Evaluation of anti-podoplanin rat monoclonal antibody NZ-1 for targeting malignant gliomas

Introduction: Podoplanin/aggrus is a mucin-like sialoglycoprotein that is highly expressed in malignant gliomas. Podoplanin has been reported to be a novel marker to enrich tumor-initiating cells, which are thought to resist conventional therapies and to be responsible for cancer relapse. The purpose of this study was to determine whether an anti-podoplanin antibody is suitable to target radionuclides to malignant gliomas. Methods: The binding affinity of an anti-podoplanin antibody, NZ-1 (rat IgG(2a)), was determined by surface plasmon resonance and Scatchard analysis. NZ-1 was radioiodinated with (125)I using lodogen [(125)I-NZ-1(lodogen)] or N-succinimidyl 4-guanidinomethyl 3-[(131)I] iodobenzoate ([(131)I]SGMIB-NZ-1), and paired-label internalization assays of NZ-I were performed. The tissue distribution of (125)I-NZ-1 (lodogen) and that of [1311]SGMIB-NZ-1 were then compared in athymic mice bearing glioblastoma xenografts. Results: The dissociation constant (K(D)) of NZ-1 was determined to be 1.2 x 10(-10) M by surface plasmon resonance and 9.8 x 10(-10) M for D397MG glioblastoma cells by Scatcharcl analysis. Paired-label internalization assays in LN319 glioblastoma cells indicated that [(131)I] SGMIB-NZ-1 resulted in higher intracellular retention of radioactivity (26.3+/-0.8% of initially bound radioactivity at 8 11) compared to that from the (125)I-NZ-1 (lodogen) (10.0+/-0.1% of initially bound radioactivity at 8 It). Likewise, tumor uptake of [(131)I]SGMIB-NZ-1 (39.9+/-8.8% ID/g at 24 h) in athymic mice bearing D2159MG xenografts in vivo was significantly higher than that of (125)I-NZ-1 (lodogen) (29.7+/-6.1 %ID/g at 24 h). Conclusions: The overall results suggest that an anti-podoplanin antibody NZ-1 warrants further evaluation for antibody-based therapy against glioblastoma. (C) 2010 Elsevier Inc. All rights reserved.