Antileukemic effects of Hes1 inactivation in T-ALL. (A) Quantitative RT-PCR analysis of Hes1 expression across tumor cells isolated from Hes1 conditional knockout T-ALL (ΔE-NOTCH1 Rosa26 Cre-ERT2 Hes1^flox/flox)-bearing mice after 24 hours of treatment with vehicle only (n = 3) or tamoxifen (n = 3) in vivo. (B) Representative image of mouse spleens and (C) quantification of spleen weight of Hes1 conditional knockout leukemia-bearing mice treated with vehicle only or tamoxifen for 24 hours. Scale bar represents 1 cm. (D) Hematoxylin and eosin-stained tissue micrographs of liver and spleen sections from Hes1 conditional knockout leukemia-bearing mice treated with vehicle or tamoxifen. Scale bars represent 50 μm. (E) Quantification of leukemia lymphoblasts as percentage of green fluorescent protein-positive cells in Hes1 conditional knockout NOTCH1-induced leukemia-bearing mice treated with vehicle only (n = 6) or tamoxifen (n = 5) in vivo. (F) Kaplan-Meier survival curves of Hes1 conditional knockout NOTCH1-induced leukemia-bearing mice treated with vehicle only (n = 6) or tamoxifen (n = 5) in vivo. (G) Quantification of apoptosis in Hes1 conditional knockout leukemia cells treated with ethanol (ETOH) as control or tamoxifen (4-OH TMX) in vitro. (H) Quantification of cell proliferation in Hes1 conditional knockout leukemia cells treated with vehicle or tamoxifen in vitro. (I) Cell cycle analysis of Hes1 conditional knockout leukemia cells treated with vehicle or tamoxifen in vitro. Bar graphs indicate mean values of triplicate measurements; error bars represent standard deviation.