Neuroendocrine cells in the normal, hyperplastic and neoplastic prostate

Cells of Origin for Prostate Cancer

Comprehensive knowledge of the normal prostate epithelial lineage hierarchy is a prerequisite to investigate the identity of the cells of origin for prostate cancer. The basal and luminal cells constitute most of the prostate epithelium and have been the major focuses of the study on the cells of origin for prostate cancer. Much progress has been made during the past few decades, mainly using mouse models, to understand the inter-lineage relationship and intra-lineage heterogeneity in adults as well as the lineage plasticity during conditions of stress. These studies have concluded that the adult mouse prostate basal and luminal cells are largely independently sustained under physiological conditions, but both types of cells possess the capacity for bipotent differentiation under stress or artificial experimental conditions. However, the existence or the identity of the putative progenitors within each lineage warrants further investigation. Whether the human prostate lineage hierarchy is completely the same as that of the mouse remains uncertain. Experiments from independent groups have demonstrated that both types of cells in mice and humans can serve as targets for transformation. But controversies remain whether the disease from distinct cells of origin display different clinical behaviors. Further investigation of the intra-lineage heterogeneity will provide new insights into this issue. Understanding the identity of the cells of origin for prostate cancer will help identify novel prognostic markers for early detection of aggressive prostate cancers, provide insights into the therapeutic vulnerability of these tumors, and inspire novel therapeutic strategies.

Prostate cancer stem cells: deciphering the origins and pathways involved in prostate tumorigenesis and aggression

The cells of the prostate gland are dependent on cell signaling pathways to regulate their growth, maintenance and function. However, perturbations in key signaling pathways, resulting in neoplastic transformation of cells in the prostate epithelium, are likely to generate subtypes of prostate cancer which may subsequently require different treatment regimes. Accumulating evidence supports multiple sources of stem cells in the prostate epithelium with distinct cellular origins for prostate tumorigenesis documented in animal models, while human prostate cancer stem-like cells (PCSCs) are typically enriched by cell culture, surface marker expression and functional activity assays. As future therapies will require a deeper understanding of its cellular origins as well as the pathways that drive PCSC maintenance and tumorigenesis, we review the molecular and functional evidence supporting dysregulation of PI3K/AKT, RAS/MAPK and STAT3 signaling in PCSCs, the development of castration resistance, and as a novel treatment approach for individual men with prostate cancer.

Alteration of loperamide-induced prostate relaxation in high-fat diet-fed rats

OBJECTIVE

To investigate the change of loperamide-induced prostate relaxation in rats fed with high-fat diet (HFD).

MATERIALS AND METHODS

Adult male Wistar rats were divided into 2 groups: (1) control rats fed with normal chow and (2) rats fed with HFD for 6 months. The prostate was removed for histology study. Isolated prostate strips were hung in organ bath and precontracted with 1 μmol/L phenylephrine or 50 mmol/L KCl. The relaxation responses to loperamide 0.1 to 10 μmol/L were recorded. Western blotting analyses were performed for prostate μ-opioid receptors (MOR) and ATP-sensitive potassium (K(ATP)) channel proteins: sulfonylurea receptor (SUR) and inwardly rectifying potassium channel (Kir) 6.2 subunits.

RESULTS

Body weight, prostate weight, plasma levels of glucose, insulin, triglyceride, and cholesterol, as well as systolic blood pressure, were significantly increased in the HFD rats. Histology showed prostatic hyperplasia in the HFD rat prostate. Prostatic relaxation induced by loperamide was markedly reduced in HFD when compared to the control. Protein expressions of MOR, SUR, and Kir 6.2 were decreased in HFD-fed rats.

CONCLUSION

Loperamide-induced prostate relaxation is decreased in HFD rats due to reduced MOR and K(ATP) channel expressions.

Opium consumption is negatively associated with serum prostate-specific antigen (PSA), free PSA, and percentage of free PSA levels

Addiction to opium continues to be a major worldwide medical and social problem. The study addressing the association between opium consumption and serum prostate-specific antigen (PSA) level is lacking. We determined the effects of opium consumption on serum PSA levels in opium-addict men. Our study subjects comprised 438 opium-addict men with a mean age of 52.2 ± 6.4 years (group 1). We compared these men with 446 men who did not indicate current or past opium use (group 2). Serum total PSA (tPSA), free PSA (fPSA), % fPSA, and sex hormones were compared between the 2 groups. The mean serum tPSA level was significantly lower in group 1 (1.05 ng/mL) than in controls (1.45 ng/mL) (P = 0.001). Opium consumption was also associated with lower fPSA (P = 0.001) and % fPSA (P = 0.001). Serum free testosterone level in opium-addict patients (132.5 ± 42 pg/mL) was significantly lower than that in controls (156.2 ± 43 pg/mL) (P = 0.03). However, no significant correlation existed between tPSA and free testosterone levels (r = 0.28, 95% CI, -0.036 to 0.51, P = 0.34). Among the patients with cancer in group 1, 35% were found to have high-grade tumor (Gleason score ≥ 7) compared with 26.7% in group 2 (P = 0.02). Total PSA and fPSA were strongly correlated with duration of opium use (r = -0.06, 95% CI, -0.04 to -0.08, P = 0.0001; and r = -0.05, 95% CI, -0.03 to -0.07, P = 0.0001, respectively). Opium consumption is independently and negatively associated with serum tPSA, fPSA, and % fPSA levels.

