The CD4+ T-Cell Response of Melanoma Patients to a MAGE-A3 Peptide Vaccine Involves Potential Regulatory T Cells

Defining Human Regulatory T Cells beyond FOXP3: The Need to Combine Phenotype with Function

Regulatory T cells (Tregs) are essential to maintain immune homeostasis by promoting self-tolerance. Reduced Treg numbers or functionality can lead to a loss of tolerance, increasing the risk of developing autoimmune diseases. An overwhelming variety of human Tregs has been described, based on either specific phenotype, tissue compartment, or pathological condition, yet the bulk of the literature only addresses CD25-positive and CD127-negative cells, coined by naturally occurring Tregs (nTregs), most of which express the transcription factor Forkhead box protein 3 (FOXP3). While the discovery of FOXP3 was seminal to understanding the origin and biology of nTregs, there is evidence in humans that not all T cells expressing FOXP3 are regulatory, and that not all Tregs express FOXP3. Namely, the activation of human T cells induces the transient expression of FOXP3, irrespective of whether they are regulatory or inflammatory effectors, while some induced T cells that may be broadly defined as Tregs (e.g., Tr1 cells) typically lack demethylation and do not express FOXP3. Furthermore, it is unknown whether and how many nTregs exist without FOXP3 expression. Several other candidate regulatory molecules, such as GITR, Lag-3, GARP, GPA33, Helios, and Neuropilin, have been identified but subsequently discarded as Treg-specific markers. Multiparametric analyses have uncovered a plethora of Treg phenotypes, and neither single markers nor combinations thereof can define all and only Tregs. To date, only the functional capacity to inhibit immune responses defines a Treg and distinguishes Tregs from inflammatory T cells (Teffs) in humans. This review revisits current knowledge of the Treg universe with respect to their heterogeneity in phenotype and function. We propose that it is unavoidable to characterize human Tregs by their phenotype in combination with their function, since phenotype alone does not unambiguously define Tregs. There is an unmet need to align the expression of specific markers or combinations thereof with a particular suppressive function to coin functional Treg entities and categorize Treg diversity.

Regulation and impact of tumor-specific CD4+ T cells in cancer and immunotherapy

CD4+ T cells are crucial in generating and sustaining immune responses. They orchestrate and fine-tune mammalian innate and adaptive immunity through cell-based interactions and the release of cytokines. The role of these cells in contributing to the efficacy of antitumor immunity and immunotherapy has just started to be uncovered. Yet, many aspects of the CD4+ T cell response are still unclear, including the differentiation pathways controlling such cells during cancer progression, the external signals that program them, and how the combination of these factors direct ensuing immune responses or immune-restorative therapies. In this review, we focus on recent advances in understanding CD4+ T cell regulation during cancer progression and the importance of CD4+ T cells in immunotherapies.

"To be or not to Be": Regulatory T cells in melanoma

In spite of progresses in the therapy of different malignancies, melanoma still remains as one of lethal types of skin tumor. Melanoma is almost easily treatable by surgery alone with higher overall survival rates when it is diagnosed at early stages. However, survival rates are decreased remarkably upon survival if the tumor is progressed to advanced metastatic stages. Immunotherapeutics have been prosperous in the development of anti-tumor responses in patients with melanoma through promotion of the tumor-specific effector T cells in vivo; nonetheless, suitable clinical outcomes have not been satisfactory. One of the underlying causes of the unfavorable clinical outcomes might stem from adverse effects of regulatory T (Treg) cell, which is a prominent mechanism of tumor cells to escape from tumor-specific immune responses. Evidence shows that a poor prognosis and low survival rate in patients with melanoma can be attributed to a higher Treg cell number and function in these subjects. As a result, to promote melanoma-specific anti-tumor responses, depletion of Treg cells appears to be a promising approach; even though the clinical efficacy of different approaches to attain appropriate Treg cell depletion has been inconsistent. Here in this review, the main purpose is to assess the role of Treg cells in the initiation and perpetuation of melanoma and to discuss effective strategies for Treg cell modulation with the aim of melanoma therapy.

A novel prognostic biomarker CD3G that correlates with the tumor microenvironment in cervical cancer

Cervical cancer (CESC) is the fourth most common and death-causing gynecological cancer, mostly induced by infection of human papillomavirus (HPV). Multiple components of the tumor microenvironment (TME), such as tumor infiltrating immune cells, could be targets of immunotherapy for HPV-related CESC. However, little is known about the TME of CESC until now. Here, we aimed to uncover the pathogenesis as well as to identify novel biomarkers to predict prognosis and immunotherapy efficacy for CESC. Combining the transcriptomic data and clinical characteristics, we identified differentially expressed genes in CESC samples from TCGA database by comparing the two groups with different ImmuneScore and StromalScore. Next, we detected ten key genes based on the PPI network and survival analyses with the univariate Cox regression model. Thereafter, we focused on CD3G, the only gene exhibiting increased RNA and protein expression in tumors by multiple analyses. Higher CD3G expression was associated with better survival; and it was also significantly associated with immune-related pathways through GSEA analysis. Furthermore, we found that CD3G expression was correlated with 16 types of TICs. Single cell RNA-sequencing data of CD3G in lymphocytes subgroup indicated its possible role in HPV defense. Hence, CD3G might be a novel biomarker in prognosis and immunotherapy for CESC patients.

Harnessing Antitumor CD4+ T Cells for Cancer Immunotherapy

Simple Summary

Diverse evidence revealed that CD4⁺ T cells play an important role in antitumor immunity by promoting or suppressing cytotoxic T cell responses. This review outlines the role of CD4⁺ T subsets within the tumor microenvironment and summarizes the latest progress regarding their potentials in cancer immunotherapy and methods for improving outcomes in cancer strategies by modulating CD4⁺ T responses.

Abstract

Over the past decades, CD4⁺ T cells have been considered as a supporting actor in the fields of cancer immunotherapy. Until recently, accumulating evidence has demonstrated the critical role of CD4⁺ T cells during antitumor immunity. CD4⁺ T cells can either suppress or promote the antitumor cytotoxic CD8⁺ T cell responses, either in secondary lymphoid organs or in the tumor. In this review, we provide an overview of the multifaceted role of different CD4⁺ T cell subsets in cancer immune response and their contribution during cancer therapies. Specifically, we focus on the latest progress regarding the impact of CD4⁺ T cell modulation on immunotherapies and other cancer therapies and discuss the prospect for harnessing CD4⁺ T cells to control tumor progression and prevent recurrence in patients.

Tnfrsf4-expressing regulatory T cells promote immune escape of chronic myeloid leukemia stem cells

Leukemia stem cells (LSCs) promote the disease and seem resistant to therapy and immune control. Why LSCs are selectively resistant against elimination by CD8⁺ cytotoxic T cells (CTLs) is still unknown. In this study, we demonstrate that LSCs in chronic myeloid leukemia (CML) can be recognized and killed by CD8⁺ CTLs in vitro. However, Tregs, which preferentially localized close to CD8⁺ CTLs in CML BM, protected LSCs from MHC class I–dependent CD8⁺ CTL–mediated elimination in vivo. BM Tregs in CML were characterized by the selective expression of tumor necrosis factor receptor 4 (Tnfrsf4). Stimulation of Tnfrsf4 signaling did not deplete Tregs but reduced the capacity of Tregs to protect LSCs from CD8⁺ CTL–mediated killing. In the BM of newly diagnosed CML patients, TNFRSF4 mRNA levels were significantly increased and correlated with the expression of the Treg-restricted transcription factor FOXP3. Overall, these results identify Tregs as key regulators of immune escape of LSCs and TNFRSF4 as a potential target to reduce the function of Tregs and boost antileukemic immunity in CML.

