Intratumoral IL-12 combined with CTLA-4 blockade elicits T cell-mediated glioma rejection

Immunobiology and immunotherapeutic targeting of glioma stem cells

For decades human brain tumors have confounded our efforts to effectively manage and treat patients. In adults, glioblastoma multiforme is the most common malignant brain tumor with a patient survival of just over 14 months. In children, brain tumors are the leading cause of solid tumor cancer death and gliomas account for one-fifth of all childhood cancers. Despite advances in conventional treatments such as surgical resection, radiotherapy, and systemic chemotherapy, the incidence and mortality rates for gliomas have essentially stayed the same. Furthermore, research efforts into novel therapeutics that initially appeared promising have yet to show a marked benefit. A shocking and somewhat disturbing view is that investigators and clinicians may have been targeting the wrong cells, resulting in the appearance of the removal or eradication of patient gliomas only to have brain cancer recurrence. Here we review research progress in immunotherapy as it pertains to glioma treatment and how it can and is being adapted to target glioma stem cells (GSCs) as a means of dealing with this potential paradigm.

Overview of current immunotherapeutic strategies for glioma

In the last decade, numerous studies of immunotherapy for malignant glioma (glioblastoma multiforme) have brought new knowledge and new hope for improving the prognosis of this incurable disease. Some clinical trials have reached Phase III, following positive outcomes in Phase I and II, with respect to safety and immunological end points. Results are encouraging especially when considering the promise of sustained efficacy by inducing antitumor immunological memory. Progress in understanding the mechanisms of tumor-induced immune suppression led to the development of drugs targeting immunosuppressive checkpoints, which are used in active clinical trials for glioblastoma multiforme. Insights related to the heterogeneity of the disease bring new challenges for the management of glioma and underscore a likely cause of therapeutic failure. An emerging therapeutic strategy is represented by a combinatorial, personalized approach, including the standard of care: surgery, radiation, chemotherapy with added active immunotherapy and multiagent targeting of immunosuppressive checkpoints.

Harnessing immunosurveillance: current developments and future directions in cancer immunotherapy

Despite improved methods of cancer detection and disease management over the last few decades, cancer remains a major public health problem in many societies. Conventional therapies, such as chemotherapy, radiation, and surgery, are not usually sufficient to prevent disease recurrence. Therefore, efforts have been focused on developing novel therapies to manage metastatic disease and to prolong disease-free and overall survival, by modulating the immune system to alleviate immunosuppression, and to enhance antitumor immunity. This review discusses protumor mechanisms in patients that circumvent host immunosurveillance, and addresses current immunotherapy modalities designed to target these mechanisms. Given the complexity of cancer immunosuppressive mechanisms, we propose that identification of novel disease biomarkers will drive the development of more targeted immunotherapy. Finally, administration of different classes of immunotherapy in combination regimens, will be the ultimate route to impact low survival rates in advanced cancer patients.

Microenvironmental clues for glioma immunotherapy

Gliomas have been viewed for decades as inaccessible for a meaningful antitumor immune response as they grow in a sanctuary site protected from infiltrating immune cells. Moreover, the glioma microenvironment constitutes a hostile environment for an efficient antitumor immune response as glioma-derived factors such as transforming growth factor β and catabolites of the essential amino acid tryptophan paralyze T-cell function. There is growing evidence from preclinical and clinical studies that a meaningful antitumor immunity exists in glioma patients and that it can be activated by vaccination strategies. As a consequence, the concept of glioma immunotherapy appears to be experiencing a renaissance with the first phase 3 randomized immunotherapy trials entering the clinical arena. On the basis of encouraging results from other tumor entities using immunostimulatory approaches by blocking endogenous T-cell suppressive pathways mediated by cytotoxic T-lymphocyte antigen 4 or programmed cell death protein 1/programmed cell death protein 1 ligand 1 with humanized antibodies, there is now a realistic and promising option to combine active immunotherapy with agents blocking the immunosuppressive microenvironment in patients with gliomas to allow a peripheral antitumor immune response induced by vaccination to become effective. Here we review the current clinical and preclinical evidence of antimicroenvironment immunotherapeutic strategies in gliomas.

Magnetic heating properties and neutron activation of tungsten-oxide coated biocompatible FePt core-shell nanoparticles

Magnetic nanoparticles are highly desirable for biomedical research and treatment of cancer especially when combined with hyperthermia. The efficacy of nanoparticle-based therapies could be improved by generating radioactive nanoparticles with a convenient decay time and which simultaneously have the capability to be used for locally confined heating. The core-shell morphology of such novel nanoparticles presented in this work involves a polysilico-tungstate molecule of the polyoxometalate family as a precursor coating material, which transforms into an amorphous tungsten oxide coating upon annealing of the FePt core-shell nanoparticles. The content of tungsten atoms in the nanoparticle shell is neutron activated using cold neutrons at the Heinz Maier-Leibnitz (FRMII) neutron facility and thereby transformed into the radioisotope W-187. The sizeable natural abundance of 28% for the W-186 precursor isotope, a radiopharmaceutically advantageous gamma-beta ratio of γβ≈30% and a range of approximately 1mm in biological tissue for the 1.3MeV β-radiation are promising features of the nanoparticles' potential for cancer therapy. Moreover, a high temperature annealing treatment enhances the magnetic moment of nanoparticles in such a way that a magnetic heating effect of several degrees Celsius in liquid suspension - a prerequisite for hyperthermia treatment of cancer - was observed. A rise in temperature of approximately 3°C in aqueous suspension is shown for a moderate nanoparticle concentration of 0.5mg/ml after 15min in an 831kHz high-frequency alternating magnetic field of 250Gauss field strength (25mT). The biocompatibility based on a low cytotoxicity in the non-neutron-activated state in combination with the hydrophilic nature of the tungsten oxide shell makes the coated magnetic FePt nanoparticles ideal candidates for advanced radiopharmaceutical applications.

