HES1 and acute lymphoblastic leukemia: In concordance with our cell line data and PDX data, in the conditional Pten-deficient T-ALL mouse model, we observed reduction in the expression of BRD4, surface CD44, HES1 (a direct target of Notch1), and MYC in BM T-ALL cells from the ARV-825-treated mice (Fig. 5F upper and lower panel).