MAPK3 and neoplasm: PMA is a well- known tumor promoter that activates almost all protein kinase C (PKC) isozymes, which are prominent upstream regulators of mitogen-activated protein (MAP) kinase pathway [22], [23].The kinetics of phosphorylation of Ras/Raf/extracellular signal-regulated kinase (ERK1/2), c-jun NH 2 -terminal kinase (JNK) and p38 MAP kinase in SW-480 cells in response to treatment with 50 ng/ml (80 nM) PMA for different time intervals were studied.