BRD4 is an epigenetic regulator and transcription cofactor whose phosphorylation by CK2 and dephosphorylation by PP2A modulates its function in chromatin targeting, factor recruitment, and cancer progression. While the bromodomains of BET family proteins, including BRD4, BRD2, BRD3 and BRDT, have been the primary targets of small compounds such as JQ1, I-BET and MS417 that show promising anticancer effects against some hematopoietic cancer and solid tumors, drug resistance upon prolonged treatment necessitates a better understanding of alternative pathways underlying not only the resistance but also persistent BET protein dependence for identifying new targets and effective combination therapy strategies.