Overview of MAPK cascade, PI3K/AKT signaling, and molecular JAK signaling interactions. Ras is a critical target linking the three pathways. Ras exists upstream of the MAPK cascade, it can activate the MAPK pathway, as well as activate AKT to activate the PI3K/AKT pathway. Ras and class I PI3K consisting of catalytic subunit P85 and regulatory subunit P110 can be activated by cytokine receptors and EGFR. The cross-linking of these targets forms a complex signal network.