T regulatory cells in cancer: recent advances and therapeutic potential

Neem components as potential agents for cancer prevention and treatment

Azadirachta indica, also known as neem, is commonly found in many semi-tropical and tropical countries including India, Pakistan, and Bangladesh. The components extracted from neem plant have been used in traditional medicine for the cure of multiple diseases including cancer for centuries. The extracts of seeds, leaves, flowers, and fruits of neem have consistently shown chemopreventive and antitumor effects in different types of cancer. Azadirachtin and nimbolide are among the few bioactive components in neem that have been studied extensively, but research on a great number of additional bioactive components is warranted. The key anticancer effects of neem components on malignant cells include inhibition of cell proliferation, induction of cell death, suppression of cancer angiogenesis, restoration of cellular reduction/oxidation (redox) balance, and enhancement of the host immune responses against tumor cells. While the underlying mechanisms of these effects are mostly unclear, the suppression of NF-κB signaling pathway is, at least partially, involved in the anticancer functions of neem components. Importantly, the anti-proliferative and apoptosis-inducing effects of neem components are tumor selective as the effects on normal cells are significantly weaker. In addition, neem extracts sensitize cancer cells to immunotherapy and radiotherapy, and enhance the efficacy of certain cancer chemotherapeutic agents. This review summarizes the current updates on the anticancer effects of neem components and their possible impact on managing cancer incidence and treatment.

Induced regulatory T cells in inhibitory microenvironments created by cancer

INTRODUCTION

Regulatory T cells (Tregs) accumulating in the peripheral circulation and tumor sites of patients contribute to tumor escape from the host immune system. Tregs encompass subsets of immune cells with distinct phenotypic and functional properties. Whereas natural (n) or thymic-derived (t) Tregs regulate responses to self-antigens, inducible (i) or peripheral (p) Tregs generated and expanded in regulatory microenvironments control immune responses to a broad variety of antigens.

AREAS COVERED

Tregs accumulating in the tumor microenvironment (TME) are contextually regulated. They acquire phenotypic and functional attributes imposed by the inhibitory molecular pathways operating in situ. Several molecular pathways active in human cancer are reviewed. The pathways may differ from one tumor to another, and environmentally induced Tregs may be functionally distinct. Potential therapeutic strategies for selective silencing of iTregs are considered in the light of the newly acquired understanding of their phenotypic and functional diversity.

EXPERT OPINION

Human Tregs accumulating in cancer comprise 'bad' subsets, which inhibit antitumor immunity, and 'good' anti-inflammatory subsets, which maintain tolerance to self and benefit the host. Future therapeutic strategies targeting Tregs will need to discriminate between these Treg subsets and will need to consider reprogramming strategies instead of Treg elimination. Re-establishment of effective antitumor immune responses in cancer patients without disturbing a normal homeostatic T-cell balance will greatly benefit from insights into inhibitory pathways engaged by human tumors.

Prognostic performance of inflammation-based prognostic indices in primary operable non-small cell lung cancer

BACKGROUND

At least 30% of patients with primary resectable non-small cell lung cancer (NSCLC) will experience a relapse in their disease within 5 years following definitive treatment. Clinicopathological predictors have proved to be suboptimal in identifying high-risk patients. We aimed to establish whether inflammation-based scores offer an improved prognostic ability in terms of estimating overall (OS) and recurrence-free survival (RFS) in a cohort of operable, early-stage NSCLC patients.

METHODS

Clinicopathological, demographic and treatment data were collected prospectively for 220 patients operated for primary NSCLC at the Hammersmith Hospital from 2004 to 2011. Pretreatment modified Glasgow Prognostic Score (mGPS), neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) were tested together with established prognostic factors in uni- and multivariate Cox regression analyses of OS and RFS.

RESULTS

Half of the patients were male, with a median age of 65. A total of 57% were classified as stage I with adenocarcinoma being the most prevalent subtype (60%). Univariate analyses of survival revealed stage (P<0.001), grade (P=0.02), lymphovascular (LVI, P=0.001), visceral pleural invasion (VPI, P=0.003), mGPS (P=0.02) and NLR (P=0.04) as predictors of OS, with stage (P<0.001), VPI (P=0.02) and NLR (P=0.002) being confirmed as independent prognostic factors on multivariate analyses. Patients with more advanced stage (P<0.001) and LVI (P=0.008) had significantly shorter RFS.

