Inducibility of globin mRNA by EPO and IL-3 in ELM cells grown with or without stroma or ELM clones grown continuously in SCF (20.5D, 13.1C) or IGF-1 (20.2B, 20.5B). ELM cells were grown for 4 days in the growth factors shown, RNA extracted and 10 μg analyzed by Northern transfer for globin mRNA expression by probing with an α-globin cDNA probe or 7S ribosomal RNA as a loading control. The amounts of growth factors used were: SCF, 10 ng/mL; IGF-1, 100 ng/mL; EPO, 5 U/mL; IL-3, 10 U/mL.