Peptide-hormone- and serotonin-immunoreactive cells in normal and hyperplastic prostate glands

Cocaine and amphetamine regulated transcript (CART): a newly characterized neuropeptide in human prostate

Cocaine and amphetamine regulated transcript (CART) is a somatostatin-like polypeptide. CART has been localized in the CNS, hypothalamo-pituitary-adrenocortical (HPA) axis, pancreatic islets and enteric nervous system. We investigated the cellular localization of CART in normal human prostate, benign prostatic hyperplasia, prostatic intraepithelial neoplasia and acinar adenocarcinoma. CART was assessed using immunohistochemistry (IHC) and in situ hybridization (ISH), and its gene expression was identified by RTqPCR. We found cellular expression of CART in both normal prostatic luminal secretory epithelial cells neuroendocrine cells (NEC) of both ducts and acini. The cellular appearance indicated a cycle of neuropeptide synthesis and secretion as validated by ISH/IHC concordance. RTqPCR analysis also validated the immunohistochemical data and gene expression, which both indicated low to moderate expression in prostatic tissues. CART expression also was increased in both neuroendocrine and glandular epithelial cell populations from samples of benign prostatic hyperplasia as validated by IHC, ISH and RTqPCR. CART expression was markedly diminished and, in some cases, entirely absent in tissues of prostatic intraepithelial neoplasia and adenocarcinoma. Owing to loss of CART expression in adenocarcinoma and its increase in benign prostatic hyperplasia, CART may prove to be an important prostate marker.

AMPK/SIRT1 signaling through p38MAPK mediates Interleukin-6 induced neuroendocrine differentiation of LNCaP prostate cancer cells

Neuroendocrine Prostate Cancer (NEPC) is an aggressive form of androgen independent prostate cancer (AIPC), correlated with therapeutic resistance. Interleukin (IL)-6 promotes proliferation and neuroendocrine differentiation (NED) of androgen dependent LNCaP cells. We treated LNCaP cells with IL-6 and observed for in vitro NED of cells and also expression of NE markers βIII tubulin, neuron-specific enolase (NSE) and chromogranin A (ChA). Here we investigated the proteins and/or pathways involved in NED of LNCaP cells induced by IL-6 and characterized their role in NED of PCa cells. We found that the altered proteins modulated AMPK signaling pathway in NE cells. Remarkably, IL-6 induces NED of LNCaP cells through activation of AMPK and SIRT1 and also both of these are co-regulated while playing a predominant role in NED of LNCaP cells. Of the few requirements of AMPK-SIRT1 activation, increased eNOS is essential for NED by elevating Nitric oxide (NO) levels. Pleiotropic effects of NO ultimately regulate p38MAPK in IL-6 induced NED. Hence, IL-6 induced AMPK-SIRT1 activation eventually transfers its activation signals through p38MAPK for advancing NED of LNCaP cells. Moreover, inactivation of p38MAPK with specific inhibitor (SB203580) attenuated IL-6 induced NED of LNCaP cells. Therefore, IL-6 promotes NED of PCa cells via AMPK/SIRT1/p38MAPK signaling. Finally, targeting AMPK-SIRT1 or p38MAPK in androgen independent PC3 cells with neuroendocrine features reversed their neuroendocrine characteristics. Taken together these novel findings reveal that targeting p38MAPK mitigated NED of PCa cells, and thus it can be a favorable target to overcome progression of NEPC.

Revisiting the Pharmacodynamic Uroselectivity of α 1-Adrenergic Receptor Antagonists

α₁-Adrenoceptor (AR) antagonists are widely used for the relief of urinary retention secondary to benign prostatic hyperplasia (BPH). While the five Food and Drug Administration-approved α ₁-AR antagonists (terazosin, doxazosin, alfuzosin, tamsulosin, and silodosin) share similar efficacy, they differ in tolerability, with reports of ejaculatory dysfunction. The aim of the present work was to revisit their α ₁-AR subtype selectivity as well as of LDT5 (1-(2-methoxyphenyl)-4-[2-(3,4-dimethoxyphenyl) ethyl]piperazine monohydrochloride), a compound previously described as a multitarget antagonist of α _1A-/α _1D-AR and 5-HT_1A receptors, and to estimate their affinity for D₂, D₃, and 5-HT_1A receptors, which are putatively involved in ejaculatory dysfunction. Competition binding assays were performed with native (D₂, 5-HT_1A) or transfected (human α _1A-, α _1B-, α _1Dt-AR, and D₃) receptors for determination of the drug's affinities. Tamsulosin and silodosin have the highest affinities for α _1A-AR, but only silodosin is clearly a selective α _1A-AR antagonist, with K _i ratios of 25.3 and 50.2 for the α _1D- and α _1B-AR, respectively. Tamsulosin, silodosin, and LDT5 (but not terazosin, doxazosin, and alfuzosin) have high affinity for the 5-HT_1A receptor (K _i around 5-10 nM), behaving as antagonists. We conclude that the uroselectivity of tamsulosin is not explained by its too-low selectivity for the α _1A- versus α _1B-AR, and that its affinity for D₂ and D₃ receptors is probably too low for explaining the ejaculatory dysfunction reported for this drug. Present data also support the design of "better-than-LDT5" new multitarget lead compounds with pharmacokinetic selectivity based on poor brain penetration and that could prevent hyperplastic cell proliferation and BPH progression. SIGNIFICANCE STATEMENT: The present work revisits the uroselectivity of the five Food and Drug Administration-approved α₁ adrenoceptor antagonists for the treatment of benign prostatic hyperplasia (BPH). Contrary to what has been claimed by some, our results indicate that the uroselectivity of tamsulosin is probably not fully explained by its too-weak selectivity for the α_1A versus α_1B adrenoceptors. We also show that tamsulosin affinity for D₃ and 5-HT_1A receptors is probably too low for explaining the ejaculatory dysfunction reported for this drug. Based on our lead compound LDT5, present data support the search for a multitarget antagonist of α_1A-α_1D and 5-HT_1A receptors with poor brain penetration as an alternative for BPH treatment.

Role of Neuroendocrine Cells in Prostate Cancer Progression

Neuroendocrine (NE) cells represent the third epithelial cell type on normal prostatic tissue (in addition to basal and secretory cells). They are localized in all regions of the human prostate at birth but rapidly decrease in the peripheral prostate after birth, and then reappear at puberty. After puberty, their number seems to increase until an apparently optimum level is reached, which persists between the age of 25 and 54. NE cells were defined by Pearse as APUD to refer to chemical characteristics of amine precursor uptake and decarboxylation, common to the cells of this system. The most predominant product of prostatic NE cells is Chromogranin A, but they also produce serotonin, CgB, secretogranin or CgC, thyroid-stimulating hormone-like peptide, calcitonin, katacalcin, PTHrP and α-human chorionic gonadotropin-like peptide. NE cells in normal and neoplastic prostates are devoid of androgen receptors, but they express epidermal growth factor (EGF) receptor and c-erbB-2. For these reason NE cells are androgen-insensitive. The NE component of prostate adenocarcinoma is resistant to hormone therapy; some studies showed that the number of NE tumor cells and CgA serum levels increase with the recovery of human prostate tumor from hormonal therapy. Currently there are no clinical data available to support an active role of radiotherapy in NE differentiation.

