Direct Tumor Irradiation Potentiates Adoptive NK Cell Targeting Against Parental and Stemlike Cancer in Human Liver Cancer Models

PURPOSE

Radiation therapy (RT) has been shown to effectively induce the expression of intercellular adhesion molecule-1 (ICAM-1), which is recognized by lymphocyte function-associated antigen 1 (LFA-1) expressed on natural killer (NK) cells. However, the potential synergistic antitumor immune response of tumor irradiation and administered NK cells has not been explored in intractable human liver cancers. Furthermore, NK cell targeting against both parental and cancer stemness has never been investigated.

METHODS AND MATERIALS

Highly activated ex vivo NK cells were administered into the human liver tumor-bearing mice. Tumor direct RT was optimized according to tumor bearing site. HepG2 and Hep3B ICAM-1 knockout cells were generated using CRISPR/CAS9. Stemness tumor spheres were generated. NK cell cytolysis against parental and tumor sphere was evaluated using flow cytometry and real-time cytotoxicity assay.

RESULTS

A combination of adoptive NK cell therapy with RT significantly improved therapeutic efficacy over monotherapies against subcutaneous, orthotopic, and metastatic human liver tumor models. Direct tumor irradiation potentiated NK cell recognition and conjugation against liver cancer through the LFA-1/ICAM-1 axis. Suppression of immune synapse formation on NK cells using high-affinity LFA-1 inhibitors or ICAM-1 knockout liver cancer induced "outside-in" signal blocking in NK cells, resulting in failure to eliminate liver tumor despite the combination therapy. NK cells effectively recognized and targeted triple-high epithelial cell adhesion molecule+CD133+CD24+ liver cancer expressing upregulated ICAM-1 in the irradiated tumor microenvironment, which led to prevention of the initiation of metastasis, improving survival in a metastatic model. In addition, the LFA-1/ICAM-1 axis interruption between NK cells and stemness liver tumor spheres significantly diminished NK cell cytolysis. Consistent with our preclinical data, the LFA-1/ICAM-1 axis correlated with survival outcomes in patients with metastatic cancer from the The Cancer Genome Atlas databases.

CONCLUSIONS

NK cells in combination with tumor irradiation can provide synergistic therapeutic effects for NK cell recognition and elimination against both parental and stemlike liver cancer through LFA-1/ICAM-1.

NK92 cells and peripheral blood NK cells respond oppositely upon dasatinib treatment

Natural killer (NK) cell is a valuable tool for immunotherapy in cancer treatment, both the cultured cell line NK92 and primary NK cells are widely studied and used in research and clinical trials. Clinical observations witnessed the improvement of patients' NK cells in terms of cell counts and cytotoxic activity upon dasatinib treatment, an approved drug for chronic myeloid leukaemia and Ph+ acute lymphocytic leukaemia. Several studies supported the clinical observations, yet others argued a detrimental effect of dasatinib on NK cells. Due to the complex conditions in different studies, the definite influence of dasatinib on NK92 and primary NK cells remains to be settled. Here, we used a well-defined in vitro system to evaluate the effects of dasatinib on NK92 cells and peripheral blood (PB)-NK cells. By co-culturing NK cells with dasatinib to test the cell counts and target cell-killing activities, we surprisingly found that the chemical influenced oppositely on these two types of NK cells. While dasatinib suppressed NK92 cell proliferation and cytotoxic activity, it improved PB-NK-killing tumour cells. RNA sequencing analysis further supported this finding, uncovering several proliferating and cytotoxic pathways responding invertedly between them. Our results highlighted an intrinsic difference between NK92 and PB-NK cells and may build clues to understand how dasatinib interacts with NK cells in vivo.

Magnetic CAR T cell purification using an anti-G4S linker antibody

Chimeric antigen receptor (CAR) redirected T cells are successfully employed in the combat against several hematological malignancies, however, are often compromised by low transduction rates making refinement of the CAR T cell products necessary. Here, we report a broadly applicable enrichment protocol relying on marking CAR T cells with an anti-glycine4-serine (G4S) linker antibody followed by magnetic activated cell sorting (MACS). The protocol is broadly applicable since the G4S peptide is an integral part of the vast majority of CARs as it links the VH and VL recognition domains. We demonstrate the feasibility by using the canonical second generation CARs specific for CEA and Her2, respectively, obtaining highly purified CAR T cell products in a one-step procedure without impairing cell viability. The protocol is also applicable to a dual specific CAR (tandem CAR). Except for CD39, T cell activation/exhaustion markers were not upregulated after separation. Purified CAR T cells retained their functionality with respect to antigen-specific cytokine secretion, cytotoxicity, and the capacity to proliferate and eliminate cognate tumor cells upon repetitive stimulation. Collectively, the one-step protocol for purifying CAR T cells extends the toolbox for preclinical research and specifically for clinical CAR T cell manufacturing.

Dual T cell receptor/chimeric antigen receptor engineered NK-92 cells targeting the HPV16 E6 oncoprotein and the tumor-associated antigen L1CAM exhibit enhanced cytotoxicity and specificity against tumor cells

The human papillomavirus type 16 (HPV16) causes a large fraction of genital and oropharyngeal carcinomas. To maintain the transformed state, the tumor cells must continuously synthesize the E6 and E7 viral oncoproteins, which makes them tumor-specific antigens. Indeed, specific T cell responses against them have been well documented and CD8+ T cells engineered to express T cell receptors (TCRs) that recognize epitopes of E6 or E7 have been tested in clinical studies with promising results, yet with limited clinical success. Using CD8+ T cells from peripheral blood of healthy donors, we have identified two novel TCRs reactive to an unexplored E618-26 epitope. These TCRs showed limited standalone cytotoxicity against E618-26-HLA-A*02:01-presenting tumor cells. However, a single-signaling domain chimeric antigen receptor (ssdCAR) targeting L1CAM, a cell adhesion protein frequently overexpressed in HPV16-induced cancer, prompted a synergistic effect that significantly enhanced the cytotoxic capacity of NK-92/CD3/CD8 cells armored with both TCR and ssdCAR when both receptors simultaneously engaged their respective targets, as shown by live microscopy of 2-D and 3-D co-cultures. Thus, virus-specific TCRs from the CD8+ T cell repertoire of healthy donors can be combined with a suitable ssdCAR to enhance the cytotoxic capacity of the effector cells and, indirectly, their specificity.

Enhanced cytotoxic activity of natural killer cells from increased calcium influx induced by electrical stimulation

Natural killer (NK) cells play a crucial role in immunosurveillance independent of antigen presentation, which is regulated by signal balance via activating and inhibitory receptors. The anti-tumor activity of NK cells is largely dependent on signaling from target recognition to cytolytic degranulation; however, the underlying mechanism remains unclear, and NK cell cytotoxicity is readily impaired by tumor cells. Understanding the activation mechanism is necessary to overcome the immune evasion mechanism, which remains an obstacle in immunotherapy. Because calcium ions are important activators of NK cells, we hypothesized that electrical stimulation could induce changes in intracellular Ca2+ levels, thereby improving the functional potential of NK cells. In this study, we designed an electrical stimulation system and observed a correlation between elevated Ca2+ flux induced by electrical stimulation and NK cell activation. Breast cancer MCF-7 cells co-cultured with electrically stimulated KHYG-1 cells showed a 1.27-fold (0.5 V/cm) and 1.55-fold (1.0 V/cm) higher cytotoxicity, respectively. Electrically stimulated KHYG-1 cells exhibited a minor increase in Ca2+ level (1.31-fold (0.5 V/cm) and 1.11-fold (1.0 V/cm) higher), which also led to increased gene expression of granzyme B (GZMB) by 1.36-fold (0.5 V/cm) and 1.58-fold (1.0 V/cm) by activating Ca2+-dependent nuclear factor of activated T cell 1 (NFAT1). In addition, chelating Ca2+ influx with 5 μM BAPTA-AM suppressed the gene expression of Ca2+ signaling and lytic granule (granzyme B) proteins by neutralizing the effects of electrical stimulation. This study suggests a promising immunotherapeutic approach without genetic modifications and elucidates the correlation between cytolytic effector function and intracellular Ca2+ levels in electrically stimulated NK cells.

