MAS1 is a GPCR and acts as an inhibitory regulator of cancer.[19] It has been suggested that activation of the Ang 1–7/MAS1 axis could represent a promising therapeutic strategy.[20] Other than activation by the endogenous MAS1 ligand, Ang 1–7, recent studies indicate the existence of an Ang 1–7‐independent mechanism by which MAS1 counteracts AGTR1 functions.[14, 21] Here, we demonstrate the signaling properties and conformation changes of MAS1/AGTR1 heterocomplexes. The gene discussed is ANGPT1; the disease is cancer.