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Hegde S, Krisnawan VE, Herzog BH, Zuo C, Breden MA, Knolhoff BL, Hogg GD, Tang JP, Baer JM, Mpoy C, Lee KB, Alexander KA, Rogers BE, Murphy KM, Hawkins WG, Fields RC, DeSelm CJ, Schwarz JK, DeNardo DG. Dendritic Cell Paucity Leads to Dysfunctional Immune Surveillance in Pancreatic Cancer. Cancer Cell 2020; 37:289-307.e9. [PMID: 32183949 PMCID: PMC7181337 DOI: 10.1016/j.ccell.2020.02.008] [Citation(s) in RCA: 233] [Impact Index Per Article: 58.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 12/04/2019] [Accepted: 02/14/2020] [Indexed: 12/26/2022]
Abstract
Here, we utilized spontaneous models of pancreatic and lung cancer to examine how neoantigenicity shapes tumor immunity and progression. As expected, neoantigen expression during lung adenocarcinoma development leads to T cell-mediated immunity and disease restraint. By contrast, neoantigen expression in pancreatic ductal adenocarcinoma (PDAC) results in exacerbation of a fibro-inflammatory microenvironment that drives disease progression and metastasis. Pathogenic TH17 responses are responsible for this neoantigen-induced tumor progression in PDAC. Underlying these divergent T cell responses in pancreas and lung cancer are differences in infiltrating conventional dendritic cells (cDCs). Overcoming cDC deficiency in early-stage PDAC leads to disease restraint, while restoration of cDC function in advanced PDAC restores tumor-restraining immunity and enhances responsiveness to radiation therapy.
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Adamo L, Rocha-Resende C, Lin CY, Evans S, Williams J, Dun H, Li W, Mpoy C, Andhey PS, Rogers BE, Lavine K, Kreisel D, Artyomov M, Randolph GJ, Mann DL. Myocardial B cells are a subset of circulating lymphocytes with delayed transit through the heart. JCI Insight 2020; 5:134700. [PMID: 31945014 DOI: 10.1172/jci.insight.134700] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 01/09/2020] [Indexed: 12/17/2022] Open
Abstract
Current models of B lymphocyte biology posit that B cells continuously recirculate between lymphoid organs, without accumulating in peripheral healthy tissues. Nevertheless, B lymphocytes are one of the most prevalent leukocyte populations in the naive murine heart. To investigate this apparent inconsistency in the literature, we conducted a systematic analysis of myocardial B cell ontogeny, trafficking dynamics, histology, and gene expression patterns. We found that myocardial B cells represent a subpopulation of circulating B cells that make close contact with the microvascular endothelium of the heart and arrest their transit as they pass through the heart. The vast majority (>95%) of myocardial B cells remain intravascular, whereas few (<5%) myocardial B cells cross the endothelium into myocardial tissue. Analyses of mice with B cell deficiency or depletion indicated that B cells modulate the myocardial leukocyte pool composition. Analysis of B cell-deficient animals suggested that B cells modulate myocardial growth and contractility. These results transform our current understanding of B cell recirculation in the naive state and reveal a previously unknown relationship between B cells and myocardial physiology. Further work will be needed to assess the relevance of these findings to other organs.
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Floberg JM, Wang L, Bandara N, Rashmi R, Mpoy C, Garbow JR, Rogers BE, Patti GJ, Schwarz JK. Alteration of Cellular Reduction Potential Will Change 64Cu-ATSM Signal With or Without Hypoxia. J Nucl Med 2019; 61:427-432. [PMID: 31586008 DOI: 10.2967/jnumed.119.230805] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 09/04/2019] [Indexed: 01/11/2023] Open
Abstract
Therapies targeting reductive/oxidative (redox) metabolism hold potential in cancers resistant to chemotherapy and radiation. A redox imaging marker would help identify cancers susceptible to redox-directed therapies. Copper(II)-diacetyl-bis(4-methylthiosemicarbazonato) (Cu-ATSM) is a PET tracer developed for hypoxia imaging that could potentially be used for this purpose. We aimed to demonstrate that Cu-ATSM signal is dependent on cellular redox state, irrespective of hypoxia. Methods: We investigated the relationship between 64Cu-ATSM signal and redox state in human cervical and colon cancer cells. We altered redox state using drug strategies and single-gene mutations in isocitrate dehydrogenases (IDH1/2). Concentrations of reducing molecules were determined by spectrophotometry and liquid chromatography-mass spectrometry and compared with 64Cu-ATSM signal in vitro. Mouse models of cervical cancer were used to evaluate the relationship between 64Cu-ATSM signal and levels of reducing molecules in vivo, as well as to evaluate the change in 64Cu-ATSM signal after redox-active drug treatment. Results: A correlation exists between baseline 64Cu-ATSM signal and cellular concentration of glutathione, nicotinamide adenine dinucleotide phosphate (NADPH), and nicotinamide adenine dinucleotide (NADH). Altering NADH and NADPH metabolism using drug strategies and IDH1 mutations resulted in significant changes in 64Cu-ATSM signal under normoxic conditions. Hypoxia likewise changed 64Cu-ATSM signal, but treatment of hypoxic cells with redox-active drugs resulted in a more dramatic change than hypoxia alone. A significant difference in NADPH was seen between cervical tumor orthotopic implants in vivo, without a corresponding difference in 64Cu-ATSM signal. After treatment with β-lapachone, there was a change in 64Cu-ATSM signal in xenograft tumors smaller than 50 mg but not in larger tumors. Conclusion: 64Cu-ATSM signal reflects redox state, and altering redox state impacts 64Cu-ATSM metabolism. Our animal data suggest there are other modulating factors in vivo. These findings have implications for the use of 64Cu-ATSM as a predictive marker for redox therapies, though further in vivo work is needed.
