The Transcription Factor Otc4A Stimulates the Proliferation, Invasion, and Stemness of Colorectal Cancer Cells by Inhibiting the Regulation of miR-7-5p on TLR4

BACKGROUND: To investigate the effects and mechanism of octamer-binding transcription factor 4 (Otc4A) on proliferation, invasion, and stemness of colorectal cancer (CRC) cells. METHODS: Firstly, normal fetal human cells (FHC, colon epithelial cells) and HT29 cells (CRC cells) were cultured. The expression levels of Otc4A, miR-7-5p, and TLR4 in cells were then detected by qRT-PCR. CCK-8 was adopted to measure cell proliferation rate after Otc4A, miR-7-5p, and TLR4, respectively, were either knocked out or overexpressed in HT29 cells. Later, the cell viability was detected by cell cloning assay; cell invasion by transwell; cell sphere-forming ability by sphere-formation assay; protein expression level of Otc4A, p65, p-p65, and TLR4 by western blot; and the targeting relationships between miR-7-5p and Otc4A as well as miR-7-5p and TLR4 by dual-luciferase reporter assay. Finally, chromatin immunoprecipitation was applied to verify the interaction between Otc4A and miR-7-5p. RESULTS: In HT29 cells, Otc4A expression was significantly increased. Additionally, the knockdown of Otc4A prevented HT29 cells from proliferating, migrating, forming spheres, and activating NF–B signaling. Otc4A could negatively regulate miR-7-5p, and miR-7-5p could target TLR4 expression. Besides, a negative correlation was found between Otc4A and miR-7-5p. Finally, the knockdown of miR-7-5p or overexpression of TLR4 could significantly reverse the effect of the knockdown of Otc4A on HT29 cells. CONCLUSION: The transcription factor Otc4A can regulate the level of TLR4 by inhibiting the expression of miR-7-5p and then promote the proliferation and invasion of CRC cell HT29 as well as enhance cell stemness.