Regulatory T cells and tumor immunity

Intravital Imaging of Regulatory T Cells in Inflamed Skin

Regulatory T cells play key roles in skin homeostasis and inflammation and in regulating antitumor responses. Understanding of the biology of this cell type has been improved by the use of intravital microscopy for their visualization in various organs. Here we describe a multiphoton microscopy-based technique for intravital imaging of regulatory T cells in the skin. We provide a protocol for a model of antigen-dependent inflammation that induces robust regulatory T cell recruitment to the skin and describe the use of a regulatory T cell reporter mouse for visualization of these cells in inflamed skin.

Clinical Significance of Heme Oxygenase 1 in Tumor Progression

Heme oxygenase 1 (HO-1) plays a key role in cell adaptation to stressors through the antioxidant, antiapoptotic, and anti-inflammatory properties of its metabolic products. For these reasons, in cancer cells, HO-1 can favor aggressiveness and resistance to therapies, leading to poor prognosis/outcome. Genetic polymorphisms of HO-1 promoter have been associated with an increased risk of cancer progression and a high degree of therapy failure. Moreover, evidence from cancer biopsies highlights the possible correlation between HO-1 expression, pathological features, and clinical outcome. Indeed, high levels of HO-1 in tumor specimens often correlate with reduced survival rates. Furthermore, HO-1 modulation has been proposed in order to improve the efficacy of antitumor therapies. However, contrasting evidence on the role of HO-1 in tumor biology has been reported. This review focuses on the role of HO-1 as a promising biomarker of cancer progression; understanding the correlation between HO-1 and clinical data might guide the therapeutic choice and improve the outcome of patients in terms of prognosis and life quality.

Validation of Gene Profiles for Analysis of Regional Lymphatic Metastases in Head and Neck Squamous Cell Carcinoma

The progress of Head and Neck Squamous Cell Carcinoma (HNSCC) is dependent on both cancer stem cells (CSCs) and immune suppression. This study was designed to evaluate the distribution of CSCs and the characteristic immune suppression status in HNSCC primary tumors and lymph nodes. A total of 303 lymph nodes from 25 patients, as well as tumor and adjacent normal tissue samples, were evaluated by a quantitative PCR assay of the markers of CSCs and the characteristic immune suppression. Expressions of selected genes in The Cancer Genome Atlas (TCGA) datasets were also analyzed. In the primary tumors, we found that expressions of CSCs markers (ALDH1L1, PECAM1, PROM1) were down-regulated, while immune suppression markers FOXP3, CD47, EGFR, SOX2, and TGFB1 were up-regulated significantly when compared to that in adjacent normal tissues. In the lymph nodes, expressions of both CSCs, and immune suppression markers were upregulated significantly compared with that in primary tumors. The mRNA expression of selected CSCs and immune suppression markers exhibited the highest expression in the level II of metastasis, then declined in the level III and remained constant at a reduced value in levels IV and V of metastases. These results reveal a comprehensive understanding of the unique genetic characteristics associated with metastatic loci and potential routes of lymphatic dissemination of HNSCC, which helps to explain why the level II has a high incidence of lymph node metastasis, and why skip metastasis straight to the level IV or level V is rarely found in the clinic.

Therapeutics and prospects of Interleukin 2

Interleukin-2 was discovered back in 1983 as an autocrine growth factor for cultured T cells and was the first biological product created through the use of recombinant DNA. IL-2 tumor immunotherapy performed the first historical clinical demonstration of the possibility to cause an effective anticancer immune reaction, mediated by cytotoxic lymphocytes activated from IL-2 stimulation. The Interleukin 2 receptor is a heterotrimeric protein that is composed of three peptide chains: the alpha chain, the beta chain and the gamma chain of the common cytokine receptor. There are 3 majors’ ways of interfering with the IL-2/IL-2R to use it as treatments: Antibodies, Aptamers, and punctual mutagenesis. Recent studies have shown, that Il-2 therapies for cancer, specifically targets restoring the individual’s natural antitumor immune response. HIV directed treatments have demonstrated the necessity of introducing the IL-2 complemented with the patient’s antiretroviral therapy.

Preventing Lck Activation in CAR T Cells Confers Treg Resistance but Requires 4-1BB Signaling for Them to Persist and Treat Solid Tumors in Nonlymphodepleted Hosts

PURPOSE

Chimeric antigen receptor (CAR) T cells have shown promise against solid tumors, but their efficacy has been limited, due in part, to immunosuppression by CD4+FoxP3+ regulatory T cells (Tregs). Although lymphodepletion is commonly used to deplete Tregs, these regimens are nonspecific, toxic, and provide only a narrow window before Tregs repopulate hosts. Importantly, CARs have also been shown to inadvertently potentiate Tregs by providing a source of IL2 for Treg consumption. We explored whether disruption of the IL2 axis would confer efficacy against solid tumors without the need for lymphodepletion.

EXPERIMENTAL DESIGN

We developed second- (CD28z) and third- (CD28-4-1BBz) generation CARs targeting EGFRvIII. To eliminate secretion of IL2, 2 amino acid substitutions were introduced in the PYAP Lck-binding motif of the CD28 domain (ΔCD28). We evaluated CARs against B16 melanomas expressing EGFRvIII.

RESULTS

CD28z CARs failed to engraft in vivo. Although 4-1BB addition improved expansion, CD28-4-1BBz CARs required lymphodepletion to treat solid tumors. CARs deficient in Lck signaling, however, significantly retarded tumor growth without a need for lymphodepletion and this was dependent on inclusion of 4-1BB. To evaluate CAR vulnerability to Tregs, we lymphodepleted mice and transferred CARs alone or with purified Tregs. Cotransfer with Tregs abrogated the efficacy of CD28-4-1BBz CARs, whereas the efficacy of ΔCD28-4-1BBz CARs remained unperturbed.

CONCLUSIONS

In the absence of lymphodepletion, CARs targeting solid tumors are hindered by Treg immunosuppression and poor persistence. Here, CARs were modified to circumvent Treg suppression and to simultaneously improve in vivo engraftment. Modified CARs treated solid tumors without a need for lymphodepletion.

Replenishing Regulatory T Cells to Halt Depigmentation in Vitiligo

Vitiligo is a cutaneous autoimmune disease, especially devastating to patients with darker skin tones because of the contrast between unaffected and lesional skin. We studied immune cells infiltrating vitiligo skin and found very few regulatory T cells (Tregs). Vitiligo was not associated with a reduced frequency or function of circulating Tregs. To manipulate Treg function, we used mouse models expressing melanocyte-reactive TCRs, following changes in pelage color. We also isolated splenocytes to measure Treg function and evaluated cutaneous Treg abundance. Even small numbers of Tregs transferred into depigmenting mice could effectively interfere with depigmentation. The same holds true for treatment with rapamycin, readily translatable for use in human patients; such treatment may be well tolerated. Because vitiligo skin is relatively devoid of cells that produce the chemokine CCL22, whereas circulating Tregs express normal levels of its receptor CCR4, we overexpressed Ccl22 in the skin of vitiligo-prone mice to assess the resulting levels of depigmentation. Markedly reduced depigmentation was accompanied by Treg infiltration to the skin. With several options available to support a healthy balance between Tregs and effector T cells, the next challenge will be to render such treatment antigen specific and avoid general immunosuppression.

Regulatory T Cell and Forkhead Box Protein 3 as Modulators of Immune Homeostasis

The transcription factor forkhead box protein 3 (FOXP3) is an essential molecular marker of regulatory T cell (Treg) development in different microenvironments. Tregs are cells specialized in the suppression of inadequate immune responses and the maintenance of homeostatic tolerance. Studies have addressed and elucidated the role played by FOXP3 and Treg in countless autoimmune and infectious diseases as well as in more specific cases, such as cancer. Within this context, the present article reviews aspects of the immunoregulatory profile of FOXP3 and Treg in the management of immune homeostasis, including issues relating to pathology as well as immune tolerance.

