GM-CSF-based cellular vaccines: a review of the clinical experience

Antitumor strategies targeting macrophages: the importance of considering the differences in differentiation/polarization processes between human and mouse macrophages

Macrophages are the immune cells that accumulate the most in the majority of established tumors and this accumulation is associated with a poor prognosis. Tumor-associated macrophages (TAMs) produce inflammatory cytokines and growth factors that promote tumor expansion and metastasis. TAMs have recently emerged as targets of choice to restore an efficient antitumor response and to limit tumor growth. Many molecules targeting TAMs are actually evaluated in clinical trials, alone or in combination. While these molecules induce tumor regression and stimulate cytotoxic responses in mouse models of tumor development, results from early clinical trials are less impressive. In this review, we list the biological differences between human and mouse macrophages that help explain the different efficacy of antitumor strategies targeting TAMs between human and animal studies. Differences in the impact of survival and polarization factors and in the cytokines produced and markers expressed as well as the limitations of extrapolations based on in vitro models of TAM-like generation should be considered in order to improve the design and efficacy of antitumor drugs targeting TAMs.

An Allogeneic Multiple Myeloma GM-CSF-Secreting Vaccine with Lenalidomide Induces Long-term Immunity and Durable Clinical Responses in Patients in Near Complete Remission

PURPOSE

This proof-of-principle clinical trial evaluated whether an allogeneic multiple myeloma GM-CSF-secreting vaccine (MM-GVAX) in combination with lenalidomide could deepen the clinical response in patients with multiple myeloma in sustained near complete remission (nCR).

PATIENTS AND METHODS

Fifteen patients on lenalidomide were treated with MM-GVAX and pneumococcal conjugate vaccine (PCV; Prevnar) at 1, 2, 3, and 6 months.

RESULTS

Eight patients (53.3%) achieved a true CR. With a median follow-up of 5 years, the median progression-free survival had not been reached, and the median overall survival was 7.8 years from enrollment. MM-GVAX induced clonal T-cell expansion and measurable cytokine responses that persisted up to 7 years in all patients. At baseline, a higher minimal residual disease was predictive of early relapse. After vaccination, a lack of both CD27^-DNAM1^-CD8⁺ T cells and antigen-presenting cells was associated with disease progression.

CONCLUSIONS

MM-GVAX, along with lenalidomide, effectively primed durable immunity and resulted in long-term disease control, as suggested by the reappearance of a detectable, fluctuating M-spike without meeting the criteria for clinical relapse. For patients in a nCR, MM-GVAX administration was safe and resulted in prolonged clinical responses.

Multicompartmental Lipopolyplex as Vehicle for Antigens and Genes Delivery in Vaccine Formulations

Vector design and its characterization is an area of great interest in current vaccine research. In this article, we have formulated and characterized a multicompartmental lipopolyplex, which associates multiple liposomes and polyplexes in the same complex. These particles allow the simultaneous delivery of lipid or water-soluble antigens associated with genes to the same cell, in much higher amounts than conventional lipopolyplexes. The vector characterization and optimization were carried out using liposomes with entrapped carboxyfluorescein and adapted electrophoretic assays. Two types of lipopolyplexes (containing hydrophilic or lipophilic antigens) were employed to evaluate their interest in vaccination. The lipopolyplex loaded with an extract of water-soluble melanoma proteins proved to efficiently induce humoral response in murine melanoma model, increasing the levels of IgM and IgG. The specificity of the immune response induced by the lipopolyplex was demonstrated in mice with the lipopolyplex containing the GD3 ganglioside lipid antigen, abundant in melanoma cells. The levels of anti-GD3 IgG increased markedly without modifying the expression of humoral antibodies against other gangliosides.

Generation of GM-CSF-producing antigen-presenting cells that induce a cytotoxic T cell-mediated antitumor response

Immunotherapy using dendritic cells (DCs) is a promising treatment modality for cancer. However, the limited number of functional DCs from peripheral blood has been linked to the unsatisfactory clinical efficacies of current DC-based cancer immunotherapies. We previously generated proliferating antigen-presenting cells (APCs) by genetically engineering myeloid cells derived from induced pluripotent stem cells (iPSC-pMCs), which offer infinite functional APCs for broad applications in cancer therapy. Herein, we aimed to further enhance the antitumor effect of these cells by genetic modification. GM-CSF gene transfer did not affect the morphology, or surface phenotype of the original iPSC-pMCs, however, it did impart good viability to iPSC-pMCs. The resultant cells induced GM-CSF-dependent CD8⁺ T cell homeostatic proliferation, thereby enhancing antigen-specific T cell priming in vitro. Administration of the tumor antigen-loaded GM-CSF-producing iPSC-pMCs (GM-pMCs) efficiently stimulated antigen-specific T cells and promoted effector cell infiltration of the tumor tissues, leading to an augmented antitumor effect. To address the potential tumorigenicity of iPSC-derived products, irradiation was applied and found to restrict the proliferation of GM-pMCs, while retaining their T cell-stimulatory capacity. Furthermore, the irradiated cells exerted an antitumor effect equivalent to that of bone marrow-derived DCs obtained from immunocompetent mice. Additionally, combination with immune checkpoint inhibitors increased the infiltration of CD8⁺ or NK1.1⁺ effector cells and decreased CD11b⁺/Gr-1⁺ cells without causing adverse effects. Hence, although GM-pMCs have certain characteristics that differ from endogenous DCs, our findings suggest the applicability of these cells for broad clinical use and will provide an unlimited source of APCs with uniform quality.

Exosomes from GM-CSF expressing embryonic stem cells are an effective prophylactic vaccine for cancer prevention

The antigenic similarity between embryos and tumors has raised the idea of using embryonic material as a preventative vaccine against neoplastic disease. Indeed, we have previously reported that a vaccine comprises allogeneic murine embryonic stem cells (ESCs) and murine fibroblasts expressing GM-CSF (to amplify immune responses) successfully blocks the outgrowth of an implantable cancer (Lewis lung carcinoma; LLC) and lung tumors generated in mice using a combination of a mutagen followed by chronic pulmonary inflammation. However, such a vaccine is obviously impractical for application to humans. The use of fibroblasts to generate GM-CSF is needlessly complicated, and intact whole ESCs carry the hazard of generating embryomas/teratomas. Here, we report the successful application of an alternative prophylactic vaccine comprises exosomes derived from murine ESCs engineered to produce GM-CSF. Vaccination of mice with these exosomes significantly slowed or blocked the outgrowth of implanted LLC while control exosomes lacking GM-CSF were ineffective. Examination of tumor-infiltrating immune cells from mice vaccinated with the GM-CSF-expressing exosomes showed robust tumor-reactive CD8⁺ T effector responses, Th1 cytokine responses, and higher CD8⁺ T effector/CD4⁺CD25⁺Foxp3⁺ T regulatory cell ratio in the tumors. We conclude that a similar vaccine derived from GM-CSF- expressing human ESCs can be employed as a preventative vaccine for humans with an increased risk of developing cancer.

Combining radiation therapy and cancer immune therapies: From preclinical findings to clinical applications

Besides its direct cytotoxic effect on the tumor cells, radiation therapy is also able to elicit an immune-mediated systemic anti-tumor response, resulting in tumor regression in irradiated sites but also within distant out of field secondary lesions and providing a long-term anti-tumor response. It is now clear that associating ionizing radiation with immune therapies can enhance radio-induced anti-tumor immune responses. Over the last decade, such a combination aroused considerable interest among the scientific community, with many preclinical models and clinical trials, using many types of immune therapies and radiation regimens. In this article, we summarize the main mechanisms underlying radio-induced anti-tumor responses. We will then present an extended overview of the recent preclinical and clinical research built on this background of combined radiation and immune therapy, shedding light on what we know so far about such a promising strategy.

