Prevention and management of prostate cancer using PC-SPES: a scientific perspective

Complementary and alternative therapies are increasingly used in the United States by individuals diagnosed with cancer. PC-SPES is a multiherb dietary supplement used by many patients with prostate cancer (CaP). The wide acceptance of PC-SPES for hormone-naive and end-stage CaP relates to clinical trials demonstrating significant efficacy and low toxicity. Although the clinical efficacy of PC-SPES is highly encouraging, its scientific basis has progressed more slowly. This article describes our understanding of the in vitro mechanisms of action of PC-SPES in androgen-dependent LNCaP cells. We first demonstrated significant suppression of cancer cell growth by restriction of cell cycle progression at G(1)/S and drastic reductions in the expression of androgen receptor and prostate-specific antigen (PSA) by PC-SPES, providing a mechanistic rationale for its observed clinical effects. Further investigation of the anti-CaP properties of PC-SPES revealed that two of its multicomponent herbs, Glycyrrhiza uralensis and Scutellaria baicalensis, inhibited cell growth and down-regulated PSA in a manner comparable with PC-SPES. Exhaustive characterization of S. baicalensis resulted in the isolation of baicalein. Here we report that baicalein effectively suppressed growth and PSA expression and induced G(1)/S arrest in LNCaP cells. Although baicalein cannot account for the entire activity of PC-SPES, it does display similar anti-CaP activities. These data suggest that a single herb or bioactive compound could suffice for CaP chemoprevention by effecting multiple changes in target cells to intervene in CaP progression. These studies provide the impetus for further evaluation of the composition herbs within PC-SPES and the precise characterization of their bioactive ingredients.