The Proinflammatory Cytokine Interleukin-18 Alters Multiple Signaling Pathways to Inhibit Natural Killer Cell Death

Natural killer cells: a new promising source for developing chimeric antigen receptor anti-cancer cells in hematological malignancies

In recent times, the application of CAR-T cell treatment has significantly progressed, showing auspicious treatment outcomes in hematologic malignancies. However, along with these advances, certain limitations and challenges hurdle the widespread utilization of this technology. Recently, CAR-NK cells have gained attention in cancer treatment, as this approach has an important advantage over CART therapy (i.e. no need for HLA matching) for targeting foreign cells. This review aims to explore the benefits of CAR NK cell therapy, and generation strategies, as well as the challenges and limitations hindering the application of CAR NK cells in experimental studies and trials on hematologic malignancies.

Haploidentical hematopoietic cell transplantation as a platform for natural killer cell immunotherapy

An innovative approach is crucially needed to manage relapse after allogeneic hematopoietic cell transplantation (HCT) in patients with advanced hematological malignancies. This review explores key aspects of haploidentical HCT with post-transplant cyclophosphamide, highlighting the potential and suitability of this platform for natural killer (NK) cell immunotherapy. NK cells, known for their unique abilities to eliminate cancer cells, can also exhibit memory-like features and enhanced cytotoxicity when activated by cytokines. By discussing promising results from clinical trials, the review delves into the recent major advances: donor-derived NK cells can be expanded ex vivo in large numbers, cytokine activation may enhance NK cell persistence and efficacy in vivo, and post-HCT NK cell infusion can improve outcomes in high-risk and/or relapsed myeloid malignancies without increasing the risk of graft-versus-host disease, severe cytokine release syndrome, or neurotoxicity. Looking ahead, cytokine-activated NK cells can be synergized with immunomodulatory agents and/or genetically engineered to enhance their tumor-targeting specificity, cytotoxicity, and persistence while preventing exhaustion. The ongoing exploration of these strategies holds promising preliminary results and could be rapidly translated into clinical applications for the benefit of the patients.

Natural Killer Cells in Cancers of Respiratory System and Their Applications in Therapeutic Approaches

BACKGROUND

Cancer is still regarded as a major worldwide health issue due to its high health and socioeconomic burden. Currently, lung cancer is the most common cause of cancer-related fatalities globally. Additionally, mesotheliomas and other cancers of the respiratory system, including those of the trachea, larynx, and bronchi, are also posing a significant health threat. Natural killer (NK) cells are lymphocytes of the innate immune system involved in response against cancer.

OBJECTIVE

This review discussed recent findings in the context of NK cell activity in the immune surveillance of respiratory system cancers and NK cell-based treatments to combat those malignancies.

RESULTS

The presence of natural killer cells in the tumor microenvironment is shown to be associated with a higher survival rate in patients with various malignancies. However, cancerous cells benefit from several mechanisms to evade natural killer cell-mediated cytotoxicity, including reduced major histocompatibility complex I expression, shedding of ligands, upregulation of inhibitory receptors, and release of soluble factors. Using NK cells to design therapeutic approaches may enhance antitumor immunity and improve clinical outcomes. Clinical trials investigating the use of natural killer cells in combination with cytokine stimulation or immune checkpoint inhibitors have exhibited promising results in various respiratory system malignancies.

CONCLUSION

Respiratory system cancers present significant health challenges worldwide, and while NK cells play a crucial role in tumor surveillance, tumors often evade NK cell responses through various mechanisms. Advances in NK cell-based therapies, including CAR-NK cells, immune checkpoint inhibitors, and cytokine stimulation, have shown promising outcomes in tackling these tactics. However, challenges such as the immunosuppressive tumor microenvironment persist. Ongoing research is crucial to improve NK cell therapies by targeting autophagy, modulating miRNAs, and developing combinatorial approaches to enhance treatment efficacy for respiratory cancers.

