Natural Killer Cell-mediated Killing Research Articles

Sijunzi decoction enhances sensitivity of colon cancer cells to NK cell destruction by modulating P53 expression

Ethnopharmacological relevanceSijunzi Decoction (SJZD), a traditional Chinese herbal remedy, is frequently employed in the treatment of various cancers, including colon cancer. Previous research suggests that SJZD plays a pivotal role in modulating the immune system and enhancing immunity against tumors. However, the precise role of SJZD in combating colon cancer and its potential molecular functions in regulating natural killer cells remain elusive. Aims of the studyTo elucidate the potential mechanism underlying the anticolon cancer effects of SJZD in synergy with natural killer (NK) cells through both in vivo and in vitro experiments. Materials and methodsIn vivo experiments: A subcutaneous tumor mouse model of colon cancer and in vivo NK cell depletion experiments were conducted to observe the anticolon cancer effects of SJZD. Flow cytometry assessed immune cell depletion in mouse spleens, while immunohistochemical (IHC) staining detected the expression of apoptotic genes in tumor tissues. In vitro experiments: The mechanism by which SJZD regulates the sensitization of colon cancer cells to NK cells was investigated using real-time polymerase chain reaction (RT-PCR), western blotting (WB), and co-culture experiments with NK cells. ResultsSijunzi Decoction (SJZD) significantly impeded tumor growth in mice; however, NK cell depletion markedly attenuated the tumor-suppressive effect of SJZD. Immunohistochemical (IHC) results indicated that SJZD increased the expression of P53, death receptor 4 (DR4), and death receptor 5 (DR5) in tumor tissues. In vitro experiments, 24 h SJZD-pretreated colon cancer cells showed a substantial elevation in P53, DR4, and DR5 levels, and the activity of colon cancer cells significantly diminished after co-culture with NK cells. These effects of SJZD were reversed with the addition of the P53 inhibitor pifithrin-α (PFT-α), resulting in reduced inhibition of colon cancer cells by NK cells. ConclusionSJZD enhances the levels of DR4 and DR5 through the modulation of P53 expression, consequently increasing the sensitivity of colon cancer cells to NK cell-mediated killing. These findings provide a theoretical foundation for the clinical application of SJZD in patients with colon cancer.In this study, we first investigated the effect of SJZD on subcutaneous tumor growth in mice with colon cancer using in vivo assays and assessed the impact of NK cells on the anticolon cancer effect of SJZD in vivo through NK cell depletion. In vitro experiments were conducted to explore the potential mechanism of action of SJZD in NK cell-mediated anticolon cancer effects.

Abstract 2358: YH41723 (IMC-202), a Novel TIGITxPD-L1 bispecific antibody, leads to potent anti-tumor immunity through T cell engaging and T/NK cell activation

Abstract Immune checkpoint inhibitors (ICIs) have been making innovative advances in current cancer therapy. In particular, the PD-L1/PD-1 blockades changed the paradigm of anti-cancer treatment, showing high efficiency compared to conventional therapy. However, drug resistance has been observed in many patients receiving PD-1/PD-L1 monoclonal antibodies (mAbs), and there are still many limitations in restoring T cell. To overcome this, various ICI targets including T cell immunoreceptor with Ig and ITIM domain (TIGIT) are being studied. TIGIT is a T cell co-inhibitory receptor, highly expressed on regulatory T (Treg) cells and memory T cells and natural killer (NK) cells. In combination with PD-1/PD-L1 inhibition, the activation of CD226 through the blocking of TIGIT/PVR ligation is important for T cell activation. In this study, we demonstrated the synergistic effect that can be obtained by simultaneously blocking of PD-L1 and TIGIT and effect of T cell engager function using TIGITxPD-L1 bispecific antibody (BsAb). We generated an anti-TIGITxPD-L1 BsAb, YH41723 (IMC-202), with Fc-engineering to enhance the effector function. In order to confirm superior efficacy of YH41723 compared to combination of two monoclonal antibodies, PD-L1 mAb+TIGIT mAb, we verified the CD8+ T cell-mediated tumor killing effect by T cell engager function of YH41723. We also observed strong antibody-dependent cell-mediated cytotoxicity (ADCC) effect of YH41723 against various cancer cell lines. In addition, YH41723 showed superior anti-tumor efficacy than combination treatment in NK cell-mediated tumor killing assay. We further confirmed the significant Treg cell depletion efficacy of YH41723 in vitro compared to combination. We tested in vivo anti-cancer efficacy of YH41723 in hPD-L1 KI CT26 with BALB/c-H/K-dKO mouse models (B cell-deficient mice). As a result, YH41723 showed superior tumor growth inhibition effect compared with anti-PD-L1 mAb and anti-TIGIT mAb combination. Even, 7 of 8 mice showed complete regression in 30 mg/kg dosing group. 60 days after the last administration, we further performed tumor re-challenge test. The tumor-free state of tumor re-challenged mice was sustained, indicating that the immune memory was generated by YH41723. Taken together, YH41723 showed strong efficacy in NK/T cell activation and Treg depletion in vitro and excellent anti-tumor efficacy in vivo, supporting that YH41723 as an effective anti-cancer immunotherapy and combination candidate with other ICIs. Citation Format: Min Hyeok Jee, Young Bong Park, Byeong-Yun An, Hee Ra Jung, Eunjung Lee, Jun Hwan Kim, Ji Eun Park, Ji Young Yoon, Seung Mi Jeong, Yang Kyun Ryu, Sung Ho Kim, Heung Tae Kim, Se-Woong Oh, Yeol Hong Kim. YH41723 (IMC-202), a Novel TIGITxPD-L1 bispecific antibody, leads to potent anti-tumor immunity through T cell engaging and T/NK cell activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2358.

Euphohelioscopin A enhances NK cell antitumor immunity through GSDME-triggered pyroptosis.

