Generation of active TGF-beta by prostatic cell cocultures using novel basal and luminal prostatic epithelial cell lines

TGFβ1 Secreted by Cancer-Associated Fibroblasts as an Inductor of Resistance to Photodynamic Therapy in Squamous Cell Carcinoma Cells

Simple Summary

Photodynamic therapy (PDT) is used for the treatment of in situ cutaneous squamous cell carcinoma (cSCC), the second most common form of skin cancer, as well as for its precancerous form, actinic keratosis. However, relapses after the treatment can occur. Transforming growth factor β1 (TGFβ1) produced by cancer-associated fibroblasts (CAFs) in the tumor microenvironment has been pointed as a key player in the development of cSCC resistance to other therapies, such as chemotherapy. Here, we demonstrate that TGFβ1 produced by CAFs isolated from patients with cSCC can drive resistance to PDT in SCC cells. This finding opens up novel possibilities for strategy optimization in the field of cSCC resistance to PDT and highlights CAF-derived TGFβ1 as a potential target to improve the efficacy of PDT.

Abstract

As an important component of tumor microenvironment, cancer-associated fibroblasts (CAFs) have lately gained prominence owing to their crucial role in the resistance to therapies. Photodynamic therapy (PDT) stands out as a successful therapeutic strategy to treat cutaneous squamous cell carcinoma. In this study, we demonstrate that the transforming growth factor β1 (TGFβ1) cytokine secreted by CAFs isolated from patients with SCC can drive resistance to PDT in epithelial SCC cells. To this end, CAFs obtained from patients with in situ cSCC were firstly characterized based on the expression levels of paramount markers as well as the levels of TGFβ1 secreted to the extracellular environment. On a step forward, two established human cSCC cell lines (A431 and SCC13) were pre-treated with conditioned medium obtained from the selected CAF cultures. The CAF-derived conditioned medium effectively induced resistance to PDT in A431 cells through a reduction in the cell proliferation rate. This resistance effect was recapitulated by treating with recombinant TGFβ1 and abolished by using the SB525334 TGFβ1 receptor inhibitor, providing robust evidence of the role of TGFβ1 secreted by CAFs in the development of resistance to PDT in this cell line. Conversely, higher levels of recombinant TGFβ1 were needed to reduce cell proliferation in SCC13 cells, and no induction of resistance to PDT was observed in this cell line in response to CAF-derived conditioned medium. Interestingly, we probed that the comparatively higher intrinsic resistance to PDT of SCC13 cells was mediated by the elevated levels of TGFβ1 secreted by this cell line. Our results point at this feature as a promising biomarker to predict both the suitability of PDT and the chances to optimize the treatment by targeting CAF-derived TGFβ1 in the road to a more personalized treatment of particular cSCC tumors.

Normal Basal Epithelial Cells Stimulate the Migration and Invasion of Prostate Cancer Cell RM-1 by TGF-β1/STAT3 Axis in vitro

Aim

Basal epithelial cells are absent in distant prostate cancer. This study aimed to investigate whether basal epithelial cells could suppress migration and invasion of prostate cancer cells to become a new treatment strategy for prostate cancer.

Main Methods

Basal epithelial cells were identified by immunofluorescence with anti-p63. Wound healing assays or transwell assays were used to explore the effects of basal epithelial cells, TGF-β1, SB431542 (inhibitor of TGF-β type I receptor) or stattic (inhibitor of phosphorylated STAT3) on migration or invasion of mouse prostate cancer cell (RM-1). Concentration of TGF-β1 was measured by ELISA assay. HE staining was used to investigate cell morphology. Immunocytochemistry with anti-p63 was used to identify basal epithelial cells. Levels of STAT3, p-STAT3 (Ser727) and proteins associated with EMT were measured with Western blot assay. Cell proliferation was measured with MTT or CCK8 assay.

