Effects of continuous localized infusion of granulocyte-macrophage colony-stimulating factor and inoculations of irradiated glioma cells on tumor regression

Immunotherapeutic Strategies for Malignant Glioma

BACKGROUND

Despite advances in surgery, radiation therapy, and chemotherapy, only modest improvement has been achieved in the survival of patients with malignant gliomas.

METHODS

The authors review the immunologic aspects of gliomas, potential targets for therapy, and issues surrounding current immunotherapeutic strategies directed against malignant gliomas.

RESULTS

The blood-brain barrier and the purported immunological privilege of the brain are not necessarily insurmountable obstacles to effective immunotherapy for brain tumors. Preclinical studies suggest a number of potential therapeutic avenues. Translational studies offer the prospect of providing substantial new information about immunological trafficking in the nervous system and suggesting the most fruitful approaches to immunotherapy for malignant gliomas.

CONCLUSIONS

More effective adjuvant treatments for malignant gliomas are needed. The applicability of immunological approaches in the treatment of these tumors warrants continued study.

Cytokines: shifting the balance between glioma cells and tumor microenvironment after irradiation

Malignant gliomas invariably recur after irradiation, showing radioresistance. Meanwhile, cranial irradiation can bring some risk for developing cognitive dysfunction. There is increasing evidence that cytokines play their peculiar roles in these processes. On the one hand, cytokines directly influence the progression of malignant glioma, promoting or suppressing tumor progression. On the other hand, cytokines indirectly contribute to the immunologic response against gliomas, exhibiting pro-inflammatory or immunosuppressive activities. We propose that cytokines are not simply unregulated products from tumor cells or immune cells, but mediators finely adjust the balance between glioma cells and tumor microenvironment after irradiation. The paper, therefore, focuses on the changes of cytokines after irradiation, analyzing how these mediate the response of tumor cells and normal cells to irradiation. In addition, cytokine-based immunotherapeutic strategies, accompanied with irradiation, for the treatment of gliomas are also discussed.

Integration of autologous dendritic cell-based immunotherapy in the standard of care treatment for patients with newly diagnosed glioblastoma: results of the HGG-2006 phase I/II trial

PURPOSE

Dendritic cell (DC)-based tumor vaccination has rendered promising results in relapsed high-grade glioma patients. In the HGG-2006 trial (EudraCT 2006-002881-20), feasibility, toxicity, and clinical efficacy of the full integration of DC-based tumor vaccination into standard postoperative radiochemotherapy are studied in 77 patients with newly diagnosed glioblastoma.

PATIENTS AND METHODS

Autologous DC are generated after leukapheresis, which is performed before the start of radiochemotherapy. Four weekly induction vaccines are administered after the 6-week course of concomitant radiochemotherapy. During maintenance chemotherapy, 4 boost vaccines are given. Feasibility and progression-free survival (PFS) at 6 months (6mo-PFS) are the primary end points. Overall survival (OS) and immune profiling, rather than monitoring, as assessed in patients' blood samples, are the secondary end points. Analysis has been done on intent-to-treat basis.

RESULTS

The treatment was feasible without major toxicity. The 6mo-PFS was 70.1 % from inclusion. Median OS was 18.3 months. Outcome improved significantly with lower EORTC RPA classification. Median OS was 39.7, 18.3, and 10.7 months for RPA classes III, IV, and V, respectively. Patients with a methylated MGMT promoter had significantly better PFS (p = 0.0027) and OS (p = 0.0082) as compared to patients with an unmethylated status. Exploratory "immunological profiles" were built to compare to clinical outcome, but no statistical significant evidence was found for these profiles to predict clinical outcome.

CONCLUSION

Full integration of autologous DC-based tumor vaccination into standard postoperative radiochemotherapy for newly diagnosed glioblastoma seems safe and possibly beneficial. These results were used to power the currently running phase IIb randomized clinical trial.

Monocyte galactose/N-acetylgalactosamine-specific C-type lectin receptor stimulant immunotherapy of an experimental glioma. Part II: combination with external radiation improves survival

Background

A peptide mimetic of a ligand for the galactose/N-acetylgalactosamine-specific C-type lectin receptors (GCLR) exhibited monocyte-stimulating activity, but did not extend survival when applied alone against a syngeneic murine malignant glioma. In this study, the combined effect of GCLRP with radiation was investigated.

