Keratinocyte growth factor: an androgen-regulated mediator of stromal-epithelial interactions in the prostate

Spatial transcriptomics identifies candidate stromal drivers of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is the nodular proliferation of the prostate transition zone in older men, leading to urinary storage and voiding problems that can be recalcitrant to therapy. Decades ago, John McNeal proposed that BPH originates with the "reawakening" of embryonic inductive activity by adult prostate stroma, which spurs new ductal proliferation and branching morphogenesis. Here, by laser microdissection and transcriptional profiling of the BPH stroma adjacent to hyperplastic branching ducts, we identified secreted factors likely mediating stromal induction of prostate glandular epithelium and coinciding processes. The top stromal factors were insulin-like growth factor 1 (IGF1) and CXC chemokine ligand 13 (CXCL13), which we verified by RNA in situ hybridization to be coexpressed in BPH fibroblasts, along with their cognate receptors (IGF1R and CXCR5) on adjacent epithelium. In contrast, IGF1 but not CXCL13 was expressed in human embryonic prostate stroma. Finally, we demonstrated that IGF1 is necessary for the generation of BPH-1 cell spheroids and patient-derived BPH cell organoids in 3D culture. Our findings partially support historic speculations on the etiology of BPH and provide what we believe to be new molecular targets for rational therapies directed against the underlying processes driving BPH.

2b or Not 2b: How Opposing FGF Receptor Splice Variants Are Blocking Progress in Precision Oncology

More than ten thousand peer-reviewed studies have assessed the role of fibroblast growth factors (FGFs) and their receptors (FGFRs) in cancer, but few patients have yet benefited from drugs targeting this molecular family. Strategizing how best to use FGFR-targeted drugs is complicated by multiple variables, including RNA splicing events that alter the affinity of ligands for FGFRs and hence change the outcomes of stromal-epithelial interactions. The effects of splicing are most relevant to FGFR2; expression of the FGFR2b splice isoform can restore apoptotic sensitivity to cancer cells, whereas switching to FGFR2c may drive tumor progression by triggering epithelial-mesenchymal transition. The differentiating and regulatory actions of wild-type FGFR2b contrast with the proliferative actions of FGFR1 and FGFR3, and may be converted to mitogenicity either by splice switching or by silencing of tumor suppressor genes such as CDH1 or PTEN. Exclusive use of small-molecule pan-FGFR inhibitors may thus cause nonselective blockade of FGFR2 isoforms with opposing actions, undermining the rationale of FGFR2 drug targeting. This splice-dependent ability of FGFR2 to switch between tumor-suppressing and -driving functions highlights an unmet oncologic need for isoform-specific drug targeting, e.g., by antibody inhibition of ligand-FGFR2c binding, as well as for more nuanced molecular pathology prediction of FGFR2 actions in different stromal-tumor contexts.

The FGF/FGFR system in the physiopathology of the prostate gland

Fibroblast growth factors (FGFs) are a family of proteins possessing paracrine, autocrine, or endocrine functions in a variety of biological processes, including embryonic development, angiogenesis, tissue homeostasis, wound repair, and cancer. Canonical FGFs bind and activate tyrosine kinase FGF receptors (FGFRs), triggering intracellular signaling cascades that mediate their biological activity. Experimental evidence indicates that FGFs play a complex role in the physiopathology of the prostate gland that ranges from essential functions during embryonic development to modulation of neoplastic transformation. The use of ligand- and receptor-deleted mouse models has highlighted the requirement for FGF signaling in the normal development of the prostate gland. In adult prostate, the maintenance of a functional FGF/FGFR signaling axis is critical for organ homeostasis and function, as its disruption leads to prostate hyperplasia and may contribute to cancer progression and metastatic dissemination. Dissection of the molecular landscape modulated by the FGF family will facilitate ongoing translational efforts directed toward prostate cancer therapy.

N-Butanol and Aqueous Fractions of Red Maca Methanolic Extract Exerts Opposite Effects on Androgen and Oestrogens Receptors (Alpha and Beta) in Rats with Testosterone-Induced Benign Prostatic Hyperplasia

Benign Prostatic Hyperplasia (BPH) affects, worldwide, 50% of 60-year-old men. The Peruvian plant red maca (Lepidium meyenii) inhibits BPH in rodents. This study aimed to determine the effects of methanolic red maca extract and its n-butanol and aqueous fractions on expression of androgen and oestrogen receptors in rats with testosterone enanthate-induced BPH. Thirty-six rats in six groups were studied. Control group received 2 mL of vehicle orally and 0.1 mL of propylene glycol intramuscularly. The second group received vehicle orally and testosterone enanthate (TE) (25 mg/0.1 mL) intramuscularly in days 1 and 7. The other four groups were BPH-induced with TE and received, during 21 days, 3.78 mg/mL of finasteride, 18.3 mg/mL methanol extract of red maca, 2 mg/mL of n-butanol fraction, or 16.3 mg/mL of aqueous fraction from red maca. Treatments with red maca extract and its n-butanol but not aqueous fraction reduced prostate weight similar to finasteride. All maca treated groups restored the expression of ERβ, but only the aqueous fraction increased androgen receptors and ERα. In conclusion, butanol fraction of red maca reduced prostate size in BPH by restoring expression of ERβ without affecting androgen receptors and ERα. This effect was not observed with aqueous fraction of methanolic extract of red maca.

