Fig. 3. Effects of p53 and hemin on differentiation of K562 cells, assayed by the capacity to oxidize benzidine. Cells at an initial concentration of 0.2 x 106 cells/ml were incubated at 32°C (i.e., the temperature permissive for the wild-type conformation of p53) with or without hemin at 5 µM. After 4 days, cells were subjected to a benzidine oxidation test. The fraction (A) or total number per ml (B) of benzidine-oxidizing cells are shown. Mean values from nine separate experiments are shown. , culture medium; , 5 µM hemin; bars, SE.