Regulatory T-cell function of adult T-cell leukemia/lymphoma cells

Novel paired CD13-negative (MT-50.1) and CD13-positive (MT-50.4) HTLV-1-infected T-cell lines with differential regulatory T cell-like activity

Adult T-cell leukemia/lymphoma (ATL) occurs after human T-cell leukemia virus type-1 (HTLV-1) infection with a long latency period exceeding several decades. This implies the presence of immune evasion mechanisms for HTLV-1-infected T cells. Although ATL cells have a CD4+CD25+ phenotype similar to that of regulatory T cells (Tregs), they do not always possess the immunosuppressive functions of Tregs. Factors that impart effective immunosuppressive functions to HTLV-1-infected cells may exist. A previous study identified a new CD13+ Treg subpopulation with enhanced immunosuppressive activity. We, herein, describe the paired CD13- (designated as MT-50.1) and CD13+ (MT-50.4) HTLV-1-infected T-cell lines with Treg-like phenotype, derived from the peripheral blood of a single patient with lymphoma-type ATL. The cell lines were found to be derived from HTLV-1-infected non-leukemic cells. MT-50.4 cells secreted higher levels of immunosuppressive cytokines, IL-10 and TGF-β, expressed higher levels of Foxp3, and showed stronger suppression of CD4+CD25- T cell proliferation than MT-50.1 cells. Furthermore, the CD13 inhibitor bestatin significantly attenuated MT-50.4 cell growth, while it did not for MT-50.1 cells. These findings suggest that CD13 expression may be involved in the increased Treg-like activity of MT-50.4 cells. Hence, MT-50.4 cells will be useful for in-depth studies of CD13+Foxp3+ HTLV-1-infected cells.

Quantifying protein abundance on single cells using split-pool sequencing on DNA-barcoded antibodies for diagnostic applications

Proteins play critical roles across all facets of biology, with their abundance frequently used as markers of cell identity and state. The most popular method for detecting proteins on single cells, flow cytometry, is limited by considerations of fluorescent spectral overlap. While mass cytometry (CyTOF) allows for the detection of upwards of 40 epitopes simultaneously, it requires local access to specialized instrumentation not commonly accessible to many laboratories. To overcome these limitations, we independently developed a method to quantify multiple protein targets on single cells without the need for specialty equipment other than access to widely available next generation sequencing (NGS) services. We demonstrate that this combinatorial indexing method compares favorably to traditional flow-cytometry, and allows over two dozen target proteins to be assayed at a time on single cells. To showcase the potential of the technique, we analyzed peripheral blood and bone marrow aspirates from human clinical samples, and identified pathogenic cellular subsets with high fidelity. The ease of use of this technique makes it a promising technology for high-throughput proteomics and for interrogating complex samples such as those from patients with leukemia.

CCR4 as a Therapeutic Target for Cancer Immunotherapy

Simple Summary

CCR4 is a chemokine receptor selectively expressed on normal T cell subsets such as type 2 helper T cells, skin-homing T cells and regulatory T cells, and on skin-associated T cell malignancies such as adult T cell leukemia/lymphoma (ATLL), which is etiologically associated with human T lymphocyte virus type 1 (HTLV-1), and cutaneous T cell lymphomas (CTCLs). Mogamulizumab is a fully humanized and glyco-engineered monoclonal anti-CCR4 antibody used for the treatment of refractory/relapsed ATLL and CTCLs, often resulting in complete remission. The clinical applications of Mogamulizumab are now being extended to solid tumors, exploring the therapeutic effect of regulatory T cell depletion. This review overviews the expression of CCR4 in various T cell subsets, HTLV-1-infected T cells, ATLL and CTCLs, and the clinical applications of Mogamulizumab.

Abstract

CCR4 is a chemokine receptor mainly expressed by T cells. It is the receptor for two CC chemokine ligands, CCL17 and CCL22. Originally, the expression of CCR4 was described as highly selective for helper T type 2 (Th2) cells. Later, its expression was extended to other T cell subsets such as regulatory T (Treg) cells and Th17 cells. CCR4 has long been regarded as a potential therapeutic target for allergic diseases such as atopic dermatitis and bronchial asthma. Furthermore, the findings showing that CCR4 is strongly expressed by T cell malignancies such as adult T cell leukemia/lymphoma (ATLL) and cutaneous T cell lymphomas (CTCLs) have led to the development and clinical application of the fully humanized and glyco-engineered monoclonal anti-CCR4 Mogamulizumab in refractory/relapsed ATLL and CTCLs with remarkable successes. However, Mogamulizumab often induces severe adverse events in the skin possibly because of its efficient depletion of Treg cells. In particular, treatment with Mogamulizumab prior to allogenic hematopoietic stem cell transplantation (allo-HSCT), the only curative option of these T cell malignancies, often leads to severe glucocorticoid-refractory graft-versus-host diseases. The efficient depletion of Treg cells by Mogamulizumab has also led to its clinical trials in advanced solid tumors singly or in combination with immune checkpoint inhibitors. The main focus of this review is CCR4; its expression on normal and malignant T cells and its significance as a therapeutic target in cancer immunotherapy.

Clinical significance of the immunoglobulin G heavy-chain repertoire in peripheral blood mononuclear cells of adult T-cell leukaemia-lymphoma patients receiving mogamulizumab

‘Monitoring of immune responses following mogamulizumab‐containing treatment in patients with adult T‐cell leukaemia–lymphoma (ATL)’ (MIMOGA) is a multicentre prospective clinical study (UMIN000008696). In the MIMOGA study, we found that a lower percentage of CD2⁻CD19⁺ B cells in peripheral blood mononuclear cells (PBMC) was a significant unfavourable prognostic factor for overall survival (OS). Accordingly, we then analysed the immunoglobulin G (IgG) heavy‐chain repertoire in PBMC by high‐throughput sequencing. Of the 101 patients enrolled in the MIMOGA study, for 81 a sufficient amount of PBMC RNA was available for repertoire sequencing analysis. Peripheral IgG B cells in patients with ATL had a restricted repertoire relative to those in healthy individuals. There was a significant positive correlation between the Shannon–Weaver diversity index (SWDI) for the IgG repertoire and proportions of B cells in the PBMC of the patients. Multivariate analysis identified two variables significantly affecting OS: a higher serum soluble interleukin‐2 receptor level, and a lower SWDI for the IgG repertoire [hazard ratio, 2·124; 95% confidence interval, 1·114–4·049; n = 44]. The present study documents the importance of humoral immune responses in patients receiving mogamulizumab‐containing treatment. Further investigation of strategies to enhance humoral immune responses in patients with ATL is warranted.

Mogamulizumab for adult T-cell leukemia-lymphoma: a multicenter prospective observational study

Monitoring of Immune Responses Following Mogamulizumab-Containing Treatment in Patients with Adult T-Cell Leukemia-Lymphoma (ATL) (MIMOGA) is a multicenter prospective observational study to establish the most effective and safe treatment strategy using mogamulizumab for ATL patients (UMIN000008696). Mogamulizumab-naive patients were enrolled (n = 102), of whom 101 received mogamulizumab-containing treatment (68 acute, 18 lymphoma, 12 chronic, and 3 smoldering subtypes). At enrollment, there was a significant inverse correlation between serum soluble interleukin-2 receptor (sIL-2R) levels and percentages of Tax-specific cytotoxic T lymphocytes (Tax-CTLs) in the entire lymphocyte population or in the CD8+ T cell subset, but there was not a correlation with cytomegalovirus pp65-specific cytotoxic T lymphocytes (CMV-CTLs). The overall response rate was 65%, and median progression-free survival and overall survival (OS) were 7.4 and 16.0 months, respectively. A higher percentage of Tax-CTLs, but not CMV-CTLs, within the entire lymphocyte population or in the CD8+ T cell subset was significantly associated with longer survival. Multivariate analysis identified the clinical subtype (acute or lymphoma type), a higher sIL-2R level, and a lower percentage of CD2-CD19+ B cells in peripheral blood mononuclear cells as significant independent unfavorable prognostic factors for OS. This indicates that a higher percentage of B cells might reflect some aspect of a favorable immune status leading to a good outcome with mogamulizumab treatment. In conclusion, the MIMOGA study has demonstrated that mogamulizumab exerts clinically meaningful antitumor activity in ATL. The patient's immunological status before mogamulizumab was significantly associated with treatment outcome. Further time series immunological analyses, in addition to comprehensive genomic analyses, are warranted.