CONCLUSIONS

An elevated NLR identifies operable NSCLC patients with a poor prognostic outlook and an OS difference of almost 2 years compared to those with a normal score at diagnosis. Our study validates the clinical utility of the NLR in early-stage NSCLC.

Immune checkpoint blockade in cancer treatment: a double-edged sword cross-targeting the host as an "innocent bystander"

Targeted immune checkpoint blockade augments anti-tumor immunity and induces durable responses in patients with melanoma and other solid tumors. It also induces specific “immune-related adverse events” (irAEs). IrAEs mainly include gastrointestinal, dermatological, hepatic and endocrinological toxicities. Off-target effects that arise appear to account for much of the toxicity of the immune checkpoint blockade. These unique “innocent bystander” effects are likely a direct result of breaking immune tolerance upon immune check point blockade and require specific treatment guidelines that include symptomatic therapies or systemic corticosteroids. What do we need going forward to limit immune checkpoint blockade-induced toxicity? Most importantly, we need a better understanding of the roles played by these agents in normal tissues, so that we can begin to predict potentially problematic side effects on the basis of their selectivity profile. Second, we need to focus on the predictive factors of the response and toxicity of the host rather than serially focusing on individual agents. Third, rigorous biomarker-driven clinical trials are needed to further elucidate the mechanisms of both the benefit and toxicity. We will summarize the double-edged sword effect of immunotherapeutics in cancer treatment.

Neuropilin 1: function and therapeutic potential in cancer

Neuropilin 1 (NRP1) is a transmembrane glycoprotein that acts as a co-receptor for a number of extracellular ligands including class III/IV semaphorins, certain isoforms of vascular endothelial growth factor and transforming growth factor beta. An exact understanding of the role of NRP1 in the immune system has been obscured by the differences in NRP1 expression observed between mice and humans. In mice, NRP1 is selectively expressed on thymic-derived Tregs and greatly enhances immunosuppressive function. In humans, NRP1 is expressed on plasmacytoid dendritic cells (pDCs) where it aids in priming immune responses and on a subset of T regulatory cells (Tregs) isolated from secondary lymph nodes. Preliminary studies that show NRP1 expression on T cells confers enhanced immunosuppressive activity. However, the mechanism by which this activity is mediated remains unclear. NRP1 expression has also been identified on activated T cells and Tregs isolated from inflammatory microenvironments, suggesting NRP1 might represent a novel T cell activation marker. Of clinical interest, NRP1 may enhance Treg tumour infiltration and a decrease in NRP1+ Tregs correlates with successful chemotherapy, suggesting a specific role for NRP1 in cancer pathology. As a therapeutic target, NRP1 allows simultaneous targeting of NRP1-expressing tumour vasculature, NRP1+ Tregs and pDCs. With the development of anti-NRP1 monoclonal antibodies and cell-penetrating peptides, NRP1 represents a promising new target for cancer therapies. This paper reviews current knowledge on the role and function of NRP1 in Tregs and pDCs, both in physiological and cancer settings, as well as its potential as a therapeutic target in cancer.

The effect of metronomic versus standard chemotherapy on the regulatory to effector T-cell equilibrium in cancer patients

BACKGROUND

The host's immune system is crucially involved in cancer development and progression. The ratio of regulatory to effector T-cells, as well as the interplay of T-cells with therapeutic agents, impact on cancer prognosis. The current study aimed to comparatively investigate the effect of metronomic and standard chemotherapy on the number and functionality of peripheral regulatory and effector T-cells in cancer patients.

METHODS

CD4+CD25+ regulatory and CD4+CD25- effector T-cells were purified from the peripheral blood of 36 cancer patients and co-cultured in the presence of a polyclonal stimulus. The proliferative capacity and frequency of CD4+CD25+/CD4+CD25- T-cells were analysed before and during various chemotherapeutic regimes, by ELISA and flow cytometry, respectively.

RESULTS

Chemotherapy shifted immune responses in favour of regulatory T-cells. The relative ratio of regulatory to effector T-cells increased, and the T-cell-mediated suppressive activity of regulatory on effector T-cells was augmented. This effect was more profound in metronomic than in standard chemotherapeutic approaches. Moreover, an association between the chemotherapy strategy followed and the mode of action of specific drugs (anti-mitotic, anti-DNA) was revealed.

