miR-106b-5p promotes renal cell carcinoma aggressiveness and stem-cell-like phenotype by activating Wnt/β-catenin signalling

PURPOSE: To examine the role of miR-106b-5p in regulating the cancer stem-cell-like phenotype in clear cell renal cell carcinomas (ccRCC). EXPERIMENTAL DESIGN: Real-time PCR was performed to evaluate miR-106b-5p levels in ccRCC cell lines and patients specimens. A series of in vivo and in vitro assays were performed to confirm the effect of miR-106b-5p on ccRCC stemness phenotype. RESULTS: ccRCC cells and tissues expressed more miR-106b-5p than normal controls. Gain- and loss-of-function studies demonstrated that overexpression of miR-106b-5p in ccRCC cells increased the spheres formation ability and the proportion of side population cells. Ectopic expression of miR-106b-5p in ccRCC cells increased tumour growth rates and the number of metastatic colonies in the lungs by using an orthotopic kidney cancer model and a tail vein injection model, respectively. Mechanistic studies revealed that, miR-106b-5p has an activating effect on Wnt/β-catenin signalling. miR-106p-5p overexpression simultaneously targets multiple negative regulators of the Wnt/β-catenin pathway, namely, LZTFL1, SFRP1 and DKK2. In addition, we also confirmed that miR-106b-5p and its targets expression correlates with the overall-survival of ccRCC patients from TCGA. CONCLUSIONS: These findings suggest that miR-106b-5p mediates the constitutive activation of Wnt/β-catenin signalling, likely serving as a potential therapeutic target for ccRCC.