NK Cell Metabolism Research Articles

Metabolic and functional recovery of tumor infiltrating NK-cells in Hepatocellular Carcinoma

Introduction: Several immune mechanisms contribute to an immunosuppressive tumour immune milieu: regulatory immune cells, checkpoint receptors, low nutrients and hypoxia that can affect immune cells metabolism and function. Metabolic profiles rather than phenotypic characteristics seem to define the functional role of NK cells and their influence in a correct anti-tumour effect. NK-cell response is functionally impaired in Hepatocellular Carcinoma (HCC), however little is still known about NK-cell metabolism in this tumour.

NK Cell Metabolism and TGFβ – Implications for Immunotherapy

NK cells are innate lymphocytes which play an essential role in protection against cancer and viral infection. Their functions are dictated by many factors including the receptors they express, cytokines they respond to and changes in the external environment. These cell processes are regulated within NK cells at many levels including genetic, epigenetic and expression (RNA and protein) levels. The last decade has revealed cellular metabolism as another level of immune regulation. Specific immune cells adopt metabolic configurations that support their functions, and this is a dynamic process with cells undergoing metabolic reprogramming during the course of an immune response. Upon activation with pro-inflammatory cytokines, NK cells upregulate both glycolysis and oxphos metabolic pathways and this supports their anti-cancer functions. Perturbation of these pathways inhibits NK cell effector functions. Anti-inflammatory cytokines such as TGFβ can inhibit metabolic changes and reduce functional outputs. Although a lot remains to be learned, our knowledge of potential molecular mechanisms involved is growing quickly. This review will discuss our current knowledge on the role of TGFβ in regulating NK cell metabolism and will draw on a wider knowledge base regarding TGFβ regulation of cellular metabolic pathways, in order to highlight potential ways in which TGFβ might be targeted to contribute to the exciting progress that is being made in terms of adoptive NK cell therapies for cancer.

CD38 Knockout Primary NK Cells to Prevent “Fratricide” and Boost Daratumumab Activity

