Novel way to increase targeting specificity to a human glioblastoma-associated receptor for interleukin 13

Chimeric Antigen Receptor Design Today and Tomorrow

ABSTRACT

The US Food and Drug Administration has approved 3 chimeric antigen receptor (CAR) T-cell therapies. For continued breakthroughs, novel CAR designs are needed. This includes different antigen-binding domains such as antigen-ligand binding partners and variable lymphocyte receptors. Another recent advancement in CAR design is Boolean logic gates that can minimize on-target, off-tumor toxicities. Recent studies on the optimization of costimulatory signaling have also shown how CAR design can impact function. By using specific signaling pathways and transcription factors, CARs can impact T-cell gene expression to enhance function. By using these techniques, the promise of CAR T-cell therapies for solid tumors can be fulfilled.

IL-13Rα2-Targeted Therapy Escapees: Biologic and Therapeutic Implications

Glioblastoma multiforme (GBM) overexpresses interleukin 13 receptor α2 (IL-13Rα2), a tumor-restricted receptor that is not present in normal brain. We and others have created targeted therapies that specifically eradicate tumors expressing this promising tumor-restricted biomarker. As these therapies head toward clinical implementation, it is critical to explore mechanisms of potential resistance. We therefore used a potent IL-13Rα2-targeted bacterial cytotoxin to select for naturally occurring "escapee" cells from three different IL-13Rα2-expressing GBM cell lines. We found that these side populations of escapee cells had significantly decreased IL-13Rα2 expression. We examined clinically relevant biologic characteristics of escapee cell lines compared to their parental cell lines and found that they had similar proliferation rates and equal sensitivity to temozolomide and radiation, the standard therapies given to GBM patients. In contrast, our escapee cell lines were less likely to form colonies in culture and migrated more slowly in wound healing assays. Furthermore, we found that escapee cells formed significantly less neurospheres in vitro, suggesting that IL-13Rα2-targeted therapy preferentially targeted the "stem-like" cell population and possibly indicating decreased tumorigenicity in vivo. We therefore tested escapee cells for in vivo tumorigenicity and found that they were significantly less tumorigenic in both subcutaneous and intracranial mouse models compared to matching parental cells. These data, for the first time, establish and characterize the clinically relevant biologic properties of IL-13Rα2-targeted therapy escapees and suggest that these cells may have less malignant characteristics than parental tumors.

Detailed analysis of inflammatory and neuromodulatory cytokine secretion from human NT2 astrocytes using multiplex bead array

Astrocytes are a very important cell type in the brain fulfilling roles in both neuroimmunology and neurotransmission. We have conducted the most comprehensive analysis of secreted cytokines conducted to date (astrocytes of any source) to determine whether astrocytes derived from the human Ntera2 (NT2) cell-line are a good model of human primary astrocytes. We have compared the secretion of cytokines from NT2 astrocytes with those produced in astrocyte enriched human brain cultures and additional cytokines implicated in brain injury or known to be expressed in the human brain. The concentration of cytokines was measured in astrocyte conditioned media using multiplex bead array (MBA), where 18 cytokines were measured simultaneously. Resting NT2 astrocytes produced low levels (∼1-30 pg/ml) of MIP1α, IL-6 and GM-CSF and higher levels of MCP-1, IP-10 and IL-8 (1-11 ng/ml) under non-inflammatory conditions. All of these in addition to IL-1β, TNFα, and IL-13, were increased by pro-inflammatory activation (TNFα or IL-1β stimulation). In contrast, IL-2, IL-4, IL-5, IL-7, IL-10, IL-12, LTα, and IFNγ were not detected in astrocyte conditioned media under any of the culture conditions tested. NT2 astrocytes were unresponsive to IL-2 and the adenyl cyclase agonist, forskolin. Interestingly, IFNγ stimulation selectively increased IP-10 secretion only. As astrocytes stimulated with IL-1β or TNFα produced several chemokines in the ng/ml range, we next assessed the chemoattractant properties of these cells. Conditioned media from TNFα-stimulated astrocytes significantly chemoattracted leukocytes from human blood. This study provides the most comprehensive analysis of cytokine production by human astrocytes thus far, and shows that NT2 astrocytes are highly responsive to pro-inflammatory mediators including TNFα and IL-1β, producing cytokines and chemokines capable of attracting leukocytes from human blood. We conclude that in the absence of adult human primary astrocytes that NT2-astrocytes may provide a valuable alternative to study the immunological behaviour of human astrocytes.

