MAPK3 and cancer: Dysregulation of MAPK cascades leads to cancer and other human diseases.1,2 There are four different MAPK families, including extracellular signal-regulated kinases 1 and 2 (ERK1/2), extracellular signal-regulated kinases (ERK5), c-Jun N-terminal kinase (JNK), and p38 MAPK (p38).