Transdifferentiation of cultured human prostate cancer cells to a neuroendocrine cell phenotype in a hormone-depleted medium

Neuroendocrine (NE) cells are enigmatically found in association with human prostate cancers and their numbers are reported to increase in advanced and hormoneresistant tumors. The origin of this cell type and the reason for their appearance in prostate tumors remains unresolved. Previously, Bang et al. (Proc Natl Acad Sci USA 1994;91:5330) reported that dibutyryl adenosine 3',5'-cyclic phosphate (db-cAMP), an agent that upregulates intracellular cAMP, was able to induce a NE cell-like phenotype of cultured human prostate cancer cells, including the androgen-sensitive LNCaP line. Here we report that chronic incubation of LNCaP cells in a medium containing 10% charcoal-stripped fetal bovine serum (CSFBS) likewise induces NE differentiation of these cells. Within 5 days of switching low density cultures of LNCaP cells to this modified medium, the cells growth arrest and acquire an altered morphology with numerous cytoplasmic secretory granules and elongated processes that resemble cultured neurons. This morphology predominates at 10 days with complete transformation seen by 20 days of culture. Electron microscopic analysis of sections of CS-FBS maintained cells showed the presence of abundant dense core secretory granules characteristic of NE cells. Immunohistochemical staining identified the upregulation of the expression of NE markers bombesin, neuron-specific enolase, and S-100 in this modified culture medium. Once established, the NE cell-like phenotype was found to be reversible upon replacement with a medium containing unmodified fetal bovine serum, but not by direct supplementation of CS-FBS medium with dihydrotestosterone (DHT) (I nM). DHT supplementation did, however, suppress the development of the NE cell-like phenotype when it was present at the initiation of exposure to CS-FBS medium. In contrast to db-cAMP treatment, which did not affect prostate specific antigen (PSA) or androgen receptor (AR) expression of LNCaP cells, NE-differentiated LNCaP cells derived in this hormone-deficient medium showed marked downregulation of PSA and AR expression. These in vitro results further support the concept that prostate cancer cells can tranform in vivo to cells with a NE phenotype and suggest that this transformation might be accelerated in patients by certain therapies for prostate cancer.

Individual rac GTPases mediate aspects of prostate cancer cell and bone marrow endothelial cell interactions

The Rho GTPases organize the actin cytoskeleton and are involved in cancer metastasis. Previously, we demonstrated that RhoC GTPase was required for PC-3 prostate cancer cell invasion. Targeted down-regulation of RhoC led to sustained activation of Rac1 GTPase and morphological, molecular and phenotypic changes reminiscent of epithelial to mesenchymal transition. We also reported that Rac1 is required for PC-3 cell diapedesis across a bone marrow endothelial cell layer. In the current study, we queried whether Rac3 and RhoG GTPases also have a role in prostate tumor cell diapedesis. Using specific siRNAs we demonstrate roles for each protein in PC-3 and C4-2 cell adhesion and diapedesis. We have shown that the chemokine CCL2 induces tumor cell diapedesis via Rac1 activation. Here we find that RhoG partially contributes to CCL2-induced tumor cell diapedesis. We also find that Rac1 GTPase mediates tight binding of prostate cancer cells to bone marrow endothelial cells and promotes retraction of endothelial cells required for tumor cell diapedesis. Finally, Rac1 leads to β1 integrin activation, suggesting a mechanism that Rac1 can mediate tight binding with endothelial cells. Together, our data suggest that Rac1 GTPase is key mediator of prostate cancer cell-bone marrow endothelial cell interactions.

GABA's control of stem and cancer cell proliferation in adult neural and peripheral niches

Aside from traditional neurotransmission and regulation of secretion, gamma-amino butyric acid (GABA) through GABA(A) receptors negatively regulates proliferation of pluripotent and neural stem cells in embryonic and adult tissue. There has also been evidence that GABAergic signaling and its control over proliferation is not only limited to the nervous system, but is widespread through peripheral organs containing adult stem cells. GABA has emerged as a tumor signaling molecule in the periphery that controls the proliferation of tumor cells and perhaps tumor stem cells. Here, we will discuss GABA's presence as a near-universal signal that may be altered in tumor cells resulting in modified mitotic activity.

