Altering regulatory T cell function in cancer immunotherapy: a novel means to boost the efficacy of cancer vaccines

CEA vaccines

Carcinoembryonic antigen (CEA) is a glycosylated cell surface oncofetal protein involved in adhesion, proliferation, and migration that is highly upregulated in multiple carcinomas and has long been a promising target for cancer vaccination. This review summarizes the progress to date in the development of CEA vaccines, examining both pre-clinical and clinical studies across a variety of vaccine platforms that in aggregate, begin to reveal some critical insights. These studies demonstrate the ability of CEA vaccines to break immunologic tolerance and elicit CEA-specific immunity, which associates with improved clinical outcomes in select individuals. Approaches that have combined replicating viral vectors, with heterologous boosting and different adjuvant strategies have been particularly promising but, these early clinical trial results will require confirmatory studies. Collectively, these studies suggest that clinical efficacy likely depends upon harnessing a potent vaccine combination in an appropriate clinical setting to fully realize the potential of CEA vaccination.

Splenic Volume, an Easy-To-Use Predictor of HCC Late Recurrence for HCC Patients After Hepatectomy

Purpose

The high recurrence rate of hepatocellular carcinoma (HCC) has a poor impact on the quality of life and survival time of patients. Especially for late recurrence, poor data are available in analysis. We aim to evaluate whether the splenic volume (SV) measured from preoperative CT images could predict late recurrence in HCC patients after hepatectomy.

Patients and Methods

A cohort of 300 HCC patients hospitalized at Xiangya Hospital of Central South University between January 2015 and June 2018 was retrospectively analyzed. The SV was calculated by using automated volumetry software from preoperative CT images. A total of 300 HCC patients were separated into the early recurrence cohort (n=167), the late recurrence cohort (n=39), and the no recurrence cohort (n=94) according to whether there is a recurrence and the recurrence time. Univariate and multivariate Cox analyses were performed to identify the independent risk factors of both early and late recurrence.

Results

AFP, Microvascular invasion (MVI), satellitosis, and BCLC staging were independent risk factors of HCC early recurrence. Splenic volume (HR=1.003, 95%CI:1.001-1.005, P<0.001) was the only predictor of HCC late recurrence. Based on X-tile software, 133 non-early recurrence patients were divided into two groups according to SV: low SV (<165ml, n=45) and high SV (≥165ml, n= 88). The low SV group had a significantly better RFS compared with the high SV group (P=0.015). Nomogram was built on the base of SV to get the probability of 3-year RFS, 4-year RFS, and 5-year RFS.

Conclusion

In our study, we drew a conclusion that splenic volume was the only predictor of HCC late recurrence because of its association with portal hypertension and liver cirrhosis. High splenic volume often indicated a worse recurrence.

Nanomaterials-Mediated Immunomodulation for Cancer Therapeutics

Immunotherapy holds great promise in overcoming the limitations of conventional regimens for cancer therapeutics. There is growing interest among researchers and clinicians to develop novel immune-strategies for cancer diagnosis and treatment with better specificity and lesser adversity. Immunomodulation-based cancer therapies are rapidly emerging as an alternative approach that employs the host’s own defense mechanisms to recognize and selectively eliminate cancerous cells. Recent advances in nanotechnology have pioneered a revolution in the field of cancer therapy. Several nanomaterials (NMs) have been utilized to surmount the challenges of conventional anti-cancer treatments like cytotoxic chemotherapy, radiation, and surgery. NMs offer a plethora of exceptional features such as a large surface area to volume ratio, effective loading, and controlled release of active drugs, tunable dimensions, and high stability. Moreover, they also possess the inherent property of interacting with living cells and altering the immune responses. However, the interaction between NMs and the immune system can give rise to unanticipated adverse reactions such as inflammation, necrosis, and hypersensitivity. Therefore, to ensure a successful and safe clinical application of immunomodulatory nanomaterials, it is imperative to acquire in-depth knowledge and a clear understanding of the complex nature of the interactions between NMs and the immune system. This review is aimed at providing an overview of the recent developments, achievements, and challenges in the application of immunomodulatory nanomaterials (iNMs) for cancer therapeutics with a focus on elucidating the mechanisms involved in the interplay between NMs and the host’s immune system.

ER stress-induced mediator C/EBP homologous protein thwarts effector T cell activity in tumors through T-bet repression

Understanding the intrinsic mediators that render CD8⁺ T cells dysfunctional in the tumor microenvironment is a requirement to develop more effective cancer immunotherapies. Here, we report that C/EBP homologous protein (Chop), a downstream sensor of severe endoplasmic reticulum (ER) stress, is a major negative regulator of the effector function of tumor-reactive CD8⁺ T cells. Chop expression is increased in tumor-infiltrating CD8⁺ T cells, which correlates with poor clinical outcome in ovarian cancer patients. Deletion of Chop in T cells improves spontaneous antitumor CD8⁺ T cell immunity and boosts the efficacy of T cell-based immunotherapy. Mechanistically, Chop in CD8⁺ T cells is elevated primarily through the ER stress-associated kinase Perk and a subsequent induction of Atf4; and directly represses the expression of T-bet, a master regulator of effector T cell function. These findings demonstrate the primary role of Chop in tumor-induced CD8⁺ T cell dysfunction and the therapeutic potential of blocking Chop or ER stress to unleash T cell-mediated antitumor immunity.

Anti-regulatory T cell vaccines in immunotherapy: focusing on FoxP3 as target

Anti- tumor vaccination elicits imperfect immune responses against tumor cells; that is related to the presence of suppressive obstacles in the tumor microenvironment. The main members of suppressive milieu of tumor are heteroogenous groups of immune cells in which regulatory T cell is a substantial component. Tregs express different immunomodulatory molecules such as FoxP3. Transcription factor, FoxP3, is a specific intracellular marker of Treg and crucial for Treg development. Therefore it is an attractive target for cancer treatment. This article reviews some recent anti-Treg vaccine focusing on FoxP3 to ameliorate anti-tumor immune responses. Among them, fusion vaccine of FoxP3-Fc(IgG) recombinant DNA vaccine and its accordant protein vaccine represents effective results.

