PIK3R1 and cancer: Genetic alterations involving the PI3K/AKT/mTOR pathway are common in cancer, with 4,689 of 10,800 (43%) cancers from The Cancer Genome Atlas (TCGA) showing an alteration in 1 or more of the following genes: PIK3CA (17%, mainly mutation and amplification), PTEN (12%, mainly deletion), PIK3R1 (4%, mainly mutation), AKT1 (2.2%, mainly amplification), RPTOR (4%, mainly amplification), TSC2 and TSC1 (3%, 2.7%, mainly mutation), and MTOR (4%, mainly amplification) (Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/JCI167861DS1).