Ha pe

Cells were gathered and washed in staining buffer containing 1% FBS and 2 mM of EDTA in PBS. In experiments utilizing the 24xFGB vector system, cells were first incubated with a biotinylated anti-cMyc antibody (Miltenyi Biotec, Bergisch Gladbach, Germany) for 30 min at 4 °C, and, after washing, they were subsequently stained for 30 min in the dark at 4 °C with an antibody cocktail consisting of streptavidin-conjugated APC secondary antibodies, Thy1.1-PE-Cy7 (clone OX-7) (both Biolegend) and HA-PE (Miltenyi, Bergisch Gladbach, Germany). Prior to analysis, cells were washed and resuspended in staining buffer containing 0.1 µg/mL of DAPI for live/dead cell exclusion. No prior antibody staining was needed for experiments using the 6xFGB vector system. Data were acquired with the CytoFlex S (Beckman Coulter, Brea, CA, USA), FACSCalibur, or FACSCanto (both BD, Franklin Lakes, NJ, USA). For cell sorting, the BD FACSAria Fusion cell sorter was used. Data analysis was performed with FlowJo 10 (BD, Franklin Lakes, NJ, USA). Gating strategies are displayed in Supplementary Figure S1.