FOXN3 Downregulation in Colorectal Cancer Enhances Tumor Cell Stemness by Promoting EP300-Mediated Epigenetic Upregulation of SOX12.

Cancer stemness plays a crucial role in promoting the progression of colorectal cancer (CRC). Forkhead box N3 (FOXN3) is a tumor suppressor protein. Herein, we investigated the role of FOXN3 in the regulation of CRC cell stemness. Cell viability, proliferation, migration, and invasion were assessed utilizing cell counting kit-8 assay, 5-ethynyl-20-deoxyuridine assay, and Transwell assay, respectively. Cell-sphere formation was assessed using a sphere-forming assay. The enrichment of H3K27ac modifications at the SRY-related HMG-box 12 (SOX12) promoter, interactions among FOXN3, SOX12, and E1A binding protein p300 (EP300) were analyzed using chromatin immunoprecipitation or dual luciferase reporter assays. We found that FOXN3 overexpression inhibited CRC cell proliferation, migration, invasion, stemness, and tumor formation in mice by inactivating the Wnt/β-catenin signaling, while these effects of FOXN3 overexpression were reversed by the overexpression of SOX12. Mechanistically, EP300 increased SOX12 expression in CRC cells by promoting H3K27ac enrichment in the SOX12 promoter. In addition, FOXN3 transcriptionally inhibited EP300 expression in CRC cells by binding to the EP300 promoter. As expected, EP300 overexpression weakened the inhibitory effect of FOXN3 overexpression on CRC cell stemness. Collectively, FOXN3 upregulation inhibited CRC cell stemness by suppressing EP300-mediated epigenetic upregulation of SOX12.
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