SRA

Glioblastomas are universally fatal cancers that contain self-renewing glioblastoma stem cells (GSCs) that initiate tumors. Traditional anti-cancer drug discovery based on in vitro cultures tends to identify targets with poor therapeutic index and fails to accurately model the effects of the tumor microenvironment. Here, leveraging in vivo genetic screening, we identified the H3K4me3 regulator DPY30 as an in vivo-specific glioblastoma dependency. Based on the hypothesis that in vivo epigenetic regulation may define critical GSC dependencies, we interrogated active chromatin landscapes of GSCs derived from intracranial xenografts and cell culture through Histone H3 lysine 4 trimethylation (H3K4me3) chromatin immunoprecipitation and transcriptome analysis. Intracranial-specific genes marked by H3K4me3 included FOS, NFkB, and phosphodiesterase family members. In intracranial tumors, DPY30 regulated angiogenesis and hypoxia pathways in an H3K4me3-dependent manner, but was dispensable in cultured GSCs. PDE4B was a key downstream effector of DPY30; the PDE4 inhibitor, rolipram, preferentially targeted DPY30-expressing cells and impaired in vivo glioblastoma growth without affecting cultured tumor cells. Collectively, DPY30 selectively regulates H3K4me3 modification on genes critical to support angiogenesis and tumor growth in vivo, laying the foundation for the DPY30-PDE4B axis as a specific and novel therapeutic target in glioblastoma with a broad therapeutic index. Overall design: RNA sequencing on 3565 and 1919 GSCs transduced with either control (nt) or DPY30 shRNA, grown either in cell culture or in immunocompromised mice for 3 weeks