Journal: Cancer Medicine
Article Title: High SOX8 expression promotes tumor growth and predicts poor prognosis through GOLPH3 signaling in tongue squamous cell carcinoma
doi: 10.1002/cam4.3041
Figure Lengend Snippet: SOX8 interacts with TFAP2A to regulate GOLPH3 expression and tongue squamous cell carcinoma (TSCC) cell growth. Co‐immunoprecipitation assay is carried out to test 4 predicted GOLPH3 promoter‐binding proteins, namely, p65, p50, SP1, and TFAP2A, using specific antibodies against each of these proteins in the flag‐SOX8‐overexpressing SCC25 and HSC6 cells. Surprisingly, SOX8 is knocked down via the anti‐TFAP2A antibodies (A). Besides, the SOX8‐TFAP2A interaction is also validated in the other co‐immunoprecipitation assay that uses the SOX8‐specific antibodies (B). Additionally, dual‐immunofluorescence assay is used for further analyzing TFAP2A and SOX8 expression as well as the sub‐cellular localization within SCC9 as well as SCC25 cells. SOX8 (green) is expressed both within the cytoplasm and nucleus, while TFAP2A (red) expression is mainly detected in cytoplasm. The TFAP2A‐SOX8 co‐localization is detected in the nucleus and cytoplasm (yellow). On the other hand, ChIP assay confirms that TFAP2A binds onto GOLPH3 promoter in SCC9 and SCC25 cells (E). Furthermore, the over‐expression of TFAP2A enhances SOX8 binding onto the GOLPH3 promoter. By contrast, the knockdown of TFAP2A weakens SOX8 binding onto GOLPH3 promoter within the SCC25 cells with SOX8 over‐expression. Knockdown of SOX8 weakens SOX8 binding onto the GOLPH3 promoter within SCC25 cells with TFAP2A over‐expression (D). Moreover, luciferase reporter gene assay is carried out, which suggests that TFAP2A over‐expression enhances activity of GOLPH3 promoter, whereas knockdown of TFAP2A suppresses activity of GOLPH3 promoter. Additionally, only SOX8 knockdown or TFAP2A knockdown reduces the GOLPH3 promoter activity in SCC25 cells with TFAP2A or SOX8 over‐expression, respectively (F). Western Blotting (H) and RT‐PCR (G) suggest that, TFAP2A over‐expression up‐regulates GOLPH3 mRNA and protein expression, whereas the expression of GOLPH3 is down‐regulated following TFAP2A knockdown, even in SOX8‐overexpressing SCC25 cells. Finally, CCK8 assay indicates that TFAP2A knockdown inhibits the increased TSCC cell growth induced by SOX8 over‐expression, while over‐expression of TFAP2A partially rescues the inhibition of cell growth mediated by SOX8 knockdown (I)
Article Snippet: The streptavidin‐agarose pull‐down experiment was carried out according to previous description to analyze the proteins binding to GOLPH3 promoter., Firstly, extracts of nuclear protein (0.5 mg) isolated based on TSCC cancer cells would be subjected to incubation with the biotin‐conjugated double strand DNA probes (20 µg)matched with the nucleotides from −585 to +1 in the promoter region of GOLPH3 (Sigma‐Aldrich), together with the agarose‐streptavidin beads (200 µL, Sigma‐Aldrich) overnight under 4°C.
Techniques: Expressing, Co-Immunoprecipitation Assay, Binding Assay, Immunofluorescence, Over Expression, Luciferase, Reporter Gene Assay, Activity Assay, Western Blot, Reverse Transcription Polymerase Chain Reaction, CCK-8 Assay, Inhibition