Testing the NKT cell hypothesis in lenalidomide-treated myelodysplastic syndrome patients

CAR-NKT cell therapy: a new promising paradigm of cancer immunotherapy

Today, cancer treatment is one of the fundamental problems facing clinicians and researchers worldwide. Efforts to find an excellent way to treat this illness continue, and new therapeutic strategies are developed quickly. Adoptive cell therapy (ACT) is a practical approach that has been emerged to improve clinical outcomes in cancer patients. In the ACT, one of the best ways to arm the immune cells against tumors is by employing chimeric antigen receptors (CARs) via genetic engineering. CAR equips cells to target specific antigens on tumor cells and selectively eradicate them. Researchers have achieved promising preclinical and clinical outcomes with different cells by using CARs. One of the potent immune cells that seems to be a good candidate for CAR-immune cell therapy is the Natural Killer-T (NKT) cell. NKT cells have multiple features that make them potent cells against tumors and would be a powerful replacement for T cells and natural killer (NK) cells. NKT cells are cytotoxic immune cells with various capabilities and no notable side effects on normal cells. The current study aimed to comprehensively provide the latest advances in CAR-NKT cell therapy for cancers.

Tumor and microenvironmental mechanisms of resistance to immunomodulatory drugs in multiple myeloma

Resistance to immunomodulatory drugs (IMiDs®) is a major cause of treatment failure, disease relapse and ultimately poorer outcomes in multiple myeloma (MM). In order to optimally deploy IMiDs and their newer derivates CRBN E3 ligase modulators (CELMoDs®) into future myeloma therapeutic regimens, it is imperative to understand the mechanisms behind the inevitable emergence of IMiD resistance. IMiDs bind and modulate Cereblon (CRBN), the substrate receptor of the CUL4CRBN E3 ubiquitin ligase, to target novel substrate proteins for ubiquitination and degradation. Most important of these are IKZF1 and IKZF3, key MM survival transcription factors which sustain the expression of myeloma oncogenes IRF4 and MYC. IMiDs directly target MM cell proliferation, but also stimulate T/NK cell activation by their CRBN-mediated effects, and therefore enhance anti-MM immunity. Thus, their benefits in myeloma are directed against tumor and immune microenvironment - and in considering the mechanisms by which IMiD resistance emerges, both these effects must be appraised. CRBN-dependent mechanisms of IMiD resistance, including CRBN genetic aberrations, CRBN protein loss and CRBN-substrate binding defects, are beginning to be understood. However, only a proportion of IMiD-resistant cases are related to CRBN and therefore additional mechanisms, which are currently less well described, need to be sought. These include resistance within the immune microenvironment. Here we review the existing evidence on both tumor and immune microenvironment mechanisms of resistance to IMiDs, pose important questions for future study, and consider how knowledge regarding resistance mechanism may be utilized to guide treatment decision making in the clinic.

Dysregulation of immune cell and cytokine signaling correlates with clinical outcomes in myelodysplastic syndrome (MDS)

OBJECTIVES

Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis. Although hypomethylating agents (HMA) have improved survival in higher-risk MDS, most patients eventually succumb to progressive disease. Utilizing samples collected prospectively from three MDS clinical trials, we analyzed genetic and immunological biomarkers and correlated them with clinical outcomes.

METHODS

154 samples were analyzed from 133 de novo MDS patients for T-cell and myeloid cell immunophenotyping and gene expression analysis. Treatments were with HMA or immunomodulatory drug (IMiD) alone or in combination.

RESULTS

We observed differences in immune cell subsets between lower and higher risk IPSS groups with NKT cells, MDSCs, intermediate-proinflammatory and non-classical monocytes being higher in the latter group while naïve CD4+ T-cells were reduced. Intermediate-proinflammatory monocytes were increased in non-responders and those failing to achieve at least a hematological improvement. Pro-inflammatory NKT cells were increased at diagnosis for patients failing to derive clinical benefit after 12 months of treatment. Gene expression analysis of paired bone marrow (BM) colony-forming units (CFUs) from diagnosis and 4 cycles post-treatment confirmed that genes involved in cytokine signaling were downregulated in C4 normal colonies.