Immune evasion by cancer cells poses a significant challenge for natural killer (NK) cell-based immunotherapy. Pyroptosis, a newly discovered form of programmed cell death, has shown great potential for enhancing the antitumor immunity of NK cells. Consequently, targeting pyroptosis has become an attractive strategy for boosting NK cell activity against cancer. In this study, various assays were conducted, including NK cell cytotoxicity assays, flow cytometry, xenograft tumor models, real-time PCR, and ELISA to assess NK cell-mediated cell killing, as well as gene and protein expressions. The results indicated that Euphohelioscopin A (Eupho-A), a potential pyroptosis activator, enhances NK cell-mediated lysis of tumor cells, resulting in inhibiting tumor growth that could be reversed by NK cell depletion. Furthermore, we found that Eupho-A significantly enhanced IFN-γ production in NK cells and synergistically up-regulated GSDME with IFN-γ in cancer cells. Eupho-A also increased the cleavage of GSDME, promoting GZMB-induced pyroptosis, which could be reversed by GSDME knockdown and IFN-γ blockade. Overall, the findings suggested that Eupho-A enhanced NK cell-mediated killing of cancer cells by triggering pyroptosis, making Eupho-A a promising pyroptosis activator with great potential for using in NK cell-based cancer immunotherapy.

Abstract B040: Trispecific killer engagers against IGF1R and fetal form of insulin receptor induce human natural killer cell mediated killing of hormone receptor positive breast cancer in vitro and in vivo

Abstract Patients with hormone receptor-positive (HR+) breast cancers frequently recur with metastatic disease 5-20 years after the initial diagnosis and completion of chemotherapy and prolonged treatment with hormonal therapy. Thus, patients with metastatic HR+ breast cancer need new therapeutic options. A potential mechanism of therapeutic resistance in HR+ patients is the presence of slow-growing, well-differentiated cancer cells that result in clinically detectable metastases after a prolonged latency. One way to eliminate these cancer cells is with immunotherapy (IT). Unfortunately HR+ breast cancers have not responded to current T-cell based IT. The objective of this study is to target HR+ breast cancers using a natural killer (NK) cell based approach that targets cell surface receptors in HR+ breast cancer. The type I IGF receptor (IGF1R) is expressed on HR+ breast cancers and its expression is tightly related to ER function. Endocrine therapy resistance is associated with increased expression of the A-isoform or fetal form of IR (IR-A) and depend on IR signaling. We hypothesized that a drug that would target NK cells to IGF1R or IR-A expressing HR+ cells will be effective in killing them. We generated IGF1R or IR-A specific Tri specific Killer Engagers (TriKE) that leverage expression of IGF1R and IR-A on HR+ cells to cause NK directed death. The IGF1R TriKE consists of humanized single domain antibody (VHH) sequence of a CD16 nanobody to engage and activate NK cells, a humanized VHH of a nanobody against IGF1R to target HR+ breast cancer cells, and an IL-15 molecule between them to drive NK cell expansion and survival. The IGF1R TriKE did not bind embryonal fibroblasts from IGF1R knock out mice (R- cells) but bound R-/IGF1R cells (R- cells engineered to express human IGF1R) and to IGF1R+ MCF-7 and T47D breast cancer cells indicating specific binding to IGF1R on cells. It did not cause downregulation of IGF1R levels in multiple HR+ breast cancer cells and did not inhibit signaling via IGF1R. It specifically induced NK cell degranulation, measured by surface CD107a expression and intracellular IFNγ, against IGF1R+ target breast cancer cells (MCF-7, T-47D, ZR-75-1) in a functional assay compared to the anti-IGF1R nanobody. It did not induce degranulation of NK cells against IGF1R negative cells suggesting that the functionality was specific for IGF1R expressing targets. The IGF1R TriKE enhanced cell killing of HR+ breast cancer cells as measured by cytotoxicity assays. IGF1R TriKE combined with human NK cells inhibited tumor growth of MCF-7 tumors in NSG mice compared to control groups. Human NK cells persisted in peripheral blood three weeks after final NK infusion based on flow cytometry assessment. The IR-A TriKE incorporated a novel engineered non-immunoglobulin IR-A specific peptide binder. Our preliminary data show that the IR-A TriKE degranulated NK cells against breast cancer cells overexpressing IR-A. These data indicate that this strategy could be an effective treatment for HR+ metastatic breast cancer and make them responsive to IT. Citation Format: Courtney Baar, Emily Chiu, Yvette Soignier, Behiye Kodal, Jeffrey S Miller, Martin Felices, Deepali Sachdev. Trispecific killer engagers against IGF1R and fetal form of insulin receptor induce human natural killer cell mediated killing of hormone receptor positive breast cancer in vitro and in vivo [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B040.

