IL-21 mediates apoptosis through up-regulation of the BH3 family member BIM and enhances both direct and antibody-dependent cellular cytotoxicity in primary chronic lymphocytic leukemia cells in vitro

Exploring the prognostic value of T follicular helper cell levels in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) presents with heterogeneous clinical outcomes, suggesting varied underlying pathogenic mechanisms. This study aims to elucidate the impact of T follicular helper (Tfh) cells on CLL progression and prognosis. Gene expression profile data for CLL were collected from GSE22762 and GSE39671 datasets. Patients were divided into high and low groups using Tfh levels using the optimal cutoff value based on overall survival (OS) and time-to-first treatment (TTFT). Differential expression analysis was performed between these groups, followed by co-expression network analysis and single-sample Gene Set Enrichment Analysis (ssGSEA). Marker genes of Tfh cells were used to construct prognostic models. Additionally, 40 CLL patients were recruited and categorized based on median Tfh levels. Marker gene expression was assessed using RT-qPCR and Western Blot, and immune cell levels were determined through flow cytometry. The high group showed better prognosis compared to the low group. Among the 1121 differentially expressed genes identified, five co-expression networks were constructed, with the turquoise module showing the highest correlation with Tfh cells. Genes within this module significantly participate in cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, and natural killer cell mediated cytotoxicity. Tfh cells were significantly negatively correlated with activated B cells and positively correlated with Tregs. The Random Survival Forest (RSF) model identified 10 marker genes, and further analysis using Lasso regression and nomogram selected CLEC4A, RAE1, CD84, and PRDX1 as prognostic markers. In the high group, levels of CLEC4A and RAE1 were higher than in the low group, whereas CD84 and PRDX1 were lower. Flow cytometry revealed that the level of activated B cells in the high Tfh group was significantly lower than in the low Tfh group, while the level of Tregs is significantly higher in the high Tfh group. This study seeks to contribute to a more detailed understanding of the pathogenesis of CLL, delving into the prognostic significance of Tfh.

Stromal cells engineered to express T cell factors induce robust CLL cell proliferation in vitro and in PDX co-transplantations allowing the identification of RAF inhibitors as anti-proliferative drugs

Several in vitro models have been developed to mimic chronic lymphocytic leukemia (CLL) proliferation in immune niches; however, they typically do not induce robust proliferation. We prepared a novel model based on mimicking T-cell signals in vitro and in patient-derived xenografts (PDXs). Six supportive cell lines were prepared by engineering HS5 stromal cells with stable expression of human CD40L, IL4, IL21, and their combinations. Co-culture with HS5 expressing CD40L and IL4 in combination led to mild CLL cell proliferation (median 7% at day 7), while the HS5 expressing CD40L, IL4, and IL21 led to unprecedented proliferation rate (median 44%). The co-cultures mimicked the gene expression fingerprint of lymph node CLL cells (MYC, NFκB, and E2F signatures) and revealed novel vulnerabilities in CLL-T-cell-induced proliferation. Drug testing in co-cultures revealed for the first time that pan-RAF inhibitors fully block CLL proliferation. The co-culture model can be downscaled to five microliter volume for large drug screening purposes or upscaled to CLL PDXs by HS5-CD40L-IL4 ± IL21 co-transplantation. Co-transplanting NSG mice with purified CLL cells and HS5-CD40L-IL4 or HS5-CD40L-IL4-IL21 cells on collagen-based scaffold led to 47% or 82% engraftment efficacy, respectively, with ~20% of PDXs being clonally related to CLL, potentially overcoming the need to co-transplant autologous T-cells in PDXs.

Harnessing the cytotoxic granule exocytosis to augment the efficacy of T-cell-engaging bispecific antibody therapy

T-cell-engaging bispecific antibody (T-BsAb, also known as BiTE) therapy has emerged as a powerful therapeutic modality against multiple myeloma. Given that T-BsAb therapy redirects endogenous T cells to eliminate tumor cells, reinvigorating dysfunctional T cells may be a potential approach to improve the efficacy of T-BsAb. While various immunostimulatory cytokines can potentiate effector T-cell functions, the optimal cytokine treatment for T-BsAb therapy is yet to be established, partly due to a concern of cytokine release syndrome driven by aberrant interferon (IFN)-γ production. Here, we functionally screen immunostimulatory cytokines to determine an ideal combination partner for T-BsAb therapy. This approach reveals interleukin (IL)-21 as a potential immunostimulatory cytokine with the ability to augment T-BsAb-mediated release of granzyme B and perforin, without increasing IFN-γ release. Transcriptome profiling and functional characterization strongly support that IL-21 selectively targets the cytotoxic granule exocytosis pathway, but not pro-inflammatory responses. Notably, IL-21 modulates multiple steps of cytotoxic effector functions including upregulation of co-activating CD226 receptor, increasing cytotoxic granules, and promoting cytotoxic granule delivery at the immunological synapse. Indeed, T-BsAb-mediated myeloma killing is cytotoxic granule-dependent, and IL-21 priming significantly augments cytotoxic activities. Furthermore, in vivo IL-21 treatment induces cytotoxic effector reprogramming in bone marrow T cells, showing synergistic anti-myeloma effects in combination with T-BsAb therapy. Together, harnessing the cytotoxic granule exocytosis pathway by IL-21 may be a potential approach to achieve better responses by T-BsAb therapy.

Role of the tumor microenvironment in CLL pathogenesis

Chronic lymphocytic leukemia (CLL) cells extensively interact with and depend on their surrounding tumor microenvironment (TME). The TME encompasses a heterogeneous array of cell types, soluble signals, and extracellular vesicles, which contribute significantly to CLL pathogenesis. CLL cells and the TME cooperatively generate a chronic inflammatory milieu, which reciprocally reprograms the TME and activates a signaling network within CLL cells, promoting their survival and proliferation. Additionally, the inflammatory milieu exerts chemotactic effects, attracting CLL cells and other immune cells to the lymphoid tissues. The intricate CLL-TME interactions also facilitate immune evasion and compromise leukemic cell surveillance. We also review recent advances that have shed light on additional aspects that are substantially influenced by the CLL-TME interplay.

Interleukin-21 as an adjuvant in cancer immunotherapy: Current advances and future directions

Immunotherapy has revolutionized cancer treatment. However, it's well-recognized that a considerable proportion of patients fail to benefit from immunotherapy, and to improve immunotherapy response is clinically urgent. Insufficient immune infiltration and immunosuppressive tumor microenvironments (TME) are main contributors to immunotherapy resistance. Thus sustaining functional self-renewal capacity for immune cells and subverting immune-suppressive signals are potential strategies for boosting the efficacy of immunotherapy. Interleukin-21 (IL-21), a crucial cytokine, which could enhance cytotoxic function of immune cells and reduces immunosuppressive cells enrichment in TME, shows promising orientations as an immunoadjuvant in tumor immunotherapy. This review focuses on IL-21 in cancer treatment, including function and mechanisms of IL-21, preclinical and clinical studies, and future directions for IL-21-assisted therapies.

IL-17 and IL-21: Their Immunobiology and Therapeutic Potentials

Studies over the last 2 decades have identified IL-17 and IL-21 as key cytokines in the modulation of a wide range of immune responses. IL-17 serves as a critical defender against bacterial and fungal pathogens, while maintaining symbiotic relationships with commensal microbiota. However, alterations in its levels can lead to chronic inflammation and autoimmunity. IL-21, on the other hand, bridges the adaptive and innate immune responses, and its imbalance is implicated in autoimmune diseases and cancer, highlighting its important role in both health and disease. Delving into the intricacies of these cytokines not only opens new avenues for understanding the immune system, but also promises innovative advances in the development of therapeutic strategies for numerous diseases. In this review, we will discuss an updated view of the immunobiology and therapeutic potential of IL-17 and IL-21.

