Epigenetic Silencing of miR-218-5p Modulates BIRC5 and DDX21 Expression to Promote Colorectal Cancer Progression

Colorectal cancer remains one of the leading causes of cancer-related deaths globally. Non-protein coding RNAs, including microRNAs, have emerged as crucial regulators in cancer progression. Herein, we analyzed publicly available datasets for miRNA expression in healthy controls, adenomatous polyps, and colorectal cancer and identified their regulatory networks using HCT116 and HT-29 CRC models. Differentially expressed miRNAs in adenomatous polyps and colorectal cancer were identified, highlighting their role in colorectal cancer initiation and progression. Notably, miR-218-5p was significantly downregulated in adenomatous polyps and colorectal cancer, suggesting a role in colorectal cancer initiation. Functional investigations revealed a tumor suppressive role for miR-218-5p in HCT116 and HT-29 CRC cell models, affecting cell proliferation and three-dimensional organoid formation and promoting cell death. RNA-Seq and bioinformatics identified <i>BIRC5</i> and <i>DDX21</i> as bona fide gene targets for miR-218-5p, validated by reverse transcription quantitative PCR and Western blotting. Further investigation into the genomic location of <i>miR-218-5p</i>, embedded within the <i>SLIT2</i> and <i>SLIT3</i> introns on chromosome 4 and chromosome 5, respectively, revealed epigenetic silencing through promoter hypermethylation in colorectal cancer cell models. These findings highlight epigenetic silencing of miR-218-5p in colorectal cancer, suggesting its potential as a biomarker and therapeutic target for early detection and intervention.