EGF and breast cancer: Isoform-specific neutralization of PI3K isoforms in breast cancer cell lines, by PI3K antibody microinjection or a p110δ-selective pharmacological inhibitor, demonstrated that p110δ is the most important class IA PI3K in the regulation of epidermal growth factor-driven motility in vitro, controlling the directionality and, to a lesser extent, the speed of migration [460].