Enhancing the clinical activity of granulocyte-macrophage colony-stimulating factor-secreting tumor cell vaccines

EDIL3 as an Angiogenic Target of Immune Exclusion Following Checkpoint Blockade

Immune checkpoint blockade (ICB) has become the standard of care for several solid tumors. Multiple combinatorial approaches have been studied to improve therapeutic efficacy. The combination of antiangiogenic agents and ICB has demonstrated efficacy in several cancers. To improve the mechanistic understanding of synergies with these treatment modalities, we performed screens of sera from long-term responding patients treated with ipilimumab and bevacizumab. We discovered a high-titer antibody response against EGF-like repeats and discoidin I-like domains protein 3 (EDIL3) that correlated with favorable clinical outcomes. EDIL3 is an extracellular protein, previously identified as a marker of poor prognosis in various malignancies. Our Tumor Immune Dysfunction and Exclusion analysis predicted that EDIL3 was associated with immune exclusion signatures for cytotoxic immune cell infiltration and nonresponse to ICB. Cancer-associated fibroblasts (CAF) were predicted as the source of EDIL3 in immune exclusion-related cells. Furthermore, The Cancer Genome Atlas Skin Cutaneous Melanoma (TCGA-SKCM) and CheckMate 064 data analyses correlated high levels of EDIL3 with increased pan-fibroblast TGFβ response, enrichment of angiogenic signatures, and induction of epithelial-to-mesenchymal transition. Our in vitro studies validated EDIL3 overexpression and TGFβ regulation in patient-derived CAFs. In pretreatment serum samples from patients, circulating levels of EDIL3 were associated with circulating levels of VEGF, and like VEGF, EDIL3 increased the angiogenic abilities of patient-derived tumor endothelial cells (TEC). Mechanistically, three-dimensional microfluidic cultures and two-dimensional transmigration assays with TEC endorsed EDIL3-mediated disruption of the lymphocyte function-associated antigen-1 (LFA-1)-ICAM-1 interaction as a possible means of T-cell exclusion. We propose EDIL3 as a potential target for improving the transendothelial migration of immune cells and efficacy of ICB therapy.

Crosstalk between epithelium, myeloid and innate lymphoid cells during gut homeostasis and disease

The gut epithelium not only provides a physical barrier to separate a noxious outside from a sterile inside but also allows for highly regulated interactions between bacteria and their products, and components of the immune system. Homeostatic maintenance of an intact epithelial barrier is paramount to health, requiring an intricately regulated and highly adaptive response of various cells of the immune system. Prolonged homeostatic imbalance can result in chronic inflammation, tumorigenesis and inefficient antitumor immune control. Here we provide an update on the role of innate lymphoid cells, macrophages and dendritic cells, which collectively play a critical role in epithelial barrier maintenance and provide an important linkage between the classical innate and adaptive arm of the immune system. These interactions modify the capacity of the gut epithelium to undergo continuous renewal, safeguard against tumor formation and provide feedback to the gut microbiome, which acts as a seminal contributor to cellular homeostasis of the gut.

Nano-hydroxyapatite-evoked immune response synchronized with controllable immune adjuvant release for strengthening melanoma-specific growth inhibition

Concerns about the potential systematic toxicity limit the extensive application of traditional therapeutic drugs for melanoma therapy, nano-hydroxyapatite (nHA) with good biocompatibility and anti-tumor ability could be an alternative choice. In this study, nHA was employed as an anti-tumor biomaterial due to its tumor-specific toxicity. Meanwhile, granulocyte-macrophage colony-stimulating factor (GM-CSF) served as the immune adjuvant to activate the immune response. The delivery platform was fabricated by co-encapsulation of both nHA and GM-CSF into a biocompatible thermosensitive PLGA-PEG-PLGA hydrogel. The results showed that the bio-activities of nHA and GM-CSF could be well-maintained within the hydrogel. Interestingly, the addition of nHA could attenuate the burst release of GM-CSF due to possible protein absorption capacity of nHA, which is beneficial for GM-CSF sustainable release at the tumor site, achieving boosted and prolonged anti-tumor immunity. The in vitro and in vivo data demonstrated that nHA/GM-CSF hydrogel exhibited greater potency to inhibit tumor growth via enhanced CD8⁺ T-cell response compared with hydrogel and nHA hydrogel groups, contributed by the synergistic effects of nHA and GM-CSF. Overall, the strategy combining nHA and immune adjuvant shows great promise, which largely broadens the choice of combinational therapies for melanoma. STATEMENT OF SIGNIFICANCE: Nano-hydroxyapatite (nHA) has been confirmed to specifically inhibit melanoma tumor growth and induce immune response. However, its antitumor efficiency and immunity-evoking capacity are limited. In this study, granulocyte-macrophage colony-stimulating factor (GM-CSF) was introduced to serve as the immune adjuvant. Both of them were encapsulated into a biocompatible thermosensitive PLGA-PEG-PLGA hydrogel. The addition of nHA could attenuate the burst release of GM-CSF due to the interaction with nHA, which is beneficial for GM-CSF sustainable release at tumor site, achieving boosted and prolonged anti-tumor immunity. Anti-tumor immune response could be activated due to the release of tumor-associated antigen and tumor debris induced by the specifically tumor inhibition effect of nHA and GM-CSF. The combination of nHA and GM-CSF could play synergistic inhibiting effect on tumor growth via boosting and prolonging anti-tumor immunity.

Cancer Vaccine in Cold Tumors: Clinical Landscape, Challenges, and Opportunities

The idea of cancer immunotherapy is to stimulate the immune system to fight tumors without destroying normal cells. One of the anticancer therapy methods, among many, is based on the use of cancer vaccines that contain tumor antigens in order to induce immune responses against tumors. However, clinical trials have shown that the use of such vaccines as a monotherapy is ineffective in many cases, since they do not cause a strong immune response. Particular tumors are resistant to immunotherapy due to the absence or insufficient infiltration of tumors with CD8+ T cells, and hence, they are called cold or non-inflamed tumors. Cold tumors are characterized by a lack of CD8+ T cell infiltration, the presence of anti-inflammatory myeloid cells, tumor-associated M2 macrophages, and regulatory T cells. It is very important to understand which stage of the antitumor response does not work properly in order to use the right strategy for the treatment of patients. Applying other therapeutic methods alongside cancer vaccines can be more rational for cold tumors which do not provoke the immune system strongly. Herein, we indicate some combinational therapies that have been used or are in progress for cold tumor treatment alongside vaccines.

A Functional GM-CSF Receptor on Dendritic Cells Is Required for Efficient Protective Anti-Tumor Immunity

Dendritic cells (DC) play a major role during the priming phase of anti-tumor immunization, as they are required for an efficient tumor-associated antigens presentation. At least one dendritic cell-based therapy has already been successfully approved by regulators for clinical application in prostate cancer patients. Moreover, DC development is dependent on the granulocyte macrophage colony stimulating factor (GM-CSF), a cytokine that has been successfully used as a potent inducer of anti-tumoral immunity. To better understand the relation between DC and GM-CSF in anti-tumor immunity, we studied the DC function in mice lacking the cytokine receptor common subunit beta (βc-/-) for GM-CSF, IL-3 and IL-5 and immunized with irradiated tumor cells. Such immunization induces a protective, specific tumor immunization in wild-type mice, while βc-/- mice failed to mount an immune response. Upon in vitro stimulation, DC from βc-/- mice (DCβc-/-) are unable to undergo a full maturation level. In vivo experiments show that they lack the ability to prevent tumor growth, in contrast to DCWT. Moreover, matured DCWT rescued immunization in βc-/- mice. DC maturation is dependent on a functional pathway involving GM-CSF signaling through a biologically functional receptor. These findings may contribute to new strategies for efficient anti-tumor immunotherapies.

