Immunotherapy of neuroblastoma by an Interleukin-21-secreting cell vaccine involves survivin as antigen

Immunotherapy for neuroblastoma by hematopoietic cell transplantation and post-transplant immunomodulation

Neuroblastoma represents a relatively common childhood tumor that imposes therapeutic difficulties. High risk neuroblastoma patients have poor prognosis, display limited response to radiochemotherapy and may be treated by hematopoietic cell transplantation. Allogeneic and haploidentical transplants have the distinct advantage of reinstitution of immune surveillance, reinforced by antigenic barriers. The key factors favorable to ignition of potent anti-tumor reactions are transition to adaptive immunity, recovery from lymphopenia and removal of inhibitory signals that inactivate immune cells at the local and systemic levels. Post-transplant immunomodulation may further foster anti-tumor reactivity, with positive but transient impact of infusions of lymphocytes and natural killer cells both from the donor, the recipient or third party. The most promising approaches include introduction of antigen-presenting cells in early post-transplant stages and neutralization of inhibitory signals. Further studies will likely shed light on the nature and actions of suppressor factors within tumor stroma and at the systemic level.

State of the art in immunotherapy of neuroblastoma

Neuroblastoma (NB) is a common and deadly malignancy mostly observed in children. Evolution of therapeutic options for NB led to the addition of immunotherapeutic modalities to the previously recruited chemotherapeutic options. Molecular studies of the NB cells resulted in the discovery of many tumor-associated genes and antigens such as MYCN gene and GD2. MYCN gene and GD2 surface antigen are two of the most practical discoveries regarding immunotherapy of neuroblastoma. The GD2 antigen has been targeted in many animal and human studies including Phase III clinical trials. Even though these antigens have changed the face of pediatric neuroblastoma, they do not take as much credit in immunotherapy of adult-onset neuroblastoma. Monoclonal antibodies have been designed to detect this antigen on the surface of NB tumor cells. Despite bettering the outcomes for NB patients, current therapies still fail in many cases. Studies are underway to discover more specific tumor-associated antigens and more effective treatment options. In the current narrative, immunotherapy of NB - from emerging of this therapeutic backbone in NB to the latest discoveries regarding this malignancy - has been reviewed.

Combined immunotherapy with anti-PDL-1/PD-1 and anti-CD4 antibodies cures syngeneic disseminated neuroblastoma

Anti-PD-1 or anti-PD-L1 blocking monoclonal antibodies (mAbs) have shown potent anti-tumor effects in adult cancer patients and clinical studies have recently been started in pediatric cancers, including high-risk/relapsing neuroblastoma (NB). Therefore, we studied the effects of anti-PD-1/PD-L1 mAbs in two syngeneic models of disseminated NB generated by the injection of either Neuro2a or NXS2 cells, which express PD-L1. In addition, we tested the combination of these agents with the immune-enhancing cytokine IL-21, the Ecto-NTPDase inhibitor POM-1, an anti-CD25 mAb targeting Treg cells, or an anti-CD4 mAb. We previously showed that CD4-transient depletion removes CD4⁺CD25⁺ Treg cells and other CD4⁺CD25⁻ regulatory subsets. Here we show that mono-therapy with anti-PD-1/PD-L1 mAbs had no effect on systemic NB progression in vivo, and also their combination with IL-21, POM-1 or anti-CD25 mAb was ineffective. The combined use of anti-PD-1 with an anti-CD4 mAb mediated a very potent, CD8-dependent, synergistic effect leading to significant elongation of tumor-free survival of mice, complete tumor regression and durable anti-NB immunity. Similar results were obtained by combining the anti-PD-L1 and anti-CD4 mAbs. These findings indicate that both PD-1/PD-L1 and CD4⁺ T cell-related immune-regulatory mechanisms must be simultaneously blocked to mediate therapeutic effects in these models.

Forced co-expression of IL-21 and IL-7 in whole-cell cancer vaccines promotes antitumor immunity

Genetic modification of whole-cell cancer vaccines to augment their efficacies has a history of over two and a half decades. Various genes and gene combinations, targeting different aspects of immune responses have been tested in pursuit of potent adjuvant effects. Here we show that co-expression of two cytokine members of the common cytokine receptor γ-chain family, IL-21 and IL-7, in whole-cell cancer vaccines boosts antitumor immunity in a CD4⁺ and CD8⁺ T cell-dependent fashion. It also generates effective immune memory. The vaccine-elicited short-term effects positively correlated with enhanced infiltration of CD4⁺ and CD8⁺ effector T cells, and the long-term effects positively correlated with enhanced infiltration of effector memory T cells, especially CD8⁺ effector memory T cells. Preliminary data suggested that the vaccine exhibited good safety profile in murine models. Taken together, the combination of IL-21 and IL-7 possesses potent adjuvant efficacy in whole-cell vaccines. This finding warrants future development of IL-21 and IL-7 co-expressing whole-cell cancer vaccines and their relevant combinatorial regimens.

