MAPK3 and breast cancer: Among the positive contributors is also circRREB1, which causes increased invasion, growth, and metastasis in BC by binding to guanine nucleotide-binding protein subunit beta-4 (GNB4) and activating the extracellular regulated kinase 1/2 (ERK1/2) pathway (Table 2) (H. Chen et al. 2024a, b).