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Muz B, Bandara N, Mpoy C, Sun J, Alhallak K, Azab F, Rogers BE, Azab AK. CXCR4-targeted PET imaging using 64Cu-AMD3100 for detection of Waldenström Macroglobulinemia. Cancer Biol Ther 2019; 21:52-60. [PMID: 31571524 DOI: 10.1080/15384047.2019.1665405] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Objective: Waldenström Macroglobulinemia (WM) is a rare B-cell malignancy characterized by secretion of immunoglobulin M and cancer infiltration in the bone marrow. Chemokine receptor such as CXCR4 and hypoxic condition in the bone marrow play crucial roles in cancer cell trafficking, homing, adhesion, proliferation, survival, and drug resistance. Herein, we aimed to use CXCR4 as a potential biomarker to detect hypoxic-metastatic WM cells in the bone marrow and in the circulation by using CXCR4-detecting radiopharmaceutical.Methods: We radiolabeled a CXCR4-inhibitor (AMD3100) with 64Cu and tested its binding to WM cells with different levels of CXCR4 expression using gamma counter in vitro. The accumulation of this radiopharmaceutical tracer was tested in vivo in subcutaneous and intratibial models using PET/CT scan. In addition, PBMCs spiked with different amounts of WM cells ex vivo were detected using gamma counting.Results: In vitro, 64Cu-AMD3100 binding to WM cell lines demonstrated a direct correlation with the level of CXCR4 expression, which was increased in cells cultured in hypoxia with elevated levels of CXCR4, and decreased in cells with CXCR4 and HIF-1α knockout. Moreover, 64Cu-AMD3100 detected localized and circulating CXCR4high WM cells with high metastatic potential.Conclusions: In conclusion, we developed a molecularly targeted system, 64Cu-AMD3100, which binds to CXCR4 and specifically detects WM cells with hypoxic phenotype and metastatic potential in the subcutaneous and intratibial models. These preliminary findings using CXCR4-detecting PET radiopharmaceutical tracer indicate a potential technology to predict high-risk patients for the progression to WM due to metastatic potential.
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Bandara N, Li Y, Diebolder P, Mpoy C, Gu X, Khanal P, Deng S, Rogers BE, Savage PB. Translation of ceragenin affinity for bacteria to an imaging reagent for infection. RSC Adv 2019; 9:14472-14476. [PMID: 32864109 PMCID: PMC7451630 DOI: 10.1039/c9ra02226k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Responses to bacterial infections may be manifest systemically without evidence of the location of the infection site. A rapid means of pinpointing infection sites would be useful in providing effective and possibly localized treatment. Successful means of identifying infection sites would require two components: (1) a molecule capable of recognizing bacteria and (2) a means of communicating recognition. For the recognition element, we used a ceragenin, a small molecule with affinity for bacterial membranes that was designed as a mimic of endogenous antimicrobial peptides. For the communication element, we used 64Cu, which is a positron emitter. By conjugating a copper chelating group to the ceragenin, the two elements were combined. Chelation of 64Cu by the conjugate was effective and provided a stable complex that allowed in vivo imaging. When administered to mice in a thigh infection model, the 64Cu-labeled conjugate accumulated at the site of infection (right thigh) without accumulation at the complementary site (left thigh). This conjugate may provide a means of identifying infection sites in patients presenting general signs of infection without localized symptoms. Infection imaged via autoradiography with ceragenin conjugated to a copper radiolabel.![]()
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Diebolder P, Vazquez-Pufleau M, Bandara N, Mpoy C, Raliya R, Thimsen E, Biswas P, Rogers BE. Aerosol-synthesized siliceous nanoparticles: impact of morphology and functionalization on biodistribution. Int J Nanomedicine 2018; 13:7375-7393. [PMID: 30519021 PMCID: PMC6237247 DOI: 10.2147/ijn.s177350] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Introduction Siliceous nanoparticles (NPs) have been extensively studied in nanomedicine due to their high biocompatibility and immense biomedical potential. Although numerous technologies have been developed, the synthesis of siliceous NPs for biomedical applications mainly relies on a few core technologies predominantly intended to produce spherical-shaped NPs. Methods In this context, the impact of different morphologies of siliceous NPs on biodistribution in vivo is limited. In the present study, we developed a novel technique based on an aerosol silane reactor to produce sintered silicon NPs of similar size but different surface areas due to distinct spherical subunits. Silica-converted particles were functionalized for radiolabeling with copper-64 (64Cu) to systematically analyze their behavior in the passive targeting of A431 tumor xenografts in mice after intravenous injection. Results While low nonspecific uptake was observed in most organs, the majority of particles were accumulated in the liver, spleen, and lung. Depending on the morphologies and function-alization, significant differences in the uptake profiles of the particles were observed. In terms of tumor uptake, spherical shapes with lower surface areas showed the highest accumulation and tumor-to-blood ratios of all investigated particles. Conclusion This study highlights the importance of shape and fuctionalization of siliceous NPs on organ and tumor accumulation as significant factors for biomedical applications.
