Traditional therapies for the treatment of malignant glioma have failed to make appreciable gains regarding patient outcome in the last decade. Therefore, immunotherapeutic approaches have become increasingly popular in the treatment of this cancer. This article reviews general immunology of the central nervous system and the immunobiology of malignant glioma to provide a foundation for understanding the rationale behind current glioma immunotherapies. A review of currently implemented immunological treatments is then provided with special attention paid to the use of vaccines, gene therapy, cytokines, dendritic cells and viruses. Insights into future and developing avenues of glioma immunotherapy, such as novel delivery systems, are also discussed. [Neurol Res 2005; 27: 703-716]
Keywords: Cytokines; dendritic cells; gene therapy; glioma; immunotherapy; neuroimmunology; vaccine; virus
Since the last decade, there has been a significant interest in developing novel immunotherapeutic approaches for malignant glioma. Given the lack of success with currently available therapeutic modalities, the appeal of this strategy is obvious-it relies solely on the ability of the immune system to recognize and destroy tumor cells while leaving normal and healthy tissue intact. To date, different immunological approaches have been utilized with various degrees of success. This review summarizes our current knowledge of immunology and glioma immunobiology and provides an overview into some of the currently tested immunotherapeutic regimens which are gaining increasing roles in clinical trials for malignant brain tumors.
The immune system is designed to recognize and eliminate pathogens. To achieve this, the system is comprised of innate and adaptive components-both mediating responses to foreign antigens.
The innate system is comprised of macrophages, granulocytes, natural killer cells and monocytes [microglia in the central nervous system (CNS)]. This system recognizes pathogen-associated molecular patterns (PAMPs) or general ligands (e.g. NKG2D ligand) that are upregulated during cellular stress, infection or transformation1-8. This recognition results in immunologie responses such as phagocytosis and the release of various cytokines (e.g. IL-1, IL-6, TNF-α) and inflammatory mediators (e.g. oxygen radicals, leukotrienes). These mediators aid in the localization and initiation of the adaptive immune response via their attractant and proliferative properties3,9-11 (Figure 7).
The adaptive immune system differs from the innate system with its specificity and capacity for the memory of foreign antigens. The specificity of this system is derived from lymphocyte receptors, which recognize unique foreign antigens presented to them in the context of a major histocompatibility complex (MHC). The action of this system typically begins with the ingestion and presentation of foreign antigens by antigen presenting cells (APCs) within the context of MHC class II molecules. If a CD4+ (helper) T cell receptor (TCR) recognizes this antigen then the leukocyte will become activated and release cytokines. Depending on specific helper T cell type (Th1 or Th2), released cytokines and the presence of required co-stimulatory molecular interactions, this results in the activation and proliferation of nearby CD8+ cytotoxic T lymphocytes (CTLs) or B cells. Activated CD8+ lymphocytes (effectors of the cell-mediated system) target cells presenting the previously mentioned antigens in the context of MHC class I complexes. These targeted cells are then eliminated by CTLs either by the initiation of apoptosis via Fas/Fas ligand interactions or by perforin-mediated cell lysis (Figure 2). Activated B cells release immunoglobulins (effectors of the humoral system) to neutralize specific antigens. However, because immunoglobulins interact with free or soluble antigen, the humoral system is poorly equipped to respond to the mostly cytoplasmic derived antigens of tumor cells. Also, because antibodies traverse the blood-brain barrier (BBB) inefficiently, their effectiveness against CNS tumors is further limited12. Lastly, in both the humoral and cell-mediated portions of the adaptive system, activated T or B cells may become long-lived memory cells that are ready to respond quickly to repeat immunological challenges.
IMMUNOLOGY OF THE CENTRAL NERVOUS SYSTEM-SPECIAL CONSIDERATIONS
The generation of an immunologic response to neoplasms in the brain has the same general requirements as that necessary for cancers in peripheral tissues. The CNS, however, has historically been viewed as 'immune privileged' with the assumption that an effective immune response is difficult to obtain13. The presence of a BBB, lack of organized lymphoid tissue or significant lymphatic drainage, paucity of MHC expression in normal brain parenchyma and presence of immunoregulatory factors all contribute to the perception of immune privilege12, 14. While the above properties contribute to the distinctive immunoreactivity of the CNS, they do not render it a completely immune privileged site. They do, however, necessitate an understanding of alterations in the traditional schema of peripheral immunobiology for one to grasp the dynamics of the CNS antitumor response.
As in the periphery, cell-mediated responses to neoplasms in the CNS require efficient antigen presentation. The precise cell type and mechanism responsible for antigen presentation in the brain has been debated; however, the requirements for APCs in the CNS are the same as for those in the periphery. They include the ability to ingest or phagocytose foreign antigens, expression of MHC complexes and the ability to induce T lymphocyte responses (probably via costimulatory molecules such as B7). Microglia have emerged as the likeliest candidates for antigen presentation in the brain15-17. In addition to their hematopoietic origin, microglial cells express MHC class I, MHC class II and certain costimulatory molecules. In vitro, these cells can induce alloreactive T cell responses and stimulate T cell lines to proliferate and secrete cytokines. In vivo, CD54 and B7 costimulatory molecules have been detected on reactive microglial cells in multiple sclerosis (MS) plaques18. Also, the CNS may participate in trafficking dendritic cells (highly effective peripheral antigen presenting cells) between normal or inflamed brain and immune system tissues. This mechanism is not entirely clear but is probably under tight environmental controls19. One possible mechanism may be through drainage of CNS antigens to cervical lymph nodes where they may interact with these APCs. Such pathways have been illustrated in primate models of experimental allergic encephalomyelitis (EAE) and human MS20. Furthermore, evidence from murine models with brain tumors suggests that tumor-specific T cells can be primed in cervical lymph nodes21.
The presence of a tight BBB also contributes to the distinctive immunoreactivity of the CNS and once was thought to effectively hinder the influx of immune cells into the brain. Despite presenting a formidable obstacle, immunologically functional cells (including activated T lymphocytes) have the ability to pass the BBB and enter brain parenchyma22-24. In fact, multiple types of lymphoid cells can be detected in the CNS during disease states25-29. Pro-inflammatory cytokines probably play critical roles in increasing BBB permeability along with enhancing the adherence and transendothelial migration of leukocytes19.
Another potential obstacle to CNS tumor reactivity is the relative lack of MHC expression and antigenicity in normal and malignant brain tissue; these molecules are indispensable for antigen recognition by TCRs. However, there is now experimental evidence that MHC antigens are upregulated at sites of brain injury, degenerative disease, tumor or after the exposure to cytokines such as interferon-γ30-35. In addition to antigen-presentation complexes, most human glioma cells have been shown to express Fas/APO-1 (CD 95) and Fas ligand, which allow these cells to undergo Fas/Fas ligand interactions with activated T lymphocytes resulting in apoptosis35,36. While no universal glioma-specific antigen presented on these MHC molecules has been found, several tumor-associated antigens shared by histogenetically related tumors have been identified (e.g. tenascin, gp240, gp1000, epidermal growth factor receptor, tyrosinase, tyrosinase-related proteins 1 and 2, MAGE-1 and MAGE-3)37-41. There is also evidence that many of these antigens are capable of generating immune responses experimentally42.
Lastly, the environment of the CNS is decidedly antiinflammatory under normal conditions. The need for such attenuation is underscored by examples of states of intense immune or inflammatory response that lead to diseases such as MS or post-infectious encephalomyelitis. Astrocytes have been shown to exert a number of important physiologic effects related to immune homeostasis, however, their exact function remains controversial43. While under normal conditions astrocytes lack MHC expression, they may be induced to express these molecules by interferon-γ44. The precise role of MHC class II positive astrocytes remains unclear; however, a prevailing view is that astroglia exert a negative immunoregulatory function that contributes to the anti-inflammatory state of the normal CNS15,45,46.
