Decrement of blood flow precedes the involution of the ventral prostate in the rat after castration

TNF Signaling Is Required for Castration-Induced Vascular Damage Preceding Prostate Cancer Regression

The mainstay treatment for locally advanced, recurrent, or metastatic prostate cancer (PrCa) is androgen deprivation therapy (ADT). ADT causes prostate cancers to shrink in volume, or regress, by inducing epithelial tumor cell apoptosis. In normal, non-neoplastic murine prostate, androgen deprivation via castration induces prostate gland regression that is dependent on TNF signaling. In addition to this direct mechanism of action, castration has also been implicated in an indirect mechanism of prostate epithelial cell death, which has been described as vascular regression. The initiating event is endothelial cell apoptosis and/or increased vascular permeability. This subsequently leads to reduced blood flow and perfusion, and then hypoxia, which may enhance epithelial cell apoptosis. Castration-induced vascular regression has been observed in both normal and neoplastic prostates. We used photoacoustic, power Doppler, and contrast-enhanced ultrasound imaging, and CD31 immunohistochemical staining of the microvasculature to assess vascular integrity in the period immediately following castration, enabling us to test the role of TNF signaling in vascular regression. In two mouse models of androgen-responsive prostate cancer, TNF signaling blockade using a soluble TNFR2 ligand trap reversed the functional aspects of vascular regression as well as structural changes in the microvasculature, including reduced vessel wall thickness, cross-sectional area, and vessel perimeter length. These results demonstrate that TNF signaling is required for vascular regression, most likely by inducing endothelial cell apoptosis and increasing vessel permeability. Since TNF is also the critical death receptor ligand for prostate epithelial cells, we propose that TNF is a multi-purpose, comprehensive signal within the prostate cancer microenvironment that mediates prostate cancer regression following androgen deprivation.

The relationship between prostatic microvessel density and different concentrations of oestrogen/androgen in Sprague-Dawley rats

BACKGROUND

Currently, there are relatively few studies on the effects of changes in oestrogen and androgen levels on prostatic microvessel density (MVD). This article aimed to study the changes in prostatic MVD in Sprague-Dawley (SD) rats after castration under the effect of oestrogen/androgen at different concentrations.

METHODS

Male SD rats aged 3-4 months were randomly divided into a control group, a castration group, and groups with different concentrations of oestrogen/androgen treatment after castration. Dihydrotestosterone (DHT) and oestradiol (E) were administered daily by subcutaneous injection for one month. All the rats were killed by cervical dislocation after one month, and the serum DHT and E concentrations of the rats in each group were measured by ELISA. Prostate tissue specimens were immunohistochemically stained with monoclonal antibodies against CD34 and factor VIII for MVD.

RESULTS

Compared with the control group, the MVD decreased significantly in the castration group (P < 0.05). When the exogenous E concentration was constant, in general, the MVD of rats in all the groups increased with increasing exogenous DHT concentration. Compared with the castration group, the MVD increased significantly in the E0.05 + DHT0.015 mg/kg, E0.05 + DHT0.05 mg/kg, E0.05 + DHT0.15 mg/kg, E0.05 + DHT0.5 mg/kg, and E0.05 + DHT1.5 mg/kg groups (P < 0.05). In addition, when the exogenous DHT concentration was constant, the MVD increased with increasing exogenous E concentration in all the groups. Among them, compared with the control and castration groups, the MVD increased significantly in the DHT0.15 + E0.015 mg/kg, DHT0.15 + E0.15 mg/kg, and DHT0.15 + E0.5 mg/kg groups (P < 0.05).

CONCLUSIONS

Androgens play an important role in the regulation of prostatic MVD in SD rats, and a decrease in DHT concentration can induce a decrease in prostatic MVD. In contrast, prostatic MVD can be increased with increasing DHT concentration. In addition, prostatic MVD can be increased gradually with increasing oestrogen concentration.

Signaling Pathways That Control Apoptosis in Prostate Cancer

Prostate cancer is the second most common malignancy and the fifth leading cancer-caused death in men worldwide. Therapies that target the androgen receptor axis induce apoptosis in normal prostates and provide temporary relief for advanced disease, yet prostate cancer that acquired androgen independence (so called castration-resistant prostate cancer, CRPC) invariably progresses to lethal disease. There is accumulating evidence that androgen receptor signaling do not regulate apoptosis and proliferation in prostate epithelial cells in a cell-autonomous fashion. Instead, androgen receptor activation in stroma compartments induces expression of unknown paracrine factors that maintain homeostasis of the prostate epithelium. This paradigm calls for new studies to identify paracrine factors and signaling pathways that control the survival of normal epithelial cells and to determine which apoptosis regulatory molecules are targeted by these pathways. This review summarizes the recent progress in understanding the mechanism of apoptosis induced by androgen ablation in prostate epithelial cells with emphasis on the roles of BCL-2 family proteins and "druggable" signaling pathways that control these proteins. A summary of the clinical trials of inhibitors of anti-apoptotic signaling pathways is also provided. Evidently, better knowledge of the apoptosis regulation in prostate epithelial cells is needed to understand mechanisms of androgen-independence and implement life-extending therapies for CRPC.

B-Mode and Doppler Ultrasonographic Findings of Prostate Gland and Testes in Dogs Receiving Deslorelin Acetate or Osaterone Acetate

Simple Summary

This article presents the use of ultrasonography (basic and advanced techniques) in dogs suffering from benign prostate hyperplasia (BPH) for the assessment of the effects of two different medications: osaterone acetate (Ypozane^TM), a registered drug for BPH in dogs, and deslorelin acetate (Suprelorin^TM), registered for pharmacological castration in dogs. Based on the obtained results it can be stated that both B-mode and color Doppler Ultrasound imaging techniques are suitable for diagnosis and progress assessment of dogs suffering from BPH. Both investigated medications (osaterone acetate and deslorelin acetate) led to a significant sonographic improvement. Deslorelin acetate reduced prostate volume more slowly, but its effect lasted longer than for osaterone acetate.

Abstract

This article presents B-mode and color Doppler imaging of the prostate and testes in dogs suffering from benign prostate hyperplasia (BPH), and receiving deslorelin acetate (Suprelorin^TM) or osaterone acetate (Ypozane^TM). The study was planned as a controlled clinical trial, dogs were divided into negative control (healthy dogs, n = 10), positive control (dogs with BPH, n = 10), and study groups, III (n = 15), receiving deslorelin acetate (DA), and IV (n = 10), receiving osaterone acetate (OA). The B-mode appearance of the prostate parenchyma improved in all investigated dogs from the DA group, and in 60% of OA dogs. Prostate volume was reduced more quickly with OA (from D14), but lasting for a shorter time (on average up to week 20), compared to DA that reduced the prostate volume more slowly (>8 weeks), but the reduction remained longer (>24 weeks). The systolic peak velocity (SPV) and mean velocity (Vmean) were higher in all dogs diagnosed with BPH, compared to Control Group I. The indices did not change in both Control Groups I and II, whereas in study Groups III and IV they decreased throughout the study period compared to day 0 and Control Group II. In Group III the highest reduction was noted from day 21 to week 8, whereas in Group IV the lowest Vmean was recorded before day 21. Testicular parenchyma and volume changed significantly in Group III receiving DA, and the velocity of blood flow in the testicular artery correlated positively with testicular volume only in this group (III). The present study proved the usefulness of B-mode and color Doppler US imaging techniques for diagnosis and progress assessment of dogs suffering from BPH. The blood flow kinetics (mainly SPV) demonstrated a time association between the blood flow changes registered in the prostatic artery, and the subsequent volumetric and sonographic improvement of the prostate parenchyma. The reduction in flow indices was noted prior to the reduction in prostate volume, suggesting that the sonographic recovery of the prostate tissue, occurs secondarily to the regression of the prostate vascular system. Both investigated medications (osaterone acetate and deslorelin acetate) led to a significant sonographic improvement. Deslorelin acetate reduced prostate volume more slowly, but its effect lasted longer than for osaterone acetate.

