Dendritic cell-based active specific immunotherapy for malignant glioma

Role of Exosomes in the Progression, Diagnosis, and Treatment of Gliomas

Gliomas are the most common primary malignant brain tumors associated with a low survival rate. Even after surgery, radiotherapy, and chemotherapy, gliomas still have a poor prognosis. Extracellular vesicles are a heterogeneous group of cell-derived membranous structures. Exosomes are a type of extracellular vesicles, their size ranges from 30 nm to 100 nm. Recent studies have proved that glioma cells could release numerous exosomes; therefore, exosomes have gained increasing attention in glioma-related research.

Recent studies have confirmed the importance of extracellular vesicles, particularly exosomes, in the development of brain tumors, including gliomas. Exosomes mediate intercellular communication in the tumor microenvironment by transporting biomolecules (proteins, lipids, deoxyribonucleic acid, and ribonucleic acid); thereby playing a prominent role in tumor proliferation, differentiation, metastasis, and resistance to chemotherapy or radiation. Given their nanoscale size, exosomes can traverse the blood-brain barrier and promote tumor progression by modifying the tumor microenvironment. Based on their structural and functional characteristics, exosomes are demonstrating their value not only as diagnostic and prognostic markers, but also as tools in therapies specifically targeting glioma cells.

Therefore, exosomes are a promising therapeutic target for the diagnosis, prognosis, and treatment of malignant gliomas. More research will be needed before exosomes can be used in clinical applications. Here, we describe the exosomes, their morphology, and their roles in the diagnosis and progression of gliomas. In addition, we discuss the potential of exosomes as a therapeutic target/drug delivery system for patients with gliomas.

Down-regulation of RBP-J mediated by microRNA-133a suppresses dendritic cells and functions as a potential tumor suppressor in osteosarcoma

BACKGROUND AND OBJECTIVE

In recent years, immunotherapy for the treatment of tumors have been established. Dendritic cells (DCs) are extremely efficient and professional antigen presenting cells (APCs), which are an important target for immune therapeutic interventions in cancer. In present study, we investigated whether RBP-J signaling regulated by miR-133a was involved in the DCs mediated tumor suppressor in osteosarcoma.

METHODS

DCs were isolated from 30 osteosarcoma patients and 30 healthy subjects. Mouse macrophage-like cell line RAW264.7 were cultured and osteosarcoma mouse model with injection of murine osteosarcoma cell line S180 were established.

RESULTS

In osteosarcoma patients, miR-133a expression level of DCs was increased, and RBP-J expression in mRNA and protein levels were decreased. MiR-133a inhibitor promoted maturation and activation of DCs in osteosarcoma patients. In osteosarcoma mouse model, miR-133a mimic suppressed the maturation and activation of spleen DCs, while miR-133a inhibitor promoted them. Overexpression of miR-133a decreased therapeutic effect of DCs on osteosarcoma mice. In RAW264.7 cells, miR-133a was observed to target RBP-J and regulate its expression. MiR-133a mimic inhibited the maturation of DCs in cells exposed to LPS, the effect of which was reversed by overexpression of RBP-J.

CONCLUSION

RBP-J mediated by miR-133a probably contributed to the regulation of DCs maturation and activation in osteosarcoma, which functioned as a therapeutic target for the immunotherapy in cancers.

Exosomes from Dendritic Cells Loaded with Chaperone-Rich Cell Lysates Elicit a Potent T Cell Immune Response Against Intracranial Glioma in Mice

Chaperone-rich cell lysates (CRCLs) may play an important role in the development of anti-tumor vaccines. Tumor-derived CRCLs have been reported to activate dendritic cells (DCs) to elicit potent anti-tumor activity. However, the role of DC-derived exosomes (DEXs) secreted from DCs loaded with CRCLs in the treatment of tumors has not been clearly determined. In the present study, DEXs were generated from DCs loaded with CRCLs derived from GL261 glioma cells. These DEXs, designated DEX (CRCL-GL261), were then used to treat DCs to create DEX (CRCL-GL261)-DCs. The DEX (CRCL-GL261)-DCs were found to promote cell proliferation and cytotoxic T lymphocyte (CTL) activity of CD4(+) and CD8(+) T cells in vitro compared with DEX (GL261)-DCs, which were loaded with DEXs derived from DCs loaded with GL261 tumor cell lysates. DEX (CRCL-GL261)-DCs significantly prolonged the survival of mice with tumors and inhibited tumor growth in vivo. In addition, DEX (CRCL-GL261)-DCs induced enhanced T cell infiltration in intracranial glioma tissues compared with other treatments. DEX (CRCL-GL261)-DCs induced strong production of anti-tumor cytokines, including interleukin-2 and interferon-γ. Moreover, depletion of CD4(+) and CD8(+) T cells significantly impaired the anti-tumor effect of DEX (CRCL-GL261)-DCs. Finally, DEX (CRCL-GL261)-DCs were found to negatively regulate Casitas B cell lineage lymphoma (Cbl)-b and c-Cbl signaling, leading to the activation of phosphatidyl inositol 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) signaling in T cells. In summary, we present evidence that DEX (CRCL-GL261)-DCs induce more potent and effective anti-tumor T cell immune responses and delineate the underlying mechanism by which DEX (CRCL-GL261)-DCs exerted their anti-tumor activity through modulating Cbl-b and c-Cbl signaling. These results provide novel and promising insight for the development of an anti-tumor vaccine.

