Vaccination with irradiated tumor cells pulsed with an adjuvant that stimulates NKT cells is an effective treatment for glioma

Systemic and local immunosuppression in glioblastoma and its prognostic significance

The effectiveness of tumor therapy, especially immunotherapy and oncolytic virotherapy, critically depends on the activity of the host immune cells. However, various local and systemic mechanisms of immunosuppression operate in cancer patients. Tumor-associated immunosuppression involves deregulation of many components of immunity, including a decrease in the number of T lymphocytes (lymphopenia), an increase in the levels or ratios of circulating and tumor-infiltrating immunosuppressive subsets [e.g., macrophages, microglia, myeloid-derived suppressor cells (MDSCs), and regulatory T cells (Tregs)], as well as defective functions of subsets of antigen-presenting, helper and effector immune cell due to altered expression of various soluble and membrane proteins (receptors, costimulatory molecules, and cytokines). In this review, we specifically focus on data from patients with glioblastoma/glioma before standard chemoradiotherapy. We discuss glioblastoma-related immunosuppression at baseline and the prognostic significance of different subsets of circulating and tumor-infiltrating immune cells (lymphocytes, CD4+ and CD8+ T cells, Tregs, natural killer (NK) cells, neutrophils, macrophages, MDSCs, and dendritic cells), including neutrophil-to-lymphocyte ratio (NLR), focus on the immune landscape and prognostic significance of isocitrate dehydrogenase (IDH)-mutant gliomas, proneural, classical and mesenchymal molecular subtypes, and highlight the features of immune surveillance in the brain. All attempts to identify a reliable prognostic immune marker in glioblastoma tissue have led to contradictory results, which can be explained, among other things, by the unprecedented level of spatial heterogeneity of the immune infiltrate and the significant phenotypic diversity and (dys)functional states of immune subpopulations. High NLR is one of the most repeatedly confirmed independent prognostic factors for shorter overall survival in patients with glioblastoma and carcinoma, and its combination with other markers of the immune response or systemic inflammation significantly improves the accuracy of prediction; however, more prospective studies are needed to confirm the prognostic/predictive power of NLR. We call for the inclusion of dynamic assessment of NLR and other blood inflammatory markers (e.g., absolute/total lymphocyte count, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, systemic immune-inflammation index, and systemic immune response index) in all neuro-oncology studies for rigorous evaluation and comparison of their individual and combinatorial prognostic/predictive significance and relative superiority.

Recruiting Natural Killer T Cells to Improve Vaccination: Lessons from Preclinical and Clinical Studies

The capacity of type I natural killer T (NKT) cells to provide stimulatory signals to antigen-presenting cells has prompted preclinical research into the use of agonists as immune adjuvants, with much of this work focussed on stimulating T cell responses to cancer. In attempting to evaluate this approach in the clinic, our recent dendritic-cell based study failed to show an advantage to adding an agonist to the vaccine. Here we present potential limitations of the study, and suggest why other simpler strategies may be more effective. These include strategies to target antigen-presenting cells in the host, either through promoting efficient transfer from injected cell lines, facilitating uptake of antigen and agonist as injected conjugates, or encapsulating the components into injected nanovectors. While the vaccine landscape has changed with the rapid uptake of mRNA vaccines, we suggest that there is still a role for recruiting NKT cells in altering T cell differentiation programmes, notably the induction of resident memory T cells.

The Role of CD4+ T Cells in the Immunotherapy of Brain Disease by Secreting Different Cytokines

Upon different stimulation, naïve CD4⁺ T cells differentiate into various subsets of T helper (Th) cells, including Th1, Th2, Th17, and Tregs. They play both protective and pathogenic roles in the central nervous system (CNS) by secreting different cytokines. Failure of the homeostasis of the subgroups in the CNS can result in different brain diseases. Recently, immunotherapy has drawn more and more attention in the therapy of various brain diseases. Here, we describe the role of different CD4⁺ T cell subsets and their secreted cytokines in various brain diseases, as well as the ways in which by affecting CD4⁺ T cells in therapy of the CNS diseases. Understanding the role of CD4⁺ T cells and their secreted cytokines in the immunotherapy of brain disease will provide new targets and therapeutics for the treatment of brain disease. The role of CD4 + T cell subtypes in different diseases and their associated regulatory genes, proteins, and enzymes. CD4 + T cell subtypes play both protective (green) and pathogenic (red) roles in different brain diseases. The immune regulatory effects of CD4 + T cells and their subtypes are promoted or inhibited by different genes, proteins, and enzymes.

Invariant NKT cell-augmented GM-CSF-secreting tumor vaccine is effective in advanced prostate cancer model

Invariant natural killer T cells (iNKT cells) express a semi-invariant T cell receptor that recognizes certain glycolipids (including α-galactosylceramide, αGC) bound to CD1d, and can induce potent antitumor responses. Here, we assessed whether αGC could enhance the efficacy of a GM-CSF-producing tumor cell vaccine in the transgenic SV40 T antigen-driven TRAMP prostate cancer model. In healthy mice, we initially found that optimal T cell responses were obtained with αGC-pulsed TRAMP-C2 cells secreting GM-CSF and milk fat globule epidermal growth factor protein-8 (MFG-E8) with an RGD to RGE mutation (GM-CSF/RGE TRAMP-C2), combined with systemic low dose IL-12. In a therapeutic model, transgenic TRAMP mice were then castrated at ~ 20 weeks, followed by treatment with the combination vaccine. Untreated mice succumbed to tumor by ~ 40 weeks, but survival was markedly prolonged by vaccine treatment, with most mice surviving past 80 weeks. Prostates in the treated mice were heavily infiltrated with T cells and iNKT cells, which both secreted IFNγ in response to tumor cells. The vaccine was not effective if the αGC, IL-12, or GM-CSF secretion was eliminated. Finally, immunized mice were fully resistant to challenge with TRAMP-C2 cells. Together these findings support further development of therapeutic vaccines that exploit iNKT cell activation.

