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M1A inhibition fuels oncolytic virus-elicited antitumor immunity via downregulating PD-L1 expression

ABSTRACT: RNA N1-methyladenosine methylation (m1A) modification is critical in regulating mRNA translation and thus protein synthesis, but the role of m1A modification in the occurrence, progression, and immunotherapy of head and neck squamous cell cancer (HNSCC) remains largely unknown. In Tgfbr1/Pten 2cKO mice, we found that the spontaneous neoplastic transformation of oral mucosa is accompanied by elevated levels of m1A modification. Analysis of m1A-associated genes identified TRMT61A as the key m1A writer associated with cancer progression, and poor prognosis. Mechanically, TRMT61A-induced tRNA-m1A modification promotes MYC protein synthesis and subsequent programmed death-ligand 1 (PD-L1) expression. In Tgfbr1/Pten 2cKO mice, RNA-m1A modification levels are also elevated in tumors that developed resistance to oncolytic herpes simplex virus (oHSV) treatment. Therapeutic inhibition of m1A modification sustains oncolytic virus-induced antitumor immunity and reduces tumor growth, providing a promising strategy for alleviating resistance to oHSV therapy. These findings indicate that m1A inhibition can prevent immune escape after oHSV therapy by reducing the expression of PD-L1. Our results provide a mutually reinforcing strategy for clinical combination immunotherapy.

ORGANISM(S): Homo sapiens

PROVIDER: GSE247024 | GEO | 2024/03/31

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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M1A inhibition fuels oncolytic virus-elicited antitumor immunity via downregulating PD-L1 expression

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