Cellular vaccine approaches

Cellular and vaccine immunotherapy for multiple myeloma

Allogeneic hematopoietic cell transplantation and donor lymphocyte infusion for multiple myeloma (MM) can induce graft-versus-myeloma immunity and long-term survivorship, but limited efficacy and associated toxicities have prevented its widespread use. Cellular immunotherapies and vaccines seek to induce more specific, reliable, and potent antimyeloma immune responses with less treatment-related risk than is possible with allogeneic transplantation. Advances in molecular biology, and basic and applied immunology, have led to promising approaches such as genetically engineered T cells with chimeric antigen receptors and T-cell receptors targeting myeloma-specific epitopes, vaccine primed ex vivo expanded autologous T cells, expanded marrow-infiltrating lymphocytes, and plasma cell/dendritic cell fusion vaccines. The addition of these emerging therapies to immunomodulatory drugs and inhibitors of programmed death-1 T-cell regulatory pathways are poised to improve outcome for our patients with myeloma.

Harnessing the immune system to improve cancer therapy

Cancer immunotherapy uses the immune system and its components to mount an anti-tumor response. During the last decade, it has evolved from a promising therapy option to a robust clinical reality. Many immunotherapeutic modalities are already approved by the Food and Drug Administration (FDA) for treating cancer patients and many others are in the pipeline for approval as standalone or combinatorial therapeutic interventions, several also combined with standard treatments in clinical studies. The two main axes of cancer immunotherapeutics refer to passive and active treatments. Prominent examples of passive immunotherapy include administration of monoclonal antibodies and cytokines and adoptive cell transfer of ex vivo "educated" immune cells. Active immunotherapy refers, among others, to anti-cancer vaccines [peptide, dendritic cell (DC)-based and allogeneic whole cell vaccines], immune checkpoint inhibitors and oncolytic viruses, whereas new approaches that can further enhance anti-cancer immune responses are also widely explored. Herein, we present the most popular cancer immunotherapy approaches and discuss their clinical relevance referring to data acquired from clinical trials. To date, clinical experience and efficacy suggest that combining more than one immunotherapy interventions, in conjunction with other treatment options like chemotherapy, radiotherapy and targeted or epigenetic therapy, should guide the way to cancer cure.

The Basis of Oncoimmunology

Cancer heterogeneity, a hallmark enabling clonal survival and therapy resistance, is shaped by active immune responses. Antigen-specific T cells can control cancer, as revealed clinically by immunotherapeutics such as adoptive T-cell transfer and checkpoint blockade. The host immune system is thus a powerful tool that, if better harnessed, could significantly enhance the efficacy of cytotoxic therapy and improve outcomes for cancer sufferers. To realize this vision, however, a number of research frontiers must be tackled. These include developing strategies for neutralizing tumor-promoting inflammation, broadening T-cell repertoires (via vaccination), and elucidating the mechanisms by which immune cells organize tumor microenvironments to regulate T-cell activity. Such efforts will pave the way for identifying new targets for combination therapies that overcome resistance to current treatments and promote long-term cancer control.

Current status of ex vivo gene therapy for hematological disorders: a review of clinical trials in Japan around the world

Gene therapies are classified into two major categories, namely, in vivo and ex vivo. Clinical trials of human gene therapy began with the ex vivo techniques. Based on the initial successes of gene-therapy clinical trials, these approaches have spread worldwide. The number of gene therapy trials approved worldwide increased gradually starting in 1989, reaching 116 protocols per year in 1999, and a total of 2210 protocols had been approved by 2015. Accumulating clinical evidence has demonstrated the safety and benefits of several types of gene therapy, with the exception of serious adverse events in several clinical trials. These painful experiences were translated backward to basic science, resulting in the development of several new technologies that have influenced the recent development of ex vivo gene therapy in this field. To date, six gene therapies have been approved in a limited number of countries worldwide. In Japan, clinical trials of gene therapy have developed under the strong influence of trials in the US and Europe. Since the initial stages, 50 clinical trials have been approved by the Japanese government. In this review, the history and current status of clinical trials of ex vivo gene therapy for hematological disorders are introduced and discussed.

Polymer-Based DNA Delivery Systems for Cancer Immunotherapy

The use of gene delivery systems for the expression of antigenic proteins is an established means for activating a patient’s own immune system against the cancer they carry. Since tumor cells are poor antigen-presenting cells, cross-presentation of tumor antigens by dendritic cells (DCs) is essential for the generation of tumor-specific cytotoxic T-lymphocyte responses. A number of polymer-based nanomedicines have been developed to deliver genes into DCs, primarily by incorporating tumor-specific, antigen-encoding plasmid DNA with polycationic molecules to facilitate DNA loading and intracellular trafficking. Direct in vivo targeting of plasmid DNA to DC surface receptors can induce high transfection efficiency and long-term gene expression, essential for antigen loading onto major histocompatibility complex molecules and stimulation of T-cell responses. This chapter summarizes the physicochemical properties and biological information on polymer-based non-viral vectors used for targeting DCs, and discusses the main challenges for successful in vivo gene transfer into DCs.

Cytokine-Induced Modulation of Colorectal Cancer

The emergence of novel immunomodulatory cancer therapies over the last decade, above all immune checkpoint blockade, has significantly advanced tumor treatment. For colorectal cancer (CRC), a novel scoring system based on the immune cell infiltration in tumors has greatly improved disease prognostic evaluation and guidance to more specific therapy. These findings underline the relevance of tumor immunology in the future handling and therapeutic approach of malignant disease. Inflammation can either promote or suppress CRC pathogenesis and inflammatory mediators, mainly cytokines, critically determine the pro- or anti-tumorigenic signals within the tumor environment. Here, we review the current knowledge on the cytokines known to be critically involved in CRC development and illustrate their mechanisms of action. We also highlight similarities and differences between CRC patients and murine models of CRC and point out cytokines with an ambivalent role for intestinal cancer. We also identify some of the future challenges in the field that should be addressed for the development of more effective immunomodulatory therapies.

