Background: Renal cell carcinoma (RCC) accounts for more than 90% of cancers in the kidney. RCC is often asymptomatic, as a result people with RCC generally have advanced disease by the time it is discovered and has a poor prognosis compared to other cancers. Therefore, it is necessary to explore its pathogenesis and identify some reliable prognostic biomarker of RCC. miRNAs are emerging as important players in the development and progression of RCC. miR-31-5p has been reported to act as a tumor suppressor in hepatocellular carcinoma (HCC). The aim of this study is to determine the detailed molecular mechanism of miR-31-5p in the progression of RCC and to investigate its potential clinical value.

Methods: In this study, RT-qPCR, EdU assay, CCK-8 assay, wound scratch assay, transwell assay, flow cytometry assay and cell cycle assay were performed to detect miR-31-5p expression and its functions in RCC. Moreover, 42 formalin-fixed paraffin-embedded (FFPE) RCC samples were used to analyze the relationship between miR-31-5p expression and patients’ overall survival. Finally, luciferase reporter assay, RT-qPCR assay and western blot were used to explore the association between miR-31-5p and its potential targets.

Results: miR-31-5p was significantly down-regulated in RCC tissues and RCC cell lines compared with paired adjacent normal tissues and normal cell lines. miR-31-5p downregulation was associated with poor prognosis in RCC patients. Overexpression of miR-31-5p inhibited RCC cell proliferation, migration and invasion and cell cycle. Conversely, down-regulation of miR-31-5p promoted cell proliferation, migration and invasion. Furthermore, cyclin-dependent kinasec1 (CDK1), a key player in cell cycle regulation, was identified as a functional target of miR-31-5p.

Conclusions: Our results suggest that miR-31-5p serves as a tumor suppressor in RCC and is expected to be a molecular biomarker for poor prognosis of RCC.