Delayed growth of glioma by a polysaccharide from Aster tataricus involve upregulation of Bax/Bcl-2 ratio, activation of caspase-3/8/9, and downregulation of the Akt

In this study, a homogeneous polysaccharide (ATP-II), with a molecular weight of 3.4 × 10(4) Da, was successfully purified from Aster tataricus by DEAE-Sepharose CL-6B ion exchange and Sepharose CL-6B gel filtration chromatography. Monosaccharide component analysis indicated that ATP-II was composed of glucose, galactose, mannose, rhamnose, and arabinose in molar ratios of 2.1:5.2:2.1:1.0:1.2. We evaluated the anticancer efficacy and associated mechanisms of ATP-II on glioma C6 cells in vitro and in vivo. The results showed that treatment of C6 cells with ATP-II inhibited cell proliferation and this biological response came from induction of DAN damage and consequent inducing apoptosis. Likewise, oral ATP-II administration resulted in consistent regression of glioma tumors and induced apoptosis of transplanted tumor tissues by increasing the ratio of Bax/Bcl-2 and activation of caspase-3, caspase-8, and caspase-9 cascade. Importantly, the efficient downregulation of Akt, which is successfully detected in tumor tissues, is a unique contribution to retard the tumor growth by ATP-II. These data suggest that ATP-II may be a potential candidate for glioma treatment.

Achieving graft-versus-tumor effect in brain tumor patients: from autologous progenitor cell transplant to active immunotherapy

Success in treating aggressive brain tumors like glioblastoma multiforme and medulloblastoma remains challenging, in part because these malignancies overcome CNS immune surveillance. New insights into brain tumor immunology have led to a rational development of immunotherapeutic strategies, including cytotoxic Tlymphocyte therapies and dendritic cell vaccines. However, these therapies are most effective when applied in a setting of minimal residual disease, so require prior use of standard cytotoxic therapies or cytoreduction by surgery. Myeloablative chemotherapy with autologous hematopoietic cell transplantation (autoHCT) can offer a platform upon which different cellular therapies can be effectively instituted. Specifically, this approach provides an inherent 'chemical debulking' through high-dose chemotherapy and a graft-versus-tumor effect through an autologous T-cell replete graft. Furthermore, autoHCT may be beneficial in 'resetting' the body's immune system, potentially 'breaking' tumor tolerance, and in providing a 'boost' of immune effector cells (NK cells or cytotoxic T lymphocytes), which could augment desired anti-tumor effects. As literature on the use of autoHCT in brain tumors is scarce, aspects of immunotherapies applied in non-CNS malignancies are reviewed as potential therapies that could be used in conjunction with autoHCT to eradicate brain tumors.

Role of IL-17 in Glioma Progression

There is increasing evidence in the literature pointing to an important role of inflammation during initiation and progression of cancer. Glioblastoma is the most common malignant primary brain tumor with approximately 23,000 newly-diagnosed cases each year in the United States, and has a dismal median survival of only 15 months. Although the blood-brain barrier maintains an immune-privileged status of the brain under steady state, intracranial tumors including gliomas are invariably infiltrated with various types of immune cells. The T helper 17 (Th17) cells, a recently discovered interleukin (IL)-17-producing T cell subtype, have been reported in several extracranial and some intracranial tumors, where they have been implicated in either pro- or antitumor activity depending on the tumor type. Here, we present a succinct review of the current literature on the prevalence and potential role of IL-17 in malignant gliomas. Further mechanistic studies on IL-17 mediated inflammatory pathway in gliomas may provide with opportunities for novel immunotherapeutic interventions.

