MMP9 and breast cancer: It is known that the RPRM regulates apoptosis by inhibiting the expression of BCL2 and regulates cell cycle by activating expression of CDKN1B, alone or in conjunction with BRCA1. Taken all together, these findings might be indicative of additional pathways to the classic PI3K/Akt/β-catenin/MMP-9 signaling that are contributing to the sensitive or resistant behavior of breast cancer cells to paclitaxel [31].