BACKGROUND:Duchenne muscular dystrophy (DMD) is a fatal X-linked recessive disease due to loss-of-function variants in the DYSTROPHIN gene. DMD-related skeletal muscle wasting is typified by an aberrant immune response involving upregulation of the TGFβ family of cytokines, like TGFβ1 and BMP4. We previously demonstrated that bone morphogenetic protein 4 (BMP4) is increased in DMD and BMP4 stimulation induces a 20-fold upregulation of Smad8 transcription in muscle cells. However, the role of BMP4 in late-stage DMD skeletal muscle is unknown. We hypothesized that BMP4 signalling is a driver of aberrant gene expression in late-stage human DMD skeletal muscle detectable by a transcriptomic signature. METHODS:Transcriptomes from skeletal muscle biopsies of late-stage DMD versus non-DMD controls and C2C12 muscle cells with or without BMP4 stimulation were generated using RNA-Seq. We tested transcriptional differences at the single transcript level in skeletal muscle biopsy samples from three patients with DMD and compared them to three non-DMD. They were then analyzed by Ingenuity Pathway Analysis, weighted gene coexpression network analyses (WGCNA) and Gene Set Enrichment Analysis (GSEA). Key hub and high-fold change genes overlapping in the DMD and BMP4 muscle transcriptomes were validated in additional primary and bulk skeletal muscle samples. RESULTS:A total of 3048 transcripts in the human muscle and 5291 transcripts in C2C12 muscle cells were differentially expressed. WGCNA identified an overlapping molecular signature of 1027 genes dysregulated in DMD muscle that were induced in BMP4-stimulated C2C12 muscle cells. SERPING1 and Aff3 were identified as the top hub genes. Highly upregulated DMD muscle transcripts that overlapped with BMP4-stimulated C2C12 muscle cells included ADAM12, SERPING1, SMAD8 and SFRP4. DMD skeletal muscle analysis showed aberrant upregulation of TGFβ signalling, extracellular matrix remodelling and collagen biosynthesis pathways, in contrast to inhibited mitochondrial and metabolic pathways. CONCLUSIONS:In summary, the DMD transcriptome was characterized by dysregulation of immune function, ECM remodelling and muscle bioenergetic metabolism. We additionally define a late-stage DMD skeletal muscle transcriptome that overlaps with a BMP4-induced molecular signature in C2C12 muscle cells. This supports BMP4/Smad8 pathway as a disease-driving regulator of transcriptomic changes in late-stage DMD skeletal muscle. Further exploration of this cross-species transcriptomic signature may expand our understanding of the evolution of dystrophic signalling pathways and the associated gene networks, which could be evaluated for therapeutic development.

Neuroinflammation is a major driver of secondary tissue damage after spinal cord injury (SCI). Within minutes after SCI, activated microglia and astrocytes produce proinflammatory mediators such as TNF-α, IL-6, iNOS, and COX-2 which induce tissue injury through cytotoxicity, vascular hyperpermeability, and secondary ischemia. The inflammatory cascade is amplified by chemokines like CCL2 and CXCL1 which recruit immune cells to the injured site. HuR is an RNA regulator that promotes glial expression of many proinflammatory factors by binding to adenylate- and uridylate-rich elements in the 3' untranslated regions of their mRNAs. SRI-42127 is a small molecule which blocks HuR function by preventing its nucleocytoplasmic translocation. This study aimed to evaluate the potential of SRI-42127 to suppress neuroinflammation after SCI and improve functional outcome. Adult female mice underwent a T10 contusion injury and received SRI-42127 1 h post injury for up to 5 days. Locomotor function was assessed by open field testing, balance beam, and rotarod. Immunohistochemistry was used to assess lesion size, neuronal loss, myelin sparing, microglial/astroglial activation, and HuR localization. Inflammatory mediator expression was assessed by qPCR, immunohistochemistry, ELISA, or western blot. We found that SRI-42127 treatment significantly attenuated loss of locomotor function and post-SCI pain. There was a reduction in lesion size and neuronal loss with an increase in myelin sparing. Microglia and astrocytes showed reduced activation and reduced nucleocytoplasmic translocation of HuR. There was a striking suppression of proinflammatory mediators at the epicenter along with peripheral suppression of inflammatory responses in serum, liver, and spleen. In conclusion, HuR inhibition with SRI-42127 may be a viable therapeutic approach for suppressing neuroinflammatory responses after SCI and improving functional outcome.

