title: Matrix metalloproteinase-activated anthrax lethal toxin demonstrates high potency in targeting tumor vasculature.
abstract: Anthrax lethal toxin (LT), a virulence factor secreted by Bacillus anthracis, is selectively toxic to human melanomas with the BRAF V600E activating mutation because of its proteolytic activities toward the mitogen-activated protein kinase kinases (MEKs). To develop LT variants with lower in vivo toxicity and high tumor specificity, and therefore greater potential for clinical use, we generated a mutated LT that requires activation by matrix metalloproteinases (MMPs). This engineered toxin was less toxic than wild-type LT to mice because of the limited expression of MMPs by normal cells. Moreover, the systemically administered toxin produced greater anti-tumor effects than wild-type LT toward human xenografted tumors. This was shown to result from its greater bioavailability, a consequence of the limited uptake and clearance of the modified toxin by normal cells. Furthermore, the MMP-activated LT had very potent anti-tumor activity not only to human melanomas containing the BRAF mutation but also to other tumor types, including lung and colon carcinomas regardless of their BRAF status. Tumor histology and in vivo angiogenesis assays showed that this anti-tumor activity is due largely to the indirect targeting of tumor vasculature and angiogenic processes. Thus, even tumors genetically deficient in anthrax toxin receptors were still susceptible to the toxin therapy in vivo. Moreover, the modified toxin also displayed lower immunogenicity compared with the wild-type toxin. All these properties suggest that this MMP-activated anti-tumor toxin has potential for use in cancer therapy.
authors.affiliation: Laboratory of Bacterial Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Shihui
authors.initials: S
authors.lastname: Liu
authors.affiliation: Laboratory of Bacterial Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Hailun
authors.initials: H
authors.lastname: Wang
authors.affiliation: Oral and Pharyngeal Cancer Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Brooke M
authors.initials: BM
authors.lastname: Currie
authors.affiliation: Oral and Pharyngeal Cancer Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Molinolo
authors.affiliation: Laboratory of Bacterial Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Leung
authors.affiliation: Laboratory of Bacterial Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Mahtab
authors.initials: M
authors.lastname: Moayeri
authors.affiliation: Oral and Pharyngeal Cancer Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: John R
authors.initials: JR
authors.lastname: Basile
authors.affiliation: Cancer Research Institute of Scott & White Memorial Hospital, Temple, Texas 76502.
authors.forename: Randall W
authors.initials: RW
authors.lastname: Alfano
authors.affiliation: Oral and Pharyngeal Cancer Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
authors.affiliation: Cancer Research Institute of Scott & White Memorial Hospital, Temple, Texas 76502.
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Frankel
authors.affiliation: Oral and Pharyngeal Cancer Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892. Electronic address: thomas.bugge@nih.gov.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Bugge
authors.affiliation: Laboratory of Bacterial Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892. Electronic address: sleppla@niaid.nih.gov.
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Leppla
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism; D001427:Bacterial Toxins / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D019073:HT29 Cells; D006801:Humans; D007150:Immunohistochemistry; D016209:Interleukin-8 / Q000378:metabolism; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009154:Mutation; D009374:Neoplasms, Experimental / Q000098:blood supply / Q000188:drug therapy* / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D023041:Xenograft Model Antitumor Assays
chemical_list: D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D016209:Interleukin-8; D011994:Recombinant Proteins; C030325:anthrax toxin; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D020929:Mitogen-Activated Protein Kinase Kinases; D020782:Matrix Metalloproteinases