Ex vivo generation of myeloid-derived suppressor cells that model the tumor immunosuppressive environment in colorectal cancer

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of cells that accumulate in tumor-bearing subjects and which strongly inhibit anti-cancer immune responses. To study the biology of MDSC in colorectal cancer (CRC), we cultured bone marrow cells in conditioned medium from CT26 cells, which are genetically modified to secrete high levels of granulocyte-macrophage colony-stimulating factor. This resulted in the generation of high numbers of CD11b(+) Ly6G(+) granulocytic and CD11b(+) Ly6C(+) monocytic MDSC, which closely resemble those found within the tumor but not the spleen of CT26 tumor-bearing mice. Such MDSC potently inhibited T-cell responses in vitro, a process that could be reversed upon blocking of arginase-1 or inducible nitric oxide synthase (iNOS). We confirmed that inhibition of arginase-1 or iNOS in vivo resulted in the stimulation of cytotoxic T-cell responses. A delay in tumor growth was observed upon functional repression of both enzymes. These data confirm the role of MDSC as inhibitors of T-cell-mediated immune responses in CRC. Moreover, MDSC differentiated in vitro from bone marrow cells using conditioned medium of GM-CSF-secreting CT26 cells, represent a valuable platform to study/identify drugs that counteract MDSC activities.

Proteomic Monitoring of B Cell Immunity

Immune monitoring is critical in settings of infection, autoimmunity, and cancer, but our understanding of the diversity of the antibody immune repertoire has been limited to selected target antigens and epitopes. Development of new vaccines requires monitoring of B cell immunity and identification of candidate antigens. As vaccines become more complex, novel techniques are required for monitoring the diversity of the B cell immune response. Since antibodies recognize both linear and conformational protein and glycoprotein epitopes, recent advances in proteomic and glycomic technologies for rapid display of antigenic structures are leading to methods for proteome-wide immune monitoring. Here, we review different approaches for protein display for immune monitoring, and provide methods for in situ protein display for the rapid detection and validation of antibody repertoires.

Development of Membrane-Bound GM-CSF and IL-18 as an Effective Tumor Vaccine

The development of effective adjuvant is the key factor to boost the immunogenicity of tumor cells as a tumor vaccine. In this study, we expressed membrane-bound granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-18 (IL-18) as adjuvants in tumor cells to stimulate immune response. B7 transmembrane domain fused GM-CSF and IL-18 was successfully expressed in the cell membrane and stimulated mouse splenocyte proliferation. Co-expression of GM-CSF and IL-18 reduced tumorigenesis (P<0.05) and enhanced tumor protective efficacy (P<0.05) significantly in comparison with GM-CSF alone. These results indicated that the combination of GM-CSF andIL-18 will enhance the immunogenicity of a cell-based anti-tumor vaccine. This membrane-bound approach can be applied to other cytokines for the development of novel vaccine strategies.

Beyond the Immune Suppression: The Immunotherapy in Prostate Cancer

Prostate cancer (PCa) is the second most common cancer in men. As well in many other human cancers, inflammation and immune suppression have an important role in their development. We briefly describe the host components that interact with the tumor to generate an immune suppressive environment involved in PCa promotion and progression. Different tools provide to overcome the mechanisms of immunosuppression including vaccines and immune checkpoint blockades. With regard to this, we report results of most recent clinical trials investigating immunotherapy in metastatic PCa (Sipuleucel-T, ipilimumab, tasquinimod, Prostvac-VF, and GVAX) and provide possible future perspectives combining the immunotherapy to the traditional therapies.

Prostate cancer vaccines in combination with additional treatment modalities

Immunotherapy has been investigated in both preclinical studies and clinical trials as a new therapy for prostate cancer. Vaccines, including those that utilize dendritic cells, viruses, or DNA, immunize against prostate-specific antigen and prostatic acid phosphatase. The vaccines have long been studied as monotherapy for the cancer, but increasingly more trials have been initiated in combination with other modalities. These include radiation, chemotherapy, and androgen deprivation therapy. This review describes and discusses the various combinations of vaccine immunotherapies.

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.

Paradoxical decrease in the capture and lymph node delivery of cancer vaccine antigen induced by a TLR4 agonist as visualized by dual-mode imaging

Traditionally, cell-mediated immune responses to vaccination in animal models are evaluated by invasive techniques such as biopsy and organ extraction. We show here that by combining two noninvasive imaging technologies, MRI and bioluminescence imaging (BLI), we can visualize both the afferent and efferent arms of cellular events following vaccination longitudinally. To this end, we evaluated the immune response elicited by a novel Toll-like receptor 4 agonist vaccine adjuvant, glucopyranosyl lipid A (GLA), using a whole-cell tumor vaccine. After magnetovaccination, MRI was used to visualize antigen-presenting cell-mediated antigen capture and subsequent migration to draining lymph nodes (DLN). Paradoxically, we observed that the incorporation of GLA in the vaccine reduced these critical parameters of the afferent immune response. For the efferent arm, the magnitude of the ensuing antigen-specific T-cell response in DLN visualized using BLI correlated with antigen delivery to the DLN as measured by MRI. These findings were confirmed using flow cytometry. In spite of the GLA-associated reduction in antigen delivery to the DLN, however, the use of GLA as a vaccine adjuvant led to a massive proliferation of vaccine primed antigen-specific T cells in the spleen. This was accompanied by an enhanced tumor therapeutic effect of the vaccine. These findings suggest that GLA adjuvant changes the temporal and anatomical features of both the afferent and efferent arms of the vaccine response and illustrates the utility of quantitative noninvasive imaging as a tool for evaluating these parameters during vaccine optimization.