Intraurethral injection with LPS: an effective experimental model of prostatic inflammation

OBJECTIVE

Chronic inflammation has been recognized as having a prominent role pathogenesis of benign prostatic hyperplasia (BPH) and cancer. It is believed that chronic inflammation induces prostatic fibromuscular growth. This correlation has been clearly illustrated by both in vivo and in vitro studies; however, current experimental models of BPH require complex surgery or hormonal treatment. Therefore, the aim of the present study was to propose a new murine model of BPH/prostatitis induced by intraurethral injection of LPS.

METHODS

Male Swiss and C57Bl/6 mice were then sacrificed 3, 7, 10, and 14 days after intraurethral injection of LPS. The prostates were quickly dissected and fixed for morphological and immunohistochemical analyses.

RESULTS

The results showed that LPS played an important role in the cell proliferation of the prostate. Histological and ultrastructural analysis showed epithelial hyperplasia, clear stromal cells, little inflammatory infiltration, and heavy bleeding. Treatment with LPS also promoted the increase of growth factor (FGF-7 and TGF-β), α-actin, and proinflammatory cytokines (IL-1, IL-6, IL-17), both in the stroma and epithelium.

CONCLUSION

According to the present findings, it can be concluded that the intraurethral administration of LPS promotes tissue remodeling, as well as stimulating the pattern of pro-inflammatory cytokines, and therefore, constitutes an effective experimental model of BPH/inflammation.

NF-κB and androgen receptor variant 7 induce expression of SRD5A isoforms and confer 5ARI resistance

BACKGROUND

Benign prostatic hyperplasia (BPH) is treated with 5α-reductase inhibitors (5ARI). These drugs inhibit the conversion of testosterone to dihydrotestosterone resulting in apoptosis and prostate shrinkage. Most patients initially respond to 5ARIs; however, failure is common especially in inflamed prostates, and often results in surgery. This communication examines a link between activation of NF-κB and increased expression of SRD5A2 as a potential mechanism by which patients fail 5ARI therapy.

METHODS

Tissue was collected from "Surgical" patients, treated specifically for lower urinary tract symptoms secondary to advanced BPH; and, cancer free transition zone from "Incidental" patients treated for low grade, localized peripheral zone prostate cancer. Clinical, molecular and histopathological profiles were analyzed. Human prostatic stromal and epithelial cell lines were genetically modified to regulate NF-κB activity, androgen receptor (AR) full length (AR-FL), and AR variant 7 (AR-V7) expression.

RESULTS

SRD5A2 is upregulated in advanced BPH. SRD5A2 was significantly associated with prostate volume determined by Transrectal Ultrasound (TRUS), and with more severe lower urinary tract symptoms (LUTS) determined by American Urological Association Symptom Score (AUASS). Synthesis of androgens was seen in cells in which NF-κB was activated. AR-FL and AR-V7 expression increased SRD5A2 expression while forced activation of NF-κB increased all three SRD5A isoforms. Knockdown of SRD5A2 in the epithelial cells resulted in significant reduction in proliferation, AR target gene expression, and response to testosterone (T). In tissue recombinants, canonical NF-κB activation in prostatic epithelium elevated all three SRD5A isoforms and resulted in in vivo growth under castrated conditions.

CONCLUSION

Increased BPH severity in patients correlates with SRD5A2 expression. We demonstrate that NF-κB and AR-V7 upregulate SRD5A expression providing a mechanism to explain failure of 5ARI therapy in BPH patients. Prostate 76:1004-1018, 2016. © 2016 Wiley Periodicals, Inc.

Targeting the relaxin hormonal pathway in prostate cancer

Targeting the androgen signalling pathway has long been the hallmark of anti-hormonal therapy for prostate cancer. However, development of androgen-independent prostate cancer is an inevitable outcome to therapies targeting this pathway, in part, owing to the shift from cancer dependence on androgen signalling for growth in favor of augmentation of other cellular pathways that provide proliferation-, survival- and angiogenesis-promoting signals. This review focuses on the role of the hormone relaxin in the development and progression of prostate cancer, prior to and after the onset of androgen independence, as well as its role in cancers of other reproductive tissues. As the body of literature expands, examining relaxin expression in cancerous tissues and its role in a growing number of in vitro and in vivo cancer models, our understanding of the important involvement of this hormone in cancer biology is becoming clearer. Specifically, the pleiotropic functions of relaxin affecting cell growth, angiogenesis, blood flow, cell migration and extracellular matrix remodeling are examined in the context of cancer progression. The interactions and intercepts of the intracellular signalling pathways of relaxin with the androgen pathway are explored in the context of progression of castration-resistant and androgen-independent prostate cancers. We provide an overview of current anti-hormonal therapeutic treatment options for prostate cancer and delve into therapeutic approaches and development of agents aimed at specifically antagonizing relaxin signalling to curb tumor growth. We also discuss the rationale and challenges utilizing such agents as novel anti-hormonals in the clinic, and their potential to supplement current therapeutic modalities.

