Cellular mechanisms of anticancer effects of Dioscorea membranacea Pierre

Dioscorea membranacea Pierre (Hua-Khao-Yen) has been used in traditional Thai medicine for the treatment of a variety of cancers. In the present study, the effects of crude ethanolic extract from rhizome of this plant on cell growth and division, cell cycle distribution, and apoptotic induction in human lung cancer cell lines, were analyzed. The results showed that the crude extract selectively inhibited cell growth on all types of cell lines examined with significantly less toxicity to normal human lung fibroblasts, MRC-5. Among all cell lines tested, COR-L23 and NCI-H226 were the most sensitive to cytotoxic effect of the extract. Flow cytometric analysis revealed that the extract caused G1 cell cycle arrest of NCI-H226 after 24 h incubation. Consistent with this observation, the cell division of treated cells also ceased at the same incubation period. After 48 and 72 h incubation, however, the percentage of cells in the G1 phase decreased along with an increase in the sub-G1 peak, indicating the induction of apoptosis. The detection of PS, the hallmark of apoptotic cells on outer leaflet of the membrane, using Annexin V showed a 4-fold increase in early apoptotic cells at 30 h incubation. In addition, there was an extensive increase in late apoptotic cells with increasing concentrations of the extract. Therefore, the results of this study indicate that the crude extract from Dioscorea membranacea Pierre exhibits anti-tumor activity through the induction of G1 cell cycle arrest, cell division inhibition, and apoptosis. Key words: Anticancer activity, Cell cycle, Cell division, Apoptosis