Natural Killer Cell Cytokine Production Research Articles

A PSMA-targeted Tri-specific Killer Engager enhances NK cell cytotoxicity against prostate cancer.

Natural killer (NK) cell tumor infiltration is associated with good prognosis in patients with metastatic castration-resistant prostate cancer (mCRPC). NK cells recognize and kill targets by a process called natural cytotoxicity. We hypothesized that promoting an antigen-specific synapse with co-activation may enhance NK cell function in mCRPC. We describe a Tri-specific Killer Engager (TriKE) construct that engages with the activating receptor CD16 on NK cells, prostate-specific membrane antigen (PSMA) on mCRPC cells, and has an interleukin (IL)-15 moiety that is essential for NK cell survival, proliferation, and priming. We show that the PSMA TriKE specifically binds to PSMA-expressing cells and significantly enhances expansion, degranulation and cytokine production of NK cells derived from healthy donors or prostate cancer patients. Bystander killing of PSMA-negative was also achieved with PSMA TriKE treatment when co-cultured with PSMA-positive cells, suggesting potential PSMA TriKE benefit in controlling tumor antigen escape. When tested under physiologic conditions recapitulating the mCRPC tumor microenvironment (TME), NK cells treated with PSMA TriKE and prolonged exposure to hypoxia or MDSCs maintained their potent function while IL-15 treated NK cells showed greatly impaired cytotoxicity. Finally, in vivo testing of PSMA TriKE showed improved tumor control and survival of mice as compared to IL-15 and untreated control groups. In conclusion, PSMA TriKE demonstrates potential as a new therapy for advanced prostate cancer by providing additional signals to NK cells to maximize their anti-tumor potential in prostate cancer, especially in the setting of a hostile TME.

Chronic stimulation desensitizes β2-adrenergic receptor responses in natural killer cells.

Adrenergic receptors (ARs) are preferentially expressed by innate lymphocytes such as natural killer (NK) cells. Here, we study the effect of epinephrine-mediated stimulation of the β2-adrenergic receptor (β2AR) on the function of human NK cells. Epinephrine stimulation inhibited early NK cell signaling events and blocked the function of the integrin LFA-1. This reduced the adhesion of NK cells to ICAM-1, explaining how NK cells are mobilized into the peripheral blood upon epinephrine release during acute stress or exercise. Additionally, epinephrine stimulation transiently reduced NK cell degranulation, serial killing, and cytokine production and affected metabolic changes upon NK cell activation via the cAMP-protein kinase A (PKA) pathway. Repeated exposure to β2AR agonists resulted in the desensitization of the β2AR via a PKA feedback loop-initiated G-protein switch. Therefore, acute epinephrine stimulation of chronically β2AR stimulated NK cells no longer resulted in inhibited signaling and reduced LFA-1 activity. Sustained stimulation by long-acting β2-agonists (LABA) not only inhibited NK cell functions but also resulted in desensitization of the β2AR. However, peripheral NK cells from LABA-treated asthma patients still reacted unchanged to epinephrine stimulation, demonstrating that local LABA administration does not result in detectable systemic effects on NK cells.

Antimicrobial activity of NK cells to Trypanosoma cruzi infected human primary Keratinocytes.

Infection with the protozoan parasite Trypanosoma cruzi is causative for Chagas disease, which is a highly neglected tropical disease prevalent in Latin America. Humans are primary infected through vectorial transmission by blood-sucking triatomine bugs. The parasite enters the human host through mucous membranes or small skin lesions. Since keratinocytes are the predominant cell type in the epidermis, they play a critical role in detecting disruptions in homeostasis and aiding in pathogen elimination by the immune system in the human skin as alternative antigen-presenting cells. Interestingly, keratinocytes also act as a reservoir for T. cruzi, as the skin has been identified as a major site of persistent infection in mice with chronic Chagas disease. Moreover, there are reports of the emergence of T. cruzi amastigote nests in the skin of immunocompromised individuals who are experiencing reactivation of Chagas disease. This observation implies that the skin may serve as a site for persistent parasite presence during chronic human infection too and underscores the significance of investigating the interactions between T. cruzi and skin cells. Consequently, the primary objective of this study was to establish and characterize the infection kinetics in human primary epidermal keratinocytes (hPEK). Our investigation focused on surface molecules that either facilitated or hindered the activation of natural killer (NK) cells, which play a crucial role in controlling the infection. To simulate the in vivo situation in humans, an autologous co-culture model was developed to examine the interactions between T. cruzi infected keratinocytes and NK cells. We evaluated the degranulation, cytokine production, and cytotoxicity of NK cells in response to the infected keratinocytes. We observed a strong activation of NK cells by infected keratinocytes, despite minimal alterations in the expression of activating or inhibitory ligands on NK cell receptors. However, stimulation with recombinant interferon-gamma (IFN-γ), a cytokine known to be present in significant quantities during chronic T. cruzi infections in the host, resulted in a substantial upregulation of these ligands on primary keratinocytes. Overall, our findings suggest the crucial role of NK cells in controlling acute T. cruzi infection in the upper layer of the skin and shed light on keratinocytes as potential initial targets of infection.