CONCLUSIONS

In comparison to standard chemotherapeutic strategies, metronomic approaches, though more patient-friendly, result in a significantly more prominent expansion of regulatory T-cells that aggravate the regulatory to effector T-cell imbalance. Our findings impact on the modulation of chemotherapy-treated patients' anti-tumor immunity and, thus, may be proven useful for selecting the most advantageous drug-delivery strategy, particularly when immunotherapeutics are eventually to be applied.

Clinical evaluation of systemic and local immune responses in cancer: time for integration

The immune system has a dual role in cancer development and progression. On the one hand, it can eradicate emerging malignant cells, but on the other hand, it can actively promote growth of malignant cells, their invasive capacities and their ability to metastasize. Immune cells with predominantly anti-tumor functionality include cells of the innate immune system, such as natural killer cells, and cells of adaptive immunity, such as conventional dendritic cells and cytotoxic T lymphocytes. Immune cells with predominantly pro-tumor functionality include a broad spectrum of cells of the innate and adaptive immune system, such as type 2 neutrophils and macrophages, plasmacytoid DC, myeloid-derived suppressor cells and regulatory T lymphocytes. The presence of immune cells with tumor-suppressive and tumor-promoting activity in the cancer microenvironment and in peripheral blood is usually associated with good clinical outcomes and poor clinical outcomes, respectively. Significant advances in experimental and clinical oncoimmunology achieved in the last decade open an opportunity for the use of modern morphologic, flow cytometric and functional tests in clinical practice. In this review, we describe an integrated approach to clinical evaluation of the immune status of cancer patients for diagnostic purposes, prognostic/predictive purposes (evaluation of patient prognosis and response to treatment) and for therapeutic purposes.

Peripheral and thymic foxp3(+) regulatory T cells in search of origin, distinction, and function

Over the past decade, much has been learnt and much more to discover about Foxp3(+) regulatory T cells (Tregs). Initially, it was thought that Tregs were a unique entity that originates in the thymus. It is now recognized that there is a fraternal twin sibling that is generated in the periphery. The difficulty is in the distinction between these two subsets. The ability to detect, monitor, and analyze these two subsets in health and disease will provide invaluable insights into their functions and purposes. The plasticity and mechanisms of action can be unique and not overlapping within these subsets. Therefore, the therapeutic targeting of a particular subset of Tregs might be more efficacious. In the past couple of years, a vast amount of data have provided a better understanding of the cellular and molecular components essential for their development and stability. Many studies are implicating their preferential involvement in certain diseases and immunologic tolerance. However, it remains controversial as to whether any phenotypic markers have been identified that can differentiate thymic versus peripheral Tregs. This review will address the validity and controversy regarding Helios, Lap/Garp and Neuropilin-1 as markers of thymic Tregs. It also will discuss updated information on distinguishing features of these two subsets and their critical roles in maternal-fetal tolerance and transplantation.

Natural and induced T regulatory cells in cancer

CD4+Foxp3+ T regulatory (Treg) cells control many facets of immune responses ranging from autoimmune diseases, to inflammatory conditions, and cancer in an attempt to maintain immune homeostasis. Natural Treg (nTreg) cells develop in the thymus and constitute a critical arm of active mechanisms of peripheral tolerance particularly to self antigens. A growing body of knowledge now supports the existence of induced Treg (iTreg) cells which may derive from a population of conventional CD4+ T cells. The fork-head transcription factor (Foxp3) typically is expressed by natural CD4+ Treg cells, and thus serves as a marker to definitively identify these cells. On the contrary, there is less consensus on what constitutes iTreg cells as their precise definition has been somewhat elusive. This is in part due to their distinct phenotypes which are shaped by exposure to certain inflammatory or "assault" signals stemming from the underlying immune disorder. The "policing" activity of Treg cells tends to be uni-directional in several pathological conditions. On one end of the spectrum, Treg cell suppressive activity is beneficial by curtailing T cell response against self-antigens and allergens thus preventing autoimmune diseases and allergies. On the other end however, their inhibitory roles in limiting immune response against pseudo-self antigens as in tumors often culminates into negative outcomes. In this review, we focus on this latter aspect of Treg cell immunobiology by highlighting the involvement of nTreg cells in various animal models and human tumors. We further discuss iTreg cells, relationship with their natural counterpart, and potential co-operation between the two in modulating immune response against tumors. Lastly, we discuss studies focusing on these cells as targets for improving anti-tumor immunity.