New immunotherapeutic strategies for the treatment of neuroblastoma

The prognosis of high-risk neuroblastoma (NB) is still poor, in spite of aggressive multimodal treatment. Recently, adjuvant immunotherapy with anti-GD2 antibodies combined with IL-2 or GM-CSF has been shown to improve survival. Several other immunotherapy strategies proved efficacy in preclinical models of NB, including different types of vaccines, adoptive cell therapies and combined approaches. The remarkable differences in the immunobiology of syngeneic models and human NB may, at least in part, limit the translation of preclinical therapies to a clinical setting. Nonetheless, several preliminary evidences suggest that new antibodies, cancer vaccines and adoptive transfer of lymphocytes, genetically engineered to acquire NB specificity, may result in clinical benefit, and clinical studies are currently ongoing.

IL-21-Expressing Mesenchymal Stem Cells Prevent Lethal B-Cell Lymphoma Through Efficient Delivery of IL-21, Which Redirects the Immune System to Target the Tumor

Interleukin (IL)-21, a proinflammatory cytokine, has been developed as an immunotherapeutic approach due to its effects on various lymphocytes, including natural killer (NK) cells and T cells; however, the clinical success in cancer patients has been limited. Recently, mesenchymal stem cells (MSCs) have emerged as vehicles for cancer gene therapy due to their inherent migratory abilities toward tumors. In the present study, we hypothesized that MSCs, genetically modified to express high levels of IL-21 (IL-21/MSCs), can enhance antitumor responses through localized delivery of IL-21. For tumor induction, BALB/c mice were injected intravenously with syngeneic A20 B-cell lymphoma cells to develop a disseminated B-cell lymphoma model. Then, 6 days following tumor induction, the tumor-bearing mice were treated with IL-21/MSCs weekly, four times. Systemic infusion of A20 cells led to hind-leg paralysis as well as severe liver metastasis in the control group. The IL-21/MSC-treated group showed delayed tumor incidence as well as improved survival, whereas the MSC- and recombinant adenovirus-expressing IL-21 (rAD/IL-21)-treated groups did not show significant differences from the untreated mice. These therapeutic effects were associated with high levels of IL-21 delivered to the liver, which prevented the formation of tumor nodules. Furthermore, the infusion of IL-21/MSCs led to induction of effector T and NK cells, while potently inhibiting immune suppressor cells. Our findings demonstrate that IL-21-expressing MSCs have the therapeutic potential to induce potent antitumor effects against disseminated B-cell lymphoma through localized IL-21 delivery and induction of systemic antitumor immunity.

IL-21: a pleiotropic cytokine with potential applications in oncology

Interleukin- (IL-) 21 is a pleiotropic cytokine that regulates the activity of both innate and specific immunity. Indeed, it costimulates T and natural killer (NK) cell proliferation and function and regulates B cell survival and differentiation and the function of dendritic cells. In addition, IL-21 exerts divergent effects on different lymphoid cell leukemia and lymphomas, as it may support cell proliferation or on the contrary induce growth arrest or apoptosis of the neoplastic lymphoid cells. Several preclinical studies showed that IL-21 has antitumor activity in different tumor models, through mechanism involving the activation of NK and T or B cell responses. Moreover, IL-21's antitumor activity can be potentiated by its combination with other immune-enhancing molecules, monoclonal antibodies recognizing tumor antigens, chemotherapy, or molecular targeted agents. Clinical phase I-II studies of IL-21 in cancer patients showed immune stimulatory properties, acceptable toxicity profile, and antitumor effects in a fraction of patients. In view of its tolerability, IL-21 is also suitable for combinational therapeutic regimens with other agents. This review will summarize the biological functions of IL-21, and address its role in lymphoid malignancies and preclinical and clinical studies of cancer immunotherapy.