Prostatic hyperplasia: Vascularization, hemodynamic and hormonal analysis of dogs treated with finasteride or orchiectomy

As a consequence of a hormonal imbalance, Prostatic Hyperplasia (PH) is characterized by increased prostate volume, along with higher local angiogenesis and vascularization. Orchiectomy is the common treatment for dogs, however it is not an option for breeding animals. Thus, finasteride arises as the drug of choice for stud dogs. Therefore, the aim of this study was to evaluate the effects of orchiectomy or finasteride therapies on hormonal and vascular dynamics of PH dogs. Fifteen dogs, aged 6–13 years were assigned to: Untreated Group (dogs diagnosed with PH—n = 5), Finasteride treated group (PH dogs treated with finasteride—n = 5) and Orchiectomy treated group (PH dogs submitted to orchiectomy–n = 5). Evaluations were performed in a monthly interval (first day of treatment; after 30 and 60 days). Doppler ultrasonography was performed to measure prostatic volume, vascularization and hemodynamic profile of prostatic artery. Dihydrotestosterone, estrogen and testosterone concentrations were measured. At day 60, prostatic biopsy was performed for histological, immunohistochemical and qPCR analysis for VEGF-A expression. At day 60, vascularization score was higher in untreated compared to treated groups (finasteride and orchiectomy). Furthermore, VEGF-A expression was lower in the Orchiectomy Treated Group, but VEGF-A was immunohistochemically lower in both treated groups (finasteride and orchiectomy) compared to the Untreated Group. The efficiency of finasteride treatment in reducing clinical signs, prostate volume and vascularization appears to be similar to orchiectomy. In conclusion, both PH medical and surgical therapy lead to reduction in prostate dimension and VEGF-A expression and, consequently, lower local vascularization. However, orchiectomy promotes marked hormonal changes, which ultimately lead to prostate atrophy.

Hypoxia induced cancer stem cell enrichment promotes resistance to androgen deprivation therapy in prostate cancer

Androgen deprivation therapy (ADT) is the main treatment to prolong survival in advance stage prostate cancer (PCa) but associated resistance leads to the development of terminal castrate resistant PCa (CRPC). Current research demonstrates that prostate cancer stem cells (PCSC) play a critical role in the development of treatment resistance and subsequent disease progression. Despite uncertainty surrounding the origin of these cells, studies clearly show they are associated with poorer outcomes and that ADT significantly enhances their numbers. Here in we highlight how activation of HIF signalling, in response to hypoxic conditions within the tumour microenvironment, results in the expression of genes associated with stemness and EMT promoting PCSC emergence which ultimately drives tumour relapse to CRPC. Hypoxic conditions are not only enhanced by ADT but the associated decrease in AR activation also promotes PI3K/AKT signalling which actively enhances HIF and its effects on PCSC's. Furthermore, emerging evidence now indicates that HIF-2α, rather than the commonly considered HIF-1α, is the main family member that drives PCSC emergence. Taken together this clearly identifies HIF and associated pathways as key targets for new therapeutic strategies that could potentially prevent or slow PCSC promoted resistance to ADT, thus holding potential to prolong patient survival.

Rat Prostate Tumor Cells Progress in the Bone Microenvironment to a Highly Aggressive Phenotype

Prostate cancer generally metastasizes to bone, and most patients have tumor cells in their bone marrow already at diagnosis. Tumor cells at the metastatic site may therefore progress in parallel with those in the primary tumor. Androgen deprivation therapy is often the first-line treatment for clinically detectable prostate cancer bone metastases. Although the treatment is effective, most metastases progress to a castration-resistant and lethal state. To examine metastatic progression in the bone microenvironment, we implanted androgen-sensitive, androgen receptor-positive, and relatively slow-growing Dunning G (G) rat prostate tumor cells into the tibial bone marrow of fully immune-competent Copenhagen rats. We show that tumor establishment in the bone marrow was reduced compared with the prostate, and whereas androgen deprivation did not affect tumor establishment or growth in the bone, this was markedly reduced in the prostate. Moreover, we found that, with time, G tumor cells in the bone microenvironment progress to a more aggressive phenotype with increased growth rate, reduced androgen sensitivity, and increased metastatic capacity. Tumor cells in the bone marrow encounter lower androgen levels and a higher degree of hypoxia than at the primary site, which may cause high selective pressures and eventually contribute to the development of a new and highly aggressive tumor cell phenotype. It is therefore important to specifically study progression in bone metastases. This tumor model could be used to increase our understanding of how tumor cells adapt in the bone microenvironment and may subsequently improve therapy strategies for prostate metastases in bone.

Prostatic Artery Embolization (PAE) for Symptomatic Benign Prostatic Hyperplasia (BPH): Part 2, Insights into the Technical Rationale

Rationale of prostatic artery embolization (PAE) in the treatment of symptomatic benign prostatic hyperplasia is conventionally believed to include two parts: shrinkage of the enlarged prostate gland as a result of PAE-induced ischemic infarction and potential effects to relax the increased prostatic smooth muscle tone by reducing the number and density of α1-adrenergic receptor in the prostate stroma. This review describes new insights into the likely mechanisms behind PAE, such as ischemia-induced apoptosis, apoptosis enhanced by blockage of androgens circulation to the embolized prostate, secondary denervation following PAE, and potential effect of nitric oxide pathway immediately after embolization. Studies on therapeutic mechanisms in PAE may shed light on potentially new treatment strategies and development of novel techniques.

Progesterone receptor expression during prostate cancer progression suggests a role of this receptor in stromal cell differentiation

BACKGROUND

The progesterone receptor, like the androgen receptor, belongs to the steroid receptor superfamily. Our previous studies have reported that the PR is expressed specifically in prostate stroma. PR inhibits proliferation of, and regulates cytokine secretion by stromal cells. However, PR protein expression in cancer-associated stroma during prostate cancer progression has not been profiled. Since the phenotypes of prostate stromal cells change dynamically as tumors progress, whether the PR plays a role in regulating stromal cell differentiation needs to be investigated.

METHODS

Immunohistochemistry assays measured PR protein levels on human prostate tissue microarrays containing 367 tissue cores from benign prostate, prostate tumors with different Gleason scores, tumors under various durations of castration therapy, and tumors at the castration-resistant stage. Immunoblotting assays determined whether PR regulated the expression of alpha smooth muscle actin (α-SMA), vimentin, and fibroblast specific protein (FSP) in human prostate stromal cells.

RESULTS

PR protein levels decreased in cancer-associated stroma when compared with that in benign prostate stroma. This reduction in PR expression was not correlated with Gleason scores. PR protein levels were elevated by castration therapy, but reduced to pre-castration levels when tumors progressed to the castration-resistant stage. Enhanced PR expression in human prostate stromal cells increased α-SMA, but decreased vimentin and FSP protein levels ligand-independently.

CONCLUSION

These results suggest that PR plays an active role in regulating stromal cell phenotypes during prostate cancer progression.

Prostate angiogenesis in development and inflammation

BACKGROUND

Prostatic inflammation is an important factor in development and progression of BPH/LUTS. This study was performed to characterize the normal development and vascular anatomy of the mouse prostate and then examine, for the first time, the effects of prostatic inflammation on the prostate vasculature.

METHODS

Adult mice were perfused with India ink to visualize the prostatic vascular anatomy. Immunostaining was performed on the E16.5 UGS and the P5, P20, and adult prostate to characterize vascular development. Uropathogenic E. coli 1677 was instilled transurethrally into adult male mice to induce prostate inflammation. RT-PCR and BrdU labeling was performed to assay anigogenic factor expression and endothelial proliferation, respectively.

RESULTS

An artery on the ventral surface of the bladder trifurcates near the bladder neck to supply the prostate lobes and seminal vesicle. Development of the prostatic vascular system is associated with endothelial proliferation and robust expression of pro-angiogenic factors Pecam1, Tie1, Tek, Angpt1, Angpt2, Fgf2, Vegfa, Vegfc, and Figf. Bacterial-induced prostatic inflammation induced endothelial cell proliferation and increased vascular density but surprisingly decreased pro-angiogenic factor expression.

CONCLUSIONS

The striking decrease in pro-angiogenic factor mRNA expression associated with endothelial proliferation and increased vascular density during inflammation suggests that endothelial response to injury is not a recapitulation of normal development and may be initiated and regulated by different regulatory mechanisms.

