Inhibitory effect of tumor metastasis in mice by saponins, ginsenoside-Rb2, 20(R)- and 20(S)-ginsenoside-Rg3, of red ginseng.

We examined the inhibitory effect of two saponin preparations from Red ginseng, 20(R)- and 20(S)-ginsenoside-Rg3, in comparison with that of ginsenoside-Rb2, on lung metastasis produced by two highly metastatic tumor cells, B16-BL6 melanoma and colon 26-M3.1 carcinoma, in syngeneic mice. In an in vitro analysis, both saponin preparations showed a significant inhibition of adhesion to fibronectin (FN) and laminin (LM) by B16-BL6 melanoma. Similarly, they significantly inhibited the invasion of B16-BL6 cells into the reconstituted basement membrane (Matrigel)/FN in a dose-dependent manner. In an experimental metastasis model using B16-BL6 melanoma, consecutive intravenous (i.v.) administrations of 100 micrograms/mouse of 20(R)- or 20(S)-ginsenoside-Rg3 1, 2, 3 and 4 d after tumor inoculation led to a significant decrease in lung metastasis. The inhibitory effect of i.v. administration of both ginseng saponins on the tumor metastasis of B16-BL6 melanoma was also recognized in a low dose of 10 micrograms/mouse. The oral administration (p.o.) of both saponins (100-1000 micrograms/mouse) induced a significant decrease in lung metastasis of B16-BL6 melanoma. Moreover, both ginseng saponins were effective in inhibiting of lung metastasis produced by colon 26-M3.1 carcinoma. When 20(R)- or 20(S)-ginsenoside-Rg3 was orally administered consecutively after tumor inoculation in a spontaneous metastasis model using B16-BL6 melanoma, both of them significantly inhibited lung metastasis. In the experiment involving neovasculization by tumor cells in vivo, both mice groups given each saponin preparation after tumor inoculation exhibited a significant decrease in the number of blood vessels oriented toward the tumor mass, with no repression of tumor size. These findings suggest that both ginseng saponins, 20(R)- and 20(S)-ginsenoside-Rg3, possess an ability to inhibit the lung metastasis of tumor cells, and the mechanism of their antimetastatic effect is related to inhibition of the adhesion and invasion of tumor cells, and also to anti-angiogenesis activity.