We have previously shown that
swainsonine, administered systemically to C57BL/6 mice, inhibited the pulmonary
metastasis of iv injected B16-F10
melanoma cells by a mechanism involving
interleukin-2 production and augmentation of natural killer cell activity. From this finding, which uses an "experimental
metastasis" model system, we considered: (a) whether
swainsonine would be effective in the inhibition of authentic or spontaneous
metastasis; (b) whether the
drug would also inhibit
metastasis formation in organs other than the lungs; and (c) whether the
drug would block the
metastasis of
tumor cells of different histological type or origin. Our data indicated that
swainsonine effectively inhibited the spontaneous
metastasis of B16-BL6
melanoma (by 88%) and M5076 reticulum
sarcoma (by 95%) murine
tumor cells to the lung and liver, respectively. In both cases, the antimetastatic activity of the
drug increased as a function of the concentration in
drinking water up to 3 micrograms/mL. These findings indicate that the antimetastatic activity of
swainsonine is not limited to artificial or experimentally induced
metastasis nor to a single
tumor type or specific organ. The inhibition of
metastasis is likely due to a combination of events, which are currently under investigation.