TRAIL expression by activated human CD4(+)V alpha 24NKT cells induces in vitro and in vivo apoptosis of human acute myeloid leukemia cells

Human CD4+ iNKT cell adoptive immunotherapy induces anti-tumour responses against CD1d-negative EBV-driven B lymphoma

Invariant natural killer T (iNKT) cells are a conserved population of innate T lymphocytes that are uniquely suitable as off-the-shelf cellular immunotherapies due to their lack of alloreactivity. Two major subpopulations of human iNKT cells have been delineated, a CD4- subset that has a TH1/cytolytic profile, and a CD4+ subset that appears polyfunctional and can produce both regulatory and immunostimulatory cytokines. Whether these two subsets differ in anti-tumour effects is not known. Using live cell imaging, we found that CD4- iNKT cells limited growth of CD1d+ Epstein-Barr virus (EBV)-infected B-lymphoblastoid spheroids in vitro, whereas CD4+ iNKT cells showed little or no direct anti-tumour activity. However, the effects of the two subsets were reversed when we tested them as adoptive immunotherapies in vivo using a xenograft model of EBV-driven human B cell lymphoma. We found that EBV-infected B cells down-regulated CD1d in vivo, and administering CD4- iNKT cells had no discernable impact on tumour mass. In contrast, xenotransplanted mice bearing lymphomas showed rapid reduction in tumour mass after administering CD4+ iNKT cells. Immunotherapeutic CD4+ iNKT cells trafficked to both spleen and tumour and were associated with subsequently enhanced responses of xenotransplanted human T cells against EBV. CD4+ iNKT cells also had adjuvant-like effects on monocyte-derived DCs and promoted antigen-dependent responses of human T cells in vitro. These results show that allogeneic CD4+ iNKT cellular immunotherapy leads to marked anti-tumour activity through indirect pathways that do not require tumour cell CD1d expression and that are associated with enhanced activity of antigen-specific T cells.

invariant Natural Killer T cell therapy as a novel therapeutic approach in hematological malignancies

Invariant Natural Killer T cell therapy is an emerging platform of immunotherapy for cancer treatment. This unique cell population is a promising candidate for cell therapy for cancer treatment because of its inherent cytotoxicity against CD1d positive cancers as well as its ability to induce host CD8 T cell cross priming. Substantial evidence supports that iNKT cells can modulate myelomonocytic populations in the tumor microenvironment to ameliorate immune dysregulation to antagonize tumor progression. iNKT cells can also protect from graft-versus-host disease (GVHD) through several mechanisms, including the expansion of regulatory T cells (Treg). Ultimately, iNKT cell-based therapy can retain antitumor activity while providing protection against GVHD simultaneously. Therefore, these biological properties render iNKT cells as a promising "off-the-shelf" therapy for diverse hematological malignancies and possible solid tumors. Further the introduction of a chimeric antigen recetor (CAR) can further target iNKT cells and enhance function. We foresee that improved vector design and other strategies such as combinatorial treatments with small molecules or immune checkpoint inhibitors could improve CAR iNKT in vivo persistence, functionality and leverage anti-tumor activity along with the abatement of iNKT cell dysfunction or exhaustion.

TNF-Related Apoptosis-Inducing Ligand: Non-Apoptotic Signalling

TNF-related apoptosis-inducing ligand (TRAIL or Apo2 or TNFSF10) belongs to the TNF superfamily. When bound to its agonistic receptors, TRAIL can induce apoptosis in tumour cells, while sparing healthy cells. Over the last three decades, this tumour selectivity has prompted many studies aiming at evaluating the anti-tumoral potential of TRAIL or its derivatives. Although most of these attempts have failed, so far, novel formulations are still being evaluated. However, emerging evidence indicates that TRAIL can also trigger a non-canonical signal transduction pathway that is likely to be detrimental for its use in oncology. Likewise, an increasing number of studies suggest that in some circumstances TRAIL can induce, via Death receptor 5 (DR5), tumour cell motility, potentially leading to and contributing to tumour metastasis. While the pro-apoptotic signal transduction machinery of TRAIL is well known from a mechanistic point of view, that of the non-canonical pathway is less understood. In this study, we the current state of knowledge of TRAIL non-canonical signalling.

Eight Weeks of Daily Cannabidiol Supplementation Improves Sleep Quality and Immune Cell Cytotoxicity

BACKGROUND

The endocannabinoid system is active in nervous and immune cells and involves the expression of two cannabinoid receptor genes (CB1 and CB2), along with endogenous endocannabinoid ligands, 2-arachidonoyl glycerol (2-AG) and arachidonoyl ethanolamide (anandamide), and their synthetic enzymes. Cannabidiol (CBD) is a non-intoxicating exogenous cannabinoid agonist derived from plants that, at high doses, has received FDA approval as an anticonvulsant for epileptic seizures, and at low doses is marketed as a food-grade supplement for improved mental health, sleep quality, and immunological function. At present, the predominance of published CBD clinical research has focused on ameliorative or disease-specific intervention, with few trials investigating CBD effects in healthy populations.

METHODS

This clinical study aimed to investigate the effects of 8 weeks of 50 mg oral CBD on mental health, sleep quantity and quality, and immune cell function in healthy, college-aged individuals. Twenty-eight participants (average age 25.9 ± 6.1 y) were randomized to receive either daily oral capsules of 50 mg of CBD (CB, n = 14) or a calorie-matched placebo (CN, n = 14). Participants completed pre- and post-intervention assessments, including anthropometric measurements, mental health surveys, sleep analysis, and immunological function assessments.

RESULTS

After completing the 8-week intervention, there were no significant changes in body weight and BMI (CN: 1.09 ± 0.89%: CB: 1.41 ± 1.07%), or body fat percentage (CN: 9.01 ± 7.51%: CB: 8.57 ± 7.81%), respectively (values are % change pre to post, p > 0.05). There were also no significant differences between CB and CN groups with respect to mental health measures, sleep quantity, or circulating immunophenotype as a result of the intervention. However, the CB group experienced significant improvements in sleep quality measured objectively using a sleep questionnaire (p = 0.0023) and enhanced Natural Killer (NK) immune cell function assessed in situ (p = 0.0125).

CONCLUSIONS

Eight weeks of daily 50 mg CBD may improve sleep quality, and NK immunosurveillance in healthy, younger adults.

Cytotoxic immune cells do not affect TDP-43 and p62 sarcoplasmic aggregation but influence TDP-43 localisation

Sporadic inclusion body myositis (sIBM) is an idiopathic inflammatory myopathy with invasion of CD8 T cells in muscle and aggregation of proteins in the sarcoplasm. TDP-43 and p62 are two proteins that aggregate in affected muscle, and have been suggested as specific markers for sIBM over other inflammatory myopathies. TDP-43 is also mislocalised from the nucleus to the sarcoplasm in sIBM. It is not clear if inflammation precedes protein aggregation in sIBM. This study investigated if exposure to cytotoxic inflammatory cells caused TDP-43 and p62 aggregation or TDP-43 mislocalisation in cultured myotubes. TALL-104 coculture was highly cytotoxic to myotubes after 24 h. Secretion of IFNγ and TNFα were higher in cocultures compared to monocultured TALL-104 cells, indicating activation. TALL-104 cells attached to and infiltrated myotubes. There was no effect of TALL-104 coculture on TDP-43 or p62 sarcoplasmic aggregate size or frequency. However, there was decreased localisation of TDP-43 to the nucleus with TALL-104 coculture compared to control. In an in vitro setting, cytotoxic immune cells did not cause TDP-43 or p62 sarcoplasmic aggregation, suggesting cellular cytotoxicity may not trigger aggregation of these proteins. However TALL-104 coculture influenced TDP-43 localisation, suggesting cytotoxic immune cells may contribute to TDP-43 localisation shifts which is observed in sIBM.

