Immunological quiescence in the central nervous system (CNS) is a potential barrier to immune mediated anti-tumor response. One suppressive mechanism results from the interaction of parenchyma-derived CD200 and its receptor on myeloid cells. We suggest that CD200/CD200R interactions on myeloid cells expand the myeloid-derived suppressor cell (MDSC) population and that blocking tumor-derived CD200 will enhance the efficacy of immunotherapy.
CD200 mRNA expression levels in human brain tumor tissue samples were measured by microarray. The amount of circulating CD200 protein in the sera of patients with brain tumors was determined by ELISA and, when corresponding peripheral blood samples were available, was correlated quantitatively with MDSCs. CD200-derived peptides were used as competitive inhibitors in a mouse model of glioblastoma immunotherapy.
CD200 mRNA levels were measured in human brain tumors, with different expression levels being noted among the sub groups of glioblastoma, medulloblastoma and ependymoma. Serum CD200 concentrations were highest in patients with glioblastoma and correlated significantly with MDSC expansion. Similarly, in vitro studies determined that GL261 cells significantly expanded a MDSC population. Interestingly, a CD200R antagonist inhibited the expansion of murine MDSCs in vitro and in vivo. Moreover, inclusion of CD200R antagonist peptide in glioma tumor lysate-derived vaccines slowed tumor growth and significantly enhanced survival.
These data suggest that CNS-derived tumors can evade immune surveillance by engaging CD200. Because of the homology between mouse and human CD200, our data also suggest that blockade of CD200 binding to its receptor will enhance the efficacy of immune mediated anti-tumor strategies for brain tumors.
Electronic supplementary material
The online version of this article (doi:10.1186/s40425-014-0046-9) contains supplementary material, which is available to authorized users.
Checkpoint inhibitors; Immunotherapy; Immune suppression; Brain tumors
Malignant gliomas are lethal cancers in the brain and heavily infiltrated by myeloid cells. Interleukin-4 receptor-α (IL-4Rα) mediates the immunosuppressive functions of myeloid cells, and polymorphisms in the IL-4Rα gene are associated with altered glioma risk and prognosis. In this study, we sought to evaluate an hypothesized causal role for IL-4Rα and myeloid suppressor cells in glioma development. In both mouse de novo gliomas and human glioblastoma cases, IL-4Rα was upregulated on glioma-infiltrating myeloid cells but not in the periphery or in normal brain. Mice genetically deficient for IL-4Rα exhibited a slower growth of glioma associated with reduced production in the glioma microenvironment of arginase, a marker of myeloid suppressor cells which is critical for their T cell inhibitory function. Supporting this result, investigations using bone marrow-derived myeloid cells showed that IL-4Rα mediates IL-13-induced production of arginase. Furthermore, glioma-derived myeloid cells suppressed T cell proliferation in an IL-4Rα-dependent manner, consistent with their identification as myeloid-derived suppressor cells. Granulocyte-macrophage colony-stimulating factor (GM-CSF) plays a central role for the induction of IL-4Rα expression on myeloid cells, and we found that GM-CSF is upregulated in both human and mouse glioma microenvironments compared with normal brain or peripheral blood samples. Together, our findings establish a GM-CSF-induced mechanism of immunosuppression in the glioma microenvironment via upregulation of IL-4Rα on myeloid-derived suppressor cells.
MDSC; Glioma; IL-4Rα; Arginase; Immunosuppression
Ependymomas are among the most challenging childhood brain tumors. Although 50–70% of ependymomas are cured with surgery and irradiation, a significant percentage of tumors recur. Ependymomas that are not amenable to complete resection at diagnosis have a particularly poor prognosis, and the vast majority of affected children experience tumor recurrence. Although transient responses have been observed in recurrent tumors treated with re-irradiation and several chemotherapy regimens, long-term disease control is rarely achieved. Children with recurrent disease commonly experience cumulative neurological morbidity from repeated surgical and adjuvant therapy interventions, and almost universally succumb to refractory tumor progression. Accordingly, conceptually new treatment approaches are needed, both to decrease the risk of tumor recurrence and to enhance disease control in those children who experience recurrent disease. This article reviews the current application of risk-based treatment stratification at diagnosis, the rationale for exploring the role of novel therapeutic strategies such as immunotherapy at recurrence, and the concept behind a vaccine-based trial for these tumors.
ependymoma; brain tumor; immunotherapy; pseudoprogression
As therapies for systemic cancer improve and patients survive longer, the risk for brain metastases increases. We evaluated whether immune mechanisms are involved in the development of brain metastasis.
