Interestingly, it has been revealed that transfection of FLSs with a dominant-negative mutant related to the ras gene in RA patients leads to the inhibition of Ras signaling, which play a critical role in decreased ERK1/2 activation, proliferation, and/or activation of FLSs, synovial hyperplasia, inflammatory cell infiltration, and high production of IL-6, which are involved in joint damage (102). Here, MAPK3 is linked to rheumatoid arthritis.