Cell Therapy as Target Therapy against Colon Cancer Stem Cells

Cancer stem cells (CSCs) are a small subpopulation of cells within tumors with properties, such as self-renewal, differentiation, and tumorigenicity. CSCs have been proposed as a plausible therapeutic target as they are responsible for tumor recurrence, metastasis, and conventional therapy resistance. Selectively targeting CSCs is a promising strategy to eliminate the propagation of tumor cells and impair overall tumor development. Recent research shows that several immune cells play a crucial role in regulating tumor cell proliferation by regulating different CSC maintenance or proliferation pathways. There have been great advances in cellular immunotherapy using T cells, natural killer (NK) cells, macrophages, or stem cells for the selective targeting of tumor cells or CSCs in colorectal cancer (CRC). This review summarizes the CRC molecular profiles that may benefit from said therapy and the main vehicles used in cell therapy against CSCs. We also discuss the challenges, limitations, and advantages of combining conventional and/or current targeted treatments in the late stages of CRC.

TCR-engineered iNKT cells induce robust antitumor response by dual targeting cancer and suppressive myeloid cells

Adoptive immunotherapy with T cells engineered with tumor-specific T cell receptors (TCRs) holds promise for cancer treatment. However, suppressive cues generated in the tumor microenvironment (TME) can hinder the efficacy of these therapies, prompting the search for strategies to overcome these detrimental conditions and improve cellular therapeutic approaches. CD1d-restricted invariant natural killer T (iNKT) cells actively participate in tumor immunosurveillance by restricting suppressive myeloid populations in the TME. Here, we showed that harnessing iNKT cells with a second TCR specific for a tumor-associated peptide generated bispecific effectors for CD1d- and major histocompatibility complex (MHC)-restricted antigens in vitro. Upon in vivo transfer, TCR-engineered iNKT (TCR-iNKT) cells showed the highest efficacy in restraining the progression of multiple tumors that expressed the cognate antigen compared with nontransduced iNKT cells or CD8+ T cells engineered with the same TCR. TCR-iNKT cells achieved robust cancer control by simultaneously modulating intratumoral suppressive myeloid populations and killing malignant cells. This dual antitumor function was further enhanced when the iNKT cell agonist α-galactosyl ceramide (α-GalCer) was administered as a therapeutic booster through a platform that ensured controlled delivery at the tumor site, named multistage vector (MSV). These preclinical results support the combination of tumor-redirected TCR-iNKT cells and local α-GalCer boosting as a potential therapy for patients with cancer.

Human iNKT Cells Modulate Macrophage Survival and Phenotype

CD1d-restricted invariant Natural Killer T (iNKT) cells are unconventional innate-like T cells whose functions highly depend on the interactions they establish with other immune cells. Although extensive studies have been reported on the communication between iNKT cells and macrophages in mice, less data is available regarding the relevance of this crosstalk in humans. Here, we dove into the human macrophage-iNKT cell axis by exploring how iNKT cells impact the survival and polarization of pro-inflammatory M1-like and anti-inflammatory M2-like monocyte-derived macrophages. By performing in vitro iNKT cell-macrophage co-cultures followed by flow cytometry analysis, we demonstrated that antigen-stimulated iNKT cells induce a generalized activated state on all macrophage subsets, leading to upregulation of CD40 and CD86 expression. CD40L blocking with a specific monoclonal antibody prior to co-cultures abrogated CD40 and CD86 upregulation, thus indicating that iNKT cells required CD40-CD40L co-stimulation to trigger macrophage activation. In addition, activated iNKT cells were cytotoxic towards macrophages in a CD1d-dependent manner, killing M1-like macrophages more efficiently than their naïve M0 or anti-inflammatory M2-like counterparts. Hence, this work highlighted the role of human iNKT cells as modulators of macrophage survival and phenotype, untangling key features of the human macrophage-iNKT cell axis and opening perspectives for future therapeutic modulation.

Adoptive Immunotherapy With Engineered iNKT Cells to Target Cancer Cells and the Suppressive Microenvironment

Invariant Natural Killer T (iNKT) cells are T lymphocytes expressing a conserved semi-invariant TCR specific for lipid antigens (Ags) restricted for the monomorphic MHC class I-related molecule CD1d. iNKT cells infiltrate mouse and human tumors and play an important role in the immune surveillance against solid and hematological malignancies. Because of unique functional features, they are attractive platforms for adoptive cells immunotherapy of cancer compared to conventional T cells. iNKT cells can directly kill CD1d-expressing cancer cells, but also restrict immunosuppressive myelomonocytic populations in the tumor microenvironment (TME) via CD1d-cognate recognition, promoting anti-tumor responses irrespective of the CD1d expression by cancer cells. Moreover, iNKT cells can be adoptively transferred across MHC barriers without risk of alloreaction because CD1d molecules are identical in all individuals, in addition to their ability to suppress graft vs. host disease (GvHD) without impairing the anti-tumor responses. Within this functional framework, iNKT cells are successfully engineered to acquire a second antigen-specificity by expressing recombinant TCRs or Chimeric Antigen Receptor (CAR) specific for tumor-associated antigens, enabling the direct targeting of antigen-expressing cancer cells, while maintaining their CD1d-dependent functions. These new evidences support the exploitation of iNKT cells for donor unrestricted, and possibly off the shelf, adoptive cell therapies enabling the concurrent targeting of cancer cells and suppressive microenvironment.

Human intestinal and circulating invariant natural killer T cells are cytotoxic against colorectal cancer cells via the perforin-granzyme pathway

Invariant natural killer T (iNKT) cells are lipid-specific T lymphocytes endowed with cytotoxic activities and are thus considered important in antitumor immunity. While several studies have demonstrated iNKT cell cytotoxicity against different tumors, very little is known about their cell-killing activities in human colorectal cancer (CRC). Our aim was to assess whether human iNKT cells are cytotoxic against colon cancer cells and the mechanisms underlying this activity. For this purpose, we generated stable iNKT cell lines from peripheral blood and colon specimens and used NK-92 and peripheral blood natural killer cells as cell-mediated cytotoxicity controls. In vitro cytotoxicity was assessed using a panel of well-characterized human CRC cell lines, and the cellular requirements for iNKT cell cytotoxic functions were evaluated. We demonstrated that both intestinal and circulating iNKT cells were cytotoxic against the entire panel of CRC lines, as well as against freshly isolated patient-derived colonic epithelial cancer cells. Perforin and/or granzyme inhibition impaired iNKT cell cytotoxicity, whereas T-cell receptor (TCR) signaling was a less stringent requirement for efficient killing. This study is the first evidence of tissue-derived iNKT cell cytotoxic activity in humans, as it shows that iNKT cells depend on the perforin-granzyme pathway and both adaptive and innate signal recognition for proper elimination of colon cancer cells.

Regulation and Functions of Protumoral Unconventional T Cells in Solid Tumors

The vast majority of studies on T cell biology in tumor immunity have focused on peptide-reactive conventional T cells that are restricted to polymorphic major histocompatibility complex molecules. However, emerging evidence indicated that unconventional T cells, including γδ T cells, natural killer T (NKT) cells and mucosal-associated invariant T (MAIT) cells are also involved in tumor immunity. Unconventional T cells span the innate-adaptive continuum and possess the unique ability to rapidly react to nonpeptide antigens via their conserved T cell receptors (TCRs) and/or to activating cytokines to orchestrate many aspects of the immune response. Since unconventional T cell lineages comprise discrete functional subsets, they can mediate both anti- and protumoral activities. Here, we review the current understanding of the functions and regulatory mechanisms of protumoral unconventional T cell subsets in the tumor environment. We also discuss the therapeutic potential of these deleterious subsets in solid cancers and why further feasibility studies are warranted.

