title: Targeted cytolysins synergistically potentiate cytoplasmic delivery of gelonin immunotoxin.
abstract: Targeted endocytic uptake is a first step toward tissue-specific cytoplasmic macromolecular delivery; however, inefficient escape from the endolysosomal compartment makes this generally impractical at present. We report here a targeted cytolysin approach that dramatically potentiates endosomal release of an independently targeted potent gelonin immunotoxin. Fibronectin domains engineered for affinity to EGF receptor or carcinoembryonic antigen were fused to the plant toxin gelonin or bacterial pore-forming cytolysins. These fusion proteins display synergistic activity in both antigen-specific cytotoxicity in vitro, enhancing potency by several orders of magnitude, and in tumor growth inhibition in vivo. In addition, the number of internalized gelonin molecules required to induce apoptosis is reduced from approximately 5 × 10(6) to less than 10(3). Targeted potentiation shows promise for enhancing cytoplasmic delivery of other macromolecular payloads such as DNA, siRNA, and miRNA.
authors.affiliation: Corresponding Author: K. Dane Wittrup, Massachusetts Institute of Technology, Building 76-261, 77 Massachusetts Avenue, Cambridge, MA 02139. wittrup@mit.edu.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Pirie
authors.forename: David V
authors.initials: DV
authors.lastname: Liu
authors.forename: K Dane
authors.initials: KD
authors.lastname: Wittrup
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000276:immunology; D003603:Cytotoxins / Q000276:immunology* / Q000494:pharmacology; D004357:Drug Synergism; D011992:Endosomes / Q000276:immunology / Q000378:metabolism*; D066246:ErbB Receptors / Q000276:immunology*; D005353:Fibronectins / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D000922:Immunotoxins / Q000276:immunology* / Q000494:pharmacology; D051379:Mice; D058990:Molecular Targeted Therapy; D009928:Organ Specificity; D054789:Ribosome Inactivating Proteins, Type 1 / Q000008:administration & dosage* / Q000276:immunology* / Q000494:pharmacology
chemical_list: D002272:Carcinoembryonic Antigen; D003603:Cytotoxins; D005353:Fibronectins; D000922:Immunotoxins; D054789:Ribosome Inactivating Proteins, Type 1; C025674:GEL protein, Gelonium multiflorum; D066246:ErbB Receptors