CONCLUSIONS

These findings support the central roles of dysregulation in innate immunity and inflammatory signaling in the pathogenesis of MDS which correlated with clinical outcomes post-treatment.

Novel in vitro invariant natural killer T cell functional assays

BACKGROUND

Invariant Natural Killer T (iNKT) cells are innate lymphocytes bridging the innate and adaptive immune systems and are critical first responders against cancer and infectious diseases. iNKT cell phenotype and functionality are studied using in vitro stimulation assays assessing cytokine response and proliferation capabilities. The most common stimulant is the glycolipid α-Galactosyl Ceramide (α-GalCer), which stimulates iNKT cells when presented by CD1d, an MHC class I-like molecule expressed by antigen-presenting cells (APC). Another stimulant used is α-GalCer-loaded DimerX, a CD1d-Ig fusion protein which stimulates iNKT cells in an APC-independent fashion. Here, we demonstrate use of the PBS-57-loaded CD1d-tetramer as an APC-independent stimulant, where PBS-57 is an α-GalCer analogue.

METHODS

Using healthy fresh (n = 4) and frozen (n = 7) peripheral blood mononuclear cells (PBMCs), 10-h cytokine response (measuring IFN-γ production) and 10-day proliferation assays were performed assessing iNKT functionality using α-GalCer, CD1d-tetramer and DimerX stimulants.

RESULTS

All stimulants effectively induced IFN-γ production in both fresh and frozen PBMC. After the 10-h activation, CD1d-tetramer was significantly more effective than α-GalCer (p = 0.032) in inducing IFN-γ production in fresh PBMC and significantly more effective than both α-GalCer (p = 0.004) and DimerX (p = 0.021) in frozen PBMC. Similarly, all stimulants induced strong proliferation responses in all samples, although this was only significant in the frozen PBMC. No significant differences in proliferation were observed between stimulants.

SIGNIFICANCE

This study supports PBS-57-loaded CD1d-tetramer as an effective in vitro APC-independent iNKT cell stimulant, which is comparable to or even more effective than α-GalCer and DimerX. As CD1d is downregulated during infectious disease and cancer as evasion strategies, in vitro assays which are APC-independent can assist in providing objective insight to iNKT activation by not relying on CD1d expression by APCs. Overall, the novel CD1d-tetramer stimulation equips researchers with an expanded "toolkit" to successfully assess iNKT cell function.

The Current Landscape of NKT Cell Immunotherapy and the Hills Ahead

Simple Summary

Natural killer T (NKT) cells are a subset of lipid-reactive T cells that enhance anti-tumor immunity. While preclinical studies have shown NKT cell immunotherapy to be safe and effective, clinical studies lack predictable therapeutic efficacy and no approved treatments exist. In this review, we outline the current strategies, challenges, and outlook for NKT cell immunotherapy.

Abstract

NKT cells are a specialized subset of lipid-reactive T lymphocytes that play direct and indirect roles in immunosurveillance and anti-tumor immunity. Preclinical studies have shown that NKT cell activation via delivery of exogenous glycolipids elicits a significant anti-tumor immune response. Furthermore, infiltration of NKT cells is associated with a good prognosis in several cancers. In this review, we aim to summarize the role of NKT cells in cancer as well as the current strategies and status of NKT cell immunotherapy. This review also examines challenges and future directions for improving the therapy.

Navigating the Role of CD1d/Invariant Natural Killer T-cell/Glycolipid Immune Axis in Multiple Myeloma Evolution: Therapeutic Implications

Multiple myeloma (MM) is an incurable B-cell malignancy. The immunotherapeutic approach for MM therapy is evolving. The Cd1d/invariant natural killer T-cell/glycolipid immune axis belongs to the innate immunity, and we have highlighted role in myeloma pathogenesis in the present study. The recent development of the chimeric antigen receptor (CAR19)-invariant natural killer T-cells resulted in our renewed interest in this immune system and offer new perspectives for future anti-MM immunotherapies.