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Zhou D, Xu J, Mpoy C, Chu W, Kim SH, Li H, Rogers BE, Katzenellenbogen JA. Preliminary evaluation of a novel 18F-labeled PARP-1 ligand for PET imaging of PARP-1 expression in prostate cancer. Nucl Med Biol 2018; 66:26-31. [PMID: 30195072 DOI: 10.1016/j.nucmedbio.2018.08.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 08/01/2018] [Accepted: 08/19/2018] [Indexed: 11/25/2022]
Abstract
INTRODUCTION Poly (ADP-ribose) polymerase-1 (PARP-1) plays many roles in prostate cancer (PC), such as mediating DNA damage repair, transcriptional regulation and nuclear hormone receptor signaling. Because of this, PARP-1 has been targeted for therapy in PC, and non-invasive imaging of PARP-1 could help predict which patients are likely to respond to such therapy. Several PARP-1 positron emission tomography (PET) imaging agents have been developed and show promise for imaging PARP-1 expression in breast, brain, and lung cancer in small animals, but not as yet in prostate cancer. [18F]WC-DZ-F is an analogue of [18F]FluorThanatrace (FTT) and [125I]KX1, which are well-established PARP-1 ligands for measuring PARP-1 expression. Herein, we evaluated the potential of [18F]WC-DZ-F for the imaging PARP-1 expression in PC. METHODS [18F]WC-DZ-F was synthesized by a two-step sequence. [18F]WC-DZ-F was evaluated by in vitro uptake studies in PC-3 cells and by in vivo biodistribution and microPET imaging using PC-3 tumor xenografts. Ex vivo autoradiography of PC-3 tumors after microPET imaging was also performed. RESULTS [18F]WC-DZ-F has high, PARP-1-specific uptake in PC-3 cells. In the microPET imaging study, [18F]WC-DZ-F accumulated in PC-3 xenograft tumors over 2 h, and the uptake was significantly reduced by blocking with olaparib. PC-3 tumors were clearly visualized in microPET images, and the imaging results were further confirmed by autoradiography of PC-3 tumors ex vivo. In the biodistribution study [18F]WC-DZ-F washed out quickly from most tissues within 2 h, except for the liver in which the uptake was not blockable by olaparib. CONCLUSIONS We synthesized a novel PARP-1 radioligand, [18F]WC-DZ-F. The preliminary evaluation of [18F]WC-DZ-F indicates that it is a suitable PET imaging agent for measuring PARP-1 expression in prostate cancer and should be applicable to other types of cancers.
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Bandara N, Jacobson O, Mpoy C, Chen X, Rogers BE. Novel Structural Modification Based on Evans Blue Dye to Improve Pharmacokinetics of a Somastostatin-Receptor-Based Theranostic Agent. Bioconjug Chem 2018; 29:2448-2454. [PMID: 29927587 DOI: 10.1021/acs.bioconjchem.8b00341] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The development of somastatin (SS) peptide analogues for the detection and treatment of neuroendocrine tumors has been successful with the recent FDA approval of 68Ga-DOTA-TATE and 177Lu-DOTA-TATE. The structure of these peptide constructs contains the peptide binding motif that binds to the receptor with high affinity, a chelator to complex the radioactive metal, and a linker between the peptide and chelator. However, these constructs suffer from rapid blood clearance, which limits their tumor uptake. In this study, this design has been further improved by incorporating a modification to control the in vivo pharmacokinetics. Adding a truncated Evans Blue (EB) dye molecule into the construct provides a prolonged half-life in blood as a result of its low micromolar affinity to albumin. We compared 177Lu-DOTA-TATE to the modified 177Lu Evans Blue compound (177Lu-DMEB-TATE), in vitro and in vivo in mice bearing A427-7 xenografts. The tumor uptake of 177Lu-DMEB-TATE was significantly greater than the uptake of 177Lu-DOTA-TATE in the biodistribution and SPECT-imaging studies. The therapeutic effect of the 177Lu-DMEB-TATE construct was superior to the that of the 177Lu-DOTA-TATE construct at the doses evaluated.
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Bandara N, Stott Reynolds TJ, Schehr R, Bandari RP, Diebolder PJ, Krieger S, Xu J, Miao Y, Rogers BE, Smith CJ. Matched-pair, 86Y/ 90Y-labeled, bivalent RGD/bombesin antagonist, [RGD-Glu-[DO3A]-6-Ahx-RM2], as a potential theranostic agent for prostate cancer. Nucl Med Biol 2018; 62-63:71-77. [PMID: 29929115 PMCID: PMC6072280 DOI: 10.1016/j.nucmedbio.2018.06.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 05/14/2018] [Accepted: 06/04/2018] [Indexed: 01/02/2023]
Abstract
INTRODUCTION In this study, we describe development of a true matched-pair theranostic agent that is able to target the αVβ3 integrin and the gastrin releasing peptide receptor (GRPR). We herein describe methods to metallate and characterize the new conjugate and to validate its biological efficacy by in vitro and in vivo methods. METHODS We have previously described the development of [RGD-Glu-6Ahx-RM2] (where RGD: Arg-Gly-Asp; Glu: glutamic acid; 6-Ahx: 6-amino hexanoic acid; RM2: (D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2)) that has been conjugated to a DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) bifunctional chelating agent (BFCA) to afford [RGD-Glu-[DO3A]-6-Ahx-RM2] peptide. In this study, we have radiolabeled [RGD-Glu-[DO3A]-6-Ahx-RM2] peptide with 86Y or 90Y. Natural-metallated (natY) conjugates were assessed for binding affinity for the αVβ3 integrin or GRPR in human glioblastoma U87-MG and prostate PC-3 cell lines, respectively. The effective stability of the new tracers was also evaluated prior to in vivo evaluation in normal CF-1 mice and SCID mice bearing xenografted tumors. RESULTS Competitive displacement binding assays in PC-3 cells showed high binding affinity for the GRPR (IC50, 5.65 ± 0.00 nM). On the other hand, competitive displacement binding assays in U87-MG cells revealed only moderate binding to the αVβ3 integrin (IC50, 346 ± 5.30 nM). Biodistribution studies in PC-3 tumor-bearing mice [RGD-Glu-[[90Y]Y-DO3A]-6-Ahx-RM2] showed high tumor uptake (8.70 ± 0.35%ID/g at 1 h post-intravenous injection) and retention of tracer (5.28 ± 0.12%ID/g) at 24 h post-intravenous injection. Micro-positron emission tomography (microPET) in PC-3 tumor-bearing mice using [RGD-Glu-[[86Y]Y-DO3A]-6-Ahx-RM2] correlated well with biodistribution investigations over the various time points that were studied. CONCLUSIONS The [RGD-Glu-[[86Y]Y-DO3A]-6-Ahx-RM2] and [RGD-Glu-[[90Y]Y-DO3A]-6-Ahx-RM2] matched-pair conjugates described herein exhibit favorable microPET and pharmacokinetic profiles and merit further investigations for molecular imaging and/or therapeutic evaluation in larger animal models and potentially humans. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE The theranostic, heterobivalent, agents described herein perform comparably with other mono- and multivalent conjugates we have reported and offer the potential of improved sensitivity for detecting prostate cancer cells that might exhibit differing profiles of receptor expression on tumor cells in human patients.