Genetic variations in immune mediators and prostate cancer risk: A field synopsis with Bayesian calculations

OBJECTIVE

Our study aimed to revaluate the significant data from meta-analyses on genetic variations in immune mediators and the risk of prostate cancer (PCa) by Bayesian approaches.

METHODS

We performed a search on the literature before September 5th, 2023, for meta-analytic studies on polymorphisms in immune mediator genes and the risk of PCa. Two Bayesian approaches were used to assess the level of noteworthiness in the meta-analytic data: the False-Positive Rate Probability (FPRP) and the Bayesian False Discovery Probability (BFDP) with a statistical power of 1.2 and 1.5 of Odds Ratio at a prior probability of 10-3 and 10-6. The quality evaluation of studies was performed with the Venice criteria. Gene-gene and protein-protein networks were designed for the genes and products enrolled in the results.

RESULTS

As results, 18 meta-analyses on 17 polymorphisms in several immune mediator genes were included (IL1B rs16944/rs1143627, IL4 rs2243250/rs2227284/rs2070874, IL6 1800795/rs1800796/rs1800797, IL8 rs4073, IL10 rs1800896/rs1800871/rs1800872, IL18 rs1946518, COX2 rs2745557, TNFA rs361525 and PTGS2 rs20417/689470). The Bayesian calculations showed the rs1143627 and the rs1946518 polymorphisms in IL1B and IL18 genes, respectively, were noteworthy. The Venice criteria showed that only four studies received the highest level of evidence. The gene-gene and protein-protein networks reinforced the findings on IL1B and IL18 genes.

CONCLUSION

In conclusion, this current Bayesian revaluation showed that the rs1143627 and the rs1946518 polymorphisms in the IL1B and IL18 genes, respectively, were noteworthy biomarker candidates for PCa risk.

Pretreatment with IL-15 and IL-18 rescues natural killer cells from granzyme B-mediated apoptosis after cryopreservation

Human natural killer (NK) cell-based therapies are under assessment for treating various cancers, but cryopreservation reduces both the recovery and function of NK cells, thereby limiting their therapeutic feasibility. Using cryopreservation protocols optimized for T cells, here we find that ~75% of NK cells die within 24 h post-thaw, with the remaining cells displaying reduced cytotoxicity. Using CRISPR-Cas9 gene editing and confocal microscopy, we find that cryopreserved NK cells largely die via apoptosis initiated by leakage of granzyme B from cytotoxic vesicles. Pretreatment of NK cells with a combination of Interleukins-15 (IL-15) and IL-18 prior to cryopreservation improves NK cell recovery to ~90-100% and enables equal tumour control in a xenograft model of disseminated Raji cell lymphoma compared to non-cryopreserved NK cells. The mechanism of IL-15 and IL-18-induced protection incorporates two mechanisms: a transient reduction in intracellular granzyme B levels via degranulation, and the induction of antiapoptotic genes.

Building a Better Defense: Expanding and Improving Natural Killer Cells for Adoptive Cell Therapy

Natural killer (NK) cells have gained attention as a promising adoptive cell therapy platform for their potential to improve cancer treatments. NK cells offer distinct advantages over T-cells, including major histocompatibility complex class I (MHC-I)-independent tumor recognition and low risk of toxicity, even in an allogeneic setting. Despite this tremendous potential, challenges persist, such as limited in vivo persistence, reduced tumor infiltration, and low absolute NK cell numbers. This review outlines several strategies aiming to overcome these challenges. The developed strategies include optimizing NK cell expansion methods and improving NK cell antitumor responses by cytokine stimulation and genetic manipulations. Using K562 cells expressing membrane IL-15 or IL-21 with or without additional activating ligands like 4-1BBL allows "massive" NK cell expansion and makes multiple cell dosing and "off-the-shelf" efforts feasible. Further improvements in NK cell function can be reached by inducing memory-like NK cells, developing chimeric antigen receptor (CAR)-NK cells, or isolating NK-cell-based tumor-infiltrating lymphocytes (TILs). Memory-like NK cells demonstrate higher in vivo persistence and cytotoxicity, with early clinical trials demonstrating safety and promising efficacy. Recent trials using CAR-NK cells have also demonstrated a lack of any major toxicity, including cytokine release syndrome, and, yet, promising clinical activity. Recent data support that the presence of TIL-NK cells is associated with improved overall patient survival in different types of solid tumors such as head and neck, colorectal, breast, and gastric carcinomas, among the most significant. In conclusion, this review presents insights into the diverse strategies available for NK cell expansion, including the roles played by various cytokines, feeder cells, and culture material in influencing the activation phenotype, telomere length, and cytotoxic potential of expanded NK cells. Notably, genetically modified K562 cells have demonstrated significant efficacy in promoting NK cell expansion. Furthermore, culturing NK cells with IL-2 and IL-15 has been shown to improve expansion rates, while the presence of IL-12 and IL-21 has been linked to enhanced cytotoxic function. Overall, this review provides an overview of NK cell expansion methodologies, highlighting the current landscape of clinical trials and the key advancements to enhance NK-cell-based adoptive cell therapy.

