OUP accepted manuscript

The two-sided battlefield of tumour-associated macrophages in glioblastoma: unravelling their therapeutic potential

Gliomas are the most common primary malignant tumours of the central nervous system (CNS), which are highly aggressive, with increasing morbidity and mortality rates year after year, posing a serious threat to the quality and expected survival time of patients. The treatment of gliomas is a major challenge in the field of neuro-oncology, especially high-grade gliomas such as glioblastomas (GBMs). Despite considerable progress in recent years in the study of the molecular and cellular mechanisms of GBMs, their prognosis remains bleak. Tumour-associated macrophages (TAMs) account for up to 50% of GBMs, and they are a highly heterogeneous cell population whose role cannot be ignored. Here, we focus on reviewing the contribution of classically activated M1-phenotype TAMs and alternatively activated M2-phenotype TAMs to GBMs, and exploring the research progress in reprogramming M1 TAMs into M2 TAMs.

Hypoxic glioma-derived exosomal miR-25-3p promotes macrophage M2 polarization by activating the PI3K-AKT-mTOR signaling pathway

BACKGROUND

Exosomes (EXO) play crucial roles in intercellular communication and glioma microenvironment modulation. Tumor-associated macrophages are more likely to become M2-like type macrophages in the immunosuppressive microenvironment. Here, we aimed to investigate the effects and molecular mechanisms of hypoxic glioma-derived exosomes mediated M2-like macrophage polarization.

METHODS

Highly expressed miRNAs in exosomes derived from glioma cells cultured under hypoxia condition compared to normoxic condition were identified through microRNA sequencing. The polarization status of macrophages was determined using qRT-PCR, Western blotting, flow cytometry, and immunohistochemistry. By using RNA-seq, we aimed to identify the downstream target genes regulated by miR-25-3p in macrophages and investigate the mechanistic pathways through which it exerts its effects. The proliferation and migration capabilities of glioma cells were assessed through EdU, Transwell assays, and in vivo experiments.

RESULTS

We found that miR-25-3p was upregulated in the exosomes derived from hypoxic glioma cells and can be transferred to the macrophage. In macrophages, miR-25-3p downregulates the expression of PHLPP2, thereby activating the PI3K-AKT-mTOR signaling pathway, ultimately leading to macrophage M2 polarization. As part of a feedback loop, M2-polarized macrophages can, in turn, promote malignant glioma progression.

CONCLUSION

Our study reveals that miR-25-3p from hypoxic glioma cells is delivered to macrophages via exosomes as a mediator, promoting M2 polarization of macrophages through the miR-25-3p/PHLPP2/PI3K-AKT signaling pathway. This study suggests that targeted interventions to modulate miR-25-3p expression, transmission, or inhibition of PI3K-AKT pathway activation can disrupt the immune-suppressive microenvironment, providing a novel approach for immunotherapy in gliomas.

Gambogic acid impairs the maintenance and therapeutic resistance of glioma stem cells by targeting B-cell-specific Moloney leukemia virus insert site 1

BACKGROUND

Glioblastoma (GBM) is the most common and lethal primary brain tumor with low effectiveness of available treatments. The tumor heterogeneity and therapeutic resistance are largely due to the presence of glioma stem cells (GSCs). Therefore, eliminating GSCs can overcome the progression, relapse, and resistance of GBM. Previous studies have shown that gambogic acid (GA), a natural active ingredient, has anti-glioma properties. Nonetheless, it is still unclear whether it has an inhibitory effect on GSCs and what its target might be. This study aimed to investigate the anti-tumor effects of GA on GSCs. In addition, this study found the target of GA in GSCs and elucidated the potential specific mechanisms by conducting both in vitro and in vivo experiments. B-cell-specific Moloney leukemia virus insert site 1 (BMI1) is a key stem cell factor of the polycomb group (PcG) family with important effects on the development, recurrence, and chemoresistance of several cancers. In both normal and cancer stem cells, BMI1 maintains stem cell self-renewal by regulating the cell cycle, cellular immortalization, and senescence. Its high expression in a variety of cancers correlates with poor clinical prognosis and chemoresistance. These mechanisms of BMI1 make it a potential therapeutic target for cancer therapy, and future studies may further reveal the specific roles of BMI1 mechanism and provide a basis for the development of new cancer therapeutic strategies.

