Molecular Imaging, vol. 14, 1,

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1. 

   Rare-Earth-Doped Nanoparticles for Short-Wave Infrared Fluorescence Bioimaging and Molecular Targeting of α_Vβ₃-Expressing Tumors

   Dominik Jan Naczynski, PhD¹, Jason H. Stafford, PhD¹, Silvan Türkcan, PhD¹, Cesare Jenkins, PhD¹, Ai Leen Koh, PhD², Conroy Sun, PhD¹³, Lei Xing, PhD¹
   Molecular Imaging, vol. 17, First Published September 24, 2018.
   Abstract

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   Abstract

   The use of short-wave infrared (SWIR) light for fluorescence bioimaging offers the advantage of reduced photon scattering and improved tissue penetration compared to traditional shorter wavelength imaging approaches. While several nanomaterials have been shown capable of generating SWIR emissions, rare-earth-doped nanoparticles (REs) have emerged as an exceptionally bright and biocompatible class of SWIR emitters. Here, we demonstrate SWIR imaging of REs for several applications, including lymphatic mapping, real-time monitoring of probe biodistribution, and molecular targeting of the α_vβ₃ integrin in a tumor model. We further quantified the resolution and depth penetration limits of SWIR light emitted by REs in a customized imaging unit engineered for SWIR imaging of live small animals. Our results indicate that SWIR light has broad utility for preclinical biomedical imaging and demonstrates the potential for molecular imaging using targeted REs.
    
2. 

   Current Practice and Emerging Molecular Imaging Technologies in Oral Cancer Screening

   Arianna Strome, BS¹, Susanne Kossatz, PhD¹, Daniella Karassawa Zanoni, MD², Milind Rajadhyaksha, PhD³, Snehal Patel, MD², Thomas Reiner, PhD¹⁴
   Molecular Imaging, vol. 17, First Published December 3, 2018.
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   Abstract

   Oral cancer is one of the most common cancers globally. Survival rates for patients are directly correlated with stage of diagnosis; despite this knowledge, 60% of individuals are presenting with late-stage disease. Currently, the initial evaluation of a questionable lesion is performed by a conventional visual examination with white light. If a lesion is deemed suspicious, a biopsy is taken for diagnosis. However, not all lesions present suspicious under visual white light examination, and there is limited specificity in differentiating between benign and malignant transformations. Several vital dyes, light-based detection systems, and cytology evaluation methods have been formulated to aid in the visualization process, but their lack of specific biomarkers resulted in high false-positive rates and thus limits their reliability as screening and guidance tools. In this review, we will analyze the current methodologies and demonstrate the need for specific intraoral imaging agents to aid in screening and diagnosis to identify patients earlier. Several novel molecular imaging agents will be presented as, by result of their molecular targeting, they aim to have high specificity for tumor pathways and can support in identifying dysplastic/cancerous lesions and guiding visualization of biopsy sites. Imaging agents that are easy to use, inexpensive, noninvasive, and specific can be utilized to increase the number of patients who are screened and monitored in a variety of different environments, with the ultimate goal of increasing early detection.
    
3. 

   Targeted Imaging of Tumor-Associated Macrophages by Cyanine 7-Labeled Mannose in Xenograft Tumors

   Chong Jiang, MD¹, Huawei Cai, PhD¹, Xiaodong Peng, MD², Ping Zhang, PhD³, Xiaoai Wu, PhD¹, Rong Tian, MD¹
   Molecular Imaging, vol. 16, First Published January 24, 2017.
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   Abstract

   Mannose receptor is considered as a hallmark of M2-oriented tumor-associated macrophages (TAMs), but its utility in TAMs was rarely reported. Therefore, deoxymannose (DM), a high-affinity ligand of mannose receptor, was labeled with near-infrared dye cyanine 7 (Cy7), and its feasibility of targeted imaging on TAMs was evaluated in vitro and in vivo. The Cy7-DM was synthesized, and its binding affinity with induced TAMs in vitro, whole-body imaging in xenograft tumor mouse model in vivo, and the cellular localization in dissected tissues were evaluated. We demonstrated a high uptake of Cy7-DM by induced M2 macrophages and TAMs in tumor tissues. In vivo near-infrared live imaging visualized abundant TAMs in tumor lesions instead of inflammatory sites by Cy7-DM imaging, and the quantity of Cy7-DM signals in tumors was significantly higher than that shown in inflammatory sites from 1 to 8 hours of imaging. Our results suggest that mannose could rapidly and specifically target TAMs and is a promising candidate for targeted diagnosis of tumor with rich TAMs.
    
4. 

