Terminal neuroendocrine differentiation of human prostate carcinoma cells in response to increased intracellular cyclic AMP

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

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

Identification of genes targeted by the androgen and PKA signaling pathways in prostate cancer cells

Progression of prostate cancer to androgen independence is suspected to involve the androgen and protein kinase A (PKA) signaling pathways. Here for the first time, the transcriptomes associated with each pathway and common transcriptional targets in response to stimulation of both pathways were identified in human prostate cancer cells using Affymetrix GeneChip technology (Human Genome U133 plus2). Statistically significant changes in the levels of 858 genes in response to androgen and 303 genes in response to activation of the PKA pathway were determined using GeneSpring software. Expression of a subset of these genes (22) that were transcriptional targets for the androgen and/or PKA pathways were validated by reverse transcriptase-polymerase chain reaction and Western blot analyses. Application of small interfering RNAs to the androgen receptor (AR) revealed that in addition to KLK3, levels of expression of KLK2 and SESN1 were regulated by AR activated by both the androgen and PKA signaling pathways. SESN1 was identified as a gene repressed by activated AR. These results provide a broad view of the effects of the androgen and PKA signaling pathways on the transcriptional program of prostate cancer cells and indicate that only a limited number of genes are targeted by cross-talk between AR and PKA pathways.

Neural transdifferentiation of mesenchymal stem cells--a critical review

The classic concept of stem cell differentiation can be illustrated as driving into a series of one-way streets, where a given stem cell through generations of daughter cells becomes correspondingly restricted and committed towards a definitive lineage with fully differentiated cells as end points. According to this concept, tissue-derived adult stem cells can only give rise to cells and cell lineages found in the natural, specified tissue of residence. During the last few years it has, however, been reported that under certain experimental conditions adult stem cells may lose their tissue or germ layer-specific phenotypes and become reprogrammed to transdifferentiate into cells of other germ layers and tissues. The transdifferentiation process is referred to as "stem cell plasticity". Mesenchymal stem cells, present in various tissues, including bone marrow, have--besides differentiation into bone, cartilage, smooth muscle and skeletal muscle--also been reported to transdifferentiate into skin, liver and brain cells (neurons and glia). Conversely, neural stem cells have been reported to give rise to blood cells. The actual occurrence of transdifferentiation is currently much debated, but would have immense clinical potential in cell replacement therapy and regenerative medicine. Controlled neural differentiation of human mesenchymal stem cells might thus become an important source of cells for cell therapy of neurodegenerative diseases, since autologous adult mesenchymal stem cells are more easily harvested and effectively expanded than corresponding neural stem cells. This article provides a critical review of the reports of neural transdifferentiation of mesenchymal stem cells, and proposes a set of criteria to be fulfilled for validation of transdifferentiation.

Immunohistochemical Distribution of cAMP- and cGMP-Phosphodiesterase (PDE) Isoenzymes in the Human Prostate

OBJECTIVES

With the introduction of sildenafil citrate (Viagra), the concept of phosphodiesterase (PDE) inhibition has gained tremendous interest in the field of urology. Cyclic nucleotide second messengers cGMP and cAMP have been assumed to be involved in the control of the normal function of the prostate. The aim of the present study was to evaluate by means of immunohistochemistry the expression and distribution of some cAMP- and cGMP-PDE isoenzymes in the prostate.

MATERIAL & METHODS

Cryostat sections (10 microM) of formaldehyde-fixated tissue segments excised from the transition zone of human prostates were incubated with primary antibodies directed against the PDE isoenzymes 3, 4, 5, and 11. Then, sections were exposed to either fluorescein isothiocyanate- (FITC) or Texas Red- (TR) labeled secondary antibodies and visualization was commenced by means of laser fluorescence microscopy.

RESULTS

TR-immunofluorescence indicating the presence of PDE4 (cAMP-PDE) was abundantly observed in the fibromuscular stroma as well as in glandular structures of the transition zone. In contrast to the distribution of PDE4, immunoactivity indicating PDE5 (cGMP-PDE) and 11 (dual substrate PDE) was mainly observed in glandular and subglandular areas. No immunostaining for PDE3 (cGMP-inhibited PDE) was detected.

CONCLUSION

Our results confirm the presence of PDE isoenzymes 4, 5 and 11 in the transition zone of the human prostate and present evidence that these isoenzymes are not evenly distributed. These findings are in support of the hypothesis that there might be a rationale for the use of PDE inhibitors in the pharmacotherapy of BPH and LUTS.

Differentiation of human bone marrow stem cells into cells with a neural phenotype: diverse effects of two specific treatments

Background

It has recently been demonstrated that the fate of adult cells is not restricted to their tissues of origin. In particular, it has been shown that bone marrow stem cells can give rise to cells of different tissues, including neural cells, hepatocytes and myocytes, expanding their differentiation potential.

Results

In order to identify factors able to lead differentiation of stem cells towards cells of neural lineage, we isolated stromal cells from human adult bone marrow (BMSC). Cells were treated with: (1) TPA, forskolin, IBMX, FGF-1 or (2) retinoic acid and 2-mercaptoethanol (BME). Treatment (1) induced differentiation into neuron-like cells within 24 hours, while a longer treatment was required when using retinoic acid and BME. Morphological modifications were more dramatic after treatment (1) compared with treatment (2). In BMSC both treatments induced the expression of neural markers such as NF, GFAP, TUJ-1 and neuron-specific enolase. Moreover, the transcription factor Hes1 increased after both treatments.

Conclusion

Our study may contribute towards the identification of mechanisms involved in the differentiation of stem cells towards cells of neural lineage.

Genetic analysis of neuroendocrine tumor cells in prostatic carcinoma

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Potent Antiandrogen and Androgen Receptor Activities of an Angelica gigas–Containing Herbal Formulation: Identification of Decursin as a Novel and Active Compound with Implications for Prevention and Treatment of Prostate Cancer

Androgen and androgen receptor (AR)-mediated signaling are crucial for the development of prostate cancer. Identification of novel and naturally occurring phytochemicals that target androgen and AR signaling from Oriental medicinal herbs holds exciting promises for the chemoprevention of this disease. In this article, we report the discovery of strong and long-lasting antiandrogen and AR activities of the ethanol extract of a herbal formula (termed KMKKT) containing Korean Angelica gigas Nakai (AGN) root and nine other Oriental herbs in the androgen-dependent LNCaP human prostate cancer cell model. The functional biomarkers evaluated included a suppression of the expression of prostate-specific antigen (PSA) mRNA and protein (IC50, approximately 7 microg/mL, 48-hour exposure) and an inhibition of androgen-induced cell proliferation through G1 arrest and of the ability of androgen to suppress neuroendocrine differentiation at exposure concentrations that did not cause apoptosis. Through activity-guided fractionation, we identified decursin from AGN as a novel antiandrogen and AR compound with an IC50 of approximately 0.4 microg/mL (1.3 micromol/L, 48-hour exposure) for suppressing PSA expression. Decursin also recapitulated the neuroendocrine differentiation induction and G1 arrest actions of the AGN and KMKKT extracts. Mechanistically, decursin in its neat form or as a component of AGN or KMKKT extracts inhibited androgen-stimulated AR translocation to the nucleus and down-regulated AR protein abundance without affecting the AR mRNA level. The novel antiandrogen and AR activities of decursin and decursin-containing herbal extracts have significant implications for the chemoprevention and treatment of prostate cancer and other androgen-dependent diseases.

cAMP induced modifications of HOX D gene expression in prostate cells allow the identification of a chromosomal area involved in vivo with neuroendocrine differentiation of human advanced prostate cancers

The acquisition of epithelial-neuroendocrine differentiation (ND) is a peculiarity of human advanced, androgen-independent, prostate cancers. The HOX genes are a network of transcription factors controlling embryonal development and playing an important role in crucial adult eukaryotic cell functions. The molecular organization of this 39-gene network is unique in the genome and probably acts by regulating phenotype cell identity. The expression patterns of the HOX gene network in human prostate cell phenotypes, representing different stages of prostate physiology and prostate cancer progression, make it possible to discriminate between different human prostate cell lines and to identify loci and paralogous groups harboring the HOX genes mostly involved in prostate organogenesis and cancerogenesis. Exposure of prostate epithelial phenotypes to cAMP alters the expression of lumbo-sacral HOX D genes located on the chromosomal region 2q31-33 where the cAMP effector genes CREB1, CREB2, and cAMP-GEFII are present. Interestingly, this same chromosomal area harbors: (i) a global cis-regulatory DNA control region able to coordinate the expression of HOX D and contiguous phylogenetically unrelated genes; (ii) a prostate specific ncRNA gene associated with high-risk prostate cancer (PCGEM1); (iii) a series of neurogenic-related genes involved with epithelial-neuronal cell conversion. We report the expression of neurexin 1, Neuro D1, dlx1, and dlx2 in untreated and cAMP treated epithelial prostate cells. The in vivo expression of Neuro D1 in human advanced prostate cancers correlate with the state of tumor differentiation as measured by Gleason score. Thus, we suggest that the chromosomal area 2q 31-33 might be involved in the epithelial-ND characteristic of human advanced prostate cancers.