Targeting SLC3A2 Sensitizes AML Cells Towards NK Cell-Mediated Killing

Acute myeloid leukemia (AML) is an aggressive hematological malignancy with poor prognosis; hence, new therapeutic strategies are urgently needed. Natural Killer (NK) cells play a key role in tumor immune surveillance, but their anti-tumor activity in AML is often attenuated due to immunosuppressive effects of the malignant cells. Thus, strategies to restore NK cell function has therapeutic potential by boosting endogenous NK cells. In particular, the identification of cell surface proteins on AML cells that inhibit NK cell-mediated killing may reveal new targets for antibody-based therapies. To identify such targets, we performed a pooled CRISPR screen directed to 1389 cell surface genes in Mono-mac-6 (MM6), a human AML cell line. The MM6 cells were co-cultured with primary human NK cells for four days in media supplemented with the cytokines IL-2 and IL-15. Among the top hits were several genes coding for MHC class I molecules, which are known negative regulators of NK cells, demonstrating that the screen was robust. Notably, the screen also identified that SLC3A2 disruption sensitized the MM6 cells towards NK cell-mediated killing. SLC3A2 encodes the heavy chain of the transmembrane protein CD98 (CD98hc), which plays a key role in integrin signaling, regulation of intracellular calcium and the transport of L-type amino acids. CRISPR-mediated deletion of SLC3A2 in MM6 cells resulted in a two-fold downregulation of the transcripts of several inhibitory ligands of NK cells, including HLA-A, HLA-B, HLA-C and HLA-E. Upon co-culture, loss of SLC3A2 expression in MM6 cells induced an upregulation of the degranulation marker CD107a on NK cells (p<0.01), resulting in increased killing of the AML cells. CD98hc consists of two functional domains - one responsible for integrin signaling and the other responsible for amino acid transport. To identify which of these processes affect the sensitivity of AML cells towards NK cell-mediated killing, we performed rescue experiments by overexpression of mutated SLC3A2 cDNAs following SLC3A2 knockdown in MM6 cells. Overexpression of SLC3A2 wild-type or an integrin signaling deficient SLC3A2 cDNA rescued the inhibitory effect on NK cells. In contrast, the SLC3A2 variant that lacked the amino acid transportation domain failed to inhibit NK cells. These findings suggest that it is the amino acid transportation function of SLC3A2 that regulates the sensitivity of AML cells to NK cells. To validate these findings, we cultured MM6 cells in media deprived of three key amino acids (leucine, isoleucine and phenylalanine) transported across the plasma membrane by CD98. Consistent with our previous findings, culturing the MM6 cells in the amino acid deprived media resulted in a two-fold downregulation of HLA class I molecules (p<0.001) accompanied by an increased killing by NK cells. To assess the clinical relevance of these findings, we measured CD98hc expression on AML patient samples and corresponding normal bone marrow cells. CD98 levels were about 1.8-fold higher (p<0,001) in the AML samples (n = 30) compared to normal bone marrow cells (n = 5). Treating the AML patient cells with a monoclonal antibody targeting CD98 resulted in a 1.63-fold increase (p<0.0001) in NK cell-mediated killing. Corresponding treatments using normal bone marrow cells resulted in a 1.36-fold (p<0.01) increase in NK cell-mediated killing. Intriguingly, the CD98 antibody also negatively affected the viability (1.41-fold, p<0.0001) of AML patient cells in the absence of NK cells, this effect was not observed on normal bone marrow cells. Taken together, we here performed CRISPR screening on AML cells co-cultured with NK cells and identified SLC3A2 as a novel regulator of NK cells. Mechanistically, it is the amino acid transport function of SLC3A2 that regulate the sensitization of AML cells towards NK cell killing. Targeting of CD98 using a monoclonal antibody selectively increased NK cell-mediated killing of AML patient cells compared to normal bone marrow cells. These findings highlight CD98 as a new promising target on AML that boost NK cell-mediated tumor immune surveillance.

Development and implementation of natural killer cell simultaneous ADCC and direct killing assay

Assays to quantify natural killer (NK) cell killing efficacy have traditionally focused on assessing either direct killing or antibody dependent cell-mediated cytotoxicity (ADCC) independently. Due to the probability that immunotherapeutic interventions affect NK cell-mediated direct killing and NK cell-mediated ADCC differently, we developed an assay with the capacity to measure NK cell-mediated direct killing and ADCC simultaneously with cells from the same human donor. Specifically, this design allows for a single NK cell population to be split into several experimental conditions (e.g., direct killing, ADCC), thus controlling for potential confounders associated with human-to-human variation when assessing immunotherapy impacts. Our Natural Killer cell Simultaneous ADCC and Direct Killing Assay (NK-SADKA) allows researchers to reproducibly quantify both direct killing and ADCC by human NK cells. Furthermore, this optimized experimental design allows for concurrent analysis of the NK cells via flow cytometric immunophenotyping of NK cell populations which will facilitate the identification of relationships between NK cell phenotype and the subsequent killing potential. This assay will be valuable for assessing the broader impact(s) of immunotherapy strategies on both modes of NK cell killing.

Type 3 Innate Lymphoid Cells Promote Acute Myeloid Leukemia Immune Evasion and Expansion

