The CCR4 as a novel-specific molecular target for immunotherapy in Hodgkin lymphoma

Evaluation of the CCL17/CCL22-CCR4 axis in pediatrics with B-cell acute lymphoblastic leukemia before and after a chemotherapy course

AIMS

Acute lymphoblastic leukemia (ALL) is the most common type of pediatrics cancer. Chemokines exert different roles in leukemia process through leukocyte recruitment and regulation of disease severity. Due to the prominent roles of chemokine/receptor axes, this study aimed to measure the blood expression levels of CCR4 and their ligands in pediatrics with B-cell ALL (B-ALL). We also evaluated the impact of cytotoxic chemotherapy on this axis.

MATERIAL AND METHOD

Thirty children suffering from B-ALL were included in the study and followed up for 30 days after completion of a chemotherapy course. The blood sampling was performed before and after chemotherapy. 30 healthy donors have also entered the study as control subjects. The mRNA expression of CCL17, CCL22 and CCR4 genes was determined by quantitative real-time PCR. The frequency of the peripheral blood mononuclear cells expressing CCR4 (CCR4 + PBMCs) was also evaluated by the flow cytometry method. Moreover, we evaluated the association of the CCL17/CCL22-CCR4 axis with some diagnostic, prognostic and predictive biomarkers in ALL patients.

RESULTS

There was overexpression of the CCL17/CCL22-CCR4 axis along with lactate dehydrogenase (LDH) in pediatrics with B-ALL compared to healthy controls. After induction of chemotherapy, the blood expression levels of the CCL17/CCL22-CCR4 axis have reached the levels of healthy controls. The findings for the blood expression levels of CCR4 were also confirmed using flow cytometry.

CONCLUSION

The CCL17/CCL22-CCR4 axis can be used as a novel predictive and prognostic biomarker in B-ALL.

Identification of a cytokine-dominated immunosuppressive class in squamous cell lung carcinoma with implications for immunotherapy resistance

BACKGROUND

Immune checkpoint blockade (ICB) therapy has revolutionized the treatment of lung squamous cell carcinoma (LUSC). However, a significant proportion of patients with high tumour PD-L1 expression remain resistant to immune checkpoint inhibitors. To understand the underlying resistance mechanisms, characterization of the immunosuppressive tumour microenvironment and identification of biomarkers to predict resistance in patients are urgently needed.

METHODS

Our study retrospectively analysed RNA sequencing data of 624 LUSC samples. We analysed gene expression patterns from tumour microenvironment by unsupervised clustering. We correlated the expression patterns with a set of T cell exhaustion signatures, immunosuppressive cells, clinical characteristics, and immunotherapeutic responses. Internal and external testing datasets were used to validate the presence of exhausted immune status.

RESULTS

Approximately 28 to 36% of LUSC patients were found to exhibit significant enrichments of T cell exhaustion signatures, high fraction of immunosuppressive cells (M2 macrophage and CD4 Treg), co-upregulation of 9 inhibitory checkpoints (CTLA4, PDCD1, LAG3, BTLA, TIGIT, HAVCR2, IDO1, SIGLEC7, and VISTA), and enhanced expression of anti-inflammatory cytokines (e.g. TGFβ and CCL18). We defined this immunosuppressive group of patients as exhausted immune class (EIC). Although EIC showed a high density of tumour-infiltrating lymphocytes, these were associated with poor prognosis. EIC had relatively elevated PD-L1 expression, but showed potential resistance to ICB therapy. The signature of 167 genes for EIC prediction was significantly enriched in melanoma patients with ICB therapy resistance. EIC was characterized by a lower chromosomal alteration burden and a unique methylation pattern. We developed a web application ( http://lilab2.sysu.edu.cn/tex & http://liwzlab.cn/tex ) for researchers to further investigate potential association of ICB resistance based on our multi-omics analysis data.

CONCLUSIONS

We introduced a novel LUSC immunosuppressive class which expressed high PD-L1 but showed potential resistance to ICB therapy. This comprehensive characterization of immunosuppressive tumour microenvironment in LUSC provided new insights for further exploration of resistance mechanisms and optimization of immunotherapy strategies.