We conducted our studies using BALB/c mice bearing syngeneic 4T1 mammary adenocarcinoma cells in the mammary gland.
The brains of mice bearing 4T1 tumors at day 14 had no detectable metastatic tumor cells but presented with marked accumulation of bone marrow–derived CD11b+Gr1+ myeloid cells, which express high levels of inflammatory chemokines S100A8 and S100A9. In vitro, S100A9 attracts 4T1 cells through Toll-like receptor 4 and CD11b+Gr1+ myeloid cells through Toll-like receptor 4 and the receptor for advanced glycation end-products. Systemic treatment of 4T1-bearing mice with anti-Gr1 (RB6-8C5) monoclonal antibody reduces accumulation of CD11b+Gr1+ myeloid cells in the day-14 premetastatic brain as well as subsequent brain metastasis of 4T1 cells detected on day 30. Furthermore, treatment of 4T1 tumor-bearing mice with the cyclooxygenase-2 inhibitor celecoxib or genetic disruption of cyclooxygenase-2 in 4T1 cells inhibits the inflammatory chemokines and infiltration of CD11b+Gr1+ myeloid cells in the premetastatic brain and subsequent formation of brain metastasis.
Our results suggest that the primary tumor induces accumulation of CD11b+Gr1+ myeloid cells in the brain to form “premetastatic soil” and inflammation mediators, such as S100A9, that attract additional myeloid cells as well as metastatic tumor cells. Celecoxib and anti-Gr1 treatment may be useful for blockade of these processes, thereby preventing brain metastasis in patients with breast cancer.
brain metastasis; breast cancer; CCL2; myeloid-derived suppressor cells; prostaglandin-E2; S100A8/A9
Allogeneic glioma cell lines that are partially matched to the patient at class I human leukocyte antigen (HLA) loci and that display tumor-associated antigens (TAA) or antigenic precursors [tumor antigen precursor proteins (TAPP)] could be used for generating whole tumor cell vaccines or, alternatively, for extraction of TAA peptides to make autologous dendritic cell vaccines.
Twenty human glioma cell lines were characterized by molecular phenotyping and by flow cytometry for HLA class I antigen expression. Twelve of the 20 cell lines, as well as analyses of freshly resected glioma tissues, were further characterized for protein and/or mRNA expression of 16 tumor antigen precursor proteins or TAA.
These 20 human glioma cell lines potentially cover 77%, 85%, and 78% of the U.S. Caucasian population at HLA-A, HLA-B, and HLA-C alleles, respectively. All cells exhibited multiple TAA expressions. Most glioma cells expressed antigen isolated from immunoselected melanoma-2 (Aim-2), B-cyclin, EphA2, GP100, β1,6-N-acetylglucosaminyltransferase V (GnT-V), IL13Rα2, Her2/neu, hTert, Mage, Mart-1, Sart-1, and survivin. Real-time PCR technology showed that glioblastoma specimens expressed most of the TAA as well. Tumor-infiltrating lymphocytes and CD8+ CTL killedT2 cells when loaded with specific HLA-A2+ restricted TAA, or gliomas that were both HLA-A2+ and also positive for specific TAA (Mart-1, GP100, Her2/neu, and tyrosinase) but not those cells negative for HLA-A2 and/or lacking the specific epitope.
These data provide proof-in-principle for the use of allogeneic, partially HLA patient – matched glioma cells for vaccine generation or for peptide pulsing with allogeneic glioma cell extracts of autologous patient dendritic cells to induce endogenous CTL in brain tumor patients.
We recently identified a pivotal role for the host type I interferon (IFN) pathway in immuno-surveillance against de novo mouse glioma development, especially through the regulation of immature myeloid cells (IMCs) in the glioma microenvironment. Using these data, we identified single nucleotide polymorphisms (SNPs) in human IFN genes that dictate altered prognosis of patients with glioma. One of these SNPs (rs12553612) is located in the promoter of IFNA8, whose promoter activity is influenced by rs12553612. Conversely, recent epidemiologic data show that chronic usage of non-steroidal anti-inflammatory drugs lowers the risk of glioma. We translated these findings back to our de novo glioma model and found that cyclooxygenase-2 inhibition enhances anti-glioma immuno-surveillance by reducing glioma-associated IMCs. Taken together, these findings suggest that alterations in myeloid cell function condition the brain for glioma development. Finally, we have begun applying novel immunotherapeutic approaches to patients with low-grade glioma with the aim of preventing malignant transformation. Future research will hopefully better integrate epidemiological, immunobiological, and translational techniques to develop novel preventive approaches for malignant gliomas.
