Androgen receptor status in endocrine-paracrine cell types of the normal, hyperplastic, and neoplastic human prostate

Primary Well-Differentiated Neuroendocrine Tumor/Carcinoid of the Prostate: Case Report and Review of Literature

Primary well-differentiated neuroendocrine tumor (WDNT)/carcinoid of the genitourinary tract is rare. Many WDNT reported in the prostate gland have been seen in close association with conventional prostatic adenocarcinoma and/or label for prostate-specific immunohistochemical markers and are best considered prostatic adenocarcinomas with "carcinoid-like" features. We present a case of primary WDNT/carcinoid incidentally detected in a 67-year-old man who underwent radical prostatectomy for Grade group 2 prostatic adenocarcinoma. Morphologically, the neuroendocrine (NE) lesion appeared distinct from the prostatic adenocarcinoma, labeled for NE markers, was negative for prostatic markers (NKX3.1, PSA, and ERG), and showed an overall low Ki-67 proliferation index (<1%). Follow-up was uneventful with no evidence of residual disease or metastasis.

Glucocorticoid Receptor and β-Catenin Interact in Prostate Cancer Cells and Their Co-Inhibition Attenuates Tumorsphere Formation, Stemness, and Docetaxel Resistance

Therapy resistance hinders the efficacy of anti-androgen therapies and taxane-based chemotherapy for advanced prostate cancer (PCa). Glucocorticoid receptor (GR) signaling mediates resistance to androgen receptor signaling inhibitors (ARSI) and has also been recently implicated in PCa resistance to docetaxel (DTX), suggesting a role in therapy cross-resistance. Like GR, β-catenin is upregulated in metastatic and therapy-resistant tumors and is a crucial regulator of cancer stemness and ARSI resistance. β-catenin interacts with AR to promote PCa progression. Given the structural and functional similarities between AR and GR, we hypothesized that β-catenin also interacts with GR to influence PCa stemness and chemoresistance. As expected, we observed that treatment with the glucocorticoid dexamethasone promotednuclear accumulation of GR and active β-catenin in PCa cells. Co-immunoprecipitation studies showed that GR and β-catenin interact in DTX-resistant and DTX-sensitive PCa cells. Pharmacological co-inhibition of GR and β-catenin, using the GR modulator CORT-108297 and the selective β-catenin inhibitor MSAB, enhanced cytotoxicity in DTX-resistant PCa cells grown in adherent and spheroid cultures and decreased CD44+/CD24- cell populations in tumorspheres. These results indicate that GR and β-catenin influence cell survival, stemness, and tumorsphere formation in DTX-resistant cells. Their co-inhibition could be a promising therapeutic strategy to overcome PCa therapy cross-resistance.

Neuroendocrine cells in prostate cancer correlate with poor outcomes: a systematic review and meta-analysis

OBJECTIVES

To perform a systematic review and meta-analysis of the literature to understand the variation in the reporting of neuroendocrine staining and determine the influence of reporting neuroendocrine staining at diagnosis on patient outcomes.

METHODS

Medical databases were searched to identify studies in which adenocarcinoma specimens were stained with any of the following four neuroendocrine markers: chromogranin A (CgA), neuron-specific enolase (NSE), synaptophysin and CD56. The prevalence of neuroendocrine staining and correlation of the prevalence of neuroendocrine staining to patient outcomes were analysed using a random-effects model. All statistical tests were two-sided.

RESULTS

Sixty-two studies spanning 7616 patients were analysed. The pooled prevalence for the most common marker, CgA (41%), was similar to that of NSE (39%) and higher than that of synaptophysin (31%). The prevalence of CgA staining was significantly influenced by reporting criteria, where objective thresholds reduced the variation in prevalence to 26%. No correlation was found between CgA prevalence and tumour grade. Patients positive for CgA staining using objective criteria had more rapid biochemical progression (hazard ratio [HR] 1.98, 95% confidence interval [CI] 1.49 to 2.65) and poorer prostate cancer-specific survival (HR 7.03, 95% CI 2.55 to 19.39) compared to negative patients, even among those with low-risk cancers.

CONCLUSION

Discrepancies in the reported prevalence of neuroendocrine cells in adenocarcinoma are driven by the inconsistent scoring criteria. This study unequivocally demonstrates that when neuroendocrine cell staining is assessed with objective criteria it identifies patients with poor clinical outcomes. Future studies are needed to determine the exact quantifiable thresholds for use in reporting neuroendocrine cell staining to identify patients at higher risk of progression.

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.

Single-cell analysis supports a luminal-neuroendocrine transdifferentiation in human prostate cancer

Neuroendocrine prostate cancer is one of the most aggressive subtypes of prostate tumor. Although much progress has been made in understanding the development of neuroendocrine prostate cancer, the cellular architecture associated with neuroendocrine differentiation in human prostate cancer remain incompletely understood. Here, we use single-cell RNA sequencing to profile the transcriptomes of 21,292 cells from needle biopsies of 6 castration-resistant prostate cancers. Our analyses reveal that all neuroendocrine tumor cells display a luminal-like epithelial phenotype. In particular, lineage trajectory analysis suggests that focal neuroendocrine differentiation exclusively originate from luminal-like malignant cells rather than basal compartment. Further tissue microarray analysis validates the generality of the luminal phenotype of neuroendocrine cells. Moreover, we uncover neuroendocrine differentiation-associated gene signatures that may help us to further explore other intrinsic molecular mechanisms deriving neuroendocrine prostate cancer. In summary, our single-cell study provides direct evidence into the cellular states underlying neuroendocrine transdifferentiation in human prostate cancer.

Neuroendocrine differentiation in usual-type prostatic adenocarcinoma: Molecular characterization and clinical significance

BACKGROUND

Small cell neuroendocrine (NE) carcinomas of the prostate classically lose androgen receptor (AR) expression, may harbor loss of the RB1, TP53, and PTEN tumor suppressor genes, and are associated with a poor prognosis. However usual-type adenocarcinomas may also contain areas of NE differentiation, and in this context the molecular features and biological significance are less certain.

METHODS

We examined the molecular phenotype and oncologic outcomes of primary prostate adenocarcinomas with ≥5% NE differentiation (≥5% chromogranin A-positive NE cells in any given tumor spot on tissue microarray) using three independent study sets: a set of tumors with paneth cell-like NE differentiation (n = 26), a retrospective case-cohort of intermediate- and high-risk patients enriched for adverse outcomes (n = 267), and primary tumors from a retrospective series of men with eventual castration-resistant metastatic prostate cancer (CRPC) treated with abiraterone or enzalutamide (n = 55).