Human invariant natural killer T cells promote tolerance by preferential apoptosis induction of conventional dendritic cells

Graft-versus-host disease (GvHD) is a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation. We recently showed in murine studies and in vitro human models that adoptively transferred invariant natural killer T (iNKT) cells protect from GvHD and promote graft-versus-leukemia effects. The cellular mechanisms underlying GvHD prevention by iNKT cells in humans, however, remain unknown. In order to study relevant cellular interactions, dendritic cells (DC) were either generated from monocytes or isolated directly from blood of healthy donors or GvHD patients and co-cultured in a mixed lymphocyte reaction (MLR) with T cells obtained from healthy donors or transplantation bags. Addition of culture-expanded iNKT cells to the MLR-induced DC apoptosis in a cell contact-dependent manner, thereby preventing T-cell activation and proliferation. Annexin V/propidium iodide staining and image stream assays showed that CD4⁺CD8^–, CD4^–CD8⁺ and double negative iNKT cells are similarly able to induce DC apoptosis. Further MLR assays revealed that conventional DC (cDC) but not plasmacytoid DC (pDC) could induce alloreactive T-cell activation and proliferation. Interestingly, cDC were also more susceptible to apoptosis induced by iNKT cells, which correlates with their higher CD1d expression, leading to a bias in favor of pDC. Remarkably, these results could also be observed in GvHD patients. We propose a new mechanism how ex vivo expanded human iNKT cells prevent alloreactivity of T cells. iNKT cells modulate T-cell responses by selective apoptosis of DC subsets, resulting in suppression of T-cell activation and proliferation while enabling beneficial immune responses through pDC.

Kaempferol Improves TRAIL-Mediated Apoptosis in Leukemia MOLT-4 Cells by the Inhibition of Anti-apoptotic Proteins and Promotion of Death Receptors Expression

INTRODUCTION

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL or Apo2L) is a member of the Tumor Necrosis Factor (TNF) superfamily, which stimulates apoptosis in a wide range of cancer cells through binding to Death Receptors 4 and 5 (DR4/5). Nevertheless, TRAIL has noticeable anti-cancer abilities; some cancer cells acquire resistance to TRAIL, and consequently, its potential for inducing apoptosis in target cells is strongly diminished. Acute lymphoblastic leukemia MOLT-4 cell line is one of the most resistant cells to TRAIL that developed resistance to TRAIL through different pathways. TRAIL plus kaempferol was used to eliminate the resistance of the MOLT-4 cells to TRAIL.

MATERIALS AND METHODS

Firstly, IC50 for kaempferol (95μM) was determined by using the MTT assay. Secondly, the viability of the MOLT-4 cells was assayed by FACS after Annexin V/PI staining, following treatment with TRAIL (50 and 100nM) and kaempferol (95μM) alone and in combination. Finally, the expression levels of the candidate genes involved in resistance to TRAIL were assayed by real-time PCR technique.

RESULTS

Kaempferol plus TRAIL induced apoptosis robustly in MOLT-4 cells at 12, 24 and 48 hours after treatment. Additionally, it was found that kaempferol could inhibit the expression of c-FLIP, X-IAP, cIAP1/2, FGF-8 and VEGF-beta, and conversely augment the expression of DR4/5 in MOLT-4 cells.

CONCLUSION

It is suggested that co-treatment of MOLT-4 cells with TRAIL plus kaempferol is a practical and attractive approach to eliminate cancers' resistance to TRAIL by inhibition of the intracellular anti-apoptotic proteins, upregulation of DR4/5 and also by suppression of the VEGF-beta (VEGFB) and FGF-8 expressions.

Combination of NKT14m and Low Dose IL-12 Promotes Invariant Natural Killer T Cell IFN-γ Production and Tumor Control

Invariant natural killer T (iNKT) cells are innate-like T lymphocytes characterized by the expression of an invariant T cell receptor (iTCR) that recognizes glycolipid antigens presented by the MHC I-like CD1d molecule. Following antigenic stimulation, iNKT cells rapidly produce large amounts of cytokines that can trans-activate dendritic cells (DC) and promote the anti-tumor functions of cytotoxic lymphocytes, such as natural killer (NK) and CD8 T cells. Additionally, iNKT cells can mediate robust and direct cytotoxicity against CD1d⁺ tumor targets. However, many tumors down-regulate CD1d and evade iNKT cell attack. To circumvent this critical barrier to iNKT cell anti-tumor activity, a novel monoclonal antibody (mAb), NKT14 has been recently developed. This agonistic antibody binds directly and specifically to the iTCR of murine iNKT cells. In the current study, we demonstrate that NKT14m mediates robust activation, cytokine production and degranulation of murine iNKT cells, in vitro. Consistently, NKT14m also promoted iNKT cell activation and immunomodulatory functions, in vivo. Finally, administration of NKT14m with low dose interleukin (IL)-12 further augmented iNKT cell IFN-γ production in vivo, and this combination conferred superior suppression of tumor cell growth compared to NKT14m or IL-12 alone. Together, these data demonstrate that a combination treatment consisting of low dose IL-12 and iTCR-specific mAb may be an attractive alternative to activate iNKT cell anti-tumor functions.

Activated invariant natural killer T cells directly recognize leukemia cells in a CD1d-independent manner

Invariant natural killer T (iNKT) cells are innate‐like CD1d‐restricted T cells that express the invariant T cell receptor (TCR) composed of Vα24 and Vβ11 in humans. iNKT cells specifically recognize glycolipid antigens such as α‐galactosylceramide (αGalCer) presented by CD1d. iNKT cells show direct cytotoxicity toward CD1d‐positive tumor cells, especially when CD1d presents glycolipid antigens. However, iNKT cell recognition of CD1d‐negative tumor cells is unknown, and direct cytotoxicity of iNKT cells toward CD1d‐negative tumor cells remains controversial. Here, we demonstrate that activated iNKT cells recognize leukemia cells in a CD1d‐independent manner, however still in a TCR‐mediated way. iNKT cells degranulated and released Th1 cytokines toward CD1d‐negative leukemia cells (K562, HL‐60, REH) as well as αGalCer‐loaded CD1d‐positive Jurkat cells. The CD1d‐independent cytotoxicity was enhanced by natural killer cell‐activating receptors such as NKG2D, 2B4, DNAM‐1, LFA‐1 and CD2, but iNKT cells did not depend on these receptors for the recognition of CD1d‐negative leukemia cells. In contrast, TCR was essential for CD1d‐independent recognition and cytotoxicity. iNKT cells degranulated toward patient‐derived leukemia cells independently of CD1d expression. iNKT cells targeted myeloid malignancies more than acute lymphoblastic leukemia. These findings reveal a novel anti–tumor mechanism of iNKT cells in targeting CD1d‐negative tumor cells and indicate the potential of iNKT cells for clinical application to treat leukemia independently of CD1d.

License to Kill: When iNKT Cells Are Granted the Use of Lethal Cytotoxicity

Invariant Natural Killer T (iNKT) cells are a non-conventional, innate-like, T cell population that recognize lipid antigens presented by the cluster of differentiation (CD)1d molecule. Although iNKT cells are mostly known for mediating several immune responses due to their massive and diverse cytokine release, these cells also work as effectors in various contexts thanks to their cytotoxic potential. In this Review, we focused on iNKT cell cytotoxicity; we provide an overview of iNKT cell subsets, their activation cues, the mechanisms of iNKT cell cytotoxicity, the specific roles and outcomes of this activity in various contexts, and how iNKT killing functions are currently activated in cancer immunotherapies. Finally, we discuss the future perspectives for the better understanding and potential uses of iNKT cell killing functions in tumor immunosurveillance.