Background:Proinflammatory mediators including COX-2, IL-1β, IL-6, and TNF-α, play major roles in the initiation of postsurgical pain. Produced primarily by activated macrophages and microglia, these mediators drive hyperexcitation of nociceptors and promote peripheral and central pain sensitization. Post-transcriptional RNA regulation is a major control point for these mediators, centering around adenine- and uridine-rich elements (ARE) in the 3' untranslated regions of their mRNA transcripts. The ARE governs RNA stability and translational efficiency through an interaction with ARE-specific RNA binding proteins (AUBP). Tristetraprolin (TTP) is an AUBP that promotes RNA degradation and translational silencing of these mediators to suppress inflammatory responses. Methods:Mice with myeloid-specific TTP knockout or TTP knock-in underwent paw incision and were assessed for mechanical allodynia and thermal sensitivity. Molecular and cellular inflammatory responses were monitored at the site of incision, dorsal root ganglia (DRG) and lumbar spinal cord (L-SC) by qPCR, ELISA, immunohistochemistry and/or flow cytometry. Results:TTP deletion exacerbated post-incisional allodynic pain in parallel with increased edema at the site of injury and delayed wound healing but without significant effects on thermal sensitivity. There was an increase in infiltrating macrophages at the incisional site, particularly at the dermal-epidermal junction, in parallel with a robust increase in proinflammatory/pronociceptive mediators. An enhanced inflammatory response was also detected in the circulation, ipsilateral DRG and L-SC which persisted through post-incisional day 7. Conversely, TTP knock-in mice showed attenuation of allodynic pain and inflammatory responses in skin, DRG, L-SC, and circulation. Conclusion:TTP plays a critical role in mitigating postsurgical pain by tamping down peripheral, central and systemic inflammatory responses, thus identifying a new target and mechanism for future development of pain therapeutics.

Amyotrophic lateral sclerosis (ALS) is an age-related and fatal neurodegenerative disease characterized by progressive muscle weakness. There is marked heterogeneity in clinical presentation, progression, and pathophysiology with only modest treatments to slow disease progression. Molecular markers that provide insight into this heterogeneity are crucial for clinical management and identification of new therapeutic targets. In a prior muscle miRNA sequencing investigation, we identified altered FGF pathways in ALS muscle, leading us to investigate FGF21. We analyzed human ALS muscle biopsy samples and found a large increase in FGF21 expression with localization to atrophic myofibers and surrounding endomysium. A concomitant increase in FGF21 was detected in ALS spinal cords which correlated with muscle levels. FGF21 was increased in the SOD1G93A mouse beginning in presymptomatic stages. In parallel, there was dysregulation of the co-receptor, β-Klotho, with higher levels detected in ALS muscle biopsies and lower levels in post-mortem muscle compared to controls. Plasma FGF21 levels were increased in ALS patients and high levels correlated with slower disease progression, prolonged survival, and increased body mass index. In cellulo, FGF21 was induced in differentiating muscle cells and ectopic treatment with FGF21 enhanced muscle differentiation. Ectopic FGF21 mitigated oxidative stress-induced loss of viability in iPSC-derived ALS motor neurons and muscle cells expressing SOD1G93A. In summary, FGF21 is a novel biomarker in ALS which exerts trophic effects in the neuromuscular system.

mechanical allodynia, and small fiber neuropathy.Using scRNA-seq, we captured keratinocyte gene expression profiles from mouse skin and from PDN-patients skin biopsy.scRNA-seq from RD and HFD mice and PDN-patients identified differentially expressed genes, showing a transcriptional profiling map of two skin cell populations, immune cells and keratinocytes at different stages of differentiation.By comparing the transcriptomes from skin of PDN patients to those of HFD mice, we have identified genes putatively expressed in both human and mouse skin, improving the understanding of neuron-keratinocyte communication in diabetic skin.Our results could be translated into new topical interventions, including those based on GPCR agonism or antagonism, which could meet the unmet need for therapy for both small-fiber degeneration and neuropathic pain in diabetes.