Innovative Therapies against Human Glioblastoma Multiforme

Glioblastoma multiforme is the most invasive and aggressive brain tumor in humans, and despite the latest chemical and radiative therapeutic approaches, it is still scarcely sensitive to these treatments and is generally considered an incurable disease. This paper will focus on the latest approaches to the treatment of this cancer, including the new chemicals such as proautophagic drugs and kinases inhibitors, and differentiating agents. In this field, there have been opening new perspectives as the discovery of possible specific targets such as the EGFRvIII, a truncated form of the EGF receptor. Antibodies against these targets can be used as proapoptotic agents and as possible carriers for chemicals, drugs, radioisotopes, and toxins. In this paper, we review the possible mechanism of action of these therapies, with particular attention to the combined use of toxic substances (for example, immunotoxins) and antiproliferative/differentiating compounds (i.e., ATRA, PPARγ agonists). All these aspects will be discussed in the view of progress clinical trials and of possible new approaches for directed drug formulations.

Getting into the brain: approaches to enhance brain drug delivery

Being the most delicate organ of the body, the brain is protected against potentially toxic substances by the blood-brain barrier (BBB), which restricts the entry of most pharmaceuticals into the brain. The developmental process for new drugs for the treatment of CNS disorders has not kept pace with progress in molecular neurosciences because most of the new drugs discovered are unable to cross the BBB. The clinical failure of CNS drug delivery may be attributed largely to a lack of appropriate drug delivery systems. Localized and controlled delivery of drugs at their desired site of action is preferred because it reduces toxicity and increases treatment efficiency. The present review provides an insight into some of the recent advances made in the field of brain drug delivery.The various strategies that have been explored to increase drug delivery into the brain include (i) chemical delivery systems, such as lipid-mediated transport, the prodrug approach and the lock-in system; (ii) biological delivery systems, in which pharmaceuticals are re-engineered to cross the BBB via specific endogenous transporters localized within the brain capillary endothelium; (iii) disruption of the BBB, for example by modification of tight junctions, which causes a controlled and transient increase in the permeability of brain capillaries; (iv) the use of molecular Trojan horses, such as peptidomimetic monoclonal antibodies to transport large molecules (e.g. antibodies, recombinant proteins, nonviral gene medicines or RNA interference drugs) across the BBB; and (v) particulate drug carrier systems. Receptor-mediated transport systems exist for certain endogenous peptides, such as insulin and transferrin, enabling these molecules to cross the BBB in vivo.The use of polymers for local drug delivery has greatly expanded the spectrum of drugs available for the treatment of brain diseases, such as malignant tumours and Alzheimer's disease. In addition, various drug delivery systems (e.g. liposomes, microspheres, nanoparticles, nanogels and bionanocapsules) have been used to enhance drug delivery to the brain. Recently, microchips and biodegradable polymers have become important in brain tumour therapy.The intense search for alternative routes of drug delivery (e.g. intranasal drug delivery, convection-enhanced diffusion and intrathecal/intraventricular drug delivery systems) has been driven by the need to overcome the physiological barriers of the brain and to achieve high drug concentrations within the brain. For more than 30 years, considerable efforts have been made to enhance the delivery of therapeutic molecules across the vascular barriers of the CNS. The current challenge is to develop drug delivery strategies that will allow the passage of drug molecules through the BBB in a safe and effective manner.

Protein- and DNA-based active immunotherapy targeting interleukin-13 receptor alpha2

High-grade astrocytoma (HGA) is an invariably fatal malignancy with a mean survival of 14 months despite surgery, radiation, and chemotherapy. We have found that a restricted receptor for interleukin-13 (IL-13), IL-13 receptor alpha 2 (IL13Ralpha2), is abundantly overexpressed in the vast majority of HGAs but is not appreciably expressed in normal tissue, with the exception of the testes. Therefore, IL-13Ralpha2 is a very attractive target for anti-HGA immunotherapy. In order to test protein and genetic vaccines that target IL13Ralpha2, we developed a G26-IL13Ralpha2-expressing syngeneic immunocompetent murine glioma model. Using this glioma model, mice were immunized with recombinant extracellular IL13Ralpha2 protein (IL13Ralpha2ex) or a DNA expression vector containing the gene for IL13Ralpha2 and were subsequently challenged with IL13Ralpha2( + ) G26 tumors. Mice immunized with either recombinant or genetic IL13Ralpha2, but not mock-immunized controls, demonstrated complete protection against IL13Ralpha2( + ) glioma growth and mortality. Of interest, only the recombinant-protein-based vaccines generated detectable anti-IL13Ralpha2 antibodies. These studies demonstrate the in vivo efficiency of protein- and DNA-based immunotherapy strategies that target IL13Ralpha2 that may play a clinical role to eradicate the residual microscopic HGA cells that inevitably cause disease recurrence and mortality.