Neoantigen-reactive T cells exhibit effective anti-tumor activity against colorectal cancer

Neoantigens play a crucial role in cancer immunotherapy. However, the effectiveness and safety of neoantigen-based immunotherapies in patients with colorectal cancer (CRC), particularly in the Chinese population, have not been well studied. This study explored the feasibility and effectiveness of neoantigens in the treatment of CRC. Whole-exome sequencing (WES) and transcriptome sequencing were used to identify somatic mutations, RNA expression, and human leukocyte antigen (HLA) alleles. Neoantigen candidates were predicted, and immunogenicity was assessed. The neoantigens TSHZ3-L523P, RARA-R83H, TP53-R248W, EYA2-V333I, and NRAS-G12D from Patient 4 (PW4); TASP1-P161L, RAP1GAP-S215R, MOSPD1-V63I, and NAV2-D1973N from Patient 10 (PW10); and HAVCR2-F39V, SEC11A-R11L, SMPDL3B-T452M, LRFN3-R118Q, and ULK1-S248L from Patient 11 (HLA-A0201⁺PW11) induced a heightened neoantigen-reactive T cell (NRT) response as compared with the controls in peripheral blood lymphocytes (PBLs) isolated from patients with CRC. In addition, we identified neoantigen-containing peptides SEC11A-R11L and ULK1-S248L from HLA-A0201⁺PW11, which more effectively elicited specific CTL responses than the corresponding native peptides in PBLs isolated from HLA-A0201⁺PW11 as well as in HLA-A2.1/K^b transgenic mice. Importantly, adoptive transfer of NRTs induced by vaccination with two mutant peptides could effectively inhibit tumor growth in tumor-bearing mouse models. These data indicate that neoantigen-containing peptides with high immunogenicity represent promising candidates for peptide-mediated personalized therapy.

Abbreviations: CRC: colorectal cancer; DCs: dendritic cells; ELISPOT: enzyme-linked immunosorbent spot; E:T: effector:target; HLA: human leukocyte antigen; MHC: major histocompatibility complex; Mut: mutant type; NGS: next-generation sequencing; NRTs: neoantigen-reactive T cells; PBMCs: peripheral blood mononuclear cells; STR: short tandem repeat; PBLs: peripheral blood lymphocytes; PBS: phosphate-buffered saline; PD-1: programmed cell death protein 1; TILs: tumor-infiltrating lymphocytes; RNA-seq: RNA sequencing; Tg: transgenic; TMGs: tandem minigenes; WES: whole-exome sequencing; WT: wild-type.

Inhibition of purinergic P2X receptor 7 (P2X7R) decreases granulocyte-macrophage colony-stimulating factor (GM-CSF) expression in U251 glioblastoma cells

Glioblastoma is the most aggressive form of primary brain cancer, with a median survival of 12-15 months. The P2X receptor 7 (P2X7R) is upregulated in glioblastoma and is associated with increased tumor cell proliferation. The cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) is also upregulated in glioblastoma and has been shown to have both pro- and anti-tumor functions. This study investigates the potential mechanism linking P2X7R and GM-CSF in the U251 glioblastoma cell line and the therapeutic potential of P2X7R antagonism in this setting. P2X7R protein and mRNA was demonstrated to be expressed in the U251 cell line as assessed by immunocytochemistry and qPCR. Its channel function was intact as demonstrated by live cell confocal imaging using a calcium indicator Fluo-4 AM. Inhibition of P2X7R using antagonist AZ10606120, decreased both GM-CSF mRNA (P < 0.05) and protein (P < 0.01) measured by qPCR and ELISA respectively. Neutralization of GM-CSF with an anti-GM-CSF antibody did not alter U251 cell proliferation, however, P2X7R antagonism with AZ10606120 significantly reduced U251 glioblastoma cell numbers (P < 0.01). This study describes a novel link between P2X7R activity and GM-CSF expression in a human glioblastoma cell line and highlights the potential therapeutic benefit of P2X7R inhibition with AZ10606120 in glioblastoma.

The Pleiotropic Effects of the GM-CSF Rheostat on Myeloid Cell Differentiation and Function: More Than a Numbers Game

Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) is a myelopoietic growth factor that has pleiotropic effects not only in promoting the differentiation of immature precursors into polymorphonuclear neutrophils (PMNs), monocytes/macrophages (MØs) and dendritic cells (DCs), but also in controlling the function of fully mature myeloid cells. This broad spectrum of GM-CSF action may elicit paradoxical outcomes-both immunostimulation and immunosuppression-in infection, inflammation, and cancer. The complexity of GM-CSF action remains to be fully unraveled. Several aspects of GM-CSF action could contribute to its diverse biological consequences. Firstly, GM-CSF as a single cytokine affects development of most myeloid cells from progenitors to mature immune cells. Secondly, GM-CSF activates JAK2/STAT5 and also activate multiple signaling modules and transcriptional factors that direct different biological processes. Thirdly, GM-CSF can be produced by different cell types including tumor cells in response to different environmental cues; thus, GM-CSF quantity can vary greatly under different pathophysiological settings. Finally, GM-CSF signaling is also fine-tuned by other less defined feedback mechanisms. In this review, we will discuss the role of GM-CSF in orchestrating the differentiation, survival, and proliferation during the generation of multiple lineages of myeloid cells (PMNs, MØs, and DCs). We will also discuss the role of GM-CSF in regulating the function of DCs and the functional polarization of MØs. We highlight how the dose of GM-CSF and corresponding signal strength acts as a rheostat to fine-tune cell fate, and thus the way GM-CSF may best be targeted for immuno-intervention in infection, inflammation and cancer.

Antigen Priming with Enantiospecific Cationic Lipid Nanoparticles Induces Potent Antitumor CTL Responses through Novel Induction of a Type I IFN Response

Certain types of cationic lipids have shown promise in cancer immunotherapy, but their mechanism of action is poorly understood. In this study, we describe the properties of an immunotherapeutic consisting of the pure cationic lipid enantiomer R-1,2-dioleoyl-3-trimethyl-ammonium-propane (R-DOTAP) formulated with modified viral or self-peptide Ags. R-DOTAP formulations with peptide Ags stimulate strong cross-presentation and potent CD8 T cell responses associated with a high frequency of polyfunctional CD8 T cells. In a human papillomavirus tumor model system, a single s.c. injection of tumor-bearing mice with R-DOTAP plus human papillomavirus Ags induces complete regression of large tumors associated with an influx of Ag-specific CD8 T cells and a reduction of the ratio of regulatory/Ag-specific CD8 T cells. R-DOTAP also synergizes with an anti-PD1 checkpoint inhibitor, resulting in a significant inhibition of B16 melanoma tumor growth. We found that R-DOTAP stimulates type I IFN production by dendritic cells in vivo and in vitro. s.c. injection of R-DOTAP results in an IFN-dependent increase in draining lymph node size and a concomitant increase in CD69 expression. Using knockout mice, we show that type I IFN is required for the induction of CD8 T cell activity following administration of R-DOTAP plus Ag. This response requires Myd88 but not TRIF or STING. We also show that R-DOTAP stimulates both TLR7 and 9. Collectively, these studies reveal that R-DOTAP stimulates endosomal TLRs, resulting in a Myd88-dependent production of type I IFN. When administered with Ag, this results in potent Ag-specific CD8 T cell responses and antitumor activity.