Androgen receptor roles in the development of benign prostate hyperplasia

Benign prostate hyperplasia (BPH) is a major cause of lower urinary tract symptoms, with an increased volume of transitional zone and associated with increased stromal cells. It is known that androgen/androgen receptor (AR) signaling plays a key role in development of BPH, and that blockade of this signaling decreases BPH volume and can relieve lower urinary tract symptoms, but the mechanisms of androgen/AR signaling in BPH development remain unclear, and the effectiveness of current drugs for treating BPH is still limited. The detailed mechanisms of androgen/AR signaling need to be clarified, and new therapies are needed for better treatment of BPH patients. This review focuses on roles of AR in epithelial and stromal cells in BPH development. In epithelial cells, AR may contribute to BPH development via epithelial cell-stromal cell interaction with alterations of epithelial-mesenchymal transition, leading to proliferation of stromal cells. Data from several mouse models with selective knockout of AR in stromal smooth-muscle cells and/or fibroblasts indicate that the AR in stromal cells can also promote BPH development. In prostatic inflammation, AR roles in infiltrating macrophages and epithelial and stromal cells have been linked to BPH development, which has led to discovery of new therapeutic targets. For example, targeting AR with the novel AR degradation enhancer, ASC-J9 offers a potential therapeutic approach against BPH development.

The differential effects of prostate stromal cells derived from different zones on prostate cancer epithelial cells under the action of sex hormones

It is well known that prostate cancer (PCa) occurs predominantly in the peripheral zone (PZ), whereas benign prostatic hyperplasia (BPH) typically develops in the transition zone. To identify possible mechanisms underlying zonal differences, we compared the effects of prostate stromal cells derived from the peripheral zone (PZsc) and the transition zone (TZsc) on a PCa epithelial cell line (PC3) in the presence of sex hormones. First, we observed that androgen receptor (AR) mRNA was more highly expressed in PZsc than TZsc when the cells were treated with dihydrotestosterone (DHT) and β-oestradiol (E2) (P<0.05). By ELISA, we looked for differences in the secretion of peptide growth factors from PZsc and TZsc. We found that keratinocyte growth factor (KGF) secretion increased with increasing concentrations of DHT (P<0.01) and was higher in PZsc than TZsc. Under treatment with DHT plus E2, PZsc secreted more transforming growth factor-β1 (TGF-β1) than TZsc, but this pattern was reversed when the cells were treated with E2 only. With increasing concentrations of DHT, insulin-like growth factor-1 (IGF-1) secretion increased in PZsc but decreased in TZsc. To further characterize the effects of PZsc and TZsc on PC3 cells, we developed a coculture model and performed MTT assays, Western blot analysis and real-time RT-PCR. We found that PZsc promoted PC3 cell proliferation and progression better than TZsc, particularly when treated with 10 nmol l(-1) DHT plus 10 nmol l(-1) E2. In conclusion, our data suggest that PZsc may have a greater capacity to induce PCa development and progression than TZsc via growth factors regulated by sex hormones. These findings provide possible mechanisms underlying zonal differences in prostate diseases, which may aid the search for novel therapeutic targets for PCa.

FGF signalling in prostate development, tissue homoeostasis and tumorigenesis

The FGFs (fibroblast growth factors) regulate a broad spectrum of biological activities by activating transmembrane FGFR (FGF receptor) tyrosine kinases and their coupled intracellular signalling pathways. In the prostate, the mesenchymal-epithelial interactions mediated by androgen signalling and paracrine factors are essential for gland organogenesis, homoeostasis and tumorigenesis. FGFs mediate these mesenchymal-epithelial interactions in the prostate by paracrinal crosstalk through a diverse set of ligands and receptors. Gain- and loss-of-function studies in mouse models have demonstrated the requirement for the FGF signalling axis in prostate development and homoeostasis. The aberrant induction of this axis in either compartment of the prostate results in developmental disorders, disrupts the homoeostatic balance and leads to prostate carcinogenesis. FGFs are also implicated in mediating androgen signalling in the prostate between mesenchymal and epithelial compartments. Therefore studying FGF signalling in the prostate will help us to better understand the underlying molecular mechanisms by which the gland develops, maintains homoeostasis and undergoes carcinogenesis; as well as yield clues on how androgens mediate these processes and how advanced-tumour prostate cells escape strict androgen regulations.

Soluble factors derived from stroma activated androgen receptor phosphorylation in human prostate LNCaP cells: roles of ERK/MAP kinase

BACKGROUND

Accumulated evidence suggests stromal-epithelial interactions are critical to the progression of prostate cancer. In this study, we characterized AR phosphorylation in LNCaP cells co-cultured with the conditioned medium (CM) from human prostate stromal fibroblasts.

METHODS

CM harvested from prostate stromal fibroblasts was added to LNCaP cells, and both anchorage-dependent and -independent growth was determined. Status of AR phosphorylation at Ser-81 and Ser-213 was assessed by immunoblot analysis. ERK kinase activity was measured using MBP-2 protein as the substrate.

RESULTS

The growth of LNCaP cells on plastic dishes increased by 1.7-fold upon exposure to stromal CM or androgen, and their combination resulted in additive growth (2.4-fold). Anchorage-independent growth of LNCaP cells in soft agar, however, was induced synergistically at 80-fold by both stromal CM and androgen. Stromal CM or androgen alone induced LNCaP cell growth by 10- and 26-fold, respectively. We observed ERK kinase inhibitor, U0126, but not phosphatidylinositol 3-kinase (PI-3K), LY294002, or protein kinase A (PKA) inhibitor, H-89, inhibited stromal CM or androgen-induced PSA promoter luciferase activities, and anchorage-independent growth of LNCaP cells. Our results demonstrated for the first time how stromal CM acts in synergy with androgen by activation of ERK kinase and AR phosphorylation at Ser-81 but not Ser-213, for AR-regulated PSA promoter and anchorage-independent growth of human prostate cancer cells.