Tune Up In Situ Autovaccination against Solid Tumors with Oncolytic Viruses

With the progress of immunotherapy in cancer, oncolytic viruses (OVs) have attracted more and more attention during the past decade. Due to their cancer-selective and immunogenic properties, OVs are considered ideal candidates to be combined with immunotherapy to increase both specificity and efficacy in cancer treatment. OVs preferentially replicate in and lyse cancer cells, resulting in in situ autovaccination leading to adaptive anti-virus and anti-tumor immunity. The main challenge in OV approaches is how to redirect the host immunity from anti-virus to anti-tumor and optimize the clinical outcome of cancer patients. Here, we summarize the conceptual updates on oncolytic virotherapy and immunotherapy in cancer, and the development of strategies to enhance the virus-mediated anti-tumor immune response, including: (1) arm OVs with cytokines to modulate innate and adaptive immunity; (2) combining OVs with immune checkpoint inhibitors to release T cell inhibition; (3) combining OVs with immune co-stimulators to enhance T cell activation. Future studies need to be enforced on developing strategies to augment the systemic effect on metastasized tumors.

High Doses of GM-CSF Inhibit Antibody Responses in Rectal Secretions and Diminish Modified Vaccinia Ankara/Simian Immunodeficiency Virus Vaccine Protection in TRIM5α-Restrictive Macaques

We tested, in rhesus macaques, the effects of a 500-fold range of an admixed recombinant modified vaccinia Ankara (MVA) expressing rhesus GM-CSF (MVA/GM-CSF) on the immunogenicity and protection elicited by an MVA/SIV macaque 239 vaccine. High doses of MVA/GM-CSF did not affect the levels of systemic envelope (Env)-specific Ab, but it did decrease the expression of the gut-homing receptor α4β7 on plasmacytoid dendritic cells (p < 0.01) and the magnitudes of Env-specific IgA (p = 0.01) and IgG (p < 0.05) in rectal secretions. The protective effect of the vaccine was evaluated using 12 weekly rectal challenges in rhesus macaques subgrouped by tripartite motif-containing protein 5α (TRIM5α) genotypes that are restrictive or permissive for infection by the challenge virus SIVsmE660. Eight of nine TRIM5α-restrictive animals receiving no or the lowest dose (1 × 105 PFU) of MVA/GM-CSF resisted all 12 challenges. In the comparable TRIM5α-permissive group, only 1 of 12 animals resisted all 12 challenges. In the TRIM5α-restrictive animals, but not in the TRIM5α-permissive animals, the number of challenges to infection directly correlated with the magnitudes of Env-specific rectal IgG (r = +0.6) and IgA (r = +0.6), the avidity of Env-specific serum IgG (r = +0.5), and Ab dependent cell-mediated virus inhibition (r = +0.6). Titers of neutralizing Ab did not correlate with protection. We conclude that 1) protection elicited by MVA/SIVmac239 is strongly dependent on the presence of TRIM5α restriction, 2) nonneutralizing Ab responses contribute to protection against SIVsmE660 in TRIM5α-restrictive animals, and 3) high doses of codelivered MVA/GM-CSF inhibit mucosal Ab responses and the protection elicited by MVA expressing noninfectious SIV macaque 239 virus-like particles.

Synergism between cryoablation and GM-CSF: enhanced immune function of splenic dendritic cells in mice with glioma

Glioma is the most common malignant primary brain tumor, and it has a poor prognosis. Studies have shown that cryoablation can activate antitumor immunoeffects by promoting the augmentation of dendritic cells (DCs). Granulocyte macrophage colony-stimulating factor (GM-CSF) has been shown to be useful for immunotherapy against glioma because it can stimulate DCs to present tumor antigen. Previous studies have shown that cryoablation and GM-CSF can exert antitumor effects. To test the hypothesis that combined therapy with cryoablation and GM-CSF for glioma could synergistically improve specific antiglioma immunity in mice, we tested the validity of this assumption in a murine subcutaneous GL261 glioma model. C57BL/6 mice with subcutaneous GL261 glioma were created and divided into four groups: no treatment, GM-CSF injection, cryoablation treatment, and GM-CSF and cryoablation combined treatment (n=20 in each group). Serial immune indicators were detected at sequential time points during treatment. Compared with the other groups, in the combined treatment group, DCs were more activated and their numbers were markedly upregulated, the secretion of interferon-γ from Th1 cells of mice spleen was increased, and the cytolytic activity of CD8 CTLs exerted a more significant cytotoxic effect on GL261 glioma cells (P<0.05 for all). Furthermore, these changes peaked on the 7th day after treatment, and then gradually reduced, until the 21st day; these changes were higher than those at pretreatment (P<0.05). It is concluded that combined therapy with argon-helium cryoablation and GM-CSF could synergistically enhance the activation of DCs and induce a robust tumor-specific immunologic response in glioma-bearing mice.

Live-Attenuated Bacterial Vectors: Tools for Vaccine and Therapeutic Agent Delivery

Genetically attenuated microorganisms, including pathogenic and commensal bacteria, can be engineered to carry and deliver heterologous antigens to elicit host immunity against both the vector as well as the pathogen from which the donor gene is derived. These live attenuated bacterial vectors have been given much attention due to their capacity to induce a broad range of immune responses including localized mucosal, as well as systemic humoral and/or cell-mediated immunity. In addition, the unique tumor-homing characteristics of these bacterial vectors has also been exploited for alternative anti-tumor vaccines and therapies. In such approach, tumor-associated antigen, immunostimulatory molecules, anti-tumor drugs, or nucleotides (DNA or RNA) are delivered. Different potential vectors are appropriate for specific applications, depending on their pathogenic routes. In this review, we survey and summarize the main features of the different types of live bacterial vectors and discussed the clinical applications in the field of vaccinology. In addition, different approaches for using live attenuated bacterial vectors for anti-cancer therapy is discussed, and some promising pre-clinical and clinical studies in this field are outlined.

Local radiotherapy and granulocyte-macrophage colony-stimulating factor to generate abscopal responses in patients with metastatic solid tumours: a proof-of-principle trial

BACKGROUND

An abscopal response describes radiotherapy-induced immune-mediated tumour regression at sites distant to the irradiated field. Granulocyte-macrophage colony-stimulating factor is a potent stimulator of dendritic cell maturation. We postulated that the exploitation of the pro-immunogenic effects of radiotherapy with granulocyte-macrophage colony-stimulating factor might result in abscopal responses among patients with metastatic cancer.

METHODS

Patients with stable or progressing metastatic solid tumours, on single-agent chemotherapy or hormonal therapy, with at least three distinct measurable sites of disease, were treated with concurrent radiotherapy (35 Gy in ten fractions, over 2 weeks) to one metastatic site and granulocyte-macrophage colony-stimulating factor (125 μg/m(2) subcutaneously injected daily for 2 weeks, starting during the second week of radiotherapy). This course was repeated, targeting a second metastatic site. A Simon's optimal two-stage design was chosen for this trial: an additional 19 patients could be enrolled in stage 2 only if at least one patient among the first ten had an abscopal response. If no abscopal responses were seen among the first ten patients, the study would be deemed futile and terminated. The primary endpoint was the proportion of patients with an abscopal response (defined as at least a 30% decrease in the longest diameter of the best responding abscopal lesion). Secondary endpoints were safety and survival. Analyses were done based on intention to treat. The trial has concluded accrual, and is registered with ClinicalTrials.gov, number NCT02474186.

