Prostate cancer is one of the four most common cancers in the U.S., affecting one of six men. Dihydrotestosterone (DHT) and testosterone (T) stimulate prostate cancer cell growth, development, and function, whereas the effects of DHT and T in prostate stromal cells, and of DHEA in prostate cancer or stromal cells are uncertain.? ? Our current investigations center on the effects of selected androgenic (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 and intracellular signal transduction pathways.? ? As a precursor to both estrogen and testosterone, DHEA excess may pose a potential cancer risk in hormone-responsive tissues such as the prostate. Both stromal and epithelial cells are involved in prostate response to DHEA; thus, we have investigated effects of DHEA on epithelial and stromal cells, grown separately and in co-culture. Prostate cancer epithelial cells exhibit differential responses, to DHEA. depending in part upon their androgen receptor (AR) activity. We recently demonstrated that LNCaP cells with a mutated AR are responsive to DHEA treatment as measured by cell proliferation, and expression of prostate specific antigen (PSA), and IGF axis proteins. In contrast, LAPC-4 cells, which harbor a normal AR, are minimally responsive. Prostatic primary stromal cells were responsive to androgens, such as DHT by increasing secretory IGF-1, whereas DHEA did not produce the same effect. ? ? We compared the effects of DHEA vs DHT in LNCaP cells model using Affymetrix HU-95 gene chips. There were consistent, measurable changes in gene expression patterns following treatment of LNCaP prostate cancer cells with DHEA vs DHT. Understanding the mechanisms of DHEA versus DHT actions in the prostate may help clarify the separate and interactive effects of androgenic and estrogenic actions in prostate cancer progression.? ? We evaluated the extent to which DHEA-modulated effects in LNCaP and LAPC-4 cells are mediated via the AR and/or ER beta. In LNCaP and LAPC-4 cells, inhibitors of AR and ER suppressed hormone-induced PSA mRNA and protein expression. These studies, in addition to others employing siRNA!|s to AR and ER, western blotting and confocal microscopic analyses, suggest that both AR and ER beta contribute to PSA expression induced by DHEA, DHT and E2 in LNCaP cells, and by DHT in LAPC-4 cells. Additional studies are underway to delineate downstream pathways of steroid hormones such as DHEA, DHT, 3 beta?nAdiol, beta?nestradiol (E2) on beta?ncatenin signaling pathway in DU145 prostate cancer cells, in which ER beta activity is normal, while that of AR is minimal. Steroid hormones cross-talk with the Wnt beta catenin pathway and may interact with ER beta in DU145 cells. ER beta is an important target in prostate cells for endogenous and exogenous estrogens and plays a role in modulating androgen activity.? ? We investigated the actions of DHT, T, DHEA, and E2 on IGF axis expression in primary cultures of human prostatic stromal cells. DHT and T modulated IGF-I, IGFBP-2 and IGFBP-3, whereas DHEA and E2did not significantly alter these measures. Flutamide abolished the effects, suggesting that the influences of DHT and T were AR mediated. These data suggest that DHT and T promote prostate growth partly via modulation of the stromal cell IGF axis, with potential paracrine effects on prostate epithelial cells.? ? Whereas the effects of DHEA on LAPC-4 and 6S cells grown separately were minimal, when grown in the presence of 6S stromal cells, DHEA stimulated LAPC-4 cell PSA protein secretion with levels approaching induction by DHT. DHEA-treated 6S stromal cells exhibited a dose-dependent increase in T secretion, suggesting that stromal cells can metabolize DHEA to T, and possibly DHT, thereby increasing PSA. Thus, multiple stromal cell mediators are likely to contribute to DHEA-modulated PSA production, and perhaps other important functions, in LAPC-4 and other prostate cancer epithelial cells. Testing of other stromal cell lots indicated that normal (non-cancer) stromal cells do not induce as dramatic an effect. ? ? We found that stromal cells from normal human prostate (PRSC) maintain a smooth muscle phenotype, whereas those from prostate cancer (6S) display reactive/fibroblastic characteristics; and that DHT modulates IGF-I and IGFBP expression in 6S versus PSRC cells.. DHT exerted anti-apoptotic, proliferative effects in co-cultured 6S + normal prostate epithelial (NPE) cells by stimulating stromal IGF-I production. Epidemiologic studies suggest that excess lycopene consumption reduces prostate cancer risk. Lycopene inhibits IGF-I and androgen signaling in rat prostates. We found that lycopene, in dietary concentrations, decreased prostate epithelial cell (PREC) cell IGF-I production; promoted 6S-mediated NPE cell apoptosis and arrested NPE growth induced by IGF-I by reducing AR and beta-catenin nuclear localization, and by attenuating IGF-I's effects on serine phosphorylation of Akt and GSK3beta, and tyrosine phosphorylation of GSK3. These data may justify prospective animal and clinical trials to determine whether lycopene is useful in the prevention or treatment of prostate cancer.? ? We hypothesize that DHEA exerts minimal effects in the normal prostate, whereas in cancer-associated tissues, the stromal microenvironment promotes prostate proliferation in the presence of DHEA via stromal metabolism to androgenic metabolites and induction of secondary growth factors. This notion is supported by literature demonstrating that the initial pre-neoplastic lesions of prostate cancer are associated with infiltration of immune cells and increased presence of cytokines. Further studies have been initiated to evaluate whether pro-inflammatory cytokines induce stromal cells to metabolize DHEA to more active androgens, thus promoting increased PSA production. Should this effect be validated, it would offer a possible in vitro model of the preneoplastic prostate to test for the effects of selected natural products on stromal regulation of epithelial cell growth and differentiation. In this regard, we have found that lycopene, a carotenoid derived principally from tomato products, promotes apoptosis in co-cultures of prostate stromal and epithelial cells exposed to DHT in part by inhibiting DHT-modulated effects of IGF-I on signal transduction in prostate epithelial cells.
