Expansion of NK cells and reduction of NKG2D expression in chronic lymphocytic leukemia. Correlation with progressive disease

Evaluation of infectious morbidity due to BTK inhibitors in indolent B-cell lymphomas: latest research findings and systematic analysis

INTRODUCTION

Randomized clinical trials (RCTs) have suggested that BTK inhibitors (BTKis) might increase infectious disease (ID) risk. Systematic analysis of this topic as derived from RCTs and clinical practice is needed.

AREAS COVERED

An extensive Medline, Embase, and Cochrane search of peer-reviewed sources reporting on ID morbidity in patients on BTKis was performed (1 January 2014 - 31 December 2013). Contribution of intrinsic immune defects in indolent B-cell lymphomas to this morbidity was carefully considered.

EXPERT OPINION

Patients with indolent B-cell lymphomas display a wide range of innate and adaptive immune defects. In addition, BTKi use is linked with an increased signal of upper respiratory tract infections (URTIs) and pneumonias, mainly grade 1-2. These agents also increase the risk of rare invasive fungal infections (IFIs), mainly due to Cryptococcus and Aspergillus spp. with a peak within several months after the start of therapy. More than half of these IFIs are fatal. Research suggests a similar ID risk across 1st, 2nd and 3rd generations of BTKis, all causing B-cell dysfunction due to BTK inhibition, along with off-target functional neutrophil/macrophage alterations. Expanding the knowledge base on ID morbidity in patients on BTKis would facilitate timely diagnosis and treatment, and improve clinical outcomes.

Adaptive natural killer cell expression in response to cytomegalovirus infection in blood and solid cancer

Natural Killer (NK) cells are conventionally thought to be an indefinite part of innate immunity. However, in a specific subset of NK cells, recent data signify an extension of their "duties" in immune surveillance and response, having characteristics of adaptive immunity, in terms of persistence and cytotoxicity. These cells are known as the adaptive or memory-like NK cells, where human cytomegalovirus (HCMV) infection has been shown to drive the expansion of adaptive NKG2C+ NK cells. HCMV is a ubiquitous pathogen whose prevalence differs worldwide with respect to the socioeconomic status of countries. The adaptive NK cell subpopulation is often characterized by the upregulated expression of NKG2C, CD16, and CD2, and restricted expression of NKG2A, FCεRγ and killer immunoglobulin-like receptors (KIR), although these phenotypes may differ in different disease groups. The reconfiguration of these receptor distributions has been linked to epigenetic factors. Hence, this review attempts to appraise literature reporting markers associated with adaptive or memory-like NK cells post-HCMV infection, in relation to solid cancers and hematological malignancies. Adaptive NK cells, isolated and subjected to ex vivo modifications, have the potential to enhance anti-tumor response which can be a promising strategy for adoptive immunotherapy.

Immune Dysfunction and Infection - Interaction between CLL and Treatment: A Reflection on Current Treatment Paradigms and Unmet Needs

BACKGROUND

Chronic lymphocytic leukemia (CLL) is a hematological malignancy characterized by immune dysfunction, which significantly contributes to increased morbidity and mortality due to infections.

SUMMARY

Advancement in therapeutic strategies based on combination chemoimmunotherapy and targeted treatment have increased life expectancy for patients affected by CLL. However, mortality and morbidity due to infection showed no improvement over the last decades. Although therapy options are highly efficient in targeting leukemic cells, several studies highlighted the interactions of different treatments with the tumor microenvironment immune components, significantly impacting their clinical efficacy and fostering increased risk of infections.

KEY MESSAGES

Given the profound immune dysfunction caused by CLL itself, treatment can thus represent a double-edged sword. Thus, it is essential to increase our understanding and awareness on how conventional therapies affect the disease-microenvironment-infection axis to ensure the best personalized strategy for each patient. This requires careful consideration of the advantages and disadvantages of efficient treatments, whether chemoimmunotherapy or targeted combinations, leading to risk of infectious complications. To this regard, our machine learning-based algorithm CLL Treatment-Infection Model, currently implemented into the local electronic health record system for Eastern Denmark, aims at early identification of patients at high risk of serious infections (PreVent-ACaLL; NCT03868722). We here review strategies for management of immune dysfunction and infections in CLL.

SOHO State of the Art Updates and Next Questions | Infections in Chronic Lymphocytic Leukemia Patients: Risks and Management

Although chronic lymphocytic leukemia (CLL) is a malignancy characterized by accumulation of tumor cells in the blood, bone marrow, lymph nodes and secondary lymphoid tissues, the hallmark of the disease and the major cause of death for patients with CLL is actually immune dysfunction and associated infections. Despite improvement in treatment based on combination chemoimmunotherapy and targeted treatment with BTK and BCL-2 inhibitors leading to longer overall survival for patients with CLL, the mortality due to infections have not improved over the last 4 decades. Thus, infections are now the main cause of death for patients with CLL, posing threats to the patient whether during the premalignant state of monoclonal B lymphocytosis (MBL), during the watch & wait phase for treatment naïve patients, or upon treatment in terms of chemoimmunotherapy or targeted treatment. To test whether the natural history of immune dysfunction and infections in CLL can be changed, we have developed the machine learning based algorithm CLL-TIM.org to identify these patients. The CLL-TIM algorithm is currently being used for selection of patients for the clinical trial PreVent-ACaLL (NCT03868722), testing whether short-term treatment with the BTK inhibitor acalabrutinib and the BCL-2 inhibitor venetoclax can improve immune function and decrease the risk of infections for this high-risk patient population. We here review the background for and management of infectious risks in CLL.

Current state of NK cell-mediated immunotherapy in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) has become one of the most common hematological diseases in western countries, with an annual incidence of 42/100,000. Conventional chemotherapy and targeted therapeutic drugs showed limitations in prognosis or in efficiency in high-risk patients. Immunotherapy represented is one of the most effective therapeutic approaches with the potential of better effect and prognosis. Natural killer (NK) cells are good options for immunotherapy as they can effectively mediate anti-tumor activity of immune system by expressing activating and inhibiting receptors and recognizing specific ligands on various tumor cells. NK cells are critical in the immunotherapy of CLL by enhancing self-mediated antibody-dependent cytotoxicity (ADCC), allogeneic NK cell therapy and chimeric antigen receptor-natural killer (CAR-NK) cell therapy. In this article, we reviewed the features, working mechanisms, and receptors of NK cells, and the available evidence of the advantages and disadvantages of NK cell-based immunotherapies, and put forward future study directions in this field.

INTERLEUKIN-6 AND NKG2D AS PROGNOSTIC FACTORS IN IRAQI FEMALES WITH PITUITARY GAND ADENOMA: A LONGITUDINAL STUDY

OBJECTIVE

The aim: To assess the role of circulating IL-6 & NKG2D in the prognosis of pituitary adenoma.

PATIENTS AND METHODS

Materials and methods: Thirty female with new diagnosis of prolactinoma (pituitary gland adenoma) were enrolled in the study. ELISA test was used to evaluate the level of IL6 and NKG2D. ELISA tests were conducted before the initiation of treatment and six months later.

RESULTS

Results: There are significant differences in mean levels of IL-6 and NKG2D, and the anatomical type (tumor size) (-418.7 & 418.9, p<0.001) of anatomical tumor (-373.72 & -373.920, p=0.001). There is a significant difference between the two immunological markers (IL-6 & NKG2D) (-0.305; p<0.001). The IL-6 markers significantly decreased in means on follow up (-197.8; p-value≤0.0001) while the reverse occur in NKG2D, which increased in levels post-treatment compared with baseline measurement. The high expression of IL-6 positively correlated with the risk of macroadenoma (>10 microns) and poor resonse to treatment and vice versa (p<0.024). High expression of NKG2D significantly (p<0.005) correlated with good prognosis and increased chance for tumor response to medicine and shrinkage in size compared with low concentration.

CONCLUSION

Conclusions: The higher the level of IL-6, the larger the size of adenoma (macroadenoma) and the poorer the response to treatment. The higher the level of NKG2D indidcate a better prognosis, therefore, IL-6 and NKG2D correlate negatively in prolactinoma patients.

Natural Killer Cells in Chronic Lymphocytic Leukemia: Functional Impairment and Therapeutic Potential

Immunotherapy approaches have advanced rapidly in recent years. While the greatest therapeutic advances so far have been achieved with T cell therapies such as immune checkpoint blockade and CAR-T, recent advances in NK cell therapy have highlighted the therapeutic potential of these cells. Chronic lymphocytic leukemia (CLL), the most prevalent form of leukemia in Western countries, is a very immunosuppressive disease but still shows significant potential as a target of immunotherapy, including NK-based therapies. In addition to their antileukemia potential, NK cells are important immune effectors in the response to infections, which represent a major clinical concern for CLL patients. Here, we review the interactions between NK cells and CLL, describing functional changes and mechanisms of CLL-induced NK suppression, interactions with current therapeutic options, and the potential for therapeutic benefit using NK cell therapies.

