Novel recombinant adenoviral vector that targets the interleukin-13 receptor alpha2 chain permits effective gene transfer to malignant glioma

Expression of Interleukin-13 Receptor Alpha 2 in Brainstem Gliomas

The objective of this study was to investigate IL13Ra2 expression in brainstem glioma (BSG) and its correlation with key markers, functions, and prognostic implications, evaluating its therapeutic potential. A total of 80 tumor samples from BSG patients were analyzed. Multiplex immunofluorescence was used to examine six markers-IL13Ra2, H3.3K27M, CD133, Ki67, HLA-1, and CD4-establishing relationships between IL13Ra2 and these markers. Survival analysis, employing Kaplan-Meier and Cox proportional hazard regression models, encompassed 66 patients with complete follow-up. RNA-Seq data from a previously published study involving 98 patients were analyzed using the DESeq2 library to determine differential gene expression between groups. Gene Ontology (GO) enrichment and single-sample gene set enrichment analysis (ssGSEA) via the clusterProfiler library were used to delineate the gene functions of differentially expressed genes (DEGs). Nearly all the BSG patients displayed varying IL13Ra2 expression, with 45.0% (36/80) exhibiting over a 20% increase. Elevated IL13Ra2 levels were notably observed in pontine gliomas, diffuse intrinsic pontine gliomas (DIPGs), H3F3A-mutant gliomas, and WHO IV gliomas. IL13Ra2 expression was strongly correlated with H3.3K27M mutant protein, Ki67, and CD133. Patients with IL13Ra2 expression >20% showed shorter overall survival compared to those with ≤20% IL13Ra2 expression. The Cox proportional hazard regression model identified H3F3A mutations, rather than IL13Ra2 expression, as an independent prognostic factor. Analysis of RNA-Seq data from our prior cohort confirmed IL13Ra2's correlation with H3.3, CD133, and Ki67 levels. Widespread IL13Ra2 expression in BSG, particularly elevated in the H3F3A mutant group, was strongly correlated with H3F3A mutations, increased proliferation, and heightened tumor stemness. IL13Ra2 represents a promising therapeutic target for BSGs, potentially benefiting patients with H3K27M mutations, DIPGs, WHO Grade IV, and pontine location-specific BSGs, particularly those with H3K27M mutations.

The IL13α 2R paves the way for anti-glioma nanotherapy

Glioblastoma (GBM) is one of the most aggressive (grade IV) gliomas characterized by a high rate of recurrence, resistance to therapy and a grim survival prognosis. The long-awaited improvement in GBM patients' survival rates essentially depends on advances in the development of new therapeutic approaches. Recent preclinical studies show that nanoscale materials could greatly contribute to the improvement of diagnosis and management of brain cancers. In the current review, we will discuss how specific features of glioma pathobiology can be employed for designing efficient targeting approaches. Moreover, we will summarize the main evidence for the potential of the IL-13R alpha 2 receptor (IL13α2R) targeting in GBM early diagnosis and experimental therapy.

Possible Roles of Interleukin-4 and -13 and Their Receptors in Gastric and Colon Cancer

Interleukin (IL)-4 and -13 are structurally and functionally related cytokines sharing common receptor subunits. They regulate immune responses and, moreover, are involved in the pathogenesis of a variety of human neoplasms. Three different receptors have been described for IL-4, but only IL-4 receptor type II (IL-4Rα/IL-13Rα1) is expressed in solid tumors. While IL-13 can also bind to three different receptors, IL-13 receptor type I (IL-4Rα/IL-13Rα1/IL-13Rα2) and type II (IL-4Rα/IL-13Rα1) are expressed in solid tumors. After receptor binding, IL-4 and IL-13 can mediate tumor cell proliferation, survival, and metastasis in gastric or colon cancer. This review summarizes the results about the role of IL-4/IL-13 and their receptors in gastric and colon cancer.

