Upregulation of miR-489-3p and miR-630 inhibits oxaliplatin uptake in renal cell carcinoma by targeting OCT2

Renal cell carcinoma(RCC) is one of the most common malignant tumors affecting the urogenital system, accounting for 90% of renal malignancies. Traditional chemotherapy options are often the front-line choice of regimen in the treatment of patients with RCC, but responses may be modest or limited due to resistance of the tumor to anticarcinogen. Downregulated expression of organic cation transporter OCT2 is a possible mechanism underlying oxaliplatin resistance in RCC treatment. In this study, we observed that mi R-489-3 p and mi R-630 suppress OCT2 expression by directly binding to the OCT2 30-UTR. Meanwhile, via 786-O-OCT2-mi RNAs stable expression cell models, we found that mi RNAs could repress the classic substrate 1-methyl-4-phenylpyridinium(MPP+), fluorogenic substrate N,N-dimethyl-4-(2-pyridin-4-ylethenyl) aniline(ASP+), and oxaliplatin uptake by OCT2 both in vitro and in xenografts. In 33 clinical samples, mi R-489-3 p and mi R-630 were significantly upregulated in RCC, negatively correlating with the OCT2 expression level compared to that in adjacent normal tissues, using tissue microarray analysis and q PCR validation. The increased binding of c-Myc to the promoter of pri-mi R-630, responsible for the upregulation of mi R-630 in RCC, was further evidenced by chromatin immunoprecipitation and dual-luciferase reporter assay. Overall, this study indicated that mi R-489-3 p and mi R-630 function as oncotherapy-obstructing micro RNAs by directly targeting OCT2 in RCC.