Blockade of MCP-1/CCR4 signaling-induced recruitment of activated regulatory cells evokes an antitumor immune response in head and neck squamous cell carcinoma

FoxP3⁺ regulatory T (Treg) cells have diverse functions in the suppression of antitumor immunity. We show that FoxP3^hiCD45RA⁻CD4⁺ Treg cells [activated Treg (aTreg) cells] are the predominant cell population among tumor-infiltrating FoxP3⁺ T cells, and that high aTreg cell-infiltrating content is associated with reduced survival in patients with head and neck squamous cell carcinoma (HNSCC). In vitro studies have demonstrated that aTreg cells can suppress tumor-associated antigen (TAA) effector T cell immune responses in HNSCC. Moreover, C-C chemokine receptor 4 (CCR4) was specifically expressed by aTreg cells in the peripheral blood of HNSCC patients. Using a RayBiotech human chemokine antibody array, we showed that monocyte chemoattractant protein-1 (MCP-1), an endogenous CCR4-binding ligand, was specifically upregulated in the HNSCC microenvironment compared to the other four CCR4-binding ligands. Blocking MCP-1/CCR4 signaling-induced aTreg cell recruitment using a CCR4 antagonist evoked antitumor immunity in mice, and lead to inhibition of tumor growth and prolonged survival. Therefore, blocking aTreg cell trafficking in tumors using CCR4-binding agents may be an effective immunotherapy for HNSCC.

Improved Anti-Treg Vaccination Targeting Foxp3 Efficiently Decreases Regulatory T Cells in Mice

INTRODUCTION

The critical role of regulatory T (Treg) cells in dampening immune responses against tumor cells is apparent. Therefore, several methods have been introduced for eliminating Treg. Among them, inducing immune responses against Treg cells expressing Foxp3 transcription factor is a hopeful approach to decrease the frequency of Tregs. In current study, we used the chimeric FoxP3-Fc(IgG) fusion construct/protein to effectively stimulate the immune responses against Treg cells.

MATERIALS AND METHODS

Previously constructed FoxP3-Fc(IgG) DNA vaccine and its protein counterpart were injected into C57BL/6 mice in a prime/boost regimen. After 2 weeks, the mice were killed to measure the frequency of Tregs in their spleens, as well as analyze their specific cytokine production, T-cell proliferation, and CD8 T-cell cytotoxicity against FoxP3 protein.

RESULTS

FACS analysis of FoxP3 CD4 cells in splenocytes revealed the efficiency of FoxP3 DNA-prime protein-boost strategy to decrease the Treg cells and further showed considerable superiority of Fc(IgG) fusion strategy. This significant reduction in Treg frequency was also concomitant with higher FoxP3-specific CTL and Th1 responses in FoxP3-Fc vaccinated animals.

CONCLUSIONS

Prime/boost vaccination against FoxP3 in addition to enhanced antigen presentation by means of Fc fusion strategy could be successfully considered for Treg depletion studies. Validity of this approach should be experimentally tested in preclinical tumor models.

Impact of Metabolism on T-Cell Differentiation and Function and Cross Talk with Tumor Microenvironment

The immune system and metabolism are highly integrated and multilevel interactions between metabolic system and T lymphocyte signaling and fate exist. Accumulating evidence indicates that the regulation of nutrient uptake and utilization in T cells is critically important for the control of their differentiation and manipulating metabolic pathways in these cells can shape their function and survival. This review will discuss some potential cell metabolism pathways involved in shaping T lymphocyte function and differentiation. It will also describe show subsets of T cells have specific metabolic requirements and signaling pathways that contribute to their respective function. Examples showing the apparent similarity between cancer cell metabolism and T cells during activation are illustrated and finally some mechanisms being used by tumor microenvironment to orchestrate T-cell metabolic dysregulation and the subsequent emergence of immune suppression are discussed. We believe that targeting T-cell metabolism may provide an additional opportunity to manipulate T-cell function in the development of novel therapeutics.

Cellular Immune Responses and Immune Escape Mechanisms in Breast Cancer: Determinants of Immunotherapy

More recently, immunotherapy has emerged as a novel potentially effective therapeutic option also for solid malignancies such as breast cancer (BC). Relevant approaches, however, are determined by the 2 main elements of cancer immunoediting - the elimination of nascent transformed cells by immunosurveillance on the one hand and tumor immune escape on the other hand. Correspondingly, we here review the role of the various cellular immune players within the host-protective system and dissect the mechanisms of immune evasion leading to tumor progression. If the immune balance of disseminated BC cell dormancy (equilibrium phase) is lost, distant metastatic relapse may occur. The relevant cellular antitumor responses and translational immunotherapeutic options will also be discussed in terms of clinical benefit and future directions in BC management.

Immunotherapy of rat glioma without accumulation of CD4(+)CD25(+)FOXP3(+) regulatory T cells

Immunotherapy may be used for the treatment of glioblastoma multiforme; however, the induced immune response is inadequate when either T cells or dendritic cells are used alone. In this study, we established a novel vaccine procedure in rats, using dendritic cells pulsed with C6 tumor cell lysates in combination with adoptive transfer of T lymphocytes from syngenic donors. On day 21 after tumor inoculation, all the rats were sacrificed, the brains were harvested for calculation of glioma volume, cytolytic T lymphocyte responses were measured by cytotoxic assay, and the frequency of regulatory T lymphocytes (CD4⁺CD25⁺FOXP3⁺) in the peripheral blood was investigated by flow cytometric analysis. The survival rate of rats bearing C6 glioma was observed. Results showed that the co-immunization strategy had significant anti-tumor potential against the pre-established C6 glioma, and induced a strong cytolytic T lymphocyte response in rats. The frequency of peripheral blood CD4⁺CD25⁺FOXP3⁺ regulatory T lymphocytes was significantly decreased following the combination therapy, and the rats survived for a longer period. Experimental findings indicate that the combined immunotherapy of glioma cell lysate-pulsed dendritic cell vaccination following adoptive transfer of T cells can effectively inhibit the growth of gliomas in rats, boost anti-tumor immunity and produce a sustained immune response while avoiding the accumulation of CD4⁺CD25⁺FOXP3⁺ regulatory T lymphocytes.

