PROS1 and Alzheimer disease: To emphasize a potential role of cell-cycle regulation and DNA repair in the symptomatic progression of AD, Yang et al. [34] showed that in brains of people who died with MCI, the percentage of hippocampal neurons positive for cell-cycle proteins (PCNA, cyclin D and cyclin B) was very close to that found in individuals who died in advanced stages of AD (demented).