Combining inhibitors of Brd4 and cyclin-dependent kinase can decrease tumor growth in neuroblastoma with MYCN amplification

Introduction High-risk neuroblastoma is a deadly disease; poor prognosticators are MYCN-amplification and TERT-overexpression. We hypothesized that Gene Set Enrichment Analysis (GSEA) could identify pathways associated with MYCN-amplification and that inhibition of these pathways could decrease tumor growth. Methods We analyzed the Neuroblastoma-Kocak dataset (GSE45547, n = 649) and identified pathways associated with MYCN-amplification. Inhibitors were selected from upregulated gene sets for in vitro cytotoxicity testing using ST16-patient-derived primary neuroblastoma cells and in vivo testing using orthotopic ST16-patient-derived xenografts (PDX) in mice. Tumor volume was measured with ultrasound and tumor sections examined after H&E staining. Results GSEA identified significantly overexpressed gene sets in MYCN-amplified tumors including MYC targets, cell cycle mitotic genes, TERT associated genes, loss of RB1 gene sets, and E2Fs targets. Several genes were potential Bromodomain-containing protein 4 (Brd4) targets, making Brd4 inhibitors - JQ1, AZD5153 - and cyclin-dependent kinase (Brd4's binding partner) inhibitors - dinaciclib - potential therapeutic agents. JQ1 and dinaciclib were synergistic in inducing cytotoxicity in vitro. Dinaciclib-AZD5153 in vivo decreased tumor size compared to control, and increased tumor lymphocyte infiltration and necrosis on histology. Conclusions GSEA is a powerful approach to identify upregulated genes and potential therapeutic targets. Dinaciclib-AZD5153 combination therapy can be effective against MYCN-amplified and TERT-overexpressing neuroblastoma tumors.