Western blot demonstrating the expression of p32 and p30 isoforms of C/EBPɛ in myeloid cell lines: Kcl22 myeloblasts (lane 3), NB4 promyelocytes (lane 4), and U937 myelomonoblasts (lane 5). The isoforms p32 and p30 were expressed at a ratio of approximately 2:1. NB4 cells treated with 10⁻⁶ mol/L ATRA for 24 hours selectively upregulate C/EBPɛ p30 (lane 7). The KG-1 early myeloblasts did not express detectable C/EBPɛ levels (lane 6). C/EBPɛ p32 (lane 1) and p30 (lane 2) cDNAs transfected and expressed in COS-1 cells were run alongside as positive controls.