Enhanced Delivery of Oncolytic Adenovirus by Neural Stem Cells for Treatment of Metastatic Ovarian Cancer

Oncolytic virotherapy is a promising approach for treating recurrent and/or drug-resistant ovarian cancer. However, its successful application in the clinic has been hampered by rapid immune-mediated clearance or neutralization of the virus, which reduces viral access to tumor foci. To overcome this barrier, patient-derived mesenchymal stem cells have been used to deliver virus to tumors, but variability associated with autologous cell isolations prevents this approach from being broadly clinically applicable. Here, we demonstrate the ability of an allogeneic, clonal neural stem cell (NSC) line (HB1.F3.CD21) to protect oncolytic viral cargo from neutralizing antibodies within patient ascites fluid and to deliver it to tumors within preclinical peritoneal ovarian metastases models. The viral payload used is a conditionally replication-competent adenovirus driven by the survivin promoter (CRAd-S-pk7). Because the protein survivin is highly expressed in ovarian cancer, but not in normal differentiated cells, viral replication should occur selectively in ovarian tumor cells. We found this viral agent was effective against cisplatin-resistant ovarian tumors and could be used as an adjunct treatment with cisplatin to decrease tumor burden without increasing toxicity. Collectively, our data suggest NSC-delivered CRAd-S-pk7 virotherapy holds promise for improving clinical outcome, reducing toxicities, and improving quality of life for patients with advanced ovarian cancer.

Receptor-Targeted Glial Brain Tumor Therapies

Among primary brain tumors, malignant gliomas are notably difficult to manage. The higher-grade tumors represent an unmet need in medicine. There have been extensive efforts to implement receptor-targeted therapeutic approaches directed against gliomas. These approaches include immunotherapies, such as vaccines, adoptive immunotherapy, and passive immunotherapy. Targeted cytotoxic radio energy and pro-drug activation have been designed specifically for brain tumors. The field of targeting through receptors progressed significantly with the discovery of an interleukin 13 receptor alpha 2 (IL-13RA2) as a tumor-associated receptor over-expressed in most patients with glioblastoma (GBM) but not in normal brain. IL-13RA2 has been exploited in novel experimental therapies with very encouraging clinical responses. Other receptors are specifically over-expressed in many patients with GBM, such as EphA2 and EphA3 receptors, among others. These findings are important in view of the heterogeneity of GBM tumors and multiple tumor compartments responsible for tumor progression and resistance to therapies. The combined targeting of multiple receptors in different tumor compartments should be a preferred way to design novel receptor-targeted therapeutic approaches in gliomas.

Tropism and transduction of oncolytic adenovirus 5 vectors in cancer therapy: Focus on fiber chimerism and mosaicism, hexon and pIX

The cellular internalization (infection of cells) of adenovirus 5 (Ad5) is mediated by the initial attachment of the globular knob domain of the capsid fiber protein to the cell surface coxsackievirus and adenovirus receptor (CAR), then followed by the interaction of the virus penton base proteins with cellular integrins. In tumors, there is a substantial intra- and intertumoral variability in CAR expression. The CAR-negative cells generally exhibit very low infectability. Since the fiber knob is a primary mediator of Ad5 binding to the cell surface, improved infectivity of Ad5-based vectors as oncolytic agents may be achieved via genetic modifications of this domain. The strategies to modify or broaden tropism and increase transduction efficiency of Ad5-based vectors include: 1) an incorporation of a targeting peptide into the fiber knob domain (the HI loop and/or C-terminus); 2) fiber knob serotype switching, or pseudotyping, by constructing chimeric fibers consisting of the knob domain derived from an alternate serotype (e.g., Ad5/3 or Ad5/35 chimeras), which binds to receptor(s) other than CAR (e.g., desmoglein 2/DSG2 and/or CD46); 3) "fiber complex mosaicism", an approach of combining serotype chimerism with peptide ligand(s) incorporation (e.g., Ad5/3-RGD); 4) "dual fiber mosaicism" by expressing two separate fibers with distinct receptor-binding capabilities on the same viral particle (e.g., Ad5-5/3 or Ad5-5/σ1); 5) fiber xenotyping by replacing the knob and shaft domains of wild-type Ad5 fiber protein with fibritin trimerization domain of T4 bacteriophage or σ1 attachment protein of reovirus. Other genetic approaches to increase the CAR-independent transduction efficiency include insertion of a targeting peptide into the hypervariable region of the capsid protein hexon or fusion to the C-terminus of pIX. Finally, we consider a yet unsolved molecular mechanism of liver targeting by Ad5-based vectors (CAR-, integrin-, fiber shaft KKTK motif-, and hepatic heparan sulfate glycosaminoglycans-independent, but fiber-, hexon- and blood factor X-dependent).