Natural and induced T regulatory cells in cancer

CD4+Foxp3+ T regulatory (Treg) cells control many facets of immune responses ranging from autoimmune diseases, to inflammatory conditions, and cancer in an attempt to maintain immune homeostasis. Natural Treg (nTreg) cells develop in the thymus and constitute a critical arm of active mechanisms of peripheral tolerance particularly to self antigens. A growing body of knowledge now supports the existence of induced Treg (iTreg) cells which may derive from a population of conventional CD4+ T cells. The fork-head transcription factor (Foxp3) typically is expressed by natural CD4+ Treg cells, and thus serves as a marker to definitively identify these cells. On the contrary, there is less consensus on what constitutes iTreg cells as their precise definition has been somewhat elusive. This is in part due to their distinct phenotypes which are shaped by exposure to certain inflammatory or “assault” signals stemming from the underlying immune disorder. The “policing” activity of Treg cells tends to be uni-directional in several pathological conditions. On one end of the spectrum, Treg cell suppressive activity is beneficial by curtailing T cell response against self-antigens and allergens thus preventing autoimmune diseases and allergies. On the other end however, their inhibitory roles in limiting immune response against pseudo-self antigens as in tumors often culminates into negative outcomes. In this review, we focus on this latter aspect of Treg cell immunobiology by highlighting the involvement of nTreg cells in various animal models and human tumors. We further discuss iTreg cells, relationship with their natural counterpart, and potential co-operation between the two in modulating immune response against tumors. Lastly, we discuss studies focusing on these cells as targets for improving anti-tumor immunity.

Adenosine as an endogenous immunoregulator in cancer pathogenesis: where to go?

Cancer is a chronic disease and its pathogenesis is well correlated with infection and inflammation. Adenosine is a purine nucleoside, which is produced under metabolic stress like hypoxic conditions. Acute or chronic inflammatory conditions lead to the release of precursor adenine nucleotides (adenosine triphosphate (ATP), adenosien diphosphate (ADP) and adenosine monophosphate (AMP)) from cells, which are extracellularly catabolized into adenosine by extracellular ectonucleotidases, i.e., CD39 or nucleoside triphosphate dephosphorylase (NTPD) and CD73 or 5'-ectonucleotidase. It is now well-known that adenosine is secreted by cancer as well as immune cells during tumor pathogenesis under metabolic stress or hypoxia. Once adenosine is released into the extracellular environment, it exerts various immunomodulatory effects via adenosine receptors (A1, A2A, A2B, and A3) expressed on various immune cells (i.e., macrophages, myeloid-derived suppressor cells (MDSCs), natural killer (NK) cells, dendritic cells (DCs), T cells, regulatory T cell (Tregs), etc.), which play very important roles in the pathogenesis of cancer. This review is intended to summarize the role of inflammation and adenosine in the immunopathogenesis of tumor along with regulation of tumor-specific immune response and its modulation as an adjunct approach to tumor immunotherapy.

Role of vaccine therapy for renal cell carcinoma in the era of targeted therapy

Renal cell carcinoma is the most common malignant tumor originating from the kidney. Compared with other solid tumors, it does not respond to traditional management modalities, such as chemotherapy and radiotherapy. However, it is well known that renal cell carcinoma represents one of the most immune-responsive cancers and several immunotherapeutic strategies have been investigated in the management of renal cell carcinoma with variable degrees of success. The development of immunotherapy with α-interferon or high-dose interleukin-2 is the best established treatment, and is associated with durable disease control. Although the lack of defined antigens in renal cell carcinoma has hindered more specific vaccine development, research regarding vaccination therapy has been of special interest for the treatment of renal cell carcinoma for more than 30 years. At present, there are three types of cell-based vaccines in renal cell carcinoma treatment: autologous tumor-cell vaccines, genetically modified tumor vaccines and dendritic cell-based vaccines. A further type is peptide-based vaccination with tumor-associated antigens as possible targets, such as carbonic anhydrase IX, survivin and telomerase that are overexpressed in renal cell carcinoma. In the present article, we review data from completed clinical trials of vaccine therapy, and discuss future trials to assess the current knowledge and future role of vaccine therapy for renal cell carcinoma in the era of recently developed targeted therapy.