Recent Development in NKT-Based Immunotherapy of Glioblastoma: From Bench to Bedside

Glioblastoma multiforme (GBM) is an aggressive and dismal disease with a median overall survival of around 15 months and a 5-year survival rate of 7.2%. Owing to genetic mutations, drug resistance, disruption to the blood–brain barrier (BBB)/blood–brain tumor barrier (BBTB), and the complexity of the immunosuppressive environment, the therapeutic approaches to GBM represent still major challenges. Conventional therapies, including surgery, radiotherapy, and standard chemotherapy with temozolomide, have not resulted in satisfactory improvements in the overall survival of GBM patients. Among cancer immunotherapeutic approaches, we propose that adjuvant NKT immunotherapy with invariant NKT (iNKT) and cytokine-induced killer (CIK) cells may improve the clinical scenario of this devastating disease. Considering this, herein, we discuss the current strategies of NKT therapy for GBM based primarily on in vitro/in vivo experiments, clinical trials, and the combinatorial approaches with future therapeutic potential.

Current Strategies for Cancer Cell-Derived Extracellular Vesicles for Cancer Therapy

Cancer cell-derived extracellular vesicles (CEVs), a novel type of therapeutic agent in cancer treatment, can be prepared from the autocrine secretion of various cancer cells, the direct extraction of cancer cells and the combination of cancer cell-derived membranes with advanced materials. With various bioactive molecules, exosomes are produced by cells for intercellular communication. Although cancer cell-derived exosomes are known to inhibit tumor apoptosis and promote the progression of cancer, researchers have developed various innovative strategies to prepare anti-tumor vesicles from cancer cells. With current strategies for anti-tumor vesicles, four different kinds of CEVs are classified including irradiated CEVs, advanced materials combined CEVs, chemotherapeutic drugs loaded CEVs and genetically engineered CEVs. In this way, CEVs can not only be the carriers for anti-tumor drugs to the target tumor area but also act as immune-active agents. Problems raised in the strategies mainly concerned with the preparation, efficacy and application. In this review, we classified and summarized the current strategies for utilizing the anti-tumor potential of CEVs. Additionally, the challenges and the prospects of this novel agent have been discussed.

The Role of NKT Cells in Glioblastoma

Glioblastoma is an aggressive and deadly cancer, but to date, immunotherapies have failed to make significant strides in improving prognoses for glioblastoma patients. One of the current challenges to developing immunological interventions for glioblastoma is our incomplete understanding of the numerous immunoregulatory mechanisms at play in the glioblastoma tumor microenvironment. We propose that Natural Killer T (NKT) cells, which are unconventional T lymphocytes that recognize lipid antigens presented by CD1d molecules, may play a key immunoregulatory role in glioblastoma. For example, evidence suggests that the activation of type I NKT cells can facilitate anti-glioblastoma immune responses. On the other hand, type II NKT cells are known to play an immunosuppressive role in other cancers, as well as to cross-regulate type I NKT cell activity, although their specific role in glioblastoma remains largely unclear. This review provides a summary of our current understanding of NKT cells in the immunoregulation of glioblastoma as well as highlights the involvement of NKT cells in other cancers and central nervous system diseases.

Harnessing NKT cells for vaccination

Natural killer T (NKT) cells are innate-like T cells capable of enhancing both innate and adaptive immune responses. When NKT cells are stimulated in close temporal association with co-administered antigens, strong antigen-specific immune responses can be induced, prompting the study of NKT cell agonists as novel immune adjuvants. This activity has been attributed to the capacity of activated NKT cells to act as universal helper cells, with the ability to provide molecular signals to dendritic cells and B cells that facilitate T cell and antibody responses, respectively. These signals can override the requirement for conventional CD4⁺ T cell help, so that vaccines can be designed without need to consider CD4⁺ T cell repertoire and major histocompatibility complex Class II diversity. Animal studies have highlighted some drawbacks of the approach, namely, concerns around induction of NKT cell hyporesponsiveness, which may limit vaccine boosting, and potential for toxicity. Here we highlight studies that suggest these obstacles can be overcome by targeted delivery in vivo. We also feature new studies that suggest activating NKT cells can help encourage differentiation of T cells into tissue-resident memory cells that play an important role in prophylaxis against infection, and may be required in cancer therapy.

Discovery of Semi- and Fully-Synthetic Carbohydrate Vaccines Against Bacterial Infections Using a Medicinal Chemistry Approach

The glycocalyx, a thick layer of carbohydrates, surrounds the cell wall of most bacterial and parasitic pathogens. Recognition of these unique glycans by the human immune system results in destruction of the invaders. To elicit a protective immune response, polysaccharides either isolated from the bacterial cell surface or conjugated with a carrier protein, for T-cell help, are administered. Conjugate vaccines based on isolated carbohydrates currently protect millions of people against Streptococcus pneumoniae, Haemophilus influenzae type b, and Neisseria meningitides infections. Active pharmaceutical ingredients (APIs) are increasingly discovered by medicinal chemistry and synthetic in origin, rather than isolated from natural sources. Converting vaccines from biologicals to pharmaceuticals requires a fundamental understanding of how the human immune system recognizes carbohydrates and could now be realized. To illustrate the chemistry-based approach to vaccine discovery, I summarize efforts focusing on synthetic glycan-based medicinal chemistry to understand the mammalian antiglycan immune response and define glycan epitopes for novel synthetic glycoconjugate vaccines against Streptococcus pneumoniae, Clostridium difficile, Klebsiella pneumoniae, and other bacteria. The chemical tools described here help us gain fundamental insights into how the human system recognizes carbohydrates and drive the discovery of carbohydrate vaccines.

