Fig. 6. Effects of selenomethionine on the viability of NB cells differentiated with RO20-1724 and PGA1. Cells (20,000/well) were plated in a 24 well tissue culture plate and were treated with differentiating agents 24 hours after plating. Various concentrations of selenomethionine were added concomitantly with the differentiating agents. Cell viability was measured 3 days after treatment by MTT assay. Each experiment was repeated three times involving 4 samples per group, and error bars indicate SEM.