bims-stacyt Biomed News
on Paracrine crosstalk between cancer and the organism
Issue of 2019‒05‒19
thirteen papers selected by
Cristina Muñoz Pinedo
L’Institut d’Investigació Biomèdica de Bellvitge


  1. Biomed Pharmacother. 2019 May 13. pii: S0753-3322(18)33476-0. [Epub ahead of print]115 108816
    Zhang B, Zhang HX, Shi ST, Bai YL, Zhe X, Zhang SJ, Li YJ.
      OBJECTIVE: Inflammation and immune responses are crucial factors associated with the onset and progression of stroke. Interleukin-11 (IL-11) is a hematopoietic IL-6 family cytokine that functions as an anti-inflammatory agent against various inflammatory diseases. However, its roles in stroke remain unknown. In this study, we investigated the effects of IL-11 on cerebral ischemia-reperfusion injury in a model of focal cerebral ischemia.METHODS: Mice were randomly divided into five groups the vehicle group, the middle cerebral artery occlusion (MCAO) group, the MCAO plus adenosine monophosphate-activated protein kinase (AMPK) inhibitor compound C group, the MCAO plus IL-11 treatment group, and the MCAO plus IL-11 treatment and compound C group. Focal cerebral ischemia was induced by occluding the left middle cerebral artery, and reperfusion was achieved by withdrawing the suture 2 h after ischemia. The protein expression levels of IL-11 were measured using Western blot analysis, and its location was detected using immunohistochemistry and immunofluorescence staining. The infarct volume was examined using 2,3,5-triphenyl tetrazolium chloride (TTC) staining, and the neurobehavioral progression was assessed using the neurological scoring system. The expression of astrocytes and microglia was detected using immunochemistry, and real-time quantitative PCR was used for the gene quantification of inflammatory cytokines. The extent of cerebral ischemia-reperfusion injury was tested using Nissl staining and the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay. The expression of the apoptotic proteins Bax, Bcl-2 and cleaved caspase-3 were detected using Western blot analysis, and the oxidative stress was also measured.
    RESULTS: The expression of IL-11 mRNA and protein significantly decreased after cerebral ischemia. Immunohistochemical staining showed a large amount of IL-11 in the cerebral cortex of the mice in the vehicle group, whereas the immunoreactivity of IL-11 remained weak for 24 h in the MCAO group. Immunofluorescent staining further confirmed that IL-11 was mainly expressed in the neurons. It was suggested that IL-11 (20 μg/kg) treatment ameliorated infarction and reduced neurological scores. In addition, IL-11 proved to reduce neuropathic damage, glial activation, and the expression of proinflammatory cytokines and increase the expression of anti-inflammatory cytokines after cerebral ischemia. IL-11 was also able to alleviate oxidative stress caused by cerebral ischemia, and AMPK inhibition enhanced the alleviation. Moreover, IL-11 was found to inhibit apoptosis caused by cerebral ischemia, which could also be facilitated by AMPK inhibitors.
    SIGNIFICANCE: Our research suggests that IL-11 is decreased during cerebral ischemia-reperfusion injury, but IL-11 treatment can improve neurological function and reduce the cerebral infarct volume, which can trigger stroke in mice. AMPK inhibition can further promote the protective effect of IL-11 in stroke. Overall, we demonstrate that IL-11 is of therapeutic interest in controlling stroke and managing cerebral ischemia-reperfusion injury.
    Keywords:  AMPK; Cerebral ischemia/reperfusion injury; Inflammatory cytokines; Interleukin-11; Oxidative stress; Stroke
    DOI:  https://doi.org/10.1016/j.biopha.2019.108816
  2. Dig Dis Sci. 2019 May 17.
    Ma F, Zhang B, Ji S, Hu H, Kong Y, Hua Y, Luo S.
