The Many Faces of C/EBPδ and their Relevance for Inflammation and Cancer

The CCAAT/enhancer binding protein delta (CEBPD, C/EBP delta) is a transcription factor that modulates many biological processes including cell differentiation, motility, growth arrest, proliferation, and cell death. The diversity of C/EBP delta's functions depends in part on the cell type and cellular context and can have opposing outcomes. For example, C/EBP delta promotes inflammatory signaling, but it can also inhibit pro-inflammatory pathways, and in a mouse model of mammary tumorigenesis, C/EBP delta reduces tumor incidence but promotes tumor metastasis. This review highlights the multifaceted nature of C/EBP delta's functions, with an emphasis on pathways that are relevant for cancer and inflammation, and illustrates how C/EBP delta emerged from the shadow of its family members as a fascinating "jack of all trades." Our current knowledge on C/EBP delta indicates that, rather than being essential for a specific cellular process, C/EBP delta helps to interpret a variety of cues in a cell-type and context-dependent manner, to adjust cellular functions to specific situations. Therefore, insights into the roles and mechanisms of C/EBP delta signaling can lead to a better understanding of how the integration of different signaling pathways dictates normal and pathological cell functions and physiology.