SIX1 predicts poor prognosis and facilitates the progression of non-small lung cancer via activating the Notch signaling pathway

【摘要】：Background: Many transcription factors involved in embryonic development and reactivated in tumors were considered to be potential biomarkers for prognosis and novel targets for treatment in various cancers. Sine oculis homeobox homolog 1(SIX1), normally a developmentally restricted transcriptional regulator, was reported to play a critical role during tumor initiation and development.However, the prognostic value and biological function of SIX1 in non-small cell lung cancer(NSCLC)are not wholly clear.Methods: Bioinformatic analyses were performed to investigate the SIX1 expression in cancer and adjacent normal tissues of NSCLC and further explore the correlation between SIX1 expression and clinical outcomes. Western blotting and RT-PCR analysis were conducted to detect the expression level of SIX1 in NSCLC cell lines and a normal bronchial epithelial cell. EdU, CCK-8, clonal formation assay, transwell, and wound healing assay were performed to investigate the effects of gainor loss-of-function of SIX1 on cellular proliferation, migration and invasion in vitro. Gene set enrichment analysis(GSEA) was used to identify the potential signaling pathways involved in SIX1 mediated biological function, and the correlation was confirmed by western blotting and RT-PCR analysis. In vivo experiment was conducted to further validate the tumor-promoting effects of SIX1.Results: Bioinformatic analysis indicated that SIX1 was markedly upregulated in cancer tissues of NSCLC,and positively correlated with poor prognosis of NSCLC patients. Ectopic expression of SIX1 facilitated proliferation, migration, invasion, and epithelial-mesenchymal transition(EMT) of NSCLC cells. On the contrary, knocking down SIX1 exhibited the opposite effects. Mechanistic studies suggested that SIX1 activated the Notch pathway to promote the malignant biological behaviors of NSCLC, which could be reversed by inhibiting the Notch signaling with γ-secretase inhibitor.Conclusions: SIX1 could facilitate multiple malignant biological behaviors by activating the Notch signaling pathway and function as a promising prognostic biomarker.