   Triphenylamines Induce Cell Death Upon 2-Photon Excitation

   Rahima Chennoufi¹, Florence Mahuteau-Betzer², Patrick Tauc¹, Marie-Paule Teulade-Fichou², Eric Deprez¹
   Molecular Imaging, vol. 16, First Published June 18, 2017.
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   Abstract

   Photodynamic therapy (PDT) is a promising therapeutic method for several diseases, in particular for cancer. This approach uses a photosensitizer, oxygen, and an external light source to produce reactive oxygen species (ROS) at lethal doses to induce cell death. One drawback of current PDT is the use of visible light which has poor penetration in tissues. Such a limitation could be overcome by the use of novel organic compounds compatible with photoactivation under near-infrared light excitation. Triphenylamines (TPAs) are highly fluorescent compounds that are efficient to induce cell death upon visible light excitation (458 nm), but outside the biological spectral window. Interestingly, we recently showed that TPAs target cytoplasmic organelles of living cells, mainly mitochondria, and induce a high ROS production upon 2-photon excitation (in the 760-860 nm range), leading to a fast apoptosis process. However, we observed significant differences among the tested TPA compounds in terms of cell distribution and time courses of cell death–related events (apoptosis vs necrosis). In summary, TPAs represent serious candidates as photosensitizers that are compatible with 2-photon excitation to simultaneously trigger and imaging cell death although the relationship between their subcellular localization and the cell death mechanism involved is still a matter of debate.
    
5. 

   Combination of Fluorescence-Guided Surgery With Photodynamic Therapy for the Treatment of Cancer

   Jun He, MD¹, Leping Yang, MD¹, Wenjun Yi, MD¹, Wentao Fan, MD¹, Yu Wen, MD¹, Xiongying Miao, MD¹, Li Xiong, MD¹
   Molecular Imaging, vol. 16, First Published August 29, 2017.
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   Abstract

   Specific visualization of body parts is needed during surgery. Fluorescence-guided surgery (FGS) uses a fluorescence contrast agent for in vivo tumor imaging to detect and identify both malignant and normal tissues. There are several advantages and clinical benefits of FGS over other conventional medical imaging modalities, such as its safety, effectiveness, and suitability for real-time imaging in the operating room. Recent advancements in contrast agents and intraoperative fluorescence imaging devices have led to a greater potential for intraoperative fluorescence imaging in clinical applications. Photodynamic therapy (PDT) is an alternative modality to treat tumors, which uses a light-sensitive drug (photosensitizers) and special light to destroy the targeted tissues. In this review, we discuss the fluorescent contrast agents, some newly developed imaging devices, and the successful clinical application of FGS. Additionally, we present the combined strategy of FGS with PDT to further improve the therapeutic effect for patients with cancer. Taken together, this review provides a unique perspective and summarization of FGS.
    
6. 

   Near-Infrared Intraoperative Imaging Can Successfully Identify Malignant Pleural Mesothelioma After Neoadjuvant Chemotherapy

   Jarrod D. Predina, MD, MTR¹², Andrew Newton, MD¹³, Greg Kennedy, BA¹, M. Kenneth Lee, MD, PhD³, Sunil Singhal, MD¹²
   Molecular Imaging, vol. 16, First Published August 31, 2017.
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   Abstract

   Malignant pleural mesothelioma is a deadly disease. Complete surgical resection provides patients with the best opportunity for long-term survival. Unfortunately, identification of disease during resection can be challenging. In this report, we describe successful intraoperative utilization of the near-infrared imaging agent, indocyanine green, to help the surgeon identify malignant disease in a patient with malignant pleural mesothelioma who had previously received neoadjuvant chemotherapy. This technology may ultimately enhance the thoracic surgeon's ability to identify small disease deposits at the time of resection.
    
7. 

   Detection and Delineation of Oral Cancer With a PARP1-Targeted Optical Imaging Agent

   Susanne Kossatz¹, Wolfgang Weber¹²³, Thomas Reiner¹³
   Molecular Imaging, vol. 16, First Published August 31, 2017.
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   Abstract

   More sensitive and specific methods for early detection are imperative to improve survival rates in oral cancer. However, oral cancer detection is still largely based on visual examination and histopathology of biopsy material, offering no molecular selectivity or spatial resolution. Intuitively, the addition of optical contrast could improve oral cancer detection and delineation, but so far no molecularly targeted approach has been translated. Our fluorescently labeled small-molecule inhibitor PARPi-FL binds to the DNA repair enzyme poly(ADP-ribose)polymerase 1 (PARP1) and is a potential diagnostic aid for oral cancer delineation. Based on our preclinical work, a clinical phase I/II trial opened in March 2017 to evaluate PARPi-FL as a contrast agent for oral cancer imaging. In this commentary, we discuss why we chose PARP1 as a biomarker for tumor detection and which particular characteristics make PARPi-FL an excellent candidate to image PARP1 in optically guided applications. We also comment on the potential benefits of our molecularly targeted PARPi-FL-guided imaging approach in comparison to existing oral cancer screening adjuncts and mention the adaptability of PARPi-FL imaging to other environments and tumor types.
    
8. 