Results

Normal basal epithelial cells acquired from mouse prostate were specific to anti-p63 and more than 90%. Basal epithelial cells and RM-1 could both secrete TGF-β1. Basal epithelial cells and TGF-β1 promoted the migration and invasion of RM-1 through changing the cell morphology and up-regulating expression of ZEB1, N-cadherin, vimentin, snail and p-STAT3 (Ser727), at the same time down-regulating E-cadherin of RM-1. SB431542 strongly suppressed migration, invasion as well as the expressions of EMT relevant proteins and p-STAT3 (Ser727) of co-cultured RM-1. In addition, stattic suppressed proliferation, migration and invasion of non-treated RM-1 and co-cultured RM-1.

Conclusion

Our study suggests that normal basal epithelial cells might stimulate the migration and invasion of RM-1 by TGF-β1/STAT3 axis which could be suppressed by inhibitor of TGF-β receptor and inhibitor of p-STAT3. So, basal epithelial cells might not become a treatment strategy for prostate cancer, but our results could provide some researching references for other diseases which include basal epithelial cells such as prostatic intraepithelial neoplasia, prostatic hyperplasia, cervical cancer, or urinary bladder cancer.

KLF4, A Gene Regulating Prostate Stem Cell Homeostasis, Is a Barrier to Malignant Progression and Predictor of Good Prognosis in Prostate Cancer

There is a considerable need to identify those individuals with prostate cancer who have indolent disease. We propose that genes that control adult stem cell homeostasis in organs with slow turnover, such as the prostate, control cancer fate. One such gene, KLF4, overexpressed in murine prostate stem cells, regulates their homeostasis, blocks malignant transformation, and controls the self-renewal of tumor-initiating cells. KLF4 loss induces the molecular features of aggressive cancer and converts PIN lesions to invasive sarcomatoid carcinomas; its re-expression in vivo reverses this process. Bioinformatic analysis links these changes to human cancer. KLF4 and its downstream targets make up a gene signature that identifies indolent tumors and predicts recurrence-free survival. This approach may improve prognosis and identify therapeutic targets for advanced cancer.

Available criteria for segregating prostate cancer patients into those requiring therapeutic intervention and those who can be followed are inadequate. Xiong et al. show that KLF4 and its downstream targets make up a gene signature that identifies indolent tumors. This approach may improve prognosis and identify therapeutic targets for advanced cancer.

CD73 Expression Is an Independent Prognostic Factor in Prostate Cancer

PURPOSE

CD73 is an adenosine-generating ecto-enzyme that suppresses antitumor immunity in mouse models of cancer, including prostate cancer. Although high levels of CD73 are associated with poor prognosis in various types of cancer, the clinical impact of CD73 in prostate cancer remains unclear.

EXPERIMENTAL DESIGN

We evaluated the prognostic value of CD73 protein expression and CD8(+) cell density in 285 cases of prostate cancer on tissue microarray (TMA). Normal adjacent and tumor tissues were evaluated in duplicates.

RESULTS

Univariate and multivariate analyses revealed that high levels of CD73 in normal adjacent prostate epithelium were significantly associated with shorter biochemical recurrence (BCR)-free survival. Notably, CD73 expression in normal epithelium conferred a negative prognostic value to prostate-infiltrating CD8(+) cells. Surprisingly, high levels of CD73 in the tumor stroma were associated with longer BCR-free survival in univariate analysis. In vitro studies revealed that adenosine signaling inhibited NF-κB activity in human prostate cancer cells via A2B adenosine receptors. Consistent with these results, CD73 expression in the prostate tumor stroma negatively correlated with p65 expression in the nuclei of prostate tumor cells.

CONCLUSIONS

Our study revealed that CD73 is an independent prognostic factor in prostate cancer. Our data support a model in which CD73 expression in the prostate epithelium suppresses immunosurveillance by CD8(+) T cells, whereas CD73 expression in the tumor stroma reduces NF-κB signaling in tumor cells via A2B adenosine receptor signaling. CD73 expression, including in normal adjacent prostate epithelium, can thus effectively discriminate between aggressive and indolent forms of prostate cancer.

