Emerging monoclonal antibody therapies for malignant gliomas

Molecular imaging using an anti-human tissue factor monoclonal antibody in an orthotopic glioma xenograft model

Nuclear medicine examinations for imaging gliomas have been introduced into clinical practice to evaluate the grade of malignancy and determine sampling locations for biopsies. However, these modalities have some limitations. Tissue factor (TF) is overexpressed in various types of cancers, including gliomas. We thus generated an anti-human TF monoclonal antibody (mAb) clone 1849. In the present study, immunohistochemistry performed on glioma specimens using anti-TF 1849 mAb showed that TF expression in gliomas increased in proportion to the grade of malignancy based on the World Health Organization (WHO) classification, and TF was remarkably expressed in necrosis and pseudopalisading cells, the histopathological hallmarks of glioblastoma multiforme (GBM). Furthermore, in both fluorescence and single-photon emission computed tomography/computed tomography (SPECT/CT) imaging studies, anti-TF 1849 IgG efficiently accumulated in TF-overexpressing intracranial tumours in mice. Although further investigation is required for a future clinical use of immuno-SPECT with ¹¹¹In-labelled anti-TF 1849 IgG, the immuno-SPECT may represent a unique imaging modality that can visualize the biological characteristics of gliomas differently from those obtained using the existing imaging modalities and may be useful to evaluate the grade of malignancy and determine sampling locations for biopsies in patients with glioma, particularly GBM.

Stereotaxic administrations of allogeneic human Vγ9Vδ2 T cells efficiently control the development of human glioblastoma brain tumors

Glioblastoma multiforme (GBM) represents the most frequent and deadliest primary brain tumor. Aggressive treatment still fails to eliminate deep brain infiltrative and highly resistant tumor cells. Human Vγ9Vδ2 T cells, the major peripheral blood γδ T cell subset, react against a wide array of tumor cells and represent attractive immune effector T cells for the design of antitumor therapies. This study aims at providing a preclinical rationale for immunotherapies in GBM based on stereotaxic administration of allogeneic human Vγ9Vδ2 T cells. The feasibility and the antitumor efficacy of stereotaxic Vγ9Vδ2 T cell injections have been investigated in orthotopic GBM mice model using selected heterogeneous and invasive primary human GBM cells. Allogeneic human Vγ9Vδ2 T cells survive and patrol for several days within the brain parenchyma following adoptive transfer and can successfully eliminate infiltrative GBM primary cells. These striking observations pave the way for optimized stereotaxic antitumor immunotherapies targeting human allogeneic Vγ9Vδ2 T cells in GBM patients.

REST regulates oncogenic properties of glioblastoma stem cells

Glioblastoma multiforme (GBM) tumors are the most common malignant primary brain tumors in adults. Although many GBM tumors are believed to be caused by self-renewing, glioblastoma-derived stem-like cells (GSCs), the mechanisms that regulate self-renewal and other oncogenic properties of GSCs are only now being unraveled. Here we showed that GSCs derived from GBM patient specimens express varying levels of the transcriptional repressor repressor element 1 silencing transcription factor (REST), suggesting heterogeneity across different GSC lines. Loss- and gain-of-function experiments indicated that REST maintains self-renewal of GSCs. High REST-expressing GSCs (HR-GSCs) produced tumors histopathologically distinct from those generated by low REST-expressing GSCs (LR-GSCs) in orthotopic mouse brain tumor models. Knockdown of REST in HR-GSCs resulted in increased survival in GSC-transplanted mice and produced tumors with higher apoptotic and lower invasive properties. Conversely, forced expression of exogenous REST in LR-GSCs produced decreased survival in mice and produced tumors with lower apoptotic and higher invasive properties, similar to HR-GSCs. Thus, based on our results, we propose that a novel function of REST is to maintain self-renewal and other oncogenic properties of GSCs and that REST can play a major role in mediating tumorigenicity in GBM.

