NPM-ALK expression protects cells from death. (A) Schematic representation of cell survival after actinomycin D treatment in control (pcDNA3 or NPM-ALK dead) or NPM-ALK-transfected NIH3T3 cells. Total RNA was extracted at different times after ActD treatment (1, 2, 4, 8, 10, 15, and 24 hours), quantified, and expressed relative to the amount of RNA found in untreated (0 hours) cells, arbitrarily expressed as 1. The vertical bars indicate the time at which 50% of the starting amount of RNA was recovered in the different cell lines (10 hours in control cells, 22 hours in NPM-ALK-expressing cells). The cells were also fixed and stained with DAPI for counting and to determine their viability. Shown are representative images of NIH3T3 cells expressing NPM-ALK or the mutated dead variant 0 hours and 36 hours after ActD. (B) At different times after ActD treatment, the different ALCL-derived cell lines were stained with trypan blue and counted in a hematocytometer. The ratios between healthy and dead cells were determined.