Regressive changes and neuroendocrine differentiation in prostate cancer after neoadjuvant hormonal treatment

Prostate Cancer Stem Cells: Biology and Treatment Implications

Stem cells differentiate into mature organ/tissue-specific cells at a steady pace under normal conditions, but their growth can be accelerated during the process of tissue healing or in the context of certain diseases. It is postulated that the proliferation and growth of carcinomas are sustained by the presence of a vital cellular compartment resembling stem cells residing in normal tissues: 'stem-like cancer cells' or cancer stem cells (CSCs). Mutations in prostate stem cells can lead to the formation of prostate cancer. Prostate CSCs (PCSCs) have been identified and partially characterized. These express surface markers include CD44, CD133, integrin α2β1, and pluripotency factors like OCT4, NANOG, and SOX2. Several signaling pathways are also over-activated, including Notch, PTEN/Akt/PI3K, RAS-RAF-MEK-ERK and HH. Moreover, PCSCs appear to induce resistance to radiotherapy and chemotherapy, while their presence has been linked to aggressive cancer behavior and higher relapse rates. The development of treatment policies to target PCSCs in tumors is appealing as radiotherapy and chemotherapy, through cancer cell killing, trigger tumor repopulation via activated stem cells. Thus, blocking this reactive stem cell mobilization may facilitate a positive outcome through cytotoxic treatment.

Nomogram for predicting the biochemical recurrence of prostate cancer after neoadjuvant androgen deprivation therapy

BACKGROUND

A predictive model for biochemical recurrence (BCR) of prostate cancer (PCa) after neoadjuvant androgen deprivation therapy (nADT) has not been established. This study was aimed at determining multiparameter variables that could be used to construct a nomogram to predict the post-nADT BCR of PCa.

METHODS

Overall, 43 radical prostatectomy specimens from PCa patients who had undergone nADT were collected. Multiparameter variables were analyzed by univariate and then multivariate logistic analyses to identify the independent prognostic factors for predicting BCR. The predictive model was established using Lasso regression analysis.

RESULTS

Univariate logistic analysis revealed six variables, pathology stage; margins; categorization as group A, B, or C; nucleolus grading; percentage of tumor involvement (PTI); and PTEN status were significantly associated with the BCR of PCa (all p < 0.05). Multivariate logistic regression analysis suggested that categorization as group C, severe nucleolus grading, PTI less than or equal to 5%, and PTEN loss were positively correlated with BCR (all p < 0.05). A nomogram comprising the four variables predicting BCR was constructed, and it exhibited good discrimination (AUC: 0.985; specificity: 86.2%; sensitivity: 100%). Calibration plots for the probability of freedom from BCR at 1 and 2 years showed a good match between the prediction by the nomogram.

CONCLUSIONS

We constructed and validated a nomogram to predict the risk of BCR in PCa patients after nADT. This nomogram is a complement to the existing risk stratification systems for PCa, which could have marked implications for clinical decision-making for PCa patients after nADT.

Neoadjuvant radiohormonal therapy for oligo-metastatic prostate cancer: safety and efficacy outcomes from an open-label, dose-escalation, single-center, phase I/II clinical trial

To evaluate the safety and efficacy of neoadjuvant radiohormonal therapy for oligometastatic prostate cancer (OMPC), we conducted a 3 + 3 dose escalation, prospective, phase I/II, single-arm clinical trial (CHiCTR1900025743), in which long-term neoadjuvant androgen deprivation was adopted 1 month before radiotherapy, comprising intensity modulated radiotherapy to the pelvis, and stereotactic body radiation therapy to all extra-pelvic bone metastases for 4-7 weeks, at 39.6, 45, 50.4, and 54 Gy. Robotic-assisted radical prostatectomy was performed after 5-14 weeks. The primary outcome was treatment-related toxicities and adverse events; secondary outcomes were radiological treatment response, positive surgical margin (pSM), postoperative prostate-specific antigen (PSA), pathological down-grading and tumor regression grade, and survival parameters. Twelve patients were recruited from March 2019 to February 2020, aging 66.2 years in average (range, 52-80). Median baseline PSA was 62.0 ng/mL. All underwent RARP successfully without open conversions. Ten patients recorded pathological tumor down-staging (83.3%), and 5 (41.7%) with cN1 recorded negative regional lymph nodes on final pathology. 66.7% (8/12) recorded tumor regression grading (TRG) -I and 25% (3/12) recorded TRG-II. Median follow-up was 16.5 months. Mean radiological progression-free survival (RPFS) was 21.3 months, with 2-year RPFS of 83.3%. In all, neoadjuvant radiohormonal therapy is well tolerated for oligometastatic prostate cancer.

Protein Tyrosine Phosphatases: Mechanisms in Cancer

Protein tyrosine kinases, especially receptor tyrosine kinases, have dominated the cancer therapeutics sphere as proteins that can be inhibited to selectively target cancer. However, protein tyrosine phosphatases (PTPs) are also an emerging target. Though historically known as negative regulators of the oncogenic tyrosine kinases, PTPs are now known to be both tumor-suppressive and oncogenic. This review will highlight key protein tyrosine phosphatases that have been thoroughly investigated in various cancers. Furthermore, the different mechanisms underlying pro-cancerous and anti-cancerous PTPs will also be explored.

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.

68Ga-DOTATATE PET/CT Uptake in Prostate With an Incidental Finding of Prostatic Acinar Adenocarcinoma and Metastatic Neuroendocrine Cancer to the Liver

ABSTRACT

A 69-year-old man with history of metastatic neuroendocrine tumor presented for initial staging with 68Ga-DOTATE PET/CT. 68Ga-DOTATATE PET/CT showed incidental focal increased DOTATATE uptake in the left apical prostate tissue, which was thought to be of benign etiology. Digital rectal examination later was consistent with a palpable nodule along with elevated prostate-specific antigen of 7.0 ng/mL. MRI of prostate demonstrated a 3.8-cm lesion followed by a targeted biopsy that revealed prostatic acinar adenocarcinoma. Chronic inflammatory cell infiltrates were also noted on biopsy, and this may have been the cause of increased DOTATATE uptake seen on 68Ga-DOTATATE PET/CT study.

Neoadjuvant Approaches Prior To Radical Prostatectomy

Patients with high-risk localized prostate cancer benefit from multimodality therapy of curative intent. Androgen-deprivation therapy (ADT) combined with radiation improves survival in this population. However, prior clinical trials of neoadjuvant ADT and surgery failed to consistently demonstrate a survival advantage. The development of novel, more potent hormonal agents presents an opportunity to revisit the potential for neoadjuvant therapy to improve long-term outcomes for patients with localized prostate cancer. We review recent advances in neoadjuvant approaches for prostate cancer and emerging clinical trials data supporting the use of neoadjuvant therapy prior to radical prostatectomy.