Role of androgen and vitamin D receptors in endothelial cells from benign and malignant human prostate

Forty years ago, Judah Folkman (Folkman. N Engl J Med 285: 1182-1186, 1971) proposed that tumor growth might be controlled by limiting formation of new blood vessels (angiogenesis) needed to supply a growing tumor with oxygen and nutrients. To this end, numerous "antiangiogenic" agents have been developed and tested for therapeutic efficacy in cancer patients, including prostate cancer (CaP) patients, with limited success. Despite the lack of clinical efficacy of lead anti-angiogenic therapeutics in CaP patients, recent published evidence continues to support the idea that prostate tumor vasculature provides a reasonable target for development of new therapeutics. Particularly relevant to antiangiogenic therapies targeted to the prostate is the observation that specific hormones can affect the survival and vascular function of prostate endothelial cells within normal and malignant prostate tissues. Here, we review the evidence demonstrating that both androgen(s) and vitamin D significantly impact the growth and survival of endothelial cells residing within prostate cancer and that systemic changes in circulating androgen or vitamin D drastically affect blood flow and vascularity of prostate tissue. Furthermore, recent evidence will be discussed about the expression of the receptors for both androgen and vitamin D in prostate endothelial cells that argues for direct effects of these hormone-activated receptors on the biology of endothelial cells. Based on this literature, we propose that prostate tumor vasculature represents an unexplored target for modulation of tumor growth. A better understanding of androgen and vitamin D effects on prostate endothelial cells will support development of more effective angiogenesis-targeting therapeutics for CaP patients.

The role of intracrine androgen metabolism, androgen receptor and apoptosis in the survival and recurrence of prostate cancer during androgen deprivation therapy

Prostate cancer (CaP) is the most frequently diagnosed cancer and leading cause of cancer death in American men. Almost all men present with advanced CaP and some men who fail potentially curative therapy are treated with androgen deprivation therapy (ADT). ADT is not curative and CaP recurs as the lethal phenotype. The goal of this review is to apply our current understanding of CaP and castration-recurrent CaP (CR-CaP) to earlier studies that characterized ADT and the molecular mechanisms that facilitate the transition from androgen-stimulated CaP to CR-CaP. Reexamination of earlier studies also may provide a better understanding of how more newly recognized mechanisms, such as intracrine metabolism, may be involved with the early events that allow CaP survival after initiation of ADT and subsequent development of CR-CaP.

Carbogen gas and radiotherapy outcomes in prostate cancer

Prostate cancer hypoxia is associated with inferior prognosis and resistance to treatment. The use of androgen deprivation therapy, both prior to and during radiotherapy, may exacerbate underlying hypoxia. Whilst larger radiation doses per fraction may achieve therapeutic gain, this is balanced by the reduced opportunity for re-oxygenation to take place during the course of treatment. Improving the underlying hypoxic tumour environment may therefore improve the treatment outcomes. Strategies to combat tumour hypoxia, with particular focus on the use of carbogen gas breathing concurrently with radiotherapy, is the subject of this review.

Androgen deprivation results in time-dependent hypoxia in LNCaP prostate tumours: informed scheduling of the bioreductive drug AQ4N improves treatment response

Androgen withdrawal induces hypoxia in androgen-sensitive tissue; this is important as in the tumour microenvironment, hypoxia is known to drive malignant progression. Our study examined the time-dependent effect of androgen deprivation therapy (ADT) on tumour oxygenation and investigated the role of ADT-induced hypoxia on malignant progression in prostate tumours. LNCaP xenografted tumours were treated with anti-androgens and tumour oxygenation measured. Dorsal skin fold (DSF) chambers were used to image tumour vasculature in vivo. Quantitative PCR (QPCR) identified differential gene expression following treatment with bicalutamide. Bicalutamide-treated and vehicle-only-treated tumours were re-established in vitro, and invasion and sensitivity to docetaxel were measured. Tumour growth delay was calculated following treatment with bicalutamide combined with the bioreductive drug AQ4N. Tumour oxygenation measurements showed a precipitate decrease following initiation of ADT. A clinically relevant dose of bicalutamide (2 mg/kg/day) decreased tumour oxygenation by 45% within 24 hr, reaching a nadir of 0.09% oxygen (0.67 ± 0.06 mmHg) by Day 7; this persisted until Day 14 when it increased up to Day 28. Using DSF chambers, LNCaP tumours treated with bicalutamide showed loss of small vessels at Days 7 and 14 with revascularisation occurring by Day 21. QPCR showed changes in gene expression consistent with the vascular changes and malignant progression. Cells from bicalutamide-treated tumours were more malignant than vehicle-treated controls. Combining bicalutamide with AQ4N (50 mg/kg, single dose) caused greater tumour growth delay than bicalutamide alone. Our study shows that bicalutamide-induced hypoxia selects for cells that show malignant progression; targeting hypoxic cells may provide greater clinical benefit.

The stroma-a key regulator in prostate function and malignancy

Prostate cancer is a very common and highly unpredictable form of cancer. Whereas many prostate cancers are slow growing and could be left without treatment, others are very aggressive. Additionally, today there is no curative treatment for prostate cancer patients with local or distant metastasis. Identification of new, improved prognostic and diagnostic biomarkers for prostate cancer and the finding of better treatment strategies for metastatic prostate cancer is therefore highly warranted. Interactions between epithelium and stroma are known to be important already during prostate development and this interplay is critical also in development, progression of primary tumors and growth of metastases. It is therefore reasonable to expect that future biomarkers and therapeutic targets can be identified in the prostate tumor and metastasis stroma and this possibility should be further explored.

Vascular responses to radiotherapy and androgen-deprivation therapy in experimental prostate cancer

BACKGROUND

Radiotherapy (RT) and androgen-deprivation therapy (ADT) are standard treatments for advanced prostate cancer (PC). Tumor vascularization is recognized as an important physiological feature likely to impact on both RT and ADT response, and this study therefore aimed to characterize the vascular responses to RT and ADT in experimental PC.

METHODS

Using mice implanted with CWR22 PC xenografts, vascular responses to RT and ADT by castration were visualized in vivo by DCE MRI, before contrast-enhancement curves were analyzed both semi-quantitatively and by pharmacokinetic modeling. Extracted image parameters were correlated to the results from ex vivo quantitative fluorescent immunohistochemical analysis (qIHC) of tumor vascularization (9 F1), perfusion (Hoechst 33342), and hypoxia (pimonidazole), performed on tissue sections made from tumors excised directly after DCE MRI.

RESULTS

Compared to untreated (Ctrl) tumors, an improved and highly functional vascularization was detected in androgen-deprived (AD) tumors, reflected by increases in DCE MRI parameters and by increased number of vessels (VN), vessel density (VD), and vessel area fraction (VF) from qIHC. Although total hypoxic fractions ( HF) did not change, estimated acute hypoxia scores (AHS)--the proportion of hypoxia staining within 50 μm from perfusion staining--were increased in AD tumors compared to in Ctrl tumors. Five to six months after ADT renewed castration-resistant (CR) tumor growth appeared with an even further enhanced tumor vascularization. Compared to the large vascular changes induced by ADT, RT induced minor vascular changes. Correlating DCE MRI and qIHC parameters unveiled the semi-quantitative parameters area under curve (AUC) from initial time-points to strongly correlate with VD and VF, whereas estimation of vessel size (VS) by DCE MRI required pharmacokinetic modeling. HF was not correlated to any DCE MRI parameter, however, AHS may be estimated after pharmacokinetic modeling. Interestingly, such modeling also detected tumor necrosis very strongly.

CONCLUSIONS

DCE MRI reliably allows non-invasive assessment of tumors' vascular function. The findings of increased tumor vascularization after ADT encourage further studies into whether these changes are beneficial for combined RT, or if treatment with anti-angiogenic therapy may be a strategy to improve the therapeutic efficacy of ADT in advanced PC.

