bims-unfpre Biomed News
on Unfolded protein response
Issue of 2024‒05‒19
thirteen papers selected by
Susan Logue, University of Manitoba
  1. IRE1α determines ferroptosis sensitivity through regulation of glutathione synthesis.
  2. Unraveling the Connection: Pain and Endoplasmic Reticulum Stress.
  3. Bax Inhibitor-1 preserves pancreatic β-cell proteostasis by limiting proinsulin misfolding and programmed cell death.
  4. SIRT1 exerts protective effects by inhibiting endoplasmic reticulum stress and NF-κB signaling pathways.
  5. A JAGN1-associated severe congenital neutropenia zebrafish model revealed an altered G-CSFR signaling and UPR activation.
  6. Molecular characterization of the ER stress-inducible factor CRELD2.
  7. Gene Expression Profiling to Unfolded Proteins Response as a Risk Modulator of Patients with Rheumatoid Arthritis.
  8. IRE1α pathway: A potential bone metabolism mediator.
  9. Development of TRIB3-Based Therapy as a Gene-Independent Approach to Treat Retinal Degenerative Disorders.
  10. Reversibility of Endoplasmic Reticulum Stress Markers During Long-Term Glucose Starvation in Astrocytes.
  11. Extracellular signals induce dynamic ER remodeling through αTAT1-dependent microtubule acetylation.
  12. Deactivation of the Unfolded Protein Response Aggravated Renal AA Amyloidosis in HSF1 Deficiency Mice.
  13. Tumor-associated NK cells drive MDSC-mediated tumor immune tolerance through the IL-6/STAT3 axis.
  1. Nat Commun. 2024 May 15. 15(1): 4114
    IRE1α determines ferroptosis sensitivity through regulation of glutathione synthesis.
    Dadi Jiang, Youming Guo, Tianyu Wang, Liang Wang, Yuelong Yan, Ling Xia, Rakesh Bam, Zhifen Yang, Hyemin Lee, Takao Iwawaki, Boyi Gan, Albert C Koong.
      Cellular sensitivity to ferroptosis is primarily regulated by mechanisms mediating lipid hydroperoxide detoxification. We show that inositol-requiring enzyme 1 (IRE1α), an endoplasmic reticulum (ER) resident protein critical for the unfolded protein response (UPR), also determines cellular sensitivity to ferroptosis. Cancer and normal cells depleted of IRE1α gain resistance to ferroptosis, while enhanced IRE1α expression promotes sensitivity to ferroptosis. Mechanistically, IRE1α's endoribonuclease activity cleaves and down-regulates the mRNA of key glutathione biosynthesis regulators glutamate-cysteine ligase catalytic subunit (GCLC) and solute carrier family 7 member 11 (SLC7A11). This activity of IRE1α is independent of its role in regulating the UPR and is evolutionarily conserved. Genetic deficiency and pharmacological inhibition of IRE1α have similar effects in inhibiting ferroptosis and reducing renal ischemia-reperfusion injury in mice. Our findings reveal a previously unidentified role of IRE1α to regulate ferroptosis and suggests inhibition of IRE1α as a promising therapeutic strategy to mitigate ferroptosis-associated pathological conditions.
    DOI:  https://doi.org/10.1038/s41467-024-48330-0
  2. Int J Mol Sci. 2024 May 03. pii: 4995. [Epub ahead of print]25(9):
    Unraveling the Connection: Pain and Endoplasmic Reticulum Stress.
    Ryoko Kawanaka, Hisayo Jin, Tomohiko Aoe.