CNS TUMOR IMMUNOLOGY-HOW GLIOMAS ESCAPE THE IMMUNE RESPONSE
In addition to the typical restraints placed upon immune regulation by the CNS, malignant brain tumors also provide means to neutralize an effective immune response (Figure 3). As stated earlier, brain neoplasms typically express low levels of class I MHC antigens47. This lack of MHC class I expression has been theorized to be a potential mechanism by which gliomas can escape recognition and subsequent lysis by CD8+ T cells. The potential for upregulation of these MHC antigens by factors such as interferon-γ, however, raises questions about this simplified scheme. Furthermore, receptors on NK cells sense MHC down-regulation and can initiate NK lysis of MHC-deficient tumor cells48. As such, there probably exists a level of glioma MHC class I expression that balances T leukocyte and NK cell detection. The regulation of this balance has yet to be precisely elucidated; however, it almost certainly plays an important role in the ability of malignant brain tumors to evade the immune response49. Also, expression of altered MHC has been identified in a variety of malignancies including glioma cells of the brain50-53. HLA (human leukocyte antigen)-G is a non-classical MHC class I (class 1b) molecule that is structurally related to the classical MHC class I (class 1a) molecule. HLA-C, however, has been recently identified to have strong immunoregulatory functions and may render the glioma cells that express it to be less susceptible to antitumoral immune responses54.
In addition to evading host immune responses, malignant brain tumors can have a profound effect upon the function of immune system components. The maturation and function of APCs can be impaired by secreted tumor factors, thus limiting their ability to activate tumor-specific T cells or participate in active immunotherapy approaches55-57. T lymphocyte function in the setting of primary intracranial tumors has also been shown to be defective with abnormal TCR mediated signaling and depressed proliferative response to mitogen58,59. Additionally, these lymphocytes exhibit a propensity for apoptosis59,60. The partial reversibility of T cell suppression following brain tumor removal along with the demonstration of down-regulated function of T cells harvested from brain tumor patients or normal patients exposed to glioma supernatants provide strong evidence of glioma-produced immunosuppressive factors61-63. Transforming growth factor beta 2 (TGF-β2) has been one of the most extensively studied of all immunosuppressive factors identified thus far. It has been shown to be significantly over-expressed in patients with glioblastoma multiforme (GBM) while virtually absent in normal brain tissue64,65. Additionally, TGF-β2 has been shown to effectively limit T cell and B cell proliferation, IL-2 receptor induction, cytokine production, natural killer cell activity, cytotoxic T lymphocyte development, lymphokine activated killer (LAK) cell generation and the cytotoxic response of tumor infiltrating lymphocytes65-70. TGF-β has also been shown to down-regulate the expression of HLA-DR (a non-classical MHC antigen expressed on glioma cells) and has important effects on blood-neural barrier properties-both may be other mechanisms by which gliomas escape immune surveillance71,72. Lastly, TGF-β probably acts as a growth promoter for glioma cells (via TGF-β type I and type II surface receptors) leading to tumor angiogenesis and stromal growth, likely, through autocrine or paracrine loops73,74. As such, TGF-β suppression in human gliomas by retroviral gene transfection has resulted in the enhancement of tumor cell susceptibility to LAK cells75. Additionally, TGF-β antagonists have been shown experimentally to inhibit malignant glioma cell proliferation, motility and TGF-β mediated morphologic changes76.
Other factors produced by glioma cells that may play a role in immune regulation and tumor cell escape include prostaglandin E^sub 2^ (PGE^sub 2^) and IL-10. PGE2 has been shown to reduce LAK cell activity and may contribute to the ability of gliomas to escape immune surveillance via the down-regulation of HLA-DR77,78. The effects of IL-10 on tumor immunology are currently not as clearly defined. While some studies have suggested that IL-10 blunts the immune response by inhibiting IFN-γ release, TNF-α release and MHC class II expression, another has shown enhanced response to tumor in animal models79-81. Clearly, further investigation will be required to better identify the role of IL-10 in CNS tumor immunology.
CNS TUMOR IMMUNOTHERAPIES
Despite the unique anatomical and physiologic barriers posed by the CNS, evidence of brain-specific antigens resulting in the priming of T cells in peripheral immune tissues does exist (see section on CNS immunology). Furthermore, systemic immunizations with brain-specific antigens resulting in CNS manifestations have been demonstrated with EAE and paraneoplastic cerebellar degeneration (PCD)82,83. These data led to the investigation of various types of peripheral vaccinations as treatment strategies for brain tumors.
As described earlier, cytokines play critical roles in CNS tumor immunology by enhancing T cell activation and MHC antigen expression. Cytokine gene transfer in cancer models resulting in tumor rejection has been demonstrated with IL-2, IL-4, IL-12, IL-18, IL-23, IFN-α and granulocyte-macrophage colonystimulating factor (GM-CSF)84-93. The use of peripheral cytokine-secreting vaccines for intracranial cancers has, therefore, been explored in hopes of overriding the tumor-induced immunosuppressive microenvironment and enhancing the activation and infiltration of host-derived APCs and lymphocytes. As such, a panel of cytokine secreting vaccines was screened in a murine glioma model with IL-2, IL-4, IL-12 and CM-CSF being most effective in producing T cell inflammation94. As an excellent review exists regarding cytokine gene therapy for malignant glioma, we will highlight the salient points95 (Table 1).
Several studies have demonstrated the efficacy of peripheral vaccinations with GM-CSF transfected tumor cells against brain tumors in animal models28,96-99. Furthermore, some studies have suggested intensified antitumoral responses when GM-CSF vaccines were coupled with those expressing IL-4 or the costimulatory molecule B70 -2(97,100,101. Interestingly, antitumor cytotoxicity only exceeded that of peripheral blood mononuclear cells (PBMCs) stimulated with wild type tumor alone when PBMCs were stimulated with both wild type tumor and B7-2/GM-CSF (but not IL-12) transduced cells100. Lastly, peripheral tumor cell inoculation coupled with continuous, peripheral GM-CSF alone or with IL-2 or IL-12 resulted in improved survival rates in the treatment of intracranial glial tumors in rat models102,103. Presumably, the antitumor activity of GM-CSF is related to its potency in generating dendritic cells (DCs). Whether GM-CSF alone or in combination with other factors will result in CNS antitumor efficacy in humans remains to be seen.
The effectiveness of IL-2 in the treatment intracerebral tumors has been investigated using multiple methods. Vaccines composed of IL-2 secreting autologous fibroblasts and glioma cells have been shown to induce cytotoxic CD8+ T cells in the blood of a patient with malignant glioma104. A later study also demonstrated a vigorous systemic antitumor response following subcutaneous injections of IL-2 secreting cells in the presence of tumor antigens in mice105. Despite the systemic response, this did not result in prolonged survival. However, this study did demonstrate significantly longer survival following intratumoral injections of IL-2 secreting allogeneic cells alone. Intracerebral injection of IL-2 secreting fibroblasts has also been found to be effective as a protective treatment in preventing the development of murine brain tumors when the tumor cells are introduced into the same site where the fibroblasts were injected earlier106. Additionally, this treatment has proven effective for established intracerebral breast carcinoma or glioma in mice107. Both of these studies involving intracerebral injection of IL-2 secreting fibroblasts resulted in significantly increased survival rates in the animal subjects. Combining peripheral vaccination and intratumoral injection of IL-2 expressing cells or IL-2 activated NK cells has also shown promise in the elimination of brain tumors in animal models108,109. Also, injection of IL-2 generated LAK cells into tumor resection cavities of humans with histologically confirmed recurrent GBM was found to be safe and resulted in higher median survival rates than those reported in other published series of patients that underwent reoperation for CBM110. Given the promising results of intracranial IL-2 treatment, novel means of delivery (including the use of biodegradable microspheres) have also been explored. The use of microspheres for delivery of IL-2 and the chemotherapeutic agent carmustine (BCNU) has shown improved median survival when compared with controls in animal models111.
The use of IL-4 for the treatment of intracranial tumors has also been explored in multiple ways. In one important study, the effectiveness of various cytokines (IL-4, IL-12, GM-CSF and IFN-α) was compared using intracerebral or intradermal injections of transfected tumor cells as prophylaxis or therapy against intracerebral glial tumors in an animal model112. All cytokine transfected cell lines were rejected following their intradermal injection; conversely, all lead to tumor outgrowth and animal death following intracerebral injection. However, intradermal IL-4 expressing cell vaccinations were the only cell lines that were effective at providing immunity (90% long-term rat survival) against later challenge with intracranial tumor. This was compared with 40% long-term survival in rats vaccinated with GM-CSF or IFN-α secreting cells and 0% in IL-12 secreting vaccinations. Additionally, only IL-4 peripherally vaccinated rats had long-term survival benefits when used as therapy for existing tumors. These results corroborated data obtained earlier demonstrating the efficacy of subcutaneous tumor cell vaccines expressing IL-4 [with and without herpes simplex virus thymidine kinase (HSVtk)/ganciclovir] as therapy or prophylaxis against intracranial glial tumors in animals85. This led to a Phase I clinical trial of vaccinations with autologous glioma cells admixed with transgene derived IL-4 expressing fibroblasts in one human patient with recurrent right temporal lobe GBM113. A transient response to the vaccine was suggested in this trial and the patient survived 10 months after treatment. Clearly, further trials with peripheral IL-4 vaccines will be needed to better assess their effectiveness.