Preclinical evaluation and first-in-dog clinical trials of PBMC-expanded natural killer cells for adoptive immunotherapy in dogs with cancer

BACKGROUND

Natural killer (NK) cells are cytotoxic cells capable of recognizing heterogeneous cancer targets without prior sensitization, making them promising prospects for use in cellular immunotherapy. Companion dogs develop spontaneous cancers in the context of an intact immune system, representing a valid cancer immunotherapy model. Previously, CD5 depletion of peripheral blood mononuclear cells (PBMCs) was used in dogs to isolate a CD5dim-expressing NK subset prior to co-culture with an irradiated feeder line, but this can limit the yield of the final NK product. This study aimed to assess NK activation, expansion, and preliminary clinical activity in first-in-dog clinical trials using a novel system with unmanipulated PBMCs to generate our NK cell product.

METHODS

Starting populations of CD5-depleted cells and PBMCs from healthy beagle donors were co-cultured for 14 days, phenotype, cytotoxicity, and cytokine secretion were measured, and samples were sequenced using the 3'-Tag-RNA-Seq protocol. Co-cultured human PBMCs and NK-isolated cells were also sequenced for comparative analysis. In addition, two first-in-dog clinical trials were performed in dogs with melanoma and osteosarcoma using autologous and allogeneic NK cells, respectively, to establish safety and proof-of-concept of this manufacturing approach.

RESULTS

Calculated cell counts, viability, killing, and cytokine secretion were equivalent or higher in expanded NK cells from canine PBMCs versus CD5-depleted cells, and immune phenotyping confirmed a CD3-NKp46+ product from PBMC-expanded cells at day 14. Transcriptomic analysis of expanded cell populations confirmed upregulation of NK activation genes and related pathways, and human NK cells using well-characterized NK markers closely mirrored canine gene expression patterns. Autologous and allogeneic PBMC-derived NK cells were successfully expanded for use in first-in-dog clinical trials, resulting in no serious adverse events and preliminary efficacy data. RNA sequencing of PBMCs from dogs receiving allogeneic NK transfer showed patient-unique gene signatures with NK gene expression trends in response to treatment.

CONCLUSIONS

Overall, the use of unmanipulated PBMCs appears safe and potentially effective for canine NK immunotherapy with equivalent to superior results to CD5 depletion in NK expansion, activation, and cytotoxicity. Our preclinical and clinical data support further evaluation of this technique as a novel platform for optimizing NK immunotherapy in dogs.

Granzyme F: Exhaustion Marker and Modulator of Chimeric Antigen Receptor T Cell-Mediated Cytotoxicity

Granzymes are a family of proteases used by CD8 T cells to mediate cytotoxicity and other less-defined activities. The substrate and mechanism of action of many granzymes are unknown, although they diverge among the family members. In this study, we show that mouse CD8+ tumor-infiltrating lymphocytes (TILs) express a unique array of granzymes relative to CD8 T cells outside the tumor microenvironment in multiple tumor models. Granzyme F was one of the most highly upregulated genes in TILs and was exclusively detected in PD1/TIM3 double-positive CD8 TILs. To determine the function of granzyme F and to improve the cytotoxic response to leukemia, we constructed chimeric Ag receptor T cells to overexpress a single granzyme, granzyme F or the better-characterized granzyme A or B. Using these doubly recombinant T cells, we demonstrated that granzyme F expression improved T cell-mediated cytotoxicity against target leukemia cells and induced a form of cell death other than chimeric Ag receptor T cells expressing only endogenous granzymes or exogenous granzyme A or B. However, increasing expression of granzyme F also had a detrimental impact on the viability of the host T cells, decreasing their persistence in circulation in vivo. These results suggest a unique role for granzyme F as a marker of terminally differentiated CD8 T cells with increased cytotoxicity, but also increased self-directed cytotoxicity, suggesting a potential mechanism for the end of the terminal exhaustion pathway.

CD155/PVR determines acute myeloid leukemia targeting by Delta One T cells

ABSTRACT

Relapsed or refractory acute myeloid leukemia (AML) remains a major therapeutic challenge. We have recently developed a Vδ1+ γδ T cell-based product for adoptive immunotherapy, named Delta One T (DOT) cells, and demonstrated their cytolytic capacity to eliminate AML cell lines and primary blasts in vitro and in vivo. However, the molecular mechanisms responsible for the broad DOT-cell recognition of AML cells remain poorly understood. Here, we dissected the role of natural killer (NK) cell receptor ligands in AML cell recognition by DOT cells. Screening of multiple AML cell lines highlighted a strong upregulation of the DNAM-1 ligands, CD155/pulmonary vascular resistance (PVR), CD112/nectin-2, as well as the NKp30 ligand, B7-H6, in contrast with NKG2D ligands. CRISPR-mediated ablation revealed key nonredundant and synergistic contributions of PVR and B7-H6 but not nectin-2 to DOT-cell targeting of AML cells. We further demonstrate that PVR and B7-H6 are critical for the formation of robust immunological synapses between AML and DOT cells. Importantly, PVR but not B7-H6 expression in primary AML samples predicted their elimination by DOT cells. These data provide new mechanistic insight into tumor targeting by DOT cells and suggest that assessing PVR expression levels may be highly relevant to DOT cell-based clinical trials.

Kill rates by immune cells: Ratio-dependent, or mass action?

We describe a cell-based fixed-lattice model to simulate immune cell and tumor cell interaction involving MHC recognition, and FasL vs perforin lysis. We are motivated by open questions about the mechanisms behind observed kill rates of tumor cells by different types of effector cells. These mechanisms play a big role in the effectiveness of many cancer immunotherapies. The model is a stochastic cellular automaton on a hexagonal grid.

An injectable hydrogel microsphere-integrated training court to inspire tumor-infiltrating T lymphocyte potential

Although tumor-infiltrating T lymphocytes (TIL-Ts) play a crucial role in solid tumor immunotherapy, their clinical application has been limited because of the immunosuppressive microenvironment. Herein, we developed an injectable hydrogel microsphere-integrated training court (MS-ITC) to inspire the function of TIL-Ts and amplify TIL-Ts, through grafting with anti-CD3 and anti-CD28 antibodies and bovine serum albumin nanoparticles encapsulated with IL-7 and IL-15. MS-ITC provided the T-cell receptor and co-stimulatory signals required for TIL-Ts activation and IL-7/IL-15 signals for TIL-Ts expansion. Afterward, the MS-ITC was injected locally into the osteosarcoma tumor tissue in mice. MS-ITC suppressed the growth of primary osteosarcoma by more than 95 %, accompanied with primed and expanded TIL-Ts in the tumor tissues, compromising significantly increased CD8+ T and memory T cells, thereby enhancing the anti-tumor effect. Together, this work provides an injectable hydrogel microsphere-integrated training platform capable of inspiring TIL-Ts potential for a range of solid tumor immunotherapy.

Immune Cytolytic Activity and Strategies for Therapeutic Treatment

Intratumoral immune cytolytic activity (CYT), calculated as the geometric mean of granzyme-A (GZMA) and perforin-1 (PRF1) expression, has emerged as a critical factor in cancer immunotherapy, with significant implications for patient prognosis and treatment outcomes. Immune checkpoint pathways, the composition of the tumor microenvironment (TME), antigen presentation, and metabolic pathways regulate CYT. Here, we describe the various methods with which we can assess CYT. The detection and analysis of tumor-infiltrating lymphocytes (TILs) using flow cytometry or immunohistochemistry provide important information about immune cell populations within the TME. Gene expression profiling and spatial analysis techniques, such as multiplex immunofluorescence and imaging mass cytometry allow the study of CYT in the context of the TME. We discuss the significant clinical implications that CYT has, as its increased levels are associated with positive clinical outcomes and a favorable prognosis. Moreover, CYT can be used as a prognostic biomarker and aid in patient stratification. Altering CYT through the different methods targeting it, offers promising paths for improving treatment responses. Overall, understanding and modulating CYT is critical for improving cancer immunotherapy. Research into CYT and the factors that influence it has the potential to transform cancer treatment and improve patient outcomes.

Are tumor-associated carbohydrates the missing link between the gut microbiome and response to immune checkpoint inhibitor treatment in cancer?

Immune checkpoint inhibitor therapy has dramatically improved survival in a significant subset of patients with several solid tumor types. Increasing the number of patients benefitting from this form of therapy is an important translational research goal. Correlations between the composition of the gut microbiome and response to immune checkpoint inhibitor therapy raised the possibility that direct modulation of the gut microbiome may significantly improve the clinical benefit of this treatment. Several lines of observations suggest that tumor-associated carbohydrates, including those recognized as blood group-related glycolipid antigens, such as the Forssman antigen, may be some of the key factors behind this clinical correlation. Such antigens are expressed in human cancer, humans often produce antibodies against those, and they can induce antibody directed cellular cytotoxicity. Importantly, these antibodies are often induced by antigens present in microbes of the gut. If identified, these antibodies could be boosted by appropriate vaccination techniques and thus enhance anti-tumor immunity with minimal side effects.