Managing the Risk of Infection in Chronic Lymphocytic Leukemia in the Era of New Therapies

PURPOSE OF REVIEW

Patients diagnosed with CLL have an increased susceptibility to infections. Over the years, there has been a shift of the treatment arsenal to an increasing use of chemotherapy-free regimens, particularly small molecule inhibitors. These therapies have proven to be effective and have a favorable toxicity profile. Infections continue to represent a significant complication in the era of novel therapies.

RECENT FINDINGS

Recent studies continue to bring new insights into the effects of modern therapies on the immune system. Evidence supporting infection prevention strategies is scarce. We will review the available recommendations to prevent infections in patients with CLL treated with novel therapies. New CLL therapies are broadly adopted in routine practice, requiring optimization of their side effects. Timely prevention, recognition, and treatment of infections should remain an important aspect of the standard management of a patient with CLL.

Harnessing Unconventional T Cells and Innate Lymphoid Cells to Prevent and Treat Hematological Malignancies: Prospects for New Immunotherapy

Unconventional T cells and innate lymphoid cells (ILCs) make up a heterogeneous set of cells that characteristically show prompt responses toward specific antigens. Unconventional T cells recognize non-peptide antigens, which are bound and presented by diverse non-polymorphic antigen-presenting molecules and comprise γδ T cells, MR1-restricted mucosal-associated invariant T cells (MAITs), and natural killer T cells (NKTs). On the other hand, ILCs lack antigen-specific receptors and act as the innate counterpart to the T lymphocytes found in the adaptive immune response. The alteration of unconventional T cells and ILCs in frequency and functionality is correlated with the onset of several autoimmune diseases, allergy, inflammation, and tumor. However, depending on the physio-pathological framework, unconventional T cells may exhibit either protective or pathogenic activity in a range of neoplastic diseases. Nonetheless, experimental models and clinical studies have displayed that some unconventional T cells are potential therapeutic targets, as well as prognostic and diagnostic markers. In fact, cell-mediated immune response in tumors has become the focus in immunotherapy against neoplastic disease. This review concentrates on the present knowledge concerning the function of unconventional T cell sets in the antitumor immune response in hematological malignancies, such as acute and chronic leukemia, multiple myeloma, and lymphoproliferative disorders. Moreover, we discuss the possibility that modulating the activity of unconventional T cells could be useful in the treatment of hematological neoplasms, in the prevention of specific conditions (such as graft versus host disease), and in the formulation of an effective anticancer vaccine therapy. The exact knowledge of the role of these cells could represent the prerequisite for the creation of a new form of immunotherapy for hematological neoplasms.

Recent Advances in CAR T-Cell Therapy for Patients with Chronic Lymphocytic Leukemia

Chimeric antigen receptor T cells (CAR T cells) have resulted in dramatic treatment responses for patients with hematologic malignancies, resulting in improved survival for patients with intractable disease. The first patient treated with CD19 directed CAR T cell therapy had chronic lymphocytic leukemia (CLL) and achieved a complete remission. Subsequent clinical trials have focused largely on patients with other B-cell hematologic malignancies, owing to the fact that CAR T cell therapy for patients with CLL has met with challenges. More recent clinical trials have demonstrated CAR T cell therapy can be well tolerated and effective for patients with CLL, making it a potential treatment option for patients with this disease. In this article we review the background on CAR T cells for the treatment of patients with CLL, focusing on the unique obstacles that patients with CLL present for the development of adoptive T cell therapy, and the novel approaches currently under development to overcome these hurdles.

Effects of B-Cell Lymphoma on the Immune System and Immune Recovery after Treatment: The Paradigm of Targeted Therapy

B-cell lymphoma and lymphoproliferative diseases represent a heterogeneous and complex group of neoplasms that are accompanied by a broad range of immune regulatory disorder phenotypes. Clinical features of autoimmunity, hyperinflammation, immunodeficiency and infection can variously dominate, depending on the immune pathway most involved. Immunological imbalance can play a role in lymphomagenesis, also supporting the progression of the disease, while on the other hand, lymphoma acts on the immune system to weaken immunosurveillance and facilitate immunoevasion. Therefore, the modulation of immunity can have a profound effect on disease progression or resolution, which makes the immune system a critical target for new therapies. In the current therapeutic scenario enriched by chemo-free regimens, it is important to establish the effect of various drugs on the disease, as well as on the restoration of immune functions. In fact, treatment of B-cell lymphoma with passive immunotherapy that targets tumor cells or targets the tumor microenvironment, together with adoptive immunotherapy, is becoming more frequent. The aim of this review is to report relevant data on the evolution of the immune system during and after treatment with targeted therapy of B-cell lymphomas.

A pilot study of high-intensity interval training in older adults with treatment naïve chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the USA, affecting predominantly older adults. CLL is characterized by low physical fitness, reduced immunity, and increased risk of secondary malignancies and infections. One approach to improving CLL patients' physical fitness and immune functions may be participation in a structured exercise program. The aims of this pilot study were to examine physical and immunological changes, and feasibility of a 12-week high-intensity interval training (HIIT) combined with muscle endurance-based resistance training on older adults with treatment naïve CLL. We enrolled eighteen participants with CLL aged 64.9 ± 9.1 years and assigned them to groups depending on distance lived from our fitness center. Ten participants (4 M/6F) completed HIIT and six participants (4 M/2F) completed a non-exercising control group (Controls). HIIT consisted of three 30-min treadmill sessions/week plus two concurrent 30-min strength training sessions/week. Physical and immunological outcomes included aerobic capacity, muscle strength and endurance, and natural killer (NK) cell recognition and killing of tumor cells. We confirmed feasibility if > 70% of HIIT participants completed > 75% of prescribed sessions and prescribed minutes, and if > 80% of high-intensity intervals were at a heart rate corresponding to at least 80% of peak aerobic capacity (VO_2peak). Results are presented as Hedge's G effect sizes (g), with 0.2, 0.5 and 0.8 representing small, medium and large effects, respectively. Following HIIT, leg strength (g = 2.52), chest strength (g = 1.15) and seated row strength (g = 3.07) were 35.4%, 56.1% and 39.5% higher than Controls, respectively, while aerobic capacity was 3.8% lower (g = 0.49) than Controls. Similarly, following HIIT, in vitro NK-cell cytolytic activity against the K562 cell line (g = 1.43), OSU-CLL cell line (g = 0.95), and autologous B-cells (g = 1.30) were 20.3%, 3.0% and 14.6% higher than Controls, respectively. Feasibility was achieved, with HIIT completing 5.0 ± 0.2 sessions/week and 99 ± 3.6% of the prescribed minutes/week at heart rates corresponding to 89 ± 2.8% of VO_2peak. We demonstrate that 12-weeks of supervised HIIT combined with muscle endurance-based resistance training is feasible, and that high adherence and compliance are associated with large effects on muscle strength and immune function in older adults with treatment naïve CLL.Trial registration: NCT04950452.

The Hydropathy Index of the HCDR3 Region of the B-Cell Receptor Identifies Two Subgroups of IGHV-Mutated Chronic Lymphocytic Leukemia Patients With Distinct Outcome

The HCDR3 sequences of the B-cell receptor (BCR) undergo constraints in length, amino acid use, and charge during maturation of B-cell precursors and after antigen encounter, leading to BCR and antibodies with high affinity to specific antigens. Chronic lymphocytic leukemia consists of an expansion of B-cells with a mixed immature and "antigen-experienced" phenotype, with either a mutated (M-CLL) or unmutated (U-CLL) tumor BCR, associated with distinct patient outcomes. Here, we investigated the hydropathy index of the BCR of 138 CLL patients and its association with the IGHV mutational status and patient outcome. Overall, two clearly distinct subgroups of M-CLL patients emerged, based on a neutral (mean hydropathy index of -0.1) vs. negatively charged BCR (mean hydropathy index of -1.1) with molecular features closer to those of B-cell precursors and peripheral/mature B-cells, respectively. Despite that M-CLL with neutral HCDR3 did not show traits associated with a mature B-cell repertoire, important differences in IGHV gene usage of tumor cells and patient outcome were observed in this subgroup of patients once compared to both U-CLL and M-CLL with negatively charged HCDR3 sequences. Compared to M-CLL with negatively charged HCDR3 sequences, M-CLL with neutral HCDR3 sequences showed predominance of men, more advanced stages of the disease, and a greater frequency of genetic alterations-e.g., del(17p)-together with a higher rate of disease progression and shorter time to therapy (TTT), independently of other prognostic factors. Our data suggest that the hydropathy index of the HCDR3 sequences of CLL cells allows the identification of a subgroup of M-CLL with intermediate prognostic features between U-CLL and the more favorable subgroup of M-CLL with a negatively charged BCR.

