In breast cancer therapy, emerging molecular targeted agents have shown promising efficacy, including monoclonal antibodies or inhibitors targeting HER-2, phosphoinositide 3-kinase (PI3K) signaling pathway, cyclin-dependent kinases (CDKs), and poly (ADP-ribose) polymerase (PARP) [19,20,21,22,23,24,25]. The gene discussed is PIK3CA; the disease is breast cancer.