Methods

C57BL/6 mice underwent stereotactic intracranial implantation of GL261 glioma cells. Animals were grouped based on randomized tumor size by magnetic resonance imaging on day seven. One group that received cranial radiation (4 Gy on days seven and nine) only were compared with animals treated with radiation and GCLRP (4 Gy on days seven and nine combined with subcutaneous injection of 1 nmol/g on alternative days beginning on day seven). Magnetic resonance imaging was used to assess tumor growth and correlated with survival rate. Blood and brain tissues were analyzed with regard to tumor and contralateral hemisphere using fluorescence-activated cell sorting analysis, histology, and enzyme-linked immunosorbent assay.

Results

GCLRP activated peripheral monocytes and was associated with increased blood precursors of dendritic cells. Mean survival increased (P < 0.001) and tumor size was smaller (P < 0.02) in the GCLRP + radiation group compared to the radiation-only group. Accumulation of dendritic cells in both the tumoral hemisphere (P < 0.005) and contralateral tumor-free hemisphere (P < 0.01) was associated with treatment.

Conclusion

Specific populations of monocyte-derived brain cells develop critical relationships with malignant gliomas. The biological effect of GCLRP in combination with radiation may be more successful because of the damage incurred by tumor cells by radiation and the enhanced or preserved presentation of tumor cell antigens by GCLRP-activated immune cells. Monocyte-derived brain cells may be important targets for creating effective immunological modalities such as employing the receptor system described in this study.

Development of a successful antitumor therapeutic model combining in vivo dendritic cell vaccination with tumor irradiation and intratumoral GM-CSF delivery

Vaccination of dendritic cells (DC) combined with GM-CSF secreting tumor cells has shown good therapeutic efficacy in several tumor models. Nevertheless, the engineering of GM-CSF secreting tumor cell line could represent a tedious step limiting its application for treatment in patients. We therefore developed in rats, an "all in vivo" strategy of combined vaccination using an in vivo local irradiation of the tumor as a source of tumor antigens for DC vaccines and an exogenous source of GM-CSF. We report here that supplying recombinant mGM-CSF by local injections or surgical implantation of osmotic pumps did not allow reproducing the therapeutic efficacy observed with in vitro prepared combined vaccines. To bypass this limitation possibly due to the short half-life of recombinant GM-CSF, we have generated adeno-associated virus coding for mGM-CSF and tested their efficacy to transduce tumor cells in vitro and in vivo. The in vivo vaccines combining local irradiation and AAV2/1-mGM-CSF vectors showed high therapeutic efficacy allowing to cure 60% of the rats with pre-implanted tumors, as previously observed with in vitro prepared vaccines. Same efficacy has been observed with a second generation of vaccines combining DC, local tumor irradiation, and the controlled supply of recombinant mGM-CSF in poloxamer 407, a biocompatible thermoreversible hydrogel. By generating a successful "all in vivo" vaccination protocol combining tumor radiotherapy with DC vaccines and a straightforward supply of GM-CSF, we have developed a therapeutic strategy easily translatable to clinic that could become accessible to a much bigger number of cancer patients.

Preliminary report on tumor stem cell/B cell hybridoma vaccine for recurrent glioblastoma multiforme

BACKGROUND

Glioblastoma multiforme (GBM), the most aggressive glioma, presents with a rapid evolution and relapse within the first year, which is attributed to the persistence of tumor stem cells (TSC) and the escape of immune surveillance. Mixed leukocyte culture (MLC) cytoimplant has been shown to function as a powerful intratumor pro-inflammatory cytokine pump. Tumor B-cell hybridoma (TBH) vaccines have been shown to function as antigen-presenting cells. We evaluated the toxicity and efficiency of each treatment alone and in combination.

PATIENTS AND METHODS

In an open study, 12 consecutive patients were evenly divided into 3 groups, each group receiving 3 different treatments. Patients in Group 1 were treated, after diagnosis, with debulking surgery (DS)+radiotherapy (Rx), and after the first relapse underwent DS+MLC treatment. Patients in Group 2 were similarly treated but after the first relapse underwent DS+MLC+TBH. Finally, patients in Group 3 were similarly treated but after the first relapse underwent DS+TBH. Nestin PAP stain assessed TSC participation in TBH.

RESULTS

Treatment with MLC had strong and rapid therapeutic effects, but was limited in duration and induced various degrees of brain inflammation. Treatment with MLC+TBH acted synergistically, provoking a rapid, strong and lasting therapeutic response but also generating different degrees of brain inflammation. A lasting therapeutic effect without generating high degrees of brain inflammation occurred in patients treated with TBH vaccine alone.

CONCLUSION

TSC vaccine consisting of TBH alone seems to have potent adjuvant reactions overcoming both persistence of tumor stem cells and immune escape of GBM without provoking an encephalitic reaction.

