MMP9 and breast cancer: It was also shown that hypoxia and the reoxygenation-driven regulation of Syk-Lck cross-talk could enhance the translocation of Sp1 into nuclei, leading to increased expression of target genes, such as urokinase-type plasminogen activator (PLAU) and matrix metalloproteinase-9 (MMP9) in MCF-7 breast cancer cells [32].