Up-regulation of flotillin-2 is associated with renal cell carcinoma progression

Flotillin-2 (FLOT2) is a highly conserved protein isolated from caveolae/lipid raft domains that tether growth factor receptors linked to signal transduction pathway. FLOT2 has recently been identified to be involved in tumorigenesis of several cancers such as breast cancer, melanoma, and gastric cancer. However, the role of FLOT2 in renal cell carcinoma (RCC) remains unclear. The expression levels of FLOT2 in RCC patients and renal cancer cell lines were evaluated by quantitative real-time PCR (qRT-PCR) and Western blot. FLOT2 protein expression was also analyzed in archived paraffin-embedded RCC tissues using immunohistochemistry (IHC), and its association with overall survival of patients was analyzed by statistical analysis. Small-interfering RNA (siRNA) was used to suppress FLOT2 expression in RCC cell lines. In vitro assays were performed to further explore its role in tumor progression. The expression level of FLOT2 was higher in RCC tissues and cell lines than in corresponding adjacent normal tissues and normal human proximal tubule epithelial cell line HK-2. IHC analysis revealed high expression levels of FLOT2 in RCC specimens. The RCC patients with higher FLOT2 expression had an advanced clinical stage and poorer prognosis than those with lower FLOT2 expression. FLOT2 expression was an independent prognostic marker of overall RCC patient survival in a multivariate analysis. In vitro assays indicated that knockdown of FLOT2 reduced cell proliferation, migration, and invasion. Our data suggest that FLOT2 is a novel molecule involved in RCC progression, which provide a potential prognostic biomarker and therapeutic target.