Balancing and Differentiating p53 Activities toward Longevity and No Cancer?

Aging and death of cells (cellular senescence and apoptosis, respectively), triggered by or associated with cellular stress and DNA damage, impair organ function and homeostasis, leading to organismal aging and death. On the other hand, defects in physiologic regulations of cellular aging and death (escape from cellular senescence and failed apoptosis of severely damaged cells) contribute to uncontrolled cell division and genetic instability in cancer. In an oversimplified scenario, p53, an inducer of cellular senescence and apoptosis, may thus unfavorably contribute to aging and favorably suppress tumorigenesis. However, physiologic mechanisms should exist and therapeutic approaches may be developed to balance between aging and tumor suppression, for example, by differentially regulating cellular senescence, apoptosis, and other p53-mediated biological processes, such as DNA repair, autophagy, and energy metabolism. Possible mechanisms for such differential regulation of different subsets of p53 target genes may involve posttranslational modifications (e.g., phosphorylation and acetylation) and DNA binding cooperativity of p53. In this issue of Cancer Research, Timofeev and colleagues show that a previously uncharacterized phosphorylation in the p53 core DNA-binding domain regulates the DNA binding cooperativity and transcriptional activity of p53. Their mice deficient for this p53 phosphorylation were resistant to spontaneous and induced tumorigenesis, while they had shortened lifespan, but did not show progeria-like phenotypes. Prompted by this study, research on p53, aging, and cancer will explore balancing and differentiating different p53 activities toward a challenging goal of achieving longevity with no cancer.See related article by Timofeev et al., p. 5231.