A novel single-chain antibody redirects adenovirus to IL13Rα2-expressing brain tumors

The generation of a targeting agent that strictly binds to IL13Rα2 will significantly expand the therapeutic potential for the treatment of IL13Rα2-expressing cancers. In order to fulfill this goal, we generated a single-chain antibody (scFv47) from our parental IL13Rα2 monoclonal antibody and tested its binding properties. Furthermore, to demonstrate the potential therapeutic applicability of scFv47, we engineered an adenovirus by incorporating scFv47 as the targeting moiety in the viral fiber and characterized its properties in vitro and in vivo. The scFv47 binds to human recombinant IL13Rα2, but not to IL13Rα1 with a high affinity of 0.9 · 10⁻⁹ M, similar to that of the parental antibody. Moreover, the scFv47 successfully redirects adenovirus to IL13Rα2 expressing glioma cells both in vitro and in vivo. Our data validate scFv47 as a highly selective IL13Rα2 targeting agent and justify further development of scFv47-modified oncolytic adenovirus and other therapeutics for the treatment of IL13Rα2-expressing glioma and other malignancies.

Interleukin-13 receptor alpha 2-targeted glioblastoma immunotherapy

Glioblastoma (GBM) is the most lethal primary brain tumor, and despite several refinements in its multimodal management, generally has very poor prognosis. Targeted immunotherapy is an emerging field of research that shows great promise in the treatment of GBM. One of the most extensively studied targets is the interleukin-13 receptor alpha chain variant 2 (IL13Rα2). Its selective expression on GBM, discovered almost two decades ago, has been a target for therapy ever since. Immunotherapeutic strategies have been developed targeting IL13Rα2, including monoclonal antibodies as well as cell-based strategies such as IL13Rα2-pulsed dendritic cells and IL13Rα2-targeted chimeric antigen receptor-expressing T cells. Advanced therapeutic development has led to the completion of several clinical trials with promising outcomes. In this review, we will discuss the recent advances in the IL13Rα2-targeted immunotherapy and evaluate the most promising strategy for targeted GBM immunotherapy.

Significance of interleukin-13 receptor alpha 2-targeted glioblastoma therapy

Glioblastoma multiforme (GBM) remains one of the most lethal primary brain tumors despite surgical and therapeutic advancements. Targeted therapies of neoplastic diseases, including GBM, have received a great deal of interest in recent years. A highly studied target of GBM is interleukin-13 receptor α chain variant 2 (IL13Rα2). Targeted therapies against IL13Rα2 in GBM include fusion chimera proteins of IL-13 and bacterial toxins, nanoparticles, and oncolytic viruses. In addition, immunotherapies have been developed using monoclonal antibodies and cell-based strategies such as IL13Rα2-pulsed dendritic cells and IL13Rα2-targeted chimeric antigen receptor-modified T cells. Advanced therapeutic development has led to the completion of phase I clinical trials for chimeric antigen receptor-modified T cells and phase III clinical trials for IL-13-conjugated bacterial toxin, with promising outcomes. Selective expression of IL13Rα2 on tumor cells, while absent in the surrounding normal brain tissue, has motivated continued study of IL13Rα2 as an important candidate for targeted glioma therapy. Here, we review the preclinical and clinical studies targeting IL13Rα2 in GBM and discuss new advances and promising applications.

