PAK4 and gastric cancer: Furthermore, in numerous normal and tumor cells with various stimuli [164,165], PAK4 activation mediates ERK1/2 stimulation, including in pancreatic cancer cells, in gastric cancer cells and in A549 human lung cancer cells [36,45,68,159], as well as stimulating the Mek1/2 cascade in gastric cancer cells and other tissues [45,164].