Search

Treatment of hyperinsulinemic hypoglycemia is challenging. Surgical treatment of insulinomas and focal lesions in congenital hyperinsulinism is invasive and carries major risks of morbidity. Medication to treat nesidioblastosis and diffuse congenital hyperinsulinism has varying efficacy and causes significant side effects. Here, we describe a novel method for therapy of hyperinsulinemic hyperglycemia, highly selectively killing β-cells by receptor-targeted photodynamic therapy (rtPDT) with exendin-4-IRDye700DX, targeting the glucagon-like peptide 1 receptor (GLP-1R). Methods: A competitive binding assay was performed using Chinese hamster lung (CHL) cells transfected with the GLP-1R. The efficacy and specificity of rtPDT with exendin-4-IRDye700DX were examined in vitro in cells with different levels of GLP-1R expression. Tracer biodistribution was determined in BALB/c nude mice bearing subcutaneous CHL-GLP-1R xenografts. Induction of cellular damage and the effect on tumor growth were analyzed to determine treatment efficacy. Results: Exendin-4-IRDye700DX has a high affinity for the GLP-1R, with a half-maximal inhibitory concentration of 6.3 nM. rtPDT caused significant specific phototoxicity in GLP-1R-positive cells (2.3% ± 0.8% and 2.7% ± 0.3% remaining cell viability in CHL-GLP-1R and INS-1 cells, respectively). The tracer accumulates dose-dependently in GLP-1R-positive tumors. In vivo, rtPDT induces cellular damage in tumors, shown by strong expression of cleaved caspase-3, and leads to a prolonged median survival of the mice (36.5 vs. 22.5 d, respectively; P < 0.05). Conclusion: These data show in vitro as well as in vivo evidence of the potency of rtPDT using exendin-4-IRDye700DX. This approach might in the future provide a new, minimally invasive, highly specific treatment method for hyperinsulinemic hypoglycemia., (© 2020 by the Society of Nuclear Medicine and Molecular Imaging.)

The treatment of choice for insulinomas and focal lesions in congenital hyperinsulinism (CHI) is surgery. However, intraoperative detection can be challenging. This challenge could be overcome with intraoperative fluorescence imaging, which provides real-time lesion detection with a high spatial resolution. Here, a novel method for targeted near-infrared (NIR) fluorescence imaging of glucagonlike peptide 1 receptor (GLP-1R)-positive lesions, using the GLP-1 agonist exendin-4 labeled with IRDye 800CW, was examined in vitro and in vivo. Methods: A competitive binding assay was performed using Chinese hamster lung (CHL) cells transfected with GLP-1R. Tracer biodistribution was determined in BALB/c nude mice bearing subcutaneous CHL-GLP-1R xenografts. In vivo NIR fluorescence imaging of CHL-GLP-1R xenografts was performed. Localization of the tracer in the pancreatic islets of BALB/c nude mice was examined using fluorescence microscopy. Laparoscopic imaging was performed to detect the fluorescent signal of the tracer in the pancreas of mini pigs. Results: Exendin-4-IRDye 800CW binds GLP-1R with a half-maximal inhibitory concentration of 3.96 nM. The tracer accumulates in CHL-GLP-1R xenografts. Subcutaneous CHL-GLP-1R xenografts were visualized using in vivo NIR fluorescence imaging. The tracer accumulates specifically in the pancreatic islets of mice, and a clear fluorescent signal was detected in the pancreas of mini pigs. Conclusion: These data provide the first in vivo evidence of the feasibility of targeted fluorescence imaging of GLP-1R-positive lesions. Intraoperative lesion delineation using exendin-4-IRDye 800CW could benefit open as well as laparoscopic surgical procedures for removal of insulinomas and focal lesions in CHI., (© 2020 by the Society of Nuclear Medicine and Molecular Imaging.)

