Identification of a glioma antigen, GARC-1, using cytotoxic T lymphocytes induced by HSV cancer vaccine

[Cytologic control of the resection margins of hemispheric gliomas and metastases]

INTRODUCTION

Postoperative MRI is the conventional method for assessing the radicalness of hemispherical tumors excision, but the method has limitations on sensitivity in the assessment of tumor infiltration of the peritumoral zone. The 'gold standard' for detecting tumor cells is the microscopic visualisation.

AIM

To study the possibilities of a cytological study of the excision margins of glial and metastatic tumors for an objective assessment of the radical nature of the operation.

MATERIAL AND METHODS

The study included 35 patients with intracerebral tumors who underwent open surgery at a university clinic of Volga Research Medical University in 2018-2019: 15 patients with metastasis, 13 patients with MRI-contrasting gliomas Grade III-IV and 7 patnents with non-MRI-contrasting gliomas Grade II-III. During the surgery, samples for cytological examination were taken from the following sites: from the tumor, from the nearest perifocal zone, and at a distance of 5-7 mm, along the border of the extended resection. 154 samples were examined: from 2 to 5 for each patient.

RESULTS

The data on the radicalness of the operation, obtained by methods of cytological analysis of the resection margins and postoperative MRI, are not only consistent (p=0.001), but also complement each other, in particular, in some cases, tumor cells were found even in those areas where the tumor tissue was not detected with MRI. In cases of cerebral metastases excision, tumor cells in the nearest perifocal zone were found in 8 out of 28 samples (28.6%), at the extended resection margins - in 3 out of 29 (10.3%). In cases of resection of MRI-contrasting gliomas Grade III-IV, tumor cells in the nearest perifocal zone were found in 22 out of 32 samples (68.8%), at the extended resection margins - in 14 out of 20 (70%). In cases of excision of diffuse gliomas Grade II-III, tumor cells in the nearest perifocal zone were found in 10 out of 17 samples (58.9%), at the extended resection margins - in 4 out of 11 (36.4%).

CONCLUSION

The first data obtained demonstrated sufficient informativeness of the cytologic examination of the peritumoral zone as an additional tool for assessing the radicalness of glioma and metastasis surgery. Cytologic analysis of the perifocal zone shows that the extension of the borders of the removal of Grade III-IV gliomas has no advantages, because tumor cells were found both in the nearest perifocal zone and at the extended resection margins with with approximately the same frequency.

Synergistic Combination of Oncolytic Virotherapy and Immunotherapy for Glioma

PURPOSE

We hypothesized that the combination of a local stimulus for activating tumor-specific T cells and an anti-immunosuppressant would improve treatment of gliomas. Virally encoded IL15Rα-IL15 as the T-cell activating stimulus and a prostaglandin synthesis inhibitor as the anti-immunosuppressant were combined with adoptive transfer of tumor-specific T cells.

EXPERIMENTAL DESIGN

Two oncolytic poxviruses, vvDD vaccinia virus and myxoma virus, were each engineered to express the fusion protein IL15Rα-IL15 and a fluorescent protein. Viral gene expression (YFP or tdTomato Red) was confirmed in the murine glioma GL261 in vitro and in vivo. GL261 tumors in immunocompetent C57BL/6J mice were treated with vvDD-IL15Rα-YFP vaccinia virus or vMyx-IL15Rα-tdTr combined with other treatments, including vaccination with GARC-1 peptide (a neoantigen for GL261), rapamycin, celecoxib, and adoptive T-cell therapy.

RESULTS

vvDD-IL15Rα-YFP and vMyx-IL15Rα-tdTr each infected and killed GL261 cells in vitro. In vivo, NK cells and CD8⁺ T cells were increased in the tumor due to the expression of IL15Rα-IL15. Each component of a combination treatment contributed to prolonging survival: an oncolytic virus, the IL15Rα-IL15 expressed by the virus, a source of T cells (whether by prevaccination or adoptive transfer), and prostaglandin inhibition all synergized to produce elimination of gliomas in a majority of mice. vvDD-IL15Rα-YFP occasionally caused ventriculitis-meningitis, but vMyx-IL15Rα-tdTr was safe and effective, causing a strong infiltration of tumor-specific T cells and eliminating gliomas in 83% of treated mice.

CONCLUSIONS

IL15Rα-IL15-armed oncolytic poxviruses provide potent antitumor effects against brain tumors when combined with adoptive T-cell therapy, rapamycin, and celecoxib.

