Ganglioside conjugate vaccines. Immunotherapy against tumors of neuroectodermal origin

PPARδ and its ligand erucic acid may act anti-tumoral, neuroprotective, and myelin protective in neuroblastoma, glioblastoma, and Parkinson's disease

In this review study, we focus on potential benefits of the transcription factor PPARδ and its ligand erucic acid (EA) in management of neuroectodermal tumors and Parkinson's Disease. PPARδ is a nuclear receptor and transcription factor that induces myelination, promotes oligodendroglial and neuronal differentiation, and possess anti-neuroinflammatory properties. While both pro-tumorigenic and anti-tumorigenic effects have been described for PPARδ, we propose that PPARδ may perform a predominantly anticancer role in tumors originating from the neuroectoderm. PPARδ ligand-activation via oleic acid and GW501516, or overexpression of PPARδ, elicits profound antitumor actions in neuroblastoma and melanoma. In glioblastomas, there is evidence indicating a differentiation failure of O2A (oligodendroglial-astrocytic biprogenitor) cells and it has been shown that EA reduced DNA synthesis in C6 rat glioblastoma spheroid cultures in clinically achievable concentrations. EA is a ω9 fatty acid which is being used in the treatment of adrenoleukodystrophy. EA is widely consumed in Asian countries via ingestion of cruciferous vegetables including mustard and rapeseed oil. EA also exerts antioxidant and anti-inflammatory activities. Recent studies of Parkinson's Disease (PD) have implicated demyelination, white matter pathology, oligodendroglial injury, and neural inflammation in the underlying pathophysiology. In the rotenone PD model in rats, PPARδ ligand GW501516 saves dopaminergic neurons during injury induced by chemical toxins and improves behavioral functioning in PD via alleviation of endoplasmic reticulum stress. PPARδ agonists also reduce the NLRP3 inflammasome-associated neural inflammation in the MPTP PD model in mice. Herein, we propose that PPARδ and its ligand EA highly deserve to be studied in animal models of neuroblastoma, glioblastoma, and PD.

Anti-GD2 immunotherapy for neuroblastoma

INTRODUCTION

Current therapeutic approaches for high-risk neuroblastoma (HR-NB) include high-dose chemotherapy, surgery and radiotherapy; interventions that are associated with long and short-term toxicities. Effective immunotherapy holds particular promise for improving survival and quality of life by reducing exposure to cytotoxic agents. GD2, a surface glycolipid is the most common target for immunotherapy. Areas covered: We review the status of anti-GD2 immunotherapies currently in clinical use for neuroblastomas and novel GD2-targeted strategies in preclinical development. Expert commentary: Anti-GD2 monoclonal antibodies are associated with improved survival in patients in their first remission and are increasingly being used for chemorefractory and relapsed neuroblastoma. As protein engineering technology has become more accessible, newer antibody constructs are being tested. GD2 is also being targeted by natural killer cells and T-cells. Active immunity can be elicited by anti-GD2 vaccines. The rational combination of currently available and soon-to-emerge immunotherapeutic approaches, and their integration into conventional multimodality therapies will require further investigation to optimize their use for HR-NB.

Induction of leukocyte infiltration at metastatic site mediates the protective effect of NGcGM3-based vaccine

While the NGcGM3/VSSP vaccine, a preparation consisting in very small sized proteoliposomes (VSSP) obtained by the incorporation of the NGcGM3 ganglioside into the outer membrane protein (OMP) complex of Neisseria meningitides, is currently studied in late stage clinical trials in breast cancer and melanoma patients, mechanisms involved in the vaccine's antitumor effect are insufficiently understood. Here we have addressed the role of adaptive and innate immune cells in mediating the protective effect of the vaccine. To this aim we selected the 3LL-D122 Lewis lung spontaneous metastasis model. Unexpectedly, inoculation of the vaccine in tumor bearing C57BL/6 mice, either by subcutaneous (sc) or intraperitoneal (ip) routes, induced similar anti-metastatic effect. Regardless the T-independent nature of NGcGM3 ganglioside as antigen, the antimetastatic effect of NGcGM3/VSSP is dependent on CD4(+) T cells. In a further step we found that the vaccine was able to promote the increase, maturation, and cytokine secretion of conventional DCs and the maturation of Bone Marrow-derived plasmacytoid DCs. In line with this result the in vivo IFNα serum level in ip vaccinated mice increased as soon as 2h after treatment. On the other hand the infiltration of NK1.1(+)CD3(-) and NK1.1(+)CD3(+) cells in lungs of vaccinated mice was significantly increased, compared with the presence of these cells in control animal lungs. In the same way NGcGM3/VSSP mobilized acquired immunity effector cells into the lungs of vaccinated tumor bearing mice. Finally and not less noteworthy, leukocyte infiltration in lungs of tumor bearing mice correlates with vaccine induced inhibition of lung metastization.