The future of glioblastoma therapy: synergism of standard of care and immunotherapy

The current standard of care for glioblastoma (GBM) is maximal surgical resection with adjuvant radiotherapy and temozolomide (TMZ). As the 5-year survival with GBM remains at a dismal <10%, novel therapies are needed. Immunotherapies such as the dendritic cell (DC) vaccine, heat shock protein vaccines, and epidermal growth factor receptor (EGFRvIII) vaccines have shown encouraging results in clinical trials, and have demonstrated synergistic effects with conventional therapeutics resulting in ongoing phase III trials. Chemoradiation has been shown to have synergistic effects when used in combination with immunotherapy. Cytotoxic ionizing radiation is known to trigger pro-inflammatory signaling cascades and immune activation secondary to cell death, which can then be exploited by immunotherapies. The future of GBM therapeutics will involve finding the place for immunotherapy in the current treatment regimen with a focus on developing strategies. Here, we review current GBM therapy and the evidence for combination of immune checkpoint inhibitors, DC and peptide vaccines with the current standard of care.

Recombinant IL-21 and anti-CD4 antibodies cooperate in syngeneic neuroblastoma immunotherapy and mediate long-lasting immunity

IL-21 is an immune-enhancing cytokine, which showed promising results in cancer immunotherapy. We previously observed that the administration of anti-CD4 cell-depleting antibody strongly enhanced the anti-tumor effects of an IL-21-engineered neuroblastoma (NB) cell vaccine. Here, we studied the therapeutic effects of a combination of recombinant (r) IL-21 and anti-CD4 monoclonal antibodies (mAb) in a syngeneic model of disseminated NB. Subcutaneous rIL-21 therapy at 0.5 or 1 μg/dose (at days 2, 6, 9, 13 and 15 after NB induction) had a limited effect on NB development. However, coadministration of rIL-21 at the two dose levels and a cell-depleting anti-CD4 mAb cured 28 and 70 % of mice, respectively. Combined immunotherapy was also effective if started 7 days after NB implant, resulting in a 30 % cure rate. Anti-CD4 antibody treatment efficiently depleted CD4(+) CD25(high) Treg cells, but alone had limited impact on NB. Combination immunotherapy by anti-CD4 mAb and rIL-21 induced a CD8(+) cytotoxic T lymphocyte response, which resulted in tumor eradication and long-lasting immunity. CD4(+) T cells, which re-populated mice after combination immunotherapy, were required for immunity to NB antigens as indicated by CD4(+) T cell depletion and re-challenge experiments. In conclusion, these data support a role for regulatory CD4(+) T cells in a syngeneic NB model and suggest that rIL-21 combined with CD4(+) T cell depletion reprograms CD4(+) T cells from immune regulatory to anti-tumor functions. These observations open new perspectives for the use of IL-21-based immunotherapy in conjunction with transient CD4(+) T cell depletion, in human metastatic NB.

Immunomodulatory monoclonal antibodies combined with peptide vaccination provide potent immunotherapy in an aggressive murine neuroblastoma model

PURPOSE

Neuroblastoma is one of the commonest extracranial tumors of childhood. The majority of patients present with metastatic disease for which outcome remains poor. Immunotherapy is an attractive therapeutic approach for this disease, and a number of neuroblastoma tumor antigens have been identified. Here, we examine the therapeutic potential of combining immunomodulatory monoclonal antibodies (mAb) with peptide vaccination in murine neuroblastoma models.

EXPERIMENTAL DESIGN

Neuroblastoma-bearing mice were treated with mAb targeting 4-1BB, CD40, and CTLA-4 alone, or in combination with a peptide derived from the tumor antigen survivin (GWEDPPNDI). Survivin-specific immune response and therapeutic efficacy were assessed.

RESULTS

In the Neuro2a model, treatment of established tumor with anti-4-1BB, anti-CD40, or anti-CTLA-4 mAb results in tumor regression and long-term survival in 40% to 60% of mice. This is dependent on natural killer (NK) and CD8(+) T cells and is associated with tumor CD8(+) lymphocyte infiltrate. Successful therapy is achieved only if mAb is given to mice once tumors are established, suggesting dependence on sufficient tumor to provide antigen. In the more aggressive AgN2a and NXS2 models, single-agent mAb therapy provides ineffective therapy. However, if mAb (anti-CTLA-4) is given in conjunction with survivin peptide vaccination, then 60% long-term survival is achieved. This is associated with the generation of survivin-specific T-cell immunity, which again is only shown in the presence of tumor antigen.

