Cells were centrifuged, the supernatant was aspirated, and 300 µl PBS was added. Cells were centrifuged, the supernatant was aspirated, and the pellet was resuspended in the appropriate volume of P3 supplement buffer (20 µl per condition by mixing 16.4 µl P3 buffer and 3.6 µl supplement 1; Lonza, V4XP-3032). The cells were transferred into 16-well nucleovette strips (Lonza). After 10 min at room temperature, electroporation was performed on an Amaxa 4D Nucleofector (Lonza) with the DS-138 custom programme unless otherwise stated. The cells were then incubated for 10 min at 37°C and then 80 µl pre-warmed medium was added to the electroporation chambers. Cells were centrifuged, supernatant was discarded, and the pellet was resuspended in 20 µl Matrigel per condition and seeded in 48-well plates (100,000 cells per well).