Unlabelled: Arginine-glycine-aspartic acid (RGD)-based imaging tracers allow specific imaging of integrin αvβ3, a protein overexpressed during angiogenesis, leading to the possibility that it might serve as a tool to stratify patients for antiangiogenic treatment. However, these tracers have generally been characterized in xenograft models in which integrin αvβ3 was constitutively expressed by the tumor cells themselves. In the studies presented here, the use of (111)In-RGD2 as a tracer to image only integrin αvβ3 expression on blood vessels in the tumor was determined using tumor xenografts in which tumor cells were integrin αvβ3-negative., Methods: DOTA-E-[c(RGDfK)]2 was radiolabeled with (111)In ((111)In-RGD2), and biodistribution studies were performed in squamous cell carcinoma of the head and neck (HNSCC) xenograft mouse models to determine the optimal peptide dose to image angiogenesis. Next, biodistribution and imaging studies were performed at the optimal peptide dose in 3 HNSCC mouse models, FaDu, SCCNij3, and SCCNij202. Immunohistochemical analysis of tumor vascular and cell surface expression of integrin αvβ3 and correlation analysis of vascular integrin αvβ3 and autoradiography were completed., Results: All 3 HNSCC xenografts expressed integrin αvβ3 on the vessels only. The optimal peptide dose of (111)In-RGD2 was 1 μg or less for specific integrin αvβ3-mediated uptake of the tracer. SPECT/CT imaging showed clear uptake of the tracer in the periphery of the tumors, corresponding with well-vascularized areas of the tumor. Within the tumor, (111)In-RGD2 autoradiography coincided with vascular integrin αvβ3 expression, as determined immunohistochemically. Integrin αvβ3-mediated uptake was also detected in nontumor tissues, which, through immunohistochemical analysis, proved positive for integrin αvβ3., Conclusion: (111)In-RGD2 allows the visualization of integrin αvβ3 in xenograft models in which integrin αvβ3 is expressed only on the neovasculature, such as in the HNSCC tumors. Thus, (111)In-RGD2 allows specific visualization of angiogenesis in tumor models lacking constitutive tumoral integrin αvβ3 expression but may be less useful for this purpose in many tumors in which tumor cells express integrin αvβ3.

Unlabelled: RS7 is an internalizing anti-Trop-2 pancarcinoma antibody capable of targeting most epithelial cancers. Because pretargeting strategies could improve the tumor localization of radionuclides, a new anti-Trop-2 × antihapten bispecific antibody for pretargeting, based on humanized RS7, was prepared and evaluated with a radiolabeled hapten-peptide in vitro and in vivo to determine whether its internalization properties would interfere with pretargeting., Methods: The anti-Trop-2 × antihapten bispecific antibody, TF12, was prepared using the modular dock-and-lock method. TF12 and humanized RS7 binding was assessed by cell binding assays and fluorescence-activated cell sorting analysis in a variety of human carcinoma cell lines. The internalization of TF12 was evaluated in vitro using a fluorescent TF12 conjugate or hapten-peptide and (111)In-labeled TF12 and RS7. The biodistribution of TF12 and its use as a pretargeting agent with an (111)In-labeled hapten-peptide were assessed in several human epithelial cancer xenografts. Dose optimization was examined in 2 tumor models., Results: TF12 internalizes, but a substantial fraction remained accessible on the tumor surface. Fluorescence-activated cell sorting analysis showed only a minor change in fluorescent signal when the tumor was probed with a fluorescent hapten-peptide over 4 h, and microscopy showed substantial membrane staining when reassessed at 24 h after TF12 exposure. Only 40.1% of (111)In-TF12 was internalized after 24 h. In vivo, excellent tumor localization of the (111)In-labeled peptide was observed in several tumor models., Conclusion: TF12 was retained sufficiently on the cell surface in several epithelial cancers, thereby making it suitable for pretargeted imaging and therapy of various Trop-2-expressing carcinomas.

Unlabelled: hRS7 is a humanized IgG1 monoclonal antibody directed against the epithelial glycoprotein-1 (EGP-1; also known as TROP2). This antigen is found in many epithelial cancers, including prostate cancer, and therefore this antibody could be suitable for targeting this cancer. In this study, the characteristics of hRS7 for targeting prostate cancer were examined. The potential for immuno-PET with (89)Zr-hRS7 and immuno-SPECT with (111)In-hRS7 was assessed using nude mice with human prostate cancer xenografts., Methods: EGP-1 expression was assessed by immunohistology in human primary and metastatic prostate cancer samples and in PC3 xenografts. The optimal antibody protein dose for prostate cancer targeting was examined in nude mice with subcutaneous PC3 xenografts, and then the biodistribution of (111)In-, (125)I-, and (89)Zr-labeled hRS7 was determined in subcutaneous PC3 xenografts at 1, 3, and 7 d after injection. Immuno-PET and immuno-SPECT were performed with (89)Zr-hRS7 and (111)In-hRS7 in mice with subcutaneous and intraprostatic PC3 xenografts, respectively., Results: Immunohistochemical analysis showed abundant EGP-1 expression in human primary and metastatic prostate cancers and in PC3 xenografts. (111)In-hRS7 and (89)Zr-hRS7 preferentially and specifically accumulated in PC3 xenografts, with tumor uptake as high as 60% injected dose per gram at a protein dose of 0.1 μg per mouse. PC3 tumors in nude mice were clearly visualized with both tracers with immuno-PET and immuno-SPECT., Conclusion: hRS7 shows excellent in vivo tumor targeting in human prostate cancer xenografts. Therefore, hRS7 is a potential vehicle for targeting prostate cancer.