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Dehdashti F, Wu N, Bose R, Naughton MJ, Ma CX, Marquez-Nostra BV, Diebolder P, Mpoy C, Rogers BE, Lapi SE, Laforest R, Siegel BA. Evaluation of [ 89Zr]trastuzumab-PET/CT in differentiating HER2-positive from HER2-negative breast cancer. Breast Cancer Res Treat 2018; 169:523-530. [PMID: 29442264 DOI: 10.1007/s10549-018-4696-z] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/29/2018] [Indexed: 11/25/2022]
Abstract
PURPOSE To evaluate whether tumor uptake of [89Zr]trastuzumab can distinguish HER2-positive from HER2-negative breast cancer. METHODS Women with HER2-positive (n = 34) and HER2-negative (n = 16) breast cancer underwent PET/CT 5 ± 2 days following [89Zr]trastuzumab administration. HER2 status was determined based on immunohistochemistry and/or fluorescence in situ hybridization of primary or metastatic/recurrent tumor. Tumor [89Zr]trastuzumab uptake was assessed qualitatively and semiquantitatively as maximum standardized uptake value (SUVmax), and correlated with HER2 status. Additionally, intrapatient heterogeneity of [89Zr]trastuzumab uptake was evaluated. RESULTS On a per-patient basis, [89Zr]trastuzumab-PET/CT was positive in 30/34 (88.2%) HER2-positive and negative in 15/16 (93.7%) HER2-negative patients. Considering all lesions, the SUVmax was not significantly different in patients with HER2-positive versus HER2-negative disease (p = 0.06). The same was true of when only hepatic lesions were evaluated (p = 0.42). However, after excluding hepatic lesions, tumor SUVmax was significantly higher in HER2-positive compared to HER2-negative patients (p = 0.003). A cutoff SUVmax of 3.2, determined by ROC analysis, demonstrated positive-predictive value of 83.3% (95% CI 65.3%, 94.4%), sensitivity of 75.8% (57.7%, 88.9%), negative-predictive value of 50% (24.7%, 75.3%), and specificity of 61.5% (95% 31.6%, 86.1%) for differentiating HER2-positive from HER2-negative lesions. There was intrapatient heterogeneity of [89Zr]trastuzumab uptake in 20% of patients with multiple lesions. CONCLUSIONS [89Zr]trastuzumab has the potential to characterize the HER2 status of the complete tumor burden in patients with breast cancer, thus obviating repeat or multiple tissue sampling to assess intrapatient heterogeneity of HER2 status.
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Bandara N, Sharma AK, Krieger S, Schultz JW, Han BH, Rogers BE, Mirica LM. Evaluation of 64Cu-Based Radiopharmaceuticals that Target Aβ Peptide Aggregates as Diagnostic Tools for Alzheimer's Disease. J Am Chem Soc 2017; 139:12550-12558. [PMID: 28823165 PMCID: PMC5677763 DOI: 10.1021/jacs.7b05937] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Indexed: 12/23/2022]
Abstract
Positron emission tomography (PET) imaging agents that detect amyloid plaques containing amyloid beta (Aβ) peptide aggregates in the brain of Alzheimer's disease (AD) patients have been successfully developed and recently approved by the FDA for clinical use. However, the short half-lives of the currently used radionuclides 11C (20.4 min) and 18F (109.8 min) may limit the widespread use of these imaging agents. Therefore, we have begun to evaluate novel AD diagnostic agents that can be radiolabeled with 64Cu, a radionuclide with a half-life of 12.7 h, ideal for PET imaging. Described herein are a series of bifunctional chelators (BFCs), L1-L5, that were designed to tightly bind 64Cu and shown to interact with Aβ aggregates both in vitro and in transgenic AD mouse brain sections. Importantly, biodistribution studies show that these compounds exhibit promising brain uptake and rapid clearance in wild-type mice, and initial microPET imaging studies of transgenic AD mice suggest that these compounds could serve as lead compounds for the development of improved diagnostic agents for AD.
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Koh EI, Robinson AE, Bandara N, Rogers BE, Henderson JP. Copper import in Escherichia coli by the yersiniabactin metallophore system. Nat Chem Biol 2017; 13:1016-1021. [PMID: 28759019 PMCID: PMC5562518 DOI: 10.1038/nchembio.2441] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 06/20/2017] [Indexed: 12/13/2022]
Abstract
Copper plays a dual role as nutrient and toxin during bacterial infections. While uropathogenic Escherichia coli (UPEC) strains can use the copper-binding metallophore yersiniabactin (Ybt) to resist copper toxicity, Ybt also converts bioavailable copper to Cu(II)-Ybt in low copper conditions. Although E. coli have long been considered to lack a copper import pathway, we observed Ybt-mediated copper import in UPEC using canonical Fe(III)-Ybt transport proteins. UPEC removed copper from Cu(II)-Ybt with subsequent re-export of metal-free Ybt to the extracellular space. Copper released through this process became available to an E. coli cuproenzyme (the amine oxidase TynA), linking this import pathway to a nutrient acquisition function. Ybt-expressing E. coli thus engage in nutritional passivation, a strategy of minimizing a metal ion's toxicity while preserving its nutritional availability. Copper acquisition through this process may contribute to the marked virulence defect of Ybt transport-deficient UPEC.