   Developing a Strategy for Interventional Molecular Imaging of Oxidized Low-Density Lipoprotein in Atherosclerosis

   Samata S. Pandey, MSc¹, Dorian O. Haskard, DM, FRCP, FMedSci¹, Ramzi Y. Khamis, MB, ChB, PhD, MRCP¹
   Molecular Imaging, vol. 16, First Published September 6, 2017.
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   Abstract

   The identification of vulnerable coronary artery atherosclerotic plaques offers the prospect of either localized or systematic therapeutic targeting in order to prevent myocardial infarction. Molecular imaging of atherosclerosis adds to morphological imaging by focusing on the immunobiology hidden in and behind the endothelium and therefore may be able to improve the identification of prospective culprit lesions. Our focus has been on identifying arterial accumulation of oxidized low-density lipoprotein (oxLDL) by exploiting advances in knowledge of vascular pathobiology. Here, we reflect on our work developing near-infrared fluorescence imaging of oxLDL using LO1, a monoclonal autoantibody generated in our laboratory. We detail progress to date and discuss our vision on taking the work through the early translational pipeline toward a multitargeted approach in imaging rupture-prone atherosclerotic plaques. Ultimately, molecular imaging of coronary arteries should be able to assess the regional risk that is specific to a lesion, which can then be used in concert with global risk factors to personalize the therapeutic strategy for patients in a way that goes beyond generalized population-based therapies.
    
9. 

   Ex Vivo and In Vivo Noninvasive Imaging of Epidermal Growth Factor Receptor Inhibition on Colon Tumorigenesis Using Activatable Near-Infrared Fluorescent Probes

   Shengli Ding, PhD¹, Randall E. Blue, MS¹, Emily Moorefield, PhD¹, Hong Yuan, PhD², Pauline K. Lund, PhD¹
   Molecular Imaging, vol. 16, First Published September 8, 2017.
   Abstract

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   Abstract

   Background:

   Near-infrared fluorescence (NIRF) imaging combined with enzyme-activatable NIRF probes has yielded promising results in cancer detection.

   Objective:

   To test whether 3-dimensional (3-D) noninvasive in vivo NIRF imaging can detect effects of epidermal growth factor receptor (EGFR) inhibitor on both polypoid and flat tumor load in azoxymethane (AOM)-induced colon tumors or tumors in Apc^Min/+ mice.

   Methods:

   The AOM-injected KK-HIJ mice received EGFR inhibitor diet or chow diet. These and Apc^Min/+ mice were given cathepsin-activatable probes (ProSense 680) before imaging. In vivo imaging was performed using quantitative tomographic NIRF imaging. Ex vivo imaging and histologic examination were performed. Dual imaging by micro computed tomography (CT) and 3D NIRF imaging was used to verify tumor location.

   Results:

   Tumor load reduction by EGFR inhibition was detected ex vivo using cathepsin B probes. In vivo imaging revealed intense activation of probes only in large tumors. Dual imaging with microCT and 3D NIRF imaging improved tumor detection in vivo.

   Conclusions:

   The 3-D NIRF imaging with ProSense 680 can detect and quantify drug effects on colon tumors ex vivo. The NIRF imaging with ProSense 680 probe has limitations as a valid nonendoscopic method for intestinal tumor detection. Combing with other imaging modalities will improve the specificity and sensitivity of intestinal tumor detection in vivo.
    
10. 

    Contrast-Enhanced Near-Infrared Optical Imaging Detects Exacerbation and Amelioration of Murine Muscular Dystrophy

    Stephen M. Chrzanowski, PhD¹, Ravneet S. Vohra, PT, PhD¹, Brittany A. Lee-McMullen, PhD², Abhinandan Batra, PT, MA, PhD³, Ray A. Spradlin, BS⁴, Jazmine Morales, BS⁴, Sean Forbes, PhD³, Krista Vandenborne, PT, PhD³, Elisabeth R. Barton, PhD⁴, Glenn A. Walter, PhD¹
    Molecular Imaging, vol. 16, First Published December 22, 2017.
    Abstract

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    Abstract

    Assessment of muscle pathology is a key outcome measure to measure the success of clinical trials studying muscular dystrophies; however, few robust minimally invasive measures exist. Indocyanine green (ICG)-enhanced near-infrared (NIR) optical imaging offers an objective, minimally invasive, and longitudinal modality that can quantify pathology within muscle by imaging uptake of ICG into the damaged muscles. Dystrophic mice lacking dystrophin (mdx) or gamma-sarcoglycan (Sgcg^−/−) were compared to control mice by NIR optical imaging and magnetic resonance imaging (MRI). We determined that optical imaging could be used to differentiate control and dystrophic mice, visualize eccentric muscle induced by downhill treadmill running, and restore the membrane integrity in Sgcg^−/− mice following adeno-associated virus (AAV) delivery of recombinant human SGCG (desAAV8hSGCG). We conclude that NIR optical imaging is comparable to MRI and can be used to detect muscle damage in dystrophic muscle as compared to unaffected controls, monitor worsening of muscle pathology in muscular dystrophy, and assess regression of pathology following therapeutic intervention in muscular dystrophies.
     
11. 