In vivo vaccination with tumor cell lysate plus CpG oligodeoxynucleotides eradicates murine glioblastoma

Dendritic cell (DC) vaccines have shown antitumor activity in experimental glioma models and in human glioma patients. The typical approach has been to generate the vaccine ex vivo, by pulsing DCs with tumor lysate or peptides, then administering the DCs back into the patient. This process requires significant expertise and expenses in DC generation. Immature DCs which present antigens to T cells in the absence of appropriate costimulatory signals can lead to induction of immune tolerance. Recent studies have shown that coadministration of toll-like receptor 9 agonists, CpG oligodeoxynucleotides, can promote DC vaccines to break immune tolerance to tumor antigens. We investigated the therapeutic efficacy of in vivo DC activation, by directly administering glioma cell lysate with CpG oligodeoxynucleotides (CpG/lysate), in glioma-bearing mice. Subcutaneous vaccination with CpG/lysate induced a significant increase (P<0.05) in the number of total T cells and activated DCs in lymph nodes draining the vaccination site as compared to mice treated with CpG or tumor lysate alone. Mice vaccinated with CpG/lysate exhibited over 2 times greater median survival than mice in the control groups (P<0.05). Up to 55% of mice vaccinated with CpG/lysate were rendered tumor-free as assessed by survival and bioluminescent imaging. Splenocytes taken from mice vaccinated with CpG/lysate elaborated significantly more IFN-gamma production and displayed greater tumor cell lysis activity compared with the control groups (P<0.05). These results suggest direct vaccination with CpG/lysate provides an alternative and effective approach to induce host antitumor immunity and warrants clinical investigation in the immunotherapy of cancer.

Efficacy of an osmotic pump delivered, GM-CSF-based tumor vaccine in the treatment of upper aerodigestive squamous cell carcinoma in rats

PURPOSE

Upper aerodigestive tract (UADT) cancer has not experienced significant overall survival improvement for over 20 years, and no successful treatments for systemic disease exist. Most patients with UADT cancer experience immune suppression, therefore immune restorative therapies may offer promise for these patients. We presently tested the efficacy of granulocyte macrophage-colony stimulating factor (GM-CSF) delivered via 28-day continuous infusion pump, in combination with irradiated tumor cells, in a flank model of UADT cancer.

METHODS

Five groups of rats were inoculated with syngeneic mucosally derived squamous carcinoma cells (FAT-7). Osmotic minipumps were implanted in the contralateral flank to deliver GM-CSF at 0 (PBS), 0.1, 1, 10, or 100 ng/day (n = 6 per group) for 28 days; 10(6) irradiated FAT-7 cells (ITC) were injected at the site of the GM-CSF infusion on days 0, 3, 7, 14, and 21 immune infiltrates in tumors were analyzed.

RESULTS

Rats that received 10 or 100 ng/day GM-CSF/ITC had a significantly slower tumor growth rate compared to those who received 0, 0.1, or 1 ng/day (ANOVA, P < 0.01). There were increased CD 4+, CD 8+, and CD 68+ cells in tumors of GM-CSF/ITC treated animals over controls.

CONCLUSION

GM-CSF (10 or 100 ng/day) delivered locally via osmotic pump with ITC slows the growth rate of mucosally derived squamous cell carcinoma in rats while improving immune cell infiltrates. The efficacy of locally delivered GM-CSF immunotherapy in this model may be a first step toward this immunotherapy strategy for humans.

Nonspecific immunotherapy with intratumoral lipopolysaccharide and zymosan A but not GM-CSF leads to an effective anti-tumor response in subcutaneous RG-2 gliomas

PURPOSE

Nonspecific stimulation of cells of the immune system may be useful in generating an anti-tumor response for a variety of cancers and may work synergistically with currently available cytotoxic therapies. In this study we examined the response of syngeneic rat gliomas to treatment with several nonspecific stimulators of dendritic cells and macrophages alone or in combination with radiation therapy.

EXPERIMENTAL DESIGN

RG-2 gliomas were implanted subcutaneously and treated with intratumoral (IT) injections of the toll-like receptor (TLR) ligands lipopolysaccharide (LPS) and zymosan A (ZymA) and the cytokine granulocyte-macrophage colony stimulating factor (GM-CSF). Combination treatment with IT LPS and single-fraction external beam radiotherapy (EBRT) was also evaluated.

