Figure 1.p16 INK4a expression during aging of healthy and malignant cells.
The expression of p16INK4a 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 p16INK4a
mRNA has the potential to negatively modulate stem cell function through
the induction of apoptosis or senescence. Our data illustrate the
importance of this p16INK4a dependent mechanism, since samples
of older cancer patients have a lower instead of higher expression of p16INK4a
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.
