Metastasis-associated phosphatase PRL-2 regulates tumor cell migration and invasion

The Phosphatase of Regenerating Liver (PRL) family, comprising PRL-1, PRL-2, and PRL-3, is a group of prenylated phosphatases, which are candidate cancer biomarkers and therapeutic targets. Although several studies have documented that altered expression of PRL-1 or PRL-3 can influence cell proliferation, migration and invasion, there is a dearth of knowledge about the biological functions of PRL-2. Thus, in the current study we have evaluated the role of PRL-2 in cell migration and invasion in human cancer cells. We found four human lung cancer cells, including A549 cells, over-express PRL-2 when compared with normal lung cells. PRL-2 knockdown by RNA interference markedly inhibited cell migration and invasion and this inhibition can be restored by over-expressing the siRNA resistant vector HA-PRL-2m. PRL-2 suppression by siRNA decreased p130Cas and vinculin expression, and decreased ERK phosphorylation, while increasing the phosphorylation of ezrin on tyrosine 146. We found no significant changes in total p53, Akt and c-Src expression levels or their phosphorylation status, suggesting PRL-2 knockdown could inhibit tumor cell migration and invasion through a Src-independent p130Cas signaling pathway. Ectopic expression of wild type PRL-2, a catalytic inactive C101S mutant and a C-terminal CAAX deletion revealed a requirement for both the PRL-2 catalytic functionality and prenylation site. Expression of wild type but not mutant forms of PRL-2 caused ERK phosphorylation and nuclear translocation. These results support a model in which PRL-2 promotes cell migration and invasion through an ERK-dependent signaling pathway.