FKBP51 promotes migration and invasion of papillary thyroid carcinoma through NF-κB-dependent epithelial-to-mesenchymal transition

Abstract

FK506-binding protein 51 (FKBP51) is a member of the immunophilin family, with relevant roles in multiple signaling pathways, tumorigenesis and chemoresistance. However, the function of FKBP51 in papillary thyroid carcinoma (PTC) remains largely unknown. In the present study, increased FKBP51 expression was detected in PTC tissues as compared with adjacent normal tissues, and the expression level was associated with clinical tumor, node and metastasis stage. Using FKBP51-overexpressing K1 cells and FKBP51-knockdown TPC-1 cells, both human PTC cell lines, it was identified that FKBP51 promoted the migration and invasion of PTC, without affecting cell proliferation. Further investigation revealed that FKBP51 activated the NF-κB pathway and epithelial-to-mesenchymal transition (EMT) genes, and EMT was suppressed when NF-κB was inhibited. It was also assessed whether FKBP51 promoted the formation of cytoskeleton to promote migration and invasion of PTC using a tubulin tracker; however, no evidence of such an effect was observed. These results suggested that FKBP51 promotes migration and invasion through NF-κB-dependent EMT.

Keywords: epithelial-to-mesenchymal; invasion; migration.

Figure 1.

FK506-binding protein 51 expression level in papillary thyroid carcinoma tissues and adjacent normal tissues (magnification, ×200). Representative images of tissues rated (A) -, (B) +, (C) ++ and (D) +++.

Figure 2.

FKBP51 promoted cell migration and invasion of papillary thyroid carcinoma cells without affecting proliferation. (A) FKBP51 overexpressing and control K1 cells and FKBP51 knockdown and control TPC-1 cells. (B) The cells migration and invasive capacities were determined using a transwell assay. The data represent the mean ± standard deviation of at least 3 independent experiments (***P<0.001). (C) Cell counting kit-8 analysis was used to determine cell proliferation difference between FKBP51-overexpressing and the control K1 cells as well as FKBP51-knockdown and the control TPC-1 cells. The result revealed no significance (P>0.05). FKBP51, FK506 binding protein 51; GFP, green fluorescent protein; vec, vector; Con, control.

Figure 3.

FKBP51 regulated the NF-κB pathway of papillary thyroid carcinoma. Western blot analysis of nuclear P65, cytoplasm P65 and IκBα in FKBP51-overexpressing and control K1 cells, and FKBP51-knockdown and control TPC-1 cells are presented. *P<0.05; **P<0.01; ***P<0.001; ****P<0.0001. FKBP51, FK506 binding protein 51; GFP, green fluorescent protein; vec, vector; TNF, tumor necrosis factor; Nuc, nuclear; Cyt, cytoplasmic.

Figure 4.

FKBP51 activated EMT through the NF-κB pathway. (A) GFP-FKBP51 K1 cells were treated with NF-κB pathway inhibitor PDTC (20 µM) for 24 h and the cells' migration and invasive capacities were determined using the transwell assay. (B) EMT-associated proteins TGF-β1, β-catenin, N-cadherin, MMP9 of K1 cells and TGF-β1, Vimentin, N-cadherin, MMP9 of TPC-1 cells were detected by western blotting. (C) FKBP51-overexpressing K1 cells were treated with NF-κB inhibitor PDTC (20 mM) for 24 h and expression of TGF-β1, β-catenin, N-cadherin and MMP9 was compared with control group was detected. *P<0.05; **P<0.01; ***P<0.001. FKBP51, FK506 binding protein 51; GFP, green fluorescent protein; vec, vector; MMP, matrix metalloproteinase; EMT, epithelial mesenchymal transition.

Figure 5.

FK506 binding protein 51 does not alter the formation of tubulin. Immunofluorescence was used to detect the tubulin formation, and relative fluorescence intensity and distribution of tubulin revealed no significant difference (P>0.05). GFP, green fluorescent protein.