RESULTS

Benign NE cells expressed significantly lower quantified AR levels compared with paired benign luminal cells (P < .001). Similarly, paneth-like NE carcinoma cells or carcinoma cells expressing chromogranin A expressed significantly lower quantified AR levels than paired non-NE carcinoma cells (P < .001). Quantified ERG protein expression, was also lower in chromogranin A-labeled adenocarcinoma cells compared with unlabeled cells (P < .001) and tumors with NE differentiation showed lower gene expression scores for AR activity compared with those without. Despite evidence of lower AR signaling, adenocarcinomas with NE differentiation did not differ by prevalence of TP53 missense mutations, or PTEN or RB1 loss, compared with those without NE differentiation. Finally, NE differentiation was not associated with time to metastasis in intermediate- and high-risk patients (P = .6 on multivariate analysis), nor with progression-free survival in patients with CRPC treated with abiraterone or enzalutamide (P = .9).

CONCLUSION

NE differentiation in usual-type primary prostate adenocarcinoma is a molecularly and clinically distinct form of lineage plasticity from that occurring in small cell NE carcinoma.

Neuroendocrine tumors of the prostate

Neuroendocrine (NE) differentiation in tumors of the prostate or in the setting of prostate cancer (PCa) is rare. A survey of these lesions is presented, including usual PCa with focal NE marker-positive cells, Paneth cell-like change, prostatic 'carcinoid', high-grade NE carcinoma, as well as other tumors that do not fit neatly into these categories. The most significant clinical and pathologic features, emerging molecular evidence and the importance of differentiating NE tumors involving the prostate from secondary involvement are highlighted.

Identification of Fibulin-1 as a Human Bone Marrow Stromal (HS-5) Cell-Derived Factor That Induces Human Prostate Cancer Cell Death

BACKGROUND

Previous studies showed that human bone marrow stromal HS-5 cells secreted unidentified factor(s) inducing PCa cell death. Herein, the HS-5-derived factor (HS-5 DF) was characterized and identified.

METHODS

Conditioned media from confluent HS-5 cells were collected and modified for biochemical characteristic testing of HS-5 DF. Cell survival was measured by apoptosis assay and live/dead assay. Fibulin-1 was identified from gel electrophoresis and mass spectrometry. The validation of Fibulin-1 as a HS-5 DF was done by immunoprecipitation (IP) and genetic knockdown by CRISPR/Cas9 system.

RESULTS

HS-5 DF was trypsin and heat sensitive, but pH stable. The tentative size of the factor fell between 30 kDa and 100 kDa. TGF-β1 treatment led to a suppression of HS-5 DF activity, a property consistent with bone metastasis in prostate cancer. Examination of TGF-β1 down regulated proteins led to identification of fibulin-1 as a candidate for the DF. IP of Fibulin-1 from HS-5 CM and CRISPR knockdown of Fibulin-1 showed a significant reduction of HS-5 CM-derived PCa cell death. These results strongly support a role for fibulin-1 in HS-5 bone marrow stromal cell induction of PCa cell death.

CONCLUSION

Our data indicate that Fibulin-1 functions as a HS-5 bone marrow stromal cell-derived factor inducing prostate cancer cell death. Prostate 77:729-742, 2017. © 2016 Wiley Periodicals, Inc.

Distribution of Neuroendocrine Cells in the Transition Zone of the Prostate

Objectives. To evaluate the distribution of neuroendocrine (NE) cells which may influence the development of benign prostatic hyperplasia (BPH) in the transition zone (TZ). Methods. We reviewed specimens from 80 patients who underwent radical prostatectomy in our institution and evaluated the density of NE cells in the TZ. They were histologically classified into 3 groups: those with no adenomatous nodule in the TZ (group A), those with small nodules with normal epithelium and stroma around them in the TZ (group B), and those with large nodules occupying the TZ (group C). In the patients of group B, intra-adenoma (adenomatous nodules) and extra-adenoma (normal tissue) NE cells in the TZ were separately counted. Results. There were 22, 23, and 35 patients in groups A, B, and C, respectively. The median density of NE cells in the TZ of group B patients, 2.80/mm², was significantly higher than that of NE cells in group A, 1.43/mm², and group C, 0.61/mm² (p < 0.001). In group B, the median density of extra-adenoma NE cells was significantly higher than that of intra-adenoma. Conclusions. Many NE cells exist around small adenoma in the TZ. NE cells may influence the initial growth of BPH in a paracrine fashion. Trial Registration. This study approved by our institutional review board was retrospectively registered (#272-14).

Chromogranin A as a valid marker in oncology: Clinical application or false hopes?

Chromogranin A, due to its primary expression throughout the neuroendocrine system, is a widely accepted biomarker for the assessment of neuro-endocrine tumors. It has been traditionally used in the management of patients with tumors of gastro-enteropancreatic origin. Lately, it has also been implicated in various conditions and diseases, both benign and malignant. However, the paucity of data of adequate strength, as well as its relation with common physiologic conditions and its interaction with commonly prescribed medications, limit its clinical use in only a narrow spectrum. Herein, we present a thorough review to the most frequent conditions where its levels are affected, focusing specifically on its potential use as a prognostic and predictive biomarker in oncology.

An Unusual Case of Resistant Hypokalaemia in a Patient with Large Bowel Obstruction Secondary to Neuroendocrine Carcinoma of the Prostate

Neuroendocrine Carcinoma of the Prostate (NECP) is rare and only few cases have been reported, constituting less than 0.5% of prostatic malignancies. We report a rare case of large bowel obstruction from NECP posing a further challenge in management due to resistant hypokalaemia. A 70-year-old man presented with clinical signs of large bowel obstruction who was known to have prostatic carcinoma three years ago, treated initially with hormone therapy then chemoradiation. The blood profile showed a severe hypokalaemia and CT scan revealed liver and lung metastases apart from confirming large bowel obstruction from local invasion of NECP. Severe hypokalaemia was believed to be caused by paraneoplastic syndrome from tumor burden or by recent administration of Etoposide. Intensive potassium correction through a central venous access in maximal doses of 150 mmol/24 hours under cardiac monitoring finally raised serum potassium to 3.8 mmol/L. This safe period allowed us to perform a trephine colostomy at the left iliac fossa. The postoperative period was relatively uneventful. This first case report is presenting a rare cause of large bowel obstruction from a neuroendocrine carcinoma of prostate and highlights the importance of an early, intensive correction of electrolytes in patients with large tumor burden from NECP.

Prostate cancer and neuroendocrine differentiation: more neuronal, less endocrine?

Neuroendocrine differentiation (NED) marks a structural and functional feature of certain cancers, including prostate cancer (PCa), whereby the malignant tissue contains a significant proportion of cells displaying neuronal, endocrine, or mixed features. NED cells produce, and can secrete, a cocktail of mediators commonly encountered in the nervous system, which may stimulate and coordinate cancer growth. In PCa, NED appears during advanced stages, subsequent to treatment, and accompanies treatment resistance and poor prognosis. However, the term “neuroendocrine” in this context is intrinsically vague. This article seeks to provide a framework on which a unified view of NED might emerge. First, we review the mutually beneficial interplay between PCa and neural structures, mainly supported by cell biology experiments and neurological conditions. Next, we address the correlations between PCa and neural functions, as described in the literature. Based upon the integration of clinical and basic observations, we suggest that it is legitimate to seek for true neural differentiation, or neuromimicry, in cancer progression, most notably in PCa cells exhibiting what is commonly described as NED.

