CDKN2A and Alzheimer disease: In this study the levels of p53 and p21WAF1/CIP1 were even decreased upon prolonged CSS culture suggesting that the AD-induced senescence is not mediated through the p53-p21WAF1/CIP1 pathway rather by ROS-induced DNA damage response and increase of p16INK4a or the Skp2-p27Kip1-pRb pathway (Fig. 1).