Neuroendocrine cells of the prostate: Histology, biological functions, and molecular mechanisms

Prostate cancer (PCa) is a common cause of cancer-related mortality in men worldwide. Although most men are diagnosed with low grade, indolent tumors that are potentially curable, a significant subset develops advanced disease where hormone therapy is required to target the androgen receptor (AR). Despite its initial effect, hormone therapy eventually fails and the tumor progresses to lethal stages even through continued inhibition of AR. This review article focuses on the role of PCa cellular heterogeneity in therapy resistance and disease progression. Although AR-positive luminal-type cells represent the vast majority of PCa cells, there exists a minor component of AR-negative neuroendocrine (NE) cells that are resistant to hormonal therapy and are enriched by the treatment. In addition, it is now well accepted that a significant subset of hormonally treated tumors recur as small cell neuroendocrine carcinoma (SCNC), further highlighting the importance of targeting NE cells in addition to the more abundant luminal-type cancer cells. Although it has been long recognized that NE cells are present in PCa, their underlying function in benign prostate and molecular mechanisms contributing to PCa progression remains poorly understood. In this article, we review the morphology and function of NE cells in benign prostate and PCa as well as underlying molecular mechanisms. In addition, we review the major reported mechanisms for transformation from common adenocarcinoma histology to the highly lethal SCNC, a significant clinical challenge in the management of advanced PCa.

Diagnosis of Mixed Adenoneuroendocrine Carcinoma (MANEC) after Neoadjuvant Chemotherapy for Pancreatic and Gastric Adenocarcinoma: Two Case Reports and a Review of the Literature

Mixed adenoneuroendocrine carcinoma (MANEC) is a rare tumor of the gastrointestinal tract involving both epithelial and neuroendocrine (NE) components, each of which represents at least 30% of the tumor. Because of the low frequency of this histotype, only a few cases have been described. In this report we discuss two cases treated with neoadjuvant chemotherapy: a pancreatic adenocarcinoma and a gastric adenocarcinoma. The histopathological specimens examined after surgery showed an additional NE component with a possible indication of the MANEC histotype. We hypothesize two possible explanations: tumor NE cells are more chemo-resistant than adenocarcinoma cells, and cytotoxic injury induces NE differentiation in tumor cells. The clinical significance and prognostic value of endocrine differentiation, however, remain controversial issues.

Neuroendocrine differentiation in castration resistant prostate cancer. Nuclear medicine radiopharmaceuticals and imaging techniques: A narrative review

BACKGROUND

Androgen Deprivation Therapy (ADT) is the primary treatment for patients suffering from relapsing or advanced prostate cancer (PC). Hormone therapy generally guarantees adequate clinical control of the disease for some years, even in those patients affected by widespread skeletal and soft tissue metastases. Despite ADT, however, most patients treated with hormones eventually progress to castration-resistant prostate cancer (CRPC), for which there are no effective treatments. This clinical reality is an open challenge to the oncologist because of those neoplasms which elaborate neuroendocrine differentiation (NED).

METHODS

An online search of current and past literature on NED in CRPC was performed. Relevant articles dealing with the biological and pathological basis of NED, with nuclear medicine imaging in CRPC and somatostatin treatment in NED were analyzed.

EVIDENCE FROM THE LITERATURE

NED may arise in prostate cancer patients in the late stages of ADT. The onset of NED offers prognostic insight because it reflects a dramatic increase in the aggressive nature of the neoplasm. Several genetic, molecular, cytological and immunohistochemical markers are associated with this transformation. Among these, overexpression of somatostatin receptors, seen through Nuclear Medicine testing, is one of the most studied.

CONCLUSIONS

Preliminary studies show that the overexpression of somatostatin receptors related to NED in CRPC may easily be studied in vivo with PET/CT. This finding offers a potentially useful objective for targeted therapy in CRPC. If the overexpression of SSTRs is shown to afflict a significant segment of patients with CRPC, this will open further study of possible therapeutic options based on this marker.

Wnt/Beta-Catenin Signaling and Prostate Cancer Therapy Resistance

Metastatic or locally advanced prostate cancer (PCa) is typically treated with androgen deprivation therapy (ADT). Initially, PCa responds to the treatment and regresses. However, PCa almost always develops resistance to androgen deprivation and progresses to castrate-resistant prostate cancer (CRPCa), a currently incurable form of PCa. Wnt/β-Catenin signaling is frequently activated in late stage PCa and contributes to the development of therapy resistance. Although activating mutations in the Wnt/β-Catenin pathway are not common in primary PCa, this signaling cascade can be activated through other mechanisms in late stage PCa, including cross talk with other signaling pathways, growth factors and cytokines produced by the damaged tumor microenvironment, release of the co-activator β-Catenin from sequestration after inhibition of androgen receptor (AR) signaling, altered expression of Wnt ligands and factors that modulate the Wnt signaling, and therapy-induced cellular senescence. Research from genetically engineered mouse models indicates that activation of Wnt/β-Catenin signaling in the prostate is oncogenic, enables castrate-resistant PCa growth, induces an epithelial-to-mesenchymal transition (EMT), promotes neuroendocrine (NE) differentiation, and confers stem cell-like features to PCa cells. These important roles of Wnt/β-Catenin signaling in PCa progression underscore the need for the development of drugs targeting this pathway to treat therapy-resistant PCa.

The long noncoding RNA landscape of neuroendocrine prostate cancer and its clinical implications

Background

Treatment-induced neuroendocrine prostate cancer (tNEPC) is an aggressive variant of late-stage metastatic castrate-resistant prostate cancer that commonly arises through neuroendocrine transdifferentiation (NEtD). Treatment options are limited, ineffective, and, for most patients, result in death in less than a year. We previously developed a first-in-field patient-derived xenograft (PDX) model of NEtD. Longitudinal deep transcriptome profiling of this model enabled monitoring of dynamic transcriptional changes during NEtD and in the context of androgen deprivation. Long non-coding RNA (lncRNA) are implicated in cancer where they can control gene regulation. Until now, the expression of lncRNAs during NEtD and their clinical associations were unexplored.