Proposed morphologic classification of prostate cancer with neuroendocrine differentiation

On July 31, 2013, the Prostate Cancer Foundation assembled a working committee on the molecular biology and pathologic classification of neuroendocrine (NE) differentiation in prostate cancer. New clinical and molecular data emerging from prostate cancers treated by contemporary androgen deprivation therapies, as well as primary lesions, have highlighted the need for refinement of diagnostic terminology to encompass the full spectrum of NE differentiation. The classification system consists of: Usual prostate adenocarcinoma with NE differentiation; 2) Adenocarcinoma with Paneth cell NE differentiation; 3) Carcinoid tumor; 4) Small cell carcinoma; 5) Large cell NE carcinoma; and 5) Mixed NE carcinoma - acinar adenocarcinoma. The article also highlights "prostate carcinoma with overlapping features of small cell carcinoma and acinar adenocarcinoma" and "castrate-resistant prostate cancer with small cell cancer-like clinical presentation". It is envisioned that specific criteria associated with the refined diagnostic terminology will lead to clinically relevant pathologic diagnoses that will stimulate further clinical and molecular investigation and identification of appropriate targeted therapies.

Neuroendocrine differentiation does not have independent prognostic value in conservatively treated prostate cancer

In vitro studies have implicated neuroendocrine differentiation in the development of hormone resistant prostate cancer following administration of androgen blockers. Studies on clinical material are equivocal. We wished to understand the significance of neuroendocrine differentiation in our large and well-characterised cohort of clinically localised prostate cancer, treated conservatively. Immunohistochemical expression of chromogranin-A was assessed semi-quantitatively on tissue samples of 806 patients in a tissue microarray approach. The correlation of expression with 10-year prostate cancer survival was examined. Multivariate analysis including contemporary Gleason score was performed and sub-group analysis of early hormone treated patients was also undertaken. Chromogranin-A expression correlated with high Gleason score (χ(2) = 28.35, p < 0.001) and early prostate cancer death (HR = 1.61, 95 %CI = 1.15-2.27, p < 0.001). In univariate analysis, NE differentiation correlated significantly with outcome (HR = 1.61, 95 % CI 1.15-2.27, p < 0.001) However in multivariate analysis including Gleason score, chromogranin-A expression was not an independent predictor of survival (HR = 0.97, 95 %CI = 0.89-1.37, p = 0.87). Although chromogranin-A expression was higher in patients with early hormone therapy (χ(2) = 7.25, p = 0.007), there was no association with prostate cancer survival in this sub-group (p = 0.083). Determination of neuroendocrine differentiation does not appear to have any bearing on the outcome of prostatic carcinoma and does not add to the established prognostic model.

Variants and unusual patterns of prostate cancer: clinicopathologic and differential diagnostic considerations

Beyond the typical acinar morphology observed in the majority of prostatic adenocarcinomas, a spectrum of morphologic variants and prostate cancer subtypes exists. These unusual entities may be classified as: (1) cancer morphologies arising by divergent differentiation of prostatic ductal, acinar, or basal cells and associated with unique clinical features and/or therapeutic approaches, and (2) histologies occurring in the context of usual prostatic adenocarcinoma that may result in diagnostic misinterpretation or difficulties in Gleason grade assignment, especially in limited samples. This article details a number of variants, with emphasis on diagnostic criteria, differential diagnoses, and clinical significance.

Cell-to-cell signaling influences the fate of prostate cancer stem cells and their potential to generate more aggressive tumors

An increasing number of malignancies has been shown to be initiated and propelled by small subpopulations of cancer stem cells (CSC). However, whether tumor aggressiveness is driven by CSC and by what extent this property may be relevant within the tumor mass is still unsettled. To address this issue, we isolated a rare tumor cell population on the basis of its CD44⁺CD24⁻ phenotype from the human androgen-independent prostate carcinoma cell line DU145 and established its CSC properties. The behavior of selected CSC was investigated with respect to the bulk DU145 cells. The injection of CSC in nude mice generated highly vascularized tumors infiltrating the adjacent tissues, showing high density of neuroendocrine cells and expressing low levels of E-cadherin and β-catenin as well as high levels of vimentin. On the contrary, when a comparable number of unsorted DU145 cells were injected the resulting tumors were less aggressive. To investigate the different features of tumors in vivo, the influence of differentiated tumor cells on CSC was examined in vitro by growing CSC in the absence or presence of conditioned medium from DU145 cells. CSC grown in permissive conditions differentiated into cell populations with features similar to those of cells held in aggressive tumors generated from CSC injection. Differently, conditioned medium induced CSC to differentiate into a cell phenotype comparable to cells of scarcely aggressive tumors originated from bulk DU145 cell injection. These findings show for the first time that CSC are able to generate differentiated cells expressing either highly or scarcely aggressive phenotype, thus influencing prostate cancer progression. The fate of CSC was determined by signals released from tumor environment. Moreover, using microarray analysis we selected some molecules which could be involved in this cell-to-cell signaling, hypothesizing their potential value for prognostic or therapeutic applications.

Notch signaling modulates hypoxia-induced neuroendocrine differentiation of human prostate cancer cells

Prostate carcinoma is among the most common causes of cancer-related death in men, representing 15% of all male malignancies in developed countries. Neuroendocrine differentiation (NED) has been associated with tumor progression, poor prognosis, and with the androgen-independent status. Currently, no successful therapy exists for advanced, castration-resistant disease. Because hypoxia has been linked to prostate cancer progression and unfavorable outcome, we sought to determine whether hypoxia would impact the degree of neuroendocrine differentiation of prostate cancer cells in vitro.

RESULTS

Exposure of LNCaP cells to low oxygen tension induced a neuroendocrine phenotype, associated with an increased expression of the transcription factor neurogenin3 and neuroendocrine markers, such as neuron-specific enolase, chromogranin A, and β3-tubulin. Moreover, hypoxia triggered a significant decrease of Notch 1 and Notch 2 mRNA and protein expression, with subsequent downregulation of Notch-mediated signaling, as shown by reduced levels of the Notch target genes, Hes1 and Hey1. NED was promoted by attenuation of Hes1 transcription, as cells expressing a dominant-negative form of Hes1 displayed increased levels of neuroendocrine markers under normoxic conditions. Although hypoxia downregulated Notch 1 and Notch 2 mRNA transcription and receptor activation also in the androgen-independent cell lines, PC-3 and Du145, it did not change the extent of NED in these cultures, suggesting that androgen sensitivity may be required for transdifferentiation to occur.

CONCLUSIONS

Hypoxia induces NED of LNCaP cells in vitro, which seems to be driven by the inhibition of Notch signaling with subsequent downregulation of Hes1 transcription.

Prognostic significance of focal neuroendocrine differentiation in prostate cancer: cases with autopsy-verified cause of death

AIMS

This study was designed to evaluate the prognostic significance of focal chromogranin A (cgA) expression in prostate cancer in a series of cases with autopsy-verified cause of death.