Generation and immunologic functions of Th17 cells in malignant gliomas

Th17 cells, a recently discovered inflammatory T cell subtype, have been implicated with autoimmune disorders. However, mechanism of generation or functions of intratumoral Th17 cells are still unclear. We have been investigating the mechanism of induction and role of Th17 cells in malignant gliomas using primary tumor as well as cell lines. We report here that: (1) a higher frequency of Th17 cells in gliomas were associated with higher number of myeloid (CD11b) cells as well as the expression of TGF-β1 or IL-6; (2) conditioned medium from glioma cells (Gl CM) induced Th17 cell differentiation, which was inhibited by anti-TGF-β1 and anti-IL-6; (3) glioma-associated monocytes secreted Th17-promoting cytokines IL-1β and IL-23; (4) CM from glioma and monocyte co-culture (Gl+Mo CM) induced high frequency of Th17 cells in naïve T cell culture, which was abrogated by anti-IL-1β and anti-IL-23 antibodies; (5) In vitro Gl+Mo CM-mediated Th17 generation was associated with a decrease in IFN-γ and a concomitant increase in IL-10 secretion. Anti-TGF-β1, but not anti-IL-6, significantly reversed this cytokine profile. These results demonstrate prevalence of Th17 cells in gliomas and implicate the cytokines derived from the tumor as well as infiltrating myeloid cells in the induction of Th17 cells in glioma microenvironment. Moreover, the data also suggest that glioma-associated Th17 cells may contribute to immune-suppression via TGF-β1-induced IL-10 secretion. Further studies on the mechanism of tumor-infiltration, developmental pathways, and pro-/anti-tumor functions of Th17 cells will provide rationale for developing novel adjuvant immunotherapeutic strategies for malignant gliomas.

Scutellaria extract and wogonin inhibit tumor-mediated induction of T(reg) cells via inhibition of TGF-β1 activity

A number of studies have implicated tumor-induced T(reg) cell activity in the sub-optimal response to therapeutic vaccines. Development of neo-adjuvant strategies targeting T(reg) cells is therefore imperative. Scutellaria extracts or constituent flavonoids have shown encouraging efficacy against various tumors, including gliomas, in both pre-clinical and clinical studies. We report here, for the first time, that Scutellaria ocmulgee leaf extract (SocL) and flavonoid wogonin could inhibit TGF-β1-induced T(reg) activity in malignant gliomas. F344 rats, subcutaneously transplanted with F98 gliomas, were treated with SocL. There was a significant inhibition of intra-tumoral TGF-β1 and T(reg) cell frequency as well as peripheral blood TGF-β1 levels in SocL-treated animals compared to the controls. SocL extract and wogonin also inhibited glioma-induced, TGF-β1-mediated T(reg) activity in vitro. SocL extract and wogonin also inhibited the secretion of IL-10 in T(reg) culture; whereas the level of IL-2 was either unchanged or marginally enhanced. We also observed an inhibition of Smad-3, GSK-3β and ERK1/2 signaling by SocL and wogonin in T(reg) cells, while phosphorylation of P38 MAPK was considerably enhanced, indicating that SocL or wogonin could inhibit the T cells' response to TGF-β1 via modulation of both Smad and non-Smad signaling pathways. Overall, this study suggests that Scutellaria can potentially reverse tumor-mediated immune suppression via inhibition of TGF-β1 secretion as well as via inhibition of T cells' response to TGF-β1. This may provide an opportunity for developing a novel adjuvant therapeutic strategy for malignant gliomas, combining Scutellaria with immunotherapy and chemo/radio-therapeutic regimen, which could potentially improve the disease outcome.

Delayed growth of glioma by Scutellaria flavonoids involve inhibition of Akt, GSK-3 and NF-κB signaling

Plants of the genus Scutellaria constitute one of the common components of Eastern as well as traditional American medicine against various human diseases, including cancer. In this study, we examined the in vivo anti-glioma activity of a leaf extract of Scutellaria ocmulgee (SocL) while also exploring their potential molecular mechanisms of action. Oral administration of SocL extract delayed the growth of F98 glioma in F344 rats, both in intracranial and subcutaneous tumor models. Immunohistochemistry revealed inhibition of Akt, GSK-3α/β and NF-κB phosphorylation in the subcutaneous tumors following treatment with Scutellaria. The SocL extract as well as the constituent flavonoid wogonin also showed dose- and time-dependent inhibition of Akt, GSK-3α/β and NF-κB in F98 cell cultures in vitro, as determined by western blot analysis. Pharmacologic inhibitors of PI3K and NF-κB also significantly inhibited the in vitro proliferation of F98 glioma cells, indicating the key role of these signaling molecules in the growth of malignant gliomas. Transfection of F98 cells with constitutively active mutant of AKT (AKT/CA), however, did not significantly reverse Scutellaria-mediated inhibition of proliferation, indicating that Scutellaria flavonoids either directly inhibited Akt kinase activity or acted downstream of Akt. In vitro Akt kinase assay demonstrated that the SocL extract or wogonin could indeed bind to Akt and inhibit its kinase activity. This study provides the first in vivo evidence and mechanistic support for anti-glioma activity of Scutellaria flavonoids and has implications in potential usage of Scutellaria flavonoids in adjuvant therapy for malignant tumors, including gliomas.

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.

