Multiple steroidogenic enzymes, including CYP17A1, are shown to be expressed in different areas of brain, such as amygdala, cerebellum, corpus callosum and hippocampus.20 CYP17A1 also aggressively participates in steroidogenesis in brain.21 Therefore, before we studied the role of CYP17A1-mediated steroidogenesis in glioma, we also confirmed the expression of CYP17A1 in immortalized human astrocyte, SVG-P12, GBM cell line, U87MG and human brain tissue (Supplementary Figure S2). This evidence concerns the gene CYP17A1 and central nervous system cancer.