Acute Myeloid Leukemia (AML) is an aggressive myeloid malignancy originated in the bone marrow with poor overall survival rates of less than 30%. The immune system has been shown to play an important role in detecting and eliminating leukemic cells. Recent studies have described a population of immune cells termed Innate lymphoid cells (ILCs). ILCs are known to regulate both innate and adaptive immunity in an antigen-independent manner and are believed to be among the first immune cells to interact with malignantly transformed cells. Natural killer (NK) cells are a subset of ILCs and are known to inhibit AML progression, however the impact of other ILCs is not yet fully understood. Type 3 ILCs (ILC3s) have key roles in maintaining homeostasis in mucosal immunity through their ability to secrete cytokines including IL-17, IL-22, TNFα and GM-CSF (pro-myeloid). An expansion of ILC3s has recently been observed in solid tumors, however the overall functional impact of ILC3s in the setting of AML remains poorly understood and warrants further investigation. We first utilized an MLL-partial tandem duplication and FLT3-internal tandem duplication Flt3-ITD double knock-in mutation murine model of AML that recapitulates two clinically relevant mutations in human AML. Using this AML model, we discovered an expansion of ILC3s in the bone marrow of leukemic mice compared to wild-type control mice (2.364% +/- 0.40% AML vs 0.045% +/- 0.40% WT, n=5, p<0.0001). We also observed an increase in ILC3s in the bone marrow of untreated AML patients relative to age matched donor controls (7.013% +/- 2.6% vs. 2.328% +/- 2.6%). Our published data have previously shown AML blasts secrete aryl hydrocarbon receptor (AHR) ligands, which can bind and activate the transcription factor AHR in ILC precursors and mature ILCs. AHR is an important transcription factor in ILC3 development. Therefore, we hypothesized that the ILC3 increase was due at least in part to AHR-mediated increased ILC3 differentiation. To address this hypothesis, we isolated the ILC precursor (ILCP) from normal human donors and co-cultured with AML cells. By regulating AHR activity in this system, we showed that ILC3s are expanded in AML in part due to AML-mediated AHR activation (28.02% +/- 3.89% without AML, 60% +/- 5.5% with AML and 27% +/- 5% AML+AHR inhibitor, n=15, p<0.001). Next, we sought to determine the direct impact of ILC3s on AML proliferation and differentiation that could contribute to AML relapse. We utilized a colony forming assay (CFU) assay in the presence or absence of ILC3s. Bone marrow from primary untreated AML patients was cultured alone or with ILC3s (Lin-CD94-NKp44+). AML samples co-cultured with ILC3s had significantly increased colony formation relative to AML alone (69.4 CFU AML+ILC3 vs 42.7 CFU AML alone, n=8, p<0.05). Post-culture, we observed significant increases in the transcript of GM-CSF and TNFα in ILC3s co-cultured with AML marrow as compared to ILC3s alone. Furthermore, in our immunocompetent murine AML model, we observed significantly higher production of GM-CSF and TNFα by ILC3s in the bone marrow of leukemic mice relative to nonleukemic controls (GM-CSF: 11.08% +/- 1.6 AML vs 1.128% +/- 1.6 WT, n=10, p<0.0001; TNFα: 5.456% +/- 1.3 AML vs 1.307% +/- 1.3 WT, n=10, p<0.05), suggesting a potential mechanism of ILC3-mediated increased colony formation. Lastly, to determine if ILC3 expansion impacted NK cell immune surveillance, we co-cultured normal donor human ILC3s with AML cells, separated by transwell, for 48 hours before subjecting the AML cells to an NK cell cytotoxicity assay. We observed significantly reduced NK cell killing of AML cells when co-cultured with ILC3s compared to controls, suggesting ILC3s protect AML cells from NK cell-mediated killing (24.3% killing +/- 3.81% AML alone vs 14.57% +/- 1.35% AML with ILC3, n=18, p<0.01). Collectively, these data support a model in which AML-mediated AHR activation promotes ILC3 expansion to both support AML proliferation and protect AML blasts from immune surveillance. Future studies will focus in exploring how to target these interactions to design effective therapeutic approaches and improve patient clinical outcomes.

Epigenetic Scarring Leads to Irreversible NK Cell Dysfunction in Myeloid Malignancies

Myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) belong to the same spectrum of myeloid malignancies and have extremely poor outcomes in the relapsed/refractory setting. Despite advances in the understanding of the pathogenesis and molecular mechanisms of these disorders, and incremental improvements in treatment regimens, patients with MDS and AML often relapse and fail to achieve cure. These and other factors underscore the urgent need for new therapeutic alternatives that will improve the clinical outcomes of these patients. Immunotherapy using checkpoint molecule inhibitors and adoptive cell therapy using autologous immune effector cells have been mostly unsuccessful in patients with MDS and AML. This could be due to the immunosuppressive tumor microenvironment in the bone marrow niche or to intrinsic dysfunction in the immune effector cells of these patients. Natural killer (NK) cells are innate lymphocytes that play an important role in cancer immune surveillance and have distinct advantages over T cells as candidates for immunotherapy. Myeloid blasts are inherently susceptible to NK cell-mediated killing as they express many of the ligands recognized by NK cell activating receptors. However, malignant myeloid blasts are capable of adapting and developing defense mechanisms that allow them to evade NK cell-mediated cytotoxicity. Little is known about the mechanisms of NK cell immune evasion developed by myeloid blasts. Here, we show that NK cells from patients with myeloid malignancies display a global dysfunction with severely impaired secretory function and killing capacity. Single cell RNAseq and mass cytometry experiments revealed that these NK cells from MDS and AML patients display an exhausted phenotype at the transcriptomic and proteomic levels. We also show that these NK cells have an altered metabolism compared with age matched healthy control NK cells. We show that this dysfunction is mediated by a crosstalk between myeloid blasts and NK cells and cell-cell contact dependent release of transforming growth factor beta (TGF-β). This crosstalk leads to a profound epigenetic reprogramming of NK cells driven by transcription factors known to mediate exhaustion and immune suppression. Myeloid blast-induced NK dysfunction and epigenetic state of exhaustion can be prevented by pharmacologically inhibiting the TGF-β pathway or knockout of TGFBR2 in NK cells. However, our data reveal that once this dysfunction occurs it is irreversible owing to epigenetic scarring driven by the transcription factor BATF. In fact, we show that TGF-β induces the expression of BATF in NK cells, which in turn mediates a gene regulatory program leading to NK cell dysfunction by driving the expression of exhaustion and inhibitory genes (e.g. HAVCR2, ENTPD1, CTLA4, TGFBR2). Collectively, our findings reveal a novel mechanism of NK cell immune evasion manifested by stable epigenetic rewiring and inactivation of NK cells by myeloid blasts. Our data support the use of allogeneic sources for adoptive NK cell therapy in combination with strategies aiming at preventing immune suppression to treat myeloid malignancies rather than therapies aiming at reversing or rescuing the function of autologous NK cells.

