title: PET Imaging of Tumor-Associated Macrophages with 89Zr-Labeled High-Density Lipoprotein Nanoparticles.
abstract: Tumor-associated macrophages (TAMs) are increasingly investigated in cancer immunology and are considered a promising target for better and tailored treatment of malignant growth. Although TAMs also have high diagnostic and prognostic value, TAM imaging still remains largely unexplored. Here, we describe the development of reconstituted high-density lipoprotein (rHDL)-facilitated TAM PET imaging in a breast cancer model.
  
  
  METHODS
  Radiolabeled rHDL nanoparticles incorporating the long-lived positron-emitting nuclide (89)Zr were developed using 2 different approaches. The nanoparticles were composed of phospholipids and apolipoprotein A-I (apoA-I) in a 2.5:1 weight ratio. (89)Zr was complexed with deferoxamine (also known as desferrioxamine B, desferoxamine B), conjugated either to a phospholipid or to apoA-I to generate (89)Zr-PL-HDL and (89)Zr-AI-HDL, respectively. In vivo evaluation was performed in an orthotopic mouse model of breast cancer and included pharmacokinetic analysis, biodistribution studies, and PET imaging. Ex vivo histologic analysis of tumor tissues to assess regional distribution of (89)Zr radioactivity was also performed. Fluorescent analogs of the radiolabeled agents were used to determine cell-targeting specificity using flow cytometry.
  
  
  RESULTS
  The phospholipid- and apoA-I-labeled rHDL were produced at 79% ± 13% (n = 6) and 94% ± 6% (n = 6) radiochemical yield, respectively, with excellent radiochemical purity (>99%). Intravenous administration of both probes resulted in high tumor radioactivity accumulation (16.5 ± 2.8 and 8.6 ± 1.3 percentage injected dose per gram for apoA-I- and phospholipid-labeled rHDL, respectively) at 24 h after injection. Histologic analysis showed good colocalization of radioactivity with TAM-rich areas in tumor sections. Flow cytometry revealed high specificity of rHDL for TAMs, which had the highest uptake per cell (6.8-fold higher than tumor cells for both DiO@Zr-PL-HDL and DiO@Zr-AI-HDL) and accounted for 40.7% and 39.5% of the total cellular DiO@Zr-PL-HDL and DiO@Zr-AI-HDL in tumors, respectively.
  
  
  CONCLUSIONS
  We have developed (89)Zr-labeled TAM imaging agents based on the natural nanoparticle rHDL. In an orthotopic mouse model of breast cancer, we have demonstrated their specificity for macrophages, a result that was corroborated by flow cytometry. Quantitative macrophage PET imaging with our (89)Zr-rHDL imaging agents could be valuable for noninvasive monitoring of TAM immunology and targeted treatment.
authors.affiliation: Centro de Investigación en Red de Enfermedades Respiratorias, CIBERES, Madrid, Spain Centro Nacional de Investigaciones Cardiovasculares, CNIC, Madrid, Spain Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York.
authors.forename: Carlos
authors.initials: C
authors.lastname: Pérez-Medina
authors.affiliation: Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Jun
authors.initials: J
authors.lastname: Tang
authors.affiliation: Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Dalya
authors.initials: D
authors.lastname: Abdel-Atti
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, New York.
authors.forename: Brandon
authors.initials: B
authors.lastname: Hogstad
authors.affiliation: Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, New York Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, New York.
authors.forename: Miriam
authors.initials: M
authors.lastname: Merad
authors.affiliation: Leon H. Charney Division of Cardiology and Marc and Ruti Bell Program in Vascular Biology, New York University School of Medicine, New York, New York.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Fisher
authors.affiliation: Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York.
authors.forename: Zahi A
authors.initials: ZA
authors.lastname: Fayad
authors.affiliation: Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York Weill Cornell Medical College, New York, New York; and.
authors.forename: Jason S
authors.initials: JS
authors.lastname: Lewis
authors.affiliation: Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York Department of Vascular Medicine, Academic Medical Center of the University of Amsterdam, Amsterdam, The Netherlands reinert@mskcc.org willem.mulder@mssm.edu.
authors.forename: Willem J M
authors.initials: WJ
authors.lastname: Mulder
authors.affiliation: Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York Weill Cornell Medical College, New York, New York; and reinert@mskcc.org willem.mulder@mssm.edu.
authors.forename: Thomas
authors.initials: T
authors.lastname: Reiner
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005434:Flow Cytometry; D008075:Lipoproteins, HDL / Q000737:chemistry*; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D049268:Positron-Emission Tomography; D011379:Prognosis; D011868:Radioisotopes / Q000737:chemistry*; D019275:Radiopharmaceuticals; D014018:Tissue Distribution; D014057:Tomography, X-Ray Computed; D015040:Zirconium / Q000737:chemistry*
chemical_list: D008075:Lipoproteins, HDL; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D015040:Zirconium
keywords: 89Zr; PET; breast cancer; high-density lipoprotein; tumor-associated macrophages