The cell line KG1 is derived from a patient with acute myeloid leukemia. Activation of KG1 cells by interleukin (IL)-18 is associated with induction of key Th1 signature parameters such as T-bet and interferon-gamma. Here we set out to characterize the genome-wide mRNA expression profile under the condition of short-term stimulation (4h) with IL-18 using the Affymetrix GeneChip((R)) Array System. Besides the chemokines CXCL10, CXCL11, and CCL1 we identified Epstein-Barr virus induced gene-3 (EBI3)/IL-27B as being among those genes that are profoundly upregulated by IL-18 in KG1 cells. Thorough investigation revealed that IL-18-induced EBI3 mRNA efficiently translates into protein. Electromobility shift analysis and mutational analysis of the human EBI3 promoter identified two nuclear factor-kappaB binding sites as being crucial for induction by pro-inflammatory cytokines like IL-18. In addition, we demonstrate that KG1 cells express the Type A IL-27 receptor chain (WSX-1) and display STAT-1, -3 activation as well as induction of SOCS-3 under the influence of IL-27. IL-18 shows therapeutic potential in murine leukemia and is currently being evaluated in phase II clinical trials for the treatment of immunologically sensitive cancers. Since IL-27 mediates anti-cancer bioactivity in animal models, data presented herein may add a novel facet to tumorsuppressive characteristics of IL-18.