New agents for targeting of IL-13RA2 expressed in primary human and canine brain tumors

Interleukin 13 receptor alpha 2 (IL-13RA2) is over-expressed in a vast majority of human patients with high-grade astrocytomas like glioblastoma. Spontaneous astrocytomas in dogs resemble human disease and have been proposed as translational model system for investigation of novel therapeutic strategies for brain tumors. We have generated reagents for both detection and therapeutic targeting of IL-13RA2 in human and canine brain tumors. Peptides from three different regions of IL-13RA2 with 100% sequence identity between human and canine receptors were used as immunogens for generation of monoclonal antibodies. Recombinant canine mutant IL-13 (canIL-13.E13K) and canIL-13.E13K based cytotoxin were also produced. The antibodies were examined for their immunoreactivities in western blots, immunohistochemistry, immunofluorescence and cell binding assays using human and canine tumor specimen sections, tissue lysates and established cell lines; the cytotoxin was tested for specific cell killing. Several isolated MAbs were immunoreactive to IL-13RA2 in western blots of cell and tissue lysates from glioblastomas from both human and canine patients. Human and canine astrocytomas and oligodendrogliomas were also positive for IL-13RA2 to various degrees. Interestingly, both human and canine meningiomas also exhibited strong reactivity. Normal human and canine brain samples were virtually negative for IL-13RA2 using the newly generated MAbs. MAb 1E10B9 uniquely worked on tissue specimens and western blots, bound live cells and was internalized in GBM cells over-expressing IL-13RA2. The canIL-13.E13K cytotoxin was very potent and specific in killing canine GBM cell lines. Thus, we have obtained several monoclonal antibodies against IL-13RA2 cross-reacting with human and canine receptors. In addition to GBM, other brain tumors, such as high grade oligodendrogliomas, meningiomas and canine choroid plexus papillomas, appear to express the receptor at high levels and thus may be appropriate candidates for IL-13RA2-targeted imaging/therapies. Canine spontaneous primary brain tumors represent an excellent translational model for human counterparts.

Derivation of a myeloid cell-binding adenovirus for gene therapy of inflammation

The gene therapy field is currently limited by the lack of vehicles that permit efficient gene delivery to specific cell or tissue subsets. Native viral vector tropisms offer a powerful platform for transgene delivery but remain nonspecific, requiring elevated viral doses to achieve efficacy. In order to improve upon these strategies, our group has focused on genetically engineering targeting domains into viral capsid proteins, particularly those based on adenovirus serotype 5 (Ad5). Our primary strategy is based on deletion of the fiber knob domain, to eliminate broad tissue specificity through the human coxsackie-and-adenovirus receptor (hCAR), with seamless incorporation of ligands to re-direct Ad tropism to cell types that express the cognate receptors. Previously, our group and others have demonstrated successful implementation of this strategy in order to specifically target Ad to a number of surface molecules expressed on immortalized cell lines. Here, we utilized phage biopanning to identify a myeloid cell-binding peptide (MBP), with the sequence WTLDRGY, and demonstrated that MBP can be successfully incorporated into a knob-deleted Ad5. The resulting virus, Ad.MBP, results in specific binding to primary myeloid cell types, as well as significantly higher transduction of these target populations ex vivo, compared to unmodified Ad5. These data are the first step in demonstrating Ad targeting to cell types associated with inflammatory disease.

A novel adenoviral vector labeled with superparamagnetic iron oxide nanoparticles for real-time tracking of viral delivery

In vivo tracking of gene therapy vectors challenges the investigation and improvement of biodistribution of these agents in the brain, a key feature for their targeting of infiltrative malignant gliomas. The glioma-targeting Ad5/3-cRGD gene therapy vector was covalently bound to super-paramagnetic iron oxide (Fe(3)O(4)) nanoparticles (SPION) to monitor its distribution by MRI. Transduction of labeled and unlabeled vectors was assessed on the U87 glioma cell line and normal human astrocytes (NHA), and was higher in U87 compared to NHA, but was similar between labeled and unlabeled virus. An in vivo study was performed by intracranial subcortical injection of labeled-Ad5/3-cRGD particles into a pig brain. The labeled vector appeared in vivo as a T2-weighted hyperintensity and a T2-gradient echo signal at the injection site, persisting up to 72 hours post-injection. We describe a glioma-targeting vector that is labeled with SPION, thereby allowing for MRI detection with no change in transduction capability.

