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OBJECTIVEMalignant peripheral nerve sheath tumors (MPNSTs) are aggressive soft tissue sarcomas that harbor a high potential for metastasis and have a devastating prognosis. Combination chemoradiation aids in tumor control and decreases tumor recurrence but causes deleterious side effects and does not extend long-term survival. An effective treatment with limited toxicity and enhanced efficacy is critical for patients suffering from MPNSTs.METHODSThe authors recently identified that interleukin-13 receptor alpha 2 (IL-13Rα2) is overexpressed on MPNSTs and could serve as a precision-based target for delivery of chemotherapeutic agents. In the work reported here, a recombinant fusion molecule consisting of a mutant human IL-13 targeting moiety and a point mutant variant of Pseudomonas exotoxin A (IL-13.E13 K-PE4E) was utilized to treat MPNST in vitro in cell culture and in an in vivo murine model.RESULTSIL-13.E13 K-PE4E had a potent cytotoxic effect on MPNST cells in vitro. Furthermore, intratumoral administration of IL-13.E13 K-PE4E to orthotopically implanted MPNSTs decreased tumor burden 6-fold and 11-fold in late-stage and early-stage MPNST models, respectively. IL-13.E13 K-PE4E treatment also increased survival by 23 days in the early-stage MPNST model.CONCLUSIONSThe current MPNST treatment paradigm consists of 3 prongs: surgery, chemotherapy, and radiation, none of which, either singly or in combination, are curative or extend survival to a clinically meaningful degree. The results presented here provide the possibility of intratumoral therapy with a potent and highly tumor-specific cytotoxin as a fourth treatment prong with the potential to yield improved outcomes in patients with MPNSTs.

The limited effectiveness of current therapeutics against malignant brain gliomas has led to an urgent need for development of new formulations against these tumors. Chelator Dp44mT (di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone) presents a promising candidate to defeat gliomas due to its exceptional anti-tumor activity and its unique ability to overcome multidrug resistance. The goal of this study is to develop a targeted nano-carrier for Dp44mT delivery to glioma tumors and to assess its therapeutic efficacy in vitro and in vivo. Dp44mT is loaded into poly(ethylene glycol) (PEG)ylated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) decorated with glioma-targeting ligand Interlukin 13 (IL13). IL13-conjugation enhanced the NP uptake by glioma cells and also improved their transport across an in vitro blood-brain-barrier (BBB) model. This targeted formulation showed an outstanding toxicity towards glioma cell lines and patient-derived stem cells in vitro, with IC50 values less than 125 nM, and caused no significant death in healthy brain microvascular endothelial cells. In vivo, when tested on a xenograft mouse model, IL13-conjugated Dp44mT-NPs reduced the glioma tumor growth by ≈62% while their untargeted counterparts reduced the tumor growth by only ≈16%. Notably, this formulation does not cause any significant weight loss or kidney/liver toxicity in mice, demonstrating its great therapeutic potential.

Background Detection of glioma with MRI contrast agent is limited to cases in which the blood-brain barrier (BBB) is compromised as contrast agents cannot cross the BBB. Thus, an early-stage infiltrating tumor is not detectable. Interleukin-13 receptor alpha 2 (IL-13Rα2), which has been shown to be overexpressed in glioma, can be used as a target moiety. We hypothesized that liposomes conjugated with IL-13 and encapsulating MRI contrast agent are capable of passing through an intact BBB and producing MRI contrast with greater sensitivity. Methods The targeted MRI contrast agent was created by encapsulating Magnevist (Gd-DTPA) into liposomes conjugated with IL-13 and characterized by particle size distribution, cytotoxicity, and MRI relaxivity. MR image intensity was evaluated in the brain in normal mice post injection of Gd-DTPA and IL-13-liposome-Gd-DTPA one day apart. The specificity for glioma detection by IL-13-liposome-Gd-DTPA was demonstrated in an intracranial glioma mouse model and validated histologically. Results The average size of IL-13-liposome-Gd-DTPA was 137 ± 43 nm with relaxivity of 4.0 ± 0.4 L/mmole-s at 7 Tesla. No significant cytotoxicity was observed with MTS assay and serum chemistry in mice. The MRI signal intensity was enhanced up to 15% post injection of IL-13-liposome-Gd-DTPA in normal brain tissue following a similar time course as that for the pituitary gland outside of the BBB. MRI enhanced by IL-13-liposome-Gd-DTPA detected small tumor masses in addition to those seen with Magnevist-enhanced MRI. Conclusions IL-13-liposome-Gd-DTPA is able to pass through the uncompromised BBB and detect an early stage glioma that cannot be seen with conventional contrast-enhanced MRI.