The nuclear factor-kappaB pathway controls the progression of prostate cancer to androgen-independent growth

Typically, the initial response of a prostate cancer patient to androgen ablation therapy is regression of the disease. However, the tumor will progress to an "androgen-independent" stage that results in renewed growth and spread of the cancer. Both nuclear factor-kappaB (NF-kappaB) expression and neuroendocrine differentiation predict poor prognosis, but their precise contribution to prostate cancer progression is unknown. This report shows that secretory proteins from neuroendocrine cells will activate the NF-kappaB pathway in LNCaP cells, resulting in increased levels of active androgen receptor (AR). By blocking NF-kappaB signaling in vitro, AR activation is inhibited. In addition, the continuous activation of NF-kappaB signaling in vivo by the absence of the IkappaBalpha inhibitor prevents regression of the prostate after castration by sustaining high levels of nuclear AR and maintaining differentiated function and continued proliferation of the epithelium. Furthermore, the NF-kappaB pathway was activated in the ARR(2)PB-myc-PAI (Hi-myc) mouse prostate by cross-breeding into a IkappaBalpha(+/-) haploid insufficient line. After castration, the mouse prostate cancer continued to proliferate. These results indicate that activation of NF-kappaB is sufficient to maintain androgen-independent growth of prostate and prostate cancer by regulating AR action. Thus, the NF-kappaB pathway may be a potential target for therapy against androgen-independent prostate cancer.

Effect of Prolactin and Bromocriptine on the Population of Prostate Neuroendocrine Cells from Intact and Cyproterone Acetate-Treated Rats: Stereological and Immunohistochemical Study

This work deals with the quantification of serotonin-immunoreactive prostate neuroendocrine cells (NECs) in rats exposed to prolactin in normal, cyproterone acetate-exposed, and bromocriptine-exposed animals to establish the possible influence of prolactin with or without androgenic blockade on this cell population. Thirty male peripubertal Sprague-Dawley rats were grouped as controls (CT) and those treated with cyproterone acetate (CA), cyproterone acetate plus prolactin, cyproterone acetate plus bromocriptine, prolactin (PL), and bromocriptine (BC). The volume of ductal epithelium (Vep) and total number (NSER) of the NECs serotonin-immunoreactive were measured. NECs were detected in the periurethral ducts. Compared to CT, Vep was increased in PL and BC and NSER was decreased in CA and increased in the prolactin or bromocriptine groups. The androgenic blockade decreases NSER in rat prostate; PL induces in normal and cyproterone acetate-treated rats the increase of NSER; and BC exerts a local effect over the prostate similar to that described for PL.

Prostate epithelial cell differentiation and its relevance to the understanding of prostate cancer therapies

Prostate cancer is the most common malignancy in males in the western world. However, little is known about its origin and development. This review highlights the biology of the normal prostate gland and the differentiation of basal epithelial cells to a secretory phenotype. Alterations in this differentiation process leading to cancer and androgen-independent disease are discussed, as well as a full characterization of prostate epithelial cells. A full understanding of the origin and characteristics of prostate cancer epithelial cells will be important if we are to develop therapeutic strategies to combat the heterogeneous nature of this disease.

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.

NE-10 neuroendocrine cancer promotes the LNCaP xenograft growth in castrated mice

Increases in neuroendocrine (NE) cells and their secretory products are closely correlated with tumor progression and androgen-independent prostate cancer. However, the mechanisms by which NE cells influence prostate cancer growth and progression, especially after androgen ablation therapy, are poorly understood. To investigate the role of NE cells on prostate cancer growth, LNCaP xenograft tumors were implanted into nude mice. After the LNCaP tumors were established, the NE mouse prostate allograft (NE-10) was implanted on the opposite flank of these nude mice to test whether NE tumor-derived systemic factors can influence LNCaP growth. Mice bearing LNCaP tumors with or without NE allografts were castrated 2 weeks after NE tumor inoculation, and changes in LNCaP tumor growth rate and gene expression were investigated. After castration, LNCaP tumor growth decreased in mice bearing LNCaP tumors alone, and this was accompanied by a loss of nuclear androgen receptor (AR) localization. In contrast, in castrated mice bearing both LNCaP and NE-10 tumors, LNCaP tumors continued to grow, had increased levels of nuclear AR, and secreted prostate-specific antigen. Therefore, in the absence of testicular androgens, NE secretions were sufficient to maintain LNCaP cell growth and androgen-regulated gene expression in vivo. Furthermore, in vitro experiments showed that NE secretions combined with low levels of androgens activated the AR, an effect that was blocked by the antiandrogen bicalutamide. Because an increase in AR level has been reported to be sufficient to account for hormone refractory prostate cancers, the NE cell population ability to increase AR level/activity can be another mechanism that allows prostate cancer to escape androgen ablation therapy.

