Treatment of recurrent glioma with intracavitary alloreactive cytotoxic T lymphocytes and interleukin-2

Immunotherapy of pediatric brain tumor patients should include an immunoprevention strategy: a medical hypothesis paper

Adults diagnosed with Glioblastoma multiforme (GBM) are frequently faced with a 7% chance of surviving 2 years compared with pediatric patients with GBM who have a 26% survival rate. Our recent screen of possible glioma-associated antigen precursor protein (TAPP) profiles displayed from different types of pediatric brain tumors showed that pediatric patients contained a subset of the tumor antigens displayed by adult GBM patients. Adult GBM possess at least 27 tumor antigens that can potentially stimulate T cell immune responses, suggesting that these tumors are quite antigenic. In contrast, pediatric brain tumors only expressed nine tumor antigens with mRNA levels that were equivalent to those displayed by adult GBM. These tumor-associated antigens could be used as possible targets of therapeutic immunization for pediatric brain cancer patients. Children have developing immune systems that peak at puberty. An immune response mounted by these pediatric patients might account for their extended life spans, even though the pediatric brain tumors express far fewer total tumor-associated antigens. Here we present a hypothesis that pediatric brain tumor patients might be the best patients to show that immunotherapy can be used to successfully treat established cancers. We speculate that immunotherapy should include a panel of tumor antigens that might prevent the out-growth of more malignant tumor cells and thereby prevent the brain tumor relapse. Thus, pediatric brain tumor patients might provide an opportunity to prove the concept of immunoprevention.

Recurrence of Intracranial Tumors following Adoptive T Cell Therapy Can Be Prevented by Direct and Indirect Killing Aided by High Levels of Tumor Antigen Cross-Presented on Stromal Cells

Elimination of peripheral tumors by adoptively transferred tumor-specific T cells may require killing of cancer cells and tumor stromal cells. Tumor Ags are cross-presented on stromal cells, resulting in direct cytotoxic T cell (CTL) killing of both Ag-expressing cancer cells and stromal cells. Indirect killing of Ag loss variant cells also occurs. We show here that similar processes occur in a brain tumor stromal environment. We used murine cancer cell lines that express high or low levels of a peptide Ag, SIYRYYGL (SIY), recognized by transgenic 2C CD8(+) T cells. The two cell lines are killed with equivalent efficiency by 2C T cells in vitro. Following adoptive transfer of 2C T cells into mice with established SIY-Hi or SIY-Lo brain tumors, tumors of both types regressed, but low-Ag-expressing tumors recurred. High-Ag-expressing tumors contained CD11b(+) cells cross-presenting SIY peptide and were completely eliminated by 2C T cells. To further test the role of cross-presentation, RAG1(-/-) H-2(b) mice were infused with H-2(k) tumor cells expressing high levels of SIY peptide. Adoptively transferred 2C T cells are able to kill cross-presenting H-2(b) stromal cells but not H-2(k) tumor cells. In peripheral models, this paradigm led to a small static tumor. In the brain, activated 2C T cells were able to kill cross-presenting CD11b(+) cells and completely eliminate the H-2(k) tumors in most mice. Targeting brain tumor stroma or increasing Ag shedding from tumor cells to enhance cross-presentation may improve the clinical success of T cell adoptive therapies.

Characterization and immunotherapeutic potential of gammadelta T-cells in patients with glioblastoma

Classical immunotherapeutic approaches to glioblastoma multiforme (GBM) have shown mixed results, and therapies focused on innate lymphocyte activity against GBM have not been rigorously evaluated. We examined peripheral blood lymphocyte phenotype, gammadelta T-cell number, mitogenic response, and cytotoxicity against GBM cell lines and primary tumor explants from GBM patients at selected time points prior to and during GBM therapy. Healthy volunteers served as controls and were grouped by age. T-cell infiltration of tumors from these patients was assessed by staining for CD3 and T-cell receptor gammadelta. Our findings revealed no differences in counts of mean absolute T-cells, T-cell subsets CD3+CD4+ and CD3+CD8+, and natural killer cells from healthy volunteers and patients prior to and immediately after GBM resection. In contrast, gammadelta T-cell counts and mitogen-stimulated proliferative response of gammadelta T-cells were markedly decreased prior to GBM resection and throughout therapy. Expanded/activated gammadelta T-cells from both patients and healthy volunteers kill GBM cell lines D54, U373, and U251, as well as primary GBM, without cytotoxicity to primary astrocyte cultures. Perivascular T-cell accumulation was noted in paraffin sections, but no organized T-cell invasion of the tumor parenchyma was seen. Taken together, these data suggest that gammadelta T-cell depletion and impaired function occur prior to or concurrent with the growth of the tumor. The significant cytotoxicity of expanded/activated gammadelta T-cells from both healthy controls and selected patients against primary GBM explants may open a previously unexplored approach to cellular immunotherapy of GBM.

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.

Immunotherapeutic approaches for glioma

The development of effective immunotherapy strategies for glioma requires adequate understanding of the unique immunological microenvironment in the central nervous system (CNS) and CNS tumors. Although the CNS is often considered to be an immunologically privileged site and poses unique challenges for the delivery of effector cells and molecules, recent advances in technology and discoveries in CNS immunology suggest novel mechanisms that may significantly improve the efficacy of immunotherapy against gliomas. In this review, we first summarize recent advances in the CNS and CNS tumor immunology. We address factors that may promote immune escape of gliomas. We also review advances in passive and active immunotherapy strategies for glioma, with an emphasis on lessons learned from recent early-phase clinical trials. We also discuss novel immunotherapy strategies that have been recently tested in non-CNS tumors and show great potential for application to gliomas. Finally, we discuss how each of these promising strategies can be combined to achieve clinical benefit for patients with gliomas.

Harnessing T-Cell Immunity to Target Brain Tumors

T-cell mediated immunotherapy is a conceptually attractive treatment option to envisage for glioma, since T lymphocytes can actively seek out neoplastic cells in the brain, and they have the potential to safely and specifically eliminate tumor. Some antigenic targets on glioma cells are already defined, and we can be optimistic that more will be discovered from progress in T-cell epitope identification and gene expression profiling of brain tumors. In parallel, advances in immunology (regional immunology, neuroimmunology, tumor immunology) now equip us to build upon the results from current immunotherapy trials in which the safety and feasibility of brain tumor immunotherapy have already been confirmed. We can now look to the next phase of immunotherapy, in which we must harness the most promising basic science advances and existing clinical expertise, and apply these to randomized clinical trials to determine the real clinical impact and applicability of these approaches for treating patients with currently incurable malignant brain tumors.