DCE and DW MRI in monitoring response to androgen deprivation therapy in patients with prostate cancer: a feasibility study

Androgen deprivation therapy (ADT) is a key primary treatment for advanced and metastatic prostate cancer and is an important neoadjuvant before radiotherapy. We evaluated 3.0 T dynamic contrast-enhanced MRI and diffusion-weighted (DW) MRI in monitoring ADT response. Twenty-three consecutive patients with prostate cancer treated by primary ADT were included. Imaging was performed at baseline and 3 months posttreatment with ADT. After 3 months therapy there was a significant reduction in all dynamic contrast-enhanced MRI parameters measured in tumor regions of interest (K(trans), k(ep), v(p), IAUGC-90); P < 0.001. Areas of normal-appearing peripheral zone showed no significant change; P = 0.285-0.879. Post-ADT, there was no significant change in apparent diffusion coefficient values in tumors, whilst apparent diffusion coefficient values significantly decreased in areas of normal-appearing peripheral zone, from 1.786 × 10(-3) mm(2) /s to 1.561 × 10(-3) mm(2) /s; P = 0.007. As expected the median Prostate-Specific Antigen (PSA) significantly reduced from 30 ng/mL to 1.5 ng/mL posttreatment, and median prostate volume dropped from 47.6 cm(3) to 24.9 cm(3) ; P < 0.001. These results suggest that dynamic contrast-enhanced MRI and diffusion-weighted MRI offer different information but that both could prove useful adjuncts to the anatomical information provided by T2-weighted imaging. dynamic contrast-enhanced as a marker of angiogenesis may help demonstrate ADT resistance and diffusion-weighted imaging may be more accurate in determining presence of tumor cell death versus residual tumor.

Etiopathogenesis of benign prostatic hypeprlasia

Benign prostatic hyperplasia (BPH) is the most common condition affecting men older than 50 years of age. It affects about 10 percent of men under the age of 40, and increases to about 80 percent by 80 years of age. BPH is a hyperplastic process of the fibromuscular stromal and glandular epithelial elements of the prostate. Aging and the presence of the functional testes are the two established risk factors for the development of BPH. The etiopathogenesis of BPH is still largely unresolved, but multiple partially overlapping and complementary theories have been proposed, all of which seem to be operative at least to some extent. This review is focused on recent progress in this area and on the growing consensus for the important mechanisms underlying the etiology and pathogenesis of BPH.

Androgen deprivation induces rapid involution and recovery of human prostate vasculature

The response of the prostate tissue microenvironment to androgen deprivation (AD) represents a critical component in the treatment of benign prostatic hyperplasia and prostate cancer (CaP). Primary xenografts of human benign and CaP tissue transplanted to immunocompromized SCID mice were used to characterize the response of the prostate vasculature during the initial 14 days of AD. Microvessel density and vascular lumen diameter in the prostate xenografts decreased rapidly after AD, reached a nadir on days 2-4, and recovered between days 4 and 14. The number of apoptotic endothelial cells peaked on day 2 after AD and decreased to precastration levels over days 4-7. Leakage of vascular contents in the interstitial space was apparent between days 1 and 3 after AD; however, the vascular permeability barrier reestablished between days 7 and 14. Expression of vascular endothelial growth factor (VEGF)-A, VEGF receptor-2, and basic fibroblast growth factor protein increased in endothelial cells between days 2 and 4 after AD, which preceded vascular recovery and appeared to be a direct and specific response of the endothelial cells to AD. Lack of comparable upregulation of these genes in primary cultures of human prostate endothelial cells in response to AD suggests a role for paracrine signaling mediated through stromal or epithelial cells. VEGF-A expression by prostate endothelial cells appears to represent a key facilitator of the vascular rebound in human prostate tissue induced by removal of circulating testicular androgens.

Targeting castration-induced tumour hypoxia enhances the acute effects of castration therapy in a rat prostate cancer model

What's known on the subject? and What does the study add? Castration therapy has rather modest effects on cell death in tumours but can be enhanced by other treatments targeting tumour stroma and vasculature. This study shows that the prostate becomes hypoxic following castration and that targeting hypoxic cells during castration therapy potently enhances the effects of castration.

OBJECTIVE

To explore the effects of castration therapy, the standard treatment for advanced prostate cancer, in relation to tumour hypoxia and to elicit its importance for the short- and long-term therapeutic response.

MATERIAL AND METHODS

We used the androgen-sensitive rat Dunning H prostate tumour model that transiently responds to castration treatment followed by a subsequent relapse, much like the scenario in human patients. Tumour tissues were analysed using stereological methods in intact, 1 and 7 days after castration therapy.

RESULTS

Hypoxia was transiently up-regulated after castration therapy and correlated with the induction of tumour cell apoptosis. When castration therapy was combined with tirapazamine (TPZ), a drug that targets hypoxic cells and the vasculature, the effects on tumour cell apoptosis and tumour volume were enhanced in comparison to either castration or TPZ alone.

CONCLUSION

The present study suggests that castration-induced tumour hypoxia is a novel target for therapy.

Antivascular effects of neoadjuvant androgen deprivation for prostate cancer: an in vivo human study using susceptibility and relaxivity dynamic MRI

PURPOSE

The antivascular effects of androgen deprivation have been investigated in animal models; however, there has been minimal investigation in human prostate cancer. This study tested the hypothesis that androgen deprivation causes significant reductions in human prostate tumor blood flow and the induction of hypoxia at a magnitude and in a time scale relevant to the neoadjuvant setting before radiotherapy.

METHODS AND MATERIALS

Twenty patients were examined, each with five multi-parameter magnetic resonance imaging scans: two scans before the commencement of androgen suppression, one scan after 1 month of hormone treatment, and two further scans after 3 months of therapy. Quantitative parametric maps of the prostate informing on relative blood flow (rBF), relative blood volume (rBV), vascular permeability (transfer constant [K(trans)]), leakage space (v(e)) and blood oxygenation (intrinsic relaxivity [R(2)∗]) were calculated.

RESULTS

Tumor blood volume and blood flow decreased by 83% and 79%, respectively, in the first month (p < 0.0001), with 74% of patients showing significant changes. The proportion of individual patients who achieved significant changes in T1 kinetic parameter values after 3 months of androgen deprivation for tumor measurements was 68% for K(trans) and 53% for v(e) By 3 months, significant increases in R(2)∗ had occurred in prostate tumor, with a rise of 41.1% (p < 0.0001).

CONCLUSIONS

Androgen deprivation induces profound vascular collapse within 1 month of starting treatment. Increased R(2)∗ in regions of prostate cancer and a decrease in blood volume suggest a reduction in tumor oxygenation.

Thrombospondin-1 regulates the normal prostate in vivo through angiogenesis and TGF-beta activation

Castration experiments in rodents show that the stromal vasculature is critical to the androgen-mediated prostate growth regulation. However, the role of angiogenesis inhibitors, such as thrombospondin-1 (TSP-1), in this process is unclear. TSP-1 is a multifunctional glycoprotein that can function as a potent angiogenesis inhibitor and an in vivo activator of latent transforming growth factor-beta (TGF-beta) in some tissues. On the basis of these observations, we hypothesized that TSP-1 regulated androgen withdrawal-induced prostate regression and that this process was mediated not only through antiangiogenic activity but also through TGF-beta activation. To test this, we evaluated angiogenic activity in human prostate epithelial and stromal cells treated with androgens and hypoxia in vitro. TSP-1 knockout mice were characterized to investigate the in vivo functions of TSP-1. In vitro, we found that androgens and hypoxia differentially regulated TSP-1 and angiogenic activity. Androgens stimulated normal epithelial cell, but inhibited normal stromal cell, angiogenic activity. Conversely, hypoxia stimulated stromal while inhibiting epithelial activity. Thus, in vivo, net angiogenic activity must reflect cellular interactions. And, we found that media conditioned by epithelial cells grown under normoxic conditions stimulated stromal cell angiogenic activity, and if epithelial cells were grown under hypoxic conditions, stromal activity was further increased. TSP-1 levels, however, were unchanged. In vivo, TSP-1 loss in a mouse model led to prostate epithelial hyperplasia by 3 months of age with only a modest stromal effect. Androgens suppressed TSP-1 as expression increased after castration both in normal mouse prostate and in human prostate cancer tissues. In addition, TSP-1 expression corresponded to increased TGF-beta activation in mouse tissues, specifically in the stromal compartment. These data show a critical role for TSP-1 in prostate epithelial and stromal growth regulation through angiogenic inhibition and activation of latent TGF-beta. Therefore, loss of TSP-1 during tumorigenesis would eliminate two barriers to cancer progression.

Effect of dutasteride on the expression of hypoxia-inducible factor-1alpha, vascular endothelial growth factor and microvessel density in rat and human prostate tissue

OBJECTIVE

To evaluate the effects of dutasteride on the expression of angiogenesis markers in rat and human prostates.