    The Drug Excipient Cyclodextrin Interacts With d-Luciferin and Interferes With Bioluminescence Imaging

    Jeyan S. Kumar, MSc¹, Lisa M. Miller Jenkins, PhD¹, Michael M. Gottesman, MD¹, Matthew D. Hall, PhD¹²
    Molecular Imaging, vol. 15, First Published January 28, 2016.
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    Abstract

    Cyclodextrins are well-characterized, barrel-shaped molecules that can solubilize organic small molecules in aqueous solution via host–guest interactions. As such, cyclodextrins are used as excipients for experimental therapeutics in vivo. We observed unanticipated modifications to bioluminescence imaging (BLI) signal intensity when 2-hydroxy-propyl-β-cyclodextrin (HPCD) was coinjected as an excipient. We hypothesized that HPCD binds d-luciferin and interferes with the BLI signal. Using luciferase-expressing cell lines, we showed that HPCD lowers the BLI signal in a concentration-dependent manner. Flow cytometry revealed that HPCD resulted in reduced cellular accumulation of d-luciferin, and mass spectrometry revealed d-luciferin HPCD species, confirming a direct interaction. In vivo imaging using a luciferase mouse model demonstrated that HPCD reduced luciferin-mediated BLI compared to luciferin alone. The implications of using HPCD as an excipient in BLI studies are discussed.
     
12. 

    Imaging Reporters for Proteasome Activity Identify Tumor- and Metastasis-Initiating Cells

    Amanda C. Stacer*, Hanxiao Wang*, Joseph Fenner, Joseph S. Dosch, Anna Salomonnson, Kathryn E. Luker, Gary D. Luker, Alnawaz Rehemtulla, Brian D. Ross
    Molecular Imaging, vol. 14, 8, First Published August 1, 2015.
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    Abstract

    Tumor-initiating cells, also designated as cancer stem cells, are proposed to constitute a subpopulation of malignant cells central to tumorigenesis, metastasis, and treatment resistance. We analyzed the activity of the proteasome, the primary organelle for targeted protein degradation, as a marker of tumor- and metastasis-initiating cells. Using human and mouse breast cancer cells expressing a validated fluorescent reporter, we found a small subpopulation of cells with low proteasome activity that divided asymmetrically to produce daughter cells with low or high proteasome activity. Breast cancer cells with low proteasome activity had greater local tumor formation and metastasis in immunocompromised and immunocompetent mice. To allow flexible labeling of cells, we also developed a new proteasome substrate based on HaloTag technology. Patient-derived glioblastoma cells with low proteasome activity measured by the HaloTag reporter show key phenotypes associated with tumor-initiating cells, including expression of a stem cell transcription factor, reconstitution of the original starting population, and enhanced neurosphere formation. We also show that patient-derived glioblastoma cells with low proteasome activity have higher frequency of tumor formation in mouse xenografts. These studies support proteasome function as a tool to investigate tumor- and metastasis-initiating cancer cells and a potential biomarker for outcomes in patients with several different cancers.
     
13. 

    A Novel Endoscopic Cerenkov Luminescence Imaging System for Intraoperative Surgical Navigation

    Tianming Song, Xia Liu, Yawei Qu, Haixiao Liu, Chengpeng Bao, Chengcai Leng, Zhenhua Hu, Kun Wang, Jie Tian
    Molecular Imaging, vol. 14, 8, First Published August 1, 2015.
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    Abstract

    Cerenkov luminescence imaging is an emerging optical technique for imaging the distribution of radiopharmaceuticals in vivo. However, because of the light scattering effect, it cannot obtain optical information from deep internal organs. To overcome this challenge, we established a novel endoscopic Cerenkov luminescence imaging system that used a clinically approved laparoscope and an electron-multiplying charge-coupled device camera. We assessed the performance of the system through a series of in vitro and in vivo experiments. The results demonstrated superior superficial imaging resolution (0.1 mm), a large field of view (500 mm² with 10 mm imaging distance), and superb imaging sensitivity (imaging 1 μCi) of our system. It captured the weak Cerenkov signal from internal organs successfully and was applied to intraoperative surgical navigation of tumor resection. It offered objective information of the tumor location and tumor residual during the surgical operation. This technique holds great potential for clinical translation.
     
14. 