Agonist OX40 immunotherapy improves survival in glioma-bearing mice and is complementary with vaccination with irradiated GM-CSF-expressing tumor cells

Background

Glioma immunotherapy is an active area of clinical investigation. Glioma-associated immunosuppression remains an obstacle to efficacious immunotherapy, and combination approaches are likely necessary for durable success. OX40 is a member of the tumor necrosis factor receptor superfamily that is upregulated on activated lymphocytes, ligation of which results in enhanced activity and may be active against cancer. We sought to confirm the efficacy of agonist anti-OX40 immunotherapy against glioma and hypothesized that it is complementary with irradiated whole tumor cell vaccination.

Methods

GL261 tumor cells were implanted into the right frontal lobes of syngeneic mice, which were then treated with controls, agonist anti-OX40 monoclonal antibody, vaccination with subcutaneous injection of irradiated granulocyte macrophage colony stimulating factor (GM-CSF)-expressing GL261 cells (GVAX), or vaccination + agonist anti-OX40 therapy. Animals were followed for survival. On day 18, splenocytes were harvested for enzyme-linked immunosorbent spot analyses and brains were harvested for immunohistochemistry and flow cytometry analyses of infiltrating lymphocytes.

Results

Combination immunotherapy with GVAX and systemic agonist anti-OX40 monoclonal antibody improved survival by 14 days over controls (median survival 36 vs 22 days, P < 0.00005). Systemically, T helper cell type 1 (Th1) antitumor immunity was enhanced significantly by combination therapy. In the brain, combination immunotherapy increased the percentage of Th1 CD4+ T lymphocytes and reduced the fraction that were Th2. In the brain, vaccination improved the ratio of CD8+ to FoxP3+ T lymphocytes, while combination immunotherapy reversed intracranial T-lymphocyte exhaustion, reducing their coexpression of programmed cell death protein 1 (PD-1) and T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) as well as PD-1 and lymphocyte-activation gene 3 (LAG-3).

Conclusions

Anti-OX40 immunotherapy is active against intracranial glioma and synergizes with GVAX. Vaccination and anti-OX40 immunotherapy are mechanistically complementary, particularly in the glioma microenvironment.

The Future of the Cytokine Discipline

The study of cytokines has evolved from the detection of functional activities present in tissue culture supernatants to the characterization of the three-dimensional molecular structures of the cytokines and their receptors. Investigators studying cytokines need to have specialized expertise in using cytokine assays, assessing their receptor interactions, signal transduction, gene activation, and biological effects, and in the therapeutic utilization of agonists and antagonists. Cytokinology can therefore be considered a discipline. In this article, I have considered studies leading to the identification of novel cytokines, potential producers of cytokine mimics such as viruses and the microbiome, and the complex interactions of the cytokine network with our vital functions. Our ever-increasing success in using cytokines and, in particular, cytokine inhibitors therapeutically suggest that cytokinology will eventually become an independent discipline.

Cytokines in the Treatment of Cancer

Cytokines are major regulators of innate and adaptive immunity that enable cells of the immune system to communicate over short distances. Cytokine therapy to activate the immune system of cancer patients has been an important treatment modality and continues to be a key contributor to current clinical cancer research. Interferon alpha (IFNα) is approved for adjuvant treatment of completely resected high-risk melanoma patients and several refractory malignancies. High-dose interleukin-2 (HDIL-2) is approved for treatment of metastatic renal cell cancer and melanoma, but both agents are currently less commonly used with the development of newer agents. Granulocyte-macrophage colony-stimulating factor (GM-CSF), IFN gamma (IFNγ), IL-7, IL-12, and IL-21 were evaluated in clinical trials and remain part of certain investigational trials. The initial single-agent clinical trials with the long-awaited IL-15 have been completed and combination trials with antitumor antibodies or checkpoint inhibitors (CPIs) have been initiated. However, cytokines in monotherapy have not fulfilled the promise of efficacy seen in preclinical experiments. They are often associated with severe dose-limiting toxicities that are manageable with appropriate dosing and are now better understood to induce immune-suppressive humoral factors, suppressive cells, and cellular checkpoints, without consistently inducing a tumor-specific response. To circumvent these impediments, cytokines are being investigated clinically with new engineered cytokine mutants (superkines), chimeric antibody-cytokine fusion proteins (immunokines), anticancer vaccines, CPIs, and cancer-directed monoclonal antibodies to increase their antibody-dependent cellular cytotoxicity or sustain cellular responses and anticancer efficacy. In this review, we summarize current knowledge and clinical application of cytokines either as monotherapy or in combination with other biological agents. We emphasize a discussion of future directions for research on these cytokines, to bring them to fruition as major contributors for the treatment of metastatic malignancy.

A2A Adenosine Receptor Gene Deletion or Synthetic A2A Antagonist Liberate Tumor-Reactive CD8+ T Cells from Tumor-Induced Immunosuppression

Tumor hypoxia-driven accumulation of extracellular adenosine was shown to facilitate tumor evasion by engaging the immunosuppressive, intracellular cAMP-elevating A₂ adenosine receptors (A₂R) on tumor-reactive effector T cells, but there remains a need for careful evaluation of the limiting factors and properties of A₂R blockade-enabled antitumor immunity. In studies of A_2AR and/or A_2BR gene-deficient mice, we found that A_2AR deletion-but not A_2BR deletion-liberates endogenous CD8⁺ T cell antitumor immunity against weakly immunogenic MCA205 sarcomas. Studies of adoptively transferred A_2AR^-/-, A_2BR^-/-, or A_2AR^-/-/A_2BR^-/- tumor-reactive T cells confirmed that immunosuppression in the tumor microenvironment was mediated by A_2AR on CD8⁺ T cells. Treatment with A_2AR antagonist mimicked A_2AR gene deletion in adoptive T cell immunotherapy. This therapeutic benefit of targeting A_2AR was independent of the anatomical location of tumor growth. The enhanced antitumor reactivity also led to the eradication of established intracranial tumors, which was associated with mouse survival and the maintenance of long-lasting, tumor-specific immunological memory. The blockade of the A_2AR on adoptively transferred T cells by synthetic A_2AR antagonist led to higher levels of IFN-γ secretion by tumor-infiltrating CD8⁺ T cells. These data clarify the mechanism of hypoxia-driven immunosuppression in the tumor microenvironment by A_2AR on tumor-reactive CD8⁺ T cells and show that selective A_2AR antagonists can be effective in improving the outcomes of T cell-based immunotherapies. Demonstration of the T cell dose dependency of tumor rejection points to a major limitation of current cancer immunotherapies, in which the presence of sufficient numbers of tumor-reactive T cells in a patient is not known.