Effects of the Treg/Th17 cell balance and their associated cytokines in patients with hepatitis B infection

The extent to which T-cell-mediated immunity is impaired in patients with hepatitis B virus (HBV) infection remains controversial. In addition, the role of T regulatory (Treg) and T helper 17 (Th17) cells and their associated cytokines in immunity is not clear. In the present study, peripheral blood samples were collected from 44 patients with chronic hepatitis B virus, 14 asymptomatic hepatitis B carriers, 19 patients with liver cirrhosis and 20 healthy individuals. Flow cytometry was used to detect the percentages of T cell subsets in the samples, including CD3⁺, CD4⁺ and CD8⁺ T cells, Treg cells and Th17 cells. A cytometric bead array was conducted to detect the levels of interleukin (IL)-17, -6, -10 and -21, and transforming growth factor (TGF)-β. The data revealed that Treg cell levels decreased, while Th17 cell levels increased in the peripheral blood of HBV patients. As the extent of inflammation and fibrosis in the hepatic tissue increased, the frequency of Treg and Th17 cells in the peripheral blood did not significantly differ. In addition, the levels of Th17 cells were found to positively correlate with TGF-β and IL-21 levels. Therefore, analyzing the balance between Treg/Th17 cells and their associated cytokines may be a useful indicator in the diagnosis of HBV.

Effects of the Treg/Th17 cell balance and their associated cytokines in patients with hepatitis B infection

The extent to which T-cell-mediated immunity is impaired in patients with hepatitis B virus (HBV) infection remains controversial. In addition, the role of T regulatory (Treg) and T helper 17 (Th17) cells and their associated cytokines in immunity is not clear. In the present study, peripheral blood samples were collected from 44 patients with chronic hepatitis B virus, 14 asymptomatic hepatitis B carriers, 19 patients with liver cirrhosis and 20 healthy individuals. Flow cytometry was used to detect the percentages of T cell subsets in the samples, including CD3⁺, CD4⁺ and CD8⁺ T cells, Treg cells and Th17 cells. A cytometric bead array was conducted to detect the levels of interleukin (IL)-17, -6, -10 and -21, and transforming growth factor (TGF)-β. The data revealed that Treg cell levels decreased, while Th17 cell levels increased in the peripheral blood of HBV patients. As the extent of inflammation and fibrosis in the hepatic tissue increased, the frequency of Treg and Th17 cells in the peripheral blood did not significantly differ. In addition, the levels of Th17 cells were found to positively correlate with TGF-β and IL-21 levels. Therefore, analyzing the balance between Treg/Th17 cells and their associated cytokines may be a useful indicator in the diagnosis of HBV.

Fully human antagonistic antibodies against CCR4 potently inhibit cell signaling and chemotaxis

BACKGROUND

CC chemokine receptor 4 (CCR4) represents a potentially important target for cancer immunotherapy due to its expression on tumor infiltrating immune cells including regulatory T cells (Tregs) and on tumor cells in several cancer types and its role in metastasis.

METHODOLOGY

Using phage display, human antibody library, affinity maturation and a cell-based antibody selection strategy, the antibody variants against human CCR4 were generated. These antibodies effectively competed with ligand binding, were able to block ligand-induced signaling and cell migration, and demonstrated efficient killing of CCR4-positive tumor cells via ADCC and phagocytosis. In a mouse model of human T-cell lymphoma, significant survival benefit was demonstrated for animals treated with the newly selected anti-CCR4 antibodies.

SIGNIFICANCE

For the first time, successful generation of anti- G-protein coupled chemokine receptor (GPCR) antibodies using human non-immune library and phage display on GPCR-expressing cells was demonstrated. The generated anti-CCR4 antibodies possess a dual mode of action (inhibition of ligand-induced signaling and antibody-directed tumor cell killing). The data demonstrate that the anti-tumor activity in vivo is mediated, at least in part, through Fc-receptor dependent effector mechanisms, such as ADCC and phagocytosis. Anti-CC chemokine receptor 4 antibodies inhibiting receptor signaling have potential as immunomodulatory antibodies for cancer.

Physiological organization of immune response based on the homeostatic mechanism of matrix reprogramming: implication in tumor and biotechnology

It is accepted that the immune system responds to pathogens with activation of antigen-independent innate and antigen-dependent adaptive immunity. However many immune events do not fit or are even inconsistent with this notion. We developed a new homeostatic model of the immune response. This model consists of four units: a sensor, a regulator, an effector and a rehabilitator. The sensor, macrophages or lymphocytes, recognize pathogenic cells and generate alarm signals. The regulator, antigen-presenting cells, Тregs and myeloid-derived suppressor cells, evaluate the signals and together with sensor cells program the effector. The effector, programmed macrophages and lymphocytes, eliminate the pathogenic cells. The rehabilitator, M2 macrophages, restrict inflammation, provide angiogenesis and reparation of tissue damage, and restore the homeostasis. We suggest the terms "immune matrix" for a biological template of immune responses to pathogens and "matrix reprogramming" for the interdependent reprogramming of different cells in the matrix. In an adequate immune response, the matrix forms a negative feedback mechanism to support the homeostasis. We defined the cellular and phenotypic composition of a tumor immune matrix. A tumor reprograms the homeostatic negative feedback mechanism of matrix into a pathogenic positive feedback mechanism. M2 macrophages play a key role in this transformation. Therefore, macrophages are an attractive target for biotechnology. Based on our hypotheses, we are developing a cell biotechnology method for creation of macrophages with a stable antitumor phenotype. We have shown that such macrophages almost doubled the survival time of mice with tumor.