Specific targeting of human interleukin (IL)-13 receptor α2-positive cells with lentiviral vectors displaying IL-13

The ability to selectively and efficiently target transgene delivery to specific cell types in vitro and in vivo remains one of the formidable challenges in gene therapy. Lentiviral vectors have several advantages that make them attractive as gene delivery vehicles and their tropism can be altered through pseudotyping, allowing transgene delivery to specific populations of cells. The human interleukin-13 receptor α2 (IL-13Rα2) is uniquely overexpressed in many different human tumors, making it an attractive target for cancer therapy. In this study, we examined whether IL-13Rα2-positive tumor cells can be specifically targeted with lentiviral vector pseudotypes containing a truncated fusion (F) protein derived from measles virus (MV) and a tail-truncated and receptor-blind MV hemagglutinin (H) protein bearing IL-13 at the C terminus. The retargeted lentiviral vector efficiently transduced cells that express high levels of IL-13Rα2, but not cells expressing low levels of IL-13Rα2 in vitro. In vivo, it specifically targeted IL-13Rα2-positive glioma cell xenografts in immunodeficient mice in the context of subcutaneous and intracranial glioma models. Similar lentiviral vectors may be developed for targeting other tumors expressing specific cell surface receptors.

Targeting the p53 signaling pathway in cancer therapy - the promises, challenges and perils

INTRODUCTION

Research over the past three decades has identified p53 as a multi-functional transcription factor. p53 influences myriad, highly diverse cellular processes, and represents one of the most important and extensively studied tumor suppressors. Activated by various stresses, p53 blocks cancer progression by provoking transient or permanent growth arrest, by enabling DNA repair, or by advancing cellular death programs. This anti-cancer activity profile, together with genomic and mutational analyses documenting inactivation of p53 in more than 50% of human cancers, motivated drug development efforts to (re-) activate p53 in established tumors.

AREAS COVERED

The complexities of p53 signaling in cancer are summarized, including current strategies and challenges to restore p53's tumor suppressive function in established tumors, to inactivate p53 inhibitors, and to restore wild type function of p53 mutant proteins.

EXPERT OPINION

p53 represents an attractive target for the development of anti-cancer therapies. Whether p53 is 'druggable', however, remains an area of active research and discussion, as p53 has pro-survival functions and chronic p53 activation accelerates aging, which may compromise the long-term homeostasis of an organism. The complex biology and dual functions of p53 in cancer prevention and age-related cellular responses pose significant challenges to the development of p53-targeting cancer therapies.

Neural stem cell-based cell carriers enhance therapeutic efficacy of an oncolytic adenovirus in an orthotopic mouse model of human glioblastoma

The potential utility of oncolytic adenoviruses as anticancer agents is significantly hampered by the inability of the currently available viral vectors to effectively target micrometastatic tumor burden. Neural stem cells (NSCs) have the ability to function as cell carriers for targeted delivery of an oncolytic adenovirus because of their inherent tumor-tropic migratory ability. We have previously reported that in vivo delivery of CRAd-S-pk7, a glioma-restricted oncolytic adenovirus, can enhance the survival of animals with experimental glioma. In this study, we show that intratumoral delivery of NSCs loaded with the CRAD-S-pk7 in an orthotopic xenograft model of human glioma is able to not only inhibit tumor growth but more importantly to increase median survival by ~50% versus animals treated with CRAd-S-pk7 alone (P = 0.0007). We also report that oncolytic virus infection upregulates different chemoattractant receptors and significantly enhances migratory capacity of NSCs both in vitro and in vivo. Our data further suggest that NSC-based carriers have the potential to improve the clinical efficacy of antiglioma virotherapy by not only protecting therapeutic virus from the host immune system, but also amplifying the therapeutic payload selectively at tumor sites.