Carbidopa abrogates L-dopa decarboxylase coactivation of the androgen receptor and delays prostate tumor progression

The androgen receptor (AR) plays a central role in prostate cancer progression to the castration-resistant (CR) lethal state. L-Dopa decarboxylase (DDC) is an AR coactivator that increases in expression with disease progression and is coexpressed with the receptor in prostate adenocarcinoma cells, where it may enhance AR activity. Here, we hypothesize that the DDC enzymatic inhibitor, carbidopa, can suppress DDC-coactivation of AR and retard prostate tumor growth. Treating LNCaP prostate cancer cells with carbidopa in transcriptional assays suppressed the enhanced AR transactivation seen with DDC overexpression and decreased prostate-specific antigen (PSA) mRNA levels. Carbidopa dose-dependently inhibited cell growth and decreased survival in LNCaP cell proliferation and apoptosis assays. The inhibitory effect of carbidopa on DDC-coactivation of AR and cell growth/survival was also observed in PC3 prostate cancer cells (stably expressing AR). In vivo studies demonstrated that serum PSA velocity and tumor growth rates elevated ∼2-fold in LNCaP xenografts, inducibly overexpressing DDC, were reverted to control levels with carbidopa administration. In castrated mice, treating LNCaP tumors, expressing endogenous DDC, with carbidopa delayed progression to the CR state from 6 to 10 weeks, while serum PSA and tumor growth decreased 4.3-fold and 5.4-fold, respectively. Our study is a first time demonstration that carbidopa can abrogate DDC-coactivation of AR in prostate cancer cells and tumors, decrease serum PSA, reduce tumor growth and delay CR progression. Since carbidopa is clinically approved, it may be readily used as a novel therapeutic strategy to suppress aberrant AR activity and delay prostate cancer progression.

Intraluminal volume homeostasis: A common sertonergic mechanism among diverse epithelia

Volume homeostasis is a common physiological phenomenon for fluid secreting organs, such as exocrine and endocrine glands. It is a manifestation of a finite intraluminal space and an ever changing demand for secretory fluids. Volume homeostasis addresses issues of fluid secretion, storage and clearance for efficient functioning. Here we discuss the evidence gathered over the past 2-3 decades on serotonin's role as a feedback inhibitor of secretion in the mammary gland, salivary gland, liver, pancreas, lung, thyroid gland and prostate gland. We propose that serotonin action is a common mechanism of regulating intraductal volume homeostasis.

Phase II study of carboplatin and etoposide in patients with anaplastic progressive metastatic castration-resistant prostate cancer (mCRPC) with or without neuroendocrine differentiation: results of the French Genito-Urinary Tumor Group (GETUG) P01 trial

BACKGROUND

In the evolution of metastatic castration-resistant prostate cancer (mCRPC), patients present visceral metastases with or without neuroendocrine differentiation in 20% of cases.

PATIENTS AND METHODS

We assessed the efficacy and toxicity of a platinum-based chemotherapy regimen in mCRPC patients with either neuroendocrine differentiation defined by high serum levels of chromogranin A (CgA) and neuron-specific enolase (NSE) or visceral metastases. Patients received the combination of carboplatin and etoposide every 3 weeks. Efficacy end points included prostate-specific antigen (PSA) and neuroendocrine marker response, objective response and toxicity.

RESULTS

Of the 60 patients included from April 2005 to January 2008, 78.6% had bone metastases, 46.4% had lymph node involvement and 57.1% had liver and/or lung localizations. The objective response rate was 8.9% in the 46 patients with measurable disease. A neuroendocrine response was observed in 31% of cases for NSE and 7% for CgA. The PSA response rate was 8%. The most common grade 3-4 treatment-related toxic effects were neutropenia (65.5%), thrombocytopenia (32.7%) and anemia (27.3%). There was 7.2% febrile neutropenia, with one toxicity-related death. The median follow-up was 9.3 months [95% confidence interval (CI) 0.2-27.1] and the median overall survival 9.6 months (95% CI 8.7-12.7).

CONCLUSION

The benefit-risk ratio of this regimen seems unfavorable due to poor response and high toxicity.

Assessment of serum chromogranin-A as prognostic factor in high-risk prostate cancer

PURPOSE

The presence of neuroendocrine differentiation may play a key role in androgen-independent tumor progression. The prognostic significance of plasma chromogranin-A (CgA) was assessed in a series of consecutive patients with high-risk prostate cancer (PCa).

PATIENTS AND METHODS

Twenty-three patients presenting high-risk PCa and 8 healthy individuals, as control group, had their blood samples collected to evaluate CgA, free and total prostate specific antigen, and free and total testosterone in a pilot study. The correlations of serum CgA levels with PSA, testosterone, Gleason score, number of foci of hypercaptation in bone scan, age, and outcomes were evaluated at baseline and after 12 months.

RESULTS

Patients with PCa had significantly higher levels of plasma CgA (mean, 8.7; range, 1.9-73) than healthy patients (mean, 3.45; range, 0.6-5.6), P = 0.02. Analyzing only the patients group through correlation of the ranks, it was observed that CgA has low, insignificant correlations with PSA (P = 0.07) and with metastatic extension (P = 0.09). No association was found between the plasma CgA levels and the Gleason score (P = 0.20), age (P = 0.15), or disease progression (P = 0.27).

CONCLUSION

The serum levels of CgA were significantly increased in the group with PCa compared with the healthy group. However, there were low correlations between serum CgA and known prognostic factors (such as total and free PSA, age, Gleason score, and bone metastases) or clinical deterioration. Although future studies are needed with larger samples and longer follow-up, the presented data envisage a limited role to serum CgA as high-risk PCa prognostic factor.

Prognostic role of neuroendocrine differentiation in prostate cancer, putting together the pieces of the puzzle

Neuroendocrine (NE) differentiation is a common feature in prostate cancer (PC). The clinical significance of this phenomenon is controversial; however preclinical and clinical data are in favor of an association with poor prognosis and early onset of a castrate resistant status. NE PC cells do not proliferate, but they can stimulate the proliferation of the exocrine component through the production of paracrine growth factors. The same paracrine signals may favor the outgrowth of castrate adapted tumors through androgen receptor dependent or independent mechanisms. Noteworthy, NE differentiation in PC is not a stable phenotype, being stimulated by several agents including androgen deprivation therapy, radiation therapy, and chemotherapy. The proportion of NE positive PC, therefore, is destined to increase during the natural history of the disease. This may complicate the assessment of the prognostic significance of this phenomenon. The majority of clinical studies have shown a significant correlation between NE differentiation and disease prognosis, confirming the preclinical rationale. In conclusion the NE phenotype is a prognostic parameter in PC. Whether this phenomenon is a pure prognostic factor or whether it can influence the prognosis by favoring the onset of a castrate resistance status is a matter of future research.

Evaluation of seminal citrate level by 1H nuclear magnetic resonance spectroscopy in men with spinal cord injury

STUDY DESIGN

A case-control evaluating seminal citrate in patients with spinal cord injury (SCI).

OBJECTIVE

Several studies have shown neurological prostatic dysfunction in patients with SCI, as confirmed by low levels of seminal prostate-specific antigen (PSA), which is used as a parameter of gland activity. However, seminal citrate, produced almost exclusively by the prostate, could also be used as a marker of prostate function. Thus, the objective of this study was to determine whether SCI causes any changes in seminal citrate concentration and to compare the results obtained for patients and healthy men (controls).

SETTING

The study was carried out in Brazil.

METHODS

We studied 30 men with SCI aged on average 37.77+/-10.04 years and 30 controls aged on average 38.03+/-10.06 years. Blood and semen samples were collected after 3 days of abstinence from ejaculation. Fifteen minutes after collection, semen was stored in liquid nitrogen and the samples were submitted to (1)H nuclear magnetic resonance ((1)H NMR). Serum was stored at a controlled temperature of -70 to -79 degrees C and later used for the determination of testosterone, prolactin and total PSA using an AxSYM instrument and Abbott reagents.

RESULTS

The median concentration of seminal citrate was significantly lower in patients than in controls (521.65 versus 858.30 mg per 100 ml, P<0.001).

CONCLUSIONS

Patients with SCI have a significant reduction of seminal citrate as a consequence of neurological dysfunction of the prostate.