interferon; glioma; non-steroidal anti-inflammatory drugs; single nucleotide polymorphism
Glioblastoma (GBM) demonstrate down-regulated expression of Human Leukocyte Antigen (HLA) Class I, thereby escaping from cytotoxic T cells and limiting the efficacy of immunotherapy. LOH of HLA Class I (6p21) and/or Beta-2 microglobulin (B2m) (15q21) regions represent irreversible down-regulation. In this study, we examined the prevalence of these LOH events and their relations with overall survival in GBM.
In a cross-sectional analysis on 60 adult GBM patients, DNA from formalin-fixed paraffin-embedded specimens were evaluated for ten microsatellite regions of HLA Class I, B2m, HLA Class II, HLA Class III, and 6q by PCR as well as immunohistochemical evaluation of HLA Class I expression and CD8+ T cell infiltration.
LOH in HLA Class I, B2m, HLA Class II, HLA Class III, and 6q regions were present in 41.4%, 18.2%, 9.4%, 77.8%, and 36.0% of informative cases, respectively. LOH of HLA Class I was associated with shorter overall survival (HR = 4.89, p = 0.0078). HLA Class I was down-regulated in 22 to 43% of cases based on immunohistochemistry. Cases that displayed negative staining were significantly younger. HLA Class I expression correlated with intratumoral CD8+ T cell infiltration.
LOH in the HLA Class I region is frequent in adult GBMs. The association of shorter survival with LOH in this region suggest a crucial role for these genes in immunosurveillance.
Loss of Heterozygosity; Human Leukocyte Antigen; Beta-2 Microglobulin; tumor immunology; Glioblastoma
Despite surgery and radiotherapy, as many as 50 % of children with ependymomas will suffer from tumor recurrences that will ultimately lead to death. Our group’s initial peptide-based glioma vaccine targeting EphA2, IL-13Rα2, and Survivin, which are overexpressed in pediatric gliomas, has shown promise in its initial phase of testing. We therefore investigated whether EphA2, IL-13Raα2, Survivin, and, additionally, Wilms’ Tumor 1 (WT1), are overexpressed in pediatric ependymomas to determine if a similar immunotherapy approach could be applicable. Immunohistochemistry was performed using antibodies specific for EphA2, IL-13Rα2, Survivin, and WT1 on paraffin-embedded specimens from 19 pediatric and 13 adult ependymomas. Normal brain and ependyma were used for background staining controls. Negative staining was defined as no staining or staining equaling the background intensity in normal brain tissues. In the 19 pediatric cases, 18 (95 %) demonstrated positive staining for EphA2, 16 (84 %) for IL-13Rα2, 18 (95 %) for Survivin, and only 7 (37 %) for WT1. Only 3 of 19 cases were positive for two or fewer tumor-associated antigens (TAAs); 16 of 19 cases were positive for three or more TAAs. In the 13 adult cases, all 13 demonstrated positive staining for EphA2, IL-13Rα2, and Survivin. Only 2 of 13 cases (15 %) demonstrated positive staining for WT1. All adult specimens were positive for three or more TAAs. Some ependymomas showed patchy variability in intensity. Pediatric and adult ependymomas frequently express EphA2, IL-13Rα2, and Survivin. This provides the basis for the utilization of an established multiple peptide vaccine for ependymoma in a clinical trial setting.
Tumor-associated antigen; EphA2; Survivin; Interleukin-13 receptor alpha 2; Wilms’ Tumor 1; Ependymoma
Expression of miR-17-92 enhances T-cell survival and interferon (IFN)-γ production. We previously reported that miR-17-92 is down-regulated in T-cells derived from glioblastoma (GBM) patients. We hypothesized that transgene-derived co-expression of miR17-92 and chimeric antigen receptor (CAR) in T-cells would improve the efficacy of adoptive transfer therapy against GBM.