Mannan-BAM, TLR Ligands, Anti-CD40 Antibody (MBTA) Vaccine Immunotherapy: A Review of Current Evidence and Applications in Glioblastoma

The foundation of precision immunotherapy in oncology is rooted in computational biology and patient-derived sample sequencing to enrich for and target immunogenic epitopes. Discovery of these tumor-specific epitopes through tumor sequencing has revolutionized patient outcomes in many types of cancers that were previously untreatable. However, these therapeutic successes are far from universal, especially with cancers that carry high intratumoral heterogeneity such as glioblastoma (GBM). Herein, we present the technical aspects of Mannan-BAM, TLR Ligands, Anti-CD40 Antibody (MBTA) vaccine immunotherapy, an investigational therapeutic that potentially circumvents the need for in silico tumor-neoantigen enrichment. We then review the most promising GBM vaccination strategies to contextualize the MBTA vaccine. By reviewing current evidence using translational tumor models supporting MBTA vaccination, we evaluate the underlying principles that validate its clinical applicability. Finally, we showcase the translational potential of MBTA vaccination as a potential immunotherapy in GBM, along with established surgical and immunologic cancer treatment paradigms.

Induction of Immune Response Against Metastatic Tumors via Vaccination of Mannan-BAM, TLR Ligands and Anti-CD40 Antibody (MBTA)

Emerging evidence is demonstrating the extent of T-cell infiltration within the tumor microenvironment has favorable prognostic and therapeutic implications. Hence, immunotherapeutic strategies that augment the T-cell signature of tumors hold promising therapeutic potential. Recently, immunotherapy based on intratumoral injection of mannan-BAM, toll-like receptor ligands and anti-CD40 antibody (MBTA) demonstrated promising potential to modulate the immune phenotype of injected tumors. The strategy promotes the phagocytosis of tumor cells to facilitate the recognition of tumor antigens and induce a tumor-specific adaptive immune response. Using a syngeneic colon carcinoma model, we demonstrate MBTA's potential to augment CD8⁺ T-cell tumor infiltrate when administered intratumorally or subcutaneously as part of a whole tumor cell vaccine. Both immunotherapeutic strategies proved effective at controlling tumor growth, prolonged survival and induced immunological memory against the parental cell line. Collectively, our investigation demonstrates MBTA's potential to trigger a potent anti-tumor immune response.

Oxidized mitochondrial DNA sensing by STING signaling promotes the antitumor effect of an irradiated immunogenic cancer cell vaccine

Exposure to ionizing radiation, a physical treatment that inactivates live tumor cells, has been extensively applied to enhance the antitumor responses induced by cancer cell vaccines in both animal research and human clinical trials. However, the mechanisms by which irradiated cells function as immunogenic tumor vaccines and induce effective antitumor responses have not been fully explored. Here, we demonstrate that oxidized mitochondrial DNA (mtDNA) and stimulator of interferon genes (STING) signaling play a key roles in the enhanced antitumor effect achieved with an irradiated tumor cell vaccine. Elevations in ROS and oxidized mtDNA 8-OHG content could be induced in irradiated tumor cells. Oxidized mtDNA derived from irradiated tumor cells gained access to the cytosol of dendritic cells (DCs). Oxidized mtDNA, as a DAMP or adjuvant, activated the STING-TBK1-IRF3-IFN-β pathway in DCs, which subsequently cross-presented irradiated tumor cell-derived antigens to CD8⁺ T cells and elicited antitumor immunity. The results of our study provide insight into the mechanism by which an irradiated cell vaccine mediates antitumor immunity, which may have implications for new strategies to improve the efficacy of irradiated vaccines.

The oncogene BCL6 is up-regulated in glioblastoma in response to DNA damage, and drives survival after therapy

The prognosis for people with the high-grade brain tumor glioblastoma is very poor, due largely to low cell death in response to genotoxic therapy. The transcription factor BCL6, a protein that normally suppresses the DNA damage response during immune cell maturation, and a known driver of B-cell lymphoma, was shown to mediate the survival of glioblastoma cells. Expression was observed in glioblastoma tumor specimens and cell lines. When BCL6 expression or activity was reduced in these lines, increased apoptosis and a profound loss of proliferation was observed, consistent with gene expression signatures suggestive of anti-apoptotic and pro-survival signaling role for BCL6 in glioblastoma. Further, treatment with the standard therapies for glioblastoma—ionizing radiation and temozolomide—both induced BCL6 expression in vitro, and an in vivo orthotopic animal model of glioblastoma. Importantly, inhibition of BCL6 in combination with genotoxic therapies enhanced the therapeutic effect. Together these data demonstrate that BCL6 is an active transcription factor in glioblastoma, that it drives survival of cells, and that it increased with DNA damage, which increased the survival rate of therapy-treated cells. This makes BCL6 an excellent therapeutic target in glioblastoma—by increasing sensitivity to standard DNA damaging therapy, BCL6 inhibitors have real potential to improve the outcome for people with this disease.

Vaccines adjuvanted with an NKT cell agonist induce effective T-cell responses in models of CNS lymphoma

Aim: The efficacy of anti-lymphoma vaccines that exploit the cellular adjuvant properties of activated natural killer T (NKT) cells were examined in mouse models of CNS lymphoma. Materials & methods: Vaccines were prepared by either loading the NKT cell agonist, α-galactosylceramide onto irradiated and heat-shocked B- and T-lymphoma cells, or chemically conjugating α-galactosylceramide to MHC-binding peptides from a lymphoma-associated antigen. Vaccine efficacy was analyzed in mice bearing intracranial tumors. Results: Both forms of vaccine proved to be effective in preventing lymphoma engraftment through activity of T cells that accessed the CNS. Established lymphoma was harder to treat with responses constrained by Tregs, but this could be overcome by depleting Tregs prior to vaccination. Conclusion: Simply designed NKT cell-activating vaccines enhance T-cell responses and have the potential to protect against CNS lymphoma development or prevent CNS relapse. To be effective against established CNS lymphoma, vaccines need to be combined with Treg suppression.

NKT Cells in Neurological Diseases

Natural killer T (NKT) cells are a unique subset of T lymphocytes with the expression of T cell receptor (TCR) and NK cell lineage receptors. These cells can rapidly release large quantities of cytokines and function as a bridge between innate and adaptive immunity. To date, multiple reports have investigated the role of NKT cells under various pathological conditions, such as cancer, autoimmune disease, and infection. Knowledge about NKT cells in neurological diseases is increasing, albeit limited. Here, we review evidence for the involvement of NKT cells in neurological diseases, and discuss immunotherapeutic potential and future study goals. As the development and function of NKT cells become increasingly well understood, the next few years should yield many new insights into NKT cell function, and mechanistic regulation in neurological disorders.