Elevated levels of circulatory follicular T helper cells in chronic lymphocytic leukemia contribute to B cell expansion

Chronic lymphocytic leukemia (CLL) is characterized by an expansion of mature B cells in the bone marrow, peripheral lymphoid organs, and blood. CD4 T helper (Th) lymphocytes significantly contribute to the physiopathology of CLL, but the subset(s) of Th cell involved in CLL pathogenesis is (are) still under debate. In this study, we performed flow cytometry analysis of the circulatory T cells of untreated CLL patients and observed an increase in follicular helper T cells (Tfh), which is a subset of T cells specialized in B cell help. Elevated numbers of Tfh cells correlated with disease severity as measured by the Binet staging system. Tfh from CLL patients were activated and skewed toward a Th1 profile as evidenced by their PD-1+IL-21+IFNγ+ phenotype and their CXCR3+CCR6- chemokine receptor profile. Tfh efficiently enhanced B-CLL survival and proliferation through IL-21 but independently of IFNγ. Finally, we observed an inverse correlation between the Tfh1 and IgA and IgG serum levels in patients, suggesting a role for this Tfh subset in the immune dysfunction associated with CLL. Altogether, our data highlight an impairment in circulatory Tfh subsets in CLL patients and their critical role in CLL physiopathology.

In Vitro and In Vivo Models of CLL–T Cell Interactions: Implications for Drug Testing

Simple Summary

Chronic lymphocytic leukemia (CLL) cells in the peripheral blood and lymphoid microenvironment display substantially different gene expression profiles and proliferative capaci-ty. It has been suggested that CLL–T-cell interactions are key pro-proliferative stimuli in immune niches. We review in vitro and in vivo model systems that mimic CLL-T-cell interactions to trigger CLL proliferation and study therapy resistance. We focus on studies describing the co-culture of leukemic cells with T cells, or supportive cell lines expressing T-cell factors, and simplified models of CLL cells’ stimulation with recombinant factors. In the second part, we summarize mouse models revealing the role of T cells in CLL biology and implications for generating patient-derived xenografts by co-transplanting leukemic cells with T cells.

Abstract

T cells are key components in environments that support chronic lymphocytic leukemia (CLL), activating CLL-cell proliferation and survival. Here, we review in vitro and in vivo model systems that mimic CLL–T-cell interactions, since these are critical for CLL-cell division and resistance to some types of therapy (such as DNA-damaging drugs or BH3-mimetic venetoclax). We discuss approaches for direct CLL-cell co-culture with autologous T cells, models utilizing supportive cell lines engineered to express T-cell factors (such as CD40L) or stimulating CLL cells with combinations of recombinant factors (CD40L, interleukins IL4 or IL21, INFγ) and additional B-cell receptor (BCR) activation with anti-IgM antibody. We also summarize strategies for CLL co-transplantation with autologous T cells into immunodeficient mice (NOD/SCID, NSG, NOG) to generate patient-derived xenografts (PDX) and the role of T cells in transgenic CLL mouse models based on TCL1 overexpression (Eµ-TCL1). We further discuss how these in vitro and in vivo models could be used to test drugs to uncover the effects of targeted therapies (such as inhibitors of BTK, PI3K, SYK, AKT, MEK, CDKs, BCL2, and proteasome) or chemotherapy (fludarabine and bendamustine) on CLL–T-cell interactions and CLL proliferation.

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.

T Follicular Helper Cell Subsets and the Associated Cytokine IL-21 in the Pathogenesis and Therapy of Asthma

For many decades, T helper 2 (T_H2) cells have been considered to predominantly regulate the pathogenic manifestations of allergic asthma, such as IgE-mediated sensitization, airway hyperresponsiveness, and eosinophil infiltration. However, recent discoveries have significantly shifted our understanding of asthma from a simple T_H2 cell-dependent disease to a heterogeneous disease regulated by multiple T cell subsets, including T follicular helper (T_FH) cells. T_FH cells, which are a specialized cell population that provides help to B cells, have attracted intensive attention in the past decade because of their crucial role in regulating antibody response in a broad range of diseases. In particular, T_FH cells are essential for IgE antibody class-switching. In this review, we summarize the recent progress regarding the role of T_FH cells and their signature cytokine interleukin (IL)-21 in asthma from mouse studies and clinical reports. We further discuss future therapeutic strategies to treat asthma by targeting T_FH cells and IL-21.

The association between interleukin-21 (rs2055979G/T) gene polymorphism and the risk of hepatocellular carcinoma and metastasis in patients with hepatitis C virus

Cancer prevalence is critically increasing worldwide; accordingly, improved prediction and therapeutic tools are necessary. Interleukin (IL)-21 is a potent antitumor cytokine, and the relationship between its gene variations and cancer risk is well established. Nevertheless, so far no study has investigated its role in hepatocellular carcinoma (HCC) progression and metastasis in hepatitis C virus (HCV)-infected people. Therefore, the present investigation was led on 267 Egyptian participants, involving 177 patients with HCV of which 90 patients had HCC (HCC group), 87 patients without HCC (non-HCC group), and 90 unrelated healthy controls. The association between rs2221903A/G and rs2055979G/T of the IL-21 gene and the risk of HCC and metastasis, as well as the clinico-pathological features, were analyzed. While rs2221903A/G polymorphism was not polymorphic in our cohort, patients carrying the genotype TT and allele T of the rs2055979G/T polymorphism had a significantly lower risk of HCC when comparing with HCC group and healthy controls. Also, participants carrying the aforementioned genotype and allele had a significantly lower risk of metastasis when comparing metastatic group with both nonmetastatic group and control group. The rs2055979G/T polymorphism was not significantly associated with clinico-pathological features of HCC. This is the first study to report a relationship between an intronic polymorphism in IL-21 gene and HCC and metastasis risk in the Egyptian people, in addition to identifying a potential new marker for the early detection and treatment of HCC.

IL-21 receptor signaling is essential for control of hepatocellular carcinoma growth and immunological memory for tumor challenge

Hepatocellular carcinoma (HCC) is a typical inflammation-associated cancer. IL-21 regulates both innate and adaptive immune responses and has key roles in antitumor and antiviral responses. However, the role of IL-21 in HCC development is poorly defined. In the current study, we explored the role of IL-21R signaling in HCC growth by using IL-21R knockout mice and HCC mouse models. We discovered that IL-21R signaling deficiency promoted HCC growth in tumor-bearing mice. We showed that IL-21R deletion reduced T cells infiltration and activation as well as their function but increased the accumulation of myeloid-derived suppressor cells in tumor tissues to enhance HCC growth. Furthermore, loss of IL-21R signaling in tumor-bearing mice resulted in an imbalance of the systemic immune system characterized by decreased antitumor immune cells and increased immunosuppressive cells in the spleen and lymph nodes. In addition, we revealed that IL-21R signaling is critical for the expansion of antitumor immune cells in the memory immune response to tumor rechallenge. Finally, we showed that the transcriptional levels of IL-21 in the peritumoral region and IL-21R within the tumor are associated with survival and recurrence of HCC patients. In conclusion, our study demonstrates that IL-21R signaling is essential for controlling the development of HCC and immunological memory response to tumor challenge.