Increased Notch signalling inhibits anoikis and stimulates proliferation of prostate luminal epithelial cells

The prostate epithelial lineage hierarchy remains inadequately defined. Recent lineage-tracing studies have implied the existence of prostate luminal epithelial progenitors with extensive regenerative capacity. However, this capacity has not been demonstrated in prostate stem cell activity assays, probably owing to the strong susceptibility of luminal progenitors to anoikis. Here we show that constitutive expression of Notch1 intracellular domain impairs secretory function of mouse prostate luminal cells, suppresses anoikis of luminal epithelial cells by augmenting NF-κB activity independent of Hes1, stimulates luminal cell proliferation by potentiating PI3K-AKT signalling, and rescues the capacities of the putative prostate luminal progenitors for unipotent differentiation in vivo and short-term self-renewal in vitro. Epithelial cell autonomous AR signalling is dispensable for the Notch-mediated effects. As Notch activity is increased in prostate cancers, and anoikis resistance is a hallmark for metastatic cancer cells, this study suggests a pro-metastatic function of Notch signalling during prostate cancer progression.

Regulated proteolysis of Trop2 drives epithelial hyperplasia and stem cell self-renewal via β-catenin signaling

The cell surface protein Trop2 is expressed on immature stem/progenitor-like cells and is overexpressed in many epithelial cancers. However the biological function of Trop2 in tissue maintenance and tumorigenesis remains unclear. In this study, we demonstrate that Trop2 is a regulator of self-renewal, proliferation, and transformation. Trop2 controls these processes through a mechanism of regulated intramembrane proteolysis that leads to cleavage of Trop2, creating two products: the extracellular domain and the intracellular domain. The intracellular domain of Trop2 is released from the membrane and accumulates in the nucleus. Heightened expression of the Trop2 intracellular domain promotes stem/progenitor self-renewal through signaling via β-catenin and is sufficient to initiate precursor lesions to prostate cancer in vivo. Importantly, we demonstrate that loss of β-catenin or Trop2 loss-of-function cleavage mutants abrogates Trop2-driven self-renewal and hyperplasia in the prostate. These findings suggest that heightened expression of Trop2 is selected for in epithelial cancers to enhance the stem-like properties of self-renewal and proliferation. Defining the mechanism of Trop2 function in self-renewal and transformation is essential to identify new therapeutic strategies to block Trop2 activation in cancer.

Androgens and prostate cancer bone metastases: effects on both the seed and the soil

Androgens are essential for normal prostate development and are necessary, but not sufficient, for the development of prostate cancer (PCa). Androgen deprivation therapy has long been the mainstay of treatment for PCa bone metastases, providing palliation of symptoms in the majority of patients, followed by relapse and progression. The majority of published preclinical studies demonstrate a stimulatory effect of androgens and androgen receptor signaling on the multistep process of PCa bone metastases, including androgenic promotion of local PCa growth, angiogenesis, invasion, bone targeting, stimulation of PCa growth factors that enhance osteoclastogenesis, and enhancement of Wnt signaling in osteoblasts.

Increased CK5/CK8-positive intermediate cells with stromal smooth muscle cell atrophy in the mice lacking prostate epithelial androgen receptor

Results from tissue recombination experiments documented well that stromal androgen receptor (AR) plays essential roles in prostate development, but epithelial AR has little roles in prostate development. Using cell specific knockout AR strategy, we generated pes-ARKO mouse with knock out of AR only in the prostate epithelial cells and demonstrated that epithelial AR might also play important roles in the development of prostate gland. We found mice lacking the prostate epithelial AR have increased apoptosis in epithelial CK8-positive luminal cells and increased proliferation in epithelial CK5-positive basal cells. The consequences of these two contrasting results could then lead to the expansion of CK5/CK8-positive intermediate cells, accompanied by stromal atrophy and impaired ductal morphogenesis. Molecular mechanism dissection found AR target gene, TGF-β₁, might play important roles in this epithelial AR-to-stromal morphogenesis modulation. Collectively, these results provided novel information relevant to epithelial AR functions in epithelial-stromal interactions during the development of normal prostate, and suggested AR could also function as suppressor in selective cells within prostate.

