Furthermore, stromal derived factor (SDF)-1 interaction with the chemokine receptor CXCR4, which is essential for normal stem/progenitor cell function, promotes carcinogenesis, metastasis [377] and trans-endothelial migration of cancer cells by stimulating gelatinase B/MMP-9 secretion, disrupting basement membrane and inducing vascular permeability, promoting tumour cell extravasation. Here, MMP9 is linked to cancer.