Cytotoxic and apoptosis-inducing properties of auriculoside A in tumor cells

The C-12-steroidal glycoside auriculoside A (1), recently isolated from the roots of Cynanchum auriculatum, was found to inhibit the growth of several human tumor cell lines and to induce apoptosis in human breast cancer (MCF-7) cells. Compound 1 was evaluated for its in vitro cytotoxicity against MCF-7, HO-8910, and Bel-7402 cells, and for its in vivo antitumor effects on implanted sarcoma-180 (S180) tumors in mice. It showed significant, concentration-dependent inhibition of the cancer cells, both in vitro and in vivo. MCF-7 Cells exposed to I displayed typical morphological apoptosis characteristics such as cytoplasm contraction and nuclear-chromatin condensation. Flow-cytometric analysis showed that the MCF-7 cell cycle was arrested at the G(0)/G(1) phase. When treated with 40 mu g/ml of 1 for 24, 48, and 72 h, respectively, the apoptotic rates of the cells were ca. 5, 8, and 18.5%, respectively.