generation-car-t-cells-for-adoptive-therapy-context-glioblastoma

Generation of CAR T Cells for Adoptive Therapy in the Context of Glioblastoma Standard of Care

Adoptive T cell immunotherapy offers a promising strategy for specifically targeting and eliminating malignant gliomas. T cells can be engineered ex vivo ...

Duke University

Chimeric antigen receptors (CAR)-transduced T cells hold great promise in the treatment of malignant disease. Here, we demonstrate that intracerebral injection with a human, epidermal growth factor receptor variant III (EGFRvIII)-specific, third generation CAR successfully treats glioma in mice. Importantly, these results endorse clinical translation of this CAR in patients with EGFRvIII-expressing brain tumors.

Intracerebral delivery of a third generation EGFRvIII-specific chimeric antigen receptor is efficacious against human glioma.

Chimeric antigen receptor (CAR) transduced T cells represent a promising immune therapy that has been shown to successfully treat cancers in mice and humans. However, CARs targeting antigens expressed in both tumors and normal tissues have led to significant toxicity. Preclinical studies have been limited by the use of xenograft models that do not adequately recapitulate the immune system of a clinically relevant host. A constitutively activated mutant of the naturally occurring epidermal growth factor receptor (EGFRvIII) is antigenically identical in both human and mouse glioma, but is also completely absent from any normal tissues.

EGFRvIII mCAR-modified T-cell therapy cures mice with established intracerebral glioma and generates host immunity against tumor-antigen loss.

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and is uniformly lethal. T-cell-based immunotherapy offers a promising platform for treatment given its potential to specifically target tumor tissue while sparing the normal brain. However, the diffuse and infiltrative nature of these tumors in the brain parenchyma may pose an exceptional hurdle to successful immunotherapy in patients. Areas of invasive tumor are thought to reside behind an intact blood brain barrier, isolating them from effective immunosurveillance and thereby predisposing the development of "immunologically silent" tumor peninsulas. Therefore, it remains unclear if adoptively transferred T cells can migrate to and mediate regression in areas of invasive GBM. One barrier has been the lack of a preclinical mouse model that accurately recapitulates the growth patterns of human GBM in vivo. Here, we demonstrate that D-270 MG xenografts exhibit the classical features of GBM and produce the diffuse and invasive tumors seen in patients. Using this model, we designed experiments to assess whether T cells expressing third-generation chimeric antigen receptors (CARs) targeting the tumor-specific mutation of the epidermal growth factor receptor, EGFRvIII, would localize to and treat invasive intracerebral GBM. EGFRvIII-targeted CAR (EGFRvIII+ CAR) T cells demonstrated in vitro EGFRvIII antigen-specific recognition and reactivity to the D-270 MG cell line, which naturally expresses EGFRvIII. Moreover, when administered systemically, EGFRvIII+ CAR T cells localized to areas of invasive tumor, suppressed tumor growth, and enhanced survival of mice with established intracranial D-270 MG tumors. Together, these data demonstrate that systemically administered T cells are capable of migrating to the invasive edges of GBM to mediate antitumor efficacy and tumor regression.

EGFRvIII-specific chimeric antigen receptor T cells migrate to and kill tumor deposits infiltrating the brain parenchyma in an invasive xenograft model of glioblastoma.

Immunotherapeutic approaches to cancer have shown remarkable promise. A critical barrier to successfully executing such immune-mediated interventions is the selection of safe yet immunogenic targets. As patient deaths have occurred when tumor-associated antigens shared by normal tissue have been targeted by strong cellular immunotherapeutic platforms, route of delivery, target selection and the immune-mediated approach undertaken must work together to maximize efficacy with safety. Selected tumor-specific targets can spare potential toxicity to normal tissue; however, they are far less common than tumor-associated antigens and may not be present on all patients. In the context of immunotherapy for high-grade glioma, 2 of the most prominently studied antigens are the tumor-associated epidermal growth factor receptor and its tumor-specific genetic deletion variant III. In this review, we will summarize the immune-mediated strategies employed against these targets as well as the caveats particular to these approaches.

Epidermal growth factor receptor and variant III targeted immunotherapy.

First-line chemotherapy to combat primary malignant brain cancer is often accompanied by lymphopenic immunologic deficiency. Although counterintuitive, chemotherapy-induced lymphopenia can provide excellent host conditioning that may actually be leveraged to potentiate antitumor immunotherapy. We discuss here our preclinical and clinical experiences applying immunotherapy against glioblastoma, the most common and lethal primary malignant brain tumor, as well as the use of immunotherapeutics in the setting of standard-of-care temozolomide chemotherapy.

Leveraging chemotherapy-induced lymphopenia to potentiate cancer immunotherapy.

CAR therapy has shown promise in treating cancer, but at the cost of unexpected toxicity against normal tissues, not predicted by preclinical testing. We are working to generate more physiologically relevant models for preclinical CAR toxicity testing, and in doing so, have discovered that CAR therapy induces immunogenic cell death, with the potential for cures.

Article	Year
Intracerebral delivery of a third generation EGFRvIII-specific chimeric antigen receptor is efficacious against human glioma. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia\| PubMed ID: 24054399	2014
EGFRvIII mCAR-modified T-cell therapy cures mice with established intracerebral glioma and generates host immunity against tumor-antigen loss. Clinical cancer research : an official journal of the American Association for Cancer Research\| PubMed ID: 24352643	2014
EGFRvIII-specific chimeric antigen receptor T cells migrate to and kill tumor deposits infiltrating the brain parenchyma in an invasive xenograft model of glioblastoma. PloS one\| PubMed ID: 24722266	2014
Epidermal growth factor receptor and variant III targeted immunotherapy. Neuro-oncology\| PubMed ID: 25342601	2014
Leveraging chemotherapy-induced lymphopenia to potentiate cancer immunotherapy. Oncoimmunology\| PubMed ID: 25610727	2014
Chimeric antigen receptor engineered T cells can eliminate brain tumors and initiate long-term protection against recurrence. Oncoimmunology\| PubMed ID: 25610729	2014

Carter M. Suryadevara

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