FBW7 loss promotes epithelial-to-mesenchymal transition in non-small cell lung cancer through the stabilization of Snail protein

The E3 ubiquitin ligase F-box and WD repeat domain containing 7 (FBW7 alpha) functions as a putative tumor suppressor in non-small cell lung cancer (NSCLC) due to its regulation of a set of oncogenic proteins associated with cell proliferation and mitosis. Increasing efforts have been focused on the understanding of FBW7 in determining cell cycle progression and apoptosis induction, however, the correlation between FBW7 and tumor metastasis is not fully understood. In this study, we reported a potential anti-metastatic effect of FBW7 in non-small cell lung cancer (NSCLC). In this model, FBW7 inhibited cancer cell metastasis primarily by inducing ubiquitination and proteolysis of the transcriptional factor Snail, which suppressed E-cadherin cell tight junction protein expression. Loss of FBW7 would stabilize the Snail protein, thus, inhibit E-cadherin expression and promote metastasis in vitro and in vivo. Moreover, Snail ubiquitination and degradation were also achieved by pharmacological approach, in which the FBW7 agonist oridonin treatment led to Snail proteolysis. Furthermore, FBW7 silencing stabilized Snail protein and induced epithelial-to mesenchymal transition (EMT), and acquisition of migration and invasion properties in NSCLC. Overall, our study provides new insights into the FBW7-Snail axis in regulating cell migration and invasion, and suggests that targeting FBW7 may be a potent approach to inhibit metastasis in NSCLC. (C) 2018 The Author(s). Published by Elsevier B.V.