PLAU and head and neck squamous cell carcinoma: uPA has been studied in human medicine in several sample types, including serum levels in patients with head and neck squamous cell carcinoma [29], breast cancer [30], ovarian cancer [31] and prostatic cancer [32], and their results suggest that uPA plays important roles in cancer evolution, particularly in processes such as angiogenesis and metastasis and might also be of prognostic and predictive value.