Irradiated tumor cells of lipopolysaccharide stimulation elicit an enhanced anti-tumor immunity

PURPOSE

Lipopolysaccharide (LPS) is a major component of the outer surface membrane of Gram-negative bacteria which has been proved an effective immune enhancer. Here, we investigated the anti-tumor effect of irradiated tumor cells that stimulated by LPS in mouse xenografts models.

METHODS

Tumor cells were irradiated after stimulation with 1 μg/mL LPS for 48 h. The C57BL/6 mice were immunized subcutaneously with irradiated tumor cells. The anti-tumor effect of lymphocytes of immunized mice was investigated. The cytotoxicity of spleen lymphocytes from immunized mice was determined by a standard (51)Cr-release assay. The roles of immune cell subsets in anti-tumor activity were assessed by injected intraperitoneally with monoclonal antibodies.

RESULTS

We observed that the vaccine of irradiated tumor cell with LPS-stimulated elicited a stronger protective anti-tumor immunity than other controls. Adoptive transfer of lymphocytes of immunized mice showed that the cellular immune response was involved in the anti-tumor effect. And this effect was achieved by activation of antigen-specific CD8(+) T cell response and reduction of myeloid-derived suppressor cells (MDSCs, Gr1(+) CD11b (+) ), which were confirmed by depletion of immune cell subsets and flow cytometry analysis.

CONCLUSIONS

In summary, our study showed that stimulation of LPS was able to enhance anti-tumor immunity of vaccination with tumor cells after irradiation treatment, which might be a new strategy for cancer therapy.

Current perspectives on immunotherapy

After many years of disappointments, the successful development and commercialization of the first immune checkpoint inhibitor, and regulatory approval of a dendritic cell (DC)-based cancer vaccine has led to renewed interest and enthusiasm for cancer immunotherapy. Approval of ipilimumab, an antibody targeting cytotoxic T-lymphocyte-associated antigen 4 for advanced melanoma, and sipuleucel-T, an autologous DC-based vaccine for advanced prostate cancer have brought immunotherapy to the forefront of cancer therapeutics and made the goal of long-term tumor control for patients with advanced metastatic disease seem achievable. Additionally, encouraging data from early clinical trials of other immune checkpoint inhibitors targeting programmed cell death 1 and programmed cell death ligand 1 and numerous therapeutic vaccines in development have further expanded interest in the potential of cancer immunotherapy. These recent developments represent the fruits of years of preclinical and clinical research to better understand the complex mechanisms of immune regulation and the ways in which tumors exploit those mechanisms to evade and avoid the antitumor immune response.

Interleukin‑15: a potent adjuvant enhancing the efficacy of an autologous whole‑cell tumor vaccine against Lewis lung carcinoma

Lung cancer is a major cause of cancer‑associated mortality worldwide due to its limited response rate to current chemotherapy and radiation, thus immunotherapy is rapidly becoming the most promising approach. Although the highly specific tumor‑associated antigen of lung cancer has been found, autologous whole‑cell tumor vaccines remain indispensable in the development of therapeutic cancer vaccines. Interleukin (IL)‑15 is a T helper type 1 cytokine that has been demonstrated to have a marked antitumor immune response and the potential ability to reverse the host tolerance of tumor antigens in certain preclinical trials. In the present study, a cationic liposome encapsulating IL‑15 gene‑loaded plasmid acted as an adjuvant of an autologous whole‑cell tumor vaccine by subcutaneous injection. The combination immunotherapy resulted in significant inhibition of tumor growth without side effects in the preventive tumor inhibition and adoptive therapy study. Cytotoxic lymphocyte assay detection of the serum antigen and cytokines using an enzyme‑linked immunosorbent assay suggested that the IL‑15 gene can significantly improve the cellular immune response and humoral immune response provoked by autologous whole‑cell tumor vaccines. These results demonstrated that the IL‑15 gene was an effective adjuvant of autologous whole‑cell tumor vaccines against mouse lung cancer and may provide an attractive vaccine strategy for cancer immunotherapy.

Pleural innate response activator B cells protect against pneumonia via a GM-CSF-IgM axis

In response to lung infection, pleural innate response activator B cells produce GM-CSF–dependent IgM and ensure a frontline defense against bacterial invasion.

Pneumonia is a major cause of mortality worldwide and a serious problem in critical care medicine, but the immunophysiological processes that confer either protection or morbidity are not completely understood. We show that in response to lung infection, B1a B cells migrate from the pleural space to the lung parenchyma to secrete polyreactive emergency immunoglobulin M (IgM). The process requires innate response activator (IRA) B cells, a transitional B1a-derived inflammatory subset which controls IgM production via autocrine granulocyte/macrophage colony-stimulating factor (GM-CSF) signaling. The strategic location of these cells, coupled with the capacity to produce GM-CSF–dependent IgM, ensures effective early frontline defense against bacteria invading the lungs. The study describes a previously unrecognized GM-CSF-IgM axis and positions IRA B cells as orchestrators of protective IgM immunity.