      Pain is a complex and multifaceted experience. Recent research has increasingly focused on the role of endoplasmic reticulum (ER) stress in the induction and modulation of pain. The ER is an essential organelle for cells and plays a key role in protein folding and calcium dynamics. Various pathological conditions, such as ischemia, hypoxia, toxic substances, and increased protein production, may disturb protein folding, causing an increase in misfolding proteins in the ER. Such an overload of the folding process leads to ER stress and causes the unfolded protein response (UPR), which increases folding capacity in the ER. Uncompensated ER stress impairs intracellular signaling and cell function, resulting in various diseases, such as diabetes and degenerative neurological diseases. ER stress may be a critical universal mechanism underlying human diseases. Pain sensations involve the central as well as peripheral nervous systems. Several preclinical studies indicate that ER stress in the nervous system is enhanced in various painful states, especially in neuropathic pain conditions. The purpose of this narrative review is to uncover the intricate relationship between ER stress and pain, exploring molecular pathways, implications for various pain conditions, and potential therapeutic strategies.
    Keywords:  ER stress; UPR; chaperone; pain; protein quality control
    DOI:  https://doi.org/10.3390/ijms25094995
  3. Cell Death Dis. 2024 May 14. 15(5): 334
    Bax Inhibitor-1 preserves pancreatic β-cell proteostasis by limiting proinsulin misfolding and programmed cell death.
    Marina Blanc, Lama Habbouche, Peng Xiao, Cynthia Lebeaupin, Marion Janona, Nathalie Vaillant, Marie Irondelle, Jérôme Gilleron, Florent Murcy, Déborah Rousseau, Carmelo Luci, Thibault Barouillet, Sandrine Marchetti, Sandra Lacas-Gervais, Laurent Yvan-Charvet, Philippe Gual, Alessandra K Cardozo, Béatrice Bailly-Maitre.
      The prevalence of diabetes steadily increases worldwide mirroring the prevalence of obesity. Endoplasmic reticulum (ER) stress is activated in diabetes and contributes to β-cell dysfunction and apoptosis through the activation of a terminal unfolded protein response (UPR). Our results uncover a new role for Bax Inhibitor-One (BI-1), a negative regulator of inositol-requiring enzyme 1 (IRE1α) in preserving β-cell health against terminal UPR-induced apoptosis and pyroptosis in the context of supraphysiological loads of insulin production. BI-1-deficient mice experience a decline in endocrine pancreatic function in physiological and pathophysiological conditions, namely obesity induced by high-fat diet (HFD). We observed early-onset diabetes characterized by hyperglycemia, reduced serum insulin levels, β-cell loss, increased pancreatic lipases and pro-inflammatory cytokines, and the progression of metabolic dysfunction. Pancreatic section analysis revealed that BI-1 deletion overburdens unfolded proinsulin in the ER of β-cells, confirmed by ultrastructural signs of ER stress with overwhelmed IRE1α endoribonuclease (RNase) activity in freshly isolated islets. ER stress led to β-cell dysfunction and islet loss, due to an increase in immature proinsulin granules and defects in insulin crystallization with the presence of Rod-like granules. These results correlated with the induction of autophagy, ER phagy, and crinophagy quality control mechanisms, likely to alleviate the atypical accumulation of misfolded proinsulin in the ER. In fine, BI-1 in β-cells limited IRE1α RNase activity from triggering programmed β-cell death through apoptosis and pyroptosis (caspase-1, IL-1β) via NLRP3 inflammasome activation and metabolic dysfunction. Pharmaceutical IRE1α inhibition with STF-083010 reversed β-cell failure and normalized the metabolic phenotype. These results uncover a new protective role for BI-1 in pancreatic β-cell physiology as a stress integrator to modulate the UPR triggered by accumulating unfolded proinsulin in the ER, as well as autophagy and programmed cell death, with consequences on β-cell function and insulin secretion. In pancreatic β-cells, BI-1-/- deficiency perturbs proteostasis with proinsulin misfolding, ER stress, terminal UPR with overwhelmed IRE1α/XBP1s/CHOP activation, inflammation, β-cell programmed cell death, and diabetes.