Interleukin-27 signaling promotes immunity against endogenously arising murine tumors

Interleukin-27 (IL-27) is a pleiotropic cytokine but its immunosuppressive effects predominate during many in vivo immunological challenges. Despite this, evidence from tumor cell line transfer models suggested that IL-27 could promote immune responses in the tumor context. However, the role of IL-27 in immunity against tumors that develop in situ and in tumor immunosurveillance remain undefined. In this study, we demonstrate that tumor development and growth are accelerated in IL-27 receptor α (Il27ra)-deficient mice. Enhanced tumor growth in both carcinogen-induced fibrosarcoma and oncogene-driven mammary carcinoma was associated with decreased interferon-γ production by CD4 and CD8 T cells and increased numbers of regulatory T-cells (T_reg). This is the first study to show that IL-27 promotes protective immune responses against endogenous tumors, which is critical as the basis for future development of an IL-27 based therapeutic agent.

Immunomodulatory effects of total intravenous and balanced inhalation anesthesia in patients with bladder cancer undergoing elective radical cystectomy: preliminary results

Background

Although surgery and anesthesia induce immunesuppression, remains largely unknown whether various anesthetic techniques have different immunosuppressive effects on cancer patients. Therefore, the aim of this study was to investigate the influence of total intravenous anesthesia with target-controlled infusion (TIVA-TCI) and balanced inhalation anesthesia (BAL) on the peri-operative levels of inflammatory cytokines and regulatory T cells (Tregs) in patients with bladder cancer undergoing surgery.

Methods

Twenty eight consecutive patients with bladder cancer who underwent radical cystectomy were prospectively randomized into two groups to receive TIVA-TCI (n = 14) or BAL (n = 14). Before the induction of anesthesia (T0), 6–8 hours (T1) post-surgery, and 5 days post-surgery (T2), Tregs and serum levels of interleukin -1beta (IL-1β), interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), interleukin −2 (IL-2), interleukin −6 (IL-6), and interleukin −10 (IL-10) were measured.

Results

In the peri-operative period all cancer patients showed a marked and significant increase in IL-6. Moreover, TIVA-TCI patients also showed a higher increase in IFN-γ, whereas in BAL patients Tregs were reduced by approximately 30% during surgery. The incidence of infections, metastases, and death was similar in both groups.

Conclusions

The increase in the Th1 response in the TIVA-TCI group and the reduction in Tregs in the BAL group seem to balance the immunosuppressive effect induced by IL-6. Therefore TIVA-TCI and BAL can be both used in major surgery in patients with bladder cancer without worsening the outcome.

Tumor-infiltrating lymphocytes predict response to chemotherapy in patients with advance non-small cell lung cancer

Accumulating preclinical evidence suggests that anticancer immune responses contribute to the success of chemotherapy. The predictive significance of tumor-infiltrating lymphocytes (TILs) for response to neoadjuvant chemotherapy in non-small cell lung cancer (NSCLC) remains unknown. The aim of this study was to investigate the prognostic and predictive value of TIL subtypes in patients with advanced NSCLC treated with platinum-based chemotherapy. In total, 159 patients with stage III and IV NSCLC were retrospectively enrolled. The prevalence of CD3(+), CD4(+), CD8(+) and Foxp3(+) TILs was assessed by immunohistochemistry in tumor tissue obtained before chemotherapy. The density of TILs subgroups was treated as dichotomous variables using the median values as cutoff. Survival curves were estimated by the Kaplan-Meier method, and differences in overall survival between groups were determined using the Log-rank test. Prognostic effects of TIL subsets density were evaluated by Cox regression analysis. The presence of CD3(+), CD4(+), CD8(+), and FOXP3(+) TILs was not correlated with any clinicopathological features. Neither the prevalence of TILs nor combined analysis displayed obvious prognostic performances for overall survival in Cox regression model. Instead, higher FOXP3(+)/CD8(+) ratio in tumor sites was an independent factor for poor response to platinum-based chemotherapy in overall cohort. These findings suggest that immunological CD8(+) and FOXP3(+)Tregs cell infiltrate within tumor environment is predictive of response to platinum-based neoadjuvant chemotherapy in advanced NSCLC patients. The understanding of the clinical relevance of the microenvironmental immunological milieu might provide an important clue for the design of novel strategies in cancer immunotherapy.

