A preclinical model for noninvasive imaging of hypoxia-induced gene expression; comparison with an exogenous marker of tumor hypoxia

Eur J Nucl Med Mol Imaging. 2004 Nov;31(11):1530-8. doi: 10.1007/s00259-004-1673-z. Epub 2004 Sep 16.


Purpose: Hypoxia is associated with tumor aggressiveness and is an important cause of resistance to radiation therapy and chemotherapy. Assays of tumor hypoxia could provide selection tools for hypoxia-modifying treatments. The purpose of this study was to develop and characterize a rodent tumor model with a reporter gene construct that would be transactivated by the hypoxia-inducible molecular switch, i.e., the upregulation of HIF-1.

Methods: The reporter gene construct is the herpes simplex virus 1-thymidine kinase (HSV1-tk) fused with the enhanced green fluorescent protein (eGFP) under the regulation of an artificial hypoxia-responsive enhancer/promoter. In this model, tumor hypoxia would up-regulate HIF-1, and through the hypoxia-responsive promoter transactivate the HSV1-tkeGFP fusion gene. The expression of this reporter gene can be assessed with the 124I-labeled reporter substrate 2'-fluoro-2'-deoxy-1-beta-D-arabinofuranosyl-5-iodouracil (124I-FIAU), which is phosphorylated by the HSV1-tk enzyme and trapped in the hypoxic cells. Animal positron emission tomography (microPET) and phosphor plate imaging (PPI) were used in this study to visualize the trapped 124I-FIAU, providing a distribution of the hypoxia-induced molecular events. The distribution of 124I-FIAU was also compared with that of an exogenous hypoxic cell marker, 18F-fluoromisonidazole (FMISO).

Results: Our results showed that 124I-FIAU microPET imaging of the hypoxia-induced reporter gene expression is feasible, and that the intratumoral distributions of 124I-FIAU and 18F-FMISO are similar. In tumor sections, detailed radioactivity distributions were obtained with PPI which also showed similarity between 124I-FIAU and 18F-FMISO.

Conclusion: This reporter system is sufficiently sensitive to detect hypoxia-induced transcriptional activation by noninvasive imaging and might provide a valuable tool in studying tumor hypoxia and in validating existing and future exogenous markers for tumor hypoxia.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenocarcinoma / diagnostic imaging*
  • Adenocarcinoma / genetics
  • Adenocarcinoma / metabolism*
  • Animals
  • Arabinofuranosyluracil / analogs & derivatives*
  • Arabinofuranosyluracil / pharmacokinetics*
  • Biomarkers, Tumor / metabolism*
  • Cell Hypoxia*
  • Cell Line, Tumor
  • DNA-Binding Proteins / metabolism*
  • Disease Models, Animal
  • Drug Evaluation, Preclinical
  • Feasibility Studies
  • Fluorine Radioisotopes / pharmacokinetics
  • Gene Expression Profiling / methods*
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Iodine Radioisotopes / pharmacokinetics
  • Misonidazole / analogs & derivatives*
  • Misonidazole / pharmacokinetics
  • Nuclear Proteins / metabolism*
  • Radionuclide Imaging
  • Radiopharmaceuticals / pharmacokinetics
  • Rats
  • Thymidine Kinase / genetics
  • Thymidine Kinase / metabolism
  • Transcription Factors / metabolism*
  • Viral Proteins / genetics
  • Viral Proteins / metabolism


  • Biomarkers, Tumor
  • DNA-Binding Proteins
  • Fluorine Radioisotopes
  • Hif1a protein, rat
  • Hypoxia-Inducible Factor 1
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Iodine Radioisotopes
  • Nuclear Proteins
  • Radiopharmaceuticals
  • Transcription Factors
  • Viral Proteins
  • fluoromisonidazole
  • Arabinofuranosyluracil
  • fialuridine
  • Misonidazole
  • thymidine kinase, Canid herpesvirus 1
  • Thymidine Kinase