ATO induces up-regulation of p21 expression in cells expressing wt p53.

Cells were cultured as above for 0, 16, 24, 32, and 48 hours with 6 μM ATO, and aliquots were taken for Western immunoblotting; 50 μg protein extract was loaded onto each lane. Loading control was performed according to the results obtained from a prerun of gels stained for protein by Coomassie blue and quantitation of protein bands by densitometry. For further experimental details, see the legend to Figure 8 and “Materials and methods.”