Abstract 1394: Acute bacterial infection increases lung cancer metastasis via toll-like receptors 2 and 4

Abstract INTRODUCTION: Surgery is required for curative treatment of lung cancer but is associated with a high rate of bacterial infections such as pneumonia. There is emerging clinical evidence to suggest that infectious complications may decrease survival after cancer surgery, but the mechanism is unclear. Interactions between bacteria and host cells are mediated by specialized pathogen recognition receptors, of which the Toll-like receptors (TLRs) are best characterized. We and others have shown that cancer cells express TLRs, but their function is largely unknown. The aim of this study is to investigate the mechanisms of bacterial infection-facilitated lung cancer metastasis with a particular focus on the role of TLRs. METHODS: Two lung cancer cell lines (murine H-59 and human A549) were incubated a) directly with heat-inactivated bacteria (S.pneumonia or E.coli) or purified bacterial antigens (lipopolysaccharide or lipoteichoic acid), or b) indirectly with an in vitro pneumonia model using conditioned media from pulmonary bronchial epithelial cells incubated with heat-inactivated bacteria or bacterial antigens. Migratory and metastatic ability of thus treated cells were determined in vitro (adhesion, migration) and in vivo (hepatic intravital microscopy and intra-splenic liver metastasis). A clinically relevant in vivo model of severe infection, cecal ligation and puncture (CLP) or sham control, was employed in some animals. To assess the role of TLRs, we used transgenic TLR4 knockout mice, and small molecule inhibiting molecules or antibodies of TLRs. RESULTS: Direct and indirect (in vitro pneumonia) infection of H-59 and A549 increased adhesion to extracellular matrix components approximately 2-8 fold and 2-4 fold over negative control, respectively. In vitro pneumonia increased in vitro migration of H-59 approximately 2-5 fold. Direct and indirect incubation of H-59 with S.pneumonia and E.coli increased the in vivo adhesion to liver sinusoids 2-4 fold. CLP (in vivo infection model) enhanced the in vivo adhesion of H-59 3-fold and increased number of liver metastases at 2 weeks post-injection approximately 12 fold. These effects were attenuated in TLR4 -/- mice and with TLR2 and TLR4 inhibition. CONCLUSION: Activation of TLR2 or TLR4 on lung cancer cells, either directly by S.pneumonia and E.coli, indirectly though activated bronchial epithelial cells, or via an in vivo infection, increases cancer cell adhesion, migration and metastasis. TLRs thus represent a potential therapeutic target in bacterial infection facilitated cancer metastasis. 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 1394. doi:1538-7445.AM2012-1394

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