Vaccination of B-CLL patients with autologous dendritic cells can change the frequency of leukemia antigen-specific CD8+ T cells as well as CD4+CD25+FoxP3+ regulatory T cells toward an antileukemia response

Exosome: From leukemia progression to a novel therapeutic approach in leukemia treatment

Exosomes, as small vesicles, are released by tumor cells and tumor microenvironment (cells and function as key intercellular mediators and effects on different processes including tumorigenesis, angiogenesis, drug resistance, and evasion from immune system. These functions are due to exosomes' biomolecules which make them as efficient markers in early diagnosis of the disease. Also, exosomes have been recently applied in vaccination. The potential role of exosomes in immune response toward leukemic cells makes them efficient immunotherapeutic agents treating leukemia. Furthermore, variations in exosomes contents make them beneficial to be used in treating different diseases. This review introduces the role of exosomes in the development of hematological malignancies and evaluates their functional role in the treatment of these malignancies.

Can Dendritic Cell Vaccination Prevent Leukemia Relapse?

Leukemias are clonal proliferative disorders arising from immature leukocytes in the bone marrow. While the advent of targeted therapies has improved survival in certain subtypes, relapse after initial therapy is a major problem. Dendritic cell (DC) vaccination has the potential to induce tumor-specific T cells providing long-lasting, anti-tumor immunity. This approach has demonstrated safety but limited clinical success until recently, as DC vaccination faces several barriers in both solid and hematological malignancies. Importantly, vaccine-mediated stimulation of protective immune responses is hindered by the aberrant production of immunosuppressive factors by cancer cells which impede both DC and T cell function. Leukemias present the additional challenge of severely disrupted hematopoiesis owing to both cytogenic defects in hematopoietic progenitors and an abnormal hematopoietic stem cell niche in the bone marrow; these factors accentuate systemic immunosuppression and DC malfunction. Despite these obstacles, several recent clinical trials have caused great excitement by extending survival in Acute Myeloid Leukemia (AML) patients through DC vaccination. Here, we review the phenotype and functional capacity of DCs in leukemia and approaches to harness DCs in leukemia patients. We describe the recent clinical successes in AML and detail the multiple new strategies that might enhance prognosis in AML and other leukemias.

The role of fibromodulin in cancer pathogenesis: implications for diagnosis and therapy

Fibromodulin (FMOD) is known as one of very important extracellular matrix small leucine-rich proteoglycans. This small leucine-rich proteoglycan has critical roles in the extracellular matrix organization and necessary for repairing of tissue in many organs. Given that the major task of FMOD is the modulation of collagen fibrillogenesis. However, recently observed that FMOD plays very important roles in the modulation of a variety of pivotal biological processes including angiogenesis, regulation of TGF-β activity, and differentiation of human fibroblasts into pluripotent cells, inflammatory mechanisms, apoptosis and metastatic related phenotypes. Besides these roles, FMOD has been considered as a new tumor-related antigen in some malignancies such as lymphoma, leukemia, and leiomyoma. Taken together, these findings proposed that FMOD could be introduced as diagnostic and therapeutic biomarkers in treatment of various cancers. Herein, for first time, we highlighted the various roles of FMOD in the cancerous conditions. Moreover, we summarized the diagnostic and therapeutic applications of FMOD in cancer therapy.

Lenalidomide as immune adjuvant to a dendritic cell vaccine in chronic lymphocytic leukemia patients

OBJECTIVES

We previously showed that immunization with ex vivo- generated autologous dendritic cells loaded with apoptotic tumor cells (Apo-DC) potentiated tumor-specific immunity in chronic lymphocytic leukemia (CLL) patients. Here, we evaluated safety and immunogenicity of Apo-DC in combination with lenalidomide, granulocyte-macrophage colony-stimulating factor (GM-CSF), and low-dose cyclophosphamide (CTX).

METHODS

Ten previously untreated patients with slowly progressing CLL received 5 Apo-DC vaccinations and lenalidomide orally for 24 weeks either alone (cohort I, n = 5) or together with subcutaneous GM-CSF and intravenous CTX (cohort II, n = 5). Tumor-specific T-cell responses were measured by proliferation and IFN-γ ELISPOT assays. Immune monitoring was performed by flow cytometry.

RESULTS

Dose-limiting toxicity was observed in 3/10 patients, 2 in cohort I and one in cohort II. One patient developed autoimmune hemolytic anemia and another grade 4 thrombocytopenia. Vaccine-induced immune responses were seen in 5/5 and 4/5 patients in cohort I and II, respectively. The expression of immune checkpoints on T cells did not change significantly.

CONCLUSIONS

Lenalidomide alone or in combination with GM-CSF and low-dose CTX as immune adjuvant to the Apo-DC vaccine elicited tumor-specific T-cell responses in CLL patients. However, unexpected toxicity was observed and caution is suggested in further exploring this drug as immune adjuvant in CLL.

Deregulation of SOCS5 suppresses dendritic cell function in chronic lymphocytic leukemia

One cause of morbidity and mortality in chronic lymphocytic leukemia (CLL) is infection, which results from defects in a number of components of the immune system. In particular, dendritic cells (DCs) are functionally defective in patients with CLL. To understand the molecular mechanism for this abnormality, we focused on signal transduction pathways that regulate the function of monocyte-derived dendritic cells (Mo-DCs). Monocytes from CLL patients exhibit high IL-4Rα expression due to the enhanced activation of STAT3. However, IL-4R signaling is decoupled from activation of its downstream mediator STAT6 by enhanced levels of the negative regulator SOCS5. This impairs differentiation of functionally mature DCs leading to decreased expression of HLA-DR and costimulatory molecules, and reduced secretion of pro-inflammatory cytokines in LPS-activated DCs. Moreover, Mo-DCs from CLL patients display a decreased ability to induce pro-inflammatory T-cell responses. IL-10-treatment of monocytes from healthy donors mimics the alteration in signaling observed in CLL patients, through enhanced STAT3-dependent expression of SOCS5. The higher level of SOCS5 inhibits STAT6 activation and leads to defective DC differentiation. These findings indicate that SOCS5 mediates the impaired function of DCs in CLL patients, and has the potential to be a new therapeutic target for reversing cancer-associated immune suppression.

Cellular Immunotherapy for Hematologic Malignancies: Beyond Bone Marrow Transplantation

Immunotherapy has changed treatment practices for many hematologic malignancies. Even in the current era of targeted therapy, chemotherapy remains the backbone of treatment for many hematologic malignancies, especially in acute leukemias, where relapse remains the major cause of mortality. Application of novel immunotherapies in hematology attempts to harness the killing power of the immune system against leukemia and lymphoma. Cellular immunotherapy is evolving rapidly for high-risk hematologic disorders. Recent advances include chimeric antigen-receptor T cells, mesenchymal stromal/stem cells, dendritic cell tumor vaccines, cytokine-induced killer cells, and virus-specific T cells. The advantages of nontransplantation cellular immunotherapy include suitability for patients for whom transplantation has failed or is contraindicated, and a potentially less-toxic treatment alternative to transplantation for relapsed/refractory patients. This review examines those emerging cellular immunotherapies that are changing treatment paradigms for patients with hematologic malignancies.