HO-1 Induction in Cancer Progression: A Matter of Cell Adaptation

The upregulation of heme oxygenase-1 (HO-1) is one of the most important mechanisms of cell adaptation to stress. Indeed, the redox sensitive transcription factor Nrf2 is the pivotal regulator of HO-1 induction. Through the antioxidant, antiapoptotic, and antinflammatory properties of its metabolic products, HO-1 plays a key role in healthy cells in maintaining redox homeostasis and in preventing carcinogenesis. Nevertheless, several lines of evidence have highlighted the role of HO-1 in cancer progression and its expression correlates with tumor growth, aggressiveness, metastatic and angiogenetic potential, resistance to therapy, tumor escape, and poor prognosis, even though a tumor- and tissue-specific activity has been observed. In this review, we summarize the current literature regarding the pro-tumorigenic role of HO-1 dependent tumor progression as a promising target in anticancer strategy.

Polymorphisms of HLA-DQB1 predict survival of hepatitis B virus-related hepatocellular carcinoma patients receiving hepatic resection

OBJECTIVE

Human leukocyte antigen (HLA)-DQB1 genetic polymorphisms are associated with an increased risk of hepatitis B virus-related hepatocellular carcinoma (HBV-related HCC). We aimed to evaluate the influence of genetic polymorphisms in HLA-DQB1 exon region and neighboring single nucleotide polymorphisms (SNPs rs9275572 and rs2244546) on survival of HBV-related HCC patients undergoing hepatic resection.

METHODOLOGY

All SNPs were genotyped by sequencing DNA isolated from tumor samples of 483 patients with HBV-related HCC.

RESULTS

We identified rs9275572 and HLA-DQB1 haplotype CCCCC (constituted by rs1130375C, rs12722107C, rs12722106C, rs36222416C and rs3189152C) were significantly associated with overall survival (OS) of HBV-related HCC patients (P=0.015 and 0.049, respectively), after adjusting for serum AFP level, the Barcelona Clinic Liver Cancer (BCLC) stages, Child-Pugh score, regional invasion, radical hepatic resection and adjuvant antiviral treatment. In stratified analyses, the AG/GG genotype of rs9275572 significantly decreased risk of death among patients with younger age, serum AFP levels ≥400ng/mL, tumor size ≥10cm, BCLC stage A and radical hepatic resection. HLA-DQB1 haplotype CCCCC was significantly protective for male patients, patients with serum AFP levels <400ng/mL, tumor size ≥10cm, BCLC stage B/C, postoperative adjuvant TACE/TAC/TAE, radical hepatic resection and patients with adjuvant antiviral treatment. Moreover, gene-dosage effects were also observed, patients with SNP rs9275572 AG/GG genotypes and Block2 CCCCC haplotype had a decreased risk of death compared to others after adjusting for serum AFP level, BCLC stages, Child-Pugh score, regional invasion, radical hepatic resection and adjuvant antiviral treatment (adjusted HR=0.38, 95% CI=0.20-0.73, P=0.004).

CONCLUSIONS

The AG/GG genotype of rs9275572 and HLA-DQB1 Block2 CCCCC haplotype may have protective effects in HBV-related HCC patients receiving hepatic resection.

Proteomic Approaches to Biomarker Discovery in Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphoma (CTCL) is the most frequently encountered type of skin lymphoma in humans. CTCL encompasses multiple variants, but the most common types are mycosis fungoides (MF) and Sezary syndrome (SS). While most cases of MF run a mild course over a period of many years, other subtypes of CTCL are very aggressive. The rapidly expanding fields of proteomics and genomics have not only helped increase knowledge concerning the carcinogenesis and tumor biology of CTCL but also led to the discovery of novel markers for targeted therapy. Although multiple biomarkers linked to CTCL have been known for a relatively long time (e.g., CD25, CD45, CD45RA, and CD45R0), compared to other cancers (lymphoma, melanoma, colon carcinoma, head and neck cancer, renal cancer, and cutaneous B-cell lymphoma), information about the antigenicity of CTCL remains relatively limited and no dependable protein marker for CTCL has been discovered. Considering the aggressive nature of some types of CTCL, it is necessary to identify circulating molecules that can help in the early diagnosis, differentiation from inflammatory skin diseases (psoriasis, nummular eczema), and aid in predicting the prognosis and evolution of this pathology. This review aims to bring together some of the information concerning protein markers linked to CTCL, in an effort to further the understanding of the convolute processes involved in this complex pathology.

Immune Suppression Mediated by Myeloid and Lymphoid Derived Immune Cells in the Tumor Microenvironment Facilitates Progression of Thyroid Cancers Driven by HrasG12V and Pten Loss

Thyroid cancer is the most common endocrine malignancy and is predicted to be the 4^th most commonly diagnosed cancer by 2030. Approximately one-half of follicular thyroid carcinomas (FTC) contain genetic alterations in RAS family members. Furthermore, Cowden's disease, which is characterized by loss of PTEN, predisposes for the development of FTC in humans. We have shown that thyroid specific expression of Hras^G12V at endogenous levels and Pten inactivation (Hras^G12V/Pten^-/-/TPO-cre mice) leads to the development of FTCs that closely recapitulate human disease, with complete penetrance at one year. In patients, FTCs metastasize via the bloodstream to distant sites, frequently the lungs, bones and brain. The first objective of the study was to determine if these mice developed de novo metastasis to relevant sites. Indeed, spontaneous metastasis to the lungs was observed in 56% of Hras^G12V/Pten^-/-/TPO-cre mice. We next sought to identify the cellular components within the tumor microenvironment (TME) of FTC that contribute to tumor progression and metastasis via FACS analysis. Surprisingly, a large amount of immune infiltrate was observed. Hras^G12V/Pten^-/-/TPO-Cre thyroid tumors were comprised of 68.5 ± 11.79% CD45⁺ cells, in stark contrast to wild-type (WT) thyroids which were comprised of 17.6% CD45⁺ cells. Further, 53.1 ± 10.9% of the CD45⁺ cells from Hras^G12V/Pten^-/-/TPO-Cre thyroid tumors were of myeloid-lineage (CD11b⁺), consisting of macrophages (F4/80⁺Gr-1^-) and myeloid-derived suppressor cells (F4/80^-Gr-1⁺). Further, Hras^G12V/Pten^-/-/TPO-cre tumors contained Arginase-1 positive cells as determined by immunohistochemical analysis, supporting an immunosuppressive TME in Hras^G12V/Pten^-/-/TPO-Cre thyroid tumors. We next evaluated whether or not cytotoxic (CD8⁺) or helper T cells (CD4⁺) were recruited to Hras^G12V/Pten^-/-/TPO-Cre tumors. The majority of T cells in these tumors were double positive for CD4 and CD25, markers of immune suppressive regulatory T cells (T_reg). Additionally, we identified Foxp3 positive cells by immunohistochemical analysis of tumor sections, indicating a functional suppressive T_reg phenotype in vivo. Hras^G12V/Pten^-/-/TPO-Cre tumor cell lines displayed increased secretion of SDF-1, I-TAC, CCL9/10, and MCP5, cytokines that have been reported to play a direct role in the chemotaxis of immune cells and thus could contribute to the increased recruitment of myeloid and lymphoid derived cells in Hras^G12V/Pten^-/-/TPO-Cre tumors. These studies are the first to identify and implicate the interaction between tumor cells and immune cells in Ras-driven thyroid cancer progression, which we hope will lead to the development of more effective therapeutic approaches for aggressive forms of thyroid cancer that target the TME.

