The REH cell line is a pre-B ALL cell line initiated from the peripheral blood of a patient with pre-B ALL in first relapse . REH cells carry the chromosomal translocation t(12;21) and chromosomal deletion del(12) producing respectively the ETV6-RUNX1 (previously known as TEL-AML1) fusion gene and the deletion of the residual ETV6 gene (previously known as TEL) . The pre-B Nalm6 cell line was also initiated from ALL relapse  and presents a near diploid karyotype with a translocation t(5;12)(q33.2; p13.2) . Nalm6 and REH cells were maintained in RPMI 1640 medium (Gibco, Thermo Fisher Scientific) containing 10% heat-inactivated fetal calf serum (Eurobio) supplemented with antibiotics (100 U/mL penicillin-G and 100 U/mL streptomycin, Gibco). The cells were maintained at 37 °C in a humidified incubator under a 5% CO2 atmosphere.