Hematologic neoplasms: Dendritic cells vaccines in motion

Dendritic cells (DCs) are bone-marrow-derived immune cells accounted for a key role in cancer vaccination as potent antigen-presenting cells within the immune system. Cancer microenvironment can modulate DCs maturation resulting in their accumulation into functional states associated with a reduced antitumor immune response. In this regard, a successful cancer vaccine needs to mount a potent antitumor immune response able to overcome the immunosuppressive tumor milieu. As a consequence, DCs-based approaches are a safe and promising strategy for improving the therapeutic efficacy in hematological malignancies, particularly in combinations with additional treatments. This review summarizes the most significant evidence about the immunotherapeutic strategies performed to target hematologic neoplasms including the tumoral associated antigens (TAA) pulsed on DCs, whole tumor cell vaccines or leukemia-derived DCs.

Next-generation dendritic cell-based vaccines for leukemia patients

Up to today treatment of leukemia patients remains challenging and different therapies have been developed, among them the generation of dendritic cell (DC) vaccines. DCs, highly specific for immunogenic cancer antigens, are generated either ex vivo or in vivo and boost the immune response against leukemic cells. Nevertheless, response rates are still heterogeneous and DC vaccines need improvement. New methods for generating DC vaccines have been summed up under the term 'next-generation DC vaccines'. They range from the analysis of human leukocyte antigen-ligandomes to immunogenic cell death inducers, from the production of viral vectors to mRNA transfection and finally from delivering peptides to DCs in vivo through either antibodies or cell-penetrating peptides. This review gives an overview of the latest developments in this still evolving field.

Cellular immunotherapy of cancer: an overview and future directions

The clinical success of checkpoint inhibitors has led to a renaissance of interest in cancer immunotherapies. In particular, the possibility of ex vivo expanding autologous lymphocytes that specifically recognize tumor cells has attracted much research and clinical trial interest. In this review, we discuss the historical background of tumor immunotherapy using cell-based approaches, and provide some rationale for overcoming current barriers to success of autologous immunotherapy. An overview of adoptive transfer of lymphocytes, tumor infiltrating lymphocytes and dendritic cell therapies is provided. We conclude with discussing the possibility of gene-manipulating immune cells in order to augment therapeutic activity, including silencing of the immune-suppressive zinc finger orphan nuclear receptor, NR2F6, as an attractive means of overcoming tumor-associated immune suppression.

Dendritic Cell Therapies for Hematologic Malignancies

Dendritic cells (DCs) are potent antigen-presenting cells that constitute a major component of the immune system’s role in the recognition, elimination, and tolerance of cancer. The unique immunologic capabilities of DCs have recently been harnessed for therapeutic use with the creation of DC-based anti-tumor vaccines, several of which have moved into testing in clinical trials for hematologic malignancies. This review summarizes how treatment strategies using DC-based anti-tumor vaccines are advancing immunotherapeutic options for these diseases.

Phase 1/2 study of immunotherapy with dendritic cells pulsed with autologous tumor lysate in patients with refractory bone and soft tissue sarcoma

BACKGROUND

There are limited options for the curative treatment of refractory bone and soft tissue sarcomas. The purpose of this phase 1/2 study was to assess the immunological and clinical effects of dendritic cells (DCs) pulsed with autologous tumor lysate (TL) in patients with advanced bone and soft tissue sarcomas.

METHODS

Thirty-seven patients with metastatic or recurrent sarcomas were enrolled in this study. Peripheral blood mononuclear cells obtained from the patients were suspended in media containing interleukin 4 (IL-4) and granulocyte-macrophage colony-stimulating factor. Subsequently, these cells were treated with TL, tumor necrosis factor α, and OK-432. The DCs were injected into the inguinal or axillary region. One treatment course comprised 6 weekly DC injections. The toxicity, clinical response (tumor volume, serum interferon-γ [IFN-γ], and serum IL-12), and oncological outcomes were observed.

RESULTS

In total, 47 courses of DC therapy were performed in 37 patients. No severe adverse events or deaths associated with the DC injections were observed in the study patients. Increased serum IFN-γ and IL-12 levels were observed 1 month after the DC injection. Among the 37 patients, 35 patients were assessed for clinical responses: 28 patients showed tumor progression, 6 patients had stable disease, and 1 patient showed a partial response 8 weeks after the DC injection. The 3-year overall and progression-free survival rates of the patients were 42.3% and 2.9%, respectively.

CONCLUSIONS

Although DC therapy appears safe and resulted in an immunological response in patients with refractory sarcoma, it resulted in an improvement of the clinical outcome in only a small number of patients. Cancer 2017;123:1576-1584. © 2017 American Cancer Society.

A seven-gene expression panel distinguishing clonal expansions of pre-leukemic and chronic lymphocytic leukemia B cells from normal B lymphocytes

Chronic lymphocytic leukemia (CLL) is a clonal disease of B lymphocytes manifesting as an absolute lymphocytosis in the blood. However, not all lymphocytoses are leukemic. In addition, first-degree relatives of CLL patients have an ~15 % chance of developing a precursor condition to CLL termed monoclonal B cell lymphocytosis (MBL), and distinguishing CLL and MBL B lymphocytes from normal B cell expansions can be a challenge. Therefore, we selected FMOD, CKAP4, PIK3C2B, LEF1, PFTK1, BCL-2, and GPM6a from a set of genes significantly differentially expressed in microarray analyses that compared CLL cells with normal B lymphocytes and used these to determine whether we could discriminate CLL and MBL cells from B cells of healthy controls. Analysis with receiver operating characteristics and Bayesian relevance determination demonstrated good concordance with all panel genes. Using a random forest classifier, the seven-gene panel reliably distinguished normal polyclonal B cell populations from expression patterns occurring in pre-CLL and CLL B cell populations with an error rate of 2 %. Using Bayesian learning, the expression levels of only two genes, FMOD and PIK3C2B, correctly distinguished 100 % of CLL and MBL cases from normal polyclonal and mono/oligoclonal B lymphocytes. Thus, this study sets forth effective computational approaches that distinguish MBL/CLL from normal B lymphocytes. The findings also support the concept that MBL is a CLL precursor.

Progress of dendritic cell-based cancer vaccines for patients with hematological malignancies

INTRODUCTION

Dendritic cells (DCs) are the most professional antigen-presenting cells eliciting cellular and humoral immune responses against cancer cells by expressing these antigens on MHC class I/II complexes to T cells. Therefore, they have been employed in many clinical trials as cancer vaccines for patients with cancer. This review focuses on the use of DCs in leukemia patients expressing leukemia-associated antigens (LAAs).

AREAS COVERED

The contribution of both stimulating vs. tolerogenic DCs as well as of other factors to the milieu of anti-leukemia immune responses are discussed. Several DC vaccination strategies like leukemia lysate, proteins and peptides have been developed. Next generation DC vaccines comprise transduction of DCs with retroviral vectors encoding for LAAs, cytokines and costimulatory molecules as well as transfection of DCs with naked RNA encoding for LAAs. Published as well as ongoing clinical trials are reported and critically reviewed.

EXPERT OPINION

Future results will demonstrate whether next-generation DCs are really superior to conventional pulsing with peptide, protein or tumor lysate. However, currently available methods based on nucleic acid transfection/transduction are tempting in terms of material production costs and time for clinical application according to good manufacturing practice (GMP).

A novel multi-drug metronomic chemotherapy significantly delays tumor growth in mice

BACKGROUND

The tumor immunosuppressive microenvironment represents a major obstacle to an effective tumor-specific cellular immune response.

METHODS

In the present study, the counterbalance effect of a novel metronomic chemotherapy protocol on such an immunosuppressive microenvironment was evaluated in a mouse model upon sub-cutaneous ectopic implantation of B16 melanoma cells. The chemotherapy consisted of a novel multi-drug cocktail including taxanes and alkylating agents, administered in a daily metronomic fashion. The newly designed strategy was shown to be safe, well tolerated and significantly efficacious.

RESULTS

Treated animals showed a remarkable delay in tumor growth and prolonged survival as compared to control group. Such an effect was directly correlated with CD4(+) T cell reduction and CD8(+) T cell increase. Furthermore, a significant reduction in the percentage of both CD25(+)FoxP3(+) and CD25(+)CD127(low) regulatory T cell population was found both in the spleens and in the tumor lesions. Finally, the metronomic chemotherapy induced an intrinsic CD8(+) T cell response specific to B16 naturally expressed Trp2 TAA.

CONCLUSION

The novel multi-drug daily metronomic chemotherapy evaluated in the present study was very effective in counterbalancing the immunosuppressive tumor microenvironment. Consequently, the intrinsic anti-tumor T cell immunity could exert its function, targeting specific TAA and significantly containing tumor growth. Overall, the results show that this represents a promising adjuvant approach to significantly enhance efficacy of intrinsic or vaccine-elicited tumor-specific cellular immunity.

Novel metronomic chemotherapy and cancer vaccine combinatorial strategy for hepatocellular carcinoma in a mouse model

Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer and represents the third and the fifth leading cause of cancer-related death worldwide in men and women, respectively. Hepatitis B virus (HBV) and hepatitis C virus (HCV) chronic infections account for pathogenesis of more than 80 % of primary HCC. HCC prognosis greatly varies according to stage at beginning of treatment, but the overall 5-year survival rate is approximately 5-6 %. Given the limited number of effective therapeutic strategies available, immunotherapies and therapeutic cancer vaccines may help in improving the clinical outcome for HCC patients. However, the few clinical trials conducted to date have shown contrasting results, indicating the need for improvements. In the present study, a novel combinatorial strategy, based on metronomic chemotherapy plus vaccine, is evaluated in a mouse model. The chemotherapy is a multi-drug cocktail including taxanes and alkylating agents, which is administered in a metronomic-like fashion. The vaccine is a multi-peptide cocktail including HCV as well as universal tumor antigen TERT epitopes. The combinatorial strategy designed and evaluated in the present study induces an enhanced specific T cell response, when compared to vaccine alone, which correlates to a reduced Treg frequency. Such results are highly promising and may pave way to relevant improvements in immunotherapeutic strategies for HCC and beyond.

Haematological malignancies: at the forefront of immunotherapeutic innovation

The recent successes of cancer immunotherapies have stimulated interest in the potential widespread application of these approaches; haematological malignancies have provided both initial proofs of concept and an informative testing ground for various immune-based therapeutics. The immune-cell origin of many of the blood malignancies provides a unique opportunity both to understand the mechanisms of cancer immune responsiveness and immune evasion, and to exploit these mechanisms for therapeutic purposes.

Trial watch: Dendritic cell-based interventions for cancer therapy

Dendritic cells (DCs) occupy a central position in the immune system, orchestrating a wide repertoire of responses that span from the development of self-tolerance to the elicitation of potent cellular and humoral immunity. Accordingly, DCs are involved in the etiology of conditions as diverse as infectious diseases, allergic and autoimmune disorders, graft rejection and cancer. During the last decade, several methods have been developed to load DCs with tumor-associated antigens, ex vivo or in vivo, in the attempt to use them as therapeutic anticancer vaccines that would elicit clinically relevant immune responses. While this has not always been the case, several clinical studies have demonstrated that DC-based anticancer vaccines are capable of activating tumor-specific immune responses that increase overall survival, at least in a subset of patients. In 2010, this branch of clinical research has culminated with the approval by FDA of a DC-based therapeutic vaccine (sipuleucel-T, Provenge^®) for use in patients with asymptomatic or minimally symptomatic metastatic hormone-refractory prostate cancer. Intense research efforts are currently dedicated to the identification of the immunological features of patients that best respond to DC-based anticancer vaccines. This knowledge may indeed lead to personalized combination strategies that would extend the benefit of DC-based immunotherapy to a larger patient population. In addition, widespread enthusiasm has been generated by the results of the first clinical trials based on in vivo DC targeting, an approach that holds great promises for the future of DC-based immunotherapy. In this Trial Watch, we will summarize the results of recently completed clinical trials and discuss the progress of ongoing studies that have evaluated/are evaluating DC-based interventions for cancer therapy.

High functional CD70 expression on α-type 1-polarized dendritic cells from patients with chronic lymphocytic leukaemia

Antigen-loaded dendritic cells (DCs) used as anticancer vaccine holds promise for therapy, but needs to be optimized. The most frequently described DC vaccine is being matured with a cocktail containing prostaglandin E2 (PGE2 DC). However, even though PGE2 DCs express both costimulatory and migratory receptors, their IL-12p70-prodcution is low, leading to an insufficient Th1 immune response. As an alternative, α-type-1 polarized DCs (αDC1s) have shown a superior production of IL-12p70 and subsequent activation of effector cells. From chronic lymphocytic leukaemia (CLL) patients, αDC1s can be generated to induce a functional Th1-immune response. Yet, another costimulatory receptor, CD70, appears to be essential for optimal DC function by promotion of T cell survival and function. So far, PGE2 is suggested as one of the most important factors for the induction of CD70 expression on DCs. Therefore, we wanted to investigate whether αDC1s have the ability to express functional CD70. We found that CD70 expression on αDC1s could be upregulated in the same manner as PGE2 DCs. In an allogeneic mixed leucocyte reaction, we found that antibody-blocking of CD70 on αDC1s from controls reduced effector cell proliferation although this could not be found when using CLL αDC1s. Nevertheless, CD70-blocking of αDC1s from both controls and patients with CLL had a negative influence on the production of both IL-12p70 and the Th1 cytokine IFN-γ, while the production of the Th2 cytokine IL-5 was enhanced. Together, this study further suggests that αDC1s should be considered as a suitable candidate for clinical antitumour vaccine strategies in patients with CLL.

