Essiac® and Flor-Essence® herbal tonics stimulate the in vitro growth of human breast cancer cells

Background. People diagnosed with cancer often self-administer complementary and alternative medicines (CAMs) to supplement their conventional treatments, improve health, or prevent recurrence. Flor-Essence (R) and Essiac (R) Herbal Tonics are commercially available complex mixtures of herbal extracts sold as dietary supplements and used by cancer patients based on anecdotal evidence that they can treat or prevent disease. In this study, we evaluated Flor-Essence (R) and Essiac (R) for their effects on the growth of human tumor cells in culture. Methods. The effect of Flor-Essence (R) and Essiac (R) herbal tonics on cell proliferation was tested in MCF-7, MDA-MB-436, MDA-MB-231, and T47D cancer cells isolated from human breast tumors. Estrogen receptor (ER) dependent activation of a luciferase reporter construct was tested in MCF-7 cells. Specific binding to the ER was tested using an ICI 182,780 competition assay. Results. Flor-Essence (R) and Essiac (R) herbal tonics at 1%, 2%, 4% and 8% stimulated cell proliferation relative to untreated controls in both estrogen receptor positive (MCF-7 and T47D) and estrogen receptor negative (MDA-MB-231 and MDA-MB-436) cell lines. Exposure to the tonics also produced a dose-dependent increase in ER dependent luciferase activity in MCF-7 cells. A 10(-7) M concentration of ICI 182,780 inhibited the induction of ER dependent luciferase activity by Flor-Essence (R) and Essiac (R), but did not affect cell proliferation. Conclusion. Flor-Essence (R) and Essiac (R) Herbal Tonics can stimulate the growth of human breast cancer cells through ER mediated as well as ER independent mechanisms of action.