The subcutaneous immunization of rats with IL-12 secreting glial tumors has been demonstrated to suppress the growth of identical cell type brain tumors114. This cytotoxic activity was limited when compared with that of IL-2. The same study also showed reduced tumor growth rates when these transduced tumor cell lines were implanted intracerebrally, but again, growth retardation was greater with IL-2 secreting cells. The use of intracerebral cytokine delivery has also been explored by other means. Significantly prolonged survival times have been demonstrated in animals challenged intracranially with glioma cells after earlier intracranial paracrine delivery of IL-T2 with transduced glial cells115. Neural stem cells (NSC) that express IL-12 (another possible mechanism of intracranial cytokine delivery) have also shown effectiveness in prolonging survival time in mice and rats with existing tumors116,117. Clear evidence for tropism of injected NSCs into infiltrating or satellite portions of tumors was also exhibited117. Finally, systemic IL-12 has also shown effectiveness in eliciting immunologic responses against transplanted and endogenous murine CNS tumors118,119.
The rationale for immunotherapy regimens utilizing dendritic cells lies in their potency as antigen presenting cells. With the advancement of techniques allowing for their isolation and propagation in vitro, these therapies have become more feasible in the treatment of gliomas. Each of these therapy regimens, however, requires patient-derived tumor antigens owing to the lack of a universal glioma-specific antigen. There are several reports of peripheral vaccinations with dendritic cells loaded with glioma antigens (e.g. tumor cell extracts, lysates, RNA) or dendritic cells fused with glioma cells (with or without recombinant IL-12), leading to the generation or augmentation of antitumor responses in the brains of animal models120-123. The promising results of glioma DC vaccines in animal models have led to several clinical trials in adults and children124-129. Initially, phase I trials established the feasibility and safety of peptide pulsed dendritic cells vaccinations124,128. More recently, vaccination with tumor lysate pulsed dendritic cells was shown to elicit the generation of antigen-specific cytotoxic T cells in patients with malignant gliomas127. In this study, the median survival for patients (n=8) with recurrent glioblastoma who were treated with the vaccine was extended to 133 weeks. Together, these results suggest that DC vaccinations are safe and can generate intracranial antitumor effects and T cell infiltration.
Intracranial/intratumoral injection with DCs has also been explored as a therapeutic strategy for intracranial glioma130-132. Interestingly, such direct intratumoral DC therapy appeared to be more effective than peripheral subcutaneous vaccination at generating tumor regression, although other studies will need to confirm this finding130. This result was mediated by the migration of DCs to extracranial lymph nodes and resulted in systemic antitumor immunity against intracranial glioma cells. Furthermore, the activity of IL-12 or IL-18 appears to enhance the effectiveness of intratumoral injection of dendritic cells132,133. These results suggest that augmenting the local immune response with cytokines can further enhance the infiltration of T cells into the tumor parenchyma, thereby promoting the interaction of T cells with tumor pulsed antigen presenting cells.
In spite of the early successes with dendritic immunizations, several problems remain to be solved in order to fully optimize this form of therapy. These include (1) sources of dendritic cells or precursor cells, (2) methods of maturation, (3) antigen-loading strategies, (4) route of administration, (5) role of administering additional cytokines and (5) endpoints for clinical trials. To date, the major sources of DCs include direct isolation from peripheral blood or in vitro generation and a direct comparison of these DCs has not yet been made. Moreover, given the different immunological properties of immature versus mature DCs (antigen uptake and presentation, MHC expression, migratory capacity, expression of adhesion molecules or co-stimulatory activity), it will be important to determine which subset provides for an optimal vaccine. In a similar fashion, the elucidation of the best antigen source, i.e. peptides, proteins, DNA, mRNA, cell lysates, apoptoic bodies and fusions, awaits further investigation. While the majority of current trials employ subcutaneous or intratumoral immunization, the availability of other strategies (intravenous, intradermal, intranodal and intralymphatic) has not been compared, with or without the use of adjuvant cytokines. Finally, we do not have any established criteria for measuring the success of vaccine therapy although the increase in overall survival is commonly used as a study endpoint. Perhaps a better determinant of success would be delay in time to progression or recurrence, given that immunotherapeutic applications are most likely to be successful in clinical situations where the volume of residual disease is low.
Oncolytic viruses and viral gene delivery
A great deal of effort has been generated about the use of viral vectors for gene therapy of cancer. Viruses, in the form of herpes virus, adenovirus, vaccinia or reovirus, have been created to be either replication incompetent or replication competent. Initial studies utilizing replication incompetent viruses have met with limited clinical success given the lack of effective transgene expression in tissue beyond the injection site. As a result, replication-competent viruses have been created where the expression of the gene is regulated either by the introduction of tissue specific promoters or genetic modification of the viral binding site. Such oncolytic viruses have gained significant interest, given their ability to infect neoplastic cells, produce progeny and lyse the tumor cell. As such, several oncolytic viruses have been developed that exhibit antitumoral properties in both animal models and clinical studies (Table 2).
While an extensive discussion of the various replication competent viral vectors is beyond the scope of this review, several vectors are worth pointing out owing to their potential of enhancing immunotherapy. The HSV-1 mutant G207 has been shown to effectively reduce the growth of subcutaneous U87 glioma cells and prolong survival of mice injected with these cells intracranially134. A recent Phase I G207 clinical trial in humans with recurrent or progressive malignant glioma has shown that no maximally tolerated dose (MTD) or dose limiting toxicities could be established135. Additionally, while the goal of this study was to ascertain a safety profile for this treatment, a therapeutic benefit was suggested. Currently, Phase Ib/II trials have begun in hopes verifying safety and tolerability of intratumoral G207 injections for malignant glioma.
The adenovirus ONYX-015 is another oncolytic replication competent virus which is being investigated for the treatment of malignant glioma in human clinical trials. This virus selectively replicates within and lyses cells with defects in p53 or the p53 pathway136. ONYX-015 has demonstrated effective antitumor activity in animal studies and Phases I and II trials for treatment of head and neck cancers have shown safety and potential efficacy as well137-140. Additionally, the recently published results of a Phase I trial for the treatment of glioma have demonstrated safety with injection of ONYX-015 within resection cavities141.
Newcastle disease virus (NDV) is an enveloped paramyxovirus that has been found to have selectively increased replication in neoplastic (as compared with non-neoplastic) cells, prompting interest in its use as an oncolytic virus142. Several animal studies have demonstrated effective tumor regression in fibrosarcoma and neuroblastoma cells using the 73-T strain administered intratumorally and systemically143-145. Interestingly, the literature also reveals case reports of patients with GBM treated with intravenous NDV resulting in progressive tumor shrinkage and long-term survival146,147.
Lastly, reovirus, a non-enveloped virus associated with mild respiratory and gastrointestinal tract symptoms in humans, is known to infect and proliferate in cells with unregulated Ras pathway activity. Since Ras pathway dysregulation is common in gliomas (coupled with the cytolytic activity of reovirus at the end of its replication cycle), the use of this virus for oncolytic therapy has become attractive. SCID mice implanted in the flank with the glioblastoma cell line U87 had significantly decreased tumor growth compared with control following intratumoral injection of reovirus148. Intratumoral/intracerebral injection of reovirus into glioma-bearing SCID mice resulted in significant tumor regression-however, significant virus related toxicities were noted in these immunodeficient hosts149. Phase I dose-escalation trials with intratumoral/intracranial injection in patients with recurrent malignant glioma are in progress150.
The significance of viruses in the potential treatment of gliomas lies not only in their inherent oncolytic ability, but more importantly, in their ability to further enhance immunotherapy (Table 3). For instance, HSV has been used to deliver IL-4, IL-10 and IL-12 against experimental glioma151-153. In fact, the combination of HSV/IL-4 was shown to augment the oncolytic effect of HSV alone and improve the survival of mice with experimental brain tumors. Likewise, local expression of IL-12 via HSV was shown to increase Th1 response and significantly increase the survival of mice with intracranial tumors. The effects observed with HSV have also been documented with adenoviral vectors for the delivery of IL-4, IL-12 and TNF-α154-156 and vaccinia mediated delivery of IL-2 and IL-12117. In all instances, mice intracerebrally implanted with viral vectors producing IL-2, IL-4, IL-12 or TNF-α survived significantly longer than those implanted with non-cytokine secreting vectors. These results further confirm the use of local cytokine delivery against brain tumors and when used in combination with oncolytic therapy, suggest a powerful means for targeted brain tumor therapy.
