OTUD5-TIF1γ-SMAD3/4 positive feedback loop inhibits TGF-β-induced EMT and metastasis in NSCLC.

The molecular mechanisms underlying non-small cell lung cancer (NSCLC) metastasis remain incompletely understood, limiting the identification of potential therapeutic targets. Here, integrating clinical data, we identify ovarian tumor domain-containing protein 5 (OTUD5), an OTU family member of deubiquitinases, as a potential metastasis suppressor in NSCLC. Reduced OTUD5 expression is observed in metastatic NSCLC specimens and correlates with poor patient survival. Using human NSCLC cell lines, we find that OTUD5 directly interacts with and deubiquitinates transcriptional intermediary factor 1 γ (TIF1γ). The latter attenuates TGF-β-induced SMAD3/4 complex formation, thereby impeding TGF-β-induced repression of OTUD5 transcription. Upon TGF-β stimulation, OTUD5 overexpression dramatically suppresses SMAD3/SMAD4 complex formation; however, this effect is abrogated when TIF1γ is silenced. OTUD5 overexpression inhibits TGF-β-induced epithelial-mesenchymal transition (EMT) and metastasis of NSCLC cells, whereas these effects are largely abrogated by TIF1γ knockdown. Notably, targeting OTUD5 with nilotinib, an FDA-approved drug for chronic myeloid leukemia (CML), enhances the OTUD5-TIF1γ interaction, reduces the ubiquitination of TIF1γ, and exerts significant anti-metastatic effects on NSCLC cells. Taken together, our findings indicate that OTUD5 inhibits TGF-β-induced EMT and NSCLC cell metastasis in a partially TIF1γ-dependent manner and reveal an OTUD5-TIF1γ-SMAD3/4 positive feedback loop for preventing TGF-β-induced EMT. These findings provide new insights into the molecular basis of NSCLC metastasis and suggest that nilotinib may be repositioned as an anti-metastatic drug by targeting OTUD5 in NSCLC treatment.