MAPK3 and cancer: The three most important subfamilies of MAPKs (extracellular signal regulated kinases 1 and 2 [ERK1/2], c-Jun NH2-terminal kinase [JNK], and p38 mitogen-activated protein) and the cell signalling cascade of the phosphatidylinositol 3-kinase/protein kinase-B (PI3K/Akt) are known to play a key role in cell growth, differentiation, and apoptosis and can be activated in many different cancers.