Regulatory T cells induce CD4- NKT cell anergy and suppress NKT cell cytotoxic function

BACKGROUND

Due to the strong tumoricidal activities of activated natural killer T (NKT) cells, invariant NKT cell-based immunotherapy has shown promising clinical efficacy. However, suppressive factors, such as regulatory T cells (Tregs), may be obstacles in the use of NKT cell-based cancer immunotherapy for advanced cancer patients. Here, we investigated the suppressive effects of Tregs on NKT cells and the underlying mechanisms with the aim to improve the antitumor activities of NKT cells.

METHODS

Peripheral blood samples were obtained from healthy donors, patients with benign tumors, and patients with head and neck squamous cell carcinoma (HNSCC). NKT cells, induced with α-galactosylceramide (α-GalCer), and monocyte-derived dendritic cells (DCs) were co-cultured with naïve CD4⁺ T cell-derived Tregs to investigate the mechanism of the Treg suppressive effect on NKT cell cytotoxic function. The functions and phenotypes of NKT cells were evaluated with flow cytometry and cytometric bead array.

RESULTS

Treg suppression on NKT cell function required cell-to-cell contact and was mediated via impaired DC maturation. NKT cells cultured under Treg-enriched conditions showed a decrease in CD4^- NKT cell frequency, which exert strong tumoricidal responsiveness upon α-GalCer stimulation. The same results were observed in HNSCC patients with significantly increased effector Tregs.

CONCLUSION

Tregs exert suppressive effects on NKT cell tumoricidal function by inducing more CD4^- NKT cell anergy and less CD4⁺ NKT cell anergy. Both Treg depletion and NKT cell recovery from the anergy state may be important for improving the clinical efficacy of NKT cell-based immunotherapy in patients with advanced cancers.

The Role of TRAIL/DRs in the Modulation of Immune Cells and Responses

Expression of TRAIL (tumor necrosis factor–related apoptosis–inducing ligand) by immune cells can lead to the induction of apoptosis in tumor cells. However, it becomes increasingly clear that the interaction of TRAIL and its death receptors (DRs) can also directly impact immune cells and influence immune responses. Here, we review what is known about the role of TRAIL/DRs in immune cells and immune responses in general and in the tumor microenvironment in particular.

SLAM-SAP-Fyn: Old Players with New Roles in iNKT Cell Development and Function

Invariant natural killer T (iNKT) cells are a unique T cell lineage that develop in the thymus and emerge with a memory-like phenotype. Accordingly, following antigenic stimulation, they can rapidly produce copious amounts of Th1 and Th2 cytokines and mediate activation of several immune cells. Thus, it is not surprising that iNKT cells play diverse roles in a broad range of diseases. Given their pivotal roles in host immunity, it is crucial that we understand the mechanisms that govern iNKT cell development and effector functions. Over the last two decades, several studies have contributed to the current knowledge of iNKT cell biology and activity. Collectively, these studies reveal that the thymic development of iNKT cells, their lineage expansion, and functional properties are tightly regulated by a complex network of transcription factors and signaling molecules. While prior studies have clearly established the importance of the SLAM-SAP-Fyn signaling axis in iNKT cell ontogenesis, recent studies provide exciting mechanistic insights into the role of this signaling cascade in iNKT cell development, lineage fate decisions, and functions. Here we summarize the previous literature and discuss the more recent studies that guide our understanding of iNKT cell development and functional responses.

Invariant NKT Cells From Donor Lymphocyte Infusions (DLI-iNKTs) Promote ex vivo Lysis of Leukemic Blasts in a CD1d-Dependent Manner

Allogeneic hematopoietic cell transplantation (allo-HCT) is a curative treatment option for hematologic malignancies but relapse remains the most common cause of death. Infusion of donor lymphocytes (DLIs) can induce remission and prolong survival by exerting graft-vs.-leukemia (GVL) effects. However, sufficient tumor control cannot be established in all patients and occurrence of graft-vs.-host disease (GVHD) prevents further dose escalation. Previous data indicate that invariant natural killer T (iNKT) cells promote anti-tumor immunity without exacerbating GVHD. In the present study we investigated lysis of leukemic blasts through iNKT cells from donor-derived lymphocytes for leukemia control and found that iNKT cells constitute about 0.12% of cryopreserved donor T cells. Therefore, we established a 2-week cell culture protocol allowing for a robust expansion of iNKT cells from cryopreserved DLIs (DLI-iNKTs) that can be used for further preclinical and clinical applications. Such DLI-iNKTs efficiently lysed leukemia cell lines and primary patient AML blasts ex vivo in a dose- and CD1d-dependent manner. Furthermore, expression of CD1d on target cells was required to release proinflammatory cytokines and proapoptotic effector molecules. Our results suggest that iNKT cells from donor-derived lymphocytes are involved in anti-tumor immunity after allo-HCT and therefore may reduce the risk of relapse and improve progression-free and overall survival.

Molecular Mode of Action of TRAIL Receptor Agonists-Common Principles and Their Translational Exploitation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its death receptors TRAILR1/death receptor 4 (DR4) and TRAILR2/DR5 trigger cell death in many cancer cells but rarely exert cytotoxic activity on non-transformed cells. Against this background, a variety of recombinant TRAIL variants and anti-TRAIL death receptor antibodies have been developed and tested in preclinical and clinical studies. Despite promising results from mice tumor models, TRAIL death receptor targeting has failed so far in clinical studies to show satisfying anti-tumor efficacy. These disappointing results can largely be explained by two issues: First, tumor cells can acquire TRAIL resistance by several mechanisms defining a need for combination therapies with appropriate sensitizing drugs. Second, there is now growing preclinical evidence that soluble TRAIL variants but also bivalent anti-TRAIL death receptor antibodies typically require oligomerization or plasma membrane anchoring to achieve maximum activity. This review discusses the need for oligomerization and plasma membrane attachment for the activity of TRAIL death receptor agonists in view of what is known about the molecular mechanisms of how TRAIL death receptors trigger intracellular cell death signaling. In particular, it will be highlighted which consequences this has for the development of next generation TRAIL death receptor agonists and their potential clinical application.

Harnessing the Power of Invariant Natural Killer T Cells in Cancer Immunotherapy

Invariant natural killer T (iNKT) cells are a distinct subset of innate-like lymphocytes bearing an invariant T-cell receptor, through which they recognize lipid antigens presented by monomorphic CD1d molecules. Upon activation, iNKT cells are capable of not only having a direct effector function but also transactivating NK cells, maturing dendritic cells, and activating B cells, through secretion of several cytokines and cognate TCR-CD1d interaction. Endowed with the ability to orchestrate an all-encompassing immune response, iNKT cells are critical in shaping immune responses against pathogens and cancer cells. In this review, we examine the critical role of iNKT cells in antitumor responses from two perspectives: (i) how iNKT cells potentiate antitumor immunity and (ii) how CD1d+ tumor cells may modulate their own expression of CD1d molecules. We further explore hypotheses to explain iNKT cell activation in the context of cancer and how the antitumor effects of iNKT cells can be exploited in different forms of cancer immunotherapy, including their role in the development of cancer vaccines.

Invariant Natural Killer T Cells in Immune Regulation of Blood Cancers: Harnessing Their Potential in Immunotherapies

Invariant natural killer T (iNKT) cells are a unique innate T lymphocyte population that possess cytolytic properties and profound immunoregulatory activities. iNKT cells play an important role in the immune surveillance of blood cancers. They predominantly recognize glycolipid antigens presented on CD1d, but their activation and cytolytic activities are not confined to CD1d expressing cells. iNKT cell stimulation and subsequent production of immunomodulatory cytokines serve to enhance the overall antitumor immune response. Crucially, the activation of iNKT cells in cancer often precedes the activation and priming of other immune effector cells, such as NK cells and T cells, thereby influencing the generation and outcome of the antitumor immune response. Blood cancers can evade or dampen iNKT cell responses by downregulating expression of recognition receptors or by actively suppressing or diverting iNKT cell functions. This review will discuss literature on iNKT cell activity and associated dysregulation in blood cancers as well as highlight some of the strategies designed to harness and enhance iNKT cell functions against blood cancers.