Functions of thymic stromal lymphopoietin in immunity and disease

Thymic stromal lymphopoietin (TSLP) is an interleukin 7-like cytokine expressed mainly by epithelial cells. Current studies provide compelling evidence that TSLP is capable of activating dendritic cells to promote T helper (Th) 2 immune responses. TSLP has also been shown to directly promote Th2 differentiation of naïve CD4(+) T cell and activate natural killer T cells, basophils and other innate immune cells at the initial stage of inflammation. In addition, TSLP affects B cell maturation and activation and can also influence regulatory T (Treg) cell differentiation and development. TSLP-induced Th2 responses are associated with the pathogenesis of allergic inflammatory diseases, including atopic dermatitis, asthma, and rhinitis. Based on recent findings in humans and mouse models, TSLP might also be involved in the pathogenesis of inflammatory bowel disease and progression of cancer. In this review, we will summarize our current understanding of the biology of TSLP and highlight the important issues for future investigations.

Silencing IDO in dendritic cells: a novel approach to enhance cancer immunotherapy in a murine breast cancer model

Cancer immunotherapeutic agents (vaccines) in the form of antigen-loaded dendritic cells (DCs) reached an important milestone with the recent approval of Provenge, the first DC vaccine for treatment of prostate cancer. Although this heralds a new era of tumor immunotherapy, it also highlights the compelling need to optimize such DC-based therapies as they are increasingly tested and used to treat human patients. In this study we sought to augment and enhance the antitumor activity of a DC-based vaccine using siRNA to silence expression of immunosuppressive enzyme indoleamine 2,3-dioxygenase (IDO) in DCs. We report here that DCs loaded with tumor antigens, but with siRNA-silenced IDO expression, were introduced into 4T1 breast tumor-bearing mice, the treatment: (i) lengthened the time required for tumor onset, (ii) decreased tumor size compared to tumors grown for equal lengths of time in mice treated with antigen-loaded DCs without IDO silencing and (iii) reduced CD4(+) and CD8(+) T cell apoptosis. Furthermore, immunization with IDO-silenced DCs enhanced tumor antigen-specific T cell proliferation and CTL activity, and decreased numbers of CD4(+) CD25(+) Foxp3(+) T(reg). This study provides evidence to support silencing of immunosuppressive genes (IDO) as an effective strategy to enhance the efficacy of DC-based cancer immunotherapeutic.

Vaccines for melanoma and renal cell carcinoma

The inherent immunogenicity of melanoma and renal cell carcinoma (RCC) has made these tumors a focus of considerable research in vaccine development. Recent data from murine studies of immunosurveillance have highlighted the importance of both innate and adaptive immune responses in shaping a tumor's inherent susceptibility to immune surveillance and immunotherapy. Melanoma has been a useful model for the identification of tumor-associated antigens and a number of putative renal cell antigens have been described more recently. These antigens have been targeted using a variety of vaccine strategies, including protein- and peptide-based vaccines, recombinant antigen-expressing vectors, and whole cell vaccine approaches. While evidence for clinical benefit has been disappointing to date, several current phase III clinical trials are in progress based on promising results from phase II studies. Accumulating data suggest that the tumor microenvironment and mechanisms of immunological escape by established tumors are significant barriers that must be overcome before vaccine therapy can be fully realized. This review will discuss the basis for vaccine development, describe some of the more promising vaccine strategies in development, and mention some of the tumor escape mechanisms that block effective anti-tumor immunity for melanoma and RCC.

Peripheral T-cell lymphoma with a regulatory T-cell phenotype: report of a nodal and an extranodal case from Peru

T-cell regulatory lymphocytes (T reg) are identified by their reactivity with CD4, CD25, and FOXP3, and are variably present in the background of various neoplasms including hematopoietic tumors, and function modulating the immune response, including control of autoimmunity. Adult T-cell leukemia/lymphoma is an aggressive lymphoma associated with human T-lymphotrophic virus 1 infection characterized by the presence of neoplastic lymphocytes with a T reg phenotype; however, this phenotype is not characteristically found in other lymphomas. Here, we report 2 apparently immunocompetent human T-lymphotrophic virus 1-negative patients with nodal and extranodal peripheral T-cell lymphoma, not otherwise specified with a T reg immunophenotype, based on the strong CD25 and FOXP3 positivity of the neoplastic cells. One patient was a 48-year-old woman with an early stage tumor in the cavum, who despite of chemotherapy subsequently developed systemic disease and died of tumor progression 46 months from diagnosis. The second patient was a 65-year-old male with generalized adenopathy and B symptoms who received chemotherapy achieving a complete remission but had recurrence and died 36 months from diagnosis. The histopathology revealed a diffuse infiltrate with an interfollicular distribution in the second case, with nodal involvement, consisted of large cells with clear cytoplasm associated with vascular proliferation and abundant mitoses. Neoplastic cells of first case showed typical T reg phenotype, whereas the second case had a CD4/CD8 double negative T reg variant. Only a single similar case was found in a review of the literature. We conclude that peripheral T-cell lymphoma, not otherwise specified with a T reg phenotype may represent a distinct category of T-cell lymphoma with an aggressive clinical course and poor prognosis.

