Neuroendocrine differentiation in human prostate tissue: is it detectable and treatable?

Metastatic Castration-Resistant Prostate Cancer with Neuroendocrine Transformation and BRCA 1 Germ-Line Mutation: A Case Report and Literature Review

A 63-year-old man with a significantly high prostate-specific antigen level was diagnosed via pathology to have advanced prostate adenocarcinoma due to multiple lung metastases. He was then treated with androgen deprivation therapy (ADT) comprising bicalutamide and goserelin. Only after 6 months of stable disease, the cancer progressed and the drug was changed to abiraterone; however, no significant therapeutic effect was observed and the disease was considered as castration-resistant prostate cancer. The histopathologic analysis of the biopsied metastatic lymph node confirmed small-cell neuroendocrine carcinoma, and genetic testing revealed BRCA1 germ-line mutation. The oral PARP inhibitor olaparib was used and achieved a partial tumor response over a period of 2.5 months. Meanwhile, palliative radiotherapy was performed for pain control in the sacrococcygeal region with complete symptom relief. The combination chemotherapy strategy of etoposide and cisplatin was used after the failure of olaparib and achieved pain alleviation in the left leg. The patient received one cycle of this chemotherapy strategy and eventually died of a rapid tumor progression, respiratory failure, and heart failure on April 27, 2019.

Prostate cancer susceptibility gene HIST1H1A is a modulator of androgen receptor signaling and epithelial to mesenchymal transition

In 2018, approximately 165,000 new prostate cancer (PC) cases will be diagnosed, and over 29,000 men will succumb to PC in the U.S. alone. The means of assessing outcome in the clinic are inaccurate, and there is a pressing need to more precisely identify men at risk of aggressive PC. We previously identified HIST1H1A as a susceptibility gene for aggressive PC. HIST1H1A encodes H1.1, a member of the linker histone family that is involved in chromatin organization and compaction. To understand the molecular basis of aggressive PC, we have characterized how germline variation modulates susceptibility to neuroendocrine differentiation, which is a form of aggressive PC. Immunohistochemistry studies revealed that HIST1H1A is over-expressed in normal human prostate tissue compared to prostate adenocarcinoma. Functional characterization of HIST1H1A in prostate LNCaP cells indicated that HIST1HA over-expression increased cell growth, as well as the expression of neuroendocrine and epithelial-to-mesenchymal markers in vitro. Assay for Transposase-Accessible Chromatin (ATAC-seq), which is used to assess chromatin compaction and thus the transcriptional availability of individual genomic regions, demonstrated that H1.1 plays a prominent role in modulating Wnt signaling pathway genes, which are implicated in prostate tumorigenesis. These results demonstrate that HIST1H1A is a modulator of aggressive PC susceptibility.

Neuroendocrine Differentiation in Prostatic Malignancy

Neuroendocrine differentiation in prostatic malignancy is receiving considerable attention; this occurs commonly as a “focal” histological variant and, most rarely, in the form of small cell carcinoma (“oat cell carcinoma”) and carcinoid tumor. In prostate cancer, neuroendocrine differentiation may be the response to androgen deprivation and neuroendocrine products, either biogenic amines or peptides, have been shown to stimulate proliferation of androgen-ablation refractory cancer cells. Serum chromogranins, neuron-specific enolase and other neuroendocrine products as well as 111-In-chromogranin A “three step” immunoscintigraphy and somatostatin-receptor scintigraphy may be useful for predicting tumor behaviour and patient prognosis.

Several of the neuroendocrine products, particularly somatostatin analogues, are candidates for new therapeutic approaches. The paper aims to outline the advances in this field on the basis of the review of the literature.

Pro-gastrin-releasing peptide (ProGRP) as a biomarker in small-cell lung cancer diagnosis, monitoring and evaluation of treatment response

Lung cancer belongs to malignant tumors that possess the highest rates of morbidity and mortality in the world. A number of morphological, biological and clinical features justify the distinction of small-cell carcinoma with respect to the other histological types of lung cancer. The predominant neuroendocrine phenotype is critical for the selection of biomarkers used in diagnostics, monitoring and evaluation of treatment response; early onset relapses in patients with small-cell lung cancer (SCLC) and the evaluation of their prognosis. Although for a long time the neuron-specific enolase (NSE) was considered to be the marker of choice for this tumor, it is now increasingly important to pay attention to concentrations of pro-gastrin-releasing peptide (ProGRP). The results of this marker have been implicated in the differential diagnosis of non-small lung cancer and SCLC, chemotherapy and radiotherapy monitoring as well as evaluation of treatment response. The subject of this series of studies is to determine the usefulness of ProGRP in the evaluation of patients’ prognosis and its predictive value. The current aim for the optimization of the effectiveness of biochemical diagnostics of SCLC is recommended by complementary ProGRP and NSE studies. The present work is a summary of the latest reports regarding diagnostic utility of these markers in SCLC.

