title: Copper chelation selectively kills colon cancer cells through redox cycling and generation of reactive oxygen species.
abstract: BACKGROUND
  Metals including iron, copper and zinc are essential for physiological processes yet can be toxic at high concentrations. However the role of these metals in the progression of cancer is not well defined. Here we study the anti-tumor activity of the metal chelator, TPEN, and define its mechanism of action.
  
  
  METHODS
  Multiple approaches were employed, including cell viability, cell cycle analysis, multiple measurements of apoptosis, and mitochondrial function. In addition we measured cellular metal contents and employed EPR to record redox cycling of TPEN-metal complexes. Mouse xenografts were also performed to test the efficacy of TPEN in vivo.
  
  
  RESULTS
  We show that metal chelation using TPEN (5μM) selectively induces cell death in HCT116 colon cancer cells without affecting the viability of non-cancerous colon or intestinal cells. Cell death was associated with increased levels of reactive oxygen species (ROS) and was inhibited by antioxidants and by prior chelation of copper. Interestingly, HCT116 cells accumulate copper to 7-folds higher levels than normal colon cells, and the TPEN-copper complex engages in redox cycling to generate hydroxyl radicals. Consistently, TPEN exhibits robust anti-tumor activity in vivo in colon cancer mouse xenografts.
  
  
  CONCLUSIONS
  Our data show that TPEN induces cell death by chelating copper to produce TPEN-copper complexes that engage in redox cycling to selectively eliminate colon cancer cells.
authors.forename: Maamoun
authors.initials: M
authors.lastname: Fatfat
authors.forename: Raghida Abou
authors.initials: RA
authors.lastname: Merhi
authors.forename: Omar
authors.initials: O
authors.lastname: Rahal
authors.forename: Detcho A
authors.initials: DA
authors.lastname: Stoyanovsky
authors.forename: Angela
authors.initials: A
authors.lastname: Zaki
authors.forename: Hazar
authors.initials: H
authors.lastname: Haidar
authors.forename: Valerian E
authors.initials: VE
authors.lastname: Kagan
authors.affiliation: Department of Biology, American University of Beirut, Beirut, Lebanon. amro@aub.edu.lb.
authors.forename: Hala
authors.initials: H
authors.lastname: Gali-Muhtasib
authors.forename: Khaled
authors.initials: K
authors.lastname: Machaca
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000378:metabolism / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D003300:Copper / Q000378:metabolism*; D005029:Ethylenediamines / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000473:pathology; D010084:Oxidation-Reduction / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000975:Antioxidants; D002614:Chelating Agents; D005029:Ethylenediamines; D017382:Reactive Oxygen Species; D003300:Copper; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine