• EC d4 are most vulnerable towards Dox-induced cytotoxicity independent of drug transport.
• EC d4 and EC d6 display higher levels of drug-induced DSB as compared to mESC.
• Dox treatment of EPC (EC d4) causes multiple dysfunctions in differentiated EC d6, including defects in mitochondrial homeostasis, endothelial barrier function, cytokine response, and LDL uptake.
• Pharmacological protection of EPC from Dox-induced damage may reduce the risk of late cardiotoxicity in Dox-based anticancer regimens.