BRD4 (bromodomain-containing protein 4) is a transcriptional regulator that recognizes and binds acetylated histones and drives transcription of many genes, including MYC. While MYC regulation by BRD4 has been extensively studied in hematological malignancies, relatively little is known about this mechanism in solid tumors, particularly in breast cancer. The gene discussed is BRD4; the disease is breast cancer.