Host Immune Response and Associated Clinical Features in a Primary Cytomegalovirus Eye Infection Model Using Anterior Chamber Inoculation

Purpose

To investigate the pathogenesis of cytomegalovirus (CMV)-associated anterior segment infection in immunocompetent hosts and evaluate the effects of ganciclovir and glucocorticoid treatment in management of the disease.

Methods

We used an inoculation model to reproduce CMV anterior segment infection in immunocompetent rats. Flow cytometry, cytokine analysis, histopathological sections, and quantitative polymerase chain reaction were performed to investigate the immune response after CMV infection. The effects of ganciclovir and glucocorticoid treatment were also assessed.

Results

Anterior chamber inoculation of CMV in rats provoked characteristic pathological features of human CMV anterior segment infection. The innate and adaptive immunity sequentially developed in an anterior segment after inoculation, and the elevation of intraocular pressure (IOP) was highly associated with ocular infiltration and inflammation. Early ocular immune response reduced virus DNA in the anterior segment and alleviated viral lymphadenopathy. Early intervention with ganciclovir enhanced the release of cytokines associated with T response and facilitated recruitment of NKT and T cells in drainage lymph nodes. Glucocorticoid treatment, alone or combined with ganciclovir, decreased elevation of IOP but also impeded DNA clearance.

Conclusions

The inoculation model reproduced characteristic pathological features of human CMV anterior segment infection. The use of glucocorticoid in current practice may hinder viral clearance, and ganciclovir therapy can assist cytokine expression to combat the virus.

Association between IL-18 -607 C/A Polymorphism and the Risk of Prostate Cancer: A Meta-Analysis of Case-Control Studies

Background: Accumulating evidence shows that cytokines play an important role in the proliferation of prostate cancer. This research is trying to determine that IL-18 -607 C/A polymorphism confers susceptibility to prostate cancer. Methods: Meta-analysis was used to collect data. The relevant studies were identified through a comprehensive search from PubMed, Excerpta Medica Database (EMBASE), Web of Science, and Chinese Biomedical Literature Database (CBM) to obtain related studies published up to December 6, 2017. The association between interleukin (IL)-18 -607 C/A polymorphism and prostate cancer risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs). Results: Nine case-control studies from 6 articles were eventually identified. In the overall population, there is a significant association between IL-18 -607 C/A polymorphism and prostate cancer risk in recessive (CC versus CA/AA: OR = 0.20, 95% CI = 0.15-0.27, P = 0.000) or dominant (CC/CA versus AA:OR = 0.42, 95% CI = 0.30–0.57, P = 0.000) models. In the sub-group analysis according to ethnicity, for Asians, IL-18 -607 C/A polymorphism was significantly associated with prostate cancer in allele contrast (C versus. A: OR=0.82, 95%CI=0.70-0.97, P=0.019), homozygote (CC versus. AA: OR=0.68, 95%CI=0.50-0.92, P=0.013), recessive (CC versus. CA/AA: OR=0.19, 95%CI=0.13-0.27, P=0.000), and dominant (CC/CA versus. AA: OR=0.37, 95%CI=0.28-0.48, P=0.000) models, for Caucasians, IL-18 -607 C/A polymorphism was significantly associated with prostate cancer risk in allele contrast (C versus. A: OR=1.27, 95%CI=1.02-1.58, P=0.033), homozygote (CC versus. AA: OR=1.86, 95%CI=1.19-2.91, P=0.007) and recessive (CC versus. CA/AA: OR=0.25, 95%CI=0.19-0.33, P=0.000) models. Conclusion: This meta-analysis has shown that IL-18 -607 C/A polymorphism contributes to a decreased risk of prostate cancer risk in the Asian population but an increased risk in the Caucasian population.

