Cell Growth Regulator with EF Hand Domain Protein 1 (CGREF1) is a secreted calcium ion binding protein. CGREF1 contains two EF-hand domains and both EF-hands are required for function. Human CGREF1 is synthesized as a 301 amino acid precursor that contains a 19 amino acid signal sequence, and a 282 amino acid mature chain. CGREF1 is probably digested extracellularly by an unknown serine protease generating extremely hydrophobic bioactive peptides. CGREF1 mediates cell-cell adhesion in a calcium-dependent manner. In addition, CGREF1 is able to inhibit growth in several cell lines.