The sweet side of tumor immunotherapy

Carbohydrate signatures on tumor cells have functional implications in tumor growth and metastasis and constitute valuable tools in cancer diagnosis and immunotherapy. Increasing data regarding the mechanisms by which they are recognized by the immune system are facilitating the design of more efficient immunotherapeutic protocols based on cancer-associated glycan structures. Recent molecular and proteomic studies revealed that carbohydrates are recognized, not only by B cells and antibodies, but also by cells from the innate arm of immunity, as well as by T cells, and are able to induce specific T-cell immunity and cytotoxicity. In this review, we discuss and update the different strategies targeting tumor-associated carbohydrate antigens that are being evaluated for antitumor immunotherapy, an approach that will be highly relevant, especially when combined with other strategies, in the future fight against cancer.

Disialoganglioside directed immunotherapy of neuroblastoma

Achieving a cure for metastatic neuroblastoma remains a challenge despite sensitivity to chemotherapy and radiotherapy. Most patients achieve remission, but a failure to eliminate minimal residual disease (MRD) often leads to relapse. Immunotherapy is potentially useful for chemotherapy-resistant disease and may be particularly effective for low levels of MRD that are below the threshold for detection by routine radiological and histological methods. Disialoganglioside (GD2), a surface glycolipid antigen that is ubiquitous and abundant on neuroblastoma cells is an ideal target for immunotherapy. Anti-GD2 monoclonal antibodies currently form the mainstay of neuroblastoma immunotherapy and their safety profile has been well-established. Although responses in patients with gross disease have been observed infrequently, histologic responses of bone marrow disease are consistently achieved in >75 percent of patients with primary refractory neuroblastoma. The advent of highly sensitive and specific molecular assays to measure MRD has confirmed the efficacy anti-GD2 antibody immunotherapy in patients with subclinical disease. Such markers will allow further optimization of other anti-MRD therapies. We review the current status of anti-GD2 clinical trials for neuroblastoma and novel preclinical GD2-targeted strategies for this rare but often lethal childhood cancer.

Immunotherapy and prostate cancer

Prostate cancer is the second leading cause of cancer death in the US, largely because of the limitations of our current therapeutic options, especially once the cancer has metastasized. Investigators have long sought new therapeutic modalities such as angiogenesis inhibitors, vaccines, and gene therapy, among others. It appears that a combination approach will be required to cure the majority of malignancies. Immunotherapy for prostate cancer appears feasible and a likely therapeutic modality in the armamentarium. Unfortunately, further research in basic immunology and the interaction of the immune system with other forms of therapy is needed. Many obstacles exist in immunotherapy, including vector design, tumouricidal specificity, and tumor evasion, which will have to be overcome in order to realize the maximum therapeutic benefit from this treatment modality.

Vectorial delivery of macromolecules into cells using peptide-based vehicles

The ability to direct the import of therapeutic agents into cells and target them to specific organelles would greatly enhance their functional efficacy. The available spectrum of peptide-based import signals and intracellular routing signals might provide practical solutions towards achieving a guided or vectorial delivery of molecules. Multiple cell-targeting signals and routing domains can be efficiently displayed on branched peptides. These constructs are typically nonimmunogenic in the absence of adjuvant and can be easily assembled using solid phase synthesis. The vectorial delivery of larger complexes, however, will necessitate the development of alternate templates that favor the optimal presentation of all functional signals.

Autoimmune and antitumor consequences of antibodies against antigens shared by normal and malignant tissues

There is now a considerable body of information documenting the autoimmune consequences of antibodies induced by growing malignancies, or by passively administered and actively induced antibodies, in cancer patients against antigens shared by normal and malignant tissues. This provides a rich source of information addressing the consequences of autoantibodies against a range of antigens. Antibodies against cell-surface or intracellular antigens in the central nervous system (CNS) or on epithelial surfaces of normal tissues do not generally result in autoimmunity, but the same types and titers of antibodies against cell surface antigens in the subepidermal skin, peripheral nerves, blood, or vascular sites such as the spleen and bone marrow readily induce autoimmunity. The blood brain barrier of the CNS and apical antigen expression and the basement membrane in epithelial tissues, may protect these sites from antibody induced damage. Cancer cells, however, are protected by neither unidirectional antigen expression nor basement membranes. Vaccine induced antibodies against a variety of cancer cell surface antigens have been associated with prevention of tumor recurrence in preclinical models and in vaccinated cancer patients, in the absence of demonstrable autoimmunity. This forms the basis for a series of ongoing Phase III trials with single or polyvalent antigen cancer vaccines designed for optimal antibody induction.