Current immunotherapeutic strategies for central nervous system tumors

Immunotherapy has emerged as a promising tool in the management of malignant central nervous system tumors. Despite improvement in patient survival, traditional approaches, which consist mostly of surgery, radiotherapy, and chemotherapy, have been largely unsuccessful in permanently controlling these aggressive tumors. Immunotherapeutic strategies offer not only a novel approach but also an advantage in a way other modalities have been failing. Specifically, the capabilities of the immune system to recognize altered cells while leaving normal cells intact offer tremendous advantage over the conventional therapeutic approaches. This article summarizes our current understanding of immunotherapeutic treatment modalities used in clinical trials for management of malignant central nervous system tumors.

Improving alloreactive CTL immunotherapy for malignant gliomas using a simulation model of their interactive dynamics

Glioblastoma (GBM), a highly aggressive (WHO grade IV) primary brain tumor, is refractory to traditional treatments, such as surgery, radiation or chemotherapy. This study aims at aiding in the design of more efficacious GBM therapies. We constructed a mathematical model for glioma and the immune system interactions, that may ensue upon direct intra-tumoral administration of ex vivo activated alloreactive cytotoxic-T-lymphocytes (aCTL). Our model encompasses considerations of the interactive dynamics of aCTL, tumor cells, major histocompatibility complex (MHC) class I and MHC class II molecules, as well as cytokines, such as TGF-beta and IFN-gamma, which dampen or increase the pro-inflammatory environment, respectively. Computer simulations were used for model verification and for retrieving putative treatment scenarios. The mathematical model successfully retrieved clinical trial results of efficacious aCTL immunotherapy for recurrent anaplastic oligodendroglioma and anaplastic astrocytoma (WHO grade III). It predicted that cellular adoptive immunotherapy failed in GBM because the administered dose was 20-fold lower than required for therapeutic efficacy. Model analysis suggests that GBM may be eradicated by new dose-intensive strategies, e.g., 3 x 10(8) aCTL every 4 days for small tumor burden, or 2 x 10(9) aCTL, infused every 5 days for larger tumor burden. Further analysis pinpoints crucial bio-markers relating to tumor growth rate, tumor size, and tumor sensitivity to the immune system, whose estimation enables regimen personalization. We propose that adoptive cellular immunotherapy was prematurely abandoned. It may prove efficacious for GBM, if dose intensity is augmented, as prescribed by the mathematical model. Re-initiation of clinical trials, using calculated individualized regimens for grade III-IV malignant glioma, is suggested.

Tumor antigen precursor protein profiles of adult and pediatric brain tumors identify potential targets for immunotherapy

OBJECTIVES

We evaluated and compared tumor antigen precursor protein (TAPP) profiles in adult and pediatric brain tumors of 31 genes related to tumor associated antigens (TAA) for possible use in immunotherapy. Antigens were selected based on their potential to stimulate T cell responses against tumors of neuroectodermal origin.

METHODS

Thirty-seven brain tumor specimens from 11 adult and 26 pediatric patients were analyzed by quantitative real-time PCR for the relative expression of 31 TAPP mRNAs. The age range of adults (4F:7M) was 27-77 years (median 51.5 +/- 14.5 years) and for pediatrics (12F:14M) was 0.9-19 years (median 8.3 +/- 5.5 years). Histological diagnoses consisted of 16 glioblastomas, 4 low grade astrocytomas, 10 juvenile pilocytic astrocytomas, and 7 ependymomas.

RESULTS

The adult gliomas expressed 94% (29 of 31) of the TAPP mRNAs evaluated compared with pediatric brain tumors that expressed 55-74% of the TAPP mRNAs, dependent on tumor histological subtype. Four types of TAPP expression patterns were observed: (1) equal expression among adult and pediatric cases, (2) greater expression in adult than pediatric cases, (3) expression restricted to adult GBM and (4) a random distribution. The pediatric brain tumors lacked expression of some genes associated with engendering tumor survival, such as hTert and Survivin.

CONCLUSIONS

The potential TAA targets identified from the TAPP profiles of 31 genes associated with adult and pediatric brain tumors may help investigators select specific target antigens for developing dendritic cell- or peptide-based vaccines or T cell-based immunotherapeutic approaches against brain tumors.

Recent progress in immunotherapy for malignant glioma: treatment strategies and results from clinical trials

BACKGROUND

Despite advances in surgical and adjuvant radiation therapy and chemotherapy strategies, malignant gliomas continue to be associated with poor prognoses.

METHODS

We review immune-mediated treatment approaches for malignant glioma and the relevance of recent clinical trials and their outcomes. We specifically address the increasing evidence implicating the role of cytotoxic T cells in ensuring adequate immune-mediated clearance of neoplastic cells and the need for the optimization of therapies that can elicit and support such antitumor T-cell activity.

RESULTS

The poor outcome of this disease has spurred the search for novel experimental therapies that can address and overcome the root biological phenomena associated with the lethality of this disease. The use of immunotherapy to bolster the otherwise impaired antitumor immune responses in glioma patients has received increasing attention.

CONCLUSIONS

An effective treatment paradigm for malignant gliomas may eventually require a multifaceted approach combining two or more different immunotherapeutic strategies. Such scenarios may involve the use of local cytokine gene therapy to enhance glioma-cell immunogenicity in conjunction with dendritic cell-based active vaccination to stimulate systemic tumoricidal T-cell immunity. Given the heterogeneity of this disease process and the potential risk of immunoediting out a selected, treatment-refractory tumor cell population, the concurrent use of multiple modalities that target disparate tumor characteristics may be of greatest therapeutic relevance.

Cellular and functional characterization of immunoresistant human glioma cell clones selected with alloreactive cytotoxic T lymphocytes reveals their up-regulated synthesis of biologically active TGF-beta

Two immunoresistant (IR) glioma cell variants, 13-06-IR29 and 13-06-IR30, were cloned from 13-06-MG glioma cell populations after receiving continuous immunoselective pressure from multiple alloreactive cytotoxic T lymphocyte (aCTL) preparations. Reapplication of aCTL immunoselective pressure to the IR clones, displaying a partial regain in sensitivity to aCTL after removal of the selective pressure, restored the resistance. The IR variants exhibited cross-resistance to non-human leukocyte antigen (HLA)-restricted effector cells and gamma-irradiation, but not to carmustine. The IR clones were characterized for factors that might contribute to the immunoresistance. The aCTL adhesion to extracellular matrix extracts derived from either the IR clones or the parental cells was similar and not impaired. Furthermore, aCTL binding to parental cells and IR clones was equal. Down-regulation of the cell recognition molecules, class I HLA or intercellular adhesion molecule-1 (ICAM-1), that would inhibit their recognition by aCTL was not observed on the IR clones. The down-regulation of Fas by the IR clones correlated with their resistance to FasL-induced apoptosis. HLA-G or FasL that might provide an immunotolerant environment or provide a means of counterattack to aCTL, respectively, were not associated with the IR phenotype. The aCTL, coincubated with the IR clones and parental cells, displayed up-regulation of multiple secreted cytokines. A significant up-regulation of bioactive transforming growth factor (TGF)-beta was observed in the IR clones compared with the parental cells. These data suggest that increased secretion of bioactive TGF-beta may inhibit aCTL lysis of the IR clones. Disruption of the TGF-beta signaling pathway may circumvent the resistance.