Reciprocal Crosstalk between Dendritic Cells and Natural Killer T Cells: Mechanisms and Therapeutic Potential

Natural killer T cells carrying a highly conserved, semi-invariant T cell receptor (TCR) [invariant natural killer T (iNKT) cells] are a subset of unconventional T lymphocytes that recognize glycolipids presented by CD1d molecules. Although CD1d is expressed on a variety of hematopoietic and non-hematopoietic cells, dendritic cells (DCs) are key presenters of glycolipid antigen in vivo. When stimulated through their TCR, iNKT cells rapidly secrete copious amounts of cytokines and induce maturation of DCs, thereby facilitating coordinated stimulation of innate and adaptive immune responses. The bidirectional crosstalk between DCs and iNKT cells determines the functional outcome of iNKT cell-targeted responses and iNKT cell agonists are used and currently being evaluated as adjuvants to enhance the efficacy of antitumor immunotherapy. This review illustrates mechanistic underpinnings of reciprocal DCs and iNKT cell interactions and discusses how those can be harnessed for cancer therapy.

Engaging Natural Killer T Cells as 'Universal Helpers' for Vaccination

Conventional vaccine adjuvants enhance peptide-specific T-cell and B-cell responses by modifying peptide stability or uptake or by binding to pattern-recognition receptors on antigen-presenting cells (APCs). This article discusses the application of a distinct mechanism of adjuvant activity: the activation of type I, or invariant, natural killer T (iNKT) cells to drive cellular and humoral immune responses. Using a semi-invariant T-cell receptor (TCR), iNKT cells recognize glycolipid antigens presented on cluster of differentiation (CD)-1d molecules. When their ligands are presented in concert with peptides, iNKT cells can provide T-cell help, 'licensing' APCs to augment peptide-specific T-cell and antibody responses. We discuss the potential benefits and limitations of exploiting iNKT cells as 'universal helpers' to enhance vaccine responses for the treatment and prevention of cancer and infectious diseases.

Cellular Adjuvant Properties, Direct Cytotoxicity of Re-differentiated Vα24 Invariant NKT-like Cells from Human Induced Pluripotent Stem Cells

Vα24 invariant natural killer T (iNKT) cells are a subset of T lymphocytes implicated in the regulation of broad immune responses. They recognize lipid antigens presented by CD1d on antigen-presenting cells and induce both innate and adaptive immune responses, which enhance effective immunity against cancer. Conversely, reduced iNKT cell numbers and function have been observed in many patients with cancer. To recover these numbers, we reprogrammed human iNKT cells to pluripotency and then re-differentiated them into regenerated iNKT cells in vitro through an IL-7/IL-15-based optimized cytokine combination. The re-differentiated iNKT cells showed proliferation and IFN-γ production in response to α-galactosylceramide, induced dendritic cell maturation and downstream activation of both cytotoxic T lymphocytes and NK cells, and exhibited NKG2D- and DNAM-1-mediated NK cell-like cytotoxicity against cancer cell lines. The immunological features of re-differentiated iNKT cells and their unlimited availability from induced pluripotent stem cells offer a potentially effective immunotherapy against cancer.

Immunotherapeutic strategies targeting natural killer T cell responses in cancer

Natural killer T (NKT) cells are a unique subset of lymphocytes that bridge the innate and adaptive immune system. NKT cells possess a classic αβ T cell receptor (TCR) that is able to recognize self and foreign glycolipid antigens presented by the nonclassical class I major histocompatibility complex (MHC) molecule, CD1d. Type I NKT cells (referred to as invariant NKT cells) express a semi-invariant Vα14Jα18 TCR in mice and Vα24Jα18 TCR in humans. Type II NKT cells are CD1d-restricted T cells that express a more diverse set of TCR α chains. The two types of NKT cells often exert opposing effects especially in tumor immunity, where type II cells generally suppress tumor immunity while type I NKT cells can enhance anti-tumor immune responses. In this review, we focus on the role of NKT cells in cancer. We discuss their effector and suppressive functions, as well as describe preclinical and clinical studies utilizing therapeutic strategies focused on harnessing their potent anti-tumor effector functions, and conclude with a discussion on potential next steps for the utilization of NKT cell-targeted therapies for the treatment of cancer.

Invariant NKT cells are resistant to circulating CD15+ myeloid-derived suppressor cells in patients with head and neck cancer

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of immature and progenitor myeloid cells with an immunosuppressive role in various types of cancer, including head and neck squamous cell carcinoma (HNSCC). However, the effect on the host immune system, especially on invariant NKT (iNKT) cells with potent anti-tumor activity, remains unclear. In this study, we investigated the effects of circulating MDSC subsets on the peripheral lymphocytes of patients with head and neck tumors. A significant accumulation of CD15+ granulocytic MDSC (G-MDSC) and CD14+ monocytic MDSC (M-MDSC) was demonstrated in HNSCC patients. The percentage of G-MDSC showed an inverse correlation with the percentage of T cells in the peripheral blood. The increased G-MDSC was significantly associated with advanced clinical stage and poor prognosis of HNSCC patients. The proliferation and viability of T cells were suppressed by CD15+ cells, and the suppression was reversed by adding the hydrogen peroxide scavenger catalase. However, iNKT cell activation upon α-galactosylceramide (αGalCer) stimulation was not affected by the presence or absence of CD15+ G-MDSC. These results indicate that increased G-MDSC negatively affects peripheral T cell immunity, but not iNKT cells, in HNSCC patients, and that T cells are more sensitive to hydrogen peroxide produced by G-MDSC than iNKT cells. Cancer immunotherapy designed to enhance the antitumor activity of iNKT cells by stimulation with αGalCer may remain effective in the presence of G-MDSC.

CD1d- and MR1-Restricted T Cells in Sepsis

Dysregulated immune responses to infection, such as those encountered in sepsis, can be catastrophic. Sepsis is typically triggered by an overwhelming systemic response to an infectious agent(s) and is associated with high morbidity and mortality even under optimal critical care. Recent studies have implicated unconventional, innate-like T lymphocytes, including CD1d- and MR1-restricted T cells as effectors and/or regulators of inflammatory responses during sepsis. These cell types are typified by invariant natural killer T (iNKT) cells, variant NKT (vNKT) cells, and mucosa-associated invariant T (MAIT) cells. iNKT and vNKT cells are CD1d-restricted, lipid-reactive cells with remarkable immunoregulatory properties. MAIT cells participate in antimicrobial defense, and are restricted by major histocompatibility complex-related protein 1 (MR1), which displays microbe-derived vitamin B metabolites. Importantly, NKT and MAIT cells are rapid and potent producers of immunomodulatory cytokines. Therefore, they may be considered attractive targets during the early hyperinflammatory phase of sepsis when immediate interventions are urgently needed, and also in later phases when adjuvant immunotherapies could potentially reverse the dangerous state of immunosuppression. We will highlight recent findings that point to the significance or the therapeutic potentials of NKT and MAIT cells in sepsis and will also discuss what lies ahead in research in this area.

The regulatory role of invariant NKT cells in tumor immunity

Invariant natural killer T (iNKT) cells are a unique population of T lymphocytes, which lie at the interface between the innate and adaptive immune systems, and are important mediators of immune responses and tumor surveillance. iNKT cells recognize lipid antigens in a CD1d-dependent manner; their subsequent activation results in a rapid and specific downstream response, which enhances both innate and adaptive immunity. The capacity of iNKT cells to modify the immune microenvironment influences the ability of the host to control tumor growth, making them an important population to be harnessed in the clinic for the development of anticancer therapeutics. Indeed, the identification of strong iNKT-cell agonists, such as α-galactosylceramide (α-GalCer) and its analogues, has led to the development of synthetic lipids that have shown potential in vaccination and treatment against cancers. In this Masters of Immunology article, we discuss these latest findings and summarize the major discoveries in iNKT-cell biology, which have enabled the design of potent strategies for immune-mediated tumor destruction.