The opioid agonist ethylketocyclazocine reverts the rapid, non-genomic effects of membrane testosterone receptors in the human prostate LNCaP cell line

Neuropeptides influence cancer cell replication and growth. Opioid peptides, and opiergic neurons are found in the prostate gland, and they are proposed to exert a role in tumor regulation, influencing cancer cell growth, as opioid agonists inhibit cell growth in several systems, including the human prostate cancer cell line LNCaP. In the same cell line, the existence of membrane testosterone receptors was recently reported, which increase, in a non-genomic manner, the secretion of PSA, and modify actin cytoskeleton dynamics, through the signaling cascade FAK-->PI-3 kinase-->Cdc42/Rac1. In the present work, we present data supporting that the general opioid agonist Ethylketocyclazocine (EKC) decreases testosterone-BSA (a non-internalizable testosterone analog) induced PSA secretion. Furthermore, we report that this opioid affects this non-genomic testosterone action, by modifying the distribution of the actin cytoskeleton in the cells, disrupting the above signaling cascade. In addition, after long (>24 h) incubation, opioids decrease the number of membrane testosterone receptors, and reverse their effect on the signaling molecules. In conclusion, our results provide some new insights of a possible action of opioids in prostate cancer control by interfering with the action and the expression of membrane testosterone receptors and signaling.

Ultrastructural and immunocytochemical analyses of opioid treatment effects on PC3 prostatic cancer cells

Some opioid peptides are able to inhibit the growth of human prostatic cancer cells; in particular, the [D-Ala(2),D-Leu(5)] enkephalin (DADLE) reduces PC3 cell growth. In order to understand how DADLE decreases cell proliferation, we investigated, by electron microscopy, its effects on PC3 cellular components. PC3 cells were incubated with DADLE and processed for both ultrastructural morphology and immunoelectron microscopy. Some cells were incubated with BrU to determine the transcriptional rate. BrU and DADLE molecules were detected by immunogold techniques and the labeling was quantitatively evaluated. Modifications of some cytoplasmic and nuclear components were observed in DADLE-treated cells. Moreover, treated cells incorporated lower amounts of BrU than control cells. DADLE molecules were located in the cytoplasm and in the nucleus, especially on mRNA transcription and early splicing sites. Our data suggest that DADLE is able to slow down the synthetic activity of PC3 cells, perhaps interfering with nuclear functions.

Effects of combined androgen blockade on bone metabolism and density in men with locally advanced prostate cancer

OBJECTIVE

To investigate whether combined androgen blockade (CAB) produces any adverse effects on bone metabolism and mineral density in patients with locally advanced prostate cancer.

MATERIALS AND METHODS

The study group consisted of 17 stage T4 prostate cancer patients treated with CAB and had no evidence of bone metastasis on bone scintigraphy. The mean duration of CAB and final total prostate specific antigen (PSA) level at the time of study were found at 28.5 +/- 15.9 (6-58) months and 0.39 +/- 0.5 (0.1-2) ngml, respectively. Twenty age and socioeconomically matched benign prostate hyperplasia (BPH) patients were taken as the control group. Both groups were compared with regard to lumbar bone mineral density (LBD), femur bone mineral density (FBD) and serum parameters of bone metabolism namely calcium (Ca), phosphate (P), magnesium (Mg) and alkaline phosphatase (ALP). Bone mineral density was measured with dual energy x-ray absorptiometry.

RESULTS

The mean FBD, LBD and serum Ca, P, Mg and ALP measurement of the patients treated with CAB were 0.85 +/- 0.1 g/cm2, 1.16 +/- 0.2 g/cm2, 9.1 +/- 0.3 mg/dl, 3.6 +/- 0.6 mg/dl, 1.95 +/- 0.14 mg/dl, 187.5 +/- 61 mg/dl, respectively. No significant difference was found between patients subjected to CAB and the age matched controls in any of the studied parameters namely age, FBD, LBD, Ca, Mg and ALP except serum phosphate. Serum phosphate levels were significantly (p = 0.001) higher in patients treated with CAB suggesting a minor effect of CAB on bone metabolism.

CONCLUSION

No convincing evidence was found about the detrimental effect of CAB on bone mineral density and metabolism in a highly selected group of patients with advanced prostate cancer without bone metastases.

Immunohistochemical detection of gastrin releasing peptide in patients with prostate cancer

Gastrin releasing peptide (GRP) is a neuropeptide that has been suggested to play a role in the development of some malignancies. Our aim was: (1) to identify the expression of GRP in cancerous prostate glands, and (2) to correlate its expression to various pathological parameters and to the patient's clinical outcome. Using standard immunohistochemistry, we evaluated GRP expression in both biopsy and radical prostatectomy specimens from 30 patients with prostatic adenocarcinomas. GRP was expressed in 18 radical prostatectomy specimens (60%) and in 15 biopsies (50%). There was an association between positive immunoexpression of GRP, relapse ( P=0.029) and advanced tumor stages (i.e. pT3, pT4) ( P=0.049). In the respective biopsies, GRP immunostatus was similar to that observed in the subsequent radical prostatectomy specimens. GRP immunoexpression may be of some value as a diagnostic and prognostic marker. Patients whose pathology specimens demonstrate GRP immunopositivity should be closely monitored, since they appear to be at higher risk of disease progression and relapse.

