MAPK3 and breast cancer: Although little has been unveiled about the functions of SDCB2 in cancer, its close sibling, syntenin-1 (SDCB1), has been regarded as a key regulator of proliferation and metastasis in many cancers, including BC [39,40,41], and is one that activates various signaling cascades promoting cell proliferation and invasion, e.g., p38/NF-κB, p38/MAPK, ERK1/2, and AKT.