EBP50(ERM-binding phosphoprotein-50)，a multifunctional adapter protein with 358 amino acids and two PDZ domains, regulates cell growth and migration. Lines of evidences indicate that it is a potential cancer suppressor protein. Loss of heterozygosity (LOH) and intragenic mutation of the ebp50 gene have been found in both primary breast tumors and breast cancer cell lines. EBP50 suppresses the breast cancer cell proliferation via its interaction with many tumor suppressor protein including PTEN, SYK, MERLIN, etc. Here the molecular structure of EBP50, signal pathway regulated by EBP50, and the relationship between breast cancer development and EBP50 are discussed.