Unlabelled: The CXC chemokines are a family of closely related chemoattractant cytokines that bind to, attract, and activate neutrophils to variable degrees. In this study, the relationship between neutrophil-binding affinity and suitability for infection imaging was investigated in a selected group of CXC chemokines. Neutrophil-activating peptide-2 (NAP-2, 70 residues; also called CXCL7) binds with high affinity to the CXCR2 receptor on neutrophils. Recently, C-terminally truncated NAP-2-variants have been described that have enhanced neutrophil-binding affinity and neutrophil-stimulating capacity. Here, NAP-2 and its C-terminal shortened variants NAP-2(1-68), NAP-2(1-66), and NAP-2(1-63) were labeled with (99m)Tc via the hydrazinonicotinamide (HYNIC) chelator and their potential for imaging of infection was investigated in a rabbit model of infection. The CXC chemokine interleukin-8 (IL-8) was used for comparison. In addition, a series of (99m)Tc-labeled CXC chemokines were screened for their potential to image infection, including CTAP-III, GCP-2, ENA-78, PF-4, and IP-10., Methods: The receptor-binding affinity of HYNIC-conjugated NAP-2 and its analogs was compared in competitive binding assays on Jurkat cells transfected with the CXCR2 receptor gene. Biodistribution of labeled NAP-2 (analogs) and other CXC chemokines in rabbits with intramuscular Escherichia coli infections was determined both by gamma-camera imaging and by counting dissected tissues at 6 h after injection., Results: The CXCR2-binding affinity of the HYNIC-conjugated NAP-2 analogs relative to NAP-2 was as follows: NAP-2(1-68), 2.5-fold; NAP-2(1-66), 10-fold; and NAP-2(1-63), 3-fold. In the rabbit model, uptake in the abscess (in percentage injected dose per gram +/- SEM) was 0.084 +/- 0.015 for NAP-2, 0.098 +/- 0.010 for NAP-2(1-68), 0.189 +/- 0.044 for NAP-2(1-66), and 0.114 +/- 0.017 for NAP-2(1-63) at 6 h after injection. In comparison, higher uptake in the abscess was found for labeled IL-8, a modest uptake was found for GCP-2 and ENA-78, and a low uptake was found for CTAP-III, PF-4, and IP-10., Conclusion: This study showed a clear relationship between affinity to receptors on neutrophils and suitability for infection imaging. Of the NAP-2 variants, NAP-2(1-66) combined highest affinity to CXCR2 with the best characteristics for imaging. IL-8 binds to both CXCR1 and CXCR2 with high affinity and showed a superior imaging quality. The other CXC chemokines tested bind to neutrophils with lower affinity and were shown to be less suitable for infection imaging in this study.

Unlabelled: Radioimmunotherapy (RIT) can be performed with various radionuclides. We tested the stability, biodistribution, and therapeutic efficacy of various radioimmunoconjugates ((131)I, (88/90)Y, (177)Lu, and (186)Re) of chimeric antirenal cell cancer monoclonal antibody G250 (mAb cG250) in nude mice with subcutaneous renal cell cancer (RCC) tumors., Methods: The (88/90)Y and (177)Lu labeling procedures of cG250 conjugated with cyclic diethylenetriaminepentaacetic acid anhydride (cDTPA), isothiocyanatobenzyl-DTPA (SCN-Bz-DTPA), or 1,4,7,10-tetraazacyclododecanetetraacetic acid (DOTA) were characterized. Stability of the labeled conjugates in plasma at 37 degrees C was assessed. Biodistribution and therapeutic efficacy of labeled cG250 were compared in nude mice with SK-RC-52 human RCC xenografts., Results: Both SCN-Bz-DTPA and DOTA were stable in vitro (<5% release of the radiolabel during 14 and 21 d of incubation) and in vivo (uptake in bone