BRD4 inhibition boosts the therapeutic effects of epidermal growth factor receptor-targeted chimeric antigen receptor T cells in glioblastoma

Glioblastoma (GBM) is the deadliest brain malignancy without effective treatments. Here, we report that epidermal growth factor receptor-targeted chimeric antigen receptor T cells (EGFR CAR-T) are effective in suppressing the growth of GBM cells in vitro and xenografts derived from GBM cell lines and patients in mice. However, mice soon acquire resistance to EGFR CAR-T cell treatment, limiting its potential use in the clinic. To find ways to improve the efficacy of EGFR CAR-T cells, we performed genomics and transcriptomics analysis for GBM cells incubated with EGFR CAR-T cells, and found that a large cohort of genes including immunosuppressive genes as well as enhancers in vicinity are activated. BRD4, an epigenetic modulator functioning on both promoter and enhancer, is required for the activation of these immunosuppressive genes. Accordingly, inhibition of BRD4 by JQ1 blocks the activation of these immunosuppressive genes. Combination therapy with EGFR CAR-T cells and JQ1 suppresses the growth and metastasis of GBM cells, and prolonged survival in mice. We demonstrate that transcriptional modulation by targeting epigenetic regulators could improve the efficacy of immunotherapy including CAR-T, providing a therapeutic avenue for treating GBM in the clinic. RNA-seq was performed to identify differential genes in U87 in different conditions.