KIR2DS1 and KIR2DL1-C245 Dominantly Repress NK Cell Degranulation Triggered by Monoclonal or Bispecific Antibodies, whereas Education by Uptuning Inhibitory Killer Ig-related Receptors Exerts No Advantage in Ab-dependent Cellular Cytotoxicity

NK cell responsiveness to target cells is tuned by interactions between inhibitory NK cell receptors and their cognate HLA class I ligands in a process termed "NK cell education." Previous studies addressing the role for NK cell education in Ab-dependent cellular cytotoxicity (ADCC) show ambiguous results and do not encompass full educational resolution. In this study, we systematically characterized human NK cell CD16-triggered degranulation toward defined human tumor cell lines in the presence of either the mAb rituximab or a recently developed CD34xCD16 bispecific killer engager. Despite positive correlation between killer Ig-related receptor (KIR)-mediated education and CD16 expression, NK cells educated by one or even two inhibitory KIRs did not perform better in terms of ADCC than uneducated NK cells in either missing-self or KIR-ligand matched settings at saturating Ab concentrations. Instead, NKG2A+ NK cells consistently showed more potent ADCC in the missing-self context despite lower levels of CD16 expression. KIR2DS1+ NK cells demonstrated dampened ADCC in both the missing-self and KIR-ligand matched settings, even in the presence of its ligand HLA C2. The lower response by KIR2DS1+ NK cells was also observed when stimulated with a bispecific killer engager. Surprisingly, repression of ADCC was also observed by NKG2A+ NK cells coexpressing the inhibitory KIR2DL1-C245 receptor that confers weak education. In conclusion, our study suggests that NK cell education by inhibitory KIRs does not augment ADCC per se, whereas expression of KIR2DS1 and KIR2DL1-C245 dominantly represses ADCC. These insights add to the fundamental understanding of NK cells and may have implications for their therapeutic use.

Bispecific antibodies promote natural killer cell-mediated elimination of HIV-1 reservoir cells

The persistence of CD4+ T cells carrying latent human immunodeficiency virus-1 (HIV-1) proviruses is the main barrier to a cure. New therapeutics to enhance HIV-1-specific immune responses and clear infected cells will probably be necessary to achieve reduction of the latent reservoir. In the present study, we report two single-chain diabodies (scDbs) that target the HIV-1 envelope protein (Env) and the human type III Fcγ receptor (CD16). We show that the scDbs promoted robust and HIV-1-specific natural killer (NK) cell activation and NK cell-mediated lysis of infected cells. Cocultures of CD4+ T cells from people with HIV-1 on antiretroviral therapy (ART) with autologous NK cells and the scDbs resulted in marked elimination of reservoir cells that was dependent on latency reversal. Treatment of human interleukin-15 transgenic NSG mice with one of the scDbs after ART initiation enhanced NK cell activity and reduced reservoir size. Thus, HIV-1-specific scDbs merit further evaluation as potential therapeutics for clearance of the latent reservoir.

A Noncanonical CD56dimCD16dim/- NK Cell Subset Indicative of Prior Cytotoxic Activity Is Elevated in Patients with Autoantibody-Mediated Neurologic Diseases

Neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein Ab disease, and autoimmune myasthenia gravis (MG) are autoantibody-mediated neurologic conditions where autoantibodies can induce Ab-dependent cellular cytotoxicity (ADCC), a NK cell-mediated effector function. However, whether ADCC is a pathogenic mechanism in patients with these conditions has not been confirmed. We sought to characterize circulatory NK cells using functional assays, phenotyping, and transcriptomics to elucidate their role in pathology. NK cells from NMOSD patients and MG patients with elevated disease burden exhibited reduced ADCC and CD56dimCD16hi NK cells, along with an elevated frequency of CD56dimCD16dim/- NK cells. We determined that ADCC induces a similar phenotypic shift in vitro. Bulk RNA sequencing distinguished the CD56dimCD16dim/- population from the canonical CD56dimCD16hi cytotoxic and CD56hiCD16- immunomodulatory subsets, as well as CD56hiCD16+ NK cells. Multiparameter immunophenotyping of NK cell markers, functional proteins, and receptors similarly showed that the CD56dimCD16dim/- subset exhibits a unique profile while still maintaining expression of characteristic NK markers CD56, CD94, and NKp44. Notably, expression of perforin and granzyme is reduced in comparison with CD56dimCD16hi NK cells. Moreover, they exhibit elevated trogocytosis capability, HLA-DR expression, and many chemokine receptors, including CCR7. In contrast with NMOSD and MG, myelin oligodendrocyte glycoprotein Ab disease NK cells did not exhibit functional, phenotypic, or transcriptomic perturbations. In summary, CD56dimCD16dim/- NK cells are a distinct peripheral blood immune cell population in humans elevated upon prior cytotoxic activity by the CD56dimCD16hi NK cell subset. The elevation of this subset in NMOSD and MG patients suggests prior ADCC activity.

Identification, sorting and profiling of functional killer cells via the capture of fluorescent target-cell lysate

Assays for assessing cell-mediated cytotoxicity are largely target-cell-centric and cannot identify and isolate subpopulations of cytotoxic effector cells. Here we describe an assay compatible with flow cytometry for the accurate identification and sorting of functional killer-cell subpopulations in co-cultures. The assay, which we named PAINTKiller (for 'proximity affinity intracellular transfer identification of killer cells'), relies on the detection of an intracellular fluorescent protein 'painted' by a lysed cell on the surface of the lysing cytotoxic cell (specifically, on cell lysis the intracellular fluorescein derivative carboxyfluorescein succinimidyl ester is captured on the surface of the natural killer cell by an antibody for anti-fluorescein isothiocyanate linked to an antibody for the pan-leucocyte surface receptor CD45). The assay can be integrated with single-cell RNA sequencing for the analysis of molecular pathways associated with cell cytotoxicity and may be used to uncover correlates of functional immune responses.

Nano-chemical priming strategy to enhance TGF-β resistance and anti-tumor activity of natural killer cells

Immunotherapy based on adoptive transfer of natural killer (NK) cells is a promising strategy for circumventing the limitations of cancer treatments. However, components of the immunosuppressive tumor microenvironment (TME), such as transforming growth factor-beta (TGF-β), compromise the therapeutic efficacy of NK cells significantly. To address these limitations, we developed a novel method of engineering NK cells for adaptive transfer. The method is based on nanogels that serve two functions: (1) they overcome the TGF-β-mediated stress environment of the TME, and (2) they enhance the direct anti-tumor activity of NK cells. Previously, we demonstrated that cationic compounds such as 25 K branched polyethylenimine (25 K bPEI) prime NK cells, putting them in a 'ready-to-fight' state. Based on these findings, we designed nanogels that have two primary characteristics: (1) they encapsulate galunisertib (Gal), which is used clinically to inhibit TGF-β receptor activity, thereby blocking TGF-β signaling; and (2) they provide cells with a surface coating of 25 K bPEI. When grown in culture medium containing TGF-β, nanogel-treated NK cells demonstrated greater migration ability, degranulation activity, and cytotoxicity towards cancer cells than untreated NK cells. Additionally, the in vivo efficacy of nanogel-treated NK cells against PC-3 xenografts was significantly greater than that of Chem_NK cells primed by 25 K bPEI alone. These findings suggest that Gal-loaded 25 K bPEI-coated nanogels exert anti-tumor effects via chemical priming, as well suppressing the effects of TGF-β on NK cells. We also expect 25 K bPEI-based nanogels to have great potential to overcome the suppressive effects of the TME through their NK cell-priming activity and delivery of the desired chemicals.

Blockade of CD300A enhances the ability of human NK cells to lyse hematologic malignancies

OBJECTIVE

The human cluster of differentiation (CD)300A, a type-I transmembrane protein with immunoreceptor tyrosine-based inhibitory motifs, was investigated as a potential immune checkpoint for human natural killer (NK) cells targeting hematologic malignancies (HMs).

