Because the main predictors of trastuzumab activity in both pre-clinical and clinicalsettings are HER2 gene amplification and activation of the PI3K pathway, defined asPTEN loss and/or PIK3CA mutation [41-44], the loss of ATG6/Beclin1might function as a positive predictor of the tumor response to HER2-targeted therapies. This evidence concerns the gene PIK3CA and neoplasm.