Stromal derived factors (SDFs) are a loosely defined group of molecules that are generated by stromal cells. Two of the stromal derived factors, SDF-1 and SDF-4 belong to the chemokine family. Other SDFs, such as SDF-2 and SDF-5 are not well defined and their biological functions are less known. SDF-2 is first isolated from the mouse stromal cell line ST2 as a secretory protein. The amino acid sequence deduced from the murine clone and the human homolog are conserved more than 92 %, and the aa sequence of SDF-2 shows similarity to those of yeast dolichyl phosphate-D-mannose, protein mannosyltransferases. SDF-1 and its receptor are strongly indicated in the progression of various cancers including breast cancer. SDF-2, SDF2-L1, SDF-4, and SDF-5 are ubiquitously expressed in various cancer cell lines and SDF-2, SDF-4 and SDF-5 are expressed in mammary tissues. These SDFs have prognostic value and warrant further investigation in their biological functions and clinical value.