BH3-only protein BIM: An emerging target in chemotherapy

BH3-only proteins constitute major proportion of pro-apoptotic members of B-cell lymphoma 2 (Bcl-2) family of apoptotic regulatory proteins and participate in embryonic development, tissue homeostasis and immunity. Absence of BH3-only proteins contributes to autoimmune disorders and tumorigenesis. Bim (Bcl-2 Interacting Mediator of cell death), most important member of BH3-only proteins, shares a BH3-only domain (9-16 aa) among 4 domains (BH1-BH4) of Bcl-2 family proteins and highly pro-apoptotic in nature. Bim initiates the intrinsic apoptotic pathway under both physiological and patho-physiological conditions. Reduction in Bim expression was found to be associated with tumor promotion and autoimmunity, while overexpression inhibited tumor growth and drug resistance as cancer cells suppress Bim expression and stability. Apart from its role in normal homeostasis, Bim has emerged as a central player in regulation of tumorigenesis, therefore gaining attention as a plausible target for chemotherapy. Regulation of Bim expression and stability is complicated and regulated at multiple levels viz. transcriptional, post-transcriptional, post-translational (preferably by phosphorylation and ubiquitination), epigenetic (by promoter acetylation or methylation) including miRNAs. Furthermore, control over Bim expression and stability may be exploited to enhance chemotherapeutic efficacy, overcome drug resistance and select anticancer drug regimen as various chemotherapeutic agents exploit Bim as an executioner of cell death. Owing to its potent anti-tumorigenic activity many BH3 mimetics e.g. ABT-737, ABT-263, obatoclax, AT-101and A-1210477 have been developed and entered in clinical trials. It is more likely that in near future strategies commanding Bim expression and stability ultimately lead to Bim based therapeutic regimen for cancer treatment.

Anti-CD20-interleukin-21 fusokine targets malignant B cells via direct apoptosis and NK-cell–dependent cytotoxicity

Delivering IL-21 to tumor B cells by fusion with anti-CD20 antibody (αCD20-IL-21 fusokine) is a potent antilymphoma therapeutic strategy. αCD20-IL-21 fusokine demonstrated superior antilymphoma activity compared with its individual components.

Interleukin 21 - its potential role in the therapy of B-cell lymphomas

Interleukin-21 (IL-21), a member of IL-2 cytokine family, has pleotropic biological effects on lymphoid and myeloid cells. During the past 15 years, since the discovery of IL-21, great advances have been made regarding its biological activity and the mechanisms controlling IL-21-mediated cellular responses, especially in hematological malignancies. Preclinical studies have shown that IL-21R is expressed on healthy and neoplastic B-cells and exogenous IL-21 can induce direct apoptosis of IL-21R expressing B-cell non-Hodgkin lymphomas (NHL), making it a potentially attractive anti-lymphoma therapy. However, in some hematological malignancies such as multiple myeloma, Hodgkin lymphoma and Burkitt lymphoma, IL-21 can induce proliferation of neoplastic B-cells. In NHL, the underlying mechanism of cell death was found to be different between the various subtypes, including activation of different JAK/STAT signal transduction pathways or other factors. Immunomodulatory effects of IL-21 have also been reported to contribute to its anti-tumor effects as described by earlier studies in solid tumors and B-cell associated malignancies. These effects are predominantly mediated by IL-21's ability to activate cytolytic activities by NK-cells and CD4⁺/CD8⁺ T-cells. In this review, we provide an overview of IL-21's effects in NHL, results from clinical trials utilizing IL-21, and propose how IL-21 can be therapeutically exploited for treating these lymphomas.

Lenalidomide Induces Interleukin-21 Production by T Cells and Enhances IL21-Mediated Cytotoxicity in Chronic Lymphocytic Leukemia B Cells

The immunomodulatory drug lenalidomide has demonstrated efficacy in patients with chronic lymphocytic leukemia (CLL), despite a lack of direct cytotoxic effects in vitro The mechanism of lenalidomide efficacy in vivo is thought to occur via a combination of enhanced immune activity and an alteration of tumor cell-microenvironment interactions. We demonstrate in whole blood from patients with CLL that lenalidomide significantly depletes malignant B cells. Lenalidomide also induced production of interleukin-21 (IL21) and its mRNA in T cells from patients with CLL. In addition, lenalidomide enhanced upregulation of functional IL21 receptor (IL21R) on the cell surface and increased receptor mRNA in vitro The in vitro combination of IL21 and lenalidomide enhanced IL21-mediated cytotoxicity toward CLL cells through a variety of mechanisms. We show association of cell death with upregulation of Bid by IL21, enhanced upregulation of Bid by the combination therapy, and diminished Lck and downstream BCR signaling activation of Syk and PLCG2. Collectively, we demonstrated an immune cell-tumor cell interaction through lenalidomide-mediated induction of IL21 and IL21R, with enhanced IL21-mediated cytotoxicity, which provides justification for this combination in clinical trials for patients with CLL. Cancer Immunol Res; 4(8); 698-707. ©2016 AACR.

Increased Th17 cells and IL-17A exist in patients with B cell acute lymphoblastic leukemia and promote proliferation and resistance to daunorubicin through activation of Akt signaling

BACKGROUND

Immune regulation is crucial for the pathogenesis of B-cell acute lymphoblastic leukemia (B-ALL). It has been reported that Th17 cells as a newly identified subset of CD4(+) T cells are involved in the pathogenesis of several hematological disorders. However, the role of Th17 cells in the pathophysiology of B-ALL is still unclear.

METHODS

The frequencies of T cells were determined by flow cytometry in the peripheral blood and bone marrow of 44 newly diagnosed B-ALL patients and 25 age-matched healthy donors. The cell viability and apoptosis were determined by CCK-8 assay and Annexin V staining, respectively. Western blot was applied to identify the level of Akt and Stat3 phosphorylation.

RESULTS

We assessed and observed a significantly increased frequency of Th17 cells and a drastically decreased frequency of Th1 cells in peripheral blood mononuclear cells and bone marrow mononuclear cells from newly diagnosed B-ALL patients compared with healthy donors. Furthermore, increased levels of Th17-related cytokines including IL-17, IL-21, IL-23, IL-1β, and IL-6 were presented in between blood and marrow in B-ALL patients. Both IL-17A and IL-21, two Th17-secreted cytokines, induced the proliferation of B-ALL cell line Nalm-6 and patient B-ALL cells isolated from B-ALL patients, herein either cytokine led to the phosphorylation of Akt and Stat3. Additionally, IL-17A promoted resistance to daunorubicin via activation of Akt signaling and the PI3K/Akt inhibitor LY294002 or perifosine almost completely rescued daunorubicin-induced cell death in B-ALL cells.

CONCLUSIONS

Our findings suggest that elevated Th17 cells secrete IL-17A by which promotes the proliferation and resistance to daunorubicin in B-ALL cells through activation of Akt signaling. Th17 cells may represent a novel target to improve B-ALL immunotherapy.

IL-21 Signaling in Immunity

IL-21 is a type I cytokine produced by T cells and natural killer T cells that has pleiotropic actions on a wide range of immune and non-immune cell types. Since its discovery in 2000, extensive studies on the biological actions of IL-21 have been performed in vitro and in vivo. Recent reports describing patients with primary immunodeficiency caused by mutations of IL21 or IL21R have further deepened our knowledge of the role of this cytokine in host defense. Elucidation of the molecular mechanisms that mediate IL-21's actions has provided the rationale for targeting IL-21 and IL-21 downstream mediators for therapeutic purposes. The use of next-generation sequencing technology has provided further insights into the complexity of IL-21 signaling and has identified transcription factors and co-factors involved in mediating the actions of this cytokine. In this review, we discuss recent advances in the biology and signaling of IL-21 and how this knowledge can be potentially translated into clinical settings.