CONCLUSIONS

A stromal factor-activated ERK pathway mediated by AR phosphorylation at Ser-81 could be responsible for stimulating the growth of human prostate cancer cells.

Androgen receptor signalling in prostate: effects of stromal factors on normal and cancer stem cells

The prostate gland is the most common site for cancer in males within the developed world. Androgens play a vital role in prostate development, maintenance of tissue function and pathogenesis of prostate disease. The androgen receptor signalling pathway facilitates that role in both the epithelial compartment and in the underlying stroma. Stroma is a key mediator of androgenic effects upon the epithelium and can regulate both the fate of the epithelial stem cell and potentially the initiation and progression of prostate cancer. Different groups of growth factors are expressed by stroma, which control proliferation, and differentiation of prostate epithelium demonstrating a critical role for stroma in epithelial growth and homeostasis. Paracrine stromal proteins may offer the possibility to control tumour stem cell growth and could permit prostate specific targeting of both therapies and of androgen responsive proteins. The effect of 5alpha-dihydrotestosterone, the more potent metabolite of testosterone, on expression of androgen-regulated genes in stroma from benign prostatic hyperplasia is a key mediator of epithelial cell fate. Global gene expression arrays have recently identified new candidate genes in androgen responsive stroma, some of which have androgen receptor binding sites in their promoter regions. Some of these genes have direct androgen receptor binding ability.

Cancer statistics, 2007

Each year, the American Cancer Society (ACS) estimates the number of new cancer cases and deaths expected in the United States in the current year and compiles the most recent data on cancer incidence, mortality, and survival based on incidence data from the National Cancer Institute, Centers for Disease Control and Prevention, and the North American Association of Central Cancer Registries and mortality data from the National Center for Health Statistics. This report considers incidence data through 2003 and mortality data through 2004. Incidence and death rates are age-standardized to the 2000 US standard million population. A total of 1,444,920 new cancer cases and 559,650 deaths for cancers are projected to occur in the United States in 2007. Notable trends in cancer incidence and mortality rates include stabilization of the age-standardized, delay-adjusted incidence rates for all cancers combined in men from 1995 through 2003; a continuing increase in the incidence rate by 0.3% per year in women; and a 13.6% total decrease in age-standardized cancer death rates among men and women combined between 1991 and 2004. This report also examines cancer incidence, mortality, and survival by site, sex, race/ethnicity, geographic area, and calendar year, as well as the proportionate contribution of selected sites to the overall trends. While the absolute number of cancer deaths decreased for the second consecutive year in the United States (by more than 3,000 from 2003 to 2004) and much progress has been made in reducing mortality rates and improving survival, cancer still accounts for more deaths than heart disease in persons under age 85 years. Further progress can be accelerated by supporting new discoveries and by applying existing cancer control knowledge across all segments of the population.

Role of phenytoin in wound healing: microarray analysis of early transcriptional responses in human dermal fibroblasts

Wound healing is a complex process involving a number of related genes and receptors. Using cDNA microarrays, we explored the global gene expression profile of phenytoin (20microg/ml) induced changes to human dermal fibroblasts. Microarray data analysis revealed approximately 1500 genes were differentially expressed by 2.5-fold. At 3, 6, 12, and 24h, the transcripts of the major growth factors involved in wound healing and their receptors were increased. This was further confirmed by RT-PCR. Genes encoding other proteins with roles in signal transduction (NFkappaB), extracellular matrix (MMP1) including type I collagen, fibronectin, and laminin were strongly induced at 6h and onwards. Genes involved in cell cycle regulation (CCND1 and CDKN1A) were down-regulated consistent with our finding that phenytoin per se did not have cell proliferation activity. Notably, phenytoin accelerates the autocrine and paracrine activity of growth factors by up-regulating the related receptors.

Cytogenetic findings in a case of nodular fasciitis of subclavicular region

We report a case of nodular fasciitis with a reciprocal translocation involving both homologues of chromosome 15 [46,XX,t(15;15)(q13;q25)]. This is the third case of nodular fasciitis with involvement of chromosome 15. Two genes that are involved in either wound healing and/or tumorigenesis have been mapped to chromosome 15. One of the genes, the keratinocyte growth factor or fibroblast growth factor 7 (KGF or FGF7) was mapped to the 15q22 region, which was involved in a cytogenetic rearrangement in one case of nodular fasciitis. KGF is implicated in wound healing, healing lung injuries and tumorigenesis of various cancers such as breast and prostate. The second gene involved is TRKC or NTRK3 mapped to the 15q25 region. TRKC is implicated in congenital fibrosarcoma, a benign proliferation of fibroblasts. The breakpoint and overexpression of the protein in our case further suggest a possible involvement of TRKC.

