Effect of gliotoxin, RO4929097, and DAPT on apoptosis in CLL cells. Sixteen CLL cases, including 3 cases with the recurrent NOTCH1ΔCT mutation (black lines), 8 cases expressing GSI-R nuclear NOTCH2 (pink lines), and 5 cases expressing GSI-S nuclear NOTCH2 (blue lines), were subjected to FACS analysis and the induction/inhibition of apoptosis in response to the indicated drug concentrations relative to controls was determined after 3 (A) and 7 days (B) in suspension cultures. The mean effects (±SD) of 0.5 µM RO4929097 on the percentage of apoptotic CLL cells after 7 days in relation to the GSI sensitivity of NOTCH2 (C) and the NOTCH1 mutational status (D) are indicated.