FOXP3/HAT1 Axis Controls Treg Infiltration in the Tumor Microenvironment by Inducing CCR4 Expression in Breast Cancer

Infiltrating T-regulatory cells in the tumor microenvironment is a key impediment to immunotherapy and is linked to a poor prognosis. We found that tumor-infiltrating Tregs express a higher expression of the chemokine receptor CCR4 than peripheral Tregs in breast cancer patients. CCL22 and CCL17 are released by tumor cells and tumor-associated macrophages, attracting CCR4+ Tregs to the tumor site. The Treg lineage-specific transcription factor FOXP3 changes the CCR4 promoter epigenetically in conjunction with HAT1 to provide a space for FOXP3 binding and activation of the CCR4 gene. To increase CCR4 expression in Tregs, the FOXP3/HAT1 axis is required for permissive (K23 and K27) or repressive (K14 and K18) acetylation of histone-3. In murine breast and melanoma tumor models, genetic ablation of FOXP3 reduced CCR4+ Treg infiltration and tumor size while also restoring anti-tumor immunity. Overexpression of FOXP3, on the other hand, increased CCR4+ Treg infiltration, resulting in a decreased anti-tumor immune response and tumor progression. These findings point to FOXP3 playing a new role in the tumor microenvironment as a transcriptional activator of CCR4 and a regulator of Treg infiltration.

CXCL2-mediated ATR/CHK1 signaling pathway and platinum resistance in epithelial ovarian cancer

Tumor microenvironment and chemokines play a significant role in cancer chemoresistance. This study was designed to reveal the important role of CXCL2 in platinum resistance in epithelial ovarian cancer (EOC). Differently expressed (DE) genes were screen out based on analysis of GSE114206 dataset in GEO database. The expression of DE chemokines was further validated in platinum- resistant and sensitive EOC. Cell viability assay and cell apoptosis assay were performed to explore the roles of CXCL2 in EOC. Cell stemness characteristics and the signaling pathway regulated by CXCL2 were also investigated in this study. As the results showed, CXCL2 was identified up-regulated in platinum-resistant EOC. The functional assays showed overexpressing CXCL2 or co-culturing with recombinant human CXCL2 promoted cell resistance to cisplatin. Conversely, knocking down CXCL2 or co-culturing with neutralizing antibody to CXCL2 increased cell response to cisplatin. CXCL2 overexpressing maintained cell stemness and activated ATR/CHK1 signaling pathway in EOC. Moreover, we further demonstrated that CXCL2-mediated resistance to cisplatin could be saved by SB225002, the inhibitor of CXCL2 receptor, as well as be rescued by SAR-020106, the inhibitor of ATR/CHK1 signaling pathway. This study identified a CXCL2-mediated mechanism in EOC platinum resistance. Our findings provided a novel target for chemoresistance prevention in EOC.

There Is (Scientific) Strength in Numbers: A Comprehensive Quantitation of Fc Gamma Receptor Numbers on Human and Murine Peripheral Blood Leukocytes

Antibodies are essential mediators of immunological defense mechanisms, are clinically used as therapeutic agents, but are also functionally involved in various immune-mediated disorders. Whereas IgG antibodies accomplish some of their biological tasks autonomously, many functions depend on their binding to activating and inhibitory Fcγ receptors (FcγR). From a qualitative point of view expression patterns of FcγR on immunologically relevant cell types are well-characterized both for mice and humans. Surprisingly, however, there is only quite limited information available on actual quantities of FcγR expressed by the different leukocyte populations. In this study we provide a comprehensive data set assessing quantitatively how many individual human and mouse FcγRs are expressed on B cells, NK cells, eosinophils, neutrophils, basophils and both classical, and non-classical monocytes under steady state conditions. Moreover, among human donors we found two groups with different expression levels of the inhibitory FcγRIIb on monocytes which appears to correlate with haplotypes of the activating FcγRIIIa.

Monoclonal Antibody Therapies for Hematological Malignancies: Not Just Lineage-Specific Targets

Today, monoclonal antibodies (mAbs) are a widespread and necessary tool for biomedical science. In the hematological cancer field, since rituximab became the first mAb approved by the Food and Drug Administration for the treatment of B-cell malignancies, a number of effective mAbs targeting lineage-specific antigens (LSAs) have been successfully developed. Non-LSAs (NLSAs) are molecules that are not restricted to specific leukocyte subsets or tissues but play relevant pathogenic roles in blood cancers including the development, proliferation, survival, and refractoriness to therapy of tumor cells. In consequence, efforts to target NLSAs have resulted in a plethora of mAbs-marketed or in development-to achieve different goals like neutralizing oncogenic pathways, blocking tumor-related chemotactic pathways, mobilizing malignant cells from tumor microenvironment to peripheral blood, modulating immune-checkpoints, or delivering cytotoxic drugs into tumor cells. Here, we extensively review several novel mAbs directed against NLSAs undergoing clinical evaluation for treating hematological malignancies. The review focuses on the structure of these antibodies, proposed mechanisms of action, efficacy and safety profile in clinical studies, and their potential applications in the treatment of hematological malignancies.

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.

