Eph and ephrin signaling in mammary gland morphogenesis and cancer

The Eph family of receptor tyrosine kinases and their membrane-bound ligands, the ephrins, play a central role in pattern formation during embryonic development and there is growing evidence that they are also instrumental in the control of tissue dynamics in the adult. The mammary gland is a paradigm for morphogenic processes occurring in the adult, since the gland develops predominantly postnatally and is subjected to continuous cyclic remodeling according to functional demands. Thus, pattern formation and the establishment of a functional organ structure are permanent themes in the mammary gland life cycle. In this paper we summarize the experimental evidence and discuss possible mechanisms by which Ephs and ephrins are modulating mammary epithelial cell adhesion, communication, and migration. Furthermore, we speculate on the different aspects of their influence on normal mammary gland development, function, and carcinogenesis.