CD155 blockade enhances allogeneic natural killer cell-mediated antitumor response against osteosarcoma.

Allogeneic bone marrow transplant (alloBMT) is curative for hematologic malignancies through the graft-versus-tumor (GVT) effect but has been ineffective for solid tumors like osteosarcoma (OS). OS expresses CD155 which interacts strongly with inhibitory receptors TIGIT and CD96 but also binds to activating receptor DNAM-1 on natural killer (NK) cells. CD155 has never been targeted after alloBMT. Combining adoptively transferred allogeneic NK (alloNK) cells with CD155 blockade after alloBMT may enhance a GVT effect against OS. Murine NK cells were activated and expanded ex vivo with soluble IL-15/IL-15Rα. AlloNK and syngeneic NK (synNK) cell phenotype, cytotoxicity, cytokine production, and degranulation against CD155-expressing murine OS cell line K7M2 were assessed in vitro. Mice bearing pulmonary OS metastases underwent alloBMT and alloNK cell infusion with anti-CD155 either before or after tumor induction, with select groups receiving anti-DNAM-1 pretreated alloNK cells. Tumor growth, GVHD and survival were monitored, and differential gene expression of lung tissue was assessed by RNA microarray. AlloNK cells exhibited superior cytotoxicity against CD155-expressing OS compared to synNK cells, and this activity was enhanced by CD155 blockade. CD155 blockade increased alloNK cell degranulation and interferon gamma production through DNAM-1. In vivo, CD155 blockade with alloNK infusion increased survival when treating OS that relapsed after alloBMT. No benefit was seen for treating established OS before alloBMT. Treatment with combination CD155 and anti-DNAM-1 pretreated alloNK ameliorated survival and tumor control benefits seen with CD155 blockade alone. RNA microarray showed mice treated with alloNK and CD155 blockade had increased expression of cytotoxicity genes and the NKG2D ligand H60a, whereas mice treated with anti-DNAM-1 pretreated alloNK cells resulted in upregulation of NK cell inhibitory receptor genes. Whereas blocking DNAM-1 on alloNK abrogated cytotoxicity, blocking NKG2D had no effect, implying DNAM-1:CD155 engagement drives alloNK activation against OS. These results demonstrate the safety and efficacy of infusing alloNK cells with CD155 blockade to mount a GVT effect against OS and show benefits are in part through DNAM-1. Defining the hierarchy of receptors that govern alloNK responses is critical to translating alloNK cell infusions and immune checkpoint inhibition for solid tumors treated with alloBMT. Allogeneic bone marrow transplant (alloBMT) has yet to show efficacy in treating solid tumors, such as osteosarcoma (OS). CD155 is expressed on OS and interacts with natural killer (NK) cell receptors, such as activating receptor DNAM-1 and inhibitory receptors TIGIT and CD96 and has a dominant inhibitory effect on NK cell activity. Targeting CD155 interactions on allogeneic NK cells could enhance anti-OS responses, but this has not been tested after alloBMT. CD155 blockade enhances allogeneic natural killer cell-mediated cytotoxicity against OS and improved event-free survival after alloBMT in an in vivo mouse model of metastatic pulmonary OS. Addition of DNAM-1 blockade abrogated CD155 blockade-enhanced allogeneic NK cell antitumor responses. These results demonstrate efficacy of allogeneic NK cells combined with CD155 blockade to mount an antitumor response against CD155-expressing OS. Translation of combination adoptive NK cell and CD155 axis modulation offers a platform for alloBMT treatment approaches for pediatric patients with relapsed and refractory solid tumors.

Cytokine Response of Natural Killer Cells to Hepatitis B Virus Infection Depends on Monocyte Co-Stimulation.

Hepatitis B virus (HBV) is a major driver of chronic hepatic inflammation, which regularly leads to liver cirrhosis or hepatocellular carcinoma. Immediate innate immune cell response is crucial for the rapid clearance of the infection. Here, natural killer (NK) cells play a pivotal role in direct cytotoxicity and the secretion of antiviral cytokines as well as regulatory function. The aim of this study was to further elucidate NK cell responses triggered by an HBV infection. Therefore, we optimized HBV in vitro models that reliably stimulate NK cells using hepatocyte-like HepG2 cells expressing the Na+-taurocholate co-transporting polypeptide (NTCP) and HepaRG cells. Immune cells were acquired from healthy platelet donors. Initially, HepG2-NTCP cells demonstrated higher viral replication compared to HepaRG cells. Co-cultures with immune cells revealed increased production of interferon-γ and tumor necrosis factor-α by NK cells, which was no longer evident in isolated NK cells. Likewise, the depletion of monocytes and spatial separation from target cells led to the absence of the antiviral cytokine production of NK cells. Eventually, the combined co-culture of isolated NK cells and monocytes led to a sufficient cytokine response of NK cells, which was also apparent when communication between the two immune cell subpopulations was restricted to soluble factors. In summary, our study demonstrates antiviral cytokine production by NK cells in response to HBV+ HepG2-NTCP cells, which is dependent on monocyte bystander activation.