Multiple myeloma (MM) is a plasma cell neoplasm typically characterized by high and uniform CD38 expression. Daratumumab (DARA), a humanized monoclonal antibody targeting CD38 has dramatically improved the outcome of patients with refractory MM, but relapse is inevitable in most cases. DARA eliminates MM cells through several mechanisms including antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity, and antibody-dependent cellular phagocytosis. Mechanisms of resistance to DARA include downregulated CD38 expression on target MM cells, impaired complement directed cytotoxicity via upregulation of complement inhibitory proteins (CD55, CD59), and impaired ADCC via DARA-induced NK cell "fratricide". As it relates to "fratricide", restoring ADCC by DARA-resistant NK cells has been proposed to bolster the therapeutic effect of DARA. Towards this goal, iPSC-derived CD38 knockout (CD38KO) NK cells have shown proof-of-concept for this approach but present major challenges towards clinical translation. Here, we used Cas9-RNP to generate CD38KO primary NK cells and characterized their resistance to DARA-induced "fratricide" and restoration of ADCC, but also assessed the impact of CD38 deletion on NK cell signaling and metabolism. First, primary NK cells were enriched from peripheral blood of healthy donors and expanded on feeder cells expressing mbIL-21 and 4-1BBL (PLoS One. 2012;7(1):e30264). Cas9/gRNA complexes targeting CD38 were electroporated into NK cells (J Vis Exp. 2018 Jun 14;(136)). Flow cytometric analysis revealed CD38KO efficiency was 81.9±6.9% (mean±SD, n=5). CD38KO cells were further purified to ≥ 95% purity using magnetic cell separation system. Whole genome sequencing identified no off-target mutations. CD38KO-NK cells alone showed no conjugation in the presence of DARA (Figure 1A) and no DARA-induced fratricide (Figure 1B), in stark contrast with wild type NK (WT-NK) cells. Consistent with these results, treatment of NSG mice with DARA had no impact on persistence of CD38KO-NK cells, whereas WT-NK cells were completely eliminated (NK cell frequency in peripheral blood 7 days after inoculation; WT-NK NO DARA 12.11±5.15%, KO-NK NO Dara 17.05±0.98%, WT-NK + Dara 0.21±0.08%, KO-NK + Dara 16.85±3.61%, mean±SD, n=4, p<0.01, ANOVA) (Figure 1C). To examine the functional status of CD38KO-NK cells, we used 6 MM cell lines with various CD38 expression levels (LP-1, RPMI8226, H929, MM.1s, OPM-2, and KMS-11) as well as three CD38+CD138+ primary MM samples isolated from bone marrow of newly diagnosed or relapsed patients. CD38KO-NK cells exhibited enhanced ADCC activity compared to WT-NK cells across all cell lines and primary samples tested in 4h and 24h cytotoxicity assay (Figure 1D). This was even observed in MM cells that express low levels of CD38, suggesting their potential efficacy in patients with relapsed disease after DARA (ADCC at E/T 5:1; MM.1s 7.8±1.8%(WT) vs 21.5±0.4%(KO), KMS-11 -3.5±0.6%(WT) vs 11.1±0.4%(KO), mean±SD). The CD38KO-NK cells preserved similar expansion potency as WT-NK counter parts. Next, to reveal any effect of manipulating CD38 expression on NK cells cytotoxicity and metabolism, we performed RNA sequencing analysis, which showed higher expression of several cytotoxic genes such as IFNG and GzmB in CD38-KO NK cells, and higher expression of glucose transporter genes and GAPDH, suggesting a favorable metabolic profile of these cells. Consistent with these data, we observed that CD38KO-NK cells have elevated capacity to take up glucose as measured by 2-NBDG glucose uptake assay (p=0.02, student t test). Taken together, these findings provide the proof-of-concept that CD38KO-NK cells generated from primary NK cells augment therapeutic effect of DARA and could be promising for adoptive immune cellular therapy targeting MM. Y.N. and M.N.K. contributed equally to this study. D.A.L. and G.G. contributed equally to this study. Figure 1 Disclosures Ali: Celgene: Research Funding; Poseida: Research Funding. Lee:Kiadis Pharma: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Deletion of CISH in Human Pluripotent Stem Cell-Derived Natural Killer Cells Enhances Anti-Tumor Activity Via Metabolic Reprogramming

Cellular metabolism is now recognized to play a key role in regulating function and differentiation of immune cells. Immune cells undergo dynamic metabolic shifts to support their activity. Recent studies have shown the importance of metabolism to regulate NK cell function under different conditions. IL-15 can regulate NK cell metabolism in a dose- and time- dependent manner. However, whether improving metabolic fitness of NK cells can lead to improved anti-tumor activity is largely unknown. Here, we deleted CIS (encoded by the CISH gene in human induced pluripotent stem cells (iPSC)-derived NK cells (CISH-/- iPSC-NK) using CRISPR/Cas9 technology. CIS is known to function as a critical negative regulator of IL-15 signaling and a potent inhibitory checkpoint in NK cell-mediated anti-tumor activity. Surprisingly, more than 3000 differentially expressed genes were identified in CISH-/- iPSC-NK cells through RNA sequencing analysis. Gene ontology (GO) enrichment analysis showed that the top 2 up-regulated signaling pathways were associated with leukocyte differentiation and activation. Notably, more than 50 genes that involved in positive regulation of lymphocyte activation including genes associated with NK cell effector functions were significantly up-regulated in CISH-/- iPSC-NK cells compared with unmodified iPSC-NK cells. As expected, CISH-/- iPSC-NK cells exhibited increased sensitivity to IL-15 stimulation. Specifically, IL-15 stimulated JAK1 tyrosine phosphorylation, STAT3 and STAT5 phosphorylation were all dramatically increased in CISH-/- iPSC-NK cells, compared with unmodified iPSC-NK cells. In addition, when incubated with low concentrations of IL-15 (5 ng/ml), a concentration that does not support the growth and functions of unmodified iPSC-NK cells, CISH-/- iPSC-NK cells maintained significantly better expansion with >10 fold expansion for CISH-/- iPSC-NK cells in 3 weeks, whereas most of WT iPSC-NK cells died under these conditions (p<0.001). These CISH-/- iPSC-NK cells exhibited improved cytotoxic against acute myeloid leukemia (AML) cell lines K562 and Molm-13. More importantly, in an AML (MOLM-13) xenograft model, CISH-/- iPSC-NK cells displayed significantly increased in vivo persistence thus lead to significantly better control of tumor progression. To further understand the underling mechanisms contributing to the increased functionality in CISH-/- iPSC-NK cells, we then analyzed the metabolic profiles of these cells using Agilent Seahorse assays. After treatment with low concentration IL-15 for 7 days, CISH-/- iPSC-NK cells displayed both increased glucose metabolism and increased mitochondrial respiration profiles when compared with unmodified iPSC-NK cells. Increased glucose metabolism include a significant increase in basal glycolysis (p=0.0003, 84.5 ± 1.0 vs 61.1 ± 1.8 mpH/min, n=6), and glycolytic capacity (p=0.0049, 15.2±0.4 vs 11.7±0.5 mpH/min, n=6). And increased mitochondrial respiration profile is characterized by an increase in the spare respiratory capacity (p=0.0009, 16.3±1.9 vs 6.9±0.5 pmol/min, n=6), maximal respiration (p<0.0001, 31.6±1.9 vs 15.7±0.8 pmol/min, n=6) and ATP-linked respiration (p<0.0001, 11.5 ± 0.4 vs 7.0±0.3 pmol/min, n=6). Interestingly, limiting the increase of glucose metabolism and mitochondrial respiration via utilization of an mTOR inhibitor (rapamycin) attenuated the increased functionality in CISH-/- iPSC-NK cells. The findings presented here show that deletion of CISH in iPSC-NK cells enhance anti-tumor activity, at least in part via metabolic reprogramming. These findings suggest that improving NK cell functions for cancer immunotherapy through metabolic reprogramming provides a promising therapeutic strategy. Disclosures Guan: OncoImmune: Equity Ownership. Kaufman:FATE Therapeutics: Consultancy, Research Funding.

Membrane bound IL-21 based NK cell feeder cells drive robust expansion and metabolic activation of NK cells

NK cell adoptive therapy is a promising cancer therapeutic approach, but there are significant challenges that limiting its feasibility and clinical efficacy. One difficulty is the paucity of clinical grade manufacturing platforms to support the large scale expansion of highly active NK cells. We created an NK cell feeder cell line termed ‘NKF’ through overexpressing membrane bound IL-21 that is capable of inducing robust and sustained proliferation (>10,000-fold expansion at 5 weeks) of highly cytotoxic NK cells. The expanded NK cells exhibit increased cytotoxic function against a panel of blood cancer and solid tumor cells as compared to IL-2-activated non-expanded NK cells. The NKF-expanded NK cells also demonstrate efficacy in mouse models of human sarcoma and T cell leukemia. Mechanistic studies revealed that membrane-bound IL-21 leads to an activation of a STAT3/c-Myc pathway and increased NK cell metabolism with a shift towards aerobic glycolysis. The NKF feeder cell line is a promising new platform that enables the large scale proliferation of highly active NK cells in support of large scale third party NK cell clinical studies that have been recently intiatied. These results also provide mechanistic insights into how membrane-bound IL-21 regulates NK cell expansion.

Immunometabolic Dysfunction of Natural Killer Cells Mediated by the Hypoxia-CD73 Axis in Solid Tumors.

