Our current investigations center on the effects of selected androgenic (dehydroepiandrosterone - DHEA), estrogenic (phytoestrogens) or other dietary supplements and/or natural products on neoplastic prostate epithelial and stromal cell growth, gene expression, and biochemical function, including cell-cell signaling. As a precursor to both estrogen and testosterone, DHEA excess may pose a potential cancer risk in hormone responsive tissues such as the prostate. Initial characterization of DHEA effects were completed using the human LNCaP prostate cell model. These cells are steroid responsive prostate cancer cells, containing a functional, but mutated androgen receptor (AR). LNCaP cells were used to compare effects of DHEA treatment with those of T, DHT, and E2 on cell proliferation, and protein and/or gene expression of AR, prostate specific antigen (PSA), insulin-like growth factor-I (IGF-I), IGF-I receptor (IGF-IR), IGF-II, IGF binding proteins ?2,3, and 5, (IGFBPs-2-5), and estrogen receptor beta (ER-beta). Our initial studies raised important questions about the role of DHEA in regulating the balance between androgenic and estrogenic effects in the prostate. This study contributes to the rapidly unfolding information regarding the importance of estrogenic effects and the role of ER-beta in the prostate. To assess the extent to which these findings in LNCaP cells may be related to the mutant AR present in these cells, we are also comparing the effects of DHEA vs DHT, T, and E2 in prostate cancer cells with a wild type AR (LAPC4 cells). LAPC4 cells did not respond to DHEA as shown by a lack of DHEA-induced expressionof PSA. However, when co-cultured with prostate stromal cells, LAPC4 cell PSA expression was increased in response to DHEA. Mechanistic studies were initiated to determine the extent to which DHEA-modulated effects in LNCaP and LAPC4 cells are mediated via the AR and/or ER beta;. The AR antagonist (Casodex?-bicalutamide) or an ER antagonist (ICI 182,780) were added to hormone treatments and effects on cell proliferation and PSA production were evaluated. These studies suggest that DHEA, as well as DHT and E2, stimulate PSA secretion in human LNCaP cells in part via the AR, and in part via an ER-beta.. The exact role(s) of ER-beta; in prostate cancer cells with wild type and mutated AR's remains to be elucidated. Additional characterization of DHEA effects on the LNCaP cell model were performed using Gene microarrays. mRNA from LNCaP cells treated with DHEA or DHT was isolated, purified and probed using the Affymetrix U95 gene chips. Differences in RNA expression between control and either treatment as well as differences between the two treatments were analyzed. These data reveal consistent, measurable differences in gene expression patterns following treatment of human LNCaP prostate cancer cells with DHEA or DHT. The physiological relevance of thes findings will be explored in further detail. Equally important in the functioning of the prostate tissue are the stromal cells. We have investigated the effects of DHEA on primary human stromal cells derived from radical prostatectomy specimens. For these studies, we targeted the IGF axis, including ligands IGF-I, IGF-II, the receptor IGF-IR, and the binding proteins, IGFBP-2, IGFBP-3 and IGFBP-5. Cells were treated with DHT, T, DHEA, and E2 and evaluated for cell proliferation, mRNA expression, and protein secretion by MTT growth assay, quantitative real time PCR, and ELISA, respectively. To our knowledge, these data are the first to show that DHT and T promote prostate growth in part via modulation of the stromal cell IGF axis with potential paracrine effects on prostate epithelial cells.