The Biological Role and Therapeutic Potential of NK Cells in Hematological and Solid Tumors

NK cells are an attractive target for cancer immunotherapy due to their potent antitumor activity. The main advantage of using NK cells as cytotoxic effectors over T cells is a reduced risk of graft versus host disease. At present, several variants of NK-cell-based therapies are undergoing clinical trials and show considerable effectiveness for hematological tumors. In these types of cancers, the immune cells themselves often undergo malignant transformation, which determines the features of the disease. In contrast, the current use of NK cells as therapeutic agents for the treatment of solid tumors is much less promising. Most studies are at the stage of preclinical investigation, but few progress to clinical trials. Low efficiency of NK cell migration and functional activity in the tumor environment are currently considered the major barriers to NK cell anti-tumor therapies. Various therapeutic combinations, genetic engineering methods, alternative sources for obtaining NK cells, and other techniques are aiming at the development of promising NK cell anticancer therapies, regardless of tumorigenesis. In this review, we compare the role of NK cells in the pathogenesis of hematological and solid tumors and discuss current prospects of NK-cell-based therapy for hematological and solid tumors.

Impact of Immune Parameters and Immune Dysfunctions on the Prognosis of Patients with Chronic Lymphocytic Leukemia

Simple Summary

In chronic lymphocytic leukemia (CLL), immune alterations—affecting both the innate and adaptive immunity—are very common. As a clinical consequence, patients with CLL frequently present with autoimmune phenomena, increased risk of infections and second malignancies. The aim of this review article is to present available data on CLL-associated alterations of immune parameters that correlate with known prognostic markers and with clinical outcome. Also, data on the impact of immune-related clinical manifestations on the prognosis of patients with CLL will be discussed.

Abstract

Chronic lymphocytic leukemia (CLL) is characterized by a wide spectrum of immune alterations, affecting both the innate and adaptive immunity. These immune dysfunctions strongly impact the immune surveillance, facilitate tumor progression and eventually affect the disease course. Quantitative and functional alterations involving conventional T cells, γδ T cells, regulatory T cells, NK and NKT cells, and myeloid cells, together with hypogammaglobulinemia, aberrations in the complement pathways and altered cytokine signature have been reported in patients with CLL. Some of these immune parameters have been shown to associate with other CLL-related characteristics with a known prognostic relevance or to correlate with disease prognosis. Also, in CLL, the complex immune response dysfunctions eventually translate in clinical manifestations, including autoimmune phenomena, increased risk of infections and second malignancies. These clinical issues are overall the most common complications that affect the course and management of CLL, and they also may impact overall disease prognosis.

NK Cells in Chronic Lymphocytic Leukemia and Their Therapeutic Implications

Key features of chronic lymphocytic leukemia (CLL) are defects in the immune system and the ability of leukemic cells to evade immune defenses and induce immunosuppression, resulting in increased susceptibility to infections and disease progression. Several immune effectors are impaired in CLL, including T and natural killer (NK) cells. The role of T cells in defense against CLL and in CLL progression and immunotherapy has been extensively studied. Less is known about the role of NK cells in this leukemia, and data on NK cell alterations in CLL are contrasting. Besides studies showing that NK cells have intrinsic defects in CLL, there is a large body of evidence indicating that NK cell dysfunctions in CLL mainly depend on the escape mechanisms employed by leukemic cells. In keeping, it has been shown that NK cell functions, including antibody-dependent cellular cytotoxicity (ADCC), can be retained and/or restored after adequate stimulation. Therefore, due to their preserved ADCC function and the reversibility of CLL-related dysfunctions, NK cells are an attractive source for novel immunotherapeutic strategies in this disease, including chimeric antigen receptor (CAR) therapy. Recently, satisfying clinical responses have been obtained in CLL patients using cord blood-derived CAR-NK cells, opening new possibilities for further exploring NK cells in the immunotherapy of CLL. However, notwithstanding the promising results of this clinical trial, more evidence is needed to fully understand whether and in which CLL cases NK cell-based immunotherapy may represent a valid, alternative/additional therapeutic option for this leukemia. In this review, we provide an overview of the current knowledge about phenotypic and functional alterations of NK cells in CLL and the mechanisms by which CLL cells circumvent NK cell-mediated immunosurveillance. Additionally, we discuss the potential relevance of using NK cells in CLL immunotherapy.

NKG2D Natural Killer Cell Receptor-A Short Description and Potential Clinical Applications

Natural Killer (NK) cells are natural cytotoxic, effector cells of the innate immune system. They can recognize transformed or infected cells. NK cells are armed with a set of activating and inhibitory receptors which are able to bind to their ligands on target cells. The right balance between expression and activation of those receptors is fundamental for the proper functionality of NK cells. One of the best known activating receptors is NKG2D, a member of the CD94/NKG2 family. Due to a specific NKG2D binding with its eight different ligands, which are overexpressed in transformed, infected and stressed cells, NK cells are able to recognize and attack their targets. The NKG2D receptor has an enormous significance in various, autoimmune diseases, viral and bacterial infections as well as for transplantation outcomes and complications. This review focuses on the NKG2D receptor, the mechanism of its action, clinical relevance of its gene polymorphisms and a potential application in various clinical settings.

Physiological Fitness and the Pathophysiology of Chronic Lymphocytic Leukemia (CLL)

Chronic lymphocytic leukemia (CLL) is associated with physical dysfunction and low overall fitness that predicts poor survival following the commencement of treatment. However, it remains unknown whether higher fitness provides antioncogenic effects. We identified ten fit (CLL-FIT) and ten less fit (CLL-UNFIT) treatment-naïve CLL patients from 144 patients who completed a set of physical fitness and performance tests. Patient plasma was used to determine its effects on an in vitro 5-day growth/viability of three B-cell cell lines (OSU-CLL, Daudi, and Farage). Plasma exosomal miRNA profiles, circulating lipids, lipoproteins, inflammation levels, and immune cell phenotypes were also assessed. CLL-FIT was associated with fewer viable OSU-CLL cells at Day 1 (p = 0.003), Day 4 (p = 0.001), and Day 5 (p = 0.009). No differences between the groups were observed for Daudi and Farage cells. Of 455 distinct exosomal miRNAs identified, 32 miRNAs were significantly different between the groups. Of these, 14 miRNAs had ≤-1 or ≥1 log2 fold differences. CLL-FIT patients had five exosomal miRNAs with lower expression and nine miRNAs with higher expression. CLL-FIT patients had higher HDL cholesterol, lower inflammation, and lower levels of triglyceride components (all p < 0.05). CLL-FIT patients had lower frequencies of low-differentiated NKG2+/CD158a/b^neg (p = 0.015 and p = 0.014) and higher frequencies of NKG2A^neg/CD158b+ mature NK cells (p = 0.047). The absolute number of lymphocytes, including CD19+/CD5+ CLL-cells, was similar between the groups (p = 0.359). Higher physical fitness in CLL patients is associated with altered CLL-like cell line growth in vitro and with altered circulating and cellular factors indicative of better immune functions and tumor control.

LAG-3 Blockade with Relatlimab (BMS-986016) Restores Anti-Leukemic Responses in Chronic Lymphocytic Leukemia

The inclusion of monoclonal antibodies targeting immune checkpoints such PD-1/PD-L1 or CTLA-4 has revolutionized the landscape of anti-cancer therapy. However, PD-1 and CTLA-4 blockade failed to achieve clinical benefit in CLL, thus attention has been focused on emerging checkpoints in this malignancy. LAG-3 is an immune checkpoint receptor that negatively regulates T cell-mediated responses by inducing an hyporesponsive state, thus promoting tumor escape. Patients with chronic lymphocytic leukemia (CLL) develop a profound immune suppression that leads to lessened immunosurveillance and increased risk of developing a secondary neoplasia. In the study herein, we report the profound dysregulation of LAG-3 on leukemic cells in CLL. Likewise, natural killer (NK) and T cells showed increased LAG-3 expression, hence suggesting a role for this checkpoint in CLL-associated immunosuppression. High LAG-3 expression, as well as high levels of soluble LAG-3 (sLAG-3), correlated with adverse cytogenetics and poor outcome in patients with CLL, highlighting the clinical relevance of this immune checkpoint. Treatment of peripheral blood mononuclear cells (PBMCs) from patients with CLL with relatlimab, a new anti-LAG-3 blocking antibody currently evaluated in numerous clinical trials, depleted leukemic cells and restored NK cell- and T cell-mediated responses. Moreover, combination of LAG-3 with the immunomodulatory drug (IMiD) lenalidomide significantly increased IL-2 production by T cells and antibody-dependent cytotoxicity (ADCC) mediated by NK cells. Altogether, these data provide new insights into the potential anti-leukemic effects of relatlimab, currently in clinical trials in CLL, and provides the rationale to further investigate its combination with IMiDs for the management of hematological malignancies.