Transforming growth factor beta1 mediates apoptotic activity of angiotensin II type I receptor blocker on prostate epithelium in vitro

BACKGROUND

The significant association of benign prostatic hyperplasia (BPH) and hypertension indicates a common pathophysiological factor for both diseases. Hyperactivity of the renin-angiotensin system (RAS) has been reported in BPH. Angiotensin II type I (AT1) receptor is the principal mediator of the RAS, and the antagonist, AT1 receptor blocker (ARB), can induce apoptosis in prostate epithelium cells and increase transforming growth factor beta1 (TGF-beta1) expression. We aimed to investigate the mechanism of inhibition of AT1 receptor in prostate epithelium cells and the role of TGF-beta1.

METHODS

Human prostate epithelium cell lines were treated with different concentrations of ARB (losartan) (0, 0.1, 1, 10, 100, and 1,000 microM) for 24-72 hr. Cell proliferation was analyzed by cell proliferation assay. The location of AT1 receptor was shown by immunocytohistochemistry and immunocytofluorescence study. Analysis of apoptosis was by use of terminal transferase TdT-mediated dUTP-biotin end labeling (TUNEL) and caspase 3/7 activity assay. Mitochondrial outer-membrane permeabilization was measured by JC-1 staining. The level of TGF-beta1 was determined by enzyme-linked immunosorbent assay.

RESULTS

Immunohistochemistry and immunofluorescence analysis showed AT1 receptor expressed in epithelium cells. Compared to control cultures, cultures treated with losartan for 24-72 hr showed a dose-dependent significant decrease in cell number, with apoptosis increased by 65.2%. Decreased cell number was reversed on treatment with anti-TGF-beta1 antibody. TUNEL staining showed increased apoptosis in prostate epithelium cells exposed to losartan. Caspase 3/7 activation was increased and mitochondrial membrane potential was downregulated. Expression of TGF-beta1 in cells treated with losartan was higher than that in untreated cells.

CONCLUSIONS

The apoptotic effect of blockade of AT1 receptor on human prostatic epithelium cells may be mediated through an autocrine the production of TGF-beta1. Furthermore, this finding may have implications for medication options. Inc.

Androgen receptor and growth factor signaling cross-talk in prostate cancer cells

Androgens promote the growth and differentiation of prostate cells through ligand activation of the androgen receptor (AR). Sensitization of the androgenic response by multifunctional growth factor signaling pathways is one of the mechanisms via which AR contributes to the emergence of androgen-independent prostate tumors. The ability of AR to cross-talk with key growth factor signaling events toward the regulation of cell cycle, apoptosis, and differentiation outcomes in prostate cancer cells is established. In this paper, we review the functional interaction between AR and an array of growth factor signal transduction events (including epidermal growth factor; fibroblast growth factor; IGF1; vascular endothelial growth factor; transforming growth factor-beta) in prostate tumors. The significance of this derailed cross-talk between androgens and key signaling networks in prostate cancer progression and its value as a therapeutic forum targeting androgen-independent metastatic prostate cancer is discussed.

Axin2 expression identifies progenitor cells in the murine prostate

BACKGROUND

We previously reported that prostatic stem/progenitor cells are concentrated in the proximal region of prostatic ducts and express stem cell antigen 1 (Sca-1). As Wnt signaling is important for the maintenance of stem cells, we determined whether Sca-1 expressing cells also express Axin2, as Axin2 expression is highly suggestive of active Wnt signaling.

METHODS

Axin2 promoter reporter mice were used for whole mount and fluorescence activated cell sorting (FACS) analysis to determine its expression in the prostate. Axin2 expressing cells were also examined for the co-expression of Sca-1. We also used a chemical activator of Wnt signaling, BIO, to determine the effects of Wnt signaling on the growth of primary prostate cells in vitro.

RESULTS

We show that Axin2 expression is present in all lobes and is regulated by androgens with the highest Axin2 expression in the lateral and dorsal prostate. Furthermore, a fraction of Axin2 expressing cells co-express Sca-1, suggesting that some progenitor cells have active Wnt signaling. Lastly, we demonstrate that activation of the Wnt pathway may result in increased growth, consistent with a role for Wnt signaling in maintenance and/or expansion of the progenitor cell population.

