Cell proliferation assay

Cell proliferation was detected with MTT assay. In brief, cells were treated differently as indicated above. After been treated for 24 h, 48 h and 72 h, the cells were incubated with 10 µl MTT (Promega, USA) at 37 °C for 4 h protected from light, followed by 150 µl DMSO incubation at 37 °C for 10 min. Finally, the fluorescence intensity of each well was measured using a microplate reader (Bio-Rad, USA) at spectrometric absorbance of 490 nm.