CCL17 and CCL22/CCR4 signaling is a strong candidate for novel targeted therapy against nasal natural killer/T-cell lymphoma

Nasal natural killer/T-cell lymphoma (NNKTL) is associated with Epstein-Barr virus and has a poor prognosis because of local invasion and/or multiple dissemination. Various chemokines play a role in tumor proliferation and invasion, and chemokine receptors including the C-C chemokine receptor 4 (CCR4) are recognized as potential targets for treating hematologic malignancies. The aim of the present study was to determine whether specific chemokines are produced by NNKTL. We compared chemokine expression patterns in culture supernatants of NNKTL cell lines with those of other lymphoma or leukemia cell lines using chemokine protein array and ELISA. Chemokine (C-C motif) ligand (CCL) 17 and CCL22 were highly produced by NNKTL cell lines as compared to the other cell lines. In addition, CCL17 and CCL22 were readily observed in the sera of NNKTL patients. The levels of these chemokines were significantly higher in patients than in healthy controls. Furthermore, we detected the expression of CCR4 (the receptor for CCL17 and CCL22) on the surface of NNKTL cell lines and in tissues of NNKTL patients. Anti-CCR4 monoclonal antibody (mAb) efficiently induced antibody-dependent cellular cytotoxicity mediated by natural killer cells against NNKTL cell lines. Our results suggest that CCL17 and CCL22 may be important factors in the development of NNKTL and open up the possibility of immunotherapy of this lymphoma using anti-CCR4 mAb.

Chemokine receptor-specific antibodies in cancer immunotherapy: achievements and challenges

The 1990s brought a burst of information regarding the structure, expression pattern, and role in leukocyte migration and adhesion of chemokines and their receptors. At that time, the FDA approved the first therapeutic antibodies for cancer treatment. A few years later, it was reported that the chemokine receptors CXCR4 and CCR7 were involved on directing metastases to liver, lung, bone marrow, or lymph nodes, and the over-expression of CCR4, CCR6, and CCR9 by certain tumors. The possibility of inhibiting the interaction of chemokine receptors present on the surface of tumor cells with their ligands emerged as a new therapeutic approach. Therefore, many research groups and companies began to develop small molecule antagonists and specific antibodies, aiming to neutralize signaling from these receptors. Despite great expectations, so far, only one anti-chemokine receptor antibody has been approved for its clinical use, mogamulizumab, an anti-CCR4 antibody, granted in Japan to treat refractory adult T-cell leukemia and lymphoma. Here, we review the main achievements obtained with anti-chemokine receptor antibodies for cancer immunotherapy, including discovery and clinical studies, proposed mechanisms of action, and therapeutic applications.

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.

Fully human antagonistic antibodies against CCR4 potently inhibit cell signaling and chemotaxis

BACKGROUND

CC chemokine receptor 4 (CCR4) represents a potentially important target for cancer immunotherapy due to its expression on tumor infiltrating immune cells including regulatory T cells (Tregs) and on tumor cells in several cancer types and its role in metastasis.

METHODOLOGY

Using phage display, human antibody library, affinity maturation and a cell-based antibody selection strategy, the antibody variants against human CCR4 were generated. These antibodies effectively competed with ligand binding, were able to block ligand-induced signaling and cell migration, and demonstrated efficient killing of CCR4-positive tumor cells via ADCC and phagocytosis. In a mouse model of human T-cell lymphoma, significant survival benefit was demonstrated for animals treated with the newly selected anti-CCR4 antibodies.

SIGNIFICANCE

For the first time, successful generation of anti- G-protein coupled chemokine receptor (GPCR) antibodies using human non-immune library and phage display on GPCR-expressing cells was demonstrated. The generated anti-CCR4 antibodies possess a dual mode of action (inhibition of ligand-induced signaling and antibody-directed tumor cell killing). The data demonstrate that the anti-tumor activity in vivo is mediated, at least in part, through Fc-receptor dependent effector mechanisms, such as ADCC and phagocytosis. Anti-CC chemokine receptor 4 antibodies inhibiting receptor signaling have potential as immunomodulatory antibodies for cancer.

IgG1 anti-epidermal growth factor receptor antibodies induce CD8-dependent antitumor activity

Anti-EGFR monoclonal antibodies (mAb) like Cetuximab are commonly used for treatment of EGFR+ solid tumors mainly by exerting their therapeutic effect through inhibition of signal transduction. Additionally, IgG1 is a potent mediator of antibody-dependent cytotoxicity (ADCC). In case of the IgG1, Cetuximab induction of ADCC in vivo is controversially discussed. In our study, we investigated the efficiency of Cetuximab-mediated ADCC in a humanized mouse tumor model in vivo and analyzed the contribution of immunologic processes toward antitumor activity. Therefore, we used immunodeficient NOD/Scid mice transgenic for human MHC class I molecule HLA-A2 and adoptively transferred human HLA-A2+ PBMC after engraftment of human epidermoid cell carcinoma A431. Here, we show that high doses of anti-EGFR mAb induced strong tumor regression independent of the immune system. However, tumor regression by low doses of anti-EGFR mAb treatment was ADCC dependent and mediated by tumor infiltrating CD8+ T effector cells. This novel mechanism of ADCC conducted by CD8+ T effector cells was restricted to IgG1 anti-EGFR mAb, dependent of binding to CD16 on T cells and could be inhibited after EGFR blockade on tumor cells. Furthermore, CD8+ T effector cell-mediated ADCC was enhanced in the presence of IL-15 and strongly improved after glycosylation of anti-EGFR mAb indicating the potential of glycoengineered therapeutic mAb as efficient biologicals in cancer therapy.

