Glioblastoma Patients Exhibit Circulating Tumor-Specific CD8+ T Cells

Potential Application of Exosomes in Vaccine Development and Delivery

Exosomes are cell-derived components composed of proteins, lipid, genetic information, cytokines, and growth factors. They play a vital role in immune modulation, cell-cell communication, and response to inflammation. Immune modulation has downstream effects on the regeneration of damaged tissue, promoting survival and repair of damaged resident cells, and promoting the tumor microenvironment via growth factors, antigens, and signaling molecules. On top of carrying biological messengers like mRNAs, miRNAs, fragmented DNA, disease antigens, and proteins, exosomes modulate internal cell environments that promote downstream cell signaling pathways to facilitate different disease progression and induce anti-tumoral effects. In this review, we have summarized how vaccines modulate our immune response in the context of cancer and infectious diseases and the potential of exosomes as vaccine delivery vehicles. Both pre-clinical and clinical studies show that exosomes play a decisive role in processes like angiogenesis, prognosis, tumor growth metastasis, stromal cell activation, intercellular communication, maintaining cellular and systematic homeostasis, and antigen-specific T- and B cell responses. This critical review summarizes the advancement of exosome based vaccine development and delivery, and this comprehensive review can be used as a valuable reference for the broader delivery science community.

Targeting the PD-1/PD-L1 pathway in glioblastoma multiforme: Preclinical evidence and clinical interventions

Glioblastoma multiforme (GBM), as one of the immunosuppressive and common intrinsic brain tumors in adults, remains an intractable malignancy to manage. Since the standard of care for treatment, which includes surgery and chemoradiation, has not provided a sustainable and durable response in affected patients, seeking novel therapeutic approaches to treat GBM seems imperative. Immunotherapy, a breakthrough for cancer treatment, has become an attractive tool for combating cancer with the potential to access the blood-brain-barrier (BBB). In this regard, programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1), as major immunological checkpoints, have drawn considerable interest due to their effectiveness in a spectrum of highly-aggressive neoplasms through negative regulation of the T-cell-mediated immune response. Nevertheless, due to the immunosuppressive microenvironment of GBM, the efficacy of these immune checkpoint inhibitors (ICIs), when used as monotherapy, has been unfavorable and lacks sufficient beneficial outcomes for GBM patients. A variety of clinical studies are attempting to evaluate the combination of ICIs (neoadjuvant/adjuvant) and existing treatment guidelines to strengthen their effectiveness; however, the exact mechanism of this signaling axis affects the consequences of immune therapy remains elusive. This review provides an overview of the PD-1/PD-L1 pathway, currently approved ICIs for clinical use, preclinical and clinical trials of PD-1/PD-L1 as monotherapy, and when used concomitantly with other GBM treatments.

Hans Joachim Scherer and His Impact on the Diagnostic, Clinical, and Modern Research Aspects of Glial Tumors

The historical descriptions of glial tumors are often poorly understood and interpreted. The gross and histological depictions of glial tumors are often credited to Virchow, and while the first true histological description is truly his, gross descriptions can be traced back to the beginning of the 1800s, with their classification and histogenesis attributed to Percival Bailey and Harvey Cushing. Without any question, the most prominent and under-credited researcher in the field of glioma pathobiology was the German neuropathologist Hans Joachim Scherer. Despite the limited armamentarium available to him, his systematic approach led to conclusions, some of which have now been molecularly explained today while some are still being widely researched. Scherer defined pseudopalisadic necrosis as a pathognomonic feature of glioblastoma multiforme (GBM), as well as secondary features due to tumor growth, known collectively as secondary Scherer figures, for example, neuronal and vascular satellitosis, tract and subpial aggregation. All these features are key points in the modern histological diagnosis of glial tumors. Other contributions by Scherer include the definition of glomeruloid vascular proliferation and his conclusion that they are caused by vascular factors released by the tumor, decades before vascular endothelial growth factor and its receptors were discovered and their role in glioma evolution was established. Furthermore, he concluded that GBMs can arise de novo (primary) or from a preceding lower-grade glioma (secondary). All his contributions find their place in all modern aspects of glioma research, with some giving a simple explanation of the phenomena observed in glial tumors.

NKILA lncRNA promotes tumor immune evasion by sensitizing T cells to activation-induced cell death

Activation-induced cell death (AICD) of T lymphocytes can be exploited by cancers to escape immunological destruction. We demonstrated that tumor-specific cytotoxic T lymphocytes (CTLs) and type 1 helper T (T_H1) cells, rather than type 2 helper T cells and regulatory T cells, were sensitive to AICD in breast and lung cancer microenvironments. NKILA, an NF-κB-interacting long noncoding RNA (lncRNA), regulates T cell sensitivity to AICD by inhibiting NF-κB activity. Mechanistically, calcium influx in stimulated T cells via T cell-receptor signaling activates calmodulin, thereby removing deacetylase from the NKILA promoter and enhancing STAT1-mediated transcription. Administering CTLs with NKILA knockdown effectively inhibited growth of breast cancer patient-derived xenografts in mice by increasing CTL infiltration. Clinically, NKILA overexpression in tumor-specific CTLs and T_H1 cells correlated with their apoptosis and shorter patient survival. Our findings underscore the importance of lncRNAs in determining tumor-mediated T cell AICD and suggest that engineering lncRNAs in adoptively transferred T cells might provide a novel antitumor immunotherapy.

Survival gain in glioblastoma patients treated with dendritic cell immunotherapy is associated with increased NK but not CD8+ T cell activation in the presence of adjuvant temozolomide

In a two-stage phase II study, 24 patients with first diagnosis of glioblastoma (GBM) were treated with dendritic cell (DC) immunotherapy associated to standard radiochemotherapy with temozolomide (TMZ) followed by adjuvant TMZ.

