title: CD95 is a key mediator of invasion and accelerated outgrowth of mouse colorectal liver metastases following radiofrequency ablation.
abstract: OBJECTIVE
  Recently, we have shown that micro-metastases, in the hypoxic transition zone surrounding lesions generated by radiofrequency ablation (RFA), display strongly accelerated outgrowth. CD95 is best known for its ability to induce apoptosis but can also promote tumorigenesis in apoptosis-resistant tumor cells. Therefore, we tested whether CD95 signaling plays a role in accelerated outgrowth of colorectal liver metastases following RFA.
  
  
  METHODS
  Hypoxia-induced invasion was assessed in three-dimensional EGFP-expressing C26 tumor cell cultures by confocal microscopy. CD95 localization was tested by immunofluorescence. Invasion and outgrowth of liver metastases following RFA were analyzed by post-mortem confocal microscopy and by morphometric assessment of tumor load. Neutralization of CD95L was performed by using antibody MFL4. CD95 was suppressed by lentiviral RNA interference. The role of host CD95L was assessed using gld mice.
  
  
  RESULTS
  Micro-metastases in the hypoxic transition zone following RFA displayed a highly invasive phenotype and increased expression of CD95 and CD95L. Hypoxia-induced tumor cell invasion in vitro increased the expression of CD95 and CD95L and induced translocation of CD95 to the invasive front. In vitro invasion, metastasis invasion, and accelerated tumor growth in the transition zone were strongly suppressed by neutralizing CD95L or by suppressing tumor cell CD95. In contrast, metastasis invasion and outgrowth were unaffected in gld mice.
  
  
  CONCLUSIONS
  Hypoxia causes autocrine activation of CD95 on colorectal tumor cells, thereby promoting local invasion and accelerated metastasis outgrowth in the hypoxic transition zone following RFA. Further pre-clinical work is needed to assess the role of CD95L neutralization, either alone or in combination with chemotherapy, in limiting aggressive recurrence of liver metastases following RFA.
authors.affiliation: Department of Surgery, University Medical Center Utrecht, Heidelberglaan 100, 3584CX Utrecht, The Netherlands.
authors.forename: Maarten W
authors.initials: MW
authors.lastname: Nijkamp
authors.forename: Frederik J H
authors.initials: FJ
authors.lastname: Hoogwater
authors.forename: Ernst J A
authors.initials: EJ
authors.lastname: Steller
authors.forename: B Florien
authors.initials: BF
authors.lastname: Westendorp
authors.forename: Taco A
authors.initials: TA
authors.lastname: van der Meulen
authors.forename: Martijn W H
authors.initials: MW
authors.lastname: Leenders
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; D017115:Catheter Ablation; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms; D053222:Fas Ligand Protein / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics; D000860:Hypoxia / Q000276:immunology / Q000473:pathology; D066298:In Vitro Techniques; D008114:Liver Neoplasms, Experimental / Q000276:immunology* / Q000473:pathology / Q000556:secondary* / Q000601:surgery; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D009361:Neoplasm Invasiveness / Q000276:immunology; D034622:RNA Interference; D015398:Signal Transduction / Q000276:immunology; D019014:fas Receptor / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
chemical_list: D053222:Fas Ligand Protein; D019014:fas Receptor