Relationship between T-lymphocyte subsets and gastric cancer

Gastric cancer is one of the most common malignant tumors in China. The occurrence and development of gastric cancer are closely related to the body's immune status. T-lymphocytes are not only the main effector cells of the body's immune system, but also important immunoregulatory cells, playing important roles in maintaining normal immune function, killing tumor cells and inhibiting tumor growth. When the number or function of peripheral T-lymphocyte subsets is abnormally altered, disorders of the body's immune system and some pathological changes may occur, which can lead to the occurrence and development of tumors. T-lymphocyte subsets have been gradually recognized to play an important role in the pathogenesis of malignant tumors. The purpose of this review is to summarize the relationship between gastric cancer and T-lymphocyte subsets.

Enhancement of regulatory T cell-like suppressive function in MT-2 by long-term and low-dose exposure to asbestos

Asbestos exposure causes lung fibrosis and various malignant tumors such as lung cancer and malignant mesothelioma. The effects of asbestos on immune cells have not been thoroughly investigated, although our previous reports showed that asbestos exposure reduced anti-tumor immunity. The effects of continuous exposure of regulatory T cells (Treg) to asbestos were examined using the HTLV-1 immortalized human T cell line MT-2, which possesses a suppressive function and expresses the Treg marker protein, Foxp3. Sublines were generated by the continuous exposure to low doses of asbestos fibers for more than one year. The sublines exposed to asbestos showed enhanced suppressive Treg function via cell-cell contact, and increased production of soluble factors such as IL-10 and transforming growth factor (TGF)-β1. These results also indicated that asbestos exposure induced the reduction of anti-tumor immunity, and efforts to develop substances to reverse this reduction may be helpful in preventing the occurrence of asbestos-induced tumors.

Manipulation of regulatory T cells and antigen-specific cytotoxic T lymphocyte-based tumour immunotherapy

The most potent killing machinery in our immune system is the cytotoxic T lymphocyte (CTL). Since the possibility for self-destruction by these cells is high, many regulatory activities exist to prevent autoimmune destruction by these cells. A tumour (cancer) grows from the cells of the body and is tolerated by the body's immune system. Yet, it has been possible to generate tumour-associated antigen (TAA) -specific CTL that are also self-antigen specific in vivo, to achieve a degree of therapeutic efficacy. Tumour-associated antigen-specific T-cell tolerance through pathways of self-tolerance generation represents a significant challenge to successful immunotherapy. CD4(+)  CD25(+)  FoxP3(+) T cells, referred to as T regulatory (Treg) cells, are selected in the thymus as controllers of the anti-self repertoire. These cells are referred to as natural T regulatory (nTreg) cells. According to the new consensus (Nature Immunology 2013; 14:307-308) these cells are to be termed as (tTreg). There is another class of CD4(+) Treg cells also involved in regulatory function in the periphery, also phenotypically CD4(+)  CD25(±) , classified as induced Treg (iTreg) cells. These cells are to be termed as peripherally induced Treg (pTreg) cells. In vitro-induced Treg cells with suppressor function should be termed as iTreg. These different Treg cells differ in their requirements for activation and in their mode of action. The current challenges are to determine the degree of specificity of these Treg cells in recognizing the same TAA as the CTL population and to circumvent their regulatory constraints so as to achieve robust CTL responses against cancer.

Vitamin D inhibits the occurrence of experimental cerebral malaria in mice by suppressing the host inflammatory response

In animal models of experimental cerebral malaria (ECM), neuropathology is associated with an overwhelming inflammatory response and sequestration of leukocytes and parasite-infected RBCs in the brain. In this study, we explored the effect of vitamin D (VD; cholecalciferol) treatment on host immunity and outcome of ECM in C57BL/6 mice during Plasmodium berghei ANKA (PbA) infection. We observed that oral administration of VD both before and after PbA infection completely protected mice from ECM. VD administration significantly dampened the inducible systemic inflammatory responses with reduced circulating cytokines IFN-γ and TNF and decreased expression of these cytokines by the spleen cells. Meanwhile, VD also resulted in decreased expression of the chemokines CXCL9 and CXCL10 and cytoadhesion molecules (ICAM-1, VCAM-1, and CD36) in the brain, leading to reduced accumulation of pathogenic T cells in the brain and ultimately substantial improvement of the blood-brain barriers of PbA-infected mice. In addition, VD inhibited the differentiation, activation, and maturation of splenic dendritic cells. Meanwhile, regulatory T cells and IL-10 expression levels were upregulated upon VD treatment. These data collectively demonstrated the suppressive function of VD on host inflammatory responses, which provides significant survival benefits in the murine ECM model.

Increased frequency of CD4+ CD25+ FOXP3+ cells correlates with the progression of 4-nitroquinoline1-oxide-induced rat tongue carcinogenesis

OBJECTIVES

CD4+ CD25+ FoxP3+ T cells (Tregs) play an essential role in sustaining self-tolerance by negatively regulating immune responses. Increased frequencies of Tregs have been reported in a variety of human cancers. The aim of this study was to evaluate the prevalence of Tregs infiltration in the peripheral blood and regional lymph nodes during rat tongue carcinogenesis induced by 4-nitroquinoline-1-oxide (4NQO).

MATERIALS AND METHODS

Forty-eight Sprague-Dawley rats were divided into the control (n = 16) and experimental groups (n = 32) to which 4NQO in drinking water was administered. Flow cytometry was used to analyze the prevalence of Tregs in lymphocytes of peripheral blood and regional lymph nodes during 4NQO-induced rat tongue carcinogenesis. CD4+ CD25+ FoxP3+ cells were expressed as a percentage of the total CD4+ cells.

RESULTS

The frequency of Tregs in peripheral blood from squamous cell carcinoma rats was significantly higher than controls (3.82 ± 0.62 versus 1.40 ± 0.31 %, P < 0.001). The proportion of Tregs was sequentially increased from moderate dysplasia to severe dysplasia and SCC (1.94 ± 0.72, 2.29 ± 0.82, and 3.82 ± 0.62 %, respectively). The frequency of Tregs in regional lymph nodes from squamous cell carcinoma rats was also significantly higher than normal rat mucosa (14.67 ± 3.09 versus 5.53 ± 2.07 %, P < 0.001). The percentage of Tregs was gradually increased in moderate dysplasia, severe dysplasia, and SCC groups (8.93 ± 1.74, 10.15 ± 0.86, 14.67 ± 3.09 %, respectively) as compared to control group (5.53 ± 2.07 %).

CONCLUSION AND CLINICAL RELEVANCE

Tregs in peripheral blood and lymph nodes were associated with disease progression during 4NQO-induced rat tongue carcinogenesis. This study indicated that the upregulation of Tregs might play important role during oral mucosa malignant transformation.

Immune regulation and evasion of Mammalian host cell immunity during viral infection

The mammalian host immune system has wide array of defence mechanisms against viral infections. Depending on host immunity and the extent of viral persistence, either the host immune cells might clear/restrict the viral load and disease progression or the virus might evade host immunity by down regulating host immune effector response(s). Viral antigen processing and presentation in the host cells through major histocompatibility complex (MHC) elicit subsequent anti-viral effector T cell response(s). However, modulation of such response(s) might generate one of the important viral immune evasion strategies. Viral peptides are mostly generated by proteolytic cleavage in the cytosol of the infected host cells. CD8(+) T lymphocytes play critical role in the detection of viral infection by recognizing these peptides displayed at the plasma membrane by MHC-I molecules. The present review summarises the current knowledge on the regulation of mammalian host innate and adaptive immune components, which are operative in defence mechanisms against viral infections and the variety of strategies that viruses have evolved to escape host cell immunity. The understanding of viral immune evasion strategies is important for designing anti-viral immunotherapies.