One-Year Follow-Up of Natural Killer Cell Activity in Multiple Myeloma Patients Treated With Adjuvant Lenalidomide Therapy

Multiple myeloma (MM) is a proliferation of tumoral plasma B cells that is still incurable. Natural killer (NK) cells can recognize and kill MM cells in vitro and can limit MM growth in vivo. Previous reports have shown that NK cell function is impaired during MM progression and suggested that treatment with immunomodulatory drugs (IMIDs) such as lenalidomide (LEN) could enhance it. However, the effects of IMIDs on NK cells have been tested mostly in vitro or in preclinical models and supporting evidence of their effect in vivo in patients is lacking. Here, we monitored NK cell activity in blood samples from 10 MM patients starting after frontline induction chemotherapy (CTX) consisting either of association of bortezomib–lenalidomide–dexamethasone (Velcade Revlimid Dexamethasone) or autologous stem-cell transplantation (SCT). We also monitored NK cell activity longitudinally each month during 1 year, after maintenance therapy with LEN. Following frontline chemotherapy, peripheral NK cells displayed a very immature phenotype and retained poor reactivity toward target cells ex vivo. Upon maintenance treatment with LEN, we observed a progressive normalization of NK cell maturation, likely caused by discontinuation of chemotherapy. However, LEN treatment neither activated NK cells nor improved their capacity to degranulate or to secrete IFN-γ or MIP1-β following stimulation with MHC-I-deficient or antibody-coated target cells. Upon LEN discontinuation, there was no reduction of NK cell effector function either. These results caution against the use of LEN as single therapy to improve NK cell activity in patients with cancer and call for more preclinical assessments of the potential of IMIDs in NK cell activation.

Laboratory and clinical risk assessment to treat myelodysplatic syndromes

Myelodisplastic syndromes (MDS) are heterogeneous myeloid disorders characterized by peripheral cytopenias and increased risk of transformation into acute myelogenous leukemia (AML). MDS are generally suspected in the presence of cytopenia on routine analysis and the evaluation of bone marrow cells morphology and cellularity leads to correct diagnosis of MDS. The incidence of MDS is approximately five cases per 100,000 people per year in the general population, but it increases up to 50 cases per 100,000 people per year after 60 years of age. Typically MDS affect the elderly, with a median age at diagnosis of 65–70 years. Here the current therapeutic approaches for MDS are evaluated by searching the PubMed database. Establishing the prognosis in MDS patients is a key element of therapy. In fact an accurate estimate of prognosis drives decisions about the choice and timing of the therapeutic options. Therapy is selected based on prognostic risk assessment, cytogenetic pattern, transfusion needs and biological characteristics of the disease, comorbidities and clinical condition of the patients. In lower-risk patients the goals of therapy are different from those in higher-risk patients. In lower-risk patients, the aim of therapy is to reduce transfusion needs and transformation to higher risk disease or AML, improving the quality of life and survival. In higher-risk patients, the main goal of therapy is to prolong survival and to reduce the risk of AML transformation. Current therapies include growth factor support, lenalidomide, immunomodulatory and hypomethylating agents, intensive chemotherapy, and allogenic stem cell transplantation. The challenge when dealing with MDS patients is to select the optimal treatment by balancing efficacy and toxicity.

Regulation of NKT Cell Localization in Homeostasis and Infection

Natural killer T (NKT) cells are a specialized subset of T lymphocytes that regulate immune responses in the context of autoimmunity, cancer, and microbial infection. Lipid antigens derived from bacteria, parasites, and fungi can be presented by CD1d molecules and recognized by the canonical T cell receptors on NKT cells. Alternatively, NKT cells can be activated through recognition of self-lipids and/or pro-inflammatory cytokines generated during infection. Unlike conventional T cells, only a small subset of NKT cells traffic through the lymph nodes under homeostatic conditions, with the largest NKT cell populations localizing to the liver, lungs, spleen, and bone marrow. This is thought to be mediated by differences in chemokine receptor expression profiles. However, the impact of infection on the tissue localization and function of NKT remains largely unstudied. This review focuses on the mechanisms mediating the establishment of peripheral NKT cell populations during homeostasis and how tissue localization of NKT cells is affected during infection.

