The lethal effect of the supernatant from the BALB/MK cells transduced with LBmSN On day 1, BALB/MK cells were seeded on a 6 well plate at 4 × 104 cells/well, and 1 × 106 cells of the virus producing cell lines PA317/LBmSN and PA317/LXSN were seeded in 25 cm2 flasks. On day 2, the media of the PA317 cell clones were replaced with the EMEM supplemented with 10 % FBS and without EGF. On day 3, the media of PA317 cells containing virus were harvested, centrifuged at 10,000 rpm per 1 min in Eppendorf centrifuge. The media of BALB/MK cells were replaced by 2 ml of virus solution and complemented with 5 ng/ml of EGF and 8 μg/ml of Polybrene. In parallel, 1 × 104 BALB/MK cells were seeded on a 24 well plate. On day 4, the media were replaced by fresh ones. On day 5, the medium of BALB/MK cells was replaced by 0.5 ml of the medium of the LBmSN transduced BALB/MK cells, which was previously centrifuged at 10,000 rpm/ 1 min. After 7 days, the cells were photographed (X 200). The results are representative of at least three experiments, which gave essentially the same results. (A) The BALB/MK cells incubated with supernatant of BALB/MK cells transduced with LXSN; (B) The BALB/MK cells incubated with supernatant of BALB/MK cells transduced with LBmSN.