title: Targeted antisense radiotherapy and dose fractionation using a (177)Lu-labeled anti-bcl-2 peptide nucleic acid-peptide conjugate.
abstract: BACKGROUND
  The overall goal of these studies was to test the hypothesis that simultaneous down-regulation of a tumor survival gene and delivery of internally emitted cytotoxic radiation will be more effective than either treatment modality alone. The objectives were to evaluate the therapeutic efficacy of a (177)Lu-labeled anti-bcl-2-PNA-Tyr(3)-octreotate antisense conjugate in a mouse model bearing human non-Hodgkin's lymphoma (NHL) tumor xenografts and to optimize targeted antisense radiotherapy by dose fractionation.
  
  
  METHODS
  In the initial therapy studies, tumor-bearing mice were given saline, nonradioactive DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate, (177)Lu-DOTA-Tyr(3)-octreotate, (177)Lu-DOTA-PNA-peptide alone, or (177)Lu-DOTA-PNA-peptide followed by a chase dose of nonradioactive PNA-peptide. The MTD of (177)Lu-DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate was then determined. Subsequently single dose MTD and four weekly fractionated doses were directly compared, followed by histopathologic evaluation.
  
  
  RESULTS
  Antisense radiotherapy using 4.44 MBq of the (177)Lu-DOTA-PNA-peptide followed by nonradioactive PNA-peptide was significantly more effective than other low dose treatment regimens. A dose of 18.5 MBq of (177)Lu-DOTA-PNA-peptide was determined to be the approximate maximum tolerated dose (MTD). The median times to progression to a 1cm(3) tumor volume were 32 and 49 days for single dose MTD and fractionated dose (4 × 4.63 MBq) groups, respectively. Histopathology revealed metastases in the single dose groups, but not in the dose fractionation group.
  
  
  CONCLUSIONS
  Targeted antisense radiotherapy using (177)Lu-DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate and DOTA-PNA-peptide conjugate effectively inhibited tumor progression in a mouse model of NHL. Furthermore, a dose fractionation regimen had a significant advantage over a single high dose, in terms of tumor growth inhibition and prevention of metastasis.
  
  
  CONCLUSIONS
  Down-regulating bcl-2, an anti-apoptotic proto-oncogene, is a mechanism to reverse chemotherapy resistance or failure in humans with NHL. We have developed a (177)Lu-DOTA-anti-bcl-2-PNA-Tyr(3)-octreotate conjugate for targeted antisense radiotherapy, in which down-regulation of bcl-2 and delivery of cytotoxic radiation occur simultaneously. Our previous studies have shown highly specific inhibition of bcl-2 protein, additive in vitro cytotoxic effects on human lymphoma cells, and favorable biodistribution and dosimetric properties. Lutetium-177 targeted antisense radiotherapy demonstrates a significant advantage over conventional (177)Lu-peptide receptor radionuclide therapy in a mouse model of NHL. Our preclinical studies identified an effective combination of antisense and radionuclide therapy, with the goal of future clinical trials in patients.
authors.affiliation: Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO 65201; Department of Veterinary Medicine Surgery, University of Missouri, Columbia, MO 65211.
authors.forename: Dijie
authors.initials: D
authors.lastname: Liu
authors.affiliation: Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO 65201; Department of Veterinary Medicine Surgery, University of Missouri, Columbia, MO 65211; Area of Pathobiology, University of Missouri, Columbia, MO 65211.
authors.forename: Ethan R
authors.initials: ER
authors.lastname: Balkin
authors.affiliation: Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO 65201; Department of Veterinary Medicine Surgery, University of Missouri, Columbia, MO 65211.
authors.forename: Fang
authors.initials: F
authors.lastname: Jia
authors.affiliation: Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO 65201; Department of Veterinary Medicine Surgery, University of Missouri, Columbia, MO 65211.
authors.forename: Varyanna C
authors.initials: VC
authors.lastname: Ruthengael
authors.affiliation: Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO 65201; Department of Radiology, University of Missouri, Columbia, MO 65212.
authors.forename: C Jeffrey
authors.initials: CJ
authors.lastname: Smith
authors.affiliation: Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO 65201; Department of Veterinary Medicine Surgery, University of Missouri, Columbia, MO 65211; Area of Pathobiology, University of Missouri, Columbia, MO 65211; Nuclear Science and Engineering Institute, University of Missouri, Columbia, MO 65211. Electronic address: LewisMic@missouri.edu.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Lewis
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D019583:Dose Fractionation, Radiation; D005260:Female; D015316:Genetic Therapy / Q000379:methods*; D007553:Isotope Labeling; D008187:Lutetium / Q000627:therapeutic use*; D051379:Mice; D016513:Mice, SCID; D058990:Molecular Targeted Therapy / Q000379:methods*; D058726:Nanoconjugates / Q000008:administration & dosage / Q000737:chemistry; D009374:Neoplasms, Experimental / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D016376:Oligonucleotides, Antisense / Q000008:administration & dosage; D020135:Peptide Nucleic Acids / Q000008:administration & dosage*; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D011868:Radioisotopes / Q000627:therapeutic use; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D016896:Treatment Outcome
chemical_list: C000715470:MAS1 protein, human; D058726:Nanoconjugates; D016376:Oligonucleotides, Antisense; D020135:Peptide Nucleic Acids; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D008187:Lutetium
keywords: Lutetium-177; Non-Hodgkin’s lymphoma; Peptide nucleic acid; Targeted antisense radiotherapy; bcl-2