Prognostic significance of neuroendocrine differentiation in clinically localized prostatic carcinoma

PET radiotracers for whole-body in vivo molecular imaging of prostatic neuroendocrine malignancies

Prostatic neuroendocrine malignancies represent a spectrum of diseases. Treatment-induced neuroendocrine differentiation (tiNED) in hormonally treated adenocarcinoma has been the subject of a large amount of recent research. However, the identification of neuroendocrine features in treatment-naïve prostatic tumor raises a differential diagnosis between prostatic adenocarcinoma with de novo neuroendocrine differentiation (dNED) versus one of the primary prostatic neuroendocrine tumors (P-NETs) and carcinomas (P-NECs). While [18F]FDG is being used as the main PET radiotracer in oncologic imaging and reflects cellular glucose metabolism, other molecules labeled with positron-emitting isotopes, mainly somatostatin-analogues labeled with 68Ga and prostate-specific membrane antigen (PSMA)-ligands labeled with either 18F or 68Ga, are now routinely used in departments of nuclear medicine and molecular imaging, and may be advantageous in imaging prostatic neuroendocrine malignancies. Still, the selection of the preferred PET radiotracer in such cases might be challenging. In the current review, we summarize and discuss published data on these different entities from clinical, biological, and molecular imaging standpoints. Specifically, we review the roles that [18F]FDG, radiolabeled somatostatin-analogues, and radiolabeled PSMA-ligands play in these entities in order to provide the reader with practical recommendations regarding the preferred PET radiotracers for imaging each entity. In cases of tiNED, we conclude that PSMA expression may be low and that [18F]FDG or radiolabeled somatostatin-analogues should be preferred for imaging. In cases of prostatic adenocarcinoma with dNED, we present data that support the superiority of radiolabeled PSMA-ligands. In cases of primary neuroendocrine malignancies, the use of [18F]FDG for imaging high-grade P-NECs and radiolabeled somatostatin-analogues for imaging well-differentiated P-NETs is recommended. KEY POINTS: • The preferred PET radiotracer for imaging prostatic neuroendocrine malignancies depends on the specific clinical scenario and pathologic data. • When neuroendocrine features result from hormonal therapy for prostate cancer, PET-CT should be performed with [18F]FDG or radiolabeled somatostatin-analogue rather than with radiolabeled PSMA-ligand. • When neuroendocrine features are evident in newly diagnosed prostate cancer, differentiating adenocarcinoma from primary neuroendocrine malignancy is challenging but crucial for selection of PET radiotracer and for clinical management.

Deciphering the enigma of neuroendocrine prostate cancer

Despite the clinical advances in managing metastatic prostate cancer in the last 20 years, treatments for patients with metastatic disease only offer a brief respite from disease progression, especially after first-line therapies. Research into treatment resistance has defined a subset of patients with neuroendocrine differentiation of their prostate adenocarcinoma. Although neuroendocrine findings in conjunction with prostate adenocarcinoma can be seen in pathology samples at all stages of disease, the neuroendocrine variant of prostate cancer associated with poor outcomes occurs in approximately 20% of men with advanced disease. In this issue of JCI, Zhao, Sperger, and colleagues present data for a promising biomarker platform that can detect neuroendocrine prostate cancer after serial sampling of patients' blood with a high degree of sensitivity and specificity. This assay will be tested in several current and future trials to better define its potential clinical role and perhaps provide a greater understanding of neuroendocrine prostate cancer itself.

Hidden clues in prostate cancer - Lessons learned from clinical and pre-clinical approaches on diagnosis and risk stratification

The heterogeneity of prostate cancer is evident at clinical, morphological and molecular levels. To aid clinical decision making, a three-tiered system for risk stratification is used to designate low-, intermediate-, and high-risk of disease progression. Intermediate-risk prostate cancers are the most frequently diagnosed, and even with common diagnostic features, can exhibit vastly different clinical progression. Thus, improved risk stratification methods are needed to better predict patient outcomes. Here, we provide an overview of the improvements in diagnosis/prognosis arising from advances in pathology reporting of prostate cancer, which can improve risk stratification, especially for patients with intermediate-risk disease. This review discusses updates to pathology reporting of morphological growth patterns, and proposes the utility of integrating prognostic biomarkers or innovative imaging techniques to enhance clinical decision-making. To complement clinical studies, experimental approaches using patient-derived tumors have highlighted important cellular and morphological features associated with aggressive disease that may impact treatment response. The intersection of urology, pathology and scientific disciplines is required to work towards a common goal of understanding disease pathogenesis, improving the stratification of patients with intermediate-risk disease and subsequently defining optimal treatment strategies using precision-based approaches.

Investigation of the Prognostic Significance of Neuroendocrine Differentiation in Gleason Score 7 to 10 Prostate Adenocarcinoma in Patients With Distant Metastasis After Definitive Radiotherapy

OBJECTIVES

We investigated the prognostic implications of neuroendocrine differentiation (NED) in prostate adenocarcinoma detected by chromogranin A (CgA) in patients who developed distant metastasis (DM) after radiotherapy.

METHODS

Patients with Gleason score 7 to 10 conventional acinar prostate adenocarcinoma treated with definitive radiotherapy and with core biopsy CgA staining completed were reviewed. Patients who developed DM, defined as disease beyond the primary tumor or pelvic lymph nodes, underwent detailed chart review. Statistical analysis included Kaplan-Meier estimates and descriptive statistics to compare based on quantification of CgA staining.

RESULTS

Thirty-five patients had confirmed DM. Twenty-five patients had less than 1% of cells staining positive for CgA, and 10 patients had more than 1%. Median overall survival (OS) time was 3.26 and 1.04 years, respectively (P = .52). Median cause-specific survival (CSS) was 6.15 and 1.04 years, respectively (P = .21). Fifty-six percent of patients with CgA less than 1% died of prostate cancer compared with 90% of those with CgA more than 1% (P = .059). There were no significant differences in sites of metastatic disease or administration of systemic therapies.

CONCLUSIONS

No significant differences in OS and CSS were observed based on NED detected by CgA. Reduced median survival time and increased cancer-related death in cases with focal NED generates the hypothesis of inferior outcomes among patients with documented DM.

Focal Neuroendocrine Differentiation of Conventional Prostate Adenocarcinoma as a Prognostic Factor after Radical Prostatectomy: A Systematic Review and Meta-Analysis

The biologic and prognostic value of focal neuroendocrine differentiation (NED) in conventional prostate adenocarcinoma (PC) patients who undergo radical prostatectomy (RP) remains controversial. In this systematic review and meta-analysis, we assessed the association of focal NED in conventional PC with oncological outcomes after RP. A literature search using PubMed, Scopus, Web of Science, and Cochrane Library was conducted on December 2018 to find relevant studies according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. We used a fixed-effect model to analyze the impact of focal NED in RP specimen on progression-free survival defined by biochemical recurrence (BCR). A total of 16 studies with the outcomes of disease progression and survival were eligible. No patient in these studies received androgen deprivation therapy prior to RP. Eleven studies found no significant correlation between focal NED and outcomes of interest, while five studies reported a significant association of focal NED assessed by immunohistochemical chromogranin A or serotonin staining with BCR or survival. Focal NED was associated with higher BCR rates after RP with a pooled HR of 1.39 (95% CI 1.07‒1.81) in five studies. No heterogeneity was reported in this analysis (I² = 21.7%, p = 0.276). In conclusion, focal NED in conventional PC is associated with worse prognosis after RP. Its presence should be reported in pathologic reports and its true clinical impact should be assessed in well-designed prospective controlled studies.

MicroRNAs in prostate cancer: From function to biomarker discovery

MicroRNAs (miRNAs) are a small functional non-coding RNAs that post-transcriptionally regulate gene expression through mRNA degradation or translational repression. miRNAs are key regulatory components of various cellular networks. Current evidence support that multiple mammalian genome-encoded miRNAs impact the cellular biology, including proliferation, apoptosis, differentiation, and tumorigenesis, by targeting specific subsets of mRNAs. This minireview is focused on the current themes underlying the interactions between miRNAs and their mRNA targets and pathways in prostate tumorigenesis and progression, and their potential clinical utility as biomarkers for prostate cancer. Impact statement The primary goal of this article was to review recent literature on miRNA biogenesis and further elaborate on the identity of newly discovered miRNAs and their potential functional significance in the complex biological network associated with prostate tumorigenesis and disease progression and as biomarkers for prostate cancer.

The Possible Role of Chromogranin A as a Prognostic Factor in Organ-Confined Prostate Cancer

The clinical significance of neuroendocrine differentiation in patients who have undergone surgery for localized prostate cancer is still unclear. The aims of this study were to assess the relationship between serum neuroendocrine markers and well-known prognostic factors in prostate cancer (pathological staging, definitive Gleason score and serum PSA) and to search for correlations between serum chromogranin A (CgA) levels and pathological findings.

Forty-one consecutive patients who had undergone radical retropubic prostatectomy for clinically localized prostate cancer were evaluated. Serum PSA, CgA and neuron-specific enolase were measured immediately before surgery. Twenty-six surgical specimens were phenotypically and immunohistochemically evaluated using an antibody against CgA.

Significant correlations were found between serum CgA, pathological staging and Gleason score (p=0.049 and p=0.038, respectively). Serum CgA did not correlate with PSA, patient age, or immunohistochemical findings. There was a significant correlation between positive immunohistochemical CgA staining and Gleason score (p=0.014).

An increase in serum CgA levels, independent of PSA values, might be the expression of pathologically more advanced tumor stage and higher Gleason score; this could help to identify a high-risk patient group eligible for adjuvant therapy.

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.

[Management of neuroendocrine prostate carcinoma: Literature review]

Neuroendocrine prostate carcinoma is a rare entity causing both diagnostic and therapeutic issues. There are basically four histological forms (adenocarcinoma with neuroendocrine differentiation, carcinoid tumors, small cell neuroendocrine carcinomas, large cell neuroendocrine carcinomas), which can be pure or mixed associated with prostatic carcinoma. There is no consensus on the management or the prognosis of these various tumor subtypes. We conducted a literature review aiming to determine the potential therapeutic implications.