Robust CD8+ T-cell proliferation and diversification after mogamulizumab in patients with adult T-cell leukemia-lymphoma

Skin-related adverse events (AEs) occur frequently in adult T-cell leukemia-lymphoma (ATL) patients treated with mogamulizumab, a humanized anti-CCR4 monoclonal antibody. This study was undertaken to elucidate the mechanisms of mogamulizumab-induced skin-related AEs. We analyzed the T-cell receptor β chain repertoire in ATL patients' peripheral blood mononuclear cells (PBMCs) before and after mogamulizumab. Skin-related AEs were present in 16 patients and were absent in 8 patients. Additionally, we included 11 patients before and after chemotherapy without mogamulizumab. Immune-related gene expression in PBMCs before and after mogamulizumab was also assessed (n = 24). Mogamulizumab treatment resulted in CCR4+ T-cell depletion, and the consequent lymphopenia provoked homeostatic CD8+ T-cell proliferation, as evidenced by increased expressions of CD8B and CD8A, which were significantly greater in patients with skin-related AEs than in those without them. We hypothesize that proliferation is driven by the engagement of self-antigens, including skin-related antigens, in the face of regulatory T-cell depletion. Together with the observed activated antigen presentation function, this resulted in T-cell diversification that was significantly greater in patients with skin-related AEs than in those without. We found that the CD8+ T cells that proliferated and diversified after mogamulizumab treatment were almost entirely newly emerged clones. There was an inverse relationship between the degree of CCR4+ T-cell depletion and increased CD8+ T-cell proliferation and diversification. Thus, lymphocyte-depleting mogamulizumab treatment provokes homeostatic CD8+ T-cell proliferation predominantly of newly emerging clones, some of which could have important roles in the pathogenesis of mogamulizumab-induced skin-related AEs.

Clinical Applications of Genomic Alterations in ATLL: Predictive Markers and Therapeutic Targets

Simple Summary

In this review paper, we aim to summarize recent findings of genomic alterations found in adult T-cell leukemia/lymphoma (ATLL), which is an incurable disease induced by a virus; human T-cell leukemia virus type 1 (HTLV-1). Genomic alterations of ATLL have been comprehensively analyzed and the identified alterations and HTLV-1 infection synergistically act for ATLL development. As HTLV-1 is an endemic disease, ATLL frequently occurs in the endemic areas. Current clinicogenomic analyses suggest the existence of regional difference in ATLL pathophysiology. From a clinical perspective, several studies identified alterations that act as predictive markers and that a part of the alterations can be targetable in ATLL. The alterations can be leveraged to improve ATLL prognosis.

Abstract

Adult T-cell leukemia/lymphoma (ATLL) is a peripheral T-cell lymphoma (PTCL) caused by human T-cell leukemia virus type 1 (HTLV-1). Recent comprehensive genomic analyses have revealed the genomic landscape. One of the important findings of genomic alterations in ATLL is that almost all alterations are subclonal, suggesting that therapeutic strategies targeting a genomic alteration will result in partial effects. Among the identified alterations, genes involved in T-cell receptor signaling and immune escape mechanisms, such as PLCG1, CARD11, and PD-L1 (also known as CD274), are characteristic of ATLL alterations. From a geographic perspective, ATLL patients in Caribbean islands tend to be younger than those in Japan and the landscape differs between the two areas. Additionally, young Japanese ATLL patients frequently have CD28 fusions, compared with unselected Japanese cases. From a clinical perspective, PD-L1 amplification is an independent prognostic factor among every subtype of ATLL case. Recently, genomic analysis using deep sequencing identified a pre-ATLL clone with ATLL-common mutations in HTLV-1 carriers before development, indicating that genomic analysis can stratify cases based on the risks of development and mortality. In addition to genomic alterations, targetable super-enhancers have been identified in ATLL. These data can be leveraged to improve the prognosis of ATLL.

Ectonucleotidase CD39 is highly expressed on ATLL cells and is responsible for their immunosuppressive function

Adult T-cell leukemia/lymphoma (ATLL) patients have an extremely poor prognosis, partly due to their immunosuppressive state. The majority of ATLL patients have leukemic cells with phenotype similar to Tregs, prompting suggestions that ATLL cells themselves have immunosuppressive functions. In this study, we detected CD39 expression on ATLL cells, particularly frequent on aggressive subtypes. CD39 and CD73 convert extracellular adenosine triphosphate (ATP) into adenosine, a key player in Tregs’ immunosuppression. In vitro culture, both CD39⁺ ATLL cells and normal Tregs converted rapidly extracellular ATP to AMP, which was disturbed by CD39 inhibitors, and was negated in the CD39 knockout MJ cell line. The proliferation of cocultured CD4⁺/CD8⁺ normal T cells was suppressed by CD39⁺ MJ cells, but not by CD39 knockout MJ cells. Supplemented ATP was exhausted by an EG7-OVA T-cell line with stable CD39 induction, but not by mock. When these cell lines were subcutaneously transplanted into murine flanks, Poly(I:C) peritoneal administration reduced tumor size to 1/3 in mock-transplanted tumors, but not in CD39 induced tumors. Overall, we found that ATLL cells express CD39 at a high rate, and our results suggest that this helps ATLL cells escape antitumor immunity through the extracellular ATPDase-Adenosine cascade. These findings will guide future clinical strategies for ATLL treatment.

Updates in lymph node and skin pathology of adult T-cell leukemia/lymphoma, biomarkers, and beyond

Adult T-cell leukemia/lymphoma (ATLL) is a mature T-cell lymphoproliferative disorder associated with the human T lymphotropic virus (HTLV-1) infection. ATLL predominantly affects individuals within HTLV-1 endemic areas such as Japan, areas of Africa, South America, and the Caribbean. HTLV-1 preferentially infects CD4+ T-cells, and several genetic hits must occur before ATLL develops. ATLL is classically divided into four clinical variants based on manifestations of disease: acute, chronic, lymphomatous, and smouldering. As of 2019, a new subtype has been described: lymphoma type of ATL, extranodal primary cutaneous. In this review, emphasis will be taken to describe the common clinicopathologic manifestations of the disease, advances in biomarker discovery, mutational landscape and targeted therapeutic approaches to treat this highly aggressive and frequently lethal type of T-cell lymphoma.

Enhancer profiling identifies critical cancer genes and characterizes cell identity in adult T-cell leukemia

A number of studies have recently demonstrated that super-enhancers, which are large cluster of enhancers typically marked by a high level of acetylation of histone H3 lysine 27 and mediator bindings, are frequently associated with genes that control and define cell identity during normal development. Super-enhancers are also often enriched at cancer genes in various malignancies. The identification of such enhancers would pinpoint critical factors that directly contribute to pathogenesis. In this study, we performed enhancer profiling using primary leukemia samples from adult T-cell leukemia/lymphoma (ATL), which is a genetically heterogeneous intractable cancer. Super-enhancers were enriched at genes involved in the T-cell activation pathway, including IL2RA/CD25, CD30, and FYN, in both ATL and normal mature T cells, which reflected the origin of the leukemic cells. Super-enhancers were found at several known cancer gene loci, including CCR4, PIK3R1, and TP73, in multiple ATL samples, but not in normal mature T cells, which implicated those genes in ATL pathogenesis. A small-molecule CDK7 inhibitor, THZ1, efficiently inhibited cell growth, induced apoptosis, and downregulated the expression of super-enhancer-associated genes in ATL cells. Furthermore, enhancer profiling combined with gene expression analysis identified a previously uncharacterized gene, TIAM2, that was associated with super-enhancers in all ATL samples, but not in normal T cells. Knockdown of TIAM2 induced apoptosis in ATL cell lines, whereas overexpression of this gene promoted cell growth. Our study provides a novel strategy for identifying critical cancer genes.

Direct targeting of cancer cells with antibodies: What can we learn from the successes and failure of unconjugated antibodies for lymphoid neoplasias?