Evaluation of the diagnostic performance of panfungal polymerase chain reaction assay in invasive fungal diseases

Timely diagnosis of invasive fungal diseases (IFDs) is important, as delays in treatment initiation are associated with increased mortality rates. However, early diagnosis of IFDs in immunocompromised patients remains difficult. The conventional diagnostic methods currently used for IFDs are not sufficiently effective. Molecular tests, such as polymerase chain reaction (PCR)-based assays, have great potential to improve the early diagnosis of IFDs due to their sensitivity and specificity. In the present study, the diagnostic performance of panfungal PCR assays in IFD patients who received bone marrow transplantation was evaluated. The results suggested that panfungal PCR assay offered a quick and convenient guide for clinical decision-making by identifying higher numbers of fungal species in comparison with the conventional blood culture method. Furthermore, panfungal PCR assay exhibited a sensitivity of 93% and a specificity of 71% in the diagnosis of IFD patients based on the EORTC/MSG criteria. Thus, the present study concluded that the reported PCR-based method was effective and sensitive in early IFD diagnosis and should be integrated into clinical decision-making for the treatment of IFDs in the future.

Dendritic cell-based immunotherapy

Immunotherapy using dendritic cell (DC)-based vaccination is an approved approach for harnessing the potential of a patient's own immune system to eliminate tumor cells in metastatic hormone-refractory cancer. Overall, although many DC vaccines have been tested in the clinic and proven to be immunogenic, and in some cases associated with clinical outcome, there remains no consensus on how to manufacture DC vaccines. In this review we will discuss what has been learned thus far about human DC biology from clinical studies, and how current approaches to apply DC vaccines in the clinic could be improved to enhance anti-tumor immunity.

Systematic review of the use of granulocyte-macrophage colony-stimulating factor in patients with advanced melanoma

Several immunomodulatory checkpoint inhibitors have been approved for the treatment of patients with advanced melanoma, including ipilimumab, nivolumab and pembrolizumab. Talimogene laherparepvec is the first oncolytic virus to gain regulatory approval in the USA; it is also approved in Europe. Talimogene laherparepvec expresses granulocyte–macrophage colony-stimulating factor (GM-CSF), and with other GM-CSF-expressing oncolytic viruses in development, understanding the clinical relevance of this cytokine in treating advanced melanoma is important. Results of trials of GM-CSF in melanoma have been mixed, and while GM-CSF has the potential to promote anti-tumor responses, some preclinical data suggest that GM-CSF may sometimes promote tumor growth. GM-CSF has not been approved as a melanoma treatment. We undertook a systematic literature review of studies of GM-CSF in patients with advanced melanoma (stage IIIB–IV). Of the 503 articles identified, 26 studies met the eligibility criteria. Most studies investigated the use of GM-CSF in combination with another treatment, such as peptide vaccines or chemotherapy, or as an adjuvant to surgery. Some clinical benefit was reported in patients who received GM-CSF as an adjuvant to surgery, or in combination with other treatments. In general, outcomes for patients receiving peptide vaccines were not improved with the addition of GM-CSF. GM-CSF may be a valuable therapeutic adjuvant; however, further studies are needed, particularly head-to-head comparisons, to confirm the optimal dosing regimen and clinical effectiveness in patients with advanced melanoma.

Advances in inducing adaptive immunity using cell-based cancer vaccines: Clinical applications in pancreatic cancer

The incidence of pancreatic ductal adenocarcinoma (PDA) is on the rise, and the prognosis is extremely poor because PDA is highly aggressive and notoriously difficult to treat. Although gemcitabine- or 5-fluorouracil-based chemotherapy is typically offered as a standard of care, most patients do not survive longer than 1 year. Therefore, the development of alternative therapeutic approaches for patients with PDA is imperative. As PDA cells express numerous tumor-associated antigens that are suitable vaccine targets, one promising treatment approach is cancer vaccines. During the last few decades, cell-based cancer vaccines have offered encouraging results in preclinical studies. Cell-based cancer vaccines are mainly generated by presenting whole tumor cells or dendritic cells to cells of the immune system. In particular, several clinical trials have explored cell-based cancer vaccines as a promising therapeutic approach for patients with PDA. Moreover, chemotherapy and cancer vaccines can synergize to result in increased efficacies in patients with PDA. In this review, we will discuss both the effect of cell-based cancer vaccines and advances in terms of future strategies of cancer vaccines for the treatment of PDA patients.

Design and characterization of the tumor vaccine MGN1601, allogeneic fourfold gene-modified vaccine cells combined with a TLR-9 agonist

The tumor vaccine MGN1601 was designed and developed for treatment of metastatic renal cell carcinoma (mRCC). MGN1601 consists of a combination of fourfold gene-modified cells with the toll-like receptor 9 agonist dSLIM, a powerful connector of innate and adaptive immunity. Vaccine cells originate from a renal cell carcinoma cell line (grown from renal cell carcinoma tissue), express a variety of known tumor-associated antigens (TAA), and are gene modified to transiently express two co-stimulatory molecules, CD80 and CD154, and two cytokines, GM-CSF and IL-7, aimed to support immune response. Proof of concept of the designed vaccine was shown in mice: The murine homologue of the vaccine efficiently (100%) prevented tumor growth when used as prophylactic vaccine in a syngeneic setting. Use of the vaccine in a therapeutic setting showed complete response in 92% of mice as well as synergistic action and necessity of the components. In addition, specific cellular and humoral immune responses in mice were found when used in an allogeneic setting. Immune response to the vaccine was also shown in mRCC patients treated with MGN1601: Peptide array analysis revealed humoral CD4-based immune response to TAA expressed on vaccine cells, including survivin, cyclin D1, and stromelysin.

Effects of tumor vaccine expressing Granulocyte-Macrophage Colony Stimulating Factor and interleukin-18 fusion on cancer cells and its possible application for cancer immunotherapy

To access antitumor effects of a combined Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) and interleukin-18 (IL-18), cDNA fusion of murine GM-CSF and mature IL-18 (GMIL-18) was constructed and transfected in mammalian cells. GMIL-18 fusion protein was highly secreted and displayed bifunctional activities, possessing immune response initiation and cytokine roles, including IFN-γ induction in mouse splenocytes and increased proliferation of GM-CSF-dependent cells, M-NSF-60. The GMIL-18 secreting tumor vaccine was generated and it strongly stimulated differentiation of dendrite cells (DCs) and effusive CD8⁺ and CD4⁺ cell infiltration into tumor mice. Moreover, growth of CT26 mouse colon cancer cells was significantly retarded by GMIL-18 (CT26GMIL-18), but not by CT26GM-CSF- or CT26IL-18. The efficiency of prophylactic vaccination was greater than that of therapeutic vaccination in terms of tumor size and its inhibitory role in proliferation. In micrometastasis analysis of tumor models, γ-ray irradiated GMIL-18 tumor vaccine showed a smaller number of liver-meta tumor nodules in mouse liver cells. We concluded that bifunctional GMIL-18 fusion protein could be applied as an immune therapy for cancer treatments.

