Immediate Early Response 3 （IER3） functions in the protection of cells from Fas- or tumor necrosis factor type alpha-induced apoptosis. IER3 has a role in the ERK signaling pathway by inhibiting the dephosphorylation of ERK by phosphatase PP2A-PPP2R5C holoenzyme. In addition， IER3 serves as an ERK downstream effector mediating survival. As a member of the NUPR1/RELB/IER3 survival pathway， IER3 provides pancreatic ductal adenocarcinoma with significant resistance to cell stress， such as starvation or gemcitabine treatment.