Three intradermal injections of mature DC loaded with autologous GBM lysate were administered before adjuvant TMZ, while 4 injections were performed during adjuvant TMZ. According to a two-stage Simon design, to proceed to the second stage progression-free survival (PFS) 12 months after surgery was expected in at least 8 cases enrolled in the first stage. Evidence of immune response and interaction with chemotherapy were investigated. After a median follow up of 17.4 months, 9 patients reached PFS12. In these patients (responders, 37.5%), DC vaccination induced a significant, persistent activation of NK cells, whose increased response was significantly associated with prolonged survival. CD8⁺ T cells underwent rapid expansion and priming but, after the first administration of adjuvant TMZ, failed to generate a memory status. Resistance to TMZ was associated with robust expression of the multidrug resistance protein ABCC3 in NK but not CD8⁺ T cells. The negative effect of TMZ on the formation of T cell-associated antitumor memory deserves consideration in future clinical trials including immunotherapy.

Metabolomics of Therapy Response in Preclinical Glioblastoma: A Multi-Slice MRSI-Based Volumetric Analysis for Noninvasive Assessment of Temozolomide Treatment

Glioblastoma (GBM) is the most common aggressive primary brain tumor in adults, with a short survival time even after aggressive therapy. Non-invasive surrogate biomarkers of therapy response may be relevant for improving patient survival. Previous work produced such biomarkers in preclinical GBM using semi-supervised source extraction and single-slice Magnetic Resonance Spectroscopic Imaging (MRSI). Nevertheless, GBMs are heterogeneous and single-slice studies could prevent obtaining relevant information. The purpose of this work was to evaluate whether a multi-slice MRSI approach, acquiring consecutive grids across the tumor, is feasible for preclinical models and may produce additional insight into therapy response. Nosological images were analyzed pixel-by-pixel and a relative responding volume, the Tumor Responding Index (TRI), was defined to quantify response. Heterogeneous response levels were observed and treated animals were ascribed to three arbitrary predefined groups: high response (HR, n = 2), TRI = 68.2 ± 2.8%, intermediate response (IR, n = 6), TRI = 41.1 ± 4.2% and low response (LR, n = 2), TRI = 13.4 ± 14.3%, producing therapy response categorization which had not been fully registered in single-slice studies. Results agreed with the multi-slice approach being feasible and producing an inverse correlation between TRI and Ki67 immunostaining. Additionally, ca. 7-day oscillations of TRI were observed, suggesting that host immune system activation in response to treatment could contribute to the responding patterns detected.

Serum exosomes and cytokines promote a T-helper cell type 2 environment in the peripheral blood of glioblastoma patients

BACKGROUND

Glioblastoma (GBM) is an aggressive infiltrative brain tumor with a particularly poor prognosis that is characterized by microvascular proliferation, necrotic tissue, and significant infiltration of M2-like monocytes. Compromised barrier function in tumor vasculature might be expected to permit communication between the tumor microenvironment and peripheral blood.

METHODS

To ascertain whether tumor-derived vesicles and/or factors might reach the bloodstream and what effects these molecules have on the peripheral compartment, we analyzed blood samples collected from primary GBM patients.

RESULTS

Notably, a significant number of patient sera samples contained tumor exosome-reactive immunoglobulin (Ig)G2 and IgG4 antibody isotypes, which are consistent with Th2 immunity. M2-like monocytes expressing CD14+ and CD163+, another indicator of Th2 bias, are elevated in GBM patient blood and associated with high serum concentrations of colony-stimulating factor 2 and 3, as well as interleukin-2, -4, and -13, the latter 2 cytokines being hallmarks of Th2 immunity. GBM patient sera samples induce high levels of CD163 expression when added to normal monocytes, providing mechanistic evidence of a basis for Th2 bias. Fractionation of GBM patient sera into samples enriched for exosomes or soluble factors proved that both fractions are capable of inducing CD163 expression in normal monocytes.

CONCLUSIONS

The results of the current study indicate a Th2 bias in the periphery of GBM patients, likely as a result of products elaborated by the tumor. Consequentially, through immune modulation these brain tumors exert systemic effects beyond the confines of the CNS.

Synergism between cryoablation and GM-CSF: enhanced immune function of splenic dendritic cells in mice with glioma

Glioma is the most common malignant primary brain tumor, and it has a poor prognosis. Studies have shown that cryoablation can activate antitumor immunoeffects by promoting the augmentation of dendritic cells (DCs). Granulocyte macrophage colony-stimulating factor (GM-CSF) has been shown to be useful for immunotherapy against glioma because it can stimulate DCs to present tumor antigen. Previous studies have shown that cryoablation and GM-CSF can exert antitumor effects. To test the hypothesis that combined therapy with cryoablation and GM-CSF for glioma could synergistically improve specific antiglioma immunity in mice, we tested the validity of this assumption in a murine subcutaneous GL261 glioma model. C57BL/6 mice with subcutaneous GL261 glioma were created and divided into four groups: no treatment, GM-CSF injection, cryoablation treatment, and GM-CSF and cryoablation combined treatment (n=20 in each group). Serial immune indicators were detected at sequential time points during treatment. Compared with the other groups, in the combined treatment group, DCs were more activated and their numbers were markedly upregulated, the secretion of interferon-γ from Th1 cells of mice spleen was increased, and the cytolytic activity of CD8 CTLs exerted a more significant cytotoxic effect on GL261 glioma cells (P<0.05 for all). Furthermore, these changes peaked on the 7th day after treatment, and then gradually reduced, until the 21st day; these changes were higher than those at pretreatment (P<0.05). It is concluded that combined therapy with argon-helium cryoablation and GM-CSF could synergistically enhance the activation of DCs and induce a robust tumor-specific immunologic response in glioma-bearing mice.