We constructed novel lentiviral vectors for miR-17-92 (FG12-EF1a-miR-17/92) and a CAR consisting of an epidermal growth factor receptor variant III (EGFRvIII)-specific, single-chain variable fragment (scFv) coupled to the T-cell receptor CD3ζ chain signaling module and co-stimulatory motifs of CD137 (4-1BB) and CD28 in tandem (pELNS-3C10-CAR). Human T-cells were transduced with these lentiviral vectors, and their anti-tumor effects were evaluated both in vitro and in vivo.
CAR-transduced T-cells (CAR-T-cells) exhibited potent, antigen-specific, cytotoxic activity against U87 GBM cells that stably express EGFRvIII (U87-EGFRvIII) and, when co-transduced with miR-17-92, exhibited improved survival in the presence of temozolomide (TMZ) compared with CAR-T-cells without miR-17-92 co-transduction. In mice bearing intracranial U87-EGFRvIII xenografts, CAR-T-cells with or without transgene-derived miR-17-92 expression demonstrated similar levels of therapeutic effect without demonstrating any uncontrolled growth of CAR-T-cells. However, when these mice were re-challenged with U87-EGFRvIII cells in their brains, mice receiving co-transduced CAR-T-cells exhibited improved protection compared with mice treated with CAR-T-cells without miR-17-92 co-transduction.
These results warrant the development of novel CAR-T-cell strategies that incorporate miR-17-92 to improve therapeutic potency, especially in patients with GBM.
microRNA; miR-17-92; Chimeric antigen receptor; Glioblastoma; Adoptive immunotherapy
Cancer immunotherapy has made tremendous progress, including promising results in patients with malignant gliomas. Nonetheless, the immunological microenvironment of the brain and tumors arising therein is still believed to be suboptimal for sufficient antitumor immune responses for a variety of reasons, including the operation of “immune-checkpoint” mechanisms. While these mechanisms prevent autoimmunity in physiological conditions, malignant tumors, including brain tumors, actively employ these mechanisms to evade from immunological attacks. Development of agents designed to unblock these checkpoint steps is currently one of the most active areas of cancer research. In this review, we summarize recent progresses in the field of brain tumor immunology with particular foci in the area of immune-checkpoint mechanisms and development of active immunotherapy strategies. In the last decade, a number of specific monoclonal antibodies designed to block immune-checkpoint mechanisms have been developed and show efficacy in other cancers, such as melanoma. On the other hand, active immunotherapy approaches, such as vaccines, have shown encouraging outcomes. We believe that development of effective immunotherapy approaches should ultimately integrate those checkpoint-blockade agents to enhance the efficacy of therapeutic approaches. With these agents available, it is going to be quite an exciting time in the field. The eventual success of immunotherapies for brain tumors will be dependent upon not only an in-depth understanding of immunology behind the brain and brain tumors, but also collaboration and teamwork for the development of novel trials that address multiple layers of immunological challenges in gliomas.
glioma; cancer vaccines; tumor immunity; T cells; tumor microenvironment; cancer immunotherapy
Dendritic cells (DCs) are the most powerful immunostimulatory cells specialized in the induction and regulation of immune responses. Their properties and the feasibility of their large-scale ex vivo generation led to the application of ex vivo-educated DCs to bypass the dysfunction of endogenous DCs in cancer patients and to induce therapeutic anti-cancer immunity. While multiple paradigms of therapeutic application of DCs reflect their consideration as cancer “vaccines”, numerous features of DC-based vaccination resemble those of autologous transplants, resulting in challenges and opportunities that distinguish them from classical vaccines. In addition to the functional heterogeneity of DC subsets and plasticity of the individual DC types, the unique features of DCs are the kinetic character of their function, limited functional stability, and the possibilitytoimprint in maturing DCs distinct functions relevant for the induction of effective cancer immunity, such as the induction of different effector functions or different homing properties of tumor-specific T cells (delivery of “signal 3” and “signal 4”). These considerations highlight the importance of the application of optimized, potentially patient-specific conditions of ex vivo culture of DCs and their delivery, with the logistic and regulatory implications shared with transplantation and other surgical procedures.
