S100A11, also called calgizzarin or S100C, is an antiproliferative 10 kDa protein that is a member of the S100 family of EF-hand calcium binding proteins. It is found in the cytosol of proliferating fibroblasts and keratinocytes, but in the nucleus in differentiating cells. TGF-beta treatment or calcium-induced S100A11 serine phosphorylation induces nuclear translocation of S100A11 and subsequent growth inhibition in normal cells.