title: Inhibition of ataxia telangiectasia- and Rad3-related function abrogates the in vitro and in vivo tumorigenicity of human colon cancer cells through depletion of the CD133(+) tumor-initiating cell fraction.
abstract: The identification of novel approaches to specifically target the DNA-damage checkpoint response in chemotherapy-resistant cancer stem cells (CSC) of solid tumors has recently attracted great interest. We show here in colon cancer cell lines and primary colon cancer cells that inhibition of checkpoint-modulating phosphoinositide 3-kinase-related (PIK) kinases preferentially depletes the chemoresistant and exclusively tumorigenic CD133(+) cell fraction. We observed a time- and dose-dependent disproportionally pronounced loss of CD133(+) cells and the consecutive lack of in vitro and in vivo tumorigenicity of the remaining cells. Depletion of CD133(+) cells was initiated through apoptosis of cycling CD133(+) cells and further substantiated through subsequent recruitment of quiescent CD133(+) cells into the cell cycle followed by their elimination. Models using specific PIK kinase inhibitors, somatic cell gene targeting, and RNA interference demonstrated that the observed detrimental effects of caffeine on CSC were attributable specifically to the inhibition of the PIK kinase ataxia telangiectasia- and Rad3-related (ATR). Mechanistically, phosphorylation of CHK1 checkpoint homolog (S. pombe; CHK1) was significantly enhanced in CD133(+) as compared with CD133(-) cells on treatment with DNA interstrand-crosslinking (ICL) agents, indicating a preferential activation of the ATR/CHK1-dependent DNA-damage response in tumorigenic CD133(+) cells. Consistently, the chemoresistance of CD133(+) cells toward DNA ICL agents was overcome through inhibition of ATR/CHK1-signaling. In conclusion, our study illustrates a novel target to eliminate the tumorigenic CD133(+) cell population in colon cancer and provides another rationale for the development of specific ATR-inhibitors.
authors.affiliation: Department of Medicine II, Campus Grosshadern, Ludwigs-Maximilian-University of Munich, Munich, Germany.
authors.forename: Eike
authors.initials: E
authors.lastname: Gallmeier
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Hermann
authors.forename: Maria-Theresa
authors.initials: MT
authors.lastname: Mueller
authors.forename: Juan G
authors.initials: JG
authors.lastname: Machado
authors.forename: Andreas
authors.initials: A
authors.lastname: Ziesch
authors.forename: Enrico N
authors.initials: EN
authors.lastname: De Toni
authors.forename: Andreas
authors.initials: A
authors.lastname: Palagyi
authors.forename: Christian
authors.initials: C
authors.lastname: Eisen
authors.forename: Joachim W
authors.initials: JW
authors.lastname: Ellwart
authors.forename: Jose
authors.initials: J
authors.lastname: Rivera
authors.forename: Belen
authors.initials: B
authors.lastname: Rubio-Viqueira
authors.forename: Manuel
authors.initials: M
authors.lastname: Hidalgo
authors.forename: Fred
authors.initials: F
authors.lastname: Bunz
authors.forename: Burkhard
authors.initials: B
authors.lastname: Göke
authors.forename: Christopher
authors.initials: C
authors.lastname: Heeschen
mesh_terms: D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor; D002469:Cell Separation / Q000379:methods; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D015316:Genetic Therapy; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D058990:Molecular Targeted Therapy / Q000379:methods; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D010455:Peptides / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology; D034741:RNA, Small Interfering / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D018797:Cell Cycle Proteins; D006023:Glycoproteins; C000606023:PROM1 protein, human; D010455:Peptides; C000606024:Prom1 protein, mouse; D034741:RNA, Small Interfering; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases