The role of trastuzumab in abrogating the PI3K/Akt signaling pathway has been addressed in two preclinical studies, where treatment of HER2-gene-amplified breast cancer cells with trastuzumab caused growth inhibition through PTEN upregulation and downregulation of PI3K activity and Akt function [12, 13]. The gene discussed is PIK3CA; the disease is breast cancer.