Dendritic cell vaccine against leukemia: advances and perspectives

As with many other types of malignancies, sustainable eradication of leukemia has been a challenge. This is related to the inevitable failure of conventional chemotherapeutic agents and radiation therapy to target the relatively quiescent leukemia stem cells, which are believed to have multidrug resistance, antiapoptotic capacity and enhanced DNA repair mechanisms allowing them to evade the immune system. Considering other therapeutic options that are minimally toxic to normal cells and effectively target not only the majority and more differentiated cancer cells, but also the rare residual leukemia cells, is of paramount importance. A number of immunotherapeutic options have been proposed to counter this challenge. One of the remarkable achievements in the field of immunotherapy has been the successful use of antigen presenting cells as vehicles of tumor/pathogenic antigens to the T-cell compartments. This review will focus on advances and perspectives of this arm of immunotherapy against leukemia.

The targeting of immunosuppressive mechanisms in hematological malignancies

The adaptive immune system has the capacity to recognize and kill leukemic cells. However, immune tolerance mechanisms that normally protect healthy tissues from autoimmune effects prevent the development of effective antitumor immunity. Tumors use several different immunosuppressive mechanisms to evade otherwise effective T-cell responses. A growing number of immune evasion mechanisms have been characterized mainly in solid tumors. In hematological malignancies, less is known about how different immune escape mechanisms influence tumor immune evasion and the extent of their impact on ongoing immune responses. The present review highlights the potential role of three well-defined immunosuppressive mechanisms in hematological malignancies: (i) inhibitory T-cell pathways (especially programmed death ligand 1/programmed death 1 (PD-L1/PD-1)), (ii) regulatory immune cells, and (iii) metabolic enzymes such as indoeamine-2,3-dioxygenase (IDO). The possible therapeutic targeting of these pathways is also discussed. Exciting new strategies that might affect future antileukemia immunotherapy include monoclonal antibodies that block inhibitory T-cell pathways (PD-1/PD-L1) and the prevention of tryptophan depletion by IDO inhibitors. Furthermore, the clinical effect of several chemotherapeutic drugs may arise from the targeting of immunosuppressive cells. Evidence for a new feedback mechanism to suppress the function of regulatory immune cells was recently provided by the identification and characterization of spontaneous cytotoxic T lymphocyte (CTL) responses against regulatory immune cells. Such specific CTLs may be immensely useful in anticancer immunotherapy (for example, by anticancer vaccination). The targeting of one or more immunosuppressive pathways may be especially interesting in combination with antileukemic immunotherapy in cases in which immunosuppressive mechanisms antagonize the desired effects of the therapy.

Breaking immunotolerance of tumors: a new perspective for dendritic cell therapy

The use of dendritic cells (DC) in cancer immunotherapy is based on their potent abilities to present antigens, so they can act as 'natural adjuvants' to enhance immunogenicity of tumor antigens and stimulate specific cytotoxic T-cells. Large amounts of DC can be generated from bone marrow, neonatal cord blood, and peripheral blood CD34(+) hematopoietic stem cells, or from peripheral blood monocytes. The DC can then be pulsed with tumor antigens and re-infused. In vitro, antigen-pulsed DC can stimulate allogeneic T-cell proliferation and induction of autologous specific cytotoxic T-cells; in vivo, the cells inhibit the growth of tumors or protect hosts (i.e. mice) from development of inoculated tumors. The results of preliminary clinical trials have shown that DC vaccines are safe and elicit immune responses; however, the rates of clinical responses are low. It has become quite clear that one key reason for unsatisfactory clinical results is tumor-induced immunosuppression. Among the factors contributing to this type of immunosuppression are populations of regulatory cells including: T-regulatory (T(reg)) cells, myeloid-derived suppressor cells (MDSC), tumor-associated macrophages (TAM), and DC expressing 2,3-dioxygenase indoleamine (IDO-DC). This review presents an overview of the current understanding about populations of regulatory cells and the most current research efforts directed to overcome immunosuppressive activity due to the tumor microenvironment.

Clinical trials of dendritic cell-based cancer vaccines in hematologic malignancies

The potential for the immune system to target hematological malignancies is demonstrated in the allogeneic transplant setting, where durable responses can be achieved. However, allogeneic transplantation is associated with significant morbidity and mortality related to graft versus host disease. Cancer immunotherapy has the capacity to direct a specific cytotoxic immune response against cancer cells, particularly residual cancer cells, in order to reduce the likelihood of disease relapse in a more targeted and tolerated manner. Ex vivo dendritic cells can be primed in various ways to present tumor associated antigen to the immune system, in the context of co-stimulatory molecules, eliciting a tumor specific cytotoxic response in patients. Several approaches to prime dendritic cells and overcome the immunosuppressive microenvironment have been evaluated in pre-clinical and early clinical trials with promising results. In this review, we summarize the clinical data evaluating dendritic cell based vaccines for the treatment of hematological malignancies.

Understanding the immunodeficiency in chronic lymphocytic leukemia: potential clinical implications

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults. Although significant advances have been made in the treatment of CLL in the last decade, it remains incurable. Treatments may be too toxic for some elderly patients, who constitute most of the individuals with this disease, and there remain subgroups of patients for which this therapy has minimal activity. This article summarizes the current understanding of the immune defects in CLL. It also examines the potential clinical implications of these findings.

The roles of hyaluronan/RHAMM/CD44 and their respective interactions along the insidious pathways of fibrosarcoma progression

Fibrosarcomas are rare malignant mesenchymal tumors originating from fibroblasts. Importantly, fibrosarcoma cells were shown to have a high content and turnover of extracellular matrix (ECM) components including hyaluronan (HA), proteoglycans, collagens, fibronectin, and laminin. ECMs are complicated structures that surround and support cells within tissues. During cancer progression, significant changes can be observed in the structural and mechanical properties of the ECM components. Importantly, hyaluronan deposition is usually higher in malignant tumors as compared to benign tissues, predicting tumor progression in some tumor types. Furthermore, activated stromal cells are able to produce tissue structure rich in hyaluronan in order to promote tumor growth. Key biological roles of HA result from its interactions with its specific CD44 and RHAMM (receptor for HA-mediated motility) cell-surface receptors. HA-receptor downstream signaling pathways regulate in turn cellular processes implicated in tumorigenesis. Growth factors, including PDGF-BB, TGFβ2, and FGF-2, enhanced hyaluronan deposition to ECM and modulated HA-receptor expression in fibrosarcoma cells. Indeed, FGF-2 through upregulation of specific HAS isoforms and hyaluronan synthesis regulated secretion and net hyaluronan deposition to the fibrosarcoma pericellular matrix modulating these cells' migration capability. In this paper we discuss the involvement of hyaluronan/RHAMM/CD44 mediated signaling in the insidious pathways of fibrosarcoma progression.