Ion channels and anti-cancer immunity

The outcome of a malignant disease depends on the efficacy of the immune system to destroy cancer cells. Key steps in this process, for example the generation of a proper Ca(2+) signal induced by recognition of a specific antigen, are regulated by various ion channel including voltage-gated Kv1.3 and Ca(2+)-activated KCa3.1 K(+) channels, and the interplay between Orai and STIM to produce the Ca(2+)-release-activated Ca(2+) (CRAC) current required for T-cell proliferation and function. Understanding the immune cell subset-specific expression of ion channels along with their particular function in a given cell type, and the role of cancer tissue-dependent factors in the regulation of operation of these ion channels are emerging questions to be addressed in the fight against cancer disease. Answering these questions might lead to a better understanding of the immunosuppression phenomenon in cancer tissue and the development of drugs aimed at skewing the distribution of immune cell types towards killing of the tumour cells.

Cellular and molecular mechanisms in cancer immune escape: a comprehensive review

Immune escape is the final phase of cancer immunoediting process wherein cancer modulates our immune system to escape from being destroyed by it. Many cellular and molecular events govern the cancer's evasion of host immune response. The tumor undergoes continuous remodeling at the genetic, epigenetic and metabolic level to acquire resistance to apoptosis. At the same time, it effectively modifies all the components of the host's immunome so as to escape from its antitumor effects. Moreover, it induces accumulation of suppressive cells like Treg and myeloid derived suppressor cells and factors which also enable it to elude the immune system. Recent research in this area helps in defining the role of newer players like miRNAs and exosomes in immune escape. The immunotherapeutic approaches developed to target the escape phase appear quite promising; however, the quest for a perfect therapeutic agent that can achieve maximum cure with minimal toxicity continues.

In vitro generated Th17 cells support the expansion and phenotypic stability of CD4(+)Foxp3(+) regulatory T cells in vivo

CD4(+) T cells stimulate immune responses through distinct patterns of cytokine produced by Th1, Th2 or Th17 cells, or inhibit immune responses through Foxp3-expressing regulatory T cells (Tregs). Paradoxically, effector T cells were recently shown to activate Tregs, however, it remains unclear which Th subset is responsible for this effect. In this study, we found that Th17 cells expressed the highest levels of TNF among in vitro generated Th subsets, and most potently promoted expansion and stabilized Foxp3 expression by Tregs when co-transferred into Rag1(-/-) mice. Both TNF and IL-2 produced by Th17 cells contributed to this effect. The stimulatory effect of Th17 cells on Tregs was largely abolished when co-transferred with TNFR2-deficient Tregs. Furthermore, Tregs deficient in TNFR2 also supported a much lower production of IL-17A and TNF expression by co-transferred Th17 cells. Thus, our data indicate that the TNF-TNFR2 pathway plays a crucial role in the reciprocal stimulatory effect of Th17 cells and Tregs. This bidirectional interaction should be taken into account when designing therapy targeting Th17 cells, Tregs, TNF and TNFR2.

New tools to expand regulatory T cells from HIV-1-infected individuals

CD4+ Regulatory T cells (Tregs) are potent immune modulators and serve an important function in human immune homeostasis. Depletion of Tregs has led to measurable increases in antigen-specific T cell responses in vaccine settings for cancer and infectious pathogens. However, their role in HIV-1 immuno-pathogenesis remains controversial, as they could either serve to suppress deleterious HIV-1-associated immune activation and thus slow HIV-1 disease progression or alternatively suppress HIV-1-specific immunity and thereby promote virus spread. Understanding and modulating Treg function in the context of HIV-1 could lead to potential new strategies for immunotherapy or HIV vaccines. However, important open questions remain on their role in the context of HIV-1 infection, which needs to be carefully studied. Representing roughly 5% of human CD4+ T cells in the peripheral blood, studying the Treg population has proven to be difficult, especially in HIV-1 infected individuals where HIV-1-associated CD4 T cell and with that Treg depletion occurs. The characterization of regulatory T cells in individuals with advanced HIV-1 disease or tissue samples, for which only very small biological samples can be obtained, is therefore extremely challenging. We propose a technical solution to overcome these limitations using isolation and expansion of Tregs from HIV-1-positive individuals. Here we describe an easy and robust method to successfully expand Tregs isolated from HIV-1-infected individuals in vitro. Flow-sorted CD3(+)CD4(+)CD25(+)CD127(low) Tregs were stimulated with anti-CD3/anti-CD28 coated beads and cultured in the presence of IL-2. The expanded Tregs expressed high levels of FOXP3, CTLA4 and HELIOS compared to conventional T cells and were shown to be highly suppressive. Easier access to large numbers of Tregs will allow researchers to address important questions concerning their role in HIV-1 immunopathogenesis. We believe answering these questions may provide useful insight for the development of an effective HIV-1 vaccine.

Effects of cyclophosphamide and IL-2 on regulatory CD4+ T cell frequency and function in melanoma patients vaccinated with HLA-class I peptides: impact on the antigen-specific T cell response

The frequency and function of regulatory T cells (Tregs) were studied in stage II–III melanoma patients who were enrolled in a phase II randomized trial of vaccination with HLA-A*0201-modified tumor peptides versus observation. The vaccinated patients received low-dose cyclophosphamide (CTX) and low-dose interleukin-2 (IL-2). Tregs were analyzed in the lymph nodes (LNs) of stage III patients who were undergoing complete lymph node dissection and in peripheral blood mononuclear cells (PBMCs) collected before vaccination and at different time points during the vaccination period. The LNs of the vaccinated patients, which were surgically removed after two rounds of vaccination and one dose of CTX, displayed a low frequency of Tregs and a less immunosuppressive environment compared with those of the untreated patients. The accurate time-course analysis of the PBMCs of patients enrolled in the vaccination arm indicated a limited and transient modulation in the frequencies of Tregs in PBMCs collected after low-dose CTX administration and a strong Treg boost in those PBMCs collected after low-dose IL-2 administration. However, a fraction of the IL-2-boosted Tregs was functionally modulated to a Th-1-like phenotype in the vaccinated patients. Moreover, low-dose IL-2 promoted the concomitant expansion of conventional activated CD4⁺ T cells. Despite the amplification of Tregs, IL-2 administration maintained or further increased the number of antigen-specific CD8⁺ T cells that were induced by vaccination as demonstrated by the ex vivo human leukocyte antigen-multimer staining and IFN-γ ELISpot assays. Our study suggests that the use of CTX as a Treg modulator should be revised in terms of the administration schedule and of patients who may benefit from this drug treatment. Despite the Treg expansion that was observed in this study, low-dose IL-2 is not detrimental to the functional activities of vaccine-primed CD8⁺ T cell effectors when used in the inflammatory environment of vaccination.

