S100A9 and metastatic melanoma: Certain S100 protein subtypes, particularly S100A8 and S100A9, play a role in the inflammatory response to many types of neoplasms.25 Melanomas expressing CCL5, CXCL9 and CXCL10 have been associated with prolonged patient survival and are more likely to respond to ipilimumab, a human monoclonal antibody that improves overall survival in metastatic melanoma patients.26, 27