CCND1 and cancer: Activated AMPK phosphorylates MDMX, a protein that regulates P53 ubiquitination and turnover, leading to its stabilization and activation in promoting apoptosis or cellular senescence.[28] Cyclin D1 is overexpressed in many cancers including cancers of the breast, esophagus, lung, and bladder due to a defect in post-translational regulation.