Dendritic cells; IL-12; Immunotherapy; Cancer; Vaccines; Cytokines; Chemokines; Chemokine receptors; Th1; CTL; NK; Treg
Noninvasive biomarkers of anti-tumoral efficacy are of great importance to the development of therapeutic agents. Tumor oxygenation has been shown to be an important indicator of therapeutic response. We report the use of intracellular labeling of tumor cells with perfluorocarbon (PFC) molecules, combined with quantitative 19F spin-lattice relaxation rate (R1) measurements, to assay tumor cell oxygen dynamics in situ. In a murine central nervous system (CNS) GL261 glioma model, we visualized the impact of Pmel-1 cytotoxic T cell immunotherapy, delivered intravenously, on intracellular tumor oxygen levels. GL261 glioma cells were labeled ex vivo with PFC and inoculated into the mouse striatum. The R1 of 19F labeled cells was measured using localized single-voxel magnetic resonance spectroscopy, and the absolute intracellular partial pressure of oxygen (pO2) was ascertained. Three days after tumor implantation, mice were treated with 2×107 cytotoxic T cells intravenously. At day five, a transient spike in pO2 was observed indicating an influx of T cells into the CNS and putative tumor cell apoptosis. Immunohistochemistry and quantitative flow cytometry analysis confirmed that the pO2 was causally related to the T cells infiltration. Surprisingly, the pO2 spike was detected even though few (∼4×104) T cells actually ingress into the CNS and with minimal tumor shrinkage. These results indicate the high sensitivity of this approach and its utility as a non-invasive surrogate biomarker of anti-cancer immunotherapeutic response in preclinical models.
We have recently shown that effective cytokine gene therapy of solid tumors in HLA-A2 Tg (HHD) mice lacking murine MHC class I molecule expression results in the generation of HLA-A2-restricted CD8+ T effector cells selectively recognizing tumor blood vessel-associated pericytes and/or vascular endothelial cells (VEC). Using an HHD model in which HLA-A2neg tumor (MC38 colon carcinoma or B16 melanoma) cells are not recognized by the CD8+ T cell repertoire, we now show that vaccines based on tumor-associated blood vessel antigens (TBVA) elicit protective Tc1-dependent immunity capable of mediating tumor regression or extending overall survival. Vaccine efficacy was not observed if (HLA-A2neg) wild-type C57BL/6 mice were instead used as recipient animals. In the HHD model, effective vaccination resulted in profound infiltration of tumor lesions by CD8+ (but not CD4+) T cells, in a coordinate reduction of CD31+ blood vessels in the tumor microenvironment (TME) and in the “spreading” of CD8+ T cell responses to alternate TBVA that were not intrinsic to the vaccine. Protective Tc1-mediated immunity was durable and directly recognized pericytes and/or VEC flow-sorted from tumor tissue, but not from tumor-uninvolved normal kidneys harvested from these same animals. Strikingly, the depletion of CD8+, but not CD4+, T cells at late time points after effective therapy frequently resulted in the recurrence of disease at the site of the regressed primary lesion. This suggests that the vaccine-induced anti-TBVA T cell repertoire can mediate the clinically-preferred outcomes of either effectively eradicating tumors or policing a state of (occult) tumor dormancy.
Vaccine; Pericyte; Vascular Endothelial Cells; Tumor; CD8+ T cells
MicroRNA (miR) are emerging as important gene expression regulators often involved in a variety of pathogenesis such as cancers and autoimmunity. Signal Transducers and Activators of Transcription (STAT) proteins are the principle signaling proteins for many cytokines and growth factors, thereby play a critical role in regulating immune cell homeostasis, differentiation and cellular functions. In this review, we discuss recent advances in the field demonstrating active interactions between STATs and miRs, with our primary focus on the promotion and inhibition of immune cells and cancer. Additionally, we review the reciprocal regulations between STATs and miR, and discuss how we can use this knowledge in the context of diseases. For example, recent findings related to STAT1 and miR-155 support the presence of a positive feedback loop of miR-155 and STAT1 in response to inflammatory signals or infection. STAT3 is known to play critical roles in tumorigenesis and cancer-induced immunosuppression. There is a growing body of evidence demonstrating that STAT3 directly activates miR-21, one of miRs that promote cancer cell survival and proliferation. While some miRs directly regulate STATs, there are findings demonstrating indirect STAT regulation by miRs also mediate important biological mechanisms. Therefore, further research is warranted to elucidate significant contributions made by direct and indirect miR-STAT mechanisms. As we learn more about miR pathways, we gain the opportunity to manipulate them in cancer cells to slow down growth or increase their susceptibility anti-tumor immunity.