Peripheral nerve sheath tumors are benign tumors that have the potential to transform into malignant peripheral nerve sheath tumors (MPNSTs). Interleukin-13 receptor alpha 2 (IL13Rα2) is a cancer associated receptor expressed in glioblastoma and other invasive cancers. We analyzed IL13Rα2 expression in several MPNST cell lines including the STS26T cell line, as well as in several peripheral nerve sheath tumors to utilize the IL13Rα2 receptor as a target for therapy. In our studies, we demonstrated the selective expression of IL13Rα2 in several peripheral nerve sheath tumors by immunohistochemistry (IHC) and immunoblots. We established a sciatic nerve MPNST mouse model in NIH III nude mice using a luciferase transfected STS26T MPNST cell line. Similarly, analysis of the mouse sciatic nerves after tumor induction revealed significant expression of IL13Rα2 by IHC when compared to a normal sciatic nerve. IL13 conjugated liposomal doxorubicin was formulated and shown to bind and internalized in the MPNST cell culture model demonstrating cytotoxic effect. Our subsequent in vivo investigation in the STS26T MPNST sciatic nerve tumor model indicated that IL13 conjugated liposomal doxorubicin (IL13LIPDXR) was more effective in inhibiting tumor progression compared to unconjugated liposomal doxorubicin (LIPDXR). This further supports that IL13 receptor targeted nanoliposomes is a potential approach for treating MPNSTs.

OBJECTIVEMalignant peripheral nerve sheath tumors (MPNSTs) are soft-tissue sarcomas arising from peripheral nerves. MPNSTs have increased expression of the oncogene aurora kinase A, leading to enhanced cellular proliferation. This makes them extremely aggressive with high potential for metastasis and a devastating prognosis; 5-year survival estimates range from a dismal 15% to 60%. MPNSTs are currently treated with resection (sometimes requiring limb amputation) in combination with chemoradiation, both of which demonstrate limited effectiveness. The authors present the results of immunohistochemical, in vitro, and in vivo analyses of MLN8237 for the treatment of MPNSTs in an orthoxenograft murine model.METHODSImmunohistochemistry was performed on tumor sections to confirm the increased expression of aurora kinase A. Cytotoxicity analysis was then performed on an MPNST cell line (STS26T) to assess the efficacy of MLN8237 in vitro. A murine orthoxenograft MPNST model transfected to express luciferase was then developed to assess the efficacy of aurora kinase A inhibition in the treatment of MPNSTs in vivo. Mice with confirmed tumor on in vivo imaging were divided into 3 groups: 1) controls, 2) mice treated with MLN8237, and 3) mice treated with doxorubicin/ifosfamide. Treatment was carried out for 32 days, with imaging performed at weekly intervals until postinjection day 42. Average bioluminescence among groups was compared at weekly intervals using 1-way ANOVA. A survival analysis was performed using Kaplan-Meier curves.RESULTSImmunohistochemical analysis showed robust expression of aurora kinase A in tumor cells. Cytotoxicity analysis revealed STS26T susceptibility to MLN8237 in vitro. The group receiving treatment with MLN8237 showed a statistically significant difference in tumor size compared with the control group starting at postinjection day 21 and persisting until the end of the study. The MLN8237 group also showed decreased tumor size compared with the doxorubicin/ifosfamide group at the conclusion of the study (p = 0.036). Survival analysis revealed a significantly increased median survival in the MLN8237 group (83 days) compared with both the control (64 days) and doxorubicin/ifosfamide (67 days) groups. A hazard ratio comparing the 2 treatment groups showed a decreased hazard rate in the MLN8237 group compared with the doxorubicin/ifosfamide group (HR 2.945; p = 0.0134).CONCLUSIONSThe results of this study demonstrate that MLN8237 is superior to combination treatment with doxorubicin/ifosfamide in a preclinical orthoxenograft murine model. These data have major implications for the future of MPNST research by providing a robust murine model as well as providing evidence that MLN8237 may be an effective treatment for MPNSTs.

Activation of microglia is a histological feature observed in neurodegenerative diseases like ALS. The oral administration of minocycline has been demonstrated to have minimal neuroprotection ability in the animal models and is also associated with inadvertent toxicity due to non-specific oral absorption of the drug. Nonetheless, the drug itself shows promise in a number of disease models suggesting it could be effective if delivered optimally. Thus, we utilized LPS modified liposomes to target TLR4 receptor on the microglia in SOD1G93A mice and compared its efficacy with non- targeted nanoliposomes. The in vitro results indicate that targeting the TLR4 receptor on microglia significantly increases (p G93A mouse model of ALS, targeted and non-targeted minocycline treatment significantly increased (p G93A mice, the non- targeted nanovesicles significantly increased the latency to rotarod failure and both targeted and non-targeted nanovesicles significantly delayed disease endpoints.

