Inhibition of the SK-N-MC human neuroblastoma cell line in vivo and in vitro by a novel nutrient mixture

Neuroblastoma, a peripheral nervous system cancer that can be highly invasive and metastatic, accounts for 8-10% of all solid childhood tumors in children under the age of 15 years. Despite multiple clinical efforts, prognosis remains poor for this enigmatic disease. A nutrient mixture (NM) containing lysine, proline, ascorbic acid and green tea extract has shown significant antitumor effects. Using the nude mouse xenograft model, we investigated the efficacy of NM. We also tested the effect of NM in vitro, evaluating cell viability, secretion of the matrix metalloproteinases (MMP)-2 and MMP-9, tissue inhibitor of metalloproteinase (TIMP)-2 secretion, Matrigel invasion and cellular apoptosis and morphology. Athymic nude mice 5-6 weeks of age were inoculated with 3x10(6) SK-N-MC neuroblastoma cells subcutaneously and randomly divided into two groups. Group A was fed a regular diet and group B a regular diet supplemented with 0.5% NM. Four weeks later, the mice were sacrificed and their tumors were excised, weighed and processed for histology. We also tested the effect of NM in vitro. NM inhibited the growth of xenograft tumors by 22% (P=0.04); and, in vitro, NM induced dose-dependent inhibition of cell proliferation with a decrease of 27% (P=0.001) and 36% (P=0.002) at 500 and 1000 mu g/ml NM compared to the control, respectively. Zymography revealed MMP-2 secretion in normal cells and PMA (100 ng/ml)-induced MMP-9 secretion. NM inhibited the secretion of both MMPs with total blockage at a concentration of 100 mu g/ml. Reverse zymography demonstrated a dose-dependent increase in TIMP-2 expression by NM. Notable, SK-N-MC human neuroblastoma cells were not invasive through Matrigel. NM induced dose-dependent apoptosis of SK-N-MC cells. The results suggest that NM may have therapeutic potential in treating neuroblastoma.