CONCLUSION

Axin2 expressing cells that co-express Sca-1 are present in all prostate lobes suggesting that progenitor cells reside within the Wnt active population. An understanding of the basic biology of signaling pathways mediating growth in the prostate may lead to rational therapies to treat benign prostatic hyperplasia and prostate cancer.

Endothelial cells support the growth of prostate tissue in vivo

INTRODUCTION

The contribution of vascular endothelial cells to prostate growth has not been investigated. We examined whether endothelial cells support growth of prostate tissue when co-inoculated with prostate epithelial cells under the renal capsule.

METHODS

Vascular endothelial cells were isolated from mice and co-inoculated under the renal capsule with a prostate luminal or basal epithelial cell line. After 60 days, kidneys were examined for growth of prostate tissue. Prostatic tissues were examined by immunohistochemistry for expression of cytokeratins 5 and 8, and vascular density was determined. To determine if increased expression of VEGF-A would increase prostatic growth, transfected endothelial cells overexpressing VEGF-A were co-inoculated with the prostate luminal or basal epithelial lines.

RESULTS

Co-inoculation of endothelial cells and prostate luminal or basal epithelial cells resulted in significant growth of prostatic tissue, whereas inoculation of any of the cell lines alone resulted in little growth. The growths from co-inoculation of endothelial cells and luminal epithelial cells contained duct-like structures that stained with antibodies to cytokeratin 8, whereas those from co-inoculation of endothelial cells and basal epithelial cells contained cords of cells that stained with antibodies to cytokeratin 5. Overexpression of VEGF-A had no effect on growth of the prostatic tissues.

CONCLUSION

Endothelial cells contribute to the growth of prostatic epithelial cells.

Prostate cells express two isoforms of fibroblast growth factor receptor 1 with different affinities for fibroblast growth factor-2

BACKGROUND

Fibroblast growth factor receptor 1 (FGFR1) mRNA can be alternatively spliced to generate isoforms containing (FGFR1alpha) or lacking (FGFR1beta) the first immunoglobulin-like domain. We examined which isoforms are expressed by cultured prostate cells, their affinities for FGF-2, and the effect of heparin on FGF-2 binding.

METHODS

FGFR1 isoform expression was examined by RT-PCR. FGFR1alpha and FGFR1beta were expressed in CHO cells mutant in heparan sulfate synthesis, and their affinities for FGF-2, FGF-1, FGF-4, and FGF-6 were determined in the presence and absence of heparin.

RESULTS

FGFR1alpha was expressed in luminal epithelial cells, whereas FGFR1beta was expressed in basal epithelial and smooth muscle cells. FGFR1beta bound FGF-2 with three-fourfold higher affinity than FGFR1alpha both in the presence and absence of heparin. Heparin increased affinity of both receptor isoforms for FGF-2 approximately four-fivefold.

CONCLUSIONS

Prostate smooth muscle and basal epithelial cells are likely to be more sensitive than luminal epithelial cells to the low concentrations of FGFs present in vivo.

Opposing actions of TGFbeta1 and FGF2 on growth, differentiation and extracellular matrix accumulation in prostatic stromal cells

TGFbeta 1 and FGF2 are autocrine growth factors in prostatic stroma and are elevated in benign prostatic hyperplasia (BPH), a disease characterized by enlargement of the stromal compartment of the prostate. TGFbeta1 has a biphasic effect on proliferation of prostatic stromal cells, inducing proliferation at low doses (< 1 ng/ml), but inhibiting growth above 1 ng/ml. This study investigated the role of TGFP 1 and FGF2 on growth factor bioavailability and extracellular matrix (ECM) accumulation synthesis in cultured prostatic stromal cells. Real-Time-PCR showed that TGFbeta1 expression is auto-inductive, whereas FGF2 is auto-repressive. FGF2 also induced TGFbeta1 secretion in the absence of increased TGFbeta1 mRNA expression. TGFbeta1 and FGF2 have opposing actions on Type 1 collagen expression, a finding confirmed by Western blotting. The bioavailability of TGFbeta1 regulated by FGF2 may represent part of a negative feedback mechanism controlling stromal growth, differentiation and ECM. Dysregulation of this pathway in favour of TGFbeta1 bioactivity may exacerbate BPH.

