Transcriptional activation of the proto-oncogene c-jun by asbestos and H2O2 is directly related to increased proliferation and transformation of tracheal epithelial cells.
Timblin-CR; Janssen-YW; Mossman-BT
Cancer Res 1995 Jul; 55(13):2723-2726
The mechanisms and role of c-jun activation in the aberrant proliferation of cells were studied. Hamster tracheal epithelial (HTE) cells were transfected with the reporter plasmid jun- luciferase and the empty expression vector Rous sarcoma virus (RSV- O). The treated cells were harvested 16 or 40 hours (hr) after exposure to crocidolite (12001284) asbestos, hydrogen-peroxide (7722841) (H2O2), or the tumor promoter 12-O-tetradecanoylphorbol-13- acetate (TPA). Significantly increased luciferase activity was detected after 16 and 40hr exposure to 2.5 or 5.0 micrograms/cubic centimeter asbestos, 10 micromolar H2O2, or 100 nanograms/milliliter TPA. Confluent cultures of RSV-jun or RSV-O transfected cells were incubated in the presence of 5-bromo-2'-deoxyuridine (BrdUrd) for 8hr. A significant increase was observed in the percent of RSV-jun cells incorporating BrdUrd compared to RSV-O cells. Subsequent 16hr incubation with asbestos decreased the percentage of BrdUrd positive transfected cells relative to untreated RSV-O control cells. The percentages of BrdUrd positive RSV-jun transfectants, whether untreated, asbestos or H2O2 exposed, were significantly higher than the corresponding RSV-O transfectants. The effect of overexpression of c-jun on cell growth rates was studied by determining cell numbers of RSV-O and RSV-jun 24hr, 48hr, and 72hr after low density plating. A significant increase in the number of RSV-jun over RSV-O cells was seen only at 48hr. When this same experiment was run concurrently with asbestos exposure, a significant increase was seen in the number of RSV-jun over RSV-O cells only after 72hr. Transfected RSV-O and RSV-jun cells were plated on soft agar and incubated for 21 days. Significantly more RSV-jun colonies were observed than RSV-O transfected cell colonies. The authors conclude that asbestos and H2O2 activate AP-1-dependent gene transcription and that overexpression of c-jun in HTE cells leads to increased proliferation and cellular transformation.
NIOSH-Publication; NIOSH-Grant; Cancer; Respiratory-system-disorders; In-vitro-studies; Cell-division; Cell-transformation; Mammalian-cells; Cell-cultures; Acute-exposure; Cell-growth
Pathology University of Vermont Medical Alumni Bldg Burlington, VT 05405
University of Vermont & St Agric College, Burlington, Vermont