title: Hemangiosarcoma and its cancer stem cell subpopulation are effectively killed by a toxin targeted through epidermal growth factor and urokinase receptors.
abstract: Targeted toxins have the potential to overcome intrinsic or acquired resistance of cancer cells to conventional cytotoxic agents. Here, we hypothesized that EGFuPA-toxin, a bispecific ligand-targeted toxin (BLT) consisting of a deimmunized Pseudomonas exotoxin (PE) conjugated to epidermal growth factor and urokinase, would efficiently target and kill cells derived from canine hemangiosarcoma (HSA), a highly chemotherapy resistant tumor, as well as cultured hemangiospheres, used as a surrogate for cancer stem cells (CSC). EGFuPA-toxin showed cytotoxicity in four HSA cell lines (Emma, Frog, DD-1 and SB) at a concentration of ≤100 nM, and the cytotoxicity was dependent on specific ligand-receptor interactions. Monospecific targeted toxins also killed these chemoresistant cells; in this case, a "threshold" level of EGFR expression appeared to be required to make cells sensitive to the monospecific EGF-toxin, but not to the monospecific uPA-toxin. The IC₅₀ of CSCs was higher by approximately two orders of magnitude as compared to non-CSCs, but these cells were still sensitive to EGFuPA-toxin at nanomolar (i.e., pharmacologically relevant) concentrations, and when targeted by EGFuPA-toxin, resulted in death of the entire cell population. Taken together, our results support the use of these toxins to treat chemoresistant tumors such as sarcomas, including those that conform to the CSC model. Our results also support the use of companion animals with cancer for further translational development of these cytotoxic molecules.
authors.affiliation: Veterinary Clinical Sciences, University of Minnesota, Minneapolis, MN, USA. scha0777@umn.edu
authors.forename: Jill T
authors.initials: JT
authors.lastname: Schappa
authors.forename: Aric M
authors.initials: AM
authors.lastname: Frantz
authors.forename: Brandi H
authors.initials: BH
authors.lastname: Gorden
authors.forename: Erin B
authors.initials: EB
authors.lastname: Dickerson
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Vallera
authors.forename: Jaime F
authors.initials: JF
authors.lastname: Modiano
mesh_terms: D000818:Animals; D001001:Anura; D001426:Bacterial Proteins / Q000494:pharmacology* / Q000633:toxicity; D002415:Cats; D045744:Cell Line, Tumor; D003603:Cytotoxins / Q000494:pharmacology / Q000633:toxicity; D004285:Dogs; D066246:ErbB Receptors / Q000378:metabolism*; D006394:Hemangiosarcoma / Q000188:drug therapy*; D006801:Humans; D000922:Immunotoxins / Q000494:pharmacology / Q000633:toxicity; D014411:Neoplastic Stem Cells / Q000187:drug effects*; D055293:Receptors, Urokinase Plasminogen Activator / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000494:pharmacology / Q000633:toxicity
chemical_list: D001426:Bacterial Proteins; D003603:Cytotoxins; D000922:Immunotoxins; D055293:Receptors, Urokinase Plasminogen Activator; D011993:Recombinant Fusion Proteins; C111749:pseudomonas exoprotein A protein, Pseudomonas aeruginosa; D066246:ErbB Receptors
keywords: cancer stem cell; epidermal growth factor; hemangiosarcoma; targeted therapies; urokinase
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