FINDINGS

From April 7, 2003, to April 3, 2012, 41 patients with metastatic cancer were enrolled. In stage 1 of the Simon's two-stage design, ten patients were enrolled: four of the first ten patients had abscopal responses. Thus, the trial proceeded to stage 2, as planned, and an additional 19 patients were enrolled. Due to protocol amendments 12 further patients were enrolled. Abscopal responses occurred in eight (27·6%, 95% CI 12·7-47·2) of the first 29 patients, and 11 (26·8%, 95% CI 14·2-42·9) of 41 accrued patients (specifically in four patients with non-small-cell lung cancer, five with breast cancer, and two with thymic cancer). The most common grade 3-4 adverse events were fatigue (six patients) and haematological (ten patients). Additionally, a serious adverse event of grade 4 pulmonary embolism occurred in one patient.

INTERPRETATION

The combination of radiotherapy with granulocyte-macrophage colony-stimulating factor produced objective abscopal responses in some patients with metastatic solid tumours. This finding represents a promising approach to establish an in-situ anti-tumour vaccine. Further research is warranted in this area.

FUNDING

New York University School of Medicine's Department of Radiation Oncology and Cancer Institute.

Viral gene therapy for head and neck cancer

BACKGROUND

Viral gene therapy is a promising new treatment modality for head and neck cancer. This paper provides the reader with a review of the relevant literature in this field.

RESULTS

There are government licensed viral gene therapy products currently in use for head and neck cancer, utilised in conjunction with established treatment modalities. The viruses target tumour-associated genes, with the first licensed virus replacing p53 gene function, which is frequently lost in tumourigenesis. Oncolytic viruses selectively destroy cancer cells through viral replication and can be armed with therapeutic transgenes.

CONCLUSION

Despite considerable advances in this field over the last 40 years, further research is needed to improve the overall efficacy of the viruses and allow their widespread utilisation in the management of head and neck cancer.

K562-Derived Whole-Cell Vaccine Enhances Antitumor Responses of CAR-Redirected Virus-Specific Cytotoxic T Lymphocytes In Vivo

PURPOSE

Adoptive transfer of Epstein-Barr virus (EBV)-specific and cytomegalovirus (CMV)-specific cytotoxic T cells (CTL) genetically modified to express a chimeric antigen receptor (CAR) induces objective tumor responses in clinical trials. In vivo expansion and persistence of these cells are crucial to achieve sustained clinical responses. We aimed to develop an off-the-shelf whole-cell vaccine to boost CAR-redirected virus-specific CTLs in vivo after adoptive transfer. As proof of principle, we validated our vaccine approach by boosting CMV-specific CTLs (CMV-CTLs) engineered with a CAR that targets the GD2 antigen.

EXPERIMENTAL DESIGN

We generated the whole-cell vaccine by engineering the K562 cell line to express the CMV-pp65 protein and the immune stimulatory molecules CD40L and OX40L. Single-cell-derived clones were used to stimulate CMV-CTLs in vitro and in vivo in a xenograft model. We also assessed whether the in vivo boosting of CAR-redirected CMV-CTLs with the whole-cell vaccine enhances the antitumor responses. Finally, we addressed potential safety concerns by including the inducible safety switch caspase9 (iC9) gene in the whole-cell vaccine.

RESULTS

We found that K562-expressing CMV-pp65, CD40L, and OX40L effectively stimulate CMV-specific responses in vitro by promoting antigen cross-presentation to professional antigen-presenting cells (APCs). Vaccination also enhances antitumor effects of CAR-redirected CMV-CTLs in xenograft tumor models. Activation of the iC9 gene successfully induces growth arrest of engineered K562 implanted in mice.

CONCLUSIONS

Vaccination with a whole-cell vaccine obtained from K562 engineered to express CMV-pp65, CD40L, OX40L and iC9 can safely enhance the antitumor effects of CAR-redirected CMV-CTLs.

Microneedle-assisted dendritic cell-targeted nanoparticles for transcutaneous DNA immunization

Transcutaneous DNA immunization with microneedle-assisted dendritic cell-targeted nanoparticles is an attractive strategy for cancer immunotherapy.

On the possibility of lipid-induced regulation of conformation and immunogenicity of influenza a virus H1/N1 hemagglutinin as antigen of TI-complexes

The tubular immunostimulating complex (TI-complex) consisting of cucumarioside A2-2, cholesterol and monogalactosyldiacylglycerol (MGDG) from marine macrophytes is the perspective antigen delivery system for subunit vaccines. MGDG is a lipid matrix for the protein antigen incorporated in the TI-complex. The aim of the present work was to study the influence of MGDGs from different macrophytes on conformation and immunogenicity of the secreted recombinant uncleaved hemagglutinin monomer (HA0S) of influenza A virus H1/N1. Differential scanning calorimetry, fluorescence spectroscopy and circular dichroism showed a dependence of the conformational changes of HA0S on the microviscosity of MGDG. The most viscous MGDG from Zostera marina induced the strongest rearrangements in protein conformation. Immunization of mice with HA0S within TI-complexes comprising different MGDGs resulted in an approximately 2-fold increase of the levels of anti-HA0S antibodies and granulocyte-macrophage colony-stimulating factor (GM-CSF) compared with those induced by HA0S alone. TI-complexes based on MGDG from Z. marina stimulated the maximal production of GM-CSF. However, humoral immune response (anti-HA0S antibodies), unlike cell-mediated immune response (GM-CSF), did not depend on the physicochemical properties of MGDGs. It is assumed that this is due to the different localization and conformational lipid sensitivity of the HA0S regions, which are responsible for these types of immune responses.

Current status of granulocyte-macrophage colony-stimulating factor in the immunotherapy of melanoma

In 2012, it was estimated that 9180 people in the United States would die from melanoma and that more than 76,000 new cases would be diagnosed. Surgical resection is effective for early-stage melanoma, but outcomes are poor for patients with advanced disease. Expression of tumor-associated antigens by melanoma cells makes the disease a promising candidate for immunotherapy. The hematopoietic cytokine granulocyte–macrophage colony-stimulating factor (GM-CSF) has a variety of effects on the immune system including activation of T cells and maturation of dendritic cells, as well as an ability to promote humoral and cell-mediated responses. Given its immunobiology, there has been interest in strategies incorporating GM-CSF in the treatment of melanoma. Preclinical studies with GM-CSF have suggested that it has antitumor activity against melanoma and can enhance the activity of anti-melanoma vaccines. Numerous clinical studies have evaluated recombinant GM-CSF as a monotherapy, as adjuvant with or without cancer vaccines, or in combination with chemotherapy. Although there have been suggestions of clinical benefit in some studies, results have been inconsistent. More recently, novel approaches incorporating GM-CSF in the treatment of melanoma have been evaluated. These have included oncolytic immunotherapy with the GM-CSF–expressing engineered herpes simplex virus talimogene laherparepvec and administration of GM-CSF in combination with ipilimumab, both of which have improved patient outcomes in phase 3 studies. This review describes the diverse body of preclinical and clinical evidence regarding use of GM-CSF in the treatment of melanoma.