Results

We implemented a next-generation sequence analysis pipeline that can detect transcripts at low expression levels and built a genome-wide catalogue (n = 37,749) of lncRNAs. We applied this pipeline to 927 clinical samples and our high-fidelity NEtD model LTL331 and identified 821 lncRNAs in NEPC. Among these are 122 lncRNAs that robustly distinguish NEPC from prostate adenocarcinoma (AD) patient tumours. The highest expressed lncRNAs within this signature are H19, LINC00617, and SSTR5-AS1. Another 742 are associated with the NEtD process and fall into four distinct patterns of expression (NEtD lncRNA Class I, II, III, and IV) in our PDX model and clinical samples. Each class has significant (z-scores >2) and unique enrichment for transcription factor binding site (TFBS) motifs in their sequences. Enriched TFBS include (1) TP53 and BRN1 in Class I, (2) ELF5, SPIC, and HOXD1 in Class II, (3) SPDEF in Class III, (4) HSF1 and FOXA1 in Class IV, and (5) TWIST1 when merging Class III with IV. Common TFBS in all NEtD lncRNA were also identified and include E2F, REST, PAX5, PAX9, and STAF. Interrogation of the top deregulated candidates (n = 100) in radical prostatectomy adenocarcinoma samples with long-term follow-up (median 18 years) revealed significant clinicopathological associations. Specifically, we identified 25 that are associated with rapid metastasis following androgen deprivation therapy (ADT). Two of these lncRNAs (SSTR5-AS1 and LINC00514) stratified patients undergoing ADT based on patient outcome.

Discussion

To date, a comprehensive characterization of the dynamic landscape of lncRNAs during the NEtD process has not been performed. A temporal analysis of the PDX-based NEtD model has for the first time provided this dynamic landscape. TFBS analysis identified NEPC-related TF motifs present within the NEtD lncRNA sequences, suggesting functional roles for these lncRNAs in NEPC pathogenesis. Furthermore, select NEtD lncRNAs appear to be associated with metastasis and patients receiving ADT. Treatment-related metastasis is a clinical consequence of NEPC tumours. Top candidate lncRNAs FENDRR, H19, LINC00514, LINC00617, and SSTR5-AS1 identified in this study are implicated in the development of NEPC. We present here for the first time a genome-wide catalogue of NEtD lncRNAs that characterize the transdifferentiation process and a robust NEPC lncRNA patient expression signature. To accomplish this, we carried out the largest integrative study that applied a PDX NEtD model to clinical samples. These NEtD and NEPC lncRNAs are strong candidates for clinical biomarkers and therapeutic targets and warrant further investigation.

Transformation of prostatic adenocarcinoma to well-differentiated neuroendocrine tumor after hormonal treatment

Carcinoid tumor of the prostate is extremely rare. Here we report a unique case of prostate cancer that underwent complete transformation from conventional adenocarcinoma to carcinoid-like tumor shortly after androgen-deprivation treatment (ADT). The patient was a 59-year-old man who presented with lower urinary tract symptoms. His biopsy specimen demonstrated a high-grade prostatic adenocarcinoma with mixed acinar and ductal features. After ADT for 6months, the patient underwent radical prostatectomy. The post-ADT tumor showed monotonous neoplastic cells with fine granular chromatin forming rosette-like structures, resembling a carcinoid tumor. No residual conventional adenocarcinoma was present. On immunostain, the tumor cells were diffusely positive for synaptophysin and chromogranin and negative for prostate-specific antigen and prostein. Thus, the carcinoid-like tumor represented complete transformation from prostatic adenocarcinoma to well-differentiated neuroendocrine tumor after ADT. This unique case highlights the important role of ADT in neuroendocrine differentiation of prostate cancer.

Small-cell neuroendocrine cancer of the prostate: an atypical presentation of a common disease

A 70-year-old man with a history of prostate cancer, previously submitted to surgical castration and trans-urethral resection of the prostate, was admitted to Accident and Emergency department. He had been suffering from osteoarticular and abdominal pain, and recent weight loss. An abdominal and a pelvic CT showed multiple hepatic metastases and a pelvic mass, but his prostate-specific antigen values were low (0.26 n/mL). A biopsy of a hepatic metastasis and of the pelvic mass revealed a small-cell neuroendocrine prostate cancer, a rare and aggressive androgen-independent form of prostate cancer with a poor prognosis. Our purpose was to report a clinical case of a rare and aggressive variant of a common disease. A high index of suspicion is required to make an early diagnosis and to ensure a proper therapeutic approach.

Neuroendocrine Immunophenotype as Predictor of Clinical Recurrence in 110 Patients with Prostate Cancer

We evaluated the relationship between NE expression and well-known prognostic factors and assessed whether tumor relapse after radical surgery correlates with the extent of NE differentiation. Radical prostatectomy specimens from 110 patients with clinically localized prostate cancer were assessed. Patients were followed up every three months for the first two years after surgery and six monthly for 5 additional years until failure, or for a mean of 48 months from the time of surgery for those who did not experience failure. The percentage of cells showing CgA immunoreactivity was evaluated using a visual quantitative method. Tumor staining was categorized as positive if >10% and negative if <10% of tumor cells were stained, to ensure that only cases with significant positivity were included in the positive group. The median follow-up was 5.4 years (range 1.8 to 7.2). The median time to clinical recurrence was 7.5 years and the median time to biochemical recurrence was 2.8 years. Of 31 patients (28%) who experienced a PSA recurrence, 15 developed a clinical recurrence. The mean preoperative PSA level was 9 ng/ml (range 2.7 to 25). Most cases were well differentiated (Gleason score <7), intraprostatic (≤pT2) tumors. Immunoreactivity in ≥10% of the cells was seen in 17.2% (n=19) of the tumor specimens. The preoperative PSA level, Gleason score, use of neoadjuvant or adjuvant therapy, lymphnode positivity were not statistically associated with NE expression. Only the primary pathologic stage appeared to be associated with CgA staining in the primary tumor (p=0.001). On the univariate analysis NE expression did not predict biochemical recurrence free survival, whereas it was associated with clinical recurrence. NE differentiation in clinically localized prostate cancer can be associated with failure after definitive surgical treatment, even if no conclusions can be drawn regarding its value as an independent prognostic factor.

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.

Development of Castration Resistant Prostate Cancer can be Predicted by a DNA Hypermethylation Profile

PURPOSE

Detection of DNA hypermethylation has emerged as a novel molecular biomarker for prostate cancer diagnosis and evaluation of prognosis. We sought to define whether a hypermethylation profile of patients with prostate cancer on androgen deprivation would predict castrate resistant prostate cancer.

MATERIALS AND METHODS

Genome-wide methylation analysis was performed using a methylation cancer panel in 10 normal prostates and 45 tumor samples from patients placed on androgen deprivation who were followed until castrate resistant disease developed. Castrate resistant disease was defined according to EAU (European Association of Urology) guideline criteria. Two pathologists reviewed the Gleason score, Ki-67 index and neuroendocrine differentiation. Hierarchical clustering analysis was performed and relationships with outcome were investigated by Cox regression and log rank analysis.

