S100 Calcium Binding Protein A9 (S100A9)

S100 calcium binding protein A9 has been implicated in the abnormal differentiation of myeloid cells in the stroma of cancer. This contributes to creating an overall immunosuppressive microenvironemnt that may contribute to the inability of a protective or therapeutic cellular immune response to be generated by the tumor-bearing host.

Outside of malignancy, S100A9 in association with its dimerization partner, S100A8 (MRP8 or calgranulin A) signals for lymphocyte recruitment in sites of inflammation. S100A9/A8 (synonyma: Calgranulin A/B; Calprotectin) are also regarded as marker proteins for a number of inflammatory diseases in humans, especially in rheumatoid arthritis.