MMP9 and breast cancer: Additionally, FN over-expression has been correlated with poor clinical outcome in breast cancer patients, whilst its involvement in breast cancer invasion and metastasis has been demonstrated to involve the up-regulation of matrix metalloproteinases (MMPs) MMP-2 and MMP-9 via the FAK/ILK//ERK/PI3K/NF-κB cascade of pathways [23,24] (Figure 1C).