FUBP1 and breast cancer: The results showed that no obvious FIR protein band was found in the FUBP1-co-immunocoprecipitates of BC cells overexpressing circACTN4, whereas FIR was clearly detected in the co-immunocoprecipitates by western blot after circACTN4 was knocked down, which suggest upregulated circACTN4 remarkably weakened the binding of FIR to FUBP1 while downregulated circACTN4 significantly strengthened the interaction between FUBP1 and FIR (Fig. 6e).