STK11/LKB1 Deficiency Promotes Neutrophil Recruitment and Proinflammatory Cytokine Production to Suppress T-cell Activity in the Lung Tumor Microenvironment

STK11/LKB1 is among the most commonly inactivated tumor suppressors in non-small cell lung cancer (NSCLC), especially in tumors harboring KRAS mutations. Many oncogenes promote immune escape, undermining the effectiveness of immunotherapies, but it is unclear whether the inactivation of tumor suppressor genes, such as STK11/LKB1, exerts similar effects. In this study, we investigated the consequences of STK11/LKB1 loss on the immune microenvironment in a mouse model of KRAS-driven NSCLC. Genetic ablation of STK11/LKB1 resulted in accumulation of neutrophils with T-cell-suppressive effects, along with a corresponding increase in the expression of T-cell exhaustion markers and tumor-promoting cytokines. The number of tumor-infiltrating lymphocytes was also reduced in LKB1-deficient mouse and human tumors. Furthermore, STK11/LKB1-inactivating mutations were associated with reduced expression of PD-1 ligand PD-L1 in mouse and patient tumors as well as in tumor-derived cell lines. Consistent with these results, PD-1-targeting antibodies were ineffective against Lkb1-deficient tumors. In contrast, treating Lkb1-deficient mice with an IL6-neutralizing antibody or a neutrophil-depleting antibody yielded therapeutic benefits associated with reduced neutrophil accumulation and proinflammatory cytokine expression. Our findings illustrate how tumor suppressor mutations can modulate the immune milieu of the tumor microenvironment, and they offer specific implications for addressing STK11/LKB1-mutated tumors with PD-1-targeting antibody therapies.

Antigen-specific vaccines for cancer treatment

Vaccines targeting pathogens are generally effective and protective because based on foreign non-self antigens which are extremely potent in eliciting an immune response. On the contrary, efficacy of therapeutic cancer vaccines is still disappointing. One of the major reasons for such poor outcome, among others, is the difficulty of identifying tumor-specific target antigens which should be unique to the tumors or, at least, overexpressed on the tumors as compared to normal cells. Indeed, this is the only option to overcome the peripheral immune tolerance and elicit a non toxic immune response. New and more potent strategies are now available to identify specific tumor-associated antigens for development of cancer vaccine approaches aiming at eliciting targeted anti-tumor cellular responses. In the last years this aspect has been addressed and many therapeutic vaccination strategies based on either whole tumor cells or specific antigens have been and are being currently evaluated in clinical trials. This review summarizes the current state of cancer vaccines, mainly focusing on antigen-specific approaches.

Immune-related strategies driving immunotherapy in breast cancer treatment: a real clinical opportunity

Because its original use as a treatment for hematologic disease, more recently immunotherapy has emerged as a novel effective therapeutic strategy for solid malignancies, such as melanoma and prostate carcinoma. For breast carcinoma, an immunologic therapeutic approach has not been well evaluated, even though there is evidence to suggest it would be a successful novel strategy, especially taking into account the high mortality rate of the most aggressive variants of this heterogeneous disease. Here, we briefly describe the most recently awarded immune-based therapies with a consolidated or potential implication for the treatment of solid malignancies. We focus on immune checkpoints and on the clinical potential of their abrogation, with a further overview of novel vaccine-based approaches and the most relevant immunotherapeutic techniques. We aim to provide an exhaustive review of the most promising immune-therapeutic agents that may have implications for breast cancer treatment.

Biologic Activity of Autologous, Granulocyte-Macrophage Colony-Stimulating Factor Secreting Alveolar Soft-Part Sarcoma and Clear Cell Sarcoma Vaccines

PURPOSE

Alveolar soft-part sarcoma (ASPS) and clear cell sarcoma (CCS) are rare mesenchymal malignancies driven by chromosomal translocations that activate members of the microphthalmia transcription factor (MITF) family. However, in contrast to malignant melanoma, little is known about their immunogenicity. To learn more about the host response to ASPS and CCS, we conducted a phase I clinical trial of vaccination with irradiated, autologous sarcoma cells engineered by adenoviral-mediated gene transfer to secrete granulocyte-macrophage colony-stimulating factor (GM-CSF).

EXPERIMENTAL DESIGN

Metastatic tumors from ASPS and CCS patients were resected, processed to single-cell suspensions, transduced with a replication-defective adenoviral vector encoding GM-CSF, and irradiated. Immunizations were administered subcutaneously and intradermally weekly three times and then every other week.

RESULTS

Vaccines were successfully manufactured for 11 of the 12 enrolled patients. Eleven subjects received from three to 13 immunizations. Toxicities were restricted to grade 1-2 skin reactions at inoculation sites. Vaccination elicited local dendritic cell infiltrates and stimulated T cell-mediated delayed-type hypersensitivity reactions to irradiated, autologous tumor cells. Antibody responses to tissue-type plasminogen activator (tTPA) and angiopoietins-1/2 were detected. Tumor biopsies showed programmed death-1 (PD-1)-positive CD8(+) T cells in association with PD ligand-1 (PD-L1)-expressing sarcoma cells. No tumor regressions were observed.

CONCLUSIONS

Vaccination with irradiated, GM-CSF-secreting autologous sarcoma cell vaccines is feasible, safe, and biologically active. Concurrent targeting of angiogenic cytokines and antagonism of the PD-1-negative regulatory pathway might intensify immune-mediated tumor destruction.

Cancer vaccines: Looking to the future

These are exciting times for the field of cancer immunotherapy. Although the clinical efficacy of monoclonal antibodies has been demonstrated since the early 1990s, the therapeutic profile of other immunotherapeutic approaches-especially vaccines-has not yet been formally clarified. However, the recent success of several immunotherapeutic regimens in cancer patients has boosted the development of this treatment modality. These achievements stemmed from recent scientific advances demonstrating the tolerogenic nature of cancer and the fundamental role of the tumor immune microenvironment in the suppression of antitumor immunity. New immunotherapeutic strategies against cancer attempt to promote protective antitumor immunity while disrupting the immunoregulatory circuits that contribute to tumor tolerance. Cancer vaccines differ from other anticancer immunotherapeutics in that they initiate the dynamic process of activating the immune system so as to successfully re-establish a state of equilibrium between tumor cells and the host. This article reviews recent clinical trials involving several different cancer vaccines and describes some of the most promising immunotherapeutic approaches that harness antitumor T-cell responses. In addition, we describe strategies whereby cancer vaccines can be exploited in combination with other therapeutic approach to overcome-in a synergistic fashion-tumor immunoevasion. Finally, we discuss prospects for the future development of broad spectrum prophylactic anticancer vaccines.

