Aiming to investigate the metabolic transformation by 27-hydroxylation of oncosterone and its precursors (5,6α-EC, 5,6β-EC, and CT), we first evaluated the expression of CYP27A1 in normal mammary tissue, breast cancer and human breast cancer cell lines through the analyses of transcriptomic databases (GTEx and TNM plot). Here, CYP27A1 is linked to breast carcinoma.