      BACKGROUND: Gastric cancer (GC) is one of the most common causes of cancer death. Hypoxia is an important property of the tumor microenvironment of GC. Increasing evidence demonstrates that tumor-associated macrophages are related to the metastasis of GC, while the precise mechanism of how hypoxic macrophages affect tumor progression is still not fully understood.AIMS: To examine whether the mediators released from hypoxic macrophages contribute to the invasion and proliferation of GC cells.
    METHODS: Cell Counting Kit-8 was utilized to determine the proliferation of SGC7901 and MKN45 cells. The invasion of SGC7901 and MKN45 cells was measured by transwell invasion assay. Expression of VEGF mRNA in THP-1-derived macrophages was determined by RT-PCR, and protein level of VEGF in the culture medium was detected by ELISA.
    RESULTS: The proliferation and invasion of SGC7901 and MKN45 cells were dramatically increased after treatment with conditioned medium (CM) collected from THP-1-derived macrophages under hypoxia (H-CM), and the phosphorylation of Akt and p38 in SGC7901 and MKN45 cells was also up-regulated by H-CM stimulation. Notably, blockage of PI3K-Akt or p38 MAP kinase abolished the effects of H-CM on the proliferation and invasion of SGC7901 and MKN45 cells. Furthermore, VEGF was increased in macrophages after hypoxia and administration with nintedanib, an inhibitor of VEGFR, significantly decreases the phosphorylation of Akt and p38, as well as the proliferation and invasion of SGC7901 and MKN45 cells in response to H-CM.
    CONCLUSIONS: Our findings suggest that hypoxia-injured macrophages contribute to the proliferation and invasion of GC cells through the release of mediators such as VEGF.
    Keywords:  Gastric cancer; Hypoxia; Macrophage; VEGF
    DOI:  https://doi.org/10.1007/s10620-019-05656-w
  3. J Clin Invest. 2019 May 13. pii: 124613. [Epub ahead of print]130
    Singer BD, Chandel NS.
      Immune cell populations determine the balance between ongoing damage and repair following tissue injury. Cells responding to a tissue-damaged environment have significant bioenergetic and biosynthetic needs. In addition to supporting these needs, metabolic pathways govern the function of pro-repair immune cells, including regulatory T cells and tissue macrophages. In this Review, we explore how specific features of the tissue-damaged environment such as hypoxia, oxidative stress, and nutrient depletion serve as metabolic cues to promote or impair the reparative functions of immune cell populations. Hypoxia, mitochondrial DNA stress, and altered redox balance each contribute to mechanisms regulating the response to tissue damage. For example, hypoxia induces changes in regulatory T cell and macrophage metabolic profiles, including generation of 2-hydroxyglutarate, which inhibits demethylase reactions to modulate cell fate and function. Reactive oxygen species abundant in oxidative environments cause damage to mitochondrial DNA, initiating signaling pathways that likewise control pro-repair cell function. Nutrient depletion following tissue damage also affects pro-repair cell function through metabolic signaling pathways, specifically those sensitive to the redox state of the cell. The study of immunometabolism as an immediate sensor and regulator of the tissue-damaged environment provides opportunities to consider mechanisms that facilitate healthy repair of tissue injury.
    DOI:  https://doi.org/10.1172/JCI124613
  4. PLoS One. 2019 ;14(5): e0216899
    AnandBabu K, Sen P, Angayarkanni N.
