Apoptosis assay
Cell apoptosis was detected by PE Annexin V Apoptosis Detection Kit I (559763, BD Pharmingen). Briefly, cells were washed with 1ml 1× Annexin V binding buffer after regular surface staining, then incubated with PE-conjugated Annexin V and 7-AAD for 15 minutes at room temperature, all the samples were analyzed by BD Accuri C6 flow cytometer (Becton Dickinson, USA).