Application of paclitaxel in low non-cytotoxic doses supports vaccination with melanoma antigens in normal mice

Chemotherapeutic agents such as paclitaxel applied in ultra-low, non-cytotoxic doses were previously shown to stimulate dendritic cell activity and anti-tumor immune responses upon vaccination in mouse transplantable tumor models. However, the mechanisms of these alterations-termed chemoimmunomodulation or chemomodulation-are still not clear. This study investigated the effect of paclitaxel applied in ultra-low, non-cytotoxic doses on the efficiency of immunization of healthy C57BL/6 mice with the peptide derived from tyrosinase related protein (TRP)-2 as a model melanoma antigen. Using an IFNγ ELISPOT assay, it was found that administration of 1 mg paclitaxel/kg in combination with the peptide vaccination strongly increased the frequencies of TRP-2 specific spleen T-cells as compared to levels due to the vaccination alone. This was associated with a significant decrease in the levels of regulatory T-cells (T(reg)) and immature myeloid cells (known as a counterpart of myeloid derived suppressor cells [MDSC] in healthy mice). Such impairments of potential immunosuppressive cells were found to correlate with a strong increase in the amount of effector CD8+ and CD4+ T-cells in the bone marrow and spleen. Furthermore, in paclitaxel-treated mice, a significant augmentation of natural killer (NK) cell numbers in the bone marrow and their ability to produce IFNγ were observed. In addition, the level of NK-T-cells in the lymph nodes was also increased. It is suggested that paclitaxel applied in ultra-low, non-cytotoxic doses may potentially enhance the efficacy of anti-tumor vaccinations by neutralizing immunosuppressive T(reg) and MDSC populations in tumor-bearing hosts.

Tumor-associated myeloid cells can be activated in vitro and in vivo to mediate antitumor effects

Tumor growth is often accompanied by the accumulation of myeloid cells in the tumors and lymphoid organs. These cells can suppress T cell immunity, thereby posing an obstacle to T cell-targeted cancer immunotherapy. In this study, we tested the possibility of activating tumor-associated myeloid cells to mediate antitumor effects. Using the peritoneal model of B16 melanoma, we show that peritoneal cells (PEC) in tumor-bearing mice (TBM) had reduced ability to secrete nitric oxide (NO) following in vitro stimulation with interferon gamma and lipopolysaccharide, as compared to PEC from control mice. This reduced function of PEC was accompanied by the influx of CD11b(+) Gr-1(+) myeloid cells to the peritoneal cavity. Nonadherent PEC were responsible for most of the NO production in TBM, whereas in naïve mice NO was mainly secreted by adherent CD11b(+) F4/80(+) macrophages. Sorted CD11b(+) Gr-1(-) monocytic and CD11b(+) Gr-1(+) granulocytic PEC from TBM had a reduced ability to secrete NO following in vitro stimulation (compared to naïve PEC), but effectively suppressed proliferation of tumor cells in vitro. In vivo, treatment of mice bearing established peritoneal B16 tumors with anti-CD40 and CpG resulted in activation of tumor-associated PEC, reduction in local tumor burden and prolongation of mouse survival. Inhibition of NO did not abrogate the antitumor effects of stimulated myeloid cells. Taken together, the results indicate that in tumor-bearing hosts, tumor-associated myeloid cells can be activated to mediate antitumor effects.

