title: Tumour interstitial fluid pressure may regulate angiogenic factors in osteosarcoma.
abstract: OBJECTIVE
  We have previously shown that osteosarcomas have states of increased interstitial fluid pressure (IFP) which correlate with increased proliferation and chemosensitivity. In this study, we hypothesized that constitutively raised IFP in osteosarcomas regulates angiogenesis.
  
  
  METHODS
  Sixteen patients with the clinical diagnosis of osteosarcomas underwent blood fl ow and IFP readings by the wick-in-needle method at the time and location of open biopsy. Vascularity was determined by capillary density in the biopsy specimens. We performed digital image analysis of immunohistochemical staining for CD31, VEGF-A, VEGF-C and TPA on paraffin-embedded tissue blocks of the biopsy samples. Clinical results were validated in a pressurised cell culture system.
  
  
  RESULTS
  IFPs in the tumours (mean 33.5 +/- SD 17.2 mmHg) were significantly higher (P = 0.00001) than that in normal tissue (2.9 +/- 5.7 mmHg). Pressure readings were significantly higher in low vascularity tumours compared to high vascularity tumours (P <0.001). In the osteosarcoma cell lines, growth in a pressurised environment was associated with VEGF-A downregulation, VEGF-C upregulation and TPA upregulation. The reverse was seen in the OB cell lines. Growth in the HUVEC cell line was not significantly inhibited in a pressurised environment. Immunohistochemical assessment for VEGF-A (P = 0.01), VEGF-C (P = 0.008) and TPA (P = 0.0001) translation were consistent with the findings on PCR.
  
  
  CONCLUSIONS
  Our data suggest that some molecules in angiogenesis are regulated by changes in IFP.
authors.affiliation: Musculoskeletal Oncology Service, Department of Orthopaedic Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. dosssn@nus.edu.sg
authors.forename: Saminathan S
authors.initials: SS
authors.lastname: Nathan
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Huvos
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Casas-Ganem
authors.forename: Rui
authors.initials: R
authors.lastname: Yang
authors.forename: Irina
authors.initials: I
authors.lastname: Linkov
authors.forename: Rebecca
authors.initials: R
authors.lastname: Sowers
authors.forename: Gene R
authors.initials: GR
authors.lastname: DiResta
authors.forename: Richard
authors.initials: R
authors.lastname: Gorlick
authors.forename: John H
authors.initials: JH
authors.lastname: Healey
mesh_terms: D000293:Adolescent; D042501:Angiogenic Proteins / Q000502:physiology*; D001859:Bone Neoplasms / Q000098:blood supply*; D002478:Cells, Cultured; D045604:Extracellular Fluid / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009389:Neovascularization, Pathologic; D012516:Osteosarcoma / Q000098:blood supply*; D011312:Pressure
chemical_list: D042501:Angiogenic Proteins