Immunotherapy of malignant brain tumors

Despite aggressive multi-modality therapy including surgery, radiation, and chemotherapy, the prognosis for patients with malignant primary brain tumors remains very poor. Moreover, the non-specific nature of conventional therapy for brain tumors often results in incapacitating damage to surrounding normal brain and systemic tissues. Thus, there is an urgent need for the development of therapeutic strategies that precisely target tumor cells while minimizing collateral damage to neighboring eloquent cerebral cortex. The rationale for using the immune system to target brain tumors is based on the premise that the inherent specificity of immunologic reactivity could meet the clear need for more specific and precise therapy. The success of this modality is dependent on our ability to understand the mechanisms of immune regulation within the central nervous system (CNS), as well as counter the broad defects in host cell-mediated immunity that malignant gliomas are known to elicit. Recent advances in our understanding of tumor-induced and host-mediated immunosuppressive mechanisms, the development of effective strategies to combat these suppressive effects, and a better understanding of how to deliver immunologic effector molecules more efficiently to CNS tumors have all facilitated significant progress toward the realization of true clinical benefit from immunotherapeutic treatment of malignant gliomas.

Other experimental therapies for glioma

Experimental therapies for glioma are mostly based on the insights into the cell biology of the tumors studied by modern methods including genomics and metabolomics. In surgery, intraoperative visualization of residual tumor by fluorescence has helped with the radicality of resection. Although temozolamide has become an important agent in the combined radiochemotherapy of newly diagnosed glioblastoma, understanding the underlying mechanisms of action and resistance has led to alterations in dosing schemes, which may be more beneficial than the introduction of new agents. Targeted therapies that have been highly promising in other solid tumors have been rather disappointing in gliomas, not for the lack of promising targets but most likely due to inefficacy of the reagents to reach their target. Direct delivery of reagents with interstitial infusion via convection-enhanced delivery has proven to be safe and effective, but the potential of that technology has not been exploited because many technicalities are still to be worked out, and better, more selective reagents are needed. Gene therapy has been reactivated with direct adeno-viral application to transfer HSV-Tk into tumor cells by adenoviral vectors, still awaiting final analysis. Oncolytic viruses are also under long-term refinement and await definitive pivotal clinical trials. Immunotherapy is currently focusing on vaccination strategies using either specifically pulsed dendritic cells or immunization with a specific peptide, which is unique to the vIII variant of the epidemal growth factor receptor. An area attracting immense attention for basic research as well as translation into clinical use is the characterization of neural stem cells and their theraputic potential when appropriately manipulated.In general, there is a wide spectrum of specific neuro-oncological therapy developments, which are not only extrapolated from general oncology but also based on translational research in the field of glioma biology.

In-vitro activation of cytotoxic T lymphocytes by fusion of mouse hepatocellular carcinoma cells and lymphotactin gene-modified dendritic cells

AIM

To investigate the in-vitro activation of cytotoxic T lymphocytes (CTLs) by fusion of mouse hepatocellular carcinoma (HCC) cells and lymphotactin gene-modified dendritic cells (DCs).

METHODS

Lymphotactin gene modified DCs (DCLptn) were prepared by lymphotactin recombinant adenovirus transduction of mature DCs which differentiated from mouse bone marrow cells by stimulation with granulocyte/macrophage colony-stimulating factor (GM-CSF), interleukin-4 (IL-4) and tumor necrosis factor alpha (TNF-alpha). DCLptn and H22 fusion was prepared using 50% PEG. Lymphotactin gene and protein expression levels were measured by RT-PCR and ELISA, respectively. Lymphotactin chemotactic responses were examined by in-vitro chemotaxis assay. In-vitro activation of CTLs by DCLptn/H22 fusion was measured by detecting CD25 expression and cytokine production after autologous T cell stimulation. Cytotoxic function of activated T lymphocytes stimulated with DCLptn/H22 cells was determined by LDH cytotoxicity assay.

RESULTS

Lymphotactin gene could be efficiently transduced to DCs by adenovirus vector and showed an effective biological activity. After fusion, the hybrid DCLptn/H22 cells acquired the phenotypes of both DCLptn and H22 cells. In T cell proliferation assay, flow cytometry showed a very high CD25 expression, and cytokine release assay showed a significantly higher concentration of IFN-gamma and IL-2 in DCLptn/H22 group than in DCLptn, DCLptn+H22, DC/H22 or H22 groups. Cytotoxicity assay revealed that T cells derived from DCLptn/H22 group had much higher anti-tumor activity than those derived from DCLptn, H22, DCLptn+H22, DC/H22 groups.

CONCLUSION

Lymphotactin gene-modified dendritoma induces T-cell proliferation and strong CTL reaction against allogenic HCC cells. Immunization-engineered fusion hybrid vaccine is an attractive strategy in prevention and treatment of HCC metastases.