New insights of common gamma chain in hematological malignancies

The common gamma chain (γc) receptor family of cytokines including interleukin-2 (IL-2), IL-4, IL-7, IL-9, IL-15, and IL-21 has the common feature of sharing γc signaling subunit of their receptors. The γc cytokines have unique biological effects that regulate differentiation, survival and activation of multiple lymphocyte lineages and control proliferation of malignant cell by influencing tumor environment. It has been also described that different types of lymphoid leukemia and lymphoma exhibit expression of divergent γc cytokines and their receptors, as they may promote malignant transformation of lymphoid cells or on the contrary lead to tumor regression by inducing cell-cycle arrest. Therefore, cytokine-based or cytokine-directed blockade in cancer immunotherapy has currently revolutionized the development of cancer treatment. In this review, we will discuss about the role of γc cytokines and their signaling pathways in hematological malignancies and also propose a novel alternative approach that regulates γc cytokine responsiveness by γc in hematological malignancies.

Common gamma chain cytokines in combinatorial immune strategies against cancer

Common γ chain (γC) cytokines, namely IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21 are important for the proliferation, differentiation, and survival of lymphocytes that display antitumor activity, thus stimulating considerable interest for the use of cytokines in cancer immunotherapy. In this review, we will focus on the γC cytokines that demonstrate the greatest potential for immunotherapy, IL-2, IL-7, IL-15, and IL-21. We will briefly cover their biological function, potential applications in cancer therapy, and update on their use in combinatorial immune strategies for eradicating tumors and hematopoietic malignancies.

IL-21-Expressing Mesenchymal Stem Cells Prevent Lethal B-Cell Lymphoma Through Efficient Delivery of IL-21, Which Redirects the Immune System to Target the Tumor

Interleukin (IL)-21, a proinflammatory cytokine, has been developed as an immunotherapeutic approach due to its effects on various lymphocytes, including natural killer (NK) cells and T cells; however, the clinical success in cancer patients has been limited. Recently, mesenchymal stem cells (MSCs) have emerged as vehicles for cancer gene therapy due to their inherent migratory abilities toward tumors. In the present study, we hypothesized that MSCs, genetically modified to express high levels of IL-21 (IL-21/MSCs), can enhance antitumor responses through localized delivery of IL-21. For tumor induction, BALB/c mice were injected intravenously with syngeneic A20 B-cell lymphoma cells to develop a disseminated B-cell lymphoma model. Then, 6 days following tumor induction, the tumor-bearing mice were treated with IL-21/MSCs weekly, four times. Systemic infusion of A20 cells led to hind-leg paralysis as well as severe liver metastasis in the control group. The IL-21/MSC-treated group showed delayed tumor incidence as well as improved survival, whereas the MSC- and recombinant adenovirus-expressing IL-21 (rAD/IL-21)-treated groups did not show significant differences from the untreated mice. These therapeutic effects were associated with high levels of IL-21 delivered to the liver, which prevented the formation of tumor nodules. Furthermore, the infusion of IL-21/MSCs led to induction of effector T and NK cells, while potently inhibiting immune suppressor cells. Our findings demonstrate that IL-21-expressing MSCs have the therapeutic potential to induce potent antitumor effects against disseminated B-cell lymphoma through localized IL-21 delivery and induction of systemic antitumor immunity.

Regulation of Bim in Health and Disease

The BH3-only Bim protein is a major determinant for initiating the intrinsic apoptotic pathway under both physiological and pathophysiological conditions. Tight regulation of its expression and activity at the transcriptional, translational and post-translational levels together with the induction of alternatively spliced isoforms with different pro-apoptotic potential, ensure timely activation of Bim. Under physiological conditions, Bim is essential for shaping immune responses where its absence promotes autoimmunity, while too early Bim induction eliminates cytotoxic T cells prematurely, resulting in chronic inflammation and tumor progression. Enhanced Bim induction in neurons causes neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's diseases. Moreover, type I diabetes is promoted by genetically predisposed elevation of Bim in β-cells. On the contrary, cancer cells have developed mechanisms that suppress Bim expression necessary for tumor progression and metastasis. This review focuses on the intricate network regulating Bim activity and its involvement in physiological and pathophysiological processes.

Interleukin 21 Controls mRNA and MicroRNA Expression in CD40-Activated Chronic Lymphocytic Leukemia Cells

Several factors support CLL cell survival in the microenvironment. Under different experimental conditions, IL21 can either induce apoptosis or promote CLL cell survival. To investigate mechanisms involved in the effects of IL21, we studied the ability of IL21 to modulate gene and miRNA expressions in CD40-activated CLL cells. IL21 was a major regulator of chemokine production in CLL cells and it modulated the expression of genes involved in cell movement, metabolism, survival and apoptosis. In particular, IL21 down-regulated the expression of the chemokine genes CCL4, CCL3, CCL3L1, CCL17, and CCL2, while it up-regulated the Th1-related CXCL9 and CXCL10. In addition, IL21 down-regulated the expression of genes encoding signaling molecules, such as CD40, DDR1 and PIK3CD. IL21 modulated a similar set of genes in CLL and normal B-cells (e.g. chemokine genes), whereas other genes, including MYC, TNF, E2F1, EGR2 and GAS-6, were regulated only in CLL cells. An integrated analysis of the miRNome and gene expression indicated that several miRNAs were under IL21 control and these could, in turn, influence the expression of potential target genes. We focused on hsa-miR-663b predicted to down-regulate several relevant genes. Transfection of hsa-miR-663b or its specific antagonist showed that this miRNA regulated CCL17, DDR1, PIK3CD and CD40 gene expression. Our data indicated that IL21 modulates the expression of genes mediating the crosstalk between CLL cells and their microenvironment and miRNAs may take part in this process.

Direct and immune-mediated cytotoxicity of interleukin-21 contributes to antitumor effects in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a distinct subtype of non-Hodgkin lymphoma characterized by overexpression of cyclin D1 in 95% of patients. MCL patients experience frequent relapses resulting in median survival of 3 to 5 years, requiring more efficient therapeutic regimens. Interleukin (IL)-21, a member of the IL-2 cytokine family, possesses potent antitumor activity against a variety of cancers not expressing the IL-21 receptor (IL-21R) through immune activation. Previously, we established that IL-21 exerts direct cytotoxicity on IL-21R-expressing diffuse large B-cell lymphoma cells. Herein, we demonstrate that IL-21 possesses potent cytotoxicity against MCL cell lines and primary tumors. We identify that IL-21-induced direct cytotoxicity is mediated through signal transducer and activator of transcription 3-dependent cMyc upregulation, resulting in activation of Bax and inhibition of Bcl-2 and Bcl-XL. IL-21-mediated cMyc upregulation is only observed in IL-21-sensitive cells. Further, we demonstrate that IL-21 leads to natural killer (NK)-cell-dependent lysis of MCL cell lines that were resistant to direct cytotoxicity. In vivo treatment with IL-21 results in complete FC-muMCL1 tumor regression in syngeneic mice via NK- and T-cell-dependent mechanisms. Together, these data indicate that IL-21 has potent antitumor activity against MCL cells via direct cytotoxic and indirect, immune-mediated effects.