Targeting the acute myeloid leukemic stem cell compartment by enhancing tumor cell-based vaccines

Harvesting the potential of the immune system in order to eradicate (residual) acute myeloid leukemia (AML) cells is the long pursued goal of immunotherapy in AML. Strategies using apoptotic tumor cell vaccines have been explored for many years, without significant clinical improvements. In recent years insight has been gained into the mechanisms activating and interfering with tumor-directed immunity. With the arrival of novel immune-modulating agents allowing for the interference with regulatory molecules and interaction with immune-propelling mechanisms, new doors are opening for increasing vaccination efficacy. Combined with advances in the design of apoptotic tumor-based vaccines, we are on the verge of creating an effective AML vaccine strategy, offering a much needed novel therapeutic option for this devastating disease.

Functional characterization of Foxp3-specific spontaneous immune responses

Tumor-infiltrating CD4+CD25+ regulatory T cells (Tregs) are associated with an impaired prognosis in several cancers. The transcription factor forkhead box P3 (Foxp3) is generally expressed in Tregs. Here, we identify and characterize spontaneous cytotoxic immune responses to Foxp3-expressing cells in peripheral blood of healthy volunteers and cancer patients. These immune responses were directed against a HLA-A2-restricted peptide epitope derived from Foxp3. Foxp3-reactive T cells were characterized as cytotoxic CD8+ T cells. These cells recognized dendritic cells incubated with recombinant Foxp3 protein indicating that this protein was indeed internalized, processed and cross-presented in the context of HLA-A2. More importantly, however, Foxp3-specific T cells were able to specifically recognize Tregs. Similarly, Foxp3+ malignant T cells established from a Cutaneous T-cell lymphomas (CTCL) patient were readily killed by the Foxp3-specific cytotoxic T lymphocytes. The spontaneous presence of Foxp3-specific cytotoxic T-cell responses suggest a general role of such T cells in the complex network of immune regulation as such responses may eliminate Tregs, that is, suppression of the suppressors. Consequently, induction of Foxp3-specific cytotoxic T-cell responses appears as an attractive tool to boost spontaneous or therapeutically provoked immune responses, for example, for the therapy of cancer.

Developing strategies in the immunotherapy of leukemias

BACKGROUND

In the current treatment paradigms for leukemias, hematopoietic stem cell transplant (HSCT) is considered the best option with a curative potential although more often than not it simply delays disease progression. Advances are needed, both in current therapies and in the development of new strategies. Partly from studying the nuances of the curative potential of stem cell transplant, we have come to appreciate the relevance of the immune response and the potential of immunotherapy.

METHODS

This review article summarizes the recent advances in the field of immunology and immunotherapy for leukemia.

RESULTS

In passive immunotherapy, recent progress in chimeric T-cell antigen receptor technology has been encouraging. In active immunotherapy, a cancer vaccine may potentially enhance HSCT. An overview of various clinical studies of peptide vaccination strategies focusing on molecular targets such as the Wilms' tumor gene 1 (WT1), proteinase 3 (PR3), and receptor for hyaluronan acid-mediated motility (RHAMM) is provided. Cell-based vaccination strategies are also briefly explored.

CONCLUSIONS

The immune system clearly has the capacity to recognize and react to leukemic cells, and recent evidence directs our attention to the importance of mounting inflammatory and CD4 T-cell responses to complement and support the cytotoxic activity elicited by peptide vaccines.

Monitoring regulatory immune responses in tumor immunotherapy clinical trials

While immune monitoring of tumor immunotherapy often focuses on the generation of productive Th1-type inflammatory immune responses, the importance of regulatory immune responses is often overlooked, despite the well-documented effects of regulatory immune responses in suppressing anti-tumor immunity. In a variety of malignancies, the frequency of regulatory cell populations has been shown to correlate with disease progression and a poor prognosis, further emphasizing the importance of characterizing the effects of immunotherapy on these populations. This review focuses on the role of suppressive immune populations (regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages) in inhibiting anti-tumor immunity, how these populations have been used in the immune monitoring of clinical trials, the prognostic value of these responses, and how the monitoring of these regulatory responses can be improved in the future.

Occupational exposure to formaldehyde and alterations in lymphocyte subsets

BACKGROUND

Formaldehyde is used in many occupational settings, most notably in manufacturing, health care, and embalming. Formaldehyde has been classified as a human carcinogen, but its mechanism of action remains uncertain.

METHODS

We carried out a cross-sectional study of 43 formaldehyde-exposed workers and 51 unexposed age and sex-matched controls in Guangdong, China to study formaldehyde's early biologic effects. To follow up our previous report that the total lymphocyte count was decreased in formaldehyde-exposed workers compared with controls, we evaluated each major lymphocyte subset (i.e., CD4(+) T cells, CD8(+) T cells, natural killer [NK] cells, and B cells) and T cell lymphocyte subset (CD4(+) naïve and memory T cells, CD8(+) naïve and memory T cells, and regulatory T cells). Linear regression of each subset was used to test for differences between exposed workers and controls, adjusting for potential confounders.

RESULTS

Total NK cell and T cell counts were about 24% (P = 0.037) and 16% (P = 0.0042) lower, respectively, among exposed workers. Among certain T cell subsets, decreased counts among exposed workers were observed for CD8(+) T cells (P = 0.026), CD8(+) effector memory T cells (P = 0.018), and regulatory T cells (CD4(+) FoxP3(+) : P = 0.04; CD25(+) FoxP3(+) : P = 0.008).

CONCLUSIONS

Formaldehyde-exposed workers experienced decreased counts of NK cells, regulatory T cells, and CD8(+) effector memory T cells; however, due to the small sample size; these findings need to be confirmed in larger studies.