Therapeutic vaccination with 4-1BB co-stimulation eradicates mouse acute myeloid leukemia

Immunomodulatory therapies can effectively control haematological malignancies. Previously we reported the effectiveness of combination immunotherapies that centre on 4-1BB-targeted co-stimulation of CD8 + T cells, particularly when simultaneously harnessing the immune adjuvant properties of Natural Killer T (NKT) cells. The objective of this study was to assess the effectiveness of agonistic anti-4-1BB antibody-based combination therapy against two aggressive forms of acute myeloid leukemia (AML). Anti-4-1BB treatment alone resulted in transient suppression of established AML-ETO9a tumor growth in 50% of mice, however the majority of these mice subsequently succumbed to disease. Combining alpha-galactosylceramide (α-GalCer)-loaded tumor cell vaccination with anti-4-1BB antibody treatment increased the proportion of responding mice to 100%, and protection led to long-term, tumor-free survival, demonstrating complete eradication of AML. This finding was extended to established mixed lymphocytic leukemia (MLL)-AF9 tumors, whereby vaccine plus anti-4-1BB combination similarly resulted in 100% protection. The addition of anti-PD-1 to anti-4-1BB treatment, although improving survival outcomes compared to anti-4-1BB alone, was not as effective as NKT cell vaccination. The effectiveness of 4-1BB combination therapies was dependent on IFN-γ signaling within host cells, but not tumors. Vaccine plus anti-4-1BB therapy elicited potent generation of functional effector and memory CD8 + T cells in all tumor-associated organs. Therapy induced KLRG1+ effector CD8 T cells were the most effective at controlling disease. We show that combining NKT cell-targeting vaccination with anti-4-1BB provides excellent therapeutic responses against AML and MLL in mice, and these results will guide ongoing efforts in finding immunotherapeutic solutions against acute myeloid leukemias.

Advances in NKT cell Immunotherapy for Glioblastoma

Type I or invariant natural killer T cells belong to a unique lineage of innate T cells, which express markers of both T lymphocytes and NK cells, namely T cell receptor (TCR) and NK1.1 (CD161C), respectively. Thus, apart from direct killing of target cells like NK cells, and they also produce a myriad of cytokines which modulate the adaptive immune responses. Unlike traditional T cells which carry a conventional αβ TCR, NKT cells express semi-invariant TCR - Vα14-Jα18, coupled with Vβ8, Vβ7 and Vβ2 in mice. In humans, the invariant TCR is composed of Vα24-Jα18, coupled with Vβ11.

Impact of genomics on the surgical management of melanoma

BACKGROUND

Although surgery for early-stage melanoma offers the best chance of cure, recent advances in molecular medicine have revolutionized the management of late-stage melanoma, leading to significant improvements in clinical outcomes. Research into the genomic drivers of disease and cancer immunology has not only ushered in a new era of targeted and immune-based therapies for patients with metastatic melanoma, but has also provided new tools for monitoring disease recurrence and selecting therapeutic strategies. These advances present new opportunities and challenges to the surgeon treating patients with melanoma.

METHODS

The literature was reviewed to evaluate diagnostic and therapeutic advances in the management of cutaneous melanoma, and to highlight the impact of these advances on surgical decision-making.

RESULTS

Genomic testing is not required in the surgical management of primary melanoma, although it can provide useful information in some situations. Circulating nucleic acids from melanoma cells can be detected in peripheral blood to predict disease recurrence before it manifests clinically, but validation is required before routine clinical application. BRAF mutation testing is the standard of care for all patients with advanced disease to guide therapy, including the planning of surgery in adjuvant and neoadjuvant settings.

CONCLUSION

Surgery remains central for managing primary melanoma, and is an important element of integrated multidisciplinary care in advanced disease, particularly for patients with resectable metastases. The field will undergo further change as clinical trials address the relationships between surgery, radiotherapy and systemic therapy for patients with high-risk, early-stage and advanced melanoma.

Blocking CTLA-4 while priming with a whole cell vaccine reshapes the oligoclonal T cell infiltrate and eradicates tumors in an orthotopic glioma model

Vaccine-mediated cancer treatment is unlikely to induce long-term survival unless suppressive mechanisms are overcome. Given the success of antibody-mediated immune checkpoint blockade in relieving regulation of endogenous anti-tumor T cell responses in tumor-burdened hosts, we investigated whether checkpoint blockade could improve the efficacy of responses induced with a whole tumor-cell vaccine. We show that administration of a single dose of blocking antibody was sufficient to significantly enhance antitumor activity of the vaccine, inducing complete radiological regression of established intracranial tumors. The antibody or vaccine alone were ineffective in this setting. The antibody had to be administered before, or close to, vaccine administration, suggesting CTLA-4 blockade had an impact on early priming events. The combined treatment resulted in enhanced trapping of leukocytes in the lymphoid tissues, including T cells that had undergone significant proliferation. There were no obvious changes in the stimulatory function of antigen-presenting cells or the number and function of regulatory T cells, suggesting T cells were the targets of the checkpoint blockade. While tumors regressing under combined treatment were highly infiltrated with a variety of leukocytes, tumor eradication was dependent on CD4⁺ T cells. Analysis of the TCR repertoire showed that the addition of anti-CTLA-4 at priming reshaped the repertoire of tumor infiltrating T cells. In particular, the oligoclonal populations became greater in magnitude and more diverse in specificity. Using anti-CTLA-4 in a restricted way to promote the priming phase of an anti-cancer vaccine may offer a useful way of harnessing clinical benefit from this powerful agent.

