Thus, activation of PI3K-mTOR signaling in CDH1-deficient gastric cancer cells might be the result of multiple signal transduction aberrations including lack of suppression of ligand-mediated EGFR activation (Fig. 1) or lack of negative feedback inhibition of the PI3K–Akt axis via reduced PTEN levels (Fig. 2). Here, EGFR is linked to gastric cancer.