A novel enhancer activated by CEBPB drives colorectal carcinogenesis via enhancer RNA-mediated DNA loop promotion of KRT80 transcription

The prognosis of colorectal cancer (CRC) is often fatal, and the underlying mechanisms are unclear. Dysregulation of enhancers is involved in several tumors, and this area is expected to become a new frontier in tumor therapy. Here, we identified a novel activated enhancer ‘Enhancer X’ from the Gene Expression Omnibus database and experimentally verified its associated RNA (EX-eRNA) in CRC. To date, there are no reports on the function of Enhancer X, and its role in CRC remains unknown. We aimed to investigate the biological functions and underlying mechanism of Enhancer X in CRC. EX-eRNA expression was elevated in CRC cells and tissues and positively correlated with CRC metastasis and shorter survival. Enhancer X knockout (CRISPR/Cas9) or EX-eRNA knockdown (siRNAs) inhibited CRC cell growth in vivo and in vitro. Mechanistically, Enhancer X activation and transcription to EX-eRNA require the binding of CEBPB to a “GTTGTGTCAC” motif within the enhancer region. Subsequently, EX-eRNA, serves as a scaffold for MED25 to stabilize the chromatin loop between Enhancer X region and the KRT80 promoter, thereby promoting KRT80 transcription and driving CRC tumorigenesis. Thus, we conclude that novel enhancer X activated by CEBPB drives colorectal carcinogenesis via EX-eRNA-mediated DNA loop promotion of KRT80 transcription, and that targeting the CEBPB / Enhancer X / EX-eRNA / KRT80 molecular axis constitutes a promising approach to treat CRC.