Endogenous Neoantigen-Specific CD8 T Cells Identified in Two Glioblastoma Models Using a Cancer Immunogenomics Approach

The "cancer immunogenomics" paradigm has facilitated the search for tumor-specific antigens over the last 4 years by applying comprehensive cancer genomics to tumor antigen discovery. We applied this methodology to identify tumor-specific "neoantigens" in the C57BL/6-derived GL261 and VM/Dk-derived SMA-560 tumor models. Following DNA whole-exome and RNA sequencing, high-affinity candidate neoepitopes were predicted and screened for immunogenicity by ELISPOT and tetramer analyses. GL261 and SMA-560 harbored 4,932 and 2,171 nonsynonymous exome mutations, respectively, of which less than half were expressed. To establish the immunogenicities of H-2K^b and H-2D^b candidate neoantigens, we assessed the ability of the epitopes predicted in silico to be the highest affinity binders to activate tumor-infiltrating T cells harvested from GL261 and SMA-560 tumors. Using IFNγ ELISPOT, we confirmed H-2D^b-restricted Imp3_D81N (GL261) and Odc1_Q129L (SMA-560) along with H-2K^b-restricted E2f8_K272R (SMA-560) as endogenous tumor-specific neoantigens that are functionally immunogenic. Furthermore, neoantigen-specific T cells to Imp3_D81N and Odc1_Q129L were detected within intracranial tumors as well as cervical draining lymph nodes by tetramer analysis. By establishing the immunogenicities of predicted high-affinity neoepitopes in these models, we extend the immunogenomics-based neoantigen discovery pipeline to glioblastoma models and provide a tractable system to further study the mechanism of action of T cell-activating immunotherapeutic approaches in preclinical models of glioblastoma. Cancer Immunol Res; 4(12); 1007-15. ©2016 AACR.

Local convection-enhanced delivery of an anti-CD40 agonistic monoclonal antibody induces antitumor effects in mouse glioma models

BACKGROUND

Glioblastoma is one of the most malignant brain tumors in adults and has a dismal prognosis. In a previous report, we reported that CD40, a TNF-R-related cell surface receptor, and its ligand CD40L were associated with glioma outcomes. Here we attempted to activate CD40 signaling in the tumor and determine if it exerted therapeutic efficacy.

METHODS

CD40 expression was examined in 3 mouse glioma cell lines (GL261, NSCL61, and bRiTs-G3) and 5 human glioma cell lines (U87, U251, U373, T98, and A172). NSCL61 and bRiTs-G3, as glioma stem cells, also expressed the glioma stem cell markers MELK and CD44. In vitro, we demonstrated direct antitumor effects of an anti-CD40 agonistic monoclonal antibody (FGK45) against the cell lines. The efficacy of FGK45 was examined by local convection-enhanced delivery of the monoclonal antibody against each glioma model.

RESULTS

CD40 was expressed in all mouse and human cell lines tested and was found at the cell membrane of each of the 3 mouse cell lines. FGK45 administration induced significant, direct antitumor effects in vitro. The local delivery of FGK45 significantly prolonged survival compared with controls in the NSCL61 and bRiTs-G3 models, but the effect was not significant in the GL261 model. Increases in apoptosis and CD4(+) and CD8(+) T cell infiltration were observed in the bRiTs-G3 model after FGK45 treatment.

CONCLUSIONS

Local delivery of FGK45 significantly prolonged survival in glioma stem cell models. Thus, local delivery of this monoclonal antibody is promising for immunotherapy against gliomas.

CD40/CD40L expression correlates with the survival of patients with glioblastomas and an augmentation in CD40 signaling enhances the efficacy of vaccinations against glioma models

BACKGROUND

The prognosis of glioblastoma (GBM) remains poor; therefore, effective therapeutic strategies need to be developed. CD40 is a costimulatory molecule whose agonistic antibody has been shown to activate antitumor effects. Recently, CD40 has been extensively targeted for immunotherapeutic purposes.

METHODS

Expressions of CD40/CD40L mRNAs were examined in 86 cases of World Health Organization grade IV GBM and 36 cases of grade III gliomas and correlated with outcomes. CD40 signaling was employed to augment the efficacy of immunotherapy against gliomas. The efficacy of FGK45, an agonistic antibody for CD40, was examined by adding it to a tumor lysate-based subcutaneous vaccination against a GL261 glioma model and an NSCL61 glioma-initiating cell-like cell tumor model.