Indoleamine 2,3-dioxygenase affects the aggressiveness of intraductal papillary mucinous neoplasms through Foxp3+CD4+CD25+ T cells in peripheral blood

OBJECTIVE

Intraductal papillary mucinous neoplasms (IPMNs) have a high malignant potential. We previously reported that peripheral Foxp3(+)CD4(+)CD25(+) T-cell (Foxp3(+) Treg) populations significantly increase with IPMN pathological aggressiveness. Dendritic cell-mediated induction of active Tregs from naive CD4(+) T cells requires indoleamine 2,3-dioxygenase (IDO). Here, we evaluated whether an IDO-Foxp3(+) Treg interaction plays a role in IPMN pathological aggressiveness.

METHODS

We evaluated peripheral blood samples and resected specimens from 12 patients with IPMN. We analyzed Foxp3(+)CD4(+)CD25(+) T cells in peripheral blood by fluorescence-activated cell sorting, evaluated the resected specimens by anti-IDO antibody staining, and compared them with the patients' clinicopathological factors.

RESULTS

The pathological aggressiveness of IPMN was significantly associated with the number of peripheral Foxp3(+) Tregs (P < 0.05) and IDO-positive cells per high-power field (HPF) (P < 0.01). There was a significant correlation between the numbers of peripheral Foxp3(+) Tregs and IDO-positive cells/HPF (r = 0.625, P < 0.01). Patients with 7 or more IDO-positive cells/HPF had a significantly higher recurrence rate than those with less than 7 IDO-positive cells/HPF (P < 0.01, log-rank test).

CONCLUSIONS

Peripheral Foxp3(+) Tregs accurately reflect the aggressiveness of IPMNs. An increase in Foxp3(+) Tregs can be induced by local IDO-positive cells in IPMN.

Melanoma vaccines and modulation of the immune system in the clinical setting: building from new realities

To endow the immune system with the capacity to fight cancer has always attracted attention, although the clinical results obtained have been until recently disappointing. Cutaneous melanoma is a highly immunogenic tumor; therefore most of the attempts to produce cancer vaccines have been addressed to this disease. New advances in the comprehension of the mechanisms of antigen presentation by dendritic cells, in the immune responses triggered by adjuvants, as well as the understanding of the role of immunosuppressor molecules such as cytotoxic T-lymphocyte antigen-4 (CTLA-4), which led to the recent approval of the anti-CTLA-4 monoclonal antibody ipilimumab, have opened new hopes about the installment of immunotherapy as a new modality to treat cancer.

Regulatory T cell migration during an immune response

CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells migrate into both inflammatory sites and draining lymph nodes (LNs) during an immune response, and have unique and overlaping functions in each location. Current studies suggest that Treg cells in draining LNs and inflamatory sites may not simply be a division of labor, but rather Treg cells migrate in a coordinated fashion between peripheral tissues and draining LNs. Trafficking between inflammatory sites and draining LNs is not only crucial for Treg cells to act, but also for them to acquire optimal immune regulatory activities. Furthermore, recent work has revealed that T helper (Th)1, Th2 and Th17 cell master transcription factors control Treg cell function by regulating genes important for Treg cell migration and suppression, and consequently affect disease pathogenesis.

1,25-Dihydroxyvitamin D3 inhibits proliferation but not the suppressive function of regulatory T cells in the absence of antigen-presenting cells

Vitamin D3 is known to induce regulatory T (Treg) cells by rendering antigen-presenting cells tolerogenic, its direct effect on human naturally occurring Treg cells is unclear. Here, we investigated if and how 1,25-dihydroxyvitamin D(3) [1,25(OH)2D3] can directly affect the proliferation and function of human naturally occurring Treg cells in vitro. First, we demonstrated that these Treg cells express vitamin D receptors that were up-regulated following anti-CD3/CD28-bead stimulation. 1,25(OH)2D3 inhibited proliferation of Treg cells even when exogenous interleukin-2 was provided. Treg cells were more susceptible to the inhibitory effect of 1,25(OH)2D3 than conventional T cells(.) 1,25(OH)2D3 neither affected the anergic state nor the suppressive function of Treg cells but induced a subtle increase in interleukin-10-secreting cells. The cell-division-inhibiting effect of 1,25(OH)2D3 on Treg cells was also demonstrated in vivo by supplementing vitamin D-deficient HIV-1-infected patients with 2000 IU cholecalciferol (vitamin D3). Increased serum 1,25(OH)2D3 levels were associated with a drop in the number and percentage of Treg cells, which may be attributed to a decrease in the proliferating Foxp3+ Treg cell population. In conclusion, 1,25(OH)2D3 directly affects Treg cell growth and promotes interleukin-10 production without apparent effects on activation status and suppressive phenotype whereas in vivo, high serum 1,25(OH)2D3 levels are associated with reduced Treg cell proliferation and a reduced number of Treg cells.

Adjuvant immunotherapy of C6 glioma in rats with pertussis toxin

PURPOSE

In spite of the recent advances in surgery and antitumor drugs, the brain tumors, like glioblastoma, have shown a poor prognosis. The aim of this study was to determine the effect of pertussis toxin (PTx) as immunomodulatory molecule on glial tumors induced by C6 glioma cells.

METHODS

Given the pleiotropic effect of PTx on the immune system, we analyzed the effect of PTx on CD4+/CD25+/FoxP3+ (Treg) cells like as immunotherapeutic adjuvant. Thirty rats with a glial tumor of 1.5 cm in diameter were separated in two groups: the first group was treated with PTx and the second group was non-treated (controls). Tumoral volume was measured weekly; tumor, blood and spleen were taken for analysis of subpopulations of T cells, apoptotic index and cytokine contents, in both groups.

RESULTS

We observed a significant decrease in tumor volume in the PTx group; this was associated with a decreased in the number of Treg cells, in both spleen and tumor. The percentage of apoptotic cells was increased as compared with that of controls. The production of proinflammatory cytokines was increased in mRNA for IL-6 as well as a small increase in the mRNA expression of perforin and granzime in tumors from rats treated with PTx. No changes were found in the mRNA expression of MCP-1 and MIP-1α.

CONCLUSION

These results suggest that PTx could be an immunotherapeutic adjuvant in the integral therapy against glial tumors.

The role of cytokine signaling in the pathogenesis of cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) displays immunosuppressive properties and phenotypic plasticity. The malignant T cells in CTCL can possess features of immunomodulating regulatory T cells (Treg) and IL-17-producing helper T cells (Th17) depending on the stimuli they receive from antigen presenting cells and other sources. IL-2-type cytokines activate STAT5 to promote expression of Treg-related FoxP3, while various cytokines can activate STAT3 to induce synthesis of IL-10 and IL-17. When the Treg phenotype is activated in the early stages of CTCL, "immune evasion" can occur, allowing the clonal T cells to expand. Late stages of CTCL lose the FoxP3 expression but continue to express an immunosuppressive cell-surface ligand PD-L1 suggesting that this and possibly other immunosuppressive proteins rather than FoxP3 are critical for the immunosuppressive state in the advanced stages of CTCL. Novel therapeutic agents may potentially exploit the phenotypic plasticity of CTCL such that the malignant T cells become vulnerable to antitumor immunity.

NKT cell self-reactivity: evolutionary master key of immune homeostasis?

