PLK1 and nonpapillary renal cell carcinoma: To show that Plk1 protein levels, as Plk1 mRNA levels, correlated with survival in ccRCC, Plk1 protein levels were analyzed by IHC on tissue microarrays (TMA cohort of 131 samples (101, M0 and 30, M1) of ccRCC patients, Supplementary Table 2 and Supplementary Fig. 3a).