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Kapoor V, Dadey DYA, Nguyen K, Wildman SA, Hoye K, Khudanyan A, Bandara N, Rogers BE, Thotala D, Hallahan DE. Tumor-Specific Binding of Radiolabeled PEGylated GIRLRG Peptide: A Novel Agent for Targeting Cancers. J Nucl Med 2016; 57:1991-1997. [PMID: 27445290 DOI: 10.2967/jnumed.115.165118] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 06/21/2016] [Indexed: 01/01/2023] Open
Abstract
Cancer-specific targeting sparing normal tissues would significantly enhance cancer therapy outcomes and reduce cancer-related mortality. One approach is to target receptors or molecules that are specifically expressed on cancer cells. Peptides as cancer-specific targeting agents offer advantages such as ease of synthesis, low antigenicity, and enhanced diffusion into tissues. Glucose-regulated protein 78 (GRP78) is an endoplasmic reticulum stress chaperone that regulates the unfolded protein response and is overexpressed in various cancers. In this study, we evaluated GIRLRG peptide that specifically targets GRP78 for cancer-specific binding (in vitro) and noninvasive tumor imaging (in vivo). METHODS GIRLRG peptide was modeled into the GRP78 ATPase domain using computational modeling. Surface plasmon resonance studies were performed to determine the affinity of GIRLRG peptide to GRP78 protein. GIRLRG was conjugated with PEG to prolong its circulation in mice. Tumor binding efficacy of PEG-GIRLRG peptide was evaluated in nude mice bearing heterotopic cervical (HT3), esophageal (OE33), pancreatic (BXPC3), lung (A549), and glioma (D54) tumors. Nano-SPECT/CT imaging of the mice was performed 48 and 72 h after injection with 111In-labeled PEG-GIRLRG or PEG-control peptide. Post-SPECT biodistribution studies were performed 96 h after injection of the radiolabeled peptides. RESULTS Using molecular modeling and surface plasmon resonance, we identified that GIRLRG was binding with an affinity constant of 2.16 × 10-3 M in the ATPase domain of GRP78. GIRLRG peptide specifically bound to cervical, lung, esophageal, and glioma cells. SPECT imaging revealed that 111In-PEG-GIRLRG specifically bound to cervical, esophageal, pancreatic, lung, and brain tumors. Post-SPECT biodistribution data also validated the SPECT imaging results. CONCLUSION GIRLRG peptide specifically binds to the ATPase domain of GRP78. Radiolabeled PEG-GIRLRG could be used to target various cancers. Further studies would be required to translate PEG-GIRLRG peptide into the clinic.
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Richter S, Wuest M, Bergman CN, Krieger S, Rogers BE, Wuest F. Metabolically Stabilized (68)Ga-NOTA-Bombesin for PET Imaging of Prostate Cancer and Influence of Protease Inhibitor Phosphoramidon. Mol Pharm 2016; 13:1347-57. [PMID: 26973098 DOI: 10.1021/acs.molpharmaceut.5b00970] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Peptide receptor-based targeted molecular imaging and therapy of cancer is on the current forefront of nuclear medicine preclinical research and clinical practice. The frequent overexpression of gastrin-releasing peptide (GRP) receptors in prostate cancer stimulated the development of radiolabeled bombesin derivatives as high affinity peptide ligands for selective targeting of the GRP receptor. In this study, we have evaluated a novel (68)Ga-labeled bombesin derivative for PET imaging of prostate cancer in vivo. In addition, we were interested in testing the recently proposed "serve-and-protect" strategy to improve metabolic stability of radiolabeled peptides in vivo and to enhance tumor uptake. GRP receptor targeting peptides NOTA-BBN2 and (nat)Ga-NOTA-BBN2 demonstrated a characteristic antagonistic profile and high binding affinity toward the GRP receptor in PC3 cells (IC50 4.6-8.2 nM). Radiolabeled peptide (68)Ga-NOTA-BBN2 was obtained from NOTA-BBN2 in radiochemical yields greater than 62% (decay-corrected). Total synthesis time was 35 min, including purification using solid-phase extraction. (68)Ga-NOTA-BBN2 exhibited favorable resistance against metabolic degradation by peptidases in vivo within the investigated time frame of 60 min. Interestingly, metabolic stability was not further enhanced in the presence of protease inhibitor phosphoramidon. Dynamic PET studies showed high tumor uptake in both PC3- and LNCaP-bearing BALB/c nude mice (SUV5min > 0.6; SUV60min > 0.5). Radiotracer (68)Ga-NOTA-BBN2 represents a novel radiometal-based bombesin derivative suitable for GRP receptor targeting in PC3 and LNCaP mouse xenografts. Further increase of metabolic stability in vivo and enhanced tumor uptake were not observed upon administration of protease inhibitor phosphoramidon. This led to the conclusion that the recently proposed "serve-and-protect" strategy may not be valid for peptides exhibiting favorable intrinsic metabolic stability in vivo.
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Kang CS, Wu N, Chen Y, Sun X, Bandara N, Liu D, Lewis MR, Rogers BE, Chong HS. Transferrin conjugates of triazacyclononane-based bifunctional NE3TA chelates for PET imaging: Synthesis, Cu-64 radiolabeling, and in vitro and in vivo evaluation. J Inorg Biochem 2015; 154:60-6. [PMID: 26583705 DOI: 10.1016/j.jinorgbio.2015.10.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 10/09/2015] [Accepted: 10/28/2015] [Indexed: 12/29/2022]
Abstract
Three different polyaminocarboxylate-based bifunctional NE3TA (7-[2-[carboxymethyl)amino]ethyl]-1,4,7-triazacyclononane-1,4-diacetic acid) chelating agents were synthesized for potential use in copper 64-PET imaging applications. The bifunctional chelates were comparatively evaluated using transferrin (Tf) as a model targeting vector that binds to the transferrin receptor overexpressed in many different cancer cells. The transferrin conjugates of the NE3TA-based bifunctional chelates were evaluated for radiolabeling with (64)Cu. In vitro stability and cellular uptake of (64)Cu-radiolabeled conjugates were evaluated in human serum and prostate (PC-3) cancer cells, respectively. Among the three NE3TA-Tf conjugates tested, N-NE3TA-Tf was identified as the best conjugate for radiolabeling with (64)Cu. N-NE3TA-Tf rapidly bound to (64)Cu (>98% radiolabeling efficiency, 1min, RT), and (64)Cu-N-NE3TA-Tf remained stable in human serum for 2days and demonstrated high uptake in PC-3 cancer cells. (64)Cu-N-NE3TA-Tf was shown to have rapid blood clearance and increasing tumor uptake in PC-3 tumor bearing mice over a 24h period. This bifunctional chelate presents highly efficient chelation chemistry with (64)Cu under mild condition that can be applied for radiolabeling of various tumor-specific biomolecules with (64)Cu for potential use in PET imaging applications.
