Irradiation-induced regulation of plasminogen activator inhibitor type-1 and vascular endothelial growth factor in six human squamous cell carcinoma lines of the head and neck

Int J Radiat Oncol Biol Phys. 2010 Feb 1;76(2):574-82. doi: 10.1016/j.ijrobp.2009.08.035.


Purpose: It has been shown that plasminogen activator inhibitor type-1 (PAI-1) and vascular endothelial growth factor (VEGF) are involved in neo-angiogenesis. The aim of this study was to investigate the irradiation-induced regulation of PAI-1 and VEGF in squamous cell carcinomas of the head and neck (SCCHN) cell lines of varying radiation sensitivity.

Methods and materials: Six cell lines derived from SCCHN were investigated in vitro. The colorimetric AlamarBlue assay was used to detect metabolic activity of cell lines during irradiation as a surrogate marker for radiation sensitivity. PAI-1 and VEGF secretion levels were measured by enzyme-linked immunosorbent assay 24, 48, and 72 h after irradiation with 0, 2, 6, and 10 Gy. The direct radioprotective effect of exogenous PAI-1 was measured using the clonogenic assay. For regulation studies, transforming growth factor-beta1 (TGF-beta1), hypoxia-inducible factor-1alpha (HIF-1alpha), hypoxia-inducible factor-2alpha (HIF-2alpha), or both HIF-1alpha and HIF-2alpha were downregulated using siRNA.

Results: Although baseline levels varied greatly, irradiation led to a comparable dose-dependent increase in PAI-1 and VEGF secretion in all six cell lines. Addition of exogenous stable PAI-1 to the low PAI-1-expressing cell lines, XF354 and FaDu, did not lead to a radioprotective effect. Downregulation of TGF-beta1 significantly decreased VEGF secretion in radiation-sensitive XF354 cells, and downregulation of HIF-1alpha and HIF-2alpha reduced PAI-1 and VEGF secretion in radiation-resistant SAS cells.

Conclusions: Irradiation dose-dependently increased PAI-1 and VEGF secretion in all SCCHN cell lines tested regardless of their basal levels and radiation sensitivity. In addition, TGF-beta1 and HIF-1alpha could be partly responsible for VEGF and PAI-1 upregulation after irradiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Carcinoma, Squamous Cell / metabolism
  • Carcinoma, Squamous Cell / radiotherapy*
  • Cell Line, Tumor
  • Cell Survival
  • Colorimetry / methods
  • Dose-Response Relationship, Radiation
  • Down-Regulation
  • Enzyme-Linked Immunosorbent Assay / methods
  • Head and Neck Neoplasms / metabolism
  • Head and Neck Neoplasms / radiotherapy*
  • Humans
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Plasminogen Activator Inhibitor 1 / metabolism*
  • RNA, Small Interfering / metabolism
  • Radiation Tolerance
  • Transforming Growth Factor beta1 / metabolism
  • Vascular Endothelial Growth Factor A / metabolism*


  • Basic Helix-Loop-Helix Transcription Factors
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Plasminogen Activator Inhibitor 1
  • RNA, Small Interfering
  • Transforming Growth Factor beta1
  • Vascular Endothelial Growth Factor A
  • endothelial PAS domain-containing protein 1