Humanization of an anti-CCR4 antibody that kills cutaneous T-cell lymphoma cells and abrogates suppression by T-regulatory cells

Cutaneous T-cell lymphoma (CTCL) is a heterogeneous group of neoplastic disorders characterized by clonally derived and skin-homing malignant T cells that express high level of chemokine receptor CCR4, which is associated with their skin-homing capacity. CCR4 is also highly expressed on T-regulatory cells (Tregs) that can migrate to several different types of chemotactic ligand CCL17- and CCL22-secreting tumors to facilitate tumor cell evasion from immune surveillance. Thus, its high-level expression on CTCL cells and Tregs makes CCR4 a potential ideal target for antibody-based immunotherapy for CTCL and other types of solid tumors. Here, we conducted humanization and affinity optimization of a murine anti-CCR4 monoclonal antibody (mAb), mAb1567, that recognizes both the N-terminal and extracellular domains of CCR4 with high affinity and inhibits chemotaxis of CCR4(+) CTCL cells. In a mouse CTCL tumor model, mAb1567 exhibited a potent antitumor effect and in vitro mechanistic studies showed that both complement-dependent cytotoxicity (CDC) and neutrophil-mediated antibody-dependent cellular cytotoxicity (ADCC) likely mediated this effect. mAb1567 also exerts human NK cell-mediated ADCC activity in vitro. Moreover, mAb1567 also effectively inhibits chemotaxis of CD4(+)CD25(high) Tregs via CCL22 and abrogates Treg suppression activity in vitro. An affinity-optimized variant of humanized mAb1567, mAb2-3, was selected for further preclinical development based on its higher binding affinity and more potent ADCC and CDC activities. Taken together, this high-affinity humanized mAb2-3 with potent antitumor effect and a broad range of mechanisms of action may provide a novel immunotherapy for CTCL and other solid tumors.

Correlation of ADCC activity with cytokine release induced by the stably expressed, glyco-engineered humanized Lewis Y-specific monoclonal antibody MB314

A major limitation to the application of therapeutic monoclonal antibodies (mAbs) is their reduced in vivo efficacy compared with the high efficacy measured in vitro. Effector functions such as antibody-dependent cell-mediated cytotoxicity (ADCC) are dramatically reduced in vivo by the presence of high amounts of endogenous IgG in the serum. Recent studies have shown that modification of the glycosylation moieties attached to the Fc part of the mAb can enhance binding affinity to FcγRIIIα receptors on natural killer cells and thus may counteract the reduced in vivo efficacy. In the present study, a humanized IgG1/κ monoclonal antibody recognizing the tumor-associated carbohydrate antigen Lewis Y was stably produced in a moss expression system that allows glyco-engineering. The glyco-modified mAb (designated MB314) showed a highly homogeneous N-glycosylation pattern lacking core-fucose. A side-by-side comparison to its parental counterpart produced in conventional mammalian cell-culture (MB311, formerly known as IGN311) by fluorescence-activated cell sorting analysis confirmed that the target specificity of MB314 is similar to that of MB311. In contrast, ADCC effector function of MB314 was increased up to 40-fold whereas complement dependent cytotoxicity activity was decreased 5-fold. Notably, a release of immunostimulatory cytokines, including interferon γ, monocyte chemotactic protein-1 (MCP-1), interleukin-6 and tumor necrosis factor (TNF) was particularly induced with the glyco-modified antibody. TNF release was associated with CD14 (+) cells, indicating activation of monocytes.

Low level of FcγRIII expression on murine natural killer cells

Cellular Fcγ-receptors are crucial for mediating the functions of therapeutic antibodies. Antibody dependent cellular cytotoxicity (ADCC) is an important mechanism by which Fcγ-receptor expressing cells of the innate immune system including natural killer (NK) cells can kill opsonized target cells. During FACS analysis, however, binding of the Fc-fragment of staining antibodies specific for cell type specific receptors can lead to false positive results and wrong interpretation of the data. Current strategies to block such unwanted binding largely target FcγRIIB and FcγRIII but not the recently identified mouse FcγRIV. In this study we demonstrate that Fc-dependent binding of the NK cell specific antibody NK1.1 by FcγRIV on monocytes results in a large overestimation of FcγRIII expression on murine NK cells. These results highlight the importance of blocking unwanted binding of FACS antibodies to FcγRIV and shed new light on the expression level of FcγRIII on NK cells in mice during the steady state.