Differentiation and Regulation of TH Cells: A Balancing Act for Cancer Immunotherapy

Current success of immunotherapy in cancer has drawn attention to the subsets of T_H cells in the tumor which are critical for activation of anti-tumor response either directly by themselves or by stimulating cytotoxic T cell activity. However, presence of immunosuppressive pro-tumorigenic T_H subsets in the tumor milieu further contributes to the complexity of regulation of T_H cell-mediated immune response. In this review, we present an overview of the multifaceted positive and negative effects of T_H cells, with an emphasis on regulation of different T_H cell subtypes by various immune cells, and how a delicate balance of contradictory signals can influence overall success of cancer immunotherapy. We focus on the regulatory network that encompasses dendritic cell-induced activation of CD4⁺ T_H1 cells and subsequent priming of CD8⁺ cytotoxic T cells, along with intersecting anti-inflammatory and pro-tumorigenic T_H2 cell activity. We further discuss how other tumor infiltrating immune cells such as immunostimulatory T_H9 and T_fh cells, immunosuppressive T_reg cells, and the duality of T_H17 function contribute to tip the balance of anti- vs pro-tumorigenic T_H responses in the tumor. We highlight the developing knowledge of CD4⁺ T_H1 immune response against neoantigens/oncodrivers, impact of current immunotherapy strategies on CD4⁺ T_H1 immunity, and how opposing action of T_H cell subtypes can be explored further to amplify immunotherapy success in patients. Understanding the nuances of CD4⁺ T_H cells regulation and the molecular framework undergirding the balancing act between anti- vs pro-tumorigenic T_H subtypes is critical for rational designing of immunotherapies that can bypass therapeutic escape to maximize the potential of immunotherapy.

Exploration of the Prognostic and Immunotherapeutic Value of B and T Lymphocyte Attenuator in Skin Cutaneous Melanoma

B and T lymphocyte attenuator (BTLA) is a newly identified immune checkpoint molecular belonging to the CD28 immunoglobulin superfamily. However, the expression and clinical value of BTLA in skin cutaneous melanoma (SKCM) has not been widely characterized. We found that BTLA levels were upregulated in metastatic melanoma compared to normal skin tissues and primary melanoma. Higher BTLA was also correlated with improved prognosis in SKCM based on several datasets. The multivariate Cox regression model revealed that BTLA was an independent survival indicator in metastatic melanoma. Tumor microenvironment analysis indicated BTLA was positively associated with the infiltrating levels of different immune cells and the activity of the anti-cancer immunity cycle. Importantly, BTLA accurately predicted the outcome of melanoma patients treated with MAGE-A3 blocker or first-line anti-PD-1. The present findings disclose that BTLA is a reliable biomarker for prognosis and immunotherapeutic response and might contribute to developing novel SKCM immunological treatment strategies.

Regulatory T Cells in the Tumor Microenvironment

Regulatory T cells (T_regs) are an immunosuppressive subpopulation of CD4⁺ T cells that are endowed with potent suppressive activity and function to limit immune activation and maintain homeostasis. These cells are identified by the hallmark transcription factor FOXP3 and the high-affinity interleukin-2 (IL-2) receptor chain CD25. T_regs can be recruited to and persist within the tumor microenvironment (TME), acting as a potent barrier to effective antitumor immunity. This chapter will discuss [i] the history and hallmarks of T_regs; [ii] the recruitment, development, and persistence of T_regs within the TME; [iii] T_reg function within TME; asnd [iv] the therapeutic targeting of T_regs in the clinic. This chapter will conclude with a discussion of likely trends and future directions.

Revisiting the role of CD4+ T cells in cancer immunotherapy-new insights into old paradigms

Cancer immunotherapy has revolutionised cancer treatment, with immune checkpoint blockade (ICB) therapy and adoptive cell therapy (ACT) increasingly becoming standard of care across a growing number of cancer indications. While the majority of cancer immunotherapies focus on harnessing the anti-tumour CD8⁺ cytotoxic T cell response, the potential role of CD4⁺ 'helper' T cells has largely remained in the background. In this review, we give an overview of the multifaceted role of CD4⁺ T cells in the anti-tumour immune response, with an emphasis on recent evidence that CD4⁺ T cells play a bigger role than previously thought. We illustrate their direct anti-tumour potency and their role in directing a sustained immune response against tumours. We further highlight the emerging observation that CD4⁺ T cell responses against tumours tend to be against self-derived epitopes. These recent trends raise vital questions and considerations that will profoundly affect the rational design of immunotherapies to leverage on the full potential of the immune system against cancer.

Tumor-infiltrating human CD4+ regulatory T cells display a distinct TCR repertoire and exhibit tumor and neoantigen reactivity

CD4⁺ regulatory T (T_reg) cells have an essential function in maintaining self-tolerance; however, they may also play a detrimental role in antitumor immune responses. The presence of elevated frequencies of T_reg cells in tumors correlates with disease progression and poor survival in patients with cancer. The antigen specificity of T_reg cells that have expanded in the tumor microenvironment is poorly understood; answering this question may provide important insights for immunotherapeutic approaches. To address this, we used a novel combinatorial approach to characterizing the T cell receptor (TCR) profiles of intratumoral T_reg cells from patients with metastatic melanoma, gastrointestinal, and ovarian cancers and elucidated their antigen specificities. The TCR repertoires of tumor-resident T_reg cells were diverse yet displayed significant overlap with circulating T_reg cells but not with conventional T cells in tumor or blood. TCRs isolated from T_reg cells displayed specific reactivity against autologous tumors and mutated neoantigens, suggesting that intratumoral T_reg cells act in a tumor antigen-selective manner leading to their activation and clonal expansion in the tumor microenvironment. Tumor antigen-specific T_reg-derived TCRs resided in the tumor and in the circulation, suggesting that both T_reg cell compartments may serve as a source for tumor-specific TCRs. These findings provide insights into the TCR specificity of tumor-infiltrating human T_reg cells that may have potential implications for cancer immunotherapy.

Combined CD44- and CD25-Targeted Near-Infrared Photoimmunotherapy Selectively Kills Cancer and Regulatory T Cells in Syngeneic Mouse Cancer Models

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed and selective cancer treatment that induces necrotic and immunogenic cell death and utilizes a mAb conjugated to a photo-absorber dye, IR700DX, activated by NIR light. Although CD44 is a surface cancer marker associated with drug resistance, anti-CD44-IR700 NIR-PIT results in inhibited cell growth and prolonged survival in multiple tumor types. Meanwhile, CD25-targeted NIR-PIT has been reported to achieve selective and local depletion of FOXP3⁺CD25⁺CD4⁺ regulatory T cells (Treg), which are primary immunosuppressive cells in the tumor microenvironment (TME), resulting in activation of local antitumor immunity. Combined NIR-PIT with CD44- and CD25-targeted agents has the potential to directly eliminate tumor cells and also amplify the immune response by removing FOXP3⁺CD25⁺CD4⁺ Tregs from the TME. We investigated the difference in therapeutic effects of CD44-targeted NIR-PIT alone, CD25-targeted NIR-PIT alone, and the combination of CD44- and CD25-targeted NIR-PIT in several syngeneic tumor models, including MC38-luc, LL/2, and MOC1. The combined NIR-PIT showed significant tumor growth inhibition and prolonged survival compared with CD44-targeted NIR-PIT alone in all tumor models and showed prolonged survival compared with CD25-targeted NIR-PIT alone in MC38-luc and LL/2 tumors. Combined CD44- and CD25-targeted NIR-PIT also resulted in some complete remissions. Therefore, combined NIR-PIT simultaneously targeting cancer antigens and immunosuppressive cells in the TME may be more effective than either type of NIR-PIT alone and may have potential to induce prolonged immune responses in treated tumors.

Overview of Current Immunotherapies Targeting Mutated KRAS Cancers

The occurrence of somatic substitution mutations of the KRAS proto-oncogene is highly prevalent in certain cancer types, which often leads to constant activation of proliferative pathways and subsequent neoplastic transformation. It is often seen as a gateway mutation in carcinogenesis and has been commonly deemed as a predictive biomarker for poor prognosis and relapse when conventional chemotherapeutics are employed. Additionally, its mutational status also renders EGFR targeted therapies ineffective owing to its downstream location. Efforts to discover new approaches targeting this menacing culprit have been ongoing for years without much success, and with incidences of KRAS positive cancer patients being on the rise, researchers are now turning towards immunotherapies as the way forward. In this scoping review, recent immunotherapeutic developments and advances in both preclinical and clinical studies targeting K-ras directly or indirectly via its downstream signal transduction machinery will be discussed. Additionally, some of the challenges and limitations of various K-ras targeting immunotherapeutic approaches such as vaccines, adoptive T cell therapies, and checkpoint inhibitors against KRAS positive cancers will be deliberated.

