CEBPD and neoplasm: To obtain insights into the mechanisms underlying the lack of effects of C/EBPδ on proliferation in vivo, we first used fluorescence microscopy to look at cross-sections of the tumors and further found that red control cells preferably grow at the periphery of the tumors while C/EBPδ-inducible cells also proliferate at the core of the tumor mass (Figure S3).