Glioblastoma (GBM) has a dismal prognosis due to therapy resistance of GBM initiating cells (GICs). GICs are preferentially found in the perivascular niche and novel therapeutic strategies are needed that target GICs and the vascular niche. The efficacy of current GBM therapies is hindered by their limited trans-endothelial permeability to the GIC perivascular niche and associated systemic toxicities. Here, we propose a new treatment option with tumor enzyme-activatable, combined therapeutic and diagnostic (theranostic) nanoparticles, which caused specific toxicity against GBM tumor cells and GICs. The theranostic cross-linked iron oxide nanoparticles (CLIO) were conjugated to a highly potent vascular disrupting agent (ICT) and secured with a matrix-metalloproteinase (MMP-14) cleavable protein cap. The purpose of this study was to evaluate tumor retention of CLIO-ICT through MR imaging and demonstrate its anti-GBM affects in vivo settings. Methods: GBM-bearing were treated i.v. with CLIO-ICT (80mg/kg of ICT), ICT (80mg/kg of ICT), CLIO (0.5 mmol Fe/kg) or PBS twice a week for 14 days. For combination treatment with temozolomide (33mg/kg), mice were treated with ICT and CLIO-ICT twice a week for 21 days. MRI studies of GBM-bearing mice were performed on a 7T MR scanner (Bruker-Agilent Technologies-General Electric Healthcare), using T2-weighted imaging sequences. BioLuminescent imaging was performed on an IVIS spectrum scanner (PerkinElmer). TNP delivery across the blood brain barrier (BBB) was confirmed by intra-vital microscopy (IVM) studies with a microscope (IV-100; Olympus, Tokyo, Japan). Flow cytometry and histopathology were performed to evaluate apoptosis in GICs upon CLIO-ICT treatment. Results are presented as mean ± SD unless otherwise presented. Tumor and organ relaxation rates and fluorescence signals were compared using one-way ANOVA. Kaplan-Meier survival curves were compared using the log‐rank (Mantel-Cox) test. The level of significance was set at p < 0.05, as compared with the control group. Results: Treatment with CLIO-ICT disrupted tumor vasculature of MMP-14 expressing GBM, induced GIC apoptosis and significantly (p< 0.05) impaired tumor growth compared to PBS-treated animals. In addition, the iron core of CLIO-ICT enabled in vivo drug tracking with MR imaging. T2-weighted MR images before and after intravenous injection of CLIO-ICT in mice showed a signal drop or negative enhancement and significant (p< 0.05) tumor retention of CLIO-ICT in GBM tissue, which was confirmed with Prussian blue histopathological evaluations. Treatment with CLIO-ICT plus temozolomide achieved tumor remission and significantly (p< 0.05) increased survival of human GBM bearing mice compared to temozolomide alone. Conclusion: We present a new, clinically translatable therapeutic strategy with significant impact on survival. Further our approach of combining CLIO-ICT with TMZ offers refinements to current less optimal standards of care in order to achieve GBM remission.
Citation Format: suchismita mohanty, Zixin Chen, Kai Li, Goreti Morais, Jessica Klockow, Ketan Yerneni, Laura Pisani, Frederick Chin, Siddhartha Mitra, Samuel Cheshier, Edwin Chang, Sanjiv Gambhir, Jianghong Rao, Paul M. Loadman, Robert A. Falconer, Heike E. Daldrup-Link. A novel theranostic strategy for MMP-14 expressing glioblastomas impacts survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-004.