Targeting neddylation induces DNA damage and checkpoint activation and sensitizes chronic lymphocytic leukemia B cells to alkylating agents

Microenvironment-mediated upregulation of the B-cell receptor (BCR) and nuclear factor-κB (NF-κB) signaling in CLL cells resident in the lymph node and bone marrow promotes apoptosis evasion and clonal expansion. We recently reported that MLN4924 (pevonedistat), an investigational agent that inhibits the NEDD8-activating enzyme (NAE), abrogates stromal-mediated NF-κB pathway activity and CLL cell survival. However, the NAE pathway also assists degradation of multiple other substrates. MLN4924 has been shown to induce DNA damage and cell cycle arrest, but the importance of this mechanism in primary neoplastic B cells has not been studied. Here we mimicked the lymph node microenvironment using CD40 ligand (CD40L)-expressing stroma and interleukin-21 (IL-21) to find that inducing proliferation of the primary CLL cells conferred enhanced sensitivity to NAE inhibition. Treatment of the CD40-stimulated CLL cells with MLN4924 resulted in deregulation of Cdt1, a DNA replication licensing factor, and cell cycle inhibitors p21 and p27. This led to DNA damage, checkpoint activation and G2 arrest. Alkylating agents bendamustine and chlorambucil enhanced MLN4924-mediated DNA damage and apoptosis. These events were more prominent in cells stimulated with IL-21 compared with CD40L alone, indicating that, following NAE inhibition, the culture conditions were able to direct CLL cell fate from an NF-κB inhibition to a Cdt1 induction program. Our data provide insight into the biological consequences of targeting NAE in CLL and serves as further rationale for studying the clinical activity of MLN4924 in CLL, particularly in combination with alkylating agents.

CpG oligodeoxynucleotide CpG-685 upregulates functional interleukin-21 receptor on chronic lymphocytic leukemia B cells through an NF-κB mediated pathway

CpG oligodeoxynucleotides (ODNs) upregulate the interleukin-21 receptor (IL21R) and enhance IL-21-mediated cytotoxicity in chronic lymphocytic leukemia (CLL) B cells. We demonstrate that treatment of CLL B cells with the ODN CpG-685 leads to increased IL21R expression, and that this increased expression enhances the effects of IL-21 treatment as evidenced by increased phosphorylation of JAK1, STAT1, and STAT3, as compared to IL-21 treatment without prior CpG stimulation. Induction of IL21R by CpG-685 also enhanced IL-21-mediated cytotoxicity. The mechanism by which CpG ODNs upregulate IL21R has not been elucidated, although IL21R regulation in T cells has been shown to be linked to T cell receptor-induced Sp1 binding to the IL21R promoter. Here, we demonstrate that luciferase reporter constructs containing the Sp1 binding site have increased basal luciferase activity compared to constructs lacking the Sp1 binding site, but fail to increase luciferase activity with CpG-685 stimulation in CLL B cells. By treating CLL cells with an NF-κB inhibitor, we inhibit the CpG ODN-mediated induction of IL21R, thus demonstrating that CpG-685 upregulates IL21R through an NF-κB mediated pathway. These findings suggest an alternative mechanism for induction of IL-21 receptor in CLL B cells and provide a basis for creation of future combination therapies.

IL-21: a pleiotropic cytokine with potential applications in oncology

Interleukin- (IL-) 21 is a pleiotropic cytokine that regulates the activity of both innate and specific immunity. Indeed, it costimulates T and natural killer (NK) cell proliferation and function and regulates B cell survival and differentiation and the function of dendritic cells. In addition, IL-21 exerts divergent effects on different lymphoid cell leukemia and lymphomas, as it may support cell proliferation or on the contrary induce growth arrest or apoptosis of the neoplastic lymphoid cells. Several preclinical studies showed that IL-21 has antitumor activity in different tumor models, through mechanism involving the activation of NK and T or B cell responses. Moreover, IL-21's antitumor activity can be potentiated by its combination with other immune-enhancing molecules, monoclonal antibodies recognizing tumor antigens, chemotherapy, or molecular targeted agents. Clinical phase I-II studies of IL-21 in cancer patients showed immune stimulatory properties, acceptable toxicity profile, and antitumor effects in a fraction of patients. In view of its tolerability, IL-21 is also suitable for combinational therapeutic regimens with other agents. This review will summarize the biological functions of IL-21, and address its role in lymphoid malignancies and preclinical and clinical studies of cancer immunotherapy.

Granzyme B expression is enhanced in human monocytes by TLR8 agonists and contributes to antibody-dependent cellular cytotoxicity

FcγRs are critical mediators of mAb cancer therapies, because they drive cytotoxic processes upon binding of effector cells to opsonized targets. Along with NK cells, monocytes are also known to destroy Ab-coated targets via Ab-dependent cellular cytotoxicity (ADCC). However, the precise mechanisms by which monocytes carry out this function have remained elusive. In this article, we show that human monocytes produce the protease granzyme B upon both FcγR and TLR8 activation. Treatment with TLR8 agonists elicited granzyme B and also enhanced FcγR-mediated granzyme B production in an additive fashion. Furthermore, monocyte-mediated ADCC against cetuximab-coated tumor targets was enhanced by TLR8 agonist treatment, and this enhancement of ADCC required granzyme B. Hence we have identified granzyme B as an important mediator of FcγR function in human monocytes and have uncovered another mechanism by which TLR8 agonists may enhance FcγR-based therapies.

All-trans-retinoic Acid differentially regulates proliferation of normal and leukemic B cells from different subsets of chronic lymphocytic leukemia

All-trans-retinoic acid (ATRA) has been shown to modulate cell growth and differentiation in a variety of tumor cell types, but little is known regarding its precise role in regulation of leukemic B cells from different subsets of chronic lymphocytic leukemia (CLL). Previously, we showed that IL-21 significantly inhibits the CpG-mediated proliferation of CLL B cells in progressive compared to nonprogressive patients. In the present study, the effect of ATRA (10(-7) mol/L) on in vitro proliferation and apoptosis of B cells was investigated in 24 CLL patients and 8 normal subjects. Our results showed that ATRA markedly enhanced CpG-mediated proliferation of normal B cells, but it slightly inhibited CpG-induced proliferation of CLL B cells [stimulation index (SI): 105.6 vs. 14.7, P = 0.0001]. Although addition of IL-21 counteracted the proliferative effect of ATRA in normal B cells, it significantly enhanced the growth of tumor B cells in presence of CpG and ATRA. This stimulatory effect was restricted to nonprogressive and unmutated patients compared to progressive and mutated groups, respectively. Our results suggest that ATRA acts differentially on normal and CLL B cells and might have therapeutic implication in patients with progressive disease.

Apoptosis inducers in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by a typical defect in apoptosis and is still an incurable disease. Numerous apoptosis inducers have been described. These synthetic compounds and natural products (mainly derived from plants) display antileukemic properties in vitro and in vivo and some have even been tested in the clinic in CLL. They act through several different mechanisms. Most of them involve proteins of the Bcl-2 family, which are the key regulators in triggering the mitochondrial pathway of caspase-dependent apoptosis. Thus, the Mcl-1/Noxa axis appeared as a target. Here I overview natural and synthetic apoptosis inducers and their mechanisms of action in CLL cells. Opportunities for developing novel, apoptosis-based therapeutics are presented.