Keyhole limpet hemocyanin (KLH): a biomedical review

In this review we present a broad survey of fundamental scientific and medically applied studies on keyhole limpet hemocyanin (KLH). Commencing with the biochemistry of KLH, information on the biosynthesis and biological role of this copper-containing respiratory protein in the marine gastropod Megathura crenulata is provided. The established methods for the purification of the two isoforms of KLH (KLH1 and KLH2) are then covered, followed by detailed accounts of the molecular mass determination, functional unit (FU) structure, carbohydrate content, immunological analysis and recent aspects of the molecular genetics of KLH. The transmission electron microscope (TEM) has contributed significantly to the understanding of KLH structure, primarily from negatively stained images. We give a brief account of TEM studies on the native KLH oligomers, the experimental manipulation of the oligomeric states, together with immunolabelling data and studies on subunit reassociation. The field of cellular immunology has provided much relevant biomedical information on KLH and has led to the expansion of use of KLH in experimental immunology and clinically as an immunotherapeutic agent; this area is presented in some detail. The major clinical use of KLH is specifically for the treatment of bladder carcinoma, with efficacy probably due to a cross-reacting carbohydrate epitope. KLH also has considerable possibilities for the treatment of other carcinomas, in particular the epithelially derived adenocarciomas, when used as a carrier for carcinoma ganglioside and mucin-like epitopes. The widespread use of KLH as a hapten carrier and generalised vaccine component represent other major on-going aspects of KLH research, together with its use for the diagnosis of Schistosomiasis, drug assay and the treatment of drug addiction. Immune competence testing, assessment of stress and the understanding of inflammatory conditions are other areas where KLH is also making a useful contribution to medical research.

Carbohydrate vaccines that induce antibodies against cancer. 1. Rationale

Carbohydrate antigens are the most abundant antigens expressed at the cancer cell surface and have been shown to be uniquely effective targets for immune recognition and attack. The basis for cancer vaccines that primarily induce an antibody response, such as vaccines against these carbohydrate antigens, is now well established in both experimental models and the clinical setting. In both cases, antibody administration or induction has been especially effective in the adjuvant setting when the targets are circulating tumor cells and micrometastases. The patterns of carbohydrate antigens expressed by different tumor types has been established, paving the way for polyvalent-antibody-inducing vaccines. This then forms the rationale for the construction and testing of carbohydrate vaccines against cancer, the focus of the second part of this review.

1H NMR ganglioside ceramide resonance region on the differential diagnosis of low and high malignancy of brain gliomas

1. The high-resolution 1H NMR (MRS) spectra of human brain tumor homogenates revealed a broad resonance at 5.3-5.4 ppm in glioblastoma multiforme (N = 16) and brain metastases (N = 3). The broad resonance was identified as ceramide, a sphingosine-fatty acid combination portion of ganglioside, indicating an elevated abundance of monounsaturated fatty acids. GLC analysis of gangliosides in the highly malignant glioblastoma multiforme revealed that the elevated monounsaturated fatty acid is oleic acid (C18:1). The resonance at 5.3-5.4 ppm region was not detectable in normal human brain (N = 2), in meningiomas (N = 2), or in low-grade astrocytomas (N = 12). In normal human brain the abundance of monounsaturated fatty acid is minimal. 2. This investigation was made possible because the method of producing homogenate resulted in (i) no loss of lipids during the process and (ii) a well-homogenised sample, with (iii) no loss in chemical integrity. 3. The properties of tumor gangliosides include antigenic specificity and immunosuppressive activity and the ceramide, a sphingosine-fatty acid combination, noticeably influences the ganglioside immunosuppressive activity. 4. The observation of 1H NMR ceramide resonance in high-malignant brain tumors emphasizes the dramatic role of aberant gangliosides and ceramide precursors on the grade of malignancy and invasiveness. 5. Further insight into the specific nature of the ceramide portion of gangliosides in grading the malignancy of brain tumors should be investigated further.