Without a doubt, immunotherapeutic approaches for malignant glioma are here to stay. We now have significant preclinical evidence regarding the safety and efficacy of different immunologie approaches. Furthermore, a number of these immune based therapies are currently in different phases of human clinical trials. Two are worth particular attention, given their common origin, method of delivery, and potential for changing the treatment of malignant glioma.
The first study is based on the expression of IL-4 receptors on malignant gliomasistt. The observation that cultured human glioma cell lines, as well as a large proportion of GBMs in situ, express IL-4 receptors has led to the use of IL-4 molecules fused with cytotoxins as a treatment for these cancers158-160. Several studies using proteins with IL-4 receptor binding domains fused to Pseudomonas aeruginosa toxins have been investigated in human patients164-164. By means of convectionenhanced delivery, these cytotoxins have been shown to have acceptable safety and toxicity profiles. A newly proposed phase III trial will hopefully confirm the effectiveness of this antitumor strategy. The second, and more promising trial, is based on IL-13 receptor expression on malignant gliomas164. This receptor is not only over-expressed on high grade gliomas but, in fact, serves as a marker of tumor progression166. Convectionenhanced delivery of IL-13/Pseudomonas exotoxin has been tested in preliminary phase I/II trials with extremely favorable results16 . The drug has recently been designed by the FDA for fast track drug development and is currently undergoing a large-scale, international, prospective and randomized phase III study.
While convection-enhanced delivery of cytotoxins targeted against glioma-specific antigens represents an exciting approach against malignant brain tumors, our ability to identify unique antigens, which are uniformly expressed in all glial tumors, remains a significant challenge. Moreover, while the capacity of tumors to develop antigen variants in the setting of ongoing therapy has been shown to be responsible for tumor recurrence and treatment failure, our ability to target these cells has met with limited success. Future studies will have to aim not only at identifying new surface markers on high grade tumors but also at markers of tumor transformation. The ability of resident CNS antigen-presenting cells to effectively present these antigens and stimulate appropriate T cells constitutes an area of active interest. Whether via cytokine-mediated augmentation of tumor-specific T cells or via clonal expansion of virally transduced T cells with tumor- specific TCRs, it is becoming increasingly clear that our ability to destroy a large tumor mass depends on a sufficient number of primed CTLs. In addition, recent identification of regulatory T cells (Treg) and their capacity to inhibit the immune response within tumor stroma has opened a new area for glioma immunotherapy. Shifting the balance from tolerance to response will be critical in enhancing the antitumor response, and the ability to target Tregs will play an important role in this process. The promise of immunotherapy against malignant brain tumors is here; the capacity to effectively employ it remains a challenge which awaits further investigations and appropriate clinical trials.
We gratefully acknowledge the artistic assistance of Lydia M. Johns who prepared the figures which appear in this manuscript.
1 Takeuchi O. Hoshino K, Kawai T. et al. Differential roles of TLR2 and TLR4 in recognition of gram-negative and gram-positive bacterial cell wall components. Immunity 1999; 11: 443-151
2 Olson JK, Miller SD. Microglia initiate central nervous system innate and adaptive immune responses through multiple TLRs. J Immunol 2004; 173: 3916-3924
3 Diefenbach A, Jamteson AM, Liu SD. et al. Ligands for the murine NKG2D receptor: Expression by tumor cells and activation of NK cells and macrophages. Nat Immunol 2000; 1: 119-126
4 Friese MA. Platten M. Lutz SZ. et al. MICA/NKG2D-mediated immunogene therapy of experimental gliomas. Cancer Res 2003; 63: 8996-9006
5 Hermisson M, Strik H, Rieger J. et al. Expression and functional activity of heat shock proteins in human glioblastoma multiforme. Neurology 2000; 54: 1357-1365
6 Kato M, Herz F, Kato S, et al. Expression of stress-response (heatshock) protein 27 in human brain tumors: an immunohistochemical study. Acta Neuropathol (Bert) 1992. 83: 420-J22
7 Kato S, Morita T, Takenaka T, et al. Stress-response (heat-shock) protein 90 expression in tumors of the central nervous system: An immunohistochemical study. Acta Neuropathol (Bert) 1995; 89: 184-188
8 Raulet DH. Roles of the NKG2D immunoreceptor and its ligands. Naf Rev Immunol 2003; 3: 781-790
9 Nguyen MD, Julien JP, Rivest S. Innate immunity: The missing link in neuroprotection and neurodegeneration? Nat Rev Neurosci 2002; 3: 216-227
10 Medzhitov R, Janeway CA, Jr. Decoding the patterns of self and nonself by the innate immune system. Science 2002; 296: 298300
11 Janeway C, Travers P, Walport M, et al. Immunobiology: The immune system in health and disease. New York: Current Biology Publications. 1999
12 Prins RM, Liau LM. Immunology and immunolherapy in neurosurgical disease. Neurosurgery 2003; 53: 144-152; discussion 152-153
13 Lampson LA. Basic principles of CNS immunology. In: Youmans J. ed. Neurological surgery. Philadelphia: Saunders, 2002: pp. 673-688
14 Cserr H, Knopf P. Cervical lymphatics, the blood brain barrier, and the immunoreactivity of the brain. In: Keane R, Mickey W, eds. Immunology of the nervous system. New York: Oxford University Press, 1997: pp. 134-154
15 Aloisi F, Ria F, Penna G, et al. Microglia are more efficient than astrocytes in antigen processing and in Th1 but not Th2 cell activation. J Immunol 1998; 160: 4671-4680
16 Aloisi F. Immune function of microglia. Glia 2001; 36: 165-179
17 Issazadeh S, Navikas V, Schaub M, et al. Kinetics of expression of costimulatory molecules and their ligands in murine relapsing experimental autoimmune encephalomyelitis in vivo. I lmmunol 1998; 161: 1104-1112
18 Williams K, Ulvestad E, Antel JP. B7/BB-1 antigen expression on adult human microglia studied in vitro and in situ. Eur J Immunol 1994; 24: 3031-3037
19 Mickey WF. Basic principles of immunological surveillance of the normal central nervous system. Glia 2001; 36: 118-124
20 de Vos AF, van Meurs M, Brok HP, et al. Transfer of central nervous system autoantigens and presentation in secondary lymphoid organs. J Immunol 2002; 169: 5415-5423
21 Walker PR, Calzascia T, Schnuriger V, ef al. The brain parenchyma is permissive for full antitumor CTL effector function, even in the absence of CD4 T cells. J Immunol 2000; 165: 31283135
22 Hickey WF, Hsu BL, Kimura H. T-lymphocyte entry into the central nervous system. J Neurosci Res 1991; 28: 254-260
23 Lampson LA. Beyond inflammation: Site-directed immunotherapy. Immunol Today 1998; 19: 17-22
24 Perry VH, Anthony DC, Bolton SJ, et al. The blood-brain barrier and the inflammatory response. Mol Med Today 1997; 3: 335-341
25 Dix AR, Brooks WH, Roszman TL, et al. Immune defects observed in patients with primary malignant brain tumors. J Neuroimmunol 1999; 100: 216-232
26 Engelhardt B, Wolburg-Buchholz K, Wolburg H. Involvement of the choroid plexus in central nervous system inflammation. Microsc Res Tech 2001; 52: 112-129
27 Gordon FL, Nguyen KB, White CA, et al. Rapid entry and downregulation of T cells in the central nervous system during the reinduction of experimental autoimmune encephalomyelitis. J Neuroimmunol 2001; 112: 15-27
28 Sampson JH, Archer GE, Ashley DM, et al. Subcutaneous vaccination with irradiated, cytokine-producing tumor cells stimulates CD8+ cell-mediated immunity against tumors located in the 'immunologically privileged' central nervous system. Proc Natl Acad Sci USA 1 996; 93: 10399-10404
29 Gordon LB, Nolan SC, Cserr HF, ef al. Growth of P511 mastocytoma cells in BALB/c mouse brain elicits CTL response without tumor elimination: A new tumor model for regional central nervous system immunity. J lmmunol 1997; 159: 23992408
30 McGeer PL, ltagaki S, McGeer EG. Expression of the histocompatibility glycoprotein HLA-DR in neurological disease. Acta Neuropathol (Berl) 1988; 76: 550-557
31 McGeer PL, ltagaki S, Boyes BE, et al. Reactive microglia are positive for HLA-DR in the substantia nigra of Parkinson's and Alzheimer's disease brains. Neurology 1988; 38: 1285-1291
32 Sethna MP, Lampson LA. Immune modulation within the brain: Recruitment of inflammatory cells and increased major histocompatibility antigen expression following intracerebral injection of interferon-gamma. ] Neuroimmunol 1991; 34: 121-132
33 Phillips LM, Lampson LA. Site-specific control of T cell traffic in the brain: T cell entry to brainstem vs. hippocampus after local injection of IFN-gamma. J Neuroimmunol 1999; 96: 218-227
34 Phillips LM, Simon PJ, Lampson LA. Site-specific immune regulation in the brain: differential modulation of major histocompatibility complex (MHC) proteins in brainstem vs. hippocampus. J Comp Neurol 1999; 405: 322-333
35 Parney IF, Farr-Jones MA, Chang LJ, ef al. Human glioma immunobiology in vitro: implications for immunogene therapy. Neurosurgery 2000; 46: 1169-77; discussion 77-8.