Generation of human innate immune responses towards membrane macrophage colony stimulating factor (mM-CSF) expressing U251 glioma cells within immunodeficient (NIH-nu/beige/xid) mice

The response of human peripheral blood mononuclear cells (PBMC) to cloned human HLA-A2+ U251 glioma cells (U251-2F11/TK) expressing membrane macrophage colony stimulating factor (mM-CSF) was investigated in vitro and in vivo. Enriched human monocytes derived from cancer patients produced a respiratory burst following 20min of interaction with mM-CSF expressing U251 glioma cells. This respiratory burst response was not observed in the enriched human monocytes following similar exposure to the viral vector control U251 (U251-VV) cells. Reactive oxygen species such as H(2)O(2) and HOCl produced death of the U251 cells. The U251-2F11/TK cells failed to grow in severely compromised combined immunodeficient (NIH-bg-nu-xidBR) mice that were depleted of murine monocyte/macrophages then reconstituted with human HLA-A2+ PBMC. Reactive oxygen species (ROS) were produced by PBMC, both in vitro and in vivo in response tomM-CSF expressing U251 cells. U251-2F11/TK cells failed to form subcutaneous tumors in macrophage depleted mice reconstituted with human PBMC; whereas, progressive growth of such tumors was observed with the U251-VV cells. U251-2F11/TK tumors formed if the initial inoculums of PBMC were depleted of monocytes. From this work it can be concluded that mM-CSF transduced U251-2F11/TK glioma cells can safely stimulate human innate immune responses in vivo.

Immunotherapy for patients with malignant glioma: from theoretical principles to clinical applications

Malignant gliomas are the most common type of primary brain tumor and are in great need of novel therapeutic approaches. Advances in treatment have been very modest, significant improvement in survival has been lacking for many decades and prognosis remains dismal. Despite 'gross total' surgical resections and currently available radio-chemotherapy, malignant gliomas inevitably recur due to reservoirs of notoriously invasive tumor cells that infiltrate adjacent and nonadjacent areas of normal brain parenchyma. In principle, the immune system is uniquely qualified to recognize and target these infiltrative pockets of tumor cells, which have generally eluded conventional treatment approaches. In the span of the last 10 years, our understanding of the cancer-immune system relationship has increased exponentially, and yet, we are only beginning to tease apart the intricacies of the CNS and immune cell interactions. This article reviews the complex associations of the immune system with brain tumors. We provide an overview of currently available treatment options for malignant gliomas, existing gaps in our knowledge of brain tumor immunology, and molecular techniques and targets that might be exploited for improved patient stratification and design of 'custom immunotherapeutics'. We will also examine major new immunotherapy approaches that are being actively investigated to treat patients with malignant glioma, and identify some current and future research priorities in this area.

Recent advances in immunotherapy for human glioma

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Clinical trials of gene therapy, virotherapy, and immunotherapy for malignant gliomas

Despite advances in surgical and adjuvant therapy, the prognosis for malignant gliomas remains dismal. This gloomy scenario has been recently brightened by the increasing understanding of the genetic and biological mechanisms at the basis of brain tumor development. These findings are being translated into innovative therapeutic approaches, including gene therapy, virotherapy, and vaccination, some of which have already been experimented in clinical trials. The advantages and disadvantages of all these different therapeutic modalities for malignant gliomas will be critically discussed, providing perspective for future investigations.

Sensitization of malignant glioma to chemotherapy through dendritic cell vaccination

Drug resistance represents a major cause of chemotherapy failure in patients with cancer. The characterization of the molecular pathways involved in drug resistance has provided new targets to circumvent or reverse chemotherapy resistance. Many of these target proteins are often overexpressed in human glioma and have been identified as tumor antigens, which implicate the development of immunotherapy as a therapeutic strategy. Dendritic cells (DCs) are the most potent antigen-presenting cells of the immune system and have been demonstrated to stimulate antibody and cell-mediated immune responses against tumor-associated antigens. Ex vivo-generated and tumor antigen-loaded DCs have been successfully introduced to clinical vaccination protocols, which have proven to be feasible and effective in some glioma patients. Most importantly, immunotherapy followed by chemotherapy could significantly increase 2-year survival in malignant glioma patients, which obviously demonstrates that DC vaccination could increase the sensitivity of tumor cells to chemotherapy. This review focuses on recent advances in the identification of tumor-associated antigen in glioma, as well as novel insights into their biological function related to drug resistance. These insights may provide the rationale for a novel strategy of a DC cancer vaccine that sensitizes tumor cells to chemotherapy. In addition, the current research status and the future direction of a DC-based vaccine to treat glioma in animal models and clinical trials will also be discussed.

Isolation of immunoresistant human glioma cell clones after selection with alloreactive cytotoxic T lymphocytes: cytogenetic and molecular cytogenetic characterization

Intratumoral heterogeneity and genetic instability within gliomas may allow intrinsically immunoresistant (IR) cells to escape alloreactive cytotoxic T lymphocyte (aCTL) cellular immunotherapy. The potential existence of aCTL-resistant variants prompted us to investigate whether cellular immunotherapy resistant glioma models could be isolated. To generate the models, repeated intermittent or continuous selective pressure (ISP or CSP) with multiple aCTL populations was applied to a low-passage glioblastoma cell explant, 13-06-MG, obtained from a patient at initial diagnosis. IL-6 and IL-8 secretion was greater in coincubates of aCTL cells with 13-06-ISP and 13-06-CSP immunoselected cells than those with 13-06-MG parental cells. Initially, the immunoselected cells were less sensitive to aCTL lysis; however, the reduced aCTL-sensitivity was not maintained upon further selection. We therefore isolated IR clones from continuously immunoselected cells (13-06-CSP). The frequency of IR clones was 1-6 cells per 10,000 immunoselected cells. Two clones selected for further study, 13-06-IR29 and 13-06-IR30, resisted aCTL lysis in the absence of immunoselective pressure. Cytogenetic analyses revealed structural anomalies and genomic imbalances unique to the IR clones. Based on these findings, a hypothetical model is proposed that traces the origin of the IR clones to a clonal variant within the 13-06-CSP and 13-06-MG populations.