RESULTS

We found 61 genes that were significantly hypermethylated in greater than 20% of tumors analyzed. Three clusters of patients were characterized by a DNA methylation profile, including 1 at risk for earlier castrate resistant disease (log rank p = 0.019) and specific mortality (log rank p = 0.002). Hypermethylation of ETV1 (HR 3.75) and ZNF215 (HR 2.89) predicted disease progression despite androgen deprivation. Hypermethylation of IRAK3 (HR 13.72), ZNF215 (HR 4.81) and SEPT9 (HR 7.64) were independent markers of prognosis. Prostate specific antigen greater than 25 ng/ml, Gleason pattern 5, Ki-67 index greater than 12% and metastasis at diagnosis also predicted a negative response to androgen deprivation. Study limitations included the retrospective design and limited number of cases.

CONCLUSIONS

Epigenetic silencing of the mentioned genes could be novel molecular markers for the prognosis of advanced prostate cancer. It might predict castrate resistance during hormone deprivation and, thus, disease specific mortality. Gene hypermethylation is associated with disease progression in patients who receive hormone therapy. It could serve as a marker of the treatment response.

Leading causes of castration-resistant prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related death in men. Androgen receptor has a key role in the initiation and progression of PCa. Currently, androgen deprivation therapy is the standard treatment for PCa patients due to its effective suppression of androgen receptor signaling. Even though androgen deprivation therapy shows its initial effectiveness on shrinking tumor size, it eventually fails to cure advanced PCa, which is determined by the occurrence of castration-resistance. In this review, we summarize the widely accepted mechanisms that account for castration-resistant PCa and discuss potential therapeutic targets.

Prognostic effect of neuroendocrine differentiation in prostate cancer: A critical review

BACKGROUND

The multiple pathways that are involved in neuroendocrine differentiation (NED) in prostate cancer (PCa) are poorly elucidated. Evidence suggests that several environmental triggers induce NED leading to the adaptation of PCa to its close environment to maintain cell proliferation. Nevertheless, there is conflicting evidence regarding the prognostic role of NED in PCa.

METHODS

In this review, we aimed to summarize all available data about NED and to assess the prognostic role of NED in disease progression and therapy resistance, and its role in routine clinical practice. This review was based on articles found through a PubMed literature search between 1993 and 2013. The study outcome measure was the effect of NED on oncologic outcomes at each PCa stage.

RESULTS

In total, 59 articles reporting on the effect of NED on oncologic outcomes have been selected. In clinical practice, immunostaining for NED markers could have interesting predictive value for assessing the oncologic outcomes in patients receiving androgen-deprivation therapy. Thus, patients with high NED burden may be candidates for more aggressive treatment strategies targeting NED pathways. Conversely, strong evidence is lacking concerning its potential independent prognostic value in hormone-naïve PCa.

CONCLUSIONS

Current published data are not sufficient to recommend the use of NE markers in routine practice, particularly at early PCa stage.

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.

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.

Expression screening of cancer/testis genes in prostate cancer identifies NR6A1 as a novel marker of disease progression and aggressiveness

BACKGROUND

Cancer/Testis (CT) genes are expressed in male gonads, repressed in most healthy somatic tissues and de-repressed in various somatic malignancies including prostate cancers (PCa). Because of their specific expression signature and their associations with tumor aggressiveness and poor outcomes, CT genes are considered to be useful biomarkers and they are also targets for the development of new anti-cancer immunotherapies. The aim of this study was to identify novel CT genes associated with hormone-sensitive prostate cancer (HSPC), and castration-resistant prostate cancer (CRPC).

METHODS

To identify novel CT genes we screened genes for which transcripts were detected by RNA profiling specifically in normal testis and in either HSPC or CRPC as compared to normal prostate and 44 other healthy tissues using GeneChips. The expression and clinicopathological significance of a promising candidate--NR6A1--was examined in HSPC, CRPC, and metastatic site samples using tissue microarrays.

RESULTS

We report the identification of 98 genes detected in CRPC, HSPC and testicular samples but not in the normal controls. Among them, cellular levels of NR6A1 were found to be higher in HSPC compared to normal prostate and further increased in metastatic lesions and CRPC. Furthermore, increased NR6A1 immunoreactivity was significantly associated with a high Gleason score, advanced pT stage and cancer cell proliferation.

CONCLUSIONS

Our results show that cellular levels of NR6A1 are correlated with disease progression in PCa. We suggest that this essential orphan nuclear receptor is a potential therapeutic target as well as a biomarker of PCa aggressiveness.

Midkine is associated with neuroendocrine differentiation in castration-resistant prostate cancer

BACKGROUND

Castration-resistant prostate cancer (CRPC) is an incurable disease and both androgen-deprivation therapy (ADT) and neuroendocrine differentiation (NED) are closely related to CRPC transition. More knowledge concerning neuroendocrine (NE)-transformed PC cells, the NED process and its association with CRPC, is needed. Expression of growth factor midkine (MDK) is correlated with poor clinical outcomes in various human cancers, including PC. In the present study, we have evaluated MDK expression and NED in two separate tumor groups: early and advanced PC.

METHODS

Immunohistochemical analysis of MDK, the neuronal marker tubulin-beta III (TUBB3) and the NE-marker chromogranin A (CGA) in a human archival material consisting of hormone naive (HN)/stage T1b (n = 29) and CRPC (n = 24) tumors. Triple immunofluorescent imaging was performed on a selection of specimens.

RESULTS

MDK, TUBB3, and CGA were upregulated in CRPC compared to HN tumors. MDK was highly associated to the expression of both CGA and TUBB3, and identified MDK-positive NE-like looking cells found to co-express CGA or, more commonly, CGA together with TUBB3. CGA and TUBB3 staining displayed a partial expression overlap, an overlap almost exclusively displaying also MDK expression.

CONCLUSIONS

MDK upregulation in CRPC is associated with NED (shown by its relation to CGA and TUBB3). The results suggest that MDK represents an over-bridging marker between different populations of NE-like tumor cells, possibly as part of the NED process and associated CRPC transition, something that needs to be evaluated experimentally as does the applicability of MDK as a future target.

Prostate cancer stem cells: are they androgen-responsive?

The prostate gland is highly dependent on androgens for its development, growth and function. Consequently, the prostatic epithelium predominantly consists of androgen-dependent luminal cells, which express the androgen receptor at high levels. In contrast, androgens are not required for the survival of the androgen-responsive, but androgen-independent, basal compartment in which stem cells reside. Basal and luminal cells are linked in a hierarchical pathway, which most probably exists as a continuum with different stages of phenotypic change. Prostate cancer is also characterised by heterogeneity, which is reflected in its response to treatment. The putative androgen receptor negative cancer stem cell (CSC) is likely to form a resistant core after most androgen-based therapies, contributing to the evolution of castration-resistant disease. The development of CSC-targeted therapies is now of crucial importance and identifying the phenotypic differences between CSCs and both their progeny will be key in this process.