Following approval in 1997 of the anti-CD20 antibody rituximab for the treatment of B-NHL and CLL, many other unconjugated IgG1 MAbs have been tested in pre-clinical and clinical trials for the treatment of lymphoid neoplasms. Relatively few have been approved however and these are directed against a limited number of target antigens (CD20, CD52, CCR4, CD38, CD319). We review here the known biological properties of these antibodies and discuss which factors may have led to their success or may, on the contrary, limit their clinical application. Common factors of the approved MAbs are that the target antigen is expressed at relatively high levels on the neoplastic targets and their mechanism of action is mostly immune-mediated. Indeed most of these MAbs induce ADCC and phagocytosis by macrophages, and many also activate complement, leading to target cell lysis. In contrast direct cell death induction is not a common feature but may enhance efficacy in some cases. Interestingly, a key factor for the success of several MAbs appears to be their capacity to skew immunity towards an anti-tumour mode, by inhibiting/depleting suppressor cells and/or activating immune cells within the microenvironment, independently of FcγRs. We also expose here some of the strategies employed by industry to expand the clinical use of these molecules beyond their original indication. Interestingly, due to the central role of lymphocytes in the control of the immune response, several of the antibodies are now successfully used to treat many different autoimmune diseases and have also been formally approved for some of these new indications. There is little doubt that this trend will continue and that the precise mechanisms of therapeutic MAbs will be further dissected and better understood in the context of both tumour immunology and autoimmunity.

Detection of Tax-specific CTLs in lymph nodes of adult T-cell leukemia/lymphoma patients and its association with Foxp3 positivity of regulatory T-cell function

Human T-cell lymphotropic virus type (HTLV)-1 Tax is a viral protein that has been reported to be important in the proliferation of adult T-cell leukemia/lymphoma (ATLL) cells and to be a target of HTLV-1-specific cytotoxic T lymphocytes (CTLs). However, it is not clear how Tax-specific CTLs behave in lymph nodes of ATLL patients. The present study analyzed the immunostaining of Tax-specific CTLs. Furthermore, ATLL tumor cells are known to be positive for forkhead box P3 (Foxp3)and to have a regulatory T (Treg)-cell-like function. The association between T-reg function and number and activity of Tax-specific CTLs was also investigated. A total of 15 ATLL lymphoma cases with human leukocyte antigen (HLA)-A24, for which Tax has a high affinity, were selected from the files of the Department of Pathology, School of Medicine, Kurume University (Kurume, Japan) using a polymerase chain reaction (PCR) method. Immunostaining was performed for cluster of differentiation (CD) 20, CD3, CD4, CD8, T-cell intracellular antigen-1 and Foxp3 in paraffin sections, and for Tax, interferon γ and HLA-A24 in frozen sections. In addition, the staining of Tax-specific CTLs (HLA-A24-restricted) was analyzed by MHC Dextramer^® assay in frozen sections. In addition, the messenger RNA expression of Tax and HTLV-1 basic leucine zipper factor were also evaluated by reverse transcription-PCR. Immunohistochemical staining of Tax protein in lymphoma tissue revealed the presence of positive lymphoma cells ranging from 5 to 80%, and immunohistochemical staining of HLA-A24 revealed the presence of positive lymphoma cells ranging from 1 to 95%. The expression of Tax and HLA-A24 was downregulated by viral function. Foxp3, a marker for Treg cells, was expressed in 0-90% of cells. Several cases exhibited Tax-specific CTL (HLA-A24-restricted)-positive cells, and there was an inverse correlation between Tax-specific CTLs and Foxp3. However, neither Tax nor HLA-A24 expression was associated with CTL or Foxp3. Our study indicated the possibility that ATLL cells, which expressed Tax, target of CTL, evade the CTL-mediated immune control by expression of Foxp3 as a Treg function.

Challenges and opportunities for checkpoint blockade in T-cell lymphoproliferative disorders

The T-cell lymphoproliferative disorders are a heterogeneous group of non-Hodgkin’s lymphomas (NHL) for which current therapeutic strategies are inadequate, as most patients afflicted with these NHL will succumb to disease progression within 2 years of diagnosis. Appreciation of the genetic and immunologic landscape of these aggressive NHL, including PD-L1 (B7-H1, CD274) expression by malignant T cells and within the tumor microenvironment, provides a strong rationale for therapeutic targeting this immune checkpoint. While further studies are needed, the available data suggests that responses with PD-1 checkpoint blockade alone will unlikely approach those achieved in other lymphoproliferative disorders. Herein, we review the unique challenges posed by the T-cell lymphoproliferative disorders and discuss potential strategies to optimize checkpoint blockade in these T-cell derived malignancies.

Multicenter Phase II Study of Lenalidomide in Relapsed or Recurrent Adult T-Cell Leukemia/Lymphoma: ATLL-002

Purpose

Few treatment options exist for adult T-cell leukemia/lymphoma (ATL), and the prognosis for this disease is poor. A phase I study of lenalidomide demonstrated preliminary antitumor activity in patients with relapsed ATL. The current phase II study evaluated the efficacy and safety of lenalidomide monotherapy in patients with relapsed or recurrent ATL.

Patients and Methods

Patients 20 years of age or older with acute, lymphoma, or unfavorable chronic subtype ATL, who had received one or more prior anti-ATL systemic chemotherapy and achieved stable disease or better on their last anti-ATL therapy with subsequent relapse or recurrence, were eligible. Patients received oral lenalidomide 25 mg/d continuously until disease progression or unacceptable toxicity. The primary end point was overall response rate; secondary end points included safety, tumor control rate (stable disease or better), time to response, duration of response, time to progression, progression-free survival, and overall survival.

Results

Objective responses were noted in 11 of 26 patients (overall response rate, 42%; 95% CI, 23% to 63%), including four complete responses and one unconfirmed complete response. The tumor control rate was 73%. The median time to response and duration of response were 1.9 months and not estimable, respectively, and the median time to progression was 3.8 months. The median progression-free survival and overall survival were 3.8 and 20.3 months, respectively. The most frequent grade ≥ 3 adverse events were neutropenia (65%), leukopenia (38%), lymphopenia (38%), and thrombocytopenia (23%), which were all manageable and reversible.

Conclusion

Lenalidomide demonstrated clinically meaningful antitumor activity and an acceptable toxicity profile in patients with relapsed or recurrent aggressive ATL, hinting at its potential to become a treatment option. Further investigations of lenalidomide in ATL and other mature T-cell neoplasms are warranted.

Novel immunotherapy for adult T-cell leukemia/lymphoma: Targeting aurora kinase A

Adult T-cell leukemia/lymphoma is caused by infection with HTLV-1, following a long latent period. Immunotherapy targeting Aurora kinase A, a tumor-associated antigen over-expressed in adult T-cell leukemia/lymphoma, holds great therapeutic potential. We review the evidence in favor of a therapeutic strategy combining vaccination and TCR-gene transfer against this target.

Effects of first-line chemotherapy on natural killer cells in adult T-cell leukemia-lymphoma and peripheral T-cell lymphoma

Purpose

Natural killer (NK) cells are well known to be the most important effector cells mediating antibody-dependent cellular cytotoxicity (ADCC) which is an important mechanism of action of antibody drugs. We evaluated the effects of chemotherapy on the cell number and activity of NK cells from patients who received the vincristine–cyclophosphamide–doxorubicin–prednisone (VCAP), doxorubicin–ranimustine–prednisone (AMP), and vindesine–etoposide–carboplatin–prednisone (VECP) (mLSG15) or mLSG15-like (-L) regimen, which is one of the standard of cares for newly diagnosed adult T-cell leukemia–lymphoma (ATL), or the cyclophosphamide–doxorubicin–vincristine–prednisone (CHOP) or CHOP-L regimen which is another standard of care for ATL and peripheral T-cell lymphoma (PTCL).

Methods

The number of lymphocytes and NK cells, and NK cell activity, were assessed using flow cytometry and a ⁵¹Cr release assay, respectively.

Results

A total of 26 patients with untreated ATL or PTCL were enrolled, and blood samples from 25 patients were evaluable. NK cell number in ATL decreased after mLSG15/-L treatment, and the degree of decrease in the NK cell number was more prominent just before VECP therapy (Day 15–17 of each cycle) than just before VCAP therapy (Day 1 of each cycle). The NK cell number in ATL after CHOP/-L treatment also decreased. Interestingly, the NK cell activity showed a tendency to increase after the treatment. NK cell number in PTCL did not decrease by CHOP/-L regimen, but the activity was slightly decreased after the treatment.

Conclusions

These results indicate that the effects of chemotherapeutic agents on NK cells vary according to the disease type and intensity of chemotherapy.