B-CLL cells acquire APC- and CTL-like phenotypic characteristics after stimulation with CpG ODN and IL-21

CpG oligodeoxynucleotides (CpG) and IL-21 are two promising agents for the treatment of B-cell chronic lymphocytic leukemia (B-CLL). Recently, we reported that the combination of CpG and IL-21 (CpG/IL-21) can induce granzyme B (GrB)-dependent apoptosis in B-CLL cells. Here, we demonstrate that treatment of B-CLL cells with CpG and IL-21 results in the development of antigen-presenting cell (APC)-like cells with cytotoxic features. These properties eventually give rise to B-CLL cell apoptosis, independently of their cytogenetic phenotype, whereas normal B-cell survival is not negatively affected by CpG/IL-21. APC- and CTL-typical molecules found to be up-regulated in CpG/IL-21-stimulated B-CLL cells include GrB, perforin, T-bet, monokine-induced by IFN-γ and IFN-γ-inducible protein 10 (IP-10), as well as molecules important for cell adhesion, antigen cross-presentation and costimulation. Also induced are molecules involved in GrB induction, trafficking and processing, whereas the GrB inhibitor Serpin B9 [formerly proteinase inhibitor-9 (PI-9)] is down-modulated by CpG/IL-21. In conclusion, CpG/IL-21-stimulated B-CLL cells acquire features that are reminiscent of killer dendritic cells, and which result in enhanced immunogenicity, cytotoxicity and apoptosis. Our results provide novel insights into the aberrant immune state of B-CLL cells and may establish a basis for the development of an innovative cellular vaccination approach in B-CLL.

Interleukin-21: a double-edged sword with therapeutic potential

Interleukin-21 is a cytokine with broad pleiotropic actions that affect the differentiation and function of lymphoid and myeloid cells. Since its discovery in 2000, a tremendous amount has been learned about its biological actions and the molecular mechanisms controlling IL-21-mediated cellular responses. IL-21 regulates both innate and adaptive immune responses, and it not only has key roles in antitumour and antiviral responses but also exerts major effects on inflammatory responses that promote the development of autoimmune diseases and inflammatory disorders. Numerous studies have shown that enhancing or inhibiting the action of IL-21 has therapeutic effects in animal models of a wide range of diseases, and various clinical trials are underway. The current challenge is to understand how to specifically modulate the actions of IL-21 in the context of each specific immune response or pathological situation. In this Review, we provide an overview of the basic biology of IL-21 and discuss how this information has been - and can be - exploited therapeutically.

Variable induction of PRDM1 and differentiation in chronic lymphocytic leukemia is associated with anergy

Despite antigen engagement and intact B-cell-receptor (BCR) signaling, chronic lymphocytic leukemia (CLL) cells fail to undergo terminal differentiation. We hypothesized that such failure may be due to anergy, as CLL cells exhibit variable levels of nonresponsiveness to surface IgM stimulation that is reversible in vitro. Moreover, anergy is associated with reduced differentiation capacity in normal B cells. We investigated responses of CLL cells to two potent differentiation-promoting agents, IL-21 and cytosine guanine dinucleotide-enriched oligo-deoxynucleotides. The induction of PR domain-containing protein 1 (PRDM1; also known as Blimp-1), a critical regulator of plasmacytic differentiation, by these agents was closely correlated but varied between individual cases, despite functionally intact IL-21 receptor- and Toll-like receptor 9-mediated signal transducer and activator of transcription 3, and nuclear factor-κB pathways. PRDM1 induction was inversely correlated with the extent of anergy as measured by the ability to mobilize intracellular Ca(2+) following BCR crosslinking. PRDM1 responsiveness was associated with other markers of differentiation and proliferation but not with differences in apoptosis. The ability to induce PRDM1 did correlate with differential transcriptional and epigenetic regulation of the PRDM1 gene. These studies extend our understanding of CLL pathobiology, demonstrating that reduced differentiation capacity may be a consequence of anergy. Epigenetic drugs may offer possibilities to reactivate PRDM1 expression as part of novel differentiation therapy approaches.

IL-21 promotes CD4 T cell responses by phosphatidylinositol 3-kinase-dependent upregulation of CD86 on B cells

The cytokine IL-21 is a potent immune modulator with diverse mechanisms of action on multiple cell types. IL-21 is in clinical use to promote tumor rejection and is an emerging target for neutralization in the setting of autoimmunity. Despite its clinical potential, the biological actions of IL-21 are not yet fully understood and the full range of effects of this pleiotropic cytokine are still being uncovered. In this study, we identify a novel role for IL-21 as an inducer of the costimulatory ligand CD86 on B lymphocytes. CD86 provides critical signals through T cell-expressed CD28 that promote T cell activation in response to Ag engagement. Expression levels of CD86 are tightly regulated in vivo, being actively decreased by regulatory T cells and increased in response to pathogen-derived signals. In this study, we demonstrate that IL-21 can trigger potent and sustained CD86 upregulation through a STAT3 and PI3K-dependent mechanism. We show that elevated CD86 expression has functional consequences for the magnitude of CD4 T cell responses both in vitro and in vivo. These data pinpoint CD86 upregulation as an additional mechanism by which IL-21 can elicit immunomodulatory effects.

Utilizing cytokines to function-enable human NK cells for the immunotherapy of cancer

Natural killer (NK) cells are innate lymphoid cells important for host defense against pathogens and mediate antitumor immunity. Cytokine receptors transduce important signals that regulate proliferation, survival, activation status, and trigger effector functions. Here, we review the roles of major cytokines that regulate human NK cell development, survival, and function, including IL-2, IL-12, IL-15, IL-18, and IL-21, and their translation to the clinic as immunotherapy agents. We highlight a recent development in NK cell biology, the identification of innate NK cell memory, and focus on cytokine-induced memory-like (CIML) NK cells that result from a brief, combined activation with IL-12, IL-15, and IL-18. This activation results in long lived NK cells that exhibit enhanced functionality when they encounter a secondary stimulation and provides a new approach to enable NK cells for enhanced responsiveness to infection and cancer. An improved understanding of the cellular and molecular aspects of cytokine-cytokine receptor signals has led to a resurgence of interest in the clinical use of cytokines that sustain and/or activate NK cell antitumor potential. In the future, such strategies will be combined with negative regulatory signal blockade and enhanced recognition to comprehensively enhance NK cells for immunotherapy.

Interleukin (IL)-21 promoter polymorphism increases the risk of thyroid cancer in Chinese population

Polymorphisms in Interleukin (IL)-21 have been researched in several cancers, but the association between IL-21 polymorphisms and thyroid cancer remains unclarified. This case-control study explored the role of five tagSNPs (rs12508721C>T, rs907715G>A, rs13143866G>A, rs2221903A>G and rs4833837A>G) in IL-21 gene in thyroid cancer development. IL-21 genotypes were examined in 615 thyroid cancer patients and 600 controls in Chinese population, and the associations with the risk of thyroid cancer were estimated by logistic regression. Moreover, the potential role of rs12508721C>T in thyroid cancer was further explored by biochemical assays. Compared with the rs12508721CC genotype, CT genotype presented a significantly decreased risk of thyroid cancer (adjusted odds ratios [OR]=0.72; 95%CI=0.57-0.94), the TT carriers had a further decreased risk of thyroid cancer (OR=0.56; 95%CI=0.41-0.87). Furthermore, our quantitative real-time PCR and Enzyme-linked immunosorbent assay (ELISA) results demonstrated that the presence of rs12508721T allele led to more IL-21 expression. However, no significant difference was found in genotype frequencies for other four sites between cases and controls. These findings suggested that rs12508721 polymorphism in IL-21 might be a genetic modifier for the development of thyroid cancer.