Effects of aging on growth factors gene and protein expression in the dorsal and ventral lobes of rat prostate

We hypothesize that various growth factors and their receptors gene and protein are modulated in dorsal and ventral lobes of aging prostate. To test this hypothesis, TGFbeta1, TGFbeta2 TGFbeta3, TGFbetaR-I, TGFbetaR-II, TGFalpha, EGF, EGFR, KGF and KGFR gene and protein expression were analyzed in dorsal and ventral lobes of aging rat prostates (1, 3, 6, 9, 12, 18, 24, and 28/30 months). KGF gene expression was very weak or absent in 1, 3, and 6 month old rat dorsal and ventral lobes of prostate whereas it re-expressed in 9, 12, 18, 24 and 30 month old rat prostate. All growth factors and their receptors expect KGF and EGFR were mainly localized in epithelium of ventral and dorsal lobes of aging rat prostates. EGF, TGFalpha, TGFbeta1, and TGFbetaR-I protein expression was lacking in stroma of dorsal and ventral lobes of 1, 3, 6, 9, 12/18 months old rat prostates. However, EGF, TGFbeta1 and TGFbetaR-I proteins re-expressed in stroma of 24 and 28 months old rat prostates. KGF protein expression was lacking in epithelium of dorsal and ventral lobes of all aging rat prostates. This is the first report to demonstrate differential gene and protein expression of growth factors in dorsal and ventral lobes is associated with aging rat prostate, suggesting their role in pathogenesis of prostatic diseases with aging.

Keratinocyte growth factor-induced motility of breast cancer cells

Endogenous growth factors and cytokines are known to have a major influence on the progression, motility and invasiveness of tumor cells. We have reported previously that conditioned media from mouse fibroblasts increases the motility of breast cancer cells. Further, we determined that keratinocyte growth factor (KGF) was an active factor from mouse fibroblasts responsible for most of the motility response in breast cancer cells. The present study examined the effect of Human KGF on the motility of estrogen receptor (ER)-positive and ER-negative human breast cancer cell lines in culture using time-lapse videomicroscopy to quantify cell motility. In the present study we observed that recombinant human KGF enhanced several parameters of cellular motility in ER-positive cells but not in ER-negative cell lines. Further, we observed that the level of KGF receptor (KGFR) expression in ER-positive cells was much greater than in the ER-negative cell lines. The motility response to KGF was found to be both dose-and time-dependent. Of the three ER-positive breast cancer cell lines tested. MCF-7 cells were the most responsive to KGF stimulation. Finally, MCF-7 cells grown in estrogen-depleted media did not respond to KGF. These results suggest that KGF from stromal tissue surrounding a primary tumor mass can enhance tumor cell motility and may be an early signal in the progression of breast cancer cells to a more motile and metastatic phenotype. Thus, KGF, KGFR and/or the KGF signaling pathway may be important therapeutic targets for the treatment or prevention of breast cancer metastasis.

Androgen regulation of the cell-cell adhesion molecule-1 (Ceacam1) gene

Previous studies have established that the cell-cell adhesion molecule-1 (CEACAM1, previously known as C-CAM1) functions as a tumor suppressor in prostate cancer and is involved in the regulation of prostate growth and differentiation. However, the molecular mechanism that modulates CEACAM1 expression in the prostate is not well defined. Since the growth of prostate epithelial cells is androgen-regulated, we investigated the effects of androgen and the androgen receptor (AR) on CEACAM1 expression. Transient transfection experiments showed that the AR can enhance the Ceacam1 promoter activity in a ligand-dependent manner and that the regulatory element resides within a relatively short (-249 to -194 bp) segment of the 5'-flanking region of the Ceacam1 gene. This androgen regulation is likely through direct AR-promoter binding because a mutant AR defective in DNA binding failed to upregulate reporter gene expression. Furthermore, electrophoretic mobility shift assays demonstrated that the AR specifically binds to this sequence, and mutation analysis of the potential ARE sequences revealed a region within the sequence that was required for the AR to activate the Ceacam1 gene. Therefore, the regulation of Ceacam1 gene expression by androgen may be one of the mechanisms by which androgen regulates prostatic function.

Prostatic intraepithelial neoplasia in mice expressing an androgen receptor transgene in prostate epithelium

Prostate cancer (PCa) is an androgen dependent disease that can be treated by androgen ablation therapy, and clinical trials are under way to prevent PCa through the reduction of androgen receptor (AR) activity. However, there are no animal models of AR-mediated prostatic neoplasia, and it remains unclear whether the AR is a positive or negative regulator of cell growth in normal prostate secretory epithelium. To assess the direct effects of the AR in prostate epithelium, a murine AR transgene regulated by the rat probasin promoter (Pb) was used to generate transgenic mice expressing increased levels of AR protein in prostate secretory epithelium. The prostates in younger (<1 year) Pb-mAR transgenic mice were histologically normal, but Ki-67 immunostaining revealed marked increases in epithelial proliferation in ventral prostate and dorsolateral prostate. Older (>1 year) transgenic mice developed focal areas of intraepithelial neoplasia strongly resembling human high-grade prostatic intraepithelial neoplasia (PIN), a precursor to PCa. These results demonstrate that the AR is a positive regulator of cell growth in normal prostate epithelium and provide a model system of AR-stimulated PIN that can be used for assessing preventative hormonal therapies and for identifying secondary transforming events relevant to human PCa.

Up-regulation of keratinocyte growth factor and receptor: a possible mechanism of action of phenytoin in wound healing

A number of studies suggest that keratinocyte growth factor (KGF) plays a major part in reepithelialisation after injury, via binding to the specific KGF receptor (KGFR). Several pharmacological agents, including the anti-epileptic drug phenytoin (PHT), have been widely used clinically to promote wound healing. Although the mechanism of action of PHT in this process is still not well understood, it is possible that the activity of PHT in wound healing is mediated via KGF and the KGFR. In the present study, using the enzyme-linked immunosorbant assay and flow cytometry we have shown that PHT increases KGF secretion and KGFR expression by more than 150% in gingival fibroblasts and epithelial cells, respectively. Moreover, semi-quantitative reverse transcriptase-polymerase chain reaction analysis showed that PHT also markedly increased both KGF and KGFR gene transcription by these cells. Our findings thus suggest that the wound healing activity of PHT in vivo may be mediated, at least partly, via KGF and its receptor.