miR-17-92; microRNA; STATs; cytokine; chemokine; T cells; B cells; Malignancy
We and others have previously demonstrated that (chronic) IL-12 gene therapy delivered intratumorally via ex vivo gene-engineered DC is competent to promote the regression of established murine tumors. In this report, we have developed a conditional expression system (rAd.RheoIL12) in order to determine the temporal requirements of transgenic IL-12p70 production by administered DC on therapeutic outcome in a subcutaneous B16 melanoma model. DC infected with rAd.RheoIL12 (DC.RheoIL12) secreted IL-12p70 in a tightly-regulated fashion in response to a synthetic diacylhydrazine small molecule ligand in vitro, and the treatment benefit of DC.RheolIL12 delivered into B16 lesions was strictly ligand-dependent in vivo. Indeed, DC.RheoIL12-based therapy promoted the regression of established day 7 B16 tumor lesions after intratumoral injection, provided that ligand administration occurred within 24h of DC injection and was sustained for approximately 5 or more days. Treatment efficacy was correlated to the magnitude of systemic anti-B16 CD8+ T cells cross-primed in vivo, which in turn, appeared dependent on the early enhanced in vivo survival of adoptively-transferred DC.RheoIL12 in tumor and tumor-draining lymph nodes. The unique safety feature of DC.RheoIL12 application was emphasized in a combined treatment model with rIL-2, where profound TNF-α-associated toxicity could be ameliorated upon discontinuation of activating ligand administration.
melanoma; gene therapy; IL-12; conditional; DC
Successful oncolytic virus treatment of malignant glioblastoma multiforme depends on widespread tumor-specific lytic virus replication and escape from mitigating innate immune responses to infection. Here we characterize a new HSV vector, JD0G, that is deleted for ICP0 and the joint sequences separating the unique long and short elements of the viral genome. We observed that JD0G replication was enhanced in certain glioblastoma cell lines compared to HEL cells, suggesting that a vector backbone deleted for ICP0 may be useful for treatment of glioblastoma. The innate immune response to virus infection can potentially impede oncolytic vector replication in human tumors. Indoleamine-2,3-dioxygenase (IDO) is expressed in response to interferon γ (IFNγ) and has been linked to both antiviral functions and to the immune escape of tumor cells. We observed that IFNγ treatment of human glioblastoma cells induced the expression of IDO and that this expression was quelled by infection with both wild-type and JD0G viruses. The role of IDO in inhibiting virus replication and the connection of this protein to the escape of tumor cells from immune surveillance suggest that IDO downregulation by HSV infection may enhance the oncolytic activity of vectors such as JD0G.
Interleukin-17 (IL-17) producing Type17 T-cells, specifically T-helper (Th)17 cells reactive to central nervous system (CNS) autoantigens, manifest a higher migratory capability to the CNS parenchyma compared with other T-cell subpopulations due to their ability to penetrate the blood brain barrier (BBB). In the field of cancer immunotherapy, there are now a number of cell therapy approaches including early studies using T-cells transduced with chimeric antigen receptors in hematologic malignancy, suggesting that the use of T-cells or genetically modified T-cells could have a significant role in effective cancer therapy. However, the successful application of this strategy in solid tumors, such as CNS tumors, requires careful consideration of critical factors to improve the tumor-homing of T-cells. The current review is dedicated to discuss recent findings on the role of Type17 T-cells in CNS autoimmunity and cancer. The insight gained from these findings may lead to the development of novel therapeutic and prophylactic strategies for CNS autoimmunity and tumors.
Th17; IL-17; autoimmunity; central nervous system; multiple sclerosis; gliomas; adoptive transfer therapy
We have previously reported that the single nucleotide polymorphism (SNP) rs12553612 in IFNA8 is associated with better overall survival of glioma patients with the AA-genotype compared with patients with the AC-genotype. As rs12553612 is located in the IFNA8 promoter, we hypothesized that the A-allele allows for an enhanced IFNA8 promoter activity compared with the C-allele. Reporter assays in the human monocyte derived THP-1 cell line demonstrated a superior promoter activity of the A-allele compared with the C-allele. Electrophoretic mobility shift assays (EMSA) further demonstrated that the A-genotype specifically binds to more nuclear proteins than the C-genotype, including the transcription factor Oct-1. Further, co-transfection of plasmids encoding Oct-1 and the reporter constructs revealed that Oct-1 enhanced the promoter activity with the A- but not the C-allele. Taken together, our data demonstrate that the A-allele in the rs12553612 SNP, which is associated with better glioma patient survival, allows for IFNA8 transcription by allowing for Oct-1 binding, which is absent in patients with C allele, and suggests a molecular mechanism of IFNA8 mediated immune-surveillance of glioma progression.