Angiotensin II type 1 receptor blocker telmisartan induces apoptosis and autophagy in adult T-cell leukemia cells

Adult T‐cell leukemia/lymphoma (ATL), an aggressive T‐cell malignancy that develops after long‐term infection with human T‐cell leukemia virus (HTLV‐1), requires new treatments. Drug repositioning, reuse of a drug previously approved for the treatment of another condition to treat ATL, offers the possibility of reduced time and risk. Among clinically available angiotensin II receptor blockers, telmisartan is well known for its unique ability to activate peroxisome proliferator‐activated receptor‐γ, which plays various roles in lipid metabolism, cellular differentiation, and apoptosis. Here, telmisartan reduced cell viability and enhanced apoptotic cells via caspase activation in ex vivo peripheral blood monocytes from asymptomatic HTLV‐1 carriers (ACs) or via caspase‐independent cell death in acute‐type ATL, which has a poor prognosis. Telmisartan also induced significant growth inhibition and apoptosis in leukemia cell lines via caspase activation, whereas other angiotensin II receptor blockers did not induce cell death. Interestingly, telmisartan increased the LC3‐II‐enriched protein fraction, indicating autophagosome accumulation and autophagy. Thus, telmisartan simultaneously caused caspase activation and autophagy. A hypertension medication with antiproliferation effects on primary and leukemia cells is intriguing. Patients with an early diagnosis of ATL are generally monitored until the disease progresses; thus, suppression of progression from AC and indolent ATL to acute ATL is important. Our results suggest that telmisartan is highly effective against primary cells and leukemia cell lines in caspase‐dependent and ‐independent manners, and its clinical use may suppress acute transformation and improve prognosis of patients with this mortal disease. This is the first report demonstrating a cell growth‐inhibitory effect of telmisartan in fresh peripheral blood mononuclear cells from leukemia patients.

Recurrence of Psoriasis Vulgaris Accompanied by Treatment with C-C Chemokine Receptor Type 4 (CCR4) Antibody (Mogamulizumab) Therapies in a Patient with Adult T cell Leukemia/ Lymphoma: Insight into Autoinflammatory Diseases

Adult T cell leukemia / lymphoma (ATL) is one of the most aggressive hematological malignancies caused by human T-lymphotropic virus type-I (HTLV-1). Mogamulizumab is a new defucosylated humanized monoclonal antibody agent which targets C-C chemokine receptor type 4 (CCR4) expressed occasionally on the surface of ATL cells. However, adverse events such as drug eruptions have also been highlighted, at least in part, via the dysfunction of regulatory T cells (Tregs). We herein report a pronounced recurrence of systemic psoriasis vulgaris accompanied by the treatment of mogamulizumab in a patient with ATL. Pathological examinations may suggest a mechanistic link between the recurrence of autoinflammatory diseases and anti-CCR4 antibody therapies.

Anti-CCR4 monoclonal antibody enhances antitumor immunity by modulating tumor-infiltrating Tregs in an ovarian cancer xenograft humanized mouse model

Recent studies have demonstrated that regulatory T cells (Tregs) are recruited to tumor sites where they can suppress antitumor immunity. The chemokine receptor CCR4 is expressed at high levels on functional CD4⁺CD25⁺FoxP3⁺ Tregs and production of the CCR4 ligand CCL22 by tumor cells and tumor-associated macrophages is associated with Treg recruitment to the tumor site. Here, we tested IgG1 and IgG4 isotypes of human anti-CCR4 mAb2-3 for their in vitro activity and in vivo capacity in a NSG mouse model bearing CCL22-secreting ovarian cancer (OvCA) xenograft to modulate Tregs and restore antitumor activity. Both mAb2-3 isotypes blocked in vitro chemoattraction of Tregs to CCL22-secreting OvCA cells. However, they differed in their in vivo mode of action with IgG1 causing Treg depletion and IgG4 blocking migration to the tumors. Primary T cells that were primed with OvCA-pulsed dendritic cells (DCs) demonstrated INFγ secretion that could be enhanced through Treg depletion by mAb2-3. Humanized mice reconstructed with allogeneic tumor-primed T cells (TP-T) were used to evaluate the restoration of OvCA immunity by depletion or blockade of Tregs with mAb2-3. We observed that IgG1 was more potent than IgG4 in inhibiting tumor growth. Mechanism studies demonstrated that mAb2-3 treatment lead to inhibition of IL-2 binding to its receptor. Further studies showed that mAb2-3 induced CD25 shedding (sCD25) from Tregs which lead to a decrease in IL-2-dependent survival. Together, the results demonstrate that mAb2-3 is an agonist antibody that can restore anti-OvCA immunity through modulation of Treg activity.

Fatal reactivation of hepatitis B virus infection in a patient with adult T-cell leukemia-lymphoma receiving the anti-CC chemokine receptor 4 antibody mogamulizumab

We report an adult T-cell leukemia-lymphoma (ATL) patient suffering from fatal reactivation of hepatitis B virus (HBV) infection after treatment with the anti-CC chemokine receptor 4 (CCR4) monoclonal antibody, mogamulizumab. HBV reactivation occurred without liver damage in this hepatitis B surface antigen (HBsAg) negative patient, who was seropositive for antibodies against the viral core and surface antigens at baseline, after two cycles of CHOP regimen (cyclophosphamide, doxorubicin, vincristine and prednisolone) followed by six cycles of THP-COP regimen (cyclophosphamide, pirarubicin, vincristine and prednisolone). Unexpectedly, mogamulizumab monotherapy for relapsed CCR4 positive ATL induced sudden and fatal liver failure due to HBV reactivation, despite antiviral prophylaxis with entecavir. This clinical course may not only offer important suggestions to prevent critical HBV reactivation in HBsAg positive cancer patients who receive immune-enhancing drugs such as anti-CCR4 antibody, but also provide a clue to understanding the pathogenesis of HBV reactivation following systemic chemotherapy.

The thyroid status reprograms T cell lymphoma growth and modulates immune cell frequencies

In spite of considerable evidence on the regulation of immunity by thyroid hormones, the impact of the thyroid status in tumor immunity is poorly understood. Here, we evaluated the antitumor immune responses evoked in mice with different thyroid status (euthyroid, hyperthyroid, and hypothyroid) that developed solid tumors or metastases after inoculation of syngeneic T lymphoma cells. Hyperthyroid mice showed increased tumor growth along with increased expression of cell cycle regulators compared to hypothyroid and control tumor-bearing mice. However, hypothyroid mice showed a higher frequency of metastases than the other groups. Hyperthyroid mice bearing tumors displayed a lower number of tumor-infiltrating T lymphocytes, lower percentage of functional IFN-γ-producing CD8(+) T cells, and higher percentage of CD19(+) B cells than euthyroid tumor-bearing mice. However, no differences were found in the distribution of lymphocyte subpopulations in tumor-draining lymph nodes (TDLNs) or spleens among different experimental groups. Interestingly, hypothyroid TDLN showed an increased percentage of regulatory T (Treg) cells, while hyperthyroid mice displayed increased number and activity of splenic NK cells, which frequency declined in spleens from hypothyroid mice. Moreover, a decreased number of splenic myeloid-derived suppressor cells (MDSCs) were found in tumor-bearing hyperthyroid mice as compared to hypothyroid or euthyroid mice. Additionally, hyperthyroid mice showed increased cytotoxic activity, which declined in hypothyroid mice. Thus, low levels of intratumoral cytotoxic activity would favor tumor local growth in hyperthyroid mice, while regional and systemic antitumor response may contribute to tumor dissemination in hypothyroid animals. Our results highlight the importance of monitoring the thyroid status in patients with T cell lymphomas.

KEY MESSAGES

T cell lymphoma phenotype is paradoxically influenced by thyroid status. Hyperthyroidism favors tumor growth and hypothyroidism rises tumor dissemination. Thyroid status affects the distribution of immune cell types in the tumor milieu. Thyroid status also modifies the nature of local and systemic immune responses.

Foxp3-dependent transformation of human primary CD4+ T lymphocytes by the retroviral protein tax

The retroviral Tax proteins of human T cell leukemia virus type 1 and 2 (HTLV-1 and -2) are highly homologous viral transactivators. Both viral proteins can immortalize human primary CD4+ memory T cells, but when expressed alone they rarely transform T cells. In the present study, we found that the Tax proteins displayed a differential ability to immortalize human CD4+Foxp3+ T cells with characteristic expression of CTLA-4 and GITR. Because epidermal growth factor receptor (EGFR) was reportedly expressed and activated in a subset of CD4+Foxp3+ T cells, we introduced an activated EGFR into Tax-immortalized CD4+Foxp3+ T cells. We observed that these modified cells were grown independently of exogenous IL-2, correlating with a T cell transformation phenotype. In Tax-immortalized CD4+Foxp3- T cells, ectopic expression of Foxp3 was a prerequisite for Tax transformation of T cells. Accordingly, treatment of the transformed T cells with erlotinib, a selective inhibitor of EGFR, induced degradation of EGFR in lysosome, consequently causing T cell growth inhibition. Further, we identified autophagy as a crucial cellular survival pathway for the transformed T cells. Silencing key autophagy molecules including Beclin1, Atg5 and PI3 kinase class III (PI3KC3) resulted in drastic impairment of T cell growth. Our data, therefore, unveiled a previously unidentified role of Foxp3 in T cell transformation, providing a molecular basis for HTLV-1 transformation of CD4+Foxp3+ T cells.

