Given the upregulation of the genes for uPA and its receptor uPAR in metastatic tumors compared to PRI- and SES (see also Supplementary Image 4) and their contribution to tumor progression through different pathways and functions, we examined spatially localized uPAR protein levels in an extended cohort of cSCC tumors of the head and neck. Here, PLAU is linked to skin squamous cell carcinoma.