title: Optical imaging of tumor hypoxia and evaluation of efficacy of a hypoxia-targeting drug in living animals.
abstract: Solid tumors containing more hypoxic regions show a more malignant phenotype by increasing the expression of genes encoding angiogenic and metastatic factors. Hypoxia-inducible factor-1 (HIF-1) is a master transcriptional activator of such genes, and thus, imaging and targeting hypoxic tumor cells where HIF-1 is active are important in cancer therapy. In the present study, HIF-1 activity was monitored via an optical in vivo imaging system by using a luciferase reporter gene under the regulation of an artificial HIF-1-dependent promoter, 5HRE. To monitor tumor hypoxia, we isolated a stable reporter-transfectant, HeLa/5HRE-Luc, which expressed more than 100-fold luciferase in response to hypoxic stress, and observed bioluminescence from its xenografts. Immunohistochemical analysis of the xenografts with a hypoxia marker, pimonidazole, confirmed that the luciferase-expressing cells were hypoxic. Evaluation of the efficacy of a hypoxia-targeting prodrug, TOP3, using this optical imaging system revealed that hypoxic cells were significantly diminished by TOP3 treatment. Immunohistochemical analysis of the TOP3-treated xenografts confirmed that hypoxic cells underwent apoptosis and were removed after TOP3 treatment. These results demonstrate that this model system using the 5HRE-luciferase reporter construct provides qualitative information (hypoxic status) of solid tumors and enables one to conveniently evaluate the efficacy of cancer therapy on hypoxia in malignant solid tumors.
authors.affiliation: Kyoto University Graduate School of Medicine, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Harada
authors.forename: Shinae
authors.initials: S
authors.lastname: Kizaka-Kondoh
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D017931:DNA Primers; D006801:Humans; D007150:Immunohistochemistry; D009369:Neoplasms / Q000188:drug therapy*; D055095:Optics and Photonics; D011993:Recombinant Fusion Proteins / Q000627:therapeutic use*
chemical_list: D017931:DNA Primers; D011993:Recombinant Fusion Proteins; C498363:TOP3 fusion protein