Poster Sessions

CANCER-20

Moinuddin Hassan

M. Hassan, V. Chernomordik, R. Zeilinski, J. Capala, A. Gandjbakhche

Near-Infrared Optical Imaging: Quantification of HER2 Receptors Expression In Vivo

HER2 overexpression has been associated with a poor prognosis and resistance to therapy in breast cancer patients. However, quantitative estimates of this important characteristic have been limited to ex vivo ELISA essays of tissue biopsies and/or PET-based analysis. We aim at developing an optical imaging modality that will not interfere with the binding of the therapeutic agents, thus, excluding competition between therapy and monitoring. We used HER2-specific Affibody molecules as targeting agents labeled with AlexaFluor750 dye for quantitative in vivo near-infrared optical imaging. We have measured NIR signal from subcutaneous xenografts of tumors expressing different levels of HER2 as a function of time post-injection and used mathematical modeling to assess correlation of the imaging parameters with HER2 expression levels obtained by the ex-vivo assays of the same tumors. We obtained good correlations between tumor cell characteristics, i.e. amplification/overexpression of HER2, and parameters, directly estimated from subsequent optical images. Our results suggest that Affibody-Alexa Fluor conjugates may be used as a specific near-infrared probe for the non-invasive imaging of HER2-positive tumors and that mathematical analysis if the imaging parameters may provide quantitative data on the HER2 expression in vivo.