METHODS AND RESULTS

Seventy seven autopsy-verified cases of prostate cancer were identified, 41 cases with metastatic disease and 36 with nonmetastatic disease at autopsy. Immunohistochemical analysis for cgA was performed in 40 cases on the archived diagnostic biopsies taken during the patients' lifetime. After exclusion of a single case of carcinoid tumor, 14 of the 18 (78%) metastatic and none of the 21 (0%) nonmetastatic tumors showed focal neuroendocrine differentiation (NED). The Gleason score and focal cgA expression further increased the accuracy of the prediction of the outcome, as all the cases with focal NED associated with high Gleason score had metastatic disease in contrast to cases without cgA-expression and low Gleason score, all of which were non-metastatic.

CONCLUSIONS

Focal NED seems to be a powerful negative prognostic parameter in prostate adenocarcinomas. The outcome of the disease in prostate cancer can be accurately predicted based on focal NED of the tumor cells either alone or in combination with Gleason score.

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.

Primitive origins of prostate cancer: in vivo evidence for prostate-regenerating cells and prostate cancer-initiating cells

Tissue stem cells have been linked to cancers of epithelial origin including the prostate. There are three relevant issues concerning stem cells and cancer that rely solely on functional studies: 1. Are there tissue-regenerating stem cells in the adult organ? 2. Can tissue-regenerating cells serve as targets for transformation? 3. Do primary tumors contain tumor-propagating (cancer stem) cells? We will review the recent literature with respect to these critical issues to provide a direct link between primitive cells and prostate cancer.

Matrix metalloproteinases contribute distinct roles in neuroendocrine prostate carcinogenesis, metastasis, and angiogenesis progression

Prostate cancer is the leading form of cancer in men. Prostate tumors often contain neuroendocrine differentiation, which correlates with androgen-independent progression and poor prognosis. Matrix metalloproteinases (MMP), a family of enzymes that remodel the microenvironment, are associated with tumorigenesis and metastasis. To evaluate MMPs during metastatic prostatic neuroendocrine cancer development, we used transgenic mice expressing SV40 large T antigen in their prostatic neuroendocrine cells, under the control of transcriptional regulatory elements from the mouse cryptdin-2 gene (CR2-TAg). These mice have a stereotypical pattern of tumorigenesis and metastasis. MMP-2, MMP-7, and MMP-9 activities increased concurrently with the transition to invasive metastatic carcinoma, but they were expressed in different prostatic cell types: stromal, luminal epithelium, and macrophages, respectively. CR2-TAg mice treated with AG3340/Prinomastat, an MMP inhibitor that blocks activity of MMP-2, MMP-9, MMP-13, and MMP-14, had reduced tumor burden. CR2-TAg animals were crossed to mice homozygous for null alleles of MMP-2, MMP-7, or MMP-9 genes. At 24 weeks CR2-TAg; MMP-2(-/-) mice showed reduced tumor burden, prolonged survival, decreased lung metastasis, and decreased blood vessel density, whereas deficiencies in MMP-7 or MMP-9 did not influence tumor growth or survival. Mice deficient for MMP-7 had reduced endothelial area coverage and decreased vessel size, and mice lacking MMP-9 had increased numbers of invasive foci and increased perivascular invasion, as well as decreased tumor blood vessel size. Together, these results suggest distinct contributions by MMPs to the progression of aggressive prostate tumor and to helping tumors cleverly find alternative routes to malignant progression.

Selective expression of CD44, a putative prostate cancer stem cell marker, in neuroendocrine tumor cells of human prostate cancer

BACKGROUND

Hormonal therapy is effective for advanced prostate cancer (PC) but the disease often recurs and becomes hormone-refractory. It is hypothesized that a subpopulation of cancer cells, that is, cancer stem cells (CSCs), survives hormonal therapy and leads to tumor recurrence. CD44 expression was shown to identify tumor cells with CSC features. PC contains secretory type epithelial cells and a minor population of neuroendocrine cells. Neuroendocrine cells do not express androgen receptor and are quiescent, features associated with CSCs. The purpose of the study was to determine the expression of CD44 in human PC and its relationship to neuroendocrine tumor cells.

METHODS

Immunohistochemistry and immunofluorescence were performed to study CD44 expression in PC cell lines, single cells from fresh PC tissue and archival tissue sections of PC. We then determined if CD44+ cells represent neuroendocrine tumor cells.

RESULTS

In human PC cell lines, expression of CD44 is associated with cells of NE phenotype. In human PC tissues, NE tumor cells are virtually all positive for CD44 and CD44+ cells, excluding lymphocytes, are all NE tumor cells.

CONCLUSIONS

Selective expression of the stem cell-associated marker CD44 in NE tumor cells of PC, in combination with their other known features, further supports the significance of such cells in therapy resistance and tumor recurrence.

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.

Variants and Unusual Patterns of Prostate Cancer

Beyond the typical acinar morphology observed in most prostatic adenocarcinoma, a spectrum of morphologic variants and prostate cancer subtypes exists. These unusual entities may be further classified into (1) cancer morphologies arising by divergent differentiation of prostatic ductal, acinar, or basal cells and associated with unique clinical features or therapeutic approaches, and (2) histologies occurring in the context of usual prostatic adenocarcinoma that may result in diagnostic misinterpretation or difficulties in Gleason grade assignment, especially in limited samples. This article details several variants, with emphasis on diagnostic criteria, differential diagnoses, and clinical significance.

Neuroendocrine differentiation in stage D2 prostate cancers

OBJECTIVES

Chromogranin A (CgA) and neuro-specific enolase (NSE) are gaining acceptance as markers of several types of neuroendocrine tumors and the concentration of CgA and NSE have been reported to be elevated in relation to neuroendocrine differentiation of prostate cancer. The aim of the present study was to examine the correlation between the immunohistochemical (IHC) findings and serum value for CgA and NSE in untreated stage D(2) prostate cancer patients.

METHODS

Immunohistochemistry was carried out using antibodies against CgA and NSE in 58 patients and, pretreatment serum CgA and NSE levels were measured by monoclonal immunoradiometric assay in 18 patients with stage D(2) prostate cancer treated by androgen ablation. We examined the relationship of the pretreatment serum level to IHC findings for CgA and NSE in prostate cancer patients to clinicopathological parameters, and prognosis. Also, we evaluated the correlation of IHC findings to serum levels for CgA and NSE.

RESULTS

There was a statistically significant correlation between CgA positivity and serum CgA level (P = 0.0421). However, there was no statistically significant correlation between NSE positivity and serum NSE level (P > 0.05). We divided stage D(2) patients into three groups according to IHC positivity of CgA and NSE. The cause-specific survival was significantly poorer in patients with strongly positive (++) patients for independent CgA and combined CgA with NSE (P = 0.0379). Multivariate analysis of cause-specific survivals in patients with stage D(2) prostate cancer demonstrated that strong IHC stain was considered as independent variable associated with greater risk of death (P = 0.0142).