METHODS

We implemented a stimulation system involving the CD300A ligand, phosphatidylserine (PS), exposed to the outer surface of malignant cells. Additionally, we utilized CD300A overexpression, a CD300A blocking system, and a xenotransplantation model to evaluate the impact of CD300A on NK cell efficacy against HMs in in vitro and in vivo settings. Furthermore, we explored the association between CD300A and HM progression in patients.

RESULTS

Our findings indicated that PS hampers the function of NK cells. Increased CD300A expression inhibited HM lysis by NK cells. CD300A overexpression shortened the survival of HM-xenografted mice by impairing transplanted NK cells. Blocking PS-CD300A signals with antibodies significantly amplified the expression of lysis function-related proteins and effector cytokines in NK cells, thereby augmenting the ability to lyse HMs. Clinically, heightened CD300A expression correlated with shorter survival and an "exhausted" phenotype of intratumoral NK cells in patients with HMs or solid tumors.

CONCLUSIONS

These results propose CD300A as a potential target for invigorating NK cell-based treatments against HMs.

Cell softness renders cytotoxic T lymphocytes and T leukemic cells resistant to perforin-mediated killing

Mechanical force contributes to perforin pore formation at immune synapses, thus facilitating the cytotoxic T lymphocytes (CTL)-mediated killing of tumor cells in a unidirectional fashion. How such mechanical cues affect CTL evasion of perforin-mediated autolysis remains unclear. Here we show that activated CTLs use their softness to evade perforin-mediated autolysis, which, however, is shared by T leukemic cells to evade CTL killing. Downregulation of filamin A is identified to induce softness via ZAP70-mediated YAP Y357 phosphorylation and activation. Despite the requirements of YAP in both cell types for softness induction, CTLs are more resistant to YAP inhibitors than malignant T cells, potentially due to the higher expression of the drug-resistant transporter, MDR1, in CTLs. As a result, moderate inhibition of YAP stiffens malignant T cells but spares CTLs, thus allowing CTLs to cytolyze malignant cells without autolysis. Our findings thus hint a mechanical force-based immunotherapeutic strategy against T cell leukemia.

Pterostilbene upregulates MICA/B via the PI3K/AKT signaling pathway to enhance the capability of natural killer cells to kill cervical cancer cells

Natural killer (NK) cells are triggered by the innate immune response in the tumor microenvironment. The extensive set of stimulating and inhibiting receptors mediates the target recognition of NK cells, and controls the strength of the effector reaction countering specific targeted cells. Yet, lacking major MHC (histocompatibility complex) MICA/B class I chain-related proteins on the membrane of tumor cells results in the failure of NK cell recognition and ability to resist NK cell destruction. Searching databases and molecular docking suggested that in cervical cancer, pterostilbene (3,5-dimethoxy-40-hydroxystilbene; PTS) in Vaccinium corymbosum extract could constrain PI3K/AKT signaling and improving the MICA/B expression. In flow cytometry, MTT assay, viability/cytotoxicity assay, and colony development assays, PTS reduced the development of cervical cancer cells and increased apoptosis. The quantitative real-time PCR (qRT-PCR) and a Western blot indicate that PTS controlled the cytolytic action of NK cells in tumor cells via increasing the MICA/B expression, thus modifying the anti-tumor immune response in cervical cancer.

Elevated levels of cell-free NKG2D-ligands modulate NKG2D surface expression and compromise NK cell function in severe COVID-19 disease

Introduction

It is now clear that coronavirus disease 19 (COVID-19) severity is associated with a dysregulated immune response, but the relative contributions of different immune cells is still not fully understood. SARS CoV-2 infection triggers marked changes in NK cell populations, but there are contradictory reports as to whether these effector lymphocytes play a protective or pathogenic role in immunity to SARS-CoV-2.

Methods

To address this question we have analysed differences in the phenotype and function of NK cells in SARS-CoV-2 infected individuals who developed either very mild, or life-threatening COVID-19 disease.

Results

Although NK cells from patients with severe disease appeared more activated and the frequency of adaptive NK cells was increased, they were less potent mediators of ADCC than NK cells from patients with mild disease. Further analysis of peripheral blood NK cells in these patients revealed that a population of NK cells that had lost expression of the activating receptor NKG2D were a feature of patients with severe disease and this correlated with elevated levels of cell free NKG2D ligands, especially ULBP2 and ULBP3 in the plasma of critically ill patients. In vitro, culture in NKG2DL containing patient sera reduced the ADCC function of healthy donor NK cells and this could be blocked by NKG2DL-specific antibodies.

Discussion

These observations of reduced NK function in severe disease are consistent with the hypothesis that defects in immune surveillance by NK cells permit higher levels of viral replication, rather than that aberrant NK cell function contributes to immune system dysregulation and immunopathogenicity.

IL-15-secreting CAR natural killer cells directed toward the pan-cancer target CD70 eliminate both cancer cells and cancer-associated fibroblasts

BACKGROUND

It remains challenging to obtain positive outcomes with chimeric antigen receptor (CAR)-engineered cell therapies in solid malignancies, like colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC). A major obstacle is the lack of targetable surface antigens that are not shared by healthy tissues. CD70 emerges as interesting target, due to its stringent expression pattern in healthy tissue and its apparent role in tumor progression in a considerable amount of malignancies. Moreover, CD70 is also expressed on cancer-associated fibroblasts (CAFs), another roadblock for treatment efficacy in CRC and PDAC. We explored the therapeutic potential of CD70 as target for CAR natural killer (NK) cell therapy in CRC, PDAC, focusing on tumor cells and CAFs, and lymphoma.

METHODS

RNA-seq data and immunohistochemical analysis of patient samples were used to explore CD70 expression in CRC and PDAC patients. In addition, CD70-targeting CAR NK cells were developed to assess cytotoxic activity against CD70+ tumor cells and CAFs, and the effect of cytokine stimulation on their efficacy was evaluated. The in vitro functionality of CD70-CAR NK cells was investigated against a panel of tumor and CAF cell lines with varying CD70 expression. Lymphoma-bearing mice were used to validate in vivo potency of CD70-CAR NK cells. Lastly, to consider patient variability, CD70-CAR NK cells were tested on patient-derived organoids containing CAFs.

RESULTS

In this study, we identified CD70 as a target for tumor cells and CAFs in CRC and PDAC patients. Functional evaluation of CD70-directed CAR NK cells indicated that IL-15 stimulation is essential to obtain effective elimination of CD70+ tumor cells and CAFs, and to improve tumor burden and survival of mice bearing CD70+ tumors. Mechanistically, IL-15 stimulation resulted in improved potency of CD70-CAR NK cells by upregulating CAR expression and increasing secretion of pro-inflammatory cytokines, in a mainly autocrine or intracellular manner.

CONCLUSIONS

We disclose CD70 as an attractive target both in hematological and solid tumors. IL-15 armored CAR NK cells act as potent effectors to eliminate these CD70+ cells. They can target both tumor cells and CAFs in patients with CRC and PDAC, and potentially other desmoplastic solid tumors.

The Power of Three: Nanomaterials for Natural Killer (NK) Cell Immunoengineering Maximize Their Potency if They Exploit Multireceptor Stimulation

Many emerging cancer treatments are immunotherapies that modulate Natural Killer- (NK) or T cell activation, posing a challenge to develop immunoengineering nanomaterials that improve on the performance of molecular reagents. In physiological activation, multiple immunoreceptors signal in consort; however, current biomaterials do not replicate this. Here, NK cells are created for the first time, activating bionanomaterials that stimulate >2 immunoreceptors. Nanoclusters of monoclonal antibodies (mAb), templated by nanoscale graphene oxide sheets (NGO) (≈75 nm size), are exploited. To inform nanoreagent design, a model system of planar substrates with anchored mAb is first investigated. Combining mAb that stimulates three NK cell activating receptors (αNKP46 + αNKG2D + αDNAM-1), activated NK cells act more potently than any single receptor or pair. Applying this insight, an NGO-mAb nanocluster combining three distinct mAb: NGO-mAb(αNKP46 + αNKG2D + αDNAM-1) is created. This construct is potent and outperforms single-receptor-simulating nanoclusters, activating nearly twice as many NK cells as NGO-mAb(αNKP46) at a similar mAb dose or delivering similar activation at 10× lower dosage. Further, NGO-mAb are more potent than planar substrates for both single- and triple-mAb stimulation. These results imply a new concept for immunoengineering biomaterials: both nanoclustering and multi-receptor stimulation should be incorporated for maximum effect.

