H2BC21 and glioblastoma: The vascular niche has been suggested as a key regulator of glioblastoma stem cells, with potential impact on GBM stem cell quiescence.[31, 32] To assess the capacity of our model to maintain a quiescent niche for GBM cells, we leveraged a doxycycline (Dox) inducible histone 2B (H2B)‐GFP quiescence reporter that we had previously developed,[23] with quiescent or slow dividing cells retaining nuclear GFP signals while fast dividing cells lose the H2B‐GFP signals over time (Figure 6a).