title: An engineered anti-CA19-9 cys-diabody for positron emission tomography imaging of pancreatic cancer and targeting of polymerized liposomal nanoparticles.
abstract: BACKGROUND
  Antibody-based therapeutics is a rapidly growing field. Small engineered antibody fragments demonstrate similar antigen affinity compared with the parental antibody but have a shorter serum half-life and possess the ability to be conjugated to nanoparticles. The goal of this study was to engineer an anti-carbohydrate antigen 19-9 (CA19-9) cys-diabody fragment in hopes of targeting nanoparticles to pancreatic cancer.
  
  
  METHODS
  The anti-CA19-9 cys-diabody was created by engineering a C-terminal cysteine residue into the DNA single-chain Fv construct of the anti-CA19-9 diabody and expressed in NS0 cells. Maleimide chemistry was used to conjugate the cys-diabody to polymerized liposomal nanoparticles (PLNs) through the cysteine residues. Flow cytometry was used to evaluate targeting of cys-diabody and cys-diabody-PLN conjugate to human pancreatic cancer cell lines. The cys-diabody was radiolabeled with a positron emitter ((124)I) and evaluated in a mouse model of CA19-9-positive and CA19-9-negative xenografts with micro-positron emission tomography/micro-computed tomography at successive time intervals after injection. Percentage of injected dose per gram of radioactivity was measured in blood and tumor to provide objective confirmation of the micro-positron emission tomographic images.
  
  
  RESULTS
  Tumor xenograft imaging of the anti-CA19-9 cys-diabody demonstrated an average tumor-to-blood ratio of 3.0 and positive-to-negative tumor ratio of 7.4. Successful conjugation of the cys-diabody to PLNs was indicated by flow cytometry showing specific binding of cys-diabody-PLN conjugate to human pancreatic cancer cells in vitro.
  
  
  CONCLUSIONS
  Our results show that the anti-CA19-9 cys-diabody targets pancreatic cancer providing specific molecular imaging in tumor xenograft models. Furthermore, the cys-diabody-PLN conjugate demonstrates target-specific binding of human pancreatic cancer cells with the potential to deliver targeted treatment.
authors.affiliation: Department of Surgery, Veterans Healthcare Affairs, Greater Los Angeles, Los Angeles, California; Department of Surgery, UCLA, Los Angeles, California.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Girgis
authors.forename: Noah
authors.initials: N
authors.lastname: Federman
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Rochefort
authors.forename: Katelyn E
authors.initials: KE
authors.lastname: McCabe
authors.forename: Anna M
authors.initials: AM
authors.lastname: Wu
authors.forename: Jon O
authors.initials: JO
authors.lastname: Nagy
authors.forename: Christopher
authors.initials: C
authors.lastname: Denny
authors.forename: James S
authors.initials: JS
authors.lastname: Tomlinson
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000737:chemistry / Q000494:pharmacology*; D018395:CA-19-9 Antigen / Q000276:immunology*; D045744:Cell Line, Tumor; D003553:Cystine / Q000737:chemistry / Q000494:pharmacology; D005260:Female; D006801:Humans; D007167:Immunotherapy / Q000379:methods; D008081:Liposomes / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D009101:Multiple Myeloma; D053758:Nanoparticles / Q000627:therapeutic use*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000628:therapy*; D049268:Positron-Emission Tomography / Q000379:methods*; D015202:Protein Engineering; D057127:Single-Chain Antibodies / Q000737:chemistry / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D018033:Antibodies, Bispecific; D018395:CA-19-9 Antigen; D008081:Liposomes; D057127:Single-Chain Antibodies; D003553:Cystine
keywords: Antibody; CA19-9; Imaging; Nanoparticle; Pancreatic cancer