Evaluation of near-Infrared fluorescence-conjugated peptides for visualization of human epidermal receptor 2-overexpressed gastric cancer.

Abstract

338 Background: HER2 is highly overexpressed in many kinds of cancers with a poor prognosis. Recently, near-infrared (NIR) fluorescence-based imaging is a growing field for both pre-clinical and clinical application. In this study, we aimed to synthesize Human Epidermal Receptor2 (HER2)-specific near-infrared (NIR) fluorescence probes and evaluate their applicability in cancer-specific image-guided surgeries using an animal model. Methods: An NIR dye emitting light of 800 nm (IRDye800CW, Li-COR, USA) was conjugated to trastuzumab and HER2-specific affibody using click mechanism. HER2 affinity was assessed by the surface plasmon resonance technique. HER2 positive/negative gastric cancer cell lines (NCI-N87 and SNU-601) were subcutaneously implanted into female BALB/c-nu (6 to 8 weeks old) mice. The biodistribution and fluorescence signal intensity were measured by Lumina II (Perkin Elmer, MA, USA) and a laparoscopic NIR camera (InTheSmart, Seoul, Korea) after injecting the probes intravenously. Results: Trastuzumab-IRDye800CW showed higher affinity to HER2 (K(D) = 2.093(3)pM) than unconjugated trastuzumab(K(D) = 25.75pM). The significant signal of fluorescence was targeted to the HER2-positive tumors at 24hr after injection, while no or low signal retention was observed in negative group. The peak appears at 24hr after injection. On the other hand, small difference of affinity was shown between HER2-target affibody-IRDye800CW (K(D) = 4.71nM) and unlabeled pure affibody(K(D) = 1.42nM). The renal clearance of HER2-target affibody conjugated with IRDye800CW was so fast that we could not detect the signal. Conclusions: Our results suggest that trastuzumab conjugated with IRDye800CW can be a feasible tool to monitor HER2 status in pre-clinical cancer imaging. Moreover, this probe can provide complementary means for assessment of HER2 expression in gastric cancer patients and/or be used to further detection of HER2-positive lesions during image-guided surgery.