Human prostate tumor antigen-specific CD8+ regulatory T cells are inhibited by CTLA-4 or IL-35 blockade

Regulatory T cells play important roles in cancer development and progression by limiting the generation of innate and adaptive anti-tumor immunity. We hypothesized that in addition to natural CD4(+)CD25(+) regulatory T cells (Tregs) and myeloid-derived suppressor cells, tumor Ag-specific Tregs interfere with the detection of anti-tumor immunity after immunotherapy. Using samples from prostate cancer patients immunized with a DNA vaccine encoding prostatic acid phosphatase (PAP) and a trans-vivo delayed-type hypersensitivity (tvDTH) assay, we found that the detection of PAP-specific effector responses after immunization was prevented by the activity of PAP-specific regulatory cells. These regulatory cells were CD8(+)CTLA-4(+), and their suppression was relieved by blockade of CTLA-4, but not IL-10 or TGF-β. Moreover, Ag-specific CD8(+) Tregs were detected prior to immunization in the absence of PAP-specific effector responses. These PAP-specific CD8(+)CTLA-4(+) suppressor T cells expressed IL-35, which was decreased after blockade of CTLA-4, and inhibition of either CTLA-4 or IL-35 reversed PAP-specific suppression of tvDTH response. PAP-specific CD8(+)CTLA-4(+) T cells also suppressed T cell proliferation in an IL-35-dependent, contact-independent fashion. Taken together, these findings suggest a novel population of CD8(+)CTLA-4(+) IL-35-secreting tumor Ag-specific Tregs arise spontaneously in some prostate cancer patients, persist during immunization, and can prevent the detection of Ag-specific effector responses by an IL-35-dependent mechanism.

Optical nanomanipulations of malignant cells: controlled cell damage and fusion

Specifically targeting and manipulating living cells is a key challenge in biomedicine and in cancer research in particular. Several studies have shown that nanoparticles irradiated by intense lasers are capable of conveying damage to nearby cells for various therapeutic and biological applications. In this work ultrashort laser pulses and gold nanospheres are used for the generation of localized, nanometric disruptions on the membranes of specifically targeted cells. The high structural stability of the nanospheres and the resonance pulse irradiation allow effective means for controlling the induced nanometric effects. The technique is demonstrated by inducing desired death mechanisms in epidermoid carcinoma and Burkitt lymphoma cells, and initiating efficient cell fusion between various cell types. Main advantages of the presented approach include low toxicity, high specificity, and high flexibility in the regulation of cell damage and cell fusion, which would allow it to play an important role in various future clinical and scientific applications.

Immunomodulatory drugs and active immunotherapy for chronic lymphocytic leukemia

BACKGROUND

The last decade witnessed the emergence of several therapeutic options for patients with chronic lymphocytic leukemia (CLL) for first-line and relapsed settings. The vast majority of patients with relapsed or refractory CLL carry poor prognostic features, which are strong predictors of shorter overall survival and resistance to first-line treatment, particularly fludarabine-based regimens.

METHODS

This article highlights the current role of immunomodulatory drugs (IMiDs) and active immunotherapy as treatment options for this select group. The rationale of using IMiDs is discussed from the perspective of lenalidomide as a novel active agent. Relevant clinical trials using IMiDs alone or in combinations are discussed. New immunotherapeutic experimental approaches are also described.

RESULTS

As a single agent, lenalidomide offers an overall response rate of 32% to 47% in patients with relapsed/refractory disease. Recent studies have shown promising activity as a single agent in treatment-naive patients. The combination of lenalidomide with immunotherapy (rituximab and ofatumumab) has also shown clinical responses. Encouraging preclinical and early clinical data have been observed with different immunotherapeutic approaches.

CONCLUSIONS

The use of IMiDs alone or in combination with immunotherapy represents a treatment option for relapsed/refractory or treatment-naive patients. Mature data and further studies are needed to validate overall and progression-free survival. The toxicity profile of lenalidomide might limit its use and delay further studies. Immunotherapy offers another potential alternative, but further understanding of the immunogenicity of CLL cells and the mechanisms of tumor fl are reaction is needed to improve the outcomes in this field.

Vaccination with dendritic cells loaded with tumor apoptotic bodies (Apo-DC) in patients with chronic lymphocytic leukemia: effects of various adjuvants and definition of immune response criteria

We previously demonstrated that autologous dendritic cells that have endocytosed apoptotic bodies of chronic lymphocytic leukemia (CLL) cells (Apo-DC) can stimulate antileukemic T cell responses in vitro. In this phase I study, we vaccinated 15 asymptomatic CLL patients at five time points with Apo-DC administered intradermally either alone (cohort I), or in combination with subcutaneous granulocyte-macrophage-colony-stimulating-factor (GM-CSF) (cohort II) or with GM-CSF and intravenous low-dose cyclophosphamide (cohort III). Aim of the study was to evaluate the safety and immunogenicity of Apo-DC alone or in combination with GM-CSF and low-dose cyclophosphamide in CLL patients. All patients completed the vaccination schedule without dose-limiting toxicity. No objective clinical responses were seen. Vaccine-induced leukemia-specific immune responses were evaluated by IFN-γ ELISpot and proliferation assays over a 52 weeks observation period and immune response criteria were defined. According to these criteria, 10/15 patients were defined as immune responders. The frequency of immune-responding patients was higher in cohorts II (3/5) and III (5/5) than in cohort I (2/5). In order to further characterize the induced immune response, estimation of secreted cytokines and CD107-degranulation assay were performed. Clustering of T and CLL cells was observed in CD107-degranulation assay and visualized by confocal microscopy. Additionally, assessment of regulatory T cells (T(regs)) revealed their significantly lower frequencies in immune responders versus non-responders (P < 0.0001). Cyclophosphamide did not reduce T(regs) frequency. In conclusion, vaccination with Apo-DC + GM-CSF and cyclophosphamide was safe and elicited anti-CLL immune responses that correlated inversely with T(regs) levels. Lack of clinical responses highlights the necessity to develop more potent vaccine strategies in B cell malignancies.

Dendritic cells in the pathogenesis and treatment of human diseases: a Janus Bifrons?

Dendritic cells (DCs) represent the bridging cell compartment between a variety of nonself antigens (i.e., microbial, cancer and vaccine antigens) and adaptive immunity, orchestrating the quality and potency of downstream immune responses. Because of the central role of DCs in the generation and regulation of immunity, the modulation of DC function in order to shape immune responses is gaining momentum. In this respect, recent advances in understanding DC biology, as well as the required molecular signals for induction of T-cell immunity, have spurred many experimental strategies to use DCs for therapeutic immunological approaches for infections and cancer. However, when DCs lose control over such 'protective' responses - by alterations in their number, phenotype and/or function - undesired effects leading to allergy and autoimmune clinical manifestations may occur. Novel therapeutic approaches have been designed and currently evaluated in order to address DCs and silence these immunopathological processes. In this article we present recent concepts of DC biology and some medical implications in view of therapeutic opportunities.

