title: PTD-modified ATTEMPTS system for enhanced asparaginase therapy: a proof-of-concept investigation.
abstract: Macromolecular drugs such as proteins and gene products are presumably the most desirable therapeutic agents due to their unmatched substrate specificity and reaction efficiency. Yet, clinical use of these drugs has met with limited success, primarily due to the impermeable nature of the cell membrane that restricts cellular drug uptake to only small (<600 Da) and hydrophobic molecules. The recent discovery of the protein transduction domain (PTD) membrane-penetrating peptides, such as HIV-TAT, has finally offered the possibility of resolving this cell-membrane barrier for macromolecular drug delivery. Via covalent linkages, these PTD peptides have been shown to ferry the attached macromolecular species across membranes of all cell types, both in vitro and in vivo. Nevertheless, the lack of selectivity for PTD-mediated internalization restricts the application of this cell uptake method in clinical practice, due to concerns of inducing systemic toxicity caused by the carried drugs. Presented herein is a modified version of our previously established "ATTEMPTS" approach in delivery of macromolecular drugs, which integrates the cell-penetrating PTDs into a heparin/protamine-regulated delivery system. In vitro findings using asparaginase (ASNase) as a model macromolecular anti-tumor agent were able to validate the feasibility of this delivery system. The chemically constructed TAT-ASNase conjugates not only were able to translocate into the MOLT-4 cells and elicit the cytotoxic effects, but also this PTD-mediated intracellular drug uptake could be regulated (with on/off control) by the addition of heparin and protamine. This modified ATTEMPTS system therefore presents a new avenue of treatment of various types of cancers and other diseases with macromolecular drugs. In vitro characterization and a preliminary proof-of-concept animal investigation that demonstrates the feasibility of this PTD-mediated ASNase therapeutic system is subsequently described.
authors.affiliation: Tianjin Key Laboratory for Modern Drug Delivery and High Efficiency, Tianjin University, Tianjin 300072, PR China.
authors.forename: Young Min
authors.initials: YM
authors.lastname: Kwon
authors.forename: Yong Tao
authors.initials: YT
authors.lastname: Li
authors.forename: Jun F
authors.initials: JF
authors.lastname: Liang
authors.forename: Yoon Jeong
authors.initials: YJ
authors.lastname: Park
authors.forename: Li-Chien
authors.initials: LC
authors.lastname: Chang
authors.forename: Victor C
authors.initials: VC
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001215:Asparaginase / Q000008:administration & dosage* / Q000737:chemistry / Q000627:therapeutic use; D002384:Catalysis; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D016503:Drug Delivery Systems / Q000379:methods*; D005260:Female; D006367:HeLa Cells; D006493:Heparin / Q000737:chemistry; D006801:Humans; D008223:Lymphoma / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D008811:Mice, Inbred DBA; D010446:Peptide Fragments / Q000737:chemistry; D011355:Prodrugs / Q000008:administration & dosage / Q000737:chemistry / Q000627:therapeutic use; D011479:Protamines / Q000737:chemistry; D021382:Protein Sorting Signals; D016019:Survival Analysis; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000737:chemistry
chemical_list: D010446:Peptide Fragments; D011355:Prodrugs; D011479:Protamines; D021382:Protein Sorting Signals; D054322:tat Gene Products, Human Immunodeficiency Virus; D006493:Heparin; D001215:Asparaginase