    Monitoring Disease Progression and Therapeutic Response in a Disseminated Tumor Model for Non-Hodgkin Lymphoma by Bioluminescence Imaging

    Margarethe Köberle, Kristin Müller, Manja Kamprad, Friedemann Horn, Markus Scholz
    Molecular Imaging, vol. 14, 6, First Published July 1, 2015.
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    Abstract

    Xenograft tumor models are widely studied in cancer research. Our aim was to establish and apply a model for aggressive CD20-positive B-cell non-Hodgkin lymphomas, enabling us to monitor tumor growth and shrinkage in a noninvasive manner. By stably transfecting a luciferase expression vector, we created two bioluminescent human non-Hodgkin lymphoma cell lines, Jeko1(luci) and OCI-Ly3(luci), that are CD20 positive, a prerequisite to studying rituximab, a chimeric anti-CD20 antibody. To investigate the therapy response in vivo, we established a disseminated xenograft tumor model injecting these cell lines in NOD/SCID mice. We observed a close correlation of bioluminescence intensity and tumor burden, allowing us to monitor therapy response in the living animal. Cyclophosphamide reduced tumor burden in mice injected with either cell line in a dose-dependent manner. Rituximab alone was effective in OCI-Ly3(luci)-injected mice and acted additively in combination with cyclophosphamide. In contrast, it improved the therapeutic outcome of Jeko1(luci)-injected mice only in combination with cyclophosphamide. We conclude that well-established bioluminescence imaging is a valuable tool in disseminated xenograft tumor models. Our model can be translated to other cell lines and used to examine new therapeutic agents and schedules.
     
15. 

    In Vivo Imaging Study of Angiogenesis in a Channelized Porous Scaffold

    Margherita Tamplenizza*, Alessandro Tocchio*, Irini Gerges*, Federico Martello, Cristina Martelli, Luisa Ottobrini, Giovanni Lucignani, Paolo Milani, Cristina Lenardi
    Molecular Imaging, vol. 14, 6, First Published May 1, 2015.
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    Abstract

    The main scientific issue hindering the development of tissue engineering technologies is the lack of proper vascularization. Among the various approaches developed for boosting vascularization, scaffold design has attracted increasing interest over the last few years. The aim of this article is to illustrate a scaffold design strategy for enhancing vascularization based on sacrificial microfabrication of embedded microchannels. This approach was combined with an innovative poly(ether urethane urea) (PEUtU) porous scaffold to provide an alternative graft substitute material for the treatment of tissue defects. Fluorescent and chemiluminescent imaging combined with computed tomography were used to study the behavior of the scaffold composition within living subjects by analyzing angiogenesis and inflammation processes and observing the variation in x-ray absorption, respectively. For this purpose, an IntegriSense 680 probe was used in vivo for the localization and quantification of integrin α_vβ₃, due to its critical involvement in angiogenesis, and a XenoLight RediJect Inflammation Probe for the study of the decline in inflammation progression during healing. Overall, the collected data suggest the advantages of embedding a synthetic vascular network into a PEUtU porous matrix to enhance in vivo tissue integration, maturation, and regeneration. Moreover, our imaging approach proved to be an efficient and versatile tool for scaffold in vivo testing.
     
16. 

    Monitoring Tumor Targeting and Treatment Effects of IRDye 800CW and GX1-Conjugated Polylactic Acid Nanoparticles Encapsulating Endostar on Glioma by Optical Molecular Imaging

    Yaqian Li*, Yang Du*, Xia Liu, Qian Zhang, Lijia Jing, Xiaolong Liang, Chongwei Chi, Zhifei Dai, Jie Tian
    Molecular Imaging, vol. 14, 7, First Published July 1, 2015.
    Abstract

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    Abstract

    Molecular imaging used in cancer diagnosis and therapeutic response monitoring is important for glioblastoma (GBM) research. Antiangiogenic therapy currently is one of the emerging approaches for GBM treatment. In this study, a multifunctional nanoparticle was fabricated that can facilitate the fluorescence imaging of tumor and deliver a therapeutic agent to the tumor region in vivo and therefore possesses broad application in cancer diagnosis and treatment. This particle was polylactic acid (PLA) nanoparticles encapsulating Endostar, which was further conjugated with GX1 peptide and the near-infrared (NIR) dye IRDye 800CW (IGPNE). We demonstrated noninvasive angiogenesis targeting and therapy of IGPNE on U87MG xenografts in vivo using dual-modality optical molecular imaging including NIR fluorescence molecular imaging (FMI) and bioluminescence imaging (BLI). The NIR FMI results demonstrated that IGPNE had more accumulation to the tumor site compared to free IRDye 800CW. To further evaluate the antitumor treatment efficacy of IGPNE, BLI and immunohistochemistry analysis were performed on tumor-bearing mice. With the aid of molecular imaging, the results confirmed that IGPNE enhanced antitumor treatment efficacy compared to free Endostar. In conclusion, IGPNE realizes real-time imaging of U87MG tumors and improves the antiangiogenic therapeutic efficacy in vivo.
     
17. 

