title: Associations between radiocurability and interstitial fluid pressure in human tumor xenografts without hypoxic tissue.
abstract: OBJECTIVE
  The interstitial fluid pressure (IFP) of the primary tumor is an independent prognostic parameter for cervical cancer patients treated with radiation therapy. The aim of this preclinical study was to investigate whether tumor radiocurability may be associated with IFP through hypoxia-independent mechanisms.
  
  
  METHODS
  Small A-07 and R-18 melanoma xenografts without hypoxic tissue were used as preclinical tumor models. IFP was measured by using the wick-in-needle method. Radiation dose resulting in 50% local tumor control (TCD(50)), cell density, cell tumorigenicity, plating efficiency in vitro, mitotic index, fraction of Ki67-positive cells, vascular endothelial growth factor-A (VEGF-A) concentration, and radiation-induced endothelial cell apoptosis were assessed in tumors with low and high IFP.
  
  
  RESULTS
  TCD(50) was found to be higher for tumors with high IFP than for tumors with low IFP by factors of 1.13 +/- 0.03 (A-07; P < 0.0001) and 1.10 +/- 0.03 (R-18; P < 0.0001). In the A-07 line, tumors with high IFP showed a larger number of clonogenic cells and a higher rate of cell proliferation than tumors with low IFP. In the R-18 line, tumors with high IFP showed a higher concentration of VEGF-A and a lower endothelial cell apoptotic index after irradiation than tumors with low IFP.
  
  
  CONCLUSIONS
  The radiation resistance of normoxic tumor tissue with highly elevated IFP may be an indirect consequence of increased tumor cell clonogenicity as well as increased VEGF-A expression, possibly caused by hypertension-induced modifications of signaling pathways regulating cell proliferation, cell survival, and/or angiogenesis.
authors.affiliation: Department of Radiation Biology, Oslo University Hospital, Oslo, Norway. einar.k.rofstad@rr-research.no
authors.forename: Einar K
authors.initials: EK
authors.lastname: Rofstad
authors.forename: Else-Beate M
authors.initials: EB
authors.lastname: Ruud
authors.forename: Berit
authors.initials: B
authors.lastname: Mathiesen
authors.forename: Kanthi
authors.initials: K
authors.lastname: Galappathi
mesh_terms: D000818:Animals; D017209:Apoptosis; D002452:Cell Count; D015687:Cell Hypoxia / Q000502:physiology; D045604:Extracellular Fluid / Q000502:physiology*; D005260:Female; D006801:Humans; D008546:Melanoma, Experimental / Q000473:pathology / Q000532:radiotherapy*; D051379:Mice; D008807:Mice, Inbred BALB C; D008940:Mitotic Index; D011312:Pressure; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D042461:Vascular Endothelial Growth Factor A