TGF-{beta} maintains dormancy of prostatic stem cells in the proximal region of ducts

We have previously shown that prostatic stem cells are located in the proximal region of mouse prostatic ducts. Here, we show that this region responds differently to transforming growth factor (TGF)-beta than the distal ductal region and that under physiological conditions androgens and TGF-beta are crucial overall regulators of prostatic tissue homeostasis. This conclusion is supported by the observations showing that high levels of TGF-beta signaling are present in the quiescent proximal region of ducts in an androgen-replete animal and that cells in this region overexpress Bcl-2, which protects them from apoptosis. Moreover, androgen ablation reverses the proximal-distal TGF-beta signaling gradient, leading to an increase in TGF-beta signaling in the unprotected distal region (low Bcl-2 expression). This reversal of TGF-beta-mediated signaling accompanies apoptosis of cells in the distal region and gland involution after androgen withdrawal. A physiological TGF-beta signaling gradient (high proximally and low distally) and its functional correlates are restored after androgen replenishment. In addition to highlighting the regulatory role of androgens and TGF-beta, these findings may have important implications for the deregulation of the stem cell compartment in the etiology of proliferative prostatic diseases.

Functions and regulation of transforming growth factor-beta (TGF-β) in the prostate

The prostate is a highly androgen-dependent tissue that in humans exhibits marked susceptibility to carcinogenesis. The malignant epithelium generated from this tissue ultimately loses dependence on androgens despite retention or amplification of the androgen receptor. Accumulating evidence support that transforming growth factor-beta (TGF-beta) plays key roles in the control of androgen dependence and acquisition of resistance to such hormonal control. Although TGF-beta functions as a key tumour suppressor of the prostate, it can also promote malignant progression and metastasis of the advanced disease, through undefined mechanisms. In addition to giving an overview of the TGF-beta field as related to its function in prostate cancer, this Review focuses on novel findings that support the tumour suppressor function of TGF-beta is lost or altered by changes in the activity of the androgen receptor, insulin-like growth factor-I, Akt, and mTOR during malignant progression. Understanding the mechanisms of cross-talk between TGF-beta and such growth modulators has important implications for the rational therapeutics of prostate cancer.

Stromal/epithelial interactions of murine prostatic cell lines in vivo: a model for benign prostatic hyperplasia and the effect of doxazosin on tissue size

BACKGROUND

One of the major constraints in elucidating the mechanisms involved in the etiology of benign prostatic hyperplasia (BPH) is the lack of suitable model systems that are readily manipulable in vitro and in vivo. To address this issue, we have used murine prostatic cell lines to establish a novel in vivo model for studying prostatic cell interactions.

METHODS

Luminal, basal, and smooth muscle (SM) cell lines were inoculated alone or in combinations under the renal capsule of intact or castrated male mice, and the growth and composition of prostatic tissue in the absence or presence of doxazosin was determined.

RESULTS

Both the luminal and basal cell lines reconstituted prostatic tissue if co-inoculated under the renal capsule with normal SM cells, whereas none of the lines formed significant tissue when inoculated alone. Luminal cells produced and secreted prostatic secretory products. The growth of prostatic tissue formed from co-inoculation of basal and SM cells was androgen responsive. In addition, a significant reduction in prostatic tissue was noted in animals treated with doxazosin.

CONCLUSION

We have established an in vivo model that uses prostatic epithelial and SM cell lines for investigating cellular interactions between epithelial and SM cells that regulate prostatic growth and function. This model will be useful for delineating the mechanisms by which prostatic cells interact and in determining the efficacy of new approaches aimed at interfering with prostatic stromal/epithelial interactions that result in abnormal cellular proliferation.

