Effects of Black Cohosh on Chemotherapies

The herbal medicine black cohosh alters the response of breast cancer cells to some agents used in cancer therapy

Sara Rockwell, Olukemi Fajolu, Yanfeng Liu, Susan A. Higgins.

Yale University School of Medicine, New Haven, CT.

Black cohosh (Cimicifuga racemosa), a widely used herbal medicine, is often assumed to be a safe and effective natural remedy for menopausal symptoms.

Although extracts of this herb are frequently used by breast cancer patients while they are receiving chemotherapy and radiotherapy, their effects on breast cancers and on the effects of anticancer therapy have not been rigorously studied.

We examined this question using EMT6 mouse breast cancer cells and "standardized" liquid extracts of black cohosh obtained from 3 commercial vendors.

None of the extracts had significant effects on the growth or viability of EMT6 cells in vitro, either at doses equivalent to those recommended or 10 or 100 times higher. One extract was administered in the drinking water of mice at a low dose, the recommended human dose, and a high dose to assess its effect on the growth of EMT6 tumors.

No significant effects were detected. We examined the effect of one extract on the response of EMT6 cells to radiation (x-rays) and to three drugs commonly used to treat breast cancer (Adriamycin, Taxotere, Cisplatin). Exponentially growing EMT6 cells in vitro were exposed to the black cohosh extract for 24h, beginning 4h before treatment, then continuing during the drug treatment or irradiation and afterward for a total of 24 hours.

Full dose response curves were performed for radiation and for each drug alone, with the vehicle used to formulate the extract, and with the black cohosh extract. Cell viability was measured by colony formation; at least 3 independent experiments were performed for each agent.

Black cohosh did not alter the response of the cells to radiation. Black cohosh protected the cells from Cisplatin slightly.

Black cohosh significantly increased the toxicity of Adriamycin and Taxotere. The other two black cohosh formulations were also tested in combination with Adriamycin, and also increased the cytotoxicity of this drug. The vehicles had no effects.

Further studies are needed to ascertain the therapeutic implications of our findings: our data could suggest the possibility that black cohosh might increase the efficacy of some drugs, but could also suggest that this herb might increase the toxic side effects of chemotherapy.

This research was supported by a grant from the Ethel F. Donaghue Women's Health Investigator Program at Yale.

Affiliation: Yale University School of Medicine, New Haven, CT . Email: sara.rockwell@yale.edu

AACR Abstract Number: 2721, 2003

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