Innate immune functions of microglia isolated from human glioma patients

Background

Innate immunity is considered the first line of host defense and microglia presumably play a critical role in mediating potent innate immune responses to traumatic and infectious challenges in the human brain. Fundamental impairments of the adaptive immune system in glioma patients have been investigated; however, it is unknown whether microglia are capable of innate immunity and subsequent adaptive anti-tumor immune responses within the immunosuppressive tumor micro-environment of human glioma patients. We therefore undertook a novel characterization of the innate immune phenotype and function of freshly isolated human glioma-infiltrating microglia (GIM).

Methods

GIM were isolated by sequential Percoll purification from patient tumors immediately after surgical resection. Flow cytometry, phagocytosis and tumor cytotoxicity assays were used to analyze the phenotype and function of these cells.

Results

GIM expressed significant levels of Toll-like receptors (TLRs), however they do not secrete any of the cytokines (IL-1β, IL-6, TNF-α) critical in developing effective innate immune responses. Similar to innate macrophage functions, GIM can mediate phagocytosis and non-MHC restricted cytotoxicity. However, they were statistically less able to mediate tumor cytotoxicity compared to microglia isolated from normal brain. In addition, the expression of Fas ligand (FasL) was low to absent, indicating that apoptosis of the incoming lymphocyte population may not be a predominant mode of immunosuppression by microglia.

Conclusion

We show for the first time that despite the immunosuppressive environment of human gliomas, GIM are capable of innate immune responses such as phagocytosis, cytotoxicity and TLR expression but yet are not competent in secreting key cytokines. Further understanding of these innate immune functions could play a critical role in understanding and developing effective immunotherapies to malignant human gliomas.

Immunologic Evaluation of Personalized Peptide Vaccination for Patients with Advanced Malignant Glioma

PURPOSE

The primary goal of this phase I study was to assess the safety and immunologic responses of personalized peptide vaccination for patients with advanced malignant glioma.

EXPERIMENTAL DESIGN

Twenty-five patients with advanced malignant glioma (8 grade 3 and 17 grade 4 gliomas) were evaluated in a phase I clinical study of a personalized peptide vaccination. For personalized peptide vaccination, prevaccination peripheral blood mononuclear cells and plasma were provided to examine cellular and humoral responses to 25 or 23 peptides in HLA-A24+ or HLA-A2+ patients, respectively; then, only the reactive peptides (maximum of four) were used for in vivo administration.

RESULTS

The protocols were well tolerated with local redness and swelling at the injection site in most cases. Twenty-one patients received more than six vaccinations and were evaluated for both immunologic and clinical responses. Increases in cellular or humoral responses specific to at least one of the vaccinated peptides were observed in the postvaccination (sixth) samples from 14 or 11 of 21 patients, respectively. More importantly, significant levels of peptide-specific IgG were detected in the postvaccination tumor cavity or spinal fluid of all of the tested patients who showed favorable clinical responses. Clinical responses were 5 partial responses, 8 cases of stable disease, and 8 cases of progressive disease. The median overall survival for patients with recurrent glioblastoma multiforme in this study (n = 17) was 622 days.

CONCLUSIONS

Personalized peptide vaccinations were recommended for the further clinical study to malignant glioma patients.

Antiangiogenic Drugs Synergize with a Membrane Macrophage Colony-Stimulating Factor-Based Tumor Vaccine to Therapeutically Treat Rats with an Established Malignant Intracranial Glioma

Combining a T9/9L glioma vaccine, expressing the membrane form of M-CSF, with a systemic antiangiogenic drug-based therapy theoretically targeted toward growth factor receptors within the tumor's vasculature successfully treated >90% of the rats bearing 7-day-old intracranial T9/9L gliomas. The antiangiogenic drugs included (Z)-3-[4-(dimethylamino)benzylidenyl]indolin-2-one (a platelet-derived growth factor receptor beta and a fibroblast growth factor receptor 1 kinase inhibitor) and oxindole (a vascular endothelial growth factor receptor 2 kinase inhibitor). A total of 20-40% of the animals treated with the antiangiogenic drugs alone survived, while all nontreated controls and tumor vaccine-treated rats died within 40 days. In vitro, these drugs inhibited endothelial cells from proliferating in response to the angiogenic factors produced by T9/9L glioma cells and prevented endothelial cell tubulogenesis. FITC-labeled tomato lectin staining demonstrated fewer and constricted blood vessels within the intracranial tumor after drug therapy. Magnetic resonance imaging demonstrated that the intracranial T9 glioma grew much slower in the presence of these antiangiogenic drugs. These drugs did not affect in vitro glioma cell growth nor T cell mitogenesis. Histological analysis revealed that the tumor destruction occurred at the margins of the tumor, where there was a heavy lymphocytic infiltrate. Real-time PCR showed more IL-2-specific mRNA was present within the gliomas in the vaccinated rats treated with the drugs. Animals that rejected the established T9/9L glioma by the combination therapy proved immune against an intracranial rechallenge by T9/9L glioma, but showed no resistance to an unrelated MADB106 breast cancer.

Immunotherapy for malignant gliomas: emphasis on strategies of active specific immunotherapy using autologous dendritic cells

REVIEW

In this review, we discuss immunotherapy for malignant gliomas.

EMPHASIS

The emphasis is on the novel strategy of active specific immunotherapy using dendritic cells as antigen-presenting cells, especially its theoretical concepts and advantages, specific requirements, critical issues, pre-clinical and early clinical experience. Dendritic cell vaccination is situated in the diversity of other immunotherapeutical approaches.

FURTHER DISCUSSION

Future directions, challenges, and drawbacks will be discussed.

AIM-2: a novel tumor antigen is expressed and presented by human glioma cells

Antigen isolated from Immunoselected Melanoma-2 (AIM-2) was recently identified using melanoma-reactive CD8 T cells. AIM-2 antigen is expressed in a wide variety of tumor types, including neuroectodermal tumors, as well as breast, ovarian and colon carcinomas. In this study, we analyzed AIM-2 expression in glioblastoma multiforme (GBM) in primary cultured cells and established GBM cell lines. We found that the primary GBM cell lines expressed 88.4% and 93.0% of non-spliced and spliced AIM-2, respectively. Five out of seven of the established GBM cell lines expressed both non-spliced and spliced AIM-2. Furthermore, the C9 CTL clone, which is specific for AIM-2 peptide (RSDSGQQARY), efficiently recognized GBM tumor cells in an antigen-specific and HLA-A1 restricted manner. IFN-gamma treatment of the GBM tumor cells dramatically increased HLA-A1 expression levels and, consequently, increased CTL recognition of the treated tumor cells. More importantly, seven out of 12 HLA-A1 and AIM-2 positive patients from our dendritic cell clinical trial generated AIM-2 specific CTL activity in their PBMC after vaccinations. These data indicate that AIM-2 could be used as a tumor antigen target for monitoring vaccine trials or to develop antigen specific active immunotherapy for glioma patients.