Proximal location of mouse prostate epithelial stem cells: a model of prostatic homeostasis

Stem cells are believed to regulate normal prostatic homeostasis and to play a role in the etiology of prostate cancer and benign prostatic hyperplasia. We show here that the proximal region of mouse prostatic ducts is enriched in a subpopulation of epithelial cells that exhibit three important attributes of epithelial stem cells: they are slow cycling, possess a high in vitro proliferative potential, and can reconstitute highly branched glandular ductal structures in collagen gels. We propose a model of prostatic homeostasis in which mouse prostatic epithelial stem cells are concentrated in the proximal region of prostatic ducts while the transit-amplifying cells occupy the distal region of the ducts. This model can account for many biological differences between cells of the proximal and distal regions, and has implications for prostatic disease formation.

Differentiation and stromal-induced growth promotion of murine prostatic tumors

BACKGROUND

We have derived a panel of p53-null prostatic "basal" and "luminal" epithelial cell lines and their ras transformed counterparts to study stromal/epithelial interactions and the properties of tumors arising from "basal" and "luminal" cells.

METHODS

Previously derived normal murine prostatic "basal" epithelial (PE-B-1) and "luminal" epithelial (PE-L-1) cell lines were transformed with N-Ras. These lines and a spontaneously transformed "luminal" cell line were inoculated subcutaneously or orthotopically into athymic mice, alone or in combination with normal prostatic smooth muscle cells (SMC).

RESULTS

All transformed lines formed subcutaneous tumors. SMC significantly enhanced the growth rate of the tumors arising from the "basal" and one of the "luminal" cell lines. The transformed "basal" line gave rise to tumors expressing both "basal" and "luminal" cytokeratins.

CONCLUSIONS

Prostatic SMC promote the growth of transformed epithelial cells, suggesting that prostatic stroma may promote tumor development. Furthermore, transformed "basal" cells give rise to tumors containing "luminal" cells, suggesting that although most human tumors have a "luminal" phenotype, they may originate from transformed "basal" cells.

Androgens modulate the balance between VEGF and angiopoietin expression in prostate epithelial and smooth muscle cells

BACKGROUND

The vasculature of the prostate responds to androgens. Androgens most likely affect the vasculature indirectly by modulating the expression of angiogenic factors in the cells of the prostate. Most studies to date have examined the production of angiogenic factors by the prostate luminal epithelium. Here we examine the effects of androgen on production of three angiogenic factors, vascular endothelial growth factor (VEGF), angiopoietin-1, and angiopoietin-2, by the three major cell types in the prostate.

METHODS

The ability of androgen to modulate VEGF, angiopoietin-1, and angiopoietin-2 production in cultured mouse prostate luminal epithelial, basal epithelial, and smooth muscle cells (SMCs) was assessed by Western blot and RT-PCR.

RESULTS

The production of VEGF was modulated by androgens in both luminal epithelial and prostate SMCs but not in basal epithelial cells. However, in prostate luminal epithelial cell cultures, VEGF was predominately secreted apically, suggesting that in vivo most of the epithelium-derived VEGF is unavailable to the underlying blood vessels. In addition, prostate luminal epithelial cells produced angiopoietin-2, an angiogenesis inhibitor. In contrast, prostate SMCs produced angiopoietin-1, a positive modulator of angiogenesis. Synthesis of the angiopoietins did not respond to androgen treatment.

CONCLUSIONS

Prostate smooth muscle may play an important role in regulating vascular responses to androgen.

Vasoactive intestinal peptide (VIP) stimulates rat prostatic epithelial cell proliferation

BACKGROUND

Androgens play a major role in supporting normal growth and functional maintenance in the prostate. However, this gland contains an array of neuroendocrine peptides that can play a regulatory role in its physiopathology. Among these peptides, one of the best studied is vasoactive intestinal peptide (VIP), which is abundant in autonomic nerves surrounding both human and rat prostatic acini. This neuropeptide may act through interaction with two types of high-affinity receptors, named VPAC(1) and VPAC(2) receptors. Another regulatory peptide, the pituitary adenylate cyclase-activating peptide (PACAP), interacts with these receptors with the same affinity as VIP, but binds with higher affinity to PAC(1) receptors. Human prostate tumors and rat prostate show a major presence of VPAC(1) receptors, whereas various findings suggest a role for VIP in prostatic development. Here we studied the effects of VIP on the proliferation of rat prostatic epithelial cells in culture.

