p53 mRNA and protein levels in HCT-116 cells treated with MNNG. HCT-116 cells were treated with different concentrations of MNNG (0–100 μM) for 15 h, and total RNA was isolated for Northern blot analysis as described in Materials and Methods. After MNNG, treatment cells were also harvested for the preparation of whole cell lysate. Panel A shows a representative autoradiogram of the p53 mRNA and 18 S RNA. Panel B shows the p53 protein level in HCT-116 cells after treatment with 50 μM MNNG treatment for different periods. Panel C is a quantitative analysis of the p53 protein level. The data are mean ± SE of three different experiments. * = significantly different than untreated cells.