BTLA/HVEM Axis Induces NK Cell Immunosuppression and Poor Outcome in Chronic Lymphocytic Leukemia

Simple Summary

Chronic lymphocytic leukemia (CLL) represents the most frequent B cell malignancy in Western countries and still remains as an incurable disease. Despite recent advances in targeted therapies including ibrutinib, idelalisib or venetoclax, resistance mechanisms have been described and patients develop a progressive immunosuppression. Since immune checkpoint blockade has demonstrated to reinvigorate T and NK cell-mediated anti-tumor responses, the aim of this work was to elucidate whether this immunosuppression relies, at least in part, in BTLA/HVEM axis in patients with CLL. Our results demonstrate that BTLA and HVEM expression is deeply dysregulated on leukemic and NK cells and correlates with poor outcome. Moreover, soluble BTLA levels correlated with adverse cytogenetics and shorter time to treatment. BTLA blockade restored, at least in part, NK cell-mediated responses in patients with CLL. Altogether, our results provide the rationale to further investigate the role of BTLA/HVEM axis in the pathogenesis of CLL.

Abstract

Chronic lymphocytic leukemia (CLL) is characterized by progressive immunosuppression and diminished cancer immunosurveillance. Immune checkpoint blockade (ICB)-based therapies, a major breakthrough against cancer, have emerged as a powerful tool to reinvigorate antitumor responses. Herein, we analyzed the role of the novel inhibitory checkpoint BTLA and its ligand, HVEM, in the regulation of leukemic and natural killer (NK) cells in CLL. Flow cytometry analyses showed that BTLA expression is upregulated on leukemic cells and NK cells from patients with CLL, whereas HVEM is downregulated only in leukemic cells, especially in patients with advanced Rai-Binet stage. In silico analysis revealed that increased HVEM, but not BTLA, mRNA expression in leukemic cells correlated with diminished overall survival. Further, soluble BTLA (sBTLA) was found to be increased in the sera of patients with CLL and highly correlated with poor prognostic markers and shorter time to treatment. BTLA blockade with an anti-BTLA monoclonal antibody depleted leukemic cells and boosted NK cell-mediated responses ex vivo by increasing their IFN-γ production, cytotoxic capability, and antibody-dependent cytotoxicity (ADCC). In agreement with an inhibitory role of BTLA in NK cells, surface BTLA expression on NK cells was associated with poor outcome in patients with CLL. Overall, this study is the first to bring to light a role of BTLA/HVEM in the suppression of NK cell-mediated immune responses in CLL and its impact on patient’s prognosis, suggesting that BTLA/HVEM axis may be a potential therapeutic target in this disease.

MITF induces escape from innate immunity in melanoma

BACKGROUND

The application of immune-based therapies has revolutionized cancer treatment. Yet how the immune system responds to phenotypically heterogeneous populations within tumors is poorly understood. In melanoma, one of the major determinants of phenotypic identity is the lineage survival oncogene MITF that integrates diverse microenvironmental cues to coordinate melanoma survival, senescence bypass, differentiation, proliferation, invasion, metabolism and DNA damage repair. Whether MITF also controls the immune response is unknown.

METHODS

By using several mouse melanoma models, we examine the potential role of MITF to modulate the anti-melanoma immune response. ChIP-seq data analysis, ChIP-qPCR, CRISPR-Cas9 genome editing, and luciferase reporter assays were utilized to identify ADAM10 as a direct MITF target gene. Western blotting, confocal microscopy, flow cytometry, and natural killer (NK) cytotoxicity assays were used to determine the underlying mechanisms by which MITF-driven phenotypic plasticity modulates melanoma NK cell-mediated killing.

RESULTS

Here we show that MITF regulates expression of ADAM10, a key sheddase that cleaves the MICA/B family of ligands for NK cells. By controlling melanoma recognition by NK-cells MITF thereby controls the melanoma response to the innate immune system. Consequently, while melanoma MITF^Low cells can be effectively suppressed by NK-mediated killing, MITF-expressing cells escape NK cell surveillance.

CONCLUSION

Our results reveal how modulation of MITF activity can impact the anti-melanoma immune response with implications for the application of anti-melanoma immunotherapies.

Engaging the Innate and Adaptive Antitumor Immune Response in Lymphoma

Immunotherapy has emerged as a powerful therapeutic strategy for many malignancies, including lymphoma. As in solid tumors, early clinical trials have revealed that immunotherapy is not equally efficacious across all lymphoma subtypes. For example, immune checkpoint inhibition has a higher overall response rate and leads to more durable outcomes in Hodgkin lymphomas compared to non-Hodgkin lymphomas. These observations, combined with a growing understanding of tumor biology, have implicated the tumor microenvironment as a major determinant of treatment response and prognosis. Interactions between lymphoma cells and their microenvironment facilitate several mechanisms that impair the antitumor immune response, including loss of major histocompatibility complexes, expression of immunosuppressive ligands, secretion of immunosuppressive cytokines, and the recruitment, expansion, and skewing of suppressive cell populations. Accordingly, treatments to overcome these barriers are being rapidly developed and translated into clinical trials. This review will discuss the mechanisms of immune evasion, current avenues for optimizing the antitumor immune response, clinical successes and failures of lymphoma immunotherapy, and outstanding hurdles that remain to be addressed.

Immune Dysfunction in Patients with Chronic Lymphocytic Leukemia and Challenges during COVID-19 Pandemic

The novel severe acute respiratory syndrome coronavirus (SARS-CoV-2) has been first described in December 2019 in Wuhan, China, and has led to a worldwide pandemic ever since. Initial clinical data imply that cancer patients are particularly at risk for a severe course of SARS-CoV-2. In patients with chronic lymphocytic leukemia (CLL), infections are a main contributor to morbidity and mortality driven by an impaired immune system. Treatment initiation is likely to induce immune modulation that further increases the risk for severe infections. This article aims to give an overview on pathogenesis and risk of infectious complications in patients with CLL. In this context, we discuss current data of SARS-CoV-2 infections in patients with CLL and how the pandemic impacts their management.

Reduced expansion of CD94/NKG2C+ NK cells in chronic lymphocytic leukemia and CLL-like monoclonal B-cell lymphocytosis is not related to increased human cytomegalovirus seronegativity or NKG2C deletions

INTRODUCTION

Dysregulated NK cell-mediated immune responses contribute to tumor evasion in chronic lymphocytic leukemia (CLL), although the NK cell compartment in CLL-like monoclonal B-cell lymphocytosis (MBL) is poorly understood. In healthy individuals, human cytomegalovirus (HCMV) induces the expansion of NK cells expressing high levels of CD94/NKG2C NK cell receptor (NKR) specific for HLA-E.

METHODS

We analyzed the expression of NKG2A, NKG2C, ILT2, KIR, CD161, and CD57 in 24 MBL and 37 CLL. NKG2C was genotyped in these patients and in 81 additional MBL/CLL, while NKG2C gene expression was assessed in 26 cases. In 8 CLL patients with increased lymphocytosis (≥20 × 10⁹ /L), tumor HLA-E and HLA-G expression was evaluated.

RESULTS

NKR distribution did not significantly differ between MBL and CLL patients, although they exhibited reduced NKG2C⁺ NK cells compared with a non-CLL group (4.6% vs 12.2%, P = .012). HCMV⁺ patients showed increased percentages of NKG2C⁺ NK cells compared with HCMV^- (7.3% vs 2.9%, P = .176). Frequencies of NKG2C deletions in MBL/CLL were similar to those of the general population. Low/undetectable NKG2C expression was found among NKG2C^+/- (45%) and NKG2C^+/+ (12%) patients. CLL cases with increased lymphocytosis displayed especially reduced NKG2C expression (1.8% vs 8.1%, P = .029) and tumor cells with high HLA-E (>98%) and variable HLA-G expression (12.4%, range: 0.5-56.4). CLL patients with low NKG2C expression (<7%) showed shorter time to first treatment (P = .037).

CONCLUSION

Reduced percentages of CD94/NKG2C⁺ NK cells were observed in CLL and MBL patients independently of HCMV serostatus and NKG2C zygosity, particularly in CLL patients with increased lymphocytosis, which could potentially be related to the exposure to tumor cells.

