Additional clues to the above question came from Will et al. [62] who showed that inhibition of PI3K, but not AKT, leads to the rapid, but transient inhibition of the RAS-ERK signalling axis in HER2+ BC cells; and this inhibition, though transient, is critical for the enhanced cell death caused by PI3K over AKT inhibitors. This evidence concerns the gene PIK3CA and breast cancer.