IFNA8; Oct-1; SNPs; glioma; type-1 interferons
Defects in human leukocyte antigen (HLA) class I antigen processing machinery (APM) component expression can have a negative impact on the clinical course of tumors and the response to T-cell-based immunotherapy. Since brain metastases of breast cancer are of increasing clinical significance, the APM component expression levels and CD8+ T-cell infiltration patterns were analyzed in primary breast and metastatic brain lesions of breast cancer by immunohistochemistry. Comparison of unpaired 50 primary and 33 brain metastases showed lower expression of β2-microgloblin, transporter associated with antigen processing (TAP) 1, TAP2 and calnexin in the brain lesions. Although no significant differences were found in APM component scores between primary breast and brain lesions in 15 paired cases, primary breast lesions of which patients eventually developed brain metastases showed lower levels of β2-microgloblin, TAP1 and calnexin compared with breast lesions without known brain metastases. The extent of CD8+ T cell infiltration was significantly higher in the lesions without metastasis compared with the ones with brain metastases, and was positively associated with the expression of TAP1 and calnexin. Furthermore, mouse tumor cells stably transfected with silencing hairpin (sh)RNA for TAP1 demonstrated a decreased susceptibility to cytotoxic T lymphocytes (CTL) in vitro and enhanced spontaneous brain metastasis in vivo. These data support the functional significance of TAP1 expression in tumor cells. Taken together, our data suggest that patients with low or defective TAP1 or calnexin in primary breast cancers may be at higher risks for developing brain metastasis due to the defects in T cell-based immunosurveillance.
breast cancer; brain metastasis; antigen processing machinery (APM) components; CD8+ T cell; transporter associated with antigen processing (TAP)1
Although recent FDA approvals on ipilimumab and sipuleucel-T represent major milestones, the ultimate success of immunotherapy approaches will likely benefit from appropriate combinations with other immunotherapeutic and/or non-immunotherapeutic approaches. However, implementation of ideal combinations in the clinic may still face formidable challenges in regulatory, drug-availability and intellectual property aspects. The 2011 SITC annual meeting hosted a workshop on combination immunotherapy to discuss: 1) the most promising combinations found in the laboratory; 2) early success of combination immunotherapy in clinical trials; 3) industry perspectives on combination approaches, and 4) relevant regulatory issues. The integrated theme was how to accelerate the implementation of efficacious combined immunotherapies for cancer patients. Rodent animal models are providing many examples of synergistic combinations that typically include more than two agents. However, mouse and human immunology differ in a significant number of mechanisms and hence we might be missing opportunities peculiar to humans. Nonetheless, incisive animal experimentation with deep mechanistic insight remains the best compass that we can use to guide our paths in combinatorial immunotherapy. Combination immunotherapy clinical trials are already in progress and preliminary results are extremely promising. As a key to translate promising combinations into clinic, real and “perceived” business and regulatory hurdles were debated. A formidable step forward would be to be able to test combinations of investigational agents prior to individual approval. Taking together the FDA and the industrial perspective on combinatorial immunotherapy, the audience was left with the clear message that this is by no means an impossible task. The general perception is that the road ahead of us is full of combination clinical trials which hopefully will bring clinical benefit to our cancer patients at a fast pace.
Immunotherapy; Combination immunotherapy; Cancer vaccines; Chemotherapy; Anti-CTLA4; Anti-PD/PD-L1
Epidemiological studies have highlighted associations between the regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) and reduced glioma risks in humans. Most NSAIDs function as cyclooxygenase-2 (COX-2) inhibitors that prevent production of prostaglandin E2 (PGE2). Since PGE2 induces expansion of myeloid-derived suppressor cells (MDSCs), we hypothesized that COX-2 blockade would suppress gliomagenesis by inhibiting MDSC development and accumulation in the tumor microenvironment (TME). In mouse models of glioma, treatment with the COX-2 inhibitors acetylsalicylic acid (ASA) or celecoxib inhibited systemic PGE2 production and delayed glioma development. ASA treatment also reduced the MDSC-attracting chemokine CCL2 in the TME along with numbers of CD11b+Ly6GhiLy6Clo granulocytic MDSCs in both the bone marrow and TME. In support of this evidence that COX-2 blockade blocked systemic development of MDSCs and their CCL2-mediated accumulation in the TME, there were defects in these processes in glioma-bearing Cox2-deficient and Ccl2-deficient mice. Conversely, these mice or ASA-treated wild-type mice displayed enhanced expression of CXCL10 and infiltration of cytotoxic T lymphocytes (CTL) in the TME, consistent with a relief of MDSC-mediated immune suppression. Antibody-mediated depletion of MDSCs delayed glioma growth in association with an increase in CXCL10 and CTLs in the TME, underscoring a critical role for MDSCs in glioma development. Lastly, Cxcl10-deficient mice exhibited reduced CTL infiltration of tumors, establishing that CXCL10 limited this pathway of immune suppression. Taken together, our findings show that the COX-2 pathway promotes gliomagenesis by directly supporting systemic development of MDSC and their accumulation in the TME, where they limit CTL infiltration.
