The frequency and suppressor function of CD4+CD25highFoxp3+ T cells in the circulation of patients with squamous cell carcinoma of the head and neck

Comparative analysis of tumor-infiltrating lymphocytes in a syngeneic mouse model of oral cancer

OBJECTIVE

To perform a comparative analysis of infiltrating immune cells in a newly developed C57BL/6 background syngeneic transplantable mouse oral cancer (MOC) model.

STUDY DESIGN/SETTING

Scientific study in an academic medical center.

METHODS

Use of carcinogen-induced tumorigenesis, tissue culture, cell line transplantation, and flow cytometric analysis techniques.

RESULTS

Previously, the authors established a series of cell line models that displayed dichotomous growth phenotypes when transplanted into immunocompetent mice. They now show that the indolent growth pattern of the MOC1-generated tumors is associated with increased baseline and inducible major histocompatibility complex class I expression and increased CD8(+) T-cell infiltration into the tumor microenvironment. Conversely, the aggressive and metastatic pattern of MOC2-generated tumors has decreased basal and inducible class I expression and is associated with FOXP3(+)CD4(+) regulatory T-cell infiltration. Delayed primary tumor growth after targeted monoclonal antibody therapy of these FOXP3(+) regulatory cells further suggests that these immune cells contribute to the aggressive phenotype of MOC2.

CONCLUSION

These data validate that key infiltrating immune cells identified here parallel findings in human head and neck cancer, making this newly developed syngeneic model a critical platform for the continued dissection of tumor-host interactions in head and neck cancer.

Head and neck squamous carcinomas with exophytic and endophytic type of growth have the same prognosis after surgery and adjuvant radiotherapy

Head and neck squamous cell carcinomas (HNSCC) are characterized by exophytic or endophytic growth. We hypothesized that the growth pattern predicts outcome and associates with distinct clinical and immunological profiles. Tumors obtained from 60 HNSCC patients treated with surgery and adjuvant radiotherapy were identified as exophytic or endophytic. Recurrence-free survival (RFS) at 42 months was determined. In a subsets of 30 patients (22 exophytic and 8 endophytic) tumor stroma and parenchyma were evaluated for infiltrating CD4(+) and CD8(+) T, dendritic, myeloid and FOXP3(+) regulatory T cells (Treg) and expression of immunosuppressive cytokines by immunohistochemistry. The localization and frequency of positive cells were determined microscopically and analyzed by hierarchical clustering to distinguish exophytic versus endophytic tumors. 34/60 patients had exophytic and 26/60 endophytic tumors. No differences in clinicopathologic data, disease progression or RFS were seen between the two cohorts. Infiltrates of CD3(+)CD8(+) T cells were larger in endophytic than exophytic tumors, while FOXP3(+) Treg, TGF-β(+), IL-10(+), Arg-1(+), CD11b(+) cells were equally prominent in both. FOXP3(+) Treg accumulated in endophytic tumor nests, while the exophytic tumor stroma was enriched in IL-10(+) cells (both at p < 0.05). Hierarchical clustering based on immunophenotyping failed to identify different clusters in these two tumor types. However, CD68(+) macrophages and FOXP3(+) Treg showed a distinct distribution. The HNSCC growth pattern did not predict RFS. Although higher numbers and differences in localization of immunosuppressive cells in endophytic versus exophytic tumors were observed, no significant relationship was established between the growth pattern and the immune profile of infiltrating lymphocytes.

The role of the adenosinergic pathway in immunosuppression mediated by human regulatory T cells (Treg)

Tumor-induced dysfunction of immune cells is a common problem in cancer. Tumors induce immune suppression by many different mechanisms, including accumulation of regulatory T cells (Treg). Adaptive Treg (Tr1) generated in the tumor microenvironment express CD39 and CD73 ectonucleotidases, produce adenosine and are COX2+PGE2+. Adenosine and PGE2 produced by Tr1 or tumor cells bind to their respective receptors on the surface of T effector cells (Teff) and cooperate in up-regulating cytosolic 3'5'-cAMP levels utilizing adenylyl cyclase isoform 7 (AC-7). In Teff, increased cAMP mediates suppression of anti-tumor functions. Treg, in contrast to Teff, seem to require high cAMP levels for mediating suppression. This differential requirement of Treg and Teff for cAMP offers an opportunity for pharmacologic interventions using selected inhibitors of the adenosine/PGE2 pathways. Blocking of adenosine/PGE2 production by Tr1 or blocking binding of these factors to their receptors on T cells or inhibition of cAMP synthesis in Teff all represent novel therapeutic strategies that used in combination with conventional therapies could restore anti-tumor functions of Teff . At the same time, these inhibitors could disarm Tr1 cells by depriving them of the factors promoting their generation and activity or by down-regulating 3'5'-cAMP levels. Thus, the pharmacologic control of Treg-Teff interactions offers a novel strategy for restoration of anti-tumor Teff functions and silencing of Treg. Used in conjunction with anti-cancer drugs or with immune therapies, this strategy has a potential to improve therapeutic effects by preventing or reversing tumor-induced immune suppression.

Phenotypic and functional characteristics of CD4+ CD39+ FOXP3+ and CD4+ CD39+ FOXP3neg T-cell subsets in cancer patients

Human CD4(+) CD39(+) regulatory T (Treg) cells hydrolyze exogenous adenosine triphosphate (ATP) and participate in immunosuppressive adenosine production. They contain two T-cell subsets whose role in mediating suppression is not understood. Frequencies of both CD4(+) CD39(+) subsets were evaluated in peripheral blood lymphocytes of 57 cancer patients and in tumor infiltrating lymphocytes (TILs) of 6 patients. CD4(+) CD39(+) and CD4(+) CD39(neg) T cells isolated using immunobeads and cell sorting were cultured under various conditions. Their conversion into CD39(+) FOXP3(+) CD25(+) or CD39(+) FOX(neg) CD25(neg) cells was monitored by multiparameter flow cytometry. Hydrolysis of exogenous ATP was measured in luminescence assays. Two CD4(+) CD39(+) cell subsets differing in expression of CD25, FOXP3, CTLA-4, CD121a, PD-1, latency associated peptide (LAP), glycoprotein A repetitions predominant (GARP), and the cytokine profile accumulated with equal frequencies in the blood and tumor tissues of cancer patients. The frequency of both subsets was significantly increased in cancer. CD39 expression levels correlated with the subsets' ability to hydrolyze ATP. Conventional CD4(+) CD39(neg) T cells incubated with IL-2 + TGF-β expanded to generate CD4(+) CD39(+) FOXP3(+) Treg cells, while CD4(+) CD39(+) FOXP3(neg) CD25(neg) subset cells stimulated via the TCR and IL-2 converted to FOXP3(+) CTLA4(+) CD25(+) TGF-β-expressing Treg cells. Among CD4(+) CD39(+) Treg cells, the CD4(+) CD39(+) FOXP3(neg) CD25(neg) subset serves as a reservoir of cells able to convert to Treg cells upon activation by environmental signals.

Circulating regulatory T cells of cancer patients receiving radiochemotherapy may be useful to individualize cancer treatment

BACKGROUND AND PURPOSE

Dendritic cells (DCs) and regulatory T cells (Treg) play a major role in anti-tumor immune response of cancer patients. We investigated the effect of radiochemotherapy on patients' blood immune cells and their predictive value for tumor response.

