FGF3/4/19 encode fibroblast growth factor family members, which interact with fibroblast growth factor receptor and thus activate mitogen-activated protein kinase and PI3K signaling cascades.24 Although the copy number of FGF3/4/19 negatively correlated with the T/C values (Supplementary Fig. S3a–c), FGF3/4/19 were hardly expressed in ESCC samples according to data from GDC TCGA database accessed with UCSC Xena (http://xena.ucsc.edu/. The gene discussed is PIK3CA; the disease is esophageal squamous cell carcinoma.