Glioblastoma exosomes and IGF-1R/AS-ODN are immunogenic stimuli in a translational research immunotherapy paradigm

Glioblastomas are primary intracranial tumors for which there is no cure. Patients receiving standard of care, chemotherapy and irradiation, survive approximately 15 months prompting studies of alternative therapies including vaccination. In a pilot study, a vaccine consisting of Lucite diffusion chambers containing irradiated autologous tumor cells pre-treated with an antisense oligodeoxynucleotide (AS-ODN) directed against the insulin-like growth factor type 1 receptor was found to elicit positive clinical responses in 8/12 patients when implanted in the rectus sheath for 24 h. Our preliminary observations supported an immune response, and we have since reopened a second Phase 1 trial to assess this possibility among other exploratory objectives. The current study makes use of a murine glioma model and samples from glioblastoma patients in this second Phase 1 trial to investigate this novel therapeutic intervention more thoroughly. Implantation of the chamber-based vaccine protected mice from tumor challenge, and we posit this occurred through the release of immunostimulatory AS-ODN and antigen-bearing exosomes. Exosomes secreted by glioblastoma cultures are immunogenic, eliciting and binding antibodies present in the sera of immunized mice. Similarly, exosomes released by human glioblastoma cells bear antigens recognized by the sera of 6/12 patients with recurrent glioblastomas. These results suggest that the release of AS-ODN together with selective release of exosomes from glioblastoma cells implanted in chambers may drive the therapeutic effect seen in the pilot vaccine trial.

An update on vaccine therapy and other immunotherapeutic approaches for glioblastoma

Outcome for glioblastoma (GBM), the most common primary CNS malignancy, remains poor. The overall survival benefit recently achieved with immunotherapeutics for melanoma and prostate cancer support evaluation of immunotherapies for other challenging cancers, including GBM. Much historical dogma depicting the CNS as immunoprivileged has been replaced by data demonstrating CNS immunocompetence and active interaction with the peripheral immune system. Several glioma antigens have been identified for potential immunotherapeutic exploitation. Active immunotherapy studies for GBM, supported by preclinical data, have focused on tumor lysate and synthetic antigen vaccination strategies. Results to date confirm consistent safety, including a lack of autoimmune reactivity; however, modest efficacy and variable immunogenicity have been observed. These findings underscore the need to optimize vaccination variables and to address challenges posed by systemic and local immunosuppression inherent to GBM tumors. Additional immunotherapy strategies are also in development for GBM. Future studies may consider combinatorial immunotherapy strategies with complimentary actions.

Glioma grade is associated with the accumulation and activity of cells bearing M2 monocyte markers

PURPOSE

This study is directed at identifying the cell source(s) of immunomodulatory cytokines in high-grade gliomas and establishing whether the analysis of associated markers has implications for tumor grading.

EXPERIMENTAL DESIGN

Glioma specimens classified as WHO grade II-IV by histopathology were assessed by gene expression analysis and immunohistochemistry to identify the cells producing interleukin (IL)-10, which was confirmed by flow cytometry and factor secretion in culture. Finally, principal component analysis (PCA) and mixture discriminant analysis (MDA) were used to investigate associations between expressed genes and glioma grade.

RESULTS

The principle source of glioma-associated IL-10 is a cell type that bears phenotype markers consistent with M2 monocytes but does not express all M2-associated genes. Measures of expression of the M2 cell markers CD14, CD68, CD163, and CD204, which are elevated in high-grade gliomas, and the neutrophil/myeloid-derived suppressor cell (MDSC) subset marker CD15, which is reduced, provide the best index of glioma grade.

CONCLUSIONS

Grade II and IV astrocytomas can be clearly differentiated on the basis of the expression of certain M2 markers in tumor tissues, whereas grade III astrocytomas exhibit a range of expression between the lower and higher grade specimens. The content of CD163(+) cells distinguishes grade III astrocytoma subsets with different prognosis.

Natural HLA class I ligands from glioblastoma: extending the options for immunotherapy

Glioblastoma multiforme is the most frequent and most malignant primary brain tumor with poor prognosis despite surgical removal and radio-chemotherapy. In this setting, immunotherapeutical strategies have great potential, but the reported repertoire of tumor associated antigens is only for HLA-A 02 positive tumors. We describe the first analysis of HLA-peptide presentation patterns in HLA-A 02 negative glioma tissue combined with gene expression profiling of the tumor samples by oligonucleotide microarrays. We identified numerous candidate peptides for immunotherapy. These are peptides derived from proteins with a well-described role in glioma tumor biology and suitable gene expression profiles such as PTPRZ1, EGFR, SEC61G and TNC. Information obtained from complementary analyses of HLA-A 02 negative tumors not only contributes to the discovery of novel shared glioma antigens, but most importantly provides the opportunity to tailor a patient-individual cocktail of tumor-associated peptides for a personalized, targeted immunotherapeutic approach in HLA-A 02 negative patients.

Methodology for Anti-Gene Anti-IGF-I Therapy of Malignant Tumours

The aim of this study was to establish the criteria for methodology of cellular “anti-IGF-I” therapy of malignant tumours and particularly for glioblastoma multiforme. The treatment of primary glioblastoma patients using surgery, radiotherapy, and chemotherapy was followed by subcutaneous injection of autologous cancer cells transfected by IGF-I antisense/triple helix expression vectors. The prepared cell “vaccines” should it be in the case of glioblastomas or other tumours, have shown a change of phenotype, the absence of IGF-I protein, and expression of MHC-I and B7. The peripheral blood lymphocytes, PBL cells, removed after each of two successive vaccinations, have demonstrated for all the types of tumour tested an increasing level of CD8⁺ and CD8⁺28⁺ molecules and a switch from CD8⁺11b⁺ to CD8⁺11. All cancer patients were supervised for up to 19 months, the period corresponding to minimum survival of glioblastoma patients. The obtained results have permitted to specify the common criteria for “anti-IGF-I” strategy: characteristics sine qua non of injected “vaccines” (cloned cells IGF-I(−) and MHC-I(+)) and of PBL cells (CD8⁺ increased level).