Antitumor cell-complex vaccines employing genetically modified tumor cells and fibroblasts

The present study evaluates the immune response mediated by vaccination with cell complexes composed of irradiated B16 tumor cells and mouse fibroblasts genetically modified to produce GM-CSF. The animals were vaccinated with free B16 cells or cell complexes. We employed two gene plasmid constructions: one high producer (pMok) and a low producer (p2F). Tumor transplant was performed by injection of B16 tumor cells. Plasma levels of total IgG and its subtypes were measured by ELISA. Tumor volumes were measured and survival curves were obtained. The study resulted in a cell complex vaccine able to stimulate the immune system to produce specific anti-tumor membrane proteins (TMP) IgG. In the groups vaccinated with cells transfected with the low producer plasmid, IgG production was higher when we used free B16 cell rather than cell complexes. Nonspecific autoimmune response caused by cell complex was not greater than that induced by the tumor cells alone. Groups vaccinated with B16 transfected with low producer plasmid reached a tumor growth delay of 92% (p ≤ 0.01). When vaccinated with cell complex, the best group was that transfected with high producer plasmid, reaching a tumor growth inhibition of 56% (p ≤ 0.05). Significant survival (40%) was only observed in the groups vaccinated with free transfected B16 cells.

Comparative antitumor effect among GM-CSF, IL-12 and GM-CSF+IL-12 genetically modified tumor cell vaccines

Genetically modified cells have been shown to be one of the most effective cancer vaccine strategies. An evaluation is made of the efficacy of both preventive and therapeutic antitumor vaccines against murine melanoma, using C57BL/6 mice and irradiated B16 tumor cells expressing granulocyte and macrophage colony-stimulating factor (GM-CSF), interleukin-12 (IL-12) or both. Tumor was transplanted by the injection of wild-type B16 cells. Tumor growth and survival were measured to evaluate the efficacy of vaccination. Specific humoral response and immunoglobulin G (IgG) switch were evaluated measuring total IgG and IgG1 and IgG2a subtypes against tumor membrane proteins of B16 cells. In preventive vaccination, all treated groups showed delayed tumor growth. In addition, the group vaccinated to express only GM-CSF achieved 100% animal survival (P<0.005). Vaccination with GM-CSF+IL-12-producing B16 cells yielded lesser results (60% survival, P<0.005). Furthermore, all surviving animals remained disease-free after second tumor implantation 1 year later. The therapeutic vaccination strategies resulted in significantly delayed tumor growth, mainly using B16 cells producing GM-CSF+IL-12 cytokines, with 70% tumor growth inhibition (P<0.001)-although none of the animals reached overall survival. The results obtained suggest that the GM-CSF+IL-12 combination only increases the efficacy of therapeutic vaccines. No differences in classical regulatory T cells were found among the different groups.

Dendritic cell-based immunotherapy in prevention and treatment of renal cell carcinoma: efficacy, safety, and activity of Ad-GM·CAIX in immunocompetent mouse models

The dendritic cell vaccine DC-Ad-GM·CAIX is an active, specific immunotherapy with the potential of providing a safe and effective therapy against renal cell carcinoma (RCC). Using immunocompetent Balb/c mouse models we tested the efficacy and mechanism of the vaccine to prevent and treat the growth of a syngeneic RCC (RENCA) engineered to overexpress the human TAA carbonic anhydrase IX (NPR-IX). In a prevention model, NPR-IX tumor development was specifically and significantly delayed by 13 days in DC-Ad-GM·CAIX-treated mice (P < 0.001), tumor volumes were 79% smaller (day 24, P < 0.007), and body weight was maintained at study termination compared with the controls. Six of these mice remained tumor-free for > 1 year. In a treatment model, NPR-IX tumors remained smaller in DC-Ad-GM·CAIX-treated mice for 8 days (P < 0.002), achieving a 60% growth inhibition at termination. No vaccine-related organ toxicity was observed in either model. The critical mechanistic parameter separating responsive from nonresponsive tumors was hCAIX protein expression, demonstrated by aggressive growth of tumors that did not express hCAIX protein and in sham-treated mice (DC-Ad-Null). No murine serum anti-hCAIX antibodies were detected. Moreover, altered mechanisms of immunoediting as a means for immune evasion were suggested by differential gene expression (Ccl1, Hmgb1, Fgl2, Cd209a, and Klra2) and therapy evasion miRNAs (miR-1186, miR-98, miR-5097, miR-1942, and miR-708) in tumors that evaded DC-Ad-GM·CAIX immunotherapy. This is the first study in immunocompetent mice that provides a proof of concept for the specificity, efficacy, safety, and activity of the DC-Ad-GM·CAIX immunotherapy, forming the basis for a first-in-human phase I trial in RCC patients.

Comparative antitumor effect of preventive versus therapeutic vaccines employing B16 melanoma cells genetically modified to express GM-CSF and B7.2 in a murine model

Cancer vaccines have always been a subject of gene therapy research. One of the most successful approaches has been working with genetically modified tumor cells. In this study, we describe our approach to achieving an immune response against a murine melanoma model, employing B16 tumor cells expressing GM-CSF and B7.2. Wild B16 cells were injected in C57BL6 mice to cause the tumor. Irradiated B16 cells transfected with GM-CSF, B7.2, or both, were processed as a preventive and therapeutic vaccination. Tumor volumes were measured and survival curves were obtained. Blood samples were taken from mice, and IgGs of each treatment group were also measured. The regulatory T cells (Treg) of selected groups were quantified using counts of images taken by confocal microscopy. Results: one hundred percent survival was achieved by preventive vaccination with the group of cells transfected with p2F_GM-CSF. Therapeutic vaccination achieved initial inhibition of tumor growth but did not secure overall survival of the animals. Classical Treg cells did not vary among the different groups in this therapeutic vaccination model.

Co-expression of HIV-1 virus-like particles and granulocyte-macrophage colony stimulating factor by GEO-D03 DNA vaccine

Here, we report on GEO-D03, a DNA vaccine that co-expresses non-infectious HIV-1 virus-like particles (VLPs) and the human cytokine, granulocyte-macrophage colony-stimulating factor (GM-CSF). The virus-like particles display the native gp160 form of the HIV-1 Envelope glycoprotein (Env) and are designed to elicit antibody against the natural form of Env on virus and virus-infected cells. The DNA-expressed HIV Gag, Pol and Env proteins also have the potential to elicit virus-specific CD4 and CD8 T cells. The purpose of the co-expressed GM-CSF is to target a cytokine that recruits, expands and differentiates macrophages and dendritic cells to the site of VLP expression. The GEO-D03 DNA vaccine is currently entered into human trials as a prime for a recombinant modified vaccinia Ankara (MVA) boost. In preclinical studies in macaques using an SIV prototype vaccine, this vaccination regimen elicited both anti-viral T cells and antibody, and provided 70% protection against acquisition during 12 weekly rectal exposures with a heterologous SIV. Higher avidity of the Env-specific Ab for the native form of the Env in the challenge virus correlated with lower likelihood of SIV infection.

Vaccination with embryonic stem cells protects against lung cancer: is a broad-spectrum prophylactic vaccine against cancer possible?

The antigenic similarity between tumors and embryos has been appreciated for many years and reflects the expression of embryonic gene products by cancer cells and/or cancer-initiating stem cells. Taking advantage of this similarity, we have tested a prophylactic lung cancer vaccine composed of allogeneic murine embryonic stem cells (ESC). Naïve C57BL/6 mice were vaccinated with ESC along with a source of granulocyte macrophage-colony stimulating factor (GM-CSF) in order to provide immunostimulatory adjuvant activity. Vaccinated mice were protected against subsequent challenge with implantable Lewis lung carcinoma (LLC). ESC-induced anti-tumor immunity was not due to a non-specific “allo-response” as vaccination with allogeneic murine embryonic fibroblasts did not protect against tumor outgrowth. Vaccine efficacy was associated with robust tumor-reactive primary and memory CD8⁺ T effector responses, Th1 cytokine response, higher intratumoral CD8⁺ T effector/CD4⁺CD25⁺Foxp3⁺ T regulatory cell ratio, and reduced myeloid derived suppressor cells in the spleen. Prevention of tumorigenesis was found to require a CD8-mediated cytotoxic T lymphocyte (CTL) response because in vivo depletion of CD8⁺ T lymphocytes completely abrogated the protective effect of vaccination. Importantly, this vaccination strategy also suppressed the development of lung cancer induced by the combination of carcinogen administration and chronic pulmonary inflammation. Further refinement of this novel vaccine strategy and identification of shared ESC/tumor antigens may lead to immunotherapeutic options for lung cancer patients and, perhaps more importantly, could represent a first step toward the development of prophylactic cancer vaccines.