Cintredekin besudotox in treatment of malignant glioma

BACKGROUND

Interleukin-13 (IL-13) receptors are overexpressed in glioblastoma multiforme (GBM). The presence of IL-13 binding sites in GBM and their absence in normal brain tissue validates IL-13 receptor as an important target in human GBM.

OBJECTIVE

This review discusses the bench-to-bedside experience with a recombinant cytotoxin composed of human IL-13 and a truncated form of Pseudomonas exotoxin A (PE38QQR), delivered via convection-enhanced delivery (CED), in GBM treatment.

METHODS

The authors review publications regarding the laboratory research and clinical development of IL-13-directed therapies and summarize the future of IL-13-targeted cytotoxin.

CONCLUSION

The IL-13 receptor remains an important potential target in GBM, and preliminary experience with the IL-13-PE38QQR cytotoxin (also called cintredekin besudotox) has helped to pave the way for study of CED as an important means of drug delivery to malignant gliomas. Ongoing analysis of recently completed clinical trials will determine the future of this agent and its potential therapeutic targets.

Novel advances in drug delivery to brain cancer

The therapy of brain tumors has been limited by a lack of effective methods of drug delivery to the brain. Systemic administration is often associated with toxic side effects and ultimately fails to achieve therapeutic concentrations within a tumor. An attractive strategy that has gained importance in brain tumor therapy has relied on local and controlled delivery of chemotherapeutic agents by biodegradable polymers. This technique allows direct exposure of tumor cells to a therapeutic agent for a prolonged period of time and has been shown to prolong the survival of patients with malignant brain tumors. The use of polymers for local drug delivery greatly expands the spectrum of drugs available for the treatment of malignant brain tumors. This review discusses the rationale for local drug delivery, describes the development of currently available polymer-based therapeutic agents, and highlights examples of promising non-polymer based drug delivery methods for use in the treatment of malignant brain tumors.

Expression of cysteinyl leukotriene receptor 1 in human traumatic brain injury and brain tumors

Cysteinyl leukotrienes (CysLTs) are potent proinflammatory mediators. CysLT receptor 1 (CysLT(1)) is one of the two CysLT receptors that has been cloned. Although the expression of CysLT(1) in the brain has been demonstrated by Northern blot and RT-PCR analyses, the location of CysLT(1) in the brain remains unknown. The objective of this study was to examine the distribution of CysLT(1) by immunohistochemical analysis in human brains with traumatic injury or tumors. CysLT(1) was expressed intensely in the microvascular endothelial cells in both normal and abnormal conditions. At 8 days after traumatic injury, microvascular regeneration was found and all of the endothelial cells highly expressed CysLT(1). In gray and white matters of the normal regions of the brain, CysLT(1) was expressed weekly or not at all. However, the CysLT(1) expression increased in the neuron- and glial-appearing cells in gray and white matters after traumatic brain injury. CysLT(1) was also detected in astrocytoma, ganglioglioma and metastatic adenocarcinoma, and the expression in the neuron- and glial-appearing cells around brain tumors increased robustly.

Interleukin-13 fusion cytotoxin arrests Schistosoma mansoni egg-induced pulmonary granuloma formation in mice

Schistosoma mansoni egg-induced lung pathology requires the actions of interleukin (IL)-4 and IL-13. Because receptors for IL-4 and IL-13 share chains, we examined the effect of a fusion protein comprised of IL-13 and Pseudomonas exotoxin (IL13-PE) on the development of pulmonary granulomas in mice. At day 8 after an intravenous injection of live S. mansoni eggs, whole lung samples from IL13-PE-treated mice exhibited significantly lower IL-4 and IL-13 gene expression, smaller granulomas, decreased collagen levels, and increased IL-13 receptor alpha2 gene expression compared to controls. The therapeutic effects of IL13-PE were also observed at day 16 despite the termination of IL13-PE treatment at day 8. These studies demonstrate that targeting IL-4- and IL-13- responsive cells with IL13-PE effectively arrests S. mansoni egg granuloma formation.

