title: The apoptotic response of liver and colorectal liver metastases to focal hyperthermic injury.
abstract: BACKGROUND
  Ablation of liver tumours by focal hyperthermia causes tissue injury not only by direct effects, but also by progressive tissue damage following the initial heat application. The mechanism by which this progressive injury occurs remains undefined. Stimulation of apoptosis following the initial heat stimulus may be involved in this progression. The role of apoptosis in the subsequent progression of focal hyperthermia injury was investigated in liver and colorectal liver metastases in a murine model.
  
  
  METHODS
  Focal hyperthermia produced by laser (Nd-YAG--wavelength 1064 nm) was applied to the liver and colorectal liver metastases in CBA mice (2 Watts for 50 seconds). The animals were killed at 0, 12, 24, 48, 72, 120 and 168 hours after the application of focal hyperthermia. Haematoxylin and eosin staining and immunohistochemistry were performed on paraffin sections to assess the extent of tissue necrosis. Apoptosis was examined by assessment of DNA fragmentation using terminal deoxynucleotidyl transferase d-uridine triphosphate nick end labelling (TUNEL) and activated Caspase 3 immunostaining. The sequence of the apoptotic response was determined at the treated tissue margins and compared to untreated liver and tumour.
  
  
  RESULTS
  Focal hyperthermia produced progressive tissue injury in both liver and colorectal liver metastases. TUNEL labelling was less specific than activated Caspase 3 in detecting apoptotic cells. Apoptosis was detected and peaked at 12 hours following therapy based on activated Caspase 3 staining, before returning to baseline at 72 hours. In tumour tissue, the apoptotic response was more sustained, peaking at 24 hours before returning to baseline levels by 96 hours following therapy.
  
  
  CONCLUSIONS
  Increased apoptosis occurs following the application of focal hyperthermia to normal liver and colorectal metastases. The apoptotic response is more sustained in tumour tissue and contributes to the progressive injury that is evident after the initial heat stimulus.
authors.affiliation: Department of Surgery, University of Melbourne, Austin Hospital Melbourne, Victoria, Australia.
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Nikfarjam
authors.forename: Vijayargavan
authors.initials: V
authors.lastname: Muralidharan
authors.forename: Caterina
authors.initials: C
authors.lastname: Malcontenti-Wilson
authors.forename: Christopher
authors.initials: C
authors.lastname: Christophi
mesh_terms: D000818:Animals; D017209:Apoptosis; D015179:Colorectal Neoplasms / Q000473:pathology*; D006979:Hyperthermia, Induced; D008113:Liver Neoplasms / Q000473:pathology / Q000556:secondary / Q000628:therapy*; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D009336:Necrosis / Q000473:pathology