Neuroendocrine Tumors of the Prostate: Emerging Insights from Molecular Data and Updates to the 2016 World Health Organization Classification

Neuroendocrine neoplasms of the prostate represent a multifarious group of tumors that exist both in pure forms and associated with prostatic adenocarcinoma. Morphologically, neuroendocrine cells in prostate neoplasms can range from being indistinguishable from surrounding prostate adenocarcinoma cells to having high-grade neuroendocrine appearances similar to neuroendocrine malignancies of other organs. On the molecular level, neuroendocrine malignancies arising in the setting of prostate adenocarcinoma have been the subject of a large amount of recent research, most of which has supported the conclusion that neuroendocrine malignancy within the prostate develops as a transdifferentiation from prostate adenocarcinoma. There has not, however, been substantial investigation into rare, pure neuroendocrine malignancies and the possibility that these tumors may have a different cell of origin and molecular genesis. Here, we discuss the morphologic spectrum of malignant neuroendocrine prostate neoplasms and review the most recent molecular data on the subject of malignant neuroendocrine differentiation in prostatic adenocarcinoma. In reflection of the most recent data, we also discuss diagnostic classification of prostate neuroendocrine tumors with reference to the 2016 World Health Organization (WHO) classification. We discuss the reporting of these tumors, placing emphasis on the differentiation between pure and mixed neuroendocrine malignancies so that, in the least, they can be easily identified for the purposes of future clinical and laboratory-based investigation. Finally, we suggest a designation for an unclassifiable (or not otherwise specified) high-grade neuroendocrine prostate malignancy whose features do not easily place it into one of the WHO diagnostic entities.

Chromogranin A is a potential prognostic marker in prostate cancer patients treated with enzalutamide

BACKGROUND

In this retrospective study, we assessed chromogranin A (CgA) baseline value as a possible factor associated with poor prognosis in metastatic castration-resistant prostate cancer (CRPC).

METHODS

Thirty-five patients with metastatic CRPC progressing after docetaxel chemotherapy treated with enzalutamide are subdivided into three groups: serum CgA level was normal when <120 ng/ml (group A, n = 10), within three times the upper normal value (UNV) when between 120 and 360 (group B, n = 17), more than three times the UNV when ≥360 ng/ml (group C, n = 8).

RESULTS

No correlation was observed in three groups among CgA baseline values and PSA response rates (RR) (P = 0.4648), whereas a significative difference was associated with median progression-free survival (PFS) and overall survival (OS) among three CgA groups (P = 0.0301 and P = 0.0011, respectively). In the multivariate analysis, PSA RR (nonresponsive vs. responsive) and CgA levels (group 3 vs. groups 1 + 2) were predictors of OS (P = 0.0029 and P = 0.0025, respectively), whereas they only were not significantly correlated with PFS, even had a borderline significance (P = 0.0628 and P = 0.0772, respectively).

CONCLUSIONS

In CRPC patients treated with enzalutamide, the evaluation of serum CgA levels could be an useful prognostic factor because of the strong association between CgA value more than three times the UNV and clinical outcome, independently from PSA response.

Small cell carcinoma of the prostate

Pure small-cell carcinoma (SCC) of the prostate is a rare entity and one of the most aggressive malignancies of the prostate. Histologically, prostatic SCCs of the prostate are part of a spectrum of anaplastic tumours of the prostate and are similar to SCCs of the lungs. In most cases, SCC of the prostate is associated with conventional prostatic adenocarcinoma. Both components of these mixed tumours frequently share molecular alterations such as ERG gene rearrangements or AURKA and MYCN amplifications, suggesting a common clonal origin. The clinical behaviour of small-cell prostate carcinomas is characterized by extensive local disease, visceral disease, and low PSA levels despite large metastatic burden. Commonly, the emergence of the SCC occurs in patients with high-grade adenocarcinoma who are often treated with androgen deprivation treatment (ADT). However, SCCs do not usually benefit from ADT. A biopsy of accessible lesions is strongly recommended to identify those with SCC pathological features, as management is undoubtedly affected by this finding. Chemotherapy is the standard approach for treating patients with either localized or advanced prostatic SCC. Despite the emergence of more-aggressive treatment modalities, the prognosis of men with prostatic SCC remains dismal.

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.

Neuroendocrine tumor cells in prostate cancer: evaluation of the neurosecretory products serotonin, bombesin, and gastrin - impact on angiogenesis and clinical follow-up

BACKGROUND

Neuroendocrine differentiated tumor cells (NETC) can be found in a large portion of prostate carcinoma (PCa) specimens. This is the first study to systematically quantify and analyze the influence of the NETC distribution and of their secretory products, serotonin, bombesin, and gastrin, on angiogenesis and in the clinical follow-up of PCa patients.

METHODS

175 PCa specimens were included in this study. NETC were displayed using the marker CgA. Specimens showing a high expression of CgA were analyzed for serotonin, bombesin, and gastrin. Blood vessels were stained with the epitope CD34. Data was analyzed for inter-correlation and its correlation to clinical-pathological parameters and the results of a mid-term follow-up.

RESULTS

The number of NETC was correlated with the pT-status and the Gleason score. Specimens with high NETC expression had an increased microvessel density (MVD). No correlation between the neurosecretory products and the clinical-pathological parameters was found. High NETC expression, high bombesin expression and increased MVD were associated with early treatment failure in the follow-up.

CONCLUSION

NETC have an influence on angiogenesis and are correlated with the clinical-pathological parameters. A high expression of NETC is associated with an early failure of treatment. Our study underlines the importance of NETC in prostate cancer.

The prognostic role of immunohistochemical chromogranin a expression in prostate cancer patients is significantly modified by androgen-deprivation therapy

BACKGROUND

Several data suggest that neuroendocrine (NE) differentiation in prostate cancer is implicated in the development of resistance to androgen-deprivation therapy (ADT). This study was undertaken to assess the prognostic role of tissue chromogranin A (CgA) expression in patients addressed to ADT as opposed to those who did not.

METHODS

Four hundred fourteen newly diagnosed prostate cancer patients, consecutively recruited in a single institution, entered the study. Two hundred fourteen patients received ADT early after diagnosis, 200 did not. Median follow-up was 85 months. CgA expression was evaluated immunohistochemically in prostate cancer needle biopsies.