Distribution and functional significance of phosphodiesterase isoenzymes in the human lower urinary tract

To date, it is widely accepted that several disorders of the male and female urogenital tract, such as erectile dysfunction, bladder overactivity, urinary stone disease and the benign prostatic syndrome, can be therapeutically approached by influencing the function of the smooth musculature of the respective organs. In order to achieve a pronounced drug effect without significant adverse events, especially on the cardiovascular system, a certain degree of tissue selectivity is mandatory. Selective intervention in intracellular pathways regulating smooth muscle tone has become a promising strategy to modulate tissue function. Since the concept of taking a pill as a cure for an illness or the relief of symptoms has become widely accepted by the consumers, the pharmacological treatment of urological diseases has focused on selective, orally available drugs, acting via influencing intracellular regulatory mechanisms, thus combining a high response rate and the advantage of an on-demand intake. PDEs play a central role in controlling the levels of cyclic nucleotides (i.e. cAMP and/or cGMP), which are important second messengers in many transmitter pathways involved in the regulation of biological processes of urogenital tissues. Specifically, the use of isoenzyme selective phosphodiesterase (PDE) inhibitors offers great hope in the medical treatment of various genitourinary diseases. These agents are regarded efficacious, having a fast onset of drug action in the target tissue and an improved effect-to-side-effect ratio. The growing experience with the use of this class of compounds in urology is mainly based on basic research efforts and this field will remain the most exciting and innovative subject in genitourinary physiology and pharmacology for the next few years. These tremendous research efforts may lead to a vast pharmacological armamentarium of possible new treatment options. The purpose of this review is to summarize the current knowledge on the distribution and potential functional significance of PDE isoenzymes in the human lower urinary tract.

The cross talk between protein kinase A- and RhoA-mediated signaling in cancer cells

The cross talk between cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) and RhoA-mediated signal transductions and the effect of this cross talk on biologic features of human prostate and gastric cancer cells were investigated. In the human gastric cancer cell line, SGC-7901, lysophosphatidic acid (LPA) increased RhoA activity in a dose-dependent manner. The cellular permeable cAMP analog, 8-chlorophenylthio-cAMP (CPT-cAMP), inhibited the LPA-induced RhoA activation and caused phosphorylation of RhoA at serine(188). Immunofluorescence microscopy, Western blotting, and green fluorescent protein (GFP)-tagged RhoA location assay in live cells revealed that RhoA was distributed in both the cytoplasm and nucleus of SGC-7901 cells. Treatment with LPA and/or CPT-cAMP did not induce obvious translocation of RhoA in the cells. The LPA treatment caused formation of F-actin in SGC-7901 cells, and CPT-cAMP inhibited the formation. In a modified Boyden chamber assay, LPA stimulated the migration of SGC-7901 cells, and CPT-cAMP dose-dependently inhibited the stimulating effect of LPA. In soft agar assay, LPA stimulated early proliferation of SGC-7901 cells, and CPT-cAMP significantly inhibited the growth of LPA-stimulated cells. In the prostate cancer cell line, PC-3, LPA caused morphologic changes from polygonal to round, and transfection with plasmid DNA encoding constitutively active RhoA(63L) caused a similar change. Treatment with CPT-cAMP inhibited the changes in both cases. However, in PC-3 cells transfected with a plasmid encoding mutant RhoA188A, LPA induced rounding, but CPT-cAMP could not prevent the change. Results of this experiment indicated that cAMP/PKA inhibited RhoA activation, and serine188 phosphorylation on RhoA was necessary for PKA to exert its inhibitory effect on RhoA activation. The cross talk between cAMP/PKA and RhoA-mediated signal transductions had significant affect on biologic features of gastric and prostate cancer cells, such as morphologic and cytoskeletal change, migration, and anchorage-independent growth. The results may be helpful in implementing novel therapeutic strategies for invasive and metastatic prostate and gastric cancers.

[Relevance of the neuroendocrine differentiation in prostatic carcinoma]

BACKGROUND

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Interferon-gamma induces neuroendocrine-like differentiation of human prostate basal-epithelial cells

BACKGROUND

Prostatic neuroendocrine (NE) cells are intraglandular hybrid epithelial-neural-endocrine cells that express and secrete numerous hormones and neuropeptides, which presumably regulate growth, differentiation, and secretory activity of the prostatic epithelium. This specialized cell type appears to differentiate from a common basal/precursor/stem cell that also gives rise to the secretory epithelium. In order to elucidate mechanisms of NE-differentiation the effects of type 1 (alpha, beta) and type 2 (gamma) interferons (IFNs) on human prostate basal cells (PrECs) were evaluated.

METHODS AND RESULTS

Application of alpha/beta IFN increased the expression of the cell-cycle inhibitor p21(CIP1) and inhibited DNA synthesis, while only IFN-gamma led to increased apoptosis, cell-cycle inhibitor p27(KIP1) upregulation, and differentiation of PrECs into NE-like cells. In vitro differentiated NE-like cells expressed the glycolytic enzyme neuron-specific enolase (NSE) and chromogranin A (CgA), known markers of NE-cells in vivo in the prostate. These NE-like cells also changed cytokeratin (CK) expression patterns by upregulating CK 8/18, predominantly found in terminally-differentiated secretory luminal/NE epithelial cells.

CONCLUSIONS

IFN-gamma produced locally in the prostate by basal cells and, under proinflammatory conditions, by infiltrating lymphocytes could support NE cell differentiation and play a role in NE differentiation processes of tumor cells in hormone-refractory prostate cancer.

Interleukin-6 regulation of prostate cancer cell growth

Interleukin-6 (IL-6) is involved in regulation of immune reaction and cell growth and differentiation. It causes multifunctional responses ranging from inhibition of proliferation to promotion of cell survival. IL-6 effects may depend on experimental conditions such as passage numbers and serum composition. IL-6 signals in target tissues through the receptor that is composed of the ligand-binding and signal-transducing subunits. IL-6 is expressed in benign and malignant prostate tissue and the levels of the cytokine and its receptor increase during prostate carcinogenesis. IL-6 is considered a positive growth factor for most prostate cells. The only exemption seems to be the LNCaP cell line, in which IL-6 causes growth arrest and induces differentiation function. In contrast, IL-6 acts as an autocrine growth factor in the subline LNCaP-IL-6+ established after chronic treatment with IL-6. IL-6 is a candidate for targeted therapy in prostate cancer because of its association with morbidity. Activation of signaling pathways of Janus kinase/signal transducers and activators of transcription factors, mitogen-activated protein kinase (MAPK), and phosphatidylinositol 3-kinase has been reported in various prostate cancer cell lines. IL-6 and the related cytokine oncostatin M induce activation of the androgen receptor (AR) in the absence of androgen. IL-6 is also involved in regulation of vascular endothelial growth factor expression as well as neuroendocrine differentiation in prostate. Anti-IL-6 antibodies showed an inhibitory effect on the PC-3 xenograft. However, the development of this therapy in prostate cancer is in early stages.