Overcoming Resistance to Natural Killer Cell Based Immunotherapies for Solid Tumors

Despite advances in the diagnostic and therapeutic modalities, the prognosis of several solid tumor malignancies remains poor. Different factors associated with solid tumors including a varied genetic signature, complex molecular signaling pathways, defective cross talk between the tumor cells and immune cells, hypoxic and immunosuppressive effects of tumor microenvironment result in a treatment resistant and metastatic phenotype. Over the past several years, immunotherapy has emerged as an attractive therapeutic option against multiple malignancies. The unique ability of natural killer (NK) cells to target cancer cells without antigen specificity makes them an ideal candidate for use against solid tumors. However, the outcomes of adoptive NK cell infusions into patients with solid tumors have been disappointing. Extensive studies have been done to investigate different strategies to improve the NK cell function, trafficking and tumor targeting. Use of cytokines and cytokine analogs has been well described and utilized to enhance the proliferation, stimulation and persistence of NK cells. Other techniques like blocking the human leukocyte antigen-killer cell receptors (KIR) interactions with anti-KIR monoclonal antibodies, preventing CD16 receptor shedding, increasing the expression of activating NK cell receptors like NKG2D, and use of immunocytokines and immune checkpoint inhibitors can enhance NK cell mediated cytotoxicity. Using genetically modified NK cells with chimeric antigen receptors and bispecific and trispecific NK cell engagers, NK cells can be effectively redirected to the tumor cells improving their cytotoxic potential. In this review, we have described these strategies and highlighted the need to further optimize these strategies to improve the clinical outcome of NK cell based immunotherapy against solid tumors.

Frontline Science: IL-18 primes murine NK cells for proliferation by promoting protein synthesis, survival, and autophagy

Combined stimulation by IL-2 and IL-18 effectively promotes proliferation of NK cells, whereas singular stimulation does not. In this study, synergistic effects of these cytokines on NK cells proliferation was analyzed, focusing on the roles of IL-18. In splenic resting NK cells from IL-18KO mice, IL-18 rapidly activated NF-κB independently of IL-2, and activated or up-regulated various molecules downstream of PI3K/AKT and mTOR, including S6, Bcl-XL, ATG5, and LC3II, accompanying increases in cell growth and survival. Thus, IL-18 alone was revealed to augment various cellular processes (gene transcription, protein synthesis, survival) in the absence or presence of IL-2. Notably, combined IL-18 and IL-2 promoted autophagosome formation. In addition, priming NK cells with IL-18 augmented IL-2R, especially CD25, and enabled cells to respond to IL-2, resulting in activation of STAT3 and STAT5, followed by increase of cyclin B1 leading to proliferation. However, IL-2 alone failed to activate STAT3 or STAT5 in resting IL18KO NK cells. These results clarify the distinct roles of IL-2 and IL-18 in NK cell proliferation, and the intrinsic roles of IL-18 in various cellular processes, suggesting a range of functions of IL-18 expressed in an array of nonhematopoietic cells.

