In this study, we will present the applicability of preclinical models using A431 and COLO205 cells to image epidermal growth factor (EGF) receptor positive colorectal tumors by near infrared (NIR) imaging. NIR bio-imaging of A431 and COLO205 cells and mice with A431 orthotopic tumors were performed, using EGF labeled with IRDye800CW (EGF-NIR). The NIR bio-imaging have indicated a specific and selective binding which reflected receptors level and internalization of EGF-NIR. Signal/background ratio of EGF-NIR binding in vitro indicated saturation after 5 min incubation with 7 nM. In vivo mice imaging showed that the highest signal/background ratio between tumor and adjacent tissue was achieved 48 hours post-injection. Dissected colorectal cancer tissues from different patients demonstrated in situ specific labling/imaging of EGF receptor using our NIR bio-imaging platform. However, in the adjacent gastrointestinal tissue of the same patients, which by Western blotting was demonstrated as EGF receptor negative, no labeling with EGF-NIR probe was detected.
Our results support the concept that molecular imaging of EGF receptor using EGF-NIR probe may provide a noninvasive tool for the detection and characterization of EGF receptor expressing tumors, without the need of radioactive imaging, proposing a novel bio-imaging tool for distinguishing those tumors in clinical setting in a real-time manner.