A human- and male-specific protocadherin that acts through the wnt signaling pathway to induce neuroendocrine transdifferentiation of prostate cancer cells

Protocadherin-PC (PCDH-PC) is a gene on the human Y chromosome that is selectively expressed in apoptosis- and hormone-resistant human prostate cancer cells. The protein encoded by PCDH-PC is cytoplasmically localized and has a small serine-rich domain in its COOH terminus that is homologous to the beta-catenin binding site of classical cadherins. Variants of prostate cancer cells that express PCDH-PC have high levels of nuclear beta-catenin protein and increased wnt-signaling. In this study, we show that transfection of human prostate cancer cells (LNCaP) with PCDH-PC or culture of these cells in androgen-free medium (a condition that up-regulates PCDH-PC expression) activates wnt signaling as assessed by nuclear accumulation of beta-catenin, increased expression of luciferase from a reporter vector promoted by Tcf binding elements and increased expression of wnt target genes. Moreover, LNCaP cells transfected with PCDH-PC or grown in androgen-free medium transdifferentiate to neuroendocrine-like cells marked by elevated expression of neuron-specific enolase and chromogranin-A. Neuroendocrine transdifferentiation was also observed when LNCaP cells were transfected by stabilized beta-catenin. Increased wnt signaling and neuroendocrine transdifferentiation of LNCaP cells induced by culture in androgen-free medium was suppressed by short interfering RNAs that target PCDH-PC as well as by dominant-negative Tcf or short interfering RNA against beta-catenin, supporting the hypothesis that increased expression of PCDH-PC is driving neuroendocrine transdifferentiation by activating wnt signaling. These findings have significant implications for the process through which prostate cancers progress to hormone resistance in humans.

Involvement of fatty acid-CoA ligase 4 in hepatocellular carcinoma growth: Roles of cyclic AMP and p38 mitogen-activated protein kinase

AIM: Fatty acid-CoA ligase 4 (FACL4) is an arachidonate-preferring enzyme which has been shown to be up-regulated in human colon cancer tissues and implicated in the colon tumorigenesis. The purpose of this study was to investigate the role of FACL4 in the human hepatocellular carcinoma (HCC) tumorigenesis and the specific signal pathways involved in this process.

METHODS: We investigated the expression and regulation of FACL4 in HCC, adjacent non-tumorous liver tissues, and cell lines.

RESULTS: In HCC patients, we demonstrated that FACL4 gene expression was markedly elevated in the cancerous tissues than in the adjacent non-cancerous liver tissues. In addition, several human hepatoma cell lines, including Hep3B and HepG2, expressed high levels of FACL4. Stable overex-pression of FACL4 knockdown plasmids (small interfering RNA, siRNA) to Hep3B cells significantly decreased FACL4 expression and subsequently limited the cell proliferation. Treatment of Hep3B cells with 8-bromo-cAMP and SB203508 (p38 MAPK inhibitor) significantly suppressed the FACL4 expression.

CONCLUSION: FACL4 is involved in the HCC tumorigenesis and both cAMP and p38 MAPK pathways are associated with the regulation of FACL4 in HCC.

Changes in chromogranin a serum levels during endocrine therapy in metastatic prostate cancer patients

INTRODUCTION

The concept of neuroendocrine (NE) differentiation in prostate cancer has become more widely recognized as its diagnostic, prognostic, and therapeutic usefulness.

PATIENTS AND METHODS

We enrolled 38 patients with stage D prostate cancer who underwent endocrine therapy by medical or surgical castration and oral antiandrogen. According to PSA response, serum levels of CGA as a marker of NE differentiation were measured at the multiple points of time; (1) pre-treatment, (2) complete response (CR), (3) a nadir level of PSA, (4) PSA failure or hormone independent progression. We compared these serum values in relation to efficacy of endocrine therapy.

RESULTS

There was no correlation between serum PSA and CGA values. Patients consisted of 27 with CR and 11 without CR. Serum CGA increased as intervals of endocrine therapy became longer with positive correlation (p < 0.05). Its velocity was higher in patients with PSA failure than in those without it (6.98 vs. 2.09 ng/ml/month, p = 0.011).

CONCLUSION

During endocrine therapy in metastatic prostate cancer patients, serum CGA values were not related to serum PSA levels, and increased as treatment periods became longer. It is suggested that CGA velocity has potential to predict androgen independent progression after endocrine therapy.

Vasoactive intestinal peptide induces neuroendocrine differentiation in the LNCaP prostate cancer cell line through PKA, ERK, and PI3K

BACKGROUND

Neuroendocrine (NE) differentiation in prostate cancer has been correlated with unfavorable clinical outcome. The mechanisms by which prostate cancer acquires NE properties are poorly understood, but several signaling pathways have been proposed. We have previously observed that vasoactive intestinal peptide (VIP) stimulates cAMP production mainly through VPAC(1) receptor, inducing NE differentiation in LNCaP cells. The aim of this study was to analyze the mechanisms involved in this process.

METHODS

Reverse transcriptase (RT)-polymerase chain reaction (PCR), quantitative real-time RT-PCR, Western blotting, and immunocytochemistry were performed.

RESULTS

LNCaP cells produce VIP, as demonstrated by RT-PCR and immunocytochemistry. VIP induced NE differentiation of LNCaP cells at a time as short as 1 hr of treatment, and the same occurred with the expression and secretion of neuronal-specific enolase (NSE, a NE differentiation marker). These effects were faster than those exerted by serum-deprivation. VIP induced extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation and NE differentiation by PKA-dependent and independent pathways, since the PKA inhibitor H89 partially blocked VIP-induced NE differentiation and did not affect ERK1/2 phosphorylation. mitogen-activated protein kinase kinase (MEK) and phosphoinositide 3-kinase (PI3K) appear to be also involved since the inhibitors PD98059 and wortmannin abolished ERK1/2 phosphorylation and decreased NE differentiation induced by VIP. Moreover, VIP activated Ras suggesting the involvement of a Ras-dependent pathway.

CONCLUSIONS

VIP behaves as autocrine/paracrine factor in LNCaP cells by inducing NE differentiation through PKA, ERK1/2, and PI3K.

Melatonin reduces prostate cancer cell growth leading to neuroendocrine differentiation via a receptor and PKA independent mechanism

BACKGROUND

Melatonin, the main secretory product of the pineal gland, inhibits the growth of several types of cancer cells. Melatonin limits human prostate cancer cell growth by a mechanism which involves the regulation of androgen receptor function but it is not clear whether other mechanisms may also be involved.

METHODS

Time-course and dose-dependent studies were performed using androgen-dependent (LNCaP) and independent (PC3) prostate cancer cells. Cell number, cell viability, and cell cycle progression were studied. Neuroendocrine differentiation of these cells was evaluated by studying morphological and biochemical markers. Finally, molecular mechanisms including the participation of melatonin membrane receptors, intracellular cAMP levels, and the PKA signal transduction pathway were also analyzed.

RESULTS

Melatonin treatment dramatically reduced the number of prostate cancer cells and stopped cell cycle progression in both LNCaP and PC3 cells. In addition, it induced cellular differentiation as indicated by obvious morphological changes and neuroendocrine biochemical parameters. The role of melatonin in cellular proliferation and differentiation of prostate cancer cells is not mediated by its membrane receptors nor related to PKA activation.

CONCLUSIONS

The treatment of prostate cancer cells with pharmacological concentrations of melatonin influences not only androgen-sensitive but also androgen-insensitive epithelial prostate cancer cells. Cell differentiation promoted by melatonin is not mediated by PKA activation although it increases, in a transitory manner, intracellular cAMP levels. Melatonin markedly influences the proliferative status of prostate cancer cells. These effects should be evaluated thoroughly since melatonin levels are diminished in aged individuals when prostate cancer typically occurs.