Human iPSC-Derived NK Cells with Knock-in of the BCL2 G101V Mutation Are Resistant to Venetoclax and Demonstrate Improved Anti-AML Activity In Vivo

Treatment options for acute myeloid leukemia (AML) patients who are unfit for intensive chemotherapy are limited. Both targeted therapy and cellular therapy have been investigated, typically as separate treatments. For patients with AML unfit for intensive induction chemotherapy, venetoclax, a BCL-2 inhibitor, containing regimens have significantly improved treatment outcomes. However, patients treated long-term with venetoclax can develop resistance. Based on the characterization of the BCL2 G101V mutation that mediates resistance to venetoclax, we investigated the ability of homozygous BCL2 G101V knock-in in induced pluripotent stem cell (iPSC)-derived natural killer (NK) cells to promote resistance to venetoclax in these effector cells to enable concurrent treatment with venetoclax and the engineered iPSC-derived NK cells that we hypothesize will provide improved NK cell-mediated killing of AML. Our group has pioneered the production of genetically modified NK cells from human iPSCs. iPSCs provide an advantage of a stable platform for genome engineering and previous studies demonstrate we can engineer iPSCs to express or delete genes of interest to derive genetically modified iPSC-NK cells with improved anti-tumor activity. To generate iPSC-derived NK cells with resistance to venetoclax, we employed CRISPR-Cas9 technology to knock-in the BCL2 G101V mutation (BCL2 G101V) in iPSCs. iPSCs homozygous for BCL2 G101V were selected and differentiated to NK cells. Homozygous BCL2 G101V engineered iPSC-NK cells demonstrated resistance to venetoclax compared to wildtype (WT) iPSC-NK cells in vitro. BCL2 G101V iPSC-NK cells were 94-fold more resistant to venetoclax compared to wildtype iPSC NK cells with an EC50 of 6018 nM, above the serum levels of patients receiving venetoclax. Analysis of cell surface proteins demonstrated that both sets of iPSC-NK cells had a typical NK cell phenotype with no differences in expression of receptors analyzed. There was no difference seen in cytotoxicity against K562 tumor cells between BCL2 G101V iPSC-NK cells and WT-iPSC NK cells. Additional functional analyses demonstrated that activity of the BCL2 G101V iPSC NK cells was preserved upon exposure to venetoclax. Cytotoxic activity, as measured by CD107a expression on WT iPSC-NK cells stimulated by MOLM13 AML tumors cells, was reduced nearly 3-fold upon addition of venetoclax. In contrast, activation of BCL2 G101V iPSC NK cells was not significantly affected by addition of venetoclax. This resistance to venetoclax was confirmed in longer term 36-hour Incucyte cytotoxicity assays where BCL2 G101V iPSC-NK cells demonstrated more than 10-fold increase in anti-AML activity compared to the WT-iPSC-NK cells. We then conducted in vivo studies to test the WT and engineered NK cells with and without addition of venetoclax in an AML xenograft model using NSG mice (Figure Panels A-D). These studies used MOLM13 AML cells made resistant to venetoclax and demonstrated that without venetoclax treatment, both the WT and the BCL2 G101V iPSC NK cells mediate effective anti-AML killing. With addition of venetoclax, the WT NK cells were unable to effectively kill the AML cells while the BCL2 G101V iPSC cells mediated potent anti-AML activity and demonstrated significantly improved survival when the NK cells are given in combination with venetoclax. Specifically, in this system, the mice treated with WT iPSC-NK cells had a median survival of 22.8 days while the median survival of mice treated with the BCL2 G101V iPSC NK cells was not reached (p<0.01) Intriguingly, BCL2 G101V iPSC NK cells also demonstrated improved activity against MOLM13 cells resistant to venetoclax. Together our results demonstrate that iPSC-NK cells can be engineered to generate venetoclax-resistance for use in combination with concurrent venetoclax therapy to markedly improve treatment of AML. Furthermore, this work demonstrates that novel drug resistance mechanisms can be introduced via genome engineering into iPSC-derived NK cells as a new strategy to produce improved cell products for “off-the-shelf” therapy.

IMMU-55. THERAPEUTIC WINDOW ENABLING ERADICATION OF RESIDUAL GLIOMA STEM CELLS BY INTRACRANIAL NK CELL AND EXTRACELLULAR VESICLE-MEDIATED THERAPY FOLLOWING TEMOZOLOMIDE-INDUCED TUMOUR DEPOPULATION

Abstract Glioblastoma (GBM) is an incurable brain cancer, where dismal outcomes result from disease recurrence driven by tumour-initiating glioma stem cells (GSCs). GSCs survive and expand in the brain after surgery, radiation and temozolomide (TMZ) amidst weak immune and natural killer (NK) cell surveillance. NK cell-mediated killing of GBM cells occurs at effector to target rations precluding effective eradication as enforced by clinical trials with autologous NK cells in an adjuvant setting. Here we explore in a human GSC xenograft model whether tumor depopulation using high dose Temozolomide (TMZ) could create a window of curative opportunity for endogenous or exogenous NK cells. We observed that while subcutaneous (sc) xenografts of patient derived GSCs are infiltrated by endogenous functional (NCR1+) NK cells in SCID mice, the corresponding intracranial (ic) tumours remained NK cell depleted. In NK-deficient NSG mice, neither site contained functional NK cells. Notably, while TMZ caused near complete regression of GSC xenografts in both strains of mice and both locations (sc and ic), this was followed by recurrence of drug resistant lesions in all cases except NK-infiltrated sc SCID xenografts. This effect was obliterated by anti-sialo GM1 treatment. To explore whether direct delivery of NK cells into depopulated intracranial tumours would change the lethal course of the disease, mice were injected with GSCs ic, and upon tumour formation were treated with a sequence of TMZ (systemically), and two days later with irradiated NK92MI. Remarkably, this combined therapy completely obliterated recurrent disease. To assess whether NK92MI cells could be replaced by their derived extracellular vesicles (NK-EVs), the latter were injected i.c. post TMZ in GSC xenograft bearing mice. A single injection of NK-EVs resulted in tumour eradication in some but not all mice. Thus, chemotherapy-dependent tumour depopulation may create a unique window of opportunity for curative NK-mediated immunotherapy in GBM.

Porcine UL-16 Binding Protein 1 Is Not a Functional Ligand for the Human Natural Killer Cell Activating Receptor NKG2D.