Perspectives of Cellular and Molecular Neurosurgery

Therapeutic efforts for human glial tumors have over the past years been redirected towards a compartmental treatment concept. The diffusely infiltrative nature of the disease calls for therapeutic agents to reach single cells far beyond the focus of attention which present therapies like surgery and radiation are able to treat. Specific drug discovery approaches which seek to define targets which are specific for gliomas have generated therapeutic options which allow for a highly selective development of new reagents. Combined with new modalities for compartmental drug delivery, systemic complications might be reduced and advantage taken of a compartmental specificity of a target which otherwise in the context of systemic application would not be as specific or burdened with side effects. From the present status of therapeutic developments in neuro-oncology it can be expected that a sufficient number of drug targets emerge which can be exploited by means of interstitial or intracavitary delivery, which are not neurotoxic and which may even be imaged in their action with the new metabolic imaging modalities. Convection enhanced delivery, conditionally replicating oncolytic viruses and motile, genetically engineered neural stem cells all seem to fulfill the distribution requirements which an effective therapeutic for gliomas will need to overcome the very limited efficacy which surgery, conventional chemotherapy and radiation have to offer. Whereas the genomics based discovery approaches are not specific for neuro-oncology, the development of delivery strategies is highly specific for the central nervous system, thus creating a unique set of organ and disease specific therapies.

Microglia phagocytose alloreactive CTL-damaged 9L gliosarcoma cells

Intracranial adoptive transfers of alloreactive cytotoxic T lymphocytes (aCTL) for brain tumor treatment were safe and showed promise in preclinical and early clinical trials. To better understand the endogenous immune responses that may ensue following cellular therapy with aCTL, we examined the ability of microglia to phagocytose aCTL-damaged and undamaged rat 9L gliosarcoma cells in vitro and in vivo. In vitro, 5.5+/-0.9% of microglial cells isolated from adult tumor-bearing rat brains phagocytosed aCTL-damaged 9L cells, whereas microglia did not bind to or ingest undamaged 9L cells. Addition of supernates from either 9L cell cultures or from aCTL+9L co-incubate cell cultures to microglia did not significantly alter their ability to bind to or phagocytose damaged glioma cells even though the latter contained T helper 1 and 2 cytokines. At 3 days following intracranial 9L cell infusion, 17.5+/-0.1% of the microglia phagocytosed CFSE-labeled aCTL-damaged 9L tumor cells within the adult rat brain, confirming the in vitro data. The results suggest that microglia within the tumor microenvironment of the adult rat glioma model selectively remove damaged, but not undamaged, glioma cells.

HER-2, gp100, and MAGE-1 are expressed in human glioblastoma and recognized by cytotoxic T cells

It has recently been demonstrated that malignant glioma cells express certain known tumor-associated antigens, such as HER-2, gp100, and MAGE-1. To further determine the possible utilization of these antigens for glioma immunotherapy and as surrogate markers for specific tumor antigen cytotoxicity, we characterized the presence of mRNA and protein expression in 43 primary glioblastoma multiforme (GBM) cell lines and 7 established human GBM cell lines. HER-2, gp100, and MAGE-1 mRNA expression was detected in 81.4%, 46.5%, and 39.5% of the GBM primary cell lines, respectively. Using immunoreactive staining analysis by flow cytometry, HER-2, gp100, and MAGE-1 protein expression was detected in 76%, 45%, and 38% of the GBM primary cell lines, respectively. HLA-A1-restricted epitope specific for MAGE-1 peptide (EADPTGHSY) CTL clone B07 and HLA-A2-restricted epitope specific for HER-2 peptide (KIFGSLAFL) CTL clone A05 and gp100 peptide (ITDQVPFSV) CTL clone CK3H6 were used in this study. The specificity of CTL clone was verified by HLA/peptide tetramer staining. Three CTL clones could efficiently recognize GBM tumor cells in an antigen-specific and MHC class I-restricted manner. IFN-gamma treatment can dramatically increase MHC class I expression of GBM tumor cells and significantly increase CTL recognition of tumor cells. Treatment with the DNA hypomethylating agent 5-aza-2'-deoxycytidine induced and up-regulated the mRNA expression of MAGE-1 and epitope presentation by autologous MHC. These data indicate that HER-2, gp100, and MAGE-1 could be used as tumor antigen targets for surrogate assays for antigen-specific CTLs or to develop antigen-specific active immunotherapy strategies for glioma patients.

Interactions of the allogeneic effector leukemic T cell line, TALL-104, with human malignant brain tumors

TALL-104 is a human leukemic T cell line that expresses markers characteristic of both cytotoxic T lymphocytes and natural killer cells. TALL-104 cells are potent tumor killers, and the use of lethally irradiated TALL-104 as cellular therapy for a variety of tumors has been explored. We investigated the interactions of TALL-104 cells with human brain tumor cells. TALL-104 cells mediated increased lysis of a panel of brain tumor cells at low effector-to-target ratios over time. We obtained evidence that TALL-104 cells injured glioma cells by both apoptotic and necrotic pathways. A 7-amino actinomycin D flow cytometry assay revealed that the percentages of both apoptotic and necrotic glioma cells increased after TALL-104 cell/glioma cell coincubations. Fluorescent microscopy studies and a quantitative morphologic assay confirmed that TALL-104 cell/glioma cell interactions resulted in tumor cell apoptosis. Cytokines are secreted when TALL-104 cells are coincubated with brain tumor cells; however, morphologic analysis assays revealed that the soluble factors contained within clarified supernates obtained from 4 h coincubates added back to brain tumor cell cultures did not trigger the glioma apoptosis. TALL-104 cells do not express Fas ligand, even upon coincubation with glioma targets, which suggests that the Fas/Fas ligand apoptotic pathway is not likely responsible for the cell injury observed. We obtained evidence that cell injury is calcium dependent and that lytic granule exocytosis is triggered by contact of TALL-104 cells with human glioma cells, suggesting that this pathway mediates glioma cell apoptosis and necrosis.

