C/EBPβ is a differentiation factor for the mammary epithelium and is produced, through alternative initiation of translation, in three isoforms: the transcriptional activators liver activating protein 1 and 2 (LAP1 and LAP2), and the LIP, which can inhibit C/EBPβ-mediated gene activation.20, 21, 22 C/EBPβ has been reported to be deregulated in breast cancer but its role in cancer progression is not fully elucidated (reviewed in Zahnow22). The gene discussed is CEBPB; the disease is breast cancer.