Circulating immune/inflammation markers in Chinese workers occupationally exposed to formaldehyde

BACKGROUND

Formaldehyde has been classified as a human myeloid leukemogen. However, the mechanistic basis for this association is still debated.

OBJECTIVES

We aimed to evaluate whether circulating immune/inflammation markers were altered in workers occupationally exposed to formaldehyde.

METHODS

Using a multiplexed bead-based assay, we measured serum levels of 38 immune/inflammation markers in a cross-sectional study of 43 formaldehyde-exposed and 51 unexposed factory workers in Guangdong, China. Linear regression models adjusting for potential confounders were used to compare marker levels in exposed and unexposed workers.

RESULTS

We found significantly lower circulating levels of two markers among exposed factory workers compared with unexposed controls that remained significant after adjusting for potential confounders and multiple comparisons using a false discovery rate of 10%, including chemokine (C-X-C motif) ligand 11 (36.2 pg/ml in exposed versus 48.4 pg/ml in controls, P = 0.0008) and thymus and activation regulated chemokine (52.7 pg/ml in exposed versus 75.0 pg/ml in controls, P = 0.0028), suggesting immunosuppression among formaldehyde-exposed workers.

CONCLUSIONS

Our findings are consistent with recently emerging understanding that immunosuppression might be associated with myeloid diseases. These findings, if replicated in a larger study, may provide insights into the mechanisms by which formaldehyde promotes leukemogenesis.

Natural killer T cell activation overcomes immunosuppression to enhance clearance of postsurgical breast cancer metastasis in mice

Metastatic lesions are responsible for over 90% of breast cancer associated deaths. Therefore, strategies that target metastasis are of particular interest. This study examined the efficacy of natural killer T (NKT) cell activation as a post-surgical immunotherapy in a mouse model of metastatic breast cancer. Following surgical resection of orthotopic 4T1 mammary carcinoma tumors, BALB/c mice were treated with NKT cell activating glycolipid antigens (α-GalCer, α-C-GalCer or OCH) or α-GalCer-loaded dendritic cells (DCs). Low doses of glycolipids transiently reduced metastasis but did not increase survival. A high dose of α-GalCer enhanced overall survival, but was associated with increased toxicity and mortality at early time points. Treatment with α-GalCer-loaded DCs limited tumor metastasis, prolonged survival, and provided curative outcomes in ∼45% of mice. However, survival was not increased further by additional DC treatments or co-transfer of expanded NKT cells. NKT cell activation via glycolipid-loaded DCs decreased the frequency and immunosuppressive activity of myeloid derived suppressor cells (MDSCs) in tumor-resected mice. In vitro, NKT cells were resistant to the immunosuppressive effects of MDSCs and were able to reverse the inhibitory effects of MDSCs on T cell proliferation. NKT cell activation enhanced antitumor immunity in tumor-resected mice, increasing 4T1-specific cytotoxic responses and IFNγ production from natural killer (NK) cells and CD8⁺ T cells. Consistent with increased tumor immunity, mice surviving to day 150 were resistant to a second tumor challenge. This work provides a clear rationale for manipulating NKT cells to target metastatic disease.

CD4+ natural killer T cells potently augment aortic root atherosclerosis by perforin- and granzyme B-dependent cytotoxicity

RATIONALE

CD4(+) natural killer T (NKT) cells augment atherosclerosis in apolipoprotein E-deficient (ApoE)(-/-) mice but their mechanisms of action are unknown.

OBJECTIVES

We investigated the roles of bystander T, B, and NK cells; NKT cell-derived interferon-γ, interleukin (IL)-4, and IL-21 cytokines; and NKT cell-derived perforin and granzyme B cytotoxins in promoting CD4(+) NKT cell atherogenicity.

METHODS AND RESULTS

Transfer of CD4(+) NKT cells into T- and B-cell-deficient ApoE(-/-)Rag2(-/-) mice augmented aortic root atherosclerosis by ≈75% that was ≈30% of lesions in ApoE(-/-) mice; macrophage accumulation similarly increased. Transferred NKT cells were identified in the liver and atherosclerotic lesions of recipient mice. Transfer of CD4(+) NKT cells into T-, B-cell-deficient, and NK cell-deficient ApoE(-/-)Rag2(-/-)γC(-/-) mice also augmented atherosclerosis. These data indicate that CD4(+) NKT cells can exert proatherogenic effects independent of other lymphocytes. To investigate the role of NKT cell-derived interferon-γ, IL-4, and IL-21 cytokines and perforin and granzyme B cytotoxins, CD4(+) NKT cells from mice deficient in these molecules were transferred into NKT cell-deficient ApoE(-/-)Jα18(-/-) mice. CD4(+) NKT cells deficient in IL-4, interferon-γ, or IL-21 augmented atherosclerosis in ApoE(-/-)Jα18(-/-) mice by ≈95%, ≈80%, and ≈70%, respectively. Transfer of CD4(+) NKT cells deficient in perforin or granzyme B failed to augment atherosclerosis. Apoptotic cells, necrotic cores, and proinflammatory VCAM-1 (vascular cell adhesion molecule) and MCP-1 (monocyte chemotactic protein) were reduced in mice receiving perforin-deficient NKT cells. CD4(+) NKT cells are twice as potent as CD4(+) T cells in promoting atherosclerosis.

CONCLUSIONS

CD4(+) NKT cells potently promote atherosclerosis by perforin and granzyme B-dependent apoptosis that increases postapoptotic necrosis and inflammation.

NKT cell networks in the regulation of tumor immunity

CD1d-restricted natural killer T (NKT) cells lie at the interface between the innate and adaptive immune systems and are important mediators of immune responses and tumor immunosurveillance. These NKT cells uniquely recognize lipid antigens, and their rapid yet specific reactions influence both innate and adaptive immunity. In tumor immunity, two NKT subsets (type I and type II) have contrasting roles in which they not only cross-regulate one another, but also impact innate immune cell populations, including natural killer, dendritic, and myeloid lineage cells, as well as adaptive populations, especially CD8⁺ and CD4⁺ T cells. The extent to which NKT cells promote or suppress surrounding cells affects the host’s ability to prevent neoplasia and is consequently of great interest for therapeutic development. Data have shown the potential for therapeutic use of NKT cell agonists and synergy with immune response modifiers in both pre-clinical studies and preliminary clinical studies. However, there is room to improve treatment efficacy by further elucidating the biological mechanisms underlying NKT cell networks. Here, we discuss the progress made in understanding NKT cell networks, their consequent role in the regulation of tumor immunity, and the potential to exploit that knowledge in a clinical setting.

Human dendritic cells derived from embryonic stem cells stably modified with CD1d efficiently stimulate antitumor invariant natural killer T cell response

Invariant natural killer T (iNKT) cells are a unique lymphocyte subpopulation that mediates antitumor activities upon activation. A current strategy to harness iNKT cells for cancer treatment is endogenous iNKT cell activation using patient-derived dendritic cells (DCs). However, the limited number and functional defects of patient DCs are still the major challenges for this therapeutic approach. In this study, we investigated whether human embryonic stem cells (hESCs) with an ectopically expressed CD1d gene could be exploited to address this issue. Using a lentivector carrying an optimized expression cassette, we generated stably modified hESC lines that consistently overexpressed CD1d. These modified hESC lines were able to differentiate into DCs as efficiently as the parental line. Most importantly, more than 50% of such derived DCs were CD1d+. These CD1d-overexpressing DCs were more efficient in inducing iNKT cell response than those without modification, and their ability was comparable to that of DCs generated from monocytes of healthy donors. The iNKT cells expanded by the CD1d-overexpressing DCs were functional, as demonstrated by their ability to lyse iNKT cell-sensitive glioma cells. Therefore, hESCs stably modified with the CD1d gene may serve as a convenient, unlimited, and competent DC source for iNKT cell-based cancer immunotherapy.

