Molecular mechanism and clinical significance of Notch3 negative regulation of BRD4 on the growth and survival of esophageal squamous cell carcinoma

Objective The aim of this study was to investigate the expression of bromodomain-containing protein 4 (BRD4) and Notch receptor protein 3 (Notch3) in esophageal squamous cell carcinoma (ESCC) and the effect of their interaction on the growth and survival of ESCC cells. Methods The expression of target genes in ESCC and the binding sites between genes were analyzed by TCGA and ChIP-Atlas databases. The expression levels, interactions and effects of target genes on tumor cell activity in ESCC were detected by immunohistochemical staining methods, WB, qRT-PCR, ChIP-qPCR and CCK-8 assays. Dual luciferase reporter gene assays were performed to investigate the regulation between target genes and the signaling mechanism. In vivo experiments were performed to further explore the regulatory effects of target genes on ESCC cell growth. Results BRD4 was highly expressed in ESCC. BRD4 regulated ESCC cell apoptosis by modulating MCL1 and Survivin. In ESCC cell lines, Notch3 silenced BRD4. Notch3 mediated apoptosis in ESCC cells partly by antagonizing BRD4. Notch3 was highly expressed in ESCC tissues. Notch3 expression correlated with the degree of tumor differentiation. When BRD4 was inhibited in ESCC cells, Notch3 expression was also reduced. In vivo, inhibition of BRD4 combined with overexpression of Notch3 better inhibited ESCC cell growth. Conclusion Notch3 negatively feedback regulates BRD4 thereby inhibiting ESCC cell growth and survival. The use of BRD4 inhibitors in combination with overexpression of Notch3 may be better highlight the clinical implication.