Stereologic estimation of the number of neuroendocrine cells in normal human prostate detected by immunohistochemistry

Neuroendocrine cells may play a role in both normal and pathologic conditions of the human prostate. It may be interesting to investigate 1) whether there are significant amounts of neuroendocrine cells in human adult normal prostate, and 2) whether the distribution of these cells shows regional differences. This study estimates both absolute and relative amounts of neuroendocrine cells immunostained for two neuronal markers (chromogranin A and protein gene product 9.5) and for serotonin in the three regions of human prostate, transition zone, central zone, and peripheral zone, using unbiased stereologic measurements. There was observed a predominance of neuroendocrine cells in the transition zone of the normal prostate. The neuroendocrine cells of this region may play a role in the genesis of benign prostate hyperplasia. The significant presence of neuroendocrine cells secreting neuropeptides in peripheral zone could be correlated with the induction of androgen-independent growth in prostate carcinogenesis. The wolffian origin attributed to the central zone can explain its poor population of neuroendocrine cells.

Precancerous lesions and conditions of the prostate: from morphological and biological characterization to chemoprevention

Prostatic intraepithelial neoplasia (PIN) is composed of dysplastic cells with a luminal cell phenotype, expressing the androgen receptor as well as prostate-specific antigen. PIN is characterized by progressive abnormalities of phenotype that are intermediate between normal prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of carcinogenesis. High-grade PIN is considered the most likely precursor of prostatic carcinoma, according to virtually all available evidence. Androgen deprivation decreases the prevalence and extent of PIN and the degree of capillary vascularization (e.g., angiogenesis) in the surrounding stroma via suppression of vascular endothelial growth factor production. Prostatic carcinoma is also likely to arise from precursor lesions other than high-grade PIN such as low-grade PIN, atypical adenomatous hyperplasia, malignancy-associated foci, and atrophy.

Localization and mRNA expression of somatostatin receptor subtypes in human prostatic tissue and prostate cancer cell lines

Somatostatin (SST) plays an important regulatory role in the physiological control of various organs including the prostate. Somatostatin receptors (SSTRs) and SST analogs are potential targets for prostate cancer treatment, especially since it has been shown that SST analogues are clinically effective in the treatment of advanced prostate cancer. The presence of SST containing neuroendocrine (NE) cells in the epithelium of the human prostate and their suggested role in the paracrine regulation of this gland prompted us to study the potential expression of somatostatin receptors (SSTRs) in human prostatic tissue and prostate cancer cell lines. Using the reverse transcriptase polymerase chain reaction (RT-PCR), we found the SSTR subtypes 1-3 in stromal cells and in prostate cancer cell lines LNCaP, PC-3 and DU 145. Immunohistochemical analysis of 27 radical prostatectomy specimens demonstrated the presence of hSSTR1 in a subpopulation of cancerous and NE cells, whereas hSSTR2 was found in the stroma, peritumoral blood vessels and tumor cells. Receptor subtype 3 was demonstrated to be present on the cell membrane of BPH and malignant areas. A strong immunoreaction (IR) of hSSTR4 was found in tumor cells, as compared with a less intense IR in adjacent BPH areas. Somatostatin receptor subtype 5 was not detectable. Western blot analysis revealed immunoreactive bands of molecular weight between 44-60 kDa. In summary, the present study clearly demonstrates the presence of hSSTR1-3 in tumoral and nontumoral epithelial cells as well as in the stromal compartment, whereas hSSTR4 was found to be confined to epithelial cells, and SSTR5 was not detectable.

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.

Semiquantitative morphology of human prostatic development and regional distribution of prostatic neuroendocrine cells

BACKGROUND

The neuroendocrine cells of the human prostate have been related to proliferative disorders such as prostatic cancer. Their origin, distribution, and development have therefore been studied and discussed in terms of current stem cell concepts in the prostate.

METHODS

Prostatic tissue specimens (n = 20) from human fetuses (n = 8), prepubertal and pubertal children (n = 8) and mature men (n = 4) were studied immunohistochemically using antibodies directed against neuroendocrine, epithelial as well as secretory markers. Semiquantitative computer-assisted evaluation of different epithelial and stromal components based on stereological principles was performed on azan-stained sections representative of all developmental stages.

RESULTS

By the end of gestational Week 9, neuroendocrine (NE) cells appear in the epithelium of the urogenital sinus and are subsequently closely associated with the formation of urethral prostatic buds. The fetal and postnatal distribution pattern of NE cells within the gland is characterized by a relatively constant number of cells per gland similar to prostatic smooth muscle cells. Likewise, a density gradient exists with the highest density in the large collicular ducts and almost no NE cells in subcapsular peripheral acini. In peripheral ducts, the distribution is random. Maturation of the NE cells precedes that of the secretory cells by about 10-16 years.