RESULTS

In multivariate analysis after adjusting for Gleason score, serum PSA, disease stage and local treatments, tissue CgA expression in overall cases was significantly associated with a shorter survival (P = 0.009) but failed to be associated with PSA progression (P = 0.10). Dividing patients according to whether they received immediate ADT or not, tissue CgA was associated with a shorter time to PSA progression in ADT-treated patients (hazard ratios (HR) 1.96, 95% confidence interval (CI): 1.37-2.81, P = 0.0001), but failed to be associated in those who did not (HR 0.87, 95% CI: 0.58-1.30, P = 0.49), interaction test P = 0.007. Conversely the survival effect of tissue CgA was not modified by ADT (interaction test, P = 0.41).

CONCLUSIONS

Tissue CgA expression, evaluated in prostate cancer needle biopsies at diagnosis, is an independent prognostic factor of survival in prostate cancer patients. The negative influence of NE differentiation on time to progression confined in ADT-treated patients suggests a role of NE differentiation in predicting endocrine resistance that deserves validation.

Correlation of three immunohistochemically detected markers of neuroendocrine differentiation with clinical predictors of disease progression in prostate cancer

BACKGROUND

The importance of immuno-histological detection of neuroendocrine differentiation in prostatic adenocarcinoma with respect to disease at presentation and Gleason grade is gaining acceptance. There is limited literature on the relative significance of three commonly used markers of NE differentiation i.e. Chromogranin A (CgA), Neuron specific enolase (NSE) and Synaptophysin (Syn). In the current work we have assessed the correlation of immuno-histological detection of neuroendocrine differentiation in prostatic adenocarcinoma with respect to disease at presentation and Gleason grade and to determine the relative value of various markers.

MATERIALS AND METHODS

Consecutive samples of malignant prostatic specimens (Transurethral resection of prostate or radical retropubic prostatectomy) from 84 patients between January 1991 and December 1998 were evaluated by immunohistochemical staining (PAP technique) using selected neuroendocrine tumor markers i.e. Chromogranin A (CgA), Neuron specific enolase (NSE), and Synaptophysin (Syn). According to the stage at diagnosis, patients were divided into three groups. Group (i) included patients who had organ confined disease, group (ii) included patients with locally invasive disease, and group (iii) with distant metastasis. NE expression was correlated with Gleason sum and clinical stage at presentation and analyzed using Chi-Square test and one way ANNOVA.

RESULTS

The mean age of the patients was 70 +/- 9.2 years. Group I had 14 patients, group II had 31 patients and group III had 39 patients. CgA was detected in 33 cases, Syn in 8 cases, and NSE in 44 cases. Expression of CgA was seen in 7% of group I, 37% in group II and 35% of group III patients (p 0.059). CgA (p 0.024) and NSE (p 0.006) had a significantly higher expression with worsening Gleason grade.

CONCLUSION

CgA has a better correlation with disease at presentation than other markers used. Both NSE and CgA had increasing expression with worsening histological grade this correlation has a potential for use as a prognostic indicator. Limitations in the current work included small number and retrospective nature of work. The findings of this work needs validation in a larger cohort.

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.

Irradiation enhances the metastatic potential of prostatic small cell carcinoma xenografts

BACKGROUND

Small cell carcinoma of the prostate (SCCP) is a rare subset of prostate cancer (0.5-2% of all prostatic carcinomas), predominantly composed of neuroendocrine (NE) cells, with a very poor prognosis. Irradiation is one of the mainstay options for SCCP local treatment, yet, little is known about the clinical response of these aggressive tumors to radiotherapy.

METHODS

Using SCID mice, the response to fractionated ionizing radiation (IR) of two unique human NE xenografts of SCCP (WISH-PC2 and WM-4A) was investigated.

RESULTS

Fractionated irradiation of WISH-PC2 xenografts using total doses of >24 Gy induced a delay in tumor growth, while total doses of >36 Gy led to local tumor eradication. However, most of the irradiated mice suffered from disseminated metastases. Similarly, in the WM-4A xenograft, a total dose of 20 Gy led to tumor growth delay and some of the mice also developed metastases. Non-irradiated local xenografts failed to disseminate, even following surgical excision of the main tumor mass; however, tumor cells administered intravenously did form metastases. Metastases of both xenografts were located in the adrenal/kidney and inter-scapular regions, areas rich in brown adipose tissue. A correlation was found between the appearance of irradiation-induced metastases and activation of the gelatinase activity of matrix metalloproteinase-9.

CONCLUSIONS

Clinically, this study raises the possibility that radiation to SCCP may promote metastatic disease. For patients in whom prostate biopsy shows a predominance of small cell cancer, it may be necessary to deliver systemic therapy together with the radiotherapy in order to prevent the development of metastases.

Chromogranin A expression in patients with hormone naïve prostate cancer predicts the development of hormone refractory disease

PURPOSE

We assessed chromogranin A as a tissue biomarker in prostate needle biopsies or as a plasma biomarker, a risk factor for hormone refractory prostate cancer.

MATERIALS AND METHODS

A total of 211 patients with newly diagnosed prostate cancer treated with luteinizing hormone releasing hormone analogues constituted the study cohort. Univariate and multivariate Cox regression analyses were used to assess the predictive role of tissue and plasma chromogranin A expression.

