Abstract
PP2A holoenzymes account nearly 50% of Ser/Thr phosphatase activities in human cells, yet their roles in oncogenesis remain largely unexplored. A PP2A holoenzyme consists of a catalytic subunit, a scaffold subunit, and a regulatory subunit. We previously reported that PR55α, a PP2A regulatory subunit, supports the tumorigenic and metastatic potential of pancreatic cancer cells, and this is associated with its role in promoting YAP activation, which is essential for tumorigenesis and progression in most solid tumors, including pancreatic cancer. However, the direct role of PR55α in tumorigenesis has not yet been assessed. Using telomerase-immortalized human pancreatic ductal cells (HPNE), this research reveals a mechanism in which PR55α/PP2A cooperates with oncogenic KRAS(G12D) to drive cellular transformation and tumorigenesis in vivo. HPNE-transduced with PR55α and KRAS(G12D) exhibited accelerated proliferation and migration, and anchorage-independent growth, hallmark features of malignant transformation. Biochemical studies demonstrated that PR55α-induced YAP activation was further enhanced by KRAS(G12D), primarily through the inhibition of the MST/LATS cascade. The essential role of YAP activation in HPNE transformation by PR55α and KRAS(G12D) was confirmed by YAP inhibition. Finally, in vivo studies revealed that HPNE cells transformed by PR55α and KRAS(G12D) were tumorigenic in mice. Collectively, these findings highlight the critical role of PR55α/PP2A in supporting KRAS-driven tumorigenesis, providing new insights into the mechanisms underlying pancreatic cancer progression.