Improved anticancer activity of betulinic acid on breast cancer through a grafted copolymer-based micelles system

Betulinic acid (3β-Hydroxy-20(29)-lupaene-28-oic acid, BA) has excellent anti-cancer activity but poor solubility and low bioavailability. To improve the antitumor activity of BA, a polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol (PVCL-PVA-PEG) graft copolymer (Soluplus) encapsulated BA micelle (Soluplus-BA) was fabricated. The Soluplus-BA micelles presented a mean size of 54.77 ± 1.26 nm and a polydispersity index (PDI) of 0.083. The MTT assay results showed that Soluplus-BA micelles increased the inhibitory effect of BA on MDA-MB-231 cells, mainly due to the enhanced accumulation of reactive oxygen species (ROS) and the destruction of mitochondrial membrane potential (MMP). Soluplus-BA micelles induced the DNA double-strand breaks (DSBs) as the γH2AX foci increased. Moreover, Soluplus-BA also inhibited the tube formation and migration of human umbilical vein endothelial cells (HUVECs), and inhibited the neovascularization of the chicken chorioallantoic membrane (CAM). This angiogenesis inhibitory effect may be accomplished by regulating the HIF-1/VEGF-FAK signaling pathway. The in vivo study confirmed the improved anti-tumor effect of Soluplus-BA and its inhibitory effect on angiogenesis, demonstrating the possibility of Soluplus-BA as an effective anti-breast cancer drug delivery system.