Humanized tumor mice--a new model to study and manipulate the immune response in advanced cancer therapy

The immunological impact on antibody-based anticancer therapies remains incompletely understood due to the lack of appropriate animal models for in vivo analysis. Here, we present a novel humanized tumor mouse (HTM) model, generated by concurrent transplantation of human hematopoietic stem cells (HSCs) and human breast cancer cells in neonatal NOD-scid IL2Rγ(null) mice. Five weeks after intrahepatic transplantation, a functional human immune system was developed in all organs, and, in addition, tumor cells were detectable in lung and bone marrow (early dissemination). After 3 months posttransplant, tumor-cell effusions and macroscopic tumors associated with liver or spleen were found. Furthermore, disseminated cells in different lymphoid and nonlymphoid organs were measurable. Tumor growth was accompanied by specific T-cell maturation and tumor cell-specific T-cell activation. In addition, Natural-Killer cell accumulation and activation were observed in HTM, which was further enhanced upon IL-15 treatment facilitating the possibility of immune cell modulation in, e.g., antibody-dependent cellular cytotoxicity-based immunotherapeutic approaches. This novel mouse model makes it possible to combine transfer of MHC mismatched tumor cells together with human HSCs resulting in a solid coexistence and interaction without evidence for rejection. Overall, humanized tumor mice represent a powerful in vivo model that for the first time permits the investigation of human immune system-related target cancer therapy and resistance.

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.

In vivo assay of human NK-dependent ADCC using NOD/SCID/gammac(null) (NOG) mice

Monoclonal antibodies are essential to the success of molecularly targeted therapies. Recently, numerous therapeutic antibodies have been developed for various diseases, including cancer and autoimmune diseases. Experimental systems to effectively evaluate these candidate antibodies are urgently needed. One of the mechanisms used by antibodies to kill tumor cells is antibody-dependent cellular cytotoxicity (ADCC), in which natural killer cells (NK) are the main mediator. The capacity to induce ADCC has conventionally been assessed in the human-mouse xeno-graft model, in which human peripheral blood mononuclear cells (PBMC), containing NK cells along with antibodies, are administered to tumor-bearing immunodeficient mice. However, contamination from other cellular populations often affects tumor growth, making it difficult to evaluate the antibody's effect. In this study, we established a new NK-dependent ADCC assay model using a supra-immunodeficient strain of mice, NOD/SCID/gammac(null) (NOG). Our model system simply consisted of three elements: isolated human NK cells, a Burkitt's lymphoma cell line (Daudi), and an anti-CD20 antibody (Rituximab). In this experimental setting, human NK cells from healthy donors retained their killing activity and suppressed the growth of Daudi cells in NOG mice when they were administered along with Rituximab. This system, therefore, is useful for evaluating the in vivo function of human NK cells.

Human T-lymphotropic virus type 1-induced CC chemokine ligand 22 maintains a high frequency of functional FoxP3+ regulatory T cells

We recently reported that human T-lymphotropic virus type 1 (HTLV-1) infection is accompanied by a high frequency of CD4(+)FoxP3(+) cells in the circulation. In asymptomatic carriers of HTLV-1 and in patients with HTLV-1-associated inflammatory and malignant diseases, a high FoxP3(+) cell frequency correlated with inefficient cytotoxic T cell-mediated killing of HTLV-1-infected cells. In adult T cell leukemia/lymphoma (ATLL), the FoxP3(+) population was distinct from the leukemic T cell clones. However, the cause of the increase in FoxP3(+) cell frequency in HTLV-1 infection was unknown. In this study, we report that the plasma concentration of the chemokine CCL22 is abnormally high in HTLV-1-infected subjects and that the concentration is strongly correlated with the frequency of FoxP3(+) cells, which express the CCL22 receptor CCR4. Further, we show that CCL22 is produced by cells that express the HTLV-1 transactivator protein Tax, and that the increased CCL22 enhances the migration and survival of FoxP3(+) cells in vitro. Finally, we show that FoxP3(+) cells inhibit the proliferation of ex vivo, autologous leukemic clones from patients with ATLL. We conclude that HTLV-1-induced CCL22 causes the high frequency of FoxP3(+) cells observed in HTLV-1 infection; these FoxP3(+) cells may both retard the progression of ATLL and HTLV-1-associated inflammatory diseases and contribute to the immune suppression seen in HTLV-1 infection, especially in ATLL.

