MAPK3 and cancer: PP2A is a prominent tumor suppressor whose dysregulation is seen in many human cancers and is a hallmark of cellular transformation,43,44 and RABL6A inhibits PP2A in another cancer type, neuroendocrine tumors.34 PP2A directly dephosphorylates Myc and promotes its degradation while also inhibiting AKT and ERK signaling, two downstream effectors of Ras capable of stabilizing Myc.45 However, tumor analyses revealed no alteration of either AKT or ERK1/2 phosphorylation at PP2A-regulated sites, suggesting other factors besides PP2A control Myc upregulation following RABL6A loss.