Complex immune responses have evolved to protect multicellular organisms against the invasion of pathogens. This has exerted strong developmental pressure for specialized functions that can also limit damage to self-tissue. Two arms of immunity, the innate and adaptive immune systems, have evolved for quick, non-specific immune responses to pathogens and more efficient, long-lasting ones upon specific recognition of recurrent pathogens. Specialized cells have arisen as the sentinels of these functions, including macrophages, natural killer (NK), and T and B-lymphocytes. Interestingly, a population of immune cells that can exert both of these complex functions, NKT cells, not only share common functions but also exhibit shared cell surface markers of cells of both arms of the immune system. These features, in combination with sophisticated maintenance of immune homeostasis, will be discussed. The recent finding of self-peptide reactivity of NKT cells in the context of CD1d, with capacity to regulate multiple autoimmune and inflammatory conditions, motivates the current proposal that self-reactive NKT cells might be the ancestral link between present NK and T cells. Their parallel selection through evolution by higher vertebrates could be related to their central function as master regulators of immune homeostasis that in part is shared with regulatory T cells. Hypothetical views on how self-reactive NKT cells secure such a central role will also be proposed.

The immune response to tumors as a tool toward immunotherapy

Until recently cancer medical therapy was limited to chemotherapy that could not differentiate cancer cells from normal cells. More recently with the remarkable mushroom of immunology, newer tools became available, resulting in the novel possibility to attack cancer with the specificity of the immune system. Herein we will review some of the recent achievement of immunotherapy in such aggressive cancers as melanoma, prostatic cancer, colorectal carcinoma, and hematologic malignancies. Immunotherapy of tumors has developed several techniques: immune cell transfer, vaccines, immunobiological molecules such as monoclonal antibodies that improve the immune responses to tumors. This can be achieved by blocking pathways limiting the immune response, such as CTLA-4 or Tregs. Immunotherapy may also use cytokines especially proinflammatory cytokines to enhance the activity of cytotoxic T cells (CTLs) derived from tumor infiltrating lymphocytes (TILs). The role of newly discovered cytokines remains to be investigated. Alternatively, an other mechanism consists in enhancing the expression of TAAs on tumor cells. Finally, monoclonal antibodies may be used to target oncogenes.

Tumour infiltrating CD25+ FoxP3+ regulatory T cells (Tregs) relate to tumour grade and stromal inflammation in oral squamous cell carcinoma

This research is aimed to quantitate and characterize the subtypes of tumour infiltrating lymphocytes (TILs), in particular the presence of FoxP3+ Tregs in different grades of oral squamous cell carcinoma using monospecific antibody staining of formalin-fixed, paraffin-embedded tissue sections. The correlation between tumour grade and the intensity of tumour infiltrating lymphocytes was tried to be tested, to assume a putative linkage between them. Thirty-four cases of histologically proven primary oral squamous cell carcinoma (OSCC) of different grades of differentiation were assorted to groups 1-3. Three-micron sections of tissue were cut and captured on electrically charged slides (Vision BioSystem, Mount Waverley, Australia) and stained using monospecific antibody against FoxP3+ Treg phenotype (dilution 1:40, Mouse monoclone No: 236A/E7, Ab 20034, IgG1; Abcam, Cambridge, UK). Automated protocols were employed for staining and scoring of staining intensity using Bond™ system (Vision BioSystem). Significant difference in staining intensities (Tregs) was noted among the histologic grades of tumour, where well-differentiated OSCC had significantly low expression of FoxP3+ Tregs in comparison with moderately and poorly differentiated tumours. A significant linear correlation was established between tumour grade and the intensity of TILs, where high grade tumours (poor differentiation) were more markedly infiltrated. There was also a significant positive correlation between FoxP3+ Tregs and TILs in cases studied. The correlation of these three variables noted in the study (FoxP3+ Tregs, tumour grade and TILs) and their significance in a meta-analysis may prove useful in targeting patients with high-risk neoplasms for more aggressive treatment protocols and management strategies.

GITR expression on T-cell receptor-stimulated human CD8 T cell in a JNK-dependent pathway

Glucocorticoid-induced tumor necrosis factor receptor (TNFR) (GITR) family-related gene is a member of the TNFR super family. GITR works as one of the immunoregulatory molecule on CD4⁺ regulatory T cells and has an important role on cell survival or cell death in CD4⁺ T cells. Little is known about the expression of GITR on human CD8⁺ T cells on antigen-specific and non-specific activation. Here, we report that expression of GITR on human CD8⁺ T cells on T-cell receptor (TCR) (anti-CD3)-mediated stimulation is dependent on the JNK pathway. The activation of CD8⁺ T cells was measured by the expression of IL-2 receptor-α (CD25), GITR and by IFN-γ production upon re-stimulation with anti-CD3 antibody. We studied the signaling pathway of such inducible expression of GITR on CD8⁺ T cells. We found that a known JNK-specific inhibitor, SP600125, significantly down-regulates GITR expression on anti-CD3 antibody-mediated activated CD8⁺ T cells by limiting JNK phosphorylation. Subsequently, after stimulation of the CD8⁺ cells, we tested for the production of IFN-γ by the activated cells following restimulation with the same stimulus. It appears that the expression of GITR on activated human CD8⁺ T cells might also be regulated through the JNK pathway when the activation is through TCR stimulation. Therefore, GITR serves as an activation marker on activated CD8⁺ cells and interference with JNK phosphorylation, partially or completely, by varying the doses of SP600125 might have implications in CD8⁺ cytotoxic T cell response in translational research.

Immunoregulation through IL-10 gene expression and the fate of cytotoxic T lymphocyte-mediated tumor immunotherapy

Gene analysis of tumor associated antigens revealed that tumor antigens are all normal gene product. Inducing tumor reactive cytotoxic T lymphocytes (CT) in the patients is same as inducing autoimmunity in the patients. Immunosuppressive cytokine interleukin-10 (IL-10) plays an important role in maintaining homeostasis or tolerance. To break the tumor tolerance, blocking and IL-10 secretion or intervention in the pathways of IL-10 gene activation is indeed important.

Tumor antigen-targeted, monoclonal antibody-based immunotherapy: clinical response, cellular immunity, and immunoescape

PURPOSE

Tumor antigen (TA) -targeted monoclonal antibodies (mAb), rituximab, trastuzumab, and cetuximab, are clinically effective for some advanced malignancies, especially in conjunction with chemotherapy and/or radiotherapy. However, these results are only seen in a subset (20% to 30%) of patients. We discuss the immunologic mechanism(s) underlying these clinical findings and their potential role in the variability in patients' clinical response.

METHODS

We reviewed the evidence indicating that the effects of TA-targeted mAb-based immunotherapy are mediated not only by inhibition of signaling pathways, but also by cell-mediated cytotoxicity triggered by the infused TA-targeted mAb. We analyzed the immunologic variables that can influence the outcome of antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro and in animal model systems. We also analyzed the correlation reported between these variables and the clinical response to mAb-based immunotherapy.

RESULTS

Of the variables that influence ADCC mediated by TA-targeted mAb, only polymorphisms of Fcγ receptors (FcγR) expressed by patients' lymphocytes were correlated with clinical efficacy. However, this correlation is not absolute and is not observed in all malignancies. Thus other variables may be responsible for the antitumor effects seen in mAb-treated patients. We discuss the evidence that triggering of TA-specific cellular immunity by TA-targeted mAb, in conjunction with immune escape mechanisms used by tumor cells, may contribute to the differential clinical responses to mAb-based immunotherapy.

CONCLUSION

Identification of the mechanism(s) underlying the clinical response of patients with cancer treated with TA-targeted mAb is crucial to optimizing their application in the clinic and to selecting the patients most likely to benefit from their use.

Treatment with interleukin-2 in malignant pleural mesothelioma: immunological and angiogenetic assessment and prognostic impact

Background:

Administration of interleukin-2 (IL-2) has shown some effects on malignant pleural mesothelioma (MPM) tumour regression. The purpose of this study was to investigate the ability of IL-2 to modify immunological effector cells and angiogenesis in MPM patients and their prognostic value.

Methods:

Tumour-infiltrating lymphocytes (CD4, CD8, Foxp3), mast cells (MCs) (tryptase and chymase), microvessel count (MVC) and VEGF were determined by immunohistochemistry in two series of MPM patients: 60 patients treated with intra-pleural preoperative IL-2 and 33 patients untreated.

