title: Detection of initiating as well as promoting activity of chemicals by a novel cell transformation assay using v-Ha-ras-transfected BALB/c 3T3 cells (Bhas 42 cells).
abstract: Cell transformation assay using BALB/c 3T3 cells, C3H10T1/2 cells and others, can simulate the two-stage carcinogenesis utilized for formation of transformed foci. A sensitive cell transformation assay for tumor initiators as well as promoters has been developed using a v-Ha-ras-transfected BALB/c 3T3 cell line, Bhas 42; these cells are regarded as initiated in the two-stage paradigm of carcinogenesis. To distinguish between initiation and promotion, the initiation assay involves a 2-day treatment of low-density cells, obtained one day after plating, with a test chemical, and the promotion assay involves treatment of near-confluent cells with a test chemical for a period of 12 days (Day 3-14). When Bhas 42 cells were treated with tumor initiators, N-methyl-N'-nitro-N-nitrosoguanidine and 3-methylcholanthrene, transformed foci were induced in the initiation assay but not in the promotion assay. In contrast, tumor promoters, 12-O-tetradecanoylphorbol-13-acetate, lithocholic acid and okadaic acid, gave negative responses in the initiation assay but positive responses in the promotion assay. The results were reproducible with various treatment protocols. Sixteen polycyclic aromatic hydrocarbons were examined using both assays. Benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene induced focus formation only in the initiation assay. Increase of focus formation was observed in the promotion assay with benzo[e]pyrene, benzo[ghi]perylene, 1-nitropyrene and pyrene. Benz[a]anthracene, benz[b]anthracene, chrysene and perylene showed positive responses in both initiation and promotion assays. Results of initiation and promotion assays of acenaphthylene, anthracene, coronene, 9,10-diphenylanthracene, naphthalene and phenanthrene were negative or equivocal. The present Bhas assays for the detection of either/both initiating and promoting activities of chemicals are sensitive and of high performance compared with other cell transformation assays.
authors.affiliation: Laboratory of Cell Toxicology, Hatano Research Institute, Food and Drug Safety Center, and Department of Hygiene Chemistry, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Asada
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Sasaki
authors.forename: Noriho
authors.initials: N
authors.lastname: Tanaka
authors.forename: Ken
authors.initials: K
authors.lastname: Takeda
authors.forename: Makoto
authors.initials: M
authors.lastname: Hayashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Umeda
mesh_terms: D000818:Animals; D041702:BALB 3T3 Cells / Q000187:drug effects; D015197:Carcinogenicity Tests; D002273:Carcinogens / Q000633:toxicity*; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced*; D003043:Cocarcinogenesis; D011905:Genes, ras / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D011083:Polycyclic Compounds / Q000633:toxicity*; D014162:Transfection
chemical_list: D002273:Carcinogens; D011083:Polycyclic Compounds