RESULTS

We demonstrated for the first time using quantitative PCR that grade III gliomas express higher levels of CD40/CD40L than does grade IV GBM. The higher expression of CD40/CD40L was associated with good prognoses in patients with GBM. Addition of FGK45 to the subcutaneous tumor cell lysate-based vaccination significantly prolonged survival in both tumor models. However, the efficacy was modest in NSCL61-model mice. Therefore, we established combination immunotherapeutic strategies using FGK45 and OX86, an agonistic antibody for OX40. Combination immunotherapy significantly prolonged survival with synergistic effects. Apoptosis increased and proliferation decreased in tumors treated with combination immunotherapy.

CONCLUSIONS

The high expression of CD40/CD40L can be used as a biomarker for better prognoses in patients with gliomas. Immunotherapy using FGK45 significantly prolonged survival and represents a potential therapeutic strategy for gliomas including glioma-initiating cells.

Effective Treatment of Established GL261 Murine Gliomas through Picornavirus Vaccination-Enhanced Tumor Antigen-Specific CD8+ T Cell Responses

Glioblastoma (GBM) is among the most invasive and lethal of cancers, frequently infiltrating surrounding healthy tissue and giving rise to rapid recurrence. It is therefore critical to establish experimental model systems and develop therapeutic approaches that enhance anti-tumor immunity. In the current study, we have employed a newly developed murine glioma model to assess the efficacy of a novel picornavirus vaccination approach for the treatment of established tumors. The GL261-Quad system is a variation of the GL261 syngeneic glioma that has been engineered to expresses model T cell epitopes including OVA257-264. MRI revealed that both GL261 and GL261-Quad tumors display characteristic features of human gliomas such as heterogeneous gadolinium leakage and larger T2 weighted volumes. Analysis of brain-infiltrating immune cells demonstrated that GL261-Quad gliomas generate detectable CD8+ T cell responses toward the tumor-specific Kb:OVA257-264 antigen. Enhancing this response via a single intracranial or peripheral vaccination with picornavirus expressing the OVA257-264 antigen increased anti-tumor CD8+ T cells infiltrating the brain, attenuated progression of established tumors, and extended survival of treated mice. Importantly, the efficacy of the picornavirus vaccination is dependent on functional cytotoxic activity of CD8+ T cells, as the beneficial response was completely abrogated in mice lacking perforin expression. Therefore, we have developed a novel system for evaluating mechanisms of anti-tumor immunity in vivo, incorporating the GL261-Quad model, 3D volumetric MRI, and picornavirus vaccination to enhance tumor-specific cytotoxic CD8+ T cell responses and track their effectiveness at eradicating established gliomas in vivo.

OX40 ligand expressed in glioblastoma modulates adaptive immunity depending on the microenvironment: a clue for successful immunotherapy

Background

Glioblastoma is the most malignant human brain tumor and has a dismal prognosis; however, some patients show long-term survival. The interaction between the costimulatory molecule OX40 and its ligand OX40L generates key signals for T-cell activation. The augmentation of this interaction enhances antitumor immunity. In this present study, we explored whether OX40 signaling is responsible for antitumor adaptive immunity against glioblastoma and also established therapeutic antiglioma vaccination therapy.

Methods

Tumor specimens were obtained from patients with primary glioblastoma (n = 110) and grade III glioma (n = 34). Quantitative polymerase chain reaction (PCR), flow cytometry, and immunohistochemistry were used to analyze OX40L expression in human glioblastoma specimens. Functional consequences of OX40 signaling were studied using glioblastoma cell lines, mouse models of glioma, and T cells isolated from human subjects and mice. Cytokine production assay with mouse regulatory T cells was conducted under hypoxic conditions (1.5% O₂).