Human alloreactive CTL interactions with gliomas and with those having upregulated HLA expression from exogenous IFN-gamma or IFN-gamma gene modification

By flow cytometry, a panel of 18 primary glioma cell explants exhibited high expression of class I HLA-A, B, C, but class II HLA-DR expression was absent. Freshly isolated normal brain cells displayed little or no HLA antigens. Alloreactive cytotoxic T lymphocytes (aCTL), sensitized to the HLA of the patient, were generated in a one-way mixed lymphocyte response (MLR). The specificity of aCTL was confirmed to be to target cells (patient glioma cells or lymphoblasts) expressing the relevant HLA antigens. However, nontumor patient-specific aCTL did not lyse normal brain cells. Titration of antibodies to HLA class I into cytotoxicity assays blocked lysis of gliomas by aCTL, confirming aCTL T cell receptor (TCR) interactions with the class I antigen on gliomas. Furthermore, aCTL interactions with glioma cells caused their apoptosis. Coincubations of aCTL with gliomas resulted in upregulated cytokine secretion. Importantly, dexamethasone, an immunosuppressive steroid used for brain edema, did not affect aCTL lytic function against tumor, indicating that steroid-dependent patients may benefit from the immunotherapy. We also explored the use of interferon-gamma (IFN-gamma) to increase aCTL tumor recognition. Coincubation of gliomas with exogenous IFN-gamma (500 U/ml, 48 h) caused a 3-fold upregulation of HLA class I and a slight induction of class II antigen expression. Gene-modified glioma cells producing IFN-gamma similarly displayed upregulated HLA expression. Glioma cells incubated with exogenous IFN-gamma or IFN-gamma-transduced glioma cells were more susceptible to lysis by aCTL than their parental counterparts, thus supporting the concept of combining IFN-gamma cytokine gene therapy with adoptive aCTL immunotherapy for brain tumor treatment.

Gamma interferon transduced 9L gliosarcoma. Cytokine gene therapy and its relevance to cellular therapy with alloreactive cytotoxic T lymphocytes

In earlier studies, we demonstrated that intratumoral infusions of alloreactive cytotoxic T lymphocytes (aCTL), sensitized to the major histocompatibility complex (MHC) antigens of the host, effectively retarded the intracranial growth of Fischer 9L gliosarcoma. We further demonstrated that continuous in vitro exposure to gamma-interferon (gammaIFN) upregulates MHC on 9L gliosarcoma cells and that they were better targets of anti-Fischer aCTL. We hypothesized that the efficacy of cellular therapy with aCTL could be further improved by in situ transduction of the tumor with retroviral vectors coding for gammaIFN, which would generate continuous secretion of the cytokine and maintain upregulated MHC expression by the tumor cells. 9L gliosarcoma and Herpes simplex virus thymidine kinase (tk) transductants of those cells were transduced with a retrovirus carrying the murine gammaIFN gene. By limiting dilution, clones of these cells, designated 9Lgamma 7, 9Lgamma tk8, and 9Lgamma tk10, which produced similar levels of gammaIFN (383-411 ng gammaIFN/10(6) cells/24 h) were isolated. The production of gammaIFN by one clone, 9Lgamma 7, was stable when monitored over 6 weeks in vitro. The clones also demonstrated upregulated MHC class I expression, and the tk-transduced clones maintained their sensitivity to ganciclovir. Compared to the wildtype cells, 9Lgamma 7 had approximate 6- and 1.5-fold increases in the relative antigen densities of MHC I and II, respectively. Addition of exogenous gammaIFN to 9Lgamma 7 cultures did not significantly increase the MHC expression. In cytotoxicity assays, 9Lgamma 7 cells, or 9Lgamma 7 incubated with exogenous gammaIFN, were better targets of aCTL than the parental 9L cells. The growth rate of 9Lgamma-transduced cells was decreased compared to the wildtype cells both in vitro and in vivo. Proliferation studies with transwell plated 9L, 9Lgamma 7, and 9Lgamma tk10 cells in various combinations revealed that the secreted cytokine itself caused a decrease in proliferation. However, the transduced cells exhibited a much reduced growth rate, which likely was a consequence of redirected metabolic activity of the cells. In vivo growth of the 9L and 9Lgamma 7 tumors in rat brains given identical inoculums similarly demonstrated significantly reduced 9Lgamma 7 tumor volumes at various timepoints, indicative of slower growth of the gammaIFN-producing tumors.

The neurosurgeon as local oncologist: cellular and molecular neurosurgery in malignant glioma therapy

Malignant gliomas are among the most challenging of all cancers to treat successfully, being characterized not only by aggressive proliferation and expansion but also by inexorable tumor invasion into distant brain tissue. Although considerable progress has been made in the treatment of these tumors with combinations of surgery, radiotherapy, and chemotherapy, these efforts have not been curative. Neurosurgeons as oncologists have increasingly turned their attention to therapies on a molecular scale. Of particular interest to neurosurgeons is the ability to deliver therapy locally to the tumor site or to take advantage of existing immunological mediators, enhancing drug concentrations or therapeutic cell numbers while bypassing the blood-brain barrier to maximize efficacy and minimize systemic toxicity. Exciting local-therapy approaches have been proposed for these devastating tumors. In this review, we discuss the potential applications of bioreactors, neural stem cells, immunotherapies, biodegradable polymers, and convection-enhanced drug delivery in the treatment of malignant gliomas. These approaches are at different stages of readiness for application in clinical neurosurgery, and their eventual effects on the morbidity and mortality rates of gliomas among human patients are difficult to ascertain from successes in animal models. Nevertheless, we are entering an exciting era of "nanoneurosurgery," in which molecular therapies such as those discussed here may routinely complement existing surgical, radiological, and chemotherapeutic approaches to the treatment of neuro-oncological disease. The potential to deploy any of a number of eloquently devised molecular therapies may provide renewed hope for neurosurgeons treating malignant gliomas.

Adoptive immunotherapy for malignant glioma

Despite remarkable advancements in imaging modalities and treatment options available to patients diagnosed with malignant brain tumors, the prognosis for those with high-grade lesions remains poor. The imprecise mechanisms of currently available treatments to manage these tumors do not spare damage to the normal surrounding brain and often result in major cognitive and motor deficits. Immunotherapy holds the promise of offering a potent, yet targeted, treatment to patients with brain tumors, with the potential to eradicate the malignant tumor cells without damaging normal tissues. The T cells of the immune system are uniquely capable of recognizing the altered protein expression patterns within tumor cells and mediating their destruction through a variety of effector mechanisms. Adoptive T-cell therapy is an attempt to harness and amplify the tumor-eradicating capacity of a patients' own T cells and then return these effectors to the patient in such a state that they effectively eliminate residual tumor. Although this approach is not new to the field of tumor immunology, new advancements in our understanding of T-cell activation and function and breakthroughs in tumor antigen discovery hold great promise for the translation of this modality into a clinical success.