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 differentiation in castration-resistant prostate cancer: a systematic diagnostic attempt

BACKGROUND

Assessing the neuroendocrine (NE) pattern in castration-resistant prostate cancer (CRPC) may prove useful in selecting potential responders to target therapies such as somatostatin analogues. The aim of this study was to define a panel of markers or examinations appropriate to characterize NE differentiation (NED).

METHODS

Forty-seven patients with CRPC underwent a systematic diagnostic attempt to characterize the NE phenotype using a plasma blood test for chromogranin A (CgA) and immunohistochemical staining of needle biopsy-obtained specimens (CgA, somatostatin receptor 2 [SSTR2], Ki-67, and androgen receptors). In a subgroup of 26 patients, somatostatin receptor scintigraphy using (111)In-DTPA-d-Phe octreotide (octreotide scintigraphy; Octreoscan, Covidien, Hazelwood, MO) was also performed.

RESULTS

NED was found in 85.1% of patients (if serum CgA, tissular CgA, and tissular SSTR2 were considered separately: 54%, 67%, and 58%, respectively). Only 15% of the 26-patient subgroup had an abnormal octreotide scintigraphy result. Although p-CgA and t-CgA were associated with more aggressive disease with a worse prognosis, patients with positive tissular SSTR2 staining had longer overall survival (OS).

CONCLUSION

This systematic approach to explore the NED in a quite homogeneous group of patients with CRPC seems reproducible and appropriate. Further investigations are required to validate this panel and better characterize potential responders to targeted therapy.

Prognostic significance of neuroendocrine differentiation in prostate adenocarcinoma

Much progress has been made toward an understanding of the development and progression of prostate cancer (PC) and the factors that drive the development of androgen independence. Neuroendocrine (NE) cells may provide an intriguing link between NE cell differentiation (NED) and tumor progression in PC. NED in PC generally confers a more aggressive clinical behavior and less favorable prognosis than conventional PC. In this article, we review the known functions of NE cells in PC and discuss the current knowledge on stimulation of cancer proliferation, invasion, apoptosis resistance, serum and immunohistochemical markers, and the prognostic significance of NED in human PC.

Role of Neuroendocrine Cells in Prostate Cancer Progression

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

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.

Macrophages induce neuroendocrine differentiation of prostate cancer cells via BMP6-IL6 Loop

BACKGROUND

Frequently associated with hormone refractory prostate cancer are neuroendocrine cells. Because these cells do not express androgen receptors and are castration-resistant, further understanding the mechanism of neuroendocrine differentiation (NED) of prostate cancer cells may yield novel intervention methods in hormone refractory prostate cancer. In this regard, the present study investigated the effect of macrophages on prostate cancer NED.

METHODS

THP-1 and LNCaP or RAW264.7 and TRAMP-C2 cell line co-cultures were used to investigate NED-macrophage interactions. Also interleukin-6 (IL-6) knockout mice and macrophage-depleted mice were used to test NED in vivo.

RESULTS

We found that co-culturing with THP-1 human monocytic cell line and RAW 264.7 murine macrophage cell line led to the NED of LNCaP and TRAMP-C2 prostate cancer cells, respectively. Specifically, the conditioned media of activated macrophages stimulated the expression of parathyroid hormone-related peptide (PTHrP), a marker of NED, in both LNCaP and TRAMP-C2 cells. Mechanistically, bone morphogenetic protein-6 (BMP-6) derived from prostate cancer cells increased the expression of IL-6 in macrophages. Subsequently, IL-6 induced the NED of prostate cancer cells. When this feedback loop was disrupted with neutralizing antibodies to either BMP-6 or IL-6, NED was no longer observed. In human prostate cancer tissues, neuroendocrine cells frequently co-localized with macrophages and BMP-6. In mice, the removal of IL-6 or macrophages blocked the BMP-6-induced NED of prostate cancer cells.

CONCLUSIONS

Therefore, we propose that BMP-6 secreted by prostate cancer cells induces IL-6 expression in macrophages; IL-6, in turn, stimulates the NED of prostate cancer cells.

Lobe-specific proteome changes in the dorsal-lateral and ventral prostate of TRAMP mice versus wild-type mice

The transgenic adenocarcinoma of mouse prostate (TRAMP) is the most widely used transgenic model for prostate cancer chemoprevention studies. Although two lobe-specific lineages of carcinogenesis have been described, the molecular mechanisms are still poorly defined. Here, we concurrently profiled the proteome of dorsal-lateral (DLP) and ventral (VP) prostate lobes of both TRAMP and littermate WT C57BL/6 mice of 18 wk by 2-D LC-MALDI-TOF/TOF with iTRAQ labeling. A total of 483 and 748 proteins were identified at critical false discovery rates of 1 and 5%. In WT mice, 84 proteins were found to have different expression levels between DLP and VP. In TRAMP mice, 118 proteins significantly changed in DLP and/or VP during TRAMP carcinogenesis. Among them, 55 and 36 proteins were uniquely changed in DLP or VP lobe, respectively, and 27 proteins in both DLP and LP lobe. Ingenuity Pathway Analysis was able to segregate proteins changed in two lobes into different pathway networks. In addition to serving as reference for prostate proteomic profiles, our data suggest that different sets of proteins are involved in the carcinogenesis in DLP versus VP in the TRAMP model.

Incidence of high chromogranin A serum levels in patients with non metastatic prostate adenocarcinoma

Background

ChromograninA in prostate carcinoma (PC) indicate NE differentiation. This tumour is more aggressive and resistant to hormone therapy.

Patients and methods

We analyzed the incidence of pre-operative ChromograninA serum levels in non metastatic PC patients. Serum PSA and ChromograninA were analyzed before treatment. Clinicopathological parameters were evaluated in relation to serum ChromograninA. 486 patients were enrolled.

Results

We found 352 pT2 and 134 pT3. 21 patients were N+. 278 patients had Gleason score levels <7; 173 patients had levels = 7 (122 were 3+4 and 51 4+3); and 35 patients with levels >7. Median PSA pre-operative level was 7.61 ng/ml. PSA was significantly associated with pT stage (pT2 with PSA abnormal 23.6% vs pT3 48.5%, p < 0.0001) and with a Gleason score (PSA abnormal 60% in the Gleason score was >7 vs 29.5% in the Gleason score = 7 vs 27.3% in the Gleason score <7, p < 0.0001). In 114 patients pre-operative ChromograninA levels were elevated (23.5%). Serum ChromograninA levels had no significant association with PSA (p = 0.44) and pT stage (p = 0.89). abnormal ChromograninA levels increased from a Gleason score of <7 (25.5%) to >7 (31.4%) (p = 0.12). The serum ChromograninA levels in the two groups of patients were subdivided before and after 2005 on the basis of different used assays, showing no correlation with serum ChromograninA and other parameters.