CONCLUSIONS

These data suggest that the combination of antigen and costimulatory mAb may provide effective immunotherapy against neuroblastoma and may be of particular use in the minimal residual disease setting.

Bone marrow of neuroblastoma patients shows downregulation of CXCL12 expression and presence of IFN signature

BACKGROUND

At diagnosis, children with neuroblastoma (NB) present with either localized or metastatic disease. Since the mechanisms responsible for BM invasion are not well known, we investigated the transcriptome of resident BM cells from NB patients as compared to healthy children.

PROCEDURE

Ninety-two and 88 children with localized and metastatic NB, respectively, and 15 healthy children were included in the study. BM resident cells recovered from BM aspirates by immunomagnetic bead manipulation were subjected to genome-wide microarray analysis. After validation in an independent set of samples, the genes significantly modulated in resident BM cells from NB patients were tested for their diagnostic/prognostic values.

RESULTS

BM resident cells, irrespective of neoplastic cell invasion, significantly overexpressed genes involved in innate immune responses, and interferon (IFN) and IFN-DRS signatures were enriched. Genes coding for metallothioneins and zinc finger proteins, and involved in histone and nucleosome/chromatin organization were also overexpressed. Resident BM cells from NB patients significantly downregulated genes involved in cell adhesion, and in erythrocyte, myeloid, and platelet differentiation pathways. Among downregulated genes, CXCL12 expression reached near complete silencing in patients with metastatic disease. The downregulation of CXCL12 expression was independent of contact between NB cell and resident BM cell.

CONCLUSIONS

We demonstrated that NB tumor growth at the primary site can alter the BM microenvironment, and the presence of BM-infiltrating NB cells makes the alterations more pronounced. Therefore, the restoration of a BM physiological state by means of IFN-α monoclonal antibody, Sifalimumab, and selective noradrenaline receptor blockers should be further studied to ameliorate patients' clinical management.

Cytokines in neuroblastoma: from pathogenesis to treatment

Cytokines released by cancer cells or by cells of the tumor microenvironment stimulate angiogenesis, act as autocrine or paracrine growth factors for malignant cells, promote tumor cell migration and metastasis or create an immunosuppressive microenvironment. These tumor-promoting effects of cytokines also apply to neuroblastoma (NB), a pediatric neuroectodermal malignancy with frequent metastatic presentation at diagnosis and poor prognosis. IL-6 and VEGF are the best characterized cytokines that stimulated tumor growth and metastasis, while others such as IFN-γ can exert anti-NB activity by inducing tumor cell apoptosis and inhibiting angiogenesis. On the other hand, cytokines are part of the anti-NB therapeutic armamentarium, as exemplified by IL-2 and granulocyte-macrophage colony stimulating factor that potentiate the activity of anti-NB antibodies. These recent results raise hope for more efficacious treatment of this ominous pediatric malignancy.

Immunology and immunotherapy of neuroblastoma

PURPOSE

This review demonstrates the importance of immunobiology and immunotherapy research for understanding and treating neuroblastoma.

PRINCIPAL RESULTS

The first suggestions of immune system-neuroblastoma interactions came from in vitro experiments showing that lymphocytes from patients were cytotoxic for their own tumor cells and from evaluations of tumors from patients that showed infiltrations of immune system cells. With the development of monoclonal antibody (mAb) technology, a number of mAbs were generated against neuroblastoma cells lines and were used to define tumor associated antigens. Disialoganglioside (GD2) is one such antigen that is highly expressed by virtually all neuroblastoma cells and so is a useful target for both identification and treatment of tumor cells with mAbs. Preclinical research using in vitro and transplantable tumor models of neuroblastoma has demonstrated that cytotoxic T lymphocytes (CTLs) can specifically recognize and kill tumor cells as a result of vaccination or of genetic engineering that endows them with chimeric antigen receptors. However, CTL based clinical trials have not progressed beyond pilot and phase I studies. In contrast, anti-GD2 mAbs have been extensively studied and modified in pre-clinical experiments and have progressed from phase I through phase III clinical trials. Thus, the one proven beneficial immunotherapy for patients with high-risk neuroblastoma uses a chimeric anti-GD2 mAb combined with IL-2 and GM-CSF to treat patients after they have received intensive cyto-reductive chemotherapy, irradiation, and surgery. Ongoing pre-clinical and clinical research emphasizes vaccine, adoptive cell therapy, and mAb strategies. Recently it was shown that the neuroblastoma microenvironment is immunosuppressive and tumor growth promoting, and strategies to overcome this are being developed to enhance anti-tumor immunotherapy.