Results:

Tryptase MCs, and CD8 and Foxp3 lymphocytes were significantly increased in the IL-2-treated group, whereas MVC was significantly lower in the same group. Moreover, in the IL-2-treated group, greater tryptase+MCs and greater Foxp3 lymphocytes were associated with improved and poorer clinical outcomes, respectively. Notably, when these two immunological parameters were combined, they predicted outcomes more effectively.

Conclusions:

This study showed that IL-2 treatment leads to a significant increase of immunological parameters, concomitantly with a reduction in vasculature, providing new insight into the cancer mechanisms mediated by IL-2. Moreover, these results suggest that tryptase-positive MCs and Foxp3+ lymphocytes predict clinical outcomes in IL-2-treated patients, highlighting the critical role of the inflammatory response in mesothelioma cancer progression.

Cutaneous T cell lymphoma and graft-versus-host disease: a comparison of in vivo effects of extracorporeal photochemotherapy on Foxp3+ regulatory T cells

Extracorporeal photochemotherapy (ECP) is a well established treatment for both cutaneous T cell lymphoma (CTCL) and graft-versus-host disease (GVHD). However, the general effector mechanism is not fully settled. Twenty-four patients with CTCL and 14 patients with GVHD were included to assess the relative numbers of regulatory T cells (Treg) and any change in the serum cytokine profile during 6 months of ECP therapy. The relative amount of Treg cells was twice as high in CTCL compared to GVHD and healthy controls. TGF-beta was on average three times higher in GVHD than in CTCL. Both patient groups had a small but significant increase in TGF-beta after treatment. Our results indicate a strengthened Treg function as a result of ECP. Elevated TGF-beta may indicate high Treg activation in GVHD, whereas an increased number of Treg cells in CTCL could be interpreted as a response that is involved in down-regulating the lymphoma cells.

The role of immunity in elderly cancer

The increased incidence of malignancies in elderly patients living in industrialized countries has led to both identify the causes that alter the normal homeostatic balance in elderly and designate the specific treatments. The progressive decline of the immune system (immunosenescence) involving cellular and molecular alterations impact both innate and adaptive immunity. The immunosenescence leads to increased incidence of infectious diseases morbidity and mortality as well as heightened rates of other immune disorders such as autoimmunity, cancer, and inflammatory conditions. Here, we summarize the knowledge on the major changes in the immune system associated with aging in primary lymphoid organs as well as a description of molecular mechanisms, and the impact on cancer development.

A novel phosphorylated STAT3 inhibitor enhances T cell cytotoxicity against melanoma through inhibition of regulatory T cells

The activation of signal transducer and activator of transcription 3 (STAT3) has been identified as a key mediator that drives the fundamental components of melanoma malignancy, including immune suppression in melanoma patients. Increasing evidence also suggests that regulatory T cells (Tregs) are important in suppressing anti-tumor immunity and play a dominant role in negating efficacious immunotherapy approaches. We hypothesized that WP1066, a novel inhibitor of STAT3 signaling, reverses immune suppression through the inhibition of Tregs and that this contributes to the antitumor activity of this agent against melanoma brain metastases. We found that the mean percentage of peripheral blood mononuclear cells expressing phosphorylated STAT3 (p-STAT3) was significantly elevated in samples from patients with melanoma brain metastases compared to healthy donors, 16.13 +/- 2.48% versus 4.17 +/- 1.79%. The p-STAT3 inhibitor WP1066 enhanced CD3+ (which contained Tregs) but not CD8+ T cell cytotoxicity against human A375 melanoma cells, indicating that this p-STAT3 blockade agent did not directly activate CD8+ T cells. Furthermore, the p-STAT3 inhibitor did not enhance the cytotoxicity of CD3+CD25- T cells (from which Tregs were excluded), indicating that the enhanced cytotoxicity of WP1066 is secondary to its inhibition of Tregs. This was confirmed by demonstrating that WP1066 inhibited FoxP3+ Treg induction in a dose-dependent manner. Moreover, CD3+ T cells exhibited markedly enhanced levels of phosphorylated ZAP-70, a critical proximal signal in T cell activation, after exposure to WP1066. Similar effects were not observed in Treg-depleted CD3+CD25- T cell populations, confirming that the T cell activation by WP compounds is secondary to their inhibition of the Tregs. These results suggest that WP1066 enhances T cell cytotoxicity against melanoma through inhibition of Tregs.

The immunosuppressive tumor microenvironment in hepatocellular carcinoma

Increasing evidence indicates the immunosuppressive nature of the local environment in tumor. The present study was focused on analyzing the immune status within hepatocellular carcinoma. In contrast to the increasing number of CD4(+) T cells, CD8(+), CD3(-)CD56(+), CD3(+)CD56(+), and gammadeltaT cells were all found to be under-represented in tumor infiltrating lymphocytes. Notably, the relative abundance of CD3(+)CD56(+) cells appeared to be correlated with patient survival. Functional analysis demonstrated that CD4(+) cells in the tumor tended to produce more IL-10 but less IFN-gamma, whereas CD8(+) cells showed impaired capacity for the production of both IFN-gamma and perforin. Consistent with previous reports, we observed a significant increase of Foxp3(+) cells in the tumor tissue. Intriguingly, although over 90% of CD4(+)CD25(high) cells were found to be Foxp3(+), the majority of Foxp3(+) cells were identified in the CD4(+)CD25(medium) and CD4(+)CD25(-) subsets. In support of its role as a negative regulator, CD4(+)CD25(high) cells suppressed the proliferation of CD4(+)CD25(-) cells isolated from the same tissues in an APC dependent manner. In conclusion, the tumor microenvironment of hepatocellular carcinoma is featured by the presence of multiple immunosuppressive factors.

Regulatory T cells and EBV associated malignancies

It has been shown that the T-regulatory cells (Tregs) not only play a key role in the establishment and maintenance of peripheral tolerance to prevent the autoimmune disease, but also inhibit the anti-tumor immunity. Recently, many studies have demonstrated that cytotoxicity T cells (CTL) can control the growth of EBV-positive tumor cells in vitro, including Hodgkin's lymphoma (HL), nasopharyngeal carcinoma, posttransplantation lymphoproliferative disorders (PTLD), depending on the large mount of EBV antigens presented by MHC molecules on the surface of these malignant cells. However, limited benefit of CTL adoptive immunotherapy has been reported in the treatment of EBV positive HL and NPC, and Tregs are regarded as a critical hurdle in this issue. In the present review, we discuss the correlation of EBV antigens expression in the tumor cells and the induction of Tregs in tumor microenvironment. Treg subsets and its possible mechanism to attenuate the anti-tumor immunity in EBV associated malignancies are also discussed, following by the possible strategies of targeting Tregs in the future immunotherapy for EBV positive cancers.

The biology of interleukin-2 efficacy in the treatment of patients with renal cell carcinoma

Renal cell carcinoma (RCC) is the eighth most common malignancy in adults in the United States. More than 50% of individuals present with metastatic disease and conventional chemotherapeutic strategies have been associated with poor response rates. Immunotherapy with Interleukin (IL)-2, however, induces durable remission, achieving >10 year recurrence free survival in 5-10% of patients with advanced RCC. First described as a T cell growth factor, IL-2 has a wide spectrum of effects in the immune system. Some of the possible mechanisms by which IL-2 carries out its anticancer effects include the augmentation of cytotoxic immune cell functions and reversal of T cell anergy, enabling delivery of immune cells and possibly serum components into tumor. IL-2 indirectly limits tumor escape mechanisms such as defective tumor cell expression of Class I or Class II molecules or expansion of regulatory T cells. Indirect effects on the tumor microenvironment are also likely and associated with rather dramatic T cell infiltration during the global delayed type hypersensitivity response that is associated with systemic IL-2 administration. The IL-2 signaling pathway, its effects on immune cells, and its role in various independent mechanisms of tumor surveillance likely play a role but little substantive data defining a clear phenotype or genotype of IL-2 responders distinguishing them from nonresponders has emerged in the last 25 years since IL-2 therapy was initiated. At best, we can only speculate that the disturbed homeostatic host/tumor interaction is reset in a small subset of patients allowing an antitumor response to recover or ensue.

