EDNRB and breast cancer: Of relevance, we confirmed the sensitization effect of macitentan in a breast cancer cell line MDA-MB-468, expressing both ETAR and ETBR [12], as shown by the increased PARP cleavage and enhanced expression of γH2A.X, upon the combination treatment of macitentan and olaparib (Supplementary Fig. 6D), indicating that ET-1R antagonists may be combined with PARPi in various ETAR-expressing tumor types.