A major hallmark of neuroinflammation is the activation of microglia and astrocytes with the induction of inflammatory mediators such as IL-1β, TNF-α, iNOS, and IL-6. Neuroinflammation contributes to disease progression in a plethora of neurological disorders ranging from acute CNS trauma to chronic neurodegenerative disease. Posttranscriptional pathways of mRNA stability and translational efficiency are major drivers for the expression of these inflammatory mediators. A common element in this level of regulation centers around the adenine- and uridine-rich element (ARE) which is present in the 3' untranslated region (UTR) of the mRNAs encoding these inflammatory mediators. (ARE)-binding proteins (AUBPs) such as Human antigen R (HuR), Tristetraprolin (TTP) and KH- type splicing regulatory protein (KSRP) are key nodes for directing these posttranscriptional pathways and either promote (HuR) or suppress (TTP and KSRP) glial production of inflammatory mediators. This review will discuss basic concepts of ARE-mediated RNA regulation and its impact on glial-driven neuroinflammatory diseases. We will discuss strategies to target this novel level of gene regulation for therapeutic effect and review exciting preliminary studies that underscore its potential for treating neurological disorders.

Duchenne muscular dystrophy (DMD) is an X-linked recessive disease characterized by skeletal muscle instability, progressive muscle wasting, and fibrosis. A major driver of DMD pathology stems from aberrant upregulation of transforming growth factor β (TGFβ) signaling. In this report, we investigated the major transducers of TGFβ signaling, i.e., receptor Smads (R-Smads), in DMD patient skeletal muscle and observed a 48-fold increase in Smad8 mRNA. Smad1, Smad2, Smad3, and Smad5 mRNA were only minimally increased. A similar pattern was observed in the muscle from the mdx5cv mouse. Western blot analysis showed upregulation of phosphorylated Smad1, Smad5, and Smad8 compared to total Smad indicating activation of this pathway. In parallel, we observed a profound diminishment of muscle-enriched microRNAs (myomiRs): miR-1, miR-133a, and miR-133b. The pattern of Smad8 induction and myomiR suppression was recapitulated in C2C12 muscle cells after stimulation with bone morphogenetic protein 4 (BMP4), a signaling factor that we found upregulated in DMD muscle. Silencing Smad8 in C2C12 myoblasts derepressed myomiRs and promoted myoblast differentiation; there was also a concomitant upregulation of myogenic regulatory factors (myogenin and myocyte enhancer factor 2D) and suppression of a pro-inflammatory cytokine (interleukin-6). Our data suggest that Smad8 is a negative regulator of miR-1, miR-133a, and miR-133b in muscle cells and that the BMP4-Smad8 axis is a driver of dystrophic pathology in DMD.

Microglial activation with the production of pro-inflammatory mediators such as IL-6, TNF-α, and IL-1β, is a major driver of neuropathic pain (NP) following peripheral nerve injury. We have previously shown that the RNA binding protein, HuR, is a positive node of regulation for many of these inflammatory mediators in glia and that its chemical inhibition or genetic deletion attenuates their production. In this report, we show that systemic administration of SRI-42127, a novel small molecule HuR inhibitor, attenuates mechanical allodynia, a hallmark of NP, in the early and chronic phases after spared nerve injury in male and female mice. Flow cytometry of lumbar spinal cords in SRI-42127-treated mice shows a reduction in infiltrating macrophages and a concomitant decrease in microglial populations expressing IL-6, TNF-α, IL-1β, and CCL2. Immunohistochemistry, ELISA, and qPCR of lumbar spinal cord tissue indicate suppression of these cytokines and other inflammatory mediators. ELISA of plasma samples in the acute phase also shows attenuation of inflammatory responses. In summary, inhibition of HuR by SRI-42127 leads to the suppression of neuroinflammatory responses and allodynia after nerve injury and represents a promising new direction in the treatment of NP.

Circular RNAs are abundant, covalently closed transcripts that arise in cells through back-splicing and display distinct expression patterns across cells and developmental stages. While their functions are largely unknown, their intrinsic stability has made them valuable biomarkers in many diseases. Here, we set out to examine circRNA patterns in amyotrophic lateral sclerosis (ALS). By RNA-sequencing analysis, we first identified circRNAs and linear RNAs that were differentially abundant in skeletal muscle biopsies from ALS compared to normal individuals. By RT-qPCR analysis, we confirmed that 8 circRNAs were significantly elevated and 10 were significantly reduced in ALS, while the linear mRNA counterparts, arising from shared precursor RNAs, generally did not change. Several of these circRNAs were also differentially abundant in motor neurons derived from human induced pluripotent stem cells (iPSCs) bearing ALS mutations, and across different disease stages in skeletal muscle from a mouse model of ALS (SOD1G93A). Interestingly, a subset of the circRNAs significantly elevated in ALS muscle biopsies were significantly reduced in the spinal cord samples from ALS patients and ALS (SOD1G93A) mice. In sum, we have identified differentially abundant circRNAs in ALS-relevant tissues (muscle and spinal cord) that could inform about neuromuscular molecular programs in ALS and guide the development of therapies.

Glial activation with the production of pro‐inflammatory mediators is a major driver of disease progression in neurological processes ranging from acute traumatic injury to chronic neurodegenerative diseases such as amyotrophic lateral sclerosis and Alzheimer's disease. Posttranscriptional regulation is a major gateway for glial activation as many mRNAs encoding pro‐inflammatory mediators contain adenine‐ and uridine‐rich elements (ARE) in the 3′ untranslated region which govern their expression. We have previously shown that HuR, an RNA regulator that binds to AREs, plays a major positive role in regulating inflammatory cytokine production in glia. HuR is predominantly nuclear in localization but translocates to the cytoplasm to exert a positive regulatory effect on RNA stability and translational efficiency. Homodimerization of HuR is necessary for translocation and we have developed a small molecule inhibitor, SRI‐42127, that blocks this process. Here we show that SRI‐42127 suppressed HuR translocation in LPS‐activated glia in vitro and in vivo and significantly attenuated the production of pro‐inflammatory mediators including IL1β, IL‐6, TNF‐α, iNOS, CXCL1, and CCL2. Cytokines typically associated with anti‐inflammatory effects including TGF‐β1, IL‐10, YM1, and Arg1 were either unaffected or minimally affected. SRI‐42127 suppressed microglial activation in vivo and attenuated the recruitment/chemotaxis of neutrophils and monocytes. RNA kinetic studies and luciferase studies indicated that SRI‐42127 has inhibitory effects both on mRNA stability and gene promoter activation. In summary, our findings underscore HuR's critical role in promoting glial activation and the potential for SRI‐42127 and other HuR inhibitors for treating neurological diseases driven by this activation.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive muscle weakness. Skeletal muscle is a prime source for biomarker discovery since it is one of the earliest sites to manifest disease pathology. From a prior RNA sequencing project, we identified FGF23 as a potential muscle biomarker in ALS. Here, we validate this finding with a large collection of ALS muscle samples and found a 13-fold increase over normal controls. FGF23 was also increased in the SOD1 G93A mouse, beginning at a very early stage and well before the onset of clinical symptoms. FGF23 levels progressively increased through end-stage in the mouse. Immunohistochemistry of ALS muscle showed prominent FGF23 immunoreactivity in the endomysial connective tissue and along the muscle membrane and was significantly higher around grouped atrophic fibers compared to non-atrophic fibers. ELISA of plasma samples from the SOD1 G93A mouse showed an increase in FGF23 at end-stage whereas no increase was detected in a large cohort of ALS patients. In conclusion, FGF23 is a novel muscle biomarker in ALS and joins a molecular signature that emerges in very early preclinical stages. The early appearance of FGF23 and its progressive increase with disease progression offers a new direction for exploring the molecular basis and response to the underlying pathology of ALS.

Extra-renal expression of Cytochrome P450 Family 27 Subfamily B Member 1 (CYP27B1) has been well recognized and reflects the importance of intracrine/paracrine vitamin D signaling in different tissues under physiological and pathological conditions. In a prior RNA sequencing project, we identified CYP27B1 mRNA as upregulated in muscle samples from patients with amyotrophic lateral sclerosis (ALS) compared to normal controls. Our aims here were: (1) to validate this finding in a larger sample set including disease controls, (2) to determine which cell type is expressing CYP27B1 protein in muscle tissue, (3) to correlate CYP27B1 mRNA expression with disease progression in the SOD1(G93A) ALS mouse and in ALS patients. We assessed CYP27B1 expression by qPCR, western blot, and immunohistochemistry in a repository of muscle samples from ALS, disease controls (myopathy and non-ALS neuropathic disease), normal subjects, and muscle samples from the SOD1(G93A) mouse. Eight ALS patients were studied prospectively over 6-12 months with serial muscle biopsies. We found that CYP27B1 mRNA and protein levels were significantly increased in ALS versus normal and myopathy muscle samples. Neuropathy samples had increased CYP27B1 mRNA and protein expression but at a lower level than the ALS group. Immunohistochemistry showed that CYP27B1 localized to myofibers, especially those with features of denervation. In the SOD1(G93A) mouse, CYP27B1 mRNA and protein were detected in skeletal muscle in early pre-symptomatic stages and increased through end-stage. In the human study, increases in CYP27B1 mRNA in muscle biopsies correlated with disease progression rates over the same time period. In summary, we show for the first time that CYP27B1 mRNA and protein expression are elevated in muscle fibers in denervating disease, especially ALS, where mRNA levels can potentially serve as a surrogate marker for tracking disease progression. Its upregulation may reflect a local perturbation of vitamin D signaling, and further characterization of this pathway may provide insight into underlying molecular processes linked to muscle denervation.