Translating p53 into the clinic

Mutations in the TP53 gene are a feature of 50% of all reported cancer cases. In the other 50% of cases, the TP53 gene itself is not mutated but the p53 pathway is often partially inactivated. Cancer therapies that target specific mutant genes are proving to be highly active and trials assessing agents that exploit the p53 system are ongoing. Many trials are aimed at stratifying patients on the basis of TP53 status. In another approach, TP53 is delivered as a gene therapy; this is the only currently approved p53-based treatment. The p53 protein is overexpressed in many cancers and p53-based vaccines are undergoing trials. Processed cell-surface p53 is being exploited as a target for protein-drug conjugates, and small-molecule drugs that inhibit the activity of MDM2, the E3 ligase that regulates p53 levels, have been developed by several companies. The first MDM2 inhibitors are being trialed in both hematologic and solid malignancies. Finally, the first agent found to restore the active function of mutant TP53 has just entered the clinic. Here we discuss the basis of these trials and the future of p53-based therapy.

p53-based cancer therapy

Inactivation of p53 functions is an almost universal feature of human cancer cells. This has spurred a tremendous effort to develop p53 based cancer therapies. Gene therapy using wild-type p53, delivered by adenovirus vectors, is now in widespread use in China. Other biologic approaches include the development of oncolytic viruses designed to replicate and kill only p53 defective cells and also the development of siRNA and antisense RNA's that activate p53 by inhibiting the function of the negative regulators Mdm2, MdmX, and HPV E6. The altered processing of p53 that occurs in tumor cells can elicit T-cell and B-cell responses to p53 that could be effective in eliminating cancer cells and p53 based vaccines are now in clinical trial. A number of small molecules that directly or indirectly activate the p53 response have also reached the clinic, of which the most advanced are the p53 mdm2 interaction inhibitors. Increased understanding of the p53 response is also allowing the development of powerful drug combinations that may increase the selectivity and safety of chemotherapy, by selective protection of normal cells and tissues.

Neural stem cells target intracranial glioma to deliver an oncolytic adenovirus in vivo

Adenoviral oncolytic virotherapy represents an attractive treatment modality for central nervous system (CNS) neoplasms. However, successful application of virotherapy in clinical trials has been hampered by inadequate distribution of oncolytic vectors. Neural stem cells (NSCs) have been shown as suitable vehicles for gene delivery because they track tumor foci. In this study, we evaluated the capability of NSCs to deliver a conditionally replicating adenovirus (CRAd) to glioma. We examined NSC specificity with respect to viral transduction, migration and capacity to deliver a CRAd to tumor cells. Fluorescence-activated cell sorter (FACS) analysis of NSC shows that these cells express a variety of surface receptors that make them amenable to entry by recombinant adenoviruses. Luciferase assays with replication-deficient vectors possessing a variety of transductional modifications targeted to these receptors confirm these results. Real-time PCR analysis of the replication profiles of different CRAds in NSCs and a representative glioma cell line, U87MG, identified the CRAd-Survivin (S)-pk7 virus as optimal vector for further delivery studies. Using in vitro and in vivo migration studies, we show that NSCs infected with CRAd-S-pk7 virus migrate and preferentially deliver CRAd to U87MG glioma. These results suggest that NSCs mediate an enhanced intratumoral distribution of an oncolytic vector in malignant glioma when compared with virus injection alone.

Biodistribution of an oncolytic adenovirus after intracranial injection in permissive animals: a comparative study of Syrian hamsters and cotton rats

Conditionally replicative adenoviruses (CRAds) are often evaluated in mice; however, normal and cancerous mouse tissues are poorly permissive for human CRAds. As the cotton rat (CR) is a semipermissive animal and the Syrian hamster (SH) is a fully permissive model for adenoviral replication, we compared them in a single study following intracranial (i.c.) injection of a novel glioma-targeting CRAd. Viral genomic copies were quantified by real-time PCR in brain, blood, liver and lung. The studies were corroborated by immunohistochemical, serological and immunological assays. CR had a multiple log higher susceptibility for adenoviral infection than SH. A similar amount of genomic copies of CRAd-Survivin-pk7 and human adenovirus serotype 5 (AdWT) was found in the brain of CR and in all organs from SH. In blood and lung of CR, AdWT had more genomic copies than CRAd-Survivin-pk7 in some of the time points studied. Viral antigens were confirmed in brain slices, an elevation of serum transaminases was observed in both models, and an increase in anti-adenoviral antibodies was detected in SH sera. In conclusion, CR represents a sensitive model for studying biodistribution of CRAds after i.c. delivery, allowing for the detection of differences in the replication of CRAd-Survivin-pk7 and AdWT that were not evident in SH.

