The protein expression levels of CDK2, CDK4, CDK6, and phospho-Rb (Ser807/811) declined in quiescent Pca cells (Figures 2C,D), and almost all of them began to recover at 12 and 16 h after quiescent LNCaP and PC-3 cell re-entry into the cell cycle, respectively. Here, CDK4 is linked to posterior cortical atrophy.