Successful combined intratumoral immunotherapy of established murine mesotheliomas requires B-cell involvement

Combination immunotherapy has resulted in a number of impressive outcomes in mouse models and clinical settings. In this study, we report that a timed triple immunotherapy (TTI) protocol using 3 agonist antibodies (anti-CD25mAb, anti-TGF-βmAb, and anti-CTLA-4mAb) produced complete clearance of established AB1 murine mesothelioma tumors. Combining all 3 agonist antibodies into a single cocktail for intratumoral injection was as effective as the TTI in tumor eradication. Cured mice showed elevated levels of tumor-specific IgG antibodies at 95 days posttreatment. Time-course studies of tumor clearance showed (1) that IgG levels were not elevated during tumor clearance and (2) that B-cell numbers were increased in the tumor-draining lymph nodes and spleens during tumor clearance. Finally, employment of B-cell knockout mice indicated a significant role for B cells in the successful eradication of the established tumors by the triple immunotherapy cocktail.

New insights into IL-12-mediated tumor suppression

During the past two decades, interleukin-12 (IL-12) has emerged as one of the most potent cytokines in mediating antitumor activity in a variety of preclinical models. Through pleiotropic effects on different immune cells that form the tumor microenvironment, IL-12 establishes a link between innate and adaptive immunity that involves different immune effector cells and cytokines depending on the type of tumor or the affected tissue. The robust antitumor response exerted by IL-12, however, has not yet been successfully translated into the clinics. The majority of clinical trials involving treatment with IL-12 failed to show sustained antitumor responses and were associated to toxic side effects. Here we discuss the therapeutic effects of IL-12 from preclinical to clinical studies, and will highlight promising strategies to take advantage of the antitumor activity of IL-12 while limiting adverse effects.

Immunotherapy advances for glioblastoma

Survival for patients with glioblastoma, the most common high-grade primary CNS tumor, remains poor despite multiple therapeutic interventions including intensifying cytotoxic therapy, targeting dysregulated cell signaling pathways, and blocking angiogenesis. Exciting, durable clinical benefits have recently been demonstrated for a number of other challenging cancers using a variety of immunotherapeutic approaches. Much modern research confirms that the CNS is immunoactive rather than immunoprivileged. Preliminary results of clinical studies demonstrate that varied vaccine strategies have achieved encouraging evidence of clinical benefit for glioblastoma patients, although multiple variables will likely require systematic investigation before optimal outcomes are realized. Initial preclinical studies have also revealed promising results with other immunotherapies including cell-based approaches and immune checkpoint blockade. Clinical studies to evaluate a wide array of immune therapies for malignant glioma patients are being rapidly developed. Important considerations going forward include optimizing response assessment and identifiying correlative biomarkers for predict therapeutic benefit. Finally, the potential of complementary combinatorial immunotherapeutic regimens is highly exciting and warrants expedited investigation.

IL-12-and IL-23 in health and disease

Interleukin (IL)-12 and IL-23 play important roles in the development of experimental autoimmune disease models and numerous afflictions affecting humans. Preclinical data over the last 20 years combined with successful clinical trials has identified a clear relationship between IL-12, IL-23 and the generation of pathogenic T helper cells capable of orchestrating tissue inflammation. Observations made in the clinic have shown that IL-12p40, a common subunit shared by IL-12 and IL-23, is critical to pathologies associated with psoriasis, inflammatory bowel disease (IBD) and tumor growth. These advancements have set in motion the development of a number of potential therapeutics aimed at manipulating IL-12/23 signaling pathways in both mice and humans. This review will discuss a brief history of the understanding and expansion of the IL-12 cytokine family, some difficulties associated with preclinical data interpretation and finally the medicinal interventions that have been developed to combat IL-12/23-driven autoimmune disorders.

Development and function of dendritic cell subsets

Classical dendritic cells (cDCs) form a critical interface between innate and adaptive immunity. As myeloid immune cell sentinels, cDCs are specialized in the sensing of pathogen challenges and cancer. They translate the latter for T cells into peptide form. Moreover, cDCs provide additional critical information on the original antigen context to trigger a diverse spectrum of appropriate protective responses. Here we review recent progress in our understanding of cDC subsets in mice. We will discuss cDC subset ontogeny and transcription factor dependencies, as well as emerging functional specializations within the cDC compartment in lymphoid and nonlymphoid tissues.

Antibody-based immunotherapy for malignant glioma

Conventional therapy for malignant glioma (MG) fails to specifically eliminate tumor cells, resulting in toxicity that limits therapeutic efficacy. In contrast, antibody-based immunotherapy uses the immune system to eliminate tumor cells with exquisite specificity. Increased understanding of the pathobiology of MG and the profound immunosuppression present among patients with MG has revealed several biologic targets amenable to antibody-based immunotherapy. Novel antibody engineering techniques allow for the production of fully human antibodies or antibody fragments with vastly reduced antigen-binding dissociation constants, increasing safety when used clinically as therapeutics. In this report, we summarize the use of antibody-based immunotherapy for MG. Approaches currently under investigation include the use of antibodies or antibody fragments to: (1) redirect immune effector cells to target tumor mutations, (2) inhibit immunosuppressive signals and thereby stimulate an immunological response against tumor cells, and (3) provide costimulatory signals to evoke immunologic targeting of tumor cells. These approaches demonstrate highly compelling safety and efficacy for the treatment of MG, providing a viable adjunct to current standard-of-care therapy for MG.