Effective TRAIL-based immunotherapy requires both plasmacytoid and CD8α dendritic cells

It is now appreciated that there are distinct subsets of dendritic cells (DC) with specialized functions. Plasmacytoid DC (pDC) and CD8α DC can contribute to the priming, activation and function of antitumor CD8 T cells; however, their specific roles and necessity in stimulating antitumor immunity are not clearly understood. We examined the importance of pDC and CD8α DC during immunotherapy of an orthotopic model of metastatic renal cell carcinoma. Immunotherapy that utilizes a recombinant adenovirus encoding tumor necrosis factor-related apoptosis-inducing ligand (Ad5-TRAIL) in combination with an immunostimulatory CpG-containing oligodeoxynucleotide (CpG) resulted in the clearance of primary and metastatic tumors in wild-type (WT) replete BALB/c mice and prolonged survival. In comparison, mice deficient in either pDC (accomplished using a depleting mAb specific for PDCA1) or CD8α DC (through utilization of CD8α DC-deficient Batf3(-/-) BALB/c mice) had uncontrolled tumor growth and high mortality after Ad5-TRAIL/CpG administration. The ineffectiveness of Ad5-TRAIL/CpG therapy in the anti-PDCA1-treated and Batf3(-/-) BALB/c mice was marked by an altered activation phenotype of the DC, as well as significantly reduced expression of type I IFN-stimulated genes and IL-15/IL-15R complex production. In addition, pDC-depleted and Batf3(-/-) BALB/c mice had significantly decreased effector CD8 T cell infiltration in the primary tumor site compared with WT mice after therapy. These data collectively suggest that pDC and CD8α DC carry out independent, but complementary, roles that are necessary to initiate an efficacious antitumor immune response after Ad5-TRAIL/CpG therapy.

Next-generation cancer vaccine approaches: integrating lessons learned from current successes with promising biotechnologic advances

With the recent approval of sipuleucel-T for metastatic castration-resistant prostate cancer and ipilimumab for metastatic melanoma, there is increasing excitement in the field of cancer immunotherapy. A large number of clinical trials are currently testing various vaccine vectors in a diverse array of cancer types. Which of these strategies will ultimately prove successful has yet to be determined. However, a better understanding of the complex interplay of tumor-specific T cells and the challenges faced at the tumor microenvironment, advances in biotechnology, and lessons learned from prior successes and failures will likely lead to approvals of other therapeutic cancer vaccines.

Challenges facing the development of cancer vaccines

Just like any other effective immunization in medicine, cancer vaccines need to have antigens with particular specificity and immunostimulatory features, the immune responses to be elicited in the body, and therapeutic effect-regression or prevention of the cancer-must be meaningful and clinically observable. There are many choices for cancer antigens, such as tissue-specific proteins, cancer-specific proteins, class I- or class II-restricted peptides derived from those, or in situ and whole-cell-derived products are some examples. Another translational issue is that cancer patients are heterogeneous with respect to the extent to which the immune system is already activated with potential to impact the tumor growth or, conversely, the extent to which the immune system has been impaired through a prior and ongoing interaction with the tumor. Conventional or immunologic tests have potential to define a subset of patients with better chance or response, so that particular vaccines can be tested. Treatment of cancer patients is expensive, and trials are slow. To meet these challenges in practical terms will require not only careful scientific technical work for product development, coordination with clinicians to define patient subsets with diseases that can show responses, but also a comprehensive, practical implementation so that we can unlock the full potential of anticancer vaccines.

Dendritic-cell-based therapeutic cancer vaccines

The past decade has seen tremendous developments in novel cancer therapies through the targeting of tumor-cell-intrinsic pathways whose activity is linked to genetic alterations and the targeting of tumor-cell-extrinsic factors, such as growth factors. Furthermore, immunotherapies are entering the clinic at an unprecedented speed after the demonstration that T cells can efficiently reject tumors and that their antitumor activity can be enhanced with antibodies against immune-regulatory molecules (checkpoint blockade). Current immunotherapy strategies include monoclonal antibodies against tumor cells or immune-regulatory molecules, cell-based therapies such as adoptive transfer of ex-vivo-activated T cells and natural killer cells, and cancer vaccines. Herein, we discuss the immunological basis for therapeutic cancer vaccines and how the current understanding of dendritic cell and T cell biology might enable the development of next-generation curative therapies for individuals with cancer.

Generation of CTL responses against pancreatic cancer in vitro using dendritic cells co-transfected with MUC4 and survivin RNA

Pancreatic cancer (PC) is one of the most devastating human malignancies without effective therapies. Tumor vaccine based on RNA-transfected dendritic cells (DCs) has emerged as an alternative therapeutic approach for a variety of human cancers including advanced PC. In the present study we compared the cytotoxic T lymphocyte (CTL) responses against PC cells in vitro, which were induced by DCs co-transfected with two mRNAs of tumor associated-antigens (TAA) MUC4 and survivin, versus DCs transfected with a single mRNA encoding either MUC4 or survivin. DCs co-transfected with two TAA mRNAs were found to induce stronger CTL responses against PC target cells in vitro, compared with the DCs transfected with a single mRNA. Moreover, the antigen-specific CTL responses were MHC class I-restricted. These results provide an experimental foundation for further clinical investigations of DC vaccines encoding multiple TAA epitopes for metastatic PC.