RESULTS

Treatment with IT LPS and ZymA delayed tumor growth compared to saline controls. Multiple doses of both substances were superior to single doses, and led to complete tumor regression in 71% (LPS) and 50% (ZymA) of animals. GM-CSF showed no anti-tumor effects in this study. Combinations of IT LPS and EBRT appeared to have a synergistic effect in delaying tumor growth. Rechallenge studies and IT LPS treatment of RG-2 tumors in nude rats suggested the importance of T cells in this treatment paradigm.

CONCLUSIONS

Direct IT treatment with the TLR ligands LPS and ZymA are effective in generating an anti-tumor response. These treatments may synergize with cytotoxic therapies such as EBRT, and appear to require T cells for a successful outcome.

Angiogenesis meets immunology: Cytokine gene therapy of cancer

Delivery of cytokine genes at the tumor site in pre-clinical models has been shown to recruit host inflammatory cells followed by inhibition of tumor growth. This local effect is often accompanied by systemic protection mediated by the immune system, mainly by CD8(+) T and NK cells. On this basis, cytokine gene-transduced tumor cells have widely been used as vaccines in clinical trials, which have shown good safety profiles and some local responses but substantial lack of systemic efficacy. Are these findings the end of the story? Possibly not, if major improvements will be attained in the coming years. These should be directed at the level of gene selection and delivery, in order to identify the optimal cytokine and achieve efficient and durable cytokine expression, and at the level of improving immune stimulation, i.e. by co-administration of co-stimulatory molecules including B7 and CD40, or boosting the expression of tumor antigens or MHC class I molecules. Interestingly, some of the cytokines which have shown encouraging anti-tumor activity, including IFNs, IL-4, IL-12 and TNF-alpha, are endowed with anti-angiogenic or vasculotoxic effects, which may significantly contribute to local tumor control. Therapeutic exploitation of this property may result in the design of novel approaches which, by maximizing immune-stimulating and anti-angiogenic effects, could possibly lead to starvation of established tumors in patients.

Cellules dendritiques et gliomes : un espoir en immunothérapie ?

Immunotherapy has been explored for several decades to try to improve the prognosis of gliomas, but until recently no therapeutic benefit has been achieved. The discovery of dendritic cells, the most potent professional antigen presenting cells to initiate specific immune response, and the possibility of producing them ex vivo gave rise to new protocols of active immunotherapy. In oncology, promising experimental and clinical therapeutic results were obtained using these dendritic cells loaded with tumor antigen. Patients bearing gliomas have deficit antigen presentation making this approach rational. In several experimental glioma models, independent research teams have showed specific antitumor responses using these dendritic cells. Phase I/II clinical trials have demonstrated the feasibility and the tolerance of this immunotherapeutic approach. In neuro-oncology, the efficiency of such an approach remains to be established, similarly in oncology where positive phase III studies are missing. Nevertheless, dendritic cells comprise a complex network which is only partially understood and capable of generating either immunotolerance or immune response. Numerous parameters remain to be explored before any definitive conclusion about their utility as an anticancer weapon can be drawn. It seems however logical that immunotherapy with dendritic cells could prevent or delay tumor recurrence in patients with minor active disease. A review on glioma and dendritic cells is presented.

Effects of irradiated tumor vaccine and infusion of granulocyte-macrophage colony-stimulating factor and interleukin-12 on established gliomas in rats

PURPOSE

We investigated granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-12 (IL-12) infused into the injection site of irradiated tumor vaccine (TV) as therapy for gliomas.

METHODS

Rats with subcutaneous RT-2 gliomas were treated with irradiated TV and/or subcutaneous infusion of GM-CSF and/or IL-12 via osmotic minipump 5 days after tumor-cell inoculation. Cytotoxic T lymphocyte (CTL) and natural killer (NK) cell activity were analyzed to investigate immune responses. Rats with intracerebral gliomas were treated with irradiated TV and infused GM-CSF/IL-12 3 days after tumor-cell inoculation. Tumor growth rates and animal survival were followed. Survivors were re-challenged with wild-type RT-2 cells subcutaneously or intracerebrally to study long-term anti-tumor immunity.

RESULTS

Rats with subcutaneous gliomas treated with GM-CSF and IL-12 or TV plus GM-CSF or IL-12 did not have increased survival rate (P>0.2), but did have prolonged survival time (P<0.05); in contrast, rats treated with TV plus GM-CSF/IL-12 had increased survival rate (P<0.05) and prolonged survival time (P<0.05) compared with controls. These treatment strategies showed enhanced CTL and NK cell activities. Rats with intra-cerebral gliomas treated with TV plus GM-CSF/IL-12 did not have increased survival rate (P=0.11), but did have prolonged survival time (P<0.0001). Survivors in each group were re-challenged with wild-type RT-2 cells, and all had long-term survival.

