BRD4 and neuroblastoma: Given the synergistic relationship of BRD4, PI3K and CDK4/6 as cell cycle regulators, we tested the ability of SRX3177, capable of targeting BRD4, PI3K and CDK4/6 simultaneously, to induce cell cycle arrest in a cyclin D1-dependent hematologic malignancy (mantle cell lymphoma, JeKo-1), PI3K-dependent solid tumor (hepatocellular carcinoma, Huh7), and MYC-dependent embryonal tumor (neuroblastoma, CHLA-255) (Fig. 2b).