Inhibition of tumor angiogenesis and metastasis by a saponin of Panax ginseng, ginsenoside-Rb2.

We studied the effect of ginsenoside-Rb2 extracted from Panax ginseng on angiogenesis and metastasis produced by B16-BL6 melanoma cells in syngeneic mice. Intravenous administration of ginsenoside-Rb2 on day 1, 3 or 7 after tumor inoculation achieved a remarkable reduction in the number of vessels oriented toward the tumor mass, but did not cause a significant inhibition of tumor growth. The anti-angiogenic effect was dose-dependent ranging from 10 to 500 micrograms/mouse. In contrast, intra-tumoral or oral administration of ginsenoside-Rb2 caused a marked inhibition of both neovascularization and tumor growth. Ginsenoside-Rb2 did not affect the growth of rat lung endothelial (RLE) cells, B16-BL6 melanoma cells or various types of murine normal cells in vitro. The invasion of RLE cells into the reconstituted basement membrane (Matrigel), which is considered to be an essential event in tumor neovascularization, was inhibited by ginsenoside-Rb2 in a concentration-dependent fashion, while ginsenoside-Rb2 did not inhibit the haptotactic migration of endothelial cells to fibronectin-substrate. Multiple administrations of ginsenoside-Rb2 after the intravenous inoculation of B16-BL6 melanoma cells resulted in a significant inhibition of lung metastasis as compared with the untreated control. These results suggest that the inhibition of tumor-associated angiogenesis by ginsenoside-Rb2 may partly contribute to the inhibition of lung tumor metastasis.