Estrogen mitogenic action. ii. negative regulation of the steroid hormone-responsive growth of cell lines derived from human and rodent target tissue tumors and conceptual implications

In an accompanying report (Moreno-Cuevas, J. E.; Sirbasku, D. A., In Vitro Cell. Dev. Biol.; 2000), we demonstrated 80-fold estrogen mitogenic effects with MTW9/PL2 rat mammary tumor cells in cultures supplemented with charcoal-dextran-treated serum. All sera tested contained an estrogen reversible inhibitor(s). The purpose of this report is to extend those observations to additional sex steroid-responsive human and rodent cell lines. Every line tested showed a biphasic response to hormone-depleted serum. Concentrations of < or = 10% (v/v) promoted substantive growth. At higher concentrations, serum was progressively inhibitory. With estrogen receptor-positive (ER+) human breast cancer cells, rat pituitary tumor cells, and Syrian hamster kidney tumor cells, 50% (v/v) serum caused significant inhibition, which was reversed by very low physiologic concentrations of estrogens. This same pattern was observed with the steroid hormone-responsive LNCaP human prostatic carcinoma cells. Because steroid hormone mitogenic effects are now easily demonstrable using our new methods, the identification of positive results has nullified our original endocrine estromedin hypothesis. We also evaluated autocrine/paracrine growth factor models of estrogen-responsive growth. We asked if insulin-like growth factors I and II, insulin, transforming growth factor alpha, or epidermal growth factor substituted for the positive effects of estrogens. Growth factors did not reverse the serum-caused inhibition. We asked also if transforming growth factor beta (TGFP) substituted for the serum-borne inhibitor. TGFbeta did not substitute. Altogether, our results are most consistent with the concept of a unique serum-borne inhibitor as has been proposed in the estrocolyone model. However, the aspect of the estrocolyone model related to steroid hormone mechanism of action requires more evaluation. The effects of sex steroids at picomolar concentrations may reflect mediation via inhibitor "activated" intracellular signaling pathways.

The prostate: development and physiology

The development of the prostate is controlled by steroid hormones that in turn induce and maintain a complex and little understood cross talk between the various cell types making up the gland. The result of this intercellular communication can be either new growth or growth quiescence, depending upon the differentiation state of the cell type being stimulated. Secretory function of the prostate is dependent upon direct stimulation of fully differentiated prostatic epithelial cells by androgens. The prostate thus seems to be regulated in a similar manner to other organs of the male and female genital tract with proliferative control mediated by cell-cell interactions, whereas differentiated function is determined by direct steroid action on the parenchymal cells.

Amphiregulin is coordinately expressed with heparin-binding epidermal growth factor-like growth factor in the interstitial smooth muscle of the human prostate

Peptide growth factors have been proposed as mediators of smooth muscle-epithelial cell interactions in the human prostate; however, the identity of these molecules has not been established. In this study, we compared expression levels of messenger RNAs (mRNAs) encoding the epidermal growth factor (EGF) receptor-related receptor tyrosine kinases (ErbB1 through 4), the six EGF receptor ligands, EGF, transforming growth factor (TGF)-alpha, amphiregulin (ARG), HB-EGF, betacellulin, and epiregulin, and the related molecule heregulin-alpha, in a series of 10 prostate tissue specimens. Only EGF showed a disease-specific association, with increased mRNA levels in four of five PCa specimens in comparison to matched normal tissue from the same subject. In contrast, ARG and HB-EGF mRNAs showed a coordinate pattern of expression in 7/10 specimens that was distinct from all other growth factor or receptor genes examined and from mRNAs for prostate specific antigen, the androgen receptor and GAPDH, a house-keeping enzyme. Analysis of an additional series of benign prostatic hyperplasia and prostate cancer specimens from 60 individuals confirmed that ARG and HB-EGF mRNA levels varied in a highly coordinate manner (r = 0.93; P < 0.0001) but showed no association with disease. ARG was immunolocalized largely to interstitial smooth muscle cells (SMC), previously identified as the site of synthesis of HB-EGF in the prostate, while the cognate ARG and HB-EGF receptor, ErbB1, was localized exclusively to ductal epithelial cells and carcinoma cells. Although ARG was a relatively poor mitogen for Balb/c3T3 cells in comparison to HB-EGF, it was similar in potency to HB-EGF in stimulating human prostate epithelial cell growth, suggesting that prostate epithelia may be a physiologic target for ARG in vivo. Expression of both ARG and HB-EGF mRNAs was induced in cultured prostate SMC by fibroblast growth factor-2, a human prostate SMC mitogen linked to prostate disease. These findings indicate that ARG and HB-EGF are likely to be key mediators of directional signaling between SMC and epithelial cells in the human prostate and appear to be coordinately regulated.