CONCLUSIONS

A second prostatic stem cell lineage, different from the urogenital sinus (UGS)-lineage is hypothesized originating from immature neuroendocrine cells. Being morphologically indistinguishable from the UGS-derived prostatic secretory cell lineage, it gives rise to neuroendocrine cells. Their presence is apparently important for proliferation regulation of the UGS-derived lineage of the prostate.

Role of stimulatory guanine nucleotide binding protein (GSalpha) in proliferation of PC-3M prostate cancer cells

Previous studies have shown that calcitonin-like immunoreactive substances are secreted by primary prostate cells. Furthermore, exogenously added calcitonin stimulates proliferation of androgen-responsive LnCaP cells. To examine the possible effect of calcitonin on growth of invasive prostate cancer cells, we tested its effects on proliferation of PC-3M cells. Calcitonin stimulated DNA synthesis of PC-3M cells in a dose-dependent fashion, and also stimulated adenylyl cyclase and protein kinase C activities. To further delineate the role of these signaling cascades in proliferation of PC-3M prostate cancer cells, we selectively activated these pathways by transfecting cDNAs expressing constitutively active forms of either Gsalpha (Gsalpha-QL) or Gqalpha (Gqalpha-QL). cDNAs expressing wild-type forms of G-proteins (Gsalpha-WT and Gqalpha-WT) were used as vehicle controls. Gqalpha-QL transfectants exhibited growth inhibition and terminal differentiation. Those expressing Gsalpha-QL exhibited a dramatic increase in growth rate. Gsalpha-QL transfectants displayed an almost 3-fold increase in [3H]-thymidine incorporation and over a 4-fold increase in growth rate when compared with parental PC-3M cells or those expressing wild-type Gsalpha (Gsalpha-WT). The growth-promoting action of Gsalpha-QL could not be mimicked by either 8-bromo cAMP or forskolin. However, nifedipine, a calcium channel antagonist, potently and selectively inhibited DNA synthesis in Gsalpha-QL transfectants. These results suggest that the growth-promoting actions of Gsalpha on PC-3M cells may be mediated by nifedipine-sensitive proliferative events.

Morphological identification of the patterns of prostatic intraepithelial neoplasia and their importance

High grade prostatic intraepithelial neoplasia (PIN) is the most likely precursor of prostatic carcinoma. PIN has a high predictive value as a marker for carcinoma, and its identification in biopsy specimens warrants repeat biopsy for concurrent or subsequent carcinoma. The only methods of detection are biopsy and transurethral resection; PIN does not greatly raise the concentration of serum prostate specific antigen (PSA) or its derivatives, does not induce a palpable mass, and cannot be detected by ultrasound. Androgen deprivation decreases the prevalence and extent of PIN, suggesting that this form of treatment might play a role in chemoprevention. Radiotherapy is also associated with a decreased incidence of PIN.

Immunohistochemical localization of protein gene product 9.5, ubiquitin, and neuropeptide Y immunoreactivities in epithelial and neuroendocrine cells from normal and hyperplastic human prostate

This study was designed to investigate (a) the presence of protein gene product 9.5 (PGP 9.5), ubiquitin, and neuropeptide Y (NPY) in the neuroendocrine and secretory epithelium of the human normal prostate and its secretions, and (b) the changes in immunoreactivity to these proteins in men with benign prostatic hyperplasia. Western blotting and light microscopic immunohistochemistry techniques were used and the numerical density of immunoreactive neuroendocrine cells, and the volume fractions of immunostained secretory epithelium were evaluated. Western blotting revealed the presence of the three antigens in both tissue homogenates and prostate secretion. Some neuroendocrine cells immunoreacted to PGP 9.5 and NPY in all the prostate regions of control specimens. Ubiquitin immunoreactivity was detected in the nuclei from both basal cells and secretory epithelial cells. The cytoplasm of the secretory cells and the glandular lumen also showed immunostaining for the three proteins. The numerical densities of both PGP 9.5 and NPY neuroendocrine cells were lower in hyperplasia than in controls. No differences in the volume fraction occupied by epithelial immunostaining to both proteins was found between hyperplastic and control prostates. We concluded that (a) PGP 9.5 and NPY, but not ubiquitin, are common antigens in both neuroendocrine and secretory prostate cells, (b) the three immunoreactive proteins contribute to the prostate secretions, and (c) the secretion of ubiquitin is markedly diminished in the hyperplastic epithelium.(J Histochem Cytochem 48:1121-1130, 2000)

Neuroendocrine cells during human prostate development: does neuroendocrine cell density remain constant during fetal as well as postnatal life?

BACKGROUND

Knowledge concerning differentiation of neuroendocrine (NE) cells during development of the human prostate is rather fragmentary. Using immunohistochemistry combined with a morphometric method, we investigated the distribution and density of NE cells in the developing human prostate, with special emphasis on the topographical relationship of NE cells with the developing gland.