The influence of monogalactosyldiacylglycerols from different marine macrophytes on immunogenicity and conformation of protein antigen of tubular immunostimulating complex

The tubular immunostimulating complex (TI-complex) is a novel nanoparticulate antigen delivery system consisting of cholesterol, triterpene glycoside cucumarioside A(2)-2, and glycolipid monogalactosyldiacylglycerol (MGDG) isolated from marine macrophytes. MGDG is crucial for the formation of a lipid matrix for the protein antigen incorporated in TI-complexes. Fatty acid composition and the physical state of this glycolipid depend on the taxonomic position of marine macrophytes. Therefore, the aim of the present work was to study the capacity of MGDGs, isolated from five species of marine macrophytes, to influence conformation and to enhance immunogenicity of porin from Yersinia pseudotuberculosis (YOmpF) as a model antigen of subunit vaccine based on TI-complexes. The trimeric porin was chosen for these experiments, because it was approximately two times more immunogenic than monomeric porin incorporated in TI-complexes. Immunization of mice with YOmpF within TI-complexes, comprised of different MGDGs, revealed a dependence of the immunostimulating effect of TI-complexes on the microvicosity of this glycolipid. TI-complexes comprising MGDGs from Sargassum pallidum and Ulva fenestrata with medium microviscosity induced maximal levels of anti-porin antibodies (four times higher when compared with those induced by pure porin). The adjuvant effect of TI-complexes based on other MGDGs varied by 2.8, 2.3 and 1.3 times for TI-complexes comprised of MGDGs from Zostera marina, Ahnfeltia tobuchiensis, and Laminaria japonica, respectively. MGDGs are also able to influence cytokine mechanisms of immunological regulation. DSC and spectroscopic studies showed that maximal immunostimulating effect of TI-complexes correlated with a moderate stabilizing influence of MGDGs from S. pallidum and U. fenestrata on the conformation of porin. The results obtained suggest lipid "nanofluidics" as a novel strategy for optimizing the immune response to protein antigens within lipid particulate systems.

Increased in vitro Cell Proliferation by Chitosan/pGM-CSF Complexes

Granulocyte macrophage colony stimulating factor, a potent hematopoietic cytokine, has been shown to stimulate production of white blood cells following chemotherapy. Therefore, the granulocyte macrophage colony stimulating factor gene is a potential candidate for the treatment of different pathological conditions. The purpose of this study is to investigate the suitability of chitosan as carrier for pORF-hGMCSF plasmid encoding granulocyte macrophage colony stimulating factor gene and also to study the effect of complexes on protein production and cell proliferation. Chitosan/pGM-CSF complexes were prepared using different (+/-) ratios (from 0.01/1 to 5/1). Complex formation was checked with agarose gel electrophoresis. The size and zeta potential values were measured. Enzyme and serum stability of complexes were studied. In vitro transfection properties of complexes were studied in HeLa cells. According to agarose gel electrophoresis, full complexation was obtained at 0.1/1 and higher chitosan/pGM-CSF ratios. Complexes having about 132 nm size and +13.7 mV zeta potential value were obtained. Chitosan complexes protected plasmid against enzymatic and serum effects. The gene expression-dependent cell proliferation after transfection of chitosan/pGM-CSF complexes at 72 h was markedly increased in comparision with the level of control group. These results indicate that the effect of chitosan/pGM-CSF complexes on cell proliferation was changed with N/P ratio and time-dependently. For GM-CSF therapy, chitosan/pGM-CSF complexes may be used as alternative to conventional protein treatments. Chitosan may be a good carrier for pORF-hGMCSF. Further, in vivo study is ongoing.

Bacteria as vectors for gene therapy of cancer

Anti-cancer therapy faces major challenges, particularly in terms of specificity of treatment. The ideal therapy would eradicate tumor cells selectively with minimum side effects on normal tissue. Gene or cell therapies have emerged as realistic prospects for the treatment of cancer, and involve the delivery of genetic information to a tumor to facilitate the production of therapeutic proteins. However, there is still much to be done before an efficient and safe gene medicine is achieved, primarily developing the means of targeting genes to tumors safely and efficiently. An emerging family of vectors involves bacteria of various genera. It has been shown that bacteria are naturally capable of homing to tumors when systemically administered resulting in high levels of replication locally. Furthermore, invasive species can deliver heterologous genes intra-cellularly for tumor cell expression. Here, we review the use of bacteria as vehicles for gene therapy of cancer, detailing the mechanisms of action and successes at preclinical and clinical levels.

Induction of specific cellular and humoral responses against renal cell carcinoma after combination therapy with cryoablation and granulocyte-macrophage colony stimulating factor: a pilot study

Cryotherapy offers a minimally invasive treatment option for the management of both irresectable and localized prostate, liver, pulmonary, and renal tumors. The antineoplastic effects of cryotherapy are mediated by direct tumor lysis and by indirect effects, such as intracellular dehydration, pH changes, and microvascular damage resulting in ischemic necrosis. In this study, we investigated whether percutaneous cryoablation of lung metastasis from renal cell carcinoma (RCC) in combination with aerosolized granulocyte-macrophage colony stimulating factor can induce systemic cellular and humoral immune responses in 6 patients with RCC. Peripheral blood mononuclear cells (PBMCs) were sequentially studied up to 63 days post cryoimmunotherapy (CI). PBMC from pre and post CI were phenotyped for lymphocyte subsets and tested for cytotoxicity and interferon-γ EliSpots directed at RCC cells. Humoral responses were measured by in vitro antibody synthesis assay directed at RCC cells. The immune monitoring data showed that CI induced tumor specific cytotoxic T lymphocyte, specific in vitro antitumor antibody responses, and enhanced Th1 cytokine production in 4 of 6 patients. More importantly, the magnitude of cellular and humoral antitumor response seems to be associated with clinical responses. These pilot data show that CI can induce robust and brisk cellular and humoral immune responses in patients with metastatic RCC, but requires further evaluation in optimized protocols.

Phase I study utilizing a novel antigen-presenting cell-targeted vaccine with Toll-like receptor stimulation to induce immunity to self-antigens in cancer patients

PURPOSE

The use of tumor-derived proteins as cancer vaccines is complicated by tolerance to these self-antigens. Tolerance may be broken by immunization with activated, autologous, ex vivo generated and antigen-loaded, antigen-presenting cells (APC); however, targeting tumor antigen directly to APC in vivo would be a less complicated strategy. We wished to test whether targeted delivery of an otherwise poorly immunogenic, soluble antigen to APC through their mannose receptors (MR) would induce clinically relevant immunity.

