Inhibition of prostate cancer-cell proliferation by Essiac®

Objective: To assess the ability of Essiac(R) tea extracts (Essiac Canada International, Ottawa, Canada) to modulate cancer cell proliferation and immune responsiveness. Design: A noncancerous transformed cell line was compared to a cancerous cell line and spleen cells that had been isolated from mice to examine proliferation responses mediated by the addition of an Essiac preparation. Results: We found in vitro evidence of decreased proliferation of both noncancerous transformed (CHO) and cancerous prostate cell line (LNCaP) when Essiac was present in the culture media. A dose response for inhibition was demonstrated by a linear regression performed on the data for both the CHO and LNCaP cells. The percent inhibition of the LNCaP cells was higher than the percent inhibition of the CHO cells suggesting that Essiac may have a more selective effect on cancer cells than transformed cells. In addition, the effects of Essiac were examined in an immune T-lymphocyte proliferation assay. At low doses of Essiac, augmentation of proliferation of these T cells was demonstrated, but at higher doses Essiac was inhibitory to T-cell proliferation. The same doses of Essiac that stimulated spleen cells were inhibitory for LNCaP cell proliferation. Conclusions: Essiac preparations may be able to inhibit tumor cell growth while enhancing immune response to antigenic stimulation. This may be especially valuable in immune-suppressed individuals.