Pathologic complete response after preoperative anti-HER2 therapy correlates with alterations in PTEN, FOXO, phosphorylated Stat5, and autophagy protein signaling

BACKGROUND

To define protein molecular characteristics of tumor cells prior to, and immediately following, preoperative human epidermal growth factor receptor 2 (HER2)-targeted therapy that correlate with pathologic complete response (pCR) or non response (no pCR) to preoperative HER2-directed therapy and chemotherapy.

METHODS

This open-label, phase II study randomized patients with HER2-positive stage II or III invasive breast cancer to trastuzumab, lapatinib, or both, 2 weeks prior to and during chemotherapy with FEC75 for 4 courses; then paclitaxel 80 mg/m2 weekly for 12 courses, then surgery. Core needle biopsies were collected at baseline and after 2 weeks of anti-HER2 therapy prior to chemotherapy. Data were correlated with pCR, defined as absence of invasive tumor in breast and lymph nodes.

RESULTS

Of 100 enrolled patients, the analysis population included those who had surgery and received ≥75% chemotherapy (78% [n=78]). pCRs by arm are: trastuzumab (n=26), 54% [n=14]; lapatinib (n=29), 45% [n=13]; trastuzumab plus lapatinib (n=23), 74% [n=17]). Paired biopsy specimens were available for 49 patients (63%). Tumor cells of patients with pCR in the trastuzumab or lapatinib treatment arms showed nonphosphorylated FOXO, phosphorylated Stat5, and sparse signal-transduction protein network crosstalk representing different patterns of connections with PI3K and autophagy proteins compared with no pCR.

CONCLUSION

In this exploratory study, pCR with preoperative anti-HER2 therapy and chemotherapy correlated with the levels and phosphorylation status of specific baseline signal pathway proteins in tumor cells. These data may provide candidate biomarkers to stratify initial treatment and potential combination therapies for future study. Tissue preservation technology introduced here makes this procedure widely feasible.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00524303.

Prognostic value of Th17 cells in acute leukemia

Th17 cells and their effector cytokines have emerged as important mediators in inflammatory and autoimmune diseases and serve as an ambitious field in current immunology research. Recent studies suggest a potential impact of Th17 cells on solid tumors but relatively little is known about their contribution in hematological malignancies. The current study was designed to investigate the possible involvement and clinical significance of circulating Th17 cells in acute leukemia. Flow cytometry was used to analyze percentages of Th17 cells in peripheral blood mononuclear cells from 93 acute leukemia patients (ALL, n = 30; AML, n = 63) and 40 healthy volunteers. Serum levels of IL-17 and IL-21 were measured using enzyme-linked immunosorbent assay. Circulating Th17 cells were increased in patients with acute leukemia (2.88 ± 0.65 % and 2.90 ± 0.57 % in ALL and AML patients, respectively) and were significantly higher than in healthy controls (1.10 ± 0.28 %; P = 0.001). Furthermore, pretreatment Th17 cells were reduced significantly in patients who achieved complete remission after induction therapy (2.25 ± 0.44 % and 1.63 ± 0.27 % in ALL and AML patients, respectively, P < 0.0001). Serum levels of IL-17 and IL-21 were significantly elevated in acute leukemia patients. Kaplan–Meier curves revealed a significantly longer overall survival in patients with high Th17 levels (P = 0.029 and P = 0.027 for ALL and AML, respectively). In the multivariate analysis, Th17 cells retained statistical significance for overall survival in patients with ALL (OR 0.331; P = 0.043) and AML (OR 0.489; P = 0.032). These results strongly suggest Th17 cells as a powerful new prognostic determinant which could serve as a potential therapeutic target to modulate anti-tumor response in acute leukemia patients.

IL-21 and CD40L signals from autologous T cells can induce antigen-independent proliferation of CLL cells

Chronic lymphocytic leukemia (CLL) cells multiply in secondary lymphoid tissue, but the mechanisms leading to their proliferation are still uncertain. In addition to B-cell receptor (BCR)-triggered signals, other microenvironmental factors might well be involved. In proliferation centers, leukemic B cells are in close contact with CD4(+)CD40L(+) T cells. Therefore, we here dissected the signals provided by autologous activated T cells (Tact) to CLL cells. Although the gene expression profile induced by Tact was highly similar to that induced by sole CD40 signaling, an obvious difference was that Tact induced proliferation of CLL cells. We determined that stimulation with only CD40L+IL-21 was sufficient to induce robust proliferation in CLL cells. We then defined an interleukin (IL)-21-induced gene signature in CLL, containing components of Janus kinase/signal transducer and activator of transcription and apoptosis pathways, and this signature could be detected in lymph node (LN) samples from patients. Finally, we could detect IL-21 RNA and protein in LN, and IL-21 production ex vivo by LN CD4(+)CXCR5(+) follicular helper T cells. These results indicate that in addition to BCR signaling, activated T cells might contribute to CLL cell proliferation via CD40 and IL-21. Targeting these signaling pathways might offer new venues for treatment of CLL.

Differential regulation of B-cell proliferation by IL21 in different subsets of chronic lymphocytic leukemia

Interleukin-21 (IL21) plays an important role in B-cell proliferation, survival and differentiation. Contrary to its stimulatory effect in normal B cells, it has been shown that it induces pro-apoptotic effect in leukemic B cells from CLL patients. Little is known regarding the biological function of IL21 in leukemic B cells from progressive and non-progressive CLL patients. In the present study, the proliferative effect of IL21 in combination with TLR9 agonist (CpG) was investigated in B cells isolated from 24 CLL patients and eight normal subjects by radioactive thymidine incorporation assay. B cells were enriched from peripheral blood mononuclear cells by negative selection using magnetic beads (MACS) and immunophenotyped by flow cytometry. Our results showed that IL21 enhanced the proliferative effects of CpG in both normal and leukemic B cells, though no significant differences were observed between CLL patients and healthy controls. Comparison between different subsets of patients revealed that while the combination of IL21 and CpG significantly inhibited the proliferation of B cells from progressive compared to non-progressive patients (p=0.001), it enhanced proliferation of leukemic B cells from IGHV mutated compared to unmutated patients (p=0.001). The inhibitory effect of IL21 on proliferation of normal and leukemic cells was found to be apoptosis-independent. Our findings suggest differential effects of IL21 in different subsets of CLL patients and suggest its potential therapeutic implication in patients with a more progressive disease.

Recent advances in mantle cell lymphoma: report of the 2012 Mantle Cell Lymphoma Consortium Workshop

Mantle cell lymphoma (MCL) is a B-cell non-Hodgkin lymphoma characterized by overexpression of cyclin D1 and the t(11;14)(q13;q32) chromosomal translocation. MCL is biologically and clinically heterogeneous and frequently disseminates to extranodal areas. While a subset of patients have an indolent clinical course, the overall outcome for patients with MCL remains poor. There is no proven curative therapy, and no standard of care has been established for initial or subsequent lines of therapy. Several regimens are highly active in previously untreated patients, and recent research has led to improvements in currently available therapy. Moreover, investigational agents have recently demonstrated promising activity in clinical trials. A workshop was held to review recent data on MCL pathogenesis, novel molecular targets and alternative approaches to immunotherapy, and to discuss recent and ongoing clinical trials in MCL. The presentations are summarized in this article, which is intended to highlight areas of active investigation and identify important avenues for future research.

