title: Potent antitumor activity of a urokinase-activated engineered anthrax toxin.
abstract: The acquisition of cell-surface urokinase plasminogen activator activity is a hallmark of malignancy. We generated an engineered anthrax toxin that is activated by cell-surface urokinase in vivo and displays limited toxicity to normal tissue but broad and potent tumoricidal activity. Native anthrax toxin protective antigen, when administered with a chimeric anthrax toxin lethal factor, Pseudomonas exotoxin fusion protein, was extremely toxic to mice, causing rapid and fatal organ damage. Replacing the furin activation sequence in anthrax toxin protective antigen with an artificial peptide sequence efficiently activated by urokinase greatly attenuated toxicity to mice. In addition, the mutation conferred cell-surface urokinase-dependent toxin activation in vivo, as determined by using a panel of plasminogen, plasminogen activator, plasminogen activator receptor, and plasminogen activator inhibitor-deficient mice. Surprisingly, toxin activation critically depended on both urokinase plasminogen activator receptor and plasminogen in vivo, showing that both proteins are essential cofactors for the generation of cell-surface urokinase. The engineered toxin displayed potent tumor cell cytotoxicity to a spectrum of transplanted tumors of diverse origin and could eradicate established solid tumors. This tumoricidal activity depended strictly on tumor cell-surface plasminogen activation. The data show that a simple change of protease activation specificity converts anthrax toxin from a highly lethal to a potent tumoricidal agent.
authors.affiliation: Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Shihui
authors.initials: S
authors.lastname: Liu
authors.forename: Hannah
authors.initials: H
authors.lastname: Aaronson
authors.forename: David J
authors.initials: DJ
authors.lastname: Mitola
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Leppla
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Bugge
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use; D016503:Drug Delivery Systems; D045683:Furin; D051379:Mice; D009374:Neoplasms, Experimental / Q000188:drug therapy*; D010958:Plasminogen / Q000502:physiology; D015202:Protein Engineering; D011956:Receptors, Cell Surface / Q000502:physiology; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins / Q000494:pharmacology; D013381:Subtilisins / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
chemical_list: D000942:Antigens, Bacterial; D000970:Antineoplastic Agents; D001427:Bacterial Toxins; C524899:Plaur protein, mouse; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins; C030325:anthrax toxin; D010958:Plasminogen; D013381:Subtilisins; D014568:Urokinase-Type Plasminogen Activator; D045683:Furin