DHT and testosterone, but not DHEA or E₂, differentially modulate IGF-I, IGFBP-2, and IGFBP-3 in human prostatic stromal cells

Abstract

Prostate cancer is one of the four most common cancers in the United States, affecting one of six men. Increased serum levels of androgens and IGF-I are associated with an augmented risk of prostate cancer. 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 dehydroepiandrosterone (DHEA) in prostate cancer or stromal cells, are uncertain. We investigated the actions of DHT, T, DHEA, and estradiol (E2) on insulinlike growth factor (IGF)-I, IGF-II, IGF-I receptor (R), IGF-binding protein (IGFBP)-2, IGFBP-3, and IGFBP-5 in primary cultures of human prostatic stromal cells by assessing cell proliferation, mRNA expression, and protein secretion by MTT growth assay, quantitative real-time PCR, and ELISA, respectively. DHT and T each increased IGF-I (7-fold) and decreased IGFBP-3 (2-fold) mRNA expression and protein secretion in a dose-and time-dependent manner and increased IGFBP-2 (2-fold) mRNA in a dose-and time-dependent manner. DHEA and E 2 did not significantly alter these measures. Flutamide abolished the DHT-modulated increases in IGF-I and IGFBP-2, suggesting that the influences of DHT and T on these measures were androgen receptor mediated. None of the four steroids significantly affected IGF-IR, IGF-II, or IGFBP-5 mRNA levels or stromal cell proliferation. The effects of DHT on IGF-I, IGFBP-2, and IGFBP-3 were more pronounced in stromal cultures that did not express desmin. 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.

Human prostate stromal cells stimulate increased PSA production in DHEA-treated prostate cancer epithelial cells

“…However, the proliferative response of LAPC-4 to the presence of stromal cells, regardless of the hormone treatment, was significant with 2-3 fold increases in cell numbers within 3 days, similar to prior results published in normal or cancer prostate cells [27]. Multiple stromal cell secreted growth factors may contribute to this proliferative effect, including IGF-1, EGF, HGF, KGF, FGF [8,[28][29][30][31], as well as nvolvement of extracellular matrix proteins [25].…”

“…The prostatic primary stromal cells used in this study (6S) were previously found to increase expression of IGF-1 and IGFBP2 and decrease IGFBP3 in response to treatment with DHT but not with DHEA [8]. The current study focuses on DHEA effects on LAPC-4 cells which, like normal (non cancerous) prostate luminal cells, contain a wild type AR [10].…”

“…But LAPC-4 cells cocultured with PRSC did not increase DHEA-induced PSA production as did the stromal cell lots from prostate cancer surgical samples, (labeled 5S, 6S, 9S, and 12S for the isolation lot number (5,6, 9 or 12) and S for "stroma"). These latter stromal cell lots have been previously characterized as having differential capacity to produce IGF-I, IGFBP-2 and IGFBP-3 [8] as well as having differential expression of cytoskeletal proteins which define the continuum from normal stroma to reactive stromal phenotypes [8,33]. While the enzymatic/ metabolic capacity may be similar in PRSC and reactive stromal cells, there may be additional or different secondary paracrine factors induced in the reactive cancer stroma beyond metabolism of the DHEA that is involved in PSA production.…”

“…Primary human prostate cancer-derived stromal cells were isolated from radical prostatectomy specimens ( [11]; cell lots from different patient samples were labeled: 5S, 6S, 9S, and 12S; kindly provided by Dr. John Isaacs, Johns Hopkins School of Medicine) and have been previously described [8]. Primary prostate stroma cells (PRSC) derived from normal prostate tissues, were obtained from Cambrex (East Rutherford, NJ).…”

“…For example, human prostate cancer LNCaP cells, which harbor a mutated androgen receptor (AR), respond to DHEA administration with increased proliferation, and expression of prostate specific antigen (PSA) and IGF axis proteins [7]. Human prostatic primary stromal cells respond to androgens, such as dihydrotestosterone (DHT), but not DHEA, by increasing IGF-I secretion [8]. Contrastingly, in in vivo studies, DHEA has been found to be an effective inhibitor to carcinogen-induced prostate cancers [9].…”