Glioblastoma-induced inhibition of Langerhans cell differentiation from CD34(+) precursors is mediated by IL-6 but unaffected by JAK2/STAT3 inhibition

AIMS

Langerhans cell (LC) infiltration has been observed in glioblastoma, but the glioblastoma microenvironment may be conditioned to resist antitumor immune responses. As little is known about how glioblastoma may affect dendritic cell differentiation, here we set out to delineate the effects of glioblastoma-derived soluble factors on LC differentiation.

METHODS

CD34(+) precursor cells of the human myeloid cell line MUTZ-3 were differentiated into LC in the presence of conditioned media of the human glioblastoma cell lines U251 or U373 and phenotypically and functionally characterized.

RESULTS

Glioblastoma-conditioned media inhibited LC differentiation, resulting in functional impairment, as determined by allogeneic mixed leukocyte reactivity, and induction of STAT3 activation. IL-6 blockade completely abrogated these glioblastoma-induced immunosuppressive effects and reduced STAT3 phosphorylation. However, neither addition of JSI-124 (cucurbitacin-I; a JAK2/STAT3 inhibitor), nor of GW5074 (a Raf-1 inhibitor), both of which interfere with signaling pathways reported to act downstream of the IL-6 receptor, prevented the observed inhibitory effects on LC differentiation.

CONCLUSION

Glioblastoma-derived IL-6 is responsible for the observed suppression of LC differentiation from CD34(+) precursors but appears to exert this effect in a STAT3 and Raf-1 independent fashion.

Split immunity: immune inhibition of rat gliomas by subcutaneous exposure to unmodified live tumor cells

Gliomas that grow uninhibited in the brain almost never metastasize outside the CNS. The rare occurrences of extracranial metastasis are usually associated with a suppressed immune system. This observation raises the possibility that some gliomas might not grow outside the CNS due to an inherent immune response, We report in this study that the highly malignant F98 Fischer rat undifferentiated glioma, which grows aggressively in the brain, spontaneously regresses when injected live s.c. We found that this regression is immune-mediated and that it markedly enhances the survival or cures rats challenged with the same tumor intracranially either before or after the s.c. live-cell treatment. Adoptive transfer experiments showed the effect was immune-mediated and that the CD8 T cell fraction, which exhibited direct tumor cytotoxicity, was more effective than the CD4 T cell fraction in mediating resistance to intracranial challenge of naive rats. Brain tumors from treated rats exhibited enhanced CD3(+)CD8(+)CD4(-) and CD3(+)CD4(+)CD8(-) T cell infiltration and IFN-γ secretion. The results in the F98 glioma were corroborated in the Lewis rat CNS-1 astrocytoma. In both tumor models, s.c. treatment with live cells was significantly better than immunization with irradiated cells. We propose in this study a location-based immunotherapeutic phenomenon we term "split immunity": a tumor that thrives in an immune-privileged site may be inhibited by injecting live, unmodified tumor cells into a site that is not privileged, generating protective immunity that spreads back to the privileged site. Split immunity could explain several long-standing paradoxes regarding the lack of overt extracranial metastasis in patients with primary brain tumors.

Immunotherapy in human glioblastoma

Glioblastoma patients spontaneously develop anti-tumour immune responses. However, the tumour itself develops several mechanisms that allow the tumor to escape the immune system. Clinical trials using infusion of activated autologous immune cells, or active immunotherapy with tumor antigens and dendritic cells have successfully induced anti-tumour immunity and some radiological responses. More recently, approaches targeting the mechanisms of tolerance have shown promising data in melanoma, and are currently under investigations in gliomas. However, large randomised trials are still needed to prove the usefulness of cancer vaccines in brain tumors.

Therapeutic vaccines for malignant brain tumors

Malignant gliomas are the most common and aggressive form of brain tumors. Current therapy consists of surgical resection, followed by radiation therapy and concomitant chemotherapy. Despite these treatments, the prognosis for patients is poor. As such, investigative therapies including tumor vaccines have targeted this devastating condition. Recent clinical trials involving immunotherapy, specifically dendritic cell (DC) based vaccines, have shown promising results. Overall, these vaccines are well tolerated with few documented side effects. In many patients receiving vaccines, tumor progression was delayed and the median overall survival of these patients was prolonged. Despite these encouraging results, several factors have limited the efficacy of DC vaccines. Here we discuss the potential of DC vaccines as adjuvant therapy and current obstacles of generating highly pure and potent DC vaccines in the context of malignant glioma. Taken together, the results from earlier clinical studies justify additional clinical trials aimed at improving the efficacy of DC vaccines.

Drug or vaccine?: selecting the appropriate treatment for malignant glioma patients

Malignant gliomas are the most common and aggressive form of brain tumour. Current combinations of aggressive surgical resection, radiation therapy and chemotherapy regimens do not significantly improve long-term patient survival for these cancers. Therefore, investigative therapies including tumour vaccines have targeted this devastating condition. This article reviews evidence and data on chemotherapy and immunotherapy for a personalized medicine approach in order to enable physicians to select the appropriate treatment for glioma patients. Dendritic cell- and peptide-based therapy for gliomas seems to be safe and without major adverse effects. Gene-modified vaccines have also shown promise in the treatment of malignant gliomas. The concept of 'personalized medicine' is currently important in oncology treatment development. Using a personalized medicine approach, it may be necessary to evaluate the molecular genetic abnormalities in individual patient tumours, and such findings should be the mainstay of immunotherapeutic strategies designed for the individual patient.

Immunobiological characterization of cancer stem cells isolated from glioblastoma patients

PURPOSE

Cancer stem cells (CSC) have been isolated from human tumors, including glioblastoma multiforme (GBM). The aims of this study were the immunobiological characterization of GBM CSCs and the assessment of whether these cells represent suitable targets for immunotherapy.