NK cell infiltration into solid tumors is often low and is largely represented by the poorly-cytotoxic CD56bright subset. Numerous studies have demonstrated that CD73, overexpressed under conditions of hypoxia, is involved in a variety of physiological processes, while its overexpression has been correlated with tumor invasiveness, metastasis and poorer patient survival in many cancers. Hypoxia itself favors aggressive glycolytic fueling of cancer cells, in turn driving reprogramming of NK cell metabolism. In addition, the hypoxia-driven activity of CD73 immunometabolically impairs NK cells in tumors, due to its catalytic role in the generation of the highly immunosuppressive metabolite adenosine. Adenosinergic signaling was shown to alter NK cell metabolic programs, leading to tumor-promoting environments characterized by NK cell dysfunction. Despite the demonstrated role of NK cell responses in the context of CD73 targeting, the engagement of NK cells in the setting of hypoxia/CD73 signaling has not been extensively studied or exploited. Here, we discuss available evidence on the role of hypoxic signaling on CD73-mediated activity, and how this relates to the immunometabolic responses of NK cells, with a particular focus on the therapeutic targeting of these pathways.

Immunometabolic Responses of Natural Killer Cells to Inhibitory Tumor Microenvironment Checkpoints

Abstract NK cell trafficking and migration into solid tumors is often poor. Altered NK cell metabolism in the tumor microenvironment has been correlated with tumor invasiveness, metastasis and cellular dysfunction. Tumor-induced stresses correlate to limited numbers of functional NK cells in solid tumors and, consequently, limited survival. Metabolic impairment of NK cells in cancer is still not fully understood, but the involvement of inhibitory checkpoints-both tumor-associated as well as NK-specific-plays a significant role in driving these responses. The metabolic reprogramming events that NK cells undergo in the tumor microenvironment are linked to their ability to support energy metabolism in scenarios of impaired glycolytic fueling and low oxygen. The contributions of inhibitory checkpoints to these events are not entirely known, but are emerging as increasingly significant to the restoration of NK cell function. Here, we discuss our understanding of the role of inhibitory receptors and checkpoints in the metabolic dysfunction of NK cells in solid tumors, as a critical key to the development of new immunotherapies.

What Defines NK Cell Functional Fate: Phenotype or Metabolism?

NK cells are capable of an array of functions that range widely from their classic anti-tumor and anti-viral cytotoxic effector functions, to their critical regulatory roles in controlling inflammatory immune responses and promoting tissue growth. However, the mechanisms that polarize NK cells to these distinct and opposing functions are incompletely understood. NK cell functional subsets are primarily identified and studied based on phenotype, which has served as an accessible means for profiling NK cells and does offer information on NK cell activation state. However, inconsistencies have emerged in using classic phenotypes to inform function, which raise the questions: Can phenotype in fact define NK cell functional fate? What factors do profile and drive NK cell fate? In other immune cells, cell metabolism has been shown to critically determine subset polarization. There is a growing body of evidence that cell metabolism is integral to NK cell effector functions. Glucose-driven glycolysis and oxidative metabolism have been shown to drive classic NK cell anti-tumor and anti-viral effector functions. Recent studies have uncovered a critical role for metabolism in NK cell development, education, and memory generation. In this review, we will draw on the evidence to date to investigate the relationship between NK cell phenotype, metabolism, and functional fate. We explore a paradigm in which the differential activity of metabolic pathways within NK cells produce distinct metabolic fingerprints that comprehensively distinguish and drive the range of NK cell functional abilities. We will discuss future areas of study that are needed to develop and test this paradigm and suggest strategies to efficiently profile NK cells based on metabolism. Given the emerging role of metabolism in driving NK cell fates, profiling and modulating NK cell metabolism holds profound therapeutic potential to tune inflammatory and regulatory NK cell responses to treat disease.

