The versatile role of HuR in Glioblastoma and its potential as a therapeutic target for a multi-pronged attack

Bergaptol inhibits glioma cell proliferation and induces apoptosis via STAT3/Bcl-2 pathway

Glioblastoma (GBM) is the most common primary malignant brain tumour and lacks therapeutic options with significant effects. The aberrant activation of STAT3 is a critical factor in glioma progression via activating multiple signalling pathways that promote glioma. Among them, the antiapoptotic gene Bcl-2 could be upregulated by p-STAT3, which is an important reason for the continuous proliferation of glioma. We previously reported that bergaptol, a natural furanocoumarin widely found in citrus products, exerts antineuroinflammatory effects by inhibiting the overactivation of STAT3. Here, we aimed to evaluate whether bergaptol could promote glioma apoptosis by inhibiting the STAT3/Bcl-2 pathway. This study found that bergaptol inhibited the proliferation and migration of GBM cell lines (U87 and A172) and promoted apoptosis in vitro. We also found that bergaptol significantly inhibited the STAT3/Bcl-2 pathway in GBM cells. U87 cells were implanted intracranially into nude mice to establish a glioma model, and glioma-bearing mice were treated with bergaptol (40 mg/kg). Bergaptol treatment significantly inhibited glioma growth and prolonged the glioma-bearing mice's survival time. In addition, bergaptol administration also significantly inhibited the STAT3/Bcl-2 pathway of tumour tissue in vivo. Overall, we found that bergaptol could effectively play an antiglioma role by inhibiting STAT3/Bcl-2 pathway, suggesting the potential efficacy of bergaptol in treating glioma.

ELAVL2 loss promotes aggressive mesenchymal transition in glioblastoma

Glioblastoma (GBM), the most lethal primary brain cancer, exhibits intratumoral heterogeneity and molecular plasticity, posing challenges for effective treatment. Despite this, the regulatory mechanisms underlying such plasticity, particularly mesenchymal (MES) transition, remain poorly understood. In this study, we elucidate the role of the RNA-binding protein ELAVL2 in regulating aggressive MES transformation in GBM. We found that ELAVL2 is most frequently deleted in GBM compared to other cancers and associated with distinct clinical and molecular features. Transcriptomic analysis revealed that ELAVL2-mediated alterations correspond to specific GBM subtype signatures. Notably, ELAVL2 expression negatively correlated with epithelial-to-mesenchymal transition (EMT)-related genes, and its loss promoted MES process and chemo-resistance in GBM cells, whereas ELAVL2 overexpression exerted the opposite effect. Further investigation via tissue microarray analysis demonstrated that high ELAVL2 protein expression confers a favorable survival outcome in GBM patients. Mechanistically, ELAVL2 was shown to directly bind to the transcripts of EMT-inhibitory molecules, SH3GL3 and DNM3, modulating their mRNA stability, potentially through an m6A-dependent mechanism. In summary, our findings identify ELAVL2 as a critical tumor suppressor and mRNA stabilizer that regulates MES transition in GBM, underscoring its role in transcriptomic plasticity and glioma progression.

HuR-positive stress granules: Potential targets for age-related osteoporosis

Aging impairs osteoblast function and bone turnover, resulting in age-related bone degeneration. Stress granules (SGs) are membrane-less organelles that assemble in response to stress via the recruitment of RNA-binding proteins (RBPs), and have emerged as a novel mechanism in age-related diseases. Here, we identified HuR as a bone-related RBP that aggregated into SGs and facilitated osteogenesis during aging. HuR-positive SG formation increased during osteoblast differentiation, and HuR overexpression mitigated the reduction in SG formation observed in senescent osteoblasts. Moreover, HuR positively regulated the mRNA stability and expression of its target β-catenin by binding and recruiting β-catenin into SGs. As a potential therapeutic target, HuR activator apigenin (API) enhanced its expression and thus aided osteoblasts differentiation. API treatment increased HuR nuclear export, enhanced the recruitment of β-catenin into HuR-positive SGs, facilitated β-catenin nuclear translocation, and contributed osteogenesis. Our findings highlight the roles of HuR and its SGs in promoting osteogenesis during skeletal aging and lay the groundwork for novel therapeutic strategies against age-related skeletal disorders.

Development of Prognostic Indicator Based on AU-Rich Elements-Related Genes in Glioblastoma

BACKGROUND

AREs (AU-rich elements) are important cis-acting short sequences in the 3'UTR (3'-untranslated region) that affect messenger RNA stability and translation. However, there were no systematic researches about AREs-related genes to predict the survival of patients with GBM (glioblastoma).

METHODS

Differentially expressed genes were acquired from The Cancer Genome Atlas and Chinese Glioma Genome Atlas databases. Differentially expressed AREs-related genes were filtered by overlapping differentially expressed genes and AREs-related genes. The prognostic genes were selected to construct a risk model. Patients with GBM were categorized into 2 risk groups depending on the medium value of risk score. Gene Set Enrichment Analysis was performed to explore the potential biological pathways. We explored the correlation between the risk model and immune cells. The chemotherapy sensitivity was predicted in different risk groups.

