In vivo molecular imaging to diagnose and sub-type tumors via receptor-targeted optically-labeled monoclonal antibodies

Yoshinori Koyama, Tristan Barrett, Yukihiro Hama, Gregory Ravizzini, Peter L Choyke and Hisataka Kobayashi

Year 2007, Volume 9, Issue 12

Abstract

Molecular imaging of receptors expressed on the cell surface offers potential for the clinical diagnosis of tumors based on their distinct expression profiles. Here we employ a multi-filter spectrally-resolved optical imaging technique with a cocktail of 3 fluorescently-labeled antibodies to simultaneously image 3 different cell surface receptors, in an attempt to distinguish the different tumor types non-invasively by in vivo optical imaging. We selected tumor cell lines over-expressing two different subtypes of EGF receptors: HER-1 (A431) and HER-2 (NIH3T3/HER2+), as well as the IL-2Rƒ¿ receptor (SP2/Tac). After establishment of the tumors, a cocktail of three fluorescently-labeled monoclonal antibodies was injected: Cy5-cetuximab (targeting HER-1), Cy7-trastuzumab (targeting HER-2), and Alexa700-daclizumab (targeting IL-2Rƒ¿). Optical fluorescence imaging was performed 24h later with both a red filter set, and 3 successive filter sets (each matched to its appropriate fluorophore). Spectrally resolved in vivo imaging of 10 mice implanted with 3 different tumor types clearly distinguished A431, NIH3T3/HER2+, and SP2-Tac tumors based on their distinct optical spectra. The use of three different filter sets significantly increased the signal-to-background ratio compared to a single filter set by reducing the background signal, thus significantly improving the differentiation of each of the receptors targeted (p<0.022). In conclusion, different types of tumors can be simultaneously distinguished and diagnosed in vivo, following multi-filter spectrally resolved imaging. Multiple filter sets increase the signal-to-noise ratio by substantially reducing the background signal, and may allow greater numbers of optical dyes to be resolved within the narrow limits of the near-infrared range.

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