S100A4 is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100 belongs to the family of calcium binding proteins such as calmodulin and troponin C. S100A is composed of an alpha and beta chain whereas S100B is composed of two beta chains. S100 protein is also expressed in the antigen presenting cells such as the Langerhans cells in skin and interdigitating reticulum cells in the paracortex of lymph nodes. S100 proteins are localized either in the cytoplasm or the nucleus of a wide range of cells. S100 proteins are involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. S100A4 may function in motility， invasion， and tubulin polymerization. There are at least 13 members in the S100 gene family， which are located as a cluster on chromosome 1q21. Chromosomal rearrangements and altered expression of the S100A4 gene have been implicated in tumor metastasis.
