Abstract 561: Role of nucleolin in activation of NF-κB signaling with Tip≤, a carcinogenic factor of H. pylori

TNF-α inducing protein (Tip≤), a carcinogenic factor secreted from H. pylori, enters the cell through binding to nucleolin, a receptor of Tip≤ on the cell surface. Internalized Tip≤ induces NF-κB activation and TNF-α gene expression and finally induces tumor promotion in the stomach. Nucleolin is a major protein in nucleoli, but significant amounts of nucleolin localize on the cell surface of several gastric cancer cell lines. We investigate the relationship between induction of both NF-κB activation and TNF-α gene expression and the presence of nucleolin, the latter of which acts as a shuttling protein of various molecules, such as Tip≤, lactoferrin and AS1411, from cell surface to cytosol or nuclei. Lactoferrin, iron-binding glycoprotein with 80 kDa, shows anti-cancer activity and preventive activity of H. pylori infection. AS1411 is a nucleolin targeted DNA aptamer associated with a potent anti-cancer activity. First, we studied the effects of lactoferrin, AS1411, and anti-NUC295 (an antibody recognizing cell surface nucleolin) on Tip≤ incorporation into the cells and Tip≤-induced TNF-α gene expression. Pretreatment of mouse gastric cancer cells (MGT-40) with lactoferrin significantly inhibited the incorporation of Tip≤ and Tip≤-induced TNF-α gene expression. However, pretreatment with AS1411 enhanced the incorporation of Tip≤, and inhibited Tip≤-induced TNF-α gene expression. It is of interest to note that Anti-NUC295 enhanced both the incorporation of Tip≤ and Tip≤-induced TNF-α gene expression. These results suggest that both lactoferrin and AS1411 inhibit tumor promoting activity of Tip≤ mediated through inhibition of NF-κB signaling. Thus we think that nucleolin acts as not only a shuttling protein but also a direct regulator of NF-κB signaling. We discuss how lactoferrin and AS1411 inhibit NF-κB activation induced by Tip≤-nucleolin complex, and how nucleolin regulates the NF-κB signaling pathway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 561. doi:1538-7445.AM2012-561