CYP27A1 and posterior cortical atrophy: Although increasing CYP27A1, the rate-limiting enzyme in the formation of 27HC, led to a corresponding increase in the 27HC content of LNCaP and 22RV1 PCa cells and conditioned medium, the increase in 27HC content directly attenuated the proliferation of LNCaP and 22RV1-derived xenografts, by decreasing intracellular cholesterol as a consequence of attenuating SREBP2 activity [33], while the expression of CYP7B1, the rate-limiting enzyme in the degradation of 27HC, increases with the development and progression of PCa [34].