Implications of circulating chromogranin A in prostate cancer

OBJECTIVE

To evaluate whether measurement of circulating chromogranin A (CgA) levels provides clinicopathological and prognostic information in prostate cancer.

MATERIAL AND METHODS

Plasma CgA levels were measured in 57 patients with histologically confirmed prostate cancer (stage B or less, n=22; stage C, n=10; stage D1, n=2; hormone-naive D2, n=12; hormone-refractory D2, n=11) and in 22 with undetected prostate cancer using an enzyme-linked immunoabsorbent assay.

RESULTS

Median plasma CgA levels were significantly higher in patients with prostate cancer than in those with undetected cancer (p=0.0271). Higher stage (p<0.0001) and higher grade (p=0.0412) tumours were also significantly associated with higher plasma CgA levels. Above-normal CgA levels were also detected in 4/27 patients (15%) who underwent radical prostatectomy. Postoperative clinical failure was not reported in the prostatectomy patients; however, prostate-specific antigen (PSA) failure was reported in 44% of patients after a median follow-up period of 20.3 months. Multivariate analysis revealed that the pathological stage of the tumour was the only independent predictive variable for postoperative PSA failure (p=0.0494). Preoperative plasma CgA levels had no impact on postoperative PSA failure in the subgroup (prostatectomy patients). Elevated plasma CgA levels were associated with a poor survival prognosis in patients with stage D2 prostate cancer after a median follow-up period of 22.5 months (p=0.0416).

CONCLUSIONS

It was demonstrated in this study that plasma CgA levels in prostate cancer increase with the severity of the disease, especially for progressive hormone-refractory prostate cancer (HRPC), after hormone therapy. Although this cross-sectional study involved only a small number of patients, we believe that plasma CgA levels may effectively predict HRPC status and prognosis in metastatic cases.

Neuroendocrine differentiation in the progression of prostate cancer

Neuroendocrine (NE) cells originally exist in the normal prostate acini and duct, regulating prostatic growth, differentiation and secretion. Clusters of malignant NE cells are found in most prostate cancer (PCa) cases. NE differentiation (NED) is the basic character of the prostate, either benign or malignant. NE cells hold certain peptide hormones or pro-hormones, which affect the target cells by endocrine, paracrine, autocrine and neuroendocrine transmission in an androgen-independent fashion due to the lack of androgen receptor. NED is accessed by immunohistochemical staining or measurement of serum levels of NE markers. The extent of NED is associated with progression and prognosis of PCa. Chromogranin A (CGA) is the most important NE marker. In metastatic PCa, pretreatment serum CGA levels can be a predictor for progression and survival after endocrine therapy. It is recommended to measure longitudinal change in serum CGA. The NE pathway can also be a therapeutic target.

Comprehensive expression analysis of l-dopa decarboxylase and established neuroendocrine markers in neoadjuvant hormone-treated versus varying Gleason grade prostate tumors

Current hormone withdrawal therapies used for treatment of advanced prostate cancer lead to androgen-independent tumor growth. Increased prostatic neuroendocrine (NE) cell density has been implicated in promoting progression of prostate cancer, but the process by which this occurs remains unclear. The aim of this study was to determine whether there is an association of increased NE differentiation with neoadjuvant hormone therapy and Gleason grade. Using adjacently sectioned tissue microarrays, the expression profile of novel and known NE markers were monitored. L-Dopa decarboxylase (DDC), a catecholamine synthesis enzyme and androgen receptor (AR) coregulator protein, was identified as an additional NE marker of prostate cancer. Immunohistochemical analysis of DDC with the established NE markers, chromogranin A and bombesin, revealed a significant increase in NE differentiation after 6 months of hormone therapy and after progression to androgen independence but no apparent correlation with Gleason grade. In addition, dual immunofluorescence analysis revealed that approximately 55% of the mixed population of DDC- and chromogranin A-expressing NE cells continue to express AR. Taken together, these results suggest that the increase of NE differentiation in prostate cancers depends specifically on duration of hormone therapy. This increase may be due to the transdifferentiation of AR-expressing epithelial-derived adenocarcinoma cells into an NE cell phenotype.

New perspective in the management of neuroendocrine differentiation in prostate adenocarcinoma

In this review, we will present some of the information that is known about neuroendocrine (NE) cells and differentiation in the prostate. We will then speculate on the potential role that NE differentiation in prostate carcinoma may play and how this differentiation may be clinically analysed and treated. The androgen-independent growth of prostate cancer can be caused by different mechanisms; one of these is receptor-specific paracrine or autocrine growth modulation of human prostatic cancer cells by neuropeptides secreted by NE cells. Our results affirm that different methods of androgen deprivation can influence the serum chromogranin A (CgA) levels to different extents in prostate cancer. In particular, bicalutamide produces a significantly lower increase in serum CgA compared with castration therapy. In the light of other evidence that supports a significant relationship between serum CgA levels, tissue CgA expression and NE activity, we hypothesise that bicalutamide may reduce the risk of NE cell hyperactivation in prostate cancer. It is important to determine whether increases in CgA levels and NE cell activation are associated with progression towards hormone-independent prostate cancer. We recently proposed as therapy of NE activation in hormone-independent prostate cancer, a combination of oestrogens and somatostatin analogues. The combination of ethinyl estradiol and lanreotide had a favourable toxicity profile, offered objective and symptomatic responses in patients with limited treatment options and refractoriness to conventional hormonal therapy strategies and, in particular, offered a median overall survival that was superior to the 10-month median survival in patients with hormone refractory disease. This combination therapy also sustains the novel concept in cancer treatment in which therapies may target not only cancer cells but also its microenvironment in combination, which can confer protection from apoptosis.

Serotonin and melatonin, neurohormones for homeostasis, as novel inhibitors of infections by the intracellular parasite chlamydia

OBJECTIVES

Chlamydiae are obligate intracellular bacteria, causing a variety of diseases, i.e. pneumonia, sexually transmitted disease, conjunctivitis and zoonosis. Tryptophan depletion by interferon-gamma (IFN-gamma) is the most important host defence system against chlamydial infection. Thus chlamydial tryptophan metabolism is thought to play key roles for IFN-gamma resistance, persistent infection and host/tissue tropisms. We tested tryptophan derivatives for activity against chlamydia-infected cells.

METHODS

Rates of chlamydial infection and sizes of the inclusions were evaluated by in vitro infection using three Chlamydiaceae species, Chlamydia trachomatis, Chlamydophila pneumoniae and Chlamydophila felis, which show significant divergence of tryptophan synthesis genes and different susceptibilities to IFN-gamma.

RESULTS

Melatonin and serotonin, which are recognized as neural hormones for maintenance of organism homeostasis, reduced chlamydial infection but not other bacterial growth tested here. Unlike IFN-gamma, melatonin limited infection of all three chlamydiae and the effects were not recovered by tryptophan supplementation. Melatonin treatment only of host cells could diminish infection and the infection reduction was neutralized by a pertussis toxin, an inhibitor of G proteins. Ligands of melatonin and serotonin receptors also hampered infection.

CONCLUSIONS

Inhibition mechanisms of chlamydial infection by melatonin and serotonin appear to be different from those of IFN-gamma and involve specific G-protein-coupled receptors. Melatonin is deemed to inhibit early progression of the chlamydial development cycle, such as establishment of intracellular infection and/or conversion from elementary body to reticulate body. Utilization of melatonin, serotonin or their derivatives may be advantageous for harmless prevention of chlamydial infection.

Neuroendocrine differentiation in prostate cancer: implications for new treatment modalities

OBJECTIVES

This review aims to provide practising clinicians with the most recent knowledge of the biological nature of prostate cancer (PC) to facilitate investigation of new treatment modalities for patients with PC, especially the hormone-refractory state of the disease.

METHODS

Review of the literature using PubMed search and scientific journal publications.