MATERIALS AND METHODS

DCs and Treg of colorectal cancer (CRC) or breast cancer (BC) patients were examined through multicolor flow cytometry before the beginning and after the first week of radiochemotherapy (RCT). DCs were stained for BDCA1 and BDCA2, Treg were stained for CD4, CD25, CD127 and FoxP3. IL-2, IL-10 and TNF-α plasma levels of CRC patients were also determined. We examined the interrelationship between immune cell count alterations, applied dose values, cytokine plasma levels as well as histopathological parameters.

RESULTS

DCs were increased in BC and CRC patients compared to healthy control individuals (HC). CRC patients had higher levels of Treg (59.0%) compared to BC patients (31.3%) and HC (27.0%). Treg of CRC (58.7% vs. 41.3% p<0.001) but not BC patients (31.3% vs. 38.8%, p=0.164) decreased distinctly after the first week of radiation therapy. Applied dose values and decrease of Treg correlated positively (r=0.216, p=0.054). We also found a positive correlation of IL-10 plasma levels and Treg levels (r=0.748, p=0.021). CRC patients with favorable tumor stage (<ypT3a) have higher levels of Treg after 5 days of RCT (49.4% vs. 34.0%, p=0.043).

CONCLUSION

Higher Treg levels are associated with favorable tumor stage. We hypothesize that a dramatic decrease of Treg after in vivo irradiation may be a good indicator for necessary dose adjustments in radiation therapy of CRC patients.

Interleukin 10 in the tumor microenvironment: a target for anticancer immunotherapy

IL-10 is an immunomodulatory cytokine that is frequently upregulated in various types of cancer. The biological role of IL-10 in cancer is quite complex; however, the presence of IL-10 in advanced metastases and the positive correlation between serum IL-10 levels and progression of disease indicates a critical role of IL-10 in the tumor microenvironment. IL-10 has been shown to directly affect the function of antigen-presenting cells by inhibiting the expression of MHC and costimulatory molecules, which in turn induces immune suppression or tolerance. Additionally, IL-10 downregulates the expression of Th1 cytokines and induces T-regulatory responses. Taken together, a combination of IL-10 antagonism and immunostimulatory treatments such as cancer vaccines, Toll-like receptor agonists, Th1 cytokines, and chemokines would be a logical approach to enhance an antitumor immune response.

What are regulatory T cells (Treg) regulating in cancer and why?

The role regulatory T cells (Treg) play in cancer development and progression is not clear. Earlier evidence suggested that CD4(+)FOXP3(+)CD25(high) Treg accumulate in tumors and the peripheral blood of patients with cancer and through suppression of anti-tumor immune responses promote tumor growth. However, more recent data indicate that in certain cancers, such as colorectal carcinoma (CRC), Treg suppress bacteria-driven inflammation which promotes carcinogenesis and thus benefit the host. Treg appear to play a dual role in cancer. This might explain why the frequency and functions of Treg are associated with a poor prognosis in some cancers but with favorable outcome in others. The clinical and prognostic significance of Treg in cancer depends on environmental factors, including infectious agents, tumor-derived products and locally-produced cytokines, which shape the nature of immune responses, including Treg generation, recruitment and survival. Adaptive or inducible (i) Treg or Tr1 are the major subset(s) of Treg present in cancer. These iTreg are a distinct subset of regulatory cells that phenotypically and functionally differ from FOXP3(+) natural (n) Treg responsible for peripheral tolerance. They mediate powerful suppression of effector T cells via diverse mechanisms, produce immunosuppressive cytokines, notably TGF-β as well as prostaglandin E2 and adenosine, and are resistant to apoptosis or oncological therapies. Strategies for silencing of Tr1 in patients with cancer will require novel approaches that can selectively deplete these cells or block molecular pathways they utilize.

Ontak reduces the immunosuppressive tumor environment and enhances successful therapeutic vaccination in HER-2/neu-tolerant mice

Disrupting tumor-mediated mechanisms suppressing host immunity represents a novel approach to tumor immunotherapy. Depletion of regulatory T cells (Tregs) increases endogenous anti-tumor immunity and the efficacy of active immunotherapy in experimental tumor models. HLA-A2.1/HLA-DR1 (A2.1/DR1) × BALB- neuT+ (neuT+) triple transgenic mice represent an improvement over neuT+ mice for evaluating vaccination regimens to overcome tolerance against HER-2/neu. We questioned whether depletion of Tregs with Denileukin diftitox (Ontak) enhances the efficacy of a therapeutic vaccine consisting of HER-2(85-94) (p85) CTL and HER-2(776-790) (p776) Th peptides against the growth of TUBO.A2 transplantable tumor in male A2.1/DR1 × neuT+ Tg mice. While the therapeutic vaccine primed the tumor-reactive CD8+ CTLs and CD4+ effector T lymphocytes (Teffs) compartment, inducing activation, tumor infiltration, and tumor rejection or delay in tumor growth, treatment with Ontak 1 day prior to vaccination resulted in enhanced CD4+ and CD8+ T-cell-mediated vaccine-specific immune responses in the periphery. This was closely associated with greater infiltration and a striking change in the intratumor balance of Tregs and vaccine-specific CTLs/Teffs that directly correlated with markedly enhanced antitumor activity. The data suggest that Tregs control both CD4+ and CD8+ T-cell activity within the tumor, emphasize the importance of the intratumor ratio of vaccine-specific lymphocytes to Tregs, and demonstrate significant inversion of this ratio and correlation with tumor rejection during Ontak/vaccine immunotherapy.

Infiltrating lymphocytes and human papillomavirus-16--associated oropharyngeal cancer

OBJECTIVES/HYPOTHESIS

Human papillomavirus-16 (HPV-16)-associated carcinoma of the oropharynx has a favorable prognosis. Such patients have elevated CD8+ T-lymphocyte levels that correlate with response to chemotherapy and survival. Tumor-infiltrating lymphocyte (TIL) subpopulations were assessed in pretreatment biopsies from a prospective patient cohort to determine if TIL subsets differed by HPV status, clinical factors, or patient outcome or correlated with peripheral blood T-cell levels.

STUDY DESIGN

Retrospective immunological correlative study of patients entered in a prospective Phase 2 clinical trial.

METHODS

Measured were CD8, CD4, CD68, and Treg (FoxP3) lymphocytes by immunohistochemistry in a tissue microarray created from patients (n=46) with advanced oropharyngeal cancer. Correlations with peripheral blood levels, HPV status, expression of epidermal growth factor receptor (EGFR), clinical tumor, and patient characteristics and outcome were determined. Median follow-up was 6.6 years.

RESULTS

HPV-16-positive patients had improved survival (P=.016). Degree of T-cell infiltration did not differ by HPV status but was significantly related to disease-specific survival (DSS) and overall survival (OS). Even after adjusting for HPV status, we found that CD8, FoxP3, and total T cells were significantly associated with DSS (P=.0236, P=.0040, and P=.0197, respectively) and OS (P=.0137, P=.0158, and P=.0115, respectively). Less T-cell infiltration (P=.0130) and CD4 cells in particular (P=.0792) were associated with higher EGFR expression.

CONCLUSIONS

Improved outcomes are associated with increased TILs independent of HPV status and suggest the local immune response may be more related to factors such as tumor size, EGFR expression, or performance status than HPV status. Further study of larger numbers of patients and infiltrates combined with functional analysis of individual subsets may be necessary to detect significant differences in local immunity in HPV-16-related cancers.

A short course of neoadjuvant IRX-2 induces changes in peripheral blood lymphocyte subsets of patients with head and neck squamous cell carcinoma

OBJECTIVE

IRX-2, a primary cell-derived biologic with pleotropic immune activity, was shown to induce increased lymphocyte infiltrations into the tumor of patients with head and neck squamous cell cancer (HNSCC) after 10 days of neoadjuvant therapy (Berinstein et al. 2011). In the same patients enrolled in the Phase II study, peripheral blood lymphocyte subsets were monitored pre- and post-IRX-2 therapy to evaluate changes induced by IRX-2.