MATERIAL AND METHODS

Eight-week-old male Sprague-Dawley rats were divided into three groups of six each according to dutasteride dose, including the control group (regular diet), 2.5 mg group (2.5 mg/kg dutasteride) and 5.0 mg group (5.0 mg/kg dutasteride). A total of 41 patients awaiting transurethral resection of the prostate (TURP) were divided into two groups: 20 patients received no medication and 21 received 0.5 mg dutasteride daily for 2-4 weeks until TURP.

RESULTS

At 2 weeks, dutasteride effected a significant decrease in body weight and prostate weight compared with the control rat group. Analysis by reverse transcription-polymerase chain reaction and Western blot revealed that hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) expression was lower in the dutasteride-treated groups than in the control group, except for HIF-1alpha protein. HIF-1alpha and VEGF expression was similar in the 2.5 mg and 5.0 mg groups. Human prostate tissues demonstrated homogeneous staining of HIF-1alpha and VEGF with regard to extent, intensity and intracellular location in both groups. There was no significant difference in microvessel density between the two groups.

CONCLUSIONS

The expression of HIF-1alpha and VEGF in rat prostates is suppressed by dutasteride. However, less than 4 weeks of dutasteride administration does not suppress the expression of HIF-1alpha, VEGF and microvessel density in human prostate tissue. Further clinical investigation with dutasteride including a larger, placebo-controlled study is warranted to establish the mechanism and duration of dutasteride.

Perspectives on Mathematical Modeling for Receptor-Mediated Processes

Mathematical modeling is a potent in silico tool that can help investigate, interpret, and predict the behavior of biological systems. The first step is to develop a working hypothesis of the biology. Then by "translating" the biological phenomena into equations, models can harness the power of mathematical analysis techniques to explore the dynamics and interactions of the biological components. Models can be used together with traditional experimental models to help design new experiments, test hypotheses, identify mechanisms, and predict outcomes. This article reviews the process of building, calibrating, and using mathematical models in the context of the kinetics of receptor and signal transduction biology. An example model related to the androgen receptor-mediated regulation of the prostate is presented to illustrate the steps in the modeling process and to highlight the potential for mathematical modeling in this area.

Androgen receptor is causally involved in the homeostasis of the human prostate endothelial cell

Androgen deprivation causes a reduction of blood flow in the prostate gland that precedes temporally apoptosis of the epithelium. The acute response of prostate endothelial cells to androgen deprivation suggested they represent a primary target for androgen. However, rat prostate endothelial cells were reported not to express androgen receptor (AR), and the role of the androgen axis in human prostate endothelial cell (HPEC) homeostasis was poorly characterized. In this study AR expression was detected in HPEC in vivo in clinical specimens of benign prostate and prostate cancer, and AR function as a transcription factor was demonstrated in HPEC in primary xenografts of human benign prostate tissue transplanted into severe combined immunodeficient mice by iv administration of adenoviral mouse mammary tumor virus-driven luciferase expression vector. AR expression and functionality were maintained in vitro in primary cultures of HPEC that coexpressed CD31, CD34, von Willebrand factor, intercellular adhesion molecule, vascular endothelial growth factor receptor 1, and vascular endothelial growth factor receptor 2 but did not express prostate-specific antigen. AR expression in primary cultures of HPEC isolated from surgical specimens of benign prostate was validated using RT-PCR, cDNA sequencing, immunocytochemistry, and Western blot analyses. Scatchard analyses demonstrated a single ligand-binding site for R1881 in primary cultures of HPEC, with dissociation constant of 0.25 nm, and AR-mediated transcriptional activity was demonstrated using adenoviral mouse mammary tumor virus-driven luciferase reporters. Dihydrotestosterone increased proliferation in primary cultures of HPEC in a dose-dependent manner without modulating endothelial tube formation in Matrigel (BD Biosciences, Bedford, MA). Therefore, HPECs express functional AR, and androgen plays a direct role in modulating HPEC biology.

Origin of androgen-insensitive poorly differentiated tumors in the transgenic adenocarcinoma of mouse prostate model

Following castration, the transgenic adenocarcinoma of mouse prostate (TRAMP) model demonstrates rapid development of SV40-Tag-driven poorly differentiated tumors that express neuroendocrine cell markers. The cell population dynamics within the prostates of castrated TRAMP mice were characterized by analyzing the incorporation of 5-bromodeoxyuridine (BrdUrd) and the expression of SV40-Tag, synaptophysin, and androgen receptor (AR). Fourteen days postcastration, the remaining epithelial cells and adenocarcinoma cells were nonproliferative and lacked detectable SV40-Tag or synaptophysin expression. In contrast, morphologically distinct intraglandular foci were identified which expressed SV40-Tag, synaptophysin, and Ki67, but that lacked AR expression. These proliferative SV40-Tag and synaptophysin-expressing intraglandular foci were associated with the rare BrdUrd-retaining cells. These foci expanded rapidly in the postcastration prostate environment, in contrast to the AR- and SV40-Tag-expressing adenocarcinoma cells that lost SV40-Tag expression and underwent apoptosis after castration. Intraglandular foci of synaptophysin-expressing cells were also observed in the prostates of intact TRAMP mice at a comparable frequency; however, they did not progress to rapidly expanding tumors until much later in the life of the mice. This suggests that the foci of neuroendocrine-like cells that express SV40-Tag and synaptophysin, but lack AR, arise independent of androgen-deprivation and represent the source of the poorly differentiated tumors that are the lethal phenotype in the TRAMP model.

A stroma targeted therapy enhances castration effects in a transplantable rat prostate cancer model

BACKGROUND

Castration results in a major involution of the normal prostate gland. This process is initiated by effects in the prostate stroma and vasculature. Castration-induced regression of androgen sensitive prostate tumors is however less prominent and hypothetically this could be related to a limited stromal/vascular response. We therefore used animal tumor models to explore the importance of stroma and vascular effects, and if castration effects could be enhanced by a simultaneous therapy targeting the tumor stroma.

METHODS

Using rats with Dunning PAP and H tumors, stereological methods, immunohistochemistry, and Western blotting, we studied the tumor response 7 and 28 days after castration and after the addition of stroma targeted therapies.

RESULTS

In the normal ventral prostate (VP) nuclear androgen receptors (AR) were rapidly downregulated after castration. In contrast, the Dunning tumors downregulated the AR in the cancerous epithelium, but not in the surrounding stroma. Vascular regulators such as the angiopoietins, tie 2, and PDGF-Rbeta were not decreased in the stroma after castration, as observed in the VP, creating an environment that prevents vascular involution. When a tumor stroma targeted therapy inhibiting the tie 2 receptor and the PDGF-Rbeta simultaneously was added to castration it resulted in a decreased vascular density, increased tumor cell apoptosis and decreased tumor growth compared to castration alone.

CONCLUSIONS

The stroma in highly differentiated androgen sensitive Dunning tumors is apparently androgen insensitive. If this unresponsive stroma is targeted the effects of castration can be enhanced.

Nuclear androgen receptors recur in the epithelial and stromal compartments of malignant and non-malignant human prostate tissue several months after castration therapy

BACKGROUND

As changed paracrine support from androgen receptor (AR)-positive cells in the prostate stroma contribute to castration-induced glandular involution, we examined if the subsequent relapse to androgen-independent epithelial cell growth could be related to reactivation of AR signaling in the stroma.

MATERIALS AND METHODS

Human prostate tissue taken before, within 14 days, and at suspected local tumor relapse after surgical castration therapy was immunostained for AR.

RESULTS

Castration initially decreased nuclear AR staining in epithelial and stroma cells, in both tumor and non-malignant tissue, but after some months, it reappeared.

CONCLUSIONS

Local tumor relapse was associated with reappearance of nuclear AR not only in tumor epithelial cells but also in the tumor stroma. Reappearance of nuclear AR in non-malignant prostate cells may be a physiological response to long-term systemic androgen ablation that could influence tumor growth.

Inhibition of the epidermal growth factor receptor enhances castration-induced prostate involution and reduces testosterone-stimulated prostate growth in adult rats

BACKGROUND

The epidermal growth factor receptor (EGFR) mediates regulatory signals in the normal prostate, but the functional importance of this is unclear.

METHODS

Adult male rats were castrated, or castrated + treated with gefitinib (Iressa, ZD1839), an EGFR tyrosine kinase inhibitor, for 3 days. Seven-day castrated rats were treated with testosterone, or testosterone + gefitinib, for 3 days.

