results suggested a reduced activity of phase-2 enzymes involved in glutathione conjugation in A31-1-1 cells. Our results give evidence that inherent metabolic capacity of cells may play a critical role in in vitro cell transformation, cautioning against possible misclassification of chemicals.
authors.affiliation: Center for Environmental Carcinogenesis and Risk Assessment, Environmental Protection and Health Prevention Agency - Emilia-Romagna Region (ER-EPA), Viale Filopanti 22, 40126 Bologna, Italy.
authors.forename: Annamaria
authors.initials: A
authors.lastname: Colacci
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Mascolo
authors.forename: Stefania
authors.initials: S
authors.lastname: Perdichizzi
authors.forename: Daniele
authors.initials: D
authors.lastname: Quercioli
authors.forename: Antonio
authors.initials: A
authors.lastname: Gazzilli
authors.forename: Francesca
authors.initials: F
authors.lastname: Rotondo
authors.forename: Elena
authors.initials: E
authors.lastname: Morandi
authors.forename: Angela
authors.initials: A
authors.lastname: Guerrini
authors.forename: Paola
authors.initials: P
authors.lastname: Silingardi
authors.forename: Sandro
authors.initials: S
authors.lastname: Grilli
authors.forename: Monica
authors.initials: M
authors.lastname: Vaccari
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000633:toxicity; D041702:BALB 3T3 Cells; D015197:Carcinogenicity Tests / Q000379:methods*; D002273:Carcinogens / Q000633:toxicity*; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D002999:Clone Cells; D015946:Ethylene Dibromide / Q000633:toxicity; D008558:Melphalan / Q000633:toxicity; D051379:Mice; D011084:Polycyclic Aromatic Hydrocarbons / Q000633:toxicity
chemical_list: D018906:Antineoplastic Agents, Alkylating; D002273:Carcinogens; D011084:Polycyclic Aromatic Hydrocarbons; D015946:Ethylene Dibromide; D008558:Melphalan