EXPERIMENTAL DESIGN

Two phase I studies were conducted with CDX-1307, a vaccine composed of human chorionic gonadotropin beta-chain (hCG-β) fused to an MR-specific monoclonal antibody, administered either locally (intradermally) or systemically (intravenously) in patients with advanced epithelial malignancies. An initial dose escalation of single-agent CDX-1307 was followed by additional cohorts of CDX-1307 combined with granulocyte-macrophage colony-stimulating factor (GM-CSF) and the Toll-like receptor (TLR) 3 agonist polyinosinic-polycytidylic acid (poly-ICLC) and TLR7/8 agonist resiquimod to activate the APC.

RESULTS

CDX-1307 induced consistent humoral and T-cell responses to hCG-β when coadministered with TLR agonists. Greater immune responses and clinical benefit, including the longest duration of stable disease, were observed with immunization combined with local TLR agonists. Immune responses were induced equally efficiently in patients with elevated and nonelevated levels of serum hCG-β. Antibodies within the serum of vaccinated participants had tumor suppressive function in vitro. Toxicity consisted chiefly of mild injection site reactions.

CONCLUSIONS

APC targeting and activation induce adaptive immunity against poorly immunogenic self-antigens which has implications for enhancing the efficacy of cancer immunotherapy.

Clinical uses of GM-CSF, a critical appraisal and update

The role of granulocyte-macrophage-colony-stimulating factor (GM-CSF) in the supportive care of cancer patients has been evaluated with promising results. More recently, GM-CSF has been added to regimens for the mobilization of hematopoietic progenitor cells. An expanding role for GM-CSF in regulating immune responses has been recognized based upon its activity on the development and maturation of antigen presenting cells and its capability for skewing the immune system toward Th1-type responses. GM-CSF has been shown to preferentially enhance both the numbers and activity of type 1 dendritic cells (DC1), the subsets of dendritic cells responsible for initiating cytotoxic immune responses. The increase in DC1 content and activity following local and systemic GM-CSF administration support a role for GM-CSF as an immune stimulant and vaccine adjuvant in cancer patients. GM-CSF has shown clinical activity as an immune stimulant in tumor cell and dendritic cell vaccines, and may increase antibody-dependent cellular cytotoxicity. The successful use of myeloid acting cytokines to enhance anti-tumor responses will likely require the utilization of GM-CSF in combination with cytotoxic or other targeted therapies.

Prevention of infection by a granulocyte-macrophage colony-stimulating factor co-expressing DNA/modified vaccinia Ankara simian immunodeficiency virus vaccine

A simian immunodeficiency virus (SIV) vaccine coexpressing granulocyte-macrophage colony stimulating factor (GM-CSF) prevented infection in 71% of macaques that received 12 rectal challenges. The SIVsmE660 challenge had the tropism of incident human immunodeficiency virus (HIV) infections and a similar genetic distance from the SIV239 vaccine as intraclade HIV isolates. The heterologous prime-boost vaccine regimen used recombinant DNA for priming and recombinant modified vaccinia Ankara for boosting. Co-expression of GM-CSF in the DNA prime enhanced the avidity of elicited immunoglobulin G for SIV envelope glycoproteins, the titers of neutralizing antibody for easy-to-neutralize SIV isolates, and antibody-dependent cellular cytotoxicity. Impressively, the co-expressed GM-CSF increased vaccine-induced prevention of infection from 25% in the non-GM-CSF co-expressing vaccine group to 71% in the GM-CSF co-expressing vaccine group. The prevention of infection showed a strong correlation with the avidity of the elicited Env-specific antibody for the Env of the SIVsmE660 challenge virus (r = 0.9; P < .0001).

AAV2-mediated in vivo immune gene therapy of solid tumours

Background

Many strategies have been adopted to unleash the potential of gene therapy for cancer, involving a wide range of therapeutic genes delivered by various methods. Immune therapy has become one of the major strategies adopted for cancer gene therapy and seeks to stimulate the immune system to target tumour antigens. In this study, the feasibility of AAV2 mediated immunotherapy of growing tumours was examined, in isolation and combined with anti-angiogenic therapy.

Methods

Immune-competent Balb/C or C57 mice bearing subcutaneous JBS fibrosarcoma or Lewis Lung Carcinoma (LLC) tumour xenografts respectively were treated by intra-tumoural administration of AAV2 vector encoding the immune up-regulating cytokine granulocyte macrophage-colony stimulating factor (GM-CSF) and the co-stimulatory molecule B7-1 to subcutaneous tumours, either alone or in combination with intra-muscular (IM) delivery of AAV2 vector encoding Nk4 14 days prior to tumour induction. Tumour growth and survival was monitored for all animals. Cured animals were re-challenged with tumourigenic doses of the original tumour type. In vivo cytotoxicity assays were used to investigate establishment of cell-mediated responses in treated animals.

Results

AAV2-mediated GM-CSF, B7-1 treatment resulted in a significant reduction in tumour growth and an increase in survival in both tumour models. Cured animals were resistant to re-challenge, and induction of T cell mediated anti-tumour responses were demonstrated. Adoptive transfer of splenocytes to naïve animals prevented tumour establishment. Systemic production of Nk4 induced by intra-muscular (IM) delivery of Nk4 significantly reduced subcutaneous tumour growth. However, combination of Nk4 treatment with GM-CSF, B7-1 therapy reduced the efficacy of the immune therapy.

Conclusions

Overall, this study demonstrates the potential for in vivo AAV2 mediated immune gene therapy, and provides data on the inter-relationship between tumour vasculature and immune cell recruitment.

Treatment with GM-CSF secreting myeloid leukemia cell vaccine prior to autologous-BMT improves the survival of leukemia-challenged mice

Vaccination with irradiated autologous tumor cells, engineered to secrete granulocyte macrophage-colony stimulating factor (GM-CSF) (GM tumor), can generate potent antitumor effects when combined with autologous bone marrow transplantation (BMT). That notwithstanding, the post-BMT milieu, characterized by marked cytopenia, can pose a challenge to the implementation of vaccine immunotherapies. To bypass this problem, partial post-BMT immune reconstitution has been allowed to develop prior to vaccination. However, delaying vaccination can also potentially allow the expansion of residual tumor cells. Other approaches have used reinfusion of "primed" autologous lymphocytes and multiple administrations of GM tumor cells, which required the processing of large amounts of tumor. Utilizing the MMB3.19 murine myeloid leukemia model, we tested whether a single dose of GM tumor cells, 7 days prior to syngeneic BMT, could be a curative treatment in MMB3.19-challenged recipient mice. This vaccination protocol significantly improved survival of mice by eliciting long-lasting host immune responses that survived lethal irradiation, and were even protective against post-BMT tumor rechallenge. Furthermore, we demonstrated that mature donor lymphocytes can also play a limited role in mounting the antitumor response, but our pre-BMT vaccination strategy obviated the need for either established de novo immune reconstitution or the use of multiple post-BMT immunizations.

Gene therapy for prostate cancer

Cancer remains a leading cause of morbidity and mortality. Despite advances in understanding, detection, and treatment, it accounts for almost one-fourth of all deaths per year in Western countries. Prostate cancer is currently the most commonly diagnosed noncutaneous cancer in men in Europe and the United States, accounting for 15% of all cancers in men. As life expectancy of individuals increases, it is expected that there will also be an increase in the incidence and mortality of prostate cancer. Prostate cancer may be inoperable at initial presentation, unresponsive to chemotherapy and radiotherapy, or recur following appropriate treatment. At the time of presentation, patients may already have metastases in their tissues. Preventing tumor recurrence requires systemic therapy; however, current modalities are limited by toxicity or lack of efficacy. For patients with such metastatic cancers, the development of alternative therapies is essential. Gene therapy is a realistic prospect for the treatment of prostate and other cancers, and involves the delivery of genetic information to the patient to facilitate the production of therapeutic proteins. Therapeutics can act directly (eg, by inducing tumor cells to produce cytotoxic agents) or indirectly by upregulating the immune system to efficiently target tumor cells or by destroying the tumor's vasculature. However, technological difficulties must be addressed before an efficient and safe gene medicine is achieved (primarily by developing a means of delivering genes to the target cells or tissue safely and efficiently). A wealth of research has been carried out over the past 20 years, involving various strategies for the treatment of prostate cancer at preclinical and clinical trial levels. The therapeutic efficacy observed with many of these approaches in patients indicates that these treatment modalities will serve as an important component of urological malignancy treatment in the clinic, either in isolation or in combination with current approaches.

