S100A9 expressed in ER(-)PgR(-) breast cancers induces inflammatory cytokines and is associated with an impaired overall survival.

Breast cancer is the most common cancer form among women today. Depending on hormone receptor status, breast cancers are divided into different subtypes with vastly varying prognosis. S100A9 is a calcium-binding protein that is associated with inflammation and expressed not only in myeloid cells but also in some tumours. The role for S100A9 in the malignant cells is not well characterised; however, previous studies have shown that the protein could have important immune-modulating properties.