title: Dihydrotanshinone induces p53-independent but ROS-dependent apoptosis in colon cancer cells.
abstract: OBJECTIVE
  The therapeutic potential of various tanshinones was examined and compared for their anti-cancer activities on colon cancer cells. The role of ROS generation in the pro-apoptotic activity of dihydrotanshinone (DHTS) was further studied.
  
  
  METHODS
  Cell viability was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis and poly-ADP-ribose-polymerase (PARP) cleavage were respectively measured by flow cytometer and Western blot. Changes of mitochondrial membrane potential (MMP), mitochondrial ROS (mitoROS) and total ROS were determined by confocal system under an inverted microscope.
  
  
  RESULTS
  Among the different tanshinones examined, DHTS produced the most potent anti-cancer effect. DHTS induced a selective cytotoxicity and apoptosis in both HCT116 p53(-/-) and HCT116 p53(+/+) colon cancer cells. A time- and concentration-dependent PARP cleavage further confirmed the apoptotic activity. In this regard, it was found DHTS provoked mitochondrial dysfunction in the early stage by decreasing MMP and mitoROS levels. This was followed by a time-dependent increase in intracellular ROS generation. Pretreatment with N-acetyl-l-cysteine (NAC) or catalase-PEG, the free radical scavengers, reduced apoptotic cell death. From these findings, it seems that leakage of ROS from mitochondria into cytosol by DHTS represents the major contributory factor leading to cell death in colon cancer cells.
  
  
  CONCLUSIONS
  We report for the first time that DHTS induces apoptosis in colon cancer cells through a p53-independent pathway. Disturbance of ROS generation at the oxidative phosphorylation (OXPHOS) complex in mitochondria followed by the decrease of MMP and increase of intracellular ROS accumulation are suggested to be involved in the pro-apoptotic activity of DHTS.
authors.affiliation: Faculty of Medicine, School of Biomedical Sciences, The Chinese University of Hong Kong, China.
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.forename: J H K
authors.initials: JH
authors.lastname: Yeung
authors.forename: T
authors.initials: T
authors.lastname: Hu
authors.forename: W Y
authors.initials: WY
authors.lastname: Lee
authors.forename: L
authors.initials: L
authors.lastname: Lu
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Shen
authors.forename: R L Y
authors.initials: RL
authors.lastname: Chan
authors.forename: W K K
authors.initials: WK
authors.lastname: Wu
authors.forename: C H
authors.initials: CH
authors.lastname: Cho
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D018938:Caco-2 Cells; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D005434:Flow Cytometry; D016166:Free Radical Scavengers / Q000494:pharmacology; D005663:Furans; D045325:HCT116 Cells; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D018613:Microscopy, Confocal; D010085:Oxidative Phosphorylation; D010616:Phenanthrenes / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011809:Quinones; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D016166:Free Radical Scavengers; D005663:Furans; D010616:Phenanthrenes; D011809:Quinones; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; C000713095:dihydrotanshinone I; D011065:Poly(ADP-ribose) Polymerases
keywords: Apoptosis; Colon cancer; Dihydrotanshinone; ROS; p53