PAK1 participates in almost every stage of a cancer cell and in every indispensable signal pathway, including EGFR/HER2/MAPK, Wnt/β-catenin, JNK/c-jun, NF-κB, cell cycle, apoptosis, autophagy and others, such as TGF-β and STAT5 signaling. This evidence concerns the gene MAPK8 and cancer.