Dendritic cells control CD4+CD25+ Treg cell suppressor function in vitro through juxtacrine delivery of IL-2

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) restrict inflammatory responses to self and nonself. Aberrant Treg activity is pathologic: Insufficient Treg activity is implicated in autoimmunity, allergy, and graft-versus-host-disease; overabundant activity is implicated in chronic infection and cancer. Tregs require IL-2 for their expansion and acquisition/execution of suppressor function; however, because Tregs cannot produce IL-2, they depend on IL-2 from an exogenous source. Until now, that IL-2 source had not been established. We asked whether dendritic cells (DCs) could supply IL-2 to Tregs and, if so, what was required for that delivery. We used flow cytometry, IL-2 ELISPOT, RT-qPCR, and IL-2 promoter-driven reporter assays to measure intracytoplasmic IL-2, secreted protein, IL-2 message and IL-2 promoter activity in bone marrow-derived (BMDC) and splenic DCs. We examined conjugate formation between Tregs, conventional CD4(+) cells, and IL-2-expressing DCs. We measured Treg levels of CD25, Foxp3, and suppressor function after co-culture with IL-2 sufficient and IL-2(-/-) DCs. We generated IL-2-mCherry-expressing DCs and used epifluorescence microscopy and flow cytometry to track IL-2 transfer to Tregs and test requirements for transfer. Between 0.7 to 2.4% of DCs constitutively produced IL-2 and diverted IL-2 secretion to Tregs by preferentially forming conjugates with them. Uptake of DC IL-2 by Tregs required cell-cell contact and CD25. Tregs increased levels of CD25 and Foxp3 from baseline and showed greater suppressor function when co-cultured with IL-2-sufficient DCs, but not when co-cultured with IL-2(-/-) DCs. Exogenous IL-2, added in excess of 500 U/ml to co-cultures with IL-2(-/-) DCs, restored Treg suppressor function. These data support a model of juxtacrine delivery of IL-2 from DCs to Tregs and suggest that a subset of DCs modulates Treg function through controlled, spatial delivery of IL-2. Knowledge of how DCs regulate Tregs should be integrated into the design of interventions intended to alter Treg function.

Comparative analyses of regulatory T cell subsets in patients with hepatocellular carcinoma: a crucial role of CD25(-) FOXP3(-) T cells

Regulatory T cells (Tregs) play pivotal role in cancer-induced immunoediting. Increment of CD25(high+) FOXP3+ natural Tregs has been reported in patients with hepatocellular carcinoma (HCC); however, the involvement of other type of Tregs remain elusive. We aimed to clarify whether FOXP3- Tregs are increased and functionally suppressive or not in patients with HCC. We enrolled 184 hepatitis C-infected patients with chronic liver diseases or HCC, 57 healthy subjects and 27 HCC patients with other etiology. Distinct Treg subsets were phenotypically identified by the expression of CD4, CD25, CD127 and forkhead/winged helix transcription factor (FOXP3). Their gene profiles, frequency and suppressor functions against T cell proliferation were compared among the subjects. To examine the molecules involving in Treg differentiation, we cultured naive CD4+ T cells in the presence of HCC cells and dendritic cells. We determined two types of CD4+ CD127- T cells with comparable regulatory ability; one is CD25(high+) cells expressing FOXP3 (CD25(high+) FOXP3+ Tregs) and the other is CD25- cells without FOXP3- expression (CD25- FOXP3- cells). The peripheral or intrahepatic frequency of CD25- FOXP3- Tregs in HCC patients is higher than those in other groups, of which significance is more than CD25(high+) FOXP3+ cells. Of importance, CD25- FOXP3- Tregs, but not CD25(high+) FOXP3+ cells, dynamically change in patients accompanied by the ablation or the recurrence of HCC. CD25- FOXP3- T cells with CD127- IL-10+ phenoype are inducible in vitro from naive CD4(+) T cells, in which programmed cell death 1 ligand 1, immunoglobulin-like transcript 4 and human leukocyte antigen G are involved.. In conclusion, CD25- FOXP3- Tregs with suppressive capacity are increased in patients with HCC, suggesting their distinct roles from CD25+ FOXP3+ Tregs.

Therapeutic cancer vaccines: current status and moving forward

Concurrent with U.S. Food and Drug Administration (FDA) approval of the first therapeutic cancer vaccine, a wide spectrum of other cancer vaccine platforms that target a diverse range of tumor-associated antigens is currently being evaluated in randomized phase II and phase III trials. The profound influence of the tumor microenvironment and other immunosuppressive entities, however, can limit the effectiveness of these vaccines. Numerous strategies are currently being evaluated both preclinically and clinically to counteract these immunosuppressive entities, including the combined use of vaccines with immune checkpoint inhibitors, certain chemotherapeutics, small-molecule targeted therapies, and radiation. The potential influence of the appropriate patient population and clinical trial endpoint in vaccine therapy studies is discussed, as well as the potential importance of biomarkers in future directions of this field.

New directions in the basic and translational biology of interleukin-27

Interleukin (IL)-27 is a member of the IL-6 and IL-12 family composed of the IL-27p28 and Epstein-Barr virus-induced gene 3 (EBI3) subunits. Although IL-27 was originally identified as a proinflammatory factor, subsequent studies have revealed the pleiotropic nature of this cytokine. This review discusses recent work that has explored the effect of IL-27 on CD4(+) T cell subsets, including T regulatory type 1 (Tr-1) cells, T follicular helper cells (Tfhs), and forkhead box P3 (Foxp3)(+) T regulatory cells (Tregs). Additionally, we highlight studies that have identified a role for the IL-27p28 subunit as a cytokine receptor antagonist. Much of the recent work on IL-27 has been relevant to human disease states characterized by inappropriate or excessive inflammation, and this review discusses potential opportunities to use IL-27 as a therapeutic agent.