RESULTS

Chromogranin A expression in less than 30% or in 30% or more tumor cells was significantly associated with a shorter time to hormone refractory disease on univariate analysis (HR 2.0, 95% CI 1.3-3.1 and HR 6.0, 95% CI 2.7-12.9), or on multivariate analysis after adjusting for Gleason score, serum prostate specific antigen and disease stage (HR 1.7, 95% CI 1.0-2.8 and HR 3.9, 95% CI 1.7-9.0), respectively. Plasma chromogranin A measured at baseline (HR 3.0, 95% CI 1.8-5.2), and after 1 year (HR 5.8, 95% CI 3.1-10.1) and 2 years (HR 3.5, 95% CI 1.6-7.6), was predictive of hormone refractory risk confirming the tissue results. Plasma as well as tissue chromogranin A expression negatively correlated with overall survival.

CONCLUSIONS

Chromogranin A expression in prostate cancer biopsies is an independent predictive factor of hormone refractory disease in patients with newly diagnosed prostate cancer on early androgen deprivation therapy. Plasma chromogranin A is also a reliable predictive marker and the predictive significance is maintained over time. These results deserve validation in another data set.

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.

Molecular markers in the diagnosis of prostate cancer

The genetic alterations leading to prostate cancer are gradually being discovered. A wide variety of genes have been associated with prostate cancer development as well as tumor progression. Knowledge of gene polymorphisms associated with disease aid in the understanding of important pathways involved in this process and may result in the near future in clinical applications. Urinary molecular markers will soon be available to aid in the decision of repeat prostate biopsies. Recent findings suggest the importance of androgen signaling in disease development and progression. The further understanding of interaction of inflammation, diet, and genetic predisposition will improve risk stratification in the near future.

Murine androgen-independent neuroendocrine carcinoma promotes metastasis of human prostate cancer cell line LNCaP

BACKGROUND

Although neuroendocrine (NE) cells in prostate cancer have been speculated to accelerate the growth and progression of surrounding cancer cells, the evidence is as yet inconclusive. We investigated the effect of an NE allograft (NE-10) and its cell line, NE-CS, which were established from the prostate of the LPB-Tag 12T-10 transgenic mouse, on human prostate cancer cell line LNCaP.

METHODS

The proliferation and pulmonary metastasis of LNCaP xenografts in athymic mice with and without NE-10 allografts were evaluated. Boyden chamber assay and microarray analysis were performed to investigate changes in invasion/migration and mRNA of LNCaP cells under the influence of the NE cells, respectively.

RESULTS

NE-10 did not influence the proliferation of LNCaP. The pulmonary metastasis of LNCaP with NE-10 significantly increased compared to mice without it. The NE-CS cells accelerated the in vitro invasion/migration of adenocarcinoma cells. Increased expression of mRNA of gelsolin was observed in LNCaP cells incubated with the supernatant of NE-CS cells.

CONCLUSIONS

The NE-10 allograft promotes pulmonary metastasis of subcutaneously inoculated LNCaP cells by facilitating cell invasion. Secretions from NE cells upregulate the expression of gelsolin, which is an actin-binding protein, resulting in acceleration of the migration of LNCaP cells.

Skewing Towards Neuroendocrine Phenotype in High Grade or High Stage Androgen-Responsive Primary Prostate Cancer

OBJECTIVE

The prognostic influence of neuroendocrine (NE) differentiation in prostate cancer patients is not yet properly established. In a series of primary hormone-naive prostate cancers from a patient population that underwent radical prostatectomy, we wanted to determine the relationship between NE phenotype expression and Gleason sum, disease stage, and serum PSA concentration.

METHODS

Chromogranin A (CgA) expression was scored and compared in 105 consecutive primary prostate cancers with their homologous preoperative tumor prostate biopsies.

RESULTS

High grade or high stage prostate cancers expressed a significantly higher CgA score than low grade or localized diseases (p < 0.005). Both the CgA score of the surgical specimens and the PSA level in the serum increased linearly (p = 0.001). In the samples of many corresponding tumor biopsies no significant CgA staining was found.

CONCLUSION

NE differentiation in primary untreated prostate cancer is closely associated with the major prognostic parameters of survival. This association cannot be shown by evaluating the CgA staining in tumor biopsies.

Neuroendocrine differentiation in prostate cancer: implications for new treatment modalities

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

M3 subtype of muscarinic receptors mediate Ca2+ release from intracellular stores in rat prostate neuroendocrine cells

Our previous studies document the expression of adrenoceptors and purinoceptors in the rat prostate neuroendocrine cells (RPNECs). However, a direct investigation of the receptors for acetylcholine (ACh) is still lacking in the prostate neuroendocrine cells. RPNECs were freshly isolated from the ventral lobes of rat prostate by using collagenase. Effects of ACh and various muscarinic antagonists on the intracellular Ca(2+) concentration ([Ca(2+)](c)) were investigated by using the fura-2 spectrofluorimetry. Single-cell RT-PCR analysis was applied to identify the transcripts for the muscarinic receptor subtypes. ACh (5 microM) induced a sharp transient increase in the [Ca(2+)](c) of RPNECs, which was independent of the extracellular Ca(2+). In the same RPNECs, high KCl (60 mM), phenylephrine (5 microM), UTP (P2Y(1/2) agonist, 50 microM), and alpha, beta-meATP (P2X(1/3) agonist, 0.5 microM) also increased the [Ca(2+)](c). The ACh-induced [Ca(2+)](c) change (delta [Ca(2+)](c)) was blocked by atropine or by para-fluorohexahydrosiladifenidol (M(3) antagonist, 0.3 microM), but not by telenzepine (M(1) antagonist, 1 microM) and himbacine (M(2) and M(4) antagonist, 1 microM). The single-cell RT-PCR demonstrated the selective expression of mRNAs for M(3) in RPNECs. In summary, RPNECs express M(3) muscarinic receptors that are linked to the release of Ca(2+) from intracellular stores. The Ca(2+) signals of RPNECs might mediate the parasympathetic regulation of prostate gland.