Comparison on in vitro characterization of fucospheres and chitosan microspheres encapsulated plasmid DNA (pGM-CSF): formulation design and release characteristics

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine used in the treatment of serious conditions resulting from chemotherapy and bone marrow transplantation such as neutropenia and aplastic anemia. Despite these effects, GM-CSF has a very short biological half-life, and it requires frequent injection during the treatment. Therefore, the cytokine production is possible in the body with plasmid-encoded GM-CSF (pGM-CSF) coding for cytokine administered to the body. However, the selection of the proper delivery system for the plasmid is important. In this study, two different delivery systems, encapsulated plasmid such as fucoidan-chitosan (fucosphere) and chitosan microspheres, were prepared and the particle physicochemical properties evaluated. Fucospheres and chitosan microspheres size ranges are 151-401 and 376-681 nm. The zeta potential values of the microspheres were changed between 8.3-17.1 mV (fucosphere) and +21.9-28.9 mV (chitosan microspheres). The encapsulation capacity of fucospheres changed between 84.2% and 94.7% depending on the chitosan molecular weight used in the formulation. In vitro plasmid DNA release from both delivery systems exhibited slower profiles of approximately 90-140 days. Integrity of released samples was checked by agarose gel electrophoresis, and any additional band was not seen. All formulations were analyzed kinetically. The calculated regression coefficients showed a higher r2 value with zero-order kinetics. In conclusion, the characterizations of the microspheres can be modulated by changing the formulation variables, and it can be concluded that fucospheres might be a potential carrier system for the controlled delivery of GM-CSF encoding plasmid DNA.

Tumor vaccines expressing flt3 ligand synergize with ctla-4 blockade to reject preimplanted tumors

The transformation of a healthy cell into a malignant neoplasm involves numerous genetic mutations and aberrations in gene expression. As few of these changes are shared between individuals or types of cancer, the best source for eliciting broad-spectrum tumor immunity remains each patient's own tumor. Previously, we have shown that combining blockade of the T-cell-negative costimulatory molecule CTL-associated antigen 4 (CTLA-4) and vaccination with irradiated B16 tumor expressing granulocyte macrophage colony-stimulating factor (GM-CSF; Gvax) promotes rejection of established murine melanomas. Here we show that, like GM-CSF, the cytokine Flt3 ligand (Flt3L) expressed in B16 and coupled with CTLA-4 blockade promotes both prophylactic and therapeutic rejection of B16. When administered at the site of growing tumor, Gvax fails to prevent tumor outgrowth in any mice, whereas the B16-Flt3L vaccine (Fl3vax) induces the rejection of 75% of melanomas implanted 3 days before vaccination. Relative to Gvax, Fl3vax promotes greater infiltration of both the vaccine site and the tumor site by CD8+ T cells and "sentinel" and plasmacytoid dendritic cells. Gvax and Fl3vax did not synergize when used in combination in treating B16 melanoma even in the context of CD25+ regulatory T-cell depletion. Further, we show that a combination of Flt3L expression and CTLA-4 blockade can also promote the rejection of established TRAMP prostate adenocarcinomas, proving that the utility of this treatment extends beyond melanoma. Engineering Flt3L to be constitutively secreted and attaching an IgG2a tail yielded a B16 vaccine that, when combined with CTLA-4 blockade, prevented the outgrowth of significantly more 5-day implanted B16-BL6 tumors than did Gvax.

GM-CSF Gene-Modifed Cancer Cell Immunotherapies: Of Mice and Men

GVAX cancer immunotherapies are composed of whole tumor cells genetically modified to secrete the immune stimulatory cytokine, granulocyte-macrophage colony-stimulating factor (GM-CSF), and then irradiated to prevent further cell division. Both autologous (patient specific) and allogeneic (non-patient specific) GVAX platforms have been evaluated either as single agents or in combination with other immunomodulatory strategies. Many early-phase clinical trials have now been completed. Results have consistently demonstrated a favorable safety profile manifested primarily by injection site reactions and flu-like symptoms. Consistent evidence of immune activation and clinical activity, including radiologic tumor regressions, has been seen across multiple cancer indications in both early- and late-stage disease. Phase 3 trials evaluating an allogeneic GVAX immunotherapy product in prostate cancer are under way.

Promises and Limitations of Murine Models in the Development of Anticancer T-Cell Vaccines

Murine models have been instrumental in defining the basic mechanisms of antitumor immunity. Most of these mechanisms have since been shown to operate in humans as well. Based on these similarities, active vaccination strategies aimed at eliciting antitumor T-cell responses have been elaborated and successfully implemented in various mouse models. However, the results of human antitumor vaccination trials have been rather disappointing thus far. This review summarizes the different experimental approaches used in mice to induce antitumor T-cell responses and identifies some critical parameters that should be considered when evaluating results from murine models.

Systemic effects of local radiotherapy

Radiotherapy is generally used to treat a localised target that includes cancer. Increasingly, evidence indicates that radiotherapy recruits biological effectors outside the treatment field and has systemic effects. We discuss the implications of such effects and the role of the immune system in standard cytotoxic treatments. Because the effects of chemotherapy and radiotherapy are sensed by the immune system, their combination with immunotherapy presents a new therapeutic opportunity. Radiotherapy directly interferes with the primary tumour and possibly reverses some immunosuppressive barriers within the tumour microenvironment-ideally, recovering the role of the primary tumour as an immunogenic hub. Local radiation also triggers systemic effects that can be used in combination with immunotherapy to induce responses outside the radiation field.

The role of granulocyte macrophage-colony-stimulating factor in acute intestinal inflammation

An imbalance of mucosal pro- and anti-inflammatory cytokines is crucial in the pathogenesis of inflammatory bowel disease (IBD). GM-CSF influences the development of hemopoietic cells. The precise role of GM-CSF in IBD remains to be elucidated. GM-CSF gene knockout (GM-CSF(-/-)) and wild-type (Wt) mice were challenged with 2.5% dextran sulfate sodium (DSS) for 7 days. The ensued clinical and pathological changes, macrophage infiltration, colonic cytokine production, and bacterial counts were examined. DSS-treated GM-CSF(-/-) mice developed more severe acute colitis than DSS-treated Wt mice, reflected by a greater body weight loss, more rectal bleeding, and aggravated histopathological changes. More infiltrating macrophages were observed in GM-CSF(-/-), compared with Wt mice following DSS challenge, correlating with monocyte chemoattractant protein-1 (MCP-1) production. The levels of colonic IL-17 and TNF-alpha were increased significantly in GM-CSF(-/-) mice, but not in Wt mice, following DSS administration. The level of IL-6 was increased by 1.5- and 2-fold in the colon of GM-CSF(-/-) and Wt mice, respectively, following DSS challenge. No significant changes in IL-4 and IFN-gamma were detected in Wt and GM-CSF(-/-) mice following DSS treatment. The bacteria recovery from colon was increased about 15- and 5-fold, respectively, in Wt mice and GM-CSF(-/-) mice following DSS challenge. These results suggest that GM-CSF(-/-) mice are more susceptible to acute DSS-induced colitis, possibly because of an impaired gut innate immune response as a result of diminished GM-CSF.