IB1/JIP-1 controls JNK activation and increased during prostatic LNCaP cells neuroendocrine differentiation

The scaffold protein Islet-Brain1/c-Jun amino-terminal kinase Interacting Protein-1 (IB1/JIP-1) is a modulator of the c-Jun N-terminal kinase (JNK) activity, which has been implicated in pleiotrophic cellular functions including cell differentiation, division, and death. In this study, we described the presence of IB1/JIP-1 in epithelium of the rat prostate as well as in the human prostatic LNCaP cells. We investigated the functional role of IB1/JIP-1 in LNCaP cells exposed to the proapoptotic agent N-(4-hydroxyphenyl)retinamide (4-HPR) which induced a reduction of IB1/JIP-1 content and a concomittant increase in JNK activity. Conversely, IB1/JIP-1 overexpression using a viral gene transfer prevented the JNK activation and the 4-HPR-induced apoptosis was blunted. In prostatic adenocarcinoma cells, the neuroendocrine (NE) phenotype acquisition is associated with tumor progression and androgen independence. During NE transdifferentiation of LNCaP cells, IB1/JIP-1 levels were increased. This regulated expression of IB1/JIP-1 is secondary to a loss of the neuronal transcriptional repressor neuron restrictive silencing factor (NRSF/REST) function which is known to repress IB1/JIP-1. Together, these results indicated that IB1/JIP-1 participates to the neuronal phenotype of the human LNCaP cells and is a regulator of JNK signaling pathway.

Constitutive activation of gp130 leads to neuroendocrine differentiation in vitro and in vivo

BACKGROUND

Neuroendocrine (NE) differentiation in prostate tumors has been correlated with androgen independent disease and increased risk of death. In vitro, IL-6 initiates NE differentiation utilizing the signal transduction initiated by the interaction with IL-6R alpha and gp130. In this study we analysed the NE differentiation process in vitro and in vivo using the LNCaP androgen dependent cell line via ligand independent induction of NE differentiation.

METHODS

LNCaP cells were transfected with a constitutively active gp130 subunit, gp130act. Cell proliferation rate was determined and clones were examined for neuroendocrine differentiation by morphological change, upregulation of CgA and serotonin and formation of dense core vesicles with LNCaP parental cells as the control. Xenograft formation was examined and compared in immunocompromised mice.

RESULTS

Gp130act expression promoted significant neuroendocrine differentiation in vitro as determined by a NE like morphology change (increased neurite like extension formation), elevated CgA expression and the formation of dense core vesicles (DCV). These measures concurred with those examined in LNCaP cells following 100 ng/ml IL-6 treatment. Further investigation of the LNCaP gp130act cells in vivo, in immunocompromised androgen intact mice, confirmed that the NE like morphology, as determined by histological and high resolution transmission electron microscopy, was maintained.

CONCLUSIONS

NE differentiation was initiated by the expression of gp130act in a ligand independent manner, highlighting the importance of gp130 in the neuroendocrine differentiation process. Further investigation of upregulated/downregulated gene expression in these cells may provide valuable insight into the NE differentiation process.

Reevaluation of in vitro differentiation protocols for bone marrow stromal cells: disruption of actin cytoskeleton induces rapid morphological changes and mimics neuronal phenotype

Bone marrow stromal cells (MSC), which represent a population of multipotential mesenchymal stem cells, have been reported to undergo rapid and robust transformation into neuron-like phenotypes in vitro following treatment with chemical induction medium including dimethyl sulfoxide (DMSO; Woodbury et al. [2002] J. Neurosci. Res. 96:908). In this study, we confirmed the ability of cultured rat MSC to undergo in vitro osteogenesis, chondrogenesis, and adipogenesis, demonstrating differentiation of these cells to three mesenchymal cell fates. We then evaluated the potential for in vitro neuronal differentiation of these MSC, finding that changes in morphology upon addition of the chemical induction medium were caused by rapid disruption of the actin cytoskeleton. Retraction of the cytoplasm left behind long processes, which, although strikingly resembling neurites, showed essentially no motility and no further elaboration during time-lapse studies. Similar neurite-like processes were induced by treating MSC with DMSO only or with actin filament-depolymerizing agents. Although process formation was accompanied by rapid expression of some neuronal and glial markers, the absence of other essential neuronal proteins pointed toward aberrantly induced gene expression rather than toward a sequence of gene expression as is required for neurogenesis. Moreover, rat dermal fibroblasts responded to neuronal induction by forming similar processes and expressing similar markers. These studies do not rule out the possibility that MSC can differentiate into neurons; however, we do want to caution that in vitro differentiation protocols may have unexpected, misleading effects. A dissection of molecular signaling and commitment events may be necessary to verify the ability of MSC transdifferentiation to neuronal lineages.

Retinoic acid slows progression and promotes apoptosis of spontaneous prostate cancer

BACKGROUND

All-trans retinoic acid (ATRA) promotes terminal differentiation in epithelial cells and anti-angiogenesis and thus, may have beneficial effects in an intervention therapy for prostate cancer.

METHODS

We used the autochthonous spontaneous transgenic adenocarcinoma of the mouse prostate (TRAMP) model system to test the ability of ATRA to prevent initiation and progression of prostate cancer in a pre-clinical setting.

RESULTS

Initial studies demonstrated that exposure of TRAMP-derived C2N prostate tumor cells to ATRA in vitro decreased total viable cell numbers with a concomitant decrease in the fraction of cells in S phase. When TRAMP mice were treated in vivo with ATRA for either 6 or 8 weeks at low, medium, or high dose, mice on average presented with lower grade and more differentiated tumors. However, ATRA therapy conferred no significant protection on incidence of tumors or frequency of metastasis at any dose. Nevertheless, we were able to observe a significant decrease in the expression of synaptophysin, a marker of neuroendocrine differentiation, in tumors of mice receiving the highest dose of ATRA. As well, expression of the cell cycle inhibitor p21 was found to be elevated only in well-differentiated tumors of mice, treated with ATRA while expression of p27, was found to be elevated only in the poorly differentiated tumors.

CONCLUSIONS

Collectively, our in vitro and in vivo data demonstrates that ATRA was able to slow prostate tumor cell proliferation, induce apoptosis, and block the emergence of the neuroendocrine phenotype. Furthermore, our study suggests the differential regulation of p21 and p27 as a molecular mechanism whereby ATRA intervention therapy can inhibit the natural history of spontaneous prostate cancer.

Ca2+ homeostasis and apoptotic resistance of neuroendocrine-differentiated prostate cancer cells

Neuroendocrine (NE) differentiation is a hallmark of advanced, androgen-independent prostate cancer, for which there is no successful therapy. NE tumor cells are nonproliferating and escape apoptotic cell death; therefore, an understanding of the apoptotic status of the NE phenotype is imperative for the development of new therapies for prostate cancer. Here, we report for the first time on alterations in intracellular Ca(2+) homeostasis, which is a key factor in apoptosis, caused by NE differentiation of androgen-dependent prostate cancer epithelial cells. NE-differentiating regimens, either cAMP elevation or androgen deprivation, resulted in a reduced endoplasmic reticulum Ca(2+)-store content due to both SERCA 2b Ca(2+) ATPase and luminal Ca(2+) binding/storage chaperone calreticulin underexpression, and to a downregulated store-operated Ca(2+) current. NE-differentiated cells showed enhanced resistance to thapsigargin- and TNF-alpha-induced apoptosis, unrelated to antiapoptotic Bcl-2 protein overexpression. Our results suggest that targeting the key players determining Ca(2+) homeostasis in an attempt to enhance the proapoptotic potential of malignant cells may prove to be a useful strategy in the treatment of advanced prostate cancer.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Osteopontin enhances the cell proliferation induced by the epidermal growth factor in human prostate cancer cells

BACKGROUND

Susceptibility to extracellular matrix and growth factors has been demonstrated to play a critical role in the development of prostate cancer (PCa) metastases. The aim of this study was to elucidate some mechanisms by which stroma controls tumor progression.

METHODS

In our study we tested the growth ability of the LNCaP human prostatic cell line in steroid-free culture conditions in response to osteopontin (OPN), a non-collageneous matrix protein, localized in large amounts in the bone.