RESULTS

Much progress has been made towards an understanding of the development and progression of PC, and the factors which drive the development of androgen independence. Neuroendocrine (NE) cells may provide an intriguing link between NE cell differentiation and tumour progression in PC with the genetically supported formation of androgen-independent clones which regulate the proliferation of neighbouring non-NE-phenotype cancer cells in a paracrine manner by secretion of NE products. Various NE peptides stimulate proliferation of androgen-independent PC through transactivation of the androgen receptors (AR). Therefore, cancerous epithelial cells that increase their responsiveness to NE factors or induce NE cells to release trophic factors may have a survival advantage over their siblings.

CONCLUSION

This review shows the need to improve our understanding of the biological nature of PC, especially cancer cells of the NE phenotype and their regulatory products to develop new therapeutic protocols and trials based on NE hormones and their agonists/antagonists.

Characterization of prostatic neuroendocrine cell line established from neuroendocrine carcinoma of transgenic mouse allograft model

BACKGROUND

The role of neuroendocrine (NE) cells in prostate cancer remains unclear. A useful model is necessary to study the biology of NE cells. We herein describe the establishment and characterization of an immortalized cell line from an NE-10 allograft of murine prostatic NE carcinoma.

METHODS

A novel cell line, designated NE-CS, was developed from an NE-10 allograft that was established from the ventral prostate of the LPB-T-antigen (Tag) transgenic mouse, line 10 (12T-10). We investigated the growth, karyotype, electron microscopic findings, expression of Tag and androgen receptor (AR), and tumorigenesis of the cells in athymic mice.

RESULTS

The immortal cell line NE-CS was maintained in vitro for more than 2 years. The NE-CS cells had dendritic-like extensions with dense core granules in the cytoplasm and produced serotonin and somatostatin in conditioned medium. The cells expressed neither Tag nor AR. They showed androgen-independent growth in vitro and a hypotetraploid karyotype similar to the original NE-10 allograft. The NE-CS cells, which were subcutaneously inoculated into athymic mice, formed tumors with the NE phenotype. The tumors exhibited accelerated growth compared to the original NE-10 allograft.

CONCLUSIONS

The established cell line has characteristics of NE differentiation and tumorigenic ability. This cell line may be a promising model to understand the molecular mechanisms associated with the acquisition of hormone refractory prostate cancer.

Long-term testosterone stimulation induces hyperplasia in the guinea-pig prostate

The relation between supraphysiologic circulating testosterone levels and prostatic diseases is unclear and difficult to study in men. Animal models may be advantageous. Based on a pilot study, testosterone enantate 50 mg (n=12) or 25 mg (n=12) was administered to guinea-pigs intramuscularly every 3 weeks, for either 7 or 14 months. The histopathology of the prostate was described. Epithelial hyperplasia was found in 14/21 animals receiving testosterone and in 7/12 very old animals, but no such changes were found in the sham or castrated animals. Testosterone stimulation seems to induce epithelial hyperplasia, but not cancer, in the guinea-pig prostate.

Prostatic neuroendocrine tumor in multiple endocrine neoplasia Type 2B

We report the unusual occurrence of a neuroendocrine prostatic tumor in two young males with multiple endocrine neoplasia (MEN) 2B. Immunohistochemistry of the tumor markers may help differentiate a primary neuroendocrine prostate tumor from the metastasis of a medullary thyroid carcinoma of poor prognosis. MEN 2B hallmarks (i.e. plasma thyrocalcitonin and urinary metanephrines) may be systematically investigated in neuroendocrine tumors of the prostate, and conversely prostate examination may be performed in the periodic screening of MEN 2B male patients.

Expression of serotonin receptors and role of serotonin in human prostate cancer tissue and cell lines

BACKGROUND

Increase in the number of serotonin (5-HT) releasing neuroendocrine (NE) cells has been shown to be correlated with tumor progression, loss of androgen dependence, and poor prognosis. Serotonin is a well-known mitogen which mediates a wide variety of physiological effects via multiple receptors, of which receptor subtype 1 (5-HTR1) has been identified in prostate cancer (PC) cell lines. Recently, 5-HT has been found to show growth-promoting activity and to be functionally related to oncogenes.

MATERIALS AND METHODS

Localization, protein content, and mRNA expression of 5-HTR subtype 1A, 1B, and 1D was studied in prostatic tissue (35 patients), metastases, PC cell lines, a benign prostatic stromal cell line (human prostate cell preparation (hPCP)), and xenografts of PC-3 cells by immunohistochemistry (IHC), Western blotting, and RT-PCR, respectively. The growth-inhibition effect of a 5-HT1A antagonist (NAN-190) on PC cell lines was studied using a bromodeoxyuridine (BrdU) assay.

RESULTS

A strong immunoreaction of 5-HTR1A and 1B was demonstrated in high-grade tumor cells (35/35) and a small number of BPH cells, whereas 5-HTR1D was confined to vascular endothelial cells. 5-HTR1A was also demonstrated in PC cells metastasized to lymph node and bone, PC-3, DU145, LNCaP, and in xenografts of PC-3 cells and hPCP. Western blot analysis gave strong bands from PC tissue extracts compared to BPH tissue. Using RT-PCR, 5-HTR1A mRNA was demonstrated in all PC cell lines. An antagonist of 5-HTR1A (NAN-190) inhibited the growth of PC-3, DU145, and LNCaP cells but not of hPCP cells.

CONCLUSIONS

This is the first study demonstrating an overexpression of 5-HTR subtypes 1A and 1B in PC cells, especially in high-grade tumors. Moreover, 5-HT stimulates proliferation of PC cells and 5-HTR1A antagonists inhibit proliferation. Thus, we propose that 5-HT has an important role in tumor progression, especially in the androgen-independent state of the disease. The design of specific antagonists for this type of receptor might be useful for the growth control of androgen-independent tumors.

RNA interference of achaete-scute homolog 1 in mouse prostate neuroendocrine cells reveals its gene targets and DNA binding sites

We have previously characterized a transgenic mouse model (CR2-TAg) of metastatic prostate cancer arising in the neuroendocrine (NE) cell lineage. Biomarkers of NE differentiation in this model are expressed in conventional adenocarcinoma of the prostate with NE features. To further characterize the pathways that control NE proliferation, differentiation, and survival, we established prostate NE cancer (PNEC) cell lines from CR2-TAg prostate tumors and metastases. GeneChip analyses of cell lines harvested at different passages, and as xenografted tumors, indicated that PNECs express consistent features ex vivo and in vivo and share a remarkable degree of similarity with primary CR2-TAg prostate NE tumors. PNECs express mAsh1, a basic helix-loop-helix (bHLH) transcription factor essential for NE cell differentiation in other tissues. RNA interference knockdown of mAsh1, GeneChip comparisons of treated and control cell populations, and a computational analysis of down-regulated genes identified 12 transcriptional motifs enriched in the gene set. Affected genes, including Adcy9, Hes6, Iapp1, Ndrg4, c-Myb, and Mesdc2, are enriched for a palindromic E-box motif, CAGCTG, indicating that it is a physiologically relevant mAsh1 binding site. The enrichment of a c-Myb binding site and the finding that c-Myb is down-regulated by mAsh1 RNA interference suggest that mAsh1 and c-Myb are in the same signaling pathway. Our data indicate that mAsh1 negatively regulates the cell cycle (e.g., via enhanced Cdkn2d, Bub1 expression), promotes differentiation (e.g., through effects on cAMP), and enhances survival by inhibiting apoptosis. PNEC cell lines should be generally useful for genetic and/or pharmacologic studies of the regulation of NE cell proliferation, differentiation, and tumorigenesis.

Presence of neuroendocrine cells during postnatal development in rat prostate: Immunohistochemical, molecular, and quantitative study

BACKGROUND

This work was undertaken to study the prostate neuroendocrine cells (PNEC) during the post-natal development of rats.