A role for IL-27 in limiting T regulatory cell populations

IL-27 is a cytokine that regulates Th function during autoimmune and pathogen-induced immune responses. Although previous studies have shown that regulatory T cells (Tregs) express the IL-27R, and that IL-27 inhibits forkhead box P3 upregulation in vitro, little is known about how IL-27 influences Tregs in vivo. The studies presented in this article show that mice that overexpress IL-27 had decreased Treg frequencies and developed spontaneous inflammation. Although IL-27 did not cause mature Tregs to downregulate forkhead box P3, transgenic overexpression in vivo limited the size of a differentiating Treg population in a bone marrow chimera model, which correlated with reduced production of IL-2, a vital cytokine for Treg maintenance. These data identify an indirect role for IL-27 in shaping the Treg pool.

Sunitinib facilitates the activation and recruitment of therapeutic anti-tumor immunity in concert with specific vaccination

The multikinase inhibitor sunitinib malate (SUT) has been reported to reduce levels of myeloid suppressor cells and Treg cells in cancer patients, hypothetically diminishing intrinsic impediments for active immunization against tumor-associated antigens in such individuals. The goal of this study was to identify longitudinal immune molecular and cellular changes associated with tumor regression and disease-free status after the treatment of established day 7 s.c. MO5 (B16.OVA) melanomas with SUT alone (1 mg/day via oral gavage for 7 days), vaccination using ovalbumin (OVA) peptide-pulsed dendritic cell [vaccine (VAC)] alone, or the combination of SUT and VAC (SUT/VAC). We observed superior anti-tumor efficacy for SUT/VAC combination approaches, particularly when SUT was applied at the time of the initial vaccination or the VAC boost. Treatment effectiveness was associated with the acute loss of (and/or failure to recruit) cells bearing myeloid-derived suppressor cells or Treg phenotypes within the tumor microenvironment (TME) and the corollary, prolonged enhancement of Type-1 anti-OVA CD8(+) T cell responses in the tumor-draining lymph node and the TME. Enhanced Type-1 T cell infiltration of tumors was associated with treatment-induced expression of vascular cell adhesion molecule-1 (VCAM-1) and CXCR3 ligand chemokines in vascular/peri-vascular cells within the TME, with SUT/VAC therapy benefits conditionally negated upon adminsitration of CXCR3 or VCAM-1 blocking antibodies. These data support the ability of a short 7 day course of SUT to (re)condition the TME to become more receptive to the recruitment and prolonged therapeutic action of (VAC-induced) anti-tumor Tc1 cells.

A Phase I safety study of plasmid DNA immunization targeting carcinoembryonic antigen in colorectal cancer patients

A plasmid DNA vaccine, encoding a truncated form of human CEA fused to a T-helper epitope (CEA66 DNA) was delivered three times intradermally at 2 mg or intramuscularly at 8 mg by Biojector® to patients with colorectal cancer. Prior to the first vaccination, all patients received cyclophosphamide (300 mg/m²) intravenously. Granulocyte-macrophage colony-stimulating factor (GM-CSF) was administered subcutaneously with each vaccination. All patients completed the vaccine schedule. There were no grade 3 or 4 adverse events (AE). The most frequently reported AE grades 1 and 2 were injection site reactions, fatigue, headache, arthralgia, chest tightness and myalgia. Vaccination with CEA66 DNA in combination with GM-CSF was well tolerated and no signs of autoimmunity have been detected.

Concomitant tumor and autoantigen vaccination supports renal cell carcinoma rejection

Efficient tumor vaccination frequently requires adjuvant. Concomitant induction of an autoimmune response is discussed as a means to strengthen a weak tumor Ag-specific response. We asked whether the efficacy of dendritic cell (DC) vaccination with the renal cell carcinoma Ags MAGE-A9 (MAGE9) and G250 could be strengthened by covaccination with the renal cell carcinoma autoantigen GOLGA4. BALB/c mice were vaccinated with DC loaded with MHC class I-binding peptides of MAGE9 or G250 or tumor lysate, which sufficed for rejection of low-dose RENCA-MAGE9 and RENCA-G250 tumor grafts, but only retarded tumor growth at 200 times the tumor dose at which 100% of animals will develop a tumor. Instead, 75-100% of mice prevaccinated concomitantly with Salmonella typhimurium transformed with GOLGA4 cDNA in a eukaryotic expression vector rejected 200 times the tumor dose at which 100% of animals will develop tumor. In a therapeutic setting, the survival rate increased from 20-40% by covaccination with S. typhimurium-GOLGA4. Autoantigen covaccination significantly strengthened tumor Ag-specific CD4(+) and CD8(+) T cell expansion, particularly in peptide-loaded DC-vaccinated mice. Covaccination was accompanied by an increase in inflammatory cytokines, boosted IL-12 and IFN-gamma expression, and promoted a high tumor Ag-specific CTL response. Concomitant autoantigen vaccination also supported CCR6, CXCR3, and CXCR4 upregulation and T cell recruitment into the tumor. It did not affect regulatory T cells, but slightly increased myeloid-derived suppressor cells. Thus, tumor cell eradication was efficiently strengthened by concomitant induction of an immune response against a tumor Ag and an autoantigen expressed by the tumor cell. Activation of autoantigen-specific Th cells strongly supports tumor-specific Th cells and thereby CTL activation.

Immunotherapy prospects for acute myeloid leukaemia

While chemotherapy is successful at inducing remission of acute myeloid leukaemia (AML), the disease has a high probability of relapse. Strategies to prevent relapse involve consolidation chemotherapy, stem cell transplantation and immunotherapy. Evidence for immunosurveillance of AML and susceptibility of leukaemia cells to both T cell and natural killer (NK) cell attack and justifies the application of immune strategies to control residual AML persisting after remission induction. Immune therapy for AML includes allogeneic stem cell transplantation, adoptive transfer of allogeneic or autologous T cells or NK cells, vaccination with leukaemia cells, dendritic cells, cell lysates, peptides and DNA vaccines and treatment with cytokines, antibodies and immunomodulatory agents. Here we describe what is known about the immunological features of AML at presentation and in remission, the current status of immunotherapy and strategies combining treatment approaches with a view to achieving leukaemia cure.