    DOI:  https://doi.org/10.1038/s41419-024-06701-x
  4. Front Cell Dev Biol. 2024 ;12 1405546
    SIRT1 exerts protective effects by inhibiting endoplasmic reticulum stress and NF-κB signaling pathways.
    Kaixuan Zhao, Haoyue Zhang, Dong Yang.
      Silent information regulator two homolog 1 (SIRT1), an NAD + -dependent histone deacetylase, plays a pivotal regulatory role in a myriad of physiological processes. A growing body of evidence suggests that SIRT1 can exert protective effects in metabolic disorders and neurodegenerative diseases by inhibiting endoplasmic reticulum (ER) stress and the nuclear factor-κB (NF-κB) inflammatory signaling pathway. This review systematically elucidates the molecular mechanisms and biological significance of SIRT1 in regulating ER stress and the NF-κB pathway. On one hand, SIRT1 can deacetylate key molecules in the ER stress pathway, such as glucose-regulated protein 78 (GRP78), X-box binding protein 1 (XBP1), PKR-like ER kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6), thereby alleviating ER stress. On the other hand, SIRT1 can directly or indirectly remove the acetylation modification of the NF-κB p65 subunit, inhibiting its transcriptional activity and thus attenuating inflammatory responses. Through these mechanisms, SIRT1 can ameliorate insulin resistance in metabolic diseases, exert cardioprotective effects in ischemia-reperfusion injury, and reduce neuronal damage in neurodegenerative diseases. However, it is important to note that while these findings are promising, the complex nature of the biological systems involved warrants further investigation to fully unravel the intricacies of SIRT1's regulatory mechanisms. Nevertheless, understanding the regulatory mechanisms of SIRT1 on ER stress and the NF-κB pathway is of great significance for expanding our knowledge of the pathogenesis of related diseases and exploring new preventive and therapeutic strategies targeting SIRT1.
    Keywords:  SIRT1; deacetylation; endoplasmic reticulum stress; metabolic diseases; neurodegenerative diseases; nuclear factor-κB
    DOI:  https://doi.org/10.3389/fcell.2024.1405546
  5. Blood Adv. 2024 May 13. pii: bloodadvances.2023011656. [Epub ahead of print]
    A JAGN1-associated severe congenital neutropenia zebrafish model revealed an altered G-CSFR signaling and UPR activation.
    Larissa Doll, Karl Welte, Julia Skokowa, Baubak Bajoghli.
      A variety of autosomal recessive mutations in the JAGN1 gene cause severe congenital neutropenia (CN). However, the underlying pathomechanism remains poorly understood, mainly due to the limited availability of primary hematopoietic stem cells from JAGN1-CN patients and the absence of animal models. In this study, we aimed to address these limitations by establishing a zebrafish model of JAGN1-CN. We found two paralogs of the human JAGN1 gene, jagn1a and jagn1b, which play distinct roles during zebrafish hematopoiesis. Using various approaches such as morpholino-based knockdown, CRISPR/Cas9-based gene-editing, and misexpression of a jagn1b harboring a specific human mutation, we successfully developed neutropenia while leaving other hematopoietic lineages unaffected. Further analysis of our model revealed significant upregulation of apoptosis and genes involved in unfolded protein response (UPR). However, neither UPR nor apoptosis is the primary mechanism leading to neutropenia in zebrafish. Instead, Jagn1b has a critical role in G-CSFR signaling and steady-state granulopoiesis, shedding light on the pathogenesis of neutropenia associated with JAGN1 mutations. The establishment of a zebrafish model for JAGN1-CN represents a significant advancement in understanding the specific pathological pathways underlying the disease. This model provides a valuable in vivo tool for further investigation and exploration of potential therapeutic strategies.
    DOI:  https://doi.org/10.1182/bloodadvances.2023011656
  6. Cell Biochem Biophys. 2024 May 16.
    Molecular characterization of the ER stress-inducible factor CRELD2.
    Shohei Hinaga, Mahmoud Kandeel, Kentaro Oh-Hashi.