METHODS

Consecutive sections from a total of 42 human prostates taken during autopsy of fetuses (12-38 weeks of gestation), prepubertal males, and young adults were immunostained for chromogranin A and serotonin. Computer-assisted image analysis was used to assess the total number of cells in the different parts of the branching glandular anlage, i.e., budding tips and acini/ducts. Next, the number of NE cells was counted manually. The NE cell density (NE cell index) was then determined.

RESULTS

NE cells could first be detected in the prostate from 13 weeks of gestation. By 21 weeks of gestation, all prostates contained NE cells. NE cells were mainly confined to the acinous/ductal regions, while most of the budding tips lacked NE staining. NE cell indexes of individuals were highly variable, mostly in the youngest age group.

CONCLUSIONS

In the normal prostate, NE cell density probably remains constant in acini/ducts from fetuses to young adulthood. The presence of neuroendocrine cells in well-developed glandular structures at such an early fetal age and their absence in the less differentiated budding tips possibly indicates that differentiation of NE cells is associated with glandular maturation. NE cells occur preferentially in the acinous/ductal region, implying a paracrine function during secretory differentiation of exocrine epithelial cells.

Androgen-independent growth is induced by neuropeptides in human prostate cancer cell lines

BACKGROUND

Androgen-independent growth leads to progressive prostate cancer after androgen-ablation therapy. This may be caused by altered specificity of the androgen receptor (AR), by ligand-independent stimulation of the AR, or by paracrine growth modulation by neuropeptides secreted by neuroendocrine (NE) cells.

METHODS

We established and characterized the androgen-independent FGC-DCC from the androgen-dependent LNCaP fast growing colony (FGC) cell line. The androgen-independent DU-145, FGC-DCC, and PC-3, and the androgen-dependent LNCaP and PC-346C cell lines were used to study growth modulation of gastrin-releasing peptide (GRP), calcitonin (CT), serotonin (5-HT), and vasoactive intestinal peptide (VIP) by (3)H-thymidine incorporation. Specificity of the growth-modulating effects was tested with the anti-GRP monoclonal antibody 2A11 and induction of cAMP by neuropeptides.

RESULTS

Androgen-independent growth stimulation by neuropeptides was shown in DU-145 and PC-346C. 2A11 inhibited GRP-induced (3)H-thymidine incorporation in DU-145 and PC-346C and inhibited proliferation of the FGC-DCC and PC-3 cell lines. With some exceptions, cAMP induction paralleled growth stimulation. Dideoxyadenosine (DDA) inhibited the GRP-induced growth effect in DU-145 and PC-346C, whereas oxadiazoloquinoxaline-1-one (ODQ) had no effect on (3)H-thymidine incorporation. None of the neuropeptides stimulated growth of LNCaP, FGC-DCC, or PC-3.

CONCLUSIONS

GRP-induced growth of DU-145 and PC-346C was specific and cAMP-mediated. Androgen-independent growth of FGC-DCC cells was mainly due to an induction of Bcl-2 expression and possibly through the activation of an autocrine and NE-like pathway, as has been shown also for the PC-3 cell line. Growth induction of non-NE cells by neuropeptides could be a possible role for NE cells in clinical prostate cancer.

Inhibition by vasoactive intestinal polypeptide (VIP) of angiogenesis induced by murine Colon 26-L5 carcinoma cells metastasized in liver

We investigated the effect of VIP on the liver metastases and angiogenesis by Colon 26-L5 carcinoma cells in mice. Daily systemic administration of VIP, beginning 3 days after tumor inoculation into a portal vein of mice, inhibited significantly the development of their liver metastases. Immunohistochemical staining for factor VIII-related antigen in the sections of liver metastases showed that the systemic administration of VIP caused significant prevention of angiogenesis within tumor masses. VIP (10-(10) to 10(-6) M) inhibited the invasion of reconstituted basement membrane (Matrigel) by hepatic sinusoidal endothelial (HSE) cells in a concentration-dependent manner in a Transwell chamber assay in vitro and achieved approximately 50% reduction of control at 10(-6) M. VIP (10(-6) M) also significantly suppressed the haptotactic migration of HSE cells to fibronectin, laminin or type I collagen substrates with a similar inhibition rate to the invasion assay. Exposure of VIP to HSE cells induced accumulation of intracellular cAMP in a concentration-dependent manner. The inhibitory effect of VIP (10(-6) M) on HSE cell migration was significantly abrogated in the presence of 3 x 10(-6) M H-89, a cAMP-dependent protein kinase inhibitor. VIP (10(-6) M) inhibited the morphogenesis of HSE cells into capillary-like structures on Matrigel-coated wells. VIP did not affect the proliferation of HSE cells and the production of gelatinases in HSE cells in vitro at the concentrations used in the invasion assay. These observations suggest that the anti-metastatic effect of VIP on liver metastases by Colon 26-L5 carcinoma cells in mice is partly due to the prevention of tumor angiogenesis probably through suppression of the motility of endothelial cells.