Natural killer (NK) cells play a vital role in xenotransplantation rejection. One approach to induce NK cell immune tolerance is to prevent the NK cell-mediated direct killing of porcine cells by targeting the interaction of the activating receptor NKG2D and its ligands. However, the identity of porcine ligands for the human NKG2D receptor has remained elusive. Previous studies on porcine UL-16 binding protein 1 (pULBP-1) as a ligand for human NKG2D have yielded contradictory results. The goal of the present study was to clarify the role of pULBP-1 in the immune response and its interaction with human NKG2D receptor. To accomplish this, the CRISPR/Cas9 gene editing tool was employed to disrupt the porcine ULBP-1 gene in a 5-gene knockout porcine endothelial cell line (GGTA1, CMAH, β4galNT2, SLA-I α chain, and β-2 microglobulin, 5GKO). A colony with two allele mutations in pULBP-1 was established as a 6-gene knockout pig cell line (6GKO). We found that pULBP-1-deficient pig cells exhibited a reduced binding capacity to human NKG2D-Fc, a recombinant chimera protein. However, the removal of ULBP-1 from porcine endothelial cells did not significantly impact human NK cell degranulation or cytotoxicity upon stimulation with the pig cells. These findings conclusively demonstrate that pULBP-1 is not a crucial ligand for initiating xenogeneic human NK cell activation.

FT538, iPSC-Derived NK Cells Are Potent Inducers of Apoptosis in AML Cells and Their Effect Is Synergistic in Combination with Approved Therapeutic Strategies

Background: Natural killer (NK) cell-based therapies have been increasingly studied with their advantages of less treatment-related toxicity and lack of HLA restriction. Induced pluripotent stem cell (iPSC)-derived NK cells offer an opportunity for a standardized, off-the-shelf treatment with the potential to treat a wider patient population. FT538 cells are triple gene-edited iPSC-derived NKs that express a high affinity non-cleavable CD16 maintaining constant activity, a CD38 knock out preventing CD38 antibody-induced fratricide, and an IL-15/IL-15R fusion preventing the need for cytokine administration, the main source of side effects in NK cell-based therapies. Several studies have shown success in treating AML with NK cell therapy, but the effect of iPSC-derived NK cell therapy in AML is unexplored. We hypothesized that FT538 cells may be able to target high-risk AML that is traditionally resistant to most chemotherapeutic agents and synergize with Venetoclax, 5-azacytidine, Cytarabine, and Gilteritinib. Methods: To examine the effect of the FT538 cells on AML cells, we co-cultured FT538 cells at ratios of 2:1, 4:1, and 8:1 with 8 AML cell lines: OCI-AML2, OCI-AML3, THP1, U937, Molm-13, Molm-14, MV4-11, and Kasumi-1, and with cells from 11 different AML patients. We analyzed the NK cell-induced apoptosis through an Annexin-V binding assay using IncuCyte live cell imaging. As Molm-13 and MV4-11 cell lines are FLT3 mutated, to determine the combination effect of FLT3 inhibitors with FT538 cells, we treated Molm-13 and MV4-11 cells with Gilteritinib for 24 hours before seeding the FT538 cells and co-culturing overnight. The effects of the combination were then analyzed through flow cytometry with a Beckman Coulter CytoFlex. Finally, to determine the combinatorial effect of the FT538 cells with approved therapies, we treated OCI-AML3 and U937 cell lines with Venetoclax, Azacitidine, and Cytarabine. After treatment, we performed flow cytometry to measure the leukemic cell death following the combinatorial therapies. Results: We observed FT538 NK-mediated killing in all the leukemic cell lines tested. A two-way ANOVA determined that an increase in the FT538 to AML cell ratio resulted in an increase in NK cell-mediated killing of AML cells (p<0.0001). Interestingly, the number of apoptotic AML cells was 1.5 to 6.1-fold higher in the OCI-AML2, OCI-AML3, U937, and THP1 cell lines than in the Molm-13, Molm-14, MV4-11, and Kasumi-1 cell lines (p<0.0001). This could be related to the FLT3 mutations in the Molm-13, Molm-14, and MV4-11 cell lines or to the TP53 mutation in the Kasumi-1 cell line. Further, to validate this finding in primary AML cells, we observed a ratio-dependent effect on FT538-mediated killing of AML cells. However, we did not observe any statistical difference by mutation, though this could be related to the limited sample size for specific mutations. Finally, flow cytometric analysis of the effects of combination treatment demonstrated that the FT538 cells synergize with Venetoclax, or Cytarabine, or Azacitidine, or Gilteritinib (p<0.05) in the killing of AML cells. This could be because NKG2DL upregulation has been shown in AML cells treated with Venetoclax and FLT3 inhibitors and in Cytarabine-resistant AML cells, and the NKG2D/NKG2DL pathway is a main mechanism of NK cell-mediated killing. Conclusion: iPSC-derived NK therapy offers a standardized, off-the-shelf option for NK cell therapies. FT538 iPSC-derived NK cells induce apoptosis in AML cell lines and patient samples in a dose-dependent manner and show a synergistic effect with Venetoclax, Gilteritinib, Azacitidine, and Cytarabine. Therefore, iPSC-derived NK cell therapy may be a promising possibility for AML treatment, particularly for patients resistant to standard therapies.

Upregulation of the NKG2D Ligand ULBP2 by JC Polyomavirus Infection Promotes Immune Recognition by Natural Killer Cells.