Targeting TRIM29 As a Negative Regulator of CAR-NK Cell Effector Function to Improve Antitumor Efficacy of these Cells: A Perspective.

Natural killer (NK) cells are among the most important cells in innate immune defense. In contrast to T cells, the effector function of NK cells does not require prior stimulation and is not MHC restricted. Therefore, chimeric antigen receptor (CAR)-NK cells are superior to CAR-T cells. The complexity of the tumor microenvironment (TME) makes it necessary to explore various pathways involved in NK cell negative regulation. CAR-NK cell effector function can be improved by inhibiting the negative regulatory mechanisms. In this respect, the E3 ubiquitin ligase tripartite motif containing 29 (TRIM29) is known to be involved in reducing NK cell cytotoxicity and cytokine production. Also, targeting TRIM29 may enhance the antitumor efficacy of CAR-NK cells. The present study discusses the negative effects of TRIM29 on NK cell activity and proposes genomic deletion or suppression of the expression of TRIM29 as a novel approach to optimize CAR-NK cell-based immunotherapy.

Restriction of Glycolysis Increases Serial Killing Capacity of Natural Killer Cells.

Tumor cells rely heavily on glycolysis to meet their high metabolic demands. While this results in nutrient deprivation within the tumor microenvironment and has negative effects on infiltrating immune cells such as natural killer (NK) cells, it also creates a potential target for cancer therapies. Here we use Glupin, an inhibitor of glucose transporters, to study the effect of limited glucose uptake on NK cells and their anti-tumor functions. Glupin treatment effectively inhibited glucose uptake and restricted glycolysis in NK cells. However, acute treatment had no negative effect on NK cell cytotoxicity or cytokine production. Long-term restriction of glucose uptake via Glupin treatment only delayed NK cell proliferation, as they could switch to glutaminolysis as an alternative energy source. While IFN-γ production was partially impaired, long-term Glupin treatment had no negative effect on degranulation. Interestingly, the serial killing activity of NK cells was even slightly enhanced, possibly due to changes in NAD metabolism. This demonstrates that NK cell cytotoxicity is remarkably robust and insensitive to metabolic disturbances, which makes cellular metabolism an attractive target for immune-mediated tumor therapies.

Engineered Natural Killer Cells Expressing Chimeric Ilt Receptors (CIR) Effectively Target HLA-G Positive AML Tumor Cells

Background Human leukocyte antigen-G (HLA-G), the immune checkpoint of pregnancy, directs immunosuppression by binding to Ig-like transcript (ILT) receptors (ILT2 in lymphoid cells and ILT4 in myeloid cells) via immunoreceptor tyrosine-based inhibitory motif (ITIM) signaling domains. HLA-G is expressed in more than 50% of solid tumors and leukemias as a mechanism to evade immune attack. As a result, HLA-G is an excellent tumor-specific antigen since its expression in normal tissues is low except for cytotrophoblasts in the placenta where it protects the fetus from the mother's immune system. We present here a novel approach to target HLA-G-expressing Acute Myeloid Leukemia (AML) cells by utilizing the natural receptors of ILT2 and ILT4 coupled to positive intracellular signaling domains. Such chimeric ILT receptors, or CIRs drive activation of Natural Killer (NK) cells. Further, we have identified unique intracellular activation modules that function to robustly enhance cytotoxicity and expansion of NK cells upon engagement with tumor cells. Methods CD56 + NK cells were isolated from PBMCs, cultured with IL-15 and activated with a feeder-free cocktail of an immobilized cytokine and activating ligand. Activated NK cells were transduced with γ-retroviruses directing expression of CIR proteins (CIR.4-1BB.CD3ζ or CIR.X.Y where X and Y are candidate activation and coactivation moieties), soluble IL-15 and a ΔCD19 marker or CAR control constructs directed to HLA-G or CD33. After 8 days of expansion, CIR- or CAR-NK cells were cocultured with GFP ffluc-expressing AML target cell lines with or without transgenic HLA-G (G1, G2 and G5) isoforms. Cytotoxicity of CIR-NK cells was determined by reduction of GFP fluorescence in Incucyte or Celligo instruments or luciferase activity and supernatants were analyzed for IFN-γ and TNF-α release by ELISA. Transduced NK cells were labeled with nuclear-RFP for measurement of expansion in coculture. In comparative experiments, T cells from PBMCs were transduced to produce CIR-T cells by standard methods. Results CIR (ILT2 or ILT4.4-1BB.ζ) constructs were efficiently and stably expressed in T and NK cells (>80% ΔCD19 + 8- and 14-days post activation). Mock-transduced NK cells displayed innate killing activity against HLA-G negative AML cells (THP1 and KG1) that was not augmented by CIR constructs (mock = 6.16E6 ± 0.77E6 vs. CIR = 6.43E6 ± 0.37E6 in coculture against KG1 cells). In cocultures against THP1 and KG1 target cells expressing exogenous G1, G2 or G5 isoforms, CIR-NK cells or CIR-T cells displayed enhanced target cell killing in 2 and 7-day assays relative to mock-transduced effector cells (mock = 1.47E6 ± 0.49E6 vs. CIR = 0.57E6 ± 0.6 in coculture against KG1-HLA-G1). Further, while mock NK cells transduced with RFP alone could kill one-third of AML cells expressing endogenous HLA-G1 and G5 (Molm13 and Kasumi1), CIR-NK cells eliminated more than 90% of these AMLs and their activivation resulted in 4-fold higher IFN-γ secretion. Notably, robust cytotoxicity of CIR-NK cells was maintained even at 28 days post activation (mock = 36.95E6 ± 21.85E6 vs. CIR = 7.38E6 ± 1.92 in coculture against Kasumi1). To further enhance the functionality of the CIR constructs, a screen of novel costimulatory molecules to replace 4-1BB and/or CD3ζ resulted in several potent candidates ultilizing MyD88 signaling that greatly improved the cytotoxicity (> 80% tumor elimination), proliferation (> 2-fold expansion) and proinflammatory cytokine production (IFN-γ and TNF-α) of NK cells in cocultures. A subset is displayed in Figure 1. Conclusions The use of natural receptors ILT2 and ILT4 to target HLA-G takes advantage of the physiological pairing of the ILT receptors with the multiple immunosuppressive HLA-G isoforms thereby circumventing the possibility of antigen escape often observed in CAR-directed therapy. We demonstrated that engineered CIR-NK cells can convert HLA-G expression in AML from a potent inhibitor of leukocyte activity into a target for anti-tumor control.