Prognostic Significance of Tryptophan Catabolism in Adult T-cell Leukemia/Lymphoma

PURPOSE

Indoleamine 2,3-dioxygenase 1 (IDO1: IDO), an enzyme catabolizing tryptophan (Trp) into the kynurenine (Kyn) pathway, is increasingly being recognized as an important microenvironmental factor suppressing antitumor immune responses. The purpose of the present study was to determine the prognostic significance of Trp catabolism in adult T-cell leukemia/lymphoma (ATL).

EXPERIMENTAL DESIGN

We quantified serum Trp and Kyn in 96 ATL patients, 38 human T-cell lymphotropic virus type-1 asymptomatic carriers (HTLV-1 ACs), and 40 healthy adult volunteer controls. The relationships between various clinical parameters including overall survival were analyzed. IDO expression was evaluated in the affected lymph nodes of ATL patients.

RESULTS

Serum Kyn concentrations and Kyn/Trp ratios were significantly higher in HTLV-1 ACs than healthy controls. Both increased significantly with progression from HTLV-1 AC to ATL. However, there were no significant differences in the serum Trp concentrations between ATL patients, HTLV-1 ACs, and controls. IDO was possibly produced by ATL and/or cells of the microenvironment. Multivariate analyses demonstrated that a high serum Kyn/Trp ratio and high Kyn level, but not a high Trp level, were significantly independent detrimental prognostic factors in ATL, as well as in that subset of patients with aggressive variant ATL.

CONCLUSIONS

Quantification of serum Kyn and Trp is useful for predicting prognosis of an individual ATL patient. Furthermore, ATL, especially in patients with a high serum Kyn/Trp ratio, is an appropriate disease for testing novel cancer immunotherapies targeting IDO.

[Development of mogamulizumab and establishment of an optimal therapy based on genomic biomarkers: from the academic viewpoint]

Mogamulizumab (Moga; KW-0761) is a defucosylated humanized anti-CC chemokine receptor 4 (CCR4) antibody engineered to exert potent antibody-dependent cellular cytotoxicity (ADCC). A collaborative investigation with industry in preclinical studies has demonstrated in vitro and in vivo efficacy via ADCC for adult T-cell leukemia/lymphoma (ATLL) and CCR4-positive peripheral T-cell lymphoma (PTCL). In a phase I study, once-weekly administration of mogamulizumab (0.01-1.0 mg/kg) for 4 weeks was well tolerated. In a phase II study of once-weekly mogamulizumab (1.0 mg/kg) for 8 weeks in relapsed/refractory ATLL patients, an overall response rate of 50% including 30% complete response rate with a median progression-free survival of 5.2 months was observed. The drug was subsequently approved by Pharmaceuticals and Medical Devices Agency(PMDA) in March 2012. Because CCR4 is abundantly expressed on the surface of effector regulatory T cells, a phase I study is being conducted to enhance antitumor immune response in patients with solid tumors. However, approximately 60% of patients receiving mogamulizumab experience skin eruption with 19% showing grade ≥ 3 rash. Postmarketing surveillance of mogamulizumab revealed a 3-4% incidence rate of skin-related serious adverse events (SAEs) such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Therefore we initiated a search for predictive genomic biomarkers in the blood of patients with ATLL or solid tumors prior to treatment with mogamulizumab for not only efficacy but also immune-related SAEs. We believe the results of this study may lead to safer and more efficient use of this agent in the near future.

Dose-intensified chemotherapy alone or in combination with mogamulizumab in newly diagnosed aggressive adult T-cell leukaemia-lymphoma: a randomized phase II study

This multicentre, randomized, phase II study was conducted to examine whether the addition of mogamulizumab, a humanized anti‐CC chemokine receptor 4 antibody, to mLSG15, a dose‐intensified chemotherapy, further increases efficacy without compromising safety of patients with newly diagnosed aggressive adult T‐cell leukaemia‐lymphoma (ATL). Patients were assigned 1:1 to receive mLSG15 plus mogamulizumab or mLSG15 alone. The primary endpoint was the complete response rate (%CR); secondary endpoints included the overall response rate (ORR) and safety. The %CR and ORR in the mLSG15‐plus‐mogamulizumab arm (n = 29) were 52% [95% confidence interval (CI), 33–71%] and 86%, respectively; the corresponding values in the mLSG15 arm (n = 24) were 33% (95% CI, 16–55%) and 75%, respectively. Grade ≥ 3 treatment‐emergent adverse events, including anaemia, thrombocytopenia, lymphopenia, leucopenia and decreased appetite, were observed more frequently (≥10% difference) in the mLSG15‐plus‐mogamulizumab arm. Several adverse events, including skin disorders, cytomegalovirus infection, pyrexia, hyperglycaemia and interstitial lung disease, were observed only in the mLSG15‐plus‐mogamulizumab arm. Although the combination strategy showed a potentially less favourable safety profile, a higher %CR was achieved, providing the basis for further investigation of this novel treatment for newly diagnosed aggressive ATL. This study was registered at ClinicalTrials.gov, identifier: NCT01173887.

Mogamulizumab and the treatment of CCR4-positive T-cell lymphomas

Glyco-engineering has been developed to enhance the pharmacological properties of monoclonal antibodies (mAbs) resulting in superior immune effector function. Mogamulizumab is the first approved glyco-engineered therapeutic antibody and first approved mAb to target the CC chemokine receptor 4 (CCR4). CCR4 is principally expressed on Tregs and helper T cells (Th) where it functions to induce homing of these leukocytes to sites of inflammation. Tregs play an essential role in maintaining immune balance; however, in malignancy, Tregs impair host antitumor immunity and provide a favorable environment for tumors to grow. CCR4 is highly expressed by aggressive peripheral T-cell lymphomas (PTCLs), particularly adult T-cell leukemia/lymphoma (ATL) and cutaneous T-cell lymphomas (CTCLs). Mogamulizumab is a humanized anti-CCR4 mAb with a defucosylated Fc region that enhances antibody-dependent cellular cytotoxicity (ADCC). In addition, mogamulizumab depletes CCR4+ Tregs, potentially evoking antitumor immune responses by autologous effector cells. This ability is highly pertinent as subsets of malignant T cells are believed to function as CD4+ Tregs, overexpressing CCR4. Clinical trials with mogamulizumab have demonstrated clinical efficacy and tolerability for the treatment of relapsed/refractory aggressive T-cell lymphomas, previously associated with very poor outcomes.

Epigenetic modification of the FoxP3 TSDR in HAM/TSP decreases the functional suppression of Tregs

HTLV-1 is a human retrovirus that is associated with the neuroinflammatory disorder HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). In these patients, HTLV-1 is primarily found in the CD4(+)CD25(+) T cell subset (Regulatory T cells:Tregs), which is responsible for peripheral immune tolerance and is known to be dysfunctional in HAM/TSP. Recent evidence suggests that FoxP3 expression and function is determined epigenetically through DNA demethylation in the Treg-specific demethylated region (TSDR). We analyzed the methylation of the TSDR in PBMCs, CD4(+) T cells, and CD4(+)CD25(+) T cells from normal healthy donors (NDs) and HAM/TSP patients. We demonstrated that there is decreased demethylation in analyzed PBMCs and CD4(+)CD25(+) T cells from HAM/TSP patients as compared to NDs. Furthermore, decreased TSDR demethylation was associated with decreased functional suppression by Tregs. Additionally, increased HTLV-1 Tax expression in HAM/TSP PBMC culture correlated with a concomitant decline in FoxP3 TSDR demethylation. Overall, we suggest that HTLV-1 infection decreases Treg functional suppressive capacity in HAM/TSP through modification of FoxP3 TSDR demethylation and that dysregulated Treg function may contribute to HAM/TSP disease pathogenesis.