Modulation of γδ T-cell activation by neutrophil elastase

γδ T cells are non-conventional, innate-like T cells, characterized by a restricted T-cell receptor repertoire. They participate in protective immunity responses against extracellular and intracellular pathogens, tumour surveillance, modulation of innate and adaptive immune responses, tissue healing, epithelial cell maintenance and regulation of physiological organ function. In this study, we investigated the role of neutrophils during the activation of human blood γδ T cells through CD3 molecules. We found that the up-regulation of CD69 expression, and the production of interferon-γ and tumour necrosis factor-α induced by anti-CD3 antibodies was potentiated by neutrophils. We found that inhibition of caspase-1 and neutralization of interleukin-18 did not affect neutrophil-mediated modulation. By contrast, the treatment with serine protease inhibitors prevented the potentiation of γδ T-cell activation induced by neutrophils. Moreover, the addition of elastase to γδ T-cell culture increased their stimulation, and the treatment of neutrophils with elastase inhibitor prevented the effect of neutrophils on γδ T-cell activation. Furthermore, we demonstrated that the effect of elastase on γδ T cells was mediated through the protease-activated receptor, PAR1, because the inhibition of this receptor with a specific antagonist, RWJ56110, abrogated the effect of neutrophils on γδ T-cell activation.

Augmentation of Immune Checkpoint Cancer Immunotherapy with IL18

PURPOSE

Recent clinical trials and animal models demonstrated that immune checkpoint blockade enhanced effector cell responses and tumor rejection; however, further development and improvement of cancer immunotherapy is necessary for more favorable objective responses. In this study, we examined the effect of IL18 on the antitumor effect of immune checkpoint inhibitors.

EXPERIMENTAL DESIGN

We examined the effect of IL18 on the peritoneal dissemination of CT-26 cells or tail vein injection metastasis of B16/F10 cells using antiprogrammed death-1 ligand-1 (αPD-L1) and/or anti-CTL-associated antigen-4 (αCTLA-4) mAbs.

RESULT

Massive ascites developed after intraperitoneal inoculation of CT-26, resulting in animal death within 30 days. Treatment of mice with αPD-L1 and/or αCTLA-4 significantly prolonged their survival, and a combination of the antibodies and IL18 provided a much greater therapeutic benefit. The combination modality led to the accumulation of precursor of mature natural killer (pre-mNK) cells in the peritoneal cavity together with increased CD8(+) T and decreased CD4(+)CD25(+)Foxp3(+) T cells. Depletion of the pre-mNK cells abrogated the therapeutic effects and increased the number of CD4(+)CD25(+)Foxp3(+) T cells. The combination treatment also suppressed tail vein injection metastasis of B16/F10 cells.

CONCLUSIONS

The results demonstrated that IL18 enhanced therapeutic effects of immune checkpoint blockade against peritoneal dissemination of carcinoma or tail vein injection metastasis of melanoma through accumulation of pre-mNK cells, memory-type CD8(+) T cells, and suppression of CD4(+)CD25(+)Foxp3(+) T cells. A combination of immune checkpoint inhibitors with IL18 may give a suggestion to the development of next-generation cancer immunotherapy. Clin Cancer Res; 22(12); 2969-80. ©2016 AACR.

Regulation of development of CD56 bright CD11c + NK-like cells with helper function by IL-18

Human γδ T cells augment host defense against tumors and infections, and might have a therapeutic potential in immunotherapy. However, mechanism of γδ T cell proliferation is unclear, and therefore it is difficult to prepare sufficient numbers of γδ T cells for clinical immunotherapy. Recently, natural killer (NK)-like CD56(bright)CD11c(+) cells were shown to promote the proliferation of γδ T cells in an IL-18-dependent manner. In this study, we demonstrated that the NK-like CD56(bright)CD11c(+) cells could directly interact with γδ T cells to promote their sustained expansion, while conventional dendritic cells (DCs), IFN-α-induced DCs, plasmacytoid DCs or monocytes did not. We also examined the cellular mechanism underlying the regulation of CD56(bright)CD11c(+) cells. CD14(+) monocytes pre-incubated with IL-2/IL-18 formed intensive interactions with CD56(int)CD11c(+) cells to promote their differentiation to CD56(bright)CD11c(+) cells with helper function. The development of CD56(bright)CD11c(+) cells was suppressed in an IFN-α dependent manner. These results indicate that CD14(+) monocytes pretreated with IL-2/IL-18, but neither DCs nor monocytes, play a determining role on the development and proliferation of CD56(bright)CD11c(+) cells, which in turn modulate the expansion of γδ T cells. CD56(bright)CD11c(+) NK-like cells may be a novel target for immunotherapy utilizing γδ T cells, by overcoming the limitation of γδ T cells proliferation.