36 Weller M, Frei K, Groscurth P, ef al. Anti-Fas/APO-1 antibodymediated apoptosis of cultured human glioma cells. Induction and modulation of sensitivity by cytokines. J Clin Invest 1994; 94: 954-964
37 Ashley DM, Sampson JH, Archer GE, ef al. A genetically modified allogeneic cellular vaccine generates MHC class I-restricted cytotoxic responses against tumor-associated antigens and protects against CNS tumors in vivo. J Neuroimmunol 1997; 78: 34-46
38 Chi DD, Merchant RE, Rand R, et al. Molecular detection of tumor-associated antigens shared by human cutaneous melanomas and gliomas. Am J Pathol 1997; 150: 2143-2152
39 Kurpad SN, Zhao XG, Wikstrand CJ, ef al. Tumor antigens in astrocytic gliomas. Glia 1995; 15: 244-256
40 McLendon RE, Wikstrand CJ, Matthews MR, et al. Gliomaassociated antigen expression in oligodendroglial neoplasms. Tenascin and epidermal growth factor receptor. J Histochem Cytochem 2000; 48: 1103-1110
41 Sampson JH, Crotty LE, Lee S, et al. Unarmed, tumor-specific monoclonal antibody effectively treats brain tumors. Proc Natl Acad Sci USA 2000; 97: 7503-7508
42 Holladay FP, Heitz T, Chen YL, et al. Successful treatment of a malignant rat glioma with cytotoxic T lymphocytes. Neurosurgery 1992; 31: 528-533
43 Dong Y, Benveniste EN. Immune function of astrocytes. Glia 2001; 36: 180-190
44 Carpentier PA, Begolka WS, Olson JK, et al. Differential activation of astrocytes by innate and adaptive immune stimuli. Glia 2004; 49: 360-374
45 Aloisi F, Penna C, Cerase J, ef al. IL-12 production by central nervous system microglia is inhibited by astrocytes. J Immunol 1997; 159: 1604-1612
46 Matsumoto Y, Ohmori K, Fujiwara M. Immune regulation by brain cells in the central nervous system: Microglia but not astrocytes present myelin basic protein to encephalitogenic T cells under in vivo-mimicking conditions. Immunology 1 992; 76: 209-216
47 Ito A, Shinkai M, Honda H, et al. Augmentation of MHC class I antigen presentation via heat shock protein expression by hyperthermia. Cancer Immunol Immunother 2001; 50: 515-522
48 Prins RM, Liau LM. Cellular immunity and immunotherapy of brain tumors. Front Biosci 2004; 9: 3124-3136
49 Yang I, Kremen TJ, Ciovannone AJ, et al. Modulation of major histocompatibility complex Class I molecules and major histocompatibility complex-bound immunogenic peptides induced by interferon-alpha and interferon-gamma treatment of human glioblastoma multiforme. J Neurosurg 2004; 100: 310-319
50 Wiendl H, Mitsdoerffer M, Hofmeister V, et al. A functional role of HLA-G expression in human gliomas: An alternative strategy of immune escape. I lmmunol 2002; 168: 4772-4780
51 Amiot L, Onno M, Lamy T, et al. Loss of HLA molecules in B lymphomas is associated with an aggressive clinical course. Br J Haematol 1998; 100: 655-663
52 Luboldt HJ, Kubens BS, Rubben H, ef al. Selective loss of human leukocyte antigen class I allele expression in advanced renal cell carcinoma. Cancer Res 1996; 56: 826-830
53 Marincola FM, Shamamian P, Alexander RB, et al. Loss of HLA haplotype and B locus down-regulation in melanoma cell lines. J Immunol 1994; 153: 1225-1237
54 Wiendl H, Mitsdoerffer M, Weller M. Hide-and-seek in the brain: A role for HLA-G mediating immune privilege for glioma cells. Semin Cancer Biol 2003; 13: 343-351
55 Gabrilovich DI, Chen HL, Girgis KR, ef al. Production of vascular endothelial growth factor by human tumors inhibits the functional maturation of dendritic cells. Nat Med 1996; 2: 1096-1103
56 Munn DH, Sharma MD, Lee JR, et al. Potential regulatory function of human dendritic cells expressing indoleamine 2,3dioxygenase. Science 2002; 297: 1867-1870
57 Prins RM, Scott GP, Merchant RE, ef al. Irradiated tumor cell vaccine for treatment of an established glioma. II. Expansion of myeloid suppressor cells that promote tumor progression. Cancer Immunol Immunother 2002; 51: 190-199
58 Morford LA, Elliott LH, Carlson SL, et al. T cell receptor-mediated signaling is defective in T cells obtained from patients with primary intracranial tumors. J Immunol 1997; 159: 4415-4425
59 Prins RM, Graf MR, Merchant RE. Cytotoxic T cells infiltrating a glioma express an aberrant phenotype that is associated with decreased function and apoptosis. Cancer lmmunol lmmunother 2001; 50: 285-292
60 Morford LA, Dix AR, Brooks WH, ef al. Apoptotic elimination of peripheral T lymphocytes in patients with primary intracranial tumors. I Neurosurg 1999; 91: 935-946
61 Brooks WH, Latta RB, Mahaley MS, et al. Immunobiology of primary intracranial tumors. Part 5: Correlation of a lymphocyte index and clinical status. J Neurosurg 1981; 54: 331-337
62 Elliott LH, Brooks WH, Roszman TL. Activation of immunoregulatory lymphocytes obtained from patients with malignant gliomas. J Neurosurg 1987; 67: 231-236
63 Roszman T, Elliolt L, Brooks W. Modulation of T-cell function by gliomas. Immunol Today 1991; 12: 370-374
64 Olofsson A, Miyazono K, Kanzaki T, et al. Transforming growth factor-beta 1. -beta 2, and -beta 3 secreted by a human glioblastoma cell line. Identification of small and different forms of large latent complexes. J Biol Chem 1992; 267: 19482-19488
65 Kuppner MC, Hamou MF, Sawamura Y, et al. Inhibition of lymphocyte function by glioblastoma-derived transforming growth factor beta 2. J Neurosurg 1989; 71:211-217
66 Kehrl JH. Roberts AB, Wakefield LM, et al. Transforming growth factor beta is an important immunomodulatory protein for human B lymphocytes. J Immunol 1986; 137: 3855-3860
67 Rook AH, Kehrl JH. Wakefield LM. et al. Effects of transforming growth factor beta on the functions of natural killer cells: Depressed cytolytic activity and blunting of interferon responsiveness. J Immunol 1986; 136: 3916-3920
68 Huber D, Philipp I, Fontana A. Prolease inhibitors interfere with the transforming growth factor-beta-dependenl but not the transforming growth factor-beta-independent pathway of tumor cell-mediated immunosuppression. J Immunol 1992; 148: 277284
69 Ranges CE. Figari IS, Espevik T. et al. Inhibition of cytotoxic T cell development by transforming growth factor beta and reversal by recombinant tumor necrosis factor alpha. J Exp Med 1987; 166: 991-998
70 Kehrl |H. Wakefield LM. Roberts AB. et al. Production of transforming growth factor beta by human T lymphocytes and its potential role in the regulation of T cell growth. J Exp Med 1986; 163: 1037-1050
71 Garcia CM, Darland DC, Massingham LI, et al. Endolhelial cellastrocyte interactions and TGF beta are required for induction of blood-neural barrier properties. Brain Res Dev Brain Res 2004; 152: 25-38
72 Zuber P, Kuppner MC, De Tribolel N. Transforming growth factor-beta 2 down-regulates HLA-DR antigen expression on human malignant glioma cells. Eur J Immunol 1988; 18: 16231626
73 Resnicoff M, Sell C, Rubini M. et al. Rat glioblasloma cells expressing an antisense RNA to the insulin-like growth factor-1 (IGF-I) receptor are nonlumorigenic and induce regression of wild-type tumors. Cancer Res 1994; 54: 2218-2222
74 Jensen RL. Growth factor-mediated angiogenesis in the malignant progression of glial tumors: A review. Surg Neurol 1998; 49: 189195; discussion 196