Co-delivery of tumor-derived exosomes with alpha-galactosylceramide on dendritic cell-based immunotherapy for glioblastoma

Dendritic cell (DC) vaccine-based immunotherapy for glioblastoma multiforme (GBM) has shown apparent benefit in animal experiments and early-phase clinical trials, but the survival benefit is variable. In this work, we analyzed the mechanism of the potent antitumor immune response induced in vivo by tumor-associated antigen (TAA)-specific DCs with an invariant natural killer T (iNKT) cell adjuvant in orthotopic glioblastoma-bearing rats vaccinated with tumor-derived exosomes and α-galactosylceramide (α-GalCer) -pulsed DCs. Compared with traditional tumor lysate, exosomes were utilized as a more potent antigen to load DCs. iNKT cells, as an effective cellular adjuvant activated by α-GalCer, strengthened TAA presentation through their interaction with DCs. Co-delivery of tumor-derived exosomes with α-GalCer on a DC-based vaccine showed powerful effects in glioblastoma immunotherapy. This vaccine induced strong activation and proliferation of tumor-specific cytotoxic T lymphocytes, synergistically breaking the immune tolerance and improving the immunosuppressive environment.

Dendritic cells loaded with tumor derived exosomes for cancer immunotherapy

Exosomes are vesicles that can be secreted by many types of cell and released into the extracellular space. Studies have found that tumor derived exosomes (TEXs) can promote tumor growth and metastasis, as well as inhibit immune response through transferring their genetic information to the recipient cells. Given their functions in tumor progression, TEXs are considered as promising biomarkers for early detection of human malignancy. Dendritic cells (DCs), a type of antigen presenting cells, can induce tumor-specific T cell immune responses in carcinogenesis. Growing evidences have demonstrated that the matured DCs induced by TEXs exhibit enhanced anti-tumor effects that may be applied for cancer immunotherapy. Thus in this review, according to the previous studies, we summarized the effects of DCs loaded with TEXs in cancer immunotherapy.

Perfluorocarbon emulsions radiosensitise brain tumors in carbogen breathing mice with orthotopic GL261 gliomas

Background

Tumour hypoxia limits the effectiveness of radiation therapy. Delivering normobaric or hyperbaric oxygen therapy elevates pO₂ in both tumour and normal brain tissue. However, pO2 levels return to baseline within 15 minutes of stopping therapy.

Aim

To investigate the effect of perfluorocarbon (PFC) emulsions on hypoxia in subcutaneous and intracranial mouse gliomas and their radiosensitising effect in orthotopic gliomas in mice breathing carbogen (95%O₂ and 5%CO₂).

Results

PFC emulsions completely abrogated hypoxia in both subcutaneous and intracranial GL261 models and conferred a significant survival advantage orthotopically (Mantel Cox: p = 0.048) in carbogen breathing mice injected intravenously (IV) with PFC emulsions before radiation versus mice receiving radiation alone. Carbogen alone decreased hypoxia levels substantially and conferred a smaller but not statistically significant survival advantage over and above radiation alone.

Conclusion

IV injections of PFC emulsions followed by 1h carbogen breathing, radiosensitises GL261 intracranial tumors.

Exploiting Antitumor Immunotherapeutic Novel Strategies by Deciphering the Cross Talk between Invariant NKT Cells and Dendritic Cells

Immune checkpoint blockade therapy has prevailed for several types of cancer; however, its effectiveness as a single therapy is still limited. In principle, dendritic cells (DCs) should be able to control the post-therapy immune response, in particular since they can link the two major arms of the immune system: innate and adaptive immunity. Therefore, DCs would be a logical and ideal target for the development of immunotherapies. Since DCs are not activated in the steady state, an adjuvant to convert their function from tolerogenic to immunogenic would be desirable. Upon ligand activation, invariant natural killer T (iNKT) cells simultaneously activate NK cells and also energize the DCs, resulting in their full maturation. To utilize such iNKT-licensed "fully" matured DCs as adjuvants, mechanisms of both intercellular communication between DC subsets and iNKT cells and intracellular molecular signaling in DCs have to be clarified and optimized. To generate both innate and adaptive immunity against cancer, a variety of strategies with the potential to target iNKT-licensed DCs in situ have been studied. The benchmark of success in these studies, each with distinct approaches, will be the development of functional NK cells and cytotoxic T cells (CTLs) as well as generation of long-term, memory CTL. In this review, we provide a framework for NKT-mediated immunotherapy through selective DC targeting in situ, describe progress in the design of licensed therapies for iNKT cell targeting of DCs, and highlight the challenge to provide maximal benefit to patients.

Enhancement of Adjuvant Functions of Natural Killer T Cells Using Nanovector Delivery Systems: Application in Anticancer Immune Therapy

Type I natural killer T (NKT) cells have gained considerable interest in anticancer immune therapy over the last decade. This “innate-like” T lymphocyte subset has the unique ability to recognize foreign and self-derived glycolipid antigens in association with the CD1d molecule expressed by antigen-presenting cells. An important property of these cells is to bridge innate and acquired immune responses. The adjuvant function of NKT cells might be exploited in the clinics. In this review, we discuss the approaches currently being used to target NKT cells for cancer therapy. In particular, we highlight ongoing strategies utilizing NKT cell-based nanovaccines to optimize immune therapy.

Engaging Natural Killer T Cells as 'Universal Helpers' for Vaccination

Conventional vaccine adjuvants enhance peptide-specific T-cell and B-cell responses by modifying peptide stability or uptake or by binding to pattern-recognition receptors on antigen-presenting cells (APCs). This article discusses the application of a distinct mechanism of adjuvant activity: the activation of type I, or invariant, natural killer T (iNKT) cells to drive cellular and humoral immune responses. Using a semi-invariant T-cell receptor (TCR), iNKT cells recognize glycolipid antigens presented on cluster of differentiation (CD)-1d molecules. When their ligands are presented in concert with peptides, iNKT cells can provide T-cell help, 'licensing' APCs to augment peptide-specific T-cell and antibody responses. We discuss the potential benefits and limitations of exploiting iNKT cells as 'universal helpers' to enhance vaccine responses for the treatment and prevention of cancer and infectious diseases.