An emerging role for immune regulatory subsets in chronic lymphocytic leukaemia

The last few years has seen the burgeoning of a new category of therapeutics for cancer targeting immune regulatory pathways. Antibodies that block the PD-1/PD-L1 interaction are perhaps the most prominent of these new anti-cancer therapies, but several other inhibitory receptor ligand interactions have also shown promise as targets in clinical trials, including CTLA-4/CD80 and Lag-3/MHC class II. Related to this is a rapidly improving knowledge of 'regulatory' lymphocyte lineages, including NKT cells, MAIT cells, B regulatory cells and others. These cells have potent cytokine responses that can influence the functioning of other immune cells and many researchers believe that they could be effective targets for therapies designed to enhance immune responses to cancer. This review will outline our current understanding of FOXP3+ 'Tregs', NKT cells, MAIT cells and B regulatory cells immune regulatory cell populations in cancer, with a particular focus on chronic lymphocytic leukaemia (CLL). We will discuss evidence linking CLL with immune regulatory dysfunction and the potential for new therapies targeting regulatory cells.

Mycobacterium tuberculosis-specific memory NKT cells in patients with tuberculous pleurisy

Natural killer T (NKT) cells from mouse and human play a protective role in the immune responses against the infection of Mycobacterium tuberculosis. However, the characteristic of CD3(+)TCRvβ11(+) NKT cells at the local site of M. tuberculosis infection remains poorly defined. In the present study, we found that the numbers of CD3(+)TCRvβ11(+) NKT cells in pleural fluid mononuclear cells (PFMCs) were significantly lower than those in peripheral blood mononuclear cells (PBMCs). However, CD3(+)TCRvβ11(+) NKT cells from PFMCs spontaneously expressed high levels of CD69 and CD25 and effector memory phenotypes of CD45RO(high)CD62L(low)CCR7(low). After stimulation with the antigens of M. tuberculosis, CD3(+)TCRvβ11(+) NKT cells from PFMCs produced high levels of IFN-γ. Sorted CD3(+)TCRvβ11(+) NKT cells from PFMCs cultured with antigen presenting cells (APCs) produced IFN-γ protein and mRNA. The production of IFN-γ could be completely inhibited by AG490 and Wortmannin. In addition, CD3(+)TCRvβ11(+) NKT cells from PFMCs expressed higher levels of Fas (CD95), FasL (CD178) and perforin but lower levels of granzyme B compared with those from PBMCs. Taken together, our data demonstrated for the first time that M. tuberculosis-specific CD3(+)TCRvβ11(+) NKT cells participated in the local immune responses against M. tuberculosis through the production of IFN-γ and the secretion of cytolytic molecules.

Natural killer T cells: drivers or passengers in preventing human disease?

Natural killer T (NKT) cells are credited with regulatory roles in immunity against cancers, autoimmune diseases, allergies, and bacterial and viral infections. Studies in mice and observational research in patient groups have suggested that NKT cell-based therapies could be used to prevent or treat these diseases, yet the translation into clinical settings has been disappointing. We support the view that NKT cells have regulatory characteristics that could be exploited in clinical settings, but there are doubts about the natural roles of NKT cells in vivo and whether NKT cell defects are fundamental drivers of disease in humans. In this Opinion article, we discuss the uncertainties and opportunities regarding NKT cells in humans, and the potential for NKT cells to be manipulated to prevent or treat disease.

