EGFR and breast cancer: Even though the concentration of Ambrisentan that we used here is in line with other studies assessing endothelin receptor antagonists (ERAs) in toxicity assays with glioblastoma and breast cancer cells, it is very likely that at high concentration off-target effects (ETBR and EGFR)69,70 are also involved in the in vitro anti-tumor effects of Ambrisentan.