Schematic of possible mechanisms by which sex hormones modulate cancer stem cells (CSCs) in glioblastoma. Sex hormones can regulate the phenotype and function of CSCs by direct binding to nuclear receptors and/or by indirect signaling from other cells expressing sex hormone receptors in the tumor microenvironment. Abbreviations: AR, androgen receptor; (m)ER, (membrane-bound) estrogen receptor; (m)PR, (membrane-bound) progesterone receptor.