Effective depletion of regulatory T cells allows the recruitment of mesothelin-specific CD8 T cells to the antitumor immune response against a mesothelin-expressing mouse pancreatic adenocarcinoma

Vaccine-induced CD8(+) T-cell responses can eradicate developing tumors in vivo in mouse models. Translating these successes into approved treatments for cancer patients has been challenging, since many of these models lack expression of clinically proven/relevant tumor antigens. We have shown that mesothelin is a clinically relevant CD8(+) T-cell target in human pancreas cancer, which is also highly conserved among species. Here, we utilize the murine mesothelin-expressing pancreatic tumor model (Panc02) to identify the immune-relevant mesothelin-derived peptides and study interventions that enhance the antitumor response. We first screened overlapping peptides of the entire murine mesothelin protein to identify two new CD8(+) mesothelin-restricted epitopes. These peptides were then evaluated for recognition by vaccine-induced T cells from mice treated with vaccine in sequence with low-dose cyclophosphamide (CY) and an anti-CD25 IL-2Ralpha monoclonal antibody (PC61). These treatments are both known to deplete subpopulations of T regulatory cells (Tregs). Our findings demonstrate that combined Treg-depleting therapies synergize to enhance vaccine efficacy. Furthermore, our data supports mesothelin as a relevant antigen in murine and clinical models and the use of Panc02 as a clinically relevant murine model of pancreatic cancer for evaluating antigen-targeted immunotherapies in immune-tolerant hosts.

HLA antigen changes in malignant cells: epigenetic mechanisms and biologic significance

Changes in classical and nonclassical HLA class I as well as HLA class II antigens have been identified in malignant lesions. These changes, which are described in this review are believed to play a major role in the clinical course of the disease since both HLA class I and class II antigens are critical to the interaction between tumor cells and components of both innate and adaptive immune system. Abnormalities in HLA antigen expression in malignant cells, which range in frequency from 0-90%, are caused by distinct mechanisms. They include defects in beta(2)-microglobulin (beta(2)m) synthesis, loss of the gene(s) encoding HLA antigen heavy chain(s), mutations, which inhibit HLA antigen heavy chain transcription or translation, defects in the regulatory mechanisms, which control HLA antigen expression and/or abnormalities in one or more of the antigen processing, machinery (APM) components. More recently, epigenetic events associated with tumor development and progression have been found to underlie changes in HLA antigen, APM component, costimulatory molecule and tumor antigen (TA) expression in malignant cells. The types of epigenetic modifications that may occur in normal and malignant cells as well as their role in changes in HLA antigen expression by malignant cells have been reviewed. The epigenetic events associated with alterations in HLA antigen expression may be clinically relevant as, in some cases, they have been shown to impair the recognition of tumor cells by components of the adaptive immune system. The functional relevance and potential clinical significance of these epigenetic alterations have been addressed. Finally, unlike genetic alterations, epigenetic modifications can, in some cases, be reversed with pharmacologic agents that induce DNA hypomethylation or inhibit histone deacetylation. Therefore, strategies to overcome epigenetic modifications underlying changes in HLA antigen expression in malignant cells have been discussed.

Gamma c-signaling cytokines induce a regulatory T cell phenotype in malignant CD4+ T lymphocytes

In this study, we demonstrate that malignant mature CD4(+) T lymphocytes derived from cutaneous T cell lymphomas (CTCL) variably display some aspects of the T regulatory phenotype. Whereas seven cell lines representing a spectrum of primary cutaneous T cell lymphoproliferative disorders expressed CD25 and TGF-beta, the expression of FOXP3 and, to a lesser degree, IL-10 was restricted to two CTCL cell lines that are dependent on exogenous IL-2. IL-2, IL-15, and IL-21, all of which signals through receptors containing the common gamma chain, induced expression of IL-10 in the IL-2-dependent cell lines as well as primary leukemic CTCL cells. However, only IL-2 and IL-15, but not IL-21, induced expression of FOXP3. The IL-2-triggered induction of IL-10 and FOXP3 expression occurred by signaling through STAT3 and STAT5, respectively. Immunohistochemical analysis of the CTCL tissues revealed that FOXP3-expressing cells were common among the CD7-negative enlarged atypical and small lymphocytes at the early skin patch and plaque stages. Their frequency was profoundly diminished at the tumor stage and in the CTCL lymph node lesions with or without large cell transformation. These results indicate that the T regulatory cell features are induced in CTCL T cells by common gamma chain signaling cytokines such as IL-2 and do not represent a fully predetermined, constitutive phenotype independent of the local environmental stimuli to which these malignant mature CD4(+) T cells become exposed.

Homeostatic proliferation plus regulatory T-cell depletion promotes potent rejection of B16 melanoma

PURPOSE

To investigate the antitumor efficacy of T-cell anergy reversal through homeostatic proliferation and regulatory T-cell (Treg) depletion in a clinically relevant murine adoptive immunotherapy model.

EXPERIMENTAL DESIGN

B16 melanoma cells were engineered to express the model SIYRYYGL (SIY) antigen to enable immune monitoring. Tumor-specific T cells expanded in tumor-challenged wild-type hosts but became hyporesponsive. To examine whether lymphopenia-induced homeostatic proliferation could reverse tumor-induced T-cell anergy, total splenic T cells were transferred into lymphopenic RAG2-/- mice or control P14/RAG2-/- mice. Tumor growth was measured, and SIY-specific immune responses were monitored using ELISPOT and SIY/K(b) tetramers. To determine whether Treg depletion could synergize with homeostatic proliferation, RAG2-/- mice received total or CD25-depleted T cells, followed or preceded by B16.SIY challenge. This approach was further investigated in wild-type mice lymphodepleted with sublethal total body irradiation.

RESULTS

Adoptive transfer of total splenic T cells into RAG2-/- mice moderately affected the growth rate of B16.SIY. As Treg expansion occurred in tumor-bearing mice, CD25+ T cells were depleted from total T cells before adoptive transfer. Interestingly, transfer of CD25-depleted T cells into RAG2-/- mice resulted in potent rejection of B16 melanoma in both prophylactic and short-term preimplanted tumor settings and was associated with maintained T-cell effector function. Using a clinically applicable approach, wild-type mice were lymphodepleted using sublethal total body irradiation, which similarly supported tumor rejection upon transfer of CD25-depleted T cells.

CONCLUSIONS

Our results indicate that combined CD25 depletion and homeostatic proliferation support a potent antitumor immune response--an approach with potential for clinical translation.

Regulatory T cells and human disease

The main function of our immune system is to protect us from invading pathogens and microorganisms by destroying infected cells, while minimizing collateral damage to tissues. In order to maintain this balance between immunity and tolerance, current understanding of the immune system attributes a major role to regulatory T cells (Tregs) in controlling both immunity and tolerance. Various subsets of Tregs have been identified based on their expression of cell surface markers, production of cytokines, and mechanisms of action. In brief, naturally occurring thymic-derived CD4+CD25+ Tregs are characterized by constitutive expression of the transcription factor FOXP3, while antigen-induced or adaptive Tregs are mainly identified by expression of immunosuppressive cytokines (interleukin-10 (IL-10) and/or transforming growth factor-beta (TGF-beta)). While Tregs in normal conditions regulate ongoing immune responses and prevent autoimmunity, imbalanced function or number of these Tregs, either enhanced or decreased, might lead, respectively, to decreased immunity (e.g., with tumor development or infections) or autoimmunity (e.g., multiple sclerosis). This review will discuss recent research towards a better understanding of the biology of Tregs, their interaction with other immune effector cells, such as dendritic cells, and possible interventions in human disease.