CONCLUSIONS

Our understanding of the immunobiology of neuroblastoma has increased immensely over the past 40 years, and clinical translation has shown that mAb based immunotherapy can contribute to improving treatment for high-risk patients. Continued immunobiology and pre-clinical therapeutic research will be translated into even more effective immunotherapeutic strategies that will be integrated with new cytotoxic drug and irradiation therapies to improve survival and quality of life for patients with high-risk neuroblastoma.

Role of common-gamma chain cytokines in NK cell development and function: perspectives for immunotherapy

NK cells are components of the innate immunity system and play an important role as a first-line defense mechanism against viral infections and in tumor immune surveillance. Their development and their functional activities are controlled by several factors among which cytokines sharing the usage of the common cytokine-receptor gamma chain play a pivotal role. In particular, IL-2, IL-7, IL-15, and IL-21 are the members of this family predominantly involved in NK cell biology. In this paper, we will address their role in NK cell ontogeny, regulation of functional activities, development of specialized cell subsets, and acquisition of memory-like functions. Finally, the potential application of these cytokines as recombinant molecules to NK cell-based immunotherapy approaches will be discussed.

Novel gamma-chain cytokines as candidate immune modulators in immune therapies for cancer

Cytokines that signal through the common-gamma chain are potent growth factors for T cells and natural killer cells. Interleukin (IL)-2, the gammac prototype, can mediate antitumor effects as a single agent or in the context of multimodality regimens but is limited by side effects and a propensity for expansion of regulatory T cells. IL-7, IL-15, and IL-21 each possess properties that can be exploited in the context of immunotherapy for cancer. Each has been demonstrated to mediate potent vaccine adjuvant effects in tumor models, and each can enhance the effectiveness of adoptive immunotherapies. Although the overlap among the agents is significant, IL-7 is uniquely immunorestorative and preferentially augments reactivity of naive populations, IL-15 potently augments reactivity of CD8 memory cells and natural killer cells, and IL-21 preferentially expands the inflammatory Th17 subset and may limit terminal differentiation of effector CD8 cells. Clinical trials of IL-7 and IL-21 have already been completed and, so far, demonstrate safety and biologic activity of these agents. Clinical trials of IL-15 are expected soon. Ultimately, these agents are expected to be most effective in the context of multimodal immunotherapy regimens, and careful clinical trial design will be needed to efficiently identify the proper doses, regimens, and settings in which to exploit their biologic properties for therapeutic gain.

Immunotherapy of melanoma by GPI-anchored IL-21 tumour vaccine involves down-regulating regulatory T cells in mouse model

In this study, we developed a tumour cell vaccine expressing a glycosylphosphatidylinositol (GPI)-anchored IL-21 to test the effect of immunotherapy of melanoma in mouse model. The results indicated that the tumour vaccine was functional, exhibiting delayed tumour growth and prolonging longevity of tumour bearing mice. The immunotherapeutic effect was associated with decreasing the numbers of CD4(+) CD25(+) Foxp3(+) Treg (Tregs) cells, increasing IFN-γ level and promoting lymphocyte-infiltration in tumour tissues. Overall, our data demonstrate that the GPI-anchored IL-21 tumour vaccine regulates immune responses at least in part by down-regulating Tregs and reveals enhanced efficacy of tumour vaccine therapy of melanoma.

Transient depletion of CD4(+) T cells augments IL-21-based immunotherapy of disseminated neuroblastoma in syngeneic mice