ERG mediates the inhibition of NK cell cytotoxicity through the HLX/STAT4/Perforin signaling pathway, thereby promoting the progression of myocardial infarction

This study aimed to investigate the role of ERG in the HLX/STAT4/Perforin signaling axis, impacting natural killer (NK) cell cytotoxicity and myocardial infarction (MI) progression. NK cell cytotoxicity was assessed via co-culture and 51Cr release assays. Datasets GSE34198 and GSE97320 identified common differentially expressed genes in MI. NK cell gene expression was analyzed in MI patients and healthy individuals using qRT-PCR and Western blotting. ERG's regulation of HLX and STAT4's regulation of perforin were studied through computational tools (MEM) and ChIP experiments. HLX's influence on STAT4 was explored with the MG132 proteasome inhibitor. Findings were validated in a mouse MI model.ERG, a commonly upregulated gene, was identified in NK cells from MI patients and mice. ERG upregulated HLX, leading to STAT4 proteasomal degradation and reduced Perforin expression. Consequently, NK cell cytotoxicity decreased, promoting MI progression. ERG mediates the HLX/STAT4/Perforin axis to inhibit NK cell cytotoxicity, fostering MI progression. These results provide vital insights into MI's molecular mechanisms.

High and selective cytotoxicity of ex vivo expanded allogeneic human natural killer cells from peripheral blood against bladder cancer: implications for natural killer cell instillation after transurethral resection of bladder tumor

BACKGROUND

Non-muscle-invasive bladder cancer (NMIBC) is treated with transurethral resection of bladder tumor (TURBT) followed by intravesical instillation of chemotherapy or Bacillus Calmette-Guérin therapy. However, these treatments have a high recurrence rate and side effects, emphasizing the need for alternative instillations. Previously, we revealed that expanded allogeneic human natural killer (NK) cells from peripheral blood are a promising cellular therapy for prostate cancer. However, whether NK cells exhibit a similar killing effect in bladder cancer (BCa) remains unknown.

METHODS

Expansion, activation, and cryopreservation of allogeneic human NK cells obtained from peripheral blood were performed as we previously described. In vitro cytotoxicity was evaluated using the cell counting kit-8. The levels of perforin, granzyme B, interferon-γ, tumor necrosis factor-α, and chemokines (C-C-motif ligand [CCL]1, CCL2, CCL20, CCL3L1, and CCL4; C-X-C-motif ligand [CXCL]1, CXCL16, CXCL2, CXCL3, and CXCL8; and X-motif ligand 1 and 2) were determined using enzyme-linked immunosorbent assay. The expression of CD107a, major histocompatibility complex class I (MHC-I), MHC-I polypeptide-related sequences A and B (MICA/B), cytomegalovirus UL16-binding protein-2/5/6 (ULBP-2/5/6), B7-H6, CD56, CD69, CD25, killer cell Ig-like receptors (KIR)2DL1, KIRD3DL1, NKG2D, NKp30, NKp46, and CD16 of NK cells or BCa and normal urothelial cells were detected using flow cytometry. Cytotoxicity was evaluated using lactate dehydrogenase assay in patient-derived organoid models. BCa growth was monitored in vivo using calipers in male NOD-scid IL2rg-/- mice subcutaneously injected with 5637 and NK cells. Differential gene expressions were investigated using RNA sequence analysis. The chemotaxis of T cells was evaluated using transwell migration assays.

RESULTS

We revealed that the NK cells possess higher cytotoxicity against BCa lines with more production of cytokines than normal urothelial cells counterparts in vitro, demonstrated by upregulation of degranulation marker CD107a and increased interferon-γ secretion, by MICA/B/NKG2D and B7H6/NKp30-mediated activation. Furthermore, NK cells demonstrated antitumor effects against BCa in patient-derived organoids and BCa xenograft mouse models. NK cells secreted chemokines, including CCL1/2/20, to induce T-cell chemotaxis when encountering BCa cells.

CONCLUSIONS

The expanded NK cells exhibit potent cytotoxicity against BCa cells, with few toxic side effects on normal urothelial cells. In addition, NK cells recruit T cells by secreting a panel of chemokines, which supports the translational application of NK cell intravesical instillation after TURBT from bench to bedside for NMIBC treatment.

IL-12 reprograms CAR-expressing natural killer T cells to long-lived Th1-polarized cells with potent antitumor activity

Human natural killer T cells (NKTs) are innate-like T lymphocytes increasingly used for cancer immunotherapy. Here we show that human NKTs expressing the pro-inflammatory cytokine interleukin-12 (IL-12) undergo extensive and sustained molecular and functional reprogramming. Specifically, IL-12 instructs and maintains a Th1-polarization program in NKTs in vivo without causing their functional exhaustion. Furthermore, using CD62L as a marker of memory cells in human NKTs, we observe that IL-12 maintains long-term CD62L-expressing memory NKTs in vivo. Notably, IL-12 initiates a de novo programming of memory NKTs in CD62L-negative NKTs indicating that human NKTs circulating in the peripheral blood possess an intrinsic differentiation hierarchy, and that IL-12 plays a role in promoting their differentiation to long-lived Th1-polarized memory cells. Human NKTs engineered to co-express a Chimeric Antigen Receptor (CAR) coupled with the expression of IL-12 show enhanced antitumor activity in leukemia and neuroblastoma tumor models, persist long-term in vivo and conserve the molecular signature driven by the IL-12 expression. Thus IL-12 reveals an intrinsic plasticity of peripheral human NKTs that may play a crucial role in the development of cell therapeutics.

Concomitant assessment of PD-1 and CD56 expression identifies subsets of resting cord blood Vδ2 T cells with disparate cytotoxic potential

Vγ9Vδ2 T lymphocytes are programmed for broad antimicrobial responses with rapid production of Th1 cytokines even before birth, and thus thought to play key roles against pathogens in infants. The process regulating Vδ2 cell acquisition of cytotoxic potential shortly after birth remains understudied. We observed that perforin production in cord blood Vδ2 cells correlates with phenotypes defined by the concomitant assessment of PD-1 and CD56. Bulk RNA sequencing of sorted Vδ2 cell fractions indicated that transcripts related to cytotoxic activity and NK function are enriched in the subset with the highest proportion of perforin+ cells. Among differentially expressed transcripts, IRF8, previously linked to CD8 T cell effector differentiation and NK maturation, has the potential to mediate Vδ2 cell differentiation towards cytotoxic effectors. Our current and past results support the hypothesis that distinct mechanisms regulate Vδ2 cell cytotoxic function before and after birth, possibly linked to different levels of microbial exposure.

TRAIL-conjugated liposomes that bind natural killer cells to induce colorectal cancer cell apoptosis

Natural killer (NK) cell functionality is a strong indicator of favorable prognosis in cancer patients, making NK cells an appealing therapeutic target to prevent lymph node dissemination. We engineered liposomes that are conjugated with anti-CD335 antibodies for NK cell targeting, and the apoptotic ligand TRAIL to kill cancer cells. Liposomes were made using a thin film hydration method followed by extrusion to approximately 100 nm in diameter and conjugation of proteins via thiol-maleimide click chemistry. TRAIL/anti-CD335 liposomes successfully bound to isolated NK cells. Once piggybacked to the surface of NK cells, these "Super Natural Killer Cells" were able to more effectively kill oxaliplatin-resistant SW620 cells and metastatic COLO205 colorectal cancer cells via TRAIL-mediated apoptosis compared to NK cells alone. Importantly, Super NK cells were more effective under physiological levels of fluid shear stress found in the lymphatics. Liposome biodistribution after intravenous administration confirmed the sustained presence of liposomes within the spleen and tumor draining mesenteric lymph nodes for at least 4 days. These results demonstrate the enhanced apoptotic effects of NK cells armored with liposomal TRAIL against clinically relevant colorectal cancer cells, providing the groundwork for in vivo treatment studies in mouse models of colorectal cancer metastasis.

Harnessing the Power of CAR-NK Cells: A Promising Off-the-Shelf Therapeutic Strategy for CD38-Positive Malignancies

Background

CD38 is highly expressed on multiple myeloma (MM) cells and has been successfully targeted by different target therapy methods. This molecule is a critical prognostic marker in both diffuse large B-cell lymphoma and chronic lymphocytic leukemia.

Objective

We have designed and generated an anti-CD38 CAR-NK cell applying NK 92 cell line. The approach has potential application as an off-the-shelf strategy for treatment of CD38 positive malignancies.

