CASP3 and neoplasm: To further investigate whether miR-HER2-E1 delivered by exosomes inhibits HER2-positive cell viability by restored the activity of executioner caspase-3/7, important markers of apoptosis, the four tumor cell lines were treated with purified exosomes produced by HEK-293 cells transfected with plasmids encoding miR-HER2-E1 or NT miRNA or remain mock treatment for 24 h.