Immune Dysfunctions and Immune-Based Therapeutic Interventions in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy characterized by a wide range of tumor-induced alterations, which affect both the innate and adaptive arms of the immune response, and accumulate during disease progression. In recent years, the development of targeted therapies, such as the B-cell receptor signaling inhibitors and the Bcl-2 protein inhibitor venetoclax, has dramatically changed the treatment landscape of CLL. Despite their remarkable anti-tumor activity, targeted agents have some limitations, which include the development of drug resistance mechanisms and the inferior efficacy observed in high-risk patients. Therefore, additional treatments are necessary to obtain deeper responses and overcome drug resistance. Allogeneic hematopoietic stem cell transplantation (HSCT), which exploits immune-mediated graft-versus-leukemia effect to eradicate tumor cells, currently represents the only potentially curative therapeutic option for CLL patients. However, due to its potential toxicities, HSCT can be offered only to a restricted number of younger and fit patients. The growing understanding of the complex interplay between tumor cells and the immune system, which is responsible for immune escape mechanisms and tumor progression, has paved the way for the development of novel immune-based strategies. Despite promising preclinical observations, results from pilot clinical studies exploring the safety and efficacy of novel immune-based therapies have been sometimes suboptimal in terms of long-term tumor control. Therefore, further advances to improve their efficacy are needed. In this context, possible approaches include an earlier timing of immunotherapy within the treatment sequencing, as well as the possibility to improve the efficacy of immunotherapeutic agents by administering them in combination with other anti-tumor drugs. In this review, we will provide a comprehensive overview of main immune defects affecting patients with CLL, also describing the complex networks leading to immune evasion and tumor progression. From the therapeutic standpoint, we will go through the evolution of immune-based therapeutic approaches over time, including i) agents with broad immunomodulatory effects, such as immunomodulatory drugs, ii) currently approved and next-generation monoclonal antibodies, and iii) immunotherapeutic strategies aiming at activating or administering immune effector cells specifically targeting leukemic cells (e.g. bi-or tri-specific antibodies, tumor vaccines, chimeric antigen receptor T cells, and checkpoint inhibitors).

Helper Innate Lymphoid Cells in Allogenic Hematopoietic Stem Cell Transplantation and Graft Versus Host Disease

Helper Innate Lymphoid Cells (hILCs), including ILC1s, ILC2s, and ILC3s, are mainly localized at the mucosal barriers where they play an important role in tissue regeneration and homeostasis through the secretion of specific sets of cytokines. The recent identification of a circulating ILC precursor able to generate all ILC mature subsets in physiological conditions, suggests that “ILC-poiesis” may be important in the context of hematopoietic stem cell transplantation (HSCT). Indeed, in HSCT the conditioning regimen (chemotherapy and radiotherapy) and Graft vs Host Disease (GvHD) may cause severe damages to mucosal tissues. Therefore, it is conceivable that rapid reconstitution of the hILC compartment may be beneficial in HSCT, by promoting mucosal tissue repair/regeneration and providing protection from opportunistic infections. In this review, we will summarize the evidence for a role of hILCs in allogenic HSCT for the treatment of hematological malignancies in all its steps, from the preparative regimen to the immune reconstitution in the recipient. The protective properties of hILCs at the mucosal barrier interfaces make them an attractive target to exploit in future cellular therapies aimed at improving allogenic HSCT outcome.

Increase of Antitumoral Effects of Cytokine-Induced Killer Cells by Antibody-Mediated Inhibition of MICA Shedding

Natural killer group 2D (NKG2D) receptor plays a pivotal role in cytokine-induced killer (CIK) cell-mediated cytotoxicity against malignancies, and the expression of NKG2D ligands might allow targets to be more susceptible to the CIK cell-mediated destruction. In this study, we investigated the synergistic effects of CIK cells antitumor activity and antibody-mediated inhibition of MICA/B shedding. This monoclonal antibody (7C6) has been previously shown to be able to specifically target MICA/B a3 domain on tumor cells, resulting in the increase in cell surface MICA/B expression by inhibition of their shedding. In the current study, we show that 7C6 antibody could substantially inhibit MICA shedding and stabilize the expression of MICA/B on Hela cells and MDA-MB-231 cells. In combination with 7C6, CIK cells showed higher degranulation rate, more IFN-γ production and elevated cytotoxic capacity against tumor cells. Furthermore, we demonstrate that NKG2D-MICA/B ligation could lead to activation of both CD3+ CD56− T cells and CD3+CD56+ NKT subset cells of CIK culture and NKT subset was more sensitive to NKG2D signaling than the counterpart T cells. 7C6-mediated inhibition of MICA shedding could strengthen this signal and eventually enhance the antitumor activity of CIK cells. With multiple advantages of easy ex vivo expansion, minor GVHD, natural tumor trafficking and non-MHC restricted, CIK cell-based therapy may serve as a potent combination partner with MICA antibody-mediated immunotherapy.

Immune dysfunction complexity in chronic lymphocytic leukemia ‒ an issue to consider when designing novel therapeutic strategies

A complex interplay between chronic lymphocytic leukemia (CLL) cells and different constituents of the immune system generally results in immune tolerance. As targeted therapies are gaining a critical role in the therapeutic landscape of this disease, their impact on the already perturbed immune milieu needs to be considered. This review addresses the issues of basic immune dysfunction in CLL which is further complicated by the effects of a number of novel targeted therapies used for this malignancy. These new approaches may simultaneously facilitate both anti- and pro-cancer activity, potentially compromising the depth of response to therapy. Current evidence suggests that exploiting combination therapy could potentially overcome at least part of these deleterious effects, thereby prolonging response to treatment and helping to restore immune activity.

Immune Response Dysfunction in Chronic Lymphocytic Leukemia: Dissecting Molecular Mechanisms and Microenvironmental Conditions

Representing the major cause of morbidity and mortality for chronic lymphocytic leukemia (CLL) patients, immunosuppression is a common feature of the disease. Effectors of the innate and the adaptive immune response show marked dysfunction and skewing towards the generation of a tolerant environment that favors disease expansion. Major deregulations are found in the T lymphocyte compartment, with inhibition of CD8⁺ cytotoxic and CD4⁺ activated effector T cells, replaced by exhausted and more tolerogenic subsets. Likewise, differentiation of monocytes towards a suppressive M2-like phenotype is induced at the expense of pro-inflammatory sub-populations. Thanks to their B-regulatory phenotype, leukemic cells play a central role in driving immunosuppression, progressively inhibiting immune responses. A number of signaling cascades triggered by soluble mediators and cell–cell contacts contribute to immunomodulation in CLL, fostered also by local environmental conditions, such as hypoxia and derived metabolic acidosis. Specifically, molecular pathways modulating T-cell activity in CLL, spanning from the best known cytotoxic T lymphocyte antigen-4 (CTLA-4) and programmed cell death 1 (PD-1) to the emerging T cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibition motif domains (TIGIT)/CD155 axes, are attracting increasing research interest and therapeutic relevance also in the CLL field. On the other hand, in the microenvironment, the B cell receptor (BCR), which is undoubtedly the master regulator of leukemic cell behavior, plays an important role in orchestrating immune responses, as well. Lastly, local conditions of hypoxia, typical of the lymphoid niche, have major effects both on CLL cells and on non-leukemic immune cells, partly mediated through adenosine signaling, for which novel specific inhibitors are currently under development. In summary, this review will provide an overview of the molecular and microenvironmental mechanisms that modify innate and adaptive immune responses of CLL patients, focusing attention on those that may have therapeutic implications.

IL-27 impact on NK cells activity: Implication for a robust anti-tumor response in chronic lymphocytic leukemia

Interleukin 27 (IL-27) belongs to IL-12 cytokine family, has shown anti-tumor potential in several solid tumors, as well as hematologic malignancies. IL-27 can inhibit tumor growth and progression through direct and indirect mechanisms, such as inhibition of proliferation, angiogenesis, induction of apoptosis in tumor cells, and anti-tumor immune response. B-CLL is characterized by remarkable immune perturbation, which leads to disease complications and reduced effectiveness of the treatment. Natural killer cells (NK) are considered as an important arm for the elimination of transformed cells. However, NK cells have shown significant impairment in patients with CLL. Here we analyzed the activity of recombinant human (rh) IL-27-stimulated NK cells in bone marrow (BM) and peripheral blood (PB) of CLL patients using cell surface flow cytometry assessment, and cytotoxicity assay. We showed that rhIL-27 can increase CD69 on NK cells both in BM and PB. Interestingly, BM-NK cells treated with rhIL-27 exhibited a significant increase in degranulation and NK cell-mediated cytotoxicity as compared with untreated NK cells, whereas it did not improve NK cell activity of PB. These observations added further explanation to the anti-tumor activity of IL-27 and also could pave the way to adoption immunostimulatory adjuvant for therapies in CLL.

