PIK3CD and cancer: This internal hypomethylated homeostasis may be related to the maintenance of cancer cell survival, as evidenced by the enrichment of biological processes, including cell–cell signaling, cell population proliferation and regulation of transport and cell differentiation through GO analysis (Fig. 3G; Fig. S 3E), and the involvement of signal transduction pathways, such as the PI3K-AKT, MAKP, and Rap1 signaling pathways (Fig. S 3E), according to KEGG classification.