The p110β has been suggested to be responsible for the reaccumulation of PIP3 and reactivation of AKT in HER2-amplified cancers treated with a p110α-specific inhibitor, and concomitant inhibition of p110α and p110β induces greater antitumor efficacy in HER2-amplified and PIK3CA mutant breast cancers. This evidence concerns the gene PIK3CA and breast cancer.