Skeletal muscle and the neuromuscular junction are the earliest sites to manifest pathological changes in amyotrophic lateral sclerosis (ALS). Based on prior studies, we have identified a molecular signature in muscle that develops early in ALS and parallels disease progression. This signature represents an intersection of signaling pathways including Smads, TGF-β, and vitamin D. Here, we show that the Wnt antagonist, Frizzled Related Protein (FRZB), was increased in ALS muscle samples and to a variable extent other denervating disease but only minimally in acquired myopathies. In the SOD1G93A mouse, FRZB was upregulated in the early stages of disease (between 40 and 60 days) until end-stage. By immunohistochemistry, FRZB was predominantly localized to endomysial connective tissue and to a lesser extent muscle membrane. There was a significant increase in immunoreactivity surrounding atrophied myofibers. Because FRZB is a Wnt antagonist, we assessed β-catenin, the canonical transducer of Wnt signaling, and found increased levels mainly at the muscle membrane. In summary, we show that FRZB is part of a molecular signature of muscle denervation that may reflect disease progression in ALS. Our findings open up avenues for future investigation as to what roles FRZB and Wnt signaling might be playing in muscle denervation/reinnervation.

Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of upper and lower motor neurons accompanied by proliferation of reactive microglia in affected regions. However, it is unknown whether the hematopoietic marker CD34 can identify a subpopulation of proliferating microglial cells in the ALS degenerating spinal cord. Immunohistochemistry for CD34 and microglia markers was performed in lumbar spinal cords of ALS rats bearing the SOD1G93A mutation and autopsied ALS and control human subjects. Characterization of CD34-positive cells was also performed in primary cell cultures of the rat spinal cords. CD34 was expressed in a large number of cells that closely interacted with degenerating lumbar spinal cord motor neurons in symptomatic SOD1G93A rats, but not in controls. Most CD34+ cells co-expressed the myeloid marker CD11b, while only a subpopulation was stained for Iba1 or CD68. Notably, CD34+ cells actively proliferated and formed clusters adjacent to damaged motor neurons bearing misfolded SOD1. CD34+ cells were identified in the proximity of motor neurons in autopsied spinal cord from sporadic ALS subjects but not in controls. Cell culture of symptomatic SOD1G93A rat spinal cords yielded a large number of CD34+ cells exclusively in the non-adherent phase, which generated microglia after successive passaging. A yet unrecognized CD34+ cells, expressing or not the microglial marker Iba1, proliferate and accumulate adjacent to degenerating spinal motor neurons, representing an intriguing cell target for approaching ALS pathogenesis and therapeutics.