Evidence of pluripotent human prostate stem cells in a human prostate primary xenograft model

INTRODUCTION

The phenotypic plasticity of the human prostate stem cell within human prostate tissue was examined to determine the response of the stem cell to changes in the androgenic environment.

METHODS

Prostate xenografts were transplanted into athymic nu/nu mice implanted with testosterone pellets, allowed to establish for 1 month time point, the hosts were castrated and pellets removed, and following 1 month of androgen deprivation, the hosts were stimulated with androgen for 2 days to induce proliferation of the residual population of stem cells (2-month time point).

RESULTS

Glands in benign xenografts harvested at the 1- and 2-month time points contained basal cell layers that expressed p63 and high molecular weight cytokeratin, and in which essentially all of the cellular proliferation was localized, consistent with the proposed localization of the prostate stem cell. Benign glandular structures in the xenografts were populated by basal, secretory epithelial, neuroendocrine (NE), or squamous cells overlaying the basal cell layer, whereas, adenocarcinoma glands in the xenografts resembled the original prostate cancer (CaP) tissue.

CONCLUSIONS

In this human prostate primary xenograft model, the residual stem cell population that survives transplantation, or androgen deprivation, maintains significant pluripotentiality as demonstrated by the capacity to generate progeny that differentiate along multiple lineages in response to microenvironmental signals, particularly along the secretory epithelial lineage in response to androgen, and along the NE cell lineage in response to androgen deprivation.

Clinical understaging in patients with prostate adenocarcinoma submitted to radical prostatectomy: predictive value of serum chromogranin A

PURPOSE

To evaluate whether the pretreatment determination of serum chromogranin A (CgA) can provide information beyond that obtained with serum prostate specific antigen (PSA) and Gleason score at biopsy as a predictive factor of clinical understaging (T2-pT3) of prostate adenocarcinoma.

MATERIALS

In this prospective study, we analyzed 83 consecutive patients with clinical T2N0M0 prostate adenocarcinoma submitted to radical prostatectomy (RRP). On the same day of RRP, before surgery, a blood sample for the determination of serum total PSA and CgA levels (RIA) was obtained.

RESULTS

After RRP, 27 of the 83 cases (32.5%) showed extracapsular disease extension (pT3) at the final pathological examination and were considered clinically understaged. A significant association between serum CgA and pathological stage (r = 0.3830; P = 0.0004) was found. At the multivariate analysis, serum CgA and PSA, but not biopsy Gleason score, were found to be significant pretreatment independent predictors of pT3 at RRP (P = 0.00004 and P = 0.0018, respectively). The relative risk of clinical understaging significantly varied according to serum CgA levels. Using a CgA cut-off value of 60 ng/ml, PPV and NPV for clinical understaging were 0.5161 and 0.7885, respectively (P = 0.0072).

CONCLUSIONS

Serum CgA could be incorporated into risk assessment models of newly diagnosed prostate cancer.

Canine prostatic intraepithelial neoplasia: is the comparative model relevant?

BACKGROUND

Histologic sections from an archival collection of a veterinary teaching hospital were examined to determine the likelihood of detection of canine high-grade prostatic intraepithelial neoplasms (HGPIN), as a prelude to use of the canine model of prostatic carcinogenesis for chemopreventive strategies.

METHODS

Tissue specimens representing clinically healthy (normal) prostate glands, benign prostatic hyperplasia, and prostatic carcinoma were examined in one tissue plane for histological evidence of HGPIN.

RESULTS

No histological evidence of HGPIN was detected in 20 normal prostate glands or 95 prostate glands with benign prostatic hyperplasia. Seven of 20 prostatic carcinomas had synchronous HGPIN.

CONCLUSIONS

Histological evidence of HGPIN is unlikely to be detected in the healthy or hyperplastic canine prostate gland with the clinically-procured biopsy. This might diminish the usefulness of canine HGPIN in temporal studies of chemoprevention of prostate cancer. HGPIN was found simultaneously with prostatic carcinoma in more than one-third of the carcinomas examined.

Adrenergic regulation of the intracellular [Ca2+] and voltage-operated Ca2+ channel currents in the rat prostate neuroendocrine cells

BACKGROUND

The prostate gland contains numerous neuroendocrine cells (PNECs) innervated by adrenergic neurons. PNECs are believed to influence the growth and physiological function of the prostate gland via paracrine release of hormones.

MATERIALS AND METHODS

Using fura-2 fluorescence measurement and patch-clamp techniques, we investigated the effects of adrenergic stimulation on cytosolic concentration of Ca2+ ([Ca2+]c) and high voltage-activated Ca2+ channel currents (HVA-I(Ca)) of the putative rat prostate neuroendocrine cells (RPNECs) freshly isolated by an enzymic digestion.