＜Editors' Choice＞ Meddling with meddlers: curbing regulatory T cells and augmenting antitumor immunity

CD4⁺ regulatory T cells (Tregs) expressing the transcription factor forkhead box P3 (FoxP3) play an important role in self-tolerance and immune homeostasis. Tregs have evolved to protect the host from aberrant immune responses against self-components and collateral damages occurring in the process of defense against invading pathogens by softening immune responses. However, they turned to be a scourge in malignant tumors by not only allowing and promoting tumor growth but also suppressing effective antitumor actions, both inherent (host’s immune surveillance) and extrinsic (anticancer therapy). An increase in the number of Tregs infiltrating into tumor sites and a concomitant decrease in the number of CD8⁺ cytotoxic T lymphocytes are associated with a poor prognosis for various types of cancers, marking Tregs as notorious meddlers with an effective antitumor response. Various cancer immunotherapy approaches are often dampened by meddling Tregs, making them one of the major targets in the treatment of cancer. The recent success of immune checkpoint inhibitors (ICIs) that target immune checkpoint molecules expressed by Tregs or effector T cells implies, that “meddling with meddlers” represents an effective strategy in cancer immunotherapy. However, clinical responses to ICIs are effective and durable only in some patients with cancer, whereas more than half of them do not show significant clinical improvement. This implies that a therapeutic approach based on the use of a single ICI, or targeting Tregs alone, is insufficient, highlighting the need for combinatorial approaches. With regard to antitumor immune stimulation, several approaches, such as vaccination with peptides (or the corresponding DNA) to stimulate antigen-presenting CD8⁺ T cells with tumor-specific neoantigens, cancer/testis antigens, or cancer stem cell antigens, that eventually boost effective cytotoxic antitumor responses are being tested. This review describes the immunosuppressive physiology of Tregs and their meddling with the host’s antitumor immunity; current and prospective approaches to curb Tregs; and approaches to augment antitumor immunity.

High-throughput Screening of Human Tumor Antigen-specific CD4 T Cells, Including Neoantigen-reactive T Cells

PURPOSE

Characterization of tumor antigen-specific CD4 T-cell responses in healthy donors and malignant melanoma patients using an in vitro amplified T-cell library screening procedure.

PATIENTS AND METHODS

A high-throughput, human leukocyte antigen (HLA)-independent approach was used to estimate at unprecedented high sensitivity level precursor frequencies of tumor antigen- and neoantigen-specific CD4 T cells in healthy donors and patients with cancer. Frequency estimation was combined with isolation and functional characterization of identified tumor-reactive CD4 T-cell clones.

RESULTS

In healthy donors, we report frequencies of naïve tumor-associated antigen (TAA)-specific CD4 T cells comparable with those of CD4 T cells specific for infectious agents (Tetanus toxoid). Interestingly, we also identified low, but consistent numbers of memory CD4 T cells specific for several TAAs. In patients with melanoma, low frequencies of circulating TAA-specific CD4 T cells were detected that increased after peptide-based immunotherapy. Such antitumor TAA-specific CD4 T-cell responses were also detectable within the tumor-infiltrated tissues. TAA-specific CD4 T cells in patients displayed a highly polyfunctional state, with partial skewing to Type-2 polarization. Finally, we report the applicability of this approach to the detection and amplification of neoantigen-specific CD4 T cells.

CONCLUSIONS

This simple, noninvasive, high-throughput screening of tumor- and neoantigen-specific CD4 T cells requires little biologic material, is HLA class II independent and allows the concomitant screening for a large number of tumor antigens of interest, including neoantigens. This approach will facilitate the immunomonitoring of preexisting and therapy-induced CD4 T-cell responses, and accelerate the development of CD4 T-cell-based therapies.

T cell pathology in skin inflammation

Forming the outer body barrier, our skin is permanently exposed to pathogens and environmental hazards. Therefore, skin diseases are among the most common disorders. In many of them, the immune system plays a crucial pathogenetic role. For didactic and therapeutic reasons, classification of such immune-mediated skin diseases according to the underlying dominant immune mechanism rather than to their clinical manifestation appears to be reasonable. Immune-mediated skin diseases may be mediated mainly by T cells, by the humoral immune system, or by uncontrolled unspecific inflammation. According to the involved T cell subpopulation, T cell–mediated diseases may be further subdivided into T1 cell–dominated (e.g., vitiligo), T2 cell–dominated (e.g., acute atopic dermatitis), T17/T22 cell–dominated (e.g., psoriasis), and Treg cell–dominated (e.g., melanoma) responses. Moreover, T cell–dependent and -independent responses may occur simultaneously in selected diseases (e.g., hidradenitis suppurativa). The effector mechanisms of the respective T cell subpopulations determine the molecular changes in the local tissue cells, leading to specific microscopic and macroscopic skin alterations. In this article, we show how the increasing knowledge of the T cell biology has been comprehensively translated into the pathogenetic understanding of respective model skin diseases and, based thereon, has revolutionized their daily clinical management.

Role of GARP in the activation of latent TGF-β1

TGF-β1, 2 and 3 cytokines are involved in many cellular processes including cell proliferation, differentiation, migration and survival. Whereas TGF-β2 and 3 play important roles in embryonic development, TGF-β1 is mostly implicated in controlling immune responses after birth. The production of TGF-β1 is a tightly regulated process, occurring mostly at a post-translational level. Virtually all cells produce the latent, inactive form of TGF-β1. In latent TGF-β1, the mature TGF-β1 dimer is non-covalently associated to the Latency Associated Peptide, or LAP, which prevents binding to the TGF-β1 receptor. Activation of the cytokine implies release of mature TGF-β1 from LAP. Only a few cell types activate latent TGF-β1, via mechanisms that are cell type specific. Proteins such as integrins, proteases and thrombospondin-1 activate TGF-β1 in epithelial cells, fibroblasts and dendritic cells. More recently, the protein GARP was shown to be involved in TGF-β1 activation by regulatory T cells (Treg), a subset of CD4⁺ T lymphocytes specialized in suppression of immune responses. GARP is a transmembrane protein that binds latent-TGF-β1 and tethers it on the Treg surface. The role of GARP was studied mostly in Tregs, and this was recently reviewed in L. Sun, H. Jin and H. Li, Oncotarget, 2016, 7, 42826-42836. However, GARP is also expressed in non-immune cells. This review focuses on the roles of GARP in latent TGF-β1 activation by immune and non-immune cells.

Correlates of immune and clinical activity of novel cancer vaccines

Cancer vaccines are solely meant to amplify the pool of type 1 cytokine oriented CD4+ and CD8+ T cells that recognize tumor antigen and ultimately foster control and destruction of a growing tumor. They are not designed to deal with all aspects of immune ignorance, exclusion, suppression and escape that are generally in place in patients with cancer and may prevent the T cells to enter the tumor or to exert their effector function. This simple fact prompted for a reappraisal of the many recent trials in which therapeutic cancer vaccines have been examined as monotherapy. In this review, I focus on trials examining therapeutic cancer vaccines at different stages of existing disease. The analysis of vaccine-induced immune responses and clinical activity of therapeutic cancer vaccines revealed four levels of evidence for vaccine efficacy. The lowest levels, reflect the many trials in which the strength of the tumor-reactive T cell response of vaccinated patients is associated with better clinical outcome or change in tumor marker. The highest levels indicate occasional regressions of tumors and metastases after vaccination or reflect a stronger clinical impact of vaccine in a randomized trial. A whole series of trials in which vaccine-induced tumor immunity correlates with the clinical impact of cancer vaccines in premalignant diseases, settings of low tumor burden or tumor regressions in patients with cancer, form an attest to the fact that cancer vaccines work. While the current number of true clinical responders in each cancer trial is too low for firm conclusions on immune correlates of clinical reactivity in cancer, extrapolation of the results from vaccinated patients with pre-cancers suggest a requirement of broad type 1 T cell reactivity.

