In vitro synergy between Notch inhibitors and multiple targeted therapies identified from the CRISPR screen. (A) Cell viability assay of T-ALL cells in response to PD-0332991, CB-103, or GSI. (B) Isobologram plots of T-ALL cells in response to a serial dilution of combination treatment of PD-0332991 with CB-103 (left) or GSI (right), starting at 3 ratios of their corresponding 50% inhibitory concentration. Purple, ratio (Notch inhibitor: PD-0332991) = 1:1; green, ratio = 1:2.5; gray, ratio = 1:0.5. x-axis shows the concentration of CB-103. The values shown are mean ± SD (n = 4 biologically independent samples, 2 independent experiments performed). (C) Table summarizing combination index (CI) of Notch inhibitors together with PD-0332991, Ruxolitinib, or CAL-101. (D) Total protein levels of NICD and c-MYC as well as phosphorylation level of p-RB in DND-41 cells (left) and RPMI-8402 cells (right). Cells were treated with DMSO or corresponding single drugs or drug combinations for 24 hours. Actin was used as the loading control.