Figure 2: The effects of low-power He-Ne laser irradiation on cell viability were determined by MTT assay. (A) BEAS2B, (B) A549, and (C) H1299 cells were seeded with 4,000 cells per well and were irradiated with 4.0 mW He-Ne laser radiations for various time courses and incubated for 1-3 days. All data are shown as the mean ± SD of the results from three independent experiments. *P<0.05 compared with the untreated control group.