The most effective DpT analogs and 311 (internal control) show selective antiproliferative activity against immortal SK-N-MC neuroepithelioma cells (S) compared with mortal MRC-5 fibroblasts (F). Cells were incubated in the presence or absence of the chelators (0-25 μM) for 72 hours at 37° C.23 After this incubation period, cellular density was measured using the MTT assay. Cellular proliferation was expressed as a percentage of that found for the untreated cells. Each data point represents the mean of 2 replicates in a typical experiment of at least 3 to 5 experiments.