Bystander effects induced by electron beam-irradiated MCF-7 cells: a potential mechanism of therapy resistance

Purpose The distinct direct and non-targeting effects of electron beam radiation on MCF-7 cells remain obscure. We aimed to investigate the effect of electron beam irradiation (EBI) and conditioned media (CM) of the irradiated MCF-7 cells on MCF-7 cells. The cytotoxic effects of CM from irradiated MCF-7 cells on the mesenchymal stem cells and human umbilical vein endothelial cells (HUVECs) were also examined. Methods Cell viability and apoptosis were assayed via MTT and flow cytometry analysis, respectively. The production of ROS (reactive oxygen species) was evaluated by the chemical fluorometric method, while the amount of extracellular vesicles was detected via acetylcholinesterase activity assay. Expression of genes involved in apoptosis, including caspase-3, -8, -9, and stemness such as Sox-2 and Oct-4, were calculated through q PCR. The wound healing rate of cells was monitored via in vitro scratch assay. Results Compared to the control group, EBI groups showed decreased cell viability but increased apoptosis and ROS as well as acetylcholinesterase activity dose-dependently ( P