IL-21 is a member of the IL-2 cytokine family, produced by CD4+ T cells. We previously showed that immunotherapy (IT) with IL-21-transduced neuroblastoma cells (Neuro2a/IL-21) cured 33% of syngeneic mice bearing systemic NB. Here, we studied whether the removal of Treg cells could potentiate the therapeutic efficacy of Neuro2a/IL-21 vaccine. The administration of anti-CD25 mAb, which targets Treg cells, slightly potentiated the effect of vaccine IT (50% cure rate), but anti-CD4 mAb had a more potent effect leading to 80% cure rate. Anti-CD25 mAb, indeed, only partially depleted CD4+CD25+FoxP3+ Treg cells, whereas anti-CD4 mAb was more effective in this respect, leading to 90% depletion of Treg cells. In mice receiving vaccine+anti-CD4 mAb, which developed systemic immunity to NB, CD4+ T cells counts completely recovered in 90 days. Depletion of CD8+ T cells abrogated the effect of the combined IT, indicating a predominant role of these cells in driving the immune response. In addition, CD8+ T cells from cured mice coinjected with Neuro2a/parental cells (pc) in NOD-SCID mice completely inhibited tumor growth. Spleen cells from mice receiving Neuro2a/IL-21 vaccination showed increased expression of IFN-alpha2, -beta1 and -gamma mRNA. Moreover, mice receiving vaccine therapy alone or vaccine+anti-CD4 mAb showed increased IFN-gamma serum levels and IFN-gamma-producing CD8+ T cells were found in spleen cells. In conclusion, anti-CD4 mAb potentiated IL-21-based IT by removing Treg cells and/or their precursors and other potentially immune-suppressive CD4+ cell subsets, thus allowing the development of an IL-21-driven CD8+ T cell response, which mediates NB rejection.

Advances in cellular therapy for the treatment of thyroid cancer

Up to now, there are no curative therapies available for the subset of metastasized undifferentiated/anaplastic thyroid carcinomas. This review describes the possible use of immunocompetent cells which may help to restore the antitumor immune recognition for treating an existing tumor or preventing its recurrence. The most prominent experimental strategy is the use of dendritic cells (DCs) which are highly potent in presenting tumor antigens. Activated DCs subsequently migrate to draining lymph nodes where they present antigens to naïve lymphocytes and induce cytotoxic T cells (CTL). Alternatively to DC therapy, adoptive cell transfer may be performed by either using natural killer cells or ex vivo maturated CTLs. Within this review article we will focus on recent advances in the understanding of anti-tumor immune responses, for example, in thyroid carcinomas including the advances which have been made for the identification of potential tumor antigens in thyroid malignancies.

Therapy-induced antitumor vaccination in neuroblastomas by the combined targeting of IL-2 and TNFalpha

L19-IL2 and L19TNFalpha are fusion proteins composed of L19(scFv), specific for the angiogenesis-associated ED-B containing fibronectin isoform and IL-2 or TNFalpha. Because of the tumor targeting properties of L19, IL-2 and TNFalpha concentrate at therapeutic doses at the tumor vascular level. To evaluate the therapeutic effects of L19-IL2 and L19mTNFalpha in neuroblastoma (NB)-bearing mice, A/J mice bearing Neuro2A or NIE115 NB were systemically treated with L19-IL2 and L19mTNFalpha, alone or in combination protocols. Seventy percent of Neuro2A- and 30% of NIE115-bearing mice were cured by the combined treatment with L19-IL2 and L19mTNFalpha, and further rejected a homologous tumor challenge, indicating specific antitumor immune memory. The immunological bases of tumor cure and rejection were studied. A highly efficient priming of CD4(+) T helper cells and CD8(+) CTL effectors was generated, paralleled by massive infiltration in the tumor tissue of CD4(+) and CD8(+) T cells at day 16 after tumor cell implantation, when, after therapy, tumor volume was drastically reduced and tumor necrosis reached about 80%. The curative treatment resulted in a long-lasting antitumor immune memory, accompanied by a mixed Th1/Th2 type of response. Concluding, L19-IL2 and L19mTNFalpha efficiently cooperate in determining a high percentage of NB cure that, in our experimental models, is strongly associated to the generation of adaptive immunity involving CD4(+) and CD8(+) T cells.

Graft versus neuroblastoma reaction is efficiently elicited by allogeneic bone marrow transplantation through cytolytic activity in the absence of GVHD

Continuous efforts are dedicated to develop immunotherapeutic approaches to neuroblastoma (NB), a tumor that relapses at high rates following high-dose conventional cytotoxic therapy and autologous bone marrow cell (BMC) reconstitution. This study presents a series of transplant experiments aiming to evaluate the efficacy of allogeneic BMC transplantation. Neuro-2a cells were found to express low levels of class I major histocompatibility complex (MHC) antigens. While radiation and syngeneic bone marrow transplantation (BMT) reduced tumor growth (P < 0.001), allogeneic BMT further impaired subcutaneous development of Neuro-2a cells (P < 0.001). Allogeneic donor-derived T cells displayed direct cytotoxic activity against Neuro-2a in vitro, a mechanism of immune-mediated suppression of tumor growth. The proliferation of lymphocytes from congenic mice bearing subcutaneous tumors was inhibited by tumor lysate, suggesting that a soluble factor suppresses cytotoxic activity of syngeneic lymphocytes. However, the growth of Neuro-2a cells was impaired when implanted into chimeric mice at various times after syngeneic and allogeneic BMT. F1 (donor-host) splenocytes were infused attempting to foster immune reconstitution, however they engrafted transiently and had no effect on tumor growth. Taken together, these data indicate: (1) Neuro-2a cells express MHC antigens and immunogenic tumor associated antigens. (2) Allogeneic BMT is a significantly better platform to develop graft versus tumor (GVT) immunotherapy to NB as compared to syngeneic (autologous) immuno-hematopoietic reconstitution. (3) An effective GVT reaction in tumor bearing mice is primed by MHC disparity and targets tumor associated antigens.

