Apr 20th, 1:00 PM - 4:00 PM
Effects of TCDD on Proliferation of the UMR-106 Osteoblast Cell Line
Dr. Kristen Mitchell
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental toxicant that is produced as a byproduct of chemical manufacturing processes and the incineration of medical and municipal waste. TCDD exerts toxicity by binding to the aryl hydrocarbon receptor (AhR), which is a soluble, ligand activated transcription factor. Recent studies indicate that AhR activation modulates cell cycle progression in numerous cell types, including primary osteoblast cultures. The exact mechanism is unknown, but it is proposed that AhR activation alters gene transcription that leads to increased expression of p27Kip1, a protein that suppresses proliferation by inhibiting progression to S-phase of the cell cycle. We tested the hypothesis that exposure to TCDD suppresses proliferation of the rat osteosarcoma cell line, UMR-106, through upregulation of p27Kip1 protein. UMR-106 cells were plated and serumstarved for 24 hr to synchronize cells in G0/G1 phase of the cell cycle. Cells were then serum-released in the presence of 6 nM TCDD or DMSO control. Cells were collected after 24, 48, and 72 hours. Protein expression was analyzed by western blot, and cell viability was evaluated by alamar blue staining. Results indicate that neither proliferation nor p27Kip1 protein expression was altered by exposure to TCDD. This study suggests that the proliferation of this immortalized osteoblast cell line is not affected by TCDD. Moreover, the use of UMR-106 cells does not appear to be a suitable model system for studying mechanisms of AhR-mediated cell cycle control.