Figure 1
From: Eph receptors in breast cancer: roles in tumor promotion and tumor suppression
Working model for Eph receptor function in tumor promotion and tumor suppression. In normal cells, engagement of Eph receptors with ephrins on adjacent cells in trans induces receptor forward signaling, leading to inhibition of Ras/mitogen-activated protein kinase (MAPK) activity, or suppression of Crk activation via Abl kinase activity, and tumor suppression. In tumor cells, disruption of cell-cell junctions inhibits Eph receptor interaction with endogenous ephrins in trans. In addition, Eph receptors are often upregulated whereas ephrins are downregulated. Crosstalk between Eph receptors and other receptor tyrosine kinases such as ErbB2 and epidermal growth factor receptor (EGFR) results in increased activity of the Ras-MAPK pathway and the RhoA GTPase, and enhanced tumor malignancy.