RESULTS

In the LNCaP cell model, OPN stimulates cell proliferation in serum-free medium and colony growth at high dilution but this effect is visible only in presence of epidermal growth factor (EGF). Proliferation induced by OPN is accompanied by a sustained activation of EGF receptor (EGFR) whose phosphorylation is detectable up to 12 hr after treatment in association with EGF. The colocalization of integrin beta1, a ligand of OPN, and of EGFR on the cellular membrane, suggests that the association of these cell surface receptors may be the principal mechanism involved in the long-term activation of the EGFR.

CONCLUSIONS

Our data describe a new possible mechanism involved in the establishment of bone metastases which may also account for the formation of androgen-independent cellular clones, frequently responsible of the clinical progression of PCa.

RNA interference of achaete-scute homolog 1 in mouse prostate neuroendocrine cells reveals its gene targets and DNA binding sites

We have previously characterized a transgenic mouse model (CR2-TAg) of metastatic prostate cancer arising in the neuroendocrine (NE) cell lineage. Biomarkers of NE differentiation in this model are expressed in conventional adenocarcinoma of the prostate with NE features. To further characterize the pathways that control NE proliferation, differentiation, and survival, we established prostate NE cancer (PNEC) cell lines from CR2-TAg prostate tumors and metastases. GeneChip analyses of cell lines harvested at different passages, and as xenografted tumors, indicated that PNECs express consistent features ex vivo and in vivo and share a remarkable degree of similarity with primary CR2-TAg prostate NE tumors. PNECs express mAsh1, a basic helix-loop-helix (bHLH) transcription factor essential for NE cell differentiation in other tissues. RNA interference knockdown of mAsh1, GeneChip comparisons of treated and control cell populations, and a computational analysis of down-regulated genes identified 12 transcriptional motifs enriched in the gene set. Affected genes, including Adcy9, Hes6, Iapp1, Ndrg4, c-Myb, and Mesdc2, are enriched for a palindromic E-box motif, CAGCTG, indicating that it is a physiologically relevant mAsh1 binding site. The enrichment of a c-Myb binding site and the finding that c-Myb is down-regulated by mAsh1 RNA interference suggest that mAsh1 and c-Myb are in the same signaling pathway. Our data indicate that mAsh1 negatively regulates the cell cycle (e.g., via enhanced Cdkn2d, Bub1 expression), promotes differentiation (e.g., through effects on cAMP), and enhances survival by inhibiting apoptosis. PNEC cell lines should be generally useful for genetic and/or pharmacologic studies of the regulation of NE cell proliferation, differentiation, and tumorigenesis.

Involvement of cholesterol-rich lipid rafts in interleukin-6-induced neuroendocrine differentiation of LNCaP prostate cancer cells

IL-6 is an inflammatory cytokine that has been linked to aggressive prostate cancer (PCa). Previous studies have demonstrated that IL-6 can enhance the differentiation of PCa cells toward a neuroendocrine (NE) phenotype, a possible indicator of hormone-refractory disease. In this report, we present evidence that the mechanism of IL-6-stimulated NE differentiation employs a detergent-resistant (lipid raft) membrane compartment for signal transduction in LNCaP PCa cells. Signal transducer and activator of transcription (STAT)3, a mediator of IL-6 signaling, was rapidly phosphorylated and translocated to the nucleus in LNCaP cells treated with IL-6. Both processes were inhibited by filipin, a cholesterol-binding compound that disrupts plasma membrane lipid rafts. Isolation of Triton X-100-insoluble raft fractions from LNCaP cells by discontinuous sucrose gradient centrifugation demonstrated that the 80-kDa IL-6 receptor localized almost exclusively to the raft compartment. Although STAT3 was located predominantly in the Triton X-100-soluble subcellular fraction in exponentially growing cells, abundant phosphorylated STAT3 was detected in the raft fraction after stimulation with IL-6. Increases in expression of the NE marker, neuron-specific enolase, and neuron-specific enolase promoter activity after IL-6 treatment were reduced after membrane rafts were disrupted by filipin treatment. LNCaP cells expressed the raft-resident proteins flotillin-2 and G(ialpha2), but notably not caveolins, the predominant structural protein present in caveolar membrane rafts in many tissues and tumor cells. These results are the first to define a role for lipid raft membrane microdomains in signal transduction mechanisms capable of promoting the NE phenotype in PCa cells, and they demonstrate that the raft compartment is capable of mediating such signals in the absence of caveolins. Our results also suggest a mechanistic role for membrane cholesterol in cell signaling events relevant to PCa progression.

Gadd45gamma is androgen-responsive and growth-inhibitory in prostate cancer cells

In our previous microarray analysis searching for genes differentially regulated by androgens in the rat ventral prostate, we identified GADD45gamma (growth arrest and DNA damage inducible, gamma) as one of the genes up-regulated by androgens. GADD45gamma was initially identified to be a gene involved in negative growth control and its overexpression induced cycle arrest and apoptosis in vitro. In this study, we showed that GADD45gamma was transiently up-regulated by androgens in the androgen-responsive human prostate cancer cell line LNCaP. The GADD45gamma up-regulation was blocked by an androgen receptor (AR) antagonist, bicalutamide, suggesting the involvement of the androgen receptor. However, this up-regulation was inhibited by cycloheximide, indicating that GADD45gamma induction by androgens requires new protein synthesis. Overexpression of GADD45gamma inhibited cell growth of LNCaP and PC3 cells and resulted in dramatic morphological changes in both cell lines, arguing that GADD45gamma is likely to participate in the differentiation program induced by androgens in the prostate. The above observations provide evidence that GADD45gamma is an androgen-responsive gene with growth-inhibitory activity in human prostate cancer cells.

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.

Proliferation of prostate cancer cells and activity of neutral endopeptidase is regulated by bombesin and IL-1beta with IL-1beta acting as a modulator of cellular differentiation

BACKGROUND

Neutral endopeptidase (NEP) is a cell-surface bound enzyme that cleaves and inactivates neuropeptides such as bombesin and substance P and is involved in the transition from hormonally regulated androgen-dependent prostate cancer (PC) to androgen-independent PC. Neuropeptides are implicated in growth regulation of different cell types and function as transmitters between the neuroendocrine and the immune system.

METHODS

NEP-expression, enzymatic activity of the membrane bound protein, cell proliferation, procalcitonin (PCT) production, and secretion as well as changes in cell morphology of prostatic cells were evaluated after treatment with the immunomodulatory cytokine interleukin-1beta (IL-1beta), neuropeptides (bombesin, substance P), and neuropeptide-conditioned media derived from a human neuroendocrine cell line.

RESULTS

Incubation of LNCaP tumor cells with IL-1beta resulted in a diminished proliferative activity, induction of neurite-like outgrowth which was accompanied by the formation of tubular-type mitochondria typical for neuronal/neuroendocrine cells, and an increased production and secretion of PCT. Conversely, proliferation of prostatic stromal cells was enhanced by the cytokine coming along with an increased number of Golgi-apparatuses and ER-cisternae. Bombesin had an antimitotic effect on LNCaP, but not on stromal cells. Substance P did not influence the growth of any of the cell types investigated, whereas neuropeptide-conditioned media exerted a slightly mitogenic effect on both cell types. The activity of LNCaP cell-surface bound NEP was enhanced by bombesin, but was diminished by substance P and neuropeptide-conditioned media.

CONCLUSIONS

Proliferation and activity of neuropeptide degrading NEP is regulated differently by immunomodulatory substances in PC cells and cells derived from the prostatic stroma with IL-1beta being a potent modulator of cellular differentiation and a potential target for anticancer drug design in PC cells.

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.

