Expression of VEGF and VEGF receptors and radiotracer uptake in tumor cells and primary endothelial cells under experimental hypoxia


Expression of VEGF and VEGF receptors and radiotracer uptake in tumor cells and primary endothelial cells under experimental hypoxia

Oswald, J.; Treite, F.; Haase, C.; Bergmann, R.; Schwenzer, B.; Pietzsch, J.

Aim:

Vascular-endothelial growth factor (VEGF) is expressed in response to various stimuli like hypoxia and plays a key role in tumor angiogenesis. In this study we analyzed the influence of experimental hypoxia on the upregulation of VEGF and its receptors in primary endothelial cells and tumor cell lines. Furthermore we quantified the uptake of radiotracers in these cells in response to experimental hypoxia in vitro.
Material and Methods:
Three types of primary endothelial cells were used: human umbilical vein endothelial cells (HUVEC), human dermal microvascular endothelial cells (HDMEC) and human aortic endothelial cells (HAEC) as well as the two tumor cell lines FaDu (squamous cell carcinoma) and HT-29 (colorectal adenocarcinoma), respectively. Experimental hypoxia was induced by cultivating cells for 24 to 72 hours in presence of <1% oxygen in a special incubator (Gasboy C40, Labotect). Expression of VEGF, and of the VEGF receptors FLT-1, KDR, FLT-4 and neuropilin 1 and 2 were quantified with quantitative PCR (Realplex, Eppendorf). Cellular uptake of [99mTc]sestamibi, [18F]FDG, and [18F]F-misonidazole was determined after one to four hours incubation and measured after cell lysis with a Cobra II gamma counter (Packard).
Results:
After 48 h of experimental hypoxia all cell lines showed a significant upregulation of VEGF expression. VEGF receptors FLT-1, KDR and FLT-4 were expressed in endothelial cells but absent in tumor cells. Cellular uptake of [99mTc]sestamibi was reduced under hypoxic conditions in all cell lines. Furthermore, we found that primary endothelial cells incorporated significantly higher amounts of [18F]FDG under experimental hypoxic conditions in comparison to normoxic conditions.
When compared to normoxia [18F]FDG uptake after 48h hypoxia was increased 4.3-fold in HUVECs, 3.4-fold in HDMECs, and 3.5-fold in HAECs. These values were substantially higher than the values for the tumor cells FaDu (1.9-fold) and HT-29 (2.1-fold).
Conclusion:
Our data show VEGF to be a suitable indicator for enhanced oxygen demand in both tumor and endothelial cells in vitro. Moreover, the results emphasize the particular relevance of endothelial cells as one important part of the tumor micromilieu.

  • Lecture (Conference)
    EANM'06 Annual Congress of the European Association of Nuclear Medicine, 30.09.-04.10.2006, Athens, Greece
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 33(2006)Suppl. 2, 661

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Publ.-Id: 8523