Conclusions

This study showed that ChromograninA levels correlated to NE differentiation and possible aggressiveness of PC. Pre-operative circulating ChromograninA could complement PSA in selecting more aggressive PC cases, particularly in the presence of a higher Gleason score. Complementary information is provided by the absence of a correlation between serum ChromograninA and PSA levels.

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.

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

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

Clinical significance of polymorphism and expression of chromogranin a and endothelin-1 in prostate cancer

PURPOSE

We investigated the clinical significance of chromogranin A and endothelin-1 polymorphism and expression in prostate cancer.

MATERIALS AND METHODS

We analyzed 2 CHGA polymorphisms by polymerase chain reaction-restriction fragment length polymorphism in DNA samples of 435 patients with prostate cancer and 316 age matched male controls. Chromogranin A and endothelin-1 expression was evaluated by immunohistochemistry in prostate specimens of 114 men with prostate cancer who underwent radical retropubic prostatectomy and in 27 with bladder cancer who underwent radical cystectomy and served as controls.

RESULTS

For the CHGA Glu264Asp polymorphism men with the GG genotype were at 2.05 times higher risk for prostate cancer than men with the CC genotype (p = 0.014). In men with prostate cancer higher chromogranin A immunohistochemistry grade was associated with higher stage and higher Gleason score (p = 0.011 and 0.044, respectively). Multivariate analysis showed that chromogranin A immunohistochemistry grade was an independent variable for predicting biochemical failure after radical prostatectomy (p = 0.023). Higher endothelin-1 expression was observed in prostate cancers (p = 0.011), especially those with a higher Gleason score (p = 0.042). There was no significant relationship between chromogranin A polymorphisms, and chromogranin A and endothelin-1 expression.

CONCLUSIONS

Polymorphism and expression of chromogranin A and endothelin-1 have clinical significance in prostate cancer. Chromogranin A expression was an independent predictor of biochemical failure after prostatectomy in patients with localized prostate cancer.

Proteomic profiling of potential molecular targets of methyl-selenium compounds in the transgenic adenocarcinoma of mouse prostate model

Because the Selenium (Se) and Vitamin E Cancer Prevention Trial (SELECT) failed to show the efficacy of selenomethionine for prostate cancer prevention, there is a critical need to identify safe and efficacious Se forms for future trials. We have recently shown significant preventive benefit of methylseleninic acid (MSeA) and Se-methylselenocysteine (MSeC) in the transgenic adenocarcinoma mouse prostate (TRAMP) model by oral administration. The present work applied iTRAQ proteomic approach to profile protein changes of the TRAMP prostate and to characterize their modulation by MSeA and MSeC to identify their potential molecular targets. Dorsolateral prostates from wild-type mice at 18 weeks of age and TRAMP mice treated with water (control), MSeA, or MSeC (3 mg Se/kg) from 8 to 18 weeks of age were pooled (9-10 mice per group) and subjected to protein extraction, followed by protein denaturation, reduction, and alkylation. After tryptic digestion, the peptides were labeled with iTRAQ reagents, mixed together, and analyzed by two-dimensional liquid chromatography/tandem mass spectrometry. Of 342 proteins identified with >95% confidence, the expression of 75 proteins was significantly different between TRAMP and wild-type mice. MSeA mainly affected proteins related to prostate functional differentiation, androgen receptor signaling, protein (mis)folding, and endoplasmic reticulum-stress responses, whereas MSeC affected proteins involved in phase II detoxification or cytoprotection, and in stromal cells. Although MSeA and MSeC are presumed precursors of methylselenol and were equally effective against the TRAMP model, their distinct affected protein profiles suggest biological differences in their molecular targets outweigh similarities.

Methyl-selenium compounds inhibit prostate carcinogenesis in the transgenic adenocarcinoma of mouse prostate model with survival benefit

Chemoprevention of prostate cancer by second-generation selenium compounds in reference to selenomethionine holds strong promise to deal with the disease at the root. Here we used the transgenic adenocarcinoma mouse prostate (TRAMP) model to establish the efficacy of methylseleninic acid (MSeA) and methylselenocysteine (MSeC) against prostate carcinogenesis and to characterize potential mechanisms. Eight-week-old male TRAMP mice (C57B/6 background) were given a daily oral dose of water, MSeA, or MSeC at 3 mg Se/kg body weight and were euthanized at either 18 or 26 weeks of age. By 18 weeks of age, the genitourinary tract and dorsolateral prostate weights for the MSeA- and MSeC-treated groups were lower than for the control (P < 0.01). At 26 weeks, 4 of 10 control mice had genitourinary weight >2 g, and only 1 of 10 in each of the Se groups did. The efficacy was accompanied by delayed lesion progression, increased apoptosis, and decreased proliferation without appreciable changes of T-antigen expression in the dorsolateral prostate of Se-treated mice and decreased serum insulin-like growth factor I when compared with control mice. In another experiment, giving MSeA to TRAMP mice from 10 or 16 weeks of age increased their survival to 50 weeks of age, and delayed the death due to synaptophysin-positive neuroendocrine carcinomas and synaptophysin-negative prostate lesions and seminal vesicle hypertrophy. Wild-type mice receiving MSeA from 10 weeks did not exhibit decreased body weight or genitourinary weight or increased serum alanine aminotransferase compared with the control mice. Therefore, these selenium compounds may effectively inhibit this model of prostate cancer carcinogenesis.

Garlic constituent diallyl trisulfide prevents development of poorly differentiated prostate cancer and pulmonary metastasis multiplicity in TRAMP mice

Identification of agents that are nontoxic but can delay onset and/or progression of prostate cancer, which is the second leading cause of cancer-related deaths among men in the United States, is highly desirable. We now show that p.o. gavage of garlic constituent diallyl trisulfide (DATS; 1 and 2 mg/day, thrice/week for 13 weeks beginning at age 8 weeks) significantly inhibits progression to poorly differentiated prostate carcinoma and pulmonary metastasis multiplicity in transgenic adenocarcinoma of mouse prostate (TRAMP) mice without any side effects. There was a trend of a decrease in average wet weights of the urogenital tract and prostate gland in 1 and 2 mg DATS-treated mice compared with controls ( approximately 25-46% decrease in DATS-treated mice compared with controls). The incidence and the area of the dorsolateral prostate occupied by the poorly differentiated carcinoma were significantly lower in both 1 and 2 mg DATS-treated mice compared with control mice. In addition, DATS administration resulted in a statistically significant decrease in pulmonary metastasis multiplicity compared with controls (P = 0.002). The dorsolateral prostate from DATS-treated TRAMP mice exhibited decreased cellular proliferation in association with induction of cyclinB1 and securin protein levels, and suppression of the expression of neuroendocrine marker synaptophysin. However, DATS administration did not have any appreciable effect on apoptosis induction, angiogenesis, or natural killer and dendritic cell function. In conclusion, the results of the present study show, for the first time, that DATS administration prevents progression to invasive carcinoma and lung metastasis in TRAMP mice.