Defucosylated humanized anti-CCR4 monoclonal antibody KW-0761 as a novel immunotherapeutic agent for adult T-cell leukemia/lymphoma

PURPOSE

Adult T-cell leukemia/lymphoma (ATLL) has a very poor prognosis. We have developed the humanized defucosylated anti-CC chemokine receptor 4 (CCR4) monoclonal antibody KW-0761 as a next generation immunotherapeutic agent. The first aim of the present study was to evaluate whether the antitumor activity of KW-0761 would likely be sufficient for therapeutic clinical application against ATLL. The second aim was to fully elucidate the mechanism of antibody-dependent cellular cytotoxicity (ADCC) mediated by this defucosylated monoclonal antibody.

EXPERIMENTAL DESIGN

The antitumor activity of KW-0761 against ATLL cell lines was evaluated in vitro using human cells and in mice in vivo. Primary ATLL cells from 23 patients were evaluated for susceptibility to autologous ADCC with KW-0761 by two independent methods.

RESULTS

KW-0761 showed potent antitumor activity against ATLL cell lines both in vitro and in the ATLL mouse model in vivo. In addition, KW-0761 showed potent antitumor activity mediated by highly enhanced ADCC against primary ATLL cells both in vitro and ex vivo in an autologous setting. The degree of KW-0761 ADCC against primary ATLL cells in an autologous setting was mainly determined by the amount of effector natural killer cells present, but not the amount of the target molecule CCR4 on the ATLL cell surface.

CONCLUSION

KW-0761 should be sufficiently active for therapeutic clinical application for ATLL. In addition, combination treatment strategies that augment natural killer cell activity should be promising for amplifying the effect of KW-0761. In the near future, the actual efficacy of KW-0761 will be established in pivotal clinical trials.

Defucosylated anti-CCR4 monoclonal antibody exercises potent ADCC-mediated antitumor effect in the novel tumor-bearing humanized NOD/Shi-scid, IL-2Rgamma(null) mouse model

PURPOSE

There are no suitable small animal models to evaluate human antibody-dependent cellular cytotoxicity (ADCC) in vivo, due to species incompatibilities. Thus, the first aim of this study was to establish a human tumor-bearing mouse model in which human immune cells can engraft and mediate ADCC, but where the endogenous mouse immune cells cannot mediate ADCC. The second aim was to evaluate ADCC mediated in these humanized mice by the defucosylated anti-CC chemokine receptor 4 (CCR4) monoclonal antibody (mAb) which we have developed and which is now in phase I clinical trials.

EXPERIMENTAL DESIGN

NOD/Shi-scid, IL-2Rgamma(null) (NOG) mice were the recipients of human immune cells, and CCR4-expressing Hodgkin lymphoma (HL) and cutaneous T-cell lymphoma (CTCL) cell lines were used as target tumors.

RESULTS

Humanized mice have been established using NOG mice. The chimeric defucosylated anti-CCR4 mAb KM2760 showed potent antitumor activity mediated by robust ADCC in these humanized mice bearing the HL or CTCL cell lines. KM2760 significantly increased the number of tumor-infiltrating CD56-positive NK cells which mediate ADCC, and reduced the number of tumor-infiltrating FOXP3-positive regulatory T (Treg) cells in HL-bearing humanized mice.

CONCLUSIONS

Anti-CCR4 mAb could be an ideal treatment modality for many different cancers, not only to directly kill CCR4-expressing tumor cells, but also to overcome the suppressive effect of Treg cells on the host immune response to tumor cells. In addition, using our humanized mice, we can perform the appropriate preclinical evaluation of many types of antibody based immunotherapy.

Expression of the ULBP ligands for NKG2D by B-NHL cells plays an important role in determining their susceptibility to rituximab-induced ADCC

Antibody-dependent cellular cytotoxicity (ADCC) is a major antitumor mechanism of action of therapeutic monoclonal antibodies (mAbs). The aim of this study was to identify tumor-associated factors which determine susceptibility to rituximab-induced ADCC. Thirty different CD20+ non-Hodgkin lymphoma cell lines were phenotyped for characteristics such as level of expression of NKG2D ligands, and the influence thereof on susceptibility to rituximab-induced ADCC was established. The present study demonstrated that tumor cell susceptibility to rituximab-induced ADCC was determined by 3 major tumor-associated factors: (i) the amount of the target molecule, CD20; (ii) the amount of the ligands for inhibitory killer Ig-like receptors, major histocompatibility complex class I; and (iii) the amounts of some of the NKG2D ligands, especially UL16-binding protein (ULBP) 1-3. The importance of the ULBPs was confirmed using antibody blockade. In conclusion, this is the first report to show the importance for rituximab-induced ADCC of ULBPs expressed on tumor cells. The ULBPs could be valuable diagnostic biological markers and significant targets for immunotherapy to improve efficacy not only of rituximab but also of other therapeutic mAbs.

