Mathematical simulation of the time course of p53 and Mdm2 protein concentrations during their interactions was carried out. The system states corresponding to threatened uncontrolled apoptotic cell death accelerating aging processes and to situation with hypersuppression of p53-dependent apoptosis fraught with high risk of cancer were modeled. New data indicate the possibility of description (within the framework of mathematical model used in the study) of the p53 and Mdm2 proteins feedback mechanism, which could guarantee adequate reaction to serious DNA damage.