      Age-related Macular Degeneration (AMD) is one of the major vision-threatening diseases of the eye. Oxidative stress is one of the key factors in the onset and progression of AMD. In this study, metabolites associated with AMD pathology more so at the systemic level namely, oxidized LDL (oxLDL), homocysteine (Hcy), homocysteine thiolactone (HCTL), advanced glycation end product (AGE) were evaluated for their pro-oxidant nature in a localized ocular environment based on in vitro studies in human retinal pigment epithelial cells (ARPE-19 cells). Human ARPE-19 cells were treated with pro-oxidants 50 μg/mL oxLDL, 500 μM Hcy, 500 nM HCTL, 100 μg/mL AGE, 200 μM H2O2 and 200 μM H2O2 with and without pre-treatment of 5 mM N-acetyl cysteine (NAC). The cytokines IL-6, IL-8 and vascular endothelial growth factor (VEGF) secreted from ARPE-19 cells exposed to pro-oxidants were estimated by ELISA. In vitro angiogenesis assay was performed with conditioned media of the pro-oxidant treated ARPE-19 cells in Geltrex-Matrigel coated 96-well plate. The human acute monocytic leukemia cell line (THP-1) was differentiated into macrophages and its migration in response to conditioned media of ARPE-19 cells insulted with the pro-oxidants was studied by transwell migration assay. Western blot was performed to detect the protein expression of Bax, Bcl-2 and NF-κB to assess apoptotic changes. The compounds involved in the study showed a significant increase in reactive oxygen species (ROS) generation in ARPE-19 cells (oxLDL; Hcy; AGE: p < 0.001 and HCTL: p < 0.05). NAC pre-treatment significantly lowered the oxidative stress brought about by pro-oxidants as seen by lowered ROS and MDA levels in the cells. Treatment with pro-oxidants significantly increased the secretion of IL-6 (oxLDL: p < 0.05; Hcy, HCTL and AGE: p < 0.01) and IL-8 cytokines (oxLDL: p < 0.05; HCTL: p <. 001 and AGE: p < 0.01) in ARPE-19 cells. Serum samples of AMD patients (n = 23) revealed significantly higher IL-6 and IL-8 levels compared to control subjects (n = 23) (IL6: p < 0.01 and IL8: p < 0.05). The pro-oxidants also promoted VEGF secretion by ARPE-19 cells compared to untreated control (oxLDL: p < 0.001; Hcy: p < 0.01; HCTL and AGE: p < 0.05). In vitro angiogenesis assay showed that the conditioned media significantly increased the tube formation in RF/6A endothelial cells. Transwell migration assay revealed significant infiltration of macrophages in response to pro-oxidants. We further demonstrated that the pro-oxidants increased the Bax/Bcl-2 ratio and increased the NF-κB activation resulting in pro-apoptotic changes in ARPE-19 cells. Thus, oxLDL, Hcy, HCTL and AGE act as pro-oxidant metabolites in RPE that promote AMD through oxidative stress, inflammation, chemotaxis and neovascularization.
    DOI:  https://doi.org/10.1371/journal.pone.0216899
  5. J Lipid Res. 2019 May 13. pii: jlr.M092510. [Epub ahead of print]
    Townsend LK, Medak KD, Peppler WT, Meers GM, Rector RS, Leblanc PJ, Wright DC.
      The relationship between liver interleukin-6 (IL-6) resistance following high fat diet (HFD)-induced obesity and glucose intolerance is unclear. The purpose of this study was to assess the temporal development of hepatic IL-6 resistance and the role of endoplasmic reticulum (ER) stress in this process. We hypothesized that HFD would rapidly induce hepatic IL-6 resistance through a mechanism involving ER stress. Male C57BL/6N mice consumed chow or HFD (60%) derived from lard (saturated) or olive oil (monounsaturated) for 4 days or 7 weeks before being injected IP with IL-6 (6 ng·kg-1). Glucose, insulin, and pyruvate tolerance tests were used as proxies for systemic glucose metabolism and hepatic glucose production, respectively. Primary mouse hepatocytes were incubated with palmitate (saturated) and oleate (unsaturated) overnight then treated with 20 ng/ml of IL-6. ER stress was induced via tunicamycin or prevented by sodium phenylbutyrate (PBA). Seven weeks of a saturated, but not monounsaturated, HFD reduced hepatic IL-6 signalling in conjunction with hepatic ER stress. Palmitate directly impaired IL-6 signalling in hepatocytes along with inducing ER stress. Pharmacologically-induced ER stress caused hepatic IL-6 resistance, while PBA reversed HFD-induced IL-6 resistance. Chronic HFD-induced obesity is associated with hepatic IL-6 resistance due to saturated fatty acid-induced ER stress.
