Cell Counting Kit (CCK)-8 proliferation assay

NPCs (normal and transformed) were seeded in 96-well plates at a density of 1×10⁴ cells. One plate was tested daily. A total of 10 µl/well CCK-8 (Dojindo Laboratories, Inc.) was added and absorbance was detected directly by a microplate reader (Bio-Tek, Synergy H1, Inc.) at a wavelength of 450 nm following 1 h incubation. The mean value was calculated from five replicates and a growth curve was constructed. The experiment was repeated three times. The optical density, determined by relative absorbance of CCK-8, was evaluated by probit regression analysis in SPSS 13.0 (SPSS).