PURPOSE

This study investigated the in vitro and in vivo effects of GA in inducing apoptosis in GSCs and inhibiting GSCs self-renewal, as well as its underlying mechanisms.

METHODS

This study synthesized biotinylated gambogic acid for the first time and angled for the target of gambogic acid using LC-MS/MS analysis, which has not been reported previously. Human-derived glioma stem cells GSC123 and GSC111 were used for in vitro studies, analyzing functions and mechanisms via microscale thermophoresis (MST), Annexin V/PI staining, Western blotting, immunofluorescence, and co-immunoprecipitation. The orthotopic glioma mouse model was used to assess the anti-tumor effects of GA in vivo.

RESULTS

This study demonstrated that GA is a specific inhibitor of BMI1, a key regulator controlling stem cell growth and self-renewal. GA binds to BMI1's RING domain, accelerating K51-dependent degradation and suppressing H2A ubiquitination. Importantly, GA induces apoptosis, and inhibits GSC self-renewal, but minimally impacts neural progenitor cells (NPCs). GA can also be combined effectively with temozolomide and radiotherapy to increase their sensitivities in resistant cells. Furthermore, exogenous induction of BMI1 expression significantly hinders the disruption of GSCs by GA. In vivo, GA inhibits tumorigenicity, enhances the effect of temozolomide, and reduces BMI1 expression.

CONCLUSION

These findings suggest that GA is a potential candidate for targeting GSCs and therefore be used to treat GBM.

Nucleophosmin 1 promotes mucosal immunity by supporting mitochondrial oxidative phosphorylation and ILC3 activity

Nucleophosmin 1 (NPM1) is commonly mutated in myelodysplastic syndrome (MDS) and acute myeloid leukemia. Concurrent inflammatory bowel diseases (IBD) and MDS are common, indicating a close relationship between IBD and MDS. Here we examined the function of NPM1 in IBD and colitis-associated colorectal cancer (CAC). NPM1 expression was reduced in patients with IBD. Npm1+/- mice were more susceptible to acute colitis and experimentally induced CAC than littermate controls. Npm1 deficiency impaired the function of interleukin-22 (IL-22)-producing group three innate lymphoid cells (ILC3s). Mice lacking Npm1 in ILC3s exhibited decreased IL-22 production and accelerated development of colitis. NPM1 was important for mitochondrial biogenesis and metabolism by oxidative phosphorylation in ILC3s. Further experiments revealed that NPM1 cooperates with p65 to promote mitochondrial transcription factor A (TFAM) transcription in ILC3s. Overexpression of Npm1 in mice enhanced ILC3 function and reduced the severity of dextran sulfate sodium-induced colitis. Thus, our findings indicate that NPM1 in ILC3s protects against IBD by regulating mitochondrial metabolism through a p65-TFAM axis.

LPS exposure alleviates multiple tissues damage by facilitating macrophage efferocytosis

Toll-like receptors (TLRs) play a crucial role in mediating immune responses by recognizing pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs), as well as facilitating apoptotic cell (ACs) clearance (efferocytosis), thus contributing significantly to maintaining homeostasis and promoting tissue resolution. In this study, we investigate the impact of TLR agonists on macrophage efferocytosis. Our findings demonstrate that pretreatment with the TLR agonist lipopolysaccharide (LPS) significantly enhances macrophage phagocytic ability, thereby promoting efferocytosis both in vitro and in vivo. Moreover, LPS pretreatment confers tissue protection against damage by augmenting macrophage efferocytic capacity in murine models. Further examination reveals that LPS modulates efferocytosis by upregulating the expression of Tim4.These results underscore the pivotal role of TLR agonists in regulating the efferocytosis process and suggest potential therapeutic avenues for addressing inflammatory diseases. Overall, our study highlights the intricate interplay between LPS pretreatment and efferocytosis in maintaining tissue homeostasis and resolving inflammation.