Human T-cell leukemia virus type 1 and Foxp3 expression: viral strategy in vivo

Human T-cell leukemia virus type 1 (HTLV-1) is the causal agent of adult T-cell leukemia (ATL) and inflammatory diseases, including HTLV-1-associated myelopathy/tropical spastic paraparesis, uveitis and infective dermatitis. However, it remains to be elucidated how HTLV-1 induces both neoplastic and inflammatory diseases. A critical component in the Treg-cell machinery is the transcription factor Forkhead box P3 (Foxp3), which is expressed in ~5% of CD4(+) T cells of healthy individuals. Foxp3 is expressed in around 80% of ATL cases. Recent studies point to the capacity of Treg cells to convert to other cell types, even to those with an inflammatory phenotype. These characteristics might indicate that Treg cells might be playing a critical role in HTLV-1 infection, either by being targeted by the virus or by regulating and modulating the immune response. In this review, we will discuss the interplay between Foxp3 expression and HTLV-1, focusing on important viral proteins that might help the virus to trigger the development of such diverse pathologies.

The combination of arsenic, interferon-alpha, and zidovudine restores an "immunocompetent-like" cytokine expression profile in patients with adult T-cell leukemia lymphoma

BACKGROUND

HTLV-I associated adult T-cell leukemia/lymphoma (ATL) carries a dismal prognosis due to chemo-resistance and immuno-compromised micro-environment. The combination of zidovudine and interferon-alpha (IFN) significantly improved survival in ATL. Promising results were reported by adding arsenic trioxide to zidovudine and IFN.

RESULTS

Here we assessed Th1/Th2/T(reg) cytokine gene expression profiles in 16 ATL patients before and 30 days after treatment with arsenic/IFN/zidovudine, in comparison with HTLV-I healthy carriers and sero-negative blood donors. ATL patients at diagnosis displayed a T(reg)/Th2 cytokine profile with significantly elevated transcript levels of Foxp3, interleukin-10 (IL-10), and IL-4 and had a reduced Th1 profile evidenced by decreased transcript levels of interferon-γ (IFN-γ) and IL-2. Most patients (15/16) responded, with CD4⁺CD25⁺ cells significantly decreasing after therapy, paralleled by decreases in Foxp3 transcript. Importantly, arsenic/IFN/zidovudine therapy sharply diminished IL-10 transcript and serum levels concomittant with decrease in IL-4 and increases in IFN-γ and IL-2 mRNA, whether or not values were adjusted to the percentage of CD4⁺CD25⁺ cells. Finally, IL-10 transcript level negatively correlated with clinical response at Day 30.

CONCLUSIONS

The observed shift from a T(reg)/Th2 phenotype before treatment toward a Th1 phenotype after treatment with arsenic/IFN/zidovudine may play an important role in restoring an immuno-competent micro-environment, which enhances the eradication of ATL cells and the prevention of opportunistic infections.

Development of a novel redirected T-cell–based adoptive immunotherapy targeting human telomerase reverse transcriptase for adult T-cell leukemia

The efficacy and safety of a novel redirected T-cell–based adoptive immunotherapy targeting hTERT for patients with adult T-cell leukemia. hTERT-specific T-cell receptor gene-transduced CD8+ T cells lyse ATL cells, but not normal cells, both in vitro and in vivo.

Virological and immunological mechanisms in the pathogenesis of human T-cell leukemia virus type 1

Human T-cell leukemia virus type 1 (HTLV-1) was the first retrovirus shown to cause human disease, such as adult T-cell leukemia and HTLV-1 associated myelopathy/tropic spastic paraparesis. HTLV-1 mainly infects CD4 T cells and deregulates their differentiation, function and homeostasis, which should contribute to the pathogenesis of HTLV-1, for example, inducing transformation of infected CD4 T cells and chronic inflammatory diseases. Therefore, not only virological approach but also immunological approach regarding CD4 T cells are required to understand how HTLV-1 causes related human diseases. This review focuses on recent advances in our understanding of the interaction between HTLV-1 and the main host cell, CD4 T cells, which should provide us some clue to the mechanisms of HTLV-1 mediated pathogenesis.

The combination of IκB kinase β inhibitor and everolimus modulates expression of interleukin-10 in human T-cell lymphotropic virus type-1-infected T cells

Adult T-cell leukaemia-lymphoma (ATLL) is an aggressive malignancy of CD4(+)  CD25(+) T lymphocytes, characterized by a severely compromised immunosystem, in which the human T-cell lymphotropic virus type 1 (HTLV-1) has been recognized as the aetiological agent. This study found that an IκB kinase β (IKKβ) inhibitor Bay11-7082 inactivated mammalian target of rapamycin (mTOR), signal transducer and activator of transcription 3 and transcription factor nuclear factor-κB in HTLV-1-infected T cells; this was significantly enhanced in the presence of the mTOR inhibitor everolimus. In addition, Bay11-7082 decreased production of the immunosuppressive cytokine interleukin-10 (IL-10), which was further down-regulated when Bay11-7082 was combined with evelolimus in HTLV-1-infected T and ATLL cells isolated from patients. Interleukin-10 is known to inhibit maturation and the antigen-presenting function of dendritic cells (DCs). The culture media of HTLV-1-infected MT-1 cells, which contained a large amout of IL-10, hampered tumour necrosis factor-α-induced maturation of DCs isolated from healthy volunteers. Culture supernatant of MT-1 cells treated with a combination of Bay11-7082 and everolimus augmented maturation of DCs in association with a decrease in production of IL-10 and enhanced the allostimulatory function of DCs. Similarly, when DCs isolated from patients with ATLL were treated with the combination of Bay11-7082 and everolimus, they were fully matured and their capability to stimulate proliferation of lymphocytes was augmented. Taken together, the combination of Bay11-7082 and everolimus might exhibit immunostimulatory properties in HTLV-1-infected T and ATLL cells isolated from patients, and this combination may be potentially therapeutic to regain the compromised immunosystem in ATLL patients.

Adult T-cell lymphoma/leukaemia with haematemesis as a prodromal manifestation

We report a case of adult T-cell leukaemia/lymphoma (ATLL) with haematemesis as a prodromal manifestation. The patient was a 34-year-old woman from Yazd. She also gave a history of a fluctuating skin lesions consisting of non-pruritic papules and ulcers on her feet. Upper gastrointestinal endoscopy disclosed obvious nodularities without ulceration in the antrum of the stomach. Histological and immunohistochemical studies of the gastric biopsy specimen showed lymphomatous infiltration of diffuse pleomorphic type with a T-cell phenotype. Laboratory investigations revealed leucocytosis (consisting of highly atypical lymphocytes, many with clover-leaf-shaped nuclei) and hypercalcaemia. She was found to be seropositive for human T-lymphotropic virus type 1. A diagnosis of overt ATLL was made. The findings in this case indicate that an awareness of the existence of this disease in a non-endemic area such as Yazd is necessary to avoid potential misdiagnosis and be helpful in appropriate therapeutic decision.

Epigenetics, autoimmunity and hematologic malignancies: a comprehensive review

The relationships between immunological dysfunction, loss of tolerance and hematologic malignancies have been a focus of attention in attempts to understand the appearance of a higher degree of autoimmune disease and lymphoma in children with congenital immunodeficiency. Although multiple hypotheses have been offered, it is clear that stochastic processes play an important role in the immunopathology of these issues. In particular, accumulating evidence is defining a role of epigenetic mechanisms as being critical in this continuous spectrum between autoimmunity and lymphoma. In this review, we focus attention predominantly on the relationships between T helper 17 (Th17) and T regulatory populations that alter local microenvironments and ultimately the expression or transcription factors involved in cell activation and differentiation. Abnormal expression in any of the molecules involved in Th17 and/or Treg development alter immune homeostasis and in genetically susceptible hosts may lead to the appearance of autoimmunity and/or lymphoma. These observations have clinical significance in explaining the discordance of autoimmunity in identical twins. They are also particularly important in the relationships between primary immune deficiency syndromes, immune dysregulation and an increased risk of lymphoma. Indeed, defining the factors that determine epigenetic alterations and their relationships to immune homeostasis will be a challenge greater or even equal to the human genome project.

