Agarose gel electrophoresis of DNA isolated from IMR-32 NB cells, SK-N-MC NB cells, HL-60 promyelocytic leukemia cells, and K-562 erythroleukemia cells after incubations for 24 or 48 hours with complete growth medium alone (control), actinomycin D (Act. D; 1 μg/mL), DFO (2.5 mmol/L), or PIH analogue 311 (10 μmol/L). The molecular weight marker was DNA molecular marker X from Boehringer Mannheim.