As shown in Figs 5A and S4A, activation of PI3K signaling (including both expression levels of the PI3K catalytic subunit p110α or the up-regulated ERK phosphorylation) was positively correlated with cell migration capacity as well as FBXO3/USP4/Twist1 protein levels in breast cancer cell lines examined. This evidence concerns the gene MAPK1 and breast cancer.