JC polyomavirus (JCPyV) causes progressive multifocal leukoencephalopathy (PML), a potentially fatal complication of severe immune suppression with no effective treatment. Natural killer (NK) cells play critical roles in defense against viral infections; however, NK-cell response to JCPyV infection remains unexplored. NK- and T-cell responses against the JCPyV VP1 were compared using intracellular cytokine staining upon stimulation with peptide pools. A novel flow cytometry-based assay was developed to determine NK-cell killing efficiency of JCPyV-infected astrocyte-derived SVG-A cells. Blocking antibodies were used to evaluate the contribution of NK-cell receptors in immune recognition of JCPyV-infected cells. In about 40% of healthy donors, we detected robust CD107a upregulation and IFN-γ production by NK cells, extending beyond T-cell responses. Next, using the NK-cell-mediated killing assay, we showed that coculture of NK cells and JCPyV-infected SVG-A cells leads to a 60% reduction in infection, on average. JCPyV-infected cells had enhanced expression of ULBP2-a ligand for the activating NK-cell receptor NKG2D, and addition of NKG2D blocking antibodies decreased NK-cell degranulation. NKG2D-mediated activation of NK cells plays a key role in controlling JCPyV replication and may be a promising immunotherapeutic target to boost NK-cell anti-JCPyV activity.

Affibody-based hBCMA x CD16 dual engagers for NK cell-mediated killing of multiple myeloma cells

We describe the development and characterization of the (to date) smallest Natural Killer (NK) cell re-directing human B Cell Maturation Antigen (hBCMA) x CD16 dual engagers for potential treatment of multiple myeloma, based on combinations of small 58 amino acid, non-immunoglobulin, affibody affinity proteins. Affibody molecules to human CD16a were selected from a combinatorial library by phage display resulting in the identification of three unique binders with affinities (KD) for CD16a in the range of 100 nM–3 µM. The affibody exhibiting the highest affinity demonstrated insensitivity towards the CD16a allotype (158F/V) and did not interfere with IgG (Fc) binding to CD16a. For the construction of hBCMA x CD16 dual engagers, different CD16a binding arms, including bi-paratopic affibody combinations, were genetically fused to a high-affinity hBCMA-specific affibody. Such 15–23 kDa dual engager constructs showed simultaneous hBCMA and CD16a binding ability and could efficiently activate resting primary NK cells and trigger specific lysis of a panel of hBCMA-positive multiple myeloma cell lines. Hence, we report a novel class of uniquely small NK cell engagers with specific binding properties and potent functional profiles.

ANGPTL3 affects the metastatic potential and the susceptibility of ovarian cancer cells to natural killer cell-mediated cytotoxicity

High metastatic potential and resistance to immunotherapy lead to poor survival in patients with ovarian cancer. Angiopoietin-like protein 3 is aberrantly expressed and exerts diverse roles in the progression of several cancers. However, its function in ovarian cancer is unknown. Here, decreased expression of angiopoietin-like protein 3 was observed in ovarian cancer tissues and cells. Moreover, patients with high expression of angiopoietin-like protein 3 had longer overall survival and progression-free survival, indicating a good prognosis for patients. Furthermore, angiopoietin-like protein 3 overexpression inhibited ovarian cancer cell proliferation. Concomitantly, high invasion and the occurrence of epithelial-to-mesenchymal transition of cancer cells were restrained after angiopoietin-like protein 3 elevation. Up-regulation of angiopoietin-like protein 3 expression further increased interleukin 2-treated natural killer cell activation by increasing CD69 expression and production of interferon gamma and tumor necrosis factor-alpha when natural killer cells were co-cultured with ovarian cancer cells. Importantly, angiopoietin-like protein 3 overexpression enhanced natural killer cell-evoked cytotoxicity and apoptosis of cancer cells, indicating the pro-tumor killing ability of angiopoietin-like protein 3 for natural killer cells. Mechanistically, angiopoietin-like protein 3 elevation inhibited activation of the Janus Kinase/Signal transducer and activator of transcription 3 signaling in ovarian cancer cells by inhibiting protein expression of phospho-Janus Kinase 2, phospho-Signal transducer and activator of transcription 3, downstream matrix metallopeptidase 2 and programmed cell death 1. Moreover, blocking the Janus Kinase/Signal transducer and activator of transcription 3 pathway via their inhibitor Stattic restrained ovarian cancer cell proliferation, invasion, epithelial-to-mesenchymal transition, and promoted natural killer cell killing to ovarian cancer cells. Thus, these findings reveal that angiopoietin-like protein 3 may act as an anti-oncogenic regulator to inhibit the metastatic potential and enhance the susceptibility of ovarian cancer cells to natural killer cell-mediated killing. Consequently, angiopoietin-like protein 3 may regulate metastatic potential and immune escape from natural killer cells, indicating a promising therapeutic strategy for ovarian cancer.

Delivery of a novel membrane-anchored Fc chimera enhances NK cell-mediated killing of tumor cells and persistently virus-infected cells.

Antibody-dependent cellular cytotoxicity (ADCC) is one of the most powerful mechanisms for Natural Killer (NK) cells to kill cancer cells or virus-infected cells. A novel chimeric protein (NA-Fc) was created, which when expressed in cells, positions an IgG Fc domain on the plasma membrane, mimicking the orientation of IgG bound to the cell surface. This NA-Fc chimera was tested with PM21-NK cells, produced through a previously developed particle-based method which yields superior NK cells for immunotherapeutic applications. Real time viability assays revealed higher PM21-NK killing of both ovarian and lung cancer cells expressing NA-Fc, which correlated with increased release of TNF-α and IFN-γ cytokines from NK cells and was dependent on CD16-Fc interactions. Lentivirus delivery of NA-Fc to target cells increased the rate of PM21-NK cell killing of A549 and H1299 lung, SKOV3 ovarian and A375 melanoma cancer cells. This NA-Fc-directed killing was extended to virus infected cells, where delivery of NA-Fc to lung cells that were persistently infected with Parainfluenza virus resulted in increased killing by PM21-NK cells. In contrast to its effect on PM21-NK cells, the NA-Fc molecule did not enhance complement mediated lysis of lung cancer cells. Our study lays the foundation for application of the novel NA-Fc chimera that could be delivered specifically to tumors during oncolytic virotherapy to mark target cells for ADCC by co-treatment with adoptive NK cells. This strategy would potentially eliminate the need to search for unique cancer specific antigens for development of new antibody therapeutics.