Biological delivery approaches for gene therapy: strategies to potentiate efficacy and enhance specificity

Nowadays many therapeutic agents such as suicide genes, anti-angiogenesis agents, cytokines, chemokines and other therapeutic genes were delivered to cancer cells. Various biological delivery systems have been applied for directing therapeutic gene to target cells. Some of these successful preclinical studies, steps forward to clinical trials and a few are examined in phase III clinical trials. In this review, the biological gene delivery systems were categorized into microorganism and cell based delivery systems. Viral, bacterial, yeast and parasite are among microorganism based delivery systems which are expanded in this review. In cell based approach, different strategies such as tumor cells, stem cells, dendritic cells and sertoli cells will be discussed. Different drawbacks are associated with each delivery system; therefore, many strategies have been improved and potentiated their direction toward specific target cells. Herein, further to the principle of each delivery system, the progresses of these approaches for development of newer generation are discussed.

Human dendritic cell subsets in vaccination

Owing to their properties, dendritic cells (DCs) are often called 'nature's adjuvants' and thus have become the natural targets for antigen delivery. DCs provide an essential link between the innate and the adaptive immune responses. DCs are at the center of the immune system owing to their ability to control both tolerance and immunity. DCs are thus key targets for both preventive and therapeutic vaccination. Herein, we will discuss recent progresses in our understanding of DC subsets physiology as it applies to vaccination.

Revisiting immune-based therapies for aggressive follicular cell-derived thyroid cancers

BACKGROUND

With our growing understanding of the immune system and mechanisms employed by tumors to evade destruction, the field of cancer immunotherapy has been revitalized. Concurrent inflammation has long been associated with follicular cell-derived thyroid cancer (FDTC). In the last decade, much research has focused on characterizing the tumor-associated immune response in patients with FDTC.

SUMMARY

Mast cells, natural killer cells, macrophages, dendritic cells, B cells, and T cells have been identified within FDTC-associated immune infiltrate. Collectively, these findings suggest that the immune response to FDTC is compromised and may even promote tumor progression. A more thorough characterization of the tumor-associated immune response in FDTC may lead to the development of immune-based adjuvant therapies for patients with aggressive disease.

CONCLUSIONS

Immune-based therapies could provide essential alternatives to patients that cannot be treated surgically, those with recurrent or persistent lymph node metastases, and those with anaplastic thyroid cancer.

Prostate cancer vaccines: Update on clinical development

Prostate cancer is a common malignancy among elderly men and is essentially incurable once it becomes metastatic. Results from clinical trials testing a panel of specific vaccines in patients with castration-resistant prostate cancer (CRPC) suggest that alternative therapies may one day substitute or support the current gold standard (docetaxel plus prednisone). Here, we summarize the results of germane clinical trials completed during the last 12 y and provide updates on some currently ongoing studies. As it stands, prostate cancer vaccines appear to be safe and capable of generating prostate-specific T lymphocyte responses with potential antitumor activity.

The evolving role of immunotherapy in prostate cancer

The prognosis for men with metastatic, castration-resistant prostate cancer (CRPC) is limited, and patients have very few treatment options, particularly if the treatment failed with docetaxel (Taxotere). As a result, there is a requirement for novel approaches to therapy. Using immunotherapy to induce immune responses to prostate cancer in preclinical and clinical studies appears to be a valid therapeutic approach. In a pivotal phase III trial, treatment with sipuleucel-T, an autologous cellular vaccine consisting of activated antigen-presenting cells loaded with prostatic acid phosphatase (PAP), gave a median overall survival of 25.8 months compared with 21.7 months for placebo-treated patients, resulting in a 22% relative reduction in the risk of death. Based on these results, sipuleucel-T became the first therapeutic vaccine approved for any type of cancer in the USA. PROSTVAC(®)-VF, a poxvirus-based vaccine engineered to present prostate-specific antigen (PSA) and three immune costimulatory molecules, and GVAX, a vaccine consisting of two prostate cancer cell lines (LnCAP and PC3) and genetically modified to secrete granulocyte-macrophage colony-stimulating factor (GM-CSF), both showed promising results in phase II studies, although GVAX failed to meet its primary end point of overall survival when compared with docetaxel in a phase III study. T-cell modulation is another potential immunotherapeutic strategy for CRPC. Ipilimumab, an antibody against the cytotoxic T-lymphocyte-associated antigen-4, is being evaluated in phase I/II studies, both alone and in combination with chemotherapy, radiotherapy or GVAX, with activity in prostate cancer. CRPC is one of the few tumour types where immunotherapy is the current standard of care. Further research, however, will be necessary to improve antitumour responses and clinical benefits, including the use of novel combinatorial approaches.

Proposed mechanisms of action for prostate cancer vaccines

Prostate cancer is responsible for the deaths of more than 33,000 American men every year. Once this disease has become metastatic, there is no curative treatment. Alternative therapies to chemotherapy and radical prostatectomy are being increasingly explored. Prostate cancer vaccines--which trigger a tumour-specific cytotoxic-T-lymphocyte-mediated immune attack by the patient's immune system--have been investigated in clinical trials with modest, yet encouraging, results. When developing and administering prostate cancer vaccines, it is critical to consider how vital parameters, such as the stage of disease progression and the nature of adjuvant therapies, could influence treatment outcome. Of particular interest are current and future strategies for diminishing the activity of regulatory T lymphocytes.

Glycan array analysis of the antigen repertoire targeted by tumor-binding antibodies

Immunization with whole cells has been used extensively to generate monoclonal antibodies, produce protective immune responses, and discover new disease antigens. While glycans are abundant on cell surfaces, anti-glycan immune responses have not been well-characterized. We used glycan microarrays to profile 49 tumor-binding monoclonal antibodies generated by immunizing mice with whole cancer cells. A substantial proportion (41%) of the tumor binding antibodies bound carbohydrate antigens. The antibodies primarily recognize a group of 5 glycan antigens: Sialyl Lewis A (SLeA), Lewis A (LeA), Lewis X (LeX), blood group A (BG-A), and blood group H on a type 2 chain (BG-H2). The results have important implications for monoclonal antibody production and cancer vaccine development.

