GSI I treatment in primary leukemic Sézary cells inhibits Notch and induces apoptosis. (A) CD7⁻ CD4⁺ cells isolated from peripheral blood of a patient diagnosed with SS were treated with GSI I 5μM for 12 and 24 hours and analyzed with Western blot for Notch1. (B) Primary leukemic Sézary cells treated with increasing concentrations of GSI I for 24 hours and analyzed for thymidine incorporation as in Figure 1G. *P < .05. (C) Induction of proapoptotic caspases 3 and 7 after treatment of primary leukemic Sézary cells with increasing concentrations of GSI I for 24 hours. Data are mean ± SD. *P < .05.