CYP19A1 and glioblastoma: In addition, TMZ-resistant GBM cells increased the expression of steroidogenic enzymes, including CYP11A1, CYP17A1, and CYP19A1, which are involved in the biosynthesis of steroids, such as pregnenolone, dehydroepiandrosterone (DHEA), and 17beta-estradiol [48, 49, 57] (Fig. 1).