title: PTD-Modified ATTEMPTS for Enhanced Toxin-based Cancer Therapy: An In Vivo Proof-of-Concept Study.
abstract: OBJECTIVE
  To investigate the feasibility of applying PTD-modified ATTEMPTS (Antibody Targeted Triggered Electrically Modified Prodrug-Type Strategy) for enhanced toxin therapy for the treatment of cancer.
  
  
  METHODS
  A heparin-functionalized murine anti-CEA monoclonal antibody (mAb), T84.66-heparin (T84.66-Hep), was chemically synthesized and characterized for specific binding to CEA overexpressed cells. The T84.66-Hep was then applied to the PTD-modified ATTEMPTS approach and the crucial features of the drug delivery system (DDS), 'antibody targeting' and 'heparin/protamine-based prodrug', were evaluated in vitro to examine whether it could selective delivery a PTD-modified toxin, recombinant TAT-gelonin chimera (TAT-Gel), to CEA high expression cancer cells (LS174T). Furthermore, the feasibility of the drug delivery system (DDS) was assessed in vivo by biodistribution and efficacy studies using LS174T s.c. xenograft tumor bearing mice.
  
  
  RESULTS
  T84.66-Hep displayed specific binding, but limited internalization (35% after 48 h incubation) to CEA high expression LS174T cells over low expression HCT116 cells. When mixed together with TAT-Gel, the T84.66-Hep formed a strong yet reversible complex. This complex formation provided an effective means of active tumor targeting of TAT-Gel, by 1) directing the TAT-Gel to CEA overexpressed tumor cells and 2) preventing nonspecific cell transduction to non-targeted normal cells. The cell transduction of TAT-Gel could, however, be efficiently reversed by addition of protamine. Feasibility of in vivo tumor targeting and "protamine-induced release" of TAT-Gel from the T84.66-Hep counterpart was confirmed by biodistribution and preliminary efficacy studies.
  
  
  CONCLUSIONS
  This study successfully demonstrated in vitro and in vivo the applicability of PTD-modified ATTEMPTS for toxin-based cancer therapy.
authors.affiliation: Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnosis, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, China.
authors.forename: Meong Cheol
authors.initials: MC
authors.lastname: Shin
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Kyoung Ah
authors.initials: KA
authors.lastname: Min
authors.forename: Huining
authors.initials: H
authors.lastname: He
authors.forename: Allan E
authors.initials: AE
authors.lastname: David
authors.forename: Yongzhuo
authors.initials: Y
authors.lastname: Huang
authors.forename: Victor C
authors.initials: VC
authors.lastname: Yang
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002272:Carcinoembryonic Antigen / Q000378:metabolism; D045744:Cell Line, Tumor; D016503:Drug Delivery Systems; D006493:Heparin / Q000008:administration & dosage / Q000627:therapeutic use; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D050506:Mutant Chimeric Proteins; D011355:Prodrugs / Q000378:metabolism*; D011479:Protamines / Q000008:administration & dosage / Q000627:therapeutic use; D011506:Proteins / Q000378:metabolism; D054789:Ribosome Inactivating Proteins, Type 1 / Q000494:pharmacology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014018:Tissue Distribution; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D002272:Carcinoembryonic Antigen; D050506:Mutant Chimeric Proteins; D011355:Prodrugs; D011479:Protamines; D011506:Proteins; D054789:Ribosome Inactivating Proteins, Type 1; C025674:GEL protein, Gelonium multiflorum; D006493:Heparin