Tax is a potential molecular target for immunotherapy of adult T-cell leukemia/lymphoma

We expanded CTL specific for Tax (a human T-lymphotropic virus type-1-encoded gene product) in vitro from PBMC of several adult T-cell leukemia/lymphoma (ATL) patients, and document its potential significance as a target for ATL immunotherapy. Tax-specific CTL responses against tumor cells were restricted by Tax-expression and the appropriate human leukocyte antigen (HLA) type. Tax-specific CTL recognized HLA/Tax-peptide complexes on autologous ATL cells, even when their Tax expression was so low that it could only be detected by RT-PCR but not by flow cytometry. Recognition resulted in interferon gamma (IFN-γ) production and target cell lysis. This would be the first report that Tax-specific CTL from ATL patients specifically recognized and killed autologous tumor cells that expressed Tax. The Tax-specific CTL responded to as little as 0.01 pM of the corresponding peptide, indicating that their T-cell receptor avidity was much higher than that of any other CTL recognizing viral or other tumor antigens. This is presumably the reason why the Tax-specific CTL recognized and killed autologous ATL cells despite their very low Tax expression. In addition, cell cycle analyses and experiments with primary ATL cell-bearing mice demonstrated that ATL cells present at the site of active cell proliferation, such as in the tumor masses, expressed substantial amounts of Tax, but it was minimally expressed by the tumor cells in a quiescent state, such as in the blood. The present study not only provides a strong rationale for exploiting Tax as a possible target for ATL immunotherapy but also contributes to our understanding of the immunopathogenesis of ATL.

The microRNA regulatory network in normal- and HTLV-1-transformed T cells

Recent efforts to understand the molecular networks governing normal T cell development and driving the neoplastic transformation of T cells have brought to light the involvement of microRNAs (miRNAs), a class of noncoding RNAs of approximately 22 nucleotides that regulate gene expression at the posttranscriptional level. In the present review, we compare the expression profiles of miRNAs in normal T cell development to that of transformed T cells using as a model adult T cell leukemia/lymphoma, an aggressive malignancy of mature CD4+ T cells that is caused by infection with human T cell leukemia virus type 1.

Cellular Factors Involved in HTLV-1 Entry and Pathogenicit

Human T cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T cell leukemia (ATL) and HTLV-1 – associated myelopathy and tropical spastic paraparesis (HAM/TSP). HTLV-1 has a preferential tropism for CD4 T cells in healthy carriers and ATL patients, while both CD4 and CD8 T cells serve as viral reservoirs in HAM/TSP patients. HTLV-1 has also been detected other cell types, including monocytes, endothelial cells, and dendritic cells. In contrast to the limited cell tropism of HTLV-1 in vivo, the HTLV receptor appears to be expressed in almost all human or animal cell lines. It remains to be examined whether this cell tropism is determined by host factors or by HTLV-1 heterogeneity. Unlike most retroviruses, cell-free virions of HTLV-1 are very poorly infectious. The lack of completely HTLV-1-resistant cells and the low infectivity of HTLV-1 have hampered research on the HTLV entry receptor. Entry of HTLV-1 into target cells is thought to involve interactions between the env (Env) glycoproteins, a surface glycoprotein (surface unit), and a transmembrane glycoprotein. Recent studies have shown that glucose transporter GLUT1, heparan sulfate proteoglycans (HSPGs), and neuropilin-1 (NRP-1) are the three proteins important for the entry of HTLV-1. Studies using adherent cell lines have shown that GLUT1 can function as a receptor for HTLV. HSPGs are required for efficient entry of HTLV-1 into primary CD4 T cells. NRP-1 is expressed in most established cell lines. Further studies have shown that these three molecules work together to promote HTLV-1 binding to cells and fusion of viral and cell membranes. The virus could first contact with HSPGs and then form complexes with NRP-1, followed by association with GLUT1. It remains to be determined whether these three molecules can explain HTLV-1 cell tropism. It also remains to be more definitively proven that these molecules are sufficient to permit HTLV-1 entry into completely HTLV-1-resistant cells.

HTLV-1 modulates the frequency and phenotype of FoxP3+CD4+ T cells in virus-infected individuals

BACKGROUND

HTLV-1 utilizes CD4 T cells as the main host cell and maintains the proviral load via clonal proliferation of infected CD4+ T cells. Infection of CD4+ T cells by HTLV-1 is therefore thought to play a pivotal role in HTLV-1-related pathogenicity, including leukemia/lymphoma of CD4+ T cells and chronic inflammatory diseases. Recently, it has been reported that a proportion of HTLV-1 infected CD4+ T cells express FoxP3, a master molecule of regulatory T cells. However, crucial questions remain unanswered on the relationship between HTLV-1 infection and FoxP3 expression.

RESULTS

To investigate the effect of HTLV-1 infection on CD4+ T-cell subsets, we used flow cytometry to analyze the T-cell phenotype and HTLV-1 infection in peripheral mononuclear cells (PBMCs) of four groups of subjects, including 23 HTLV-1-infected asymptomatic carriers (AC), 10 patients with HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP), 10 patients with adult T-cell leukemia (ATL), and 10 healthy donors. The frequency of FoxP3+ cells in CD4+ T cells in AC with high proviral load and patients with HAM/TSP or ATL was higher than that in uninfected individuals. The proviral load was positively correlated with the percentage of CD4+ T cells that were FoxP3+. The CD4+FoxP3+ T cells, themselves, were frequently infected with HTLV-1. We conclude that FoxP3+ T- cells are disproportionately infected with HTLV-1 during chronic infection. We next focused on PBMCs of HAM/TSP patients. The expression levels of the Treg associated molecules CTLA-4 and GITR were decreased in CD4+FoxP3+ T cells. Further we characterized FoxP3+CD4+ T-cell subsets by staining CD45RA and FoxP3, which revealed an increase in CD45RA-FoxP3low non-suppressive T-cells. These findings can reconcile the inflammatory phenotype of HAM/TSP with the observed increase in frequency of FoxP3+ cells. Finally, we analyzed ATL cells and observed not only a high frequency of FoxP3 expression but also wide variation in FoxP3 expression level among individual cases.

CONCLUSIONS

HTLV-1 infection induces an abnormal frequency and phenotype of FoxP3+CD4+ T cells.

Defucosylated Anti-CCR4 Monoclonal Antibody (KW-0761) for Relapsed Adult T-Cell Leukemia-Lymphoma: A Multicenter Phase II Study

Purpose

Adult T-cell leukemia-lymphoma (ATL) is usually resistant to conventional chemotherapies, and there are few other treatment options. Because CC chemokine receptor 4 (CCR4) is expressed on tumor cells from most patients with ATL, KW-0761, a humanized anti-CCR4 monoclonal antibody, which markedly enhances antibody-dependent cellular cytotoxicity, was evaluated in the treatment of patients with relapsed ATL.

Patients and Methods

A multicenter phase II study of KW-0761 for patients with relapsed, aggressive CCR4-positive ATL was conducted to evaluate efficacy, pharmacokinetic profile, and safety. The primary end point was overall response rate, and secondary end points included progression-free and overall survival from the first dose of KW-0761. Patients received intravenous infusions of KW-0761 once per week for 8 weeks at a dose of 1.0 mg/kg.

Results

Of 28 patients enrolled onto the study, 27 received at least one infusion of KW-0761. Objective responses were noted in 13 of 26 evaluable patients, including eight complete responses, with an overall response rate of 50% (95% CI, 30% to 70%). Median progression-free and overall survival were 5.2 and 13.7 months, respectively. The mean half-life period after the eighth infusion was 422 ± 147 hours (± standard deviation). The most common adverse events were infusion reactions (89%) and skin rashes (63%), which were manageable and reversible in all cases.

Conclusion

KW-0761 demonstrated clinically meaningful antitumor activity in patients with relapsed ATL, with an acceptable toxicity profile. Further investigation of KW-0761 for treatment of ATL and other T-cell neoplasms is warranted.

Cancer/testis antigens are novel targets of immunotherapy for adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is an intractable hematologic malignancy caused by human T-lymphotropic virus type 1 (HTLV-1), which infects approximately 20 million people worldwide. Here, we have explored the possible expression of cancer/testis (CT) antigens by ATLL cells, as CT antigens are widely recognized as ideal targets of cancer immunotherapy against solid tumors. A high percentage (87.7%) of ATLL cases (n = 57) expressed CT antigens at the mRNA level: NY-ESO-1 (61.4%), MAGE-A3 (31.6%), and MAGE-A4 (61.4%). CT antigen expression was confirmed by immunohistochemistry. This contrasts with other types of lymphoma or leukemia, which scarcely express these CT antigens. Humoral immune responses, particularly against NY-ESO-1, were detected in 11.6% (5 of 43) and NY-ESO-1-specific CD8(+) T-cell responses were observed in 55.6% (5 of 9) of ATLL patients. NY-ESO-1-specific CD8(+) T cells recognized autologous ATLL cells and produced effector cytokines. Thus, ATLL cells characteristically express CT antigens and therefore vaccination with CT antigens can be an effective immunotherapy of ATLL.