Receptor protein tyrosine phosphatase alpha signaling is involved in androgen depletion-induced neuroendocrine differentiation of androgen-sensitive LNCaP human prostate cancer cells

The neuroendocrine (NE) cells represent the third cell population in the normal prostate. Results of several clinical studies strongly indicate that the NE cell population is greatly increased in prostate carcinomas during androgen ablation therapy that correlates with hormone-refractory growth and poor prognosis. However, the mechanism of NE cell enrichment in prostate carcinoma remains an enigma. We investigated the molecular mechanism by which androgen-sensitive C-33 LNCaP human prostate cancer cells become NE-like cells in an androgen-reduced environment, mimicking clinical phenomenon. In the androgen-depleted condition, androgen-sensitive C-33 LNCaP cells gradually acquired the NE-like morphology and expressed an increased level of neuron-specific enolase (NSE), a classical marker of neuronal cells. Several NE-like subclone cells were established. Biochemical characterizations of these subclone cells showed that receptor-type protein-tyrosine phosphatase alpha (RPTPalpha) is elevated and ERK is constitutively activated, several folds higher than that in parental cells. In androgen-depleted condition, PD98059, an MEK inhibitor, could efficiently block not only the activation of ERK, but also the acquisition of the NE-like morphology and the elevation of NSE in C-33 LNCaP cells. In RPTPalpha cDNA-transfected C-33 LNCaP cells, ERK was activated and NSE was elevated. In those cells in the presence of PD98059, the ERK activation and NSE elevation were abolished, following a dose-response fashion. Additionally, in constitutively active MEK mutant cDNA-transfected C-33 LNCaP cells, ERK was activated and NSE level was elevated, and cells obtained the NE-like phenotype. Our data collectively indicated that RPTPalpha signaling via ERK is involved in the NE transdifferentiation of androgen-sensitive C-33 LNCaP human prostate cancer cells in the androgen-depleted condition.

Epithelial cell differentiation in the human prostate epithelium: implications for the pathogenesis and therapy of prostate cancer

Within the human prostate epithelium four cell populations are discriminated by their expression of keratins (K). While basal cells co-localize K5 and K14 combined with low levels of K18 (K5(++)/14(++)/18(+)), luminal cells highly express K18 (K18(++)). In addition, two intermediate subpopulations are characterized either by basal K5(++)/18(+)- or luminal K5(+)/18(++)- expression. The entire prostate epithelium is putatively derived from a basal stem cell population. They give rise to intermediate cells that transiently proliferate and mature towards differentiated luminal epithelium. Within prostate carcinoma luminal exocrine, neuro-endocrine and intermediate cells are distinguished. Intermediate cells have been postulated as progenitors for prostate carcinogenesis and targets for androgen-independent tumor progression. Androgen-independency is associated with an enrichment of intermediate cells and over-expression of peptide growth factor receptors. Targeting intermediate cells by inhibition of their peptide growth factor receptors, therefore, offers novel treatment modalities for prostate cancer.

In vitro differentiation of human processed lipoaspirate cells into early neural progenitors

Human processed lipoaspirate (PLA) cells are multipotent stem cells, capable of differentiating into multiple mesenchymal lineages (bone, cartilage, fat, and muscle). To date, differentiation to nonmesodermal fates has not been reported. This study demonstrates that PLA cells can be induced to differentiate into early neural progenitors, which are of an ectodermal origin. Undifferentiated cultures of human PLA cells expressed markers characteristic of neural cells such as neuron-specific enolase (NSE), vimentin, and neuron-specific nuclear protein (NeuN). After 2 weeks of treatment of PLA cells with isobutylmethylxanthine, indomethacin, and insulin, about 20 to 25 percent of the cells differentiated into cells with typical neural morphologic characteristics, accompanied by increased expression of NSE, vimentin, and the nerve-growth factor receptor trk-A. However, induced PLA cells did not express the mature neuronal marker, MAP, or the mature astrocyte marker, GFAP. It was also found that neurally induced PLA cells displayed a delayed-rectifier type K+ current (an early developmental ion channel) concomitantly with morphologic changes and increased expression of neural-specific markers. The authors concluded that human PLA cells might have the potential to differentiate in vitro into cells that represent early progenitors of neurons and/or glia.

Dual effect of pituitary adenylate cyclase activating polypeptide on prostate tumor LNCaP cells: short- and long-term exposure affect proliferation and neuroendocrine differentiation

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide that elicits the increase of intracellular cAMP levels and protein kinase A activity in various cell systems. Here we show that the pattern of cAMP elevation triggered by PACAP is critical for the fate of LNCaP prostate cancer cells. We demonstrate that these cells express PACAP and its type 1 receptor. A short-term stimulation with PACAP, which generates a transient cAMP rise, induces proliferation of LNCaP cells through a protein kinase A-dependent activation of the MAPK cascade. On the contrary, we observed that chronic PACAP stimulation, giving rise to a sustained cAMP accumulation, leads to proliferation arrest and neuroendocrine differentiation. Moreover, PACAP stimulates phosphory-lation and activation of the cAMP response element binding transcription factor (CREB), and MAPK activation is necessary for its full transcriptional activity, indicating a direct involvement of cAMP response element in PACAP action. These findings demonstrate that a crucial event determining the outcome of prostatic cancer cells progression is the sustained vs. transient intracellular cAMP increase.

Molecular characterization of prostatic small-cell neuroendocrine carcinoma

OBJECTIVES

A subset of prostate carcinomas is composed predominantly, even exclusively, of neuroendocrine (NE) cells. In this report, we sought to characterize the gene expression profile of a prostate small cell NE carcinoma by assessing the diversity and abundance of transcripts in the LuCaP 49 prostate small cell carcinoma xenograft.

METHODS

We constructed a cDNA library (PRCA3) from the LuCap 49 prostate small cell xenograft. Single pass DNA sequencing of randomly selected cDNA clones followed by sequence assembly and annotation produced a library of Expressed Sequence Tags (ESTs) representing the LuCaP 49 transcriptome. Comparative sequence analysis with ESTs derived from prostate adenocarcinoma libraries was performed using statistical algorithms designed to identify differentially expressed sequences. Putative NE cell-specific genes were further examined by Northern analysis.

RESULTS

Sequence assembly and analysis identified 1,447 distinct genes expressed in the LuCaP 49 cDNA library. These include cDNAs encoding the NE markers secretogranin (SCG2), CD24, and ENO2. Northern analysis revealed that three additional genes, ASCL1, INA, and SV2B are expressed in LuCaP 49 but not in various prostate cancer cell lines or xenografts. Fifteen genes were identified with a statistical probability (P > 0.9) of being up-regulated in LuCaP 49 small cell carcinoma relative to prostate adenocarcinoma (two primary prostate adenocarcinomas and the LNCaP prostate adenocarcinoma cell line).

CONCLUSIONS

Prostate small cell carcinoma expresses a diverse repertoire of genes that reflect characteristics of their NE cell of origin. ASCL1, INA, and SV2B are potential molecular markers for small cell NE tumors and NE cells of the prostate. This small cell NE carcinoma gene expression profile may yield insights into the development, progression, and treatment of subtypes of prostate cancer.

Hormone-refractory prostate cancer: a multi-step and multi-event process

Since the pioneering studies of Huggins in 1941, it has been known that prostate cancer cells, like certain normal epithelial cells, can chronically depend on a critical level of androgenic stimulation for their continuous growth and survival. The entire issue of the development of resistance to androgen ablation therapy for metastatic prostate cancer is based on the fact that a portion of cells can survive without androgen stimulation. The cell mechanism of androgen independent status is unclear. For some authors, a portion of the cells present within a patient with a prostate cancer before therapy is naturally androgen independent (selection hypothesis). However, this hypothesis does not consider gene alteration during prostate cancer natural history and probably hormone-refractory prostate cancer (HRPC) is due to a multi-step and multi-event process. In this literature review, different cell pathways that lead to HRPC are described.Prostate Cancer and Prostatic Diseases (2001) 4, 204-212.

