Fig. 4

Regorafenib suppressed drug-resistant CRC cells via miR-34a induction. a Screening of tumor suppressor microRNAs post regorafenib treatment. Regorafenib treatment increased the level of microRNAs associated with tumor suppression. miR-34a was found to be increased most significantly (approximately 4 and 2.5-fold in HTC-116R and DLD-1R respectively). b Quantitative PCR analysis of stemness genes affected by regorafenib and miR-34a mimic treatment. In both HCT-116R and DLD-1R cells, stemness genes including Notch1, WNT1, CD44 and c-Myc were both suppressed by either regorafenib and exogenous miR-34a. a, p < 0.05; b, p < 0.01. c Comparative western blot analysis. Stemness markers including Notch1, WNT1 and c-Myc were decreased by the treatment of regorafenib and the addition of miR-34a mimic molecules. The insert demonstrates the binding of miR-34a to the 3’UTR of Wnt gene (TargetScan software). d Tumor sphere forming assay. Exogenous miR-34a suppressed the tumor sphere generating ability in both HCT-116R and DLD-1R cells. **, p < 0.01