Epigenetic priming induces cancer testis antigens and human endogenous retroviruses in glioma for enhanced T cell responses at single cell resolution (scRNA-Seq)

Glioblastoma (GBM) is the most common malignant primary brain tumor and remains incurable. Previous work has shown that systemic administration of Decitabine (DAC) induces sufficient expression of NY-ESO-1 in GBM for targeting by adoptive T-cell therapy in vivo. However, the mechanisms by which DAC enhances immunogenicity in GBM remain to be elucidated. Using patient tissue, immortalized glioma cells, and primary patient-derived gliomaspheres, we demonstrate in vitro that basal NY-ESO-1 expression is restricted by promoter hypermethylation in gliomas. DAC treatment of glioma cells specifically inhibits DNA methylation silencing and renders NY-ESO-1 an inducible tumor antigen. Targeting of DAC-induced NY-ESO-1 in primary GBM cells promotes specific and polyfunctional NY-ESO-1 TCR-T cell responses. DAC further upregulates other tumor-associated cancer testis antigens concomitantly with tumor-intrinsic reactivation of human endogenous retroviruses (hERV) and type I interferon. Overall, we demonstrate that DAC promotes an inducible tumor antigen and enhances T cell functionality against GBM.