Distal axonopathy is a recognized pathological feature of amyotrophic lateral sclerosis (ALS). In the peripheral nerves of ALS patients, motor axon loss elicits a Wallerian-like degeneration characterized by denervated Schwann cells (SCs) together with immune cell infiltration. However, the pathogenic significance of denervated SCs accumulating following impaired axonal growth in ALS remains unclear. Here, we analyze SC phenotypes in sciatic nerves of ALS patients and paralytic SOD1G93A rats, and identify remarkably similar and specific reactive SC phenotypes based on the pattern of S100β, GFAP, isolectin and/or p75NTR immunoreactivity. Different subsets of reactive SCs expressed colony-stimulating factor-1 (CSF1) and Interleukin-34 (IL-34) and closely interacted with numerous endoneurial CSF-1R-expressing monocyte/macrophages, suggesting a paracrine mechanism of myeloid cell expansion and activation. SCs bearing phagocytic phenotypes as well as endoneurial macrophages expressed stem cell factor (SCF), a trophic factor that attracts and activates mast cells through the c-Kit receptor. Notably, a subpopulation of Ki67+ SCs expressed c-Kit in the sciatic nerves of SOD1G93A rats, suggesting a signaling pathway that fuels SC proliferation in ALS. c-Kit+ mast cells were also abundant in the sciatic nerve from ALS donors but not in controls. Pharmacological inhibition of CSF-1R and c-Kit with masitinib in SOD1G93A rats potently reduced SC reactivity and immune cell infiltration in the sciatic nerve and ventral roots, suggesting a mechanism by which the drug ameliorates peripheral nerve pathology. These findings provide strong evidence for a previously unknown inflammatory mechanism triggered by SCs in ALS peripheral nerves that has broad application in developing novel therapies.

Objective: To validate CYP27B1 as a novel muscle biomarker in amyotrophic lateral sclerosis (ALS). Background: Pathological changes in skeletal muscle, including the neuromuscular junction, occur at the earliest stages of ALS and progress in parallel with clinical disease. Molecular changes that underlie skeletal muscle pathology in ALS may therefore serve as biomarkers that can assist with diagnosis and/or monitoring of disease progression. We previously performed RNA sequencing on muscle biopsies from ALS patients and identified an elevation of the vitamin D activator, CYP27B1. Design/Methods: RNA was extracted from muscle biopsy samples from patients with definite or probable ALS (n = 29), myopathy (n = 8), neuropathy (n = 12), or no neuromuscular disease (n = 10) and assessed by qPCR for CYP27B1. For some of the biopsies, CYP27B1 protein expression was assessed by western blot and immunohistochemistry. To evaluate disease progression, muscle samples from the SOD1G93A ALS mouse were collected at different ages and assayed for CYP27B1 expression. Results: CYP27B1mRNA and protein levels were significantly increased in human ALS muscle samples versus control and myopathy samples. Neuropathy-associated samples also had increased levels, but to a lesser extent than the ALS group. In the SOD1G93A mouse, mRNA and protein levels were similarly elevated and showed progressive increases with clinical progression, beginning in the pre-symptomatic stage up to end-stage. Immunohistochemistry showed intense CYP27B1 staining of atrophied muscle fibers in both human and mouse ALS muscle. Conclusions: These data validate CYP27B1 as a muscle biomarker in ALS and indicate its potential as a marker of ALS disease progression. These findings also suggest a perturbation of vitamin D signaling in the denervated myofiber. Further characterization of this pathway may provide insight into underlying molecular processes linked to muscle denervation. Disclosure: Dr. Si has nothing to disclose. Dr. Kwan has nothing to disclose. Dr. Zhou has nothing to disclose. Dr. Kazamel has nothing to disclose. Dr. Lee has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Alexion. Dr. Anderson has nothing to disclose. Dr. King has nothing to disclose.

Glioblastoma is a malignant brain tumor that portends a poor prognosis. Its resilience, in part, is related to a remarkable capacity for manipulating the microenvironment to promote its growth and survival. Microglia/macrophages are prime targets, being drawn into the tumor and stimulated to produce factors that support tumor growth and evasion from the immune system. Here we show that the RNA regulator, HuR, plays a key role in the tumor-promoting response of microglia/macrophages. Knockout (KO) of HuR led to reduced tumor growth and proliferation associated with prolonged survival in a murine model of glioblastoma. Analysis of tumor composition by flow cytometry showed that tumor-associated macrophages (TAMs) were decreased, more polarized toward an M1-like phenotype, and had reduced PD-L1 expression. There was an overall increase in infiltrating CD4+ cells, including Th1 and cytotoxic effector cells, and a concomitant reduction in tumor-associated polymorphonuclear myeloid-derived suppressor cells. Molecular and cellular analyses of HuR KO TAMs and cultured microglia showed changes in migration, chemoattraction, and chemokine/cytokine profiles that provide potential mechanisms for the altered tumor microenvironment and reduced tumor growth in HuR KO mice. In summary, HuR is a key modulator of pro-glioma responses by microglia/macrophages through the molecular regulation of chemokines, cytokines, and other factors. Our findings underscore the relevance of HuR as a therapeutic target in glioblastoma.