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Glioblastoma, the most lethal primary brain tumor, harbors glioma stem cells (GSCs) that not only initiate and maintain malignant phenotypes but also enhance therapeutic resistance. Although frequently mutated in glioblastomas, the function and regulation of PTEN in PTEN-intact GSCs are unknown. Here, we found that PTEN directly interacted with MMS19 and competitively disrupted MMS19-based cytosolic iron-sulfur (Fe-S) cluster assembly (CIA) machinery in differentiated glioma cells. PTEN was specifically succinated at cysteine (C) 211 in GSCs compared with matched differentiated glioma cells. Isotope tracing coupled with mass spectrometry analysis confirmed that fumarate, generated by adenylosuccinate lyase (ADSL) in the de novo purine synthesis pathway that is highly activated in GSCs, promoted PTEN C211 succination. This modification abrogated the interaction between PTEN and MMS19, reactivating the CIA machinery pathway in GSCs. Functionally, inhibiting PTEN C211 succination by reexpressing a PTEN C211S mutant, depleting ADSL by shRNAs, or consuming fumarate by the US Food and Drug Administration–approved prescription drug N-acetylcysteine (NAC) impaired GSC maintenance. Reexpressing PTEN C211S or treating with NAC sensitized GSC-derived brain tumors to temozolomide and irradiation, the standard-of-care treatments for patients with glioblastoma, by slowing CIA machinery–mediated DNA damage repair. These findings reveal an immediately practicable strategy to target GSCs to treat glioblastoma by combination therapy with repurposed NAC. Editor's summary: Glioma stem cells promote glioblastoma growth and therapy resistance but are hard to target. Yin et al. report that posttranslational succination of PTEN at residue 211 (cysteine) promotes glioma stem cell maintenance by reactivating cytosolic iron-sulfur cluster assembly formation. This PTEN succination was driven by purine biosynthesis–derived fumarate. Administration of N-acetylcysteine to deplete the fumarate sensitized xenografted tumors in mice to both standard-of-care temozolomide and irradiation, indicating potential translational relevance for this difficult-to-treat cancer. —Catherine Charneski [ABSTRACT FROM AUTHOR]

Background: Glucose metabolic reprogramming is a significant hallmark of malignant tumors including GBM. Previous studies suggest that microRNAs play key roles in modulating this process in GBM cells. miR-181b acts as a tumor suppressor miRNA in influencing glioma tumorigenesis. Our previous results showed that miR-181b was down-regulated in glioma cells and tissues. Methods: The extracellular acidification rate (ECAR), colony formation assay and levels of Glut1 and PKM2 were measured to assess the glucose metabolic and proliferation changes in GBM cells overexpressing miR-181b. Immunoblotting and luciferase reporter assay were performed to confirm the expression and role of SP1 as a direct target of miR-181b. ChIP assay was used to figure out the transcriptional regulation of SP1 on Glut1 and PKM2. In vivo study was examined for the role of miR-181b in GBM cells. Results: MiR-181b overexpression significantly reduced the glucose metabolic and colony formation ability of GBM cells. And, SP1 was confirmed as a direct target of miR-181b while upregulation of SP1 could reverse the influence of overexpression of miR-181b. Furthermore, Glut1 and PKM2 could be regulated by SP1. Finally, miR-181b could inhibit the tumor growth in vivo. Conclusions: Our article demonstrated the inhibitory effect of miR-181b on glucose metabolism and proliferation in GBM by suppressing SP1 expression. [ABSTRACT FROM AUTHOR]

Cancer-specific TERT promoter mutations have been linked to the reactivation of epigenetically silenced TERT gene by creating de novo binding motifs for E-Twenty-Six transcription factors, especially GABPA. How these mutations switch on TERT from epigenetically repressed states to expressed states have not been defined. Here, we revealed that EGFR activation induces ERK1/2-dependent phosphorylation of argininosuccinate lyase (ASL) at Ser417 (S417), leading to interactions between ASL and GABPA at the mutant regions of TERT promoters. The ASL-generated fumarate inhibits KDM5C, leading to enhanced trimethylation of histone H3 Lys4 (H3K4me3), which in turn promotes the recruitment of c-Myc to TERT promoters for TERT expression. Expression of ASL S417A, which abrogates its binding with GABPA, results in reduced TERT expression, inhibited telomerase activity, shortened telomere length, and impaired brain tumor growth in mice. This study reveals an unrecognized mechanistic insight into epigenetically activation of mutant TERT promoters where GABPA-interacted ASL plays an instrumental role. [Display omitted] • GABPA binds with S417-phosphorylated ASL and directs ASL to mutant TERT promoter • ASL-generated fumarate enhances H3K4me3 at mutant TERT promoter by inhibiting KDM5C • GABPA/ASL interaction is prerequisite for recruiting c-Myc to mutant TERT promoter • ASL S417 phosphorylation promotes TERT expression and GBM tumorigenesis Shi et al. report that through interacting with GABPA, S417-phosphorylated ASL locates on mutant regions of TERT promoters, where it generates fumarate to inhibit KDM5C and subsequently facilitates enrichment of H3K4me3 in these regions. This event promotes the recruitment of c-Myc for TERT transcription and GBM tumorigenesis. [ABSTRACT FROM AUTHOR]

Radiotherapy is a standard-of-care treatment approach for glioblastoma (GBM) patients, but therapeutic resistance to radiotherapy remains a major challenge. Here we demonstrate that diallyl trisulfide (DATS) directly conjugates with cysteine (C) 32 and C35 (C32/35) residues of thioredoxin 1 (Trx1) through Michael addition reactions. Due to localizing in activity center of Trx1, the conjugation between DATS and C32/35 results in inhibition of Trx1 activity, therefore disturbing thioredoxin system and leading to accumulated levels of reactive oxygen species (ROS). High levels of Trx1 expression are correlated with poor prognosis of glioma patients. Notably, we reveal that DATS synergistically enhances irradiation (IR)-induced ROS accumulation, apoptosis, DNA damage, as well as inhibition of tumor growth of GBM cells. These findings highlight the potential benefits of DATS in sensitizing radiotherapy of GBM patients. [Display omitted] • Thioredoxin 1 (Trx1) was identified as the direct target of Diallyl trisulfide (DATS). • DATS conjugates with C32/35 residues of Trx1 through Michael addition reactions. • The conjugation of DATS with Trx1 inhibited Trx1 activity and disturbed redox balance. • DATS synergistically enhanced the radiotherapy effects of GBM cells. [ABSTRACT FROM AUTHOR]