Human U251MG glioma cells expressing the membrane form of macrophage colony-stimulating factor (mM-CSF) are killed by human monocytes in vitro and are rejected within immunodeficient mice via paraptosis that is associated with increased expression of three different heat shock proteins

Human U251MG glioma cells retrovirally transduced with the human gene for the membrane form of macrophage colony-stimulating factor (mM-CSF) were investigated. The clones, MG-2F11 and MG-2C4, that expressed the most mM-CSF, but not the viral vector or the parental U251MG cells, were killed by both murine and human monocyte/macrophages in cytotoxicity assays. MG-2F11 cells failed to form subcutaneous tumors in either nude or NIH-bg-nu-xidBR mice, while mice inoculated with the U251MG viral vector (MG-VV) cells developed tumors. Electron microscopy studies showed that 4 hours after subcutaneous injection, the mM-CSF-transduced cells began dying of a process that resembled paraptosis. The dying tumor cells were swollen and had extensive vacuolization of their mitochondria and endoplasm reticulum. This killing process was complete within 24 hours. Macrophage-like cells were immediately adjacent to the killed MG-2F11 cells. Immunohistological staining for the heat shock proteins HSP60, HSP70 and GRP94 (gp96) showed that 18 hours after inoculation into nude mice, the MG-2F11 injection site was two to four times more intensely stained than the MG-VV cells. This study shows that human gliomas transduced with mM-CSF have the potential to be used as a safe live tumor cell vaccine.

Effects of IFN-gamma and interleukin-1beta on major histocompatibility complex antigen and intercellular adhesion molecule-1 expression by 9L gliosarcoma: relevance to its cytolysis by alloreactive cytotoxic T lymphocytes

To enhance the efficacy of cellular immunotherapy for gliomas, we tested the concept of using proinflammatory cytokine treatment with interferon-gamma (IFN-gamma) or interleukin-1beta (IL-1beta) or both to render glioma cells more susceptible to cytolysis by alloreactive cytotoxic T lymphocytes (aCTL). The cytokines, separately or in combination, were able to upregulate major histocompatibility complex (MHC) class I antigen or intercellular adhesion molecule-1 (ICAM-1) on Fischer rat 9L gliosarcoma cells. 9L cells were incubated in vitro for 24, 48, or 72 h with varying concentrations of rat IFN-gamma (0-2000 U/ml) or recombinant human IL-1 (rHUIL-1) (0-1000 U/ml) or both. By 48 h, IFN-gamma (500 U/ml) maximally induced the percentage of positive expressing cells and the relative antigen density of MHC class I and ICAM-1 on 9L cells, whereas IL-1 induced only ICAM-1 expression. Simultaneous incubation of IL-1 with IFN-gamma did not further affect the induction of class I on 9L cells more than that achieved with IFN-gamma alone. 9L cells with upregulated MHC class I and ICAM-1 expression were more sensitive to lysis by aCTL in in vitro cytotoxicity assays, regardless of whether the precursor aCTL came from naive or from 9L-immunized rats. Furthermore, inhibition of 9L cytotoxicity in assays that included blocking antibodies to MHC class I or to ICAM-1 revealed that T cell receptor (TCR) interactions with MHC class I and that ICAM-1 interactions with lymphocyte function-associated-1 (LFA-1) antigen account for a portion of the glioma lysis by aCTL.

Clinical immunotherapy for brain tumors

As an immunization platform for brain tumors, dendritic cells supply an impressive host of advantages. On the simplest level, they provide the safety and tumor-specificity so wanted by current therapeutic options. Yet, in addition, as the fundamental antigen-presenting cell, they circumvent many of the immunologic challenges that gliomas and the CNS proffer and that other immunotherapeutic modes fail to overcome. Directions to take now include the identification of new tumor-specific and tumor-associated antigens; the determination of the optimal dendritic cell subtype, generation, loading method, maturation state, dose, and route of delivery for immunizations; the further characterization of dendritic cells and their activities; and, potentially, the discovery of ways to pulse dendritic cells efficiently in vivo. Preclinical studies continue to play an important role in refining this form of active immunotherapy.

T9 glioma cells expressing membrane-macrophage colony stimulating factor produce CD4+ T cell-associated protective immunity against T9 intracranial gliomas and systemic immunity against different syngeneic gliomas

Cloned T9 glioma cells (T9-C2) expressing the membrane form of macrophage colony stimulating factor (mM-CSF) inoculated subcutaneously into rats do not grow and glioma-specific immunity is stimulated. Immunotherapy experiments showed that intracranial T9 tumors present for one to four days could be successfully eradicated by peripheral vaccination with T9-C2 cells. CD4+ and CD8+ T splenocytes from immunized rats, when restimulated in vitro with T9 cells, produced interleukin-2 and -4. Protective immunity against intracranial T9 gliomas could only be adoptively transferred into naive rats by the CD4+ splenocytes obtained from T9-C2 immunized rats. Rats immunized by the T9-C2 tumor cells also resisted two different syngeneic gliomas (RT2 and F98) but allowed a syngeneic NUTU-19 ovarian cancer to grow. Such cross-protective immunity against unrelated gliomas suggests that mM-CSF transfected tumor cells have immunotherapeutic potential for use as an allogeneic tumor vaccine.

Strategies using the immune system for therapy of brain tumors

Phase II immunotherapy and gene therapy studies should be pursued because of encouraging results in many phase I studies. Future testing in this field may consider modifications of some of the above-mentioned combined strategies. For instance, in the immunization and adoptive transfer studies performed by Holladay et al and by Plautz et al, the systemic adoptive transfer could be altered to intratumoral placements of effector cells. This permutation may be more efficacious because local adoptive immunotherapy approaches involve placement of effector cells where they are needed. Additionally, new avenues of gene therapy are being explored that may offer added beneficial effects for immunization, local or systemic adoptive immunotherapy, or combined chemotherapy and adoptive immunotherapy of tumors. With new genetic tools, such as microarray analyses, SEREX, and creation of cDNA libraries from tumor cells, significant progress in the treatment of neoplasms in the immunologically privileged brain should be forthcoming.

Chemo-immunotherapy and chemo-adoptive immunotherapy of cancer

The chemo-immunotherapy (CIT) and chemo-adoptive immunotherapy (CAIT) regimens tested in the past decade are summarized. From them we have learned a great deal about the interactions between various chemotherapeutic agents, immune modulating agents and effector cells. The most commonly reported result in multi-modality experiments with CAIT has been a synergistic enhancement in antitumor activity. Clinical trials usually demonstrated improvement in patient quality of life, an extension of survival time, and occasional complete regression of tumor. In many animal models, this enhancement often meant the complete regression and apparent cure of tumor in the animal. One mechanism by which this synergistic enhancement takes place appears to be a suppression of tumor-associated suppressor T cell activity by the chemotherapeutic agents, thereby inducing enhanced cytolytic activity against tumor by the adoptively transferred, activated effector cells. In CAIT the most commonly used drug has been cyclophosphamide. In CIT a wide variety of chemotherapy agents have been used but none of the clinical trials made use of cyclophosphamide. Thus, direct comparisons are not possible. Suggestive of the intricate regulatory processes involved, many CIT studies indicate a synergy only when specific doses of chemotherapy and immunotherapy agents are given, and in a specific sequence. CIT has become less toxic, is being handled on a cost-effective outpatient basis, while maintaining similar objective response rates to earlier inpatient treatments. In the future, CAIT and CIT will probably have an increasing role in the management of patients with specific cancers.