Interleukin-13 displaying retargeted oncolytic measles virus strains have significant activity against gliomas with improved specificity

The majority of glioblastoma multiforme (GBM) tumors (80%) overexpress interleukin-13 receptor alpha2 (IL-13Ralpha2), but there is no expression of IL-13Ralpha2 in normal brain. Vaccine strains of measles virus have significant antitumor activity against gliomas. We tested the hypothesis that measles virus entry could be retargeted via the IL-13Ralpha2. MV-GFP-H(AA)-IL-13 was generated from the Edmonston-NSe vaccine strain, by displaying human IL-13 at the C-terminus of the H protein, and introducing CD46 and signaling lymphocyte activation molecule (SLAM)-ablating mutations in H. The IL-13 retargeted virus showed significant cytopathic effect (CPE) against IL-13Ralpha2 overexpressing glioma lines, and lack of CPE/viral replication in normal human astrocytes and normal human fibroblasts not expressing IL-13Ralpha2. In vivo treatment of orthotopically implanted GBM12 xenografts demonstrated significant prolongation of survival in mice treated with the retargeted strain (P < 0.0001), and comparable activity between the IL-13R retargeted strain and MV-GFP (P = 0.6377). In contrast to MV-GFP-treated mice, administration of the retargeted strain in the central nervous system of measles replication-permissive Ifnar(ko) CD46 Ge mice resulted in lack of neurotoxicity. Strains of measles virus retargeted against the glioma-specific IL-13Ralpha2 receptor have comparable therapeutic efficacy, and improved specificity as compared with the unmodified measles virus strain MV-GFP in vitro and in vivo.

Interleukin-13 receptor alpha 2, EphA2, and Fos-related antigen 1 as molecular denominators of high-grade astrocytomas and specific targets for combinatorial therapy

PURPOSE

We investigated the expression of interleukin-13 receptor alpha2 (IL-13R alpha 2), EphA2, and Fos-related antigen 1 (Fra-1) in astrocytomas and normal brain. We sought to document whether the expression of the three factors changed with progression to higher grade malignancy and whether two or three targets in combination might be sufficient to target all patients with high-grade astrocytomas.

EXPERIMENTAL DESIGN

Immunohistochemistry was done for IL-13R alpha 2, EphA2, and Fra-1 using human brain tumor tissue microarrays containing 30 specimens of WHO grades II and III astrocytomas, 46 glioblastoma multiformes (GBM), and 9 normal brain samples. Sections were scored based on frequency and intensity of expression. Western blotting was done for all three markers using GBM tumor specimens and xenograft cell lines. Two cytotoxins, IL-13.E13K.PE38QQR and ephrinA1-PE38QQR, which target IL-13R alpha 2 or EphA2, respectively, were tested for cytotoxicity against human GBM primary explant cells and established cells.

RESULTS

Expression of all three proteins was significantly higher in GBM compared with normal brain, low-grade, and anaplastic astrocytomas. Greater than 95% of GBM overexpressed at least two of the three markers. Importantly, every GBM overexpressed at least one marker. Human GBM primary explant cells and cell lines were potently killed by IL-13.E13K.PE38QQR and ephrinA1-PE38QQR, in accordance with their level of expression of IL-13R alpha 2 and EphA2, respectively.

CONCLUSIONS

IL-13R alpha 2, EphA2, and Fra-1 are attractive therapeutic targets representing molecular denominators of high-grade astrocytomas. One hundred percent of GBM tumors overexpress at least one of these proteins, providing the basis for rational combinatorial targeted therapies/diagnostics suitable for all patients with this disease.