CDK5/FBW7-dependent ubiquitination and degradation of EZH2 inhibits pancreatic cancer cell migration and invasion.

Pancreatic cancer is one of the most lethal cancer types. Enhancer of zeste homolog 2 (EZH2) is an oncogenic protein overexpressed in pancreatic cancer, and EZH2 could be a potential therapeutic target for the treatment of pancreatic cancer. Although significant progress has been made toward understanding the function and deregulation of EZH2 in cancer cells, the posttranslational regulation of EZH2 in cancer cells is still unclear. F-box and WD repeat domain-containing 7 (FBW7) acts as a tumor suppressor by targeting multiple oncoprotein substrates for ubiquitination and degradation. Here we demonstrate that EZH2 is a bona fide substrate of FBW7 in pancreatic cancer cells. We provide evidence that the activated CDK5 kinase is involved in the EZH2 phosphorylation that is required for FBW7-mediated degradation. We further show that FBW7 suppresses EZH2 activity and inhibits tumor migration and invasion via degradation of EZH2 in pancreatic cancer cells. Furthermore, immunohistochemistry analysis revealed that expression of EZH2 protein negatively correlates with FBW7 protein levels in a cohort of human pancreatic cancer specimens. Collectively, our findings demonstrate that FBW7 is a novel E3 ligase of EZH2 that regulates the EZH2 protein level in pancreatic cancer and represents a viable strategy for effective treatment of pancreatic cancer.