A novel cycloartane triterpenoid from Cimicifuga induces apoptotic and autophagic cell death in human colon cancer HT-29 cells

The extract from Cimicifuga, a genus of flowering plants, has been demonstrated to have mainly therapeutic effects on menstrual and menopausal symptoms and also exhibits immunomodulatory, anti-inflammatory and antimicrobial activity. Moreover, the anticancer effects of Cimicifuga have been reported, but the underlying mechanism causing cancer cell death has been poorly described. The present study was designed to investigate the antitumor effects and underlying molecular mechanisms of cimigenol (KY17), a novel cycloartane triterpenoid from Cimicifuga. KY17-induced autophagy and apoptotic cell death in human colon cancer cells (HT-29) was investigated. KY17 treatment induced growth inhibition and apoptotic cell death in a concentration-dependent manner. The induction of apoptosis was confirmed by a change in cell morphology, and an increase in the G2/M phase, as well as increased protein levels of cleaved-caspase-8 and -3; cleavage of poly(ADP-ribose) polymerase (PARP) in the HT-29 cells following KY17 treatment. In addition, autophagy was evaluated by the accumulation of acridine orange, the appearance of green fluorescent protein-light-chain 3 (LC3) punctate structures and increased levels of LC3-II protein expression. Furthermore, combination treatment with the autophagy inhibitor bafilomycin A1 enhanced the induction of apoptosis by KY17. Taken together, the present study provides new insight into the role of KY17 as a potential antitumor compound. Combination of KY17 with an autophagy inhibitor may be a valuable strategy for the chemoprevention or treatment of colon cancer.