Preclinical Evaluation of Antitumoral and Cytotoxic Properties of Viscum album Fraxini Extract on Pediatric Tumor Cells.

In Europe, especially in German-speaking countries, administration of mistletoe extracts is the most common and popular complementary and alternative therapy approach reported in oncology. Mistletoe therapy is applied to children with cancer for curative and palliative therapeutic regimes with increasing frequency, but at the same time, there are only a few studies on the effectiveness of this therapy. Therefore, we have investigated the response of various pediatric cell lines (acute myeloid leukemia, Ewing's sarcoma, hepatocellular carcinoma, medulloblastoma, neuroblastoma, and osteosarcoma) to mistletoe extract, abnobaVISCUM Fraxini. Effects on cell proliferation, cell cycle distribution as well as on mitochondrial integrity and caspase-mediated apoptosis were investigated in neuroblastoma cell lines, SH-SY5Y and Kelly. Additionally, in vitro tumor cell migration and invasion were studied. In vivo effects of the mistletoe extract were investigated in a syngeneic neuroblastoma mouse model. We could show that tumor cell lines were from 5- to 640-fold more sensitive to abnobaVISCUM Fraxini treatment than non-tumorigenic fibroblasts, whereby neuroblastoma cell lines were the most sensitive. For two neuroblastoma cell lines, SH-SY5Y and Kelly, induction of caspase-9-mediated apoptosis, a decrease of mitochondrial integrity as well as attenuation of migration and invasion were observed. In vivo experiments revealed a reduction of tumor growth and a prolonged survival of tumor-bearing animals. In summary, we can state that these results provide the first preclinical data for cytotoxic activities of abnobaVISCUM Fraxini for a broad panel of pediatric tumor cell lines, in particular, neuroblastoma cells. Thus, it might be a potential remedy for the supportive treatment of neuroblastoma.