Regulatory T-cell depletion synergizes with gp96-mediated cellular responses and antitumor activity

Despite its potent immunostimulatory properties, vaccination with autologous tumor-derived gp96 has relatively modest antitumor effect in a range of clinical trials. Based on our previous study showing a gp96-mediated immune balance between CTL and Tregs, here we investigated possible synergy between gp96 vaccine and systemic Treg depletion on induction of antitumor T-cell immunity and the mechanisms accounting for synergistic efficacy. In gp96-peptide complex immunized BALB/c mice, anti-CD25 mAb treatment significantly increased IFN-γ-producing CD8(+) and CD4(+) T cells by about 1-2-fold in spleen and 40-50% in lymph node. A significantly higher number of peptide-specific CTL were observed under anti-CD25 mAb treatment compared with no treatment. Moreover, Treg depletion synergistically improved the anticancer activity of tumor-derived gp96 vaccine in the poorly immunogenic and highly tumorigenic B16 melanoma model in C57BL/6 J mice. While gp96 immunization alone led to the modest enhancement of CTL activities in spleen, the combination with Treg depletion dramatically increased tumor-specific CTL responses. In addition, the combination resulted in a significant increase of CD8(+) T-cell infiltration in tumor, which correlated with an enhanced inhibition of tumor growth. Our results provide evidence that targeting Tregs may provide a more efficient strategy to potentiate gp96-mediated T-cell responses and enhance the antitumor efficiency of gp96-based therapeutic vaccine.

Anti-glioma response of autologous T cells stimulated by autologous dendritic cells electrofused with CD133+ or CD133- glioma cells

Glioma, the most common tumor of the central nervous system (CNS), currently results in a high rate of morbidity and mortality. The expression of CD133, a stem-like cell marker expressed in the glioma cells, is believed to lead to tumorigenesis in the human brain. Thus, it is necessary to find a proper method to specifically kill the CD133(+) glioma cells. Dendritic cell (DC)/tumor hybrids are proven to be able to induce an effective immune response, leading to killing of glioma cells in vitro. We isolated CD133(+) cells from a population of primary glioma cells, and cultured autologous DCs and T cells at the same time. Next, we electrofused the DCs with the CD133(+) glioma cells and with CD133- ones, in order to explore a new strategy for glioma therapy. We then exposed the T cells to five separate groups of cells: DC/CD133(+) hybrids, DC/CD133(-) hybrids, DCs alone, unsorted glioma cells alone and mixed DCs-glioma cells. A cytotoxicity assay showed that T cells stimulated by either type of hybrid were able to kill cultured autologous glioma cells significantly more effectively than those stimulated by the other three cell types (P<0.05). The amounts of IFN-γ secreted by T cells stimulated by the two types of fused cells were obviously increased compared to those stimulated by the other three cell types (P<0.05). However, no significant differences were noted between the effects of the two hybrids, neither in the cytotoxicity assay nor in the IFN-γ release assay (P>0.05). Therefore, both DC/CD133(+) and DC/CD133(-) hybrids can cause significant T cell immune responses in vitro. There were no significant differences between the immune responses caused by the two types of hybrids.

Mechanism of synergy between T cell signals and C8-substituted guanine nucleosides in humoral immunity: B lymphotropic cytokines induce responsiveness to 8-mercaptoguanosine

B lymphocytes require a source of T cell-like help to produce antibody to T cell-dependent antigens. T cell-derived lymphokines and C8-substituted guanine ribonucleosides (such as 8-mercaptoguanosine; 8MGuo) are effective sources of such T cell-like help. Addition of T cell-derived lymphokines to antigen-activated B cells together with 8MGuo results in synergistic B cell differentiation, amplifying the sum of the individual responses twofold to four-fold. Lymphokine activity is required at initiation of culture for optimal synergy with 8MGuo, whereas the nucleoside can be added up to 48 hr after the lymphokines with full synergy. 8MGuo provides a perceived T cell-like differentiation signal to B cells from immunodeficient xid mice, thereby distinguishing a subset of Lyb-5- nucleoside-responsive B cells from those activated by soluble anti-mu followed by B cell stimulatory factor-1, interleukin 1, and B cell differentiation factors, which are Lyb-5+. Moreover, at least a subset of the B cells recruited by the synergistic interaction of lymphokines and nucleoside is distinct from that responsive to 8MGuo + antigen, insofar as Sephadex G-10 nonadherent xid B cells fail to respond to either 8MGuo or lymphokines alone, but do respond to the combination. A distinct subpopulation can also be demonstrated among normal B cells by limiting dilution analysis in which the precursor frequency of antigen-reactive B cells in the presence of lymphokines or nucleoside alone increases substantially when both agents are present together. In concert with the kinetic data, these observations suggest that synergy derives at least in part from the ability of lymphokines to induce one or more elements the absence of which limits the capacity of a distinct B cell subpopulation to respond to 8MGuo.