Methods

A second generation of anti-CD38 CAR-NK cell was designed and generated, and their efficacy against CD38-positive cell lines was assessed in vitro. The PE-Annexin V and 7-AAD methods were used to determine the percentage of apoptotic target cells. Flow cytometry was used to measure IFN-γ, Perforin, and Granzyme-B production following intracellular staining. Using in silico analyses, the binding capacity and interaction interface were evaluated.

Results

Using Lentivirus, cells were transduced with anti-CD38 construct and were expanded. The expression of anti-CD38 CAR on the surface of NK 92 cells was approximately 25%. As we expected from in silico analysis, our designed CD38-chimeric antigen receptor was bound appropriately to the CD38 protein. NK 92 cells that transduced with the CD38 chimeric antigen receptor, generated significantly more IFN-γ, perforin, and granzyme than Mock cells, and successfully lysed Daudi and Jurkat malignant cells in a CD38-dependent manner.

Conclusion

The in vitro findings indicated that the anti-CD38 CAR-NK cells have the potential to be used as an off-the-shelf therapeutic strategy against CD38-positive malignancies. It is recommended that the present engineered NK cells undergo additional preclinical investigations before they can be considered for subsequent clinical trial studies.

HIV vaccines induce CD8+ T cells with low antigen receptor sensitivity

Current HIV vaccines designed to stimulate CD8+ T cells have failed to induce immunologic control upon infection. The functions of vaccine-induced HIV-specific CD8+ T cells were investigated here in detail. Cytotoxic capacity was significantly lower than in HIV controllers and was not a consequence of low frequency or unaccumulated functional cytotoxic proteins. Low cytotoxic capacity was attributable to impaired degranulation in response to the low antigen levels present on HIV-infected targets. The vaccine-induced T cell receptor (TCR) repertoire was polyclonal and transduction of these TCRs conferred the same reduced functions. These results define a mechanism accounting for poor antiviral activity induced by these vaccines and suggest that an effective CD8+ T cell response may require a vaccination strategy that drives further TCR clonal selection.

Advances in research based on antibody-cell conjugation

Antibody-cell conjugation (ACC) technology is a new research direction in medicine and biotechnology in recent years. The concept of ACC was proposed by Hsiao et al. and developed into a viable cell therapy technology, which refers to the cells with specific functions. Such as natural killer cells (NK cells), cytokine induced killer cells (CIK) and other immune cells and monoclonal antibodies through the linker together formed conjugate. ACC directly modifies specific antibodies on the cell surface through a simple and effective chemical coupling method to enable cells to have new functions. ACC has been developed for the treatment of various diseases, including cancers of the blood system and solid tumors. This paper reviews the current ACC construction methods, challenges and future development directions.

Limocitrin increases cytotoxicity of KHYG-1 cells against K562 cells by modulating MAPK pathway

Natural killer (NK) cells are gaining popularity in the field of cancer immunotherapy. The present study was designed to investigate the effect of a natural flavonol compound limocitrin in increasing cytotoxicity of a permanent NK leukemia cell line KHYG-1 against an aggressive leukemia cell line K562. The findings revealed that limocitrin increased the expressions of cytolytic molecules perforin, granzymes A and B, and granulysin in KHYG-1 cells by inducing phosphorylation of transcription factor CREB, leading to increased lysis of K562 cells. Mechanistically, limocitrin was found to increase the expressions of t-Bid, cleaved caspase 3, and cleaved PARP to induce K562 cell apoptosis. Moreover, limocitrin reduced the expressions of SET and Ape1 to inhibit DNA repair mechanism, leading to caspase-independent K562 cell death. At the molecular level, limocitrin was found to increase the phosphorylation of ERK, p38, and JNK to increase granzyme B expression in KHYG-1 cells. Taken together, the study indicates that limocitrin increases cytotoxicity of NK cells against a range of cancer cells.

Exploring TCR-like CAR-Engineered Lymphocyte Cytotoxicity against MAGE-A4

TCR-like chimeric antigen receptor (CAR-T) cell therapy has emerged as a game-changing strategy in cancer immunotherapy, offering a broad spectrum of potential antigen targets, particularly in solid tumors containing intracellular antigens. In this study, we investigated the cytotoxicity and functional attributes of in vitro-generated T-lymphocytes, engineered with a TCR-like CAR receptor precisely targeting the cancer testis antigen MAGE-A4. Through viral transduction, T-cells were genetically modified to express the TCR-like CAR receptor and co-cultured with MAGE-A4-expressing tumor cells. Flow cytometry analysis revealed a significant surge in cells expressing activation markers CD69, CD107a, and FasL upon encountering tumor cells, indicating robust T-cell activation and cytotoxicity. Moreover, immune transcriptome profiling unveiled heightened expression of pivotal T-effector genes involved in immune response and cell proliferation regulation. Additionally, multiplex assays also revealed increased cytokine production and cytotoxicity driven by granzymes and soluble Fas ligand (sFasL), suggesting enhanced anti-tumor immune responses. Preliminary in vivo investigations revealed a significant deceleration in tumor growth, highlighting the therapeutic potential of these TCR-like CAR-T cells. Further investigations are warranted to validate these revelations fully and harness the complete potential of TCR-like CAR-T cells in overcoming cancer's resilient defenses.

Surface nanotopography and cell shape modulate tumor cell susceptibility to NK cell cytotoxicity

Natural killer (NK) cells are innate cytotoxic lymphocytes exerting cytotoxicity against virally infected cells and tumor cells. NK cell cytotoxicity is primarily determined by biochemical signals received from ligands expressed on target cell surfaces, but it is also possible that biophysical environments of tumor cells, such as nanoscale surface topography typically existing on extracellular matrixes (ECMs) or cell morphology determined by ECM spaces or cell density, regulate NK cell cytotoxicity. In this study, micro/nanofabrication technology was applied to examine this possibility. Tumor cells were plated on flat or nanogrooved surfaces, or micropatterned into circular or elliptical geometries, and the effects of surface topography and tumor cell morphology on NK cell cytotoxicity were investigated. NK cells exhibited significantly higher cytotoxicity against tumor cells on nanogrooved surfaces or tumor cells in elliptical patterns than tumor cells on flat surfaces or tumor cells in circular patterns, respectively. The amounts of stress fiber formation in tumor cells positively correlated with NK cell cytotoxicity, indicating that increased cellular tension of tumor cells, either mediated by nanogrooved surfaces or elongated morphologies, was a key factor regulating NK cell cytotoxicity. These results may provide insight into the design of NK cell-based cancer immunotherapy.

Chimeric HLA antibody receptor T cells to target HLA-specific B cells in solid organ transplantation

HLA-sensitized patients on the transplant waiting list harbor antibodies and memory B cells directed against allogeneic HLA molecules, which decreases the chance to receive a compatible donor organ. Current desensitization strategies non-specifically target circulating antibodies and B cells, warranting the development of therapies that specifically affect HLA-directed humoral immune responses. We developed Chimeric HLA Antibody Receptor (CHAR) constructs comprising the extracellular part of HLA-A2 or HLA-A3 coupled to CD28-CD3ζ domains. CHAR-transduced cells expressing reporter constructs encoding T-cell activation markers, and CHAR-transduced CD8+ T cells from healthy donors were stimulated with HLA-specific monoclonal antibody-coated microbeads, and HLA-specific B cell hybridomas. CHAR T cell activation was measured by upregulation of T cell activation markers and IFNγ secretion, whereas CHAR T cell killing of B cell hybridomas was assessed in chromium release assays and by IgG ELISpot. HLA-A2- and HLA-A3-CHAR expressing cells were specifically activated by HLA-A2- and HLA-A3-specific monoclonal antibodies, either soluble or coated on microbeads, as shown by CHAR-induced transcription factors. HLA-A2 and HLA-A3 CHAR T cells efficiently produced IFNγ with exquisite specificity and were capable of specifically lysing hybridoma cells expressing HLA-A2- or HLA-A3-specific B-cell receptors, respectively. Finally, we mutated the α3 domain of the CHAR molecules to minimize any alloreactive T-cell reactivity against CHAR T cells, while retaining CHAR activity. These data show proof of principle for CHAR T cells to serve as precision immunotherapy to specifically desensitize (highly) sensitized solid organ transplant candidates and to treat antibody-mediated rejection after solid organ transplantation.