METHODS

Forty male Wistar rats (pre-pubertals, pubertals, young, and aged adults) were used for immunohistochemistry of chromogranin A (cgA), serotonin (SER), and protein gene product 9.5 (PGP9.5). They were also evaluated for numerical cell density (NV SER) and PNEC number per prostate (N SER). Five additional young adult rats were used for a RT-PCR study (mRNA cgA detection).

RESULTS

Weak immunoreactivity to cgA was observed in pubertal rats. No PNEC immunostained to PGP 9.5 was observed. Cells expressing SER were detected in all the groups exclusively located in periurethral ducts. The NV SER increased significantly in pubertal animals. In aged animals, it decreased to levels observed in pre-pubertal rats. The N SER increased significantly from pre-pubertal to young adults, decreasing in aged adults. There was weak production of cgA mRNA, with more expression in the dorsal prostate.

CONCLUSIONS

PNEC differ in rats when compared to humans: they are weakly immunopositive to cgA, do not express PGP 9.5, only show immunoreactivity to SER, and do not appear in acini. The changes in the amount of rat PNEC during the post-natal development suggest an androgenic influx. PNEC might regulate the contractility of periurethral ducts.

Pharmacological characterization of isolated human prostate

PURPOSE

Human prostate contains alpha-1 adrenergic, cholinergic and nonadrenergic noncholinergic neuroreceptors. Using agonistic and antagonistic agents at these neuroreceptors we studied the resultant contractile responses in isolated human prostate.

MATERIALS AND METHODS

Human prostate tissue was obtained at prostatectomy for benign prostatic hyperplasia in 37 adult male patients. Tissues were suspended in tissue bath chambers connected to force displacement transducers. Specimens were subjected to agonist induced contractions, the first always being norepinephrine (NE). Specimens were pretreated with antagonist (adrenergic, cholinergic, nonadrenergic noncholinergic or none if control), followed by contraction with a second agonist (NE or other). Contractile tensions were recorded on a polygraph and then statistically analyzed.

RESULTS

The order of highest to lowest agonist induced tensile forces was NE, dopamine, acetylcholine, bethanechol, histamine and serotonin. Excitatory concentration EC(50) values were determined for each agonist tested. Significant differences were found between specific alpha-1 adrenergic receptor blockers (terazosin, prazosin and the experimental drug LY253352). In addition, many other agents antagonized the alpha-1 adrenergic receptor. Inhibitory concentration IC(50) values were obtained and the order of alpha-1 adrenergic antagonistic strengths from strongest to weakest was LY253352, prazosin, terazosin, ketanserin, SCH23390, diphenhydramine, DO710, dopamine, serotonin and histamine.

CONCLUSIONS

Human prostate neuroreceptors were determined to be alpha-1 adrenergic, dopaminergic, muscarinic cholinergic, 2A serotonergic and H1 histaminergic. Dopamine, serotonin, histamine and their antagonists blocked the adrenergic response, indicating possible receptor-receptor interaction. Further study of the pharmacology of human prostate would likely identify new drugs for treating patients with bladder outlet obstruction due to benign prostatic hyperplasia.

Neuroendocrine pathogenesis in adenocarcinoma of the prostate

BACKGROUND

In the prostate, the importance of sex hormones for its normal development and function is well known. However, it has been proposed that various neuroendocrine (NE) hormones and growth factors may be involved in the pathogenesis of prostatic carcinoma (CaP). Neuroendocrine differentiation appears to be associated with tumour progression and the androgen-independent state, for which there is currently no successful therapy. Therefore, we need to improve our understanding of NE cells, their regulatory products and influence on the prostate gland. Finally, new therapeutic protocols need to be developed.

METHODS

Information is presented on prostatic NE cells and neuroendocrine differentiation (NED) in prostatic carcinoma. Neuroendocrine secretory products and interactions with epithelial prostate cells are investigated in order to understand their significance for the pathogenesis of the prostate gland, prognosis and therapy.

RESULTS

Recent research suggests that NE-secreted products. such as serotonin, somatostatin and bombesin, may influence growth, invasiveness, metastatic processes and angiogenesis in CaP. During recent years. new experimental models for NED have been developed to provide evidence that NE products may promote proliferation and confer antiapoptotic capabilities on non-neuroendocrine cells in close proximity to NE cells. Cancerous epithelial cells may become more responsive to NE factors by upregulation of receptors for neuropeptides, or may induce NE cells to upregulate the secretion and synthesis of NE factors. In the androgen independent state, neuropeptides and their intracellular signals may activate the androgen receptor. Furthermore, androgen ablation may lead to downregulation of neural endopeptidase 24.11 (a zinc-dependent metalloproteinase) and PSA, which would lead to increased levels of NE products becoming available. These studies confirm that NE cells and NED may have a significant impact on prostate cancer, especially in the androgen independent state.

CONCLUSIONS

Recent developments in molecular biology and pathophysiology of prostate cancer have increased our understanding of the NE regulatory mechanisms. Hopefully, this will lead to the development of entirely new therapeutic modalities. For example, somatostatin agonists may suppress angiogenesis and proliferation, and simultaneously promote apoptosis in prostate cancer cells. Somatostatin may thus have an important role in tumour biology, and in the future there may be a potential role for somatostatin analogues in the treatment of prostate cancer, but also for serotonin and bombesin receptor antagonists. However, a review of the accumulated knowledge in this field suggests that we still need to improve our understanding of NE cells and their regulatory products and influence on the prostate gland. and that clinical trials are needed, to test drugs based on neuroendocrine hormones and their agonists/antagonists.

Different profiles of neuroendocrine cell differentiation evolve in the PC-310 human prostate cancer model during long-term androgen deprivation

BACKGROUND

Neuroendocrine (NE) cells are androgen-independent cells and secrete growth-modulating peptide hormones via a regulated secretory pathway (RSP). We studied NE differentiation after long-term androgen withdrawal in the androgen-dependent human prostate cancer xenograft PC-310.

METHODS

Tumor-bearing nude mice were killed at 0, 2, 5, 7, 14, 21, 47, 84, and 154 days after castration. The half-life of the PC-310 tumor was 10 days, with a stable residual tumor volume of 30--40% after 21 days and longer periods of androgen deprivation.

RESULTS

Proliferative activity and prostate-specific antigen serum levels decreased to zero after castration, whereas cell-cycle arrest was manifested by increased p27(kip1) expression. A temporary downregulation of androgen receptor (AR) expression was noted after androgen deprivation. The expression of chromogranin A, secretogranin III, and secretogranin V (7B2) increased 5 days after castration and later. Subsequently, pro-hormone convertase 1 and peptidyl alpha--amidating monooxygenase as well as vascular endothelial growth factor were expressed from 7 days after castration on. Finally, such growth factors as gastrin-releasing peptide and serotonin were expressed in a small part of the NE cells 21 days after castration, but strong expression was induced late during androgen deprivation, that is, 84 and 154 days after castration, respectively.

CONCLUSIONS

Androgen deprivation of the NE-differentiated PC-310 model induced the formation of NE-differentiated AR(minus sign) and non-NE AR(+) tumor residues. The NE-differentiated cells actively produced growth factors via an RSP that may lead to hormone-refractory disease. The dormant non-NE AR(+) tumor cells were shown to remain androgen sensitive even after long-term androgen deprivation. In the PC-310 xenograft, time-dependent NE differentiation and subsequent maturation were induced after androgen depletion. The androgen-dependent PC-310 xenograft model constitutes an excellent model for studying the role of NE cells in the progression of clinical prostate cancer.

Chromogranin a concentration as a serum marker to predict prognosis after endocrine therapy for prostate cancer

PURPOSE

Chromogranin A is gaining acceptance as a serum marker of neuroendocrine tumors and the concentration is thought to be elevated in relation to neuroendocrine differentiation of prostate cancer. We examined the significance of the chromogranin A level as a serum marker for prostate cancer.