Enforced expression of FGF-7 promotes epithelial hyperplasia whereas a dominant negative FGFR2iiib promotes the emergence of neuroendocrine phenotype in prostate glands of transgenic mice

The minimal rat probasin (PB) promoter was used to target expression of human fibroblast growth factor-7 (FGF-7)/keratinocyte growth factor (KGF) directly to prostatic epithelium of transgenic mice, converting FGF-7 from a paracrine to an autocrine factor. Four independent lines were established that expressed the transgene (PKS) in the prostate. Upon histologic analysis, the prostatic epithelium of PKS mice was found to be hyperplastic. Many of the prostatic ducts were filled with secretory epithelial cells tightly associated with a highly enfolded basement membrane. Distortions of the ductal smooth muscle layer were also observed. Prostates from year-old PKS mice had significantly more abnormal ducts than their wild-type nontransgenic littermates. The minimal rat PB promoter was also used to target a truncated FGFR2iiib receptor to prostatic epithelium to functionally abrogate endogenous FGF-7 signaling. Three lines were established that expressed the transgene (KDNR) in the prostate. Upon dissection it was noted that all four lobes of the prostates of KDNR mice were present but smaller in size. Histologic analysis indicated that the epithelium in many of the prostatic ducts was disorganized and contained numerous rounded cytokeratin-positive cells that were not tightly associated with the basement membrane. The stroma was disorganized and did not form a tight layer of smooth muscle around the epithelial ducts. Surprisingly, abrogation of FGF signaling in KDNR mice correlated with the emergence of a neuroendocrine-like phenotype that was not observed as a consequence of enforced FGF-7 expression in the PKS mice.

Interleukin-6 regulates androgen receptor activity and prostate cancer cell growth

Interleukin-6 (IL-6) is a multifunctional cytokine which is involved in regulation of growth of various malignant tumors. IL-6 binds to its receptor, which is composed of a ligand-binding and a signal-transducing subunit and activates pathways of signal transducers and activators of transcription and mitogen-activated protein kinases (MAPKs). In prostate cancer cells, IL-6 induces divergent proliferative responses. Serum levels of IL-6 are elevated in patients with therapy-resistant carcinoma of the prostate. We have investigated whether IL-6 interacts with the androgen signaling pathway in prostate cancer cells. In DU-145 cells, transiently transfected with androgen receptor (AR) cDNA, IL-6 caused ligand-independent and synergistic activation of the AR. Nonsteroidal antagonists of the AR down-regulated AR activity induced by IL-6. In LNCaP cells, IL-6-induced expression of the AR-regulated prostate-specific antigen gene. Inhibitors of protein kinase A and C and MAPK down-regulated IL-6-induced AR activity. IL-6 expression in human prostate tissue was studied by immunohistochemistry. In benign prostatic tissue, IL-6 immunoreactivity was confined to basal cells. In prostate intraepithelial neoplasia and in cancer tissue, atypical intraluminal and cancer cells expressed IL-6. The expression of IL-6 receptor was demonstrated in benign and malignant tissue in both epithelium and stroma. In the authors' laboratory, IL-6-inhibited proliferation of parental LNCaP cells. A new LNCaP subline was generated to investigate changes in signal transduction which might occur after prolonged treatment with IL-6. In the subline LNCaP-IL-6+, IL-6 neither reduced a number of cells nor caused G1 growth arrest. IL-6 receptor expression declined during long-term IL-6 treatment. However, IL-6-up-regulated AR expression and was capable of inducing AR activity in LNCaP-IL-6+ cells. Parental LNCaP cells do not express IL-6. In contrast, IL-6 mRNA and protein expression were detectable in high passages of LNCaP-IL-6+ cells. Thus changes in signal transduction occur in prostate cancer cells after prolonged IL-6 treatment

ICER reverses tumorigenesis of rat prostate tumor cells without affecting cell growth

BACKGROUND

Inducible cAMP early repressor (ICER) is an important mediator of cAMP antiproliferative activity that acts as a putative tumor suppressor gene product. ICER is a transcriptional repressor that negatively regulates cAMP-mediated gene expression. Here, we report the effect of ectopically increasing the expression of ICER on in vitro and in vivo proliferation of the highly metastatic and androgen-insensitive AT6.3 rat prostate cells.

METHODS

The proliferative potential of stable AT6.3 cell clones expressing ICER was studied by cell counts, thymidine incorporation, flow cytometry, colony formation in soft agar, and growth in immunodeficient nude mice.

RESULTS

cAMP inhibits the growth of AT6.3 cells. ICER mRNA and protein levels were markedly induced by cAMP in AT6.3 cells. Forced expression of ICER in AT6.3 cells did not affect cell growth, thymidine incorporation, or the cell cycle. However, these ICER-bearing AT6.3 cells were rendered unable to grow in soft agar or to form tumors in nude mice.

CONCLUSION

These results show that ICER specifically affects the tumorigenicity of prostate cancer cell without affecting their growth. Therefore, the manipulation of ICER expression could be used for the treatment of androgen-insensitive prostate tumors without causing undesirable toxicity to the cells.

Neuroendocrine differentiation of human prostatic primary epithelial cells in vitro

BACKGROUND

Dispersed prostatic neuroendocrine cells are involved in growth regulation of the prostate and are considered to play a role in the pathogenesis of prostate carcinoma and benign prostatic hyperplasia (BPH). They are meant either to be derived from the neural crest during embryogenesis or by direct differentiation of the cells from locally present precursor cells.

METHODS

An in vitro model was developed for human prostatic epithelial and neuroendocrine cell differentiation. Minced explants from radical prostatectomies were seeded on collagen I-coated plates.

RESULTS

The majority of outgrowing cells were basal cells, positive for cytokeratin markers K 5/14 and CD 44, as determined by confocal laser scanning microscopy. A small fraction of interdispersed single cells expressing c-kit, which is found on pluripotent precursors, was identified by immunofluorescence. From these basal cells, in vitro differentiation of cells with neuroendocrine morphology could be achieved within 3 days. These were at rest, i.e., non-bromodeoxyuridine incorporating cells and characteristically coexpressed K 5/14, K 18, and the neuroendocrine marker chromogranin A. Luminal cells staining for K 8 or 18 were not observed.

CONCLUSION

Neuroendocrine differentiation of adult prostatic cells was achieved in vitro, favoring the hypothesis that neuroendocrine cells are derived from peripheral precursor cells. The acceleration of this differentiation pathway may be the reason for the increased presence of neuroendocrine cells in areas of epithelial hyperplasia in BPH.

Characterization of human ribosomal S3a gene expression during adenosine 3':5' cyclic monophosphate induced neuroendocrine differentiation of LNCaP cells. Regulation of S3a gene expression in LNCaP

Elevation of intracellular cAMP levels in the human prostatic adenocarcinoma cell line LNCaP results in the induction of reversible neuroendocrine differentiation and cell growth arrest. We have used the differential display technique to identify genes that are differentially expressed during cAMP induced neuroendocrine differentiation in LNCaP cells. We identified the human ribosomal S3a gene as being down regulated in response to LNCaP differentiation. The S3a gene is known to be expressed at high levels in both tumors and cancer cell lines. It has also been shown that down regulation of S3a is associated with a loss of the transformed phenotype. In order to better ascertain the mechanism by which S3a gene expression is decreased during differentiation, the promoter region for this gene was analyzed. Electrophoretic mobility shift assay, antibody supershift assays, site-directed mutagenesis, and luciferase reporter gene analysis were employed to authenticate the roles of several transcription factors in the regulation of the S3a gene. We found that two cyclic AMP response elements, a Sp1 element, and a GA-binding protein element were involved in the regulation of S3a gene expression. The CRE elements were found to be necessary for high level expression of the 53a gene in undifferentiated LNCaP cells. Mutations in the CRE elements abolished CREB-1 binding and resulted in a 57% decrease in S3a gene expression. The addition of cAMP elevating agents to LNCaP cells in sufficient quantity to induce differentiation generated a 50% decrease in S3a gene expression. These results suggest that the CRE elements participate in cAMP-induced down regulation of gene expression. Furthermore, our experiments demonstrate that occupation of the GABP binding site results in a substantial decrease in S3a promoter activity.