Abstract CT146: First-in-human phase I combination of the IL-15 receptor super agonist complex ALT-803 with a therapeutic (anti-CD20) monoclonal antibody (mAb) for patients with relapsed or refractory indolent non-Hodgkin lymphoma (iNHL)

Abstract Immunotherapy is an effective modality for cancer treatment. IL-15 is a cytokine that stimulates CD8+ T cell and NK cell survival, metabolism, and anti-tumor immunity. We hypothesized that IL-15 therapy will augment anti-cancer immune responses in concert with tumor-targeting therapeutic mAbs. Pre-clinical studies have shown that the IL-15 receptor super agonist complex, ALT-803, enhanced the anti-tumor effects of anti-CD20 mAb against iNHL in vitro and in vivo (Rosario M et al., Clin Ca Res, 2016). Here, we conducted the first clinical study combining ALT-803 with a tumor-targeting mAb, in patients with rel/ref iNHL. A total of 21 iNHL patients [N=16 FL (FLIPI low: 4, int: 4, high: 8), N=4 MZL, N=1 SLL] were treated. Median age was 64 years (range 54-81), median number of prior therapies was 2 (range 1-18), and 5 patients were refractory to prior anti-CD20 mAb therapy. Treatment included an induction cycle of 4 weekly doses of rituximab (375 mg/m2 intravenously, IV) and ALT-803. The ALT-803 dose levels were 1, 3, and 6 mcg/kg IV followed by 6, 10, 15, and 20 mcg/kg subcutaneously (SC, N=3 per dose level). In patients with SD, PR or CR, consolidation therapy with ALT-803 (at the same dose level) and rituximab was then administered every 8 weeks for 4 cycles. No dose limiting toxicities were observed, and the recommended phase 2 dose was 20 mcg/kg SC. Overall ALT-803 was well tolerated with no grade 4 or 5 adverse events. Grade 3 AEs (regardless of attribution to ALT-803) included transient hypertension (14%), anemia (5%), nausea (5%), chills (5%), fever (5%), neutropenia (5%), and hyperglycemia (5%). Patients who received ALT-803 SC had a self-limited injection site reaction. To date, best ORR was 10/21 (48%), with 7 CR, 3 PR, 8 SD (all with decreased tumor volume), and 3 PD. Of the 12 patients treated with SC ALT-803, only 1 patient had PD, with the remainder receiving ongoing consolidation. In the 5 rituximab-refractory patients we observed 1 CR, 2 SD (45% and 36% tumor volume decrease), and 2 PD. PK analysis showed that SC ALT-803 administration resulted in a lower Cmax and prolonged blood levels compared to IV. At the 15 and 20 mcg/kg SC dose levels of ALT-803, NK cells were significantly increased by percentage (mean peak 30+5%, 6-fold, P<0.001) and number (mean peak 687+347/uL, 10-fold, P<0.001). This was accompanied by a marked increase in proliferation (Ki67, 97+0.5%, P<0.001) and activation (CD69, 10-fold, P<0.01) in vivo. CD8+ T cell number (2-fold, P<0.01) and proliferation (Ki67, 56+6%, P<0.001) were also significantly increased, without increases in CD4+ or regulatory T cell numbers. Patient NK cells exhibited enhanced functional responses (degranulation and IFN-γ production) against anti-CD20 mAb coated NHL targets after ALT-803 administration, compared to pre-ALT-803 samples. NK cells (P<0.05) and CD8 T cells (P<0.05) were also increased at the 6 and 10 mcg/kg SC ALT-803 levels. Thus, the immunostimulatory IL-15-based agent ALT-803 may be safely combined with a therapeutic mAb to significantly enhance NK and CD8+ T cell number and function in patients with iNHL. Phase 2 testing is underway in iNHL. Clinical investigations combining ALT-803 with additional therapeutic mAbs, complementary types of immunotherapy, and in additional malignancies are warranted. Citation Format: Todd A. Fehniger, Brian T. Hess, Veronika Bachanova, Michelle Becker-Hapak, Ethan McClain, Melissa Berrien-Elliott, Julia Wagner, Nancy L. Bartlett, Brad Kahl, Neha Mehta-Shah, Amanda F. Cashen, Feng Gao, Kyle Conradi, Amy D. Rock, Emily K. Jeng, Liza Hernandez, Jack O. Egan, Peter R. Rhode, Hing C. Wong. First-in-human phase I combination of the IL-15 receptor super agonist complex ALT-803 with a therapeutic (anti-CD20) monoclonal antibody (mAb) for patients with relapsed or refractory indolent non-Hodgkin lymphoma (iNHL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT146.