Isolation and Characterization of an HLA-DPB1*04: 01-restricted MAGE-A3 T-Cell Receptor for Cancer Immunotherapy

Long-term tumor regressions have been observed in patients following the adoptive transfer of autologous tumor-infiltrating lymphocytes or genetically modified T cells expressing MHC class I-restricted T-cell receptors (TCRs), but clinical trials have not evaluated responses to genetically modified T cells expressing antitumor MHC class II-restricted TCRs. As studies carried out in a murine tumor model system have demonstrated that the adoptive transfer of CD4 T cells could lead to the regression of established tumors, we plan to test the hypothesis that CD4 T cells can also induce tumor regressions in cancer patients. In this study, 2 MAGE-A3-specific TCRs were isolated from a regulatory T-cell clone (6F9) and an effector clone (R12C9), generated from the peripheral blood of 2 melanoma patients after MAGE-A3 vaccination. The results indicated that T cells transduced with 6F9 TCR mediated stronger effector functions than R12C9 TCR. The 6F9 TCR specifically recognized MAGE-A3 and the closely related MAGE-A6 gene product, but not other members of the MAGE-A family in the context of HLA-DPB1*04:01. To test the feasibility of a potential clinical trial using this TCR, a clinical-scale procedure was developed to obtain a large number of purified CD4 T cells transduced with 6F9 TCR. Because HLA-DPB1*04:01 is present in ∼60% of the Caucasian population and MAGE-A3 is frequently expressed in a variety of cancer types, this TCR immunotherapy could potentially be applicable for a significant portion of cancer patients.

Cancer‑testis antigen HCA587/MAGEC2 interacts with the general transcription coactivator TAF9 in cancer cells

Hepatocellular carcinoma-associated antigen 587/melanoma antigen gene (HCA587/MAGEC2) is a cancer‑testis antigen, which is highly expressed in various types of tumors, but not in normal tissues with the exception of male germ‑line cells. HCA587/MAGEC2 has been previously recognized as a tumor‑specific target for immunotherapy; however, its biological functions have been relatively understudied. To investigate the function of HCA587/MAGEC2, the amino acid sequence of HCA587/MAGEC2 was analyzed by bioinformatics and it was demonstrated that HCA587/MAGEC2 contains a 9‑amino acid transactivation domain which may mediate the interaction of most transcription factors with TATA‑box binding protein associated factor 9 (TAF9), a general transcription coactivator. Co‑immunoprecipitation experiments revealed that HCA587/MAGEC2 interacted with TAF9 in transfected 293T and in A375 melanoma cells endogenously expressing HCA587/MAGEC2, and confirmed the endogenous interaction of HCA587/MAGEC2 and TAF9 within cells. Endogenous HCA587/MAGEC2 and TAF9 were demonstrated to be co‑localized principally in the nucleus of tumor cells using immunofluorescence. Glutathione-S-transferase pull‑down experiments demonstrated that HCA587/MAGEC2 interacts with TAF9 directly and the conserved region in the TAF9 may becrucial for HCA587/MAGEC2 binding. The present study demonstrated that the cancer‑testis antigen HCA587/MAGEC2 directly interacted with TAF9, which may provide novel information for identifying the oncogenic functions of HCA587/MAGEC2 in tumor cells.

Therapeutic blockade of Foxp3 in experimental breast cancer models

PURPOSE

Regulatory T cells (Tregs) impair the clinical benefit of cancer immunotherapy. To optimize the antitumor efficacy of therapeutic dendritic cell (DC) vaccines, we aimed to inhibit Foxp3, a transcription factor required for Treg function.

METHODS

Mice bearing established syngeneic LM3 and 4T1 breast tumors were treated with antitumor DC vaccines and a synthetic peptide (P60) that has been shown to inhibit Foxp3.

RESULTS

Treatment with P60 improved the therapeutic efficacy of DC vaccines in these experimental models. In addition, monotherapy with P60 inhibited tumor growth in immunocompetent as well as in immuno-compromised animals bearing established tumors. We found expression of Foxp3 in human and murine breast tumor cells. P60 inhibited IL-10 secretion in breast cancer cells that expressed Foxp3.

CONCLUSIONS

Our results suggest that Foxp3 blockade improves the therapeutic efficacy of DC vaccines by inhibition of Tregs and through a direct antitumor effect. This strategy could prove useful to neutralize the immunosuppressive microenvironment and to boost antitumor immunity in breast cancer.

Cancer-testis antigen MAGE-C2 binds Rbx1 and inhibits ubiquitin ligase-mediated turnover of cyclin E

Cancer-testis antigen MAGE-C2 is normally expressed in testis but aberrantly expressed in various kinds of tumors. Its functions in tumor cells are mostly unknown. Here, we show that MAGE-C2 binds directly to the RING domain protein Rbx1, and participates in Skp1-Cullin1-F box protein (SCF) complex. Furthermore, MAGE-C2 can inhibit the E3 ubiquitin ligase activity of SCF complex. Ablation of endogenous MAGE-C2 decreases the level of cyclin E and accelerates cyclin E turnover by inhibiting ubiquitin-mediated proteasome degradation. Overexpression of MAGE-C2 increases the level of cyclin E and promotes G1-S transition and cell proliferation, and the results are further confirmed by knockdown of MAGE-C2. Overall, the study indicates that MAGE-C2 is involved in SCF complex and increases the stability of cyclin E in tumor cells.

Regulatory T Cells in the Tumor Microenvironment and Cancer Progression: Role and Therapeutic Targeting

Recent years have seen significant efforts in understanding and modulating the immune response in cancer. In this context, immunosuppressive cells, including regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), have come under intense investigation for their proposed roles in suppressing tumor-specific immune responses and establishing an immunosuppressive tumor microenvironment, thus enabling tumor immune evasion. Additionally, recent evidence indicates that Tregs comprise diverse and heterogeneous subsets; phenotypically and functionally distinct subsets of tumor-infiltrating Tregs could contribute differently to cancer prognosis and clinical outcomes. Understanding Treg biology in the setting of cancer, and specifically the tumor microenvironment, is important for designing effective cancer therapies. In this review, we critically examine the role of Tregs in the tumor microenvironment and in cancer progression focusing on human studies. We also discuss the impact of current therapeutic modalities on Treg biology and the therapeutic opportunities for targeting Tregs to enhance anti-tumor immune responses and clinical benefits.

The present status and future prospects of peptide-based cancer vaccines

Tumor cells commonly express several antigens, such as tumor-associated antigens (TAAs) or mutation-derived antigens (neoantigens), that can be regarded as foreign antigens and elicit anti-tumor immune responses in cancer patients. Various TAAs or neoantigens expressed in cancer cells have been identified and utilized as targets for cancer vaccines. One approach to elicit tumor-specific immune responses is termed peptide-based cancer vaccination; it involves administrating TAAs or neoantigen-derived peptide for treatment of cancers. There have been several forms of peptide-based cancer vaccines depending on which effector cells, such as CTLs or CD4(+) T-helper cells, are targeted to be activated. Many phase I and II clinical trials of peptide-based cancer vaccines using TAA-derived CTL epitopes, T-helper cell epitopes or dendritic cells loaded with TAA-derived peptides for various malignant tumors have been conducted and provide clinical benefits in a small fraction of patients. Nowadays, to improve the efficiency of peptide-based cancer vaccines, combination immunotherapy of peptide-based cancer vaccines with the immune-checkpoint blockade therapies using mAbs specific for CTLA-4, programmed cell death 1 (PD-1), or PD-1 ligand 1 (PD-L1) have been developed for clinical application. Furthermore, along with the recent technological progress in genetic and bioinformatic analysis, it has become easier to identify neoantigens from individual cancer patients. It is expected that peptide-based cancer vaccines targeting neoantigens as a personalized cancer immunotherapy will be developed.

