CTSB and cancer: Cathepsin B and L are secreted from cancer cells to the extracellular space where they are directly involved in the proteolytic cleavage and activation of heparanase, matrix metalloproteases (MMP), and urokinase plasminogen activator (uPa), which are important mediators of extracellular matrix degradation and actively involved in cancer invasion and metastasis [116,117].