Apoptosis and immaturity in acute myeloid leukemia

The primary cause of treatment failures in acute myeloid leukemia (AML) is the emergence of both resistant disease and early relapse. Among the most frequent agents of these phenomena are defects in the mitochondrial-mediated apoptotic pathway. This pathway is regulated by bcl-2 family of anti-apoptotic (bcl-2, bcl-xl, mcl-1) and pro-apoptotic proteins (bax, bad, bak). In particular, bcl-2 dimerizes with several members of bcl-2 family of proteins, altering the threshold of cell death. The flow cytometric quantitative measurement of bcl-2 and bax expression for the determination of bax/bcl-2 ratio provided crucial clinical information in AML: in our hands, lower bax/bcl-2 ratio conferred a very poor prognosis with decreased rates of complete remission (CR) and overall survival (OS). Moreover, striking correlations were found between lower bax/bcl-2 ratio and higher progenitor marker expression, such as CD34, CD117 and CD133 antigens, confirming the link between this apoptotic index and the maturation pathways. However, the capacity of bax/bcl-2 ratio to clearly identify patients with different prognosis with regard to CR and OS within the CD34+, CD117+ and CD133+ subgroups implies that other mechanisms, such as proliferation and/or cell cycle dysregulation may be involved to explain its clinical significance. Finally, small molecules that target both the receptor- and mitochondrial-mediated pathway of apoptosis are providing encouraging results in patients with relapsed and/or refractory disease (i.e. CDDOMe, bcl-2 antisense oligonucleotides, CEP-701, etc), confirming the key role of apoptotic mechanisms on the outcome of AML patients.

The adaptor molecule SAP plays essential roles during invariant NKT cell cytotoxicity and lytic synapse formation

The adaptor molecule signaling lymphocytic activation molecule-associated protein (SAP) plays critical roles during invariant natural killer T (iNKT) cell ontogeny. As a result, SAP-deficient humans and mice lack iNKT cells. The strict developmental requirement for SAP has made it difficult to discern its possible involvement in mature iNKT cell functions. By using temporal Cre recombinase-mediated gene deletion to ablate SAP expression after completion of iNKT cell development, we demonstrate that SAP is essential for T-cell receptor (TCR)-induced iNKT cell cytotoxicity against T-cell and B-cell leukemia targets in vitro and iNKT-cell-mediated control of T-cell leukemia growth in vivo. These findings are not restricted to the murine system: silencing RNA-mediated suppression of SAP expression in human iNKT cells also significantly impairs TCR-induced cytolysis. Mechanistic studies reveal that iNKT cell killing requires the tyrosine kinase Fyn, a known SAP-binding protein. Furthermore, SAP expression is required within iNKT cells to facilitate their interaction with T-cell targets and induce reorientation of the microtubule-organizing center to the immunologic synapse (IS). Collectively, these studies highlight a novel and essential role for SAP during iNKT cell cytotoxicity and formation of a functional IS.

Invariant NKT cells increase drug-induced osteosarcoma cell death

BACKGROUND AND PURPOSE

In osteosarcoma (OS) patients, only a limited number of drugs are active and the regimens currently in use include a combination of at least two of these drugs: doxorubicin, cisplatin, methotrexate and ifosfamide. Today, 30-40% of patients still die of OS highlighting the urgent need for new treatments. Invariant NKT (iNKT) cells are a lymphocyte lineage with features of both T and NK cells, playing important roles in tumour suppression. Our aim was to test whether the cytoxicity induced by cisplatin, doxorubicin and methotrexate against OS cells can be enhanced by iNKT cell treatment.

EXPERIMENTAL APPROACH

iNKT cells were purified from human peripheral blood mononuclear cells by cell sorting (Vα24Vβ11(+) cells) and used as effector cells against OS cells (U2-OS, HOS, MG-63). Cell death (calcein-AM method), perforin/granzyme B and Fas/FasL expressions were determined by flow cytometry. CD1d expression was analysed at both the gene and protein level.

KEY RESULTS

iNKT cells were cytotoxic against OS cells through a CD1d-dependent mechanism. This activity was specific for tumour cells, because human CD1d(+) mesenchymal stem cells and CD1d(-) osteoblasts were not affected. iNKT cell treatment enhanced drug-induced OS cell death in a concentration-dependent manner and this effect was reduced in CD1d-silenced OS cells.

CONCLUSION AND IMPLICATIONS

iNKT cells kill malignant, but not non-malignant, cells. iNKT cell treatment enhances the cytotoxicity of anti-neoplastic drugs against OS cells in a CD1d-dependent manner. The present data encourage further studies on the use of iNKT cells in OS therapy.

Evidence for BCR-ABL-dependent dysfunctions of iNKT cells from chronic myeloid leukemia patients

Chronic myeloid leukemia (CML) is a clonal hematopoietic stem-cell malignancy characterized by the presence of the chimeric BCR-ABL oncoprotein with deregulated tyrosine-kinase (TK) activity. Although conventional T cells are acknowledged as important players in the control of CML, a possible modification of invariant NKT (iNKT) cells, known for their antitumoral activity, has not been established as yet. Here, we showed that the expression of perforin, CD95L, and promyelocytic leukemia zinc finger, a transcription factor required for maintenance of iNKT cell functions, was reduced or suppressed in CML patients at diagnosis, as compared with healthy individuals. The proliferation rate of blood iNKT cells in response to their cognate ligand was likewise diminished. These functional deficiencies were corrected in patients having achieved complete cytogenetic remission following TK inhibitor or IFN-α therapy. iNKT cells from CML patients in the chronic phase did not display increased TK activity, which argued against a direct autonomous action of BCR-ABL. Instead, we found that their anergic status originated from both intrinsic and APC-dependent dysfunctions. Our data demonstrate that chronic phase CML is associated with functional deficiencies of iNKT cells that are restored upon remission. These results suggest a possible contribution to disease control by TK inhibitor therapies.

Natural killer T cell based Immunotherapy

Natural killer T (NKT) cells play an important immunoregulatory role and are thought to bridge the innate and adaptive immune responses. Following activation through cognate interactions with lipid antigen presented in the context of CD1d molecules, NKT cells rapidly produce a plethora of cytokines and can also mediate cytotoxicity. Due to their potent effector functions, extensive research has been performed to increase our understanding on how to effectively modulate these cells. In fact, NKT cell agonists have been used as vaccine adjuvants to enhance antigen specific T and B cell responses to infections and malignancy. In this review, we will focus on recent advances in NKT cell-based vaccination strategies. Given the role that NKT cells play in autoimmune disease, infectious diseases, cancer, transplant immunology and dermatology, it is important to understand how to effectively guide their effector functions in order to develop novel immunotherapeutic strategies.

Targeting TNF superfamily members for therapeutic intervention in rheumatoid arthritis

Rheumatoid arthritis (RA) is an inflammatory disease is one of the most serious medical problems, affecting ∼1% of all people worldwide, irrespective of race. The disease is autoimmune in nature and characterized by chronic inflammation of the synovial tissues in multiple joints that leads to joint destruction. Although T cells are central players in RA development, B cells are required for full penetrance of disease largely via their production of autoantibodies against Fc domain of IgG rheumatoid factor (RF). Treatment options for RA are limited and if any, are inadequate due to associated side effects. Members of the tumor necrosis factor (TNF) superfamily play important roles in a number of autoimmune diseases, including RA. In this review, we briefly summarize key features of the superfamily, we will consider how the well-characterized members concerned with immune regulation are coordinated and their roles in rheumatoid arthritis.