Tyrosine kinases expressed in vivo by human prostate cancer bone marrow metastases and loss of the type 1 insulin-like growth factor receptor

An important biological feature of prostate cancer (PCa) is its marked preference for bone marrow as a metastatic site. To identify factors that may support the growth of PCa in bone marrow, expression of receptor and nonreceptor tyrosine kinases by androgen-independent PCa bone marrow metastases was assessed. Bone marrow biopsies largely replaced by PCa were analyzed using reverse transcriptase-polymerase chain reaction amplification with degenerate primers that amplified the conserved kinase domain. Sequence analyses of the cloned products demonstrated expression of multiple kinases. Expression of the receptor and nonreceptor tyrosine kinases, alpha platelet-derived growth factor receptor and Jak 1, respectively, was confirmed by immunohistochemistry. In contrast, the type 1 insulin-like growth factor receptor, thought to play a role in PCa development, was lost in metastatic PCa. These results implicate several specific growth factors and signaling pathways in metastatic androgen-independent PCa and indicate that loss of the type 1 insulin-like growth factor receptor contributes to PCa progression.

Prostatic growth and development are regulated by FGF10

We have examined the role of Fibroblast Growth Factor 10 (FGF10) during the growth and development of the rat ventral prostate (VP) and seminal vesicle (SV). FGF10 transcripts were abundant at the earliest stages of organ formation and during neonatal organ growth, but were low or absent in growth-quiescent adult organs. In both the VP and SV, FGF10 transcripts were expressed only in a subset of mesenchymal cells and in a pattern consistent with a role as a paracrine epithelial regulator. In the neonatal VP, FGF10 mRNA was expressed initially in mesenchymal cells peripheral to the peri-urethral mesenchyme and distal to the elongating prostatic epithelial buds. At later stages, mesenchymal cells surrounding the epithelial buds also expressed FGF10 transcripts. During induction of the SV, FGF10 mRNA was present in mesenchyme surrounding the lower Wolffian ducts and, at later stages, FGF10 transcripts became restricted to mesenchymal cells subadjacent to the serosa. We investigated whether the FGF10 gene might be regulated by androgens by analysing the levels of FGF10 transcripts in SV and VP organs grown in serum-free organ culture. While FGF10 transcript levels increased after treatment with testosterone in the SV (but not VP), these changes were not sensitive to anti-androgen treatment, and thus it is likely that FGF10 mRNA was not directly regulated by testosterone. Also, FGF10 mRNA was observed in the embryonic female reproductive tract in a position analogous to that of the ventral prostate in males suggesting that FGF10 is not regulated by androgens in vivo. Recombinant FGF10 protein specifically stimulated growth of Dunning epithelial and BPH1 prostatic epithelial cell lines, but had no effect on growth of Dunning stromal cells or primary SV mesenchyme. Furthermore, FGF10 protein stimulated the development of ventral prostate and seminal vesicle organ rudiments in serum-free organ culture. When both FGF10 and testosterone were added to organs in vitro, there was no synergistic induction of development. Additionally, development induced by FGF10 was not inhibited by the addition of the anti-androgen Cyproterone Acetate demonstrating that the effects of FGF10 were not mediated by the androgen receptor. Taken together, our experiments suggest that FGF10 functions as a mesenchymal paracrine regulator of epithelial growth in the prostate and seminal vesicle and that the FGF10 gene is not regulated by androgens

Androgen responsiveness of stromal cells of the human prostate: regulation of cell proliferation and keratinocyte growth factor by androgen

PURPOSE

Growth and development of the prostate are androgen dependent and mainly influenced by stromal-epithelial interaction. It is believed that indirect androgenic activation of paracrine factors like keratinocyte growth factor (KGF) in the prostatic stroma influences the growth of epithelial cells. In this study we investigated the role androgen plays in stromal cell growth and stimulation of KGF in the human prostate.

MATERIALS AND METHODS

Stromal cells were derived from explant primary culture of human normal or benign prostatic tissue. The effect of different dihydrotestosterone (DHT) concentrations on cell proliferation was measured using 3[H]thymidine incorporation assay. The effect of DHT on levels of KGF protein was determined by Western blotting. The effect of DHT on levels of KGF gene expression was measured by various cycles of polymerase-chain-reaction (PCR) and multiplex PCR.

RESULTS

Characterization of stromal cells showed epithelial cells less than 9.5% in all passages. DHT stimulated human prostate stromal cells in a dose dependent fashion over a concentration range of 0.001-10 nM. Immunocytochemical evaluation of KGF after DHT exposure showed a higher staining intensity. Relative quantitation of Western blotting showed a 1.93-fold increase in KGF protein in the androgen treated stromal cells. At 1 nM DHT conventional and multiplex PCR revealed a significant stimulation of the KGF mRNA expression.

CONCLUSIONS

These data show for the first time that androgen stimulates cell proliferation as well as KGF protein and gene expression in human prostate stromal cells. This supports the hypothesis that androgen-induced stromal-derived KGF stimulates prostate epithelial cell growth.