RESULTS

A risk model was constructed by 10 differentially expressed AREs-related genes (GNS, ANKH, PTPRN2, NELL1, PLAUR, SLC9A2, SCARA3, MAPK1, HOXB2, and EN2), and it could accurately predict the prognosis of patients with GBM. Higher risk scores for patients with GBM had a lower survival probability. The predictive power of risk model was decent. The risk score and treatment type were regarded as independent prognostic indicators. The mainly Gene Set Enrichment Analysis enrichment pathways were primary immunodeficiency and chemokine signaling pathway. Six immune cells were significant different in the 2 risk groups. There were higher abundance of macrophages M2 and neutrophils and higher sensitivity of 11 chemotherapy drugs in the high-risk group.

CONCLUSIONS

The 10 biomarkers might be important prognostic markers and potential therapeutic targets for patients with GBM.

RNA regulation of inflammatory responses in glia and its potential as a therapeutic target in central nervous system disorders

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.

Cryo-Shocked Cancer Cells as an Oncolytic Adenovirus Reservoir for Glioblastoma Immunotherapy

Glioblastoma is the most common type of primary brain tumor, which has a high recurrence rate and a high mortality rate. Immunotherapy shows promise in cancer therapy due to its capacity to manipulate the immune system to attack tumor cells with less toxic and durable immune responses. However, the low immunogenicity and limited immune cell infiltration in a glioblastoma lead to a weakened antitumor immune response, resulting in suboptimal therapeutic efficacy. A compelling solution is provided by oncolytic adenovirus (OAs), which can selectively replicate within tumor cells while simultaneously promoting antitumor immunity. Herein, we constructed an oncolytic adenovirus reservoir (OAR) by shocking OA-loaded tumor cells in liquid nitrogen to eliminate proliferation and pathogenicity. OARs showed sustained OAs release and effectively lysed tumor cells in vitro and in vivo. In a mouse intracranial glioblastoma model, OARs could efficiently induce dendritic cells' maturation, facilitate the tumor recruitment, and promote the infiltration of cytotoxic effector T lymphocytes via a single treatment, resulting in specific antitumor immune responses and long-term animal survival. Taken together, these results demonstrated that OAR is a promising synergistic therapeutic strategy for treating glioblastoma.

A novel protein encoded by ZCRB1-induced circHEATR5B suppresses aerobic glycolysis of GBM through phosphorylation of JMJD5

Background

RNA-binding proteins (RBPs) and circular RNAs (circRNAs) play important roles in glioblastoma multiforme (GBM). Aerobic glycolysis is a metabolic characteristic of GBM. However, the roles of RBPs and circRNAs in aerobic glycolysis in GBM remain unclear. The aim of this study is to explore the mechanisms by which RBPs and circRNAs regulate aerobic glycolysis in GBM cells.

Methods

RNA sequencing and circRNA microarray analysis were performed to identify RBPs and circRNAs for further study. Mass spectrometry validated the encoded protein and its interacting proteins. Quantitative reverse transcription PCR and western blot assays were used to determine the mRNA and protein expression, respectively. Furthermore, immunofluorescence and fluorescence in situ hybridization assays were used to determine the protein and RNA localization, respectively. Glucose and lactate measurement assays, Seahorse XF glycolysis stress assays and cell viability assays were conducted to investigate the effects on glycolysis and proliferation in GBM cells.

Results

We selected zinc finger CCHC-type and RNA-binding motif 1 (ZCRB1) and circRNA HEAT repeat containing 5B (circHEATR5B) as candidates for this study. These genes were expressed at low levels in GBM tissues and cells. Both ZCRB1 and circHEATR5B overexpression suppressed aerobic glycolysis and proliferation in GBM cells. ZCRB1 overexpression promoted the Alu element-mediated formation of circHEATR5B. In addition, circHEATR5B encoded a novel protein HEATR5B-881aa which interacted directly with Jumonji C-domain-containing 5 (JMJD5) and reduced its stability by phosphorylating S361. JMJD5 knockdown increased pyruvate kinase M2 (PKM2) enzymatic activity and suppressed glycolysis and proliferation in GBM cells. Finally, ZCRB1, circHEATR5B and HEATR5B-881aa overexpression inhibited GBM xenograft growth and prolonged the survival time of nude mice.

Conclusions

This study reveals a novel mechanism of regulating aerobic glycolysis and proliferation in GBM cells through the ZCRB1/circHEATR5B/HEATR5B-881aa/JMJD5/PKM2 pathway, which can provide novel strategies and potential targets for GBM therapy.

ARPC1B promotes mesenchymal phenotype maintenance and radiotherapy resistance by blocking TRIM21-mediated degradation of IFI16 and HuR in glioma stem cells

Background

Intratumoral heterogeneity is the primary challenge in the treatment of glioblastoma (GBM). The presence of glioma stem cells (GSCs) and their conversion between different molecular phenotypes contribute to the complexity of heterogeneity, culminating in preferential resistance to radiotherapy. ARP2/3 (actin-related protein-2/3) complexes (ARPs) are associated with cancer migration, invasion and differentiation, while the implications of ARPs in the phenotype and resistance to radiotherapy of GSCs remain unclear.