MHC class II tetramer analyses in AE37-vaccinated prostate cancer patients reveal vaccine-specific polyfunctional and long-lasting CD4(+) T-cells

Realizing the basis for generating long-lasting clinical responses in cancer patients after therapeutic vaccinations provides the means to further ameliorate clinical efficacy. Peptide cancer vaccines stimulating CD4(+) T helper cells are often promising for inducing immunological memory and persistent CD8(+) cytotoxic T cell responses. Recent reports from our clinical trial with the AE37 vaccine, which is a HER2 hybrid polypeptide, documented its efficacy to induce CD4(+) T cell immunity, which was associated with clinical improvements preferentially among HLA-DRB1*11(+) prostate cancer patients. Here, we performed in-depth investigation of the CD4(+) T cell response against the AE37 vaccine. We used the DR11/AE37 tetramer in combination with multicolor flow cytometry to identify and characterize AE37-specific CD4(+) T cells regarding memory and Tregs phenotype in HLA-DRB1*11(+) vaccinated patients. To verify vaccine-specific immunological memory in vivo, we also assessed AE37-specific CD4(+) T cells in defined CD4(+) memory subsets by cell sorting. Finally, vaccine-induced AE37-specific CD4(+) T cells were assessed regarding their functional profile. AE37-specific memory CD4(+) T cells could be detected in peptide-stimulated cultures from prostate cancer patients following vaccination even 4 y post-vaccination. The vast majority of vaccine-induced AE37-specific CD4(+) T cells exhibited a multifunctional, mostly Th1 cytokine signature, with the potential of granzyme B production. In contrast, we found relatively low frequencies of Tregs among AE37-specific CD4(+) T cells. This is the first report on the identification of vaccine-induced HER2-specific multifunctional long-lasting CD4(+) T cells in vaccinated prostate cancer patients.

An oncofetal antigen, IMP-3-derived long peptides induce immune responses of both helper T cells and CTLs

Insulin-like growth factor II mRNA-binding protein 3 (IMP-3), an oncofetal antigen identified using genome-wide cDNA microarray analyses, is overexpressed in several malignancies. IMP-3-derived cytotoxic T lymphocyte (CTL) epitopes have been used for peptide-based immunotherapies against various cancers. In addition to CTLs, induction of tumor-associated antigen (TAA)-specific helper T (Th) cells is crucial for establishment of effective antitumor immunity. In this study, we aimed to identify IMP-3-derived long peptides (IMP-3-LPs) carrying CTL and promiscuous Th-cell epitopes for use in cancer immunotherapy. IMP-3-derived Th-cell epitopes that bind to multiple HLA-class II molecules were predicted by in silico analysis, and their immunogenicity was determined by utilizing human T cells. We identified two highly immunogenic IMP-3-LPs presented by multiple HLA-class II molecules. One of the IMP-3-LPs encompassed two CTL epitopes that have been used for peptide-vaccine immunotherapy in ongoing clinical trials. IMP-3-LPs-specific Th cells responded to autologous dendritic cells (DCs) loaded with the recombinant IMP-3 proteins, suggesting that these s (LPs) can be naturally processed and presented. The IMP-3-LPs and specific Th cells augmented the expansion of IMP-3-specific CTLs, which was further enhanced by programmed cell death-1 (PD-1) blockade. In addition, IMP-3-LP encapsulated in liposomes was efficiently cross-presented in vitro, and this LP successfully cross-primed CTLs in HLA-A2 transgenic mice (Tgm) in vivo. Furthermore, one of the IMP-3-LPs induced IMP-3-specific Th cells from peripheral blood mononuclear cells (PBMCs) of head-and-neck malignant tumor (HNMT) patients. These findings suggest the potential usefulness of IMP-3-LPs in propagating both Th cells and CTLs and may have implications for IMP-3-LPs-based cancer immunotherapy.

Low-dose cyclophosphamide enhances antigen-specific CD4(+) T cell responses to NY-ESO-1/ISCOMATRIX™ vaccine in patients with advanced melanoma

Clinical outcomes from cancer vaccine trials in patients with advanced melanoma have so far been disappointing. This appears at least partially due to a state of immunosuppression in these patients induced by an expansion of regulatory cell populations including regulatory T cells (Tregs). We have previously demonstrated potent immunogenicity of the NY-ESO-1/ISCOMATRIX™ vaccine in patients with resected melanoma (study LUD99-08); however, the same vaccine induced only a few vaccine antigen-specific immune responses in patients with advanced disease (study LUD2002-013). Pre-clinical models suggest that the alkylating agent cyclophosphamide can enhance immune responses by depleting Tregs. Therefore, we have enrolled a second cohort of patients with advanced melanoma in the clinical trial LUD2002-013 to investigate whether pre-treatment with cyclophosphamide could improve the immunogenicity of the NY-ESO-1/ISCOMATRIX™ vaccine. The combination treatment led to a significant increase in vaccine-induced NY-ESO-1-specific CD4(+) T cell responses compared with the first trial cohort treated with vaccine alone. We could not detect a significant decline in regulatory T cells in peripheral blood of patients 14 days after cyclophosphamide administration, although a decline at an earlier time point cannot be excluded. Our observations support the inclusion of cyclophosphamide in combination trials with vaccines and other immune-modulatory agents.

Resiquimod as an immunologic adjuvant for NY-ESO-1 protein vaccination in patients with high-risk melanoma

The Toll-like receptor (TLR) 7/8 agonist resiquimod has been used as an immune adjuvant in cancer vaccines. We evaluated the safety and immunogenicity of the cancer testis antigen NY-ESO-1 given in combination with Montanide (Seppic) with or without resiquimod in patients with high-risk melanoma. In part I of the study, patients received 100 μg of full-length NY-ESO-1 protein emulsified in 1.25 mL of Montanide (day 1) followed by topical application of 1,000 mg of 0.2% resiquimod gel on days 1 and 3 (cohort 1) versus days 1, 3, and 5 (cohort 2) of a 21-day cycle. In part II, patients were randomized to receive 100-μg NY-ESO-1 protein plus Montanide (day 1) followed by topical application of placebo gel [(arm A; n = 8) or 1,000 mg of 0.2% resiquimod gel (arm B; n = 12)] using the dosing regimen established in part I. The vaccine regimens were generally well tolerated. NY-ESO-1-specific humoral responses were induced or boosted in all patients, many of whom had high titer antibodies. In part II, 16 of 20 patients in both arms had NY-ESO-1-specific CD4⁺ T-cell responses. CD8⁺ T-cell responses were only seen in 3 of 12 patients in arm B. Patients with TLR7 SNP rs179008 had a greater likelihood of developing NY-ESO-1-specific CD8⁺ responses. In conclusion, NY-ESO-1 protein in combination with Montanide with or without topical resiquimod is safe and induces both antibody and CD4⁺ T-cell responses in the majority of patients; the small proportion of CD8⁺ T-cell responses suggests that the addition of topical resiquimod to Montanide is not sufficient to induce consistent NY-ESO-1-specific CD8⁺ T-cell responses.

Tumor antigen-specific CD4+ T cells in cancer immunity: from antigen identification to tumor prognosis and development of therapeutic strategies

CD4(+) T cells comprise a large fraction of tumor infiltrating lymphocytes and it is now established that they may exert an important role in tumor immune-surveillance. Several CD4(+) T cell subsets [i.e. T helper (Th)1, Th2, T regulatory (Treg), Th17, Th22 and follicular T helper (Tfh)] have been described and differentiation of each subset depends on both the antigen presenting cells responsible for its activation and the cytokine environment present at the site of priming. Tumor antigen-specific CD4(+) T cells with different functional activity have been found in the blood of cancer patients and different CD4(+) T cell subsets have been identified at the tumor site by the expression of specific transcription factors and the profile of secreted cytokines. Importantly, depending on the subset, CD4(+) T cells may exert antitumor versus pro-tumor functions. Here we review the studies that first identified the presence of tumor-specific CD4(+) T cells in cancer patients, the techniques used to identify the tumor antigens recognized, the role of the different CD4(+) T cell subsets in tumor immunity and in cancer prognosis and the development of therapeutic strategies aimed at activating efficient antitumor CD4(+) T cell effectors.