Natural killer T cell defects in multiple myeloma and the impact of lenalidomide therapy

The causes of multiple myeloma (MM) remain obscure and there are few known risk factors; however, natural killer T (NKT) cell abnormalities have been reported in patients with MM, and therapeutic targeting of NKT cells is promoted as a potential treatment. We characterized NKT cell defects in treated and untreated patients with MM and determined the impact of lenalidomide therapy on the NKT cell pool. Lenalidomide is an immunomodulatory drug with co-stimulatory effects on NKT cells in vitro and is an approved treatment for MM, although its mode of action in that context is not well defined. We find that patients with relapsed/progressive MM had a marked deficiency in NKT cell numbers. In contrast, newly diagnosed patients had relatively normal NKT cell frequency and function prior to treatment, although a specific NKT cell deficiency emerged after high-dose melphalan and autologous stem cell transplantation (ASCT) regimen. This also impacted NK cells and conventional T cells, but the recovery of NKT cells was considerably delayed, resulting in a prolonged, treatment-induced NKT cell deficit. Longitudinal analysis of individual patients revealed that lenalidomide therapy had no in-vivo impact on NKT cell numbers or cytokine production, either as induction therapy, or as maintenance therapy following ASCT, indicating that its clinical benefits in this setting are independent of NKT cell modulation.

Toll-like receptor alterations in myelodysplastic syndrome

Recent studies have implicated the innate immunity system in the pathogenesis of myelodysplastic syndromes (MDS). Toll-like receptor (TLR) genes encode key innate immunity signal initiators. We recently identified multiple genes, known to be regulated by TLRs, to be overexpressed in MDS bone marrow (BM) CD34+ cells, and hypothesized that TLR signaling is abnormally activated in MDS. We analyzed a large cohort of MDS cases and identified TLR1, TLR2 and TLR6 to be significantly overexpressed in MDS BM CD34+ cells. Deep sequencing followed by Sanger resequencing of TLR1, TLR2, TLR4 and TLR6 genes uncovered a recurrent genetic variant, TLR2-F217S, in 11% of 149 patients. Functionally, TLR2-F217S results in enhanced activation of downstream signaling including NF-κB activity after TLR2 agonist treatment. In cultured primary BM CD34+ cells of normal donors, TLR2 agonists induced histone demethylase JMJD3 and interleukin-8 gene expression. Inhibition of TLR2 in BM CD34+ cells from patients with lower-risk MDS using short hairpin RNA resulted in increased erythroid colony formation. Finally, RNA expression levels of TLR2 and TLR6, as well as presence of TLR2-F217S, are associated with distinct prognosis and clinical characteristics. These findings indicate that TLR2-centered signaling is deregulated in MDS, and that its targeting may have potential therapeutic benefit in MDS.

Ex-vivo analysis of human natural killer T cells demonstrates heterogeneity between tissues and within established CD4(+) and CD4(-) subsets

Our understanding of human type 1 natural killer T (NKT) cells has been heavily dependent on studies of cells from peripheral blood. These have identified two functionally distinct subsets defined by expression of CD4, although it is widely believed that this underestimates the true number of subsets. Two recent studies supporting this view have provided more detail about diversity of the human NKT cells, but relied on analysis of NKT cells from human blood that had been expanded in vitro prior to analysis. In this study we extend those findings by assessing the heterogeneity of CD4(+) and CD4(-) human NKT cell subsets from peripheral blood, cord blood, thymus and spleen without prior expansion ex vivo, and identifying for the first time cytokines expressed by human NKT cells from spleen and thymus. Our comparative analysis reveals highly heterogeneous expression of surface antigens by CD4(+) and CD4(-) NKT cell subsets and identifies several antigens whose differential expression correlates with the cytokine response. Collectively, our findings reveal that the common classification of NKT cells into CD4(+) and CD4(-) subsets fails to reflect the diversity of this lineage, and that more studies are needed to establish the functional significance of the antigen expression patterns and tissue residency of human NKT cells.

The different immunoregulatory functions on dendritic cells between mesenchymal stem cells derived from bone marrow of patients with low-risk or high-risk myelodysplastic syndromes

