Evaluation of the Antiproliferative Effects of Essiac™ on In Vitro and In Vivo Models of Prostate Cancer Compared to Paclitaxel

Abstract

Essiac™, a widely consumed, sparsely tested herbal tea, was evaluated for preparation consistency and antiproliferative effects on prostate cancer cells and xenografts. High performance liquid chromatography (HPLC) was used to compare different lots of Essiac and evaluate extraction consistency by comparing peak areas in concentrated preparations. Repeated analysis of one lot showed < 2% RSD between corresponding peaks. Absolute peak areas varied widely between lots, but similarity in relative size of corresponding peaks was observed. Cytotoxic effects of Essiac were tested in vitro by crystal violet assay and analysis of cell cycle distribution by flow cytometry, but no differences between control and treatment groups was observed. Paclitaxel was used as a positive control in cell cycle analysis and was the only treatment which showed significant effects on cell cycle distribution. Toxicity in nude mice was tested, and efficacy in inhibiting PC-3 xenograft growth. No toxicity or tumour size difference was observed dosing up to 240 mg/kg QD, over 28 days, excepting the positive control group treated with paclitaxel. Ki-67 and PCNA expression was analyzed in treated tumors, but no difference in expression of either marker was observed. These evaluations suggest Essiac has no marked antiproliferative effect on the models tested.

Acknowledgments and Notes

We thank Essiac™ Products Inc. for donating the Essiac and Dr. Helen Burt for supplying the micellar paclitaxel used in this study. This research was supported by a private donation from John Scrymgeour and the CPCRI Large Centre Training Award.

Notes

^a Percent positive immunohistochemical staining of control and Essiac™ treated PC-3 tumors with Ki-67 and proliferating cell nuclear antigen antibodies. The values shown reflect the percentage of positively stained cells. The animal number refers to the identifier of the individual mouse from which the tumor was harvested. Although sections were taken from 11 tumors, many lacked sufficient tissue to allow quantification of the proliferation markers of interest. The number of cores used to determine the average staining levels has been indicated. The overall averages of the treated and control sections have no statistically significant difference (P < 0.05) determined using a Student t-test.