Tumour-loaded α-type 1-polarized dendritic cells from patients with chronic lymphocytic leukaemia produce a superior NK-, NKT- and CD8+ T cell-attracting chemokine profile

Tumour-loaded dendritic cells (DCs) from patients with chronic lymphocytic leukaemia (CLL) matured using an α-type 1-polarized DC cocktail (IL-1β/TNF-α/IFN-α/IFN-γ/poly-I:C;αDC1) were recently shown to induce more functional CD8(+) T cells against autologous tumour cells in vitro than DCs matured with the 'standard' cocktail (IL-1β/TNF-α/IL-6/PGE(2) ;PGE(2) DCs). However, the ability of vaccine DCs to induce a type 1-polarized immune response in vivo probably relies on additional features, including their ability to induce a CXCR3-dependent recruitment of NK cells into vaccine-draining lymph nodes. Moreover, their guiding of rare tumour-specific CD8(+) T cells to sites of DC-CD4(+) T cell interactions by secretion of CCL3 and CCL4 is needed. We therefore analysed the chemokine profile and the lymphocyte-attracting ability in vitro of monocyte-derived PGE(2) DCs and αDC1s from patients with CLL. αDC1s produced much higher levels of CXCR3 ligands (CXCL9/CXCL10/CXCL11) than PGE(2) DCs. Functional studies further demonstrated that αDC1s were superior recruiters of both NK and NKT cells. Moreover, αDC1s produced higher levels of CCL3/CCL4 upon CD40 ligation. These findings suggest that functional αDC1s, derived from patients with CLL, produce a desirable NK-, NKT- and CD8(+) T cell-attracting chemokine profile which may favour a guided and Th1-deviated priming of CD8(+) T cells, supporting the idea that αDC1-based vaccines have a higher immunotherapeutic potential than PGE(2) DCs.

Role of receptor for hyaluronic acid-mediated motility (RHAMM) in low molecular weight hyaluronan (LMWHA)-mediated fibrosarcoma cell adhesion

Hyaluronan (HA) modulates key cancer cell functions through interaction with its CD44 and receptor for hyaluronic acid-mediated motility (RHAMM) receptors. HA was recently found to regulate the migration of fibrosarcoma cells in a manner specifically dependent on its size. Here, we investigated the effect of HA/RHAMM signaling on the ability of HT1080 fibrosarcoma cells to adhere onto fibronectin. Low molecular weight HA (LMWHA) significantly increased (p ≤ 0.01) the adhesion capacity of HT1080 cells, which high molecular weight HA inhibited. The ability of HT1080 RHAMM-deficient cells, but not of CD44-deficient ones, to adhere was significantly decreased (p ≤ 0.001) as compared with control cells. Importantly, the effect of LMWHA on HT1080 cell adhesion was completely attenuated in RHAMM-deficient cells. In contrast, adhesion of RHAMM-deficient cells was not sensitive to high molecular weight HA treatment, which identifies RHAMM as a specific conduit of the LMWHA effect. Western blot and real time-PCR analyses indicated that LMWHA significantly increased RHAMM transcript (p ≤ 0.05) and protein isoform levels (53%, 95 kDa; 37%, 73 kDa) in fibrosarcoma cells. Moreover, Western blot analyses showed that LMWHA in a RHAMM-dependent manner enhanced basal and adhesion-dependent ERK1/2 and focal adhesion kinase (FAK) phosphorylation in HT1080 cells. Utilization of a specific ERK1/2 inhibitor completely inhibited (p ≤ 0.001) LMWHA-dependent adhesion, suggesting that ERK1/2 is a downstream effector of LMWHA/RHAMM signaling. Likewise, the utilization of the specific ERK1 inhibitor resulted in a strong down-regulation of FAK activation in HT1080 cells, which identifies ERK1/2 as a FAK upstream activator. In conclusion, our results suggest that RHAMM/HA interaction regulates fibrosarcoma cell adhesion via the activation of FAK and ERK1/2 signaling pathways.

Induction of the glucocorticoid-induced leucine zipper gene limits the efficacy of dendritic cell vaccines

Dendritic cell (DC) vaccines have shown great promise in generating anti-tumor immune responses but have generally fallen short of producing durable cures. Determining mechanisms by which these vaccines fail will provide one strategy towards improving their success. Several manipulations of DCs have improved their migration and longevity, but the immune inhibitory environment surrounding tumors provides a powerful suppressive influence. To determine the mechanisms by which DCs at the site of the tumor convert to a suppressive phenotype, we evaluated pathways in DCs that become expressed at the tumor site. Our results revealed that tumors lead to induction of the glucocorticoid induced leucine zipper (GILZ) gene in DCs, and that this gene is critical for the development of tumor induced tolerance of both DCs and T cells. Previous data suggested that GILZ is a pivotal gene in the balance between activation and tolerance of DCs. Our new data show that GILZ is highly upregulated in DCs in the tumor microenvironment in vivo and that blockade of this gene in DC vaccines significantly improves long term survival. These results suggest that GILZ may be an ideal candidate gene to target for novel immune-based tumor therapies.

Active and passive immunotherapy for lymphoma: proving principles and improving results

Conventional chemotherapy for lymphoma has advanced greatly over the past 50 years, changing some lymphoma subtypes from uniformly lethal to curable; however, the majority of lymphomas in patients remain incurable, and there is a need for novel therapies with less toxicity and more specific targeting of tumor cells. The vertebrate immune system has evolved the capacity for such specific targeting through the B-cell and T-cell receptors; passive immunotherapies utilizing these receptors, such as monoclonal antibodies (mAbs) or T cells, have shown efficacy in treating lymphomas. The first generation of mAb-based therapies has transformed the standard of care for lymphoma, and newer antibodies may improve on this approach. Clinical activity has been shown by T cells bearing receptors that target viral antigens as well as T cells bearing re-engineered receptors that target antigens recognized by antibodies. Active immunotherapies, such as vaccines and immune checkpoint blockades, have prolonged survival in certain solid tumors and are being actively pursued to treat lymphoma. A variety of vaccines (eg, protein- and cell-based vaccines) are being tested in ongoing trials, and the most recent iterations show therapeutic activity. Newer trials are addressing the problem of tumor-induced immunosuppression by the use of antibodies against immunologic checkpoints or by the reinfusion of primed T cells after lymphodepletion, a process we refer to as immunotransplantation. Herein, we discuss results of the various immunotherapy strategies applied to lymphoma and the ongoing approaches for their improvement.

Definition of a target for immunotherapy and results of the first Peptide vaccination study in chronic lymphocytic leukemia