Local treatment of brain tumors with targeted chimera cytotoxic proteins

High-grade astrocytomas (HGA) are the most prevalent brain tumors that represent a unique pharmaceutical challenge. Their cerebral localization and characteristic features of tumor progression primarily dictate this challenge. Targeted chimera conjugate/fusion cytotoxic proteins have become the newest class of investigative drug candidates for the treatment of HGA due to their inherent properties that are compatible with drug deliveries to brain tumors. A conjugate of a human transferrin with bacterial toxin, Diphtheria toxin, has shown clinical efficacy in Phase I and II trials when administered intratumorally through convection-enhanced delivery. This immunotoxin belongs to the first group of immunotoxins that started to live up to early expectations. Other anti-brain tumor cytotoxins have entered or will enter the clinic shortly. The clinical applicability of targeted bacterial toxin-containing cytotoxins in the treatment of brain tumors warrants further development and careful clinical evaluation.

Biologic response modifiers in pediatric cancer

Biologic response modifiers are becoming an important addition to surgery, chemotherapy, and radiotherapy in the management of cancer. As this field of research grows and expands, more biologic response modifiers will be incorporated into therapeutic regimens. By stimulating the immune system to eradicate minimal residual disease, these agents may improve the disease-free and long-term survival rates of patients with a variety of malignancies. The challenge is to incorporate biologic response modifiers into the treatment armamentarium in ways that will maximize their tumorigenicity.

Molecular targeting of malignant gliomas with novel multiply-mutated interleukin 13-based cytotoxins

A vast majority of high-grade gliomas over-express a receptor for interleukin 13 (IL13). This glioma-associated receptor for IL13 is interleukin 4 (IL4)-independent. This is in contrast to the physiological and IL4-shared receptor for the IL13, IL13/4 receptor, which is found on many normal organs. IL13-based Pseudomonas exotoxin (PE)-containing cytotoxic fusion proteins have been shown to be very potent anti-glioma agents. However, native IL13-based cytotoxins interact with both forms of the IL13 receptor. Therefore, mutations in IL13 were made in order to diminish/eliminate IL13's interaction with the shared IL13/4 receptor of normal tissue. These mutations encompassed amino acids located on alpha-helix A and C of IL13. We have engineered double or triple mutants of IL13 linked to various forms of PE. We found that these mutations could be successfully incorporated into IL13 without the loss of the protein's ability to selectively deliver the toxin to glioma cells while reducing their toxicity.

Conversion of interleukin-13 into a high affinity agonist by a single amino acid substitution

We created a novel mutated form of human interleukin-13 (IL-13) in which a positively charged arginine (R) at position 112 was substituted to a negatively charged aspartic acid (D). This mutant, termed IL-13R112D, was expressed in Escherichia coli and purified to near homogeneity. IL-13R112D was found to be a potent IL-13 agonist with 5-10-fold improved binding affinity to IL-13 receptors compared with wild-type IL-13 (wtIL-13). The conclusion of IL-13 agonist activity was drawn on the basis of approximately 10-fold improved activity over wtIL-13 in several assays: (a) inhibition of CD14 expression in primary monocytes; (b) proliferation of TF-1 and B9 cell lines; and (c) activation of STAT6 in Epstein-Barr virus-immortalized B cells, primary monocytes, and THP-1 monocytic cell line. Furthermore, mutant IL-13R112D neutralized the cytotoxic activity of a chimeric fusion protein composed of wtIL-13 and a Pseudomonas exotoxin A (IL-13-PE38) approximately 10 times better than wtIL-13. Based on these results, it was concluded that IL-13R112D interacts with much stronger affinity than wtIL-13 on all cell types tested and that Arg-112 plays an important role in the interaction with its receptors (IL-13R). Thus, these results suggest that IL-13R112D may be a useful ligand for the study of IL-13 interaction with its receptors or, alternatively, in designing specific targeted agents for IL-13R-positive malignancies.

Targeted drug delivery for brain cancer treatment

The blood brain barrier (BBB) and the systemic toxicity of conventional chemotherapy present obstacles to the success of future blood-borne drug therapies of brain tumors. The work with polymer-encapsulated cancer drugs suggests an alternative and more focused treatment approach. Our experimental strategy integrates direct intracerebral drug delivery, sustained drug release from liposomes or polymer implants, and increased targeting of the drug either by chemically modifying the drug or by using tumor-specific carriers. This review will present some of the recent work on targeted drug delivery for brain cancer treatment.