Therefore, we examined whether lupeol could induce apoptosis in PCNA-1 cells in this study. Results from MTT, Hoechst 33342 staining, Annexin V–FITC/PI staining, and western blot analysis suggested that lupeol inhibited the proliferation and induced the apoptosis of PCNA-1 cells in a dose-dependent manner in the range of 15–60 μM, and induced cell cycle arrest at G0/G1 phase by upregulating p27 and p21 and downregulating cyclin D1.