Chimeric Antigen Receptor-Engineered NK Cells Overcome CD226 Downregulation As an Immune Escape Mechanism in Acute Myeloid Leukemia

Background: Natural killer (NK) cells are part of the innate immune system, and their killing capacity depends on the inputs from activating and inhibitory receptors. CD226 is an activating receptor that plays a role in the immune surveillance of acute myeloid leukemia (AML). AML cells have developed mechanisms to escape NK cell cytotoxicity including downregulating activating receptors such as CD226 on the surface of NK cells. Chimeric antigen receptors (CARs) are synthetic receptors integrated into NK cells to direct their anti-leukemia activity, and CD38 is a potential target for NK CAR-based cellular therapy against AML. Understanding the dynamics between the endogenous activating and inhibitory NK cell receptors (such as CD226) and the introduced CAR can determine the development of more effective NK CAR-based therapy for AML. We hypothesize that CD38-directed CAR NK cells may overcome CD226 downregulation as a mechanism of immune escape in AML. Purpose: we aimed to investigate (1) the mechanisms developed by AML cells to escape recognition by the activating receptor CD226, (2) whether and how anti-CD38 CAR-armed NK cells can overcome AML immune escape mechanisms. Methods: we performed multiparametric mass spectrometry to characterize changes in CD226 expression in NK cells of individuals with AML. Then, we investigated CD226 expression in NK cell-AML cocultures to characterize CD226-related mechanisms by imaging flow cytometry. Finally, to explore the impact of CD226 knockout (KO) together with the role of CD38 CAR in NK cell functionality, we retrovirally transduced CD38 CAR combined with CRISPR-Cas9 CD226 KO followed by short- and long-term cytotoxicity assays, cytokine production techniques and immune synapse assays by imaging flow cytometry. Results: NK cells from AML patients expressed low levels of CD226 with impaired cytotoxicity compared to heathy donor NK cells. Co-culture of healthy donor NK cells with AML blasts resulted in CD226 downregulation secondary to its internalization and was dependent on expression of the CD226 ligand CD155 in AML cells. CD226 KO diminished NK cell cytokine production and decreased their killing capacity against AML cells. In contrast, CD38-targeting NK cells displayed enhanced and specific cytotoxic activity against primary AML cells. When we combined the CD38 CAR with a CD226 KO in NK cells, these cells maintained their activating potential, cytokine secretion levels, and anti-leukemic cytotoxicity (Figure 1). CD38 CAR / CD226 KO NK cells could build strong immune synapses (Figure 2) even in the absence of LFA-1, an integrin activated by CD226 signaling and essential for NK cell immune synapse formation, suggesting that the CAR molecule compensates for the absence of CD266-mediated LFA signaling. Furthermore, CD38 CAR NK cells were capable of forming immune synapses, that were at least partially independent from LFA-1. Conclusion: CAR-directed NK cells can surpass resistance mechanisms in AML, such as CD226 downregulation and dampening of LFA-1 recruitment into the immunological synapse. Thus, NK cell activation by artificially introduced and germline-encoded receptors can overcome distinct tumor-resistance mechanisms, CAR-driven NK cells being a potent option for the treatment of AML.