METHODS

We studied the [(3)H]-thymidine uptake by rat prostatic epithelial cells in culture, characterized previously by using biomarkers such as cytokeratin and vimentin. In these cells we tested the effect of VIP and PACAP-27 on two different signaling pathways, the cyclic AMP (cAMP) and the inositol phosphate (IPs).

RESULTS

The rat prostatic cells in culture were cytokeratin (5,6,8) and vimentin positive, indicating that the culture was predominantly epithelial. The proliferation curves showed that the cells followed different states of growth: a quiescent, an exponential proliferative, and a steady state. Cyclic AMP production, but not inositol phosphate production, was increased in the presence of VIP and PACAP-27, which suggests the expression of VPAC(1) and/or VPAC(2) receptors primarily. VIP significantly increased prostatic cell proliferation in a bimodal manner, as shown for dibutyryl cyclic AMP (dbcAMP), which suggests that the effect of VIP upon prostatic proliferation is cAMP-dependent.

CONCLUSIONS

Here, we demonstrate that VIP increased [(3)H]thymidine uptake by rat prostatic epithelial cells in culture, conceivably by the activation of the adenylate cyclase.

Transforming growth factor beta in the human prostate: its role in stromal-epithelial interactions in non-cancerous cell culture

BACKGROUND

Stromal-epithelial interactions play a critical role in prostate development, but the precise mechanisms are still unknown. Transforming growth factor-beta (TGFbeta) could be a potential mediator of these interactions, but there is as yet no clear demonstration of its role.

METHODS

Separate cultures and co-cultures of fibroblasts and epithelial human prostate cells were performed. We measured TGFbeta1 and TGFbeta2 secretion by specific ELISA assay, cell growth by DNA assay, and TGFbeta type II receptor expression by RT-PCR.

RESULTS

Co-culture resulted in a 20% inhibition of epithelial cell growth, similar to that obtained after TGFbeta treatment (2 ng/ml for 48 hr), but without affecting fibroblast proliferation. This was accompanied by a five- to six-fold increase in epithelial TGFbeta2 secretion.

CONCLUSIONS

These results demonstrate for the first time that TGFbeta2 secretion by prostate epithelial cells is under the direct control of a diffusible factor secreted by fibroblasts. They emphasize the role of TGFbeta in stromal-epithelial interactions.

Transforming growth factor-beta is an autocrine mitogen for a novel androgen-responsive murine prostatic smooth muscle cell line, PSMC1

A prostatic smooth muscle cell line (PSMC1) was established from the dorsolateral prostate of p53 null mice. The cell line is nontumorigenic when inoculated subcutaneously, under the renal capsule or intraprostatically in syngeneic mice. These cells express alpha-smooth muscle actin (alpha-SMA), indicating their smooth muscle origin, and TGF-beta significantly enhances expression of alpha-SMA. The cells express both androgen receptor (AR) mRNA and protein, and respond mitogenically to physiological concentrations of androgens. PSMC1 cells produce significant amounts of TGF-beta, which stimulates growth by an autocrine mechanism. Dihydrotestosterone (DHT) increases proliferation of PSMC1 cells by promoting TGF-beta secretion. Considering the significant inhibitory effect of TGF-beta on prostatic epithelial cells and its stimulatory effect on the PSMC1 cells, we postulate that TGF-beta produced by prostatic smooth muscle cells may have a paracrine effect on the prostatic epithelium. We also postulate that TGF-beta may be involved in the etiology of benign prostatic hyperplasia (BPH) by stimulating excessive stromal proliferation. Line PSMC1 is the first reported androgen-responsive murine smooth muscle cell line. It will be useful for in vivo and in vitro experiments to study the mechanisms of androgen action on prostatic stroma and for delineating the interactions that occur between prostatic smooth muscle and epithelium that may lead to prostatic diseases such as BPH.