Immune activation and increased IL-21R expression are associated with the loss of memory B cells during HIV-1 infection

OBJECTIVES

Microbial translocation and chronic immune activation were previously shown to be associated with impairment of T cell functions and disease progression during infection with human immunodeficiency virus type-1 (HIV-1); however, their impact on B cell function and number remains unknown. By measuring markers of immune activation and molecules involved in apoptosis regulation, we have evaluated the association between microbial translocation and loss of memory B cells in HIV-1-infected patients.

METHODS

Markers of activation [the interleukin-21 receptor (IL-21R) and CD38] and apoptosis (Bim, Bcl-2 and annexin V) were measured in B cell subpopulations by multicolour flow cytometry. Levels of soluble CD14 (sCD14) and lipopolysaccharide (LPS), measures of microbial translocation, were determined in plasma. Purified B cells were also exposed in vitro to Toll-like receptor (TLR) ligands.

RESULTS

IL-21R expression was higher in cells from HIV-1-infected patients, compared with control subjects, with the highest levels in nontreated patients. An inverse correlation was observed between IL-21R expression and percentages of circulating resting memory (RM) B cells. IL-21R-positive memory B cells were also more susceptible to spontaneous apoptosis and displayed lower levels of Bcl-2. It is interesting that the levels of sCD14, which are increased during HIV-1 infection, were correlated with decreased percentages of RM B cells and high IL-21R expression. In the plasma of HIV-1-infected individuals, a correlation was found between sCD14 and LPS levels. TLR activation of B cells in vitro resulted in IL-21R up-regulation.

CONCLUSIONS

Microbial translocation and the associated immune activation during HIV-1 infection may lead to high expression levels of the IL-21R activation marker in RM B cells, a feature associated with increased apoptosis and a reduced number of these cells in the circulation.

IL-21 in the bone marrow microenvironment contributes to IgM secretion and proliferation of malignant cells in Waldenstrom macroglobulinemia

Cytokines within the tumor microenvironment play an important role in supporting the growth and survival of B-cell malignancies. One such cytokine, IL-21, promotes the growth of myeloma and Hodgkin lymphoma cells while inducing apoptosis in chronic lymphocytic leukemia. However, the biologic significance of IL-21 has not been examined in Waldenstrom macroglobulinemia (WM), a B-cell lymphoma characterized by elevated serum IgM and a lymphoplasmacytic bone marrow infiltrate. We report here on the presence of IL-21 in the bone marrow of patients with WM and have identified activated T cells as the source of this cytokine. We readily detected the IL-21 receptor on malignant WM B cells and show that IL-21 significantly increases both IgM secretion and cellular proliferation of these cells with no effect on viability. IL-21 rapidly induces phosphorylation of STAT3 in WM cells, and treatment of the WM cell line MWCL-1 with a STAT3 inhibitor abolished the IL-21-mediated increases in cellular proliferation and IgM secretion. IL-21 also increased the expression of known STAT3 targets involved in B-cell differentiation, including BLIMP-1, XBP-1, IL-6, and IL-10. Overall, our data indicate that IL-21 in the bone marrow microenvironment significantly affects the biology of WM tumor cells through a STAT3-dependent mechanism.

Inhibition of intracellular antiviral defense mechanisms augments lentiviral transduction of human natural killer cells: implications for gene therapy

Adoptive immunotherapy with genetically modified natural killer (NK) cells is a promising approach for cancer treatment. Yet, optimization of highly efficient and clinically applicable gene transfer protocols for NK cells still presents a challenge. In this study, we aimed at identifying conditions under which optimum lentiviral gene transfer to NK cells can be achieved. Our results demonstrate that stimulation of NK cells with interleukin (IL)-2 and IL-21 supports efficient transduction using a VSV-G pseudotyped lentiviral vector. Moreover, we have identified that inhibition of innate immune receptor signaling greatly enhances transduction efficiency. We were able to boost the efficiency of lentiviral genetic modification on average 3.8-fold using BX795, an inhibitor of the TBK1/IKKɛ complex acting downstream of RIG-I, MDA-5, and TLR3. We have also observed that the use of BX795 enhances lentiviral transduction efficiency in a number of human and mouse cell lines, indicating a broadly applicable, practical, and safe approach that has the potential of being applicable to various gene therapy protocols.

A phase I dose-finding trial of recombinant interleukin-21 and rituximab in relapsed and refractory low grade B-cell lymphoproliferative disorders

PURPOSE

We conducted a phase I study to determine the safety, maximum-tolerated dose (MTD), and efficacy of weekly bolus recombinant human interleukin-21 (rIL-21) plus rituximab in patients with indolent B-cell malignancies.

EXPERIMENTAL DESIGN

One week after a lead-in rituximab dose, cohorts of three patients were treated with 30, 100, or 150 μg/kg rIL-21 weekly for four weeks, concurrent with four weekly doses of rituximab. Patients with stable disease or better were eligible for a second course of therapy.

RESULTS

Twenty-one patients with relapsed small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL, n = 11), follicular lymphoma (n = 9), or marginal zone lymphoma (n = 1) were enrolled, with 19 completing at least one course of therapy. The MTD for rIL-21 was 100 μg/kg, based on observed toxicities including nausea, vomiting, diarrhea, hypotension, edema, and hypophosphatemia. Clinical responses were seen in 8 of 19 evaluable patients (42%; 3 CR/CRu, 5 PR), with 4 of longer duration than the patient's previous response to rituximab-based treatment (median 9 months vs. 3 months).

CONCLUSIONS

Outpatient therapy of indolent B-cell malignancies with rituximab and weekly rIL-21 was well tolerated and clinically active, with durable complete remissions in a small subset of patients. Additional studies of rIL-21 and anti-CD20 antibodies in lymphoma and SLL/CLL are warranted.

The transcription factor C/EBP delta has anti-apoptotic and anti-inflammatory roles in pancreatic beta cells

In the course of Type 1 diabetes pro-inflammatory cytokines (e.g., IL-1β, IFN-γ and TNF-α) produced by islet-infiltrating immune cells modify expression of key gene networks in β-cells, leading to local inflammation and β-cell apoptosis. Most known cytokine-induced transcription factors have pro-apoptotic effects, and little is known regarding “protective” transcription factors. To this end, we presently evaluated the role of the transcription factor CCAAT/enhancer binding protein delta (C/EBPδ) on β-cell apoptosis and production of inflammatory mediators in the rat insulinoma INS-1E cells, in purified primary rat β-cells and in human islets. C/EBPδ is expressed and up-regulated in response to the cytokines IL-1β and IFN-γ in rat β-cells and human islets. Small interfering RNA-mediated C/EBPδ silencing exacerbated IL-1β+IFN-γ-induced caspase 9 and 3 cleavage and apoptosis in these cells. C/EBPδ deficiency increased the up-regulation of the transcription factor CHOP in response to cytokines, enhancing expression of the pro-apoptotic Bcl-2 family member BIM. Interfering with C/EBPδ and CHOP or C/EBPδ and BIM in double knockdown approaches abrogated the exacerbating effects of C/EBPδ deficiency on cytokine-induced β-cell apoptosis, while C/EBPδ overexpression inhibited BIM expression and partially protected β-cells against IL-1β+IFN-γ-induced apoptosis. Furthermore, C/EBPδ silencing boosted cytokine-induced production of the chemokines CXCL1, 9, 10 and CCL20 in β-cells by hampering IRF-1 up-regulation and increasing STAT1 activation in response to cytokines. These observations identify a novel function of C/EBPδ as a modulatory transcription factor that inhibits the pro-apoptotic and pro-inflammatory gene networks activated by cytokines in pancreatic β-cells.