Proliferation, Apoptosis, and Invasion Effects of Mistletoe Alkali on Human Osteosarcoma U2OS In Vitro

The objective of this study was to evaluate the effects of mistletoe alkali on human osteosarcoma cells (U2OS) in vitro. Osteosarcoma is the most common primary malignant bone tumor; although there are a lot of therapies such as surgery, radiotherapy, and chemotherapy, its prognosis is still very poor. There is increasing interest in the protective biological function of natural antioxidants contained in Chinese medicinal herbs, which are candidates for the prevention of tumors. Mistletoe alkali is one of the compounds extracted from Viscum coloratum (Komar.) Nakai, one kind of mistletoe, whose extracts contribute to the improvement of the prognosis of patients with malignancies. The effect of mistletoe alkali on the growth of U2OS cells was compared with 5-fluorouracil (5-FU), using a cell counting kit-8 (CCK-8). The influence of mistletoe alkali on U2OS's proliferation and apoptosis was tested by terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling staining and immunocytochemical staining of caspase 3 and proliferating cell nuclear antigen. Additionally, the invasion ability of U2OS cells was detected using a Boyden chamber transwell migration assay. CCK-8 assays gave an IC50 of 7 mu g/mL for mistletoe alkali. Compared with 5-FU, mistletoe alkali inhibited U2OS proliferation and induced apoptosis more effectively. The invasion ability of U2OS was also weaker in mistletoe alkali than in 5-FU. Mistletoe alkali significantly inhibited growth and invasion abilities of U2OS cells and induced their apoptosis in vitro. Mistletoe alkali may be a more effective drug for human osteosarcoma than the standard chemotherapeutic drug 5-FU.