Hormonal regulation of beta2-adrenergic receptor level in prostate cancer

BACKGROUND

Androgen deprivation is the only effective systemic therapy available for patients with prostatic carcinoma, but is associated with a gradual transition to a hormone-refractory prostate cancer (HRCAP) in which ligand-independent activation of the androgen receptor has been implicated. The beta(2)-adrenergic receptor (beta(2)-AR) is a well-known activator of the androgen receptor.

METHODS

Prostatic cell lines were analyzed using cDNA micro-array, real time RT-PCR, radioligand binding assay, cAMP measurements, transfection and thymidine incorporation assay. Clinical specimens were studied by immunohistochemistry and Affymetrix microarrays.

RESULTS

Here, we show that beta(2)-AR was transiently down-regulated both at mRNA- and protein levels when hormone-sensitive prostate cancer cells, LNCaP, were cultured in steroid stripped medium (charcoal-stripped fetal calf serum) or when the cells were treated with the anti-androgen, bicalutamide (Casodex). The number of beta-adrenergic receptors was modestly up-regulated in androgen independent cell lines (LNCaP-C4, LNCaP-C4-2 and DU145) compared to LNCaP. Triiodothyronine (T3) increased the level of beta(2)-AR and the effect of T3 was inhibited by bicalutamide. Immunohistochemical staining of human prostate specimens showed high expression of beta(2)-AR in glandular, epithelial cells and increased expression in malignant cells compared to benign hyperplasia and normal tissue. Interestingly, beta(2)-AR mRNA was strongly down-regulated by androgen ablation therapy of prostate cancer patients.

CONCLUSION

The level of beta(2)-AR was increased by T3 in prostatic adenocarcinoma cells and reduced in prostate cancer patients who had received androgen ablation therapy for 3 months.

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

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

Is there a role for platinum chemotherapy in the treatment of patients with hormone-refractory prostate cancer?

Docetaxel chemotherapy is the current standard of care for metastatic hormone-refractory prostate cancer (HRPC). Platinum chemotherapy drugs, such as cisplatin and carboplatin, have moderate single-agent activity in HRPC. Next-generation platinum drugs, including satraplatin and oxaliplatin, may have additional activity in the management of HRPC. Furthermore, neuroendocrine differentiation may play a role in disease progression, providing a rationale for platinum-based chemotherapy in the management of HRPC. The authors reviewed the MEDLINE database for reports related to platinum-based chemotherapy in patients with advanced prostate cancer and evaluated studies that reviewed the role of neuroendocrine differentiation in the progression of HRPC. Older studies from the 1970s and 1980s suggested a lack of activity of cisplatin and carboplatin; however, those studies were flawed at least in part by their methods of response assessment. More recent Phase II studies of carboplatin suggested a moderate level of clinical and palliative activity when it was used as a single agent. However, when carboplatin was combined with a taxane and estramustine, high response rates were observed in several recent clinical trials. In addition, a randomized trial suggested that satraplatin plus prednisone improved progression-free survival compared with prednisone alone. For patients who progressed after docetaxel, no standard options existed in the literature that was reviewed. Several preliminary reports suggested that carboplatin and oxaliplatin may have activity as second-line chemotherapy. Platinum chemotherapy drugs historically have been considered inactive in HRPC, although a review of the data suggested otherwise. Carboplatin, in particular, induced very high response rates when it was combined with estramustine and a taxane, but it also appeared to have activity in patients who progressed after docetaxel. Satraplatin plus prednisone is being investigated in a large Phase III trial as second-line chemotherapy for HRPC. Targeting neuroendocrine cells may provide a new therapeutic approach to HRPC.

The significance of neuroendocrine differentiation in adenocarcinoma of the esophagus and esophagogastric junction after preoperative chemoradiation

BACKGROUND

Esophageal and esophagogastric junction (EGJ) adenocarcinomas frequently have neuroendocrine (NE) differentiation, but the significance of NE differentiation in patients who have undergone preoperative chemoradiation and resection remains unclear.

METHODS

The authors evaluated the presence of NE differentiation in esophageal and EGJ adenocarcinomas by immunohistochemistry for chromogranin A and synaptophysin and evaluated the clinical significance of NE differentiation in 83 patients (10 patients who had a complete tumor response and 73 patients who had residual tumor in resection specimens) who received preoperative chemoradiation.

RESULTS

Of 73 patients who had residual tumor after preoperative treatment, 52% showed NE differentiation. The proportion of tumor cells with NE differentiation had increased from 6% +/- 18% in pretreatment biopsy specimens to 47% +/- 42% (P = .00003) in posttreatment resection specimens in 30 patients who had paired pretreatment biopsy and resection specimens available. Disease-free survival (P = .002) and overall survival (P = .006) were significantly better in patients who had a complete tumor response than in patients who had residual tumor. Among patients who had residual tumor after preoperative chemoradiation, disease-free survival (P = .03) and overall survival (P = .045) were significantly better in patients who had residual tumor without NE differentiation than in patients who had residual tumor with NE differentiation. In multivariate analysis, the presence of NE differentiation in residual tumor was a prognostic factor for worse disease-free survival (P = .02) independent of pathologic stage and extent of residual tumor.

CONCLUSIONS

The results from this study suggested that tumor cells with NE differentiation were more resistant to neoadjuvant chemoradiation in patients with esophageal and EGJ adenocarcinomas. The presence of NE differentiation in residual tumor was associated with poor survival after preoperative neoadjuvant therapy.

Clinical implications of neuroendocrine differentiation in prostate cancer

The cellular signaling pathways of the prostate play a central role in the induction, maintenance, and progression of prostate cancer (CaP). Neuroendocrine (NE) cells demonstrate attributes that suggest they are an integral part of these signaling cascades. We summarize what is known regarding NE cells in CaP focusing on NE cellular transdifferentiation. This significant event in CaP progression appears to be accelerated by androgen deprivation (AD) treatment. We examine biochemical pathways that may impact NE differentiation in a chronological manner focusing on AD therapy (ADT) as a central event in inducing androgen-independent CaP. Our analysis is limited to the common adenocarcinoma pattern of CaP and excludes small-cell and carcinoid prostatic variants. In conclusion, we speculate on the future of treatment and research in this area.

Neo-adjuvant and adjuvant hormone therapy for localised and locally advanced prostate cancer

BACKGROUND

Hormone therapy for early prostate cancer has demonstrated an improvement in clinical and pathological variables, but not always an improvement in overall survival. We performed a systematic review of both adjuvant and neo-adjuvant hormone therapy combined with surgery or radiotherapy in localised or locally advanced prostate cancer.

