title: Oncogenic K-Ras turns death receptors into metastasis-promoting receptors in human and mouse colorectal cancer cells.
abstract: OBJECTIVE
  Death receptors expressed on tumor cells can prevent metastasis formation by inducing apoptosis, but they also can promote migration and invasion. The determinants of death receptor signaling output are poorly defined. Here we investigated the role of oncogenic K-Ras in determining death receptor function and metastatic potential.
  
  
  METHODS
  Isogenic human and mouse colorectal cancer cell lines differing only in the presence or absence of the K-Ras oncogene were tested in apoptosis and invasion assays using CD95 ligand and tumor necrois factor-related apoptosis-inducing ligand (TRAIL) as stimuli. Metastatic potential was assessed by intrasplenic injections of green fluorescent protein- or luciferase-expressing tumor cells, followed by intravital fluorescence microscopy or bioluminescence imaging, and confocal microscopy and immunohistochemistry. Ras-effector pathway control of CD95 output was assessed by an RNA-interference and inhibitor-based approach.
  
  
  RESULTS
  CD95 ligand and TRAIL stimulated invasion of colorectal tumor cells and liver metastases in a K-Ras-dependent fashion. Loss of mutant K-Ras switched CD95 and TRAIL receptors back into apoptosis mode and abrogated metastatic potential. Raf1 was essential for the switch in CD95 function, for tumor cell survival in the liver, and for K-Ras-driven formation of liver metastases. K-Ras and Raf1 suppressed Rho kinase (ROCK)/LIM kinase-mediated phosphorylation of the actin-severing protein cofilin. Overexpression of ROCK or LIM kinase allowed CD95L to induce apoptosis in K-Ras-proficient cells and prevented metastasis formation, whereas their suppression protected K-Ras-deficient cells against apoptosis.
  
  
  CONCLUSIONS
  Oncogenic K-Ras and its effector Raf1 convert death receptors into invasion-inducing receptors by suppressing the ROCK/LIM kinase pathway, and this is essential for K-Ras/Raf1-driven metastasis formation.
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Frederik J H
authors.initials: FJ
authors.lastname: Hoogwater
authors.forename: Maarten W
authors.initials: MW
authors.lastname: Nijkamp
authors.forename: Niels
authors.initials: N
authors.lastname: Smakman
authors.forename: Ernst J A
authors.initials: EJ
authors.lastname: Steller
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Emmink
authors.forename: B Florien
authors.initials: BF
authors.lastname: Westendorp
authors.forename: Danielle A E
authors.initials: DA
authors.lastname: Raats
authors.forename: Martin R
authors.initials: MR
authors.lastname: Sprick
authors.forename: Uta
authors.initials: U
authors.lastname: Schaefer
authors.forename: Winan J
authors.initials: WJ
authors.lastname: Van Houdt
authors.forename: Menno T
authors.initials: MT
authors.lastname: De Bruijn
authors.forename: Ron C J
authors.initials: RC
authors.lastname: Schackmann
authors.forename: Patrick W B
authors.initials: PW
authors.lastname: Derksen
authors.forename: Jan-Paul
authors.initials: JP
authors.lastname: Medema
authors.forename: Henning
authors.initials: H
authors.lastname: Walczak
authors.forename: Inne H M
authors.initials: IH
authors.lastname: Borel Rinkes
authors.forename: Onno
authors.initials: O
authors.lastname: Kranenburg
mesh_terms: D000818:Animals; D017209:Apoptosis; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000473:pathology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D006801:Humans; D054461:Lim Kinases / Q000502:physiology; D008113:Liver Neoplasms / Q000556:secondary*; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D019908:Proto-Oncogene Proteins c-raf / Q000502:physiology; D016283:Proto-Oncogene Proteins p21(ras); D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology*; D019014:fas Receptor / Q000502:physiology*; D018631:ras Proteins / Q000502:physiology*; D054460:rho-Associated Kinases / Q000502:physiology
chemical_list: C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D019014:fas Receptor; D054461:Lim Kinases; D019908:Proto-Oncogene Proteins c-raf; D054460:rho-Associated Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D053181:Caspase 8; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins