Investigating the Potential Carcinogenic Effects of Chronic Tungsten (VI) Oxide Exposure to Immortalize Human Lung Cells

Rationale: Tungsten oxide (WO3) is an occupational exposure hazard. The primary route of WO3 exposure is inhalation and WO3 is known as a pulmonary irritant. This work investigated exposure of WO3 to immortalized human bronchial epithelial cells (Beas-2B) to investigate cytotoxicity and carcinogenic potential. Experimental procedures: Insoluble WO3 particles were sonicated to reduce aggregation and create suspensions of WO3 particles small enough for Beas-2B cells to engulf (<10 microns in diameter). Beas-2B cells were chronically exposed to varying doses (0.25, 0.5, 1.0, 5.0, 10 and 15 μg/cm2) of WO3 for 6 weeks. Proliferation rate was measured; soft agar cell migration testing and scratch test assays were performed. Results: After 2 weeks, Beas-2B cells with the highest doses of WO3 started to proliferate just as quickly as the cells that had low doses of WO3. After 6 weeks of WO3 exposure, in the control transformation there was an average of 8 colonies per soft agar well. In the lower doses (0.25-1.0 μg/cm2) there was an average of 25 colonies per well. In the higher doses (5.0- 15.0 μg/cm2) colonies ranged from 30 to 75 per well. Scratch testing revealed that WO3 treated cells migrated significantly more quickly than control transformed cells. Conclusions: Chronic treatment of Beas-2B cells with WO3 induced transformation in the cells. Inhaled WO3 may not only be a lung irritant, but also a potential pulmonary carcinogen at high doses.