METHODS

Absolute lymphocyte numbers were determined in whole blood using the TetraONE System. Lymphocytes were further separated on Ficoll-Hypaque gradients and evaluated by multiparameter flow cytometry. Lymphocyte numbers, including regulatory T cells (Treg) and naïve, memory and effector T cells, were compared in pre- and post-therapy specimens.

RESULTS

Total lymphocyte numbers remained unchanged after IRX-2 therapy. Significant changes occurred in numbers of circulating B cells and NKT cells, which decreased following IRX-2 therapy. The frequency of circulating Treg (CD4(+)CD25(high)) remained unaltered (e.g., 6.7 ± 0.6% vs. 7.5 ± 0.8%; means ± SEM) as was the CD8(+)/Treg ratio (6.6 before and 6.7 after IRX-2 therapy). The mean absolute number of CD3(+)CD45RA(+)CCR7(+) (naïve) T cells was decreased after IRX-2 therapy but numbers of total memory (i.e., central and peripheral) and terminally differentiated T cells were unchanged.

CONCLUSIONS

IRX-2-mediated reductions in B and NKT cell numbers in the blood suggest a redistribution of these cells to tissues. A decrease in naïve T cells implies their up-regulated differentiation to memory T cells. Unchanged Treg numbers after IRX-2 therapy indicate that IRX-2 does not expand this compartment, potentially benefiting anti-tumor immune responses.

A gynecologic oncology group phase II trial of two p53 peptide vaccine approaches: subcutaneous injection and intravenous pulsed dendritic cells in high recurrence risk ovarian cancer patients

PURPOSE

Peptide antigens have been administered by different approaches as cancer vaccine therapy, including direct injection or pulsed onto dendritic cells; however, the optimal delivery method is still debatable. In this study, we describe the immune response elicited by two vaccine approaches using the wild-type (wt) p53 vaccine.

EXPERIMENTAL DESIGN

Twenty-one HLA-A2.1 patients with stage III, IV, or recurrent ovarian cancer overexpressing the p53 protein with no evidence of disease were treated in two cohorts. Arm A received SC wt p53:264-272 peptide admixed with Montanide and GM-CSF. Arm B received wt p53:264-272 peptide-pulsed dendritic cells IV. Interleukin-2 (IL-2) was administered to both cohorts in alternative cycles.

RESULTS

Nine of 13 patients (69%) in arm A and 5 of 6 patients (83%) in arm B developed an immunologic response as determined by ELISPOT and tetramer assays. The vaccine caused no serious systemic side effects. IL-2 administration resulted in grade 3 and 4 toxicities in both arms and directly induced the expansion of T regulatory cells. The median overall survival was 40.8 and 29.6 months for arm A and B, respectively; the median progression-free survival was 4.2 and. 8.7 months, respectively.

CONCLUSION

We found that using either vaccination approach generates comparable specific immune responses against the p53 peptide with minimal toxicity. Accordingly, our findings suggest that the use of less demanding SC approach may be as effective. Furthermore, the use of low-dose SC IL-2 as an adjuvant might have interfered with the immune response. Therefore, it may not be needed in future trials.

IRX-2, a novel biologic, favors the expansion of T effector over T regulatory cells in a human tumor microenvironment model

IRX-2, a natural cytokine biological with multiple components, has been used in preclinical and clinical studies to promote antitumor activity of T lymphocytes. To define cellular mechanisms responsible for antitumor effects of IRX-2, its ability to induce effector T cells (Teff) was examined in a model simulating the tumor microenvironment. An in vitro model containing conventional CD4⁺CD25⁻ cells co-cultured with autologous immature dendritic cells, irradiated tumor cells, and cytokines was used to study differentiation and expansion of regulatory T cells (Treg) and Teff in the presence and absence of IRX-2. Phenotype, suppressor function, signaling, and cytokine production were serially measured using flow cytometry, Western blots, CFSE-based suppressor assays, and Luminex-based analyses. The presence of IRX-2 in the co-cultures promoted the induction and expansion of IFN-γ⁺Tbet⁺ Teff and significantly (p < 0.01) decreased the induction of inducible IL-10⁺TGF-β⁺ Treg. The responsible mechanism involved IFN-γ-driven T cell polarization towards Teff and suppression of Treg differentiation. In an in vitro model simulating the human tumor microenvironment, IRX-2 promoted Teff expansion and antitumor activity without inducing Treg. Thus, IRX-2 could be considered as a promising component of future antitumor therapies.

Targeting human inducible regulatory T cells (Tr1) in patients with cancer: blocking of adenosine-prostaglandin E₂ cooperation

INTRODUCTION

Emerging data suggest that human inducible regulatory T cells (Tr1) produce adenosine and prostaglandin E(2) and that these factors cooperate in mediating immune suppression.

AREAS COVERED

Human Tr1 present in human tumors or blood of cancer patients express ectonucleotidases, CD39 and/or CD73, hydrolyze ATP to adenosine and are COX-2 positive. Expression of CD39 and/or CD73 on human tumors favors expansion and suppressor functions of Tr1. Adenosine and PGE(2) signal via adenosine 2A receptor (A(2A)R) and prostaglandin E(2) receptor 2 (EP(2)R) expressed on effector T (Teff) cells, suppressing their anti-tumor functions by a common mechanism involving upregulation of cytosolic cAMP levels and protein kinase A (PKA) type I activation. The frequency and activity of circulating CD4(+)CD39(+) and CD4(+)COX-2(+) Treg subsets increase in advanced disease and also following oncologic therapies.

EXPERT OPINION

Pharmacologic blocking of adenosine-PGE(2) collaboration provides a clinically-feasible strategy for disarming of Treg. Used in conjunction with conventional anti-cancer drugs or immune interventions, pharmacologic inhibitors could improve outcome of oncologic therapies.

[Expression of Foxp3 and RORgamma t in peripheral blood mononuclear cells in patients with laryngeal carcinoma as indicators of tumor stage--preliminary study]

INTRODUCTION

The degree of activation of cells involved in cellular immune response against tumor antigens (cytotoxic lymphocytes Tc) as well as efficiency of the mechanisms which promote immunosuppression (Treg - regulatory cells CD4(+)CD25(+)Foxp3(+)) may determine the course of the neoplastic disease. The aim of this study was to assess the function of autologous peripheral blood mononuclear cells (PBMCs) involved in the immunological processes on the basis of expression of Foxp3 and RORgamma t molecules as well as analysis of the relationships with clinical and morphological features of the tumor (pT and pN stage, G feature, degree of invasiveness according to the TFG classification) in laryngeal carcinoma.

MATERIAL AND METHODS

The analysis included a group of 59 patients with verified squamous cell carcinoma of the larynx. In the pathologic evaluation pTNM classification criteria, depth of invasion and degree of histological differentiation were used. Expression levels of mRNA for Foxp3 and RORgamma t in peripheral blood mononuclear cells by quantitative analysis of the amplified product in real time (real-time RT(2)-PCR) were evaluated. The level of Foxp3 and RORgamma t protein expression by Western blot analysis was determined.

RESULTS

In squamous cell carcinomas of the larynx, with the highest tumor aggressiveness the significantly highest level of mRNA and protein expression for Foxp3 molecule were observed. The severity of Foxp3 expression at both gene and protein level were positively linearly correlated with the degree of local extent of the tumor (pT3-4), depth of invasion (invasion of cartilage) and the degree of histological differentiation (low-differentiated tumors G3). In the study group of laryngeal cancers significantly lower level of RORgamma t expression in carcinomas with less invasive changes (pT1-2, high-differentiated tumors G1, carcinomas with microinvasion without evidence of invasion beyond the lamina propria) was also noted.

