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-kappa B) signaling pathway has been recently shown to participate in inflammation-induced cancer progression. Here, we describe a detailed analysis of the NF-kappa B-dependent gene regulatory network in the well-established Mdr2 knockout mouse model of inflammation-associated liver carcinogenesis. Expression profiling of NF-kappa B-deficient and NF-kappa B-proficient hepatocellular carcinoma (HCC) revealed a comprehensive list of known and novel putative NF-kappa B 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-kappa B 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. (HEPATOLOGY 2009;50: 1251-1262.)