Effect of doxycycline-induced BCR/ABL expression on factor-independent growth. (A) MTT proliferation assay on (▪) TonB210.1, (•) B210 (constitutively expressing BCR/ABL), or (▴) parental BaF3 cells grown for 3 days with varying concentrations of doxycycline in growth media without IL-3. OD 570 nm is directly related to proliferation. (B) Cell viability of TonB210.1 cells over time upon doxycycline withdrawal. Cell viability was assayed by trypan blue exclusion over a 3-day period following removal (−dox; ▪) or continuation (+dox; •) of doxycycline in the growth media.