The DRD2 Antagonist Haloperidol Mediates Autophagy-Induced Ferroptosis to Increase Temozolomide Sensitivity by Promoting Endoplasmic Reticulum Stress in Glioblastoma.

PURPOSE: Temozolomide resistance remains a major obstacle in the treatment of glioblastoma (GBM). The combination of temozolomide with another agent could offer an improved treatment option if it could overcome chemoresistance and prevent side effects. Here, we determined the critical drug that cause ferroptosis in GBM cells and elucidated the possible mechanism by which drug combination overcomes chemoresistance. EXPERIMENTAL DESIGN: Haloperidol/temozolomide synergism was assessed in GBM cell lines with different dopamine D2 receptor (DRD2) expression in vitro and in vivo. Inhibitors of ferroptosis, autophagy, endoplasmic reticulum (ER) stress and cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) were used to validate the specific mechanisms by which haloperidol and temozolomide induce ferroptosis in GBM cells. RESULTS: In the present work, we demonstrate that the DRD2 level is increased by temozolomide in a time-dependent manner and is inversely correlated with temozolomide sensitivity in GBM. The DRD2 antagonist haloperidol, a butylbenzene antipsychotic, markedly induces ferroptosis and effectively enhances temozolomide efficacy in vivo and in vitro. Mechanistically, haloperidol suppressed the effect of temozolomide on cAMP by antagonizing DRD2 receptor activity, and the increases in cAMP/PKA triggered ER stress, which led to autophagy and ferroptosis. Furthermore, elevated autophagy mediates downregulation of FTH1 expression at the posttranslational level in an autophagy-dependent manner and ultimately leads to ferroptosis. CONCLUSIONS: Our results provide experimental evidence for repurposing haloperidol as an effective adjunct therapy to inhibit adaptive temozolomide resistance to enhance the efficacy of chemoradiotherapy in GBM, a strategy that may have broad prospects for clinical application.

RBBP4 regulates the expression of the Mre11-Rad50-NBS1 (MRN) complex and promotes DNA double-strand break repair to mediate glioblastoma chemoradiotherapy resistance.

For treatment of glioblastoma (GBM), temozolomide (TMZ) and radiotherapy (RT) exert antitumor effects by inducing DNA double-strand breaks (DSBs), mainly via futile DNA mismatch repair (MMR) and inducing apoptosis. Here, we provide evidence that RBBP4 modulates glioblastoma resistance to chemotherapy and radiotherapy by recruiting transcription factors and epigenetic regulators that bind to their promoters to regulate the expression of the Mre11-Rad50-NBS1(MRN) complex and the level of DNA-DSB repair, which are closely associated with recovery from TMZ- and radiotherapy-induced DNA damage in U87MG and LN229 glioblastoma cells, which have negative MGMT expression. Disruption of RBBP4 induced GBM cell DNA damage and apoptosis in response to TMZ and radiotherapy and enhanced radiotherapy and chemotherapy sensitivity by the independent pathway of MGMT. These results displayed a possible chemo-radioresistant mechanism in MGMT negative GBM. In addition, the RBBP4-MRN complex regulation axis may provide an interesting target for developing therapy-sensitizing strategies for GBM.

SMARCC2 mediates the regulation of DKK1 by the transcription factor EGR1 through chromatin remodeling to reduce the proliferative capacity of glioblastoma.

Switch/sucrose-nonfermenting (SWI/SNF) complexes play a key role in chromatin remodeling. Recent studies have found that SMARCC2, as the core subunit of the fundamental module of the complex, plays a key role in its early assembly. In this study, we found a unique function of SMARCC2 in inhibiting the progression of glioblastoma by targeting the DKK1 signaling axis. Low expression of SMARCC2 is found in malignant glioblastoma (GBM) compared with low-grade gliomas. SMARCC2 knockout promoted the proliferation of glioblastoma cells, while its overexpression showed the opposite effect. Mechanistically, SMARCC2 negatively regulates transcription by dynamically regulating the chromatin structure and closing the promoter region of the target gene DKK1, which can be bound by the transcription factor EGR1. DKK1 knockdown significantly reduced the proliferation of glioblastoma cell lines by inhibiting the PI3K-AKT pathway. We also studied the functions of the SWIRM and SANT domains of SMARCC2 and found that the SWIRM domain plays a more important role in the complete chromatin remodeling function of SMARCC2. In addition, in vivo studies confirmed that overexpression of SMARCC2 could significantly inhibit the size of intracranial gliomas in situ in nude mice. Overall, this study shows that SMARCC2, as a tumor suppressor, inhibits the proliferation of glioblastoma by targeting the transcription of the oncogene DKK1 through chromatin remodeling, indicating that SMARCC2 is a potentially attractive therapeutic target in glioblastoma.

