MAPK3 and cancer: While the roles of canonical MAPKs, such as MAPK3/1 [extracellular signal–regulated kinase 1/2 (ERK1/2)], MAPK11-14 (p38β/γ/δ/α), and MAPK8-10 (c-Jun N-terminal kinase 1/2/3), are well established in carcinogenesis and tumor progression (2, 3), the role of MAPK6 in human cancers remains unclear.