MATERIALS AND METHODS

Serum chromogranin A values were determined by monoclonal immunoradiometric assay in 108 patients with prostate cancer before treatment and in 66 with benign prostatic hyperplasia. In those with prostate cancer clinicopathological parameters, the response to endocrine therapy and the prognosis were evaluated in relation to serum chromogranin A.

RESULTS

Mean serum chromogranin A plus or minus standard deviation in prostate cancer and benign prostatic hyperplasia cases was 59.4 +/- 52.5 and 59.3 +/- 44.3 ng./ml., respectively (not significant). Poorly differentiated adenocarcinoma was associated with higher chromogranin A than well differentiated disease (p = 0.044). Of the stage D cases with a median prostate specific antigen (PSA) of 172.1 ng./ml. or less those with higher chromogranin A had a poorer prognosis than those with lower chromogranin A. In contrast, in stage D cases with a PSA of greater than 172.1 ng./ml. there was no difference in the prognosis between the higher and lower chromogranin A groups.

CONCLUSIONS

Serum chromogranin A tends to be elevated in patients with high grade prostate cancer. When combined with PSA, this marker may effectively predict a poor prognosis after endocrine therapy.

Neuroendocrine differentiation of the LNCaP prostate cancer cell line maintains the expression and function of VIP and PACAP receptors

The molecular mechanisms involved in differentiation of prostate cancer cells to a neuroendocrine (NE) cell phenotype are not well understood. Here we used the androgen-dependent human prostate cancer cell line LNCaP to perform a systematic and broad analysis of the expression, pharmacology, and functionality of vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase-activating peptide (PACAP) receptors. Reverse transcription polymerase chain reaction experiments, together with pharmacological approaches with a set of specific agonists and antagonists, demonstrated the presence of the three VIP/PACAP receptor subtypes (PAC1, VPAC1, and VPAC2 with a major role for VPAC1, acting through adenylate cyclase (AC) stimulation. An essentially similar pattern was observed by NE differentiated cells (4 days after serum deprivation) in spite of the important morphological changes observed. However, the expression of the prostate-specific antigen (PSA) decreased in NE cells (and increased again by dihydrotestosterone, DHT, treatment). The present demonstration of the induction of NE transdifferentiation in LNCaP cells by increasing concentrations of VIP adds value to previous observations on the role of cAMP in this process, an interesting topic in the comprehension of the molecular changes that are involved in the progression of prostate cancer to androgen independence.

Hypothalamic hormones and cancer

The use of peptide analogs for the therapy of various cancers is reviewed. Inhibition of the pituitary-gonadal axis forms the basis for oncological applications of luteinizing hormone-releasing hormone (LH-RH) agonists and antagonists, but direct effects on tumors may also play a role. Analogs of somatostatin are likewise used for treatment of various tumors. Radiolabeled somatostatin analogs have been successfully applied for the localization of tumors expressing somatostatin receptors. Studies on the role of tumoral LH-RH, growth hormone-releasing hormone (GH-RH), and bombesin/GRP and their receptors in the proliferation of various tumors are summarized, but the complete elucidation of all the mechanisms involved will require much additional work. Human tumors producing hypothalamic hormones are also discussed. Treatment of many cancers remains a major challenge, but new therapeutic modalities are being developed based on antagonists of GH-RH and bombesin, which inhibit growth factors or their receptors. Other approaches consist of the use of cytotoxic analogs of LH-RH, bombesin, and somatostatin, which can be targeted to receptors for these peptides in various cancers and their metastases. These new classes of peptide analogs should lead to a more effective treatment for various cancers.

Neuroendocrine cells and nerves in the prostate of the guinea pig: effects of peripheral denervation and castration

BACKGROUND

Neuroendocrine (NE) cells and nerves in the prostate gland are thought to play a central role in the regulation of growth, cellular differentiation and homeostasis of secretory activity. The objective of this experimental study was to describe the effects of peripheral denervation and castration on NE cells and nerves in the guinea pig prostate.

METHODS

Guinea pigs underwent sham-operation, unilateral and bilateral hypogastric nerve resection, extirpation of the right anterior major pelvic ganglion (AMPG), autotransplantation of prostatic tissue and castration. Cryostat sections of prostatic tissue were examined with immunohistochemistry by using serotonin (5-HT) and chromogranin A (CgA) and various neuropeptides.

RESULTS

The number of 5-HT-IR NE cells was four-fold higher than CgA-IR NE cells. The innervation pattern was uniform throughout the gland with subepithelial nerves in close proximity to NE cells. Autotransplants of prostatic tissue showed total loss of nerves, but the number and morphology of 5-HT-IR NE cells were unaltered. Extirpation of the right AMPG showed significant reduction in prostate weight, decreased density of nerve terminals in the superior part of the ipsilateral prostate, whereas the number and morphological feature of 5-HT-IR NE cells remained unaffected in the entire prostate. Castration induced atrophy of the gland with a significant reduction in weight (unpaired t-test, P < 0.001), but without effect upon 5-HT-IR NE cells.

CONCLUSIONS

The guinea pig seems to be a useful animal model for studies on the role of the NE cells in the prostate. NE cells seem to be independent of innervation and androgens. It seems that other factors influence the NE cell population to a greater extent.

Effects of hyperprolactinemia on rat prostate growth: evidence of androgeno-dependence

The effects of the polypeptide hormone prolactin (PRL) in the development and regulation of benign prostate hyperplasia (BPH) and also in prostate cancer are not very well characterized. This study examines the action of PRL, either alone or in association with androgens [testosterone (T) or dihydrotestosterone (DHT)], in the rat prostate gland. The effects of PRL and androgens were investigated after 30 and 60 days in control, castrated, castrated with a substitutive implant of T or DHT, and sham-operated Wistar rats. To enhance PRL release, we induced hyperprolactinemia by administering chronic injections of sulpiride (40 mg. kg(-1). day(-1)). Chronic hyperprolactinemia induces enlargement and inflammation of the lateral rat prostate without any histological changes on ventral and dorsal lobes. We also demonstrate that hyperprolactinemia induces Bcl-2 overexpression in the lateral rat prostate and that this could inhibit the level of apoptosis. The in vivo model established here is a useful in vivo approach for studying the hormonal regulation of normal and pathological prostate development.

Neuroendocrine differentiation is not prognostic of failure after radical prostatectomy but correlates with tumor volume

OBJECTIVES

To study neuroendocrine (NE) tumor cell differentiation in prostate cancer in relation to failure after radical prostatectomy.

METHODS

Radical prostatectomy specimens from 103 of 111 patients randomized to 3-month neoadjuvant luteinizing hormone-releasing hormone-analogue treatment (neoadjuvant group) or to surgery alone (control group) were available for analysis. Immunohistochemistry using antibodies to chromogranin A (CGA) enabled detection of tumor cells with NE differentiation. NE differentiation was scored as NE-negative (0 to 1+) or NE-positive (2 to 3+). The number of CGA-positive cells/cm(2) tumor area on the slides was assessed in a separate analysis. The patients were followed up for 39 months after surgery, and a prostate-specific antigen value of 0.5 ng/mL or greater in two consecutive blood samples was considered biochemical failure.

RESULTS

Kaplan-Meier analysis stratified for neoadjuvant hormonal treatment showed the failure rate to be significantly greater among those with NE-positive tumors than among those with NE-negative tumors. However, the number of CGA-positive cells/cm(2) was not a variable of prognostic significance. Instead, both NE differentiation and the CGA-positive cell count correlated with the tumor area on the slides (P = 0.0001). Multivariate analysis revealed the tumor area on the slide (P <0.0001) and positive surgical margins (P = 0.03) to be the only significant predictors of biochemical failure.

