Antiproliferative activity of Chinese medicinal herbs on breast cancer cells in vitro

Chinese medicinal herbs are traditionally used to prevent and treat a variety of diseases, including cancer. These herbal preparations are purported to have many biological effects including direct antiproliferative effects on cancer cells, antimutagenic activity, and stimulatory or suppressive effects on immune responses. The present study investigates the effects of aqueous extracts from seventy-one Chinese medicinal herbs on the growth of five breast cancer cell lines (SK-BR-3, MCF7, MDA-MB-231, BT-474 and MCNeuA). Twenty-one percent (15 out of 71) of the extracts demonstrated greater than 50% growth inhibition on at least 4 of the 5 cell lines. Dose-response curves were obtained for several of the most potent crude extracts and demonstrated IC50 values ranging from < 10 mug/ml to > 1 mg/ml. Six of seven herbs tested induced high molecular weight DNA fragmentation, an early marker of apoptosis, while one of these also induced low molecular weight DNA fragmentation. Flow cytometric analysis of breast cancer cells exposed to one of these herbs (Rheum palmatum) suggested that it arrests cells in the G2/M phase of the cell cycle. These results indicate that many of the herbs used in traditional Chinese medicine for the treatment of cancer have significant growth inhibitory effects on breast cancer cells in vitro.