Clinico-Biological Implications of Modified Levels of Cytokines in Chronic Lymphocytic Leukemia: A Possible Therapeutic Role

B-cell chronic lymphocytic leukemia (B-CLL) is the main cause of mortality among hematologic diseases in Western nations. B-CLL is correlated with an intense alteration of the immune system. The altered functions of innate immune elements and adaptive immune factors are interconnected in B-CLL and are decisive for its onset, evolution, and therapeutic response. Modifications in the cytokine balance could support the growth of the leukemic clone via a modulation of cellular proliferation and apoptosis, as some cytokines have been reported to be able to affect the life of B-CLL cells in vivo. In this review, we will examine the role played by cytokines in the cellular dynamics of B-CLL patients, interpret the contradictions sometimes present in the literature regarding their action, and evaluate the possibility of manipulating their production in order to intervene in the natural history of the disease.

Recent Advances in Molecular Mechanisms of the NKG2D Pathway in Hepatocellular Carcinoma

Hepatocellular carcinoma is a common malignant tumor with high mortality. Its malignant proliferation, invasion, and metastasis are closely related to the cellular immune function of the patients. NKG2D is a key activated and type II membrane protein molecule expressed on the surface of almost all NK cells. The human NKG2D gene is 270 kb long, located at 12p12.3-p13.1, and contains 10 exons and 9 introns. The three-dimensional structure of the NKG2D monomeric protein contains two alpha-helices, two beta-lamellae, and four disulfide bonds, and its' signal of activation is transmitted mainly by the adaptor protein (DAP). NKG2D ligands, including MICA, MICB, and ULBPs, can be widely expressed in hepatoma cells. After a combination of NKG2D and DAP10 in the form of homologous two polymers, the YxxM motif in the cytoplasm is phosphorylated and then signaling pathways are also gradually activated, such as PI3K, PLCγ2, JNK-cJunN, and others. Activated NK cells can enhance the sensitivity to hepatoma cells and specifically dissolve by releasing a variety of cytokines (TNF-α and IFN-γ), perforin, and high expression of FasL, CD16, and TRAIL. NK cells may specifically bind to the over-expressed MICA, MICB, and ULBPs of hepatocellular carcinoma cells through the surface activating receptor NKG2D, which can help to accurately identify hepatoma, play a critical role in anti-hepatoma via the pathway of cytotoxic effects, and obviously delay the poor progress of hepatocellular carcinoma.

Boosting Natural Killer Cell-Mediated Targeting of Sarcoma Through DNAM-1 and NKG2D

Sarcomas are malignancies of mesenchymal origin that occur in bone and soft tissues. Many are chemo- and radiotherapy resistant, thus conventional treatments fail to increase overall survival. Natural Killer (NK) cells exert anti-tumor activity upon detection of a complex array of tumor ligands, but this has not been thoroughly explored in the context of sarcoma immunotherapy. In this study, we investigated the NK cell receptor/ligand immune profile of primary human sarcoma explants. Analysis of tumors from 32 sarcoma patients identified the proliferative marker PCNA and DNAM-1 ligands CD112 and/or CD155 as commonly expressed antigens that could be efficiently targeted by genetically modified (GM) NK cells. Despite the strong expression of CD112 and CD155 on sarcoma cells, characterization of freshly dissociated sarcomas revealed a general decrease in tumor-infiltrating NK cells compared to the periphery, suggesting a defect in the endogenous NK cell response. We also applied a functional screening approach to identify relevant NK cell receptor/ligand interactions that induce efficient anti-tumor responses using a panel NK-92 cell lines GM to over-express 12 different activating receptors. Using GM NK-92 cells against primary sarcoma explants (n = 12) revealed that DNAM-1 over-expression on NK-92 cells led to efficient degranulation against all tested explants (n = 12). Additionally, NKG2D over-expression showed enhanced responses against 10 out of 12 explants. These results show that DNAM-1⁺ or NKG2D⁺ GM NK-92 cells may be an efficient approach in targeting sarcomas. The degranulation capacity of GM NK-92 cell lines was also tested against various established tumor cell lines, including neuroblastoma, Schwannoma, melanoma, myeloma, leukemia, prostate, pancreatic, colon, and lung cancer. Enhanced degranulation of DNAM-1⁺ or NKG2D⁺ GM NK-92 cells was observed against the majority of tumor cell lines tested. In conclusion, DNAM-1 or NKG2D over-expression elicited a dynamic increase in NK cell degranulation against all sarcoma explants and cancer cell lines tested, including those that failed to induce a notable response in WT NK-92 cells. These results support the broad therapeutic potential of DNAM-1⁺ or NKG2D⁺ GM NK-92 cells and GM human NK cells for the treatment of sarcomas and other malignancies.

Natural Killer Cell Hypo-responsiveness in Chronic Lymphocytic Leukemia can be Circumvented In Vitro by Adequate Activating Signaling

Chronic lymphocytic leukemia (CLL) is characterized by an acquired immune dysfunction, which may underlie the hampered efficacy of cellular immunotherapy. Most data on dampened immune responses in CLL come from studies investigating CLL and T cell interactions. Natural killer (NK) cells may be an attractive alternative source of effector cells in immunotherapy in CLL, provided that functionality is retained within the CLL micro-environment. Despite their important role in anti-tumor responses, NK cells are not extensively characterized in CLL. Here, we studied the expression of activating and inhibitory receptors on CLL-derived and healthy control (HC) NK cells, and their functional response towards several stimuli.

NK cells from CLL patients have an increased maturation stage, with an expansion of NKG2C⁺ NK cells in CMV seropositive individuals. The cytotoxicity receptor NKG2D is downregulated, and the killing capacity through this receptor was markedly reduced in CLL-derived NK cells. In contrast, activation via CD16 (FCγRIII) led to adequate activation and functional responses in CLL-derived NK cells. These findings indicate that NK cells in CLL are not intrinsically defect and still perform effector functions upon adequate activating signaling. Clinical relevance of this finding was shown by treatment with novel nanobody-Fc constructs, which induced cytotoxic responses in both CLL- and HC-derived NK cells via CD16. Our results show that NK cells, in contrast to the T cell compartment, retain their function within the CLL micro-environment, provided that they receive an adequate activating signal. These findings warrant future studies on NK cell mediated immunotherapeutic strategies in CLL.

NK Cells in the Treatment of Hematological Malignancies

Natural killer (NK) cells have the innate ability to kill cancer cells, however, tumor cells may acquire the capability of evading the immune response, thereby leading to malignancies. Restoring or potentiation of this natural antitumor activity of NK cells has become a relevant therapeutic approach in cancer and, particularly, in hematological cancers. The use of tumor-specific antibodies that promote antibody-dependent cell-mediated cytotoxicity (ADCC) through the ligation of CD16 receptor on NK cells has become standard for many hematologic malignancies. Hematopoietic stem cell transplantation is another key therapeutic strategy that harnesses the alloreactivity of NK cells against cancer cells. This strategy may be refined by adoptive transfer of NK cells that may be previously expanded, activated, or redirected (chimeric antigen receptor (CAR)-NK cells) against cancer cells. The antitumor activity of NK cells can also be boosted by cytokines or immunostimulatory drugs such as lenalidomide or pomalidomide. Finally, targeting immunosubversive mechanisms developed by hematological cancers and, in particular, using antibodies that block NK cell inhibitory receptors and checkpoint proteins are novel promising therapeutic approaches in these malignant diseases.

Engaging Cytotoxic T and NK Cells for Immunotherapy in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is characterized by an acquired immune dysfunction. CLL cells affect the phenotype and function of the entire spectrum of innate and adaptive immune cells, including monocytes, T cells, and natural killer (NK) cells, leading to a tumor-supportive environment and reduced immunosurveillance. Novel immunotherapies like immune checkpoint blockade, bi- and tri-specific antibodies, and chimeric antigen receptor (CAR) T cells use the patients' immune system to induce therapeutic responses. Although these novel immunotherapies showed impressive results in several B cell lymphomas, responses in CLL were often disappointing. The strong immunomodulatory effect of CLL is believed to play a pivotal role in the low response rates to these immunotherapeutic strategies. In this review, we summarize how CLL influences the function of non-malignant lymphocytes, with a special focus on T and NK cells, two important cellular mediators for immunotherapy. Secondly, we provide a short overview of the activity of several immunotherapeutics in CLL, and discuss how novel strategies may overcome the disappointing response rates in CLL.