The 16th Annual Scientific Meeting of the Society for Neuro-Oncology in Conjunction with the AANS/CNS Section on Tumors, Orange County, California, USA, 17-20 November 2011. In Neuro-Oncology, 2011, v. 13 n. Suppl. 3, p. iii111, abstract no. ET-18

Glioblastoma (GBM) is the most common primary central nervous system (CNS) tumor in the United States and yet despite aggressive treatment, the median survival remains at 8 months. About 75% of human glioblastoma tumors selectively overexpress the α(2) subtype of interleukin 13 (IL-13Rα(2)), considered a “decoy receptor” for GBM, allowing it to evade apoptosis normally induced by IL-13 binding. Our laboratory and others have developed targeting strategies to take advantage of IL-13Rα(2) expression on GBMs. We showed that wildtype IL-13 targeted nanoliposomes delivering doxorubicin (WT-IL13-Dox), resulted in over 5-fold reduction of orthotopic tumors, with 60% of mice surviving for >200 days compared to mice treated with unconjugated liposomes. WT-IL13, however, also binds to the shared IL-13/IL-4 receptor α(1) subunit found in multiple organs, including the heart and lungs, suggesting potential cross-reactivity with surrounding tissues. To address off-target effects, a mutant version of IL-13 was developed known as Targeted Quadruple Mutant-13 (TQM), which display improved binding affinity to the IL-13Rα(2) receptor, and decreased affinity to the IL-13/IL-4 receptor α(1) subunit. Twenty mice were normalized by tumor burden into two groups, one treated with WT-IL13-Dox and the other group with TQM-13-conjugated liposomal doxorubicin (TQM-13-Lip-Dox). Each group received 5mg/kg of doxorubicin in the liposomes for 4 weeks. Mice treated with TQM-targeted liposomes had slower tumor growth, smaller tumor burden, and prolonged survival (33 vs 23 days, p=0.009) than those treated with WT-IL13 liposomes. WBC counts in WT-IL13 mice suggested they were immunocompromised in comparison to TQM mice (p=0.02), which may contribute to worse survival. These findings suggest that TQM-13 bound nanoliposomes may enable the development of targeted therapy with a decreased side effect profile for delivery of chemotherapeutic agents to GBMs.

Malignant peripheral nerve sheath tumor is a soft tissue sarcoma that poses tremendous challenges for effective therapy. Several therapeutic approaches using drugs such as doxorubicin and rapamycin have been tried in the past with minimum success. Therapeutic resistant property mediated by MDR proteins, in combination with DNA damage repair was proposed as a major cause leading to therapeutic inefficacy of chemotherapeutics in MPNST tumors. To overcome this issue, we encapsulated doxorubicin in lipid nanovesicles and targeted to IL13Rα2, a receptor that is selectively overexpressed in several malignant peripheral nerve sheath tumor cell lines. In the present investigation, a MPNST mouse model was developed using STS26T-Luc cell line stably transfected with luciferase reporter gene. These cells were implanted into the sciatic nerve that could be imaged by Intravital Imaging Spectroscopy (IVIS). After confirming the tumor formation, the mice were injected with 7 mg/kg body weight of (a) IL13 linked liposomal doxorubicin (IL3LIPDXR) (b) unconjugated liposomal doxorubicin (LIPDXR) and (c) control mice injected with equal volume of saline. The mice were treated weekly once for 7 weeks. The mice which received IL13LIPDXR and LIPDXR showed significant reduction in tumor volume compared to the control group. Among the targeted and non-targeted liposomes, IL13LIPDXR showed rapid tumor regression. However, beyond 4 weeks, the drug was ineffective in shrinking or maintaining the tumor volume. This concludes that although the targeted delivery of doxorubicin, seems to be effective initially however in the later course of treatment they are ineffective in controlling the tumor progression. Approaches such as combining doxorubicin with a small molecule Ras inhibitor or other agents in the liposome formulation which are currently underway may help to improve the therapeutic efficacy.

Glioblastoma Multiforme (GBM) is the most common CNS malignancy in adults, and even with multimodal therapies, carries a poor prognosis. These tumors are heterogeneous and modify their environment, promoting tumor growth, invasion, and therapeutic resistance. The intratumoral heterogeneity of GBM is accentuated during treatment. Even in the face of surgical resection and adjuvant chemoradiation, the unfortunate but inevitable recurrence and progression of GBM is nearly universal. This mechanism of acquired radiation resistance is not understood. We believe that acquired resistance of GBM is due to exosomes secreted from radiated GBM cells conferring resistance to the local cell population. Exosomes are nanometer cell-derived vesicles containing RNAs and proteins. Growing evidence demonstrates exosomes are instrumental to a cell’s interaction with its microenvironment, and have the ability to transfer information to recipient cells contributing to tumorigenicity. We utilized nanoparticle tracking analysis to analyze characteristics of exosome secretion after exposure to radiation. We used cell proliferation assays and cell survival assays to interrogate radiation derived exosome effects on the local cancer cell population. We assessed the potential of exosome blocking agents as a possible avenue for therapeutic manipulation to abrogate this oncogenic effect. We demonstrate that resistance and proliferative factors in GBM derived exosomes change after radiation exposure. Moreover, radiation derived exosomes have functional impact on tumor cell proliferation and radiation resistance. We also demonstrate the therapeutic potential of exosome blocking agents to inhibit acquired resistance, which develops in nearly all GBM patients. Radiation-derived exosomes cause increases in cellular proliferation and survival in the local cancer cell population and may be the hidden mediators of an ultimately radiation resistant tumor recurrence and the dire prognosis that follows. Adjuvant therapy with exosome blocking agents may be used to inhibit these oncogenic effects, leading to optimal patient outcomes.