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 antigen-transfected, NKT cell ligand-loaded, human cells elicits robust in situ immune responses by dendritic cells

Both innate and adaptive immunity are crucial for cancer immunosurveillance, but precise therapeutic equations to restore immunosurveillance in patients with cancer patients have yet to be developed. In murine models, α-galactosylceramide (α-GalCer)-loaded, tumor antigen-expressing syngeneic or allogeneic cells can act as cellular adjuvants, linking the innate and adaptive immune systems. In the current study, we established human artificial adjuvant vector cells (aAVC) consisting of human HEK293 embryonic kidney cells stably transfected with the natural killer T (NKT) immune cell receptor CD1d, loaded with the CD1d ligand α-GalCer and then transfected with antigen-encoding mRNA. When administered to mice or dogs, these aAVC-activated invariant NKT (iNKT) cells elicited antigen-specific T-cell responses with no adverse events. In parallel experiments, using NOD/SCID/IL-2rγc(null)-immunodeficient (hDC-NOG) mouse model, we also showed that the human melanoma antigen, MART-1, expressed by mRNA transfected aAVCs can be cross-presented to antigen-specific T cells by human dendritic cells. Antigen-specific T-cell responses elicited and expanded by aAVCs were verified as functional in tumor immunity. Our results support the clinical development of aAVCs to harness innate and adaptive immunity for effective cancer immunotherapy.

Apoptotic tumor cells induce IL-27 release from human DCs to activate Treg cells that express CD69 and attenuate cytotoxicity

Intrinsic immunosuppression is a major obstacle for successful cancer therapy. The mechanisms for the induction and regulation of immunosuppression in humans are ill defined. A microenvironmental component that might prevent antitumor immunity is the presence of dying tumor cells, which are abundant following conventional cancer ablation methods such as chemo- or radiotherapy. Shedding of apoptotic debris and/or secretion of factors to the tumor bed or draining lymph nodes thus might have a profound impact on professional phagocytes, such as DCs, and subsequent priming of lymphocytes. Here, we exposed human DCs to supernatants of live, apoptotic, or necrotic human breast cancer cells and cocultured them with autologous T cells. Priming with apoptotic debris prevented DCs from establishing cytotoxicity toward live human tumor cells by inducing a Treg-cell population, defined by coexpression of CD39 and CD69. Immunosuppression via Treg cells was transferable and required the release of sphingosine-1-phosphate (S1P) from apoptotic cells, acting via S1P receptor 4 on DCs to induce IL-27 secretion. We propose that CD69 expression on CD39(+) Treg cells enables them to interact with CD73-expressing CD8(+) T cells to generate adenosine, thereby suppressing cytotoxicity. These findings aid the understanding of how dying tumor cells limit antitumor immunity.

Whole cell vaccines--past progress and future strategies

Cancer vaccines have shown success in curing tumors in preclinical models. Accumulating evidence also supports their ability to induce immune responses in patients. In many cases, these responses correlate with improved clinical outcomes. However, cancer vaccines have not yet demonstrated their true potential in clinical trials. This is likely due to the difficulty in mounting a significant anti-tumor response in patients with advanced disease because of pre-existing tolerance mechanisms that are actively turning off immune recognition in cancer patients. This review will examine the recent progress being made in the design and implementation of whole cell cancer vaccines, one vaccine approach that simultaneously targets multiple tumor antigens to activate the immune response. These vaccines have been shown to induce antigen-specific T-cell responses. Preclinical studies evaluating these vaccines given in sequence with other agents and cancer treatment modalities support the use of immunomodulating doses of chemotherapy and radiation, as well as immune-modulating pathway-targeted monoclonal antibodies, to enhance the efficacy of cancer vaccines. Based on emerging preclinical data, clinical trials are currently exploring the use of combinatorial immune-based therapies for the treatment of cancer.

Diet-induced obesity alters dendritic cell function in the presence and absence of tumor growth

Obesity is a mounting health concern in the United States and is associated with an increased risk for developing several cancers, including renal cell carcinoma (RCC). Despite this, little is known regarding the impact of obesity on antitumor immunity. Because dendritic cells (DC) are critical regulators of antitumor immunity, we examined the combined effects of obesity and tumor outgrowth on DC function. Using a diet-induced obesity (DIO) model, DC function was evaluated in mice bearing orthotopic RCC and in tumor-free controls. Tumor-free DIO mice had profoundly altered serum cytokine and chemokine profiles, with upregulation of 15 proteins, including IL-1α, IL-17, and LIF. Tumor-free DIO mice had elevated percentages of conventional splenic DC that were impaired in their ability to stimulate naive T cell expansion, although they were phenotypically similar to normal weight (NW) controls. In DIO mice, intrarenal RCC tumor challenge in the absence of therapy led to increased local infiltration by T cell-suppressive DC and accelerated early tumor outgrowth. Following administration of a DC-dependent immunotherapy, established RCC tumors regressed in normal weight mice. The same immunotherapy was ineffective in DIO mice and was characterized by an accumulation of regulatory DC in tumor-bearing kidneys, decreased local infiltration by IFN-γ-producing CD8 T cells, and progressive tumor outgrowth. Our results suggest that the presence of obesity as a comorbidity can impair the efficacy of DC-dependent antitumor immunotherapies.

