The role of Pygopus 2 in rat glioma cell growth.

Glioma is a common malignant tumor of the human neural system, and Wnt signaling activation is closely connected with glioma malignancy. Pygopus 2 (Pygo2) was recently discovered as a component of the Wnt signaling pathway regulating β-catenin/Tcf dependent transcription. However, the role of Pygo2 in glioma cells has not yet been defined. In the current study, we investigated the role of Pygo2 in rat glioma C6 cells for the first time. Our results showed that over-expression of Pygo2 promoted cell proliferation as well as enhanced cell cycle progression from G₁ to S phase associated with an increase in the expression of the Wnt target gene cyclin D1. In contrast, knockdown of Pygo2 suppressed cell proliferation with cell cycle block from G₁ to S phase and down-regulation of cyclin D1. In addition, the expression of Pygo2 and cyclin D1 in 67 glioma tissue samples was quantified by real-time reverse transcription polymerase chain reaction (RT-PCR) and immunochemistry. The data indicated that tumor grade was significantly associated with over-expression of Pygo2 and cyclin D1. We conclude that Pygo2 is highly expressed in and promotes the growth of glioma cells by an increase in the expression of cyclin D1 to improve G₁/S transition.