A Potential Role of Adhesion Molecules on Lung Metastasis Enhanced by Local Inflammation

Local and systemic inflammations are associated with negative long-term outcomes; however, their precise mechanism of action remains unclear. We previously demonstrated that hepatocyte growth factor (HGF)/c-Met signaling contributed to the enhancement of liver metastasis associated with peritonitis model. The aim of this study is to investigate the effect of local inflammation on the development of lung metastasis.

NL-17 cells were injected into BALB/c mice via the tail vein to produce a high potential model for lung metastasis. After injection of NL-17 cells, lipopolysaccharide (LPS) and live Pseudomonas aeruginosa, and phosphate-buffered saline were administered intratracheally to induce acute lung injury (ALI) and pneumonia, respectively.

In both ALI and pneumonia mice, lung metastasis was significantly promoted compared to control mice. Concentrations of Interleukin-6, tumor necrosis factor-α, and HGF in the bronchoalveolar lavage fluid were significantly higher in ALI and pneumonia mice than in control mice. Neither administration of recombinant mouse HGF nor c-Met knockdown in NL-17 cells influenced the magnitude of lung metastasis. Yet stimulation with LPS increased the expression of α2 integrin, vascular cell-adhesion protein-1, and intercellular adhesion molecule-1 (ICAM-1) in the lung. Invasive activity of NL-17 cells was significantly up-regulated by LPS, but was suppressed by anti-ICAM-1 antibody. While LPS-stimulated NL-17 cells showed significantly promoted lung metastasis, E-selectin expression in the lungs of mice with ALI or pneumonia was significantly enhanced compared with control mice.

Up-regulation of adhesion molecules, but not HGF/c-Met signaling, may contribute to the lung metastasis enhanced by local infection/inflammation.