CONCLUSIONS

The study results indicate the important role of immune cell activity as indicators of advancement of clinical and morphological changes in squamous cell carcinoma of the larynx.

Serum IL10 and circulating CD4(+) CD25(high) regulatory T cell numbers as predictors of clinical outcome and survival in patients with head and neck squamous cell carcinoma

BACKGROUND

Patients with head and neck squamous cell carcinoma (HNSCC) commonly have an imbalance in T helper (Th)1/Th2-type cytokines and elevated levels of CD4(+) CD25(high) regulatory T cells (Treg). Here, we investigated the association of circulating interleukin (IL)10, IL12, and Treg-cells with clinical outcome in patients with HNSCC.

METHODS

Serum cytokine levels were determined by enzyme-linked immunosorbent assay (ELISA) in patients' pretreatment (n = 107) and 4 to 6 weeks posttreatment (n = 43), and in nontumor controls (n = 40). Treg-cell levels were determined by flow cytometry.

RESULTS

IL10 detectability was significantly higher in patients than controls (p = .001). Pretreatment IL10 levels in all anatomical subsites, except the oral cavity, were significantly elevated in stages III/IV, N+ patients, and in T3/4-tumors (p = .005, .037, and .001, respectively). The detectability of IL10 significantly correlated with poorer survival after a maximum follow-up of 36 months. Treg-cell levels did not correlate with any clinical parameters.

CONCLUSION

IL10 is a potential independent factor in predicting a poor clinical outcome in newly presenting tumors of laryngeal and pharyngeal origin. The role of circulating Treg-cells as predictors of clinical outcome requires further investigation.

Mechanisms of tumor escape from the immune system: adenosine-producing Treg, exosomes and tumor-associated TLRs

Human tumors utilize many different mechanisms of immunosuppression to prevent immune cells from exercising their antitumor activities. These mechanisms, which enable the tumor to escape from the host immune system and to progress, are being intensively investigated in hope of finding therapeutically safe and effective inhibitors able to counteract tumor-induced immunosuppression. Three of more recently discovered tumor-related suppression mechanisms, i.e. accumulations of adenosine-producing regulatory T-cells (Treg) in the tumor microenvironment, release by tumors of suppressive microvesicles (TMV) and expression of toll-like receptors (TLR) on the tumor cell surface, are described in this review. All contribute in a varying degree to creating a milieu favorable for the tumor and unfavorable for immune effector cells. Tumor escape has been a major problem in cancer immunotherapy and it has been held responsible for the failure of many immune interventions in cancer. For this reason, it is important to study and understand the various suppressive pathways human tumors utilize. Future antitumor immunotherapies are likely to include inhibitors of tumor-induced suppression with the goal of restoring antitumor immune responses in patients with cancer.

Dendritic cell generation and CD4+ CD25high FOXP3+ regulatory t cells in human head and neck carcinoma during radio-chemotherapy

Background

Regulatory T cells (Treg) and dendritic cells (DC) play an important role in tumor immunity and immune escape. However, their interplay and the effects of anti-cancer therapy on the human immune system are largely unknown.

Methods

For DC generation, CD14⁺ monocytes were enriched by immunomagnetic selection from peripheral blood of advanced head and neck squamous cell carcinoma (HNSCC) patients and differentiated into immature DC using GM-SCF and IL-4. DC maturation was induced by addition of TNFα. The frequency of CD4⁺CD25^highF0XP3⁺ Treg in HNSCC patients was analyzed before and after radio-chemotherapy (RCT) by four-color flow cytometry.

Results

In HNSCC patients, the frequency of Treg (0.33 ± 0.06%) was significantly (p = 0.001) increased compared to healthy controls (0.11 ± 0.02%), whereas RCT had variable effects on the Treg frequency inducing its increase in some patients and decrease in others. After six days in culture, monocytes of all patients had differentiated into immature DC. However, DC maturation indicated by CD83 up-regulation (70.7 ± 5.5%) was successful only in a subgroup of patients and correlated well with lower frequencies of peripheral blood Treg in those patients.

Conclusion

The frequency of regulatory T cells is elevated in HNSCC patients and may be modulated by RCT. Monocyte-derived DC in HNSCC patients show a maturation deficiency ex vivo. Those preliminary data may have an impact on multimodality clinical trials integrating cellular immune modulation in patients with advanced HNSCC.

Frequency of CD45RO+ subset in CD4+CD25(high) regulatory T cells associated with progression of hepatocellular carcinoma

The purpose of this study was to assess the properties of CD4+CD25(high/low/negative) T cell subsets and analyze their relation with dendritic cells (DCs) in patients with hepatocellular carcinoma (HCC). In HCC patients, the prevalence of CD45RO+ cells in CD4+CD25(high) T cells was increased and associated with higher frequencies of plasmacytoid DCs. Larger proportions of this T cell subset were detected in the patients with larger tumor burdens. These results suggest that increased frequencies of the CD45RO+ subset in CD4+CD25(high) Tregs in HCC patients may establish the immunosuppressive environment cooperatively with tolerogenic plasmacytoid DCs to promote disease progression of liver cancer.

Separation of human CD4+CD39+ T cells by magnetic beads reveals two phenotypically and functionally different subsets

OBJECTIVE

The ectonucleotidase CD39 is an enzyme involved in adenosine production. Its surface expression on human regulatory T cells (Treg) allows for their flow-cytometry-based isolation from peripheral blood. To further develop and improve this method on a scale supporting translational studies, we introduced capture of CD39(+) Treg on magnetic immunobeads.

METHODS

Peripheral blood mononuclear cells (PBMC) obtained from healthy donors were used for negative selection of CD4(+) T cells on AutoMACS using antibodies (Abs) specific for all lineage(+) cells. CD4(+)CD39(+) Treg were captured by biotin-conjugated anti-CD39 Abs and anti-biotin Ab-coated magnetic beads. Isolated CD4(+)CD39(+) T cells were phenotyped by flow cytometry for Treg-associated markers: CD39, CD73, FOXP3, CD25, CTLA-4, CCR4, CD45RO and CD121a or for the absence of CD127 and CD49d. CFSE-based proliferation assays and ATP hydrolysis were used to measure Treg functions.

RESULTS

The purity, recovery and viability of the separated CD4(+)CD39(+) T cells were satisfactory. The isolated CD4(+)CD39(+) T cell population consisted of FOXP3(+)CD25(+) T cells which hydrolyzed exogenous ATP and suppressed autologous CD4(+) T cell proliferation and of FOXP3(neg)CD25(neg) T cells without suppressor function. The same two subsets were detectable by flow cytometry in normal PBMC, gating on CD4(+)CD39(+), CD4(+)CD127(neg), CD4(+)CD49d(neg) or CD4(+)CD25(high) Treg.

CONCLUSION

CD4(+)CD39(+) Treg capture on immunobeads led to a discovery of two CD39(+) subsets. Similar to CD39(+) Treg in the peripheral blood, half of these cells are CD25(+)FOXP3(+) active suppressor cells, while the other half are CD25(neg)FOXP3(neg) and do not mediate suppression.