Targeting the Immune Microenvironment in Lymphomas of B-Cell Origin: From Biology to Clinical Application

In lymphomas of B-cell origin, cancer cells orchestrate an inflammatory microenvironment of immune and stromal cells that sustain the tumor cell survival and growth, known as a tumor microenvironment (TME). The features of the TME differ between the different lymphoma types, ranging from extremely inflammatory, such as in Hodgkin lymphoma, to anergic, leading to immune deficiency and susceptibility to infections, such as in chronic lymphocytic leukemia. Understanding the characteristic features of the TME as well as the interactions between cancer and TME cells has given insight into the pathogenesis of most lymphomas and contributed to identify novel therapeutic targets. Here, we summarize the preclinical data that contributed to clarifying the role of the immune cells in the TME of different types of lymphomas of B-cell origin, and explain how the understanding of the biological background has led to new clinical applications. Moreover, we provide an overview of the clinical results of trials that assessed the safety and efficacy of drugs directly targeting TME immune cells in lymphoma patients.

Regulation of murine NK cell exhaustion through the activation of the DNA damage repair pathway

NK cell exhaustion (NCE) due to sustained proliferation results in impaired NK cell function with loss of cytokine production and lytic activity. Using murine models of chronic NK cell stimulation, we have identified a phenotypic signature of NCE characterized by up-regulation of the terminal differentiation marker KLRG1 and by down-regulation of eomesodermin and the activating receptor NKG2D. Chronic stimulation of mice lacking NKG2D resulted in minimized NCE compared to control mice, thus identifying NKG2D as a crucial mediator of NCE. NKG2D internalization and downregulations on NK cells has been previously observed in the presence of tumor cells with high expression of NKG2D ligands (NKG2DL) due to the activation of the DNA damage repair pathways. Interestingly, our study revealed that during NK cell activation there is an increase of MULT1, and NKG2DL, that correlates with an induction of DNA damage. Treatment with the ATM DNA damage repair pathway inhibitor KU55933 (KU) during activation reduced NCE by improving expression of activation markers and genes involved in cell survival, by sustaining NKG2D expression and by preserving cell functionality. Importantly, NK cells expanded ex vivo in the presence of KU displayed increased anti-tumor efficacy in both NKG2D-dependent and -independent mouse models. Collectively, these data demonstrate that NCE is caused by DNA damage and regulated, at least in part, by NKG2D. Further, the prevention of NCE is a promising strategy to improve NK cell-based immunotherapy.

CD4+CD25+Foxp3+ regulatory T cells suppress NKG2D-mediated NK cell cytotoxicity in peripheral blood

BACKGROUND

Studies have shown that CD4CD25Foxp3Treg cells suppress NKG2D expression on NK cells via a cell contact-dependent mechanism and increased TGF-β and IL-10 production in some cancer models. We herein aimed to explore whether CD4CD25Foxp3Tregs suppress NKG2D-mediated NK cell cytotoxicity in peripheral blood and elucidate the exact mechanism underlying this phenomenon.

METHODS

To explore the function of NKG2D, NK cell cultures were treated with an NKG2D-blocking antibody to block these receptors. Additionally, TGF-β- and IL-10-blocking antibodies were added to NK and CD4CD25Foxp3Treg cell cocultures to evaluate whether the latter cells suppress NKG2D expression of NK cells via increasing the production of TGF-β and IL-10. The expression of NKG2D on NK cells was detected by 3-color flow cytometry, and NK cell activity was assessed by 3 assays: a nonradioactive cytotoxicity assay, an ELISA measuring IFN-γ production and a flow cytometry assay to evaluate CD107a expression.

RESULTS

Blocking NKG2D decreased NK cell cytotoxicity, IFN-γ production and CD107a expression. Moreover, blocking TGF-β and IL-10 substantially increased the NKG2D expression in NK and CD4CD25Foxp3Treg cell cocultures. Similarly, blocking TGF-β and IL-10 enhanced NK cell cytotoxicity, IFN-γ production and CD107a expression; Transwell insert assays also revealed increased IFN-γ production and CD107a and NKG2D expression.

CONCLUSION

CD4CD25Foxp3Tregs suppress NKG2D-mediated NK cell cytotoxicity in peripheral blood via a cell contact-dependent mechanism and increased TGF-β and IL-10 production.

Curcumin as a therapeutic agent in leukemia

Leukemia comprises a group of hematological malignancies responsible for 8% of all cancers and is the most common cancer in children. Despite significant improvements in leukemia treatment, the efficacy of conventional chemotherapeutic agents is low and the disease carries a poor prognosis with frequent relapses and high mortality. Curcumin is a yellow polyphenol compound with diverse pharmacological actions including anticancer, antioxidant, antidiabetic, anti-inflammatory, immunomodulatory, hepatoprotective, lipid-regulating, antidepressant, and antiarthritic. Many cellular and experimental studies have reported the benefits of curcumin in treating leukemia. Curcumin's anticancer effects are exerted via various mechanisms. Here, we review the effects of curcumin on various types of leukemia whilst considering its mechanisms of action.

Ig-Like Transcript 2 (ILT2) Blockade and Lenalidomide Restore NK Cell Function in Chronic Lymphocytic Leukemia

One of the cardinal features of chronic lymphocytic leukemia (CLL) is its association with a profound immunosuppression. NK cell function is markedly impaired in CLL patients, who show a significant dysregulation of the expression of activating and inhibitory receptors. Here, we analyzed the role of the novel inhibitory receptor Ig-like transcript 2 (ILT2, also termed LIR-1, LILRB1) in the regulation of NK cells in CLL. Our results show that ILT2 expression was significantly decreased on leukemic cells and increased on NK cells of CLL patients, particularly in those with advanced disease and with bad prognostic features, such as those carrying chromosome del(11q). The immunomodulatory drug lenalidomide may regulate the expression of ILT2 and its ligands in CLL since it significantly increased the expression of ILT2 and partially reestablished the expression of its ligands on leukemic cells. Furthermore, lenalidomide significantly increased the activation and proliferation of NK cells, which was strongly enhanced by ILT2 blockade. Combining ILT2 blockade and lenalidomide activated NK cell cytotoxicity resulting in increased elimination of leukemic cells from CLL patients. Overall, we describe herein the role of an inhibitory receptor involved in the suppression of NK cell activity in CLL, which is restored by ILT2 blockade in combination with lenalidomide, suggesting that it may be an interesting therapeutic strategy to be explored in this disease.

NK cell function is markedly impaired in patients with chronic lymphocytic leukaemia but is preserved in patients with small lymphocytic lymphoma

Chronic lymphocytic leukemia (B-CLL) and small lymphocytic lymphoma (SLL) are part of the same disease classification but are defined by differential distribution of tumor cells. B-CLL is characterized by significant immune suppression and dysregulation but this is not typical of patients with SLL. Natural killer cells (NK) are important mediators of immune function but have been poorly studied in patients with B-CLL/SLL. Here we report for the first time the NK cell phenotype and function in patients with B-CLL and SLL alongside their transcriptional profile. We show for the first time impaired B-CLL NK cell function in a xenograft model with reduced activating receptor expression including NKG2D, DNAM-1 and NCRs in-vitro. Importantly, we show these functional differences are associated with transcriptional downregulation of cytotoxic pathway genes, including activating receptors, adhesion molecules, cytotoxic molecules and intracellular signalling molecules, which remain intact in patients with SLL. In conclusion, NK cell function is markedly influenced by the anatomical site of the tumor in patients with B-CLL/SLL and lymphocytosis leads to marked impairment of NK cell activity. These observations have implications for treatment protocols which seek to preserve immune function by limiting the exposure of NK cells to tumor cells within the peripheral circulation.

Elevated absolute NK cell counts in peripheral blood predict good prognosis in chronic lymphocytic leukemia

PURPOSE

The aim of this study was to investigate the prognostic significance of the absolute natural killer (NK) cell counts in peripheral blood in patients with chronic lymphocytic leukemia (CLL).

METHODS

A total of 273 previously untreated patients with CLL from April 2004 and October 2015 were enrolled into this retrospective study. We analysed the T cell subsets of all patients and figured out the number of NK cells. Comparisons of NK cell count as continuous parameter in different groups were described using Mann-Whitney U test and the Kruskal-Wallis test. Kaplan-Meier method was used to survival analysis, and the Cox proportional hazards models were used for the estimation of prognostic factors.

RESULTS

NK cell counts were calculated in 273 therapy-naive CLL patients, and higher number of NK cell was observed in those with Binet stage A/B, ZAP-70 < 20%, normal serum albumin and β₂-microglobulin levels. Using a NK cell count cut-off of 0.40 × 10⁹/L, patients with lower NK cell count (< 0.40 × 10⁹/L) had a significantly shorter overall survival (OS) than those with higher NK cell count (≥ 0.40 × 10⁹/L) (P = 0.0014). Multivariate analysis showed that NK cell counts remained its prognostic value. However, the effect of NK cell count on time to treatment was not significant.

CONCLUSIONS

Our results suggest that NK cell count is an independent prognostic marker for OS in patients with CLL and NK cell counts ≥ 0.40 × 10⁹/L can routinely be used to identify patients with favorable survival.

