Abstract 1046: AS1411 activity is regulated by epidermal growth factor receptor signaling pathway.

Abstract

Abstract The anticancer AS1411 agent is a G-rich phosphodiester oligodeoxynucleotide, which forms a stable quadruplex structure and binds specifically to nucleolin as an aptamer. It efficiently inhibits proliferation and induces cell death in many types of cancer cells, but has little effect on normal cells. We have also shown that AS1411 is taken up by macropinocytosis and stimulates further macropinocytosis by a nucleolin-dependent mechanism in several cancer cells. AS1411 activity correlates with stimulated macropinocytosis, suggesting this hyperstimulation of macropinocytosis may explain the unusual cancer cell death caused by AS1411. Macropinocytosis is a ligand-independent endocytic pathway that is normally activated by growth factor receptor stimulation. On the other hand, nucleolin has been reported that can enhance growth factor signaling by binding directly to some growth factor receptors. Therefore in this study, we determine the participation of growth factor signaling pathway in AS1411-induced macropinocytosis and cell death. Pre-incubation of DU145 cells with a specific EGFR inhibitor, but not PDGFR or JAK2 inhibitors, significantly inhibited the stimulation of AS1411-mediated macropinocytosis, suggesting that AS1411 activates EGFR signaling pathways. This was confirmed by observing that DU145 cells treated with AS1411 induced tyrosine phosphorylation of EGFR and activation of its downstream effectors, including p38, PI3K and Rac1. Furthermore, AS1411 seem to induce the interaction between EGFR and nucleolin in accord with EGFR activation. We also found that the activation of EGFR signaling pathway by AS1411 might regulate its cancer cellular response. Simulation of macropinocytosis by AS1411 was significantly inhibited in DU145 cells pre-treated with pharmacological inhibitors of Rac1 or PI3K, but not by Src inhibitor. Moreover the ability of AS1411 to inhibit cell proliferation and induce cell death was reduced by an EGFR-neutralizing antibody (cetuximab) or by downregulating the expression of Rac1 using siRNAs. These results indicate that AS1411 mediates the activation of EGFR signaling pathway to induce cancer cell death, and suggest that AS1411 might redirect EGFR signaling pathway from a cell survival signal to a cell death signal. Citation Format: Elsa M. Reyes-Reyes, Francesca R. Salipur, Paula J. Bates. AS1411 activity is regulated by epidermal growth factor receptor signaling pathway. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1046. doi:10.1158/1538-7445.AM2013-1046