Potential therapeutic effect of epigenetic therapy on treatment-induced neuroendocrine prostate cancer

Although adenocarcinomas of the prostate are relatively indolent, some patients with advanced adenocarcinomas show recurrence of treatment-induced neuroendocrine prostate cancer, which is highly aggressive and lethal. Detailed biological features of treatment-induced neuroendocrine prostate cancer have not been characterized owing to limited biopsies/resections and the lack of a cellular model. In this study, we used a unique cellular model (LNCaP/NE1.8) to investigate the potential role of cancer stem cells in treatment-induced neuroendocrine prostate cancer with acquired resistance to hormonal therapy and chemotherapy. We also studied the role of cancer stem cells in enhancing invasion in treatment-induced neuroendocrine prostate cancer cells that recurred after long-term androgen-ablation treatment. Using an in vitro system mimicking clinical androgen-ablation, our results showed that the neuroendocrine-like subclone NE1.8 cells were enriched with cancer stem cells. Compared to parental prostate adenocarcinoma LNCaP cells, NE1.8 cells are more resistant to androgen deprivation therapy and chemotherapeutic agents and show increased cancer cell invasiveness. Results from this study also suggest a potential epigenetic therapeutic strategy using suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, as a chemotherapeutic agent for therapy-resistant treatment-induced neuroendocrine prostate cancer cells to minimize the risk of prostate cancer recurrence and metastasis.

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.

Factors implicated in radiation therapy failure and radiosensitization of prostate cancer

Tissue markers may be helpful in enhancing prediction of radiation therapy (RT) failure of prostate cancer (PCa). Among the various biomarkers tested in Phase III randomized trials conducted by the Radiation Therapy Oncology Group, p16, Ki-67, MDM2, COX-2, and PKA yielded the most robust data in predicting RT failure. Other pathways involved in RT failure are also implicated in the development of castration-resistant PCa, including the hypersensitive androgen receptor, EGFR, VEGF-R, and PI3K/Akt. Most of them are detectable in PCa tissue even at the time of initial diagnosis. Emerging evidence suggests that RT failure of PCa results from a multifactorial and heterogeneous disease process. A number of tissue markers are available to identify patients at high risk to fail RT. Some of these markers have the promise to be targeted by drugs currently available to enhance the efficacy of RT and delay disease progression.

Small-cell prostate carcinoma: A retrospective analysis of five newly reported cases

Five cases of small-cell carcinoma (SCC) of prostate were identified, at the Rhode Island Hospital and the Miriam Hospital from 1984 to 2006, with an average age of 71 years at the time of diagnosis. Three of these patients had a prior diagnosis of prostatic adenocarcinoma, with all of the five patients receiving anti-androgen treatment. The average time between the diagnosis of adenocarcinoma and of SCC in these patients was 6.7 years. The PSA levels varied greatly, with two patients possessing markedly elevated levels and the remaining patients with normal levels. Approximately 3/5 patients developed liver metastases, 2/5 patients had bone metastases, and 1/5 patients developed carcinomatous meningitis. Of the four patients who expired, the median survival time after diagnosis of SCC was 3.6 months (0.5–12 months).

[Current diagnostic procedure on neuroendocrine differentiation of prostate cancer]

Chromogranin A (CgA) is considered as a major specific neuroendocrine tumor marker. It belongs to the secretogranin family, which is present in the gastrointestinal tract, respiratory system, endocrine glands and in a group of endocrine cells such us pancreas and thyroid. Serum levels of CgA could reflect the neuroendocrine activity and could be used when evaluating advance prostate carcinoma. Moreover, there are also several factors that may increase the serum level of CgA: treatment with proton-pump inhibitors or H2-receptor blockers, chronic atrophic gastritis, rheumatoid arthritis, liver and renal failure. Another method to evaluate NE differentiation is scintigraphy with the 111In-labeled somatostatin analogue (DTPA-D-Phe)-octrotide, (Octreoscan). This method takes advantage of the overexpression of type II somatostatin receptors on the cell surface of NE tumors. With this technique the presence of NE differentiation can be detected both at the primary (prostate) and the metastatic sites. A more specific system to detect NE cell activity is obtained by analyzing CgA gene expression in prostate tissue by a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR).