CONCLUSION

Neuroendocrine differentiation in stage D(2) prostate cancer has attracted considerable attention as a potentially findings prognosis. Thus, CgA had a stronger relationship between serum levels and IHC positivity in contrast to NSE, suggesting clinical usefulness as a tumor marker in predicting the extent of neuroendocrine differentiation in prostate cancer.

Neuroendocrine lesions of the genitourinary tract

Neuroendocrine differentiation in tumors of the upper and lower urinary tracts, prostate, and testis is rare. The current review surveys the most significant pathologic and clinical features of primary neuroendocrine lesions at these sites, with emphasis on the cell types from which they derive. As many tumors in this spectrum often bear strong morphologic resemblance to similar neoplasms in other organs, the importance of considering secondary involvement of the genitourinary tract cannot be overstated.

Prostate Cancer Associated withp53andRbDeficiency Arises from the Stem/Progenitor Cell–Enriched Proximal Region of Prostatic Ducts

Recently, we have shown that prostate epithelium-specific deficiency for p53 and Rb tumor suppressors leads to metastatic cancer, exhibiting features of both luminal and neuroendocrine differentiation. Using stage-by-stage evaluation of carcinogenesis in this model, we report that all malignant neoplasms arise from the proximal region of the prostatic ducts, the compartment highly enriched for prostatic stem/progenitor cells. In close similarity to reported properties of prostatic stem cells, the cells of the earliest neoplastic lesions express stem cell marker stem cell antigen 1 and are not sensitive to androgen withdrawal. Like a subset of normal cells located in the proximal region of prostatic ducts, the early neoplastic cells coexpress luminal epithelium markers cytokeratin 8, androgen receptor, and neuroendocrine markers synaptophysin and chromogranin A. Inactivation of p53 and Rb also takes place in the lineage-committed transit-amplifying and/or differentiated cells of the distal region of the prostatic ducts. However, the resulting prostatic intraepithelial neoplasms never progress to carcinoma by the time of mouse death. Interestingly, in an ectopic transplantation assay, early mutant cells derived from either region of the prostatic ducts are capable of forming neoplasms within 3 months. These findings indicate that p53 and Rb are critically important for the regulation of the prostatic stem cell compartment, the transformation in which may lead to particularly aggressive cancers in the context of microenvironment.

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.

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.

Immunohistochemical characterization of neuroendocrine cells in prostate cancer

BACKGROUND

Neuroendocrine (NE) cells increase in high grade/stage prostate cancer (PC) and may contribute to androgen-independent cancer. Their immunohistochemical phenotype has not been studied in detail and conflicting results have been reported.

METHODS

PC tissue was stained immunohistochemically for luminal secretory cell-associated cytokeratin, basal cell markers, ki-67, androgen receptor (AR), PSA, prostate acid phosphatase (PAP), and alpha-methylacyl coenzyme A racemase (AMACR).

RESULTS

The NE cells are positive for AE1/AE3, Cam 5.2, and negative for basal cell markers. They are negative for AR, PSA, and Ki-67 but positive for PAP. The benign NE cells are negative for AMACR while the malignant NE cells are positive for AMACR.

CONCLUSIONS

NE cells of PC constitute a unique subset of cancer cells, which have a unique immunohistochemical profile. They do not express AR, consistent with their resistance to hormonal therapy. They are post-mitotic cells but are malignant and part of the tumor.

Large cell neuroendocrine carcinoma of prostate: a clinicopathologic summary of 7 cases of a rare manifestation of advanced prostate cancer

Neuroendocrine (NE) differentiation in prostate cancer is typically detected by immunohistochemistry as single cells in conventional adenocarcinoma. Prostatic NE tumors, such as carcinoid or small cell carcinoma, are rare and large cell NE carcinoma (LCNEC) is described only in case reports. We identified 7 cases of LCNEC and compiled their clinicopathologic characteristics. In 6 cases, there was a history of adenocarcinoma treated with hormone therapy for a mean of 2.4 years (range: 2 to 3 y). The remaining case was de novo LCNEC. LCNEC was incidentally diagnosed in palliative transurethral resection specimens in 5 cases. The mean patient age at diagnosis with LCNEC was 67 years (range: 43 to 81 y). LCNEC comprised solid sheets and ribbons of cells with abundant pale to amphophilic cytoplasm, large nuclei with coarse chromatin and prominent nucleoli along with brisk mitotic activity and foci of necrosis. In 6 cases, there were foci of admixed adenocarcinoma, 4 of which showed hormone therapy effects. LCNEC was strongly positive for CD56, CD57, chromogranin A, synaptophysin, and P504S/alpha methylacyl CoA racemase. There was strong bcl-2 overexpression, expression of MIB1, and p53 in >50% of nuclei, focally positive staining for prostate specific antigen and prostatic acid phosphatase and negative androgen receptor staining. Follow-up was available for 6 patients, all of who died with metastatic disease at mean of 7 months (range: 3 to 12 mo) after platinum-based chemotherapy. LCNEC of prostate is a distinct clinicopathologic entity that typically manifests after long-term hormonal therapy for prostatic adenocarcinoma and likely arises through clonal progression under the selection pressure of therapy.

[Neuroendocrine differentiation in prostate cancer: an unrecognized and therapy resistant phenotype]

Neuroendocrine (NE) differentiation frequently occurs in common prostatic malignancies but usually escapes pathological and clinical detection. The present review focuses on biological properties of NE tumor cells making them resistant to androgen deprivation and radiation therapy. Recent data have shown that NE prostate cancer cells (as defined by the most commonly used endocrine marker chromogranin A) are arrested in the G0-phase of the cell cycle and do not undergo apoptosis. This particular phenotype consistently lacks the nuclear androgen receptor in both benign and malignant conditions but produces a series of hormonal growth factors exerting mitogenic stimuli on adjacent, exocrine tumor cells. Neoplastic NE cells devoid of the nuclear androgen receptor constitute an androgen-insensitive cell population in prostate cancer. The absence of proliferative and apoptotic activity makes NE tumor cells particularly resistant towards cytotoxic drugs and radiation therapy. Pathological and clinical detection of NE features is recommended for all prostate cancer patients for whom radiation therapy and androgen deprivation is being considered.

Genetic analysis of neuroendocrine tumor cells in prostatic carcinoma

BACKGROUND

Neuroendocrine differentiated tumor cells can be found in the majority of prostatic adenocarcinomas. During antiandrogen or androgen-withdrawal therapy the neuroendocrine differentiation is often increased but its prognostic value is discussed controversially. The origin of neuroendocrine tumor cells is under discussion. While double staining experiments suggest a non-neoplastic pluripotent stem cell, in vitro studies demonstrate a transdifferentiation of exocrine tumor cells to a neuroendocrine phenotype.

METHODS

Neuroendocrine differentiated LNCaP cells and laser captured microdissected cells of eight radical prostatectomies were allelotyped using 11 microsatellite markers from seven different loci.