Determining mean fractional anisotropy using DDCOSY: preliminary results in biological tissues

Complex materials are ubiquitous in science, engineering and nature. One important parameter for characterising their morphology is the degree of anisotropy. Magnetic resonance imaging offers non-invasive methods for quantitative measurements of the materials anisotropy, most commonly via diffusion tensor imaging and the subsequent extraction of the spatially resolved fractional anisotropy (FA) value. Here, we propose an alternative way of determining the FA as a sample average for cases where spatially resolved methods are not needed or not applicable. It is based on a particular diffusion-diffusion correlation spectroscopy protocol, allowing for the extraction of the mean (i.e. sample averaged) FA value. We demonstrate that mean FA values obtained from three anisotropic biological tissues are consistent with those extracted using diffusion tensor imaging. Moreover, we show that differences of mean FA values in healthy and tumour-bearing mouse brains allow to distinguish these tissue types. We anticipate that the proposed method will be beneficial in the wider context of medical and material science. Copyright © 2016 John Wiley & Sons, Ltd.

A combination of tyrosine kinase inhibitors, crizotinib and dasatinib for the treatment of glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor. Despite the advances in surgery, radiotherapy and chemotherapy, patient survival averages only 14.6 months. In most GBM tumors, tyrosine kinases show increased activity and/or expression and actively contribute to the development, recurrence and onset of treatment resistance; making their inhibition an appealing therapeutic strategy. We compared the cytotoxicity of 12 tyrosine kinase inhibitors in vitro. A combination of crizotinib and dasatinib emerged as the most cytotoxic across established and primary human GBM cell lines. The combination treatment induced apoptotic cell death and polyploidy. Furthermore, the combination treatment led to the altered expression and localization of several tyrosine kinase receptors such as Met and EGFR and downstream effectors as such as SRC. Furthermore, the combination treatment reduced the migration and invasion of GBM cells and prevented endothelial cell tube formation in vitro. Overall, our study demonstrated the broad specificity of a combination of crizotinib and dasatinib across multiple GBM cell lines. These findings provide insight into the development of alternative therapy for the treatment of GBM.

ErbB2/HER2-Specific NK Cells for Targeted Therapy of Glioblastoma

BACKGROUND

Glioblastoma (GBM) is the most common and malignant intracranial tumor in adults and currently incurable. To specifically target natural killer (NK) cell activity to GBM, we employed NK-92/5.28.z cells that are continuously expanding human NK cells expressing an ErbB2-specific chimeric antigen receptor (CAR).

METHODS

ErbB2 expression in 56 primary tumors, four primary cell cultures, and seven established cell lines was assessed by immunohistochemistry and flow cytometry. Cell killing activity of NK-92/5.28.z cells was analyzed in in vitro cytotoxicity assays. In vivo antitumor activity was evaluated in NOD-SCID IL2Rγ(null) (NSG) mice carrying orthotopic human GBM xenografts (6 to 11 mice per group) and C57BL/6 mice carrying subcutaneous and orthotopic ErbB2-expressing murine GBM tumors (5 to 8 mice per group). Statistical tests were two-sided.

RESULTS

We found elevated ErbB2 protein expression in 41% of primary GBM samples and in the majority of GBM cell lines investigated. In in vitro assays, NK-92/5.28.z in contrast to untargeted NK-92 cells lysed all ErbB2-positive established and primary GBM cells analyzed. Potent in vivo antitumor activity of NK-92/5.28.z was observed in orthotopic GBM xenograft models in NSG mice, leading to a marked extension of symptom-free survival upon repeated stereotactic injection of CAR NK cells into the tumor area (median survival of 200.5 days upon treatment with NK-92/5.28.z vs 73 days upon treatment with parental NK-92 cells, P < .001). In immunocompetent mice, local therapy with NK-92/5.28.z cells resulted in cures of transplanted syngeneic GBM in four of five mice carrying subcutaneous tumors and five of eight mice carrying intracranial tumors, induction of endogenous antitumor immunity, and long-term protection against tumor rechallenge at distant sites.

CONCLUSIONS

Our data demonstrate the potential of ErbB2-specific NK-92/5.28.z cells for adoptive immunotherapy of glioblastoma, justifying evaluation of this approach for the treatment of ErbB2-positive GBM in clinical studies.

Chronic alcohol consumption inhibits melanoma growth but decreases the survival of mice immunized with tumor cell lysate and boosted with α-galactosylceramide

Alcohol consumption increases the incidence of multiple types of cancer. However, how chronic alcohol consumption affects tumor progression and host survival remains largely unexplored. Using a mouse B16BL6 melanoma model, we studied the effects of chronic alcohol consumption on s.c. tumor growth, iNKT cell antitumor immune response, and host survival. The results indicate that although chronic alcohol consumption inhibits melanoma growth, this does not translate into increased host survival. Immunizing mice with a melanoma cell lysate does not significantly increase the median survival of water-drinking, melanoma-bearing mice, but significantly increases the median survival of alcohol-consuming, melanoma-bearing mice. Even though survival is extended in the alcohol-consuming mice after immunization, the median survival is not different from the immunized mice in the water-drinking group. Immunization with tumor cell lysate combined with α-galatosylceramide activation of iNKT cells significantly increases host survival of both groups of melanoma-bearing mice compared to their respective non-immunized counterparts; however, the median survival of the alcohol-consuming group is significantly lower than that of the water-drinking group. Alcohol consumption increases NKT cells in the thymus and blood and skews NKT cell cytokine profile from Th1 dominant to Th2 dominant in the tumor-bearing mice. In summary, these results indicate that chronic alcohol consumption activates the immune system, which leads to the inhibition of s.c. melanoma growth and enhances the immune response to immunization with melanoma lysate. With tumor progression, alcohol consumption accelerates iNKT cell dysfunction and compromises antitumor immunity, which leads to decreased survival of melanoma-bearing mice.