Molecular and Cellular Mechanism of Leukemogenesis of ATL: Emergent Evidence of a Significant Role for HBZ in HTLV-1-Induced Pathogenesis

Adult T-cell leukemia (ATL) is a leukemia derived from mature CD4⁺ T cells and induced by human T-cell leukemia virus type 1 (HTLV-1) infection. Previous studies have revealed many possible molecular and cellular mechanisms of HTLV-1-induced leukemogenesis, but it still remains unknown how HTLV-1 transforms peripheral CD4 T cells in infected individuals. Given the fact that only 2–5% of infected individuals develop ATL, HTLV-1 infection alone is not sufficient for the transformation of infected cells. Host genetic and epigenetic abnormalities and host immunological status should be considered in attempting to understand the mechanism of the oncogenesis of ATL. Nonetheless, it is obvious that HTLV-1 infection dramatically increases the risk of leukemia generation from peripheral CD4 T-cells, in which the incidence of leukemia is quite low. Furthermore, the evidence that all ATL cases retain the HTLV-1 provirus, especially the 3′ region, indicates that HTLV-1-encoded genes play a critical role in leukemogenesis. Since increasing evidence indicates that the HTLV-1 bZIP factor (HBZ) gene plays a significant role in the pathogenesis of HTLV-1, we will discuss the cellular and molecular mechanism of ATL generation from the virological point of view, particularly focusing on HBZ.

Cutaneous T-cell lymphoma: 2011 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Cutaneous T-cell lymphomas are a heterogenous group of T-cell lymphoproliferative disorders involving the skin, the majority of which may be classified as Mycosis fungoides (MF) or Sézary syndrome (SS).

DIAGNOSIS

The diagnosis of MF or SS requires the integration of clinical and histopathologic data.

RISK-ADAPTED THERAPY

Tumor, node, metastasis, and blood (TNMB) staging remains the most important prognostic factor in MF/SS and forms the basis for a "risk-adapted," multidisciplinary approach to treatment. For patients with disease limited to the skin, expectant management or skin-directed therapies is preferred, as both disease-specific and overall survival for these patients is favorable. In contrast, patients with advanced-stage disease with significant nodal, visceral, or blood involvement are generally approached with biologic-response modifiers, denileukin diftitox, and histone deacetylase inhibitors before escalating therapy to include systemic, single-agent chemotherapy. Multiagent chemotherapy may be used for those patients with extensive visceral involvement requiring rapid disease control. In highly-selected patients with disease refractory to standard treatments, allogeneic stem-cell transplantation may be considered.

Adult T cell leukemia/lymphoma: FoxP3(+) cells and the cell-mediated immune response to HTLV-1

Human T-lymphotropic virus type 1 (HTLV-1) causes adult T-cell leukaemia/lymphoma (ATLL) in ∼5% of HTLV-1-infected people. ATLL cells frequently express several molecules that are characteristic of regulatory T cells (Tregs), notably CD4, CD25 and the transcription factor FoxP3. It has therefore recently been suggested that HTLV-1 selectively infects and transforms Tregs. We show that HTLV-1 induces and maintains a high frequency of FoxP3+ T cells by inducing expression of the chemokine CCL22; the frequency is especially high in patients with chronic ATLL. In turn, the FoxP3+ T cells exert both potentially beneficial and harmful effects: they suppress the growth of autologous ATLL clones and may also suppress the host's cytotoxic T lymphocyte response, which normally limits HTLV-1 replication and reduces the risk of HTLV-1-associated diseases. Although ATLL cells may exert immune suppressive effects, we conclude that ATLL is not necessarily a tumour of classical FoxP3+ Tregs.

Aberrant expression of chemokine receptor CCR4 in human gastric cancer contributes to tumor-induced immunosuppression

The chemokine receptor CCR4 is preferentially expressed on certain immune cells and some hematological tumor cells, which play pivotal roles in suppression of host immune response. However, the reasons for the upmodulation of CCR4 and its immune functions in solid tumors remain unclear. Herein, we aimed to determine the expression profiles of CCR4 in gastric cancer cells and its role in regulating antitumor immunity. CCR4 expression was assessed in 63 cases of gastric carcinomas by immunohistochemistry. We found cancer cells in lymphocyte-rich carcinomas more frequently showed moderate to strong positive staining for CCR4 than those in conventional carcinomas (P = 0.041), and also found a positive relationship between expression of CCR4 and tumor necrosis factor-α (P = 0.012). Stimulation of gastric cell lines with various cytokines showed that tumor necrosis factor-α uniquely upmodulated CCR4 expression through activation of nuclear factor-κB. Additional coculture experiments showed the forced expression of CCR4 in SGC-7901 cells caused a significant reduction of γ-interferon and elevation of interleukin-10 secretion in the supernatants from cocultured SGC-7901 cells and PBMCs. In addition, granzyme A production in cancer cell-cocultured CD56(+) natural killer cells was significantly downregulated. Inhibition of the overexpressed CCR4 in cancer cells by an inhibitor of CCR4, compound 39, proved to partly restore the antitumor immunity in respect of the inverse changes in those factors. Our studies suggest that the aberrant expression of CCR4 in human gastric cancer could contribute to tumor-induced immunosuppression. Conceivably, downmodulation of CCR4 expression could be a promising immunotherapy for human gastric cancer.

Leukemic T cells are specifically enriched in a unique CD3(dim) CD7(low) subpopulation of CD4(+) T cells in acute-type adult T-cell leukemia

The morphological discrimination of leukemic from non-leukemic T cells is often difficult in adult T-cell leukemia (ATL) as ATL cells show morphological diversity, with the exception of typical "flower cells." Because defects in the expression of CD3 as well as CD7 are common in ATL cells, we applied multi-color flow cytometry to detect a putative leukemia-specific cell population in the peripheral blood from ATL patients. CD4(+) CD14(-) cells subjected to two-color analysis based on a CD3 vs CD7 plot clearly demonstrated the presence of a CD3(dim) CD7(low) subpopulation in each of nine patients with acute-type ATL. The majority of sorted cells from this fraction showed a flower cell-like morphology and carried a high proviral load for the human T-cell leukemia virus type 1 (HTLV-I). Genomic integration site analysis (inverse long-range PCR) and analysis of the T cell receptor Vβ repertoire by flow cytometry indicated that the majority of leukemia cells were included in the CD3(dim) CD7(low) subpopulation. These results suggest that leukemic T cells are specifically enriched in a unique CD3(dim) CD7(low) subpopulation of CD4(+) T cells in acute-type ATL.

Current concepts regarding the HTLV-1 receptor complex

The identity of the Human T lymphotropic Virus type 1 (HTLV-1) receptor remained an unsolved puzzle for two decades, until the recent demonstration that three molecules, Glucose Transporter 1, Neuropilin-1 and Heparan Sulfate Proteoglycans are involved in HTLV-1 binding and entry. Despite these advances, several questions remain unanswered, including the precise role of each of these molecules during virus entry. In light of the most recent data, we propose a model of the HTLV-1 receptor complex and discuss its potential impact on HTLV-1 infection.

Immunopathogenesis of lymphoma: focus on CCR4

Evading immune surveillance is one of the common hallmarks of cancer. Herein we describe two major evasion mechanisms in lymphoma, focusing on regulatory T (Treg) cells and C-C chemokine receptor 4 (CCR4) expressed on these cells. First, the tumor cells themselves function as Treg cells, characterized by expression of CCR4, contributing to tumor survival by downregulating host immunity. Second, CCR4 ligands are produced by tumor cells, which attract other CCR4(+) Treg cells to the vicinity of the tumor. CCR4(+) adult T-cell leukemia//lymphoma is an example of the former phenomenon, and Hodgkin lymphoma of the latter, for which an almost identical immunopathogenesis has been reported in many types of cancer. Awareness of the importance of CCR4 allows the rational design of more effective cancer treatments. Accordingly, we have developed a defucosylated anti-CCR4 mAb, the first therapeutic agent targeting CCR4 to be used clinically for cancer. The therapeutic anti-CCR4 mAb represents a promising treatment method for patients with CCR4(+) neoplasms by directly killing the cancer cells, but could also be used as a novel treatment strategy for many types of CCR4(-) cancers to overcome the suppressive effect of CCR4(+) Treg cells.