Immune suppression in head and neck cancers: a review

Head and neck squamous cell carcinomas (HNSCCs) are the sixth most common cancer in the world. Despite significant advances in the treatment modalities involving surgery, radiotherapy, and concomitant chemoradiotherapy, the 5-year survival rate remained below 50% for the past 30 years. The worse prognosis of these cancers must certainly be link to the fact that HNSCCs strongly influence the host immune system. We present a critical review of our understanding of the HNSCC escape to the antitumor immune response such as a downregulation of HLA class I and/or components of APM. Antitumor responses of HNSCC patients are compromised in the presence of functional defects or apoptosis of T-cells, both circulating and tumor-infiltrating. Langerhans cells are increased in the first steps of the carcinogenesis but decreased in invasive carcinomas. The accumulation of macrophages in the peritumoral areas seems to play a protumoral role by secreting VEGF and stimulating the neoangiogenesis.

Elevated frequencies of CD4⁺ CD25⁺ CD127lo regulatory T cells is associated to poor prognosis in patients with acute myeloid leukemia

Regulatory T cells (Treg) mediate amelioration of disease and immune homeostasis by inhibiting immune activation and maintaining peripheral immune tolerance. The suppressive mechanisms and clinical significance of Treg have not been completely elucidated in patients with acute myeloid leukemia (AML). Here, we demonstrated that CD127 in combination with CD4 and CD25 can identify FoxP3(+) Treg in peripheral blood (PB) and bone marrow (BM) using multicolor flow cytometry. We showed that the CD4(+) CD25(+) CD127(lo) Treg frequencies were significantly increased and their phenotypes were different in PB from newly diagnosed AML patients compared to those from healthy volunteers (HVs). Moreover, the Treg frequencies were significantly higher in BM than those from PB in the same patients. The Treg frequencies were reduced when patients achieved complete remission (CR) and were increased when patients relapsed. The Treg frequencies at diagnosis in PB and BM of patients who had achieved CR were lower than those of patients who had persistent leukemia or died, respectively. CD4(+) CD25(+) Treg were isolated by magnetic-activated cell sorting and tested for suppressive functions in coculture with allogeneic carboxyfluorescein diacetate succinimidylester-labeled CD4(+) CD25(-) responder cells. Suppression mediated by Treg was higher in AML patients compared to HVs. No significant differences were observed in the cytokines production of Treg, including interferon-gamma (IFN-γ), interleukin (IL)-4,IL-2 and IL-10, between patients with AML and HVs. Our study suggests that Treg may play a role in the pathogenesis of AML, and sequential measurements of Treg frequency may have clinical value in the evaluation of therapeutic effects and clinical outcome.

A tritherapy combination of a fusion protein vaccine with immune-modulating doses of sequential chemotherapies in an optimized regimen completely eradicates large tumors in mice

Tumor-induced immunosuppression plays a critical role in both impeding tumor-specific immune responses and limiting the effects of cancer immunotherapy. Analyses of regulatory cells recruited during the growth of the E7-expressing tumor, TC-1, revealed a high percentage of regulatory T cells (Tregs) as well as myeloid-derived suppressor cells (MDSCs) in spleens and tumors. In this study, we proposed that treatment with immune-modulating doses of cyclophosphamide (CTX) and all-trans retinoic acid (ATRA) would result in a beneficial tumor microenvironment with the suppression of Tregs and MDSCs and, thus, enhance the effect of a human papillomavirus protein vaccine. Our results showed that CTX preconditioning and persistent ATRA treatment along with the vaccine achieved long-term survival and induced long-term memory responses. However, the effect of the antitumor response sharply declined when the tritherapy was initiated after the optimal therapeutic time. The more intensive regimen could rescue the effect of the tritherapy accompanied by the decreased percentage of Tregs and MDSCs in spleens and tumors. Besides, a favorable host environment was created by the reduced secretion of interleukin-10 and 6 and vascular endothelial growth factor (VEGF) in the tumor niche and decreased the expression of phosphorylation-signal transducer and activator of transcription 3 of TC-1 tumors. Our data shed light on the immune-modulating doses of sequential chemoimmunotherapeutic strategy targeting not only the tumor but also its microenvironment, which suggests a potential clinical benefit for the immunotherapy of HPV-associated malignancies.

[Prophylactic and therapeutic vaccines against human papilloma virus]

Infection with human papilloma virus (HPV) has been identified as the cause of recurrent papillomatosis and of a subgroup of squamous cell carcinomas of the head and neck. A change in prevalence of these lesions, especially for oropharyngeal carcinoma, can be expected as a consequence of the introduction of prophylactic HPV vaccines for young women, targeting the most frequent high- and low-risk HPV subtypes. Vaccination for the major low-risk HPV types has proven to be highly effective against genital warts and activity against papillomatosis can be expected. The possibilities of prophylactic HPV vaccination as well as new developments and the rationale for therapeutic vaccines are discussed on the basis of the current literature.

T cell-tumor interaction directs the development of immunotherapies in head and neck cancer

The competent immune system controls disease effectively due to induction, function, and regulation of effector lymphocytes. Immunosurveillance is exerted mostly by cytotoxic T-lymphocytes (CTLs) while specific immune suppression is associated with tumor malignancy and progression. In squamous cell carcinoma of the head and neck, the presence, activity, but also suppression of tumor-specific CTL have been demonstrated. Functional CTL may exert a selection pressure on the tumor cells that consecutively escape by a combination of molecular and cellular evasion mechanisms. Certain of these mechanisms target antitumor effector cells directly or indirectly by affecting cells that regulate CTL function. This results in the dysfunction or apoptosis of lymphocytes and dysregulated lymphocyte homeostasis. Another important tumor-escape mechanism is to avoid recognition by dysregulation of antigen processing and presentation. Thus, both induction of functional CTL and susceptibility of the tumor and its microenvironment to become T cell targets should be considered in CTL-based immunotherapy.

Better understanding tumor-host interaction in head and neck cancer to improve the design and development of immunotherapeutic strategies

Head and neck cancers are heavily infiltrated by immune cells, the significance of which is complex. The natural immune response against head and neck tumors, including anti-human papillomavirus (HPV) T cells, and humoral responses has been clearly documented. However, during the course of tumor progression, co-option of the immune system by tumor cells for their own advantage and increased resistance of tumor cells to immune attack also occur. Inflammation and immune subversion to support angiogenesis are key factors promoting tumor growth. Only a better understanding of this tumor-host interaction will permit a rational design of new immunotherapeutic approaches combining immunostimulation with drugs endowed with the ability to counteract immunoevasion mechanisms.

Regulation of tumor immunity by tumor/dendritic cell fusions

The goal of cancer vaccines is to induce antitumor immunity that ultimately will reduce tumor burden in tumor environment. Several strategies involving dendritic cells- (DCs)- based vaccine incorporating different tumor-associated antigens to induce antitumor immune responses against tumors have been tested in clinical trials worldwide. Although DCs-based vaccine such as fusions of whole tumor cells and DCs has been proven to be clinically safe and is efficient to enhance antitumor immune responses for inducing effective immune response and for breaking T-cell tolerance to tumor-associated antigens (TAAs), only a limited success has occurred in clinical trials. This paper reviews tumor immune escape and current strategies employed in the field of tumor/DC fusions vaccine aimed at enhancing activation of TAAs-specific cytotoxic T cells in tumor microenvironment.

Correlation between gp96 expression and the surgical outcome in patients with esophageal squamous cell carcinoma

BACKGROUND

Heat-shock protein gp96 plays an important role in antitumor immunoreactions. Gp96 has a close relationship with antitumor immunity. This study evaluated the correlation between gp96 expression and the prognosis in esophageal squamous cell carcinoma.