CONCLUSIONS

The extension of NE differentiation in prostate cancer correlates with tumor volume and is not an independent prognostic factor of failure after radical prostatectomy.

Calcitonin and calcitonin gene-related peptide in the human prostate gland

BACKGROUND

Calcitonin-related peptides have been found in the human prostate, and calcitonin (CT) and calcitonin gene-related peptide (CGRP) have been demonstrated in subpopulations of neuroendocrine (NE) cells. The purpose of this study was to determine the concentrations of CT and CGRP as well as the densities of NE cells in normal prostates, benign prostatic hyperplasia (BPH), and carcinoma of the prostate (CAP).

METHODS

In 42 specimens of radical prostatectomy, the number of CT- and CGRP-immunoreactive NE cells in areas of normal and BPH tissue was determined, and compared with CAP tissue using immunocytochemistry. In addition, by radioimmunoassay (RIA), tissue levels of CT and CGRP were analyzed in extracts from areas of normal, BPH, and CAP tissue, as verified by adjacent histologic sections.

RESULTS

A significant decrease in CT-immunoreactive NE cells was observed in hyperplastic nodules of BPH in comparison to normal tissue. These findings were in parallel with a significant reduction in tissue CT level in BPH compared to normal tissue. There was also a marked, but statistically nonsignificant, reduction in CT levels in CAP tissue. In contrast, levels of CGRP in BPH and CAP tissue did not show any significant differences compared to normal tissue.

CONCLUSIONS

CT and CGRP are present in NE cells of the human prostate. Calcitonin levels are significantly reduced in BPH, in parallel with a decreased number of CT-immunoreactive NE cells, whereas no significant changes in tissue levels of CGRP were observed. The functional significance of these findings is discussed.

Prostate cancer and neuroendocrine differentiation

A retrospective study was conducted in 41 patients with adenocarcinoma of the prostate to investigate the correlation between pathological stage, Gleason score and neuroendocrine differentiation in order to evaluate the prognostic significance of neuroendocrine differentiation. Patients' ages ranged from 50 to 84 (mean 69.1) years. Clinical staging was done by rectal examination, serum PSA, transrectal ultrasonography, bone scan and abdominal CT followed by pathological staging after the operation. After that malignant prostatic tissue sections obtained from radical prostatectomy and transurethral prostatectomy specimens were stained with haemotoxylin-eosin and Gleason scores were determined. From each patient paraffin blocks representative of the primary prostate adenocarcinoma were chosen for immunohistochemical staining with monoclonal neuron specific enolase and chromogranin A antibodies for the determination of neuroendocrine differentiation. Neuroendocrine cells were found to be present in 53.66% of the patients. The incidence of neuroendocrine differentiation was higher in poorly differentiated (Gleason 7-10) tumours when compared to moderately and well differentiated tumours (Gleason <7) although not statistically significant (p=0.09). Although the percentage of neuroendocrine differentiation was greater in advanced prostate carcinoma (stage C, D) than localized (stage A, B) the difference was not statistically significant (p=0.18). Nevertheless, a significant correlation was present between Gleason score and pathological stage (p=0.002). In 34 cases followed for 5 years there was no relationship between the presence of neuroendocrine cells and 5-year tumour progression (p=0.41). However, significant increase in tumour progression rate was observed with increase in Gleason score (p=0.02) and pathological stage (p=0.00001). As a conclusion, no significant correlation was found between neuroendocrine differentiation and prognostic markers such as Gleason score and pathological stage in adenocarcinoma of the prostate.

Neuroendocrine differentiation in prostatic carcinoma

BACKGROUND

Information is presented on prostatic neuroendocrine cells and neuroendocrine differentiation in prostatic carcinoma. The prognostic and therapeutic implications of neuroendocrine differentiation in prostatic carcinoma are reviewed.

METHODS

Data are presented that support the intriguing link between neuroendocrine differentiation, tumor progression, and androgen-independent prostate cancer. The hormones, and the receptors, expressed by prostatic neuroendocrine cells are investigated in order to elucidate their significance for prognosis and therapy.

RESULTS

The prognostic significance of neuroendocrine differentiation in prostatic malignancy has been controversial, but recent studies employing markers such as chromogranin A and neuron-specific enolase suggest that neuroendocrine differentiation, as reflected by increased tissue expression and/or blood levels of these neuroendocrine secretory products, correlates with poor prognosis, tumor progression, and androgen-independence. Since all malignant neuroendocrine cells are devoid of androgen receptors and since neuroendocrine phenotypic expression is not suppressed by androgen ablation, clonal propagation of androgen receptor-negative neuroendocrine cells may play an important role in the pathway towards the androgen-independent state of prostatic carcinoma. This would have significant implications for the treatment of prostate cancer, as several of the hormones known to be expressed by neuroendocrine-differentiated, malignant prostatic cells are potential candidates for drug therapy. A limited number of hormones have been tested in this context, in particular somatostatin, bombesin, and serotonin.

CONCLUSIONS

Neuroendocrine differentiation in carcinoma of the prostate appears to be associated with poor prognosis, tumor progression, and the androgen-independent state, for which there is currently no successful therapy. Therefore, new therapeutic protocols and trials need to be developed to test drugs based on neuroendocrine hormones and/or their antagonists. An evaluation of this new therapeutic approach against prostatic carcinoma with neuroendocrine differentiation, including hormone-refractory cancer, is easily justified, since these tumors are unresponsive to current modes of therapy.

Neurogenic origin of human prostate endocrine cells

OBJECTIVES

To determine the histogenetic origin of prostate neuroendocrine cells in human embryos.

METHODS

Prostatic tissue in human fetuses, ranging in gestational age from early week 10 to term, and infantile and pubertal glands were studied immunohistochemically. The distribution of neuroendocrine cells within the developing gland was semiquantitatively determined. Antibodies against the neuroendocrine markers chromogranin A (CgA) and protein gene product 9.5 (PGP), along with markers of prostatic secretion (prostate-specific antigen [PSA], prostatic acid phosphatase [PAP]), were used. They were applied either individually or in double-labeling experiments, as well as in experiments combining CgA immunohistochemical analysis with in situ hybridization or in situ end-labeling.

RESULTS

In embryos of less than 65-mm crown-rump length (CRL) (ie, younger than 12 weeks of gestation), the epithelium of the urogenital sinus was free of endocrine cells. On either side of the future prostatic mesenchyme, paraganglia containing CgA-immunoreactive cells are present, which start to penetrate the urogenital mesenchyme. In the late 10th week, these CgA-immunoreactive cells are found dispersed in the urogenital mesenchyme. In embryos of 65-mm CRL, when prostatic anlagen start to sprout from the urogenital epithelium, very few (but typically shaped) neuroendocrine cells appear in the urogenital sinus epithelium. Later, after the 12th week, when solid prostatic ducts have started forming, CgA-immunoreactive neuroendocrine cells are also present in these buds. The number of neuroendocrine cells in the urethral epithelium is considerably increased, and with the continuous sprouting and lumen formation of prostatic anlagen, neuroendocrine cells are transported into the future gland. Neuroendocrine cells observed in stroma of prenatal and postnatal prostates may also contribute to the neuroendocrine cell population of the gland.

CONCLUSIONS

Our results provide the first evidence that human prostate neuroendocrine cells represent a cell lineage of their own, being of neurogenic origin and therefore distinct from the urogenital sinus-derived prostate secretory and basal cells.

