Abstract
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.
Highlights
Cigarette smoking has been accepted as the main cause of cancers of the head and neck, lung, and bladder and is a major contributing factor for cancers of the esophagus, pancreas, and kidney [1,2]
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
The invasion of B16-BL6 cells pretreated with CSE was dose-dependently suppressed, and the invasion at 1% CSE was decreased by 32%, which was significantly lower than the control (Figure 2)
Summary
Cigarette smoking has been accepted as the main cause of cancers of the head and neck, lung, and bladder and is a major contributing factor for cancers of the esophagus, pancreas, and kidney [1,2]. In previous in vivo studies, nicotine, its derivatives, and cigarette smoke condensate including almost all cigarette smoke components enhanced experimental metastasis [3,4]. Cigarette smoke contains harmful ingredients as mentioned above, cigarette smoke, tobacco leaves and flowers contain many useful compounds [5]. Saito et al reported the identification of cembratriene-4,6-diol as an antitumor-promoting agent from cigarette smoke condensate, a particle phase extract [6]. Tobacco cembratriene-4,6-diol was reported to inhibit tumor cell invasion [7]. There have been few studies determining whether nicotine- and tar-free cigarette smoke extract (CSE), a gas phase extract, can enhance or suppress the metastasis of tumor cells
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