Dihydrotanshinone induced apoptosis in colon cancer cells by p53‐independent but ROS dependent pathway mediated by mitochondria

Abstract

ObjectiveAnti‐cancer action of dihydrotanshinone (DHTS) in colon cancer was evaluated and its underlying mechanisms were studied.MethodsCytotoxity of DHTS was measured in colon normal and cancer cells by MTT assay. Apoptotic activity of DHTS was evaluated by FCM. Intracellular Ca2+, ROS generation and MMP were detected by FCM or laser confocal microscopy assay.ResultsDHTS produced a selective cytotoxity against colon cancer cells through induction of apoptosis. The IC50 values for cell viability and apoptosis rates induced by DHTS were similar between HCT116 p53+/+ and HCT116 p53−/−cells. In a separate experiment, pretreatment with N‐Acety‐L‐Cysteine (NAC) or catalase‐PEG, both known to be free radical scavengers, significantly decreased apoptosis induced by DHTS. We also found that DHTS produced a time‐ and dose‐dependent increase in intracellular Ca2+ and ROS generation, which were blocked by pretreatment with BAPTA‐AM (a Ca2+ chelator), catalase‐PEG (a hydrogen peroxide inhibitor) or cotreatment with antimycin A or rotenone. Decrease of MMP was significantly blocked by rotenone or antimycin A while that of mitochondrial ROS was found to be postponed only by antimycin A.ConclusionApoptosis induced by DHTS is p53 independent but ROS dependent. This was initiated from mitochondria dysfunction and promoted by increase of intracellular Ca2+.