Results of bone marrow transplantation, as well as remission phenomena after viral infections, suggest that chronic lymphocytic leukemia (CLL) might be targeted effectively by T-cell-based immunotherapy. Antigen-targeted immunotherapies represent novel treatments for CLL patients. Earlier, we screened the mRNA expression of several tumor associated antigens (TAAs), observing the presence of RHAMM/CD168, fibromodulin, syntaxin, and NY-Ren60 in 55%-90% of CLL patients. RHAMM/CD168, fibromodulin, PRAME, and MPP11 were expressed in CLL patients but not in healthy volunteers. Quantitative reverse transcriptase polymerase chain reaction revealed higher RHAMM expression in high-risk CLL patients as well as in advanced stages of the disease. CLL cases with higher RHAMM expressions showed significantly shorter median treatment-free survivals. Among patients with mutated IgVH genes, an analysis of RHAMM expression enabled us to distinguish a subgroup of patients with a favorable prognosis. In lymph nodes, RHAMM staining correlated with a higher Ki-67 index and CD40L expression. Functionally, stimulation with CD40L enhanced RHAMM expression in CLL. Because of the exquisite tissue expression of RHAMM and its high expression frequency in CLL patients, we further characterized RHAMM-specific CD8+ T cells in these patients. CD8+ T cells primed with the RHAMM-derived epitope R3, which is restricted by human leukocyte antigen (HLA)A2, lysed RHAMM+ CLL cells. Therefore, we initiated a Phase I clinical trial of R3 peptide vaccination. Four patients exhibited reduced white blood cell counts during the vaccination process. In 5/6 patients, R3-specific CD8+ T cells were detected with the corresponding peptide/HLA-A2 tetrameric complex; these populations were verified functionally in 4/5 patients using ELISpot assays. In conclusion, RHAMM expression seems to be of prognostic value, and may reflect the proliferative capacity of CLL cells; it may therefore represent an interesting target for immunotherapy. Peptide vaccination in CLL patients was safe eliciting specific CD8+ T-cell responses against the tumor antigen RHAMM.

Dendritic-cell tumor vaccines

Most cancers remain incurable. Introduction of novel therapeutic methods, including new cytostatic regimens and targeted therapies, such as monoclonal antibodies and tyrosine kinase inhibitors, have increased remission rates as well as improved patient survival, but the ability to cure many cancer patients remains elusive. It is thus necessary to further develop alternative strategies to improve patient prognosis. The majority of patients who respond to induction therapy inevitably relapse, mainly because of the proliferation of residual malignant cells that have escaped control by induction chemotherapy. Therefore the eradication of minimal residual disease may be crucial to prevent a relapse and achieve a long-term remission. It seems that an advantageous treatment option may be cellular immunotherapy with dendritic-cell vaccines which might induce long-term specific anticancer responses with immune memory cells, which could contribute to effective and lasting elimination of malignant cells.

NCI First International Workshop on the Biology, Prevention, and Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation: Report from the Committee on Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation

Relapse is a major cause of treatment failure after allogeneic hematopoietic stem cell transplantation (alloHSCT). Treatment options for relapse have been inadequate, and the majority of patients ultimately die of their disease. There is no standard approach to treating relapse after alloHSCT. Withdrawal of immune suppression and donor lymphocyte infusions are commonly used for all diseases; although these interventions are remarkably effective for relapsed chronic myelogenous leukemia, they have limited efficacy in other hematologic malignancies. Conventional and novel chemotherapy, monoclonal antibody therapy, targeted therapies, and second transplants have been utilized in a variety of relapsed diseases, but reports on these therapies are generally anecdotal and retrospective. As such, there is an immediate need for well-designed, disease-specific trials for treatment of relapse after alloHSCT. This report summarizes current treatment options under investigation for relapse after alloHSCT in a disease-specific manner. In addition, recommendations are provided for specific areas of research necessary in the treatment of relapse after alloHSCT.

Silencing of ROR1 and FMOD with siRNA results in apoptosis of CLL cells

We have previously demonstrated that ROR1 and FMOD (fibromodulin) are two genes upregulated in chronic lymphocytic leukaemia (CLL) cells compared to normal blood B cells. In this study, siRNAs were used to specifically silence ROR1 and FMOD expression in CLL cells, healthy B cells and human fibroblast cell lines. siRNA treatment induced a specific reduction (75-95%) in FMOD and ROR1 mRNA. Western blot analysis with specific antibodies for FMOD and ROR1 demonstrated that the proteins were significantly downregulated 48 h after siRNA treatment. Silencing of FMOD and ROR1 resulted in statistically significant (P ≤ 0·05-0·001) apoptosis of CLL cells but not of B cells from normal donors. Human fibroblast cell lines treated with FMOD and ROR1 siRNA did not undergo apoptosis. This is the first report demonstrating that ROR1 and FMOD may be involved in the survival of CLL cells. ROR1 in particular is further explored as potential target for therapy in CLL.

The microenvironment differentially impairs passive and active immunotherapy in chronic lymphocytic leukaemia - CXCR4 antagonists as potential adjuvants for monoclonal antibodies

Direct contact with stromal cells protects chronic lymphocytic leukaemia (CLL) B cells from chemotherapy-induced apoptosis in vitro. Blockade of CXCR4 signalling antagonizes stroma-mediated interactions and restores CLL chemosensitivity. In vivo, administration of CXCR4 antagonists effectively mobilizes haematopoietic progenitor cells. Therefore, combinations of CXCR4 blockade and cytoreductive treatment with selective activity on CLL cells may avoid potential haematotoxicity. Hence, we tested CXCR4 antagonists in the context of passive and active immunotherapeutic approaches. We evaluated how efficiently rituximab, alemtuzumab and cytotoxic T cells killed CLL cells cocultured with stromal cells in the presence and absence of a CXCR4 antagonist. Stromal cell contact attenuated rituximab- and alemtuzumab-induced complement-dependent cytotoxicity of CLL cells. Addition of CXCR4 antagonists abrogated the protective effect of stroma. In contrast, stromal cells did not impair antibody-dependent cell-mediated cytotoxicity and cytotoxicity induced by activated T cells. Destruction of microtubules in CLL target cells restored the protective effect of stroma coculture for CLL cells during Natural Killer cell attack by preventing mitochondrial relocalization towards the immunological synapse. Our data identify the combination of CXCR4 antagonists with passive - but not active - immunotherapy as a promising potential treatment concept in CLL.

Regulatory T cells in cancer

At the present time, regulatory T cells (Tregs) are an integral part of immunology but the route from discovery of "suppressive" lymphocytes in the 1980s to the current established concept of Tregs almost 20 years later has been a rollercoaster ride. Tregs are essential for maintaining self-tolerance as defects in their compartment lead to severe autoimmune diseases. This vitally important function exists alongside the detrimental effects on tumor immunosurveillance and antitumor immunity. Beginning with the identification of CD4(+)CD25(+) Tregs in 1995, the list of Treg subsets, suppressive mechanisms, and knowledge about their various origins is steadily growing. Increase in Tregs within tumors and circulation of cancer patients, observed in early studies, implied their involvement in pathogenesis and disease progression. Several mechanisms, ranging from proliferation to specific trafficking networks, have been identified to account for their systemic and/or local accumulation. Since various immunotherapeutic approaches are being utilized for cancer therapy, various strategies to overcome the antagonistic effects exerted by Tregs are being currently explored. An overview on the biology of Tregs present in cancer patients, their clinical impact, and methods for modulating them is given in this review. Despite the extensive studies on Tregs in cancer many questions still remain unanswered. Even the paradigm that Tregs generally are disadvantageous for the control of malignancies is now under scrutiny. Insight into the specific role of Tregs in different types of neoplasias is the key for targeting them in a way that is beneficial for the clinical outcome.