RESULTS

Both castration alone and testosterone treatment in castrated animals increased the mRNA and protein levels of EGFR and phospho-EGFR in the ventral prostate. Inhibition of EGFR during castration and during testosterone-stimulated prostate growth resulted in a decrease in total epithelial weight, epithelial cell proliferation, endothelial cell proliferation, and increased epithelial cell apoptosis.

CONCLUSIONS

This study suggests that increased EGFR signaling during castration mediates stimulatory effects balancing castration-induced prostate regression, and that EGFR signaling is a necessary component in testosterone-stimulated prostate growth.

Androgen-insensitive prostate cancer cells transiently respond to castration treatment when growing in an androgen-dependent prostate environment

BACKGROUND

Castration-induced involution of the normal prostate is caused by primary effects in the prostate stroma and vasculature, but if this is the case also in tumors is unknown.

METHODS

Androgen-independent AT-1 prostate tumor cells were therefore injected into the ventral prostate (VP) in Copenhagen rats. Seven days later when the growing tumor was surrounded by normal VP tissue the rats were castrated and the effect examined 3 and 7 days later.

RESULTS

Castration reduced vascular density in the surrounding VP tissue and this was accompanied by tumor cell hypoxia, apoptosis, and temporarily retarded tumor growth. Castration-induced VP tissue regression occurred more rapidly in the contra-lateral than in the tumor-bearing lobe.

CONCLUSIONS

Androgen-independent tumor cell respond to castration when growing in an androgen-dependent environment. The presence of a tumor influences the castration response in the surrounding normal tissue. The microenvironment determines how prostate epithelial cells respond to castration.

Castration-induced epithelial cell death in human prostate tissue is related to locally reduced IGF-1 levels

BACKGROUND

Castration rapidly reduces stroma insulin-like growth factor (IGF)-1 synthesis and action in mouse prostate epithelium. We explore if similar changes are of importance for castration-induced prostate regression in humans.

METHODS

Epithelial and surrounding stroma cells were micro-dissected from patient biopsies obtained before and shortly after castration. IGF-1 mRNA levels were quantified by RT-PCR and related to epithelial apoptosis and IGF-1, IGF-1 receptor, and androgen receptor (AR) immunoreactivity.

RESULTS

IGF-1 mRNA was principally produced in the stroma and IGF-R1 in the epithelium. Stroma IGF-1 mRNA levels were significantly decreased after castration in non-malignant but not malignant tissue. Lack of stroma IGF-1 reduction after castration was associated with low stroma AR expression before therapy. Reduction of IGF-1 mRNA levels in the tumor stroma and/or epithelium was associated with epithelial apoptosis after therapy.

CONCLUSIONS

Low AR expression and maintained stroma IGF-1 synthesis may result in limited tumor cell death after castration therapy.

Inhibitory Effects of Castration in an Orthotopic Model of Androgen-Independent Prostate Cancer Can Be Mimicked and Enhanced by Angiogenesis Inhibition

PURPOSE

Today, the most important treatment of advanced prostate cancer is castration; unfortunately, however, the long-term effect of this therapy is insufficient. Recent studies suggest that castration-induced prostate involution could be caused by primary effects in the prostate vasculature; therefore, we examined if antivascular treatments could mimic the effects of castration.

EXPERIMENTAL DESIGN

Androgen-independent AT-1 prostate cancer cells were grown inside the ventral prostate in adult rats. Tumor-bearing animals were treated with an inhibitor of vascular endothelial growth factor receptor 2 and epidermal growth factor receptor signaling, N-(4-bromo-2-fluorophenyl)-6-methoxy-7-[(1-methylpiperidin-4-yl)methoxy]quinazolin-4-amine (ZD6474, AstraZeneca, Södertälje, Sweden), and short-term effects (after 3 days) were compared with those induced by castration.

RESULTS

Castration caused decreased vascular density in the normal tissue surrounding the tumor and consequently increased tumor hypoxia and apoptosis, and moderately decreased tumor growth. ZD6474 treatment resulted in decreased tumor vascular density accompanied by increased tumor hypoxia, apoptosis, and decreased tumor growth, suggesting that castration and antiangiogenic therapy work through similar mechanisms. Interestingly, castration or ZD6474 alone worked by reducing vascular density in the surrounding normal tissue and ZD6474 also in the tumor. Combined treatment with castration + ZD6474 was more effective than castration and ZD6474 alone in inducing tumor hypoxia, apoptosis, necrosis, and decreasing tumor vascular density.

CONCLUSION

These findings show that a drug that targets the vasculature in the tumor and in the surrounding ventral prostate lobe could mimic and even enhance the effects of castration. Our present findings thus suggest that castration + ZD6474 could be a particularly effective way to treat prostate tumors.

Participation of adrenomedullin and its relation with vascular endothelial growth factor in androgen regulation of prostatic blood flow in vivo

OBJECTIVES

We had previously reported that androgen-regulated prostatic blood flow and vascular endothelial growth factor (VEGF) were involved in the signal transduction pathway. Adrenomedullin (ADM) is a multifunctional regulatory peptide with mitogenic and angiogenic capabilities that are regulated by androgen. ADM is abundantly expressed in the prostate. We focused on ADM and evaluated its participation and relation with VEGF in androgen prostatic blood flow regulation using a castrated rat model.

METHODS

We examined the effect of locally injected dihydrotestosterone (DHT) and ADM, and the co-administration of DHT with an ADM receptor antagonist (ADM 22-52) on prostatic blood flow. Furthermore, prostatic blood flow was evaluated after ADM and VEGF administration with each other's antagonist, VEGF neutralizing antibody and ADM 22-52, respectively. Changes in the mRNA expression levels of ADM in the prostate after castration and successive androgen stimulation were also evaluated.

RESULTS

The administration of ADM promptly increased prostatic blood flow in a dose-dependent manner within 30 minutes. The DHT-induced increase in prostatic blood flow was completely abolished by co-administration with anti-ADM. Anti-ADM inhibited the VEGF-induced prostatic blood flow elevation, but a VEGF neutralizing antibody did not affect the ADM-mediated blood flow elevation. Furthermore, upregulation of the ADM gene induced by DHT was inhibited by co-administration with a VEGF-neutralizing antibody.

CONCLUSIONS

These results have clearly demonstrated the direct regulation of prostatic blood flow by ADM and its involvement in androgenic prostatic blood flow regulation. Furthermore, ADM was estimated to be a downstream mediator of VEGF action in the signal transduction pathway.

Castration rapidly decreases local insulin-like growth factor-1 levels and inhibits its effects in the ventral prostate in mice

BACKGROUND

The mechanisms by which castration induces prostate involution are largely unknown.

METHODS

Early responses to castration in mouse ventral prostate (VP) were explored by quantitative microscopy, cDNA array expression, quantitative RT-PCR, and Western blot analysis. As several changes occurred in the insulin-like growth factor (IGF) system this was studied in more detail. Laser micro-dissection was used to localize sites of IGF-1 and IGF-1 receptor (IGF-R1) production. IGF-1 protein levels and IGF-R1 mediated signaling via insulin regulated substrate 1 and 2 (IRS-1 and 2) were examined. IGF-1 was injected into the VP in intact, and castrated mice and effects studied 1 day later.

RESULTS

IGF-1 and IGF binding protein 2 (IGFBP-2) mRNA were rapidly reduced whereas IGFBP-3 and IGF-R1 mRNA were increased after castration. IGF-1 was principally produced in the stromal compartment, while IGF-R1 was produced in both epithelial and stromal cells. IGF-1 and IRS-1 protein levels were decreased 1 and 3 days after castration, respectively, while IRS-2 was unchanged. Inactivating phosphorylation of IRS-1 at serine 307 was increased 1 day after castration, and activating phosphorylation at tyrosine 612 was decreased 2 days later. These changes were accompanied by decreased cell proliferation and increased cell death in the glandular and vascular compartment. Local injection of IGF-1 increased vascular density and epithelial cell proliferation in intact mice, but had no effect in castrated animals.

CONCLUSION

Decreased IGF-1 levels and action may mediate some of the key features of castration-induced prostate involution.