    Keywords:  Endoplasmic reticulum; Fatty acid; Glucose; Liver; Obesity; hepatic glucose output; interleukin-6
    DOI:  https://doi.org/10.1194/jlr.M092510
  6. Cell Rep. 2019 May 14. pii: S2211-1247(19)30487-5. [Epub ahead of print]27(7): 2063-2074.e5
    Qiu J, Villa M, Sanin DE, Buck MD, O'Sullivan D, Ching R, Matsushita M, Grzes KM, Winkler F, Chang CH, Curtis JD, Kyle RL, Van Teijlingen Bakker N, Corrado M, Haessler F, Alfei F, Edwards-Hicks J, Maggi LB, Zehn D, Egawa T, Bengsch B, Klein Geltink RI, Jenuwein T, Pearce EJ, Pearce EL.
      Competition for nutrients like glucose can metabolically restrict T cells and contribute to their hyporesponsiveness during cancer. Metabolic adaptation to the surrounding microenvironment is therefore key for maintaining appropriate cell function. For instance, cancer cells use acetate as a substrate alternative to glucose to fuel metabolism and growth. Here, we show that acetate rescues effector function in glucose-restricted CD8+ T cells. Mechanistically, acetate promotes histone acetylation and chromatin accessibility and enhances IFN-γ gene transcription and cytokine production in an acetyl-CoA synthetase (ACSS)-dependent manner. Ex vivo acetate treatment increases IFN-γ production by exhausted T cells, whereas reducing ACSS expression in T cells impairs IFN-γ production by tumor-infiltrating lymphocytes and tumor clearance. Thus, hyporesponsive T cells can be epigenetically remodeled and reactivated by acetate, suggesting that pathways regulating the use of substrates alternative to glucose could be therapeutically targeted to promote T cell function during cancer.
    Keywords:  T cell exhaustion; T cell hyporesponsiveness; T cells; acetate; acetyl-CoA synthetase; chromatin remodeling; effector functions; tumor immunity; tumor-infiltrating lymphocytes
    DOI:  https://doi.org/10.1016/j.celrep.2019.04.022
  7. Biomed Res Int. 2019 ;2019 5068258
    Wang Y, Wang Y, Lu Y, Yu J.
      Objective: The transport and metabolism of glucose are important during mammalian development. High glucose can mediate the biological characteristics of mesenchymal stem cells (MSCs). However, the role of high glucose in the odonto/osteogenic differentiation of stem cells from apical papilla (SCAPs) is unclear.Materials and Methods: SCAPs were isolated and identified in vitro. Then, SCAPs were cultured in normal α-MEM and high glucose α-MEM separately. MTT assay was applied to observe the proliferation of SCAPs. ALP activity, alizarin red staining, real-time RT-PCR, and western blot were used to detect the odonto/osteogenic capacity of SCAPs as well as the participation of NF-κB pathway.
    Results: SCAPs in 25mmol/L glucose group expressed the maximum proteins of RUNX2 and ALP as compared with those in 5, 10, and 15 mmol/L groups. MTT assay showed that 25 mmol/L glucose suppressed the proliferation of SCAPs. ALP assay, alizarin red staining, real-time RT-PCR, and western blot showed 25 mmol/L high glucose can obviously enhance the odonto/osteogenic capacity of SCAPs. Moreover, the NF-κB pathway was activated in 25mmol/L glucose-treated SCAPs and the odonto/osteogenic differentiation was inhibited following the inhibition of NF-κB signaling pathway.
    Conclusions: High glucose can enhance the odonto/osteogenic capacity of SCAPs via NF-κB pathway.
