Serine/threonine kinase TBK1 promotes Intrahepatic cholangiocarcinoma progression via direct regulation of β-catenin

Abstract Intrahepatic cholangiocarcinoma (ICC) is an aggressive liver bile duct malignancy with limited therapeutic options. Metastasis is one of the main contributors to ICC progression and poor prognosis. However, the underlying mechanism of ICC metastasis remains largely unknown. Here, we showed that TANK-binding kinase 1 (TBK1), a serine/threonine-protein kinase, was significantly upregulated in tumor tissues of ICC patients with larger tumor diameter, lymph node metastasis, and advanced TNM stage. Consistently, during the different stages of cholangiocarcinoma (CCA) carcinogenesis (hyperplasia, dysplasia, and CCA), TBK1 showed a dynamic increase in spontaneous rat and mouse models. Functional studies showed that enforced expression of TBK1 promoted metastasis both in vitro and in vivo. Mechanistically, TBK1 directly interacts with β-catenin and stimulates its nuclear translocation, further activating the β-catenin-mediated epithelial-mesenchymal transition (EMT) process. Moreover, we demonstrate that the S172 site of TBK1 kinase domain was essential for the interaction between TBK1 and β-catenin as well as for TBK1 mediated β-catenin activation. In addition, high levels of TBK1 in clinical ICC tissues were correlated with elevated nuclear β-catenin levels and predicted worse overall and disease-free survival. A TBK1 inhibitor GSK-8612 and the liver-specific accumulation of DNA/RNA heteroduplex oligonucleotide (TBK1-HDO) significantly reduced TBK1 expression of ICC and inhibited its intrahepatic metastasis. In summary, our study demonstrated that TBK1 could activate β-catenin via protein-protein interaction, then promote EMT and ICC metastasis, which might serve as a potential therapeutic target for patients with cholangiocarcinoma.