      Previously, we found by constructing various luciferase reporters that a well-conserved ATF6-binding element in the CRELD2 promoter is activated by transient ATF6 overexpression. In this study, we established ATF6-deficient and ATF4-deficient cell lines to analyze CRELD2 mRNA and protein expression together with that of other ER stress-inducible factors. Our results showed that ATF6 deficiency markedly suppressed tunicamycin (Tm)-induced expression of unglycosylated CRELD2. This reduction reflected a decrease in the CRELD2 transcription level. On the other hand, a putative ATF4-binding site in the mouse CRELD2 promoter did not respond to Tm stimulation, but ATF4 loss resulted in reductions in CRELD2 mRNA and protein expression, accompanied by a decrease in Tm-induced ATF6 expression. In contrast, transient suppression of GADD34, an ATF4 downstream factor, suppressed Tm-induced CRELD2 protein expression without a decrease in ATF6 protein expression. Furthermore, we investigated the association of CRELD2 with a well-known ERAD substrate, namely, an α1-antitripsin truncation mutant, NHK, by generating various CRELD2 and NHK constructs. Coimmunoprecipitation of these proteins was observed only when the cysteine in the CXXC motif on the N-terminal side of CRELD2 was replaced with alanine, and the interaction between the two was found to be disulfide bond-independent. Taken together, these findings indicate that CRELD2 expression is regulated by multiple factors via transcriptional and posttranscriptional mechanisms. In addition, the N-terminal structure of CRELD2, including the CXXC motif, was suggested to play a role in the association of the target proteins. In the future, the identification and characterization of factors interacting with CRELD2 will be useful for understanding protein homeostasis under various ER stress conditions.
    Keywords:  ATF4; ATF6; CRELD2; ER stress; GADD34
    DOI:  https://doi.org/10.1007/s12013-024-01300-1
  7. Int J Mol Sci. 2024 Apr 29. pii: 4854. [Epub ahead of print]25(9):
    Gene Expression Profiling to Unfolded Proteins Response as a Risk Modulator of Patients with Rheumatoid Arthritis.
    Aleksandra Kucharska-Lusina, Maciej Skrzypek, Aleksandra Binda, Ireneusz Majsterek.
      Rheumatoid arthritis (RA) is a chronic inflammatory disease. Despite new methods of diagnostics and treatment as well as extensive biological and immunosuppressive treatment, the etiology of RA is not fully understood. Moreover, the problem of diagnosis and treatment of RA patients is still current and affects a large group of patients. It is suggested that endoplasmic reticulum (ER)-related features may impair adaptation to chronic stress, inferring the risk of rheumatoid arthritis. The main goal in this study was evaluation of changes in mRNA translation to determine chronic ER stress conditions in rheumatoid arthritis patients. The study group consist of 86 individuals including a total of 56 rheumatoid arthritis patients and 30 healthy controls. The expression level of mRNA form blood samples of RA patients as well as controls of the unfolded protein response (UPR)-associated genes (p-eIF2, BCL-2, PERK, ATF4, and BAX) were investigated using real-time qPCR. GAPDH expression was used as a standard control. Considering the median, the expression levels of PERK, BCL-2, p-eIF2, ATF4, and BAX were found to be significantly increased in the blood of RA patients compared with the control group. The p-value for the PERK gene was 0.0000000036, the p-value for the BCL-2 gene was 0.000000014, the p-value for the p-eIF2 gene was 0.006948, the p-value for the ATF4 gene was 0.0000056, and the p-value for the BAX gene was 0.00019, respectively. Thus, it can be concluded that the targeting of the components of the PERK-dependent UPR signaling pathway via small-molecule PERK inhibitors may contribute to the development of novel, innovative treatment strategies against rheumatoid arthritis.
