Abstract 4879: Cancer cell-mediated signaling of TLR 2, 4, and 9 causes activation of PI3K/Akt/mTOR pathway and induces tumor cell proliferation in pancreatic cancer

Background: Toll like receptor (TLR) ligands are in clinical use for the immunotherapy of different cancers. They are supposed to induce an inflammatory immune response against the tumor. Interestingly, several studies showed that TLRs were expressed by cancer cells in different tumor entities and that their activation can contribute to an inflammatory microenvironment. Yet, for pancreatic cancer, TLR expression and its impact in tumor cells is only poorly understood. Therefore this study analyzed the influence of TLR2, 4, and 9 expression and activation on tumor cell signaling and proliferation in pancreatic cancer. Methods: The expression of TLR 2, 4, and 9 was analyzed in vitro in several established as well as primary human pancreatic cancer cell lines by qRT-PCR and Western Blot. TLR stimulation was then performed in BxPC-3, MIA Paca2, and PacaDD135 cells using the TLR ligands oligodeoxyribonucleotide2006 (ODN2006), lipoteichonic acid of Staphylococcus aureus (LTA-SA) and High-Mobility Group Box 1 (HMGB1). Expression of MyD88 and pAkt was then analyzed by Western Blot. Functional analysis on proliferation (ATP assay) and cytokine expression (Luminex) was additionally performed. Results: Expression of TLR2, 4 and/or 9 was demonstrated in all investigated human pancreatic cancer cell lines. Receptor activation by single or combined use of TLR ligands resulted in increased MyD88 and pAkt (Ser473) expression. Additionally, up-regulated anti-apoptotic protein Bcl-2 expression was found in stimulated cells, but not in the unstimulated cells. Furthermore, TLR activation resulted in the production of the interleukin(IL)-6, IL-8 and tumor necrosis factor a (TNF-a). Interestingly, tumor cell proliferation was increased within 24 and 48 hours of stimulation. Conclusion: Our results demonstrate TLR2, 4 and/or 9 expression in all human pancreatic cancer cell lines. Additionally, our findings on TLR activation suggest chronic inflammation-mediated TLR signaling to negatively influence tumor cell apoptosis and to shift the cytokine release in pancreatic cancer towards an inflammatory microenvironment. These findings emphasize the particular role of TLR2, 4 and 9 and their activation in pancreatic cancer, outlining their relevance as potential targets for cancer therapy. Citation Format: Jennifer Kreckel, Tanja Grimmig, Romana Moench, Christoph T. Germer, Martin Gasser, Ana Maria Waaga-Gasser. Cancer cell-mediated signaling of TLR 2, 4, and 9 causes activation of PI3K/Akt/mTOR pathway and induces tumor cell proliferation in pancreatic cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4879.