Aberrant expression of chemokine receptor CXCR4 in gastrointestinal cancer tissues and cancer cell lines

AIM: To determine the expression status of chemokine receptor CXCR4 in gastrointestinal cancer and to explore its role in gastrointestinal carcinogenesis.

METHODS: Real-time PCR was used to detect mRNA expression of CXCR4 in gastrointestinal cancer samples. Reverse-transcription PCR (RT-PCR) and Western blot were used to determine the expression of CXCR4 in gastrointestinal cancer cell lines.

RESULTS: Level of CXCR4 mRNA was significantly higher in 24 colorectal cancer samples than in matched normal tissues (P < 0.001). Level of CXCR4 mRNA was also significantly higher in 30 gastric cancer samples than in matched normal tissues (P < 0.001). Both CXCR4 mRNA and CXCR4 protein were expressed strongly in colon cell lines HT-29 and SW-480, and gastric cell lines SGC-7901 and AGS. CXCR4 expression was correlated significantly with staging and lymph node metastasis in gastric cancers (P = 0.01 and P = 0.02, respectively).

CONCLUSION: CXCR4 is over-expressed in gastrointestinal cancers, and plays a role in gastrointestinal carcinogenesis.

Revisiting the seed and soil in cancer metastasis

Metastasis remains the overwhelming cause of death for cancer patients. During metastasis, cancer cells will leave the primary tumor, intravasate into the bloodstream, arrest at a distant organ, and eventually develop into gross lesions at the secondary sites. This intricate process is influenced by innumerable factors and complex cellular interactions described in 1889 by Stephen Paget as the seed and soil hypothesis. In this review, we revisit this seed and soil hypothesis with an emerging understanding of the cancer cell (i.e. seed) and its microenvironment (i.e. soil). We will provide background to suggest that a critical outcome of the seed-soil interaction is resistance of the stresses that would otherwise impede metastasis.

Detrimental role of CC chemokine receptor 4 in murine polymicrobial sepsis

CC chemokine receptor 4 (CCR4) and its two ligands, CCL17 and CCL22, are critically involved in different immune processes. In models of lipopolysaccharide-induced shock, CCR4-deficient (CCR4(-/-)) mice showed improved survival rates associated with attenuated proinflammatory cytokine release. Using CCR4(-/-) mice with a C57BL/6 background, this study describes for the first time the role of CCR4 in a murine model of polymicrobial abdominal sepsis, the colon ascendens stent peritonitis (CASP). CASP-induced sepsis led to a massive downregulation of CCR4 in lymphoid and nonlymphoid tissues, whereas the expression of CCL17 and CCL22 was independent of the presence of CCR4. After CASP, CCR4(-/-) animals showed a strongly enhanced bacterial clearance in several organs but not in the peritoneal lavage fluid and the blood. In addition, significantly reduced levels of proinflammatory cytokines/chemokines were measured in organ supernatants as well as in the sera of CCR4(-/-) mice. CCR4 deficiency consequently resulted in an attenuated severity of systemic sepsis and a strongly improved survival rate after CASP or CASP with intervention. Thus, our data provide clear evidence that CCR4 plays a strictly detrimental role in the course of polymicrobial sepsis.

Defucosylated anti CC chemokine receptor 4 monoclonal antibody combined with immunomodulatory cytokines: a novel immunotherapy for aggressive/refractory Mycosis fungoides and Sezary syndrome

PURPOSE

Sézary syndrome (SS) and Mycosis fungoides (MF) in the advanced stage have dismal prognoses. Because CC chemokine receptor 4 (CCR4) has an important role in the skin-homing capacity of MF/SS cells, we postulated that anti-CCR4 monoclonal antibody (mAb) could represent a novel therapeutic agent against aggressive/refractory MF/SS.

EXPERIMENTAL DESIGN

The defucosylated next-generation therapeutic mAb KM2760 induces enhanced antibody-dependent cellular cytotoxicity (ADCC). Here, we assessed the therapeutic potential of this antibody against aggressive MF/SS tumor cells in vitro and in animal models in vivo.

RESULTS

KM2760 induced robust ADCC by peripheral blood mononuclear cell (PBMC) from healthy controls against a MF/SS cell line as well as against primary tumor cells from patients with aggressive MF/SS. KM2760 also showed significant antitumor activity in disseminated and nondisseminated MF/SS mouse models. In addition, approximately 30% of autologous MF/SS tumor cells were killed in in vitro assays of KM2760-induced ADCC mediated by patients' PBMC after only 4 h, despite the low numbers of natural killer cells present in these PBMCs. It is also shown that ADCC induced by defucosylated therapeutic mAb can be greatly augmented by the immunomodulatory cytokines interleukin-12, IFN-alpha-2b, and IFN-gamma.

