PLAU and cancer: Recently, we demonstrated that TMPRSS4 upregulates expression of the urokinase-type plasminogen activator (uPA) gene, which encodes a well-known serine protease and whose expression correlates with invasion and metastasis, through c-Jun N-terminal kinase (JNK) signaling activation and subsequent activating protein-1 (AP-1) activation to induce cancer cell invasion [19], and that TMPRSS4 upregulates pro-uPA processing through its proteolytic activity [20].