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Richter S, Wuest M, Bergman CN, Way JD, Krieger S, Rogers BE, Wuest F. Rerouting the metabolic pathway of (18)F-labeled peptides: the influence of prosthetic groups. Bioconjug Chem 2015; 26:201-12. [PMID: 25572982 DOI: 10.1021/bc500599m] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Current translational cancer research is directed to the development of high affinity peptide ligands for targeting neuropeptide receptors overexpressed in different types of cancer. Besides their desired high binding affinity to the receptor, the suitability of radiolabeled peptides as targeting vectors for molecular imaging and therapy depends on additional aspects such as high tumor-to-background ratio, favorable clearance pattern from nontarget tissue, and sufficient metabolic stability in vivo. This study reports how a switch from the prosthetic group, N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB), to 2-deoxy-2-[(18)F]fluoro-d-glucose ([(18)F]FDG) effects the metabolic pathway of an (18)F-labeled bombesin derivative, QWAV-Sar-H-FA01010-Tle-NH2. (18)F-Labeled bombesin derivatives represent potent peptide ligands for selective targeting of gastrin-releasing peptide (GRP) receptor-expressing prostate cancer. Radiosynthesis of (18)F-labeled bombesin analogues [(18)F]FBz-Ava-BBN2 and [(18)F]FDG-AOAc-BBN2 was achieved in good radiochemical yields of ~50% at a specific activity exceeding 40 GBq/μmol. Both nonradioactive compounds FBz-Ava-BBN2 and FDG-AOAc-BBN2 inhibited binding of [(125)I]Tyr(4)-bombesin(1-14) in PC3 cells with IC50 values of 9 and 16 nM, respectively, indicating high inhibitory potency. Influence of each prosthetic group was further investigated in PC3 mouse xenografts using dynamic small animal PET imaging. In comparison to [(18)F]FBz-Ava-BBN2, total tumor uptake levels were doubled after injection of [(18)F]FDG-AOAc-BBN2 while renal elimination was increased. Blood clearance and in vivo metabolic stability were similar for both compounds. The switch from [(18)F]SFB to [(18)F]FDG as the prosthetic group led to a significant reduction in lipophilicity which resulted in more favorable renal clearance and increased tumor uptake. The presented single step radiolabeling-glycosylation approach represents an innovative strategy for site-directed peptide labeling with the short-lived positron emitter (18)F while providing a favorable pharmacokinetic profile of (18)F-labeled peptides.
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Liu L, Rogers BE, Aladyshkina N, Cheng B, Lokitz SJ, Curiel DT, Mathis JM. Construction and Radiolabeling of Adenovirus Variants that Incorporate Human Metallothionein into Protein IX for Analysis of Biodistribution. Mol Imaging 2014; 13. [DOI: 10.2310/7290.2014.00022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Cai Z, Ouyang Q, Zeng D, Nguyen KN, Modi J, Wang L, White AG, Rogers BE, Xie XQ, Anderson CJ. 64Cu-labeled somatostatin analogues conjugated with cross-bridged phosphonate-based chelators via strain-promoted click chemistry for PET imaging: in silico through in vivo studies. J Med Chem 2014; 57:6019-29. [PMID: 24983404 PMCID: PMC4261236 DOI: 10.1021/jm500416f] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
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Somatostatin
receptor subtype 2 (sstr2) is a G-protein-coupled
receptor (GPCR) that is overexpressed in neuroendocrine tumors. The
homology model of sstr2 was built and was used to aid the design of
new somatostatin analogues modified with phosphonate-containing cross-bridged
chelators for evaluation of using them as PET imaging radiopharmaceuticals.
The new generation chelators were conjugated to Tyr3-octreotate
(Y3-TATE) through bioorthogonal, strain-promoted alkyne azide cycloaddition
(SPAAC) to form CB-TE1A1P–DBCO–Y3-TATE (AP) and CB-TE1K1P–PEG4–DBCO–Y3-TATE
(KP) in improved yields compared to standard direct conjugation methods
of amide bond formation. Consistent with docking studies, the clicked
bioconjugates showed high binding affinities to sstr2, with Kd values ranging from 0.6 to 2.3 nM. Selected
isomers of the clicked products were used in biodistribution and PET/CT
imaging. Introduction of the bulky dibenzocyclooctyne group in AP
decreased clearance rates from circulation. However, the additional
carboxylate group and PEG linker from the KP conjugate significantly
improved labeling conditions and in vivo stability of the copper complex
and ameliorated the slower pharmacokinetics of the clicked somatostatin
analogues.
