Objective To make a review about MAPK and apoptosis of tumor cells.Methods We collected a large number of related experimental papers,and summarized key points.Results mitogen activated protein kinase(MAPK)is one of the four biggest signal transduction systems which contain four subtribes named p38,ERK5,ERK and JNK/SAPK respectively.MAPK pathways constitute numerous modular network that regulates a variety of physiological processes,such as cell growth,roliferation,differentiation,and apoptotic cell death.Specially,the function of induced apoptosis in tumor cells has gradually become main focus.Both in-vitro and ex-vivo findings demonstrated that in apoptotic tumor cells the level of phosphorylation of JNK kinase is significantly improved.That means JNK kinase is activated in these tumor cells.At the same time,contrary to JNK kinase,the activity of ERK kinase is usually weakened.So,for most apoptotic tumor cells,JNK is a positive factor,however,ERK kinases is a negative factor.As for the p38 kinase,which can be activated to outside stimulus,also has the promotion of apoptosis.Importantly,ERK kinase activity is suppressed by JNK/p38 kinase during apoptosis induction.Further study demonstrate that the regulatory mechanisms of MAPK in apoptotic tumor cells are:working on upstream of caspase;starting death receptor channel;activating pro-apoptotic Bcl-2 protein family;changing mitochondrial permeability;participating in Fas/Fasl-mediated apoptosis;enhancing the expression of TNF-a and so on.Conclusions The relationship between MAPK and apoptosis of tumor cells is intimate.It is expected to be a new target for tumor in clinical treatment. Objective To make a review about MAPK and apoptosis of tumor cells. Methods We collected a large number of related experimental papers, and summarized key points. Results mitogen activated protein kinase (MAPK) is one of the four biggest signal transduction systems which contains four subtribes named p38, ERK5, ERK and JNK / SAPK respectively. MAPK pathways constitute numerous modular networks that regulates a variety of physiological processes, such as cell growth, roliferation, differentiation, and apoptotic cell death. Particularly, the function of induced apoptosis in tumor cells has gradually become main focus.Both in-vitro and ex-vivo findings in in apoptotic tumor cells the level of phosphorylation of JNK kinase is significantly improved. That means JNK kinase is activated in these tumor cells. At the same time, contrary to JNK kinase, the activity of ERK kinase is usually weakened. So, for most apoptotic tumor cells, JNK is a positive factor, however, ERK kinases are a negative factor. As for t he p38 kinase, which can be activated to outside stimulus, also has the promotion of apoptosis. Implantantly, ERK kinase activity is suppressed by JNK / p38 kinase during apoptosis induction. Further clinical demonstration demonstrate the regulatory mechanisms of MAPK in apoptotic tumor cells are: working on upstream of caspase; starting death receptor channel; activating pro-apoptotic Bcl-2 protein family; changing mitochondrial permeability; participation in Fas / Fasl -mediated apoptosis; enhancing the expression of TNF-a and so on. Conclusions The relationship between MAPK and apoptosis of tumor cells is intimate. It is expected to be a new target for tumor in clinical treatment.