CircDIAPH1 Promotes Liver Metastasis and Development of Colorectal Cancer by Initiation of CEACAM6 Expression.

Liver metastasis is a critical factor influencing the 5-year survival rate in colorectal cancer (CRC). However, the biological function of most circRNAs in liver metastasis of CRC is still unknown. In this study, we identified differentially expressed circRNAs associated with liver metastasis (LM-DE-circRNAs). A total of 247 LM-DE-circRNAs were identified, and crucial signaling pathways, including the regulation of actin cytoskeleton, were significantly enriched, featuring six LM-DE-circRNAs. Notably, circDIAPH1 (hsa_circ_0074323), with the highest AUC value, emerged as a potential biomarker for CRC liver metastasis (CRLM). Functional assays following circDIAPH1 knockdown demonstrated induced apoptosis, suppressed proliferation, reduced metastasis, and invasion in CRC cell lines in vitro. The circDIAPH1 knockdown attenuated tumor growth in a cell-derived xenograft model. Furthermore, circDIAPH1 knockdown lessened the liver metastasis. Transcriptome profiling revealed that CEACAM6 was the most downregulated gene while circDIAPH1 was knocked down, and possesses high expression value in CRC. Most importantly, we found that circDIAPH1 recruited transcription factor FOXA1 to bind in the promoter region of CEACAM6 and initiated CEACAM6 expression. Additionally, the study identified the transcription factor BRD4 as a regulator of circDIAPH1 expression in CRC. In conclusion, this study reveals that circDIAPH1 recruits FOXA1 to initiate CEACAM6 expression, promoting liver metastasis and development of CRC.