CYP27A1 and breast carcinoma: Our data showing the link between 27OHC and ER-β are consistent with the results from the TCGA and METABRIC database, as we found that tumours that had high mRNA levels of CYP27A1 (and thus expected elevated 27OHC) also presented the increased expression of ER-β, suggesting that 27OHC may be a positive regulator of ER-β expression in breast cancer tumours [42].