14-3-3γ Induces Oncogenic Transformation by Stimulating MAP Kinase and PI3K Signaling

The 14-3-3 proteins are a set of highly conserved scaffolding proteins that have been implicated in the regulation of a variety of important cellular processes such as the cell cycle, apoptosis and mitogenic signaling. Recent evidence indicates that the expression of some of the family members is elevated in human cancers suggesting that they may play a role in tumorigenesis. In the present study, the oncogenic potential of 14-3-3 gamma was shown by focus formation and tumor formation in SCID mice using 14-3-3 gamma transfected NIH3T3 mouse fibroblast cells. In contrast, 14-3-3 sigma, a putative tumor suppressor, inhibited NIH3T3 transformation by H-ras and c-myc. We also report that activation of both MAP kinase and PI3K signaling pathways are essential for transformation by 14-3-3 gamma. In addition, we found that 14-3-3 gamma interacts with phosphatidylinositol 3-kinase (PI3K) and TSC2 proteins indicating that it could stimulate PI3K signaling by acting at two points in the signaling pathway. Overall, our studies establish 14-3-3 gamma as an oncogene and implicate MAPK and PI3K signaling as important for 14-3-3 gamma induced transformation.