Circular EZH2-Encoded EZH2-92aa Mediates Immune Evasion in Glioblastoma via Inhibition of Surface NKG2D Ligands

Glioblastoma (GBM) is a highly aggressive primary brain tumour and is resistant to nearly all available treatments, including natural killer (NK) cell immunotherapy. However, the factors mediating NK cell evasion in GBM remain largely unclear. Here, we report that EZH2-92aa, a protein encoded by circular EZH2, is overexpressed in GBM and induces the immune evasion of glioblastoma stem cells (GSCs) from NK cells. Positively regulated by DEAD-box polypeptide 3, EZH2-92aa directly binds the major histocompatibility complex class I chain-related gene A/B (MICA/B) promoters and represses their transcription; it also indirectly represses UL16-binding protein (ULBP) transcription by stabilizing EZH2. The downregulation of NK group 2D ligands (NKG2DLs, including MICA/B and ULBPs) in GSCs mediates NK cell resistance. Moreover, stable EZH2-92aa knockdown enhances NK cell-mediated GSC eradication in vitro and in vivo and synergizes with anti-PD1 therapy. Our results highlight the immunosuppressive function of EZH2-92aa in inhibiting the NK cell response in GBM and the clinical potential of targeting EZH2-92aa for NK-cell-directed immune therapy. The data includes RNA-seq of MES28 GSCs with stable circEZH2 knockdown and control MES28 GCSs, which can be used to explore different gene expression under the regulation of circEZH2.