Adoptive cellular immunotherapy for the treatment of malignant gliomas

The median survival for adults with recurrent primary malignant gliomas is 56 weeks following surgery, radiation, and chemotherapy. Generally, reoperation can extend the median survival an additional 26-32 weeks. We have developed an aggressive treatment program that utilizes low doses of interleukin-2 (IL-2) combined with ex vivo activated killer cells (LAK) infused via an indwelling catheter placed into the surgical resection cavity. Autologous leukocytes were collected during a standard 3-4 h, outpatient leukapheresis procedure, then activated ex vivo for 4-5 days with high doses of IL-2. The treatment protocol consisted of two 2-week cycles of therapy over a 6-week period. Patients with stable disease or objective response on follow-up MRI scans were retreated at 3-month intervals. Acute and cumulative IL-2-related toxicities were observed, but limited, and included fever, headache and transient neurologic irritation. Corticosteroid levels and usage were strictly controlled during immunotherapy, although higher doses were used intermittently to mitigate toxicity. Biologic changes included lymphocytic infiltration, regional eosinophilia, tumor necrosis, and the localized production of IL-2, IFN-gamma and IL-12, demonstrated by in situ hybridization and immunohistochemistry.

SUMMARY

IL-2 plus autogeneic LAK cells can be safely administered intracavitary to treat high grade primary brain tumors with limited toxicity within the central nervous system. Six out of 28 patients had long-term survival of greater than 2 years post-reoperation plus immunotherapy with 2 patients alive over 8 years. The presence of a marked regional eosinophilia appeared to correlate with increased survival and may be predictive of a biologic and therapeutic response. Regional adoptive immune therapy was well tolerated and should be considered an option for patients with high-grade tumors refractive to standard therapeutic approaches.

Treatment of refractory recurrent malignant glioma with adoptive cellular immunotherapy: a case report

We report the successful treatment of a patient with recurrent malignant glioma with adoptive cellular immunotherapy. The patient is a young adult with recurrent progressive disease refractory to aggressive multi-modality therapy including repetitive surgical resection, radiation, radiosurgery and chemotherapy. He received multiple courses of local administration of autologous lymphokine-activated killer (LAK) cells in combination with a low dose of interleukin-2 (IL-2) through an Ommaya reservoir-catheter system. The side-effects of this treatment were limited and manageable. The patient achieved a complete remission, as demonstrated by MRI and confirmed by glucose-positron emission tomography (PET) imaging 11 months after initiation of immune therapy. Twenty-six months later, the patient is still in remission with improving performance status. Adoptive cellular immunotherapy utilizing autologous LAK cells with low dose IL-2 appears to be a safe and effective therapy for a subset of patients with primary, recurrent or progressive malignant glioma following conventional therapy.

Immunologic approaches to therapy for brain tumors

Malignant brain tumors are notoriously invasive. Although surgical debulking can relieve the patient of the main mass of tumor, adjuvant treatments are needed to target the glioma cells that infiltrate through normal parenchyma as single cells or pockets of tumor cells from which recurrent tumors arise. Successful adjuvant cellular therapy of brain tumors, or activation of endogenous immune cells, requires that either cell effectors make direct contact with tumor cells or come within close proximity to them and exert an indirect effect. This review examines current clinical trials aimed at direct lysis of glioma cells and trials making gliomas more visible to the endogenous immune system.

Interleukin-2 and histamine in combination inhibit tumour growth and angiogenesis in malignant glioma

Biotherapy including interleukin-2 (IL-2) treatment seems to be more effective outside the central nervous system when compared to the effects obtained when the same tumour is located intracerebrally. Recently published studies suggest that reduced activity of NK cells in tumour tissue can be increased by histamine. The present study was designed to determine whether IL-2 and histamine, alone or in combination, can induce anti-tumour effects in an orthotopic rat glioma model. One group of rats was treated with histamine alone (4 mg kg(-1)s.c. as daily injections from day 6 after intracranial tumour implantation), another group with IL-2 alone as a continuous subcutaneous infusion and a third group with both histamine and IL-2. The animals were sacrificed at day 24 after tumour implantation. IL-2 and histamine in combination significantly reduced tumour growth. The microvessel density was significantly reduced, an effect mainly affecting the small vessels. No obvious alteration in the pattern of VEGF mRNA expression was evident and no significant changes in apoptosis were observed. Neither IL-2 nor histamine alone caused any detectable effects on tumour growth. Histamine caused an early and pronounced decline in tumour blood flow compared to normal brain. The results indicate that the novel combination of IL-2 and histamine can be of value in reducing intracerebral tumour growth and, thus, it might be of interest to re-evaluate the therapeutic potential of biotherapy in malignant glioma.

Glioma immunology and immunotherapy

OBJECTIVE

Despite advances in conventional therapy, the prognosis for most glioma patients remains dismal. This has prompted an intensive search for effective treatment alternatives. Immunotherapy, one such alternative, has long been recognized as a potentially potent cancer treatment but has been limited by an inadequate understanding of the immune system. Now, increased insight into immunology is suggesting more rational approaches to immunotherapy. In this article, we explore key aspects of modern immunology and discuss their implications for glioma therapy.

METHODS

A thorough literature review of glioma immunology and immunotherapy was undertaken to inquire into the basic immunology, central nervous system immunology, glioma immunobiology, standard glioma immunotherapy, and recent immunotherapeutic advances in glioma treatment.

RESULTS

Although gliomas express tumor-associated antigens and appear potentially sensitive to immune responses, many factors work together to inhibit antiglioma immunity. Not surprisingly, most clinical attempts at glioma immunotherapy have met with little success to date. However, novel immunostimulatory strategies, such as immunogene therapy, directed cytokine delivery, and dendritic cell manipulation, have recently yielded dramatic preclinical results in glioma models. This suggests that glioma-derived immunosuppression can be overcome.

CONCLUSION

Modern molecular biology and immunology techniques have yielded a wealth of new data about glioma immunobiology. Armed with this information, many investigators have proposed novel means to stimulate antiglioma immune responses. Although definitive clinical results remain to be seen, the current renaissance in glioma immunology and immunotherapy shows great promise for the future.