title: Response of the plasma hypoxia marker osteopontin to in vitro hypoxia in human tumor cells.
abstract: BACKGROUND
  Osteopontin (OPN) is recognized as a tumor-associated protein and has recently been shown to be a potential plasma marker of tumor hypoxia in head and neck cancer patients. We sought to detect patterns of OPN accumulation and secretion in human tumor cells during in vitro hypoxia.
  
  
  METHODS
  The human tumor cell lines A 549 lung carcinoma, U 87 malignant glioma, HT 1080 fibrosarcoma, FaDu pharyngeal carcinoma and HT 29 and HCT 116 colorectal carcinoma were treated with 1, 6 or 24 h of hypoxia (0.1% O2) or 24 h followed by 4 h or 20 of reoxygenation. OPN concentration in the supernatant was measured by ELISA, OPN protein and mRNA levels by Western and Northern blotting.
  
  
  RESULTS
  In FaDu, HT 29 and HCT 116, OPN levels in the supernatant remained below 10 ng/ml under all conditions. In A 549, HT 1080 and U 87, mean aerobic OPN concentrations were 2296, 164 and 115 ng/ml, respectively. No increase of OPN in the medium during 24h of hypoxia, but moderate increases during subsequent 24-hour-reoxygenation were observed in these three cell lines. Intracellular OPN protein was present to a similar extent in all six-cell lines under aerobic conditions and also did not accumulate during hypoxia treatment. OPN mRNA response to hypoxia and reoxygenation was very heterogeneous between cell lines.
  
  
  CONCLUSIONS
  Reoxygenation rather than hypoxia appears to induce OPN secretion from human tumor cells in a cell-type specific manner.
authors: Department of Radiation Oncology, University of Würzburg, Würzburg, Germany.
authors: Harun M
authors: HM
authors: Said
authors: Astrid
authors: A
authors: Katzer
authors: Michael
authors: M
authors: Flentje
authors: Dirk
authors: D
authors: Vordermark
mesh_terms: D002448:Cell Adhesion; D015687:Cell Hypoxia; D045744:Cell Line, Tumor / Q000378:metabolism*; D006801:Humans; D009363:Neoplasm Proteins / Q000378:metabolism*; D053495:Osteopontin; D012795:Sialoglycoproteins / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D009363:Neoplasm Proteins; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; D053495:Osteopontin