MiR-20a-5p regulates gemcitabine chemosensitivity by targeting RRM2 in pancreatic cancer cells and serves as a predictor for gemcitabine based chemotherapy.

Ribonucleotide reductase subunit M2 ( RRM2 ) acts as an important gemcitabine resistance-related gene in pancreatic cancer (PC). Here, we aimed to investigate the potential microRNA which regulates gemcitabine chemosensitivity by targeting RRM2 and explore the clinical significance of candidate miRNA in PC. MTT assay and Western blot analysis revealed that long-time gemcitabine treatment in PC cells induced drug resistance and RRM2 increase, and silence of RRM2 blocked gemcitabine resistance. Among the predicted eight RRM2-related microRNAs, the expression of miR-20a-5p showed the most significant discrepancy between gemcitabine-resistant cells and parental cells. Furthermore, the Dual-Luciferase reporter gene assay indicated that miR-20a-5p directly targeted RRM2 3'UTR, thus inhibited expression of RRM2 and overcame gemcitabine resistance of PC cells. Retrospective study suggested that plasma miR-20a-5p level was correlated with gemcitabine resistance in PC patient. ROC curve showed that miR-20a-5p abundant level might predict gemcitabine resistance with an AUC of 89% (p<0.0001). Additionally, the PFS of patients with high and low expression levels miR-20a-5p was 2.8 months and 4.5 months (p<0.001), respectively. Taken together, our results suggests that miR-20a-5p regulated gemcitabine chemosensitivity by targeting RRM2 in PC cells and could serve as a predictor for predicting the efficacy of gemcitabine based chemotherapy in first-line treatment of PC patients.