Targeting inhibitory pathways in cancer immunotherapy

The clinical success of adaptive transfer of in vitro expanded antigen-specific CD8(+) T cells isolated from patients' tumors has demonstrated that effector cells of the adaptive immune system can effectively eliminate even large tumor masses. Nevertheless, cancer vaccines that aim to expand such CD8(+) T cells in situ have had remarkably little success in spite of numerous attempts. Recent advances in basic immunology have revealed layers of complexity controlling activation and maintenance of adaptive immune responses that are tightly controlled by immunoinhibitory pathways to avoid horror autotoxicus. During tumor progression the activities of negative pathways increase and together with cancer immune evasion tactics presumably prevent induction of an efficacious immune response by cancer vaccines that solely provide more antigen to an already suppressed system. Cancer vaccines may thus need to readjust the imbalance of the cancer patients' immune system by inhibiting immunoinhibitors; such regimens have shown preclinical efficacy and are now entering clinical trials hopefully ending the Kafkaesque futility of cancer vaccines.

Breaking tolerance in a mouse model of multiple myeloma by chemoimmunotherapy

A unique mouse model of multiple myeloma (MM), namely 5T2MM-bearing mouse, was useful for elucidating the pathophysiological mechanisms underlying the disease. Increased accumulation of suppressive CD4(+)CD25(High)Foxp3(+) regulatory T cells (Tregs) was observed in the thymus and lymphoid peripheral organs during disease progression. Adoptive transfer of Tregs, but not other thymocytes, from 5T2MM-bearing mice led to increased progression of disease manifestations in young syngeneic mice. Depletion of Tregs, a proposed strategy in cancer immunotherapy, was tested using cyclophosphamide (CYC), an alkylating agent with selective cytotoxicity. Both low- and high-dose CYC, administered to sick mice with hind limb paralysis, caused the paralysis to disappear, the plasma tumor cells in the bone marrow (BM) cavity to be replaced by normal cell populations, and the survival of the mice to be significantly prolonged. Low-dose CYC, which selectively depletes Tregs, decreased MM incidence, in contrast to high-dose CYC, which was generally cytotoxic, and did not reduce MM incidence. In contrast, low-dose CYC induced Tregs to become susceptible to apoptosis by downregulating Bcl-xL and CTLA-4 in these cells, and by decreasing the production of IL-2 by effector CD4 cells. This treatment consequently triggered the recovery of IFN-gamma-producing natural killer T cells and the maturation of dendritic cells. Transient gradual depletion of Tregs in low-dose CYC-treated 5T2MM mice was maintained beyond 45 days. Thus, less frequent injections of low-dose CYC enabled us to recruit compatible immune-derived cells that would reduce tumor load and delay or prevent tumor recurrence, hence breaking immune tolerance toward MM tumor cells.

DNA vaccines: developing new strategies against cancer

Due to their rapid and widespread development, DNA vaccines have entered into a variety of human clinical trials for vaccines against various diseases including cancer. Evidence that DNA vaccines are well tolerated and have an excellent safety profile proved to be of advantage as many clinical trials combines the first phase with the second, saving both time and money. It is clear from the results obtained in clinical trials that such DNA vaccines require much improvement in antigen expression and delivery methods to make them sufficiently effective in the clinic. Similarly, it is clear that additional strategies are required to activate effective immunity against poorly immunogenic tumor antigens. Engineering vaccine design for manipulating antigen presentation and processing pathways is one of the most important aspects that can be easily handled in the DNA vaccine technology. Several approaches have been investigated including DNA vaccine engineering, co-delivery of immunomodulatory molecules, safe routes of administration, prime-boost regimen and strategies to break the immunosuppressive networks mechanisms adopted by malignant cells to prevent immune cell function. Combined or single strategies to enhance the efficacy and immunogenicity of DNA vaccines are applied in completed and ongoing clinical trials, where the safety and tolerability of the DNA platform are substantiated. In this review on DNA vaccines, salient aspects on this topic going from basic research to the clinic are evaluated. Some representative DNA cancer vaccine studies are also discussed.

Consecutive low doses of cyclophosphamide preferentially target Tregs and potentiate T cell responses induced by DNA PLG microparticle immunization

Cyclophosphamide in combination with immunotherapeutic approaches preferentially impinges on T(reg) activity and allows for robust generation of T cell effectors. Reduced dosages of cyclophosphamide are necessary to restrict its cytotoxic effects to the negative regulatory cell populations while sparing effector lymphocytes. We investigated cyclophosphamide dosing in combination with ZYC300, a PLG-encapsulated plasmid DNA vaccine which encodes the cytochrome P450 family member, CYP1B1, a known human tumor-associated antigen. In mice, three consecutive, low doses of cyclophosphamide comprised a superior regimen in enhancing the magnitude, diversity of epitopes, and avidity to individual epitopes of specific T cell responses when compared to regimens that used either a single low or a single high dose. Consecutive low doses of cyclophosphamide predominantly targeted T(regs) while sparing overall T lymphocyte counts. Thus, we report the synergistic activity of pharmacologic T(reg) depletion with cyclophosphamide on quantitatively and qualitatively increasing T cell responses to a known human tumor-associated antigen.

Blocking ovarian cancer progression by targeting tumor microenvironmental leukocytes

Current therapies for metastatic ovarian carcinoma are based on surgical debulking followed by chemotherapy. After more than three decades implementing treatments that selectively target the tumor cell, the 5-year survival rate for metastatic ovarian cancer patients is still lower than 30%. Novel strategies are therefore urgently needed to complement classical treatments for this malignancy. Recently, leukocytes in the ovarian cancer microenvironment such as regulatory T cells and immature pro-angiogenic/tolerogenic myeloid cells have been demonstrated to play a fundamental role in tumor progression. This review focuses on our recent understanding of the potential of eliminating and/or modulating the phenotype of these leukocytes in vivo and in situ as a novel intervention to complement standard ovarian cancer treatments. The significant effects of targeting these crucial microenvironmental players on cancer vascularization, local tumor growth, distal metastatic spreading and spontaneous anti-tumor immune responses are discussed.

