Activation of Rac1-PI3K/Akt is required for epidermal growth factorinduced PAK1 activation and cell migration in MDA-MB-231 breast cancer cells

Epidermal growth factor (EGF) may increase cell motility,an event implicated in cancer cell invasion and metastasis.However,the underlying mechanisms for EGF-induced cell motility remain elusive.In this study,we found that EGF treatment could activate Ras-related C3 botulinum toxin substrate 1 (Rac1),PI3K/Akt and p21actived kinase (PAK1) along with cell migration.Ectopic expression of PAK1 K299R,a dominant negative PAK1 mutant,could largely abolish EGF-induced cell migration.Blocking PI3K/Akt signalling with LY294002 or Akt siRNA remarkably inhibited both EGF-induced PAK1 activation and cell migration.Furthermore,expression of dominant-negative Rac1 (T17N) could largely block EGF-induced PI3K/Akt-PAK1 activation and cell migration.Interestingly,EGF could induce a significant production of ROS,and N-acetyl-L-cysteine,a scavenger of ROS which abolished the EGF-induced ROS generation,cell migration,as well as activation of PI3K/Akt and PAK,but not Rac1.Our study demonstrated that EGF-induced cell migration involves a cascade of signalling events,including activation of Rac1,generation of ROS and subsequent activation of PI3K/Akt and PAK1.