Apoptosis analysis by flow cytometry using annexin-PI staining

The apoptosis of SK-MES-1 cells was assessed by flow cytometry using annexin V-FITC/PI staining. Briefly, the SK-MES-1 cells were seeded into 6-well plates and incubated overnight. Costunolide at concentrations of 0, 40 and 80 µM was added to the cells and incubated for 24 h. The cells were then collected, washed, and resuspended in PBS. The apoptotic cell death rate was examined by Annexin V-FITC and PI double staining using the Annexin V-FITC apoptosis detection kit (catalog no., KGA105; Nanjing KeyGen Biotech Co., Ltd.), according to the manufacturer's instructions. Following the Annexin V and PI staining, the cells were subjected to flow cytometric analysis and data were analyzed using Cell Quest software.