NOTCH1 and glioblastoma: We then further studied ZR30’s effect on NOTCH1 expression in six cell lines of GBM, under active (in the first two days) or slow (the second two days) growth stages, controlled by their growth medium with, or without, serum supplementation (A172, T98G, U87, LG11) or growth factors (U251-NS, 51A), respectively.