OBJECTIVES

The objective of this review was to undertake a systematic review and, if possible, a meta-analysis of neo-adjuvant and adjuvant hormone therapy in localised or locally advanced prostate cancer.

SEARCH STRATEGY

We searched MEDLINE (1966-2006), EMBASE, The Cochrane Library, Science Citation Index, LILACS, and SIGLE for relevant randomised trials. Handsearching of appropriate publications was also undertaken.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials of patients with localised or locally advanced prostate cancer, that is, stages T1-T4, any N, M0, comparing neo-adjuvant or adjuvant hormonal deprivation in combination with primary therapy (radical radiotherapy or radical prostatectomy) versus primary therapy alone were included in this review.

DATA COLLECTION AND ANALYSIS

Data were extracted from eligible studies and assessed for quality, and included information on study design, participants, interventions, and outcomes. Comparable data were pooled together for meta-analysis with intention-to treat principle.

MAIN RESULTS

Men with prostate cancer have different clinical outcomes based on their risk (T1-T2, T3-T4, PSA levels and Gleason score). However, the majority of studies included in this review did not report results by risk groups; therefore, it was not possible to perform sub-group analysis. Neo-adjuvant hormonal therapy prior to prostatectomy did not improve overall survival (OR 1.11, 95% CI 0.67 to 1.85, P = 0.69). However, there was a significant reduction in the positive surgical margin rate (OR 0.34, 95% CI 0.27 to 0.42, P < 0.00001) and a significant improvement in other pathological variables such as lymph node involvement, pathological staging and organ confined rates. There was a borderline significant reduction of disease recurrence rates (OR 0.74, 95% CI 0.55 to 1.0, P = 0.05), in favour of treatment. The use of longer duration of neo-adjuvant hormones, that is either 6 or 8 months prior to prostatectomy, was associated with a significant reduction in positive surgical margins (OR 0.56, 95% CI 0.39 to 0.80, P = 0.002). In one study, neo-adjuvant hormones prior to radiotherapy significantly improved overall survival for Gleason 2 to 6 patients; although, in two studies, there was no improvement in disease-specific survival (OR 0.99, 95% CI 0.75 to 1.32, P = 0.97). However, there was a significant improvement in both clinical disease-free survival (OR 1.86, 95% CI 1.93 to 2.40, P < 0.00001) and biochemical disease-free survival (OR 1.93, 95% CI 1.45 to 2.56, P < 0.00001). Adjuvant androgen deprivation following prostatectomy did not significantly improve overall survival at 5 years (OR 1.50, 95% CI 0.79 to 2.85, P = 0.2); although one study reported a significant disease-specific survival advantage with adjuvant therapy (P = 0.001). In addition, there was a significant improvement in disease-free survival at both 5 years (OR 3.73, 95%CI 2.30 to 6.03, P < 0.00001) and 10 years (OR 2.06, 95% CI 1.34 to 3.15, P = 0.0009). Adjuvant therapy following radiotherapy resulted in a significant overall survival gain apparent at 5 (OR 1.46, 95% CI 1.17 to 1.83, P = 0.0009) and 10 years (OR 1.44, 95% CI 1.13 to 1.84, P = 0.003); although there was significant heterogeneity (P = 0.09 and P = 0.07, respectively). There was also a significant improvement in disease-specific survival (OR 2.10, 95% CI 1.53 to 2.88, P = 0.00001) and disease-free survival (OR 2.53, 95% CI 2.05 to 3.12, P < 0.00001) at 5 years.

AUTHORS' CONCLUSIONS

Hormone therapy combined with either prostatectomy or radiotherapy is associated with significant clinical benefits in patients with local or locally advanced prostate cancer. Significant local control may be achieved when given prior to prostatectomy or radiotherapy, which may improve patient's quality of life. When given adjuvant to these primary therapies, hormone therapy, not only provides a method for local control, but there is also evidence for a significant survival advantage. However, hormone therapy is associated with significant side effects, such as hot flushes and gynaecomastia, as well as cost implications. The decision to use hormone therapy should, therefore, be taken at a local level, between the patient, clinician and policy maker, taking into account the clinical benefits, toxicity and cost. More research is needed to guide the choice, the duration, and the schedule of hormonal deprivation therapy, and the impact of long-term hormone therapy with regard to toxicity and the patient's quality of life.

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.

Protein tyrosine phosphatase PTP1B is involved in neuroendocrine differentiation of prostate cancer

BACKGROUND

Prostate cancer (PC) contains a minor component of neuroendocrine (NE) cells that may stimulate androgen-independent growth of the tumor. The mechanism of neuroendocrine differentiation remains unknown.

METHODS

The expression of PTP1B, a protein tyrosine phosphatase, was studied in LNCaP cells induced to show neuroendocrine phenotype by androgen withdrawal. Wild-type PTP1B and its dominant-negative mutant were transfected into LNCaP cells to study their effects on neuroendocrine differentiation. In vivo expression of PTP1B in human prostate cancer was studied by immunohistochemistry.

RESULTS

Androgen withdrawal of LNCaP cells led to increased expression of PTP1B with a corresponding increase in its tyrosine phosphatase activity. Overexpression of PTP1B in LNCaP cells led to neuroendocrine differentiation while expression of its dominant-negative mutant inhibited neuroendocrine differentiation. Immunohistochemical study showed that PTP1B was exclusively expressed in neuroendocrine cells of human prostate cancer tissue.

CONCLUSION

Our findings suggest that PTP1B plays an important role in neuroendocrine differentiation, and therefore, may possibly be involved in the progression of prostate cancer.

The methyl-CpG-binding protein MECP2 is required for prostate cancer cell growth

The incidence of prostate cancer is increasing in western countries because of population aging. Prostate cancer begins as an androgen-dependent disease, but it can become androgen independent at a later stage or in tumors recurring after an antihormonal treatment. Although many genetic events have been described to be involved in androgen-dependent and/or -independent prostate cancer growth, little is known about the contribution of epigenetic events. Here we have examined the possibility that the methyl-CpG-binding protein MECP2 might play a role in controlling the growth of prostate cancer cells. Inhibition of MECP2 expression by stable short hairpin RNA stopped the growth of both normal and cancer human prostate cells. In addition, ectopic expression of the MECP2 conferred a growth advantage to human prostate cancer cells. More importantly, this expression allowed androgen-dependent cells to grow independently of androgen stimulation and to retain tumorigenic properties in androgen-depleted conditions. Analysis of signaling pathways showed that this effect is independent of androgen receptor signaling. Instead, MECP2 appears to act by maintaining a constant c-myc level during antihormonal treatment. We further show that MECP2-expressing cells possess a functional p53 pathway and are still responsive to chemotherapeutic drugs.