Expression And Role Of SPOP In Human Renal Cell Carcinoma

Background:Speckle-type POZ protein(SPOP)is a substrate adapter of CUL3 ubiquitin ligase,that plays an important role in solid tumors by promoting ubiquitination and degradation of substrates.Some studies have shown that SPOP is upregulated in human renal cell carcinoma tissue.However,the exact role of SPOP in renal cell carcinoma remains unclear and needs to be further elucidated.Our preliminary results showed that the expression levels of SPOP were different in different RCC cell lines.The purpose of this study was to detect the expression of SPOP in renal cell carcinoma and investigate the correlation between the SPOP epression and the biological behavior and clinicopathological features.Methods:ACHN,caki-1 and caki-2 was selected for the cell experiments,that SPOP was overexpressed in ACHN and Caki-1 cells by lentiviral vector transfection,and the SPOP was knocked down in Caki-2 cells with the similar transfection methods.The role of SPOP in the migration and invasion ability of cell lines was determined with wound-healing assays and transwell assays.The transfection efficiency was evaluated by quantitative PCR and the expression levels of SPOP protein in the cytoplasm of transfected cell lines were determined by western blotting analyses.At the same time,immunohistochemiscal staining of SPOP was performed in tissue microarrays(TMA)and 18 cases of renal cell carcinoma tissues and corresponding 13 cases of adjacent normal tissues.Finally,the relationship between SPOP and the overall survival of patients and the correlation of pathological grading were analyzed based on the data of different SPOP expression levels in TMA and clinicopathological characteristics data of patients.Results:Cell experiments results showed that overexpression of SPOP inhibited the invasion and migration of RCC cells in vitro,suggesting that the SPOP protein could inhibit the malignant biological behavior of renal carcinoma cells.In tissue microarrays,SPOP was lowly expressed in the most of RCC tissues(84%,75/90)and relatively higher expressed in the majority of adjacent normal tissues(88%,79/90).The similar findings were observed in the immunohistochemical staining of histological section of renal carcinoma(72%,13/18)as compared with the adjacent normal tissues(69%,9/13).There was no significant correlation between the expression of SPOP and clinicopathologic feature,such as histopathological grade and overall survival.Conclusion: Quite different to the earlier studies,SPOP was mainly down-regulated in renal cell carcinoma and suppressed the invasion and migration ability of RCC cells in vitro.It demonstrated that SPOP might be a potential tumor inhibitor in RCC.