RESULTS

Noradrenaline (NA, 1 microM) induced a sharp, transient increase of [Ca2+]c measured by the fura-2 fluorescence. Pharmacological studies showed that alpha1-adrenoceptors (alpha1-ARs) coupled with PLC/IP3 signaling pathway induce the release of stored Ca2+, which subsequently recruits store-operated Ca2+ entry pathways. In the whole-cell voltage clamp experiment, NA decreased the amplitude of HVA-I(Ca) by 40%, which was mimicked by an alpha2-AR agonist (UK14304) but not by an alpha1-AR agonist (phenyleprine). After selective blockade of N-type Ca2+ channels by omega-conotoxin GVIA, the addition of NA showed no further inhibition on the remaining L-type Ca2+ channel currents. The adrenergic inhibition of HVA-I(Ca) was partially prevented by the pretreatment with pertussis toxin (PTX) (5 microg/ml, 4 hr, 37 degrees C).

CONCLUSIONS

RPNECs express both alpha1- and alpha2-ARs, signaling the release of stored Ca2+ and the inhibition of N-type Ca2+ channels, respectively.

Relationship between neuroendocrine features and prognostic parameters in human prostate adenocarcinoma

PURPOSE

The biological behaviour of prostate cancer is highly variable and prediction by the commonly employed prognostic parameters is not sufficient. The concept of neuroendocrine (NE) differentiation in prostate adenocarcinoma has recently received increasing attention due to possible implications for prognosis and therapy.

MATERIALS AND METHODS

Core needle biopsies from 142 newly diagnosed patients were immunohistochemically examined for the coexistence of NE differentiation using an antibody against chromogranin A (CgA). Circulating CgA was available in 106 of these patients.

RESULTS

NE differentiation was found in 64 (45.1%) tumors. Among them 29 (20.4%) had CgA positive cells scattered or focally distributed in less than 5% per mm3 of tumor tissues, 26 (18.3%) between 5% and 10% and 9 (6.4%) more than 10%, respectively. There was a significant correlation between the extent of NE features and either Gleason score (P < 0.01) or stage of disease. Circulating CgA but not PSA correlated with immunohistochemical CgA (P < 0.03) particularly in metastatic cases.

CONCLUSIONS

These data support the concept that NE differentiation in human prostate cancer has a negative prognostic significance. Circulating CgA levels reflect immunohistochemical findings.

Neuroendocrine differentiation and prognosis in breast adenocarcinoma

AIMS

Neuroendocrine differentiation has been detected, and its prognostic value studied, in a number of common human carcinomas. To date there are few detailed studies examining its relevance in breast carcinoma. In this study we evaluate the frequency and prognostic importance of neuroendocrine differentiation in breast adenocarcinoma.

METHODS AND RESULTS

The presence of neuroendocrine differentiation, defined as positive reactivity for three markers, neuron-specific enolase (NSE), chromogranin A and/or synaptophysin, has been evaluated in 99 patients with primary operable breast cancer using standard immunocytochemical techniques. A consecutive cohort of patients were selected from the Nottingham/Tenovus series. Comprehensive patient and tumour records have been maintained, and patients were followed up according to a defined protocol. Eighteen cases were positive for NSE, 10 for chromogranin A and 13 for synaptophysin. Eleven percent were positive with more than one neuroendocrine marker. No significant association was found between neuroendocrine differentiation and tumour size, grade, stage or the prevalence of vascular invasion. There was no significant difference in either overall or disease-free survival between patients with or without neuroendocrine differentiation.

CONCLUSIONS

In this study we confirm that neuroendocrine differentiation can be identified in a subset (10-18%) of human breast carcinomas. This phenomenon appears to have no relationship to established prognostic factors or patient outcome.

Progression of prostate cancer to neuroendocrine cell tumor

BACKGROUND

The progression to endocrine therapy-resistant prostate cancer is partly due to clonal change to neuroendocrine cell tumor. To elucidate this pathologic process, the clinical courses of four cases of neuroendocrine cell tumor that were found at autopsy are reported.

METHODS

Between 1995 and 1999, autopsies were performed for 20 cases of prostate cancer. Lesions predominantly composed of a neuroendocrine cell tumor (small cell carcinoma) were found in four men. The clinical courses of these cases were compared to 16 other non-neuroendocrine cell tumors (adenocarcinomas).

RESULTS

The outstanding features of the neuroendocrine cell tumors were: (i) survival was brief after relapse, although the duration of control by employing endocrine therapy varied; (ii) the prostate-specific antigen level did not increase after relapse; and (iii) the sites of metastasis were similar to those of common adenocarcinomas.

CONCLUSION

The progression to a neuroendocrine cell tumor indicated a poor prognosis and slight (if any) changes in the serum prostate-specific antigen level. This tumor might not appear to respond to any therapeutic attempt.

Pathologic assessment of the surgical specimen

Despite the wealth of information obtained by conventional histology, long-term studies are needed to provide novel information on the correlation of pathologic findings with prognosis. Findings need to be correlated not only with PSA progression but with the more clinically important parameters of distant metastases and survival. Although conventional histology still will have a role in the evaluation of prostate cancer at radical prostatectomy and its correlation with outcome, it undoubtedly will be augmented by newer techniques. These developments must be approached critically and rationally to determine whether they provide additional prognostic information beyond that currently available using more conventional parameters.

Neuroendocrine cells in human prostate over-express the anti-apoptosis protein survivin

BACKGROUND

Neuroendocrine (NE) differentiation may be related to the growth and progression of prostate cancer, especially androgen-insensitive tumors. Recently the over-expression of a new anti-apoptosis protein, survivin, has attracted attention for its potential implication in many human cancers. The fact that NE cells in prostate are bcl-2 negative prompted us to investigate if the prostatic NE cells over-express survivin.

