PIK3CA and breast cancer: The upregulation of HER2 in breast cancer cells results in the initiation of its subsequent signaling pathways, including PI3K/Akt (Ruiz-Saenz et al., 2018) and RAS/RAF/MAPK (Goltsov et al., 2014), which in turn promote cellular proliferation, survival, angiogenesis, and metastasis (Wilks, 2015).