BCO2 and adrenal cortex carcinoma: BCO2 is a mitochondrial enzyme involved in the production of retinoids from provitamin A carotenoids, which is a key source of retinoids in our diet.46 Specifically, BCO2 asymmetrically cleaves β-carotene to generate β-apo-10′-carotenal, which is then converted to retinoids by BCO1.47,48 In the paediatric ACC cohorts, shorter PFS was seen in patients with low transcript levels of Aldehyde Dehydrogenase 1 Family Member A2 (ALDH1A2).