Chinese medicinal herb, Acanthopanax gracilistylus, extract induces cell cycle arrest of human tumor cells in vitro

We investigated the effect of a Chinese medicinal herb, Acanthopanax gracil istylus (AG), extract (E) on the growth of human tumor cell lines in vitro, AGE markedly inhibited the proliferation of several tumor cell lines such as MT-2, Raji, HL-60, TMK-1 and HSC-2. The activity was associated with a p rotein of 60 kDa, which was purified by gel-filtration chromatography, Cell viability analyses indicated that the treatment with AGE inhibits cell pro liferation, but does not induce cell death. The mechanism of AGE-induced in hibition of tumor cell growth involves arrest of the cell cycle at the G(0) /G(1) stage without a direct cytotoxic effect. The cell cycle arrest induce d by AGE was accompanied by a decrease of phosphorylated retinoblastoma (Rb ) protein. Furthermore, cyclin-dependent kinases 2 and 4 (Cdk2 and Cdk4), w hich are involved in the phosphorylation of Rb, were also decreased. These results suggest that AGE inhibits tumor cell growth by affecting phosphoryl ated Rb proteins and Cdks.