BRD4 profiling identifies critical Chronic Lymphocytic Leukemia oncogenic circuits and reveals sensitivity to PLX51107, a novel structurally distinct BET inhibitor [expression profiling]

Bromodomain and extra-terminal (BET) family proteins are key regulators of gene expression in cancer. Herein, we utilize BRD4 profiling to identify critical pathways involved in pathogenesis of chronic lymphocytic leukemia (CLL). BRD4 is over-expressed in CLL and is enriched proximal to genes up-regulated or de novo expressed in CLL with known function in disease pathogenesis and progression. These genes, including key members of the BCR signaling pathway, provide rationale for this therapeutic approach to identify new targets in alternative types of cancer. Additionally, we describe PLX51107, a structurally distinct BET inhibitor with novel in vitro and in vivo pharmacologic properties that emulates or exceeds the efficacy of BCR signaling agents in pre-clinical models of CLL. Herein, the discovery of the involvement of BRD4 in the core CLL transcriptional program provides a compelling rationale for clinical investigation of PLX51107 as epigenetic therapy in CLL and application of BRD4 profiling in other cancers. Microarray analysis for primary patient's derived B-CLL cells purifed under basal, stimulated and tretated conditions. A, B and C are pools of 3 individual CLL primary samples each. Samples were treated inbdividually, RNA extracted and equal amount of DNA was pooled for microarray analysis.