CONCLUSIONS

The present study has encouraged us in the conducting of a phase I clinical trial of a completely defucosylated anti-CCR4 mAb in patients with CCR4-positive T-cell lymphomas, including aggressive MF/SS (ClinicalTrials.gov identifier: NCT00355472). In the near future, the efficacy not only of defucosylated anti-CCR4 mAb single-agent treatment but also of combination therapy with immunomodulatory cytokines will be clinically established to target aggressive/refractory MF/SS.

Chemokines and cancer: migration, intracellular signalling and intercellular communication in the microenvironment

Inappropriate chemokine/receptor expression or regulation is linked to many diseases, especially those characterized by an excessive cellular infiltrate, such as rheumatoid arthritis and other inflammatory disorders. There is now overwhelming evidence that chemokines are also involved in the progression of cancer, where they function in several capacities. First, specific chemokine–receptor pairs are involved in tumour metastasis. This is not surprising, in view of their role as chemoattractants in cell migration. Secondly, chemokines help to shape the tumour microenvironment, often in favour of tumour growth and metastasis, by recruitment of leucocytes and activation of pro-inflammatory mediators. Emerging evidence suggests that chemokine receptor signalling also contributes to survival and proliferation, which may be particularly important for metastasized cells to adapt to foreign environments. However, there is considerable diversity and complexity in the chemokine network, both at the chemokine/receptor level and in the downstream signalling pathways they couple into, which may be key to a better understanding of how and why particular chemokines contribute to cancer growth and metastasis. Further investigation into these areas may identify targets that, if inhibited, could render cancer cells more susceptible to chemotherapy.

A mechanistic perspective of monoclonal antibodies in cancer therapy beyond target-related effects

Several monoclonal antibodies are now in clinical use for cancer therapy, and many others are currently undergoing clinical evaluation. These agents offer unique specificity against key molecular targets on tumor cells or in the tumor microenvironment. The clinical efficacy of monoclonal antibodies is generally attributed to target-specific mechanisms resulting from neutralizing or inhibiting a growth factor or receptor that drives cell proliferation and tumor growth. Several targets, including CD20, human epidermal growth factor receptor 2, vascular endothelial growth factor, and epidermal growth factor receptor, have been validated in specific malignancies on the basis of monoclonal antibody efficacy. However, monoclonal antibodies also have the potential to activate immune-mediated effector functions, including antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. These functions result from interactions involving the Fc domain of the antibody, and, consequently, may vary by antibody, isotype, and Fc modification, such as changes in glycosylation. Accordingly, all monoclonal antibodies directed against a given target should not be considered equivalent in their ability to stimulate immune-mediated effector functions.

Immune cell recruitment and cell-based system for cancer therapy

Immune cells, such as cytotoxic T lymphocytes, natural killer cells, B cells, and dendritic cells, have a central role in cancer immunotherapy. Conventional studies of cancer immunotherapy have focused mainly on the search for an efficient means to prime/activate tumor-associated antigen-specific immunity. A systematic understanding of the molecular basis of the trafficking and biodistribution of immune cells, however, is important for the development of more efficacious cancer immunotherapies. It is well established that the basis and premise of immunotherapy is the accumulation of effective immune cells in tumor tissues. Therefore, it is crucial to control the distribution of immune cells to optimize cancer immunotherapy. Recent characterization of various chemokines and chemokine receptors in the immune system has increased our knowledge of the regulatory mechanisms of the immune response and tolerance based on immune cell localization. Here, we review the immune cell recruitment and cell-based systems that can potentially control the systemic pharmacokinetics of immune cells and, in particular, focus on cell migrating molecules, i.e., chemokines, and their receptors, and their use in cancer immunotherapy.

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

Adult T-cell leukemia/lymphoma (ATLL) patients are highly immunocompromised, but the underlying mechanism responsible for this state remains obscure. Recent studies demonstrated that FOXP3, which is a master control gene of naturally occurring regulatory T (Treg) cells, is expressed in the tumor cells from a subset of patients with ATLL. Since most ATLL cells express both CD4 and CD25, these tumors might originate from CD4(+)CD25(+)FOXP3(+) Treg cells, based on their phenotypic characteristics. However, whether ATLL cells actually function as Treg cells has not yet been clearly demonstrated. Here, we show that ATLL cells from a subset of patients are not only hypo-responsive to T-cell receptor-mediated activation, but also suppress the proliferation of autologous CD4(+) non-ATLL cells. Furthermore, ATLL cells from this subset of patients secrete only small amounts of IFN-gamma, and suppress IFN-gamma production by autologous CD4(+) non-ATLL cells. These are the first data showing that ATLL cells from a subset of patients function as Treg cells in an autologous setting. The present study provides novel insights into understanding the immunopathogenesis of ATLL, i.e., how HTLV-1-infected cells can survive in the face of host immune responses. It also adds to our understanding of ATLL patients' severely immunocompromised state.