Regulatory T cells: what role do they play in antitumor immunity in patients with head and neck cancer?

Advances in the treatment modalities for head and neck squamous cell carcinoma (HNSCC) over the last 20 years involving surgery, radiotherapy, chemotherapy, and immunotherapy are not fully reflected in increases in the 5-year survival rates, mainly due to locoregional recurrences and to a lesser extent, distant metastasis. This can, in part, be attributed to the fact that HNSCC induces severe depression of a patient's immune system. Recent advances in understanding the complex host-tumor interactions have led to the identification of a distinct suppressor cell population known as regulatory T cells that play a crucial role in maintaining T-cell tolerance to self-antigens. Here, we present a critical review of our understanding of the involvement of regulatory T cells in controlling the T-cell immune response in tumor occurrence and progression in HNSCC with an emphasis on current and future immunotherapeutic approaches involving regulatory T cells.

CD137 costimulation of CD8+ T cells confers resistance to suppression by virus-induced regulatory T cells

Chronic viral infections cause high levels of morbidity and mortality worldwide, making the development of effective therapies a high priority for improving human health. We have used mice infected with Friend virus as a model to study immunotherapeutic approaches to the cure of chronic retroviral infections. In chronic Friend virus infections CD4(+) T regulatory (Treg) cells suppress CD8(+) T cell effector functions critical for virus clearance. In this study, we demonstrate that immunotherapy with a combination of agonistic anti-CD137 Ab and virus-specific, TCR-transgenic CD8(+) T cells produced greater than 99% reductions of virus levels within 2 wk. In vitro studies indicated that the CD137-specific Ab rendered the CD8(+) T cells resistant to Treg cell-mediated suppression with no direct effect on the suppressive function of the Treg cells. By 2 weeks after transfer, the adoptively transferred CD8(+) T cells were lost, likely due to activation-induced cell death. The highly focused immunological pressure placed on the virus by the single specificity CD8(+) T cells led to the appearance of escape variants, indicating that broader epitope specificity will be required for long-term virus control. However, the results demonstrate a potent strategy to potentiate the function of CD8(+) T cells in the context of immunosuppressive Treg cells.

Cloning of feline FOXP3 and detection of expression in CD4+CD25+ regulatory T cells

Regulatory T cells (Treg) are increased and directly infected by feline immunodeficiency virus (FIV) and likely play a role in other feline autoimmune, neoplastic, and infectious diseases. Phenotypically, Treg are best characterized by surface expression of CD4 and CD25 and intranuclear expression of the forkhead transcription factor Foxp3. Our objective was to clone and sequence feline FOXP3 for the purpose of developing assays to enhance studies of feline Treg. We determined the feline FOXP3 is 1293 nucleotides in length and codes for a protein that shares high homology to other species. A splice variant devoid of exon 2 was also identified. A real-time PCR assay was developed and used to show Foxp3 mRNA expression occurs primarily in CD4+CD25+ T cells. Two cross-reacting antibodies were identified by immunocytochemical staining of HEK293 cells transfected with feline FOXP3. The antibody labeling confirmed the nuclear localization of the protein. A flow cytometric assay was also validated and used to correlate the phenotypic and functional characteristics of feline Treg induced by treatment of lymph node lymphocytes with flagellin or LPS in combination with mitogen or IL2. Together, these studies provide useful tools to further investigate Foxp3 and Tregs in cats.

Tumor-induced senescent T cells with suppressor function: a potential form of tumor immune evasion

Senescent and suppressor T cells are reported to be increased in select patients with cancer and are poor prognostic indicators. Based on the association of these T cells and poor outcomes, we hypothesized that tumors induce senescence in T cells, which negatively effects antitumor immunity. In this report, we show that human T cells from healthy donors incubated with tumor for only 6 h at a low tumor to T-cell ratio undergo a senescence-like phenotype, characterized by the loss of CD27 and CD28 expression and telomere shortening. Tumor-induced senescence of T cells is induced by soluble factors and triggers increases in expression of senescence-associated molecules such as p53, p21, and p16. Importantly, these T cells are not only phenotypically altered, but also functionally altered as they can suppress the proliferation of responder T cells. This suppression requires cell-to-cell contact and is mediated by senescent CD4(+) and CD8(+) subpopulations, which are distinct from classically described natural T regulatory cells. Our observations support the novel concept that tumor can induce senescent T cells with suppressor function and may effect both the diagnosis and treatment of cancer.

Regulatory T cells: potential target in anticancer immunotherapy

The concept of regulatory T cells was first described in the early 1970s, and regulatory T cells were called suppressive T cells at that time. Studies that followed have demonstrated that these suppressive T cells negatively regulated tumor immunity and contributed to tumor growth in mice. Despite the importance of these studies, there was extensive skepticism about the existence of these cells, and the concept of suppressive T cells left the center stage of immunologic research for decades. Interleukin-2 receptor alpha-chain, CD25, was first demonstrated in 1995 to serve as a phenotypic marker for CD4+ regulatory cells. Henceforth, research of regulatory T cells boomed. Regulatory T cells are involved in the pathogenesis of cancer, autoimmune disease, transplantation immunology, and immune tolerance in pregnancy. Recent evidence has demonstrated that regulatory T cell-mediated immunosuppression is one of the crucial tumor immune evasion mechanisms and the main obstacle of successful cancer immunotherapy. The mechanism and the potential clinical application of regulatory T cells in cancer immunotherapy are discussed.

The role of the CTLA4 blockade in the treatment of malignant melanoma

Metastatic melanoma remains a disease with few effective treatments. The anti-tumor immune response has long been felt to be important in the prognosis of melanoma, and much work has focused on harnessing the immune system to fight this disease. Tumor-specific vaccines, immunomodulatory cytokines and non-specific immunostimulants (such as Bacille Calmette Guerin/BCG) have all been investigated. A new strategy has been identified involving cytotoxic T-lymphocyte antigen-4 (CTLA4). This molecule is expressed on the surface of activated T-lymphocytes and exerts a suppressive effect on the induction of immune responses after interaction between T-cell receptor (TCR) and human lymphocyte antigen (HLA) molecules on the antigen-presenting cell (APC). Work in animal models demonstrated that antibody-mediated blockade of this target could lead to anti-tumor responses. Two fully human monoclonal antibodies, ipilimumab (MDX-010) and tremelimumab (CP-675, 206; formerly known as ticilimumab), are in clinical development. Both have demonstrated hints of clinical activity in metastatic melanoma. Both also have a toxicity profile consistent with their mechanism of action, involving inactivation of a normal immunosuppressive homeostatic mechanism: development of auto-immune breakthrough events (IBE). These include inflammatory bowel disease (IBD), uveitis, dermatitis, arthritis, and others. Generally, these events have been easily managed by cessation of therapy and intravenous or topical steroid therapy and supportive care in most patients, although colectomy had been required in several severe cases and there have been several deaths. Interestingly, patients who develop IBE seem to have the greatest likelihood of clinical benefit, but it is unclear whether clinical benefit and IBE are dissociable events. Other than IBE, no other pharmacodynamic measure has been able to predict response, although certain autoimmune antibody titers may have promise in this regard. Further research will confirm the clinical benefit of these agents alone and in combination with other agents, further define the safety profile and protocols for toxicity management, and identify pharmacodynamic parameters predicting clinical benefit and toxicity.