EXPERIMENTAL DESIGN

GBM CSC lines and their fetal bovine serum (FBS)-cultured non-CSC pair lines were generated and examined by flow cytometry for expression of known tumor antigens, MHC-I and MHC-II molecules, antigen-processing machinery components, and NKG2D ligands. In addition, immunogenicity and immunosuppression of such cell lines for autologous or allogeneic T lymphocytes were tested by cytokine secretion (ELISPOT) or proliferation (carboxyfluorescein diacetate succinimidyl ester) assays, respectively.

RESULTS

Both GBM CSC and FBS lines were weakly positive and negative for MHC-I, MHC-II, and NKG2D ligand molecules, respectively. Antigen-processing machinery molecules were also defective in both cell types. Upregulation of most molecules was induced by IFNs or 5-Aza deoxycytidine, although more efficiently in FBS than in CSCs. Patient T-cell responses, mediated by both TH1 and the TH2 subsets, against autologous CSC could be induced in vitro. In addition, CSC but not their paired FBS tumor lines inhibited T-cell proliferation of healthy donors. Notably, a differential gene signature that was confirmed at the protein levels for some immunologic-related molecules was also found between CSC and FBS lines.

CONCLUSIONS

These results indicate lower immunogenicity and higher suppressive activity of GBM CSC compared with FBS lines. The immunogenicity, however, could be rescued by immune modulation leading to anti-GBM T cell-mediated immune response.

Dendritic cell therapy of high-grade gliomas

The prognosis of patients with malignant glioma is poor in spite of multimodal treatment approaches consisting of neurosurgery, radiochemotherapy and maintenance chemotherapy. Among innovative treatment strategies like targeted therapy, antiangiogenesis and gene therapy approaches, immunotherapy emerges as a meaningful and feasible treatment approach for inducing long-term survival in at least a subpopulation of these patients. Setting up immunotherapy for an inherent immunosuppressive tumor located in an immune-privileged environment requires integration of a lot of scientific input and knowledge of both tumor immunology and neuro-oncology. The field of immunotherapy is moving into the direction of active specific immunotherapy using autologous dendritic cells (DCs) as vehicle for immunization. In the translational research program of the authors, the whole cascade from bench to bed to bench of active specific immunotherapy for malignant glioma is covered, including proof of principle experiments to demonstrate immunogenicity of patient-derived mature DCs loaded with autologous tumor lysate, preclinical in vivo experiments in a murine orthotopic glioma model, early phase I/II clinical trials for relapsing patients, a phase II trial for patients with newly diagnosed glioblastoma (GBM) for whom immunotherapy is integrated in the current multimodal treatment, and laboratory analyses of patient samples. The strategies and results of this program are discussed in the light of the internationally available scientific literature in this fast-moving field of basic science and translational clinical research.

Genetic epidemiology of glioblastoma multiforme: confirmatory and new findings from analyses of human leukocyte antigen alleles and motifs

Background

Human leukocyte antigen (HLA) class I genes mediate cytotoxic T-lymphocyte responses and natural killer cell function. In a previous study, several HLA-B and HLA-C alleles and haplotypes were positively or negatively associated with the occurrence and prognosis of glioblastoma multiforme (GBM).

Methodology/Principal Findings

As an extension of the Upper Midwest Health Study, we have performed HLA genotyping for 149 GBM patients and 149 healthy control subjects from a non-metropolitan population consisting almost exclusively of European Americans. Conditional logistic regression models did not reproduce the association of HLA-B*07 or the B*07-Cw*07 haplotype with GBM. Nonetheless, HLA-A*32, which has previously been shown to predispose GBM patients to a favorable prognosis, was negatively associated with occurrence of GBM (odds ratio = 0.41, p = 0.04 by univariate analysis). Other alleles (A*29, A*30, A*31 and A*33) within the A19 serology group to which A*32 belongs showed inconsistent trends. Sequencing-based HLA-A genotyping established that A*3201 was the single A*32 allele underlying the observed association. Additional evaluation of HLA-A promoter and exon 1 sequences did not detect any unexpected single nucleotide polymorphisms that could suggest differential allelic expression. Further analyses restricted to female GBM cases and controls revealed a second association with a specific HLA-B sequence motif corresponding to Bw4-80Ile (odds ratio = 2.71, p = 0.02).

Conclusions/Significance

HLA-A allelic product encoded by A*3201 is likely to be functionally important to GBM. The novel, sex-specific association will require further confirmation in other representative study populations.

Recent Advances of Dendritic Cells (DCs)-Based Immunotherapy for Malignant Gliomas

Immunotherapy is a new light of hope for the treatment of malignant gliomas. The brain is no longer believed to be an immunologically privileged organ. The major advantage of immunotherapy is the tumor-specific cytotoxic effect on the tumor cells with minimal side effects. Autologous dendritic cells (DCs)-based immunotherapy is a promising and feasible method. DCs are the most potent antigen-presenting cells (APCs). DCs prime T lymphocytes by epitopic major histocompatibility (MHC) class I and II for CD8+ cytotoxic T lymphocytes (CTLs) and CD4+ T helper cells, respectively. From the tissue specimen examination after DCs-based immunotherapy, CD8+ CTLs have replaced T regulatory cells (Tregs) as the major dominant tissue infiltrating lymphocytes (TILs). CD8+ CTLs play a key role in the tumor response, which may also be effective against cancer stem cells. DCs themselves also produce many cytokines including interferon-γ and interleukin (IL-2) to kill the tumor cells. From the preliminary better outcomes in the literature for malignant gliomas, DC-based immunotherapy may improve tumor response by increasing the survival rate and time. It is recommended that DC-based immunotherapy is applied as soon as possible with conjunctive radiotherapy and chemotherapy. Malignant gliomas have heterogeneity of tissue-associated antigens (TAAs). To find universal common antigens through different kinds of tumor culture may be the essential issue for tumor vaccine development in the future.