Results

OX40L mRNA was expressed in glioblastoma specimens and higher levels were associated with prolonged progression-free survival of patients with glioblastoma, who had undergone gross total resection. In this regard, OX40L protein was expressed in A172 human glioblastoma cells and its expression was induced under hypoxia, which mimics the microenvironment of glioblastoma. Notably, human CD4 T cells were activated when cocultured in anti-CD3-coated plates with A172 cells expressing OX40L, as judged by the increased production of interferon-γ. To confirm the survival advantage of OX40L expression, we then used mouse glioma models. Mice bearing glioma cells forced to express OX40L did not die during the observed period after intracranial transplantation, whereas all mice bearing glioma cells lacking OX40L died. Such a survival benefit of OX40L was not detected in nude mice with an impaired immune system. Moreover, compared with systemic intraperitoneal injection, the subcutaneous injection of the OX40 agonist antibody together with glioma cell lysates elicited stronger antitumor immunity and prolonged the survival of mice bearing glioma or glioma-initiating cell-like cells. Finally, OX40 triggering activated regulatory T cells cultured under hypoxia led to the induction of the immunosuppressive cytokine IL10.

Conclusion

Glioblastoma directs immunostimulation or immunosuppression through OX40 signaling, depending on its microenvironment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0307-3) contains supplementary material, which is available to authorized users.

Combination of an agonistic anti-CD40 monoclonal antibody and the COX-2 inhibitor celecoxib induces anti-glioma effects by promotion of type-1 immunity in myeloid cells and T-cells

Malignant gliomas are heavily infiltrated by immature myeloid cells that mediate immunosuppression. Agonistic CD40 monoclonal antibody (mAb) has been shown to activate myeloid cells and promote antitumor immunity. Our previous study has also demonstrated blockade of cyclooxygenase-2 (COX-2) reduces immunosuppressive myeloid cells, thereby suppressing glioma development in mice. We therefore hypothesized that a combinatory strategy to modulate myeloid cells via two distinct pathways, i.e., CD40/CD40L stimulation and COX-2 blockade, would enhance anti-glioma immunity. We used three different mouse glioma models to evaluate therapeutic effects and underlying mechanisms of a combination regimen with an agonist CD40 mAb and the COX-2 inhibitor celecoxib. Treatment of glioma-bearing mice with the combination therapy significantly prolonged survival compared with either anti-CD40 mAb or celecoxib alone. The combination regimen promoted maturation of CD11b(+) cells in both spleen and brain, and enhanced Cxcl10 while suppressing Arg1 in CD11b(+)Gr-1(+) cells in the brain. Anti-glioma activity of the combination regimen was T-cell dependent because depletion of CD4(+) and CD8(+) cells in vivo abrogated the anti-glioma effects. Furthermore, the combination therapy significantly increased the frequency of CD8(+) T-cells, enhanced IFN-γ-production and reduced CD4(+)CD25(+)Foxp3(+) T regulatory cells in the brain, and induced tumor-antigen-specific T-cell responses in lymph nodes. Our findings suggest that the combination therapy of anti-CD40 mAb with celecoxib enhances anti-glioma activities via promotion of type-1 immunity both in myeloid cells and T-cells.

Immunocompetent murine models for the study of glioblastoma immunotherapy

Glioblastoma remains a lethal diagnosis with a 5-year survival rate of less than 10%. (NEJM 352:987-96, 2005) Although immunotherapy-based approaches are capable of inducing detectable immune responses against tumor-specific antigens, improvements in clinical outcomes are modest, in no small part due to tumor-induced immunosuppressive mechanisms that promote immune escape and immuno-resistance. Immunotherapeutic strategies aimed at bolstering the immune response while neutralizing immunosuppression will play a critical role in improving treatment outcomes for glioblastoma patients. In vivo murine models of glioma provide an invaluable resource to achieving that end, and their use is an essential part of the preclinical workup for novel therapeutics that need to be tested in animal models prior to testing experimental therapies in patients. In this article, we review five contemporary immunocompetent mouse models, GL261 (C57BL/6), GL26 (C57BL/6) CT-2A (C57BL/6), SMA-560 (VM/Dk), and 4C8 (B6D2F1), each of which offer a suitable platform for testing novel immunotherapeutic approaches.