    Keywords:  ER-adaptosome; PERK inhibitor; endoplasmic reticulum stress; rheumatoid arthritis; unfolded protein response
    DOI:  https://doi.org/10.3390/ijms25094854
  8. Cell Prolif. 2024 May 12. e13654
    IRE1α pathway: A potential bone metabolism mediator.
    Chengbo Yu, Zhixiang Zhang, Li Xiao, Mi Ai, Ying Qing, Zhixing Zhang, Lianyi Xu, Ollie Yiru Yu, Yingguang Cao, Yong Liu, Ke Song.
      Osteoblasts and osteoclasts collaborate in bone metabolism, facilitating bone development, maintaining normal bone density and strength, and aiding in the repair of pathological damage. Endoplasmic reticulum stress (ERS) can disrupt the intracellular equilibrium between osteoclast and osteoblast, resulting in dysfunctional bone metabolism. The inositol-requiring enzyme-1α (IRE1α) pathway-the most conservative unfolded protein response pathway activated by ERS-is crucial in regulating cell metabolism. This involvement encompasses functions such as inflammation, autophagy, and apoptosis. Many studies have highlighted the potential roles of the IRE1α pathway in osteoblasts, chondrocytes, and osteoclasts and its implication in certain bone-related diseases. These findings suggest that it may serve as a mediator for bone metabolism. However, relevant reviews on the role of the IRE1α pathway in bone metabolism remain unavailable. Therefore, this review aims to explore recent research that elucidated the intricate roles of the IRE1α pathway in bone metabolism, specifically in osteogenesis, chondrogenesis, osteoclastogenesis, and osteo-immunology. The findings may provide novel insights into regulating bone metabolism and treating bone-related diseases.
    DOI:  https://doi.org/10.1111/cpr.13654
  9. Int J Mol Sci. 2024 Apr 26. pii: 4716. [Epub ahead of print]25(9):
    Development of TRIB3-Based Therapy as a Gene-Independent Approach to Treat Retinal Degenerative Disorders.
    Trong Thuan Ung, Christopher R Starr, Assylbek Zhylkibayev, Irina Saltykova, Marina Gorbatyuk.
      Inherited retinal degeneration (RD) constitutes a heterogeneous group of genetic retinal degenerative disorders. The molecular mechanisms underlying RD encompass a diverse spectrum of cellular signaling, with the unfolded protein response (UPR) identified as a common signaling pathway chronically activated in degenerating retinas. TRIB3 has been recognized as a key mediator of the PERK UPR arm, influencing various metabolic pathways, such as insulin signaling, lipid metabolism, and glucose homeostasis, by acting as an AKT pseudokinase that prevents the activation of the AKT → mTOR axis. This study aimed to develop a gene-independent approach targeting the UPR TRIB3 mediator previously tested by our group using a genetic approach in mice with RD. The goal was to validate a therapeutic approach targeting TRIB3 interactomes through the pharmacological targeting of EGFR-TRIB3 and delivering cell-penetrating peptides targeting TRIB3 → AKT. The study employed rd10 and P23H RHO mice, with afatinib treatment conducted in p15 rd10 mice through daily intraperitoneal injections. P15 P23H RHO mice received intraocular injections of cell-penetrating peptides twice at a 2-week interval. Our study revealed that both strategies successfully targeted TRIB3 interactomes, leading to an improvement in scotopic A- and B-wave ERG recordings. Additionally, the afatinib-treated mice manifested enhanced photopic ERG amplitudes accompanied by a delay in photoreceptor cell loss. The treated rd10 retinas also showed increased PDE6β and RHO staining, along with an elevation in total PDE activity in the retinas. Consequently, our study demonstrated the feasibility of a gene-independent strategy to target common signaling in degenerating retinas by employing a TRIB3-based therapeutic approach that delays retinal function and photoreceptor cell loss in two RD models.
