EDNRA and neoplasm: Within the SOC-associated tumor-promoting factors, the peptide endothelin-1 (ET-1) and its interactions with the cognate G-protein coupled receptors (GPCRs), Endothelin A (ETAR), and B (ETBR) receptors, support tumor progression, activating key pathways in invasion and metastasis, through the differential cooperation of β-arrestins (β-arrs) with proteins in cytosolic and nuclear compartments [22, 23].