Rofo 2015; 187 - WISS405_4
DOI: 10.1055/s-0035-1551231

Optical imaging using an Hsp70 NIR probe to monitor the therapeutic efficiency of hyperthermia in vitro and in vivo

J Grandke 1, S Rosenhain 1, U Teichgräber 2, I Hilger 1
  • 1Uniklinikum Jena, Zentrum für Radiologie AG Experimentelle Radiologie, Jena
  • 2Uniklinikum Jena, Zentrum für Radiologie, Jena

Zielsetzung:

Hyperthermia as cancer treatment is capable to induce cell death and consequently stop tumor growth. Tumor cells are specifically prone to hyperthermic temperatures; therefore, heat shock proteins (Hsp) like Hsp70 are expressed upon cellular stress. Here, an optical near-infrared (NIR) probe was developed to assess the therapeutic efficiency of magnetic hyperthermia on a molecular level in breast cancer.

Material und Methodik:

The Hsp70 antibody was covalently coupled to the fluorophore Dy700. The breast cancer cell line MDA-MB-231 was used for immunofluorescence, affinity studies and FACS analysis. The effects of magnetic hyperthermia were assessed in 23 nude mice carrying MDA-MB-231 tumors. Iron oxide nanoparticles (core 12nm) were used to generate temperatures near 43 °C. The Hsp70-Dy700 probe (100pM) was intravenously injected before as well as 1 and 8 d after hyperthermia and the fluorescence quantified in an animal scanner.

Ergebnisse:

The tumor marker Hsp70 was overexpressed on the surface of breast cancer cells compared to control cells using immunofluorescence. The Hsp70-Dy700 probe was successfully synthesized and physico-chemically characterized. The NIR probe specifically binds to MDA-MB-231 cells quantified by FACS in vitro. The high affinity of the Hsp70 probe to the cells was confirmed (KD value –5nM). The highest fluorescence intensity of the Hsp70-Dy700 probe was detected 30h post injection in the tumor of the mice (n = 3). The tumor-to-muscle-ratio was reduced after magnetic hyperthermia, exemplarily a reduction of the fluorescence intensity from 0.005 to 0.0015 was observed, due to the efficient cellular destruction in the tumor. The tumor volume was significantly reduced after hyperthermia compared to control mice (n = 7, p≤0.05).

Schlussfolgerungen:

The Hsp70-Dy700 probe is suitable to assess the therapeutic efficiency of hyperthermia in breast cancer. The level of vascularization as well as the apoptotic or necrotic status of the tumor should also be analyzed to assess the accessibility of the NIR probe.