    DOI:  https://doi.org/10.1155/2019/5068258
  8. J Cell Mol Med. 2019 May 13.
    Cheng M, Yang L, Dong Z, Wang M, Sun Y, Liu H, Wang X, Sai N, Huang G, Zhang X.
      Recent studies revealed that folic acid deficiency (FD) increased the likelihood of stroke and aggravated brain injury after focal cerebral ischaemia. The microglia-mediated inflammatory response plays a crucial role in the complicated pathologies that lead to ischaemic brain injury. However, whether FD is involved in the activation of microglia and the neuroinflammation after experimental stroke and the underlying mechanism is still unclear. The aim of the present study was to assess whether FD modulates the Notch1/nuclear factor kappa B (NF-κB) pathway and enhances microglial immune response in a rat middle cerebral artery occlusion-reperfusion (MCAO) model and oxygen-glucose deprivation (OGD)-treated BV-2 cells. Our results exhibited that FD worsened neuronal cell death and exaggerated microglia activation in the hippocampal CA1, CA3 and Dentate gyrus (DG) subregions after cerebral ischaemia/reperfusion. The hippocampal CA1 region was more sensitive to ischaemic injury and FD treatment. The protein expressions of proinflammatory cytokines such as tumour necrosis factor-α, interleukin-1β and interleukin-6 were also augmented by FD treatment in microglial cells of the post-ischaemic hippocampus and in vitro OGD-stressed microglia model. Moreover, FD not only dramatically enhanced the protein expression levels of Notch1 and NF-κB p65 but also promoted the phosphorylation of pIkBα and the nuclear translocation of NF-κB p65. Blocking of Notch1 with N-[N-(3, 5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester partly attenuated the nuclear translocation of NF-κB p65 and the protein expression of neuroinflammatory cytokines in FD-treated hypoxic BV-2 microglia. These results suggested that Notch1/NF-κB p65 pathway-mediated microglial immune response may be a molecular mechanism underlying cerebral ischaemia-reperfusion injury worsened by FD treatment.
    Keywords:  Notch pathway; folic acid; hippocampus; inflammatory; ischaemia-reperfusion; microglial
    DOI:  https://doi.org/10.1111/jcmm.14368
  9. Cell Mol Life Sci. 2019 May 17.
    Nisr RB, Shah DS, Ganley IG, Hundal HS.
      Sustained nutrient (fuel) excess, as occurs during obesity and diabetes, has been linked to increased inflammation, impaired mitochondrial homeostasis, lipotoxicity, and insulin resistance in skeletal muscle. Precisely how mitochondrial dysfunction is initiated and whether it contributes to insulin resistance in this tissue remains a poorly resolved issue. Herein, we examine the contribution that an increase in proinflammatory NFkB signalling makes towards regulation of mitochondrial bioenergetics, morphology, and dynamics and its impact upon insulin action in skeletal muscle cells subject to chronic fuel (glucose and palmitate) overloading. We show sustained nutrient excess of L6 myotubes promotes activation of the IKKβ-NFkB pathway (as judged by a six-fold increase in IL-6 mRNA expression; an NFkB target gene) and that this was associated with a marked reduction in mitochondrial respiratory capacity (>50%), a three-fold increase in mitochondrial fragmentation and 2.5-fold increase in mitophagy. Under these circumstances, we also noted a reduction in the mRNA and protein abundance of PGC1α and that of key mitochondrial components (SDHA, ANT-1, UCP3, and MFN2) as well as an increase in cellular ROS and impaired insulin action in myotubes. Strikingly, pharmacological or genetic repression of NFkB activity ameliorated disturbances in mitochondrial respiratory function/morphology, attenuated loss of SDHA, ANT-1, UCP3, and MFN2 and mitigated the increase in ROS and the associated reduction in myotube insulin sensitivity. Our findings indicate that sustained oversupply of metabolic fuel to skeletal muscle cells induces heightened NFkB signalling and that this serves as a critical driver for disturbances in mitochondrial function and morphology, redox status, and insulin signalling.
