VCPIP1 facilitates pancreatic cancer progression via Hippo/YAP signaling

The dys-regulation of Hippo signaling was observed in pancreatic adenocarcinoma (PAAD), while the over-activation of YAP was crucial for tumor progression. It is unclear why YAP was hyper-activated in PAAD, although the inhibitory phospho-cascade was still functional. Recently studies revealed that the ubiquitin modification of YAP also play important roles in Hippo/YAP axis and cancer progression. In order to understand the potential mechanisms of ubiquitination and deubiquitination process in YAP function, we carried out siRNA screening for critical deubiquitinases in PAAD. Via the deubiquitinases (DUB) library, we identified Valosin Containing Protein Interacting Protein 1 (VCPIP1) as an important effector in YAP function and PAAD progression. Inhibition of VCPIP1 hampered PAAD progression via Hippo signaling. Clinical data revealed that VCPIP1 was elevated in PAAD and correlated with poor survival in PAAD patients. Biochemical assays showed that VCPIP1 could interact with YAP and inhibit K48-linked poly-ubiquitination, which subsequently increased YAP stability. Interestingly, YAP could direct bind to VCPIP1 promoter region and facilitate its transcription in PAAD. Our study revealed a forward feedback loop between VCPIP1 and Hippo signaling in PAAD, indicating VCPIP1 as a potential therapeutic drug targets in PAAD.