Current status of autologous breast tumor cell-based vaccines

Approximately nine out of ten breast cancer-related deaths are attributable to metastasis. Yet, less than 4% of breast cancer patients are initially diagnosed with metastatic cancer. Therefore, the majority of breast cancer-related deaths are due to recurrence and progression of non-metastatic disease. There is tremendous clinical opportunity for novel adjuvant strategies, such as immunotherapies, that have the potential to prevent progressive recurrences. In particular, autologous tumor cell-based vaccines (ATCVs) can train a patient's immune system to recognize and eliminate occult disease. ATCVs have several advantages including safety, multivalency and patient specificity. Furthermore, because lumpectomy or mastectomy is indicated for the vast majority of breast cancer patients, resected tumors offer a readily available, patient-specific source of tumor antigen. Disadvantages of ATCVs include poor immunogenicity and production inconsistencies. This review summarizes recent progress in the development of autologous breast tumor vaccines and offers insight for overcoming existing limitations.

Relationship of vaccine efficacy to the kinetics of DC and T-cell responses induced by PLG-based cancer vaccines

Cancer vaccines are typically formulated for bolus injection and often produce short-lived immunostimulation resulting in poor temporal control over immune cell activation and weak oncolytic activity. One means of overcoming these limitations utilizes immunologically active biomaterial constructs. We previously reported that antigen-laden, macroporous PLG scaffolds induce potent dendritic cell (DC) and cytotoxic T-lymphocyte (CTL) responses via the controlled signaling of inflammatory cytokines, antigen and toll-like receptor agonists. In this study, we describe the kinetics of these responses and illustrate their fundamental relationship to potent tumor rejection when implanted subcutaneously in a mouse B16 model of melanoma. By explanting scaffolds from mice at times ranging from 1–7 d, a seamless relationship was observed between the production of controlled CTL responses, tumor growth and long-term survival in both prophylactic and therapeutic models. Scaffolds must be implanted for > 7 d to augment CTL responses via the prolonged presentation of tumor antigen, and the benefits included a notable regression of established tumors. Host DC infiltration into the porous material persisted for 12 days (peaking at day 5 ~1.4 x 10⁶ cells), and a sharp attenuation in DC numbers coincided with peak CD8⁺ CTL infiltration at day 12 (~8 x 10⁵ cells). Importantly, these PLG systems enhanced DC numbers in the draining lymph node, resulting in increased CD8(+) CTL subsets at days 10–16 of vaccination. These results indicate that material systems can finely control innate and adaptive immune cell responses to kill typically untreatable melanoma tumors and provide critical kinetic data for the design of vaccine carriers.

Microbiota-dependent crosstalk between macrophages and ILC3 promotes intestinal homeostasis

The intestinal microbiota and tissue-resident myeloid cells promote immune responses that maintain intestinal homeostasis in the host. However, the cellular cues that translate microbial signals into intestinal homeostasis remain unclear. Here, we show that deficient granulocyte-macrophage colony-stimulating factor (GM-CSF) production altered mononuclear phagocyte effector functions and led to reduced regulatory T cell (T(reg)) numbers and impaired oral tolerance. We observed that RORγt(+) innate lymphoid cells (ILCs) are the primary source of GM-CSF in the gut and that ILC-driven GM-CSF production was dependent on the ability of macrophages to sense microbial signals and produce interleukin-1β. Our findings reveal that commensal microbes promote a crosstalk between innate myeloid and lymphoid cells that leads to immune homeostasis in the intestine.

Cellular immunotherapy using irradiated lung cancer cell vaccine co-expressing GM-CSF and IL-18 can induce significant antitumor effects

Background

Although the whole tumor cell vaccine can provide the best source of immunizing antigens, there is still a limitation that most tumors are not naturally immunogenic. Tumor cells genetically modified to secrete immune activating cytokines have been proved to be more immunogenic. IL-18 could augment proliferation of T cells and cytotoxicity of NK cells. GM-CSF could stimulate dendritic cells, macrophages and enhance presentation of tumor antigens. In our study, we used mouse GM-CSF combined with IL-18 to modify Lewis lung cancer LL/2, then investigated whether vaccination could suppress tumor growth and promote survival.

Methods

The Lewis lung cancer LL/2 was transfected with co-expressing mouse GM-CSF and IL-18 plasmid by cationic liposome, then irradiated with a sublethal dose X ray (100 Gy) to prepare vaccines. Mice were subcutaneously immunized with this inactivated vaccine and then inoculated with autologous LL/2 to estimate the antitumor efficacy.

Results

The studies reported here showed that LL/2 tumor cell vaccine modified by a co-expressing mouse GM-CSF and IL-18 plasmid could significantly inhibit tumor growth and increased survival of the mice bearing LL/2 tumor whether prophylactic or adoptive immunotherapy in vivo. A significant reduction of proliferation and increase of apoptosis were also observed in the tumor treated with vaccine of co-expressing GM-CSF and IL-18. The potent antitumor effect correlated with higher secretion levels of pro-inflammatory cytokines such as IL-18, GM-CSF, interferon-γ in serum, the proliferation of CD4⁺ IFN-γ⁺, CD8⁺ IFN-γ⁺ T lymphocytes in spleen and the infiltration of CD4⁺, CD8⁺ T in tumor. Furthermore, the mechanism of tumor-specific immune response was further proved by ⁵¹Cr cytotoxicity assay in vitro and depletion of CD4, CD8, NK immune cell subsets in vivo. The results suggested that the antitumor mechanism was mainly depended on CD4⁺, CD8⁺ T lymphocytes.

Conclusions

These results provide a new insight into therapeutic mechanisms of IL-18 plus GM-CSF modified tumor cell vaccine and provide a potential clinical cancer immunotherapeutic agent for improved antitumor immunity.

Boosting leukemia-specific T cell responses in patients following stem cell transplantation

Whole tumor cell-based vaccines administered within the first 2 to 3 months after allogeneic stem cell transplantation stand out as a promising approach to enhance graft-vs.-leukemia responses. Herein, the implications of this finding for the development of strategies to improve the outcome of patients subjected to allogeneic stem cell transplantation are discussed.

Is cancer gene therapy an empty suit?

Gene therapy as a treatment for cancer is regarded as high in promise, but low in delivery, a deficiency that has become more obvious with ever-increasing reports of the successful correction of monogenic disorders by this approach. We review the commercial and scientific obstacles that have led to these delays and describe how they are progressively being overcome. Recent and striking successes and correspondingly increased commercial involvement suggest that gene transfer could finally become a powerful method for development of safe and effective cancer therapeutic drugs.

Autologous CLL cell vaccination early after transplant induces leukemia-specific T cells

BACKGROUND

Patients with advanced hematologic malignancies remain at risk for relapse following reduced-intensity conditioning (RIC) allogeneic hematopoietic stem cell transplantation (allo-HSCT). We conducted a prospective clinical trial to test whether vaccination with whole leukemia cells early after transplantation facilitates the expansion of leukemia-reactive T cells and thereby enhances antitumor immunity.

METHODS

We enrolled 22 patients with advanced chronic lymphocytic leukemia (CLL), 18 of whom received up to 6 vaccines initiated between days 30 and 45 after transplantation. Each vaccine consisted of irradiated autologous tumor cells admixed with GM-CSF-secreting bystander cells. Serial patient PBMC samples following transplantation were collected, and the impact of vaccination on T cell activity was evaluated.

