HMGCS1 and glioblastoma: Additionally, the expression of 3-hydroxy-3-methylglutaryl-CoA synthase 1 (HMGCS1), HMGCR, and 3β-hydroxysteroid-Δ24 reductase (DHCR24), which play a key role in cholesterol de novo synthesis, is reduced in GBM cells 34, indicating that the de novo synthesis pathway of cholesterol in GBM is suppressed.