Immunotherapy for neuroblastoma: turning promise into reality

Neuroblastoma is one of the commonest and most aggressive paediatric malignancies. The majority of children present with metastatic disease for which long-term survival remains poor despite intensive multi-modal therapies. Toxicity from current treatment regimes is already significant, and there is little room to further intensify therapy. Alternative treatment strategies are therefore needed in order to improve survival. Immunotherapy is an attractive therapeutic option for these children as it potentially offers a much more specific and less toxic treatment than conventional therapies. This review discusses the different immunotherapy strategies that may be useful in neuroblastoma, their advantages and disadvantages and the challenges that need to be overcome to successfully use them clinically.

New therapeutic targets for the treatment of high-risk neuroblastoma

High-risk neuroblastoma remains a major problem in pediatric oncology, accounting for 15% of childhood cancer deaths. Although incremental improvements in outcome have been achieved with the intensification of conventional chemotherapy agents and the addition of 13-cis-retinoic acid, only one-third of children with high-risk disease are expected to be long-term survivors when treated with current regimens. In addition, the cost of cure can be quite high, as surviving children remain at risk for additional health problems related to long-term toxicities of treatment. Further advances in therapy will require the targeting of tumor cells in a more selective and efficient way so that survival can be improved without substantially increasing toxicity. In this review we summarize ongoing clinical trials and highlight new developments in our understanding of the molecular biology of neuroblastoma, emphasizing potential targets or pathways that may be exploitable therapeutically.

Immune therapies for neuroblastoma

Neuroblastoma, a solid tumor arising from developing cells of the sympathetic nervous system, is the most common extracranial tumor in children. The prognosis for high-risk neuroblastoma remains poor with conventional treatment, and new approaches are therefore being explored to treat this disease. One such alternative therapy that holds promise is immune therapy. We review here the recent advances in four types of immune therapy-cytokine, vaccine, antibody and cellular therapy-to treat neuroblastoma. We present preclinical research and clinical trials on several promising candidates such as IL-12, dendritic cell vaccines, anti-GD2 antibodies and allogeneic hematopoietic stem cell transplant. An optimal treatment plan for neuroblastoma will most likely involve multimodal approaches and combinations of immune therapies.

Cytokines as Adjuvants for Vaccine and Cellular Therapies for Cancer

PROBLEM STATEMENT: The development of a potent vaccine that can help treat tumors resistant to conventional cytotoxic therapies remains elusive. While part of the problem may be that trials have focused on patients with bulky residual disease, the desire to maximize responses to the vaccine remains. APPROACH: The gamma(c) family of cytokines offer a unique opportunity to support the expansion and effector potential of vaccine-responding T-cells, as well as stimulate other effectors, such as natural killer (NK) cells, to become activated. RESULTS: Combining vaccines with cytokines seems logical but can bring unwanted toxicity, as has been observed with interleukin (IL)-2. In addition, the nonspecific activation or expansion of unwanted cell subsets, such as regulatory T-cells, can contribute to global immunosuppression and limit vaccine responses. The development of IL-7 and IL-21 for the clinic offers the promise of enhancing anti-tumor responses but with far less systemic toxicity and no expansion of regulatory T cells. Preclinical studies demonstrate that IL-15 could also improve T-cell, and especially NK-cell, responses as well. CONCLUSIONS/RECOMMENDATIONS: Future work should expand the use of vaccines with IL-7, IL-21 and hopefully IL-15 in high-risk patients, and consider treatment while in a state of minimal residual disease to maximize benefit. Identifying tumors that can signal through gamma(c) cytokines will also be essential so that induction of relapse will be avoided.