SPIN1 accelerates tumorigenesis and confers radioresistance of non-small cell lung cancer via orchestrating the FOXO3a/FOXM1 axis

Abstract

Background Radioresistance is a predominant obstacle of effective treatments in non-small cell lung cancer (NSCLC), while the underlying mechanism remains incompletely elucidated. Spindlin 1(SPIN1) has been reported to participate in tumor initiation and progression. Herein, this study aims to explore the role and mechanism of SPIN1 in NSCLC progression and radioresistance.Methods Bioinformatics analysis, immunohistochemistry (IHC) and western blotting were performed to test SPIN1 expression in NSCLC samples and cell lines. The carcinogenic role of SPIN1 was evaluated by cell growth and proliferation, EdU staining, transwell and colony formation assays. Besides, the radiosensitivity of NSCLC cells was determined by clonogenic cell survival, neutral comet and γ-H2AX and Rad51 foci formation assays. Xenograft tumor model was constructed to access the effects of SPIN1 on tumorigenesis and radiosensitivity. RNA sequencing, quantitative real-time PCR, CHX and ubiquitination assays were applied to elucidate the correlation between SPIN1 and FOXO3a-FOXM1 axis.Results We found that SPIN1 was highly expressed in NSCLC tissues and cell lines compared with corresponding controls. And SPIN1 overexpression was closely correlated with disease progression and poor prognosis in NSCLC patients. Functionally, depletion of SPIN1 impaired cell proliferation, delayed cell cycle progression and suppressed migration and invasion. Moreover, SPIN1 knockdown reduced the clonogenic capacity, impaired double-strand break (DSB) repair and enhanced NSCLC radiosensitivity. Mechanistically, forkhead box M1 (FOXM1) was identified as a key downstream effector of SPIN1 in NSCLC cells. Furthermore, SPIN1 facilitates MDM2 mediated FOXO3a ubiquitination and degradation, leading to FOXM1 upregulation. More convincingly, reintroduction of FOXM1 markedly abolished the inhibitory effects and elevated radiosensitivity induced by SPIN1 depletion.Conclusion Our results suggest that the SPIN1-MDM2-FOXO3a/FOXM1 signaling axis is essential for NSCLC progression and radioresistance, and it could serve as therapeutic targets in irradiation-resistance NSCLC.