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Marquez BV, Ikotun OF, Parry JJ, Rogers BE, Meares CF, Lapi SE. Development of a Radiolabeled Irreversible Peptide Ligand for PET Imaging of Vascular Endothelial Growth Factor. J Nucl Med 2014; 55:1029-34. [PMID: 24732153 DOI: 10.2967/jnumed.113.130898] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Accepted: 01/24/2014] [Indexed: 01/30/2023] Open
Abstract
UNLABELLED Imaging agents based on peptide probes have desirable pharmacokinetic properties provided that they have high affinities for their target in vivo. An approach to improve a peptide ligand's affinity for its target is to make this interaction covalent and irreversible. For this purpose, we evaluated a (64)Cu-labeled affinity peptide tag, (64)Cu-L19K-(5-fluoro-2,4-dinitrobenzene) ((64)Cu-L19K-FDNB), which binds covalently and irreversibly to vascular endothelial growth factor (VEGF) as a PET imaging agent. We compared the in vivo properties of (64)Cu-L19K-FDNB in VEGF-expressing tumor xenografts with its noncovalent binding analogs, (64)Cu-L19K-(2,4-dinitrophenyl) ((64)Cu-L19K-DNP) and (64)Cu-L19K. METHODS The L19K peptide (GGNECDIARMWEWECFERK-CONH2) was constructed with 1,4,7-triazacyclononane-1,4,7-triacetic acid at the N terminus for radiolabeling with (64)Cu with a polyethylene glycol spacer between peptide and chelate. 1,5-difluoro-2,4-dinitrobenzene was conjugated at the C-terminal lysine for cross-linking to VEGF, resulting in L19K-FDNB. (64)Cu-L19K-FDNB was assayed for covalent binding to VEGF in vitro. As a control, L19K was conjugated to 1-fluoro-2,4-dinitrobenzene, resulting in L19K-DNP. PET imaging and biodistribution studies of (64)Cu-L19K-FDNB, (64)Cu-L19K-DNP, and the native (64)Cu-L19K were compared in HCT-116 xenografts. Blocking studies of (64)Cu-L19K-FDNB was performed with a coinjection of excess unlabeled L19K-FDNB. RESULTS In vitro binding studies confirmed the covalent and irreversible binding of (64)Cu-L19K-FDNB to VEGF, whereas (64)Cu-L19K-DNP and (64)Cu-L19K did not bind covalently. PET imaging showed higher tumor uptake with (64)Cu-L19K-FDNB than with (64)Cu-L19K-DNP and (64)Cu-L19K, with mean standardized uptake values of 0.62 ± 0.05, 0.18 ± 0.06, and 0.34 ± 0.14, respectively, at 24 h after injection (P < 0.05), and 0.53 ± 0.05, 0.32 ± 0.14, and 0.30 ± 0.09, respectively, at 48 h after injection (P < 0.05). Blocking studies with (64)Cu-L19K-FDNB in the presence of excess unlabeled peptide showed a 53% reduction in tumor uptake at 48 h after injection. CONCLUSION In this proof-of-concept study, the use of a covalent binding peptide ligand against VEGF improves tracer accumulation at the tumor site in vivo, compared with its noncovalent binding peptide analogs. This technique is a promising tool to enhance the potency of peptide probes as imaging agents.
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Li H, Zhou H, Krieger S, Parry JJ, Whittenberg JJ, Desai AV, Rogers BE, Kenis PJA, Reichert DE. Triazine-based tool box for developing peptidic PET imaging probes: syntheses, microfluidic radiolabeling, and structure-activity evaluation. Bioconjug Chem 2014; 25:761-72. [PMID: 24661266 PMCID: PMC3993951 DOI: 10.1021/bc500034n] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
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This
study was aimed at developing a triazine-based modular platform
for targeted PET imaging. We synthesized mono- or bis-cyclo(RGDfK)
linked triazine-based conjugates specifically targeting integrin αvβ3 receptors. The core molecules could be
easily linked to targeting peptide and radiolabeled bifunctional chelator.
The spacer core molecule was synthesized in 2 or 3 steps in 64–80%
yield, and the following conjugation reactions with cyclo(RGDfK) peptide
or bifunctional chelator were accomplished using “click”
chemistry or amidation reactions. The DOTA-TZ-Bis-cyclo(RGDfK) 13 conjugate was radiolabeled successfully with 64Cu(OAc)2 using a microfluidic method, resulting in higher
specific activity with above 95% labeling yields compared to conventional
radiolabeling (SA ca. 850 vs 600 Ci/mmol). The dimeric cyclo(RGDfK)
peptide was found to display significant bivalency effect using I125-Echistatin binding assay with IC50 value as 178.5 ± 57.1 nM, which displayed a 3.6-fold enhancement
of binding affinity compared to DOTA-TZ-cyclo(RGDfK) 14 conjugate on U87MG human glioblastoma cell. Biodistribution of all
four conjugates in female athymic nude mice were evaluated. DOTA-“Click”-cyclo(RGDfK) 15 had the highest tumor uptake among these four at 4 h p.i.
with 1.90 ± 0.65%ID/g, while there was no clear bivalency effect
for DOTA-TZ-BisRGD in vivo, which needs further experiments
to address the unexpected questions.
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Sin I, Kang CS, Bandara N, Sun X, Zhong Y, Rogers BE, Chong HS. Novel hexadentate and pentadentate chelators for ⁶⁴Cu-based targeted PET imaging. Bioorg Med Chem 2014; 22:2553-62. [PMID: 24657050 DOI: 10.1016/j.bmc.2014.02.041] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 02/10/2014] [Accepted: 02/19/2014] [Indexed: 11/26/2022]
Abstract
A series of new hexadentate and pentadentate chelators were designed and synthesized as chelators of (64)Cu. The new pentadentate and hexadentate chelators contain different types of donor groups and are expected to form neutral complexes with Cu(II). The new chelators were evaluated for complex kinetics and stability with (64)Cu. The new chelators instantly bound to (64)Cu with high labeling efficiency and maximum specific activity. All (64)Cu-radiolabeled complexes in human serum remained intact for 2 days. The (64)Cu-radiolabeled complexes were further challenged by EDTA in a 100-fold molar excess. Among the (64)Cu-radiolabeled complexes evaluated, (64)Cu-complex of the new chelator E was well tolerated with a minimal transfer of (64)Cu to EDTA. (64)Cu-radiolabeled complex of the new chelator E was further evaluated for biodistribution studies using mice and displayed rapid blood clearance and low organ uptake. (64)Cu-chelator E produced a favorable in vitro and in vivo complex stability profiles comparable to (64)Cu complex of the known hexadentate NOTA chelator. The in vitro and in vivo data highlight strong potential of the new chelator E for targeted PET imaging application.