CONCLUSIONS

Irradiated TV plus continuous localized infusion of GM-CSF/IL-12 may induce a tumor-specific anti-tumor immune response on established subcutaneous or intra-cerebral gliomas, and such a treatment strategy deserves consideration as adjuvant treatment for glioma.

Effects of syngeneic cellular vaccinations alone or in combination with GM-CSF on the weakly immunogenic F98 glioma model

Cancer vaccines are one approach for the treatment of brain tumors. Most experimental studies are performed on so-called "immunogenic" brain tumor models such as the rat 9L glioma which does not reflect characteristics of human glioblastoma. In the present study, we tested syngeneic cellular vaccinations alone or in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF) on the weakly immunogenic F98 glioma model. Previous studies have shown the efficacy of this treatment on the 9L glioma model. Fisher rats received an intracerebral implantation of F98 cells. Three days later, two subcutaneous vaccinations with irradiated F98 cells were realized in presence or absence of GM-CSF. This scheme of vaccination induced a systemic cellular and humoral immune response capable of in vitro cytolytic activity against F98 cells. However, no significant differences in survival times were noted between vaccinated and untreated animals. Animals vaccinated with GM-CSF or without GM-CSF had respectively a survival time of 26 +/- 2.1 and 25 +/- 4.4 days following tumor challenge versus 26.5 +/- 2.4 days for untreated rats. Fourteen days after the intracerebral tumor implantation, the tumors of vaccinated animals showed a robust infiltration by T lymphocytes, NK cells, dendritic cells, granulocytes and CD11b/c+ myeloid cells. This infiltration was nearly absent in untreated animals except for CD11b/c+ myeloid cells. This study shows that, contrary to the 9L glioma model, the F98 glioma model is resistant to syngeneic cellular vaccinations although a strong peripheral and intratumoral immune response can be induced. These results suggest that the F98 glioma is an attractive model to understand the mechanisms of glioma immunotherapy resistance.

Immunotherapy for malignant glioma: current approaches and future directions

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.

Highly Successful Therapeutic Vaccinations Combining Dendritic Cells and Tumor Cells Secreting Granulocyte Macrophage Colony-stimulating Factor

In an attempt to induce potent immune antitumor activities, we investigated, within the rat 9L gliosarcoma model, distal therapeutic vaccinations associating three therapies: dendritic cell vaccination, intratumoral granulocyte macrophage colony-stimulating factor (GM-CSF) gene transfer, and tumor apoptosis induction. Vaccines of dendritic cells coinjected with processed GM-CSF secreting 9L cells induced systemic responses, resulting in the complete regression of distant preimplanted 9L tumor masses in, with the best strategy, 94% of male rats. All of the cured rats developed a long-term resistance to a rechallenge with parental cells. The curative responses were correlated with the detection of elevated specific cytotoxic activities and a CD4+, CD8+ T cell-, and natural killer (NK) cell-mediated IFN-gamma production. The survival rate of the rat seemed more directly linked to the amount of GM-CSF secreted by the transduced tumor cells, which in turn depended on the toxicity of the apoptosis-inducing treatment, than to the level of apoptosis induced. Unexpectedly, alive GM-CSF secreting 9L cells became apoptotic when injected in vivo. Thus we documented the positive role of apoptosis in the induction of therapeutic antitumor responses by comparing, at equal GM-CSF exogenous supply, the effects of dendritic cells coinjected with apoptotic or necrotic 9L cells. The data showed the superior therapeutic efficiency of combined vaccines containing apoptotic tumor cells. In conclusion, vaccinations with dendritic cells associated with apoptotic tumor cells secreting GM-CSF show a very high therapeutic potency that should show promise for the treatment of human cancer.

Dendritic Cell-Based Immunotherapy of Malignant Gliomas

The failure of conventional treatment modalities for gliomas, in spite of tremendous progress in research in the past two decades, has led to increasing interest in alternative treatment strategies, including immunotherapy. It has become evident that vaccination with dendritic cells (DC), designed to express tumor antigens, is a potent strategy to elicit anti-tumor immune response in both pre-clinical and clinical settings. Various methods have been applied in order to induce DC to express tumor antigens including: pulsing with isolated tumor peptides or whole tumor lysate; fusion with tumor cells; and pulsing with apoptotic tumor cells. Herein, we review the recent progress in DC biology with regard to tumor immunity and discuss current DC-based strategies and future prospects in immunotherapy for malignant gliomas.