[Neuroendocrine target therapies for prostate cancer]

It is important to determine whether an increase in Chromogranin A levels and neuroendocrine (NE) cell activation are associated with progression towards on hormone-independent prostate-cancer. We proposed a combination of estrogens and somatostatin analogues as therapy of NE activation in hormone-independent prostate cancer. The combined therapy with ethinyl estradiol and lanreotide offered objective and symptomatic responses in patients with limited treatment options and refractoriness to conventional hormonal therapy strategies; in particular, it offered a median overall survival that was superior to the 10-month median survival in patients with hormone refractory disease. This combined therapy also sustains the new concept in cancer treatment in which therapies may target not only cancer cells but also its microenvironment, which can yield protection against apoptosis.

Wnt/β-catenin activation promotes prostate tumor progression in a mouse model

Our previous studies have found that activation of Wnt/β-Catenin signaling resulted in mouse prostatic intraepithelial neoplasia (mPIN). In the large probasin promoter directed SV40-Large T-antigen (LPB-Tag) expressing mouse prostate, mPIN forms with rare areas of adenocarcinoma. Combining expression of both Wnt-signaling and Tag expression in the mouse prostate, we have studied the role of Wnt/β-Catenin signaling in the progression from mPIN to adenocarcinoma. Our results show that the prostates of mice expressing Tag alone or nuclear β-Catenin alone developed mPIN while the activation of both Tag and the Wnt/β-Catenin pathway resulted in invasive prostate adenocarcinoma. Also, Foxa2, a forkhead transcription factor, was induced by active Wnt/β-Catenin signaling; and the expression of Foxa2 was associated with the invasive phenotype in the primary prostate cancer. In the LPB-Tag/dominant active (D.A.) β-Catenin prostates, MMP7, a Wnt/β-Catenin target gene, was up-regulated. Furthermore, we also assessed AR and AR signaling pathway in these LPB-Tag/D.A. β-Catenin mice. Although β-Catenin is a well known AR co-activator in vitro, our study provides strong in vivo evidences indicating that both AR protein and the AR pathway were down-regulated in the prostate of LPB-Tag/D.A. β-Catenin mice. Histological analysis shows that prostate sections derived from the LPB-Tag/D.A. β-Catenin mice display neuroendocrine differentiation (NED) but NE cancer does not develop. Together, our findings indicate that Wnt/β-Catenin signaling plays an important role in the progression of mPIN to prostate adenocarcinoma.

From pathogenesis to prevention of castration resistant prostate cancer

BACKGROUND

Significant progress in understanding the molecular basis of castration resistant prostate cancer (CRPCa) has been achieved in recent years. Despite this progress, CRPCa still remains a lethal disease. Early detection and prevention of CRPCa may provide a new strategy to improve survival of patients diagnosed with PCa at risk to fail standard androgen deprivation therapy (ADT).

METHODS

Herein, we review pathogenetic mechanisms implicated in PCa progression toward castration resistant disease that are detectable in hormone naive PCa to define relevant therapeutic targets for prevention.

RESULTS

Upregulation of androgen receptor (AR) expression has been recognized a major determinant for the development of CRPCa. This hypersensitive pathway is further boosted by the increase of intratumoral androgen synthesis. AR mutants bind promiscuous steroids, and may convert AR antagonists to agonists. Various non-hormonal growth factor receptors transactivate the AR, even in absence of androgens (outlaw pathway). Finally, PCa cells can bypass the AR through various mechanisms, including BCL-2, COX-2, neuroendocrine differentiation. Most of these pathogenetic factors involved in the development of CRPCa are detectable in hormone naive PCa tissue even at the time of initial diagnosis, and could be targeted by drugs currently available.

CONCLUSIONS

CRPCa is the end-stage of a multifactorial and heterogeneous disease process. Pathogenetic factors responsible for the development of the CRPCa phenotype are detectable in the patient's PCa tissue long before the clinical onset of the disease. This approach provides opportunity for early detection and prevention by targeting pathways relevant for the individual disease process.

Pigment epithelium-derived factor and interleukin-6 control prostate neuroendocrine differentiation via feed-forward mechanism

PURPOSE

PEDF (pigment epithelium-derived factor) promotes the differentiation and survival of neuronal cells, and expands the adult neuronal stem cell niche. In the prostate PEDF is suppressed by androgen with unclear physiological consequences. We report that PEDF induced the neuroendocrine differentiation of prostate cancer cells, which was accompanied by neurite outgrowth and chromogranin A expression.

MATERIALS AND METHODS

We performed neuroendocrine differentiation assay, Western blot analysis, immunostaining and reverse transcriptase-polymerase chain reaction in the human prostate cancer cell lines LNCaP, PC-3 and DU145, and the prostate epithelial strain RWPE-1 (ATCC).