NK cells in childhood obesity are activated, metabolically stressed, and functionally deficient.

Childhood obesity is a major global concern, with over 50 million children now classified as obese. Obesity has been linked to the development of numerous chronic inflammatory diseases, including type 2 diabetes and multiple cancers. NK cells are a subset of innate effector cells, which play an important role in the regulation of adipose tissue and antitumor immunity. NK cells can spontaneously kill transformed cells and coordinate subsequent immune responses through their production of cytokines. We investigated the effect of obesity on NK cells in a cohort of obese children, compared to children with a healthy weight. We demonstrated a reduction in peripheral NK cell frequencies in childhood obesity and inverse correlations with body mass index and insulin resistance. Compared with NK cells from children with normal weight, we show increased NK cell activation and metabolism in obese children (PD-1, mTOR activation, ECAR, and mitochondrial ROS), along with a reduced capacity to respond to stimulus, ultimately leading to loss of function (proliferation and tumor lysis). Collectively we show that NK cells from obese children are activated, metabolically stressed, and losing the ability to perform their basic duties. Paired with the reduction in NK cell frequencies in childhood obesity, this suggests that the negative effect on antitumor immunity is present early in the life course of obesity and certainly many years before the development of overt malignancies.

Assessment of NK Cell Metabolism.

There has been increasing recognition of the importance of metabolism on immune cell differentiation, homeostasis, and function. Recently, our lab and others have begun to investigate the metabolic requirements for NK cell differentiation and activation. Here, we describe approaches for the in vitro assessment of NK cell metabolism. We present methods for using inhibitors to alter cellular metabolism, measurement of intracellular ATP in NK cells, assessment of real-time glycolysis and oxidative phosphorylation by an extracellular flux assay from Seahorse Biosciences, and some basic protocols for stimulation of NK cells via cytokines and receptors.

Natural killer cell maturation is blocked by mTOR inhibition in C57Bl/6 mice

Recent work established a pathway by which the energy sensitive kinase mammalian target of rapamycin (mTOR) regulates T cell biology, and this pathway is directly influenced by energy intake. Energy restriction (ER) is a dietary intervention shown to increase lifespan and reduce the incidence of tumors in rodents. The objective of this study was to examine the role of mTOR in NK cell metabolism and biology, based on the observation that ER results in fewer mature NK cells. NK cells from 40% ER mice exhibited mTOR inhibition directly ex vivo, and reduced expression of the transcription factors Eomes and T‐bet, which are required for NK cell maturation. Consequences of mTOR inhibition on NK cell biology was examined in vitro and revealed IL‐12 + IL‐18 induced NK cell maturation and function was impaired following rapamycin treatment. mTOR inhibition reduced upregulation of metabolic transporters, and repressed expression of NK cell maturation markers. Concurrently, mTOR inhibition in NK cells blocked upregulation of transcription factors Eomes and T‐bet following stimulation. Mature NK cells play a critical role in killing tumor cells and here we show NK cell maturation is linked to metabolic signaling through mTOR. Thus, manipulation of energy intake or energy sensitive pathways directly influences NK cell maturation, which has significant implications during the immune response to cancers or viral infections.Grant Funding Source: R01AG034949