Research Perspective Volume 1, Issue 11 pp 949—953

Figure 1. p16 ^INK4a expression during aging of healthy and malignant cells. The expression of p16^INK4a mRNA increases with advancing age to ensure that potentially dangerous lesions, due to accumulated DNA damage, do not lead to malignancy. The increased expression of p16^INK4a mRNA has the potential to negatively modulate stem cell function through the induction of apoptosis or senescence. Our data illustrate the importance of this p16^INK4a dependent mechanism, since samples of older cancer patients have a lower instead of higher expression of p16^INK4a mRNA compared to samples of younger cancer patients. So, we hypothesize that suppression of defense mechanisms which protect older stem cells against accumulated cellular and DNA damage facilitates the development of cancer in older individuals.