A changing world for DCvax: a PSMA loaded autologous dendritic cell vaccine for prostate cancer

BACKGROUND

Northwest Therapeutics' DCvax-prostate consists of autologous dendritic cells (DCs) loaded with prostate-specific membrane antigen (PSMA) peptides, administered intravenously. Phase I-II testing, a decade ago, showed clinical benefit and immunological response in some patients. More recently DCvax brain, a product using a similar DC platform showed encouraging Phase I-II results and sipleucel-T, a prostatic acid phosphatase (PAP)-directed DC immunotherapy had positive Phase III results.

OBJECTIVE

Features of the clinical setting into which a new immunotherapy could be introduced are discussed, to refine a perspective on DCvax-prostate in the context of evolving prostate cancer therapeutics. PSMA-directed therapeutics and immune anticancer technologies are reviewed, and the clinical and immunological correlative testing of DCvax-prostate is discussed.

METHODS

Clinical and preclinical data from peer-reviewed literature, meetings proceedings and manufacturer-provided information are considered.

CONCLUSION

DCvax-prostate had encouraging early-phase trial results, but development and testing had stalled. As a more detailed understanding of patient-selection for capacity for anticancer immune response, the quantitation of immunological correlates, and the changing marketplace develop, it is appealing to consider a well tolerated, PSMA-directed autologous dendritic cell therapeutic product. Further clinical trial development of DCvax-prostate is warranted, and required if it is to find a relevant clinical application.

Immunotherapy of cancer: key findings and commentary on the third Tegernsee conference

Cancer immunotherapy broadly includes active immunization, as in the use of cancer vaccines, passive immunization, such as the use of adoptive cell therapy and antibodies that modulate tumor function, and immunostimulation, using antibodies and small molecules to treat malignancy by activating or unleashing an endogenous immune response against tumor cells. Currently, >100 different monoclonal antibodies are in use or under evaluation for use as therapeutic agents in various malignancies. Active stimulation of the host's immune system holds promise for achieving durable remission of malignant disease and represents a nontoxic method of therapy if tumor-specific effector cells can be selectively targeted. However, no active-specific treatment strategy (i.e., a therapeutic cancer vaccine) has yet found its way into the clinical armamentarium, although several promising recent reports suggest that, for follicular lymphoma, prostate cancer, and melanoma, clinical benefit was shown for the first time in randomized trials with a vaccine approach. Here, we report on the key findings of the Third Tegernsee Conference on Immunotherapy of Cancer (Feldafing, Germany, July 2-4, 2009) and provide short commentaries on data presented at this meeting regarding the future role of cancer vaccines, recent developments in adoptive cellular therapy, ways to improve immunotherapeutic treatment modalities (e.g., by manipulating the tumor microenvironment), and some novel targeted therapies that are well advanced in clinical testing, all of which have implications for future oncology practice.

The role of regulatory T cells in cancer

There has been an explosion of literature focusing on the role of regulatory T (Treg) cells in cancer immunity. It is becoming increasingly clear that Treg cells play an active and significant role in the progression of cancer, and have an important role in suppressing tumor-specific immunity. Thus, there is a clear rationale for developing clinical strategies to diminish their regulatory influences, with the ultimate goal of augmenting antitimor immunity. Therefore, manipulation of Treg cells represent new strategies for cancer treatment. In this Review, I will summarize and review the explosive recent studies demonstrating that Treg cells are increased in patients with malignancies and restoration of antitumor immunity in mice and humans by depletion or reduction of Treg cells. In addition, I will discuss both the prognostic value of Treg cells in tumor progression in tumor-bearing hosts and the rationale for strategies for therapeutic vaccination and immunotherapeutic targeting of Treg cells with drugs and microRNA.

Enhancing immune responses to tumor-associated antigens

The goal of vaccine-based cancer immunotherapy is to induce a tumor-specific immune response that ultimately reduces tumor burden. However, the immune system is often tolerant to antigens presented by the tumor, as the cancer originates from within a patient and is therefore recognized as self. This article reviews selected clinical strategies for overcoming this immune tolerance, and approaches to enhance generation of immunity to tumor-associated antigens by activating innate immunity, potentiating adaptive immunity, reducing immunosuppression, and enhancing tumor immunogenicity. Success in the field of cancer vaccines has yet to be fully realized, but intelligent choice of immunomodulators, tumor antigens and patient populations will likely lead to clinically relevant uses for cancer vaccines.

Regulatory T cells and treatment of cancer

CD4+CD25+FOXP3+ regulatory T cells (Tregs) are elevated in cancers and can thwart protective antitumor immunity. Recent human cancer trials suggest that depleting Tregs can be clinically beneficial. Additional types of deleterious regulatory cells are also increased in cancer. Tregs also play unanticipated roles in cancer therapy in that some drugs unexpectedly increase (e.g. cancer vaccines or IL-2 treatment) or decrease (e.g. antineoangiogenesis agents or receptor tyrosine kinase inhibitors) their numbers or function. Managing deleterious effects of regulatory cells represents a novel and potentially effective way to give immunotherapy for cancer. New insights into molecular mechanisms governing trafficking, differentiation, and function of these cells suggest novel approaches to manipulating them as treatment strategies.

Tregs and rethinking cancer immunotherapy

Tumors express antigens that should induce immune-mediated rejection, but spontaneous rejection of established tumors is rare. Recent work demonstrates that one reason for the lack of tumor rejection is that tumors actively defeat host immunity. This concept forces us to rethink current approaches to harnessing potent, specific host immunity to battle cancer, most of which are based on the paradigm that inducing more antitumor immune cells alone is therapeutic. However, as I discuss in this Personal Perspective, a newer paradigm predicts that reducing tumor-driven immune suppression will be clinically beneficial. CD4+CD25+ Tregs are one mechanism of tumor-driven immune evasion that provide prototypical targets for testing novel anticancer treatment strategies within the newer paradigm.