Site-specific anti-tumor immunity: differences in DC function, TGF-beta production and numbers of intratumoral Foxp3+ Treg

Gliomas localized within the CNS are generally not rejected by the immune system despite being immunogenic. This failure of the immune system has been associated both with glioma-derived immunosuppressive molecules and the immune-privileged state of the CNS. However, the relative contribution of tumor location to the glioma-mediated immunosuppression, as well as the immune mechanisms involved in the failure of glioma rejection are not fully defined. We report here that syngeneic GL261 gliomas growing either intracranially or subcutaneously in mice are infiltrated by DC and T cells. However, only subcutaneous gliomas elicit an effective anti-tumor immune response. In contrast to DC infiltrating subcutaneously grown GL261 gliomas, tumor-infiltrating DC from intracranial gliomas do not activate antigen-dependent T-cell proliferation in vitro. In addition, brain-localized GL261 gliomas are characterized by significantly higher numbers of Foxp3(+) Treg and higher levels of TGF-beta1 mRNA and protein expression when compared with GL261 gliomas in the skin. Our data show that gliomas in the CNS, but not in the skin, give rise to TGF-beta production and accumulation of both Treg and functionally impaired DC. Thus, not the tumor itself, but its location dictates the efficiency of the anti-tumor immune response.

Flow cytometry and in vitro analysis of human glioma-associated macrophages. Laboratory investigation

OBJECT

To date, glioma immunotherapy has been focused mostly on stimulating antitumor peripheral lymphocyte responses; however, some data suggest that microglia and/or macrophages (not lymphocytes) are the predominant inflammatory cells infiltrating gliomas. To study this hypothesis further, the authors analyzed inflammatory cell infiltrates in fresh human malignant glioma specimens and primary cultures.

METHODS

Single-cell suspensions from fresh operative malignant glioma specimens, obtained by stereotactic localization, were analyzed for CD11b and CD45 by using flow cytometry. A comparison was made with peripheral blood mononuclear cells. In a subset of patients, a more detailed flow cytometry analysis of Class I and II major histocompatibility complex, B7-1, B7-2, CD11c, and CD14 expression was performed. Macrophage-like cells in primary glioma cultures were similarly assessed.

RESULTS

Operative samples were obtained from 9 newly diagnosed malignant gliomas. The mean percent of CD45(+)/CD11b(-) cells (lymphocytes) was 2.48% (range 0.65-5.50%); CD45(dim)/CD11b(+) cells (microglia), 1.65% (range 0.37-3.92%); and CD45(bright)/CD11b+ (monocytes/macrophages), 6.25% (range 1.56-15.3%). More detailed fluorescence-activated cell sorting suggested that macrophage-like cells expressed Class I and II major histocompatibility complex, B7-2, and CD11c but not CD14 or B7-1. Primary human glioma cultures contained significant numbers of macrophage-like (CD45(bright)/CD11b(+)) cells, but these cells were lost with successive passages. These cells maintained the immunomarker profiles of macrophage-like cells from fresh specimens only if they were cultured in serum-free media.

CONCLUSIONS

The CD45(+)/CD11b(+) cells are the predominant inflammatory cell infiltrating human gliomas. Of this type, the CD45(bright)/CD11b(+) cells, a phenotype compatible with circulating macrophages in rodent models, and not microglia, are the most common. Their immunomarker profile is compatible with an immature antigen-presenting cell. They are present in primary glioma cultures but are lost in successive passages. Their role is enigmatic, and they may prove an important target for future glioma immunotherapy studies.

Postoperative adjuvant dendritic cell-based immunotherapy in patients with relapsed glioblastoma multiforme

PURPOSE

To investigate the therapeutic role of adjuvant vaccination with autologous mature dendritic cells (DC) loaded with tumor lysates derived from autologous, resected glioblastoma multiforme (GBM) at time of relapse.

EXPERIMENTAL DESIGN

Fifty-six patients with relapsed GBM (WHO grade IV) were treated with at least three vaccinations. Children and adults were treated similarly in three consecutive cohorts, with progressively shorter vaccination intervals per cohort. Feasibility and toxicity were assessed as well as effect of age, extent of resection, Karnofsky Performance Score, and treatment cohort on the progression-free (PFS) and overall survival (OS) using univariable and multivariable analysis.

RESULTS

Since the prevaccine reoperation, the median PFS and OS of the total group was 3 and 9.6 months, respectively, with a 2-year OS of 14.8%. Total resection was a predictor for better PFS both in univariable analysis and after correction for the other covariates. For OS, younger age and total resection were predictors of a better outcome in univariable analysis but not in multivariable analysis. A trend to improved PFS was observed in favor of the faster DC vaccination schedule with tumor lysate boosting. Vaccine-related edema in one patient with gross residual disease before vaccination was the only serious adverse event.

CONCLUSION

Adjuvant DC-based immunotherapy for patients with relapsed GBM is safe and can induce long-term survival. A trend to PFS improvement was shown in the faster vaccination schedule. The importance of age and a minimal residual disease status at the start of the vaccination is underscored.

Treg depletion inhibits efficacy of cancer immunotherapy: implications for clinical trials

Background

Regulatory T lymphocytes (Treg) infiltrate human glioblastoma (GBM); are involved in tumor progression and correlate with tumor grade. Transient elimination of Tregs using CD25 depleting antibodies (PC61) has been found to mediate GBM regression in preclinical models of brain tumors. Clinical trials that combine Treg depletion with tumor vaccination are underway to determine whether transient Treg depletion can enhance anti-tumor immune responses and improve long term survival in cancer patients.