Profound impairment of adaptive immune responses by alkylating chemotherapy

Overall, cancer vaccines have had a record of failure as an adjuvant therapy for malignancies that are treated with alkylating chemotherapy, and the contribution of standard treatment to that failure remains unclear. Vaccines aim to harness the proliferative potential of the immune system by expanding a small number of tumor-specific lymphocytes into a large number of antitumor effectors. Clinical trials are often conducted after treatment with alkylating chemotherapy, given either as standard therapy or for immunomodulatory effect. There is mounting evidence for synergy between chemotherapy and adoptive immunotherapy or vaccination against self-Ags; however, the impact of chemotherapy on lymphocytes primed against tumor neoantigens remains poorly defined. We report that clinically relevant dosages of standard alkylating chemotherapies, such as temozolomide and cyclophosphamide, significantly inhibit the proliferative abilities of lymphocytes in mice. This proliferative impairment was long-lasting and led to quantitative and qualitative defects in B and T cell responses to neoantigen vaccines. High-affinity responder lymphocytes receiving the strongest proliferative signals from vaccines experienced the greatest DNA damage responses, skewing the response toward lower-affinity responders with inferior functional characteristics. Together, these defects lead to inferior efficacy and overall survival in murine tumor models treated by neoantigen vaccines. These results suggest that clinical protocols for cancer vaccines should be designed to avoid exposing responder lymphocytes to alkylating chemotherapy.

Glioma antigen

Because several antigenic peptides of human tumors that are recognized by T-lymphocytes have been identified, immune responses against cancer can now be artificially manipulated. Furthermore, since T-lymphocytes have been found to play an important role in the rejection of tumors by the host and also to have antigen-specific proliferative potentials and memory mechanisms, T-lymphocytes are thought to play a central role in cancer vaccination. Although multidisciplinary therapies have been attempted for the treatment of gliomas, the results remain unsatisfactory. For the development of new therapies against gliomas, it is required to identify tumor antigens as targets for specific immunotherapy. In this chapter, recent progress in research on glioma antigens is described.

Downregulation of KIF23 suppresses glioma proliferation

To identify therapeutic molecular targets for glioma, we performed modified serological identification of antigens by recombinant complementary DNA (cDNA) expression cloning using sera from a mouse glioma model. Two clones, kinesin family member 23 (Kif23) and structural maintenance of chromosomes 4 (Smc4), were identified as antigens through immunological reaction with sera from mice harboring synergic GL261 mouse glioma and intratumoral inoculation with a mutant herpes simplex virus. The human Kif23 homolog KIF23 is a nuclear protein that localizes to the interzone of mitotic spindles, acting as a plus-end-directed motor enzyme that moves antiparallel microtubules in vitro. Expression analysis revealed a higher level of KIF23 expression in glioma tissues than in normal brain tissue. The introduction of small interfering RNA (siRNA) targeting KIF23 into two different glioma cell lines, U87MG and SF126, downregulated KIF23 expression, which significantly suppressed glioma cell proliferation in vitro. KIF23 siRNA-treated glioma cells exhibited larger cell bodies with two or more nuclei compared with control cells. In vivo analysis using mouse xenograft showed that KIF23 siRNA/DNA chimera-treated tumors were significantly smaller than tumors treated with control siRNA/DNA chimera. Taken together, our results indicate that downregulation of KIF23 decreases proliferation of glioma cells and that KIF23 may be a novel therapeutic target in malignant glioma.

Gene therapy and targeted toxins for glioma

The most common primary brain tumor in adults is glioblastoma. These tumors are highly invasive and aggressive with a mean survival time of 15-18 months from diagnosis to death. Current treatment modalities are unable to significantly prolong survival in patients diagnosed with glioblastoma. As such, glioma is an attractive target for developing novel therapeutic approaches utilizing gene therapy. This review will examine the available preclinical models for glioma including xenographs, syngeneic and genetic models. Several promising therapeutic targets are currently being pursued in pre-clinical investigations. These targets will be reviewed by mechanism of action, i.e., conditional cytotoxic, targeted toxins, oncolytic viruses, tumor suppressors/oncogenes, and immune stimulatory approaches. Preclinical gene therapy paradigms aim to determine which strategies will provide rapid tumor regression and long-term protection from recurrence. While a wide range of potential targets are being investigated preclinically, only the most efficacious are further transitioned into clinical trial paradigms. Clinical trials reported to date are summarized including results from conditionally cytotoxic, targeted toxins, oncolytic viruses and oncogene targeting approaches. Clinical trial results have not been as robust as preclinical models predicted; this could be due to the limitations of the GBM models employed. Once this is addressed, and we develop effective gene therapies in models that better replicate the clinical scenario, gene therapy will provide a powerful approach to treat and manage brain tumors.

