The use of botanical mixtures is commonplace in patients with
prostate cancer, yet the majority of these products have not been rigorously tested in clinical trials. Here we use
PC-SPES, a combination of eight herbs that has been shown to be effective in clinical trials in patients with
prostate cancer, as a model system to demonstrate 'proof of principle' as to how gene expression profiling coupled with promoter assays can evaluate the effect of herbal cocktails on human
prostate cancer. In addition, we demonstrate how such approaches may be used for standardization of herbal extract activity by comparing the gene profile of
PC-SPES with that of
PC-CARE, a product with a similar herbal composition. Since prior studies have shown that
PC-SPES contains estrogenic organic compounds, and such compounds are known to affect
prostate cancer, an important issue is whether these are the primary drivers of the gene profile. Our data suggest that gene expression profiles of LNCaP human
prostate cancer cells in response to
PC-SPES are different from those found when
diethylstilbestrol (DES), a
synthetic estrogen, is used, suggesting that the estrogenic moieties within
PC-SPES do not drive this expression signature. In contrast, the expression profile of
PC-CARE was almost identical to that of DES, highlighting that mixtures containing similar herbal compositions do not necessarily result in similar
biological activities. Interestingly, these three agents cause similar in vitro morphological changes and growth effects on LNCaP. To validate the expression profiling data, we evaluated the
protein expression and promoter activity of
prostate-specific antigen (PSA), a gene induced by
PC-SPES but repressed by DES. In order to gain a mechanistic understanding of how
PC-SPES and DES affect PSA expression differently, LNCaP cells were transiently transfected with wild-type and mutagenized PSA promoter, ARE concatemers and appropriate controls. We provide evidence that
androgen response elements (ARE) II and III within the promoter region are responsible for the suppressive effects of DES and stimulatory effects of
PC-SPES. In addition, we show that the effects on PSA transcription are ARE specific in the case of DES while
PC-SPES affects this promoter nonspecifically. In conclusion, expression profiling coupled with mechanistic target validation yield valuable clues as to the mode of action of complex botanical mixtures and provides a new way to compare objectively mixtures with similar components either for effect or quality assurance prior to their use in clinical trials.