Circular RNA FAT Atypical Cadherin 1 (Circfat1)/microrna-525-5p/spindle and Kinetochore-Associated Complex Subunit 1 (SKA1) Axis Regulates Oxaliplatin Resistance in Breast Cancer by Activating the Notch and Wnt Signaling Pathway

Increasing evidence has confirmed the vital roles of circular RNAs (CircRNAs) in the drug resistance of breast cancer (BC). Herein, we intended to study the effect of circular RNA FAT atypical cadherin 1 (circFAT1) on BC oxaliplatin (OX) resistance and find out the potential molecular mechanism in it. In this study, mRNA and protein levels of genes were measured by RT-qPCR and western blotting, respectively. Luciferase reporter assay confirmed the relationship between microRNA-525-5p (miR-525-5p) and circFAT1 or spindle and kinetochore-associated complex subunit 1 (SKA1). CCK-8, transwell, and flow cytometry experiments were utilized to investigate the chemosensitivity, migration, invasion, and apoptosis of BC cells. Gene Set Enrichment Analysis (GSEA) was applied to discover possible pathways related to SKA1. It was uncovered that circFAT1 was overexpressed in OX-resistant BC tissues and cells. Functional experiments showed that circFAT1 depletion reduced the level of chemoresistance-related genes. Moreover, circFAT1 knockdown remarkably facilitated apoptosis and decreased OX (half-maximal inhibitory concentration) IC50 value, migration, and invasion in OX-resistant BC cells. It was identified that miR-525-5p directly targeted circFAT1 and SKA1. Besides, rescue assays exhibited that circFAT1 promoted OX resistance in BC cells via the miR-525-5p/SKA1 regulatory network. Furthermore, GSEA and western blotting identified that SKA1 activated the Notch and Wnt pathway in OX-resistant BC cells. In conclusion, our results demonstrated that circFAT1 conferred OX resistance in BC by regulating the miR-525-5p/SKA1 via the Notch and Wnt pathway, providing a potential therapeutic target for patients with OX-resistant BC.