Ethanolic extracts of herbal supplement Equiguard™ suppress growth and control gene expression in CWR22Rv1 cells representing the transition of prostate cancer from androgen dependence to hormone refractory status

Abstract

Dietary supplements and botanical products are widely used by patients diagnosed with prostate cancer (CaP) as a primary or adjuvant form of treatment for their medical conditions in the United States. Many of the available products are complex mixtures composed of extracts from foreign plants, whose mechanism of action typically is not systematically and rigorously investigated. Laboratory studies employing precisely defined conditions and referenced methodologies are essential not only for standardization and characterization of the products, but are also important requisites for providing scientific evidence and molecular insights in regard to the clinical efficacies some of these products purportedly demonstrate. In previous studies from this laboratory, we serendipitously observed that Equiguard, a dietary supplement formulated with extracts from nine Chinese herbs for preventing decline in renal functions associated with the aging process, contain 70% ethanol-extractable ingredients that displayed potent growth inhibitory activities in androgen-dependent (AD) LNCaP and androgen-independent (AI) DU-145 and PC-3 cells. Moreover, significant reduction in expression of the androgen receptor (AR) and prostate specific antigen (PSA) also occurred in Equiguard-treated LNCaP cells. Although these results offer the possibility that Equiguard confers chemoprevention for CaP, it remains undetermined whether Equiguard functions in CaP cell types that represent the transition of AD to the AI status. Further, details of its mechanism of action have not been fully elucidated. The studies described in this report focusing on CWR22Rv1 cells are intended to fill these gaps. These cells express AR and PSA, yet show weak responsiveness to androgens and largely proliferate in an AI-independent manner - features that mimic AD --> AI in clinically advanced disease. Using the CWR22Rv1 cells, we showed that 70% ethanolic extracts of Equiguard effectively suppressed colony formation, inhibited cell proliferation, reduced expression of cell cycle regulatory proteins including cyclin D1, E2F, as well as lowered AR and PSA levels. Treatment of CWR22Rv1 cells with Equiguard also decreased cyclooxygenase 2 and led to increases in quinone reductase 1 and 2. These results provide further support that Equiguard possess multiple, chemopreventive attributes capable of disrupting the transition of AD --> AI in clinically advanced CaP.