    Optimization of Dual-Labeled Antibodies for Targeted Intraoperative Imaging of Tumors

    Mark Rijpkema, Desirée L. Bos, Alex S. Cornelissen, Gerben M. Franssen, David M. Goldenberg, Wim J. Oyen, Otto C. Boerman
    Molecular Imaging, vol. 14, 7, First Published July 1, 2015.
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    Abstract

    For intraoperative imaging, antibodies labeled with both a radionuclide and a fluorophore may be used to tag the tumor lesion with a radiolabel and a fluorescent signal at high tumor to background ratios. However, labeling antibodies with fluorescent moieties may affect the in vivo behavior of the antibody depending on the dye to antibody substitution ratio. To investigate the optimal substitution ratio for use in dual-modality image-guided surgery, we conjugated three different antibodies, MN-14 (anti-CEACAM5), girentuximab (anti-CAIX), and cetuximab (anti-EGFR), with both diethylene triamine pentaacetic acid (DTPA, for labeling with ¹¹¹In) and IRdye 800CW at dye to antibody ratios of 0, 1, 1.5, 2, and 3 and assessed in vivo behavior. Biodistribution studies showed that at high dye to antibody ratios, liver uptake of the dual-labeled antibodies increased, whereas tumor uptake decreased. Conversely, very low ratios may not be optimal either because in that case, only a few antibody molecules will be dual-labeled (i.e., contain both a DTPA and an IRDye 800CW moiety), which may complicate interpretation of dual-modality data. The present study shows that, provided that the chelator to antibody ratio is high enough, a dye to antibody ratio in the range of 1 to 1.5 is optimal for antibody-targeted dual-modality imaging applications. However, the optimal configuration is antibody dependent and should be determined for each dual-labeled antibody individually.
     
18. 

    X-Ray Fluorescence Microscopy Demonstrates Preferential Accumulation of a Vanadium-Based Magnetic Resonance Imaging Contrast Agent in Murine Colonic Tumors

    Devkumar Mustafi, Jesse Ward, Urszula Dougherty, Marc Bissonnette, John Hart, Stefan Vogt, Gregory S. Karczmar
    Molecular Imaging, vol. 14, 5, First Published May 1, 2015.
    Abstract

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    Abstract

    Contrast agents that specifically enhance cancers on magnetic resonance imaging (MRI) will allow earlier detection. Vanadium-based chelates (VCs) selectively enhance rodent cancers on MRI, suggesting selective uptake of VCs by cancers. Here we report x-ray fluorescence microscopy (XFM) of VC uptake by murine colon cancer. Colonic tumors in mice treated with azoxymethane/dextran sulfate sodium were identified by MRI. Then a gadolinium-based contrast agent and a VC were injected intravenously; mice were sacrificed and colons sectioned. VC distribution was sampled at 120 minutes after injection to evaluate the long-term accumulation. Gadolinium distribution was sampled at 10 minutes after injection due to its rapid washout. XFM was performed on 72 regions of normal and cancerous colon from five normal mice and four cancer-bearing mice. XFM showed that all gadolinium was extracellular, with similar concentrations in colon cancers and normal colon. In contrast, the average VC concentration was twofold higher in cancers versus normal tissue (p < .002). Cancers also contained numerous "hot spots" with intracellular VC concentrations sixfold higher than the concentration in normal colon (p < .0001). No hot spots were detected in normal colon. This is the first direct demonstration that VCs selectively accumulate in cancer cells and thus may improve cancer detection.
     
19. 

    Near-Infrared Fluorescent Digital Pathology for the Automation of Disease Diagnosis and Biomarker Assessment

    Summer L. Gibbs, Elizabeth Genega, Jeffery Salemi, Vida Kianzad, Haley L. Goodwill, Yang Xie, Rafiou Oketokoun, Parmeshwar Khurd, Ali Kamen, John V. Frangioni
    Molecular Imaging, vol. 14, 5, First Published June 1, 2015.
    Abstract

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    Abstract

    Hematoxylin-eosin (H&E) staining of tissue has been the mainstay of pathology for more than a century. However, the learning curve for H&E tissue interpretation is long, whereas intra- and interobserver variability remain high. Computer-assisted image analysis of H&E sections holds promise for increased throughput and decreased variability but has yet to demonstrate significant improvement in diagnostic accuracy. Addition of biomarkers to H&E staining can improve diagnostic accuracy; however, coregistration of immunohistochemical staining with H&E is problematic as immunostaining is completed on slides that are at best 4 μm apart. Simultaneous H&E and immunostaining would alleviate coregistration problems; however, current opaque pigments used for immunostaining obscure H&E. In this study, we demonstrate that diagnostic information provided by two or more independent wavelengths of near-infrared (NIR) fluorescence leave the H&E stain unchanged while enabling computer-assisted diagnosis and assessment of human disease. Using prostate cancer as a model system, we introduce NIR digital pathology and demonstrate its utility along the spectrum from prostate biopsy to whole mount analysis of H&E-stained tissue.
     
20. 

