MicroRNA-21 stimulates epithelial-to-mesenchymal transition and tumorigenesis in clear cell renal cells

Clear cell renal cell carcinoma (ccRCC) metastasis may result from epithelial-to-mesenchymal transition and mesenchymal stem cells that contribute to the development of the primary tumor. In this study, it was demonstrated that microRNA-21 (miR-21) acts as an oncogenic driver of ccRCC. ccRCC spheres were isolated and it was shown that they exhibited cancer stem cell-like properties, including the formation of self-renewing spheres. Spheres showed increased expression of stem cell-related transcription factors and epithelial-mesenchymal transition (EMT) markers. In addition, secondary sphere formation capacity was assessed after miR-21 transfection. miR-21 accelerated the formation of ccRCC spheres, which shared molecular characteristics with the spontaneous ccRCC spheres. It was demonstrated that miR-21 overexpression facilitates ccRCC sphere formation. Thus, a single miRNA may have an impact on the formation of highly tumorigenic cancer spheres in kidney cancer.