Characterization of 9L glioma model of the Wistar rat

The aim of our study was to develop and characterize solid brain tumors in Wistar rats, which could be used in investigations concerning the molecular mechanisms that lay beneath the genesis of the gliomas as well as in the testing of curative potentials of various therapeutics. The tumors were induced by intracerebral inoculation of 9L glioma cells and characterized by morphometrical, histological and immunohistochemical analysis after 7, 14 and 21 postimplantation days. Immunohistochemical characterization included detection of the nuclear antigene Ki-67 as the proliferative cell marker, GFAP as a tracer of reactive gliosis surrounding the tumor mass, and CD4/CD8 and ED1 antigens, as markers of the immunological response. Our results showed that after 7 days all experimental animals developed solid, well-circumcised tumors, which were clearly separated from the surrounding brain tissue. Tumors showed progressive growth from the 7th to the 21st day despite the observed immunological response starting after 14 days. Histologically tumors were hypercellular with neovascularization and necrosis. These results indicate that reproducible morphometric evaluation can be performed on 9L tumors growing in immunocompetent Wistar rats, enabling its use as an animal tumor model for the evaluation of various therapeutic approaches.

Current and future strategies for the treatment of malignant brain tumors

Glioblastoma (GB) is the most common subtype of primary brain tumor in adults. These tumors are highly invasive, very aggressive, and often infiltrate critical neurological areas within the brain. The mean survival time after diagnosis of GB has remained unchanged during the last few decades, in spite of advances in surgical techniques, radiotherapy, and also chemotherapy; patients' survival ranges from 9 to 12 months after initial diagnosis. In the same time frame, with our increasing understanding and knowledge of the physiopathology of several cancers, meaningful advances have been made in the treatment and control of several cancers, such as breast, prostate, and hematopoietic malignancies. Although a number of the genetic lesions present in GB have been elucidated and our understanding of the progressions of this cancer has increased dramatically over the last few years, it has not yet been possible to harness this information towards developing effective cures. In this review, we will focus on the classical ways in which GB is currently being treated, and will introduce a novel therapeutic modality, i.e., gene therapy, which we believe will be used in combination with classical treatment strategies to prolong the life-span of patients and to ultimately be able to control and/or cure these brain tumors. We will discuss the use of several vector systems that are needed to introduce the therapeutic genes within either the tumor mass, if these are not resectable, or the tumor bed, after successful tumor resection. We also discuss different therapeutic modalities that could be exploited using gene therapy, i.e., conditional cytotoxic approach, direct cytotoxicity, immunotherapy, inhibition of angiogenesis, and the use of pro-apoptotic genes. The advantages and disadvantages of each of the current vector systems available to transfer genes into the CNS are also discussed. With the advances in molecular techniques, both towards the elucidation of the physiopathology of GB and the development of novel, more efficient and less toxic vectors to deliver putative therapeutic genes into the CNS, it should be possible to develop new rationale and effective therapeutic approaches to treat this devastating cancer.

Cell-mediated immunotherapy: a new approach to the treatment of malignant glioma

BACKGROUND

The dismal prognosis for patients harboring intracranial gliomas has prompted an intensive search for effective treatment alternatives such as immunotherapy. Our increased knowledge in basic immunology, glioma immunobiology, and molecular biology may lead to the development of effective, rational immunotherapy approaches.

METHODS

The authors reviewed the literature on glioma immunology, the status of tumor vaccine therapy and on novel techniques to monitor the tumor-specific immune response.

RESULTS

Experimental conditions currently exist whereby potent antitumor cell-mediated immune responses can be generated. However, clinically, no therapeutic regimen has proven effective. Obstacles to establishing an effective immunotherapy regimen are the lack of a well-defined glioma-specific antigen, the heterogeneity of tumor cells in gliomas, and the modulating effect of the glioma itself on the immune system. Unique strategies to overcome these barriers are being developed.

CONCLUSIONS

Novel strategies to generate an anti-glioma immune response through use of dendritic cell vaccination, directed cytokine delivery, gene-based immunotherapy, and reversal of tumor-induced immunosuppression are promising. These strategies carry the potential of overcoming the resistance of gliomas to immunotherapeutic manipulation and, undoubtedly, will become a part of our future therapeutic armamentarium.