Mineralocorticoid promotes intestinal inflammation through receptor dependent IL17 production in ILC3s

Aldosterone is a key mineralocorticoid involved in regulating the concentration of blood electrolytes and physiological volume balance. Activation of mineralocorticoid receptor (MR) has been recently reported to participate in adaptive and innate immune responses under inflammation. Here, we evaluated the role of aldosterone and MR in inflammation bowel diseases (IBD). Aldosterone elevated in the colon of DSS-induced colitis mice. Aldosterone addition induced IL17 production and ROS/RNS level in group 3 innate lymphoid cells (ILC3s) and exacerbated intestinal injury. A selective mineralocorticoid receptor antagonism, eplerenone, inhibited IL17-producing ILC3s and its ROS/RNS production, protected mice from DSS-induced colitis. Mice lacking Nr3c2 (MR coding gene) in ILC3s exhibited decreased IL17 and ROS/RNS production, which alleviated colitis and colitis-associated colorectal cancer (CAC). Further experiments revealed that MR could directly bind to IL17A promoter and facilitate its transcription, which could be enhanced by aldosterone. Thus, our findings demonstrated the critical role of aldosterone-MR-IL17 signaling in ILC3s and gut homeostasis, indicating the therapeutic strategy of eplerenone in IBD clinical trial.

The Cytidine N-Acetyltransferase NAT10 Participates in Peripheral Nerve Injury-Induced Neuropathic Pain by Stabilizing SYT9 Expression in Primary Sensory Neurons

RNA N4-acetylcytidine (ac4C) modification is increasingly recognized as an important layer of gene regulation; however, the involvement of ac4C in pain regulation has not been studied. Here, we report that N-acetyltransferase 10 protein (NAT10; the only known ac4C "writer") contributes to the induction and development of neuropathic pain in an ac4C-dependent manner. Peripheral nerve injury increases the levels of NAT10 expression and overall ac4C in injured dorsal root ganglia (DRGs). This upregulation is triggered by the activation of upstream transcription factor 1 (USF1), a transcription factor that binds to the Nat10 promoter. Knock-down or genetic deletion of NAT10 in the DRG abolishes the gain of ac4C sites in Syt9 mRNA and the augmentation of SYT9 protein, resulting in a marked antinociceptive effect in nerve-injured male mice. Conversely, mimicking NAT10 upregulation in the absence of injury evokes the elevation of Syt9 ac4C and SYT9 protein and induces the genesis of neuropathic-pain-like behaviors. These findings demonstrate that USF1-governed NAT10 regulates neuropathic pain by targeting Syt9 ac4C in peripheral nociceptive sensory neurons. Our findings establish NAT10 as a critical endogenous initiator of nociceptive behavior and a promising new target for treating neuropathic pain.SIGNIFICANCE STATEMENT The cytidine N4-acetylcytidine (ac4C), a new epigenetic RNA modification, is crucial for the translation and stability of mRNA, but its role for chronic pain remains unclear. Here, we demonstrate that N-acetyltransferase 10 (NAT10) acts as ac4C N-acetyltransferase and plays an important role in the development and maintenance of neuropathic pain. NAT10 was upregulated via the activation of the transcription factor upstream transcription factor 1 (USF1) in the injured dorsal root ganglion (DRG) after peripheral nerve injury. Since pharmacological or genetic deleting NAT10 in the DRG attenuated the nerve injury-induced nociceptive hypersensitivities partially through suppressing Syt9 mRNA ac4C and stabilizing SYT9 protein level, NAT10 may serve as an effective and novel therapeutic target for neuropathic pain.

Dedifferentiated cells obtained from glioblastoma cell lines are an easy and robust model for mesenchymal glioblastoma stem cells studies

Glioblastoma is an aggressive brain tumor with a poor prognosis. Glioblastoma Stem Cells (GSC) are involved in glioblastoma resistance and relapse. Effective glioblastoma treatment must include GSC targeting strategy. Robust and well defined in vitroGSC models are required for new therapies evaluation. In this study, we extensively characterized 4 GSC models obtained by dedifferentiation of commercially available glioblastoma cell lines and compared them to 2 established patient derived GSC lines (Brain Tumor Initiating Cells). Dedifferentiated cells formed gliospheres, typical for GSC, with self-renewal ability. Gene expression and protein analysis revealed an increased expression of several stemness associated markers such as A2B5, integrin α6, Nestin, SOX2 and NANOG. Cells were oriented toward a mesenchymal GSC phenotype as shown by elevated levels of mesenchymal and EMT related markers (CD44, FN1, integrin α5). Dedifferentiated GSC were similar to BTIC in terms of size and heterogeneity. The characterization study also revealed that CXCR4 pathway was activated by dedifferentiation, emphasizing its role as a potential therapeutic target. The expression of resistance-associated markers and the phenotypic diversity of the 4 GSC models obtained by dedifferentiation make them relevant to challenge future GSC targeting therapies.