RESULTS

Ectopic and endogenous PEDF caused neuroendocrine differentiation of prostate cancer cells, as manifested by neurite-like outgrowths and chromogranin A expression. The transdifferentiated cells expressed axonal and dendritic markers, as ascertained by immunoblotting for specific markers. Neuroendocrine cells formed multiple synaptophysin positive protrusions resembling dendritic spines and vesicles containing serotonin, pointing to possible synapse formation. The known transdifferentiating agent interleukin-6 induced PEDF secretion. Moreover, PEDF neutralizing antibodies abolished the transdifferentiation of interleukin-6 treated cells, suggesting an autocrine loop. Neurogenic events were independent of cyclic adenosine monophosphate. Instead, PEDF activated in this order RhoA, nuclear factor kappaB and Stat3. Inhibitors of the Rho, nuclear factor kappaB and STAT pathways abolished differentiation and synapse formation. Additionally, nuclear factor kappaB activation caused interleukin-6 expression.

CONCLUSIONS

We discovered that nuclear factor kappaB controls the formation of neuronal communications in the prostate due to PEDF. We defined a feed-forward loop, in which nuclear factor kappaB induction elicits Stat3 activation and pro-differentiating interleukin-6 expression causes the further expansion of neuroendocrine communications. Our findings point to the role of nuclear factor kappaB and PEDF in coordinated prostate development.

Comparison of chromogranin A, insulin-like growth factor 1 and prostate-specific antigen serum markers in prostate adenocarcinoma and benign prostatic hyperplasia

BACKGROUND/AIM

To compare serum chromogranin A (CgA) and insulin-like growth factor 1 (IGF-1) with the classical prostate-specific antigen (PSA) marker in clinically localized prostate adenocarcinomas.

MATERIALS AND METHODS

This is a prospective single-center study that included 64 consecutive men with newly diagnosed clinically localized prostate adenocarcinoma and 20 consecutive men with histologically confirmed benign prostatic hyperplasia (BPH). A blood sample for the determination of serum total PSA, CgA and IGF-1 levels (RIA) was obtained from all cases. Analysis of variance was performed to evaluate their variations according to disease and the pathological characteristics of prostate adenocarcinoma.

RESULTS

Only serum PSA levels (p < 0.0001) and not IGF-1 (p = 0.5475) or CgA (p = 0.5043) were significantly higher in the prostate cancer (PCa) group as compared to the BPH group. A significant variance between BPH and PCa divided on the basis of pT stage was found for PSA levels (p < 0.0001) but not for CgA (p = 0.0869) and IGF-1 (p = 0.6883) levels. Dividing PCa on the basis of Gleason score, a significant variance was found for CgA (p = 0.0100) and for PSA (p < 0.001), but not for IGF-1 (p = 0.6895) levels.

CONCLUSIONS

In our population the quantification of PSA and CgA serum levels and not of IGF-1 provides independent significant information in the diagnosis and aggressiveness of PCa, respectively.

Hepatocyte nuclear factor-3 alpha (HNF-3alpha) negatively regulates androgen receptor transactivation in prostate cancer cells

The androgen receptor (AR) is involved in the development and progression of prostate cancers. However, the mechanisms by which this occurs remain incompletely understood. In previous reports, hepatocyte nuclear factor-3alpha (HNF-3alpha) has been shown to be expressed in the epithelia of the prostate gland, and has been determined to regulate the transcription of prostate-specific genes. In this study, we report that HNF-3alpha functions as a novel corepressor of AR in prostatic cells. HNF-3alpha represses AR transactivation on target promoters containing the androgen response element (ARE) in a dose-dependent manner. HNF-3alpha interacts physically with AR, and negatively regulates AR transactivation via competition with AR coactivators, including GRIP1. Furthermore, HNF-3alpha overexpression reduces the androgen-induced expression of prostate-specific antigen (PSA) in LNCaP cells. Taken together, our findings indicate that HNF-3alpha is a novel corepressor of AR, and predict its effects on the proliferation of prostate cancer cells.

Relapsed prostate cancer with neuroendocrine differentiation and high serum levels of carcinoembryonic antigen without elevation of prostrate-specific antigen: A case report

A 62-year-old man had been treated with combined androgen blockade due to cT2bN1M0 prostate cancer, and his serum prostate-specific antigen (PSA) levels decreased and remained under the level of 0.5 ng/mL during therapy. Approximately 40 months after the initial therapy, difficulty on urination and constipation developed gradually, and serum carcinoembryonic antigen (CEA) and pro-gastrin-releasing peptide (ProGRP) levels were high at this point. He underwent transrectal and transurethral biopsy of the prostate, which revealed adenocarcinoma positive for CEA and chromogranin A. He received palliative pelvic irradiation, and oral estramustine phosphate and etoposide combined therapy. Tumor markers decreased and clinical symptoms improved for several months. The patient died of encephalopathy of unknown etiology approximately 11 months after the relapse.