Intrinsic suppression of type I interferon production underlies the therapeutic efficacy of IL-15-producing natural killer cells in B-cell acute lymphoblastic leukemia

BackgroundType I interferons (IFN-Is), secreted by hematopoietic cells, drive immune surveillance of solid tumors. However, the mechanisms of suppression of IFN-I-driven immune responses in hematopoietic malignancies including B-cell acute lymphoblastic...

Signatures of HIV-infected CD4 +T cell resistance to NK cell-mediated killing

Abstract BACKGROUND: In vitroexperiments in which HIV-infected CD4 +T cells are co-cultured with natural killer (NK) cells yield incomplete elimination of the infected cells. We therefore hypothesize that cell-intrinsic pathways in CD4 +T cells are differentially regulated in HIV-infected cells to mediate resistance to NK cell-mediated killing. METHODS: Mock-infected and HIV-89.6-infected CD4 +T cells from 6 HIV −donors were co-cultured overnight +/− autologous NK cells. Following co-culture, cells were stained for the surface exposed HIV envelope protein using fluorescently conjugated HIV antibodies. Fluorescence activated cell sorting was then used to isolate infected and uninfected cells, followed by bulk RNA-sequencing. Transcripts from infected and uninfected cells co-cultured overnight with versus without NK cells were compared. RESULTS: RNA-seq analysis of CD4 +T cells that survived co-culture with NK cells revealed dozens of differentially expressed genes in infected, but not uninfected cells. This included upregulation of interferon-stimulated genes, including PD-L1 (p adj=3×10 −6), and NF-kB-related genes. Additional upregulated genes in the surviving infected cells included c-Fos (p adj=1.9×10 −5), c-Jun (p adj=4.9×10 −8), and cathepsin L (p adj=5×10 −3). CONCLUSIONS: NF-kB genes that are downregulated in infected cells, potentially through Vpu activity, are normalized in surviving infected cells. This may be due to NK cell targeting of Vpu-mediated HLA-C downregulation. Deconvolution of the relative contributions of specific genes/proteins to target cell resistance will reveal novel targets for the development of therapeutics to eliminate the HIV reservoir.

IFN-β activates cytotoxic function of human natural killer cells toward IL-27 and poly(I:C) stimulated PC3 and DU145 cells

Natural killer (NK) cell phenotype and function are altered in patients with prostate cancer, and increased NK cell activity is associated with a better prognosis in patients with disease. For patients with advanced stage prostate cancer, immunotherapies are a promising approach when standard treatment options have been exhausted. With the rapid emergence of NK cell-based therapies, it is important to understand the mechanisms by which NK cells can be triggered to kill cancer cells that have developed immune-evasive strategies. Altering the cytokine profiles of advanced prostate cancer cells may be an area to explore when considering ways in which NK cell activation can be modulated. We have previously demonstrated that combining the cytokine, IL-27, with TLR3 agonist, poly(I:C), changes cytokine secretion in the advanced prostate cancer models, PC3 and DU145 cells. Herein, we extend our previous work to study the effect of primary human NK cells on prostate cancer cell death in an in vitro co-culture model. Stimulating PC3 and DU145 cells with IL-27 and poly(I:C) induced IFN-β secretion, which was required for activation of primary human NK cells to kill these stimulated prostate cancer cells. PC3 cells were more sensitized to NK cell-mediated killing when compared to DU145 cells, which was attributed to differential levels of IFN-β produced in response to stimulation with IL-27 and poly(I:C). IFN-β increased granzyme B secretion and membrane-bound TRAIL expression by co-cultured NK cells. We further demonstrated that these NK cells killed PC3 cells in a partially TRAIL-dependent manner. This work provides mechanistic insight into how the cytotoxic function of NK cells can be improved to target cancer cells.

Abstract 1806: Modulation of natural killer cell immune response to tumor with novel synthetic tumor -immune cell agonist, NK-TICA(r)

Abstract The tumor specific activation of natural killer (NK) cells with Bicycles is an area of active investigation in immune oncology. NK cells are highly responsive immune cells that can detect and eliminate tumor cells and bridge innate to adaptive immune responses. Bicycles are small (ca.1.5kDa), chemically synthetic, structurally constrained peptides discovered via phage display and optimized using structure-driven design and medicinal chemistry approaches. We have applied the Bicycle platform technology to discover and evaluate a new class of fully synthetic molecules termed NK tumor immune cell agonists (NK-TICA®). The NK-TICA® consists of chemically coupled Bicycles® that bind specifically to the key activating receptor, NKp46, and to tumor antigens, that results in highly potent, antigen-dependent receptor activation and NK cell activation. We demonstrate potent, selective binding of our Bicycles to receptor-expressing cells and the capability of the bifunctional molecule to induce NK cell function in vitro. With Bicycle’s novel NK-TICA® compound, we demonstrate the engagement of NK cells, the specific activation and function of NK cells, and enhanced tumor cytotoxicity in a tumor target- and dose-dependent manner. In conclusion, NK-TICAs drive NK cell-mediated tumor cell killing and cytokine production in vitro and as such have the potential to catalyze the development of durable anti-tumor immunity in tumor types not well served by current therapies. We hypothesize that utilization of Bicycle NK-TICA® as a multifunctional immune cell engager will promote the modulation of NK cells, as well as the infiltration and anti-tumor activity of NK cells in solid tumors. Citation Format: Fay Dufort, Christopher J. Leitheiser, Kathleen Ho, Tucker Ezell, Alexandra Rezvaya, Peter Brown, Liuhong Chen, Philip Brandish, Kevin McDonnell, Michael Skynner, Nicholas Keen. Modulation of natural killer cell immune response to tumor with novel synthetic tumor -immune cell agonist, NK-TICA(r) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1806.