RESULTS

At a median follow-up of 2.9 (range, 1-4) years, the estimated 2-year progression-free and overall survival rates of vaccinated subjects were 82% (95% CI, 54%-94%) and 88% (95% CI, 59%-97%), respectively. Although vaccination only had a modest impact on recovering T cell numbers, CD8+ T cells from vaccinated patients consistently reacted against autologous tumor, but not alloantigen-bearing recipient cells with increased secretion of the effector cytokine IFN-γ, unlike T cells from nonvaccinated CLL patients undergoing allo-HSCT. Further analysis confirmed that 17% (range, 13%-33%) of CD8+ T cell clones isolated from 4 vaccinated patients by limiting dilution of bulk tumor-reactive T cells solely reacted against CLL-associated antigens.

CONCLUSION

Our studies suggest that autologous tumor cell vaccination is an effective strategy to advance long-term leukemia control following allo-HSCT.

TRIAL REGISTRATION

Clinicaltrials.gov NCT00442130.

FUNDING

NCI (5R21CA115043-2), NHLBI (5R01HL103532-03), and Leukemia and Lymphoma Society Translational Research Program.

Sequential immunotherapy by vaccination with GM-CSF-expressing glioma cells and CTLA-4 blockade effectively treats established murine intracranial tumors

Malignant glioma is an incurable disease with a relatively short median survival. Several clinical trials have demonstrated that immunotherapy with vaccination is a safe and possibly effective way of prolonging survival. Antibody-based blockade of cytotoxic T-lymphocyte antigen 4 (CTLA-4) ligation on T lymphocytes is associated with enhanced antitumor immunity in animal models of cancer and in patients with advanced melanoma. We hypothesized that sequential therapy with granulocyte-macrophage-colony-stimulating factor (GM-CSF)-expressing whole-glioma-cell vaccination and CTLA-4 blockade is an effective strategy for treating established intracranial gliomas. GL261 glioma cells were injected into the right frontal lobes of syngeneic C57/BL6 mice. At days 3, 6, and 9 after tumor implantation, mice were treated with subcutaneous injection of irradiated GM-CSF-expressing GL261 cells. Mice were also treated with intraperitoneal injection of anti-CTLA-4 monoclonal antibodies (mAbs), either at days 3, 6, and 9 or days 12, 15, and 18. Animals were followed for survival. Splenocytes were harvested at day 22 for use in enzyme-linked immunosorbent spot assays. Early treatment of established intracranial gliomas with high-dose CTLA-4 blockade was associated with increased survival in GL261-bearing mice. Later treatment with anti-CTLA-4 monoclonal antibodies did not significantly improve survival compared with control-treated mice. Early vaccination followed by subsequent CTLA-4 blockade was associated with significantly improved survival versus either treatment alone and intensified tumor-specific immunity as measured by interferon-γ enzyme-linked immunosorbent spot assay. Sequential immunotherapy with GM-CSF-expressing irradiated glioma cells and CTLA-4 blockade synergistically prolongs survival in mice bearing established intracranial gliomas.

Immune-dependent and independent antitumor activity of GM-CSF aberrantly expressed by mouse and human colorectal tumors

Granulocyte-macrophage colony-stimulating factor (GM-CSF/CSF2) is a cytokine produced in the hematologic compartment that may enhance antitumor immune responses, mainly by activation of dendritic cells. Here, we show that more than one-third of human colorectal tumors exhibit aberrant DNA demethylation of the GM-CSF promoter and overexpress the cytokine. Mouse engraftment experiments with autologous and homologous colon tumors engineered to repress the ectopic secretion of GM-CSF revealed the tumor-secreted GM-CSF to have an immune-associated antitumor effect. Unexpectedly, an immune-independent antitumor effect was observed that depended on the ectopic expression of GM-CSF receptor subunits by tumors. Cancer cells expressing GM-CSF and its receptor did not develop into tumors when autografted into immunocompetent mice. Similarly, 100% of the patients with human colon tumors that overexpressed GM-CSF and its receptor subunits survived at least 5 years after diagnosis. These data suggest that expression of GM-CSF and its receptor subunits by colon tumors may be a useful marker for prognosis as well as for patient stratification in cancer immunotherapy.

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.

Antigen-specific versus antigen-nonspecific immunotherapeutic approaches for human melanoma: the need for integration for optimal efficacy?

Due to its immunogenecity and evidence of immune responses resulting in tumor regression, metastatic melanoma has been the target for numerous immunotherapeutic approaches. Unfortunately, based on the clinical outcomes, even the successful induction of tumor-specific responses does not correlate with efficacy. Immunotherapies can be divided into antigen-specific approaches, which seek to induce T cells specific to one or several known tumor associated antigens (TAA), or with antigen-nonspecific approaches, which generally activate T cells to become nonspecifically lytic effectors. Here the authors critically review the different immunotherapeutic approaches in melanoma.

Variation of tumor-infiltrating lymphocytes in human cancers: controversy on clinical significance

Tumors develop and progress under the influence of a microenvironment comprising a variety of immune cell subsets and their products. Recent studies have shown that tumor-infiltrating lymphocytes (TILs) are not randomly distributed, but organized to accumulate more or less densely in different regions within tumors, and interact with each other. Substantial evidence has suggested that not only CD8(+) and/or CD4(+) αβ T cells but also other lymphocyte subsets, including γδ T cells, B cells, NK cells, and NKT cells, infiltrate tumor tissues in variable quantities and play a key role in the regulation of antitumor immunity. In this article, we summarize available information regarding the diversity and composition of TILs, which may positively or negatively affect tumor growth and patient clinical outcomes. The clinical significance of TILs in human cancers remains unclear and is a subject of considerable controversy; largely due to the lack of functional data for TILs, as well as due to enormous variability of TILs in different tumors. A great deal more functional data about TILs needs to be obtained for individual tumors before TILs can be considered as a prognostic parameter in human cancers.

Compartment-Specific Bioluminescence Imaging platform for the high-throughput evaluation of antitumor immune function

Conventional assays evaluating antitumor activity of immune effector cells have limitations that preclude their high-throughput application. We adapted the recently developed Compartment-Specific Bioluminescence Imaging (CS-BLI) technique to perform high-throughput quantification of innate antitumor activity and to show how pharmacologic agents (eg, lenalidomide, pomalidomide, bortezomib, and dexamethasone) and autologous BM stromal cells modulate that activity. CS-BLI-based screening allowed us to identify agents that enhance or inhibit innate antitumor cytotoxicity. Specifically, we identified compounds that stimulate immune effector cells against some tumor targets but suppressed their activity against other tumor cells. CS-BLI offers rapid, simplified, and specific evaluation of multiple conditions, including drug treatments and/or cocultures with stromal cells and highlights that immunomodulatory pharmacologic responses can be heterogeneous across different types of tumor cells. This study provides a framework to identify novel immunomodulatory agents and to prioritize compounds for clinical development on the basis of their effect on antitumor immunity.

