NPM1 and breast cancer: Importantly, we observed that NPM phosphorylation was significantly reduced in rKSHV.219-EA.hy926 (4.8-fold) and BC-3 cells (3.7-fold) silenced for CDK6 as compared to cells stably expressing the scrambled control (Figures 1B–D) or sh-CDK4 (Figures 1C and 1D).