    Keywords:  TRIB3; afatinib; cell-penetrating peptides; retinal degeneration; unfolded protein response
    DOI:  https://doi.org/10.3390/ijms25094716
  10. J Mol Neurosci. 2024 May 16. 74(2): 53
    Reversibility of Endoplasmic Reticulum Stress Markers During Long-Term Glucose Starvation in Astrocytes.
    Clara Voelz, Lena E M Schaack, Vanessa Kogel, Cordian Beyer, Jochen Seitz, Stefanie Trinh.
      Previous studies have demonstrated a brain volume decrease linked to long-term starvation in patients with anorexia nervosa (AN). Food intake is critically diminished in this disorder, leading to one of the highest mortality rates within the psychiatric disease spectrum. As reported in animal models, astrocytes seem to be the most affected cell type in AN. In a recently established primary cell culture model, an elevated unfolded protein response (UPR) was observed in long-term glucose semi-starved astrocytes. A well-functioning protein machinery is essential for every cell, and prolonged UPR will lead to cell death. As a nucleic acid stress-sensing pathway with the activator located in the endoplasmic reticulum, the regulation of the cGAS-STING pathway (cyclic GMP-AMP synthase/stimulator of interferon genes) was additionally investigated in the starvation context. In the current study, a glucose semi-starvation protocol of 15 days, during which cells were supplied with 2 mM glucose in the medium, was prolonged with an additional 6-day long recovery period. Our findings showed that increased UPR mRNA expression was reversible after re-establishing the standard glucose concentration of 25 mM. Furthermore, we were able to verify the presence of cGAS and STING in astrocytes with a characteristic presence of cGAS in the astrocyte nucleus during starvation. A correlation between STING and the glial fibrillary acidic protein (GFAP) could be established, hinting at a conditional presence of STING with a specific astrocyte phenotype.
    Keywords:  Anorexia nervosa; Astrocytes; Endoplasmic reticulum stress; Glucose starvation; Unfolded protein response; cGAS-STING pathway
    DOI:  https://doi.org/10.1007/s12031-024-02223-5
  11. Neoplasia. 2024 May 16. pii: S1476-5586(24)00045-9. [Epub ahead of print]53 101003
    Extracellular signals induce dynamic ER remodeling through αTAT1-dependent microtubule acetylation.
    Hannah R Ortiz, Paola Cruz Flores, Julia Podgorski, Aaron Ramonett, Tasmia Ahmed, Nadine Hempel, Pascale G Charest, Nathan A Ellis, Paul R Langlais, William R Montfort, Karthikeyan Mythreye, Sanjay Kumar, Nam Y Lee.
      Dynamic changes in the endoplasmic reticulum (ER) morphology are central to maintaining cellular homeostasis. Microtubules (MT) facilitate the continuous remodeling of the ER network into sheets and tubules by coordinating with many ER-shaping protein complexes, although how this process is controlled by extracellular signals remains unknown. Here we report that TAK1, a kinase responsive to various growth factors and cytokines including TGF-β and TNF-α, triggers ER tubulation by activating αTAT1, an MT-acetylating enzyme that enhances ER-sliding. We show that this TAK1/αTAT1-dependent ER remodeling promotes cell survival by actively downregulating BOK, an ER membrane-associated proapoptotic effector. While BOK is normally protected from degradation when complexed with IP3R, it is rapidly degraded upon their dissociation during the ER sheets-to-tubules conversion. These findings demonstrate a distinct mechanism of ligand-induced ER remodeling and suggest that the TAK1/αTAT1 pathway may be a key target in ER stress and dysfunction.
    Keywords:  Alpha TAT1; BOK; Endoplasmic reticulum; Microtubules; TAK1; TGF-beta
    DOI:  https://doi.org/10.1016/j.neo.2024.101003
  12. Mol Cell Biol. 2024 May 17. 1-13
    Deactivation of the Unfolded Protein Response Aggravated Renal AA Amyloidosis in HSF1 Deficiency Mice.