METHODS

Seventy-eight patients with primarily resected esophageal squamous cell carcinoma were enrolled onto this study, and gp96 expression was evaluated by immunohistochemical staining. The association of clinicopathological factors and patients' survival was calculated by univariate (log rank test) and multivariate (Cox proportional hazard regression method) analyses.

RESULTS

Fifty-seven (73%) of 78 cases were gp96 positive, and 21 were negative (27%). The survival of patients with gp96-negative disease was significantly shorter (5-year survival, 22.9 months) than with gp96-positive disease (45.8 months; P = 0.049), and the multivariate analysis showed that gp96 negativity is an independent risk factor for poor survival (hazard ratio, 2.577; P = 0.040). Gp96-negative cases had more metastatic lymph nodes than did negative cases, especially in T1 cases (4.8 in gp96-negative cases vs. 0.84 in gp96-positive cases; P = 0.064)

CONCLUSIONS

The downregulation of gp96 expression is closely correlated with poor survival in esophageal squamous cell carcinoma.

Tumor-derived microvesicles induce, expand and up-regulate biological activities of human regulatory T cells (Treg)

BACKGROUND

Tumor-derived microvesicles (TMV) or exosomes are present in body fluids of patients with cancer and might be involved in tumor progression. The frequency and suppressor functions of peripheral blood CD4(+)CD25(high)FOXP3(+) Treg are higher in patients with cancer than normal controls. The hypothesis is tested that TMV contribute to induction/expansion/and activation of human Treg.

METHODOLOGY/PRINCIPAL FINDINGS

TMV isolated from supernatants of tumor cells but not normal cells induced the generation and enhanced expansion of human Treg. TMV also mediated conversion of CD4(+)CD25(neg) T cells into CD4(+)CD25(high)FOXP3(+) Treg. Upon co-incubation with TMV, Treg showed an increased FasL, IL-10, TGF-beta1, CTLA-4, granzyme B and perforin expression (p<0.05) and mediated stronger suppression of responder cell (RC) proliferation (p<0.01). Purified Treg were resistant to TMV-mediated apoptosis relative to other T cells. TMV also increased phospho-SMAD2/3 and phospho-STAT3 expression in Treg. Neutralizing Abs specific for TGF-beta1 and/or IL-10 significantly inhibited TMV ability to expand Treg.

CONCLUSIONS/SIGNIFICANCE

This study suggests that TMV have immunoregulatory properties. They induce Treg, promote Treg expansion, up-regulate Treg suppressor function and enhance Treg resistance to apoptosis. Interactions of TMV with Treg represent a newly-defined mechanism that might be involved in regulating peripheral tolerance by tumors and in supporting immune evasion of human cancers.

Adenosine and prostaglandin E2 cooperate in the suppression of immune responses mediated by adaptive regulatory T cells

Adaptive regulatory T cells (Tr1) are induced in the periphery upon encountering cognate antigens. In cancer, their frequency is increased; however, Tr1-mediated suppression mechanisms are not yet defined. Here, we evaluate the simultaneous involvement of ectonucleotidases (CD39/CD73) and cyclooxygenase 2 (COX-2) in Tr1-mediated suppression. Human Tr1 cells were generated from peripheral blood mononuclear cell-derived, sorted CD4(+)CD25(-) T cells and incubated with autologous immature dendritic cells, irradiated COX-2(+) or COX-2(-) tumor cells, and IL-2, IL-10, and IL-15 (each at 10-15 IU/ml) for 10 days as described (Bergmann, C., Strauss, L., Zeidler, R., Lang, S., and Whiteside, T. L. (2007) Cancer Immunol. Immunother. 56, 1429-1442). Tr1 were phenotyped by multicolor flow cytometry, and suppression of proliferating responder cells was assessed in carboxyfluorescein diacetate succinimidyl ester-based assays. ATP hydrolysis was measured using a luciferase detection assay, and levels of adenosine or prostaglandin E(2) (PGE(2)) in cell supernatants were analyzed by mass spectrometry or ELISA, respectively. Intracellular cAMP levels were measured by enzyme immunoassay. The COX-2(+) tumor induced a greater number of Tr1 than COX-2(-) tumor (p < 0.05). Tr1 induced by COX-2(+) tumor were more suppressive, hydrolyzed more exogenous ATP (p < 0.05), and produced higher levels of adenosine and PGE(2) (p < 0.05) than Tr1 induced by COX-2(-) tumor. Inhibitors of ectonucleotidase activity, A(2A) and EP(2) receptor antagonists, or an inhibitor of the PKA type I decreased Tr1-mediated suppression (p < 0.05), whereas rolipram, a PDE(4) inhibitor, increased the intracellular cAMP level in responder cells and their susceptibility to Tr1-mediated suppression. Tr1 present in tumors or the peripheral blood of head and neck squamous cell carcinoma patients co-expressed COX-2, CD39, and CD73. A concomitant inhibition of PGE(2) and adenosine via the common intracellular cAMP pathway might be a novel approach for improving results of immune therapies for cancer.

Selective depletion of CD4+CD25+Foxp3+ regulatory T cells by low-dose cyclophosphamide is explained by reduced intracellular ATP levels

CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells have been shown to play important roles in mediating cancer development. Although cyclophosphamide (CY) has shown promise as a drug to selectively target Treg cells with low-dose in vivo, the underlying molecular mechanism remains unclear. In this report, we provide evidence that ATP, the energy molecule and signal element, accounts for the selective depletion of Treg cells by low-dose CY. Relative to conventional T cells or other cell types, ATP levels were much lower in Treg cells. This was due to Treg cells that downregulate one microRNA, miR-142-3p, and upregulate ecto-nucleoside triphosphate diphosphohydrolase CD39. The transfection of miR-142-3p or the blockade of CD39 could increase intracellular ATP levels of Treg cells, consequently decreasing the sensitivity of Treg cells to low-dose CY. On the other hand, the transfection of miR-142-3p inhibitor or the addition of soluble CD39 to the cultured CD4(+)CD25(-) T cells resulted in the decrease of intracellular ATP levels and increase of sensitivity of conventional T cells to low-dose CY. Furthermore, we found that the low levels of ATP attenuated the synthesis of glutathione, leading to the decrease of CY detoxification, thus increasing the sensitivity of Treg cells to low-dose CY. Therefore, we here identify a molecular pathway through which low-dose CY selectively ablates Treg cells. Our findings also imply that low levels of ATP are probably related to Treg cell function.

Identification and characterization of a HER-2/neu epitope as a potential target for cancer immunotherapy

Our aim is to develop peptide vaccines that stimulate tumor antigen-specific T-lymphocyte responses against frequently detected cancers. We describe herein a novel HLA-A*0201-restricted epitope, encompassing amino acids 828-836 (residues QIAKGMSYL), which is naturally presented by various HER-2/neu (+) tumor cell lines. HER-2/neu(828-836), [HER-2(9(828))], possesses two anchor residues and stabilized HLA-A*0201 on T2 cells in a concentration-dependent Class I binding assay. This peptide was stable for 3.5 h in an off-kinetic assay. HER-2(9(828)) was found to be immunogenic in HLA-A*0201 transgenic (HHD) mice inducing peptide-specific and functionally potent CTL and long-lasting anti-tumor immunity. Most important, using HLA-A*0201 pentamer analysis we could detect increased ex vivo frequencies of CD8(+) T-lymphocytes specifically recognizing HER-2(9(828)) in 8 out of 20 HLA-A*0201(+) HER-2/neu (+) breast cancer patients. Moreover, HER-2(9(828))-specific human CTL recognized the tumor cell line SKOV3.A2 as well as the primary RS.A2.1.DR1 tumor cell line both expressing HER-2/neu and HLA-A*0201. Finally, therapeutic vaccination with HER-2(9(828)) in HHD mice was proven effective against established transplantable ALC.A2.1.HER tumors, inducing complete tumor regression in 50% of mice. Our data encourage further exploitation of HER-2(9(828)) as a promising candidate for peptide-based cancer vaccines.