In vitro and in vivo antitumor effects of 50 to 100-KDa components from B16 melanoma culture supernatant

The development of immunological therapies for melanoma has been of considerable concern in recent years. Whole tumor cell lysates have been used to develop antitumor vaccines, but the effective components of the lysates have not been identified. In the present study, protein elements were purified from the B16 supernatant to analyze the in vitro chemotaxis towards mouse spleen lymphocytes using a Boyden chamber. Prior to establishing a B16 melanoma model, C57BL/6 mice were vaccinated with these proteins, and melanoma growth, tumor appearance time and behavioral changes were observed. Next, the cytotoxicity and subsets of the tumor infiltrating lymphocytes, and the histological characteristics of the melanoma were analyzed. The isolated purified fragments of B16 melanoma culture supernatant had strong antitumor effects. The possible antitumor mechanism was delineated, and was identified to possibly be through the activation of cluster of differentiation 8-positive T cells and the promotion of B16 cell differentiation. These methods will provide a novel insight into understanding antitumor immunological mechanisms and provide a potential avenue for immunotherapy.

NKT cell-targeted vaccination plus anti-4-1BB antibody generates persistent CD8 T cell immunity against B cell lymphoma

Harnessing the immune adjuvant properties of natural killer T (NKT) cells is an effective strategy to generate anticancer immunity. The objective of this study was to increase the potency and durability of vaccine-induced immunity against B cell lymphoma by combining α-galactosylceramide (α-GalCer)-loaded tumor cell vaccination with an agonistic antibody targeting the immune checkpoint molecule 4–1BB (CD137). We observed potent synergy when combining vaccination and anti-4–1BB antibody treatment resulting in significantly enhanced survival of mice harboring Eμ-myc tumors, including complete eradication of lymphoma in over 50% of mice. Tumor-free survival required interferon γ (IFNγ)-dependent expansion of CD8⁺ T cells and was associated with 4–1BB-mediated differentiation of KLRG1⁺ effector CD8⁺ T cells. 'Cured' mice were also resistant to lymphoma re-challenge 80 days later indicating successful generation of immunological memory. Overall, our results demonstrate that therapeutic anticancer vaccination against B cell lymphoma using an NKT cell ligand can be boosted by subsequent co-stimulation through 4–1BB leading to a sustainable immune response that may enhance outcomes to conventional treatment.

Pharmacological doses of daily ascorbate protect tumors from radiation damage after a single dose of radiation in an intracranial mouse glioma model

Pharmacological ascorbate is currently used as an anti-cancer treatment, potentially in combination with radiation therapy, by integrative medicine practitioners. In the acidic, metal-rich tumor environment, ascorbate acts as a pro-oxidant, with a mode of action similar to that of ionizing radiation; both treatments kill cells predominantly by free radical-mediated DNA damage. The brain tumor, glioblastoma multiforme (GBM), is very resistant to radiation; radiosensitizing GBM cells will improve survival of GBM patients. Here, we demonstrate that a single fraction (6 Gy) of radiation combined with a 1 h exposure to ascorbate (5 mM) sensitized murine glioma GL261 cells to radiation in survival and colony-forming assays in vitro. In addition, we report the effect of a single fraction (4.5 Gy) of whole brain radiation combined with daily intraperitoneal injections of ascorbate (1 mg/kg) in an intracranial GL261 glioma mouse model. Tumor-bearing C57BL/6 mice were divided into four groups: one group received a single dose of 4.5 Gy to the brain 8 days after tumor implantation, a second group received daily intraperitoneal injections of ascorbate (day 8-45) after implantation, a third group received both treatments and a fourth control group received no treatment. While radiation delayed tumor progression, intraperitoneal ascorbate alone had no effect on tumor progression. Tumor progression was faster in tumor-bearing mice treated with radiation and daily ascorbate than in those treated with radiation alone. Histological analysis showed less necrosis in tumors treated with both radiation and ascorbate, consistent with a radio-protective effect of ascorbate in vivo. Discrepancies between our in vitro and in vivo results may be explained by differences in the tumor microenvironment, which determines whether ascorbate remains outside the cell, acting as a pro-oxidant, or whether it enters the cells and acts as an anti-oxidant.

Balance is a key for happiness

Eliminating one immunosuppressive mechanism is rarely sufficient to overcome cancer. One of reasons underlying this fact is that whether regulatory T cells (Tregs) or type II natural killer T (NKT) cells dominate immunosuppression depends on the mutual interactions between the latter and their type I counterparts. Thus, the balance among three immunomodulatory cell types dictates whether eliminating Tregs relieves or not immunosuppression.

Exploiting invariant NKT cells to promote T-cell responses to cancer vaccines

Invariant natural killer T (iNKT) cells have the capacity to amplify adaptive immune responses by licensing antigen-presenting cells. A simple vaccine consisting of whole tumor cells pulsed with an iNKT-cell agonist efficiently delivers antigens plus adjuvants to endogenous dendritic cells and has potential for clinical applications.

CD4+ invariant natural killer T cells protect from murine GVHD lethality through expansion of donor CD4+CD25+FoxP3+ regulatory T cells

Dysregulated donor T cells lead to destruction of host tissues resulting in graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT). We investigated the impact of highly purified (>95%) donor CD4(+) invariant natural killer T (iNKT) cells on GVHD in a murine model of allogeneic HCT. We found that low doses of adoptively transferred donor CD4(+) iNKT cells protect from GVHD morbidity and mortality through an expansion of donor CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs). These Tregs express high levels of the Ikaros transcription factor Helios and expand from the Treg pool of the donor graft. Furthermore, CD4(+) iNKT cells preserve T-cell-mediated graft-versus-tumor effects. Our studies reveal new aspects of the cellular interplay between iNKT cells and Tregs in the context of tolerance induction after allogeneic HCT and set the stage for clinical translation.

