Mitogen Activated Protein Kinases (MAPK), including ERK, JNK, and P38MAP kinase (P38), play the major role in stress-induced cellular responses such as cell proliferation, survival, apoptosis and invasion and are intracellular effector molecules that are embedded in a highly active signaling cascade in RA-FLSs (29). Here, MAPK8 is linked to rheumatoid arthritis.