Findings

Using a syngeneic intracrabial glioblastoma (GBM) mouse model we show that systemic depletion of Tregs 15 days after tumor implantation using PC61 resulted in a decrease in Tregs present in tumors, draining lymph nodes and spleen and improved long-term survival (50% of mice survived >150 days). No improvement in survival was observed when Tregs were depleted 24 days after tumor implantation, suggesting that tumor burden is an important factor for determining efficacy of Treg depletion in clinical trials. In a T cell dependent model of brain tumor regression elicited by intratumoral delivery of adenoviral vectors (Ad) expressing Fms-like Tyrosine Kinase 3 ligand (Flt3L) and Herpes Simplex Type 1-Thymidine Kinase (TK) with ganciclovir (GCV), we demonstrate that administration of PC61 24 days after tumor implantation (7 days after treatment) inhibited T cell dependent tumor regression and long term survival. Further, depletion with PC61 completely inhibited clonal expansion of tumor antigen-specific T lymphocytes in response to the treatment.

Conclusions

Our data demonstrate for the first time, that although Treg depletion inhibits the progression/eliminates GBM tumors, its efficacy is dependent on tumor burden. We conclude that this approach will be useful in a setting of minimal residual disease. Further, we also demonstrate that Treg depletion, using PC61 in combination with immunotherapy, inhibits clonal expansion of tumor antigen-specific T cells, suggesting that new, more specific targets to block Tregs will be necessary when used in combination with therapies that activate anti-tumor immunity.

Treatment of Intracerebral Glioblastomas with G422 Tumour Cell Vaccine in a Mouse Model

The aim of this study was to develop a tumour vaccine with the ability to induce and expand higher affinity cytotoxic T lymphocytes and stimulate an effective antitumour immune response. The hypothesis tested was that G422 glioblastoma cells modified with B7-1 and interferon (IFN)-γ genes could serve as a tumour vaccine. It was found that therapeutic subcutaneous immunizations with this tumour vaccine significantly induced a cytotoxic T-cell response and prolonged the survival of female Kuming mice with intracerebral G422 tumour isografts. The data collectively suggested that G422 glioblastoma cells genetically modified with B7-1 and IFN-γ genes could serve as a tumour vaccine.

Emerging Role of Combination of All-trans Retinoic Acid and Interferon-gamma as Chemoimmunotherapy in the Management of Human Glioblastoma

Glioblastoma is the most malignant and common type of brain tumor with devastating outcome. Because current treatment modalities are mostly ineffective in controlling and curing glioblastoma, new and innovative therapeutic strategies must be developed. This article describes recent advances in chemoimmunotherapy, which is combination of chemotherapy and immunotherapy, against glioblastoma. We provide an overview of available treatment options for glioblastomas, gaps in our knowledge of immune recognition of these malignant tumors, and chemotherapeutic and immunotherapeutic agents that need to be further explored for designing novel chemoimmunotherapeutic strategy for the management of human glioblastomas. Our recent study demonstrated that combination of the chemotherapeutic agent all-trans retinoic acid (ATRA) and the immunotherapeutic agent interferon-gamma (IFN-gamma) could concurrently induce differentiation, apoptotic death, and immune components in two different human glioblastoma cell lines. We propose that combination of ATRA and IFN-gamma can become an efficacious chemoimmunotherapy for the treatment of human glioblastoma.

Dendritic cell-based active specific immunotherapy for malignant glioma

Immunotherapy is an appealing therapeutic modality for malignant gliomas because of its potential to selectively target residual tumor cells that have invaded the normal brain. Most immunotherapeutic studies are designed to exploit the capacity of dendritic cells for inducing cell-mediated effects as well as immune memory responses for destroying residual tumor cells and preventing recurrence. Although initial clinical studies on dendritic cell-based immunotherapy resulted in very limited success, they have prompted many new studies on exploring strategies to induce a more robust antitumor immune response by using novel adjuvants for maturation and activation of dendritic cells. More studies have focused on the mechanisms of immune suppression by tumor cells and the role of regulatory T cells in tumor growth and progression. In this article, the authors review the evolution of dendritic cell-based immunotherapeutic strategies for adjuvant treatment of malignant gliomas. The authors also discuss how new knowledge on tumor-intrinsic mechanisms of tolerance induction and immunosuppression are likely to shape the future of immunotherapy for high-grade gliomas.

Genetic analysis of intracranial tumors in a murine model of glioma demonstrate a shift in gene expression in response to host immunity

For the study of malignant glioma, we have previously characterized a highly tumorigenic murine astrocytoma, SMA-560, which arose spontaneously in an inbred, immunocompetent VM/Dk mouse. Using this cell line as a model of murine glioma, we performed DNA microarray analysis of autologous normal murine astroctyes (NMA) and SMA-560 tumor cells grown in monolayer culture or intracranially in syngeneic immunocompetent or immunocompromised hosts in order to determine whether tumors grown in vitro recreate the complex genetic regulation that occurs in vivo. Our findings support our hypothesis that glioma phenotype in vitro may be quite different in vivo and significantly altered by in situ growth factors and other invading cell populations.

Human T-cell responses to vaccinia virus envelope proteins

One approach for a safer smallpox vaccine is to utilize recombinant subunits rather than live vaccinia virus (VACV). The products of the VACV envelope genes A27L, L1R, B5R, and A33R induce protective antibodies in animal models. We propose that proteins that elicit T-cell responses, as well as neutralizing antibodies, will be important to include in a molecular vaccine. To evaluate VACV-specific memory T-cell responses, peripheral blood mononuclear cells (PBMC) from four VACV vaccinees were tested against whole VACV and the individual envelope proteins A27, B5, L1, and A33, using gamma interferon enzyme-linked immunospot and cytokine flow cytometry assays. PBMC were stimulated with autologous dendritic cells infected with VACV or electroporated with individual VACV protein mRNAs. T-cell lines from all donors, vaccinated from 1 month to over 20 years ago, recognized all four VACV envelope proteins. Both CD4(+) and CD8(+) T-cell responses to each protein were detected. Further analysis focused on representative proteins B5 and A27. PBMC from a recent vaccinee exhibited high frequencies of CD4(+) and CD8(+) T-cell precursors to both B5 (19.8 and 20%, respectively) and A27 (6.8 and 3.7%). In comparison, B5- and A27-specific T-cell frequencies ranged from 0.4 to 1.3% in a donor vaccinated 3 years ago. Multiple CD4(+) and CD8(+) T-cell epitopes were identified from both A27 and B5, using overlapping 15-mer peptides. These data suggest that all four VACV envelope proteins may contribute to protective immunity, not only by inducing antibody responses, but also by eliciting T-cell responses.