Expression and role of Foxa proteins in prostate cancer

The molecular mechanism(s) for prostate cancer progression to androgen independence are poorly understood. We have recently shown that Foxa1 and Foxa2 proteins are differentially expressed in epithelial cells during murine prostate development, growth, and adult function. Currently, the role of Foxa proteins in prostate cancer development and progression is unknown. Foxa protein expression was investigated in the LPB-Tag LADY mouse prostate cancer models, in human prostate cancer specimens, and various prostate cancer cell lines using Western blot and immunostaining analysis. In vitro transient transfection, studies were performed to investigate Foxa/prostate-specific gene regulation. Foxa1 was strongly expressed in areas of prostatic intraepithelial neoplasia (PIN) in both the androgen dependent 12T-7f and in the metastatic, androgen independent 12T-10 LADY models. Prominent Foxa1 and Foxa2 expression was observed in 12T-10 invasive undifferentiated neuroendocrine carcinomas, in the hormone independent and metastasizing 12T-10 derived, NE-10 allograft tumors, and in all metastatic lesions isolated from 12T-10 mice. Foxa1 protein expression was always observed in human prostate carcinomas, regardless of Gleason grade score, while Foxa2 was only detected in neuroendocrine small cell carcinomas and in some high Gleason score adenocarcinomas. Foxa proteins were also differentially expressed in three prostate cancer cell lines. Importantly, in vitro functional assays demonstrated that Foxa2 could activate androgen-dependent prostate-specific genes in an androgen receptor and ligand-independent manner. These results suggest that Foxa proteins are important in prostate carcinogenesis. In particular, Foxa2 may be involved in progression of prostate cancer to androgen independence. As such, Foxa proteins may represent novel targets for therapeutic intervention.

The chromogranin-A (CgA) in prostate cancer

Prostate cancer is one of the most frequent tumors in men. The neuroendocrine differentiation in prostate cancer has become more widely recognized and has attracted considerable attention as a potentially new finding with major diagnostic, prognostic and therapeutic implications. We investigated the role of the serum concentrations of CgA in a group of 57 patients with prostate cancer and in 61 elderly subjects with benign prostate hyperplasia (BPH). Neuron-specific enolase (NSE) is the most frequently employed marker to detect neuroendocrine features. Serum prostate-specific antigen (PSA), CgA and NSE levels were determined. Comparing prostate cancer group versus BPH group, the CgA level difference was 63.00 ng/ml (p<0.0001) and the PSA level difference was 50.86 mcg/ml (p<0.0001). Between prostate cancer group and control group the CgA level difference was 94.3 ng/ml (p<0.0001), the PSA level difference was 52.91 mcg/ml (p<0.0001), and the NSE level difference was 1.34 microg/l (p<0.0001). Patients with higher CgA levels had poorer prognosis and survival, compared to those with lower CgA levels. These results support the concept that serum CgA level determination before treatment is a potential prognostic factor for prostate cancer.

Neuroendocrine differentiation in prostate cancer: a sheep in wolf's clothing?

Neuroendocrine differentiation of the prostate is often associated with a dismal prognosis. Whilst it is relatively rare compared with other forms of prostate cancer, it nevertheless remains difficult to treat these cancers effectively and to maintain a durable response. Research aimed at understanding the complexity of neuroendocrine differentiation of the prostate has been conducted for some time. The cells involved in this process secrete a variety of factors that can influence growth patterns and regulatory pathways. Many of these factors can be monitored serologically, but the relationship between the biology of the tumor and clinical response is often discordant. This review outlines the difficulties in treating this disease, both at the time of diagnosis and in the metastatic setting, and focuses on an area of research that remains challenging to both the researcher and clinician.

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

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

New perspective in the management of neuroendocrine differentiation in prostate adenocarcinoma

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

Chromogranin A expression in familial versus sporadic prostate cancer

OBJECTIVES

To evaluate whether a significant difference in chromogranin A (CgA) levels exist between patients with familial and sporadic cancer.

METHODS

The study included 146 patients with clinically localized prostate adenocarcinoma (Stage T2N0M0), who underwent radical prostatectomy between June 1999 and June 2004. Patients were considered to have a positive family history for prostate cancer when the index patient confirmed the diagnosis of prostate cancer in a first-degree relative (brother or father). On the day of surgery, a blood sample for the determination of serum prostate-specific antigen and CgA levels (radioimmunoassay) was obtained from all patients. In a subgroup of 20 patients, CgA mRNA expression was also evaluated by reverse transcriptase-polymerase chain reaction at the prostatic tissue level.