Heat shock protein 70-binding protein 1 is highly expressed in high-grade gliomas, interacts with multiple heat shock protein 70 family members, and specifically binds brain tumor cell surfaces

Chaperone proteins and heat shock proteins (HSP) are essential components of cellular protein folding systems under normal conditions; their expression and activities are upregulated during stress. Chronically stressed tumors frequently exhibit high chaperone protein levels, exploiting their anti-apoptotic mechanisms and general proteome homeostasis amidst a background of genetic instability. Co-chaperones interact with chaperones as malleable regulatory components of protein folding activity and may represent a conduit for modification of chaperone activity to the detriment of the tumor. We have initially characterized one such co-chaperone, heat shock protein 70-binding protein (HspBP) 1 from human brain tumors, their xenografts grown in immune-compromised mice, and in syngeneic murine models in immune-competent mice. Immunohistochemical analyses show HspBP1 overexpression (with unusual subcellular localizations) in patient brain tumors relative to normal brain tissue. This holds true for the xenograft and syngeneic murine tumor models. In biochemical affinity chromatography assays, HspBP1 interacts with members of the HSP70 family from brain tumor lysates and from surface-derived samples, including HSP70, glucose regulated protein (GRP)75, GRP78, and HSP110. From normal brain lysates, only heat shock cognate (HSC)70, GRP75, and HSP110 bind to HspBP1. FACS analyses indicate that HspBP1 binds to brain tumor cell surfaces, possibly via HSP70 family members, and internalizes into cells. This has implications for HspBP1 biology as well as its utility as a tumor-targeting agent. Our results suggest that HspBP1 may play a role in tumor (dys)regulation of chaperone proteins, and that HspBP1 may have extracellular roles with therapeutic implications.

Use of antibodies and immunoconjugates for the therapy of more accessible cancers

There are currently 6 unconjugated antibodies and 3 immunoconjugates approved for use in the United States in a variety of cancers, with a considerable number of new agents in clinical testing and preclinical development. Unconjugated antibodies alone can be effective, but more often, antibodies need to be combined with chemotherapy, which enhances the efficacy of the standard treatment. Immunoconjugates tend to be more effective than their unconjugated counterparts, but their increased toxicity often restricts when and how they are used. In order to improve efficacy, a number of immunoconjugates are being examined in settings where the disease is more easily accessible, such as leukemias, or within compartments that allow easier and more direct access to the tumor, such as in the peritoneal cavity or brain, or both locally and systemically, in adjuvant situations, where the disease burden has been reduced by some other means, and with the main goal of these treatments being to kill residual disease.

Alpha-CTLA-4 mAb-associated panenteritis: a histologic and immunohistochemical analysis

Monoclonal antibodies (mAbs) against the cytotoxic T lymphocyte antigen-4 (CTLA-4) molecule are used as an adjuvant to experimental tumor immunization protocols in the treatment of malignant melanomas and ovarian cancers. Aside from noted early therapeutic successes, a spectrum of adverse effects, including severe gastroenteritis, has been reported. We report herein our observations of 5 patients who developed severe gastrointestinal toxicity affecting the gastric, small intestinal, and colonic mucosa. The endoscopic findings were variable, ranging from normal to diffusely erythematous and ulcerated mucosa. The constant histologic findings included a lymphoplasmacytic expansion of the lamina propria with increase in intraepithelial lymphocytes. Increased epithelial apoptosis was also a distinctive feature. Cryptitis and glandular inflammation were observed in the colon, ileum, and stomach, whereas villous blunting was present in the ileal and duodenal mucosa. Immunohistochemical analysis revealed a marked increase of all T-cell subsets (CD3+, CD4+, and CD8+) and of CD4CD25 regulatory T cells. We conclude that the panenteritis associated with injection of alpha-CTLA-4 mAbs demonstrates histology resembling autoimmune enteropathy. Furthermore, although the pathogenesis of immune dysregulation after the infusion of alpha-CTLA-4 mAbs remains unclear, we suspect that the increased number of regulatory T cells in the gastrointestinal mucosa may play a role in the pathogenicity.

Progress and problems in the application of focused ultrasound for blood-brain barrier disruption

Advances in neuroscience have resulted in the development of new diagnostic and therapeutic agents for potential use in the central nervous system (CNS). However, the ability to deliver the majority of these agents to the brain is limited by the blood-brain barrier (BBB), a specialized structure of the blood vessel wall that hampers transport and diffusion from the blood to the brain. Many CNS disorders could be treated with drugs, enzymes, genes, or large-molecule biotechnological products such as recombinant proteins, if they could cross the BBB. This article reviews the problems of the BBB presence in treating the vast majority of CNS diseases and the efforts to circumvent the BBB through the design of new drugs and the development of more sophisticated delivery methods. Recent advances in the development of noninvasive, targeted drug delivery by MRI-guided ultrasound-induced BBB disruption are also summarized.