title: Copper-64-labeled anti-bcl-2 PNA-peptide conjugates selectively localize to bcl-2-positive tumors in mouse models of B-cell lymphoma.
abstract: BACKGROUND
  The bcl-2 gene is overexpressed in non-Hodgkin's lymphoma (NHL). We have reported micro-SPECT/CT imaging of Mec-1 human lymphoma xenografts in SCID mice, using [(111)In]DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate. In order to reduce normal organ accumulation and improve imaging contrast, modified monomers with neutral hydrophilic (serine, TS) or negatively charged (aspartic acid, TD) residues were synthesized as substitutes for glycine at T(14) in the PNA sequence. The parent and modified PNA-peptide conjugates were labeled with (64)Cu and evaluated in biodistribution studies and high resolution PET/CT imaging of SCID mice bearing bcl-2-positive Mec-1 xenografts as well as bcl-2-negative Ramos xenografts.
  
  
  METHODS
  Mice were administered the (64)Cu-labeled conjugates for biodistribution and imaging studies. Biodistributions were obtained from 1 to 48 h post-injection. Mice were imaged from 1 to 48 h post-injection.
  
  
  RESULTS
  The parent glycine conjugate and two modified conjugates all showed selective tumor uptake in Mec-1 xenografts. The liver uptake of the serine conjugate was significantly reduced compared to the two other PNA conjugates. Its kidney uptake was highest of the three at 47.1% ID/g at 1h and dropped to 20.6% ID/g at 24h. [Copper-64]DOTA-anti-bcl-2-TS-PNA-Tyr(3)-octreotate showed tumor uptake of 1.38% ID/g at 1h and 1.06% ID/g at 24h. The tumor-to-blood ratio was increased by factor of 2 from 1h to 24h. This compound detected Mec-1 tumors by micro-PET/CT as early as 1h post-injection and at time points out to 48 h. However, the negative control Ramos tumor could not be detected.
  
  
  CONCLUSIONS
  These (64)Cu-labeled, amino acid-modified PNA conjugates showed selective tumor targeting in vivo, and tumor xenografts were detected by micro-PET/CT as early as 1h post-injection, suggesting that bcl-2 expression at the mRNA level can detected by PET in mouse models of NHL. Advances in knowledge and implications for patient care Down-regulating bcl-2, an anti-apoptotic proto-oncogene, is a mechanism to reverse chemotherapy resistance in humans with NHL. Thus, bcl-2 overexpression might be considered a new independent prognostic parameter in NHL, aiding in the identification of patients at risk for treatment failure. We have developed [(64)Cu]DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate conjugates for targeted antisense PET imaging. Our preclinical studies identified an effective combination of antisense and radionuclide imaging, with the goal of future clinical trials in patients. This imaging modality may improve clinical care by identifying patients who might respond better to conventional chemotherapy.
authors.affiliation: Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO, 65211.
authors.forename: Fang
authors.initials: F
authors.lastname: Jia
authors.affiliation: Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO, 65211.
authors.forename: Baghavathy S
authors.initials: BS
authors.lastname: Balaji
authors.affiliation: Molecular Biology Program, University of Missouri, Columbia, MO, 65211.
authors.forename: Fabio
authors.initials: F
authors.lastname: Gallazzi
authors.affiliation: Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO, 65211; Nuclear Science and Engineering Institute, University of Missouri, Columbia, MO, 65211; Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, 65201. Electronic address: LewisMic@missouri.edu.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Lewis
mesh_terms: D000818:Animals; D001692:Biological Transport; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D056831:Coordination Complexes / Q000737:chemistry*; D003301:Copper Radioisotopes; D005260:Female; D006801:Humans; D016393:Lymphoma, B-Cell / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D015282:Octreotide / Q000031:analogs & derivatives* / Q000737:chemistry; D016376:Oligonucleotides, Antisense / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000493:pharmacokinetics; D020135:Peptide Nucleic Acids / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000493:pharmacokinetics; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism*; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon; D055114:X-Ray Microtomography
chemical_list: C572954:111indium-DOTA, Tyr(3)-octreotate; D056831:Coordination Complexes; D003301:Copper Radioisotopes; C000715470:MAS1 protein, human; D016376:Oligonucleotides, Antisense; D020135:Peptide Nucleic Acids; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2; D015282:Octreotide
keywords: Antisense imaging; Micro-PET/CT; Peptide nucleic acid; bcl-2