Thus, both Eph and Ephrins engage signaling cascades in their respective cells: The signal mediated by Eph receptors is called “forward signaling” and the signal mediated by Ephrins is called “reverse signaling.” In many cancer cell lines, Eph receptors are highly expressed 61; however, the receptors are poorly activated based on the low levels of phosphorylation that are detected 61. Here, EPHA1 is linked to cancer.