Experimental immunotherapy for malignant glioma: lessons from two decades of research in the GL261 model

Nearly twenty years of experimental immunotherapy for malignant glioma yielded important insights in the mechanisms governing glioma immunology. Still considered promising, it is clear that immunotherapy does not on its own represent the magic bullet in glioma therapy. In this review, we summarize the major immunotherapeutic achievements in the mouse GL261 glioma model, which has emerged as the gold standard syngeneic model for experimental glioma therapy. Gene therapy, monoclonal antibody treatment, cytokine therapy, cell transfer strategies and dendritic cell therapy were hereby considered. Apart from the considerable progress made in understanding glioma immunology in this model, we also addressed its most pertinent issues and shortcomings. Despite these, the GL261 model will remain indispensable in glioma research since it is a fast, highly reproducible and easy-to-establish model system.

Poly-ICLC promotes the infiltration of effector T cells into intracranial gliomas via induction of CXCL10 in IFN-alpha and IFN-gamma dependent manners

Stimulation of double-stranded (ds)RNA receptors can increase the effectiveness of cancer vaccines, but the underlying mechanisms are not completely elucidated. In this study, we sought to determine critical roles of host IFN-alpha and IFN-gamma pathways in the enhanced therapeutic efficacy mediated by peptide vaccines and polyinosinic-polycytidylic acid [poly(I:C)] stabilized by lysine and carboxymethylcellulose (poly-ICLC) in the murine central nervous system (CNS) GL261 glioma. C57BL/6-background wild type (WT), IFN-alpha receptor-1 (IFN-alphaR1)(-/-) or IFN-gamma(-/-) mice bearing syngeneic CNS GL261 glioma received subcutaneous (s.c.) vaccinations with synthetic peptides encoding CTL epitopes with or without intramuscular (i.m.) injections of poly-ICLC. The combinational treatment induced a robust transcription of CXCL10 in the glioma site. Blockade of CXCL10 with a specific monoclonal antibody (mAb) abrogated the efficient CNS homing of antigen-specific type-1 CTL (Tc1). Both IFN-alphaR(-/-) and IFN-gamma(-/-) hosts failed to up-regulate the CXCL10 mRNA and recruit Tc1 cells to the tumor site, indicating non-redundant roles of type-1 and type-2 IFNs in the effects of poly-ICLC-assisted vaccines. The efficient trafficking of Tc1 also required Tc1-derived IFN-gamma. Our data point to critical roles of the host-IFN-alpha and IFN-gamma pathways in the modulation of CNS glioma microenvironment, and the therapeutic effectiveness of poly-ICLC-assisted glioma vaccines.

Virally mediated immunotherapy for brain tumors

Brain tumors are a leading cause of mortality and morbidity in the United States. Malignant brain tumors occur in approximately 80,000 adults. Furthermore, the average 5-year survival rate for malignant brain tumors across all ages and races is approximately 30% and has remained relatively static over the past few decades, showing the need for continued research and progress in brain tumor therapy. Improved techniques in molecular biology have expanded understanding of tumor genetics and permitted viral engineering and the anticancer therapeutic use of viruses as directly cytotoxic agents and as gene vectors. Preclinical models have shown promising antitumor effects, and generation of clinical grade vectors is feasible. In parallel to these developments, better understanding of antitumor immunity has been accompanied by progress in cancer immunotherapy, the goal of which is to stimulate host rejection of a growing tumor. This article reviews the intersection between the use of viral therapy and immunotherapy in the treatment of malignant gliomas. Each approach shows great promise on its own and in combined or integrated forms.

Systemic inhibition of transforming growth factor-beta in glioma-bearing mice improves the therapeutic efficacy of glioma-associated antigen peptide vaccines

PURPOSE

A variety of cancers, including malignant gliomas, overexpress transforming growth factor-beta (TGF-beta), which helps tumors evade effective immune surveillance through a variety of mechanisms, including inhibition of CD8(+) CTLs and enhancing the generation of regulatory T (T(reg)) cells. We hypothesized that inhibition of TGF-beta would improve the efficacy of vaccines targeting glioma-associated antigen (GAA)-derived CTL epitopes by reversal of immunosuppression.

EXPERIMENTAL DESIGN

Mice bearing orthotopic GL261 gliomas were treated systemically with a TGF-beta-neutralizing monoclonal antibody, 1D11, with or without s.c. vaccinations of synthetic peptides for GAA-derived CTL epitopes, GARC-1 (77-85) and EphA2 (671-679), emulsified in incomplete Freund's adjuvant.