Mathematical model for the androgenic regulation of the prostate in intact and castrated adult male rats

The testicular-hypothalamic-pituitary axis regulates male reproductive system functions. Understanding these regulatory mechanisms is important for assessing the reproductive effects of environmental and pharmaceutical androgenic and antiandrogenic compounds. A mathematical model for the dynamics of androgenic synthesis, transport, metabolism, and regulation of the adult rodent ventral prostate was developed on the basis of a model by Barton and Anderson (1997). The model describes the systemic and local kinetics of testosterone (T), 5alpha-dihydrotestosterone (DHT), and luteinizing hormone (LH), with metabolism of T to DHT by 5alpha-reductase in liver and prostate. Also included are feedback loops for the positive regulation of T synthesis by LH and negative regulation of LH by T and DHT. The model simulates maintenance of the prostate as a function of hormone concentrations and androgen receptor (AR)-mediated signal transduction. The regulatory processes involved in prostate size and function include cell proliferation, apoptosis, fluid production, and 5alpha-reductase activity. Each process is controlled through the occupancy of a representative gene by androgen-AR dimers. The model simulates prostate dynamics for intact, castrated, and intravenous T-injected rats. After calibration, the model accurately captures the castration-induced regression of the prostate compared with experimental data that show that the prostate regresses to approximately 17 and 5% of its intact weight at 14 and 30 days postcastration, respectively. The model also accurately predicts serum T and AR levels following castration compared with data. This model provides a framework for quantifying the kinetics and effects of environmental and pharmaceutical endocrine active compounds on the prostate.

Positive effect of prostaglandin on regulation of prostatic blood flow

OBJECTIVES

To investigate the effects of prostaglandin E2 (PGE2) and its antireceptor antibody on prostatic blood flow regulation using a rat model. We estimated that PGE2 participated in the signaling pathway of hormonal regulation of the prostatic blood flow.

METHODS

The rats were castrated and injected locally with dihydrotestosterone (200 ng/head) or PGE2 (250 ng/head) directly into the prostatic membrane. After local dihydrotestosterone or PGE2 administration, anti-PGE2 receptor antibody (200 ng/head) was injected locally to investigate interruption of the signaling pathway. After administration, we evaluated the relative prostatic blood flow using a laser blood flow meter. The change in cyclooxgenase-2 mRNA expression and the changes in PGE2 concentration in response to androgen stimulation were also examined.

RESULTS

PGE2 was involved in blood flow regulation with activity equal to that of androgen. The effect of dihydrotestosterone was abolished by coadministration with anti-PGE2 receptor antibody. Cyclooxgenase-2 gene expression was upregulated in response to androgen stimulation. The PGE2 concentration also increased in response to androgen stimulation.

CONCLUSIONS

Our finding of PGE2 participation in androgen regulation of prostatic blood flow might lead to pathophysiologic elucidation of prostatic diseases.

Androgen and fibroblast growth factor 8 (FGF8) downregulation of thrombospondin 1 (TSP1) in mouse breast cancer cells

In the search for androgen target genes responsible for malignant growth in S115 mouse mammary tumor cells we found that thrombospondin 1 (TSP1) expression was strongly downregulated by testosterone (Te). Experiments with cycloheximide suggested that Te repression of TSP1 was dependent on de novo protein synthesis. TSP1 repression by Te was preceded by the induction of fibroblast growth factor 8 (FGF8) expression. FGF8 has previously been shown to mediate androgen effects on proliferation of S115 cells by autocrine/paracrine mechanisms. It has also been shown to increase breast cancer cell growth as tumors in nude mice and to stimulate tumor angiogenesis. We studied here the possibility that FGF8 belonged to the Te-induced de novo synthesized proteins that mediate the effect of Te on TSP1 expression in these cells. We found that addition of FGF8b to in vitro cultures or ectopic expression of FGF8b in S115 cells repressed TSP1 expression at mRNA and protein levels even in the absence of Te. FGF2, another angiogenic member of FGF family, also downregulated TSP1 mRNA level in the in vitro cultures of S115 cells. The antisense oligonucleotides for FGF8 did not, however, prevent Te-repression of TSP1 mRNA expression and a neutralizing anti-FGF8b antibody only partially opposed Te induced downregulation of TSP1. These results suggest that both androgen and FGF8 inhibit TSP1 expression independently. They also suggest that opposite to many other androgen-induced responses in S115 cells, the effect of Te on the expression TSP1 is not mediated by FGF8.

Effects of finasteride on the vascular surface density, number of microvessels and vascular endothelial growth factor expression of the rat prostate

INTRODUCTION

Finasteride is a 5-alpha-reductase inhibitor used in the medical treatment of benign prostatic hyperplasia (BPH) and appears to be effective in treating prostatic bleeding secondary to BPH. The exact mechanism of this effect is not known. The aim of this study was to evaluate the effects of finasteride on the vascular surface density (VSD), number of microvessels (NVES) and vascular endothelial growth factor (VEGF) expression of the rat prostate.

MATERIALS AND METHODS

Nineteen adult male rats were used. Finasteride was given to 14, and there were 5 in the control group. Finasteride 80 mg/kg was administered daily via orogastric tube as a suspension for three months. Rats were sacrificed and vascular structures of the prostates were labelled immunohistochemically using CD31 antibodies. VSD and NVES of the prostates were assessed by means of a peroxidase labeled streptavidin-biotin method. VEGF expression was examined by immunohistochemistry using VEGF monoclonal antibody.

RESULTS

Mean prostatic weights were decreased significantly in rats given finasteride (p=0.0001). Although an increase in VSD was detected in the finasteride group it was not significant (p=0.26). NVES was significantly increased in the finasteride group (p=0.033). No significant difference was detected between the two groups in terms of VEGF expression (p=0.48).

CONCLUSION

Finasteride does not seem to decrease VSD, NVES and VEGF expression at the level of the rat prostate. The effect of reduction of bleeding in BPH is likely to be due to its effect on shrinking glandular hyperplasia which might enhance vessel wall stability rather than decreasing overall vascularity.

TNF-alpha-related apoptosis-inducing ligand decoy receptor DcR2 is targeted by androgen action in the rat ventral prostate

The apoptotic cell death process in the prostate is known to be under the control of androgens. Tumor necrosis factor-alpha (TNF-alpha)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF-alpha family of cytokines, known to induce apoptosis upon binding to its death domain-containing receptors, DR4/TRAIL-R1 and DR5/TRAIL-R2. Two additional TRAIL receptors, DcR1/TRAIL-R3 and DcR2/TRAIL-R4, lack functional death domains and act as decoy receptors for TRAIL. In this study, we examined whether TRAIL and cellular receptors expression was targeted by androgens during the apoptotic cell death process in the hormone sensitive ventral prostate. The role of androgens was investigated using two sets of experiment. (1) Androgen deprivation associated with an apoptotic process resulted in a decrease in DcR2 mRNA and protein expression in the ventral prostate 3 days after castration. Testosterone administration to castrated adult rats prevented the decrease in DcR2 mRNA and protein levels in the ventral prostate. In contrast, DcR2 expression was modified, neither in the dorsolateral nor in the anterior prostate following castration. No changes were observed in DR4, DR5, DcR1, and TRAIL mRNA and protein levels in prostate after castration. (2) A specific decrease in DcR2 expression was observed in the ventral prostate after treatment of rats with the anti-androgen flutamide. Together, the present results suggest that testosterone specifically controls DcR2 expression in the adult rat ventral prostate. Androgen withdrawal, by reducing DcR2 expression, might leave the cells vulnerable to cell death signals generated by TRAIL via its functional receptors.

Effect of short-term finasteride therapy on peroperative bleeding in patients who were candidates for transurethral resection of the prostate (TUR-P): a randomized controlled study

In the present study we aimed to demonstrate the efficacy of short-term pretreatment with finasteride in patients undergoing transurethral resection of the prostate (TUR-P). For this purpose 40 patients with BPH, who were candidates for TUR-P, were randomized into two groups. The first group (n=20) received 5 mg finasteride/day for 4 weeks prior to surgery and the second group (n=20) remained as the control. Patients who underwent prior prostate or urethral surgery and had a diagnosis of prostate cancer or chronic renal failure, patients who received finasteride, aspirin, coumadin or similar anticoagulant drugs prior to surgery and patients who had capsule perforations or open sinuses during the surgery were excluded from the study. All patients had a normal digital rectal examination and PSA values less than 4 ng/ml. As we look at the results there was no statistically significant difference between the finasteride group and control group regarding age, IPSS, PSA, prostate volumes, preoperative serum hemoglobin, hematocrit values and mean operating times and used irrigating fluids. The total amount of bleeding and bleeding per gram resected tissue were significantly lower in the finasteride group regardless of prostate volume. Furthermore the decrease in the hemoglobin and hematocrit values was higher in the control group. As a conclusion four weeks of finasteride pretreatment provided a significant decrease in peroperative bleeding regardless of prostate volume without any major side effects.