Expression and clinical significance of Centrosomal protein 55 (CEP55) in human urinary bladder transitional cell carcinoma

Bladder cancer (BC) is one among the most common and lethal urothelial malignancies worldwide. The expression of cancer-testis (CT) antigens in some tumours and restricted expression among normal tissues make CT antigens as attractive vaccine targets. In this context, we evaluated Centrosomal protein 55 kDa (CEP55), which is specifically expressed in normal human testis and various malignancies. Until the expression pattern of CEP55 in transitional cell carcinoma (TCC) of human urinary bladder and its clinical significance are not known. The aim of the present study is to evaluate mRNA/protein expression of CEP55 in TCCs of urinary bladder and correlate its expression with the clinicopathological characteristics of BC patients. In this study, the methods of quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC) were used to investigate mRNA/protein expression of CEP55 in TCC. Independent Student's t test, ANOVA and Chi-square (χ(2)) were used to analyze the data statistically. We observed CEP55 mRNA overexpression in testis and 48.7% of BC patients. Relative mean fold expression of CEP55 mRNA was found to be significantly (p<0.01) higher in muscle-invasive bladder cancer (MIBC) as compared to non-muscle-invasive bladder cancer (NMIBC) patients (7.88±3.88 vs. 4.75±2.30, p=0.01). CEP55 protein expression was evaluated using IHC and cytoplasmic staining pattern was recorded in formalin fixed, paraffin-embedded (FFPE) bladder tumour tissues. No significant difference was observed in protein expression of CEP55 between the two groups (NMIBC and MIBC patients) (72.2% vs. 69.0%, p=0.774). No significant protein expression of CEP55 was observed among adjacent noncancerous tissues (ANCTs) and benign prostatic hyperplasia (BPH) used as control. Our study results suggest that CEP55 mRNA/protein expression was observed is specific to TCC of human urinary bladder and might be used as a diagnostic biomarker and vaccine target in development of BC specific immunotherapy.

Identification of CDCA1-derived long peptides bearing both CD4+ and CD8+ T-cell epitopes: CDCA1-specific CD4+ T-cell immunity in cancer patients

We recently identified a novel cancer-testis antigen, cell division cycle associated 1 (CDCA1) using genome-wide cDNA microarray analysis, and CDCA1-derived cytotoxic T lymphocyte (CTL)-epitopes. In this study, we attempted to identify CDCA1-derived long peptides (LPs) that induce both CD4+ helper T (Th) cells and CTLs. We combined information from a recently developed computer algorithm predicting HLA class II-binding peptides with CDCA1-derived CTL-epitope sequences presented by HLA-A2 (A*02:01) or HLA-A24 (A*24:02) to select candidate CDCA1-LPs encompassing both Th cell epitopes and CTL-epitopes. We studied the immunogenicity of CDCA1-LPs and the cross-priming potential of LPs bearing CTL-epitopes in both human in vitro and HLA-class I transgenic mice in vivo. Then we analyzed the Th cell response to CDCA1 in head-and-neck cancer (HNC) patients before and after vaccination with a CDCA1-derived CTL-epitope peptide using IFN-γ enzyme-linked immunospot assays. We identified two CDCA1-LPs, CDCA1(39–64)-LP and CDCA1(55–78)-LP, which encompass naturally processed epitopes recognized by Th cells and CTLs. CDCA1-specific CTLs were induced through cross-presentation of CDCA1-LPs in vitro and in vivo. In addition, CDCA1-specific Th cells enhanced induction of CDCA1-specific CTLs. Furthermore, significant frequencies of CDCA1-specific Th cell responses were detected after short-term in vitro stimulation of peripheral blood mononuclear cells (PBMCs) with CDCA1-LPs in HNC patients (CDCA1(39–64)-LP, 74%; CDCA1(55–78)-LP, 68%), but not in healthy donors. These are the first results demonstrating the presence of CDCA1-specific Th cell responses in HNC patients and underline the possible utility of CDCA1-LPs for propagation of both CDCA1-specific Th cells and CTLs.

MART-1 peptide vaccination plus IMP321 (LAG-3Ig fusion protein) in patients receiving autologous PBMCs after lymphodepletion: results of a Phase I trial

Background

Immunotherapy offers a promising novel approach for the treatment of cancer and both adoptive T-cell transfer and immune modulation lead to regression of advanced melanoma. However, the potential synergy between these two strategies remains unclear.

Methods

We investigated in 12 patients with advanced stage IV melanoma the effect of multiple MART-1 analog peptide vaccinations with (n = 6) or without (n = 6) IMP321 (LAG-3Ig fusion protein) as an adjuvant in combination with lymphodepleting chemotherapy and adoptive transfer of autologous PBMCs at day (D) 0 (Trial registration No: NCT00324623). All patients were selected on the basis of ex vivo detectable MART-1-specific CD8 T-cell responses and immunized at D0, 8, 15, 22, 28, 52, and 74 post-reinfusion.

Results

After immunization, a significant expansion of MART-1-specific CD8 T cells was measured in 83% (n = 5/6) and 17% (n = 1/6) of patients from the IMP321 and control groups, respectively (P < 0.02). Compared to the control group, the mean fold increase of MART-1-specific CD8 T cells in the IMP321 group was respectively >2-, >4- and >6-fold higher at D15, D30 and D60 (P < 0.02). Long-lasting MART-1-specific CD8 T-cell responses were significantly associated with IMP321 (P < 0.02). At the peak of the response, MART-1-specific CD8 T cells contained higher proportions of effector (CCR7⁻ CD45RA^+/−) cells in the IMP321 group (P < 0.02) and showed no sign of exhaustion (i.e. were mostly PD1⁻CD160⁻TIM3⁻LAG3⁻2B4^+/−). Moreover, IMP321 was associated with a significantly reduced expansion of regulatory T cells (P < 0.04); consistently, we observed a negative correlation between the relative expansion of MART-1-specific CD8 T cells and of regulatory T cells_. Finally, although there were no confirmed responses as per RECIST criteria, a transient, 30-day partial response was observed in a patient from the IMP321 group.

Conclusions

Vaccination with IMP321 as an adjuvant in combination with lymphodepleting chemotherapy and adoptive transfer of autologous PBMCs induced more robust and durable cellular antitumor immune responses, supporting further development of IMP321 as an adjuvant for future immunotherapeutic strategies.

Regulatory T cells in cancer immunotherapy

FOXP3(+)CD25(+)CD4(+) regulatory T (Treg) cells, crucial for the maintenance of immunological self-tolerance, are abundant in tumors. Most of them are chemo-attracted to tumor tissues, expanding locally and differentiating into a Treg-cell subpopulation that strongly suppresses the activation and expansion of tumor-antigen-specific effector T cells. Several cancer immunotherapies targeting FOXP3(+)CD4(+) Treg cells, including depletion of Treg cells, are currently being tested in the clinic. In addition, clinical benefit of immune-checkpoint blockade, such as anti-CTLA-4 monoclonal antibody therapy, could be attributed at least in part to depletion of FOXP3(+)CD4(+) Treg cells from tumor tissues. Thus, optimal strategies need to be established for reducing Treg cells or attenuating their suppressive activity in tumor tissues, together with activating and expanding tumor-specific effector T cells.

PD-1 and Tim-3 regulate the expansion of tumor antigen-specific CD8⁺ T cells induced by melanoma vaccines

Although melanoma vaccines stimulate tumor antigen-specific CD8(+) T cells, objective clinical responses are rarely observed. To investigate this discrepancy, we evaluated the character of vaccine-induced CD8(+) T cells with regard to the inhibitory T-cell coreceptors PD-1 and Tim-3 in patients with metastatic melanoma who were administered tumor vaccines. The vaccines included incomplete Freund's adjuvant, CpG oligodeoxynucleotide (CpG), and the HLA-A2-restricted analog peptide NY-ESO-1 157-165V, either by itself or in combination with the pan-DR epitope NY-ESO-1 119-143. Both vaccines stimulated rapid tumor antigen-specific CD8(+) T-cell responses detected ex vivo, however, tumor antigen-specific CD8(+) T cells produced more IFN-γ and exhibited higher lytic function upon immunization with MHC class I and class II epitopes. Notably, the vast majority of vaccine-induced CD8(+) T cells upregulated PD-1 and a minority also upregulated Tim-3. Levels of PD-1 and Tim-3 expression by vaccine-induced CD8(+) T cells at the time of vaccine administration correlated inversely with their expansion in vivo. Dual blockade of PD-1 and Tim-3 enhanced the expansion and cytokine production of vaccine-induced CD8(+) T cells in vitro. Collectively, our findings support the use of PD-1 and Tim-3 blockades with cancer vaccines to stimulate potent antitumor T-cell responses and increase the likelihood of clinical responses in patients with advanced melanoma.

