CDKN2A and Alzheimer disease: However, many investigations utilizing immunostaining methods have demonstrated that various cell types, such as astrocytes, microglia, neurons, and ECs, in the AD brain exhibit elevated concentrations of senescence‐linked proteins, such as cell cycle inhibitors p16, p53, and p21 [205, 207, 213, 218, 219, 220, 221, 222, 223].