TIPE3 promotes non-small cell lung cancer progression via the protein kinase B/extracellular signal-regulated kinase 1/2-glycogen synthase kinase 3β-β-catenin/Snail axis

BACKGROUND: Tumor necrosis factor-α-induced protein 8-like 3 (TNFAIP8L3, also called TIPE3) has been shown to activate PI3K-AKT and MEK-ERK pathways. However, the roles of TIPE3 in progression of lung cancer are largely unknown. METHODS: Immunohistochemistry and western blotting were carried out to analyze the expression of TIPE3 in lung cancer clinical tissues and cells. TIPE3-overexpressing and knock-down NSCLC cell lines were established by transfer of TIPE3 coding sequence and shRNA, respectively. In vitro functional assays were performed to assess the effects of TIPE3 on proliferation and metastasis of NSCLC cells. Tumor xenograft mouse model was used to examine the roles of TIPE3 in growth of NSCLC cells in vivo. Western blotting, immunofluorescence, and immunohistochemistry were conducted to evaluate the association of TIPE3 and molecules related to AKT/ERK1/2-GSK3β-β-catenin/Snail pathway. PI3K, MEK, or GSK3β kinase and proteasome inhibition assays as well as β-Trcp and STUB1 siRNA assays were employed to determine the contribution of AKT/ERK1/2-GSK3β signaling and ubiquitin-proteasome pathway to the regulatory effects of TIPE3 on expression of β-catenin, Snail1, and Slug. RESULTS: We demonstrated that TIPE3 was elevated in lung cancer tissues and cells. The expression level of TIPE3 was positively correlated with malignant clinicopathological characteristics of lung cancer patients, such as tumor size, pathologic stage, and lymph node metastasis. Knockdown of TIPE3 suppressed the proliferation and growth of NSCLC cells as well as their migration and invasion ability, whereas TIPE3 overexpression facilitated these biological processes. Mechanistic data showed that TIPE3 promoted AKT and ERK1/2 signaling, inactivated GSK3β activity, and enhanced the expression and transcriptional activity of β-catenin, Snail1, and Slug in NSCLC cells. Kinase or proteasome inhibition and β-Trcp or STUB1 knockdown assays further revealed that TIPE3 upregulated β-catenin, Snail1, and Slug via the AKT/ERK1/2-GSK3β pathway, in an ubiquitin-proteasome-dependent manner. More importantly, clinical data demonstrated that the expression level of TIPE3 was positively associated with the activation of AKT/ERK1/2-GSK3β-β-catenin/Snail pathway in lung cancer. CONCLUSIONS: Our findings indicate that upregulation of TIPE3 promotes the progression of human NSCLC considerably by activating β-catenin, Snail1, and Slug transcriptional signaling via the AKT/ERK1/2-GSK3β axis. Therefore, TIPE3 may represent a potential therapeutic target for NSCLC.