PIK3CA and cancer: To assess the ability of candidate AKT driver mutations to induce aberrant PI3K pathway activity, we stably expressed the wild-type (WT) allele and 25 unique missense and small in-frame indel mutations in AKT1 and AKT2 in MCF10a primary breast epithelial cells, the lineage with the greatest frequency of AKT mutations in cancer (Fig. 1a).