Natural Killer Cells: Angels and Devils for Immunotherapy

In recent years, the relevance of the immune system to fight cancer has led to the development of immunotherapy, including the adoptive cell transfer of immune cells, such as natural killer (NK) cells and chimeric antigen receptors (CAR)-modified T cells. The discovery of donor NK cells’ anti-tumor activity in acute myeloid leukemia patients receiving allogeneic stem cell transplantation (allo-SCT) was the trigger to conduct many clinical trials infusing NK cells. Surprisingly, many of these studies did not obtain optimal results, suggesting that many different NK cell parameters combined with the best clinical protocol need to be optimized. Various parameters including the high array of activating receptors that NK cells have, the source of NK cells selected to treat patients, different cytotoxic mechanisms that NK cells activate depending on the target cell and tumor cell survival mechanisms need to be considered before choosing the best immunotherapeutic strategy using NK cells. In this review, we will discuss these parameters to help improve current strategies using NK cells in cancer therapy. Moreover, the chimeric antigen receptor (CAR) modification, which has revolutionized the concept of immunotherapy, will be discussed in the context of NK cells. Lastly, the dark side of NK cells and their involvement in inflammation will also be discussed.

Ig-like transcript 2 (ILT2) suppresses T cell function in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is associated with a profound dysregulation of the immune system. Loss of T cell function is frequently caused in cancer by sustained signaling of inhibitory receptors. Here, we analyzed the role of the novel inhibitory receptor Ig-like transcript 2 (ILT2) in the pathogenesis of CLL. We observed that ILT2 expression was markedly reduced on leukemic cells, whereas it was increased on CD8 and CD4 T cells from CLL patients, particularly in those patients harboring chromosome 11q deletion, which includes the ATM gene. A deep dysregulation of ILT2 ligands expression in leukemia cells was also observed. ILT2 impaired the activation and proliferation of CD4 and CD8 T cells in CLL patients, but it had no effect in leukemic cells. ILT2 downregulated the production of IL-2 by CD4 T cells of CLL patients and induced the expression of cytokines that promote the survival of leukemic cells, such as IFN-γ, by T cells. Importantly, ILT2 blockade restored the activation, proliferation and cytokine production of T cells. In conclusion, we describe a novel immune inhibitory pathway that is upregulated in CLL and delineate a new potential target to be explored in this disease.

NK cell dysfunction in chronic lymphocytic leukemia is associated with loss of the mature cells expressing inhibitory killer cell Ig-like receptors

A prospective analysis of natural killer (NK) cell phenotype and function was performed on fresh peripheral blood samples from untreated patients with B-cell chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL). Compared to healthy controls, CD56^dim NK cells in CLL patients displayed reduced expression of the NKG2D activating receptor and increased CD27 expression, which indicates declines in mature cells. In addition, NK cells from CLL patients showed reduced degranulation responses toward transformed B cells alone or with rituximab and were more sensitive to activation-induced cell death. We further noted a striking reduction in the frequency and viability of NK cells expressing the inhibitory killer cell Ig-like receptors (KIR)2DL1 and/or KIR3DL1, which progressed over time in most patients. Comparisons between a CLL patient and healthy monozygotic twin were consistent with our results in the larger cohorts. Functional and biomarker alterations were less pronounced on NK cells from SLL patients, which have lower tumor burden in peripheral blood than CLL, but significant reduction in degranulation under ADCC conditions and lower frequency and viability of KIR-expressing NK cells were still evident in SLL. We conclude that mature KIR-expressing NK cells respond to the high circulating B cell tumor burden in CLL, but undergo activation-induced apoptosis. Consequently, CLL patients may benefit from therapies that augment NK cell survival and function.

Lenalidomide in the treatment of chronic lymphocytic leukemia

INTRODUCTION

Lenalidomide is an immunomodulatory drug (IMiD) with a unique mode of action (MOA) that may vary across disease-type. It is currently approved in multiple myeloma (MM), myelodysplastic syndrome (MDS) and mantle cell lymphoma (MCL), yet is also clinically active in a host of lymphoproliferative diseases, including chronic lymphocytic leukemia (CLL). Due to its protean effects on the immune system, lenalidomide may be particularly appealing in CLL, which is distinct in its ability to evade immune recognition and cause immunosuppression. Areas covered: This review recaps the biological mechanisms of lenalidomide specific for CLL, and summarizes the clinical data in previously untreated and relapsed/refractory (R/R) CLL patients, with emphasis on toxicity. Moreover, lenalidomide treatment is put into the context of the highly effective targeted agents that are drastically changing the therapeutic approach in CLL. Expert opinion: Lenalidomide is a potent drug in CLL, both in first line and relapse. However, in comparison to other newly available agents, lenalidomide has slow onset of efficacy and notable toxicity profile that limits both its single agent use and combinations with chemotherapy. Future trials will hopefully direct our ability to harness lenalidomide MOA to best incorporate it in the rapidly evolving landscape of CLL treatment.

Chitosan nanoparticle-based delivery of fused NKG2D-IL-21 gene suppresses colon cancer growth in mice

Nanoparticles can be loaded with exogenous DNA for the potential expression of cytokines with immune-stimulatory function. NKG2D identifies major histocompatibility complex class I chain-related protein in human and retinoic acid early induced transcript-1 in mouse, which acts as tumor-associated antigens. Biologic agents based on interleukin 21 (IL-21) have displayed antitumor activities through lymphocyte activation. The NKG2D-IL-21 fusion protein theoretically identifies tumor cells through NKG2D moiety and activates T cells through IL-21 moiety. In this study, double-gene fragments that encode the extracellular domains of NKG2D and IL-21 genes were connected and then inserted into the pcDNA3.1(-) plasmid. PcDNA3.1-dsNKG2D-IL-21 plasmid nanoparticles based on chitosan were generated. Tumor cells pretransfected with dsNKG2D-IL-21 gene nanoparticles can activate natural killer (NK) and CD8⁺ T cells in vitro. Serum IL-21 levels were enhanced in mice intramuscularly injected with the gene nanoparticles. DsNKG2D-IL-21 gene nanoparticles accumulated in tumor tissues after being intravenously injected for ~4-24 h. Treatment of dsNKG2D-IL-21 gene nanoparticles also retarded tumor growth and elongated the life span of tumor-bearing mice by activating NK and T cells in vivo. Thus, the dsNKG2D-IL-21 gene nanoparticles exerted efficient antitumor activities and would be potentially used for tumor therapy.

Coevolution of Leukemia and Host Immune Cells in Chronic Lymphocytic Leukemia

Cumulative studies on the dissection of changes in driver genetic lesions in cancer across the course of the disease have provided powerful insights into the adaptive mechanisms of tumors in response to the selective pressures of therapy and environmental changes. In particular, the advent of next-generation-sequencing (NGS)-based technologies and its implementation for the large-scale comprehensive analyses of cancers have greatly advanced our understanding of cancer as a complex dynamic system wherein genetically distinct subclones interact and compete during tumor evolution. Aside from genetic evolution arising from interactions intrinsic to the cell subpopulations within tumors, it is increasingly appreciated that reciprocal interactions between the tumor cell and cellular constituents of the microenvironment further exert selective pressures on specific clones that can impact the balance between tumor immunity and immunologic evasion and escape. Herein, we review the evidence supporting these concepts, with a particular focus on chronic lymphocytic leukemia (CLL), a disease that has been highly amenable to genomic interrogation and studies of clonal heterogeneity and evolution. Better knowledge of the basis for immune escape has an important clinical impact on prognostic stratification and on the pursuit of new therapeutic opportunities.

Neutrophils from chronic lymphocytic leukemia patients exhibit an increased capacity to release extracellular traps (NETs)

Chronic lymphocytic leukemia (CLL) is characterized by immune defects that contribute to a high rate of infections and autoimmune cytopenias. Neutrophils are the first line of innate immunity and respond to pathogens through multiple mechanisms, including the release of neutrophil extracellular traps (NETs). These web-like structures composed of DNA, histones, and granular proteins are also produced under sterile conditions and play important roles in thrombosis and autoimmune disorders. Here we show that neutrophils from CLL patients are more prone to release NETs compared to those from age-matched healthy donors (HD). Increased generation of NETs was not due to higher levels of elastase, myeloperoxidase, or reactive oxygen species production. Instead, we found that plasma from CLL patients was able to prime neutrophils from HD to generate higher amounts of NETs upon activation. Plasmatic IL-8 was involved in the priming effect since its depletion reduced plasma capacity to enhance NETs release. Finally, we found that culture with NETs delayed spontaneous apoptosis and increased the expression of activation markers on leukemic B cells. Our study provides new insights into the immune dysregulation in CLL and suggests that the chronic inflammatory environment typical of CLL probably underlies this inappropriate neutrophil priming.