    Breast Cancer Imaging Using the Near-Infrared Fluorescent Agent, CLR1502

    Melissa L. Korb, Jason M. Warram, Joseph Grudzinski, Jamey Weichert, Justin Jeffery, Eben L. Rosenthal
    Molecular Imaging, vol. 14, 1, First Published January 1, 2015.
    Abstract

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    Abstract

    Positive margins after breast conservation surgery represent a significant problem in the treatment of breast cancer. The near-infrared fluorescence agent CLR1502 (Cellectar Biosciences, Madison, WI) was studied in a preclinical breast cancer model to determine imaging properties and ability to detect small islands of malignancy. Nude mice bearing human breast cancer flank xenografts were given a systemic injection of CLR1502, and imaging was performed using LUNA (Novadaq Technologies Inc., Richmond, BC) and Pearl Impulse (LI-COR Biosciences, Lincoln, NE) devices. Normal tissues were examined for fluorescence signal, and conventional and fluorescence histology was performed using the Odyssey scanner. Peak tumor to background ratio occurred 2 days after injection with CLR1502. The smallest amount of tumor that was imaged and detected using these devices was 1.9 mg, equivalent to 1.9 × 10⁶ cells. The highest fluorescence signal was seen in tumor and normal lymph node tissue, and the lowest fluorescence signal was seen in muscle and plasma. Human breast cancer tumors can be imaged in vivo with multiple optical imaging platforms using CLR1502. This pilot study supports further investigations of this fluorescent agent for improving surgical resection of malignancies, with the goal of eventual clinical translation.
     
    

Molecular Imaging

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1. 

   Ultrasound Detection of Myocardial Ischemic Memory Using an E-Selectin Targeting Peptide Amenable to Human Application

   Xiaoping Leng*, Jianjun Wang*, Andrew Carson, Xucai Chen, Huili Fu, Susanne Ottoboni, William R. Wagner, Flordeliza S. Villanueva
   Molecular Imaging, vol. 13, 4, First Published June 1, 2014.
   Abstract

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   Abstract

   Vascular endothelial leukocyte adhesion molecules, such as E-selectin, are acutely upregulated in myocardial ischemia/reperfusion and are thus "ischemic memory" biomarkers for recent cardiac ischemia. We sought to develop an ultrasound molecular imaging agent composed of microbubbles (MBs) targeted to E-selectin to enable the differential diagnosis of myocardial ischemia in patients presenting with chest pain of unclear etiology. Biodegradable polymer MBs were prepared bearing a peptide with specific human E-selectin affinity (MB_ESEL). Control MBs had scrambled peptide (MB_CTL) or nonspecific IgG (MB_IgG). MB_ESEL adhesion to activated rat endothelial cells (ECs) was confirmed in vitro in a flow system and in vivo with intravital microscopy of rat cremaster microcirculation. Ultrasound molecular imaging of recent myocardial ischemia was performed in rats 4 hours after transient (15 minutes) coronary occlusion. MB_ESEL adhesion was higher to inflamed versus normal ECs in vitro; there was no difference in MB_CTL or MB_IgG adhesion to inflamed versus normal ECs. There was greater adhesion of MB_ESEL to inflamed versus noninflamed microcirculation and minimal adhesion of MB_CTL or MB_IgG under any condition. Ultrasound imaging after injection of MB_SEL demonstrated persistent contrast enhancement of the previously ischemic region. Videointensity in postischemic myocardium after MB_ESEL was higher than that in the nonischemic bed (11.6 ± 2.7 dB vs 3.6 ± 0.8 dB, p < .02) and higher than that after MB_CTL (4.0 ± 1.0 dB, p < .03) or MB_IgG (1.7 ± 0.1 dB, p < .03). MBs targeted to E-selectin via a short synthetic peptide with human E-selectin binding affinity enables echocardiographic detection of recent ischemia, setting the stage for clinical myocardial ischemic memory imaging to identify acute coronary syndromes.
    
2. 

   The Antiangiogenic Effects of a Vascular Endothelial Growth Factor Decoy Receptor Can Be Monitored in Vivo Using Contrast-Enhanced Ultrasound Imaging

   Flemming Forsberg, Raymond J. Ro, Andrew Marshall, Ji-Bin Liu, See-Ying Chiou, Daniel A. Merton, Priscilla Machado, Adam P. Dicker, Levon N. Nazarian
   Molecular Imaging, vol. 13, 2, First Published March 1, 2014.
   Abstract

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   Abstract

   The development of antiangiogenic therapies has stimulated interest in noninvasive imaging methods to monitor response. We investigated whether the effects of a vascular endothelial growth factor decoy receptor (VEGF Trap, Regeneron Pharmaceuticals, Tarrytown, NY) could be monitored in vivo using contrast-enhanced ultrasonography (CEUS). Twenty nude mice (in two groups) were implanted with a human melanoma cell line (DB-1). The active group received VEGF Trap (4 × 25 mg/kg over 2 weeks), whereas the control group received an inactive protein. An ultrasound contrast agent was injected followed by power Doppler imaging (PDI) and pulse inversion harmonic imaging (PIHI; regular and intermittent). Specimens were sectioned in the same planes as the images and stained for endothelial cells (CD31), cyclooxygenase-2 (COX-2), VEGF, and hypoxia (Glut1). Measures of tumor vascularity obtained with the different imaging modes were compared to immunohistochemical markers of angiogenesis. Mean tumor volume was smaller in the active group than in the control group (656 ± 225 vs 1,160 ± 605 mm³). Overall, PDI and VEGF correlated (r = .34; p = .037). Vascularity decreased from control to treated mice with intermittent PIHI, as did the expression of CD31 and COX-2 (p # .02), whereas VEGF increased (p = .05). CEUS appears to allow in vivo monitoring of the antiangiogenic effects of VEGF Trap in the DB-1 human melanoma xenograft model.
    
