Antitumor Activity of Herbal Supplements in Human Prostate Cancer Xenografts Implanted in Immunodeficient Mice

Background: Prostate cancer is the second leading cause of cancer death in American men. Therapeutic options for metatstatic prostate cancer are limited. The use of herbal therapies in the treatment of this malignancy remains controversial. Materials and Methods: We tested five herbal supplements, designated FB, FM, PP, HF and FBL101, which contain different combinations of various natural herbs such as licorice, black cohosh, Dong Quai, false unicorn and vitex berry root extracts, fennel seed extract, red clover blossoms extract as well as genistein and gamma oryzanol, for antitumor activity in severely combined immunodeficient mice bearing CWR22R and PC3 prostate cancer xenografts. Their mechanisms of action were also explored. Results: FB, FM, PP, HF and FBL101 inhibited PC3 tumor growth by 53%, 75%, 80%, 81% and 87%, respectively. In CWR22R tumors, similar growth suppression was observed with all supplements. Total plasma testosterone levels were not significantly altered by the supplements relative to the untreated control. PP and FBL101 significantly reduced VEGF levels in PC3 and CWR22R tumors, respectively. Intratumoral microvessel density was decreased in PC3 tumors treated with all five supplements but only in CWR22R tumors treated with HF. Conclusion: Our results demonstrated that herbal supplements containing the aforementioned extracts inhibit the growth of prostate tumor xenografts, possibly in part by antiangiogenic mechanisms. The potential use of these herbal supplements as preventive and therapeutic agents in prostate cancer warrants further investigation.