Abstract 5279: LPS-TLR4 binding increases metastatic potential of colorectal cancer cells

Abstract

Abstract Objective: Infectious complications in colorectal cancer patients undergoing curative resection are associated with cancer recurrence, but the exact mechanism is not well understood. Toll-like receptor 4 (TLR4) is the sole receptor for lipopolysaccharide (LPS), a gram-negative bacterial antigen involved in such infectious complication. TLR4 expression has been found on several cancer types. We hypothesize that LPS promotes cancer cell metastatic potential via TLR4 signaling in colorectal cancer cells. Methods: We compared the effects of LPS stimulation on two well-characterized colorectal cancer cell lines: Caco-2 (non-metastatic) and HT-29 (metastatic). Flow cytometry was performed to detect cell surface TLR4 and various integrin expression. Cancer cells were incubated with or without 0.1 µg/mL LPS for 4 hours. In vitro static adhesion assay was used to study the ability of cell adhesion to extracellular matrix proteins (fibronectin, collagen I and collagen IV). Intravital microscopy, a technique used to study microcirculation in vivo, was carried out to observe dynamic attachment of intra-splenic injected cancer cells to C57/BL6 mouse liver sinusoids. Results: Caco-2 cells lack TLR4 receptors and are unresponsive to LPS treatment. In contrast, HT-29 cells were shown to express TLR4 receptors and HT-29 responds to LPS by a 2-fold increase of β1, but not α5, integrin expression in LPS-treated HT-29 cells (Mean Fluorescence Intensity:1041 vs. 458(untreated)). LPS-treated HT-29 cells showed enhanced attachment to fibronectin (1.6-fold; p < 0.01), collagen I (3-fold; p < 0.01) and collagen IV (2-fold; P < 0.01) relative to controls in vitro. Similarly, adherence of HT-29 cells to hepatic sinusoids in vivo was increased by LPS treatment (2 fold; p < 0.05). Conclusion: These data suggest that LPS-TLR4 signaling in colorectal cancer cells increases the metastatic potential. LPS-TLR4 mediated signaling cascade may be a valuable therapeutic target for the prevention of cancer metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5279.