FIGURE 1.

TPA enhances p53 levels. A, a time course study of TPA effect (100 nmol/liter) on cellular p53 levels. JB6 cells were treated with TPA for the indicated period of time. Cell lysates were prepared, and p53 protein was detected by Western blotting. Band intensities were quantified by densitometric scanning, and the relative intensity of p53 was calculated by normalizing to corresponding glyceraldehyde-3-phosphate dehydrogenase (GAPDH) band intensity. Each data point represents the mean ± S.D. of four independent samples. *, p < 0.05; **, p < 0.01 compared with the DMSO-treated group. B, detection of p53 in purified mitochondria and following treatment of TPA for 1 h by Western blotting. The purity of mitochondrial fractions was verified by reprobing the membrane with antibodies specific to nuclear protein PCNA.