Mec1 cells

All work with primary human material was performed in compliance with the national and local regulations. Primary CLL cells were isolated from PB and BM of CLL patients via Biocoll (Biochrom AG, Berlin, Germany) density gradient centrifugation and cultured in RPMI 1640 medium supplemented with 10% fetal calf serum, penicillin (62.5 μg/ml) and streptomycin (100 μg/ml) at a density of 1 × 10⁶ cells/ml. MEC1 cells (ATCC, Manassas, VA, USA) were cultured in IMDM medium containing 10% fetal calf serum, penicillin and streptomycin. Cells were split twice a week at a density of 10⁶ cells per ml medium. For lentiviral packaging, HEK293FT (ATCC) cells were grown in DMEM supplemented with 10% fetal bovine serum (Life Technologies), penicillin and streptomycin, L-glutamate (100x concentrate, Life Technologies) and essential amino acids (100 × concentrate, Life Technologies) and split three times a week in a ratio of 1:5. Dactolisib, pictilisib, rapamycin, wortmannin (LC Laboratories, Woburn, MA, USA) and GANT61 (Merck, Darmstadt, Germany) were dissolved in dimethylsulfoxide, stored as stock solution at −20 and diluted to final concentrations as indicated in the Results section.