Annexin-V positive HCT116 and MDA-MB-231-Luc cells treated with costunolide (COS), doxorubicin (DOX), costunolide + doxorubicin (COS + DOX), costunolide-nanoparticles (COS-NPs), and costunolide-nanoparticles + doxorubicin (COS-NPs + DOX). (A) Flow cytometric analysis of HCT116, (B) Annexin-positive HCT116 cells percentages, (C) Flow cytometric analysis of MDA-MB-231-Luc, and (D) Annexin-positive MDA-MB-231-Luc cells percentages treated with costunolide (COS), doxorubicin (DOX), costunolide + doxorubicin (COS + DOX), costunolide-nanoparticles (COS-NPs), and costunolide-nanoparticles + doxorubicin (COS-NPs + DOX). Values are presented as mean ± SD. * p < 0.05, ** p < 0.01 and *** p < 0.001.