ABSTRACT
Purpose@#A near-infrared (NIR) fluorescence imaging is a promising tool for cancer-specific image guided surgery. Human epidermal receptor 2 (HER2) is one of the candidate markers for gastric cancer. In this study, we aimed to synthesize HER2-specific NIR fluorescence probes and evaluate their applicability in cancer-specific image-guided surgeries using an animal model. @*Materials and Methods@#An NIR dye emitting light at 800 nm (IRDye800CW; Li-COR) was conjugated to trastuzumab and an HER2-specific affibody using a click mechanism. HER2 affinity was assessed using surface plasmon resonance. Gastric cancer cell lines (NCI-N87 and SNU-601) were subcutaneously implanted into female BALB/c nu (6–8 weeks old) mice.After intravenous injection of the probes, biodistribution and fluorescence signal intensity were measured using Lumina II (Perkin Elmer) and a laparoscopic NIR camera (InTheSmart). @*Results@#Trastuzumab-IRDye800CW exhibited high affinity for HER2 (KD =2.093(3) pM).Fluorescence signals in the liver and spleen were the highest at 24 hours post injection, while the signal in HER2-positive tumor cells increased until 72 hours, as assessed using the Lumina II system. The signal corresponding to the tumor was visually identified and clearly differentiated from the liver after 72 hours using a laparoscopic NIR camera. AffibodyIRDye800CW also exhibited high affinity for HER2 (KD =4.71 nM); however, the signal was not identified in the tumor, probably owing to rapid renal clearance. @*Conclusions@#Trastuzumab-IRDye800CW may be used as a potential NIR probe that can be injected 2–3 days before surgery to obtain high HER2-specific signal and contrast. Affibodybased NIR probes may require modifications to enhance mobilization to the tumor site.
ABSTRACT
PURPOSE: The utility of 18-fluordesoxyglucose positron emission tomography ([¹⁸F]-FDG-PET) combined with computer tomography or magnetic resonance imaging (MRI) in gastric cancer remains controversial and a rationale for patient selection is desired. This study aims to establish a preclinical patient-derived xenograft (PDX) based [¹⁸F]-FDG-PET/MRI protocol for gastric cancer and compare different PDX models regarding tumor growth and FDG uptake.MATERIALS AND METHODS: Female BALB/c nu/nu mice were implanted orthotopically and subcutaneously with gastric cancer PDX. [¹⁸F]-FDG-PET/MRI scanning protocol evaluation included different tumor sizes, FDG doses, scanning intervals, and organ-specific uptake. FDG avidity of similar PDX cases were compared between ortho- and heterotopic tumor implantation methods. Microscopic and immunohistochemical investigations were performed to confirm tumor growth and correlate the glycolysis markers glucose transporter 1 (GLUT1) and hexokinase 2 (HK2) with FDG uptake.RESULTS: Organ-specific uptake analysis showed specific FDG avidity of the tumor tissue. Standard scanning protocol was determined to include 150 μCi FDG injection dose and scanning after one hour. Comparison of heterotopic and orthotopic implanted mice revealed a long growth interval for orthotopic models with a high uptake in similar PDX tissues. The H-score of GLUT1 and HK2 expression in tumor cells correlated with the measured maximal standardized uptake value values (GLUT1: Pearson r=0.743, P=0.009; HK2: Pearson r=0.605, P=0.049).CONCLUSIONS: This preclinical gastric cancer PDX based [¹⁸F]-FDG-PET/MRI protocol reveals tumor specific FDG uptake and shows correlation to glucose metabolic proteins. Our findings provide a PET/MRI PDX model that can be applicable for translational gastric cancer research.
ABSTRACT
Near-infrared (NIR) fluorescence imaging is a promising method for image-guided surgery, providing robust functional images with relatively good cost-effectiveness. A cyanine vital dye indocyanine green (ICG) is a safe NIR fluorophore emitting 800~840 nm of light and has been used in numerous surgical procedures. The technique has been applied to lymph node navigation of gastric cancer surgery with an expectation of better visualization of lymphatic structures without any risk of radio-hazard compared with a “dual method” using both vital dyes and radioisotopes. Given the characteristics of ICG, such as fast distribution and quenching effect, diluted concentrations, such as 0.05~0.1 mg/ml, are thought to be optimal for sentinel node navigation. Injection into the subserosal layer is feasible; however, endoscopic submucosal injection has advantages of improved accuracy of the injection site and feasibility of injection one day prior to surgery; these advantages are preferred by some investigators due to a smaller number of sentinel nodes compared with injection in the operation theatre. The technology requires evaluation of the sensitivity and specificity, as well as the non-inferiority, compared with the dual method in a large cohort for justification as a safe node navigation method.