Autologous versus allogeneic cell-based vaccines?

Devitalized tumor cells either autologous or allogeneic have been used as anti-cancer vaccines with the purpose of facilitating the induction of an immune response able to destroy growing tumor cells since the identification of tumor antigens was deemed not to be necessary, particularly in the autologous system. Such vaccines were tested first in animal models and then in the clinics as unmodified tumor cells or after insertion of genes coding for factors known to increase the immune response against tumors. These vaccines were usually given by subcutaneous injections along with different immunological adjuvants. Such immunization approaches were found to be effective in mice when carried out in a tumor preventive setting but significantly less in the therapeutic context, that is, in the presence of an established tumor. By analyzing several clinical trials of vaccination using either autologous or allogeneic unmodified and gene-modified tumor cells published in the last 10 to 15 years, we conclude for a lack of sufficient evidence for efficacy of this strategy in inducing both a strong immune response and a therapeutic response. A potential variant of this strategy is the direct intratumoral injection of immunostimulatory genes delivered by vectors in vivo. But even this approach failed to provide a statistically significant clinical benefit for the cancer patients.We also point out the inherent drawbacks of the tumor cell-based vaccine strategy that include (a) a limited frequency by which human tumor lines can be obtained from clinical samples, (b) the low number of available cells for vaccination, (c) the release of immune-suppressive factors by tumor cells, and (d) the cost and time necessary for standardization and collecting/expanding a number of cells according to the approved regulatory requirements. Thus, taking into consideration the new developments in cancer vaccines, we believe that tumor cell-based vaccines should be dismissed as anti-cancer vaccines unless a clear benefit could be demonstrated by the few ongoing trials of combination with new immunomodulating reagents (eg, anti-CTLA4, PD-1, chemotherapy).

Monocytic CCR2(+) myeloid-derived suppressor cells promote immune escape by limiting activated CD8 T-cell infiltration into the tumor microenvironment

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of cells that accumulate during tumor formation, facilitate immune escape, and enable tumor progression. MDSCs are important contributors to the development of an immunosuppressive tumor microenvironment that blocks the action of cytotoxic antitumor T effector cells. Heterogeneity in these cells poses a significant barrier to studying the in vivo contributions of individual MDSC subtypes. Herein, we show that granulocyte-macrophage colony stimulating factor, a cytokine critical for the numeric and functional development of MDSC populations, promotes expansion of a monocyte-derived MDSC population characterized by expression of CD11b and the chemokine receptor CCR2. Using a toxin-mediated ablation strategy to target CCR2-expressing cells, we show that these monocytic MDSCs regulate entry of activated CD8 T cells into the tumor site, thereby limiting the efficacy of immunotherapy. Our results argue that therapeutic targeting of monocytic MDSCs would enhance outcomes in immunotherapy.

Immunization with dendritic cells pulsed ex vivo with recombinant chlamydial protease-like activity factor induces protective immunity against genital chlamydiamuridarum challenge

We have shown that immunization with soluble recombinant chlamydial protease-like activity factor (rCPAF) and a T helper 1 type adjuvant can induce significantly enhanced bacterial clearance and protection against Chlamydia-induced pathological sequelae in the genital tract. In this study, we investigated the use of bone marrow derived dendritic cells (BMDCs) pulsed ex vivo with rCPAF + CpG in an adoptive subcutaneous immunization for the ability to induce protective immunity against genital chlamydial infection. We found that BMDCs pulsed with rCPAF + CpG efficiently up-regulated the expression of activation markers CD86, CD80, CD40, and major histocompatibility complex class II (MHC II), and secreted interleukin-12, but not IL-10 and IL-4. Mice adoptively immunized with rCPAF + CpG-pulsed BMDCs or UV-EB + CpG-pulsed BMDCs produced elevated levels of antigen-specific IFN-γ and enhanced IgG1 and IgG2a antibodies. Moreover, mice immunized with rCPAF + CpG-pulsed BMDCs or UV-EB + CpG-pulsed BMDCs exhibited significantly reduced genital Chlamydia shedding, accelerated resolution of infection, and reduced oviduct pathology when compared to infected mock-immunized animals. These results suggest that adoptive subcutaneous immunization with ex vivo rCPAF-pulsed BMDCs is an effective approach, comparable to that induced by UV-EB–BMDCs, for inducing robust anti-Chlamydia 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.

Emerging cancer vaccines: the promise of genetic vectors

Therapeutic vaccination against cancer is an important approach which, when combined with other therapies, can improve long-term control of cancer. In fact, the induction of adaptive immune responses against Tumor Associated Antigens (TAAs) as well as innate immunity are important factors for tumor stabilization/eradication. A variety of immunization technologies have been explored in last decades and are currently under active evaluation, such as cell-based, protein, peptide and heat-shock protein-based cancer vaccines. Genetic vaccines are emerging as promising methodologies to elicit immune responses against a wide variety of antigens, including TAAs. Amongst these, Adenovirus (Ad)-based vectors show excellent immunogenicity profile and have achieved immunological proof of concept in humans. In vivo electroporation of plasmid DNA (DNA-EP) is also a desirable vaccine technology for cancer vaccines, as it is repeatable several times, a parameter required for the long-term maintenance of anti-tumor immunity. Recent findings show that combinations of different modalities of immunization (heterologous prime/boost) are able to induce superior immune reactions as compared to single-modality vaccines. In this review, we will discuss the challenges and requirements of emerging cancer vaccines, particularly focusing on the genetic cancer vaccines currently under active development and the promise shown by Ad and DNA-EP heterologous prime-boost.