Glucagon-like peptide-1 therapy in people with obesity restores natural killer cell metabolism and effector function.

People with obesity (PWO) have functionally defective natural killer (NK) cells, with a decreased capacity to produce cytokines and kill target cells, underpinned by defective cellular metabolism. It is plausible that the changes in peripheral NK cell activity are contributing to the multimorbidity in PWO, which includes an increased risk of cancer. This study investigated whether therapy with long-acting glucagon-like peptide-1 (GLP-1) analogues, which are an effective treatment for obesity, could restore NK cell functionality in PWO. In a cohort of 20 PWO, this study investigated whether 6 months of once weekly GLP-1 therapy (semaglutide) could restore human NK cell function and metabolism using multicolor flow cytometry, enzyme-linked immunosorbent assays, and cytotoxicity assays. These data demonstrate that PWO who received GLP-1 therapy have improved NK cell function, as measured by cytotoxicity and interferon-γ/granzyme B production. In addition, the study demonstrates increases in a CD98-mTOR-glycolysis metabolic axis, which is critical for NK cell cytokine production. Finally, it shows that the reported improvements in NK cell function appear to be independent of weight loss. The restoration, by GLP-1 therapy, of NK cell functionality in PWO may be contributing to the overall benefits being seen with this class of medication.

Modulation of NK cell activation by exogenous calcium from alginate dressings in vitro.

Natural Killer (NK) cells participate in the defense against infection by killing pathogens and infected cells and secreting immuno-modulatory cytokines. Defects in NK cell activity have been reported in obese, diabetic, and elderly patients that are at high risk of developing infected chronic wounds. Calcium alginate dressings are indicated for the debridement during the inflammatory phase of healing. Since calcium ions are major activators of NK cells, we hypothesized that these dressings could enhance NK functions, as investigated in vitro herein. Primary human blood NK cells were freshly-isolated from healthy volunteers and exposed to conditioned media (CM) from two alginate dressings, Algosteril® (ALG, pure Ca2+ alginate) and Biatain® Alginate (BIA, Ca2+ alginate with CMC), in comparison with an exogenous 3mM calcium solution. Our results demonstrated that exogenous calcium and ALG-CM, but not BIA-CM, induced NK cell activation and enhanced their capacity to kill their targets as a result of increased degranulation. NK cell stimulation by ALG depended on the influx of extracellular Ca2+ via the SOCE Ca2+ permeable plasma membrane channels. ALG-CM also activated NK cell cytokine production of IFN-γ and TNF-α through a partly Ca2+-independent mechanism. This work highlights the non-equivalence between alginate dressings for NK cell stimulation and shows that the pure calcium alginate dressing Algosteril® enhances NK cell cytotoxic and immuno-modulatory activities. Altogether, these results underline a specific property of this medical device in innate defense that is key for the cutaneous wound healing process.

HIV-Associated Microbial Translocation May Affect Cytokine Production of CD56bright NK Cells via Stimulation of Monocytes.

The mechanisms involved in HIV-associated natural killer (NK) cell impairment are still incompletely understood. We observed HIV infection to be associated with increased plasma levels of IFABP, a marker for gut epithelial barrier dysfunction, and LBP, a marker for microbial translocation. Both IFABP and LBP plasma concentrations were inversely correlated with NK cell interferon-γ production, suggesting microbial translocation to modulate NK cell functions. Accordingly, we found lipopolysaccharide to have an indirect inhibitory effect on NK cells via triggering monocytes' transforming growth factor-β production. Taken together, our data suggest increased microbial translocation to be involved in HIV-associated NK cell dysfunction.

The ectromelia virus virulence factor C15 facilitates early viral spread by inhibiting NK cell contact.

The success of poxviruses as pathogens depends on their antagonism of host responses by multiple immunomodulatory proteins. The largest of these expressed by ectromelia virus (the agent of mousepox) is C15, one member of a well-conserved poxviral family previously shown to inhibit Tcell activation. Here, we demonstrate by quantitative immunofluorescence imaging that C15 also limits contact between natural killer (NK) cells and infected cells invivo. This corresponds to an inhibition in the number of total and degranulating NK cells, exvivo and invitro, with no detectable impact on NK cell cytokine production or the transcription of factors related to NK cell recruitment or activation. Thus, in addition to its previously identified capacity to antagonize CD4 Tcell activation, C15 inhibits NK cell cytolytic function, which results in increased viral replication and dissemination invivo. This work builds on a body of literature demonstrating the importance of early restriction of virus within the draining lymph node.

TXNIP Promotes Human NK Cell Development but Is Dispensable for NK Cell Functionality.

