title: Quantitative assessment of hypoxia subtypes in microcirculatory supply units of malignant tumors using (immuno-)fluorescence techniques.
abstract: OBJECTIVE
  Hypoxia is a characteristic of tumors, is known to increase aggressiveness, and causes treatment resistance. Traditional classification suggests two types of hypoxia: chronic and acute. Acute hypoxia is mostly caused by transient disruptions in perfusion, while chronic hypoxia is caused by diffusion limitations. This classification may be insufficient in terms of pathogenetic and pathophysiological mechanisms. Therefore, we quantified hypoxia subtypes in tumors based on (immuno-)fluorescent marker distribution patterns in microcirculatory supply units (MCSUs).
  
  
  METHODS
  Cryosections from hSCC lines (SAS, FaDu, UT-SCC-5, UT-SCC-14, UT-SCC-15) were analyzed. Hypoxia was identified by pimonidazole, perfusion by Hoechst 33342, and endothelial cells by CD31. The following patterns were identified in vital tumor tissue: (1) normoxia: Hoechst 33342 fluorescence around microvessels, no pimonidazole, (2) chronic hypoxia: Hoechst 33342 fluorescence around microvessels, pimonidazole distant from microvessels, (3) acute hypoxia: no Hoechst 33342 fluorescence around microvessels, pimonidazole in immediate vicinity of microvessels, and (4) hypoxemic hypoxia: Hoechst 33342 fluorescence and pimonidazole directly around microvessels.
  
  
  RESULTS
  Quantitative assessment of MCSUs show predominance for normoxia in 4 out of 5 tumor lines (50.1-72.8%). Total hypoxia slightly prevails in UT-SCC-15 (56.9%). Chronic hypoxia is the dominant subtype (65.4-85.9% of total hypoxia). Acute hypoxia only accounts for 12.9-29.8% and hypoxemic hypoxia for 1.2-6.4% of total hypoxia. The fraction of perfused microvessels ranged from 82.5-96.6%.
  
  
  CONCLUSIONS
  Chronic hypoxia is the prevailing subtype in MCSUs. Acute hypoxia and hypoxemic hypoxia account for only a small fraction. This approach enables assessment and recognition of different hypoxia subtypes including hypoxemic hypoxia and may facilitate methods to (clinically) identify and eliminate hypoxia.
authors: Department of Radiotherapy and Radiation Oncology, Technical University of Munich, Munich, Germany.
authors: Constantin-Alin
authors: CA
authors: Maftei
authors: Christine
authors: C
authors: Bayer
authors: Kuangyu
authors: K
authors: Shi
authors: Sabrina T
authors: ST
authors: Astner
authors: Peter
authors: P
authors: Vaupel
mesh_terms: D001562:Benzimidazoles; D015687:Cell Hypoxia / Q000502:physiology*; D045744:Cell Line, Tumor; D004058:Diffusion; D006801:Humans; D008833:Microcirculation / Q000502:physiology*; D008856:Microscopy, Fluorescence; D055806:Microvessels; D009369:Neoplasms / Q000098:blood supply*; D009593:Nitroimidazoles; D055420:Perfusion Imaging; D011379:Prognosis; D011838:Radiation-Sensitizing Agents; D014407:Tumor Cells, Cultured / Q000145:classification* / Q000473:pathology*
chemical_list: D001562:Benzimidazoles; D009593:Nitroimidazoles; D011838:Radiation-Sensitizing Agents; C033815:pimonidazole; C017807:bisbenzimide ethoxide trihydrochloride