Inhibition of CD4+CD25+ regulatory T cell function and conversion into Th1-like effectors by a Toll-like receptor-activated dendritic cell vaccine

Despite the success of vaccines against some microbial pathogens, their utility in the prevention and treatment of cancer has thus far been limited. We have previously demonstrated that vaccination with dendritic cells activated with the TLR-4 ligand LPS and IFN-γ promotes an antigen-specific anti-tumor response that prevents tumor recurrence. To evaluate this mechanistically, we here studied the effects of this TLR-activated DC on regulatory T cell activity. Dendritic cells activated with LPS and IFN- γ negated the effects of regulatory T cells on responder cell proliferation. Restoration of responder cell proliferation was noted when TLR-activated dendritic cells were separated from both regulators and responders by a semi-permeable membrane. The effect is therefore mediated by a soluble factor but was independent of both IL-6 and IL-12. Furthermore, the soluble mediator appeared to act at least in part on the regulators themselves rather than responder cells exclusively. Because recent studies have demonstrated conversion of T regulatory cells into IL-17-producing effectors, we further questioned whether the TLR-activated dendritic cell would induce cytokine production and effector function in our system. We found that regulators produced a substantial amount of IFN- γ in the presence of TLR-activated dendritic cells but not immature dendritic cells. IFN-γ production was associated with upregulation of the Th1 transcriptional regulator T-bet, and a significant fraction of IFN-γ-producing regulators coexpressed T-bet and FoxP3. While the effects of the LPS-activated dendritic cell on responder cell proliferation were IL-12 independent, upregulation of T-bet was inhibited by a neutralizing anti-IL-12 antibody. Collectively, these and prior data suggest that varying innate immune signals may direct the phenotype of the immune response in part by inhibiting suppressor T cells and promoting differentiation of these regulators into particular subsets of effectors.

AE37 peptide vaccination in prostate cancer: a 4-year immunological assessment updates on a phase I trial

In our recent phase I trial, we demonstrated that the AE37 vaccine is safe and induces HER-2/neu-specific immunity in a heterogeneous population of HER-2/neu (+) prostate cancer patients. Herein, we tested whether one AE37 boost can induce long-lasting immunological memory in these patients. Twenty-three patients from the phase I study received one AE37 boost 6-month post-primary vaccinations. Local/systemic toxicities were evaluated following the booster injection. Immunological responses were monitored 1-month (long-term booster; LTB) and 3-year (long-term immunity; LTI) post-booster by delayed-type hypersensitivity, IFN-γ ELISPOT and proliferation assays. Regulatory T cell (Treg) frequencies, plasma transforming growth factor-β (TGF-β) and indoleamine 2,3-deoxygenase (IDO) activity levels were also determined at the same time points. The AE37 booster was safe and well tolerated. Immunological monitoring revealed vaccine-specific long-term immunity in most of the evaluated patients during both LTB and LTI, although individual levels of immunity during LTI were decreased compared with those measured 3 years earlier during LTB. This was paralleled with increased Tregs, TGF-β levels and IDO activity. One AE37 booster generated long-term immunological memory in HER-2/neu (+) prostate cancer patients, which was detectable 3 years later, albeit with a tendency to decline. Boosted patients had favorable clinical outcome in terms of overall and/or metastasis-free survival compared with historical groups with similar clinical characteristics at diagnosis. We suggest that more boosters and/or concomitant disarming of suppressor circuits may be necessary to sustain immunological memory, and therefore, further studies to optimize the AE37 booster schedule are warranted.

Convergences and divergences of thymus- and peripherally derived regulatory T cells in cancer

The expansion of regulatory T cells (T_reg) is a common event characterizing the vast majority of human and experimental tumors and it is now well established that T_reg represent a crucial hurdle for a successful immunotherapy. T_reg are currently classified, according to their origin, into thymus-derived T_reg (tT_reg) or peripherally induced T_reg (pT_reg) cells. Controversy exists over the prevalent mechanism accounting for T_reg expansion in tumors, since both tT_reg proliferation and de novo pT_reg differentiation may occur. Since tT_reg and pT_reg are believed as preferentially self-specific or broadly directed to non-self and tumor-specific antigens, respectively, the balance between tT_reg and pT_reg accumulation may impact on the repertoire of antigen specificities recognized by T_reg in tumors. The prevalence of tT_reg or pT_reg may also affect the outcome of immunotherapies based on tumor-antigen vaccination or T_reg depletion. The mechanisms dictating pT_reg induction or tT_reg expansion/stability are a matter of intense investigation and the most recent results depict a complex landscape. Indeed, selected T_reg subsets may display peculiar characteristics in terms of stability, suppressive function, and cytokine production, depending on microenvironmental signals. These features may be differentially distributed between pT_reg and tT_reg and may significantly affect the possibility of manipulating T_reg in cancer therapy. We propose here that innovative immunotherapeutic strategies may be directed at diverting unstable/uncommitted T_reg, mostly enriched in the pT_reg pool, into tumor-specific effectors, while preserving systemic immune tolerance ensured by self-specific tT_reg.

Monitoring regulatory immune responses in tumor immunotherapy clinical trials

While immune monitoring of tumor immunotherapy often focuses on the generation of productive Th1-type inflammatory immune responses, the importance of regulatory immune responses is often overlooked, despite the well-documented effects of regulatory immune responses in suppressing anti-tumor immunity. In a variety of malignancies, the frequency of regulatory cell populations has been shown to correlate with disease progression and a poor prognosis, further emphasizing the importance of characterizing the effects of immunotherapy on these populations. This review focuses on the role of suppressive immune populations (regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages) in inhibiting anti-tumor immunity, how these populations have been used in the immune monitoring of clinical trials, the prognostic value of these responses, and how the monitoring of these regulatory responses can be improved in the future.

MELOE-1 antigen contains multiple HLA class II T cell epitopes recognized by Th1 CD4+ T cells from melanoma patients

MELOE-1 is an overexpressed melanoma antigen containing a HLA-A2 restricted epitope, involved in melanoma immunosurveillance of patients adoptively transferred with tumour infiltrating lymphocytes (TIL). The use of the full-length antigen (46 aa) for anti-melanoma vaccination could be considered, subject to the presence of Th epitopes all along MELOE-1 sequence. Thus, in this study we evaluated in vitro the immunoprevalence of the different regions of MELOE-1 (i.e. their ability to induce CD4 T cell responses in vitro from PBMC). Stimulation of PBMC from healthy subjects with MELOE-1 induced the amplification of CD4 T cells specific for various regions of the protein in multiple HLA contexts, for each tested donor. We confirmed these results in a panel of melanoma patients, and documented that MELOE-1 specific CD4 T cells, were mainly Th1 cells, presumably favourable to the amplification of CD8 specific T cells. Using autologous DC, we further showed that these class II epitopes could be naturally processed from MELOE-1 whole protein and identified minimal epitopes derived from each region of MELOE-1, and presented in four distinct HLA contexts. In conclusion, vaccination with MELOE-1 whole polypeptide should induce specific Th1 CD4 responses in a majority of melanoma patients, stimulating the amplification of CD8 effector cells, reactive against melanoma cells.

Profound tumor-specific Th2 bias in patients with malignant glioma

Background

Vaccination against tumor-associated antigens is one promising approach to immunotherapy against malignant gliomas. While previous vaccine efforts have focused exclusively on HLA class I-restricted peptides, class II-restricted peptides are necessary to induce CD4⁺ helper T cells and sustain effective anti-tumor immunity. In this report we investigated the ability of five candidate peptide epitopes derived from glioma-associated antigens MAGE and IL-13 receptor α2 to detect and characterize CD4⁺ helper T cell responses in the peripheral blood of patients with malignant gliomas.