    Keywords:  Glucose; Insulin; Metabolism; Mitochondria; Muscle; NFkB; Palmitate; Respiration
    DOI:  https://doi.org/10.1007/s00018-019-03148-8
  10. Cytotherapy. 2019 May;pii: S1465-3249(18)30704-7. [Epub ahead of print]21(5): 497-508
    Shi Y, Shi H, Nomi A, Lei-Lei Z, Zhang B, Qian H.
      Over the past few decades, extracellular vesicles (EVs) have emerged as crucial mediators of intercellular communication. EVs encapsulate and convey information to surrounding cells or distant cells, where they mediate cellular biological responses. Among their multifaceted roles in the modulation of biological responses, the involvement of EVs in vascular development, growth and maturation has been widely documented and their potential therapeutic application in regenerative medicine or in the treatment of angiogenesis-related diseases is drawing increasing interest. In this review, we have summarized the details about the current knowledge on biogenesis of EVs and conventional isolation methods. Evidence supporting the use of EVs derived from mesenchymal stromal cells (MSCs) to enhance angiogenesis in the development of insufficient angiogenesis, such as chronic wounds, stroke and myocardial infarction, will also be discussed critically. Finally, the main challenges and prerequisites for their therapeutic applications will be evaluated.
    Keywords:  angiogenesis; extracellular vesicles; mesenchymal stromal cells; tissue regeneration
    DOI:  https://doi.org/10.1016/j.jcyt.2018.11.012
  11. Cancer Immunol Res. 2019 May 14. pii: canimm.0507.2018. [Epub ahead of print]
    Deng J, Li J, Sarde A, Lines JL, Lee YC, Qian DC, Pechenick DA, Manivanh R, Le Mercier I, Lowrey CH, Varn FS, Cheng C, Leib DA, Noelle RJ, Mabaera R.
      Tumor hypoxia is a negative prognostic factor that is implicated in oncogenic signal activation, immune escape, and resistance to treatment. Identifying the mechanistic role of hypoxia in immune escape and resistance to immune checkpoint inhibitors may aid identification of therapeutic targets. We and others have shown that V-domain Ig suppressor of T-cell activation (VISTA), a negative checkpoint regulator in the B7 family, is highly expressed in the tumor microenvironment in tumor models and primary human cancers. In this study, we show that VISTA and HIF-1α activity are correlated in a cohort of colorectal cancer patients. High VISTA expression was associated with worse overall survival. We used the CT26 colon cancer model to investigate the regulation of VISTA by hypoxia. Compared to less hypoxic tumor regions or draining lymph nodes, regions of profound hypoxia in the tumor microenvironment were associated with increased VISTA expression on tumor-infiltrating myeloid-derived suppressor cells (MDSCs). Using chromatin immunoprecipitation and genetic silencing, we show that hypoxia-inducible factor (HIF)-1α binding to a conserved hypoxia response element in the VISTA promoter upregulated VISTA on myeloid cells. Further, antibody targeting or genetic ablation of VISTA under hypoxia relieved MDSC-mediated T-cell suppression, revealing VISTA as a mediator of MDSC function. Collectively, these data suggest that targeting VISTA may mitigate the deleterious effects of hypoxia on antitumor immunity.
    DOI:  https://doi.org/10.1158/2326-6066.CIR-18-0507
  12. J Cell Physiol. 2019 May 13.
    Chen B, Li Y, Liu Y, Xu Z.