TRAIL and DR5 promote thyroid follicular cell apoptosis in iodine excess-induced experimental autoimmune thyroiditis in NOD mice

Death receptor-mediated apoptosis has been implicated in target organ destruction in patients with chronic autoimmune thyroiditis. Several apoptosis signaling pathways, such as Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), have been shown to be active in thyroid cells and may be involved in destructive thyroiditis. Thyroid toxicity of iodide excess has been demonstrated in animals fed with an iodide-rich diet, but its pathogenic role remains unclear. The effects of excessive iodine on TRAIL and its death receptor expression in thyroid were investigated. Experimental autoimmune thyroiditis (EAT) was induced by excessive iodine and thyroglobulin (Tg) in non-obese diabetic mice. The expression of TRAIL and its death receptor DR5 was detected by immunofluorescence staining. Following administration of excessive iodine alone, Tg, and excessive iodine combined with Tg, TRAIL-positive cells appear not only in follicular cells but also in lymphocytes infiltrated in the thyroid, whereas DR5-positive cells appear only in follicular cells. Large numbers of CD3-positive cells and a few CD22-positive cells were detected in thyroid. A great amount of follicular cells were labeled specifically by terminal deoxynucleotide transferase-mediated deoxynucleotide triphosphate nick-end labeling assay. Taken together, our results suggest that excessive iodine could induce TRAIL and DR5 abnormal expression in thyroid. TRAIL band with DR5 to promote follicular cells apoptosis thus mediate thyroid destruction in EAT.

The apelin/APJ system induces maturation of the tumor vasculature and improves the efficiency of immune therapy

Immature and unstable tumor vasculature provides an aberrant tumor microenvironment and leads to resistance of tumors to conventional therapy. Hence, normalization of tumor vessels has been reported to improve the effect of immuno-, chemo- and radiation therapy. However, the humoral factors, which can effectively induce maturation of tumor vasculature, have not been elucidated. In this study, we found that the novel peptide apelin and its receptor APJ can induce the morphological and functional maturation of blood vessels in tumors. This apelin-induced tumor vascular maturation enhances the efficacy of cancer dendritic cell-based immunotherapy and significantly suppresses tumor growth by promoting the infiltration of invariant natural killer T cells into the central region of the tumor and thereby robustly inducing apoptosis of tumor cells. Additionally, we showed APJ expression to be enhanced in the tumor endothelium in comparison with normal-state endothelial cells. These findings provide a new target for tumor vascular-specific maturation, which is expected to improve the efficacy of conventional cancer therapies.

The cytotoxic potential of interleukin-15-stimulated cytokine-induced killer cells against leukemia cells

BACKGROUND AIMS

Cytokine-induced killer (CIK) cells may serve as an alternative approach to adoptive donor lymphocyte infusions (DLI) for patients with acute leukemia relapsing after haplo-identical hematopoietic stem cell transplantation (HSCT). We investigated the feasibility of enhancing CIK cell-mediated cytotoxicity by interleukin (IL)-15 against acute myeloid and lymphoblastic leukemia/lymphoma cells.

METHODS

CIK cells were activated using IL-2 (CIK(IL-2)) or IL-15 (CIK(IL-15)) and phenotypically analyzed by fluorescence-activated cell sorting (FACS). Cytotoxic potential was measured by europium release assay.

RESULTS

CIK(IL-2) cells showed potent cytotoxicity against the T-lymphoma cell line H9, T-cell acute lymphoblastic leukemia (T-ALL) cell line MOLT-4 and subtype M4 acute myeloid leukemia (AML) cell line THP-1, but low cytotoxicity against the precursor B (pB)-cell ALL cell line Tanoue. IL-15 stimulation resulted in a significant enhancement of CIK cell-mediated cytotoxicity against acute lymphoblastic leukemia/lymphoma cell lines as well as against primary acute myeloid and defined lymphoblastic leukemia cells. However, the alloreactive potential of CIK(IL-15) cells remained low. Further analysis of CIK(IL-15) cells demonstrated that the NKG2D receptor is apparently involved in the recognition of target cells whereas killer-cell immunoglobulin-like receptor (KIR)-HLA mismatches contributed to a lesser extent to the CIK(IL-15) cell-mediated cytotoxicity. In this context, CD3 (+) CD8 (+) CD25 (+) CD56(-) CIK(IL-15) cell subpopulations were more effective in the lysis of AML cells, in contrast with CD56 (+) CIK(IL-15) cells, which showed the highest cytotoxic potential against ALL cells.

CONCLUSIONS

This study provides the first evidence that CIK(IL-15) cells may offer a therapeutic option for patients with refractory or relapsed leukemia following haplo-identical HSCT.

TRAIL is associated with impaired regulation of CD4+CD25- T cells by regulatory T cells in patients with rheumatoid arthritis

Thirty-five rheumatoid arthritis (RA) patients and 27 healthy volunteers were enrolled in the study. Regulatory T (Treg) cell numbers were significantly reduced in RA patients. RA Treg cells exhibited an impaired capacity to inhibit proliferation and cytokine secretion of autologous T effector (Teff) cells. However, the crossover experiments further indicated that this impaired suppression was due to resistance of Teff cells but not to an intrinsic defect of Treg cells in RA patients. RA Teff cells showed a higher expression of membrane tumor necrosis factor-related apoptosis-inducing ligand and secreted more soluble tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL could induce apoptosis in Treg cells. Neutralization of TRAIL restored the regulation of Teff by Treg in RA patients. In summary, our data suggest that reduced peripheral Treg cell numbers and an increased resistance of Teff cells to suppression by Treg cells were present in RA patients, and TRAIL may be an underlying mechanism for the impaired regulation of Teff cells by Treg cells.

Comparison of clinical and immunological effects of intravenous and intradermal administration of α-galactosylceramide (KRN7000)-pulsed dendritic cells

PURPOSE

Human Vα24+Vβ11+ natural killer T-cells (NKT cells) have antitumor activity via direct cytotoxicity and by induction of antitumor actions of T and NK cells. Activation of NKT cells is crucial for their antitumor activity and is induced by α-galactosylceramide (α-GalCer, KRN7000) presented by CD1d on dendritic cells (DC). We conducted a phase I clinical trial of therapy with α-GalCer-pulsed DC to determine safety, tolerability, immune effects and an optimal dose, and administration route.

EXPERIMENTAL DESIGN

Twelve subjects (3 cohorts) with metastatic malignancy received 4 treatments of α-GalCer-pulsed DC, 2 treatments intravenously (IV), and 2 treatments intradermally (ID). Each successive cohort received a log higher cell dose. Clinical and immunological outcomes were evaluated, including secondary effects on NK and T cells.

RESULTS

Substantial effects on peripheral blood NKT cells were observed but were greater following IV treatment. Secondary immune effects including activation of T and NK cells, increases in T- and NK-cell cytoplasmic interferon-γ, and increases in serum interferon-γ levels were seen after IV but not after ID treatment. Therapy was well tolerated, but 9 of 12 subjects had tumor flares with clinical findings consistent with transient tumor inflammation. Disease response (minor) or stabilization of disease progressing up to enrollment was observed in 6 of the 12 subjects. Stabilization of previously progressive disease lasted for at least one year in three subjects.

CONCLUSION

We conclude that therapy with α-GalCer-pulsed DC induced clinically beneficial immune responses that are highly dependent on cell dose and administration route.

The tumour necrosis factor/TNF receptor superfamily: therapeutic targets in autoimmune diseases

Autoimmune diseases are characterized by the body's ability to mount immune attacks on self. This results from recognition of self-proteins and leads to organ damage due to increased production of pathogenic inflammatory molecules and autoantibodies. Over the years, several new potential therapeutic targets have been identified in autoimmune diseases, notable among which are members of the tumour necrosis factor (TNF) superfamily. Here, we review the evidence that certain key members of this superfamily can augment/suppress autoimmune diseases.