Unlike most CYPs, it displays low expression levels in normal tissues, but is frequently overexpressed in tumours.7,8 It has been even considered as a “universal tumor antigen”9 and was included in a list of cancer antigen prioritisation for targeted therapies by the National Cancer Institute (NCI).10 As all CYPs, CYP1B1 is able to catalyse oxidation reactions, and its main known substrates are oestradiol and polyaromatic carcinogens such as benzopyrene.8 However, these catalytic functions cannot explain its characteristic overexpression in tumour tissues. Here, CYP1B1 is linked to cancer.