Randomized, placebo-controlled trial showing that finasteride reduces prostatic vascularity rapidly within 2 weeks

OBJECTIVE

To measure expression of vascular endothelial growth factor (VEGF) and microvessel density (MVD) in the prostates of men after transurethral resection of the prostate (TURP) following 2 weeks of treatment with finasteride.

PATIENTS AND METHODS

Sixty-four men scheduled to undergo TURP were randomized to receive 5 mg of finasteride or placebo daily for 2 weeks before surgery. Sections of prostatic urothelium were stained for VEGF expression and for CD31 to assess MVD. Ten consecutive, non-overlapping high-power fields were analysed in a blinded fashion.

RESULTS

In all, 31 men received finasteride and 33 placebo; the groups were similar in patient age, resected prostate weight, preoperative catheterization, prostate-specific antigen level, aspirin use, spinal anaesthesia and postoperative diagnosis of prostate cancer. The mean (95% confidence interval) MVD was significantly lower in the finasteride group (60, 55-65) than in the placebo group (71, 64-78; P < 0.01). Similarly, the mean expression of VEGF was significantly lower in the finasteride group (47, 43-52 vs 61, 54-67; P < 0.001)

CONCLUSION

Finasteride inhibits angiogenic growth factors leading to reduced vascularity, and this is the basis of its action in reducing haematuria of prostatic origin. The present study shows that finasteride influences the prostatic microvasculature after only 2 weeks exposure.

Vascular endothelial growth factor expression in untreated and androgen-deprived patients with prostate cancer

The aim of the study was to investigate immunohistochemically the expression of vascular endothelial growth factor (VEGF) in untreated and androgen-deprived patients with prostate cancer. The study included 20 patients with prostate cancer who had undergone transurethral prostatectomy due to infravesical obstruction. All patients had been receiving androgen deprivation therapy for at least 3 months. Transurethral prostatectomy specimens were examined for VEGF expression after androgen deprivation, and the biopsy samples of the same patients were used for the evaluation of VEGF expression before androgen deprivation. VEGF expression was analyzed using immunohistochemistry. Staining patterns determined by the staining scores were compared before and after treatment. The correlation of VEGF expression with PSA, Gleason score, and the percent change in PSA after treatment was also investigated. Eligible biopsy specimens were available in 15 of the 20 patients, allowing for the evaluation of VEGF expression before treatment. All prostate cancer specimens were positive. VEGF was localized mainly in the cytoplasm or on the membrane of carcinoma cells. Staining was strong in 86.7% of patients before androgen deprivation. Heterogeneous staining (strong in 25%, moderate in 35%, and weak in 40%) was observed after treatment. Staining scores were significantly higher in patients before androgen deprivation and showed a significant decrease after androgen deprivation (p = 0.007). Tumor staining correlated with Gleason score. No significant correlation was determined between VEGF expression and pre-treatment PSA and percent change of PSA after treatment. Immunohistochemical results indicate that VEGF expression is downregulated by androgen deprivation therapy. VEGF may be a potential target for therapeutic intervention in prostate cancer.

Breast cancer resistance protein-mediated efflux of androgen in putative benign and malignant prostate stem cells

Malignantly transformed stem cells represent a potential common nidus for the primary cancer and the recurrent cancer that arises after treatment failure. Putative prostate stem cells and prostate tumor stem cells in benign and malignant human prostate tissue, in primary human prostate xenografts, and in the transgenic adenocarcinoma of the mouse prostate (TRAMP) mouse model of prostate cancer, are defined by expression of breast cancer resistance protein (BCRP), a marker of pluripotent hematopoietic, muscle, and neural stem cells, and by an absence of androgen receptor (AR) protein. Inhibition of BCRP-mediated efflux of dihydrotestosterone by novobiocin or fumitremorgin C in a rat prostate progenitor cell line that expresses BCRP and AR mRNAs, but minimal AR protein, results in stabilization and nuclear translocation of AR protein, providing a mechanism for lack of AR protein in BCRP-expressing stem cells. In both benign and malignant human prostate tissue, the rare epithelial cells that express BCRP and lack AR protein are localized in the basal cell compartment, survive androgen deprivation, and maintain proliferative potential in the hypoxic, androgen-deprived prostate. Putative prostate tumor stem cells that express BCRP but not AR protein in TRAMP are the source of a BCRP-negative and AR-negative, Foxa2- and SV40Tag-expressing, transit amplifying compartment that progresses to the poorly differentiated carcinomas that arise rapidly after castration. Therefore, BCRP expression isolates prostate stem/tumor stem cells from the prostate tissue microenvironment through constitutive efflux of androgen, protecting the putative tumor stem cells from androgen deprivation, hypoxia, or adjuvant chemotherapy, and providing the nidus for recurrent prostate cancer.

Effect of androgen concentration on seminal vesicle blood flow in rats—establishment of new highly sensitive simultaneous androgen measurement method

OBJECTIVES

To clarify the effect of androgen concentration on blood flow regulation in seminal vesicles and to identify the androgen most responsible for this effect.

METHODS

The androgen concentrations in the seminal vesicles and the seminal vesicle blood flow were measured at 0, 3, 6, 12, 24, 48, and 72 hours after castration. The androgen concentration was measured with a newly developed highly sensitive simultaneous androgen quantification method that uses liquid chromatography-tandem mass spectrometry. The blood flow was measured with the radioactive microsphere injection method. The change in seminal vesicle blood flow in 6-hour castrated rats after administration of 3 mg/kg testosterone, 3 mg/kg dihydrotestosterone (DHT), 3 mg/kg dehydroepiandrosterone, or 3 mg/kg testosterone plus 20 mg/kg finasteride was evaluated.

RESULTS

A correlation was observed between the DHT concentration and blood flow in the rat seminal vesicle after castration. The DHT concentration and blood flow decreased after castration to 31.6% and 37.9%, respectively, of the normal level at 6 hours. The decline in DHT concentration and blood flow decreased further thereafter to 2.2% and 18.1%, respectively, of the normal level at 72 hours. Both testosterone and DHT fully restored the organ blood flow in castrated rat seminal vesicles. However, the blood-flow-increasing effect of testosterone was attenuated by more than 50% when administered in combination with finasteride. Dehydroepiandrosterone did not increase seminal vesicle blood flow.

CONCLUSIONS

The results of our study showed a strong correlation between the organ DHT concentration and blood flow in rat seminal vesicles. Of the various androgens, the most active androgen in the regulation of seminal vesicle blood flow was DHT.

Cell proliferation and apoptosis in prostate tumors and adjacent non-malignant prostate tissue in patients at different time-points after castration treatment

BACKGROUND

Androgen ablation is the standard treatment for advanced prostate cancer but the short-term cellular effects are largely unknown.

METHODS

Sextant prostate biopsies were taken from 77 prostate cancer patients before and 1-10 days after castration treatment. Apoptosis, cell proliferation, and morphology were studied in malignant and non-malignant tissue, using stereological and immunohistochemical methods.

RESULTS

Epithelial cell proliferation was significantly decreased both in non-malignant and malignant epithelium already 1 day after therapy. It remained low until day 7, but increased thereafter in the remaining non-malignant epithelial cells and in some tumors. Epithelial cell apoptosis was significantly increased during the first week and then returned to basal levels. The maximal apoptotic indexes, seven- and two-times the intact levels in the non-malignant and malignant glands, respectively, were found at days 3-4 or even earlier in the tumors. Signs of tumor shrinkage such as glandular collapse and decreased tumor cell size were observed from day 3 in most tumors.

DISCUSSION

The present study shows that the magnitude and kinetics of the response to castration in the normal human prostate is very similar to the response previously described in rodents. We also demonstrate that most human prostate tumors rapidly respond to castration indicating the need for further evaluation of when and how to best monitor the effects of hormone ablation therapy in prostate cancer patients.