Rs4 11 cells

Human HT1080 cells were purchased from the American Type Culture Collection. HT1080 cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM; Thermo Fisher Scientific) supplemented with 10% (v/v) fetal bovine serum (FBS; Thermo Fisher Scientific), penicillin (100 U/ml), and streptomycin (100 μg/ml) (Thermo Fisher Scientific). RS4;11 cells were purchased from the German Collection of Microorganisms and Cell Cultures (DSMZ) and cultured in α-MEM with ribo- and deoxyribonucleosides (Thermo Fisher Scientific) supplemented with 10% (v/v) FBS (Thermo Fisher Scientific), penicillin (100 U/ml), and streptomycin (100 μg/ml) (Thermo Fisher Scientific). Jurkat T cells were provided by A. Rösen-Wolff and cultured in RPMI 1640 medium (Thermo Fisher Scientific) supplemented with 10% (v/v) FBS (Thermo Fisher Scientific), penicillin (100 U/ml), and streptomycin (100 μg/ml) (Thermo Fisher Scientific). Murine thymocytes were isolated as described below and cultured in RPMI 1640 medium (Thermo Fisher Scientific) supplemented with 10% (v/v) FBS (Thermo Fisher Scientific), penicillin (100 U/ml), and streptomycin (100 μg/ml) (Thermo Fisher Scientific). All cells were cultured in a humidified 5% CO₂ atmosphere.

RS4‐11 cells and MV4‐11 cells were obtained from German Collection of Microorganisms and Cell Cultures GmbH (Braunschweig, Germany) and were maintained as previously described.11 The FLT3‐GFP hybrid genes were lentivirally packed and subsequently transduced in 32D cells. Cells were sorted for similar GFP production. Further details are outlined in the Supporting information.