Tumor vaccines in 2010: need for integration

Induction of tumor-specific immunity is an attractive approach to cancer therapy, however to date every major pivotal trial has resulted in failure. While the phenomena of tumor-mediated immune suppression has been known for decades, only recently have specific molecular pathways been elucidated, and for the first time, rationale means of intervening and observing results of intervention have been developed. In this review we describe major advances in our understanding of tumor escape from immunological pressure and provide some possible therapeutic scenarios for enhancement of efficacy in future cancer vaccine trials.

Reciprocal granzyme/perforin-mediated death of human regulatory and responder T cells is regulated by interleukin-2 (IL-2)

Human CD4(+)CD25(high)FOXP3(+) T regulatory cells (Treg) can suppress responder T cell (RC) functions by various mechanisms. In co-cultures of Treg and autologous activated RC, both cell subsets up-regulate the expression of granzymes and perforin, which might contribute to Treg-mediated suppression. Here, we investigate the sensitivity and resistance of Treg and RC to granzyme/perforin-mediated death. CD4(+)CD25(neg) RC were single cell-sorted from the peripheral blood of 25 cancer patients and 15 normal controls. These RC were carboxyfluorescein diacetate succinimidyl ester (CFSE) labeled and co-cultured with autologous CD4(+)CD25(high)FOXP3(+) Treg +/- 150 or +/-1,000 IU/mL of interleukin-2 (IL-2) to evaluate suppression of RC proliferation. In addition, survival of the cells co-cultured for 24 h and 5 days was measured using a flow-based cytotoxicity assay. Freshly isolated Treg and RC expressed granzyme A (GrA), granzyme B (GrB), and perforin. Percentages of positive cells were higher in cancer patients than controls (p < 0.01) and increased upon OKT3 and IL-2 stimulation. Treg, co-cultured with RC at 150 IU/mL of IL-2, no longer expressed cytotoxins and became susceptible to RC-mediated, granzyme/perforin-dependent death. However, in co-cultures with 1,000 IU/mL of IL-2, Treg became resistant to apoptosis and induced GrB-dependent, perforin-independent death of RC. When the GrB inhibitor I or GrB-specific and GrA-specific small inhibitory ribonucleic acids were used to block the granzyme pathway in Treg, RC death, and Treg-mediated suppression of RC, proliferation were significantly inhibited. Human CD4(+)CD25(high) Treg and CD4(+)CD25(neg) RC reciprocally regulate death/growth arrest by differentially utilizing the granzyme-perforin pathway depending on IL-2 concentrations.

The role of regulatory T cells in cancer

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

Elevated expression of Foxp3 in tumor-infiltrating Treg cells suppresses T-cell proliferation and contributes to gastric cancer progression in a COX-2-dependent manner

The transcription factor Foxp3 plays a key role in CD4(+)CD25(+) regulatory T (Treg) cell function. A correlation has been shown between survival and the frequency of tumor-infiltrating Foxp3-positive Treg cells in cancer patients. However, few studies have characterized the regulation of Foxp3 expression and function in Treg cells, which are known to comprise distinct subsets, with different roles in the complex tumor microenvironment. Here, we show that significantly more Foxp3-positive Treg cells accumulated in gastric tumors. In addition, we found increased expression of Foxp3 protein per cell in tumor-infiltrating Treg cells. Moreover, elevated Foxp3 expression in tumor-infiltrating Treg cells was associated with the TNM stage in gastric cancer patients. Importantly, further investigation within the tumor microenvironment showed that expression of Foxp3 in Treg cells correlated with expression of cyclooxygenase-2 (COX-2) and prostaglandin E(2) (PGE(2)). Furthermore, Treg cells with higher levels of Foxp3 were able to suppress the proliferation of autologous CD4(+)CD25(-) T cells. The suppression of the effector T-cell response was reversed by COX inhibitors and PGE(2) receptor-specific antagonists. Our data demonstrate a mechanism by which tumor-infiltrating Treg cells with increased Foxp3 expression can mediate immune suppression via COX-2/PGE(2) production in the gastric cancer microenvironment. Thus, we provide new insights into overcoming regulatory T-cell activity, which may be beneficial for the treatment of human gastric cancer.

Generation and accumulation of immunosuppressive adenosine by human CD4+CD25highFOXP3+ regulatory T cells

Naturally occurring regulatory T cells (nTreg) are crucial for maintaining tolerance to self and thus preventing autoimmune diseases and allograft rejections. In cancer, Treg down-regulate antitumor responses by several distinct mechanisms. This study analyzes the role the adenosinergic pathway plays in suppressive activities of human nTreg. Human CD4(+)CD25(high)FOXP3(+) Treg overexpress CD39 and CD73, ectonucleotidases sequentially converting ATP into AMP and adenosine, which then binds to A(2a) receptors on effector T cells, suppressing their functions. CD4(+)CD39(+) and CD4(+)CD25(high) T cells express low levels of adenosine deaminase (ADA), the enzyme responsible for adenosine breakdown, and of CD26, a surface-bound glycoprotein associated with ADA. In contrast, T effector cells are enriched in CD26/ADA but express low levels of CD39 and CD73. Inhibitors of ectonucleotidase activity (e.g. ARL67156) and antagonists of the A(2a) receptor (e.g. ZM241385) blocked Treg-mediated immunosuppression. The inhibition of ADA activity on effector T cells enhanced Treg-mediated immunosuppression. Thus, human nTreg characterized by the presence of CD39 and the low expression of CD26/ADA are responsible for the generation of adenosine, which plays a major role in Treg-mediated immunosuppression. The data suggest that the adenosinergic pathway represents a potential therapeutic target for regulation of immunosuppression in a broad variety of human diseases.

Increased ectonucleotidase expression and activity in regulatory T cells of patients with head and neck cancer

PURPOSE

Regulatory T cell (Treg) frequency and activity are increased in cancer patients and play a major role in tumor escape. Although disease progression is favored by the presence of Treg, mechanisms used by Treg to suppress antitumor immunity are unknown. The ectonucleotidases CD39 and CD73 are expressed in Treg and convert ATP into immunosuppressive adenosine. In this study, the involvement of the adenosinergic pathway in Treg-mediated suppression in head and neck squamous cell carcinoma (HNSCC) patients was evaluated.

EXPERIMENTAL DESIGN

HNSCC patients with an active disease (n = 19) and patients with no evident disease after therapy (n = 14) were studied. Ectonucleotidase expression on CD4(+) T cells and CD4(+)CD25(high) Treg was evaluated by flow cytometry and compared with normal controls. Ectonucleotidase activity was also compared within these three groups. The data were analyzed for associations of ectonucleotidase expression/function with disease stage.

RESULTS

The percentages and expression levels of CD39 and CD73 in CD4(+) T cells and Treg were greater in HNSCC than in normal controls and highest in patients with no evident disease. Patients' Treg hydrolyzed ATP at higher rates and produced higher levels of adenosine than normal controls' Treg. The increased frequency and enzymatic activity of CD4(+)CD39(+) cells corresponded to increased adenosine-mediated suppression of effector T cells, which was partly inhibited by ARL67156, an ectonucleotidase inhibitor, and by ZM241385, a selective A(2a)/A(2b) receptor antagonist.