A necroptosis-related lncRNA signature was identified to predict the prognosis and immune microenvironment of IDH-wild-type GBM.

Introduction: Necroptosis-related genes are essential for the advancement of IDH-wild-type GBM. However, the putative effects of necroptosis-related lncRNAs (nrlncRNAs) in IDH-wild-type GBM remain unknown. Methods: By using the TCGA and GTEx databases, a nrlncRNA prognostic signature was created using LASSO Cox regression. The median risk score was used to categorize the patients into low and high-risk groups. To confirm the validity, univariate, multivariate Cox regression and ROC curves were used. Furthermore, by enrichment analysis, immune correlation analysis, and drug sensitivity analysis, the targeted lncRNAs were selected for further verification. As the highest upregulated expression in tumor than peritumor specimens, RP11-131L12.4 was selected for phenotype and functional experiments in primary GBM cells. Results: Six lncRNAs were proved to be closely related to necroptosis in IDH-1-wild-type GBM, which were used to create a new signature. For 1-, 2-, and 3-year OS, the AUCs were 0.709, 0.645 and 0.694, respectively. Patients in the low-risk group had a better prognosis, stronger immune function activity, and more immune cell infiltration. In contrast, enrichment analysis revealed that the malignant phenotype was more prevalent in the high-risk group. In vitro experiments indicated that RP11-131L12.4 increased the tumor proliferation, migration and invasion, but decreased the necroptosis. Moreover, this nrlncRNA was also proved to be negatively associated with patient prognosis. Conclusion: The signature of nrlncRNAs may aid in the formulation of tailored and precise treatment for individuals with IDH-wild-type GBM. RP11-131L12.4 may play indispensable role in necroptosis suppression.

SMARCC2 combined with c­Myc inhibits the migration and invasion of glioma cells via modulation of the Wnt/ß­catenin signaling pathway.

Glioma is the most common type of central nervous system tumor. SWItch/sucrose non­fermentable (SWI/SNF) is a tumor suppressor that serves an important role in epithelial­mesenchymal transition (EMT). The present study aimed to identify key molecules involved in the EMT process. SWI/SNF related, matrix associated, actin dependent regulator of chromatin subfamily c member 2 (SMARCC2) is mutated in and its expression is low in multiple types of cancer. SMARCC2 is the core subunit of the chromatin­remodeling complex, SWI/SNF. Relative mRNA SMARCC2 expression levels in human glioma tissue were analyzed via reverse transcription­quantitative PCR, whereas the protein expression levels were determined via immunohistochemistry staining. SMARCC2 expression was knocked down in glioma cells using small interfering RNA (si) and overexpressed by infection with adenovirus vectors carrying SMARCC2 cDNA. Wound healing and Transwell assays were performed to assess cell migration and invasion, respectively. Subsequently, immunofluorescence and western blotting were performed to analyze the expression levels of the oncogene c­Myc, which is associated with SMARCC2. SMARCC2 combines with C­MYC to downregulate its expression. Consistent with the results of the bioinformatics analysis, which revealed that the upregulated expression levels of SMARCC2 were associated with a more favorable prognosis in patients with glioma, the mRNA and protein expression levels of SMARCC2 were significantly upregulated in low­grade glioma tissues compared with high­grade glioma tissues. The results of the wound healing assay demonstrated that cell migration was significantly increased in the siSMARCC2­1/3 groups compared with the negative control (NC) group. By contrast, the migratory ability of cells was significantly reduced following transduction with adenovirus overexpressing SMARCC2, which upregulated the expression of SMARCC2, compared with the lentiviral vector­non­specific control (LVS­NC) group. The Transwell assay results further showed that SMARCC2 overexpression significantly inhibited the migratory and invasive abilities of U87MG and LN229 cells compared with the LVS­NC group. Co­immunoprecipitation assays were subsequently conducted to validate the binding of SMARCC2 and c­Myc; the results demonstrated that the expression of c­Myc was downregulated in adenovirus­transfected cells compared with LVS­NC­transfected cells. The results of the western blotting experiments demonstrated that the expression levels of N­cadherin, vimentin, snail family transcriptional repressor 1 and ß­catenin were notably downregulated, whereas the expression levels of T­cadherin were markedly upregulated in cell lines stably overexpressing SMARCC2 compared with the LVS­NC group. In conclusion, the results of the present study suggested that SMARCC2 may inhibit Wnt/ß­catenin signaling by regulating c­Myc expression in glioma. SMARCC2 regulates the EMT status of the glioblastoma cell line by mediating the expression of the oncogene C­MYC to inhibit its migration and invasion ability. Thus, SMARCC2 may function as a tumor suppressor or oncogene by regulating associated oncogenes or tumor suppressor genes.