5-azaC toxicity in ERK1-GFP transduced cells. Vector control (square), early passage ERK1-GFP (circle) and late passage ERK1-GFP (triangle) were maintained in media supplemented with 5-azaC at the indicated concentrations for 7 days at which time cell viability was measured using a neutral red assay as described . Values represent the mean ± se (n = 3). *Significantly different from vector control. Similar results were observed in three independent experiments.