A phase I/II trial was performed to evaluate the safety and immunogenicity of a novel vaccination with α-type 1 polarized dendritic cells (αDC1) loaded with synthetic peptides for glioma-associated antigen (GAA) epitopes and administration of polyinosinic-polycytidylic acid [poly(I:C)] stabilized by lysine and carboxymethylcellulose (poly-ICLC) in HLA-A2+ patients with recurrent malignant gliomas. GAAs for these peptides are EphA2, interleukin (IL)-13 receptor-α2, YKL-40, and gp100.
Patients and Methods
Twenty-two patients (13 with glioblastoma multiforme [GBM], five with anaplastic astrocytoma [AA], three with anaplastic oligodendroglioma [AO], and one with anaplastic oligoastrocytoma [AOA]) received at least one vaccination, and 19 patients received at least four vaccinations at two αDC1 dose levels (1 × or 3 × 107/dose) at 2-week intervals intranodally. Patients also received twice weekly intramuscular injections of 20 μg/kg poly-ICLC. Patients who demonstrated positive radiologic response or stable disease without major adverse events were allowed to receive booster vaccines. T-lymphocyte responses against GAA epitopes were assessed by enzyme-linked immunosorbent spot and HLA-tetramer assays.
The regimen was well-tolerated. The first four vaccines induced positive immune responses against at least one of the vaccination-targeted GAAs in peripheral blood mononuclear cells in 58% of patients. Peripheral blood samples demonstrated significant upregulation of type 1 cytokines and chemokines, including interferon-α and CXCL10. Nine (four GBM, two AA, two AO, and one AOA) achieved progression-free status lasting at least 12 months. One patient with recurrent GBM demonstrated sustained complete response. IL-12 production levels by αDC1 positively correlated with time to progression.
These data support safety, immunogenicity, and preliminary clinical activity of poly-ICLC-boosted αDC1-based vaccines.
Tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs) inhibit anti-tumor immune responses and facilitate tumor growth. Precursors for these immune cell populations migrate to the tumor site in response to tumor secretion of chemokines, such as monocyte chemoattractant protein-1 (MCP-1/CCL2), which was originally purified and identified from human gliomas. In syngeneic mouse GL261 glioma and human U87 glioma xenograft models, we evaluated the efficacy of systemic CCL2 blockade by monoclonal antibodies (mAb) targeting mouse and/or human CCL2. Intraperitoneal (i.p.) administration of anti-mouse CCL2 mAb as monotherapy (2 mg/kg/dose, twice a week) significantly, albeit modestly, prolonged the survival of C57BL/6 mice bearing intracranial GL261 glioma (p=0.0033), which was concomitant with a decrease in TAMs and MDSCs in the tumor microenvironment. Similarly, survival was modestly prolonged in severe combined immunodeficiency (SCID) mice bearing intracranial human U87 glioma xenografts treated with both anti-human CCL2 mAb and anti-mouse CCL2 antibodies (2 mg/kg/dose for each, twice a week) compared to mice treated with control IgG (p=0.0159). Furthermore, i.p. administration of anti-mouse CCL2 antibody in combination with temozolomide (TMZ) significantly prolonged the survival of C57BL/6 mice bearing GL261 glioma with 8 of 10 treated mice surviving longer than 70 days, while only 3 of 10 mice treated with TMZ and isotype IgG survived longer than 70 days (p=0.0359). These observations provide support for development of mAb-based CCL2 blockade strategies in combination with the current standard TMZ-based chemotherapy for treatment of malignant gliomas.
glioma; chemokine; CCL2; monoclonal antibody; chemotherapy; temozolomide