Lymphocyte activation gene-3 fusion protein increases the potency of a granulocyte macrophage colony-stimulating factor-secreting tumor cell immunotherapy

PURPOSE

The purpose of the present study was to evaluate granulocyte macrophage colony-stimulating factor (GM-CSF)-secreting tumor cell immunotherapy, which is known to stimulate a potent and long-lasting antigen-specific immune response in combination with lymphocyte activation gene-3 fusion protein (LAG-3Ig), which has been shown to act as an adjuvant for priming T helper type 1 and cytotoxic T-cell responses.

EXPERIMENTAL DESIGN

Survival and immune monitoring studies were done in the B16 melanoma model. GM-CSF-secreting tumor cell immunotherapy was administered as a single s.c. injection and LAG-3Ig was administered s.c. at the immunotherapy site.

RESULTS

The studies reported here show that combining LAG-3Ig with GM-CSF-secreting tumor cell immunotherapy prolonged the survival of tumor-bearing animals compared with animals treated with either therapy alone. Prolonged survival correlated with increased numbers of systemic IFN gamma-secreting CD8+ T cells and a significantly increased infiltration of activated effector CD8+ T cells into the tumor. Moreover, an increase in antigen-specific IgG1 humoral responses was detected in serum of animals injected with the combination therapy compared with animals injected with either therapy alone.

CONCLUSION

LAG-3Ig combined with a GM-CSF-secreting tumor cell immunotherapy stimulated both cellular and humoral antitumor immune responses that correlated with prolonged survival in tumor-bearing animals.

Therapeutics targeting tumor immune escape: towards the development of new generation anticancer vaccines

Despite the evidence that immune effectors can play a significant role in controlling tumor growth under natural conditions or in response to therapeutic manipulation, it is clear that malignant cells evade immune surveillance in most cases. Considering that anticancer vaccination has reached a plateau of results and currently no vaccination regimen is indicated as a standard anticancer therapy, the dissection of the molecular events underlying tumor immune escape is the necessary condition to make anticancer vaccines a therapeutic weapon effective enough to be implemented in the routine clinical setting. Recent years have witnessed significant advances in our understanding of the molecular mechanisms underlying tumor immune escape. These mechanistic insights are fostering the development of rationally designed therapeutics aimed at reverting the immunosuppressive circuits that undermine an effective antitumor immune response. In this review, the best characterized mechanisms that allow cancer cells to evade immune surveillance are overviewed and the most debated controversies constellating this complex field are highlighted. In addition, the latest therapeutic strategies devised to overcome tumor immune escape are described, with special regard to those entering clinical phase investigation.

Combination of Fasl and GM-CSF confers synergistic antitumor immunity in an in vivo model of the murine Lewis lung carcinoma

Gene transfer of Fas ligand (FasL) to tumor cells has been demonstrated to inhibit tumor growth in vivo, and neutrophils are primarily responsible for this immunoprotection. The granulocyte-macrophage colony stimulating factor (GM-CSF) secreted by tumor vaccine can recruit dendritic cells (DCs) for efficient antigen presentation to T cells that generate the tumor-specific response. To investigate whether the combination of FasL and GM-CSF can efficiently suppress tumor growth, we have established Lewis lung carcinoma (LLC-1) cells that are transduced with GM-CSF (LLC/GM-CSF), FasL (LLC/FasL) or both genes (LLC/FasL/GM-CSF) to test their tumorigenic potential in vivo. Mice inoculated with LLC/GM-CSF display high survival rates along with reduction of tumor growth. In contrast, none of the mice injected with LLC/FasL or LLC/FasL/GM-CSF develop tumors. Specific memory immune response and delayed LLC-1 tumor growth are found in mice immunized with LLC-1/FasL or LLC-1/FasL/GM-CSF. Furthermore, therapeutic effects are observed only when LLC-1/FasL/GM-CSF tumor vaccine is employed to retard growth of preexisting LLC-1 tumors. Tumor growth is also completely suppressed in mice injected with a mixture of LLC-1 and LLC-1/FasL/GM-CSF. In addition, IL-12 production, cytotoxic T-cell activity and IgG against LLC-1 are manifested in mice injected with LLC/FasL/GM-CSF. Our data show that FasL-induced pathway triggers expression of proinflammatory cytokines, including IL-1 beta, IL-6, MIP-2 and MCP-1, while GM-CSF-dependent pathway promotes functional maturation and activation of DCs. Taken together, the results indicate that dual gene-based delivery with FasL and GM-CSF may serve as a more effective tumor vaccine to suppress lung cancer cell growth in vivo.

Bead-selected antitumor genetic cell vaccines

Cancer vaccines have always been in the scope of gene therapy research. One of the most successful approaches has been working with genetically modified tumor cells. However, to become a clinical reality, tumor cells must suffer a long and risky process from the extraction from the patient to the reimplantation as a vaccine. In this work, we explain our group’s approach to reduce the cell number required to achieve an immune response against a melanoma murine model, employing bead-selected B16 tumor cells expressing GM-CSF and B7.2.

Treatment of pulmonary metastatic tumors in mice using lentiviral vector-engineered stem cells

Active cancer immunotherapy relies on functional tumor-specific effector T lymphocytes for tumor elimination. Dendritic cells (DCs), as most potent antigen-presenting cells, have been popularly employed in clinical and experimental tumor treatments. We have previously demonstrated that lentiviral vector-mediated transgene delivery to DC progenitors, including bone marrow cells and hematopoietic stem cells, followed by transplantation supports systemic generation of great numbers of tumor antigen-presenting DCs. These DCs subsequently stimulate marked and systemic immune activation. Here, we examined whether this level of immune activation is sufficient to overcome tumor-induced tolerogenic environment for treating an established aggressive epithelial tumor. We showed that a combination treatment of granulocyte macrophage-colony stimulating factor and cytosine-phosphate-guanine-containing oligonucleotide stimulated large numbers of tumor antigen-presenting DCs in situ from transgene-modified stem cells. Moreover, these in situ generated and activated DCs markedly stimulated activation of antigen-specific CD4 and CD8 T cells by augmenting their numbers, as well as function, even in a tumor-bearing tolerogenic environment. This leads to significant improvement in the therapeutic efficacy of established pulmonary metastases. This study suggests that lentiviral vector-modified stem cells as DC progenitors may be used as an effective therapeutic regimen for treating metastatic epithelial tumors.

GM-CSF DNA: an adjuvant for higher avidity IgG, rectal IgA, and increased protection against the acute phase of a SHIV-89.6P challenge by a DNA/MVA immunodeficiency virus vaccine

Single intradermal or intramuscular inoculations of GM-CSF DNA with the DNA prime for a simian-human immunodeficiency virus (SHIV)-89.6 vaccine, which consists of DNA priming followed by modified vaccinia Ankara (MVA) boosting, increased protection of both the blood and intestines against the acute phase of an intrarectal SHIV-89.6P challenge. GM-CSF appeared to contribute to protection by enhancing two antibody responses: the avidity maturation of anti-Env IgG in blood (p=or<0.01) and the presence of long lasting anti-viral IgA in rectal secretions (p<0.01). The avidity of anti-Env IgG showed strong correlations with protection both pre and post challenge. Animals with the highest avidity anti-Env Ab had 1000-fold reductions in peak viremia over those with the lowest avidity anti-Env Ab. The enhanced IgA response was associated with the best protection, but did not achieve significance.