Recent advances in immunotherapy for human glioma

PURPOSE OF REVIEW

The present review focuses on recent progress in tumour immunology and immunotherapeutic trials in malignant gliomas.

RECENT FINDINGS

Major advances have been made in the understanding of antitumour immunity in patients with glioma. Patients with glioblastoma can spontaneously develop antitumour activity with activated CD8+ T cells. Infiltration of myeloid suppressor cells into tumours and increased regulatory T-cell fraction appear to play a critical role in tumour tolerance, however. T-regulatory removal suppresses CD4+ T-cell proliferative defects and can induce tumour rejection in a murine model. Clinical trials using active immunotherapy with dendritic cells loaded with tumour-eluted peptides or tumour lysate have successfully induced antitumour cytotoxicity and some radiologic responses. Other promising approaches targeting the mechanisms of tolerance that could be referred to as 'corrective immunotherapy' are currently on going.

SUMMARY

Improvements in clinical methods and large randomized trials are now needed to prove the usefulness of cancer vaccines. Indeed, comprehensive analysis of tumour immunology and new immunization protocols suggest that immunotherapy can become an efficacious treatment in the near future. Combination with radiotherapy or chemotherapy should be investigated.

Immunization with autologous T cells enhances in vivo anti-tumor immune responses accompanied by up-regulation of GADD45β

Immunization with inactivated autoreactive T cells may induce idiotype anti-idiotypic reactions to deplete autoreactive T cells, which are involved in autoimmune diseases. However, it is unknown whether attenuated activated healthy autologous T-cell immunization could increase anti-tumor immune responses. To this end, C57Bl/6 mice were immunized with attenuated activated autologous T cells. The splenocytes from immunized mice showed a higher proliferative ability than that from naive mice. The special phenotype analysis showed that there were more CD8+ T cells and CD62L+ T cells in immunized mice after 24 h of culture with 10% fetal calf serum complete medium in vitro (P<0.01). These results demonstrated that this immunization may activate T cells in vivo. Furthermore, the splenocytes from immunized mice revealed resistance to activation-induced cell death (AICD) in vitro. To further study the relative genes that are responsible for the higher proliferation and resistance to AICD, the expression of Fas/Fas ligand (FasL) and GADD45b was measured by real-time PCR. The results indicated that GADD45beta transcription was higher in the splenocytes from immunized mice than that in the naive mice. In addition, the Fas expression showed a parallel higher, but FasL did not change obviously. To investigate the biologic functions induced by immunization in vivo, a tumor model was established by EL-4 tumor cell inoculation in C57/Bl mice. Mice receiving autologous T-cell immunization had significantly inhibited tumor growth in vivo (P<0.01). This study implicated that immunization with attenuated activated autologous T cells enhances anti-tumor immune responses that participate in tumor growth inhibition.

Human CD8+ cytotoxic T cell responses to adenovirus capsid proteins

Adenoviruses (Ads) cause fatal disease in allogeneic stem cell transplant recipients, but there is no established therapy. Ad-specific CD8+ T cells were detected in PBMC from healthy adults at a mean frequency of 77 per 10(5) CD8+ T cells (range 8-260) by interferon-gamma ELISPOT and cytokine flow cytometry assays. CD8+ T cell lines from 7 of 7 donors exhibited MHC-class-I-restricted killing of targets expressing the capsid protein hexon. In contrast, cytotoxicity against the capsid proteins fiber and penton base was weaker or not detected. Two HLA-A2-restricted hexon epitopes and one HLA-B-restricted epitope were identified, all of which are adjacent to or overlap an HLA-DP4-restricted epitope in the highly conserved C-terminus. Thus, hexon is the immunodominant T cell target among capsid proteins and contains multiple C-terminal epitopes conserved among serotypes. These data support evaluation of donor lymphocyte infusions for treatment of Ad disease post-transplant.

Paraneoplastic neurodegeneration in a murine host following progressive growth of a spontaneous T-Cell lymphoma: role of proinflammatory internal responses

OBJECTIVE(S)

In the present study, the mechanism of paraneoplastic neurodegeneration associated with progressive in vivo growth of a T-cell lymphoma of spontaneous origin has been investigated.

METHODS

Histologically, the brain was investigated by hematoxylin-eosin staining of brain sections. Western blotting was performed to detect the expression of cytokines and other proteins. Macrophage-derived interleukin-1 (IL-1) and tumor necrosis factor (TNF) was estimated by immunoassays. Induction of apoptosis in brain and tumor cells was determined by percent specific DNA fragmentation.

RESULTS

Tumor growth was associated with the development of multiple lesions in various regions of the brain along with alterations in the structure and alignment of Purkinje cells, and an increase in the water content in the brain. Brain extract and serum of tumor-bearing mice showed higher levels of proinflammatory cytokines. Induction of apoptosis is suggested to be the cause underlying the loss of cellularity of tumor-bearing hosts in the brain owing to an augmentation in the induction of the caspase-dependent pathway of programmed cell death. Further, the study presents investigations to show the role of nitric oxide and proinflammatory cytokines IL-1, TNF, interferon-gamma and alkaline phosphatase in the manifestation of paraneoplastic neurodegeneration.

CONCLUSIONS

Growth of a T-cell lymphoma is associated with the manifestation of neurodegeneration caused by soluble proinflammatory factors of tumor and/or host origin.