Interleukin 18: friend or foe in cancer

In the last few years, the field of tumor immunology has significantly expanded and its boundaries, never particularly clear, have become less distinct. Although the immune system plays an important role in controlling tumor growth, it has also become clear that tumor growth can be promoted by inflammatory immune responses. A good example that exemplifies the ambiguous role of the immune system in cancer progression is represented by interleukin 18 (IL-18) that was first identified as an interferon-γ-inducing factor (IGIF) involved in T helper type-1 (Th1) immune response. The expression and secretion of IL-18 have been observed in various cell types from immune cells to circulating cancer cells. In this review we highlighted the multiple roles played by IL-18 in immune regulation, cancer progression and angiogenesis and the clinical potential that may result from such understanding.

Effect of IL-18 on expansion of gammadelta T cells stimulated by zoledronate and IL-2

Zoledronate (Zol) has recently been shown to expand gammadelta T cells that play important roles in host defenses against infection and tumors. In this study, we examined effects of interleukin-18 (IL-18) on expansion of gammadelta T cells in human peripheral blood mononuclear cells (PBMCs) stimulated by Zol and IL-2. The expansion of gammadelta T cells stimulated by Zol and IL-2 was strongly promoted by exogenous IL-18, and to the contrary, inhibited by neutralizing anti-IL-18 receptor antibody. The gammadelta T cells that expanded in the presence of Zol, IL-2, and IL-18 exhibited the phenotype of effector memory cells characterized by CD44 (+), CD27 (-), and CD45RA (-). In addition, they expressed NKG2D, perforin, CD94, CD25, and CD122, and 15% to 40% of them were positive for CD56. Incubation of gammadelta T cells in the presence with IL-18 produced GM-CSF, IFN-gamma, and TNF-alpha at much higher levels than those incubated without IL-18. They showed strong cytotoxicity against tumor cells including mesothelioma cells and inhibited growth of xenograft of mesothelioma in mice. These observations indicate that IL-18 can efficiently promote expansion of gammadelta T cells with potent antitumor activity.

Cytokine regulation of natural killer cell effector functions

Initially described as effectors of natural cytotoxicity and critical players for the control of viral infections and tumor growth, recent investigations unraveled more widespread functions for the natural killer (NK) cells. Through the establishment of a crosstalk with dendritic cells, NK cells promote T helper-1- and cytotoxic T lymphocyte-mediated immunity, whereas through the establishment of a crosstalk with macrophages, NK cells contribute to the activation of their microbicidal functions. Recent evidence has shown that NK cells also display memory, a characteristic thought to be privative of T and B cells, and that NK cells acquire their mature phenotype during a complex ontogeny program which tunes their activation threshold. Cytokines play critical roles in regulating all aspects of immune responses, including lymphoid development, homeostasis, differentiation, tolerance, and memory. Cytokines such as interleukin (IL)-2, IL-12, IL-15, IL-18, IL-21, and type I interferons constitute pivotal factors involved in the maturation, activation, and survival of NK cells. In addition, the discovery of novel cytokines is increasing the spectrum of soluble mediators that regulate NK cell immunobiology. In this review, we summarize and integrate novel concepts about the role of different cytokines in the regulation of NK cell function. We believe that a full understanding of how NK cells become activated and develop their effector functions in response to cytokines and other stimuli may lead to the development of novel immunotherapeutic strategies for the treatment of different types of cancer, viral infections, and chronic autoimmune diseases.

