As further evidence of the importance of TGF-β activity in the impact of statins on GBM cells, we showed that simvastatin had a greater effect on the viability in high TGF-β activity GIC lines G34 and JWL-131 when exogenous TGF-β was added in both two-dimensional growth conditions (Figure 2F) and three-dimensional growth conditions in G34 (Supplementary Figure 3E), but not in low TGF-β activity GIC lines G44 and G528 (data not shown). Here, TGFB1 is linked to glioblastoma.