RESULTS

A positive familial history was found in 28 (19.2%) of the 146 patients. The mean patient age in the familial group was significantly (P < 0.0001) lower than that in the sporadic group. No significant difference between the familial and sporadic groups was found in terms of prostate-specific antigen level (P = 0.9625) or Gleason score distribution (P = 0.4891). The familial group had significantly (P = 0.0013) lower serum CgA levels (43.3 +/- 12.7 ng/mL, median 39.9) compared with the sporadic group (55.9 +/- 19.4 ng/mL, median 54.1). The familial group also had significantly (P = 0.0432) lower expression of tissue CgA mRNA compared with the sporadic group.

CONCLUSIONS

The result of significantly lower CgA expression in familial compared with sporadic prostate cancer cases suggests that neuroendocrine activity is not increased in familial cases and also confirms that familial cancer is not a more aggressive disease.

Tumour markers for managing men who present with metastatic prostate cancer and serum prostate-specific antigen levels of <10 ng/mL

OBJECTIVE

To define immunohistochemical features of the primary cancers that might help in the differential diagnosis and monitoring of treatment in men presenting with metastatic prostate cancer and low serum levels of prostate-specific antigen (PSA), who can be difficult to diagnose and manage.

PATIENTS AND METHODS

Paraffin blocks of prostate biopsies were obtained for 33 patients presenting with untreated metastatic prostate cancer and serum PSA levels of <10 ng/mL. Sections were immunostained for PSA, prostatic acid phosphatase (PAP), prostate-specific membrane antigen (PSMA), androgen receptor (AR), chromogranin A and CD 56.

RESULTS

The combined Gleason scores were 8-10 in 25 men (76%) and 6 or 7 in the other eight (24%). Morphologically, there were no neuroendocrine features. PSA immunostaining was equivocal in 12 (36%) cases and in a further 19 (58%) was strong but focal and could be missed on biopsy sampling. PSMA was expressed in 90% of cases, and staining was widely distributed in nine of the 12 in which PSA staining was equivocal. There was strong AR expression in 30 (91%) cases and it was present in areas where PSA was absent.

CONCLUSION

In this patient group, immunohistochemical assessments of PSMA and AR are potentially useful as diagnostic markers.

Expression of Foxa transcription factors in the developing and adult murine prostate

BACKGROUND

The Foxa family (a1, a2, and a3) of proteins are transcription factors that are central to endodermal development. Recently, Foxa1 has been shown to regulate the transcription of several murine and human prostate specific genes involved in differentiated function by interacting with DNA promoter sequences and androgen receptors. Currently, the developmental expression pattern of Foxa proteins in the murine prostate is unknown.

METHODS

Male CD-1 mice (embryonic, prepubertal, pubertal, and adult) were used for immunohistochemical analysis of Foxa1, a2, and a3. Immunofluorescence was also performed for androgen receptor and cytokeratin 14 expression. Prostate tissue from pre-pubertal, pubertal, and adult mice were analyzed by Western blot and RT-PCR analysis for Foxa1, a2, and a3 expression.

RESULTS

Strong Foxa1 immunoreactivity was observed in epithelial cells throughout prostate development, growth, and adult differentiation. Prominent Foxa2 protein expression was only observed in the early stages of prostate development and was exclusively localized to epithelial cells of the forming buds. RT-PCR analysis identified low Foxa2 mRNA expression levels in the ventral and dorsolateral lobes of the adult prostate, with Foxa2 epithelial cell expression being localized to periurethral regions of the murine adult prostatic complex. Foxa3 expression was not observed in the murine prostate.

CONCLUSIONS

Foxa proteins represent epithelial cell markers in the murine prostate gland. The early expression of Foxa1 and a2 proteins in prostate formation suggests that these proteins play an important role in normal prostate development, in addition to differentiated secretory function.

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

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

Which patients with prostate cancer are actually candidates for hormone therapy?

In this article, we will try to address the following aspects: which factors are responsible of the introduction of new candidates for hormone therapy in prostate cancer, who are actually candidates for hormone therapy, classifying them on the basis of the stage of the disease, and which treatment modalities can be proposed for each candidate. Since the introduction of hormone therapy for the treatment of prostate cancer, there has been a debate about the optimal timing of hormone therapy. A modification in the timing of hormone therapy produced new candidates for hormone manipulation. In particular, the use of hormone treatment for younger patients, longer periods and early prostate cancer, absolutely requires a whole re-evaluation of which therapy is indicated and it may produce new problems such as higher risk of over-treatment, need of a better evaluation of quality of life in younger patients and the research for better tolerated therapies. Therapies that resist for longer periods without the production of a hormone-refractory disease are also required.