75 Yamanaka R, Tanaka R, Yoshida S, et al. Suppression of TGFbetal in human gliomas by retroviral gene transfection enhances susceptibility to LAK cells. J Neurooncol 1999; 43: 27-34
76 Hjelmeland MD, Hjelmeland AB, Sathomsumetee S, et al. SB431542. a small molecule transforming growth factor-betareceptor antagonist, inhibits human glioma cell line proliferation and motility. Mol Cancer Ther 2004; 3: 737-745
77 Kuppner MC, Sawamura Y. Hamou MF, et al. Influence of PGE2and cAMP-modulating agents on human glioblastoma cell killing by interleukin-2-activated lymphocytes. J Neunxurg 1990; 72: 619-625
78 Wojtowicz-Praga S. Reversal of tumor-induced immunosuppression by TGF-beta inhibitors. Invest New Drugs 2003; 21: 21-32
79 Hishii M, Nitta T, Ishida H, et al. Human glioma-derived interleukin-10 inhibits antitumor immune responses in vitro. Neumsurgery 1995; 37: 1160-1166; discussion 1166-1167
80 Huettner C, Czub S, Kerkau S. et al. Interleukin 10 is expressed in human gliomas in vivo and increases glioma cell proliferation and molility in vitro. Anticancer Res 1997; 17: 3217-3224
81 Berman RM, Suzuki T, Tahara H, et al. Systemic administration of cellular IL-10 induces an effective, specific, and long-lived immune response against established tumors in mice. J Immunol 1996; 157: 231-238
82 Albert ML, Darnell JC. Bender A, et al. Tumor-specific killer cells in paraneoplastic cerebellar degeneration. Nar Med 1998; 4: 1321-1324
83 Krakowski ML, Owens T. The central nervous system environment controls effector CD4+ T cell cytokine profile in experimental allergic encephalomyelitis. fur J Immunol 1997; 27: 2840-2847
84 Click RP, Lichlor T, de Zoeten E, et al. Prolongation of survival of mice with glioma treated with semiallogeneic flbroblasts secreting interleukin-2. Neumsurgery 1999; 45: 867-874
85 Okada H, Ciezeman-Smits KM, Tahara H, et al. Effective cytokine gene therapy against an inlracranial glioma using a retrovirally transduced IL-4 plus HSVtk tumor vaccine. Gene Ther 1999; 6: 219-226
86 Dranoff C. CM-CSF-based cancer vaccines. Immunol Rev 2003; 188: 147-154
87 Sampalh P, Hanes J. DiMeco F. et al. Paracrine immunotherapy with interleukin-2 and local chemotherapy is synergistic in the treatment of experimental brain tumors. Cancer Res 1999; 59: 2107-2114
88 Ferrantini M, Ciovarelli M, Modesti A. et al. IFN-alpha 1 gene expression into a metastatic murine adenocarcinoma (TS/A) results in CD8+ T cell-mediated tumor rejection and development of antitumor immunity. Comparative studies with IFNgamma-producing TS/A cells. J Immunol 1994; 153: 4604-4615
89 Hiroishi K, luting T, Tahara H, ef al. Interferon-alpha gene therapy in combination with CD80 transduction reduces lumorigenicity and growth of established tumor in poorly immunogenic tumor models. Gene Ther 1999; 6: 1988-1994
90 Norton HM, Anderson D, Hemandez P. et al. A gene therapy for cancer using intramuscular injection of plasmid DNA encoding inlerferon alpha. Proc Nail Acad Sci USA 1999; 96: 1553-1558
91 Lo CH, Lee SC, Wu PY, et al. Antilumor and antimetastatic activity of IL-23. J Immunol 2003; 171: 600-607
92 Osaki T. Hashimolo W, Gambotto A. et al. Potent anlitumor effects mediated by local expression of the mature form of the inlerferon-gamma inducing factor, interleukin-18 (IL-18). Gene Ther 1999; 6: 808-815
93 Tahara H, Zitvogel L. Storkus WJ. et al. Effective eradication of established murine tumors with IL-12 gene therapy using a polycistronic retroviral vector. J Immunol 1995; 154: 6466-6474
94 Lumniczky K. Desaknai S, Mangel L, et al. Local tumor irradiation augments the antitumor effect of cytokine-producing autologous cancer cell vaccines in a murine glioma model. Cancer Gene Ther 2002; 9: 44-52
95 Okada H, Pollack IF. Cytokine gene therapy for malignant glioma. Expert Opin Biol Ther 2004; 4: 1609-1620
96 Yu IS, Burwick JA, Dranoff G, et al. Gene therapy lor metastalic brain tumors by vaccination with granulocyte-macrophage colony-stimulating factor-transduced tumor cells. Hum Gene Ther 1997; 8: 1065-1072
97 Wakimolo H, Abe ), Tsunoda R, et al. Intensified anlitumor immunity by a cancer vaccine that produces granulocytemacrophage colony-stimulating factor plus interleukin 4. Cancer Res 1996, 56: 1828-1833
98 Herrlinger U, Kramm CM, Johnston KM, et al. Vaccination for experimental gliomas using GM-CSF-transduced glioma cells. Cancer Gene Trier 1997; 4: 345-352
99 Lefranc F, Cool V, Velu T, et al. Granulocyte macrophage-colony stimulating factor gene transfer to induce a protective anlitumoral immune response against the 9L rat gliosarcoma model. Int J Oncol 2002; 20: 1077-1085
100 Parney IF, Farr-Jones MA, Kane K, et al. Human autologous in vitro models of glioma immunogene therapy using B7-2, GMCSF, and IL12. Can I Neurol Sci 2002; 29: 267-275
101 Parney IF, Petruk KC, Zhang C, et al. Granulocyte-macrophage colony-stimulating factor and B7-2 combination immunogene therapy in an allogeneic Hu-PBL-SCID/beige mouse-human glioblastoma multiforme model. Hum Gene Ther 1997; 8: 1073-1085
102 Wallenfriedman MA, Conrad JA, DelaBarre L. ef al. Effects of continuous localized infusion of granulocyte-macrophage colony-stimulating factor and inoculations of irradiated glioma cells on tumor regression. J Neurosurg 1999; 90: 1064-1071
103 Jean WC, Spellman SR. Wallenfriedman MA. ef al. Effects of combined granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-2, and interleukin-12 based immunotherapy against intracranial glioma in the rat. J Neurooncol 2004; 66: 39-49
104 Soool RE, Fakhrai H, Shawler D, et al. Interleukin-2 gene therapy in a patient with glioblasloma. Gene Ther 1995; 2: 164-167
105 Lichtor T, Click RP. Cytokine immuno-gene therapy for treatment of brain tumors. J Neurooncol 2003; 65: 247-259
106 Click RP, Lichtor T, Panchal R, et al. Treatment with allogeneic interleukin-2 secreting fibroblasts protects against the development of malignant brain tumors. J Neurooncol 2003; 64: 139146
107 Lichtor T, Click RP, Tarlock K, et al. Application of interleukin-2secreting syngeneic/allogeneic fibroblasts in the treatment of primary and metastatic brain tumors. Cancer Gene Ther 2002; 9: 464-469
108 Iwadate Y, Yamaura A, Sato Y, et al. Induction of immunity in peripheral tissues combined with intracerebral transplantation of interleukin-2-producing cells eliminates established brain tumors. Cancer Res 2001; 61: 8769-8774
109 Ishikawa E, Tsuboi K, Takano S, et al. Intratumoral injection of IL-2-activated NK cells enhances the antitumor effect of intradermally injected paraformaldehyde-fixed tumor vaccine in a rat intracranial brain tumor model. Cancer Sci 2004; 95: 98-103
110 Dillman RO, Duma CM, Schiltz PM, et al. Intracavitary placement of autologous lymphokine-activated killer (LAK) cells after resection of recurrent glioblastoma. J Immunother 2004; 27: 398-404
111 Rhines LD, Sampath P, DiMeco F, et al. Local immunotherapy with interleukin-2 delivered from biodegradable polymer microspheres combined with interstitial chemotherapy: A novel treatment for experimental malignant glioma. Neurosurgery 2003; 52: 872-879; discussion 879-880