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.

Modulation of the estrogen-regulated proteins cathepsin D and pS2 by opioid agonists in hormone-sensitive breast cancer cell lines (MCF7 and T47D): evidence for an interaction between the two systems

In many cancer cell lines, including breast, prostate, lung, brain, head and neck, retina, and the gastrointestinal tract, opioids decrease cell proliferation in a dose-dependent and reversible manner. Opioid and/or other neuropeptide receptors mediate this decrease. We report that only the steroid-hormone-sensitive cell lines MCF7 and T47D respond to opioid growth inhibition in a dose-dependent manner. Therefore, an interaction of the opioid and steroid receptor system might exist, as is the case with insulin. To investigate this interaction, we have assayed two estrogen-inducible proteins (pS2 and the lysosomal enzyme cathepsin D) in MCF7 and T47D cells. When cells were grown in the presence of FBS (in which case a minimal quantity of estrogens and/or opioids is provided by the serum), we observed either no effect of etorphine or ethylketocyclazocine (EKC) or an increase of secretion and/or production of pS2 and cathepsin D. However, when cells were cultured in charcoal-stripped serum and in the absence of phenol red, the effect of the two opioids is different: EKC decreased the production and/or secretion of pS2 and cathepsin D, whereas etorphine increased their synthesis and/or secretion. The differential effect of the two general opioids was attributed to their different receptor selectivity. Furthermore, the variations of the ratio of secreted/produced protein and the use of cycloheximide indicate that opioids selectively modify the regulatory pathway of each protein discretely. In conclusion, through the interaction with opioid and perhaps other membrane-receptor sites, opioid agonists modify in a dose-dependent manner the production and the secretion of two estrogen-regulated proteins. Opioids may therefore disturb hormonal signals mediated by the estrogen receptors. Hence, these chemicals may have potential endocrine disrupting activities.

Opioid alkaloids and casomorphin peptides decrease the proliferation of prostatic cancer cell lines (LNCaP, PC3 and DU145) through a partial interaction with opioid receptors

Opioid agonists (ethylketocyclazocine, etorphine, [D-Ala2,D-Leu5]enkephalin (DADLE), [D-Ala2, N-Me-Phe4-Gly-ol]enkephalin (DAGO), [D-Ser2,Leu5]enkephalin-Thr6 (DSLET) and morphine were found to inhibit the proliferation of human prostate cancer cell lines (LNCaP, DU145, and PC3), in a dose-dependent manner. The 50% inhibitory concentrations (IC50) were in the picomolar range. In many cases, this effect was antagonized by the general opioid antagonist, diprenorphine, indicating the existence of specific opioid binding sites. Saturation binding experiments with selective ligands and effectors showed no opioid sites on the LNCaP cell line, kappa1 and mu sites on the PC3 cell line, and kappa1, kappa3 and mu sites on the DU145 cell line. In other cases, the opioid effect was not antagonized by diprenorphine, indicating that the action of opioids might be mediated through other membrane receptors. Furthermore, casomorphin peptides, issued from bovine alpha- (alpha-casein-90-95 and alpha-casein-90-96) and beta-caseins (beta-casomorphin and beta-casomorphin-1-5), and human alphaS1-casein (alphas -casomorphin and alphaS1-casomorphin amide) inhibited cell proliferation of human prostate cell lines, also by a mechanism partly involving opioid receptors. As opioid neurons can be found in the prostate gland, and casomorphin peptides might reach the gland through the general circulation, the above findings indicate a putative role of opioids in prostate cancer cell growth.

The prognostic influence of neuroendocrine cells in prostate cancer: results of a long-term follow-up study with patients treated by radical prostatectomy

The distribution of immunohistochemically defined neuroendocrine (NE) cells in benign, pre-cancerous and neoplastic prostatic tissues and the prognostic value of these cells in prostate cancer were studied in the radical prostatectomy specimens of 90 patients from whom complete long-term follow-up data were available. The tissue blocks containing all the different Gleason patterns observed in a particular tumor were selected and immunostained. Since chromogranin B stained only a few cells compared to chromogranin A (CgA), NE cells were only defined by their reactivity with CgA. A semi-quantificative CgA score was assessed for all distinct pathological areas. Cox's regression model was used to analyze the influence of final TNM classification (TNM, 1992), Gleason sum score (GSS), age and CgA score on the probability of progression and tumor-specific death. NE cells were demonstrated in all normal prostatic tissues and in most hyperplastic and intra-epithelial neoplastic lesions. CgA staining was seen in 78% of the tumors. CgA scores were not related with Gleason growth patterns, GSS or TNM classification and had no prognostic value. The independent prognostic variables in Cox's regression model were: GSS and pT stage for progression and GSS for tumor-specific survival. Theoretically, NE cells could influence tumor behavior and this discrepancy suggests the need for experimental studies to investigate the role of NE cells in the normal and neoplastic prostate.