Siah1 promotes the proliferation of NSCLC cells through ubiquitinating and stabilizing Notch1.

Seven in absentia homolog 1 (Siah1) has been shown plays important roles in the pathogenesis and development of multiple cancers. However, the functions and mechanisms of Siah1 in non-small cell lung cancer (NSCLC) remain unclear. In our study, we found that knock down of Siah1 could inhibit the proliferation of NSCLC cells, while over-expression of Siah1 had the opposite effects. Molecularly, the bioinformatics analysis determined that notch receptor 1 (Notch1) might be the potential target of Siah1. Subsequently, we identified that Siah1 acted as an E3 ligase to promote the ubiquitination and stabilization of Notch1 through the proteasome pathway. Furthermore, the results showed that the Siah1 expression was directly correlated with CTR9 in human NSCLC tissues. Finally, Siah1 could promote Akt phosphorylation through regulating Notch1, thus promoting the proliferation of NSCLC cells. In conclusion, our study demonstrated that Siah1 acts as an oncogene, can ubiquitinate and stabilize Notch1 by proteasome pathway, which promotes Akt phosphorylation and ultimately leads to NSCLC cell proliferation.