The ability of natural killer (NK) cells to kill tumor cells without prior sensitization makes them a rising player in immunotherapy. Increased understanding of the development and functioning of NK cells will improve their clinical utilization. As opposed to murine NK cell development, human NK cell development is still less understood. Here, we studied the role of thioredoxin-interacting protein (TXNIP) in human NK cell differentiation by stable TXNIP knockdown or overexpression in cord blood hematopoietic stem cells, followed by in vitro NK cell differentiation. TXNIP overexpression only had marginal effects, indicating that endogenous TXNIP levels are sufficient in this process. TXNIP knockdown, however, reduced proliferation of early differentiation stages and greatly decreased NK cell numbers. Transcriptome analysis and experimental confirmation showed that reduced protein synthesis upon TXNIP knockdown likely caused this low proliferation. Contrary to its profound effects on the early differentiation stages, TXNIP knockdown led to limited alterations in NK cell phenotype, and it had no effect on NK cell cytotoxicity or cytokine production. Thus, TXNIP promotes human NK cell differentiation by affecting protein synthesis and proliferation of early NK cell differentiation stages, but it is redundant for functional NK cell maturation.

P618: SECOND-GENERATION CD19 TARGETING TRI-SPECIFIC KILLER ENGAGER DRIVES ROBUST NK CELL FUNCTION AGAINST B CELL MALIGNANCIES

Background: Chronic Lymphocytic Leukemia (CLL) involves uncontrollable clonal expansion of CD5+/CD19+ B lymphocytes. While patients can sometimes coexist with CLL for years, eventually there is progression to bulky adenopathy and pancytopenia from marrow suppression requiring therapy. In recent years, targeted therapies, including utilization of the inhibitors for B cell receptor (BCR) signaling and for B cell lymphoma 2 (Bcl-2) protein, have been effective treatment options. However, these treatments are associated with limitations such as development of drug resistance and the lower treatment efficacy ratio in high-risk patients. Meanwhile, CAR-T cell immunotherapy failed to produce effective treatment outcomes against CLL, mostly due to defects in the effector T cells leading to product failures, as well as being associated with high levels of off-target cytotoxicity. Aims: Thus, approaches to CLL treatment are necessary and NK cell immunotherapy presents a viable and non-toxic option to this problem. Methods: Our group previously demonstrated the immunotherapeutic potential of utilizing first-generation CD19-targeting 161519 Tri-Specific Killer Engager (TriKE®) to drive natural killer (NK) cell cytotoxicity against B-cell malignancies. We have now produced a novel second-generation CD19 TriKE, ‘CAM161519’, utilizing a humanized camelid anti-CD16 VHH single domain antibody (sdAb) ‘CAM16’, a wild-type IL-15 component, and anti-CD19 tumor antigen scFv all linked via short peptide linkers. The TriKE primarily works by generating a cytolytic bridge between NK cells and CD19 expressing B cell malignancies while also providing an expansion and survival signal to the NK cells. Using flow-based assays and imaging based cytolytic assays we explored the capability of CAM161519 to target a variety of B cell lines (Raji, Daudi, and Nalm6) and primary B cell malignancies from patients with CLL and B cell acute lymphoblastic leukemia (B-ALL). Expanded NK cells were incubated with primary CLL targets from 6 different patients and no treatment (NT), rhIL-15 (30 nM), Rituximab (10 ug/mL), or CAM16159 (30 nM). NK cell degranulation and IFNg production was evaluated after 5 hours of co-culture (Figure). CLL killing was evaluated in a similar co-culture, but with a staining mix containing CD5 and CD19, to identify CLL tumor cells in order to determine the percent CLL targets killed normalized to incubation of CLL cells with NK cells alone (Figure Image). Results: The CAM161519 robustly activated NK cell degranulation (CD107a) and inflammatory cytokine production (IFNg) against B cell lines. The activation was specific as it was strongly reduced against CD19 knockout Nalm6 cells. The TriKE also induced specific NK cell proliferation. IncuCyte imaging based cytolytic assays demonstrated strong killing activity against Raji targets. When evaluating activity against primary targets, CAM161519 induced enhanced NK cell degranulation, cytokine production, and cytotoxicity using flow cytometry-based assays against primary CLL (Figure Image) and B-ALL targets when compared to IL-15 treatment. CAM161519 also rescued functionality of NK cells from CLL patients against their autologous CLL cells. Image:Summary/Conclusion: Taken together, these data are indicative of the potential for clinical translation of the CAM161519 TriKE in the CLL and B-ALL settings alone or in combination with cellular products.