Myelodysplastic syndrome (MDS) is a group of progressive,clonal, neoplastic bone marrow disorders characterized by hematopoietic stem cell dysregulation and abnormalities in the immune system. Mesenchymal stem cells (MSC) appear to modulate the immune system at the very first step of the immune response through the inhibition of dendritic cells (DCs) differentiation and maturation. However, it is still unclear whether the effects of MSC on the development of DCs will be altered with disease state. In addition, it is not clear whether there are differences in the effects between low-risk and high-risk MDS-MSC on DCs development. In this study, our data confirm that MDS-MSC mediate a potent inhibition of DCs differentiation. Additionaly, MDS-MSC greatly alter DCs functions, including endocytosis, IL-12 secretion, their ability to inhibit T cell proliferation. Moreover, our results show that there are major differences in DCs development and function between low-risk and high-risk MDS-MSC. Compared to high-risk MDS-MSC, low-risk MDS-MSC is characterized by a poor ability to inhibit DCs differentiation and maturation; and correspondingly, less dysfunctional DC endocytosis, mildly decreased IL-12 secretion, and a reduction in DC-mediated inhibition of T cell proliferation. Finally, our results demonstrate that MDS-MSC derived TGF-β1 is largely responsible for the inhitory effects. These results elucidate the different immunoregulatory role of MSC in low-risk and high-risk MDS on DCs development, which may be important for understanding the pathogenesis of MDS and the development of novel immune therapies for the treatment of MDS.

Myelodysplastic syndromes: the role of the immune system in pathogenesis

The myelodysplastic syndromes (MDS) represent a complex spectrum of clonal hematopoietic stem cell disorders manifested by cytopenias, risk of infection, and variable risk of progression to acute myelogenous leukemia. Several theories of MDS pathogenesis exist, with contributions of genetic, epigenetic, apoptotic, differentiation, and cytokine milieu abnormalities. Immune dysregulation has also been implicated in MDS pathogenesis. In some forms of MDS it is evident that immune dysregulation may be a primary pathophysiologic abnormality, while in others the abnormal immune function may represent only a small part of the pathologic puzzle. We review the current literature regarding natural killer (NK) cell, T cell, and myeloid derived suppressor cell abnormalities in the spectrum of MDS.

Presumed guilty: natural killer T cell defects and human disease

Natural killer T (NKT) cells are important regulatory lymphocytes that have been shown in mouse studies, to have a crucial role in promoting immunity to tumours, bacteria and viruses, and in suppressing cell-mediated autoimmunity. Many clinical studies have indicated that NKT cell deficiencies and functional defects might also contribute to similar human diseases, although there is no real consensus about the nature of the NKT cell defects or whether NKT cells could be important for the diagnosis and/or treatment of these conditions. In this Review, we describe the approaches that have been used to analyse the NKT cell populations of various patient groups, suggest new strategies to determine how (or indeed, if) NKT cell defects contribute to human disease, and discuss the prospects for using NKT cells for therapeutic benefit.

Harnessing natural killer T (NKT) cells in human myeloma: progress and challenges

Multiple myeloma is a hematologic malignancy characterized by growth of malignant plasma cells in the bone marrow. Tumor cells in myeloma express CD1d and are sensitive to lysis by CD1d restricted natural killer T (NKT) cells. Here we discuss recent studies to harness the properties of these cells in the context of human myeloma. In spite of large body of preclinical data, attempts to fully harness the properties of these cells in the clinic are in early stages. Early phase clinical studies document the capacity of human monocyte-derived dendritic cells to expand NKT cells in vivo in myeloma patients. These results have set the stage for ongoing studies combining NKT activation with immune-modulatory drugs. Lessons learnt from these studies may inform the optimal application of human NKT based therapies in other settings as well.

Immunomodulating drugs in myelodysplastic syndromes

Based on immune mechanisms that appear to play an important role in the pathophysiology of at least part of the lower-risk myelodysplastic syndrome (MDS), the immunomodulating drug (IMID) thalidomide and its derivative lenalidomide (LEN) have been used in MDS, principally in lower-risk MDS. LEN has become the first-line US Food and Drug Administration (FDA)-approved treatment for lower-risk MDS with 5q deletion (del5q), in which its main mechanism of action is probably a direct cytotoxic activity on the del5q clone. This possibly specific effect is currently being investigated in higher-risk MDS-and even acute myeloid leukemia (AML)-with del5q, but LEN has also demonstrated some efficacy in MDS and AML without del5q. Thalidomide also has some activity in lower-risk MDS without del5q, but its side effects limit its practical use in these patients.