SP1 and glioblastoma: In addition to studying CYP17A1, we also evaluated whether Sp1 affects other steroidogenic enzymes, such as CYP11A1 and steroidogenic acute regulatory protein, both of which mediate the rate-limiting and the conversion of cholesterol to pregnenolone.1 Although these proteins are regulated by Sp1 in the adrenal gland,35 we did not identify their upregulation in GBM patients and did not observe any positive effects of Sp1 on these two genes (data not shown).