Dox-inducible down-regulation of Bcl-X_L in stable pTet-ON transfectants in vitro. (A) Western blot analysis of Bcl-X_L expression in a representative Ba/F3-NPM/ALK⁺ clone (N/A-pAS) cultured in absence/presence of a single dose of doxycycline (Dox 1 μg/mL) for the indicated times. (B) A Ba/F3-N/A.ASBcl-X_L antisense-inducible clone (N/A-pAS) and a Ba/F3-NPM/ALK⁺ clone bearing an empty vector (N/A-pEV) were grown in triplicate in the absence (-Dox) or presence (+Dox) of doxycycline for 4 days. A single dose of doxycycline (1 μg/mL) was added in the culture medium at the beginning of the experiment and replaced after 2 days. Apoptosis was evaluated by AO staining as reported in Figure 4D. Error bars indicate SD.