Functional TRPA1 Channels Regulate CD56dimCD16+ NK Cell Cytotoxicity against Tumor Cells

Transient receptor potential ankyrin 1 (TRPA1) channels are expressed on the surface of different cell types, including immune cells. However, TRPA1's role in the context of innate and adaptive immune responses has not been fully elucidated so far. In this study, we aimed at investigating the expression and function of TRPA1 channels on NK cells. Among NK cells, TRPA1 was highly expressed by the CD56dimCD16+ subpopulation, but not by CD56brightCD16- cells, as detected by FACS. TRPA1 activation with the potent ligand allyl isothiocyanate (AITC) induces intracellular calcium flux in CD56dimCD16+ cells, which was prevented by the TRPA1 antagonist HC-030031. AITC treatment increased the membrane around NKp44 and strongly decreased CD16 and CD8 expression, while CD158a, CD159a, NKG2d, NKp46 were substantially unaffected. Importantly, AITC increased the granzyme production and CD107 expression and increased NK cell-mediated cytotoxicity towards the K562 cell line and two different melanoma cell lines. In parallel, TRPA1 activation also plays regulatory roles by affecting the survival of NK cells to limit uncontrolled and prolonged NK cell-mediated cytotoxicity. Our results indicate that the activation of TRPA1 is an important regulatory signal for NK cells, and agonists of TRPA1 could be used to strengthen the tumor response of the immune system.

Modulation of lytic molecules restrain serial killing in γδ T lymphocytes

γδ T cells play a pivotal role in protection against various types of infections and tumours, from early childhood on and throughout life. They consist of several subsets characterised by adaptive and innate-like functions, with Vγ9Vδ2 being the largest subset in human peripheral blood. Although these cells show signs of cytotoxicity, their modus operandi remains poorly understood. Here we explore, using live single-cell imaging, the cytotoxic functions of γδ T cells upon interactions with tumour target cells with high temporal and spatial resolution. While γδ T cell killing is dominated by degranulation, the availability of lytic molecules appears tightly regulated in time and space. In particular, the limited co-occurrence of granzyme B and perforin restrains serial killing of tumour cells by γδ T cells. Thus, our data provide new insights into the cytotoxic arsenal and functions of γδ T cells, which may guide the development of more efficient γδ T cell based adoptive immunotherapies.

CPT1A-mediated fatty acid oxidation confers cancer cell resistance to immune-mediated cytolytic killing

Although tumor-intrinsic fatty acid β-oxidation (FAO) is implicated in multiple aspects of tumorigenesis and progression, the impact of this metabolic pathway on cancer cell susceptibility to immunotherapy remains unknown. Here, we report that cytotoxicity of killer T cells induces activation of FAO and upregulation of carnitine palmitoyltransferase 1A (CPT1A), the rate-limiting enzyme of FAO in cancer cells. The repression of CPT1A activity or expression renders cancer cells more susceptible to destruction by cytotoxic T lymphocytes. Our mechanistic studies reveal that FAO deficiency abrogates the prosurvival signaling in cancer cells under immune cytolytic stress. Furthermore, we identify T cell-derived IFN-γ as a major factor responsible for induction of CPT1A and FAO in an AMPK-dependent manner, indicating a dynamic interplay between immune effector cells and tumor targets. While cancer growth in the absence of CPT1A remains largely unaffected, established tumors upon FAO inhibition become significantly more responsive to cellular immunotherapies including chimeric antigen receptor-engineered human T cells. Together, these findings uncover a mode of cancer resistance and immune editing that can facilitate immune escape and limit the benefits of immunotherapies.

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.

Novaferon gene modification promotes NK92 cell anti-tumor activity

With significant developments in chimeric antigen receptor T-cell therapy, adoptive immunotherapy has unlocked new levels of treatment for malignancies. Natural killer (NK) cells are promising alternative immune effector cells for this strategy. Multiple anti-tumor therapies are largely dependent on type I interferon (IFN) signaling. Type I IFNs enhance NK cell cytotoxicity. Novaferon (nova) is an unnatural, novel IFN-like protein produced by gene shuffling of IFN-α with strong biological activity. To augment the antitumor activity of NK cells, we generated NK92-nova cells that stably express nova. We found that NK92-nova cells mediated enhanced pan-cancer antitumor activity compared to NK92-vec cells. The increased antitumor activity was associated with the enhanced secretion of cytokines, such as IFN-γ, perforin, and granzyme B. Meanwhile, most of the activating receptors were upregulated in the NK92-nova cells. After co-culture with NK92-nova cells, the expression of NKG2D ligands on the HepG2 cells increased, resulting in an enhanced susceptibility of HepG2 cells to NK92 cell-mediated cytolysis. NK92-nova cells significantly inhibited HepG2 tumor growth in a xenograft model without systemic toxicity. Therefore, NK92-nova cells are a novel and safe strategy for cancer immunotherapy.

Profiling of Natural Killer Interactions With Cancer Cells Using Mass Cytometry

We developed a comprehensive method for functional assessment of the changes in immune populations and killing activity of peripheral blood mononuclear cells after cocultures with cancer cells using mass cytometry. In this study, a 43-marker mass cytometry panel was applied to a coculture of immune cells from healthy donors' peripheral blood mononuclear cells with diverse cancer cell lines. DNA content combined with classical CD45 surface staining was used as gating parameters for cocultures of immune cells (CD45high/DNAlow) with hematological (CD45low/DNAhigh) and solid cancer cell lines (CD45neg/DNAhigh). This strategy allows for universal discrimination of cancer cells from immune populations without the need for a specific cancer cell marker and simultaneous assessment of phenotypical changes in both populations. The use of mass cytometry allows for simultaneous detection of changes in natural killer, natural killer T cell, and T cell phenotypes and degranulation of immune populations upon target recognition, analysis of target cells for cytotoxic protein granzyme B content, and cancer cell death. These findings have broad applicability in research and clinical settings with the aim to phenotype and assess functional changes following not only NK-cancer cell interactions but also the effect of those interactions on other immune populations.

CD4 T cells in chronic myeloid leukemia present MHC class II-dependent and IFN-γ-dependent cytotoxic capacity

At present, many therapeutic schemes have been used to improve the prognosis of patients with chronic myeloid leukemia (CML), but response remains poor in a small group of patients. CD4 T cell-mediated cytotoxicity has been found in various autoimmune diseases. This study analyzed the characteristics of CD4 T cell mediated cytotoxicity in CML patients and healthy people. The cytotoxicity of CD4 T cells was tested in using two CML cell lines, including the MHC class II-deficient K562 cells and the MHC class II-expressing KU812 cells. CD4 T cell-mediated lysis was minimal in K562 cells but was much higher in KU812 cells. In CML patients, the level of CD4 T cell-mediated lysis was limited to a certain level. Interestingly, pre-treating KU812 cells with IFN-γ could significantly elevate the expression of MHC class II and elevate the level of CD4 T cell-mediated lysis. Overall, these data indicated CD4 T cells could become a potential candidate for cytotoxic elimination of CML cells.

Co-expression of HLA-E and HLA-G on genetically modified porcine endothelial cells attenuates human NK cell-mediated degranulation

Natural killer (NK) cells play an important role in immune rejection in solid organ transplantation. To mitigate human NK cell activation in xenotransplantation, introducing inhibitory ligands on xenografts via genetic engineering of pigs may protect the graft from human NK cell-mediated cytotoxicity and ultimately improve xenograft survival. In this study, non-classical HLA class I molecules HLA-E and HLA-G were introduced in an immortalized porcine liver endothelial cell line with disruption of five genes (GGTA1, CMAH, β4galNT2, SLA-I α chain, and β-2 microglobulin) encoding three major carbohydrate xenoantigens (αGal, Neu5Gc, and Sda) and swine leukocyte antigen class I (SLA-I) molecules. Expression of HLA-E and/or HLA-G on pig cells were confirmed by flow cytometry. Endogenous HLA-G molecules as well as exogenous HLA-G VL9 peptide could dramatically enhance HLA-E expression on transfected pig cells. We found that co-expression of HLA-E and HLA-G on porcine cells led to a significant reduction in human NK cell activation compared to the cells expressing HLA-E or HLA-G alone and the parental cell line. NK cell activation was assessed by analysis of CD107a expression in CD3-CD56+ population gated from human peripheral blood mononuclear cells. CD107a is a sensitive marker of NK cell activation and correlates with NK cell degranulation and cytotoxicity. HLA-E and/or HLA-G on pig cells did not show reactivity to human sera IgG and IgM antibodies. This in vitro study demonstrated that co-expression of HLA-E and HLA-G on genetically modified porcine endothelial cells provided a superior inhibition in human xenoreactive NK cells, which may guide further genetic engineering of pigs to prevent human NK cell mediated rejection.