RNA-binding protein DHX9 promotes glioma growth and tumor-associated macrophages infiltration via TCF12

BACKGROUND

Glioma is the most common malignant tumor of the central nervous system, with high heterogeneity, strong invasiveness, high therapeutic resistance, and poor prognosis, comprehending a serious challenge in neuro-oncology. Until now, the mechanisms underlying glioma progression have not been fully elucidated.

METHODS

The expression of DExH-box helicase 9 (DHX9) in tissues and cells was detected by qRT-PCR and western blot. EdU and transwell assays were conducted to assess the effect of DHX9 on proliferation, migration and invasion of glioma cells. Cocultured model was used to evaluate the role of DHX9 on macrophages recruitment and polarization. Animal study was performed to explore the role of DHX9 on macrophages recruitment and polarization in vivo. Bioinformatics analysis, dual-luciferase reporter assay and chromatin immunoprecipitation (ChIP)-qPCR assay was used to explore the relation between DHX9 and TCF12/CSF1.

RESULTS

DHX9 was elevated in gliomas, especially in glioblastoma multiforme (GBM). Besides promoting the proliferation, migration, and invasion of glioma cells, DHX9 facilitated the infiltration of macrophages into glioma tissues and polarization to M2-like macrophages, known as tumor-associated macrophages (TAMs). DHX9 silencing decreased the expression of colony-stimulating factor 1 (CSF1), which partially restored the inhibitory effect on malignant progress of glioma and infiltration of TAMs caused by DHX9 knockdown by targeting the transcription factor 12 (TCF12). Moreover, TCF12 could directly bind to the promoter region of CSF1.

CONCLUSION

DHX9/TCF12/CSF1 axis regulated the increases in the infiltration of TAMs to promote glioma progression and might be a novel potential target for future immune therapies against gliomas.

Comparing DRD2 Promoter Methylation Between Blood and Brain in Alcohol Dependence

AIMS

The dopamine receptor D2 (DRD2) is substantially involved in several forms of addiction. In addition to genetic polymorphisms, epigenetic mechanisms have emerged as an important means of regulation. Previously, DRD2 hypo- and hyper-methylation have been observed in alcohol use disorder (AUD). Blood samples are commonly used as a surrogate marker of epigenetic alterations in epigenetic research, but few specific comparisons between blood and brain tissue samples in AUD exist.

METHODS

We used post-mortem brain tissue samples of 17 deceased patients with AUD and 31 deceased controls to investigate the relationship between blood and brain methylation of the DRD2 promoter.

RESULTS

When investigating individual cytosine methylation sites (CpG), several significant differences were found in the nucleus accumbens and hippocampus in the study population. Investigating binding sites with significant differences in methylation levels revealed hypomethylated CpGs targeting mainly activating transcription factors.

CONCLUSION

These findings support an altered transcription of the DRD2 gene in AUD specimens with a consecutively changed reward response in the brain. While methylation between specific brain regions and blood is comparable, our study further suggests that blood methylation cannot provide meaningful perspectives on DRD2 promoter methylation in the brain.

Targeting tumor-associated macrophages for the immunotherapy of glioblastoma: Navigating the clinical and translational landscape

Tumor-associated macrophages (TAMs) can directly clear tumor cells and enhance the phagocytic ability of immune cells. An abundance of TAMs at the site of the glioblastoma tumor indicates that TAM-targeting immunotherapy could represent a potential form of treatment for this aggressive cancer. Herein, we discuss: i) the dynamic role of TAMs in glioblastoma; ii) describe the formation of the immunosuppressive tumor microenvironment; iii) summarize the latest clinical trial data that reveal how TAM function can be regulated in favor tumor eradication; and lastly, iv) evaluate the implications of existing and novel translational approaches for treating glioblastoma in clinical practice.