Considering that CYP1B1 expression has been reported increased in tumor tissues compared to the normal counterpart [16, 39] and given that the levels of 4OHE2 have been found higher in hormone-sensitive tumors like breast cancer respect to normal tissues [20], this cytochrome has attracted increasing interest as potential target in further anticancer strategies, especially in the treatment of hormone-related tumors [40]. This evidence concerns the gene CYP1B1 and breast carcinoma.