RESULTS

Identical allelic profiles were detected in untreated and neuroendocrine differentiated LNCaP cells for all markers confirming their clonality. Neuroendocrine and exocrine tumor cells from radical prostatectomies shared identical allelic profiles for all markers, suggesting a common origin for both cell populations.

CONCLUSIONS

Our results support the concept of transdifferentiation of exocrine tumor cells to a neuroendocrine tumor cell phenotype.

[Relevance of the neuroendocrine differentiation in prostatic carcinoma]

BACKGROUND

NE tumor cells are present in virtually all prostatic adenocarcinomas. As they express no androgen receptor they are hormone independent. During anti-androgenic therapy their number increases. Their prognostic value is controversial.

MATERIAL AND METHODS

In 233 patients with prostatic carcinoma the NE differentiation was determined in a hot spot (7.9 mm(2)) with maximum CgA positive cell density. A high NE differentiation (HNE) was defined by a least 30 NE tumor cells, while less means a low NE differentiation (LNE). In addition the occurrence of NE tumor cells was defined as solitary or clustered (> or =5 NE tumor cells in close proximity).

RESULTS

In advanced and high grade tumors more and clustered NE tumor cells could be found than in low grade and organ confined tumors. Moreover HNE tumors and occurrence of NE clusters resulted in a significant shorter progression-free interval.

CONCLUSIONS

Besides the quantity of NE differentiation the quality of the growth pattern of NE tumor cells is of relevance in prostatic carcinoma.

Influence of neuroendocrine tumor cells on proliferation in prostatic carcinoma

Neuroendocrine (NE) tumor cells in prostatic carcinoma (PCa) may influence tumor proliferation by a paracrine stimulus. The role of NE tumor cells is discussed controversially. This study investigates the influence of NE tumor differentiation on proliferation in PCa. Neuroendocrine differentiation, Ki-67, and Polo-like kinase 1 were studied immunohistochemically in 73 consecutive prostatectomies. Polo-like kinase 1 (PLK1) expression was also studied by Western and Northern blot analysis. Tumors were classified as high NE (HNE) and low NE differentiated (LNE), and depending on the growth pattern, with solitary and clusters of NE tumor cells. Low NE differentiated tumors were defined as less than 30 and HNE as 30 or more NE tumor cells per hot spot. Patients were followed by serum prostate-specific antigen (PSA) analysis. Neuroendocrine differentiation was present at least focally in 70% of tumors; 57% were HNE and 43% LNE. Solitary NE tumor cells were more often found in low-grade PCa, whereas clusters of NE tumor cells were more frequent in high-grade PCa. PLK1 messenger RNA and protein as well as Ki-67 were overexpressed in tumor tissue compared with tumor-free tissue. A stronger proliferation as determined by Ki-67 and PLK1 expression was present in HNE tumors compared with LNE tumors and in tumors with clusters in contrast to tumors with solitary NE tumor cells. Analysis for PSA relapse-free survival showed an earlier progression in HNE than in LNE tumors and in PCa with clusters of NE tumor cells. A significant and clustered NE differentiation in PCa may lead to an increased proliferation and earlier tumor progression, whereas few and solitary NE tumor cells have no prognostic impact.

[Neuroendocrine differentiation in prostate cancer. An unrecognized and therapy-resistant phenotype]

Neuroendocrine (NE) differentiation frequently occurs in common prostatic malignancies and has attracted increasing attention in contemporary prostate cancer research. This particular phenotype, however, usually escapes pathological and clinical detection in routine practice. The present review focuses on the biological properties of NE tumor cells that make them resistant to androgen deprivation and radiation therapy. NE cells produce a number of hormonal growth factors (e.g., serotonin) that may act through endocrine, paracrine, and autocrine mechanisms. Morphogenetic studies have identified intermediate phenotypes between the three basic cell types of the prostatic epithelium indicating their common origin from stem cells located in the basal cell layer. Virtually all prostatic adenocarcinomas show NE differentiation as defined by the most commonly used endocrine marker chromogranin A. Clinical studies suggest that the extent of NE differentiation increases with tumor progression and the development of androgen insensitivity. NE differentiation exclusively occurs in the G0 phase of the cell cycle in which tumor cells are usually resistant to radiation therapy and cytotoxic drugs. In addition, NE tumor cells also escape programmed cell death. Even under androgen deprivation, only 0.16% of NE tumor cells show apoptotic activity. This indicates that the vast majority of NE tumor cells represent an immortal cell population in prostate cancer. Although NE tumor cells do not proliferate, they produce a number of NE growth factors with mitogenic properties that maintain cell proliferation in adjacent (exocrine) tumor cells through a paracrine mechanism. NE tumor cells consistently lack the androgen receptor and are androgen insensitive in all stages of the disease. They derive through a process of intermediate differentiation from exocrine tumor cells, the most prevalent phenotype in common prostatic adenocarcinoma. Elevated serum levels of chromogranin A in prostate cancer patients correlate with poor prognosis and are scarcely influenced by either androgen deprivation or chemotherapy. Looking for NE differentiation is recommended in the pathological and clinical evaluation of prostate cancer patients for whom radiation and androgen deprivation are therapeutic options.

Neuroendocrine differentiation in hormone refractory prostate cancer following androgen deprivation therapy

OBJECTIVE

To evaluate the relationship between neuroendocrine differentiation (NED) status and hormone refractory prostate cancer (HRPC) following hormone therapy based on immunohistochemical study.

METHODS

Seventy-two prostate cancer specimens obtained at radical prostatectomy and 21 prostate cancer autopsy specimens from patients who died from HRPC after androgen deprivation therapy were examined for NED status using an antibody against chromogranin A. These specimens were classified into 3 arms: 38 radical prostatectomy specimens from patients with no neoadjuvant hormone therapy (Group 1); 34 from patients with neoadjuvant hormone therapy for 3 to 6 months (Group 2); and 21 autopsy specimens from patients with HRPC following androgen deprivation therapy for more than 1 year (Group 3). Staining of prostatic carcinoma was scored as: 0 = no staining; 1 = staining cells <10%; 2 = staining cells 10-20%; and 3 = staining cells >20%. Differences in scores among the groups were compared using the Kruskal-Wallis rank test. Multivariate analysis using a logistic regression model was performed to examine whether NED status was associated with pathological stage (pT), grade and group.

RESULTS

Forty-nine (53%) tumors had CgA stained cells. NED status increased with longer duration of hormone therapy (p<0.0001). The mean staining score (and standard deviation) was 0.4+/-0.7 in Group 1, 0.7+/-0.7 in Group 2, and 1.4+/-1.1 in Group 3, respectively. By multivariate analysis Group 3 had a relative risk of 5.46 (95%CI 1.28-23.29) for NED compared to the other groups. But other variables were not related to NED. HRPC following Long-term hormonal therapy was the only independent predictor of NED.

CONCLUSIONS

The results of this study demonstrated that NED status was significantly increased in patients with HRPC following long-term androgen deprivation therapy, but it could not be discriminate whether the increase of NED is attributable to condition of hormone refractoriness or long-term hormonal therapy.

