CYP27A1 and breast cancer: In summary, the findings of prior human studies suggest a potential dual role for 27-HC in breast cancer progression as higher CYP27A1, the enzyme converting 27-HC, expression was generally associated with a poorer prognosis among postmenopausal participants [13] and a better prognosis among pre-menopausal [12] or presumably pre-menopausal breast cancer patients [11].