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Determine whether AsiDNA and belinostat alter chromatin accessbility genome-wide in glioblastoma cells. [NicE-Seq]

ABSTRACT: An effective long-term inhibition of multiple DNA repair signals is required to design a novel and effective therapeutic for glioblastoma (GBM), a highly DNA repair ‘addicted’ cancer. AsiDNA, a double-strand DNA break (DSB) mimetic, is an innovative approach that shuts down the entire DNA repair system in cancer cells by sequestering DSB repair factors. We showed that inhibition of class I histone deacetylases (HDACs) dislodges repair factors from sites of DNA damage. We therefore tested whether AsiDNA and pan HDAC inhibitor Belinostat combination can impart a chromatin-based long-term DNA damage and impair DNA repair in GBM cells. We performed mass spectrometry with chromatin isolated from AsiDNA and Belinostat and found that Belinostat reduces histone H1.2 levels. To this end, we assessed whether AsiDNA and Belinostat alter histone H1.2 occupancy genome-wide. In order to understand the long-term effects of AsiDNA on DNA repair, we treated U87 cells with AsiDNA for 6 days followed by 6 days recovery from the drug. We used this protocol to create long-term AsiDNA treated cells (LTAU87) according to the clinical trial protocol. We performed NicE-seq with LTAU87 cells and MTU87 (mock treated U87; control) in the presence or absence of belinostat treatment in order to address whether they alter the global chromatin structure.

ORGANISM(S): Homo sapiens

PROVIDER: GSE266621 | GEO | 2024/05/13

REPOSITORIES: GEO

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Project description:PD-L1 Inhibitor Regulates the miR-33a-5p/PTEN Signaling Pathway and Can Be Targeted to Sensitize Glioblastomas to Radiation. Glioblastoma (GBM) is the most common and lethal brain tumor in adults. Ionizing radiation (IR) is a standard treatment for GBM patients and results in DNA damage. However, the clinical efficacy of IR is limited due to therapeutic resistance. The programmed death ligand 1 (PD-L1) blockade has a shown the potential to increase the efficacy of radiotherapy by inhibiting DNA damage and repair responses. The miR-33a-5p is an essential microRNA that promotes GBM growth and self-renewal. In this study, we investigated whether a PD-L1 inhibitor (a small molecule inhibitor) exerted radio-sensitive effects to impart an anti-tumor function in GBM cells by modulating miR-33a-5p. U87 MG cells and U251 cells were pretreated with PD-L1 inhibitor. The PD-L1 inhibitor-induced radio-sensitivity in these cells was assessed by assaying cellular apoptosis, clonogenic survival assays, and migration. TargetScan and luciferase assay showed that miR-33a-5p targeted the phosphatase and tensin homolog (PTEN) 3' untranslated region. The expression level of PTEN was measured by western blotting, and was also silenced using small interfering RNAs. The levels of DNA damage following radiation was measured by the presence of γ-H2AX foci, cell cycle, and the mRNA of the DNA damage-related genes, BRCA1, NBS1, RAD50, and MRE11. Our results demonstrated that the PD-L1 inhibitor significantly decreased the expression of the target gene, miR-33a-5p. In addition, pretreatment of U87 MG and U251 cells with the PD-L1 inhibitor increased radio-sensitivity, as indicated by increased apoptosis, while decreased survival and migration of GBM cells. Mir-33a-5p overexpression or silencing PTEN in U87 MG and U251 cells significantly attenuated PD-L1 radiosensitive effect. Additionally, PD-L1 inhibitor treatment suppressed the expression of the DNA damage response-related genes, BRCA1, NBS1, RAD50, and MRE11. Our results demonstrated a novel role for the PD-L1 inhibitor in inducing radio- sensitivity in GBM cells, where inhibiting miR-33a-5p, leading to PTEN activated, and inducing DNA damage was crucial for antitumor immunotherapies to treat GBM.

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Determine whether AsiDNA and belinostat alter chromatin accessbility genome-wide in glioblastoma cells. [NicE-Seq]

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