Investigating the susceptibility of treatment-resistant oesophageal tumours to natural killer cell-mediated responses

The majority of oesophageal adenocarcinoma (OAC) patients do not respond to multimodal treatment regimens and face dismal survival rates. Natural killer (NK) cells are crucial anti-tumour immune cells, and this study investigated the susceptibility of treatment-resistant OAC cells to these potent tumour killers. Natural killer receptor (NKR) ligand expression by OE33CisP (cisplatin-sensitive) and OE33CisR (cisplatin-resistant) cells was investigated. The immunomodulatory effects of OE33CisP and OE33CisR cells on NK cell phenotype and function were assessed. Finally, the impact of chemotherapy regimens on NKR ligand shedding was examined. Our data revealed significantly less surface expression of activating ligands B7-H6, MICA/B, ULBP-3 and activating/inhibitory ligands PVRL-1 and PVRL-4 by OE33CisR cells, compared to OE33CisP cells. Co-culture with OE33CisR cells reduced the frequencies of NKp30+ and NKp46+ NK cells and increased frequencies of TIGIT+, FasL+ and TRAIL+ NK cells. Frequencies of IFN-γ-producing NK cells increased while frequencies of TIM-3+ NK cells decreased after culture with OE33CisP and OE33CisR cells. Frequencies of circulating NKp30+ NK cells were significantly lower in OAC patients with the poorest treatment response and in patients who received FLOT chemotherapy, while B7-H6 shedding by OAC tumour cells was induced by FLOT. Overall, OE33CisR cells express less activating NKR ligands than OE33CisP cells and have differential effects on NKR expression by NK cells. However, neither cell line significantly dampened NK cell cytokine production, death receptor expression or degranulation. In addition, our data indicate that FLOT chemotherapy may promote B7-H6 shedding and immune evasion with detrimental consequences in OAC patients.

Filamin A Is Required for NK Cell Cytotoxicity at the Expense of Cytokine Production via Synaptic Filamentous Actin Modulation.

Natural killer (NK) cells are innate cytotoxic lymphocytes that efficiently eliminate malignant and virus-infected cells without prior activation via the directed and focused release of lytic granule contents for target cell lysis. This cytolytic process is tightly regulated at discrete checkpoint stages to ensure the selective killing of diseased target cells and is highly dependent on the coordinated regulation of cytoskeletal components. The actin-binding protein filamin crosslinks cortical actin filaments into orthogonal networks and links actin filament webs to cellular membranes to modulate cell migration, adhesion, and signaling. However, its role in the regulation of NK cell functions remains poorly understood. Here, we show that filamin A (FLNa), a filamin isoform with preferential expression in leukocytes, is recruited to the NK cell lytic synapse and is required for NK cell cytotoxicity through the modulation of conjugate formation with target cells, synaptic filamentous actin (F-actin) accumulation, and cytotoxic degranulation, but not granule polarization. Interestingly, we also find that the loss of FLNa augments the target cell-induced expression of IFN-γ and TNF-α by NK cells, correlating with enhanced activation signals such as Ca2+ mobilization, ERK, and NF-κB, and a delayed down-modulation of the NKG2D receptor. Thus, our results identify FLNa as a new regulator of NK cell effector functions during their decision to kill target cells through a balanced regulation of NK cell cytotoxicity vs cytokine production. Moreover, this study implicates the cross-linking/bundling of F-actin mediated by FLNa as a necessary process coordinating optimal NK effector functions.

Toll-like receptor 8 agonists improve NK-cell function primarily targeting CD56brightCD16− subset

BackgroundToll-like receptors (TLRs) are pattern-recognition sensors mainly expressed in innate immune cells that directly recognize conserved pathogen structures (pathogen-associated molecular patterns-PAMPs). Natural killer (NK) cells have been described to express...

Eomes and T-Bet Expression Are Required By Mature Primary Human NK Cells for Anti-Leukemia Responses In Vivo

