MMP9 and breast carcinoma: It has been demonstrated that coupling of S1P to S1PR3 can induce CRP expression via CCAAT/enhancer-binding protein β (C/EBPβ), activate Rac1/Nox-4/ROS/ERK pathways, and upregulate MMP9 activity, contributing to the aggressiveness and invasion of breast cancer (Kim et al., 2011; Kim et al., 2014).