Methods

Primary T cell responses were determined by stimulating freshly isolated PBMCs from patients with primary glioblastoma (GBM) (n = 8), recurrent GBM (n = 5), meningioma (n = 7), and healthy controls (n = 6) with each candidate peptide, as well as anti-CD3 monoclonal antibody (mAb) and an immunodominant peptide epitope derived from myelin basic protein (MBP) serving as positive and negative controls, respectively. ELISA was used to measure IFN-γ and IL-5 levels, and the ratio of IFN-γ/IL-5 was used to determine whether the response had a predominant Th1 or Th2 bias.

Results

We demonstrate that novel HLA Class-II restricted MAGE-A3 and IL-13Rα2 peptides can detect T cell responses in patients with GBMs as well as in healthy subjects. Stimulation with a variety of peptide antigens over-expressed by gliomas is associated with a profound reduction in the IFN-γ/IL-5 ratio in GBM patients relative to healthy subjects. This bias is more pronounced in patients with recurrent GBMs.

Conclusions

Therapeutic vaccine strategies to shift tumor antigen-specific T cell response to a more immunostimulatory Th1 bias may be needed for immunotherapeutic trials to be more successful clinically.

Human prostate tumor antigen-specific CD8+ regulatory T cells are inhibited by CTLA-4 or IL-35 blockade

Regulatory T cells play important roles in cancer development and progression by limiting the generation of innate and adaptive anti-tumor immunity. We hypothesized that in addition to natural CD4(+)CD25(+) regulatory T cells (Tregs) and myeloid-derived suppressor cells, tumor Ag-specific Tregs interfere with the detection of anti-tumor immunity after immunotherapy. Using samples from prostate cancer patients immunized with a DNA vaccine encoding prostatic acid phosphatase (PAP) and a trans-vivo delayed-type hypersensitivity (tvDTH) assay, we found that the detection of PAP-specific effector responses after immunization was prevented by the activity of PAP-specific regulatory cells. These regulatory cells were CD8(+)CTLA-4(+), and their suppression was relieved by blockade of CTLA-4, but not IL-10 or TGF-β. Moreover, Ag-specific CD8(+) Tregs were detected prior to immunization in the absence of PAP-specific effector responses. These PAP-specific CD8(+)CTLA-4(+) suppressor T cells expressed IL-35, which was decreased after blockade of CTLA-4, and inhibition of either CTLA-4 or IL-35 reversed PAP-specific suppression of tvDTH response. PAP-specific CD8(+)CTLA-4(+) T cells also suppressed T cell proliferation in an IL-35-dependent, contact-independent fashion. Taken together, these findings suggest a novel population of CD8(+)CTLA-4(+) IL-35-secreting tumor Ag-specific Tregs arise spontaneously in some prostate cancer patients, persist during immunization, and can prevent the detection of Ag-specific effector responses by an IL-35-dependent mechanism.

Epigenetic biomarkers of T-cells in human glioma

Immune factors are thought to influence glioma risk and outcomes, but immune profiling studies to further our understanding of the immune response are limited by current immunodiagnostic methods. We developed a new assay to capture glioma immune biology based on quantitative methylation specific PCR (qMSP) of two T-cell genes (CD3Z: T-cells, and FOXP3: Tregs). Flow cytometry of T-cells correlated well with the CD3Z demethylation assay (r = 0.93; p < 2.2 × 10 (-16) ), demonstrating the validity of the assay. Furthermore, there was a high correlation between qMSP and immunohistochemistry (IHC) in quantifying tumor infiltrating T-cells (r = 0.85; p = 3.4 × 10 (-11) ). Applying our qMSP methods to archival whole blood from 65 glioblastoma multiforme (GBM) cases and 94 non-diseased controls, GBM cases had highly statistically significantly lower T-cells (p = 1.7 × 10 (-9) ) as well as Tregs (p = 5.2 × 10 (-11) ) and a modestly lower ratio of Tregs/T-cells (p = 0.024). Applying the methods to 120 excised glioma tumors, we observed that tumor infiltrating CD3+ T-cells were positively correlated with glioma tumor grade (p = 5.7 × 10 (-7) ), and that Tregs were enriched in tumors compared with peripheral blood indicating active chemoattraction of suppressive Tregs into the tumor compartment. Poorer patient survival was correlated with higher levels of tumor infiltrating T-cells (p = 0.01) and Tregs (p = 0.04). DNA methylation based immunodiagnostics represent a new generation of powerful laboratory tools offering many advantages over conventional methods that will facilitate large clinical epidemiologic studies and capitalize on stored archival blood and tissue banks.

Tumor-infiltrating regulatory T cells: phenotype, role, mechanism of expansion in situ and clinical significance

In immunocompetent individuals, the immune system initially eradicates potentially tumorigenic cells as they develop, a capacity that is progressively lost when malignant cells acquire alterations that sustain immunosubversion and/or immunoevasion. One of the major mechanisms whereby cancer cells block antitumor immune responses involves a specific class of immunosuppressive T cells that-in the vast majority of cases-express the Forkhead box P3 (FOXP3) transcription factor. Such FOXP3(+) regulatory T cells (Tregs) accumulate within neoplastic lesions as a result of several distinct mechanisms, including increased infiltration, local expansion, survival advantage and in situ development from conventional CD4(+) cells. The prognostic/predictive significance of tumor infiltration by Tregs remains a matter of debate. Indeed, high levels of intratumoral Tregs have been associated with poor disease outcome in cohorts of patients affected by multiple, but not all, tumor types. This apparent discrepancy may relate to the existence of functionally distinct Treg subsets, to the fact that Tregs near-to-invariably infiltrate neoplastic lesions together with other cells from the immune system, notably CD4(+) and CD8(+) T lymphocytes and/or to peculiar features of some oncogenic programs that involve a prominent pro-inflammatory component. In this review, we will discuss the phenotype, function and clinical significance of various Treg subsets.

A cancer vaccine induces expansion of NY-ESO-1-specific regulatory T cells in patients with advanced melanoma

Cancer vaccines are designed to expand tumor antigen-specific T cells with effector function. However, they may also inadvertently expand regulatory T cells (Treg), which could seriously hamper clinical efficacy. To address this possibility, we developed a novel assay to detect antigen-specific Treg based on down-regulation of surface CD3 following TCR engagement, and used this approach to screen for Treg specific to the NY-ESO-1 tumor antigen in melanoma patients treated with the NY-ESO-1/ISCOMATRIX^TM cancer vaccine. All patients tested had Treg (CD25^bright FoxP3⁺ CD127^neg) specific for at least one NY-ESO-1 epitope in the blood. Strikingly, comparison with pre-treatment samples revealed that many of these responses were induced or boosted by vaccination. The most frequently detected response was toward the HLA-DP4-restricted NY-ESO-1_157–170 epitope, which is also recognized by effector T cells. Notably, functional Treg specific for an HLA-DR-restricted epitope within the NY-ESO-1_115–132 peptide were also identified at high frequency in tumor tissue, suggesting that NY-ESO-1-specific Treg may suppress local anti-tumor immune responses. Together, our data provide compelling evidence for the ability of a cancer vaccine to expand tumor antigen-specific Treg in the setting of advanced cancer, a finding which should be given serious consideration in the design of future cancer vaccine clinical trials.

Primary chemotherapy and radiation as a treatment strategy for HPV-positive oropharyngeal cancer

The incidence of human papillomavirus-positive oropharyngeal cancer (HPV/OPSCC) is rapidly increasing, which will represent a major public health burden for decades to come. Although HPV/OPSCC is generally associated with a better prognosis than HPV-negative OPSCC, the survival rate of individuals with higher-risk clinical and pathologic features remains unchanged. Emerging evidence suggests that HPV/OPSCC is pathologically and molecularly distinct from HPV-negative OPSCC. This review focuses on summarizing treatment strategies for HPV/OPSCC by reviewing the peer-reviewed literature and noting ongoing and planned clinical trials in this disease. We also discuss the potential of designing targeted therapy based on the recent genomic findings of HPV/OPSCC.