Methods

We screened the expression of ARPs in TCGA-GBM and CGGA-GBM databases. Tumor sphere formation assays and limiting dilution assays were applied to assess the implications of ARPC1B in tumorigenesis. Apoptosis, comet, γ-H2AX immunofluorescence (IF), and cell cycle distribution assays were used to evaluate the effect of ARPC1B on radiotherapy resistance. Immunoprecipitation (IP) and mass spectrometry analysis were used to detect ARPC1B-interacting proteins. Immune blot assays were performed to evaluate protein ubiquitination, and deletion mutant constructs were designed to determine the binding sites of protein interactions. The Spearman correlation algorithm was performed to screen for drugs that indicated cell sensitivity by the expression of ARPC1B. An intracranial xenograft GSC mouse model was used to investigate the role of ARPC1B in vivo.

Results

We concluded that ARPC1B was significantly upregulated in MES-GBM/GSCs and was correlated with a poor prognosis. Both in vitro and in vivo assays indicated that knockdown of ARPC1B in MES-GSCs reduced tumorigenicity and resistance to IR treatment, whereas overexpression of ARPC1B in PN-GSCs exhibited the opposite effects. Mechanistically, ARPC1B interacted with IFI16 and HuR to maintain protein stability. In detail, the Pyrin of IFI16 and RRM2 of HuR were implicated in binding to ARPC1B, which counteracted TRIM21-mediated degradation of ubiquitination to IFI16 and HuR. Additionally, the function of ARPC1B was dependent on IFI16-induced activation of NF-κB pathway and HuR-induced activation of STAT3 pathway. Finally, we screened AZD6738, an ataxia telangiectasia mutated and rad3-related (ATR) inhibitor, based on the expression of ARPC1B. In addition to ARPC1B expression reflecting cellular sensitivity to AZD6738, the combination of AZD6738 and radiotherapy exhibited potent antitumor effects both in vitro and in vivo.

Conclusion

ARPC1B promoted MES phenotype maintenance and radiotherapy resistance by inhibiting TRIM21-mediated degradation of IFI16 and HuR, thereby activating the NF-κB and STAT3 signaling pathways, respectively. AZD6738, identified based on ARPC1B expression, exhibited excellent anti-GSC activity in combination with radiotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02526-8.

Targeting the TREM1-positive myeloid microenvironment in glioblastoma

Background

Tumor cellular and molecular heterogeneity is a hallmark of glioblastoma and underlies treatment resistance and recurrence. This manuscript investigated the myeloid-derived microenvironment as a driver of glioblastoma heterogeneity and provided a pharmacological pathway for its suppression.

Methods

Transcriptomic signatures of glioblastoma infiltrated myeloid-derived cells were assessed using R2: genomic platform, Ivy Glioblastoma Spatial Atlas, and single-cell RNA-seq data of primary and recurrent glioblastomas. Myeloid-derived cell prints were evaluated in five PDX cell lines using RNA-seq data. Two immunocompetent mouse glioblastoma models were utilized to isolate and characterize tumor-infiltrated myeloid-derived cells and glioblastoma/host cell hybrids. The ability of an inhibitor of HuR dimerization SRI42127 to suppress TREM1⁺-microenvironment and glioblastoma/myeloid-derived cell interaction was assessed in vivo and in vitro.

Results

TREM1⁺-microenvironment is enriched in glioblastoma peri-necrotic zones. TREM1 appearance is enhanced with tumor grade and associated with poor patient outcomes. We confirmed an expression of a variety of myeloid-derived cell markers, including TREM1, in PDX cell lines. In mouse glioblastoma models, we demonstrated a reduction in the TREM1⁺-microenvironment and glioblastoma/host cell fusion after treatment with SRI42127. In vitro assays confirmed inhibition of cell fusion events and reduction of myeloid-derived cell migration towards glioblastoma cells by SRI42127 and TREM1 decoy peptide (LP17) versus control treatments.

Conclusions

TREM1⁺-myeloid-derived microenvironment promulgates glioblastoma heterogeneity and is a therapeutic target. Pharmacological inhibition of HuR dimerization leads to suppression of the TREM1⁺-myeloid-derived microenvironment and the neoplastic/non-neoplastic fusogenic cell network.

Inhibition of the RNA Regulator HuR by SRI-42127 Attenuates Neuropathic Pain After Nerve Injury Through Suppression of Neuroinflammatory Responses

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.

Post-Transcriptional Modifications of RNA as Regulators of Apoptosis in Glioblastoma

This review is devoted to changes in the post-transcriptional maturation of RNA in human glioblastoma cells, which leads to disruption of the normal course of apoptosis in them. The review thoroughly highlights the latest information on both post-transcriptional modifications of certain regulatory RNAs, associated with the process of apoptosis, presents data on the features of apoptosis in glioblastoma cells, and shows the relationship between regulatory RNAs and the apoptosis in tumor cells. In conclusion, potential target candidates are presented that are necessary for the development of new drugs for the treatment of glioblastoma.