112 Okada H, Villa L, Attanucci J, et al. Cytokine gene therapy of gliomas: Effective induction of therapeutic immunity to intracranial tumors by peripheral immunization with interleukin-4 transduced glioma cells. Gene Ther 2001; 8: 1157-1166
113 Okada H, Lieberman FS, Edington HD, et al. Autologous glioma cell vaccine admixed with interleukin-4 gene transfected fibroblasts in the treatment of recurrent glioblastoma: Preliminary observations in a patient with a favorable response to therapy. J Neurooncol 2003; 64: 13-20
114 Iwadate Y, Namba H, Sakiyama S, et al, lnterleukin-12-mediated induction of systemic immunity in the periphery and recruitment of activated T cells into the brain produce limited antitumor effects compared with interleukin-2. Int J Mol Med 2002; 10: 741-747
115 DiMeco F, Rhines LD, Hanes J, ef al. Paracrine delivery of IL-12 against intracranial 9L gliosarcoma in rats. J Neurosurg 2000; 92: 419-427
116 Yang SY, Liu H, Zhang JN. Gene therapy of rat malignant gliomas using neural stem cells expressing IL-12. DNA Cell Biol 2004; 23: 381-389
117 Ehtesham M, Kabos P, Kabosova A, ef al. The use of interleukin 12-secreting neural stem cells for the treatment of intracranial glioma. Cancer Res 2002; 62: 5657-5663
118 Roy EJ, Gawlick U, Orr BA, et al. IL-12 treatment of endogenously arising murine brain tumors. J Immunol 2000; 165: 7293-7299
119 Kishima H, Shimizu K, Miyao Y, et al. Systemic interleukin 12 displays anti-tumour activity in the mouse central nervous system. Br J Cancer 1998; 78: 446-453
120 Ni HT, Spellman SR, Jean WC, et al. Immunization with dendritic cells pulsed with tumor extract increases survival of mice bearing intracranial gliomas. J Neurooncol 2001; 51: 1-9
121 Insug O, Ku C, Ertl HC, et al. A dendritic cell vaccine induces protective immunity to intracranial growth of glioma. Anticancer Res 2002; 22: 613-621
122 Saito R, Mizuno M, Nakahara N, et al. Vaccination with tumor cell lysate-pulsed dendritic cells augments the effect of IFN-beta gene therapy for malignant glioma in an experimental mouse intracranial glioma. Int J Cancer 2004; 111: 777-782
123 Kikuchi T, Akasaki Y, Abe T, ef al. Vaccination of glioma patients with fusions of dendritic and glioma cells and recombinant human interleukin 12. J Irnmunother 2004; 27: 452-459
124 Rutkowski S, De Vleeschouwer S, Kaempgen E, et al. Surgery and adjuvant dendritic cell-based tumour vaccination for patients with relapsed malignant glioma, a feasibility study. Br J Cancer 2004; 91: 1656-1662
125 Yamanaka R, Abe T, Yajima N, et al. Vaccination of recurrent glioma patients with tumour lysate-pulsed dendritic cells elicits immune responses: results of a clinical phase I/II trial. Br J Cancer 2003; 89: 1172-1179
126 de Vleeschouwer S, van Calenbergh F, Demaerel P, et al. Transient local response and persistent tumor control in a child with recurrent malignant glioma: Treatment with combination therapy including dendritic cell therapy. Case report. J Neurosurg Spine 2004; 100: 492-497
127 Yu JS, Liu G, Ying H, et al. Vaccination with tumor lysate-pulsed dendritic cells elicits antigen-specific, cytotoxic T-cells in patients with malignant glioma. Cancer Res 2004; 64: 49734979
128 Yu JS, Wheeler CJ, Zeltzer PM, et al. Vaccination of malignant glioma patients with peptide-pulsed dendritic cells elicits systemic cytotoxicity and intracranial T-cell infiltration. Cancer Res 2001; 61: 842-847
129 Caruso DA, Orme LM, Neale AM, et al. Results of a phase 1 study utilizing monocyte-derived dendritic cells pulsed with tumor RNA in children and young adults with brain cancer. Neurooncol 2004; 6: 236-246
130 Kikuchi T, Akasaki Y, Abe T, et al. Intratumoral injection of dendritic and irradiated glioma cells induces anti-tumor effects in a mouse brain tumor model. Cancer Immunol Immunother 2002; 51: 424-430
131 Ehtesham M, Kabos P, Cutierrez MA, ef al. intratumoral dendritic cell vaccination elicits potent tumoricidal immunity against malignant glioma in rats. J Immunother 2003; 26: 107-116
132 Yamanaka R, Tsuchiya N, Yajima N, ef al. Induction of an antitumor immunological response by an Intratumoral injection of dendritic cells pulsed with genetically engineered Semliki Forest virus to produce interleukin-18 combined with the systemic administration of interleukin-12. J Neurosurg 2003; 99: 746-753
133 Yamanaka R, Yajima N, Tsuchiya N, et al. Administration of interleukin-12 and -18 enhancing the antitumor immunity of genetically modified dendritic cells that had been pulsed with Semliki Forest virus-mediated tumor complementary DNA. 7 Neurosurg 2002; 97: 1184-1190
134 Mineta T, Rabkin SD, Yazaki T, et al. Attenuated multi-mutated herpes simplex virus-1 for the treatment of malignant gliomas. Nat Med 1995; 1: 938-943
135 Markert JM, Medlock MD, Rabkin SD, et al. Conditionally replicating herpes simplex virus mutant, G207 for the treatment of malignant glioma: Results of a phase I trial. Gene Ther2000; 7: 867-74
136 Bischoff JR, Kirn DH, Williams A, et al. An adenovirus mutant that replicates selectively in p53-deficient human tumor cells. Science 1996; 274: 373-376
137 Ganly I, Kim D, Eckhardt G, ef ai. A phase I study of Onyx-015, an E1B attenuated adenovirus, administered intratumorally to patients with recurrent head and neck cancer. Clin Cancer Res 2000; 6: 798-806
138 Heise C, Sampson-Johannes A, Williams A, et al. ONYX-015, an E1B gene-attenuated adenovirus, causes tumor-specific cytolysis and antitumoral efficacy that can be augmented by standard chemotherapeutic agents. Nat Med 1997; 3: 639-645
139 Nemunaitis J, Ganly I, Khuri F, ef al. Selective replication and oncolysis in p53 mutant tumors with ONYX-015, an E1B-55kD gene-deleted adenovirus, in patients with advanced head and neck cancer: A phase II trial. Cancer Res 2000; 60: 63596366
140 Khuri FR, Nemunaitis J, Ganly I, et al. A controlled trial of lntratumoral ONYX-015, a selectively-replicating adenovirus, in combination with cisplatin and 5-fluorouracil in patients with recurrent head and neck cancer. Nat Med 2000; 6: 879-885
141 Chiocca EA, Abbed KM, Tatter S, et al. A phase I open-label, dose-escalation, multi-institutional trial of injection with an E1BAttenuated adenovirus, ONYX-015, into the peritumoral region of recurrent malignant gliomas, in the adjuvant setting. Mol Ther 2004; 10: 958-966
142 Reichard KW, Eorence RM, Cascino CJ, et al. Newcastle disease virus selectively kills human tumor cells. J Surg Res 1992; 52: 448-453
143 Phuangsab A, Lorence RM. Reichard KW, et al. Newcastle disease virus therapy of human tumor xenografts: antilumor effects of local or systemic administration. Cancer Lett 2001; 172: 27-36
144 Lorence RM, Kalubig BB, Reichard KW, et al. Complete regression of human fibrosarcoma xenografts after local Newcastle disease virus therapy. Cancer Res 1994; 54: 60176021
145 Lorence RM, Reichard KW, Kalubig BB, et al. Complete regression of human neuroblastoma xenografts in athymic mice after local Newcastle disease virus therapy. J Natl Cancer Inst 1994; 86: 1228-1233
146 Csalary LK, Bakacs T. Use of Newcastle disease virus vaccine (MTH-68/H) in a patient with high-grade glioblastoma.JIAMA 1999; 281: 1588-1589