    Wei Liu, Shunjie Xia, Fang Yao, Jia Huo, Junqiao Qian, Xiaomeng Liu, Langning Bai, Yu Song, Jinze Qian.
      Systemic amyloid A (AA) amyloidosis, which is considered the second most common form of systemic amyloidosis usually takes place several years prior to the occurrence of chronic inflammation, generally involving the kidney. Activated HSF1, which alleviated unfolded protein response (UPR) or enhanced HSR, is the potential therapeutic target of many diseases. However, the effect of HSF1 on AA amyloidosis remains unclear. This study focused on evaluating effect of HSF1 on AA amyloidosis based on HSF1 knockout mice. As a result, aggravated amyloid deposits and renal dysfunction have been found in HSF1 knockout mice. In progressive AA amyloidosis, HSF1 deficiency enhances serum amyloid A production might to lead to severe AA amyloid deposition in mice, which may be related to deactivated unfolded protein response as well as enhanced inflammation. Thus, HSF1 plays a significant role on UPR related pathway impacting AA amyloid deposition, which can mitigate amyloidogenic proteins from aggregation pathologically and is the possible way for intervening with the pathology of systemic amyloid disorder. In conclusion, HSF1 could not only serve as a new target for AA amyloidosis treatment in the future, but HSF1 knockout mice also can be considered as a valuable novel animal model for renal AA amyloidosis.
    Keywords:  AA amyloidosis; HSF1 deficiency; mice model; microarray; unfolded protein response
    DOI:  https://doi.org/10.1080/10985549.2024.2347937
  13. Sci Transl Med. 2024 May 15. 16(747): eadi2952
    Tumor-associated NK cells drive MDSC-mediated tumor immune tolerance through the IL-6/STAT3 axis.
    Shi Yong Neo, Le Tong, Joni Chong, Yaxuan Liu, Xu Jing, Mariana M S Oliveira, Yi Chen, Ziqing Chen, Keene Lee, Nutsa Burduli, Xinsong Chen, Juan Gao, Ran Ma, Jia Pei Lim, Jianxin Huo, Shengli Xu, Evren Alici, Stina L Wickström, Felix Haglund, Johan Hartman, Arnika K Wagner, Yihai Cao, Rolf Kiessling, Kong Peng Lam, Lisa S Westerberg, Andreas Lundqvist.
      Apart from their killer identity, natural killer (NK) cells have integral roles in shaping the tumor microenvironment. Through immune gene deconvolution, the present study revealed an interplay between NK cells and myeloid-derived suppressor cells (MDSCs) in nonresponders of immune checkpoint therapy. Given that the mechanisms governing the outcome of NK cell-to-myeloid cell interactions remain largely unknown, we sought to investigate the cross-talk between NK cells and suppressive myeloid cells. Upon contact with tumor-experienced NK cells, monocytes and neutrophils displayed increased expression of MDSC-related suppressive factors along with increased capacities to suppress T cells. These changes were accompanied by impaired antigen presentation by monocytes and increased ER stress response by neutrophils. In a cohort of patients with sarcoma and breast cancer, the production of interleukin-6 (IL-6) by tumor-infiltrating NK cells correlated with S100A8/9 and arginase-1 expression by MDSCs. At the same time, NK cell-derived IL-6 was associated with tumors with higher major histocompatibility complex class I expression, which we further validated with b2m-knockout (KO) tumor mice models. Similarly in syngeneic wild-type and IL-6 KO mouse models, we then demonstrated that the accumulation of MDSCs was influenced by the presence of such regulatory NK cells. Inhibition of the IL-6/signal transducer and activator of transcription 3 (STAT3) axis alleviated suppression of T cell responses, resulting in reduced tumor growth and metastatic dissemination. Together, these results characterize a critical NK cell-mediated mechanism that drives the development of MDSCs during tumor immune escape.
    DOI:  https://doi.org/10.1126/scitranslmed.adi2952
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