SOS (Son of sevenless) is a group of guanine nucleotide exchange factors, including family members like SOS1 and SOS2. They are mainly located in the cytoplasm and widely expressed in various cells and tissues. SOS participates in regulating cell proliferation, differentiation, and survival by activating Ras proteins. They promote the transition of Ras from a GDP-bound state to a GTP-bound activated state, thereby activating signaling pathways such as MAPK. Mutations or abnormal expression of SOS are associated with the development of various cancers, developmental abnormalities, and genetic diseases.