tokens: Antibodies to pMEK1 / 2 , MEK1 / 2 , ERK1 / 2 , Myc , pAKT , AKT , beta - tubulin ( all Cell Signaling , Danvers , MA , USA ) , beta - actin and dpERK1 / 2 ( both Sigma , St . Louis , MO , USA ) were used according to manufacturers ' recommendations .