Interactions between adult human prostatic epithelium and rat urogenital sinus mesenchyme in a tissue recombination model

Tissue recombinants composed of adult human prostatic epithelium (hPrE) and rat urogenital sinus mesenchyme (rUGM) were grafted beneath the renal capsule of athymic rodent hosts. The pseudostratified human epithelium initially became multilayered, solid epithelial cords emerged, grew into the surrounding mesenchyme and canalized to regenerate a pseudostratified epithelium. Basal cells expressed cytokeratins 5 and 14, while luminal cells expressed cytokeratins 8 and 18, prostate specific antigen and prostatic acid phosphatase. The rat mesenchymal component differentiated into thick sheets of smooth muscle, characteristic of the human but not the rat prostate. These findings indicate that epithelial-mesenchymal interactions were reciprocal. Rat UGM induced adult hPrE to form new ductal-acinar tissue, involving epithelial proliferation, ductal branching morphogenesis and functional cytodifferentiation. Concurrently the epithelium dictated smooth muscle differentiation and patterning. Species-specific reverse transcriptase polymerase chain reaction SC (RT-PCR) analysis of the tissue recombinants was performed to separately examine the expression of epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), epidermal growth factor receptor (EGFR), TGF-beta 1, and TGF-beta 3 in the epithelium, stroma and host components of the graft. All of these genes, except TGF-beta 1, were expressed in all three tissues. Human TGF-beta 1 was not detected, indicating that this gene was not expressed in human prostatic epithelium but was present in stroma.

Developmental and hormonal regulation of keratinocyte growth factor expression and action in the ovarian follicle

The developing ovarian follicle is one of the most rapidly proliferating normal tissues in vivo. Mesenchymal-epithelial cell interactions between theca cells and granulosa cells are essential for this follicular expansion. Ovarian hormones (i.e. estrogen and LH) may promote follicular development by regulating the local production of mesenchymal inducer proteins that mediate theca cell-granulosa cell interactions. Recently, theca cells were shown to produce keratinocyte growth factor (KGF) that can act in a paracrine manner to stimulate granulosa cell growth. In this study, the developmental and hormonal regulation of KGF was examined during follicular development in the bovine ovary. Expression of KGF in theca cells and the KGF receptor (KGFR, or splice variant of the fibroblast growth factor family receptor family, FGFR-2) in granulosa cells was examined using RT-PCR. Both KGF and KGFR were detected throughout follicular development in small (<5 mm), medium (5-10 mm), and large (>10 mm) follicles. Quantitative RT-PCR assays were used to determine steady-state levels of KGF and KGFR messenger RNAs. Developmental regulation of KGF and KGFR was analyzed in freshly isolated theca cells and granulosa cells from small, medium, and large follicles. Observations demonstrated that expression of KGF (in theca cells) and KGFR (in granulosa cells) was highest in large follicles. These results suggest that KGF actions are important for the rapid proliferation of granulosa cells in large follicles. Estrogen and LH are the primary endocrine hormones that regulate theca cell function in vivo. Therefore, hormonal regulation of KGF was analyzed by treating serum-free theca cell cultures with estrogen and human CG (hCG, an LH agonist). Results showed that both estrogen and hCG stimulated KGF gene expression in theca cells. These results suggest that estrogen and LH may promote follicular growth (i.e. granulosa cell proliferation), in part, by stimulating the local production of KGF. Effects of KGF on granulosa cell differentiated functions were examined. Treatment with KGF reduced basal levels and FSH-stimulated levels of aromatase activity in bovine and rat granulosa cells. In addition, KGF inhibited the ability of hCG to stimulate progesterone production by granulosa cells. The inhibition of granulosa cell steroid production by KGF was likely the indirect effect of promoting cellular proliferation. Therefore, KGF directly stimulates granulosa cell proliferation and indirectly inhibits granulosa cell differentiated functions. Combined results suggest that theca cell production of KGF may be important for ovarian folliculogenesis. This is the first report of the regulation of KGF expression in the ovary. The developmental and hormonal regulation of KGF and KGFR during folliculogenesis provides evidence that KGF may be important for hormone-induced granulosa cell proliferation. As a result, KGF may be essential for establishing the microenvironment required for oocyte maturation in the ovary.

Analysis of growth factor and receptor mRNA levels during development of the rat seminal vesicle and prostate

Development of the mammalian male accessory sexual organs requires both androgens and mesenchymal/epithelial interactions. Paracrine acting factors whose expression is mesenchymal and androgen dependent have been proposed to regulate development of these organs, although the identity of these paracrine mediators is unknown. Keratinocyte growth factor (Kgf) has been shown to play an important role in the development of the mouse seminal vesicle and rat ventral prostate. Also, Kgf is expressed in mesenchymal cells and has been shown to be regulated by androgens in prostatic cells grown in vitro. Thus Kgf has been proposed as a mediator of androgen action. We have investigated the expression of Kgf mRNA during development of the rat seminal vesicle and prostate, both in vitro and in vivo. Additionally we have examined mRNAs for Kgf receptor (KgfR), transforming growth factor alpha (Tgf alpha), epidermal growth factor receptor (EgfR) and cytokeratin 19 (CK19). The levels of growth factor and receptor mRNAs fluctuated during androgen-regulated development; however, these changes reflected variations in the mesenchymal/epithelial ratio rather than regulation by testosterone. Expression of Kgf is mesenchymal, while KgfR is epithelial and Tgf alpha is predominantly epithelial. The changes in the levels of mRNAs for these factors correlated well with changes in the level of an epithelial marker, CK19, suggesting they were due to alterations in the relative abundance of tissue compartments in which they were expressed. Kgf has been shown to mimic androgen action in explant cultures of seminal vesicle and prostate. We demonstrate here that anti-androgens are able to block Kgf stimulated development, suggesting that Kgf and androgen receptor signalling pathways may interact. Taken together our data suggest that, in vivo, Kgf may interact with androgen receptor signalling but it is not a direct target of androgen action.