Kinetics of neuroendocrine differentiation in an androgen-dependent human prostate xenograft model

It was previously shown in the PC-295 xenograft that the number of chromogranin A (CgA)-positive neuroendocrine (NE) cells increased after androgen withdrawal. NE cells did not proliferate and differentiated from G0-phase-arrested cells. Here we further characterized NE differentiation, androgen receptor status, and apoptosis-associated Bcl-2 expression in the PC-295 model after androgen withdrawal to assess the origin of NE cells. PC-295 tumor volumes decreased by 50% in 4 days. Intraperitoneal bromodeoxyuridine (BrdU) incorporation and MIB-1 labeling decreased to 0%, and the apoptosis was maximal at day 4. Androgen receptor expression and prostate-specific antigen (PSA) serum levels decreased rapidly within 2 days. The number of NE cells increased 6-fold at day 4 and 30-fold at day 7. Five and ten percent of the CgA-positive cells were BrdU positive after continuous BrdU labeling for 2 and 4 days, respectively. However, no MIB-1 expression was observed in CgA-positive cells. NE cells expressed the regulated secretory pathway marker secretogranin III but were negative for androgen receptor and Bcl-2. Bcl-2 expression did increase in the non-NE tumor cells. In conclusion, androgen withdrawal leads to a rapid PC-295 tumor regression and a proliferation-independent induction of NE differentiation. The strictly androgen-independent NE cells that were still present after 21 days differentiated mainly from G0-phase-arrested cells.

Prostate-thyroid axis: stimulatory effects of ventral prostate secretions on thyroid function

BACKGROUND

Endocrine cells of the prostate secrete thyrotropin (TSH)-releasing hormone (TRH), TRH- and TSH-like peptides, and growth factors. Propylthiouracil- and methimazole-induced hypothyroidism increased prostatic levels of TRH in rats as in hypothalamus, whereas thyroxine (T4) replacement decreased TRH. From these reports, we inferred the existence of a prostate-thyroid axis.

METHODS

The influence of the prostate on the thyroid gland was studied in albino rats. Ventral prostate was surgically removed on day 31 postpartum. The animals were sacrificed on day 60 postoperation. Serum thyroid hormones were assayed by radioimmunoassay (RIA). For in vitro studies, normal thyroid and ventral prostate glands were cocultured with or without thyroid-stimulating hormone (TSH) antibody, to assess the direct influence of prostatic secretions on thyroid hormone secretion.

RESULTS

Serum total and free T4 and triiodothyronine (T3) were significantly reduced in ventral prostatectomized rats. Histological analysis of the thyroid showed that the diameters of the peripheral and middle follicles, colloid epithelial cells, and nuclei were increased in prostatectomized rats, indicating hypothyroid status. Total T3 and T4 were significantly elevated in the culture medium when thyroid and prostate were cocultured, irrespective of the presence of TSH antibody.

CONCLUSIONS

The present study suggests that ventral prostatic secretions have a stimulatory role on the thyroid gland.

Neuroendocrine cells of the prostate and neuroendocrine differentiation in prostatic carcinoma: a review of morphologic aspects

Neuroendocrine cells of the prostate are intraepithelial regulatory cells that secrete serotonin and a variety of peptide hormones. It is hypothesized that these cells regulate both growth and differentiation, as well as exocrine secretory activity through endocrine, paracrine, neurocrine, and lumenocrine mechanisms. Neuroendocrine differentiation in prostatic carcinoma occurs as pure neuroendocrine malignancies, such as small-cell carcinoma and carcinoid/carcinoid-like tumors, as well as focal neuroendocrine differentiation in a more conventional prostatic adenocarcinoma. Neuroendocrine differentiation in prostatic carcinoma may have diagnostic and prognostic significance.

Pure small cell carcinoma of the prostate

Pure small cell carcinoma of the prostate is a rare anaplastic tumour. This report presents the clinicopathological findings of two patients presenting with this disease. Immunohistochemistry was positive for protein gene product 9.5, neurone specific enolase and calcitonin. Staining was negative for prostate specific antigen and prostate acid phosphatase. androgen ablation has no place in the management of this lesion and patients with this disease should be managed as if they have a neuroendocrine tumour.

Neurohormonal stimulation of histamine release from neuroendocrine cells of the human adenomatous prostate

BACKGROUND

Neuroendocrine cells (NE) constitute a population of highly specialized cells in prostatic glands; histamine has never been described in these cells. This article shows the presence and the regulation of release of histamine in NE.

METHODS

In 21 prostatic adenomas, NE were identified by specific antisera against neuroendocrine markers (chromogranin-A, synaptophysin), histamine, and histidine decarboxylase (HDC); a rate HDC-cDNA probe was used to detect this enzyme by in situ hybridization.

RESULTS

Immunoreactive cells for chromogranin-A, histamine, and HDC were found among luminal epithelial glandular cells. Similar cells were also labeled with the HDC-cDNA probe. Glandular cells, isolated from prostatic adenomas, were shown to contain histamine (7-40 pmol/mg cellular protein). L(-) norepinephrine causes a time-dependent (t1/2 = 22 min) histamine release; the alpha 1-receptor antagonists WB-4101 and YM-617 specifically inhibited this release, in agreement with a mediation by alpha 1-adrenoreceptor subtype.

CONCLUSIONS

There is some evidence for the presence in prostatic adenomas of histamine-forming cells of neuroendocrine type; histamine release from these cells is under the control of alpha 1-adrenoreceptor subtype.

The relationship between prostatic intraepithelial neoplasia and prostate cancer: critical issues

PURPOSE

Prostatic intraepithelial neoplasia (PIN) is often considered to be a premalignant lesion and the main precursor of invasive carcinoma of the prostate. We evaluated the evidence for and against PIN as a premalignant lesion and determined guidelines for the clinical management of PIN.

MATERIALS AND METHODS

Literature analysis of histopathological, morphometric, phenotypic and molecular genetic evidence of progression and of clinical findings regarding PIN was done. Literature searches were performed on MEDLINE with relevant key words.

RESULTS

PIN, like prostate cancer, occurs most frequently in the peripheral zone of the prostate and is usually located in close proximity to prostate cancer. The relative PIN and prostate cancer volumes vary inversely. Prostate specific antigen in cases of PIN appears to be intermediate between prostate cancer and normal levels, although this elevation may be explained by concomitant prostate cancer or benign prostatic hyperplasia. Deoxyribonucleic acid ploidy in PIN follows the aneuploid proportion as in the concomitant prostate cancer. Prostate cancer and PIN show evidence of loss of putative tumor suppressor genes on chromosome 8p. The clinical relevance of PIN biopsy findings is based on the association of neoplasia and prostate cancer. High grade PIN in core biopsies without concomitant prostate cancer has a substantial risk for prostate cancer in subsequent biopsies (24 to 73%, up to 100% when the digital rectal examination is suspicious) and should cause further biopsy sampling.

CONCLUSIONS

There is convincing evidence that PIN is a precursor lesion to prostate cancer, with a close association of PIN and prostate cancer in biopsy and prostatectomy specimens. A biopsy finding of high grade PIN necessitates further investigation in patients who are candidates for radical treatment for localized prostate cancer.

Application of a novel phenylpiperazine formation reaction to the radiosynthesis of a model fluorine-18-labeled radiopharmaceutical (18FTFMPP)

The labeled serotonin agonist 3-[18F]fluoro-N-(alpha,alpha,alpha-trifluoro-m-tolyl)piperazine (18FTFMPP) was prepared rapidly using the labeling procedure for trifluorotoluenes, [18F]fluoro-for-nitro exchange, followed by an alumina-supported bis-alkylation. After normal-phase HPLC purification, the labeled product was obtained in 20-32% (n = 20) decay-corrected radiochemical yield with a radiochemical purity > 98% and a specific activity of 100 GBq/mumol. The synthesis time including purification was 3 h. The receptor binding affinity of FTFMPP to rat brain membranes was found to be similar to that of the nonfluorinated parent compound (TFMPP). Although TFMPP has been proposed by others as an agent for the imaging of serotonin receptors, only minimal receptor-mediated uptake was observed.