Tumor necrosis factor-alpha causes release of cytosolic interleukin-18 from human neutrophils

Neutrophils (PMNs) are a vital part of host defense and are the principal leukocyte in innate immunity. Interleukin (IL)-18 is a proinflammatory cytokine with roles in both innate and adaptive immunity. We hypothesize that PMNs contain preformed IL-18, which is released in response to specific inflammatory stimuli. Isolated PMNs were stimulated with a battery of chemoattractants (5 min to 24 h), and IL-18 release was measured. PMNs were also separated into subcellular fractions and immunoblotted with antibodies against IL-18 or were fixed and probed with antibodies to IL-18 as well as to the contents of granules, intracellular organelles, and filamentous actin (F-actin), incubated with fluorescent secondary antibodies, and examined by digital microscopy. Quiescent PMNs contained IL-18 in the cytoplasm, associated with F-actin, as determined by positive fluorescence resonance energy transfer (FRET+). In turn, TNF-alpha stimulation disrupted the association of IL-18 with F-actin, induced a FRET+ interaction of IL-18 with lipid rafts, and elicited IL-18 release. Manipulation of F-actin status confirmed the relationship between IL-18 and F-actin in resting PMNs. Consequently, incubation with monomeric IL-18 binding protein inhibited TNF-alpha-mediated priming of the PMN oxidase. We conclude that human PMNs contain IL-18 associated with F-actin in the cytoplasm and TNF-alpha stimulation causes dissociation of IL-18 from F-actin, association with lipid rafts, and extracellular release. Extracellular IL-18 participates in TNF-alpha priming of the PMN oxidase as demonstrated by inhibition with the IL-18 binding protein.

Interleukin-15 enhances proteasomal degradation of bid in normal lymphocytes: implications for large granular lymphocyte leukemias

Large granular lymphocyte (LGL) leukemia is a clonal proliferative disease of T and natural killer (NK) cells. Interleukin (IL)-15 is important for the development and progression of LGL leukemia and is a survival factor for normal NK and T memory cells. IL-15 alters expression of Bcl-2 family members, Bcl-2, Bcl-XL, Bim, Noxa, and Mcl-1; however, effects on Bid have not been shown. Using an adoptive transfer model, we show that NK cells from Bid-deficient mice survive longer than cells from wild-type control mice when transferred into IL-15-null mice. In normal human NK cells, IL-15 significantly reduces Bid accumulation. Decreases in Bid are not due to alterations in RNA accumulation but result from increased proteasomal degradation. IL-15 up-regulates the E3 ligase HDM2 and we find that HDM2 directly interacts with Bid. HDM2 suppression by short hairpin RNA increases Bid accumulation lending further support for HDM2 involvement in Bid degradation. In primary leukemic LGLs, Bid levels are low but are reversed with bortezomib treatment with subsequent increases in LGL apoptosis. Overall, these data provide a novel molecular mechanism for IL-15 control of Bid that potentially links this cytokine to leukemogenesis through targeted proteasome degradation of Bid and offers the possibility that proteasome inhibitors may aid in the treatment of LGL leukemia.

Potential role of interleukin-18 in the immunopathogenesis of AIDS: involvement in fratricidal killing of NK cells

We had shown earlier that the concentrations of circulating interleukin-18 (IL-18) are increased significantly in human immunodeficiency virus (HIV)-infected persons compared to HIV-seronegative healthy subjects. In the present study, we investigated the consequences of these elevated levels of IL-18 on natural killer (NK) cells and the immunopathogenesis of AIDS. We show here an inverse correlation between IL-18 concentrations and absolute numbers of various subsets of NK cells in infected persons. Recombinant human IL-18 caused increased death of a human NK cell line, as well as of primary human NK cells in vitro. The IL-18-mediated cell death was dependent upon Fas-FasL interactions and tumor necrosis factor alpha. IL-18 induced the expression of FasL on NK cells, increased the transcription from the human FasL promoter, reduced the expression of Bcl-X(L) in NK cells, and increased their sensitivity to FasL-mediated cell death. These results suggest that increased IL-18 concentrations present in the circulation of HIV-infected persons contribute to the immunopathogenesis of AIDS by altering NK cell homeostasis.