Natural Killer (NK) cells are innate lymphoid cells that respond to hematologic cancers via cytotoxicity (perforin/granzyme and death receptors) and cytokine/chemokine production, yet the molecular determinants underlying their proliferation, function, and persistence are poorly understood. There are promising reports of pre-clinical and clinical NK cell responses to leukemia and lymphoma, which represent a nascent cellular therapy for these blood cancers. The T-box transcription factors (TFs) Eomes and T-bet are expressed by NK cells throughout their lifespan, and are required for development as evidenced by NK cell loss in Eomes and T-bet deficient mice. However, the roles of these TFs in mature human NK cell molecular programs and functions remain unclear.We hypothesized Eomes and T-bet, which are the only T-box TFs expressed in NK cells, are critical regulators of NK cell homeostasis and functionality, and are necessary for proper mature NK cell responses. To address this, we utilized the CRISPR-Cas9 system to genetically delete both Eomes and T-bet in primary human NK cells isolated from healthy donors, and investigated their role beyond guiding NK cell development, specifically in the anti-leukemia response. Gene-editing of primary human NK cells has been technically challenging, thus most reports that modified NK cells were performed with cell lines, in vitro-differentiated, or highly expanded NK cells that likely do not reflect primary human NK cell biology.Here, we introduced Cas9 mRNA and sgRNA targeting T-bet and Eomes by electroporation into unexpanded primary human NK cells isolated from healthy donors using the MaxCyte GT system. We observed highly efficient reductions of Eomes and T-bet protein expression, quantified by flow cytometry (p < 0.0001, Fig A-B) without viability differences between control (sgRNA targeting TRAC, an unexpressed locus in NK cells), and Eomes/T-bet double CRISPR-edited (DKO) cells after one week in vitro. To study Eomes and T-bet in NK cell anti-leukemia response, control or DKO primary human NK cells were engrafted into NSG mice, supported with human IL-15, and challenged with K562 leukemia cells. Utilizing bioluminescent imaging to visualize leukemia burden, we observed that NK cells lacking both TFs were unable to suppress leukemia growth in vivo.To understand the mechanism responsible for impaired leukemia control, we investigated in vivo persistence and proliferation, cytotoxic effector molecule expression, as well as ex vivo degranulation and cytokine production of DKO NK cells compared to control NK cells. DKO or control human NK cells were transferred into NSG mice and supported with human IL-15. After 2-3 weeks, significantly fewer (<30%) DKO NK cells persisted compared to control NK cells: spleen (5-fold decrease, control 240e3±65e3 vs DKO 47e3±15e3 NK cells, p<0.01, Figure C), blood (6-fold decrease, p<0.01), and liver (4-fold decrease, p<0.05). Using intracellular flow cytometry, double T-bet/Eomes CRISPR-edited NK cells that lacked both Eomes and T-bet protein after in vivo transfer were identified. A proliferative defect was evident in flow-gated DKO (62±6% undivided), compared to unedited (WT) NK cells (4±2% undivided) assessed by CellTrace Violet dilution (Figure D). In addition, there were marked reductions in granzyme B and perforin protein (p<0.001) in flow-gated DKO NK cells compared to controls. To assess DKO NK cell functional capacity, we performed an ex vivo functional assay on NK cells from spleens of the NSG mice as effectors, and K562 targets or IL-12/15/18 stimulation for 6 hours. Degranulation to K562 targets was impaired (p<0.05), and IFN-γ production was reduced (p<0.0001) after cytokine stimulation in flow-gated DKO NK cells (Figure E).Thus, CRISPR-editing of unexpanded, primary human NK cells revealed that Eomes and T-bet are required by mature human NK cells for their function and homeostasis, distinct from their role in development. This is translationally relevant, as defects in proliferation and function of human DKO NK cells manifested markedly reduced response against human leukemia cells in vivo in xenografts. These findings expand our understanding of key molecular regulators of mature NK cell homeostasis and function, with the potential to provide new avenues to enhance NK cell therapy. [Display omitted] DisclosuresBerrien-Elliott: Wugen: Consultancy, Patents & Royalties: 017001-PRO1, Research Funding. Foltz-Stringfellow: Kiadis: Patents & Royalties: TGFbeta expanded NK cells; EMD Millipore: Other: canine antibody licensing fees. Fehniger: HCW Biologics: Research Funding; Compass Therapeutics: Research Funding; Affimed: Research Funding; ImmunityBio: Research Funding; Wugen: Consultancy, Current equity holder in publicly-traded company, Patents & Royalties: related to memory like NK cells, Research Funding; Kiadis: Other; OrcaBio: Other; Indapta: Other.

Heparanase is a regulator of natural killer cell activation and cytotoxicity.

Heparanase is the only mammalian enzyme capable of cleaving heparan sulfate, a glycosaminoglycan of the extracellular matrix and cell surfaces. Most immune cells express heparanase that contributes to a range of functions including cell migration and cytokine expression. Heparanase also promotes natural killer (NK) cell migration; however, its role in other NK cell functions remains to be defined. In this study, heparanase-deficient (Hpse-/- ) mice were used to assess the role of heparanase in NK cell cytotoxicity, activation, and cytokine production. Upon challenge with the immunostimulant polyinosinic:polycytidylic acid (poly(I:C)), NK cells isolated from Hpse-/- mice displayed impaired cytotoxicity against EO771.LMB cells and reduced levels of activation markers CD69 and NKG2D. However, in vitro cytokine stimulation of wild-type and Hpse-/- NK cells resulted in similar CD69 and NKG2D expression, suggesting the impaired NK cell activation in Hpse-/- mice results from elements within the in vivo niche. NKcells are activated in vivo by dendritic cells (DCs) in response to poly(I:C). Poly(I:C)-stimulated Hpse-/- bone marrow DCs (BMDCs) expressed less IL-12, and when cultured with Hpse-/- NK cells, less MCP-1 mRNA and protein was detected. Although cell-cell contact is important for DC-mediated NK cell activation, co-cultures of Hpse-/- BMDCs and NK cells showed similar levels of contact to wild-type cells, suggesting heparanase contributes to NK cell activation independently of cell-cell contact with DCs. These observations define a role for heparanase in NKcell cytotoxicity and activation and have important implications for how heparanase inhibitors currently in clinical trials for metastatic cancer may impact NK cell immunosurveillance.