      Aberrant regulation in mesangial cell proliferation, extracellular matrix (ECM) accumulation, oxidative stress, and inflammation under hyperglycemic condition contributes significantly to the occurrence and development of diabetic nephropathy (DN). However, the mechanisms underlying the hyperglycemia-induced dysregulations have not been clearly elucidated. Here, we reported that high mobility group box 1 (HMGB1) was highly elevated in high glucose (HG)-treated mesangial cells, and induced the phosphorylation, nuclear translocation, and DNA binding activity of NF-κB via toll-like receptor 4 (TLR4). Function assays showed that inhibition of HMGB1 mitigated HG-induced proliferation, oxidative stress, ECM accumulation, and inflammation in mesangial cells via TLR4/NF-κB pathway. Increasing evidence has shown that circRNA, a large class of noncoding RNAs, functions by binding with miRNAs and terminating regulation of their target genes. We further investigated whether HMGB1 is involved in circRNA-miRNA-mRNA regulatory network. First, HMGB1 was identified and confirmed to be the target of miR-205, and miR-205 played a protective role against HG-induced cell injure via targeting HMGB1. Then circLRP6 was found to be upregulated in HG-treated mesangial cells, and regulate HG-induced mesangial cell injure via sponging miR-205. Besides, overexpression of miR-205 or knockdown of circLRP6 inhibited the NF-κB signaling pathway. Collectively, these data suggest that circLRP6 regulates HG-induced proliferation, oxidative stress, ECM accumulation, and inflammation in mesangial cells via sponging miR-205, upregulating HMGB1 and activating TLR4/NF-κB pathway. These findings provide a better understanding for the pathogenesis of DN.
    Keywords:  HMGB1; TLR4/NF-κB pathway; circLRP6; diabetic nephropathy; miR-205
    DOI:  https://doi.org/10.1002/jcp.28730
  13. Redox Biol. 2019 May 02. pii: S2213-2317(19)30050-3. [Epub ahead of print]24 101210
    Lee S, Hallis SP, Jung KA, Ryu D, Kwak MK.
      Hypoxia, a common element in the tumor environment, leads to Hypoxia-Inducible Factor-1α (HIF-1α) stabilization to modulate cellular metabolism as an adaptive response. In a previous study, we showed that inhibition of the nuclear factor erythroid 2-like-2 (NFE2L2; NRF2), a master regulator of many genes coping with electrophilic and oxidative stress, elevated the level of miR-181c and induced mitochondrial dysfunction in colon cancer cells. In this study, we demonstrate that NRF2-silencing hindered HIF-1α accumulation in hypoxic breast cancer cells and subsequently suppressed hypoxia-inducible expression of glycolysis-associated glucose transporter-1, hexokinase-2, pyruvate dehydrogenase kinase-1, and lactate dehydrogenase A. HIF-1α dysregulation in NRF2-silenced cancer cells was associated with miR-181c elevation. Overexpression of miR-181c in breast cancer cells blocked HIF-1α accumulation and diminished hypoxia-inducible levels of glycolysis enzymes, whereas the inhibition of miR-181c in NRF2-silenced cells restored HIF-1α accumulation. In a subsequent metabolomic analysis, hypoxic incubation increased the levels of metabolites involved in glycolysis and activated the pentose phosphate pathway (PPP) in control cells. However, these elevations were less pronounced in NRF2-silenced cells. In particular, hypoxic incubation increased the levels of amino acids, which implies a shift to catabolic metabolism, and the increased levels were higher in control cells than in NRF2-silenced cells. Concurrently, hypoxia activated BCL2 interacting protein 3 (BNIP3)-mediated autophagy in the control cells and miR-181c was found to be involved in this autophagy activation. Taken together, these results show that hypoxia-induced metabolic changes to glycolysis, the PPP, and autophagy are inhibited by NRF2-silencing through miR-181c-mediated HIF-1α dysregulation. Therefore, targeting NRF2/miR-181c could be an effective strategy to counteract HIF-1α-orchestrated metabolic adaptation of hypoxic cancer cells.
    Keywords:  Autophagy; HIF-1α; Hypoxia; Metabolism; Metabolome; NFE2L2/NRF2
    DOI:  https://doi.org/10.1016/j.redox.2019.101210