Interleukin-18 prevents apoptosis via PI3K/Akt pathway in normal human keratinocytes

Interleukin-18 (IL-18) is a pleiotropic cytokine expressed in both immune and non-immune cells. In the present study, we demonstrate an anti-apoptotic role of IL-18 in normal human neonatal foreskin epidermal keratinocytes (NHEK-F). Cultured NHEK-F spontaneously produced the active form of IL-18. Treatment of NHEK-F cells with anti-IL-18 receptor alpha-chain neutralizing antibody increased apoptosis and caspase-3 activity. Exogenous IL-18 augmented phosphorylation of Akt and activation of NF-kappaB. The promotion of Akt phosphorylation by IL-18 was abolished by LY294002, a PI3K inhibitor, but not SN50, an NF-kappaB inhibitor, indicating that IL-18 functions via the PI3K/Akt pathway and independently of NF-kappaB. In addition, IL-18 was found to augment expression of anti-apoptotic proteins, Bcl-2, XIAP and glucose regulated protein78/BiP, while anti-IL-18 receptor alpha-chain neutralizing antibody suppressed expression of Bcl-2, XIAP, glucose regulated protein94 and protein disulfide isomerase. Taken together, these results indicate that IL-18 plays an important role in keratinocyte survival.

Glial Expression of Interleukin-18 and its Receptor After Excitotoxic Damage in the Mouse Hippocampus

Interleukin (IL)-18, a member of the IL-1 cytokine family, is an important mediator of peripheral inflammation and host defence responses. However, although IL-1 is a key proinflammatory cytokine in the brain, little is known about IL-18 changes in glial cells under excitotoxic neurodegeneration. In this study, we characterized the expressions of IL-18 and IL-18 receptor (IL-18R) in kainic acid (KA)-induced excitotoxicity in mouse hippocampus by immunohistochemistry and Western blotting. IL-18 immunoreactivity was found in microglia whereas IL-18R immunoreactivity was observed in astrocytes. Levels of IL-18 and IL-18R in hippocampus homogenates increased progressively from day 1 post-KA and peaked at 3 days. This study demonstrates the cellular sources of IL-18 and IL-18R, and their temporal correlations after KA-insult, and suggests roles for IL-18 and IL-18R in glial cells in response to excitotoxic damage in the hippocampus.

Therapeutic Effect of pEgr-IL18-B7.2 Gene Radiotherapy in B16 Melanoma-Bearing Mice

To evaluate the antitumor role of genes B7.2 and IL18, the radiation-inducible dual-gene coexpression plasmid pEgr-IL18-B7.2 was constructed and its effects on tumor were detected both in vitro and in vivo. After the introduction of pEgr-IL18-B7.2 into B16 melanoma cells, followed by X-ray irradiation, higher expression levels of B7.2 and IL18 compared with control were found both by flow cytometry and enzyme-linked immunosorbent assay. It was shown that even low-dose irradiation was able to induce their expression, which could be tightly regulated either by giving cells different doses of radiation or the same dose at different time points. pEgr-IL18-B7.2 was then packaged with liposome and injected into melanoma tumor-bearing mice. The tumors received 5 Gy of local X-ray irradiation every other day for a total of five treatments. B16 tumor growth slowed significantly when treated with pEgr-IL18-B7.2 plus X-radiation versus either treatment separately. Both 1 and 3 days after the last irradiation the group of mice with combined gene and radiation therapy showed significantly higher tumor necrosis factor (TNF)-alpha secretion in peritoneal macrophages, upregulated splenic cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells, and higher interferon (IFN)-gamma secretion than those in either individual treatment group or the control group. The stimulation of host anticancer immunity by increased secretion of IL-18 and upregulated immunogenicity of the tumor cells by increased expression of B7.2 on their surface, in addition to the direct effect of local X-irradiation on the tumor cells, may contribute to the novel effect of the combined therapy.