In addition, IL-8 and other pro-inflammatory cytokines also cooperate with TGF-β1 in the production of matrix metalloproteinase-9 (MMP-9) by breast cancer cells, and TGF-β-activated protein kinase 1 is required for this response, contributing to the metastatic potential of breast cancer cells [30]. This evidence concerns the gene CXCL8 and breast cancer.