RESULTS

Mice receiving the combination regimen exhibited significantly prolonged survival compared with mice receiving either 1D11 alone, GAA vaccines alone, or mock treatments alone. TGF-beta neutralization enhanced the systemic induction of antigen-specific CTLs in glioma-bearing mice. Flow cytometric analyses of brain-infiltrating lymphocytes revealed that 1D11 treatment suppressed phosphorylation of Smad2, increased GAA-reactive/IFN-gamma-producing CD8(+) T cells, and reduced CD4(+)/FoxP3(+) T(reg) cells in the glioma microenvironment. Neutralization of TGF-beta also upregulated plasma levels of interleukin-12, macrophage inflammatory protein-1 alpha, and IFN-inducible protein-10, suggesting a systemic promotion of type-1 cytokine/chemokine production. Furthermore, 1D11 treatment upregulated plasma interleukin-15 levels and promoted the persistence of GAA-reactive CD8(+) T cells in glioma-bearing mice.

CONCLUSIONS

These data suggest that systemic inhibition of TGF-beta by 1D11 can reverse the suppressive immunologic environment of orthotopic tumor-bearing mice both systemically and locally, thereby enhancing the therapeutic efficacy of GAA vaccines.

Effective immunotherapy against murine gliomas using type 1 polarizing dendritic cells--significant roles of CXCL10

In an attempt to develop effective vaccines against central nervous system (CNS) tumors, we evaluated the ability of vaccines with standard dendritic cells (DC) versus type 1 polarizing DCs (DC1) to induce glioma-specific type 1 CTLs with CNS tumor-relevant homing properties and the mechanism of their action. C57BL/6 mouse-derived bone marrow cells were cultured with mouse granulocyte/macrophage colony-stimulating factor (GM-CSF) for 6 days, and CD11c(+) cells were subsequently cultured with GM-CSF, rmIFN-gamma, rmIFN-alpha, rmIL-4, and polyinosinic-polycytidylic acid stabilized by lysine and carboxymethylcellulose for 24 hours to generate DC1s. In analogy to their human counterparts, mouse DC1s exhibited surface marker profiles of mature DCs and produced high levels of IL-12 and CXCL10. Importantly for their application as cancer vaccines, such DC1s stably retained their type 1 phenotype even when exposed to type 2-promoting or regulatory T cell (Treg)-promoting environments. Consistently, mouse DC1s induced antigen-specific type 1 CTLs more efficiently than nonpolarized DCs in vitro. DC1s given s.c. migrated into draining lymph nodes, induced antigen-specific CTLs, and suppressed Treg accumulation. In addition, s.c. immunization with DC1s loaded with glioma-associated antigen (GAA)-derived CTL epitope peptides prolonged the survival of CNS GL261 glioma-bearing mice, which was associated with efficient CNS glioma homing of antigen-specific CTLs. Intratumoral injections of GAA peptide-loaded DC1s further enhanced the anti-CNS glioma effects of DC1-based s.c. immunization. Interestingly, the antitumor functions were abrogated with CXCL10(-/-) mouse-derived DC1s. Collectively, these findings show the anti-CNS glioma effects of DC1-based therapy and a novel role of CXCL10 in the immunologic and therapeutic activity of DC-based cancer vaccines.

Induction of protective and therapeutic antitumor immunity by a DNA vaccine with a glioma antigen, SOX6

We previously reported identifying SOX6 as a glioma antigen by serological screening using a testis cDNA library. Its preferential expression and frequent IgG responses in glioma patients indicate that SOX6 may be a useful target for immunotherapy. To examine whether cytotoxic T-lymphocyte (CTL) responses specific for SOX6 to destroy glioma can be generated in vivo, we treated glioma-bearing mice by vaccination with a plasmid DNA encoding murine full-length SOX6 protein. Following SOX6-DNA vaccination, CTLs specific for SOX6-expressing glioma cells were induced, while normal autologous-cells that had restrictedly expressed SOX6 during embryogenesis were not destroyed. Furthermore, DNA vaccination with SOX6 exerted protective and therapeutic antitumor responses in the glioma-bearing mice. This antitumor activity was abrogated by the depletion of CD4 positive T cells and/or CD8 positive T cells. These results suggest that the SOX6 protein has multiple CTL and helper epitopes to induce antitumor activity and the effectiveness of SOX6-DNA vaccine for the prevention and treatment of glioma.