Metastatic conventional prostatic adenocarcinoma with diffuse chromogranin A and androgen receptor positivity

Conventional prostate adenocarcinomas consist mainly of tumour cells of luminal immunophenotype with scattered neuroendocrine (NE) cells. NE cells are defined by chromogranin A (CGA) immunoreactivity. Unlike luminal cells, NE cells lack androgen receptor (AR) and prostate specific antigen (PSA) immunoreactivity. This report describes the first case of conventional prostate adenocarcinoma expressing CGA, PSA, and AR as determined by immunohistochemistry. A 64 year old man was diagnosed with conventional prostate adenocarcinoma in 1993; he underwent cystoprostatectomy in 1994; he developed an iliac bone metastasis in 1997 and mediastinal lymph node metastases in 1999. All specimens obtained during the progression of the disease consisted primarily of luminal cells with only scattered NE cells. In contrast, in samples of non-osseous and osseous metastases obtained at necropsy in 2001, greater than 80% of tumour cells were shown to express PSA, AR, and CGA. This suggests that during tumour progression, conventional prostate adenocarcinomas may evolve into an NE cell phenotype.

An allograft model of androgen independent prostatic neuroendocrine carcinoma derived from a large probasin promoter-T antigen transgenic mouse line

PURPOSE

Animal models that mimic this hormone refractory prostate cancer may be useful for developing and testing novel treatment strategies.

MATERIALS AND METHODS

Using the prostate of the 12T-10 transgenic mouse an allograft model was established by transplantation into a nude mouse. To our knowledge we describe the first allograft model derived from the primary prostate tumor of a transgenic mouse.

RESULTS

The primary tumor progressed from high grade prostatic intraepithelial neoplasm to invasive, undifferentiated and metastatic cancer with loss of androgen receptor expression. After 10 passages in nude mice the allograft retained the same histological and immunohistochemical features as the primary tumors, including neuroendocrine differentiation. The allograft demonstrated androgen independent growth and metastases to liver and lung, paralleling tumor behavior in the original transgenic line. Cytogenetic characterization of the allograft revealed consistent chromosomal abnormalities for multiple in vivo passages.

CONCLUSIONS

This allograft model may give insight into the mechanism by which human prostate cancer progresses to an androgen independent state and provide a system for testing drugs that can inhibit this disease.

Steroid hormones, polypeptide growth factors, hormone refractory prostate cancer, and the neuroendocrine phenotype

The growth, development, and differentiation of the prostate gland is largely dependent on the action of androgens and peptide growth factors that act differentially at the level of the mesenchymal and epithelial compartments. It is our premise that to understand the emergence of metastatic and hormone refractory prostate cancer we need to investigate: (1) how androgen action at the level of the mesenchyme induces the production of peptide growth factors that in turn can facilitate the growth and development of the epithelial compartment; (2) how androgen action at the level of the epithelium induces and maintains cellular differentiation, function, and replicative senescence; and (3) how transformation of the prostate gland can corrupt androgen and growth factor signaling homeostasis. To this end, we focus our discussion on how deregulation of the growth factor signaling axis can cooperate with deregulation of the androgen signaling axis to facilitate transformation, metastasis, and the emergence of the hormone refractory and neuroendocrine phenotypes associated with progressive androgen-independent prostate cancer. Finally, we suggest a working hypothesis to explain why hormone ablation therapy works to control early disease but fails to control, and may even facilitate, advanced prostate cancer.

Pretreatment serum level of neuron specific enolase (NSE) as a prognostic factor in metastatic prostate cancer patients treated with endocrine therapy

OBJECTIVE

The serum level of neuron specific enolase (NSE) is gaining acceptance as a marker of neuroendocrine tumors. To clarify the role of NSE in prostate cancer progression, we examined the relationship of NSE to clinicopathological parameters.

METHODS

The pretreatment serum NSE level was measured in 104 patients with histologically confirmed prostatic adenocarcinoma (PCa) and 59 patients in whom prostate cancer was not detected (non-PCa). PCa patients consisted of 5 T1N0M0, 20 T2N0M0, 31 T3N0M0, 7 TxN1M0 and 41 TxNxM1 cases.

RESULTS

Non-PCa patients had significantly higher serum NSE than PCa patients. Serum NSE in metastatic PCa patients was significantly higher than that in non-metastatic patients, while NSE did not significantly differ with regard to histological grade, or prostate specific antigen (PSA) response to endocrine therapy. In PCa patients, serum NSE was not correlated to serum PSA nor chromogranin A. In metastatic patients who underwent endocrine therapy, the higher NSE group had significantly poorer cause-specific survival.

CONCLUSION

The pretreatment serum level of NSE can predict survival of metastatic PCa patients treated with endocrine therapy.

Apoptosis resistance of neuroendocrine phenotypes in prostatic adenocarcinoma

BACKGROUND

Neuroendocrine (NE) differentiation has been implicated in prostate cancer progression and hormone therapy failure. It has been shown that prostate cancer cells with NE features lack proliferation activity in vitro and in vivo. The current study reports on the apoptotic status of NE phenotypes in human prostate cancer.

METHODS

Double-label techniques were used for simultaneous demonstration of the endocrine marker chromogranin A (ChrA) and DNA fragmentation assessed by the terminal transferase-mediated biotinylated 16-desoxy-uridine-tri-phosphate (bio-16-dUTP) nick-end-labeling (TUNEL) assay. The material included primary prostatic adenocarcinoma (n = 18), lymph node metastases (n = 5), bone metastases (n = 2), and recurrent lesions (n = 10) showing NE differentiation at the immunohistochemical level.

RESULTS

Irrespective of grades, stages, and the degree of NE differentiation, DNA fragmentation was restricted to exocrine (ChrA-negative) tumor cells and was undetectable in most of NE tumor cells expressing ChrA. At least 0.16% of ChrA-positive tumor cells revealed DNA fragmentation assessed by the TUNEL assay.

CONCLUSION

The present data suggest that the vast majority of prostate cancer cells with NE features escapes programmed cell death. This escape may contribute significantly to their drug resistance and their malignant potential.

Metastatic prostate carcinoma to bone: clinical and pathologic features associated with cancer-specific survival

BACKGROUND

The objective of this study was to examine the clinical and pathologic features of metastatic prostate carcinoma to bone in a large cohort of men, and the associations of these features with outcome.

METHODS

Sixty-eight men who underwent surgery for metastatic prostate carcinoma to bone for stabilization of a pathologic fracture or impending fracture were studied. Clinical characteristics included the type of treatment for the primary and metastatic prostate carcinoma, age and serum prostate specific antigen (PSA) at the diagnosis of the metastatic prostate carcinoma, radiographic findings of the metastasis (osteoblastic, osteolytic, or mixed), and the number of metastatic sites at the time of the surgery for the metastasis. Pathologic features examined included Gleason score of the metastatic prostate carcinoma. Immunohistochemical stains for MIB-1, cytokeratin, PSA, synaptophysin, chromogranin A, serotonin, estrogen receptor, progesterone receptor, and androgen receptor were performed for all cases. The Kaplan-Meier method was used to estimate cancer-specific survival. The duration of follow-up was defined as the interval from the date of surgery for the metastasis to the date of death or last follow-up. Univariate and multivariate Cox proportional hazards models were fit to assess the features that were associated with death from prostate carcinoma.

