Abstract
Retinoblastoma is one of the most common ocular malignancies in children under the age of six. Occasionally, retinoblastoma metastasizes to extraocular organs including the bone, lung and brain. Left untreated, retinoblastoma is fatal. At present, there is no effective treatment for metastatic retinoblastoma. We investigated the antineoplastic activity of a nutrient mixture (NM) (lysine, proline, ascorbic acid and green tea extract) at concentrations of 10, 50, 100, 500 and 1,000 µg/ml in triplicate at each dose in the human malignant retinoblastoma Y-79 cell line. The parameters used were cell proliferation, expression of matrix metalloproteinases (MMPs), invasion through Matrigel, morphology and apoptosis. Cell viability was assessed by trypan blue dye exclusion test. Invasion was evaluated through Matrigel and MMP activity by gelatinase zymography. H&E staining for morphological cell alterations and apoptotic studies using the Live Green Poly Caspase Detection kit were also conducted. The nutrient mixture at 10-100 µg/ml demonstrated approximately 25% toxicity towards Y-79 retinoblastoma cells and significant toxicity at 500 and 1,000 µg/ml. The Y-79 cells secreted only MMP-2 as demonstrated by zymography; the nutrient mixture had no effect on MMP-2 expression up to 100 µg/ml, but completely blocked it at 500 µg/ml. Importantly, Y-79 retinoblastoma cells were not invasive through Matrigel. H&E staining showed cell morphological changes related to apoptosis, which was confirmed using the Live Green Poly Caspase Detection kit. Our results suggest that this nutrient mixture, which inhibited cell proliferation, expression of MMP-2 and induced apoptosis, may be a candidate for further exploration for its therapeutic potential in metastatic retinoblastoma.