MAPK3 and prostate cancer: It has been recently reported, indeed, that GRP78 present on prostate cancer cells can bind the prostate-specific antigen/activated a2-macroglobulin complex causing the activation of ERK1/2 (extracellular-signal-regulated kinase 1/2), p38 MAPK (mitogen-activated protein kinase), and PI3K (phosphoinositide 3-kinase) signaling pathways and promoting cell survival by the Akt and NF-κB (nuclear factor κB) signaling cascade (38).