Targeting the endothelin system:: novel therapeutic options in gynecological, urological and breast cancers

The endothelin system comprises the three peptide hormones endothelin (ET)-1, -2, -3, their G protein-coupled receptors, endothelin-A-receptor (ETAR) and endothelin-B-receptor (ETBR), and the enzymes of endothelin biosynthesis and degradation. In the past two decades, an impressive amount of data has been accumulated investigating the role of the endothelin system in a variety of malignancies. In many cancers, ET-1/ETAR interaction induces proliferation, angiogenesis, antiapoptosis and resistance to chemotherapy. Data indicate a pivotal role of the endothelin system in tumorigenesis, local progression and metastasis. Subsequently, novel drugs have been designed inhibiting ET-1 biosynthesis or ETAR interaction. A wide range of preclinical data is available on the role of ETAR antagonists in gynecological, urological and breast cancers providing evidence for their antiangiogenic, proapoptotic and growth inhibitory effects. Of particular interest is the anti-invasive and antimetastatic efficacy of ETAR antagonists and synergism when co-administered with established cancer therapies. Data indicate a future role of ETAR antagonists in oncologic therapies.