MTT assay

An MTT assay was used to determine the viability of NSCLC cells. Briefly, BEAS-2B and H460 cells, A549 and SK-MES-1 cells were transfected with PTEN-shRNA or negative control shRNA for 48, 72 or 96 h. Cells were subsequently incubated at 37°C with 20 µl of MTT (5 mg/ml) for 4 h and the purple crystals were dissolved in dimethylsulfoxide for 15 min. A total of 150 µl/well was transferred into 96-well plates and the absorbance was measured using a microplate reader at 490 nm (iMark Microplate Reader; Bio-Rad Laboratories, Inc., Hercules, CA, USA). The inhibition rate was calculated using Microsoft Excel software 2016 (Microsoft Corporation, Redmond, WA, USA).