TOP2B and glioma: To further confirm that Top2β is selectively expressed in GSC, we analyzed its expression levels in different GBM cell lines such as U87, U251, and T98G as well as glioma stem cells NCH421k [both undifferentiated (abbreviated as NCH) and differentiated with all-trans retinoic acid (NCH-A)], normal neural stem cells (NSC), and normal human astrocytes.