Radiosensitisation by pharmacological ascorbate in glioblastoma multiforme cells, human glial cells, and HUVECs depends on their antioxidant and DNA repair capabilities and is not cancer specific

We previously showed that 5 mM ascorbate radiosensitized early passage radioresistant glioblastoma multiforme (GBM) cells derived from one patient tumor. Here we investigate the sensitivity of a panel of cell lines to 5 mM ascorbate and 6 Gy ionizing radiation, made up of three primary human GBM cells, three GBM cell lines, a human glial cell line, and primary human vascular endothelial cells. The response of different cells lines to ascorbate and/or radiation was determined by measuring viability, colony-forming ability, generation and repair of double-stranded DNA breaks (DSBs), cell cycle progression, antioxidant capacity and generation of reactive oxygen species. Individually, radiation and ascorbate both decreased viability and clonogenicity by inducing DNA damage, but had differential effects on cell cycle progression. Radiation led to G2/M arrest in most cells whereas ascorbate caused accumulation in S phase, which was moderately associated with poor DSB repair. While high dose ascorbate radiosensitized all cell lines in clonogenic assays, the sensitivity to radiation, high dose ascorbate, and combined treatment varied between cell lines. Normal glial cells were similar to GBM cells with respect to free radical scavenging potential and effect of treatment on DNA damage and repair, viability, and clonogenicity. Both GBM cells and normal cells coped equally poorly with oxidative stress caused by radiation and/or high dose ascorbate, dependent primarily on their antioxidant and DSB repair capacity.

Irradiated tumor cells of lipopolysaccharide stimulation elicit an enhanced anti-tumor immunity

PURPOSE

Lipopolysaccharide (LPS) is a major component of the outer surface membrane of Gram-negative bacteria which has been proved an effective immune enhancer. Here, we investigated the anti-tumor effect of irradiated tumor cells that stimulated by LPS in mouse xenografts models.

METHODS

Tumor cells were irradiated after stimulation with 1 μg/mL LPS for 48 h. The C57BL/6 mice were immunized subcutaneously with irradiated tumor cells. The anti-tumor effect of lymphocytes of immunized mice was investigated. The cytotoxicity of spleen lymphocytes from immunized mice was determined by a standard (51)Cr-release assay. The roles of immune cell subsets in anti-tumor activity were assessed by injected intraperitoneally with monoclonal antibodies.

RESULTS

We observed that the vaccine of irradiated tumor cell with LPS-stimulated elicited a stronger protective anti-tumor immunity than other controls. Adoptive transfer of lymphocytes of immunized mice showed that the cellular immune response was involved in the anti-tumor effect. And this effect was achieved by activation of antigen-specific CD8(+) T cell response and reduction of myeloid-derived suppressor cells (MDSCs, Gr1(+) CD11b (+) ), which were confirmed by depletion of immune cell subsets and flow cytometry analysis.

CONCLUSIONS

In summary, our study showed that stimulation of LPS was able to enhance anti-tumor immunity of vaccination with tumor cells after irradiation treatment, which might be a new strategy for cancer therapy.

Optimization of natural killer T cell-mediated immunotherapy in cancer using cell-based and nanovector vaccines

α-Galactosylceramide (α-GalCer) represents a new class of immune stimulators and vaccine adjuvants that activate type I natural killer T (NKT) cells to swiftly release cytokines and to exert helper functions for acquired immune responses. This unique property prompted clinicians to exploit the antitumor potential of NKT cells. Here, we review the effects of α-GalCer in (pre)clinics and discuss current and future strategies that aim to optimize NKT cell-mediated antitumor therapy, with a particular focus on cell-based and nanovector vaccines.

A personalized view on cancer immunotherapy

Recent progress in cancer immunotherapy has resulted in complete responses in patients refractory to current standard cancer therapies. However, due to tumor heterogeneity and inter-individual variations in anti-tumor immunity, only subsets of patients experience clinical benefit. This review highlights the implementation of a personalized approach to enhance treatment efficacy and reduce side effects, including the identification of tumor-specific antigens for cancer vaccination and adoptive T cell therapies. Furthermore, together with the current advances and promising clinical outcomes of combination cancer (immuno-)therapies, the screening for predictive biomarkers in a patient-specific manner is emphasized.

Using magnetic resonance imaging to evaluate dendritic cell-based vaccination

Cancer immunotherapy with antigen-loaded dendritic cell-based vaccines can induce clinical responses in some patients, but further optimization is required to unlock the full potential of this strategy in the clinic. Optimization is dependent on being able to monitor the cellular events that take place once the dendritic cells have been injected in vivo, and to establish whether antigen-specific immune responses to the tumour have been induced. Here we describe the use of magnetic resonance imaging (MRI) as a simple, non-invasive approach to evaluate vaccine success. By loading the dendritic cells with highly magnetic iron nanoparticles it is possible to assess whether the injected cells drain to the lymph nodes. It is also possible to establish whether an antigen-specific response is initiated by assessing migration of successive rounds of antigen-loaded dendritic cells; in the face of a successfully primed cytotoxic response, the bulk of antigen-loaded cells are eradicated on-route to the node, whereas cells without antigen can reach the node unchecked. It is also possible to verify the induction of a vaccine-induced response by simply monitoring increases in draining lymph node size as a consequence of vaccine-induced lymphocyte trapping, which is an antigen-specific response that becomes more pronounced with repeated vaccination. Overall, these MRI techniques can provide useful early feedback on vaccination strategies, and could also be used in decision making to select responders from non-responders early in therapy.

Invariant NKT cells induce plasmacytoid dendritic cell (DC) cross-talk with conventional DCs for efficient memory CD8+ T cell induction

A key goal of vaccine immunotherapy is the generation of long-term memory CD8(+) T cells capable of mediating immune surveillance. We discovered a novel intercellular pathway governing the development of potent memory CD8(+) T cell responses against cell-associated Ags that is mediated through cross-presentation by XCR1(+) dendritic cells (DCs). Generation of CD8(+) memory T cells against tumor cells pulsed with an invariant NKT cell ligand depended on cross-talk between XCR1(+) and plasmacytoid DCs that was regulated by IFN-α/IFN-αR signals. IFN-α production by plasmacytoid DCs was stimulated by an OX40 signal from the invariant NKT cells, as well as an HMGB1 signal from the dying tumor cells. These findings reveal a previously unknown pathway of intercellular collaboration for the generation of tumor-specific CD8(+) memory T cells that can be exploited for strategic vaccination in the setting of tumor immunotherapy.