Neuroendocrine differentiation in prostate cancer

BACKGROUND

In numerous recent studies attention has been focused to neuroendocrine differentiation (NED) in prostate cancer (PC). Focal NED is present in almost all PCs, but it is prominent in only 5-10% of the carcinomas. The prognostic significance of focal NED in PC is controversial, but current evidence suggests its influence on the onset and/or conversion of hormone resistant tumor phenotype. The aim of this study was to evaluate the relationship between NED status, based only on immunohistochemical use of neuroendocrine (NE) markers, with PC grade and stage, and preoperative serum levels of prostate-specific antigen (PSA).

METHODS

The study included the biopsy material of 73 untreated PC patients (pts.) obtained by transurethral resection (TUR) (37 pts.), and radical retropubic prostatectomy (RRP) (36 pts.). Two representative tissue samples (typically the block containing the largest amount of neoplasm) were selected for immunohistochemical (IMM) staining. NE cells were identified using a panel of IMM markers: chromogranin A, neuron-specific enolase, and serotonin. The level of PC exocrine differentiation was detected by monoclonal antibodies against PSA.

RESULTS

Significant expression of NE cells was demonstrated in 26 (70.2%) pts. with PC after TUR. In this group, serum preoperative PSA values ranged from 0.1 to 9.6 ng/ml. The majority of pts. with NED had low differentiated PC with Gleason grade score (GGS) > 7, and normal PSA values below 4 ng/ml (77%), in clinical stage D (54%). Statistically significant correlation (p<0.01) of positive NED with higher stage and grade and low PSA values was established. Among the pts. with localized PC in whom RRP was performed (n=36), significant expression of NE cells was found in 15 pts. (41.7%), 8 (53.3%) in pT2 stage, and 7 (46.7%) in pT3 stage. Significant correlation between NED with preoperative PSA values and stage of PC in pts. with RRP was not found.

CONCLUSION

We demonstrated the significant NED in poorly differentiated PC in patients in the advanced stage of the disease. The expression of NED in organ-confined PC did not correlate with tumor stage, but it correlated with tumor grade (GGS < or = 7).

Long-term response to combination therapy with estramustine and somatostatin analogue in a patient with androgen ablation-refractory prostate cancer

We report on a patient with androgen ablation-refractory prostate adenocarcinoma who had an objective response for longer than 24 months using a combination of estramustine and lanreotide. At baseline from our combination therapy, his prostate-specific antigen level was 21.30 ng/mL and serum chromogranin A level was 816 ng/mL. The patient discontinued complete androgen deprivation therapy and underwent combination therapy with oral estramustine 420 mg/day plus lanreotide acetate 73.9 mg intramuscularly every 4 weeks. After 33 months of follow-up, the patient was alive without clinical disease progression, and his prostate-specific antigen and chromogranin A level was 0.10 and 12 ng/mL, respectively.

SOMATOSTATIN ANALOGUES AND ESTROGENS IN THE TREATMENT OF ANDROGEN ABLATION REFRACTORY PROSTATE ADENOCARCINOMA

PURPOSE

Prostate cancer progression to androgen ablation refractory stage D3 corresponds to cancer cell escape from androgen withdrawal induced apoptosis. Of note, salvage chemotherapy can extend the median survival of approximately 10 months in patients with stage D3. Therefore, novel therapeutic strategies that target the molecular basis of androgen resistance are required.

MATERIALS AND METHODS

The MEDLINE and Current Content databases were used to find studies of the use of estrogens and somatostatin analogues for D3 prostate adenocarcinoma. We also analyzed the rationale and clinical results of our combination therapy using lanreotide and ethinylestradiol.

RESULTS

Negative experiences have been reported with somatostatin analogues as monotherapy. On the other hand, the median progression-free survival reported in our experience using lanreotide acetate plus ethinylestradiol clearly surpassed the 10-month survival historically described in stage D3 cases.

CONCLUSIONS

The use of somatostatin analogues in combination therapy for D3 prostate cancer sustains the novel concept in cancer treatment in which therapies may target not only cancer cells, but also the microenvironment in combination, which can confer protection from apoptosis.

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

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

Genetically modified mice and their use in developing therapeutic strategies for prostate cancer

PURPOSE

At the National Cancer Institute a comprehensive program has been developed for accelerating prostate cancer research, especially in the area of mouse models for human cancers. This review focuses on transgenic mouse models for elucidating the molecular and cellular processes that lead to prostate cancer initiation, progression and metastasis, and on their suitability for therapeutic and chemopreventive trials.

