PLAU and renal cell carcinoma: Interestingly, Chautard et al.[22] observed clear differences in uPA and PAI-1 levels between tissue specimens from ccRCC (n = 85), papillary RCC (n = 11) and sarcomatoid RCC (n = 4) indicating that the RCC subtype is of importance and the use of mixed patient cohorts hampers the drawing of definite conclusions (Table 6).