MicroRNA­197 reverses the drug resistance of fluorouracil­induced SGC7901 cells by targeting mitogen­activated protein kinase 1.

MicroRNAs (miRNAs) are a group of small non­coding RNA molecules, which serve an important function in the development of multidrug resistance in cancer through the post­transcriptional regulation of gene expression and RNA silencing. In the present study, the functional effects of miR­197 were analyzed in chemo­resistant gastric cancer cells. Low expression levels of miR­197 were observed in the fluorouracil (5­FU)­resistant gastric cell line SGC7901/5­FU when compared with those in the parental gastric cell line SGC7901. Overexpression of miR­197 in SGC7901/5­FU cells was identified to partially restore 5­FU sensitivity. miRNA target prediction algorithms suggested that mitogen­activated protein kinase 1 (MAPK1) is a candidate target gene for miR­197. A luciferase reporter assay confirmed that miR­197 led to silencing of the MAPK1 gene by recognizing and then specifically binding to the predicted site of the MAPK1 mRNA 3'­untranslated region. When miR­197 was overexpressed in SGC7901 cells, the protein levels of MAPK1 were downregulated. Furthermore, MAPK1 knockdown significantly increased the growth inhibition rate of the SGC7901/5­FU cells compared with those in the control group. These results indicated that miR­197 may influence the sensitivity of 5­FU treatment in a gastric cancer cell line by targeting MAPK1.