MOGAD patient autoantibodies induce complement, phagocytosis, and cellular cytotoxicity

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is an inflammatory demyelinating CNS condition characterized by the presence of MOG autoantibodies. We sought to investigate whether human MOG autoantibodies are capable of mediating damage to MOG-expressing cells through multiple mechanisms. We developed high-throughput assays to measure complement activity (CA), complement-dependent cytotoxicity (CDC), antibody-dependent cellular phagocytosis (ADCP), and antibody-dependent cellular cytotoxicity (ADCC) of live MOG-expressing cells. MOGAD patient sera effectively mediate all of these effector functions. Our collective analyses reveal that (a) cytotoxicity is not incumbent on MOG autoantibody quantity alone; (b) engagement of effector functions by MOGAD patient serum is bimodal, with some sera exhibiting cytotoxic capacity while others did not; (c) the magnitude of CDC and ADCP is elevated closer to relapse, while MOG-IgG binding is not; and (d) all IgG subclasses can damage MOG-expressing cells. Histopathology from a representative MOGAD case revealed congruence between lesion histology and serum CDC and ADCP, and we identified NK cells, mediators of ADCC, in the cerebrospinal fluid of relapsing patients with MOGAD. Thus, MOGAD-derived autoantibodies are cytotoxic to MOG-expressing cells through multiple mechanisms, and assays quantifying CDC and ADCP may prove to be effective tools for predicting risk of future relapses.

Anti-GD2 CAR-NKT cells in relapsed or refractory neuroblastoma: updated phase 1 trial interim results

Vα24-invariant natural killer T cells (NKTs) have anti-tumor properties that can be enhanced by chimeric antigen receptors (CARs). Here we report updated interim results from the first-in-human phase 1 evaluation of autologous NKTs co-expressing a GD2-specific CAR with interleukin 15 (IL15) (GD2-CAR.15) in 12 children with neuroblastoma (NB). The primary objectives were safety and determination of maximum tolerated dose (MTD). The anti-tumor activity of GD2-CAR.15 NKTs was assessed as a secondary objective. Immune response evaluation was an additional objective. No dose-limiting toxicities occurred; one patient experienced grade 2 cytokine release syndrome that was resolved by tocilizumab. The MTD was not reached. The objective response rate was 25% (3/12), including two partial responses and one complete response. The frequency of CD62L+NKTs in products correlated with CAR-NKT expansion in patients and was higher in responders (n = 5; objective response or stable disease with reduction in tumor burden) than non-responders (n = 7). BTG1 (BTG anti-proliferation factor 1) expression was upregulated in peripheral GD2-CAR.15 NKTs and is a key driver of hyporesponsiveness in exhausted NKT and T cells. GD2-CAR.15 NKTs with BTG1 knockdown eliminated metastatic NB in a mouse model. We conclude that GD2-CAR.15 NKTs are safe and can mediate objective responses in patients with NB. Additionally, their anti-tumor activity may be enhanced by targeting BTG1. ClinicalTrials.gov registration: NCT03294954 .

Three distinct mechanisms underlying human γδ T cell-mediated cytotoxicity against malignant pleural mesothelioma

Introduction

Malignant pleural mesothelioma (MPM) is a rare and highly aggressive thoracic tumor with poor prognosis and limited therapeutic options. Although immune checkpoint inhibitors exhibit a promising effect in some patients with unresectable MPM in clinical trials, the majority of MPM patients show only modest response rates to the currently available treatments. It is thus imperative to develop novel and innovative therapeutic modalities for MPM, including immune effector cell-based therapies.

Methods

γδ T cells were expanded using tetrakis-pivaloyloxymethyl 2-(thiazole-2-ylamino) ethylidene-1,1-bisphosphonate (PTA) and interleukin-2, and the therapeutic potential of γδ T cells was examined through analyzing cell surface markers and cellular cytotoxicity against MPM in vitro using a europium chelate-based time-resolved fluorescence assay system and a luciferase-based luminescence assay system.

Results and discussion

We successfully expanded γδ T cells from peripheral blood mononuclear cells of healthy donors and MPM patients. γδ T cells expressed natural killer receptors such as NKG2D and DNAM-1 and exhibited a moderate level of cytotoxicity to MPM cells in the absence of antigens. The inclusion of PTA, (E)-4-hydroxy-3- methylbut-2-enyl diphosphate (HMBPP) or zoledronic acid (ZOL) induced a TCR-dependent cytotoxicity in γδ T cells and secreted interferon-γ (IFN-γ). In addition, γδ T cells expressing CD16 exhibited a significant level of cytotoxicity against MPM cells in the presence of an anti-epidermal growth factor receptor (EGFR) mAb, at lower concentrations than in clinical settings, whereas a detectable level of IFN-γ was not produced. Taken together, γδ T cells showed cytotoxic activity against MPM in three distinct mechanisms through NK receptors, TCRs and CD16. Since major histocompatibility complex (MHC) molecules are not involved in the recognition, both autologous and allogeneic γδ T cells could be used for the development of γδ T cell-based adoptive immunotherapy for MPM.

Insights into the cellular pathophysiology of familial hemophagocytic lymphohistiocytosis

Familial hemophagocytic lymphohistiocytosis (fHLH) encompasses a group of rare inherited immune dysregulation disorders characterized by loss-of-function mutations in one of several genes involved in the assembly, exocytosis, and function of cytotoxic granules within CD8+ T cells and natural killer (NK) cells. The resulting defect in cytotoxicity allows these cells to be appropriately stimulated in response to an antigenic trigger, and also impairs their ability to effectively mediate and terminate the immune response. Consequently, there is sustained lymphocyte activation, resulting in the secretion of excessive amounts of pro-inflammatory cytokines that further activate other cells of the innate and adaptive immune systems. Together, these activated cells and pro-inflammatory cytokines mediate tissue damage that leads to multi-organ failure in the absence of treatment aimed at controlling hyperinflammation. In this article, we review these mechanisms of hyperinflammation in fHLH at the cellular level, focusing primarily on studies performed in murine models of fHLH that have provided insight into how defects in the lymphocyte cytotoxicity pathway mediate rampant and sustained immune dysregulation.

Serpin B9 controls tumor cell killing by CAR T cells

BACKGROUND

Initial clinical responses with gene engineered chimeric antigen receptor (CAR) T cells in cancer patients are highly encouraging; however, primary resistance and also relapse may prevent durable remission in a substantial part of the patients. One of the underlying causes is the resistance mechanisms in cancer cells that limit effective killing by CAR T cells. CAR T cells exert their cytotoxic function through secretion of granzymes and perforin. Inhibition of granzyme B (GrB) can underlie resistance to T cell-mediated killing, and it has been shown that serine proteinase inhibitor serpin B9 can effectively inhibit GrB. We aimed to determine whether expression of serpin B9 by cancer cells can lead to resistance toward CAR T cells.

METHODS

Serpin B9 gene and protein expression were examined by R2 or DepMap database mining and by western blot or flow cytometric analysis, respectively. Coculture killing experiments were performed with melanoma cell line MeWo, diffuse large B cell lymphoma (DLBCL) cell line OCI-Ly7 or primary chronic lymphocytic leukemia (CLL) cells as target cells and natural killer cell line YT-Indy, CD20 CAR T cells or CD19 CAR T cells as effector cells and analyzed by flow cytometry.

RESULTS

Serpin B9 protein expression was previously shown to be associated with clinical outcome in melanoma patients and in line with these observations we demonstrate that enforced serpin B9 expression in melanoma cells reduces sensitivity to GrB-mediated killing. Next, we examined serpin B9 expression in a wide array of primary tumor tissues and human cell lines to find that serpin B9 is uniformly expressed in B-cell lymphomas and most prominently in DLBCL and CLL. Subsequently, using small interfering RNA, we silenced serpin B9 expression in DLBCL cells, which increased their sensitivity to CD20 CAR T cell-mediated killing. In addition, we showed that co-ulture of primary CLL cells with CD20 CAR T cells results in selection of serpin B9-high CLL cells, suggesting these cells resist CAR T-cell killing.

CONCLUSIONS

Overall, the data indicate that serpin B9 is a resistance mediator for CAR T cell-mediated tumor cell killing that should be inhibited or bypassed to improve CAR T-cell responses.