The FBXO32/ATR/ATM axis acts as a molecular switch to control the sensitivity of osteosarcoma cells to irradiation through its regulation of EXO1 expression

Abstract

Background: Osteosarcoma (OS) is the most common primary bone cancer in children and adolescents. In clinical treatments, the insensitivity of OS to conventional radiotherapy regimens significantly contributes to poor patient prognosis and survival. EXO1 is responsible for DNA repair pathways and telomere maintenance. Meanwhile, ATM and ATR are considered switches as they can regulate the expression of EXO1. However, their expression and interaction in OS cells under irradiation (IR) remains unclear. This study aimed to investigate the roles of FBXO32, ATM, ATR and EXO1 in OS radiotherapy insensitivity and poor patient prognosis and explore potential pathogenic mechanisms. Methods: Bioinformatics methods were employed to analyze differential gene expression and the correlations with prognosis in OS. Cell counting kit 8 assays, clone formation assays, and flow cytometry were used to evaluate cell survival and apopotosis under IR. Co-IP assays detected protein-protein interactions. Results: Bioinformatics analysis revealed that EXO1 is closely related to the survival, apoptosis and poorer prognosis in OS. The silencing of EXO1 suppressed cell proliferation and increased the sensitivity of OS cells. Molecular biological experiments showed that the ATM and ATR acted as the switch to regulate EXO1 expression under IR. Conclusion: Higher expression of EXO1, which was closely correlated with IR insensitivity and poorer prognosis, might be used as a prognostic indicator for OS. Phosphorylated-ATM enhanced the expression of EXO1, and phosphorylated-ATR induced the degradation of EXO1. More importantly, FBXO32 degraded ATR via ubiquitination in time dependent. Our data may provide a reference for future research on mechanisms, clinical diagnosis, and treatment of OS.