24-Hydroxycholesterol Suppresses Steroid 5Α-Reductase-catalyzed Conversion in Human Glioblastoma Cell Lines: a Novel Link Between Brain Cholesterol Homeostasis and Androgen Metabolism

Glioblastoma is the most aggressive primary brain tumor in adults. Androgens are reported to influence the development of glioblastoma. Dihydrotestosterone (DHT) is formed from testosterone by action of the enzyme steroid 5α-reductase and is the most potent growth-inducing androgen metabolite.24-Hydroxycholesterol, another steroid in the brain, is pivotal for brain cholesterol homeostasis and has been suggested to influence glioblastoma cells. However, a connection between 24-hydroxycholesterol and androgen metabolism related to glioblastoma has not previously been reported. The present study reports that human T98G glioblastoma cells metabolize testosterone into DHT, 3α-androstanediol and androstenedione. The 5α-reductase pathway converted testosterone to DHT and further to 3α-androstanediol. The 17β-hydroxysteroid dehydrogenase pathway metabolized testosterone to androstenedione. Results indicated that the 5α-reductase pathway is the major pathway for testosterone metabolism in this cell line. 24-Hydroxycholesterol significantly suppressed the conversion of testosterone to DHT and 3α-androstanediol, to a similar degree as the synthetic 5α-reductase inhibitor finasteride. Suppression of DHT formation resulted in increased metabolism to androstenedione. Similar effects on DHT formation were observed with the LXR agonist T0901317 as with 24-hydroxycholesterol. In addition, 24-hydroxycholesterol suppressed DHT formation in patient-derived primary GB cell lines U3009 and U3013, indicating that the observed connection between 24-hydroxycholesterol and androgen metabolism is not unique for T98G cells. Furthermore, 24-hydroxycholesterol-mediated suppression of DHT formation was also observed in human neuroblastoma SH-SY5Y cells.To summarize, the present data provide information on androgen metabolism in glioblastoma cells and indicate a previously unknown link between cholesterol homeostasis and growth-inducing androgens in glioblastoma and potentially other cell types.