CYP27A1 and breast cancer: The literature to date on the role of 27HC in the etiology of breast cancer is conflicting with potentially different roles for this oxysterol in risk and progression, for example experimental models suggested a growth-promotion role [6, 7], and epidemiologic studies showing an inverse association between circulating 27HC and breast cancer risk in postmenopausal women [8] and CYP27A1 mRNA expression and death in breast cancer patients age 50 years and younger [10].