Abstract
Prostate cancer morbidity and mortality demonstrate a need for more effective targeted therapies. One potential target is EphA2, although paradoxically, pro- and anti-oncogenic effects have been shown to be mediated by EphA2. We demonstrate that unique activating and blocking EphA2-targeting monoclonal antibodies display opposing tumor-suppressive and oncogenic properties in vivo. To further explore this complexity, we performed detailed phosphoproteomic analysis following ligand-induced EphA2 activation. Our analysis identified altered phosphorylation of 73 downstream proteins related to the PI3K/AKT/mTOR and ERK/MAPK pathways, with the majority implicated in cell junction and cytoskeletal organization, cell motility, and tumor metastasis. We demonstrate that the adapter protein SHB is an essential component in mediating the inhibition of the ERK/MAPK pathway in response to EphA2 receptor activation. Furthermore, we identify the adherence junction protein afadin as an EphA2-regulated phosphoprotein which is involved in prostate cancer migration and invasion.