CONCLUSIONS

CD39(+) Treg frequency and adenosine-mediated suppression are significantly increased in HNSCC patients. The adenosinergic pathway is involved in Treg-mediated immunosuppression in cancer and its attenuation could be a promising immunotherapeutic strategy for patients with HNSCC.

[Head and neck squamous cell carcinoma: What's new in 2009]

Classical epidermoid carcinoma is the most frequent head and neck malignant neoplasm. Some particular variants are nevertheless of interest as they harbor a different prognosis, require specific care management and may arise from an alternate oncogenesis path. Best examples are verrucous carcinoma, basal-like or spindle cell carcinoma. Recent studies pointed out the critical role of infection with oncogenic HPV strains in the development of these carcinomas, especially in the oropharynx. In addition, HPV infection is changing the epidemiological profile of these cancers seems to have a prognostic value. New targeted therapies and prognostic markers will be discussed as they may dramatically improve the outcome of these tumors.

Tumor-derived microvesicles promote regulatory T cell expansion and induce apoptosis in tumor-reactive activated CD8+ T lymphocytes

Sera of patients with cancer contain membraneous microvesicles (MV) able to induce apoptosis of activated T cells by activating the Fas/Fas ligand pathway. However, the cellular origin of MV found in cancer patients' sera varies as do their molecular and cellular profiles. To distinguish tumor-derived MV in cancer patients' sera, we used MAGE 3/6(+) present in tumors and MV. Molecular profiles of MAGE 3/6(+) MV were compared in Western blots or by flow cytometry with those of MV secreted by dendritic cells or activated T cells. These profiles were found to be distinct for each cell type. Only tumor-derived MV were MAGE 3/6(+) and were variably enriched in 42-kDa Fas ligand and MHC class I but not class II molecules. Effects of MV on signaling via the TCR and IL-2R and proliferation or apoptosis of activated primary T cells and T cell subsets were also assessed. Functions of activated CD8(+) and CD4(+) T lymphocytes were differentially modulated by tumor-derived MV. These MV inhibited signaling and proliferation of activated CD8(+) but not CD4(+) T cells and induced apoptosis of CD8(+) T cells, including tumor-reactive, tetramer(+)CD8(+) T cells as detected by flow cytometry for caspase activation and annexin V binding or by DNA fragmentation. Tumor-derived but not dendritic cell-derived MV induced the in vitro expansion of CD4(+)CD25(+)FOXP3(+) T regulatory cells and enhanced their suppressor activity. The data suggest that tumor-derived MV induce immune suppression by promoting T regulatory cell expansion and the demise of antitumor CD8(+) effector T cells, thus contributing to tumor escape.

Spontaneous apoptosis of tumor-specific tetramer+ CD8+ T lymphocytes in the peripheral circulation of patients with head and neck cancer

BACKGROUND

In cancer, tumor escape from the host immune system includes apoptosis of circulating CD3(+)CD8(+) effector T lymphocytes. Here, we compare sensitivity to apoptosis of virus- with tumor-specific circulating CD8(+) T cells in patients with head and neck cancer.

METHODS

Wild-type p53 peptide-specific (p53(264-272) and p53(149-157)) and viral peptide-specific (EBV BMLF(259-267) and CMVpp65(495-503)) tetramers were used to measure the frequency of reactive T cells by flow cytometry. Annexin V (ANX) binding to circulating 7-amino-actinomycin D-negative but tetramer(+)CD8(+) T cells in PBMC obtained from 21 patients with head and neck cancer and 11 normal controls (NC) was evaluated.

RESULTS

In patients with head and neck cancer, a higher percentage of tetramer(+)CD8(+) than tetramer(-)CD8(+) T cells bound ANX (p < .023-.005). Although most tumor-epitope(+)CD8(+) T cells bound ANX, lower percentages of virus-specific CD8(+) T cells were ANX(+) in the same patients.

CONCLUSIONS

Preferential demise of circulating tumor-specific CD8(+) T cells and their paucity in head and neck cancer contribute to tumor escape.

CD44 costimulation promotes FoxP3+ regulatory T cell persistence and function via production of IL-2, IL-10, and TGF-beta

Work by our group and others has demonstrated a role for the extracellular matrix receptor CD44 and its ligand hyaluronan in CD4(+)CD25(+) regulatory T cell (Treg) function. Herein, we explore the mechanistic basis for this observation. Using mouse FoxP3/GFP(+) Treg, we find that CD44 costimulation promotes expression of FoxP3, in part through production of IL-2. This promotion of IL-2 production was resistant to cyclosporin A treatment, suggesting that CD44 costimulation may promote IL-2 production through bypassing FoxP3-mediated suppression of NFAT. CD44 costimulation increased production of IL-10 in a partially IL-2-dependent manner and also promoted cell surface TGF-beta expression. Consistent with these findings, Treg from CD44 knockout mice demonstrated impaired regulatory function ex vivo and depressed production of IL-10 and cell surface TGF-beta. These data reveal a novel role for CD44 cross-linking in the production of regulatory cytokines. Similar salutary effects on FoxP3 expression were observed upon costimulation with hyaluronan, the primary natural ligand for CD44. This effect is dependent upon CD44 cross-linking; while both high-molecular-weight hyaluronan (HA) and plate-bound anti-CD44 Ab promoted FoxP3 expression, neither low-molecular weight HA nor soluble anti-CD44 Ab did so. The implication is that intact high-molecular weight HA can cross-link CD44 only in those settings where it predominates over fragmentary LMW-HA, namely, in uninflamed tissue. We propose that intact but not fragmented extracellular is capable of cross-linking CD44 and thereby maintains immunologic tolerance in uninjured or healing tissue.

Differential responses of human regulatory T cells (Treg) and effector T cells to rapamycin

Background

The immunosuppressive drug rapamycin (RAPA) promotes the expansion of CD4⁺ CD25^highFoxp3⁺ regulatory T cells via mechanisms that remain unknown. Here, we studied expansion, IL-2R-γ chain signaling, survival pathways and resistance to apoptosis in human Treg responding to RAPA.

Methodology/Principal Findings

CD4⁺CD25⁺ and CD4⁺CD25^neg T cells were isolated from PBMC of normal controls (n = 21) using AutoMACS. These T cell subsets were cultured in the presence of anti-CD3/CD28 antibodies and 1000 IU/mL IL-2 for 3 to 6 weeks. RAPA (1–100 nM) was added to half of the cultures. After harvest, the cell phenotype, signaling via the PI3K/mTOR and STAT pathways, expression of survival proteins and Annexin V binding were determined and compared to values obtained with freshly-separated CD4⁺CD25^high and CD4⁺CD25^neg T cells. Suppressor function was tested in co-cultures with autologous CFSE-labeled CD4⁺CD25^neg or CD8⁺CD25^neg T-cell responders. The frequency and suppressor activity of Treg were increased after culture of CD4⁺CD25⁺ T cells in the presence of 1–100 nM RAPA (p<0.001). RAPA-expanded Treg were largely CD4⁺CD25^highFoxp3⁺ cells and were resistant to apoptosis, while CD4⁺CD25^neg T cells were sensitive. Only Treg upregulated anti-apoptotic and down-regulated pro-apoptotic proteins. Treg expressed higher levels of the PTEN protein than CD4⁺CD25^neg cells. Activated Treg±RAPA preferentially phosphorylated STAT5 and STAT3 and did not utilize the PI3K/mTOR pathway.

Conclusions/Significance

RAPA favors Treg expansion and survival by differentially regulating signaling, proliferation and sensitivity to apoptosis of human effector T cells and Treg after TCR/IL-2 activation.