S100A8 and S100A9 are novel nuclear factor kappa b target genes during malignant progression of murine and human liver carcinogenesis

The nuclear factor-kappaB (NF-κB) signaling pathway has been recently shown to participate in inflammation-induced cancer progression. Here, we describe a detailed analysis of the NF-κB-dependent gene regulatory network in the well-established Mdr2 knockout mouse model of inflammation-associated liver carcinogenesis. Expression profiling of NF-κB-deficient and NF-κB-proficient hepatocellular carcinoma (HCC) revealed a comprehensive list of known and novel putative NF-κB target genes, including S100a8 and S100a9. We detected increased co-expression of S100A8 and S100A9 proteins in mouse HCC cells, in human HCC tissue, and in the HCC cell line Hep3B on ectopic RelA expression. Finally, we found a synergistic function for S100A8 and S100A9 in Hep3B cells resulting in a significant induction of reactive oxygen species (ROS), accompanied by enhanced cell survival. Conclusion: We identified S100A8 and S100A9 as novel NF-κB target genes in HCC cells during inflammation-associated liver carcinogenesis and provide experimental evidence that increased co-expression of both proteins supports malignant progression by activation of ROS-dependent signaling pathways and protection from cell death.