Of note, although the proposed p21-dependent control of E2F1 activity by miR-10b was observed only in a subset of cultured glioma cell lines, specifically those expressing high levels of p21, this mechanism may be widely applicable, as the majority of GBM tumor samples express high levels of p21 (Figure 4F, [11–13]). This evidence concerns the gene CDKN1A and central nervous system cancer.