Phosphatidylinositol 3-kinase α (PI3Kα) is involved in cell proliferation forming interactions with adapter proteins such as insulin receptor substrate 1 (IRS1) in the presence of growth factor stimulation, stimulating the catalytic activity of PI3Kα.47 The two most common mutations found in cancer (E545K and H1047R) were explored experimentally identifying IRS1 as a binder of E545K mutant protein but not of H1074R mutant protein in pull-down experiments.48 It was also shown that the interaction of E545K mutant PI3Kα with IRS1 is required for the growth of colon cancer cells in vivo. Here, IRS1 is linked to cancer.