147 Csalary LK, Gosztonyi C, Szeberenyi J, et al. MTH-68/H oncolytic viral treatment in human high-grade gliomas. J Neurooncol 2004; 67: 83-93
148 Coffey MC, Strong IE, Forsyth PA, et al. Reovirus therapy of tumors with activated Ras pathway. Science 1998; 282: 13321334
149 Wilcox ME, Yang W. Senger D, et al. Reovirus as an oncolytic agent against experimental human malignant gliomas. J Natl Cancer Inst 2001; 93: 903-912
150 Shah AC, Benos D, Cillespie CY, et al. Oncolytic viruses: clinical applications as vectors for the treatment of malignant gliomas. J Neurooncol 2003; 65: 203-226
151 Miyatake S, Martuza RL, Rabkin SD. Defective herpes simplex virus vectors expressing thymidine kinase for the treatment of malignant glioma. Cancer Gene Ther 1997; 4: 222-228
152 Parker JN, Cillespie CY, Love CE, et al. Engineered herpes simplex virus expressing IL-12 in the treatment of experimental murine brain tumors. Proc Natl Acad Sci USA 2000; 97: 22082213
153 Andreansky S, He B. van Cott J, et al. Treatment of intracranial gliomas in immunocompetent mice using herpes simplex viruses that express murine inlerleukins. Gene Ther 1998; 5: 121-130
154 Liu Y, Ehtesham M, Samoto K. et al. In situ adenoviral inlerleukin 12 gene transfer confers potent and long-lasting cytotoxic immunity in glioma. Cancer Gene Ther 2002; 9: 9-15
155 Yoshikawa K, Kajiwara K, ldeguchi M, et al. Immune gene therapy of experimental mouse brain tumor with adenovirusmediated gene transfer of murine interleukin-4. Cancer Immunol Immunother 2000; 49: 23-33
156 Yamini B, Yu X. Cillespie GY, et al. Transcriptional targeting of adenovirally delivered tumor necrosis factor alpha by temozolomide in experimental glioblastoma. Cancer Res 2004; M: 63816384
157 Chen B, Timiryasova TM, Haghighat P, et al. Low-dose vaccinia virus-mediated cytokine gene therapy of glioma. J Immunother 2001; 24: 46-57
158 Puri RK, Leland P, Kreitman RJ, et al. Human neurological cancer cells express interleukin-4 (IL-4) receptors which are targets for the toxic effects of IL4-Pseudomonas exotoxin chimeric protein. Int I Cancer 1994; 58: 574-581
159 Joshi BH, Leland P, Silber I, ef al. IL-4 receptors on human medulloblastoma tumours serve as a sensitive target for a circular permuted IL-4-Pseudomonas exotoxin fusion protein. Br J Cancer 2002; 86: 285-291
160 Joshi BH, Leland P, Asher A, et al. In situ expression of interleukin-4 (IL-4) receptors in human brain tumors and cytotoxicity of a recombinant IL-4 cytoloxin in primary glioblastoma cell cultures. Cancer Res 2001; 61: 8058-8061
161 Weber F, Asher A, Bucholz R, et al. Safety, tolerability, and tumor response of IL4-Pseudomonas exoloxin (NBI-3001) in patients with recurrent malignant glioma. J Neurooncol 2003; 64: 125137
162 Weber FW, Floeth F. Asher A, et al. Local convection enhanced delivery of IL4-Pseudomonas exotoxin (NBI-3001) for treatment of patients with recurrent malignant glioma. Acta Neurochir Suppl 2003; 88: 93-103
163 Kawakami M. Kawakami K. Puri RK. Interleukin-4-Pseudomonas exotoxin chimeric fusion protein for malignant glioma therapy. J Neurooncol 2003. 65: 15-25
164 Rainov NC, Heidecke V. Long term survival in a patient with recurrent malignant glioma treated with intratumoral infusion of an IL4-targeted toxin (NBI-3001). J Neurooncol 2004; 66: 197201
165 Debinski W, Obiri NI. Powers SK. et al. Human glioma cells overexpress receptors for interleukin 13 and are extremely sensitive to a novel chimeric protein composed of interleukin 13 and pseudomonas exotoxin. Clin Cancer Res 1995; 1: 12531258
166 Debinski W, Gibo DM. Hulel SW. et al. Receptor for inlerleukin 13 is a marker and therapeutic target for human high-grade gliomas. Clin Cancer Res 1999; 5: 985-990
167 Kunwar S. Convection enhanced delivery of IL13-PE38QQR for treatment of recurrent malignant glioma: Presentation of interim findings from ongoing phase 1 studies. Acta Neurochir Suppl 2003; 88: 105-111
168 Graf MR, Prins RM, Poulsen GA, et al. Contrasting effects of interleukin-2 secretion by rat glioma cells contingent upon anatomical location: Accelerated tumorigenesis in the central nervous system and complete rejection in the periphery. J Neuroimmunol 2003; 140: 49-60
169 Saleh M, Wiegmans A, Malone Q. et al. Effect of in situ retroviral interleukin-4 transfer on established intracranial tumors. J Mail Cancer Inst 1999; 91: 438-445
170 Hunter WD, Martuza RL, Feigenbaum F, et al. Attenuated, replication-competent herpes simplex virus type 1 mutant G207: Safety evaluation of inlracerebral injection in nonhuman primates. J Virol 1999; 73: 6319-6326
171 Kesari S, Randazzo BP, Valyi-Nagy T. et al. Therapy of experimental human brain tumors using a neuroattenuated herpes simplex virus mutant. Lab Invest 1995; 73: 636-648
172 Randazzo BP. Kesari S. Cesser RM. et al. Treatment of experimental intracranial murine melanoma with a neuroattenuated herpes simplex virus 1 mutant. Virology 1995; 211: 94101
173 Valyi-Nagy T, Farced MU, O'Keefe JS, et al. The herpes simplex virus type 1 strain 17+ gamma 34.5 deletion mutant 1716 is avirulent in SCID mice. J Gen Virol 1994; 75 (Pt 8): 20592063
174 Rampling R, Cruickshank G, Papanastassiou V, et al. Toxicity evaluation of replication-competent herpes simplex virus (ICP 34.5 null mutant 1716) in patients with recurrent malignant glioma. Gene Ther 2000; 7: 859-866
175 Harrow S, Papanaslassiou V, Harland J. et al. HSV1716 injection into the brain adjacent to tumour following surgical resection of high-grade glioma: Safety data and long-term survival. Gene Ther 2004; 11: 1648-1658
176 Papanastassiou V. Rampling R, Fraser M, et al. The potential for efficacy of the modified (ICP 34.5(-)) herpes simplex virus HSVI716 following intratumoural injection into human malignant glioma: A proof of principle study. Gene Ther 2002: 9: 398406
177 Lorence RM, Pecora AL, Major PP, ef al. Overview of phase I studies of intravenous administration of PV701, an oncolytic virus. Curr Opin Mol Ther 2001; 5: 618-624
178 Csatary LK, Eckhardt S, Bukosza I, et al. Attenuated veterinary virus vaccine for the treatment of cancer. Cancer Detect Prev 1993; 17: 619-627
179 Yang WQ, Lun X, Palmer CA, et al. Efficacy and safety evaluation of human reovirus type 3 in immunocompelent animals: Racine and nonhuman primates. Clin Cancer Res 2004; 10: 8561-8576
180 Oncolytics Biotech releases REOLYSIN phase I clinical trial results. Expert Rev Anticancer Ther 2002; 2: 139
181 Wei MX, Li F, Ono Y, et al. Effects on brain tumor cell proliferation by an adenovirus vector that bears the interleukin-4 gene. J Neurovirol 1998; 4: 237-241
Christian W. Sikorski and Maciej S. Lesniak
Division of Neurosurgery, The University of Chicago Pritzker School of Medicine, 584 7 South Maryland Avenue, MC 3026, Chicago, Illinois 60637, USA
Correspondence and reprints requests to: Maciej S. Lesniak, Division of Neurosurgery, The University of Chicago Pritzker School of Medicine, 5841 South Maryland Avenue, MC 3026, Chicago, Illinois 60637, USA. [firstname.lastname@example.org] Accepted for publication June 2005.
Copyright Maney Publishing Oct 2005
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