Augmenting the immunogenicity of carbohydrate tumor antigens

Antibody responses have identified cell surface carbohydrate antigens as potentially immunogenic cancer antigens in a variety of different tumors, but immunization with whole tumor cells or cell lysates has only occasionally induced immune responses against these antigens. Three approaches to further augmenting their immunogenicity have been explored, mixture with immunological adjuvants, synthesis of more immunogenic derivatives and conjugation to immunogenic proteins. Conjugation to proteins such as KLH plus the use of potent adjuvants such as QS-21 proved most immunogenic. Carbohydrate epitopes on gangliosides (GM2 and GD2), neutral glycolipids (Ley and Globo H) and glycoproteins (Ley, Globo H, TF, sTn and Tn) are of special interest. Each of these antigens has been synthesized and conjugated to KLH. Their use in preclinical or clinical vaccination studies has resulted in increased IgM and IgG antibody responses against tumors expressing these antigens. Phase I-II clinical trials in patients with cancer have been initiated with each to optimize immunogenicity. The GM2 vaccine has progressed to Phase III trials and the sTn vaccine to Phase II trials aimed at determining the impact of vaccination on survival.

A recombinant vaccinia virus expressing human prostate-specific antigen (PSA): safety and immunogenicity in a non-human primate

Prostate-specific antigen (PSA) is a serine protease secreted by prostatic epithelial cells and is widely used as a marker for prostate cancer. The tissue specificity of PSA makes it a potential target for active specific immunotherapy, especially in prostate cancer patients who have undergone prostatectomy and in whom the only PSA-expressing tissue in the body resides in metastatic deposits. We report here the cloning, construction and immunological consequences of immunization of rhesus monkeys with a recombinant vaccinia virus expressing human PSA (designated rV-PSA). The prostate gland of the rhesus is structurally and functionally similar to the human prostate. While rodent and other mammalian species do not share homology with human PSA, there is 94% homology between the amino acid sequences of rhesus and human PSA. Immunization of rhesus monkeys with wild-type vaccinia virus or rV-PSA elicited the usual low-grade constitutional symptoms of vaccinia virus infection. There was no evidence of any adverse effects in any immunized monkeys. A short-lived PSA-specific IgM antibody response was noted in all rV-PSA immunized monkeys regardless of dose level. All monkeys receiving the 10(8)pfu dose of rV-PSA demonstrated PSA-specific T-cell responses that were maintained up to 270 days. No differences in anti-PSA immune responses or toxicity were observed in animals that received prostatectomy prior to immunization. Our results thus demonstrate the safety and immunogenicity of rV-PSA in a non-human primate and have implications for potential specific immunotherapy protocols using PSA as a target.

Approaches to augmenting the immunogenicity of melanoma gangliosides: from whole melanoma cells to ganglioside-KLH conjugate vaccines

Gangliosides are neuraminic acid containing glycosphingolipids that are anchored into the lipid bilayer of the plasma membrane by their lipophilic ceramide moiety. They are overexpressed on tissues of neuroectodermal origin, particularly in tumors such as melanomas, sarcomas, neuroblastomas and astrocytomas. With the ganglioside-KLH plus immunological adjuvant QS-21 conjugate vaccine, GM2 and GD2 have been shown to be consistently immunogenic, inducing cytotoxic IgM antibodies in most patients. The immunogenicity of other gangliosides also expressed on melanoma cells such as 9-0-acetyl GD3 and GD3 lactone is currently being tested with this conjugate vaccine approach. From the initiation of our adjuvant vaccine trials in 1975 to the present, the immunogenicity of ganglioside vaccines has increased significantly as vaccine development has progressed. For instance, GM2 antibody responses increased from low titer IgM antibodies induced in occasional patients after whole cell vaccines, to moderate titer IgM antibodies in 86% of patients after GM2/BCG vaccines, to higher titer IgM antibodies in 100% of patients treated with the GM2-KLH plus QS-21 vaccine. These antibodies are capable of mediating complement mediated cytotoxicity of GM2 expressing melanoma cells in the majority of patients and such antibodies, whether naturally produced or vaccine induced, have been associated with a significantly improved disease-free and overall survival. An initial double-blind randomized trial in AJCC Stage III melanoma patients comparing GM2/BCG with BCG alone, demonstrated a 14% improvement in disease-free interval at 4 years and an 11% improvement in overall survival, though neither result achieved statistical significance. Based on these encouraging clinical results and the clearly improved immunogenicity of the GM2-KLH plus QS-21 vaccine compared to the previous GM2/BCG vaccine, the following two large clinical trials are anticipated to begin in 1995-1996. The GM2-KLH plus QS-21 vaccine will be tested in the intergroup setting by ECOG in 450 patients with AJCC Stage II or III melanoma who are free of disease after surgery. Also to be tested in a multicenter trial is a GM2-KLH plus GD2-KLH plus QS-21 vaccine in patients with high risk AJCC Stage II-IV sarcoma after surgical excision of all known disease.