The calcium-binding Protein S100-A2 is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100-A2 was first detected in lung and kidney, and is mainly expressed in a subset of tissues and cells such as breast epithelia and liver. The S100A2 protein is a homodimer that undergoes a conformational change upon binding of calcium, and the active form functions in regulating cell proliferation and differentiation, gene transcription, and p53-dependent growth arrest and apoptosis. This protein is regarded as a putative tumor suppressor, and thus chromosomal rearrangements and reduced expression of S100A2 gene have been implicated in certain carcinomas.