CYP1B1 and renal cell carcinoma: While CYP1B1 expression was weak or not detected in most of the normal kidney tissues, the majority of RCC samples showed moderate or strong CYP1B1 immunoreactivity with an average staining score of 1.84 ± 0.10 (versus 1.16 ± 0.21 in normal kidney tissues) (p < 0.01; Fig. 1b).