Effect of long-term GM-CSF deprivation on expression of MDM2 and p53 proteins in TF-1 control vector transfectants, in TF-1 MDM2 transfectants, and in GM-CSF–independent TF-1 cells. GM-CSF–independent TF-1 AML cells were cultured in fresh media with GM-CSF (1 ng/mL) for 2 days, washed three times with PBS, and resuspended in fresh media with or without GM-CSF (1 ng/mL) for 16 hours. TF-1 cells transfected with either control vector or the MDM2 gene were cultured in media with G418 (400 μg/mL) and GM-CSF (1 ng/mL) for an additional 16 hours. Expression of MDM2, p53, and actin proteins were examined by immunoblotting.