Effects of irradiated tumor vaccine and continuous localized infusion of granulocyte-macrophage colony-stimulating factor on neuroblastomas in mice

BACKGROUND/PURPOSE

Immunomodulatory treatment has been proposed as a feasible strategy for neuroblastoma treatment. In this study, the antitumor effects of a continuous localized subcutaneous infusion of granulocyte-macrophage colony-stimulating factor (GM-CSF) into the injection site of irradiated tumor vaccine used as a source of tumor antigens on mouse neuroblastoma were investigated.

METHODS

A/J mice were inoculated subcutaneously with wild type neuro-2a neuroblastoma cells and then treated with 5 doses of irradiated tumor vaccine or continuous localized infusion of GM-CSF (1 ng/d or 10 ng/d) via an osmotic minipump. Survival rates and survival times were compared among the groups. Tumor growth rates and animal survival times were followed and compared among different groups. Histologic and immunohistochemical analyses were performed to observe the immune response induced by various treatment strategies.

RESULTS

Tumor growth rates were reduced significantly and survival times prolonged significantly by the treatment using tumor vaccine and continuous infusion of 10 ng/d of GM-CSF when compared with the control group (P <.05). One mouse treated with tumor vaccine and a 10 ng/d infusion of GM-CSF showed tumor regression and long-term survival, and no tumor growth was noted after rechallenge with wild-type neuro-2a cells. In contrast, using tumor vaccine only, or tumor vaccine combined with a 1 ng/d infusion of GM-CSF was less effective than tumor vaccine combined with a 10 ng/d infusion of GM-CSF (P <.05). Infusion of GM-CSF alone had no antitumor effects. Immunohistologic analyses showed significant CD4+ and CD8+ T cell infiltration of the tumor in the mice treated with tumor vaccine and a 10 ng/d infusion of GM-CSF.

CONCLUSIONS

The results suggest that an irradiated tumor vaccine combined with continuous localized infusion of GM-CSF may induce a tumor-specific antitumor immune response that can suppress tumor growth and prolong survival. Such a treatment strategy deserves consideration as a possible adjuvant treatment for neuroblastoma.

The combination of X-ray-mediated radiosurgery and gene-mediated immunoprophylaxis for advanced intracerebral gliosarcomas in rats

Rats with advanced, imminently lethal, approximately 4 mm diameter, left-sided intracerebral 9L gliosarcoma (9LGS), a well characterized malignant tumor with some similarities to human high-grade astrocytomas, were used as a therapy model 14 days post-implantation of 10(4) cells. Such tumor-bearing rats die within two weeks (median, 6 days) thereafter if untreated. However, if these tumors are exposed on day 14 to 12-25 Gy of an electron-equilibrated 6 MV photon beam (radiosurgery), survival is extended about 5-6 fold to a median of 34 days, but long-term survival (> 1 year) is increased only to approximately 18%. Multiple subcutaneous inoculations of radiation-disabled 9LGS cells post-radiosurgery (immunoprophylaxis) extended lifespan and long-term (> 1 year) survival minimally (median, 37 days; 25%, respectively). In sharp contrast, radiosurgery followed by multiple subcutaneous inoculations of radiation-disabled 9LGS cells that had been transfected with granulocyte macrophage colony stimulating factor (GMCSF), a cytokine with demonstrated immune-enhancing properties (i.e. gene-mediated immunoprophylaxis, GMIMPR) increased long-term survival to approximately 67%. To our knowledge, these results are the first to show that the combination of photon radiosurgery and GMIMPR is effective for an advanced, imminently lethal brain tumor in a mammal. These data raise the possibility that GMIMPR following radiation therapy might prove effective for the treatment of some human malignant gliomas.

Cytokine gene therapy of gliomas: effective induction of therapeutic immunity to intracranial tumors by peripheral immunization with interleukin-4 transduced glioma cells

To provide a means for comparing strategies for cytokine gene therapy against intracranial (i.c.) tumors, we generated rat gliosarcoma 9L cells transfected with interleukin-4 (9L-IL4), interleukin-12 (9L-IL12), granulocyte-macrophage colony-stimulating factor (9L-GMCSF) or interferon-alpha (9L-IFNalpha). To simulate direct and highly efficient cytokine gene delivery, cytokine transfected 9L tumors were implanted i.c. into syngeneic rats. i.c. injection led to tumor-outgrowth in the brain and killed most animals, whereas these cell lines were rejected following intradermal (i.d.) injection. Cytokine-expressing i.c. 9L tumors, however, had a greater degree of infiltration by immune cells compared with control, mock-transfected 9L-neo, but to a lesser degree than i.d. cytokine-expressing tumors. Tumor angiogenesis was suppressed in cytokine-transfected tumors. In a prophylaxis model, i.d. vaccination with 9L-IL4 resulted in long-term survival of 90% of rats challenged i.c. with parental 9L; whereas 40% of 9L-GM-CSF, 40% of 9L-IFNalpha and 0% of 9L-IL12-immunized rats were protected. In a therapy model (day 3 i.c. 9L tumors), only i.d. immunization with 9L-IL4 had long-term therapeutic benefits as 43% of rats survived >100 days. These data indicate that peripheral immunization with 9L-IL4 had the most potent therapeutic benefit among various cytokines and approaches tested against established, i.c. 9L tumors.

