Inhibitory Effect of Cigarette Smoke Extract on Experimental Lung Metastasis of Mouse Melanoma by Suppressing Tumor Invasion

We investigated the effect of a nicotine-and tar-free cigarette smoke extract (CSE) using an experimental metastasis mouse model which was intravenously injected with B16-BL6 mouse melanoma cells. Three-hour pretreatment of cells with various concentrations of CSE (0, 0.1, 0.3, and 1%) dose-dependently reduced the number of lung metastatic nodules 14 days after tumor injection. To elucidate the mechanism of this anti-metastatic effect of CSE, we examined the invasion and migration activities of B16-BL6 cells pretreated with CSE for three hours in vitro. CSE significantly reduced the invasion of cells at 1% and the migration at 0.3% and 1%. Under the same pretreatment conditions, CSE had no effect on the proliferation of cells. These findings suggest that CSE contains some ingredients that suppress hematogenic lung metastasis via inhibition of the invasion and migration activities of mouse melanoma cells.