3. 

   Ultrasound Backscatter Microscopy Image-Guided Intraventricular Gene Delivery at Murine Embryonic Age 9.5 and 10.5 Produces Distinct Transgene Expression Patterns at the Adult Stage

   Jiwon Jang, Jyhyun Ahn, Nayeon Lee, Seong-Tae Kim, Dae-Hyuk Kweon, Jae Youl Cho, Kye Won Park, Sunyoung Kim, Keejung Yoon
   Molecular Imaging, vol. 12, 8, First Published November 1, 2013.
   Abstract

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   Abstract

   In utero injection of a retroviral vector into the embryonic telencephalon aided by ultrasound backscatter microscopy permits introduction of a gene of interest at an early stage of development. In this study, we compared the tissue distribution of gene expression in adult mice injected with retroviral vectors at different embryonic ages in utero. Following ultrasound image-guided gene delivery (UIGD) into the embryonic telencephalon, adult mice were subjected to whole-body luciferase imaging and immunohistochemical analysis at 6 weeks and 1 year postinjection. Luciferase activity was observed in a wide range of tissues in animals injected at embryonic age 9.5 (E9.5), whereas animals injected at E10.5 showed brain-localized reporter gene expression. These results suggest that mouse embryonic brain creates a closed and impermeable structure around E10. Therefore, by injecting a transgene before or after E10, transgene expression can be manipulated to be local or systemic. Our results also provide information that widens the applicability of UIGD beyond neuroscience studies.
    
4. 

   In Vivo Demonstration of Cancer Molecular Imaging with Ultrasound Radiation Force and Buried-Ligand Microbubbles

   Mark A. Borden, Jason E. Streeter, Shashank R. Sirsi, Paul A. Dayton
   Molecular Imaging, vol. 12, 6, First Published September 1, 2013.
   Abstract

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   Abstract

   In designing targeted contrast agent materials for imaging, the need to present a targeting ligand for recognition and binding by the target is counterbalanced by the need to minimize interactions with plasma components and to avoid recognition by the immune system. We have previously reported on a microbubble imaging probe for ultrasound molecular imaging that uses a buried-ligand surface architecture to minimize unwanted interactions and immunogenicity. Here we examine for the first time the utility of this approach for in vivo molecular imaging. In accordance with previous results, we showed a threefold increase in circulation persistence through the tumor of a fibrosarcoma model in comparison with controls. The buried-ligand microbubbles were then activated for targeted adhesion through the application of noninvasive ultrasound radiation forces applied specifically to the tumor region. Using a clinical ultrasound scanner, microbubbles were activated, imaged, and silenced. The results showed visually conspicuous images of tumor neovasculature and a twofold increase in ultrasound radiation force enhancement of acoustic contrast intensity for buried-ligand microbubbles, whereas no such increase was found for exposed-ligand microbubbles. We therefore conclude that the use of acoustically active buried-ligand microbubbles for ultrasound molecular imaging bridges the demand for low immunogenicity with the necessity of maintaining targeting efficacy and imaging conspicuity in vivo.
    
5. 

   Shear Forces from Flow Are Responsible for a Distinct Statistical Signature of Adherent Microbubbles in Large Vessels

   Shiying Wang, F. William Mauldin, Jr, Alexander L. Klibanov, John A. Hossack
   Molecular Imaging, vol. 12, 6, First Published September 1, 2013.
   Abstract

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   Abstract

   Real-time ultrasound-based targeted molecular imaging in large blood vessels holds promise for early detection and diagnosis of stroke risk by identifying early markers for atherosclerosis prior to plaque formation. Singular spectrum-based targeted molecular (SiSTM) imaging is a recently proposed method that uses changes in statistical dimensionality—quantified by a normalized singular spectrum area (NSSA)—to image receptor-ligand–bound adherent microbubbles. However, the precise physical mechanism responsible for the distinct statistical signature was previously unknown. In this study, in vitro flow phantom experiments were performed to elucidate the physical mechanism in large blood vessel environments. In the absence of flow, an increase in the NSSA of adherent microbubbles with respect to tissue was not observed with increased microbubble concentration or pulse length (p > .23; n = 5) but was observed with increased flow rate (p < .01; n = 10). When observing the dynamics of the adherent microbubble statistics, a good correlation was observed between the NSSA and the derivative of image intensity (R² > .97). In addition, a monotonic relationship between the NSSA and decorrelation was demonstrated. These findings confirm the hypothesis that the statistical signature of adherent microbubbles is derived from frame-to-frame decorrelation, which is induced by flow shear forces.

Oncogenesis - nature.com

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