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Dmitriev IP, Kashentseva EA, Kim KH, Matthews QL, Krieger SS, Parry JJ, Nguyen KN, Akers WJ, Achilefu S, Rogers BE, Alvarez RD, Curiel DT. Monitoring of biodistribution and persistence of conditionally replicative adenovirus in a murine model of ovarian cancer using capsid-incorporated mCherry and expression of human somatostatin receptor subtype 2 gene. Mol Imaging 2014; 13:7290.2014.00024. [PMID: 25249483 DOI: 10.2310/7290.2014.00024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
A significant limiting factor to the human clinical application of conditionally replicative adenovirus (CRAd)-based virotherapy is the inability to noninvasively monitor these agents and their potential persistence. To address this issue, we proposed a novel imaging approach that combines transient expression of the human somatostatin receptor (SSTR) subtype 2 reporter gene with genetic labeling of the viral capsid with mCherry fluorescent protein. To test this dual modality system, we constructed the Ad5/3Δ24pIXcherry/SSTR CRAd and validated its capacity to generate fluorescent and nuclear signals in vitro and following intratumoral injection. Analysis of 64Cu-CB-TE2A-Y3-TATE biodistribution in mice revealed reduced uptake in tumors injected with the imaging CRAd relative to the replication-incompetent, Ad-expressing SSTR2 but significantly greater uptake compared to the negative CRAd control. Optical imaging demonstrated relative correlation of fluorescent signal with virus replication as determined by viral genome quantification in tumors. Positron emission tomography/computed tomography studies demonstrated that we can visualize radioactive uptake in tumors injected with imaging CRAd and the trend for greater uptake by standardized uptake value analysis compared to control CRAd. In the aggregate, the plasticity of our dual imaging approach should provide the technical basis for monitoring CRAd biodistribution and persistence in preclinical studies while offering potential utility for a range of clinical applications.
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Richter S, Wuest M, Krieger SS, Rogers BE, Friebe M, Bergmann R, Wuest F. Synthesis and radiopharmacological evaluation of a high-affinity and metabolically stabilized 18F-labeled bombesin analogue for molecular imaging of gastrin-releasing peptide receptor-expressing prostate cancer. Nucl Med Biol 2013; 40:1025-34. [DOI: 10.1016/j.nucmedbio.2013.07.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 06/19/2013] [Accepted: 07/11/2013] [Indexed: 01/28/2023]
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Guo Y, Parry JJ, Laforest R, Rogers BE, Anderson CJ. The role of p53 in combination radioimmunotherapy with 64Cu-DOTA-cetuximab and cisplatin in a mouse model of colorectal cancer. J Nucl Med 2013; 54:1621-9. [PMID: 23873478 DOI: 10.2967/jnumed.112.118539] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED Radioimmunotherapy has been successfully used in the treatment of lymphoma but thus far has not demonstrated significant efficacy in humans beyond disease stabilization in solid tumors. Radioimmunotherapy with (64)Cu was highly effective in a hamster model of colorectal cancer, but targeted radiotherapies with this radionuclide have since not shown as much success. It is widely known that mutations in key proteins play a role in the success or failure of cancer therapies. For example, the KRAS mutation is predictive of poor response to anti-epidermal growth factor receptor therapies in colorectal cancer, whereas p53 is frequently mutated in tumors, causing resistance to multiple therapeutic regimens. METHODS We previously showed that nuclear localization of (64)Cu-labeled DOTA-cetuximab was enhanced in p53 wild-type tumor cells. Here, we examine the role of p53 in the response to radioimmunotherapy with (64)Cu-DOTA-cetuximab in KRAS-mutated HCT116 tumor-bearing mice, with and without cisplatin, which upregulates wild-type p53. RESULTS Experiments with HCT116 cells that are p53 +/+ (p53 wild-type) and -/- (p53 null) grown in cell culture demonstrated that preincubation with cisplatin increased expression of p53 and subsequently enhanced localization of (64)Cu from (64)Cu-acetate and (64)Cu-DOTA-cetuximab to the tumor cell nuclei. Radioimmunotherapy studies in p53-positive HCT116 tumor-bearing mice, receiving either radioimmunotherapy alone or in combination with cisplatin, showed significantly longer survival in mice receiving unlabeled cetuximab or cisplatin alone or in combination (all, P < 0.01). In contrast, the p53-negative tumor-bearing mice treated with radioimmunotherapy alone or combined with cisplatin showed no survival advantage, compared with control groups (all, P > 0.05). CONCLUSION Together, these data suggest that (64)Cu specifically delivered to epidermal growth factor receptor-positive tumors by cetuximab can suppress tumor growth despite the KRAS status and present opportunities for personalized clinical treatment strategies in colorectal cancer.
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Nanda PK, Wienhoff BE, Rold TL, Sieckman GL, Szczodroski AF, Hoffman TJ, Rogers BE, Smith CJ. Positron-emission tomography (PET) imaging agents for diagnosis of human prostate cancer: agonist vs. antagonist ligands. In Vivo 2012; 26:583-592. [PMID: 22773572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
AIM The present study adds scientific support to the growing debate regarding the superiority of radiolabeled bombesin-based antagonist peptides over agonists for molecular imaging and therapy of human tumors overexpressing the gastrin-releasing peptide receptor (GRPR) and describes a detailed in vitro and in vivo comparison of 64Cu-NODAGA-6-Ahx-BBN(7-14)NH2 agonist and 64Cu-NODAGA-6-Ahx-DPhe6-BBN(6-13)NHEt antagonist ligands. MATERIALS AND METHODS Conjugates were synthesized by solid-phase peptide synthesis, purified by reversed-phase high-performance liquid chromatography, and characterized by electrospray ionization-mass spectroscopy. The conjugates were radiolabeled with 64Cu. RESULTS In vitro and in vivo data support the hypothesis for targeting of the GRPR by these tracer molecules. Maximum-intensity micro Positron Emission Tomography (microPET) imaging studies show the agonist ligand to provide high-quality, high-contrast images with very impressive tumor uptake and background clearance, with virtually no residual gastrointestinal or renal-urinary radioactivity. CONCLUSION Based on microPET imaging experiments, we conclude the agonist peptide ligand to be a superior molecular imaging agent for targeting GRPR.
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