PIK3CA and cancer: PI3K/Akt signalling is one of the most critical cancer-promoting pathways through upregulation of growth factor receptors (EGFR, IGF1R, HER2, etc) or PTEN inactivation (Lu et al, 1999) and recently considered a major determinant of trastuzumab resistance (Nagata et al, 2004; Berns et al, 2007; Esteva et al, 2011; Razis et al, 2011).