PCSK9 siRNA significantly increased apoptosis of A549 cells. (A) After 48 h transfection, cells were incubated with Hoechst 33258 staining buffer. Healthy cells showed round and intact nuclei, whereas apoptotic cells exhibited nuclear karyopyknosis or fragmentation as indicated by arrows (magnification, ×200). (B) Quantification of apoptotic cells by counting the number of apoptotic cells three times. At least six fields and six samples were examined for each group. The cells transfected with PCSK9 siRNA exhibited higher ratio of apoptotic cells as compared to the control siRNA group. Values are expressed as the mean ± standard deviation (n=3). *P<0.05 vs. control siRNA group. PCSK9, proprotein convertase subtilisin/kexin type 9; siRNA, small interfering RNA.