Fisetin Modulates Chemoresistance-Associated miR-21, miR-181a, miR-203, miR-101 and miR-381 in Capecitabine-Resistant HT29 Colorectal Cancer Cells

Capecitabine is a key component of colorectal cancer (CRC) chemotherapy; however, acquired resistance markedly limits its efficacy. MicroRNAs (miRNAs) are central regulators of drug response, and the flavonoid fisetin has been reported to exert anti-tumor and chemosensitizing effects. Here, we investigated whether fisetin modulates the expression of chemoresistance-associated miRNAs in a capecitabine-resistant CRC cell model. Candidate miRNAs were prioritized from the publicly available dataset GSE30894 using differential expression analysis, which identified miR-21, miR-181a, miR-203, miR-101, and miR-381 as differentially expressed between sensitive and resistant colorectal cancer cells. These miRNAs were quantified by RT-qPCR in parental HT29 and capecitabine-resistant HT29 (CR/HT29) cells under basal conditions and after 24-h exposure to capecitabine (40 µM), fisetin (120 µM), or the combination. Nuclear morphology was assessed by DAPI staining. At baseline, CR/HT29 cells showed lower expression of miR-381, miR-21, miR-203, and miR-101 and a trend towards higher miR-181a compared with parental HT29 cells. Treatment with capecitabine, fisetin, or their combination differentially modulated these miRNAs in the two cell lines. In both parental and resistant cells, fisetin-containing regimens reduced miR-21, while in CR/HT29 cells, fisetin significantly decreased miR-181a expression compared with fisetin-treated parental cells. Fisetin and fisetin + capecitabine also altered miR-203 and miR-101 levels, with a more pronounced suppression in HT29 than in CR/HT29 cells. These changes were accompanied by marked morphological alterations in resistant cells. Fisetin modulates chemoresistance-associated miRNAs in colorectal cancer, particularly in capecitabine-resistant HT29 cells, suggesting a chemosensitizing adjuvant role and offering an in vitro basis for in vivo studies.