METHODS

Double immunohistochemical staining and immunofluorescence of chromogranin A (CgA) and survivin were performed in 57 patients with localized prostate cancer who underwent radical prostatectomy. The terminal deoxynucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end-labeling (TUNEL) method was used for apoptosis detection in three prostate cancer specimens with NE differentiation. The relationship between NE differentiation and clinicopathological characteristics, disease progression as well as patient survival, were analyzed retrospectively.

RESULTS

It was found that NE cells in both benign and malignant prostate tissues over-expressed the anti-apoptosis protein survivin. While apoptosis was detected in non-NE epithelial cells, all NE cells were negative for apoptosis detection. During the period of follow-up, 17 (63%) of 27 patients with NE differentiation had prostate cancer progression, while 12 (40%) of 30 patients without NE differentiation had systemic prostate cancer progression. 10 (37%) of 27 patients with NE differentiation died from prostate cancer during the period of follow up, while 6 (20%) of 30 patients without NE differentiation died from prostate cancer. However, none of these characteristics reached statistical significance, probably because of the small number of cases enrolled.

CONCLUSIONS

This study discovers that all the prostatic NE cells express the new anti-apoptosis protein survivin. This provides a strong molecular basis for the hypothesis that NE cells may endure stressful conditions and escape from apoptosis. While our results suggest a trend of NE differentiation with poorer prognosis, the prognosis implication cannot be concluded due to our small sample size.

Prognostic value of neuroendocrine serum markers and PSA in irradiated patients with pN0 localized prostate cancer

BACKGROUND

The prognosis of patients with localized prostate cancer depends on clinical stage, histological grade, and pretreatment prostate-specific antigen (PSA). We evaluated the additional prognostic impact of serum levels of neuron-specific enolase (NSE) and chromograninA (CgA) after curative radiotherapy and the importance of serum PSA, analyzed 3 months after irradiation.

METHODS

From 1988 to 1995, 161 patients with localized T1-4, pN0M0, prostate adenocarcinoma were treated with external radiation (66Gy, 2Gy/5 fractions per week). Frozen serum samples were assessed for CgA, NSE, and PSA before and 3 months after radiotherapy. CgA was analyzed in only 100 patients. NSE and CgA were determined by a immunometric assay. Total PSA was measured by a time-resolved fluoro-immunometric assay.

RESULTS

Prior to radiotherapy CgA was elevated in 16 of 100 patients, and NSE was elevated in 33 of the 161 patients. There was no association between grade, T category or pretreatment PSA and the levels of neuroendocrine markers. Pretreatment-elevated serum NSE, but not initial CgA, identified patients with an unfavorable prognosis. A < 50% reduction of PSA 3 months after radiotherapy was associated with decreased failure-free 10 years urvival. Multivariate analysis demonstrated an increased risk of failure for patients with elevated pretreatment NSE and PSA values, T3 category, and decline of PSA less than 50% 3 months after radiotherapy. The presence of none or several risk factors (1-4) defined clearly separable groups.

CONCLUSIONS

Together with T category and pretreatment serum PSA values, serum NSE values before radiotherapy and decrease of serum PSA 3 months after radiotherapy represent easily assessable prognostic parameters in patients undergoing curative radiation treatment for prostate cancer.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Prostate tumor progression and prognosis. interplay of tumor and host factors

The prognosis for prostate cancer is largely dependent on the probability of metastatic dissemination. Prognostic markers currently in use are very poor predictors of metastatic potential, and as of yet none of the battery of new molecular markers has proven greatly superior. This may be due in part to their inability to assess the degree of interaction of subpopulations of prostate cancer cells with each other and with their microenvironment. A growing body of evidence indicates that these types of interactions are a major factor in the eventual genesis of cancer cells capable of metastasis. Recent research has demonstrated that specialized components of prostate tumors may play a critical supporting role for the overall growth of the larger tumor. The multifocal nature and apparent polyclonal origins of prostate tumors suggest that carcinogenesis and tumor progression are promoted by global influences or "field effects." It appears that these effects extend beyond the proliferating epithelial component to the tissue stroma. Prostate cancer cells and stromal cells seem to act in concert to modify the microenvironment, leading to metastasis. An understanding of this synergy may provide a new class of prognostic markers which more accurately measure the complex set of interactions that determine tumor behavior.

[Effect of the neuropeptides bombesin and calcitonin on the growth of prostate cell lines, PC-3, DU 145, and LNCaP]

Neuroendocrine cells are present in normal and tumoral prostate tissue, the neuropeptides secreted by this cells have a biological functions that have not been fully elucidated. The presence of neuroendocrine cells in prostatic carcinoma have been shown to increase tumor progression. We characterized the in vitro proliferative influence of bombesin and calcitonin in androgen-insensitive, PC-3 and DU-145, and androgen-sensitive, LNCaP, cell lines of human prostate cancers. The influence of these neuropeptides on proliferation were assessed using the colorimetric XTT assay and by cells counts with a hemocytometer. The growth of PC-3 and DU-145 cell lines is stimulated by bombesin and calcitonin but exerted any stimulatory effect on the proliferation of the LNCaP cell line. This indicate that bombesin and calcitonin can modulate proliferation of androgen-insensitive human prostate cell lines "in vitro" and may be potential paracrine growth promoters in stablished androgen irresponsive human prostatic carcinoma cells.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Neuroendocrine differentiation in prostatic carcinoma

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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