Oxygen is a master regulator of the immunogenicity of primary human glioma cells

With recent approval of the first dendritic cell (DC) vaccine for patient use, many other DC vaccine approaches are now being tested in clinical trials. Many of these DC vaccines employ tumor cell lysates (TL) generated from cells cultured in atmospheric oxygen (∼20% O₂) that greatly exceeds levels found in tumors in situ. In this study, we tested the hypothesis that TLs generated from tumor cells cultured under physiologic oxygen (∼5% O₂) would be more effective as a source for DC antigens. Gene expression patterns in primary glioma cultures established at 5% O₂ more closely paralleled patient tumors in situ and known immunogenic antigens were more highly expressed. DCs treated with TLs generated from primary tumor cells maintained in 5% O₂ took up and presented antigens to CD8 T cells more efficiently. Moreover, CD8 T cells primed in this manner exhibited superior tumoricidal activity against target cells cultured in either atmospheric 20% O₂ or physiologic 5% O₂. Together, these results establish a simple method to greatly improve the effectiveness of DC vaccines in stimulating the production of tumoricidal T cells, with broad implications for many of the DC-based cancer vaccines being developed for clinical application.

Therapeutic vaccines for gastrointestinal cancers

Despite progress in the management of gastrointestinal malignancies, these diseases remain devastating maladies. Conventional treatment with chemotherapy and radiation is still only partially effective and highly toxic. In the era of increasing knowledge of the molecular biology of tumors and the interaction between the tumor and immune system, the development of targeted agents, including cancer vaccines, has emerged as a promising modality. In this paper, we discuss the principals of vaccine development, and we review most of the published trials on gastrointestinal cancer vaccines that have been conducted over the last decade. Many antigens and various treatment approaches have already been tested in colon, pancreatic, and other cancers. Some of these approaches have already shown some clinical benefit. In this paper, we discuss these different strategies and some of the future directions for targeting gastrointestinal malignancies with vaccines.

Broad antigenic coverage induced by vaccination with virus-based cDNA libraries cures established tumors

Effective cancer immunotherapy requires the release of a broad spectrum of tumor antigens in the context of potent immune activation. We show here that a cDNA library of normal tissue, expressed from a highly immunogenic viral platform, cures established tumors of the same histological type from which the cDNA library was derived. Immune escape occurred with suboptimal vaccination, but tumor cells that escaped the immune pressure were readily treated by second-line virus-based immunotherapy. This approach has several major advantages. Use of the cDNA library leads to presentation of a broad repertoire of (undefined) tumor-associated antigens, which reduces emergence of treatment-resistant variants and also permits rational, combined-modality approaches in the clinic. Finally, the viral vectors can be delivered systemically, without the need for tumor targeting, and are amenable to clinical-grade production. Therefore, virus-expressed cDNA libraries represent a novel paradigm for cancer treatment addressing many of the key issues that have undermined the efficacy of immuno- and virotherapy to date.

Vaccines as consolidation therapy for myeloid leukemia

Immunotherapy for myeloid leukemias remains a cornerstone in the management of this highly aggressive group of malignancies. Allogeneic (allo) stem cell transplantation (SCT), which can be curative in acute and chronic myeloid leukemias, exemplifies the success of immunotherapy for cancer management. However, because of its nonspecific immune response against normal tissue, allo-SCT is associated with high rates of morbidity and mortality, secondary to graft-versus-host disease, which can occur in up to 50% of allo-SCT recipients. Targeted immunotherapy using leukemia vaccines has been heavily investigated, as these vaccines elicit specific immune responses against leukemia cells while sparing normal tissue. Peptide and cellular vaccines have been developed against tumor-specific and leukemia-associated self-antigens. Although not yet considered the standard of care, leukemia vaccines continue to show promising results in the management of the myeloid leukemias.

Therapeutic response in patients with advanced malignancies treated with combined dendritic cell-activated T cell based immunotherapy and intensity-modulated radiotherapy

Successful cancer immunotherapy is confounded by the magnitude of the tumor burden and the presence of immunoregulatory elements that suppress an immune response. To approach these issues, 26 patients with advanced treatment refractory cancer were enrolled in a safety/feasibility study wherein a conventional treatment modality, intensity modulated radiotherapy (IMRT), was combined with dendritic cell-based immunotherapy. We hypothesized that radiation would lower the tumor burdens, decrease the number/function of regulatory cells in the tumor environment, and release products of tumor cells that could be acquired by intratumoral injected immature dendritic cells (iDC). Metastatic lesions identified by CT (computed tomography) were injected with autologous iDC combined with a cytokine-based adjuvant and KLH (keyhole limpet hemocyanin), followed 24 h later by IV-infused T-cells expanded with anti-CD3 and IL-2 (AT). After three to five days, each of the injected lesions was treated with fractionated doses of IMRT followed by another injection of intratumoral iDC and IV-infused AT. No toxicity was observed with cell infusion while radiation-related toxicity was observed in seven patients. Five patients had progressive disease, eight demonstrated complete resolution at treated sites but developed recurrent disease at other sites, and 13 showed complete response at various follow-up times with an overall estimated Kaplan-Meier disease-free survival of 345 days. Most patients developed KLH antibodies supporting our hypothesis that the co-injected iDC are functional with the capacity to acquire antigens from their environment and generate an adaptive immune response. These results demonstrate the safety and effectiveness of this multimodality strategy combining immunotherapy and IMRT in patients with advanced malignancies.