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.

The combination of boron neutron-capture therapy and immunoprophylaxis for advanced intracerebral gliosarcomas in rats

Glioblastoma multiforme (GBM) is the most common primary human brain tumor. About 7000 new cases are diagnosed yearly in the USA and GBM is almost invariably fatal within a few years after it is diagnosed. Despite current neurosurgical and radiotherapeutic tumor cytoreduction methods, in most cases occult foci of tumor cells infiltrate surrounding brain tissues and cause recurrent disease. Therefore the combination of neurosurgical and radiotherapeutic debulking methods with therapies to inhibit occult GBM cells should improve prognosis. In this study we have combined boron neutron-capture therapy (BNCT), a novel binary radiotherapeutic treatment modality that selectively irradiates tumor tissue and largely spares normal brain tissue, with immunoprophylaxis, a form of active immunization initiated soon after BNCT treatment, to treat advanced, clinically relevantly-sized brain tumors in rats. Using a malignant rat glioma model of high immunogenicity, the 9L gliosarcoma, we have shown that about half of the rats that would have died after receiving BNCT debulking alone, survived after receiving BNCT plus immunoprophylaxis. Further, most of the surviving rats display immunological-based resistance to recurrent 9LGS growth six months or more after treatment. To our knowledge this study represents the first time BNCT and immunoprophylaxis have been combined to treat advanced brain tumors in rats.

Adoptive immunotherapy in patients with recurrent malignant glioma: preliminary results of using autologous whole-tumor vaccine plus granulocyte-macrophage colony–stimulating factor and adoptive transfer of anti-CD3–activated lymphocytes

Object

This trial was designed to determine the ability of autologous whole–tumor cell vaccines to induce cell-mediated immune responses in patients with recurrent malignant glioma, as well as to determine whether combining such vaccination with adoptive transfer of in vitro activated T lymphocytes prolongs patient survival.

Methods

Nineteen patients with recurrent malignant glioma, in whom previous external beam radiotherapy and at least one course of chemotherapy had failed were vaccinated twice with irradiated autologous whole tumor cells by using granulocyte-marcrophage colony–stimulating factor as an adjuvant. Patients then underwent leukapheresis followed by adoptive transfer of peripheral blood lymphocytes activated in vitro with anti-CD3 and interleukin-2. In vivo immune response, radiological response, clinical outcome, and survival were monitored.

Seventeen patients developed a delayed-type hypersensitivity (DTH) response to vaccination that appeared to be directed against the autologous tumor. In eight patients there was radiological evidence of a response and in five there was evidence of clinical improvement. Median survival was 12 months (range 6–28 months), and both the presence of a DTH response and the radiological response correlated with survival (p < 0.02 and p < 0.04, respectively).

Conclusions

These preliminary results suggest that autologous whole–tumor cell vaccines induce a cell-mediated immune response, which appears to be tumor specific in most patients. Furthermore, vaccination combined with adoptive immunotherapy with in vitro activated cells may induce a radiologically demonstrated tumor response and improved survival despite a condition of advanced disease and immunosuppression resulting from previous treatment or tumor burden. Further studies of immunotherapy are warranted.

Progress in active-specific immunotherapy of brain malignancies

Despite the significant advances in neurosurgical techniques and oncology treatment regimens, the prognosis of patients with brain malignancies remains dismal. Brain tumours remain as lethal in the beginning of this new millennium as they were 30 years ago. Among the promising treatment modalities being tested are various immunotherapeutic approaches. Development of cancer vaccines, also known as active-specific immunotherapy, for malignant brain tumours is summarised in this review. Understanding the mechanisms behind vaccinations and the initiation of immune response have helped the design and improvement of the efficacy of clinical vaccines. The emergence of the antigen-presenting properties of dendritic cells brings the cancer vaccine field into a new generation. Preclinical work on the use of dendritic cell-based vaccine for malignant brain tumours are encouraging. The move from these preliminary studies to the clinic is anticipated with high hope.

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.