another study warning against black cohosh use--but this one done on her2+ mice

[Lani]

Black Cohosh Tied to Breast Cancer Spread: Black Cohosh May Not Promote New Breast Tumors but May Spur Breast Cancer Spread, Lab Tests Show [MedicineNet.com]
Nov. 11, 2008 — Black cohosh, a supplement taken to ease menopausal symptoms, may have a mixed relationship with breast cancer.
That's according to a study published recently in Cancer Research.
In the study, female mice with a genetic predisposition for breast cancer ate either normal chow or chow laced with black cohosh throughout their adult lives.
The mice in the black cohosh group weren't more likely than the other mice to develop breast cancer. But they were more likely to have their breast cancer spread to their lungs.
That's "concerning," researcher Vicki Davis, PhD, tells WebMD.
Davis, an assistant professor of pharmacology-toxicology at Duquesne University in Pittsburgh, notes that the black cohosh dose used in the study is equivalent to the amount typically recommended for women, but it remains to be seen if the results apply to women, to other types of cancer, and to cancer's spread to organs other than the lungs.
It's also not yet clear if the timing of exposure to black cohosh makes a difference. "Whether we needed black cohosh to be present as the tumors were developing in order for them to be more aggressive, we don't know that," Davis says.

ABSTRACT: Black Cohosh Increases Metastatic Mammary Cancer in Transgenic Mice Expressing c-erbB2 [Cancer Research]
Black cohosh is an herbal extract that is often used as an alternative to estrogen-based replacement therapies to treat hot flushes that frequently accompany the transition to menopause. Although cancer-free women as well as breast cancer patients and survivors use black cohosh to relieve vasomotor symptoms, there is limited information on its potential to influence breast cancer development or progression. Therefore, in this study, the effects of black cohosh on mammary tumorigenesis were investigated in the MMTV-neu mouse model due to its similarities to HER2+ breast cancer, including stochastic development of mammary tumors, which frequently progress to metastatic disease. Using an adjusted dose for the mice to correlate to the recommended dose in women (40 mg/d), no differences were detected in the incidence or onset of mammary tumors in black cohosh-treated versus control females. The lack of effect on mammary tumor development suggests that black cohosh would not influence breast cancer risk if given to women before tumor formation. In contrast, black cohosh significantly increased the incidence of lung metastases in tumor-bearing animals compared with mice fed the isoflavone-free control diet. Additional studies will be needed to correlate these findings to women taking different black cohosh products at various times during breast cancer development; however, these results suggest caution for women using black cohosh, especially for extended periods of time. As metastatic progression is linked to patient survival, these data stress the importance of investigating how women's therapies influence all stages of mammary tumorigenesis, particularly for assessing their safety.