RESULTS

The average (standard deviation) time from the surgery for the metastasis to death from prostate carcinoma was 1.5 (1.9) years, ranging from 0 days to 10 years, with a median of 1 year. The estimated cancer-specific survival rates at 1 year, 2 years, and 3 years were 54.3%, 28.8%, and 22.9%, respectively. Median cancer-specific survival occurred at 1.1 years. After 4 years of follow-up, there were only seven patients left at risk for death from prostate carcinoma. Features that were found to be significantly associated with death from prostate carcinoma univariately included the interval between the diagnosis of metastasis and the surgery for metastasis (P < 0.001), androgen deprivation therapy before surgery for the metastasis (P = 0.002), presentation with metastasis (P = 0.003), the number of metastatic sites (P = 0.034), Gleason score of the metastasis (P = 0.002), and tumor positivity for chromogranin A (P = 0.041). On multivariate analysis, the interval between the diagnosis of metastasis and the surgery for metastasis (P < 0.001), Gleason score of the metastasis (P < 0.001), and tumor positivity for chromogranin A (P = 0.009) were associated significantly with death from prostate carcinoma.

CONCLUSIONS

Although cancer-specific survival for patients after surgery for prostate carcinoma metastatic to bone is poor, assessments of tumor differentiation of the metastasis and chromogranin A positivity provide prognostic information.

A neuroendocrine/small cell prostate carcinoma xenograft-LuCaP 49

The late stages of progression of prostate carcinoma are typically characterized by an androgen-insensitive, rapidly proliferative state. Some late-stage tumors are composed predominantly of neuroendocrine cells. Virtually no animal models of a neuroendocrine/small cell variant of prostate carcinoma are available for experimental studies. We report a human neuroendocrine/small cell prostate carcinoma xenograft that was developed from a nodal metastasis of a human prostate carcinoma and that has been propagated as serial subcutaneous implants in severe combined immunodeficient mice for >4 years. Designated LuCaP 49, all tumor passages exhibit a neuroendocrine/small cell carcinoma phenotype-insensitivity to androgen deprivation, expression of neuroendocrine proteins, lack of expression of prostate-specific antigen or androgen receptor, and an unusually rapid growth (a doubling time of 6.5 days) for prostate cancer xenografts. Genetically this tumor exhibits loss of heterozygosity for the short arm of chromosome 8 and has a complex karyotype. This xenograft should prove to be useful in the investigation of mechanisms underlying the androgen-insensitive state of progressive prostate carcinoma.

Expression of growth hormone-releasing hormone (GHRH) and splice variants of GHRH receptors in human experimental prostate cancers

The expression of mRNA for GHRH and splice variants (SVs) of GHRH receptors in LNCaP, MDA-PCa-2b and PC-3 human prostate cancers grown in nude mice was investigated by RT-PCR. The expression of mRNA for GHRH was detected in LNCaP and PC-3, but not in MDA-PCa-2b prostatic carcinoma. RT-PCR analyses of mRNA isolated from LNCaP, MDA-PCa-2b and PC-3 cancers, revealed the presence of 720 and 566 bp products, corresponding to SV(1) and SV(2) isoforms of GHRH receptors. In PC-3 tumor membranes a radiolabeled GHRH antagonist [125I]-JV-1-42 was bound to one class of high-affinity binding sites (K(d)=1.81+/-0.47 nM) and maximum binding capacity of 332.7+/-27.8 fmol/mg membrane protein. The in vivo uptake of [125I]-JV-1-42 was observed in all xenografts of human prostate cancer, the tracer accumulation being the highest in PC-3 tumors. These results indicate that GHRH and SVs of its receptors, different from those found in the pituitary, are present in experimental human prostate cancers and may form a local mitogenic loop. The antiproliferative effects of GHRH antagonists on growth of prostate cancer could be exerted in part by an interference with this local GHRH system.

Androgen ablation promotes neuroendocrine cell differentiation in dog and human prostate

BACKGROUND

Mechanisms triggering prostatic NE differentiation are poorly understood. Since dog and man naturally develop prostatic proliferative diseases with age, our objectives were to confirm the presence of NE cells in the dog prostate and test their hormonal regulation in both species.

METHODS

Serotonin staining was examined by immunohistochemistry in 37 dog prostates: 17 from intact and 20 from castrated animals. In intact dogs, 9 prostates were normal and 8 hyperplastic. In the castrated group, 6 dogs were left untreated while androgens and estrogens were administered to 7 dogs, each. Human prostates were from 48 prostate cancer patients; half of them were submitted to androgen ablation prior to prostatectomy. The density of serotonin-positive NE cells was expressed relatively to the number of acini.

RESULTS

Serotonin-positive NE cells were morphologically similar in dog and human prostates and identified in all groups, independent of the hormonal status. NE cell densities were within the same range in normal and hyperplastic dog prostates but significantly higher after castration. Androgens and estrogens after castration restored NE cell density to normal values and induced luminal differentiation and basal metaplasia, respectively. In human, the density of serotonin-positive NE cells was also significantly higher in benign glands after androgen ablation.

CONCLUSIONS

The dog is a suitable animal model and mimics the human, since androgen ablation favored prostatic NE differentiation in both species. The down-regulation elicited by steroids suggests that the process may be reversible and hormonally-repressed.

Neuroendocrine differentiation in human prostate cancer. Morphogenesis, proliferation and androgen receptor status

BACKGROUND

The frequent occurrence of neuroendocrine (NE) differentiation in common prostatic malignancies has attracted increasing attention in contemporary prostate cancer research.

METHODS

The present review focuses on growth properties and the androgen receptor (AR) status of NE phenotypes, and discusses their morphogenetic origin in benign and malignant prostate tissue.

RESULTS

Recent data have documented a phenotype link between NE cells and other cell lineages encountered in benign and malignant prostate tissue. NE tumor cells (as defined by the most commonly used endocrine marker chromogranin A) do not proliferate or show apoptotic activity. This particular phenotype also lacks the nuclear AR in both benign and malignant conditions.

CONCLUSIONS

Prostatic NE cells most likely derive from local stem cells and represent terminally differentiated and androgen-insensitive cell populations in benign prostate tissue. The frequent occurrence of NE differentiation in prostatic adenocarcinoma obviously reflects the differentiation repertoire of its stem cells. Neoplastic NE cells devoid of nuclear AR constitute an androgen-insensitive cell population in prostate cancer. The absence of proliferative and apoptotic activity may endow NE tumor cells with relative resistance towards cytotoxic drugs and radiation therapy.