Muscle CARs and TcRs: turbo-charged technologies for the (T cell) masses

A central role for T cells in the control of cancer has been supported by both animal models and clinical observations. Accordingly, the development of potent anti-tumor T cell immunity has been a long-standing objective of immunotherapy. Emerging data from clinical trials that test T cell immune-modulatory agents and genetically engineered and re-targeted T cells have begun to realize the profound potential of T cell immunotherapy to target cancer. This review will focus on a description of recent conceptual and technological advances for the genetic engineering of T cells to enhance anti-tumor T cell immunity through the introduction of tumor-specific receptors, both Chimeric Antigen Receptors (CAR) and T cell receptors (TcR), as well as an overview of emerging data from ongoing clinical trials that highlight the potential of these approaches to effect dramatic and potent anti-tumor immunity.

Neuroantigen-specific, tolerogenic vaccines: GM-CSF is a fusion partner that facilitates tolerance rather than immunity to dominant self-epitopes of myelin in murine models of experimental autoimmune encephalomyelitis (EAE)

Background

Vaccination strategies that elicit antigen-specific tolerance are needed as therapies for autoimmune disease. This study focused on whether cytokine-neuroantigen (NAg) fusion proteins could inhibit disease in chronic murine models of experimental autoimmune encephalomyelitis (EAE) and thus serve as potential therapeutic modalities for multiple sclerosis.

Results

A fusion protein comprised of murine GM-CSF as the N-terminal domain and the encephalitogenic MOG35-55 peptide as the C-terminal domain was tested as a tolerogenic, therapeutic vaccine (TTV) in the C57BL/6 model of EAE. Administration of GMCSF-MOG before active induction of EAE, or alternatively, at the onset of EAE blocked the development and progression of EAE. Covalent linkage of the GM-CSF and MOG35-55 domains was required for tolerogenic activity. Likewise, a TTV comprised of GM-CSF and PLP139-151 was a tolerogen in the SJL model of EAE.

Conclusion

These data indicated that fusion proteins containing GM-CSF coupled to myelin auto-antigens elicit tolerance rather than immunity.

Cytokines in cancer immunotherapy

Cytokines are molecular messengers that allow the cells of the immune system to communicate with one another to generate a coordinated, robust, but self-limited response to a target antigen. The growing interest over the past two decades in harnessing the immune system to eradicate cancer has been accompanied by heightened efforts to characterize cytokines and exploit their vast signaling networks to develop cancer treatments. The goal of this paper is to review the major cytokines involved in cancer immunotherapy and discuss their basic biology and clinical applications. The paper will also describe new cytokines in pre-clinical development, combinations of biological agents, novel delivery mechanisms, and potential directions for future investigation using cytokines.

Dichotomous effects of IFN-γ on dendritic cell function determine the extent of IL-12-driven antitumor T cell immunity

Sustained intratumoral delivery of IL-12 and GM-CSF can overcome tumor immune suppression and promote T cell-dependent eradication of established disease in murine tumor models. However, the antitumor effector response is transient and rapidly followed by a T suppressor cell rebound. The mechanisms that control the switch from an effector to a regulatory response in this model have not been defined. Because dendritic cells (DC) can mediate both effector and suppressor T cell priming, DC activity was monitored in the tumors and the tumor-draining lymph nodes (TDLN) of IL-12/GM-CSF-treated mice. The studies demonstrated that therapy promoted the recruitment of immunogenic DC (iDC) to tumors with subsequent migration to the TDLN within 24-48 h of treatment. Longer-term monitoring revealed that iDC converted to an IDO-positive tolerogenic phenotype in the TDLN between days 2 and 7. Specifically, day 7 DC lost the ability to prime CD8(+) T cells but preferentially induced CD4(+)Foxp3(+) T cells. The functional switch was reversible, as inhibition of IDO with 1-methyl tryptophan restored immunogenic function to tolerogenic DC. All posttherapy immunological activity was strictly associated with conventional myeloid DC, and no functional changes were observed in the plasmacytoid DC subset throughout treatment. Importantly, the initial recruitment and activation of iDC as well as the subsequent switch to tolerogenic activity were both driven by IFN-γ, revealing the dichotomous role of this cytokine in regulating IL-12-mediated antitumor T cell immunity.

Active immunotherapy induces antibody responses that target tumor angiogenesis

The inhibition of VEGF signaling with antibodies or small molecules achieves clinical benefits in diverse solid malignancies. Nonetheless, therapeutic effects are usually not sustained, and most patients eventually succumb to progressive disease, indicating that antiangiogenic strategies require additional optimization. Vaccination with lethally irradiated, autologous tumor cells engineered to secrete granulocyte-macrophage colony stimulating factor (GM-CSF) and antibody blockade of cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) trigger a tumor vasculopathy in some long-term responding subjects. These reactions are characterized by disrupted tumor blood vessels in association with lymphocyte and granulocyte infiltrates and zonal areas of ischemic tumor necrosis. However, the mechanisms underlying this immune-mediated destruction of the tumor vasculature remain to be clarified. Here, we show that GM-CSF-secreting tumor cell vaccines and CTLA-4 blockade elicit a functionally important humoral reaction against multiple angiogenic cytokines. Antibodies to angiopoietin-1 and angiopoietin-2 block Tie-2 binding, downstream signaling, endothelial cell tube formation, and macrophage chemotaxis. Antibodies to macrophage inhibitory factor (MIF) attenuate macrophage Tie-2 expression and matrix metalloproteinase-9 (MMP-9) production. Together, these results delineate an immunotherapy-induced host response that broadly targets the angiogenic network in the tumor microenvironment.

Translating tumor antigens into cancer vaccines

Vaccines represent a strategic successful tool used to prevent or contain diseases with high morbidity and/or mortality. However, while vaccines have proven to be effective in combating pathogenic microorganisms, based on the immune recognition of these foreign antigens, vaccines aimed at inducing effective antitumor activity are still unsatisfactory. Nevertheless, the effectiveness of the two licensed cancer-preventive vaccines targeting tumor-associated viral agents (anti-HBV [hepatitis B virus], to prevent HBV-associated hepatocellular carcinoma, and anti-HPV [human papillomavirus], to prevent HPV-associated cervical carcinoma), along with the recent FDA approval of sipuleucel-T (for the therapeutic treatment of prostate cancer), represents a significant advancement in the field of cancer vaccines and a boost for new studies in the field. Specific active immunotherapies based on anticancer vaccines represent, indeed, a field in continuous evolution and expansion. Significant improvements may result from the selection of the appropriate tumor-specific target antigen (to overcome the peripheral immune tolerance) and/or the development of immunization strategies effective at inducing a protective immune response. This review aims to describe the vast spectrum of tumor antigens and strategies to develop cancer vaccines.

Directing dendritic cell immunotherapy towards successful cancer treatment

The use of dendritic cells (DCs) for tumor immunotherapy represents a powerful approach for harnessing the patient's own immune system to eliminate tumor cells. However, suboptimal conditions for generating potent immunostimulatory DCs, as well as the induction of tolerance and suppression mediated by the tumors and its microenvironment have contributed to limited success. Combining DC vaccines with new approaches that enhance immunogenicity and overcome the regulatory mechanisms underlying peripheral tolerance may be the key to achieving effective and durable anti-tumor immune responses that translate to better clinical outcomes.