Human glioblastoma tumors selectively express receptors for interleukin 13 (IL-13). In a previous study, we showed that liposomes, when conjugated with IL-13, will deliver chemotherapeutics to a subcutaneous glioma tumor model in mice much more effectively than conventional unconjugated liposomes. Based on this observation, we developed an intracranial brain tumor model in nude mice using human U87 glioma cells. Mice receiving weekly i.p. injections of 15 mg/kg of doxorubicin encapsulated in IL-13–conjugated liposomes had a 5-fold reduction in the intracranial tumor volume over 6 weeks and four of seven animals survived >200 days after tumor implantation. In contrast, the animals receiving unconjugated liposomes with the same doxorubicin concentration did not survive beyond 35 days and there was no evidence of tumor size reduction. The presence of liposomes with doxorubicin in the tumor was shown by taking advantage of the selective expression of IL-13 receptors on the tumor cells and the endogenous fluorescence of doxorubicin. There was no increase in the indices of toxicity in animals receiving the doxorubicin-containing liposomes. Finally, a model of the blood-brain barrier was used to show that the nanovesicles do not harm the endothelial cells yet maintain their toxicity to astrocytoma cells. This approach is necessary to show the efficacy of this targeting platform for tumors in which the blood-brain barrier is not compromised and as a potential use of the nanovesicle system as a surveillance mechanism to prevent recurrence. These data show that IL-13 targeted nanovesicles are a viable option for the treatment of brain tumors. [Mol Cancer Ther 2009;8(3):648–54]

We have previously demonstrated the therapeutic effect of interleukin-13 (IL13) linked liposomal doxorubicin (IL13LDXR) on glioma tumors. These tumors selectively overexpress IL13 receptor α2, a receptor for IL13. In our subsequent study, we found that malignant peripheral nerve sheath tumors (MPNST) also express the receptor for IL13. This observation prompted us to investigate the therapeutic value of IL13LDXR in a MPNST model. IL13LDXR was formulated and characterized in our laboratory using our previously established method. In vitro binding and internalization studies and subsequent fluorescence microscopy demonstrated the effective nuclear delivery of the doxorubicin in the MPNST cells expressing IL13Rα2 receptor. The cytotoxic potential of IL13LDXR was demonstrated in MPNST cell lines sNF96.2, ST88-14 and #215. Immunohistochemistry was performed on malignant and benign peripheral nerve sheath tumor (PNST) sections ex vivo to determine the expression of IL13Rα2 receptor. In addition we also demonstrated the expression of P-glycoprotein, a multidrug resistant protein in MPNST cell lines by immunocytochemistry. We also studied the effect of IL-13 protein in altering the expression of Pgp expression in established MPNST cell lines. We confirmed by an immunoblot that IL13 protein at 5µM concentration was able to decrease the Pgp expression in ST88-14 and sNF96.2 cells. This may explain the mechanism by which the IL-13 conjugated liposomes can deliver the encapsulated doxorubicin in a much more effective manner to drug resistant MPNST cell lines. We investigated the correlation of IL13Rα2 receptor expression with P-glycoprotein a drug resistance associated protein by immunocytochemistry. We confirmed the expression of IL13Rα2 in PNST tumors and established MPNST cell lines. We attempted to develop a MPNST tumor model in athymic nude mice by matrigel implantation method. We administered a single injection of 15 mg/kg of IL13 linked liposomal doxorubicin in a mouse tumor model by intraperitoneal route and observed the selective accumulation of doxorubicin in the tumor by endogenous fluorescence of doxorubicin, whereas no fluorescence was observed in the normal skin region as observed under fluorescence microscope. In conclusion consistent expression of IL13Ra2 receptors in PNST and MPNST cells and tissues indicate a viable approach to use this receptor as a target for MPNST therapy. The doxorubicin accumulation property and its cytotoxic potential on MPNST cells when delivered though the targeted liposomes envisage IL13LDXR as a potential drug for MPNST. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5521.