MATERIALS AND METHODS

Published data from MEDLINE, http://emice.nci.nih.gov/, our laboratory and other investigators are reviewed.

RESULTS

Currently no 1 mouse model displays the entire continuum of human prostate cancer initiation, development and metastasis. The loss or over expression of a single gene results primarily in epithelial hyperplasia, prostatic intraepithelial neoplasia or more aggressive localized adenocarcinoma. To date the only models that develop lung, liver and occasionally bone metastasis are those that express SV40 large T antigen. A number of models have been used to investigate the efficacy of androgen deprivation, lovastatin, vitamin D, the anti-inflammatory drug E-7869, genistein and (-)-epigallocatechin-3-gallate as therapeutic or chemopreventive agents. Noninvasive optical imaging technologies facilitate the detection of metastatic lesions and the effects of therapeutic agents on tumor regression.

CONCLUSIONS

Integrating mouse studies with human clinical trials would ensure that mechanisms that promote prostate cancer are identified and potential therapeutic targets are validated.

Neuroendocrine cell differentiation in the CWR22 human prostate cancer xenograft: association with tumor cell proliferation prior to recurrence

BACKGROUND

Neuroendocrine (NE) cell differentiation is proposed to facilitate prostate cancer (CaP) recurrence following androgen deprivation through secretion by NE cells of growth factors and neuropeptides that support survival and proliferation of CaP cells and vasculature.

METHODS

The effect of androgen deprivation on NE differentiation and tumor cell proliferation in the CWR22 model of human CaP was determined by immunohistochemical analysis of the NE cell marker synaptophysin and the cell proliferation marker Ki67.

RESULTS

A significant increase in the number of NE cells was observed in CWR22 tumors between 28 and 66 days after castration compared to intact mice, that preceded the increase in tumor cell proliferation that began 70 days after androgen deprivation heralding recurrence. There was a significant positive correlation between the number of tumor-associated NE cells and proliferating CaP cells in tumors from mice after 28-34 days of androgen withdrawal.

CONCLUSION

In the CWR22 model, androgen deprivation induces an increase in tumor-associated NE cells prior to increased tumor cell proliferation, with NE cells possibly promoting tumor survival and recurrent disease.

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.

Interleukin-6 inhibits the growth of prostate cancer xenografts in mice by the process of neuroendocrine differentiation

In vitro, the human prostate cancer (PCA) cell line LNCaP can be permanently transdifferentiated into a quiescent neuroendocrine (NE) phenotype by the cytokine interleukin-6 (IL-6). Recently, we have shown that the growth of prostate cancer cells is significantly suppressed when cocultured with NE cells. In order to explore the inhibitory activity of IL-6 on prostate tumor growth, nude mice bearing xenografts of the PCA cell lines LNCaP and DU-145 (a line that is incapable of NE transdifferentiation by IL-6 in vitro) were treated with IL-6 for 3 weeks, either injected around the tumor or systematically released from implanted minipumps. Both administration forms of IL-6 inhibited the growth of LNCaP xenografts by more than 75% compared to the control group. In contrast, there was no difference in DU-145 tumor growth between IL-6-treated animals and controls. In comparison to control and DU-145 tumors, both IL-6 injected and pump-infused LNCaP tumors exhibited a significant increase in the expression of the NE markers neuron-specific enolase (NSE) and betaIII tubulin. Serum NSE levels were also significantly elevated in both IL-6-treated LNCaP tumor groups when compared to controls. IL-6 treatment resulted in G(0) cell cycle accumulation as evidenced by a loss of Ki-67 expression in > 90% of LNCaP tumor cells. These combined results demonstrate that IL-6-induced NE transdifferentiation of PCA cells has a significant inhibitory effect on tumor growth in mice. Agents, like IL-6, capable of NE transdifferentiation of PCA cells, should be considered as a new therapeutic approach for the treatment of prostate cancer.

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

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

Prostate-specific deletion of the murine Pten tumor suppressor gene leads to metastatic prostate cancer

The murine Pten prostate cancer model described in this study recapitulates the disease progression seen in humans: initiation of prostate cancer with prostatic intraepithelial neoplasia (PIN), followed by progression to invasive adenocarcinoma, and subsequent metastasis with defined kinetics. Furthermore, while Pten null prostate cancers regress after androgen ablation, they are capable of proliferating in the absence of androgen. Global assessment of molecular changes caused by homozygous Pten deletion identified key genes known to be relevant to human prostate cancer, including those "signature" genes associated with human cancer metastasis. This murine prostate cancer model provides a unique tool for both exploring the molecular mechanism underlying prostate cancer and for development of new targeted therapies.