title: A novel ligand delivery system to non-invasively visualize and therapeutically exploit the IL13Rα2 tumor-restricted biomarker.
abstract: Our objective was to exploit a novel ligand-based delivery system for targeting diagnostic and therapeutic agents to cancers that express interleukin 13 receptor alpha 2 (IL13Rα2), a tumor-restricted plasma membrane receptor overexpressed in glioblastoma multiforme (GBM), meningiomas, peripheral nerve sheath tumors, and other peripheral tumors. On the basis of our prior work, we designed a novel IL13Rα2-targeted quadruple mutant of IL13 (TQM13) to selectively bind the tumor-restricted IL13Rα2 with high affinity but not significantly interact with the physiologically abundant IL13Rα1/IL4Rα heterodimer that is also expressed in normal brain. We then assessed the in vitro binding profile of TQM13 and its potential to deliver diagnostic and therapeutic radioactivity in vivo. Surface plasmon resonance (SPR; Biacore) binding experiments demonstrated that TQM13 bound strongly to recombinant IL13Rα2 (Kd∼5 nM). In addition, radiolabeled TQM13 specifically bound IL13Rα2-expressing GBM cells and specimens but not normal brain. Of importance, TQM13 did not functionally activate IL13Rα1/IL4Rα in cells or bind to it in SPR binding assays, in contrast to wtIL13. Furthermore, in vivo targeting of systemically delivered radiolabeled TQM13 to IL13Rα2-expressing subcutaneous tumors was demonstrated and confirmed non-invasively for the first time with 124I-TQM13 positron emission tomography imaging. In addition, 131I-TQM13 demonstrated in vivo efficacy against subcutaneous IL13Rα2-expressing GBM tumors and in an orthotopic synergeic IL13Rα2-positive murine glioma model, as evidenced by statistically significant survival advantage. Our results demonstrate that we have successfully generated an optimized biomarker-targeted scaffolding that exhibited specific binding activity toward the tumor-associated IL13Rα2 in vitro and potential to deliver diagnostic and therapeutic payloads in vivo.
authors.affiliation: The Brain Tumor Center of Excellence, Department of Neurosurgery, USA.
authors.forename: Van
authors.initials: V
authors.lastname: Nguyen
authors.forename: Jesse M
authors.initials: JM
authors.lastname: Conyers
authors.forename: Dongqin
authors.initials: D
authors.lastname: Zhu
authors.forename: Denise M
authors.initials: DM
authors.lastname: Gibo
authors.forename: Roy R
authors.initials: RR
authors.lastname: Hantgan
authors.forename: Steven M
authors.initials: SM
authors.lastname: Larson
authors.forename: Waldemar
authors.initials: W
authors.lastname: Debinski
authors.forename: Akiva
authors.initials: A
authors.lastname: Mintz
mesh_terms: D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002855:Chromatography, Thin Layer; D002942:Circular Dichroism; D024202:Electrophoretic Mobility Shift Assay; D005909:Glioblastoma / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007124:Immunoenzyme Techniques; D018793:Interleukin-13 / Q000235:genetics* / Q000378:metabolism; D053661:Interleukin-13 Receptor alpha1 Subunit / Q000378:metabolism*; D053663:Interleukin-13 Receptor alpha2 Subunit / Q000378:metabolism*; D008024:Ligands; D008297:Male; D051379:Mice; D008819:Mice, Nude; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D049268:Positron-Emission Tomography; D011485:Protein Binding; D011994:Recombinant Proteins; D023041:Xenograft Model Antitumor Assays
chemical_list: D018793:Interleukin-13; D053661:Interleukin-13 Receptor alpha1 Subunit; D053663:Interleukin-13 Receptor alpha2 Subunit; D008024:Ligands; D011994:Recombinant Proteins