The deprivation syndrome is the driving force of phylogeny, ontogeny and oncogeny

Energy is the motor of life. Energy ensures the organism's survival and competitive advantage for reproductive success. For almost 3 billion years, unicellular organisms were the only life form on earth. Competition for limited energy resources and raw materials exerted an incessant selective pressure on organisms. In the adverse environment and due to their 'feast and famine' life style, hardiness to a variety of stressors, particularly to nutrient deprivation, was the selection principle. Both resistance and mutagenic adaptation to stressors were established as survival strategies by means of context-specific processes creating stability or variability of DNA sequence. The conservation of transduction pathways and functional homology of effector molecules clearly bear witness that the principles of life established during prokaryotic and eukaryotic unicellular evolution, although later diversified, have been unshakably cast to persist during metazoan phylogenesis. A wealth of evidence suggests that unicellular organisms evolved the phenomena of differentiation and apoptosis, sexual reproduction, and even aging, as responses to environmental challenges. These evolutionary accomplishments were elaborated from the dichotomous resistance/mutagenesis response and sophisticated the capacity of cells to tune their genetic information to changing environmental conditions. Notably, the social deprivation responses, differentiation and apoptosis, evolved as intercellularly coordinated events: a multitude of differentiation processes were elaborated from sporulation, the prototypic stress resistance response, while apoptosis, contrary to current concepts, is no altruistic cell suicide but was programmed as a mutagenic survival response; this response, however, is socially thwarted leading into mutagenic error catastrophe. In the hybrid differentiation-apoptosis process, cytocide and cannibalism of apoptotic cells thus serve the purpose of fueling the survival of the selfish genes in the differentiating cells. However, successful mutagenesis, although repressed, persisted in the asocial stress response of carcinogenesis as a regression to primitive unicellular behavior following failure of intercellular communication. While somatic mutagenesis was largely prevented, Metazoa elaborated germ cell mutagenesis as an evolutionary vehicle. Genetic competence, a primitive, stress-induced mating behavior, evolved into sexual reproduction which harnessed mutagenesis by subjecting highly mutable germ cells to a rigid viability selection. These processes were programmatically fixed as life- and cell-cycle events but retained their deprivation response phenotypes. Thus, the differentiation-apoptosis tandem evolved as the 'clay' to mold the specialized structures and functions of a multicellular organism while sexual reproduction elaborated the principle of quality-checked mutagenesis to create the immense diversity of Metazoa following the Cambrian explosion. Throughout these events, reactive oxygen and nitrogen species, which are regulated by energy homeostasis, shape the genetic information in a regulated but random, uncoded process providing the fitness-related feedback of phenotype to genotype. The interplay of genes and environment establishes a dynamic stimulus-response feedback cycle which, in animate nature, may be the organizing principle to contrive the reciprocal duality of energy and matter.

Overexpression of an alpha 1H (Cav3.2) T-type calcium channel during neuroendocrine differentiation of human prostate cancer cells

Neuroendocrine differentiation of prostate epithelial cells is usually associated with an increased aggressivity and invasiveness of prostate tumors and a poor prognosis. However, the molecular mechanisms involved in this process remain poorly understood. We have investigated the possible expression of voltage-gated calcium channels in human prostate cancer epithelial LNCaP cells and their modulation during neuroendocrine differentiation. A small proportion of undifferentiated LNCaP cells displayed a voltage-dependent calcium current. This proportion and the calcium current density were significantly increased during neuroendocrine differentiation induced by long-term treatments with cyclic AMP permeant analogs or with a steroid-reduced culture medium. Biophysical and pharmacological properties of this calcium current suggest that it is carried by low-voltage activated T-type calcium channels. Reverse transcriptase-PCR experiments demonstrated that only a single type of LVA calcium channel mRNA, an alpha(1H) calcium channel mRNA, is expressed in LNCaP cells. Quantitative real-time reverse transcriptase-PCR revealed that alpha(1H) mRNA was overexpressed during neuroendocrine differentiation. Finally, we show that this calcium channel promotes basal calcium entry at resting membrane potential and may facilitate neurite lengthening. This voltage-dependent calcium channel could be involved in the stimulation of mitogenic factor secretion and could therefore be a target for future therapeutic strategies.

Neuroendocrine pathogenesis in adenocarcinoma of the prostate

BACKGROUND

In the prostate, the importance of sex hormones for its normal development and function is well known. However, it has been proposed that various neuroendocrine (NE) hormones and growth factors may be involved in the pathogenesis of prostatic carcinoma (CaP). Neuroendocrine differentiation appears to be associated with tumour progression and the androgen-independent state, for which there is currently no successful therapy. Therefore, we need to improve our understanding of NE cells, their regulatory products and influence on the prostate gland. Finally, new therapeutic protocols need to be developed.

METHODS

Information is presented on prostatic NE cells and neuroendocrine differentiation (NED) in prostatic carcinoma. Neuroendocrine secretory products and interactions with epithelial prostate cells are investigated in order to understand their significance for the pathogenesis of the prostate gland, prognosis and therapy.

RESULTS

Recent research suggests that NE-secreted products. such as serotonin, somatostatin and bombesin, may influence growth, invasiveness, metastatic processes and angiogenesis in CaP. During recent years. new experimental models for NED have been developed to provide evidence that NE products may promote proliferation and confer antiapoptotic capabilities on non-neuroendocrine cells in close proximity to NE cells. Cancerous epithelial cells may become more responsive to NE factors by upregulation of receptors for neuropeptides, or may induce NE cells to upregulate the secretion and synthesis of NE factors. In the androgen independent state, neuropeptides and their intracellular signals may activate the androgen receptor. Furthermore, androgen ablation may lead to downregulation of neural endopeptidase 24.11 (a zinc-dependent metalloproteinase) and PSA, which would lead to increased levels of NE products becoming available. These studies confirm that NE cells and NED may have a significant impact on prostate cancer, especially in the androgen independent state.

CONCLUSIONS

Recent developments in molecular biology and pathophysiology of prostate cancer have increased our understanding of the NE regulatory mechanisms. Hopefully, this will lead to the development of entirely new therapeutic modalities. For example, somatostatin agonists may suppress angiogenesis and proliferation, and simultaneously promote apoptosis in prostate cancer cells. Somatostatin may thus have an important role in tumour biology, and in the future there may be a potential role for somatostatin analogues in the treatment of prostate cancer, but also for serotonin and bombesin receptor antagonists. However, a review of the accumulated knowledge in this field suggests that we still need to improve our understanding of NE cells and their regulatory products and influence on the prostate gland. and that clinical trials are needed, to test drugs based on neuroendocrine hormones and their agonists/antagonists.

Jolkinolide B induces neuroendocrine differentiation of human prostate LNCaP cancer cell line

Euphorbia fischeriana is a Chinese herbal medicine which has been reported to possess chemotherapeutic effects, yet the underlying mechanism is unclear. In order to understand its possible anti-tumor property, we have isolated a number of chemical compounds from the roots of this plant [Phytochemistry 52 (1999) 117] and studied their in vitro effects by using human prostate LNCaP cancer cell line. Among the six compounds tested, jolkinolide B exhibited the most potent anti-proliferative activity (IC(50)=12.5 microg/mL=40 microM) and it inhibited DNA synthesis by down-regulating bromodeoxyuridine (BrdU) incorporation in LNCaP cells in a dose-dependent manner. Jolkinolide B, at concentrations up to 25 microg/mL, induced G1 arrest and neuroendocrine differentiation of LNCaP cells. Immunoblotting analysis confirmed the increased expression of neuroendocrine markers, keratin 8/18 (K8/18) and neuron specific enolase (NSE), in these cells. Apoptotic bodies and DNA fragmentation were observed by fluorescence microscopy and flow cytometry when the cells were exposed to a concentration higher than 25 microg/mL jolkinolide B. Taken all data together, jolkinolide B seems to play a role in the regulation of proliferation, differentiation, and apoptosis of LNCaP cells.

Proline-rich tyrosine kinase 2 regulates proliferation and differentiation of prostate cells

Proline-rich tyrosine kinase 2 (Pyk2) expression in prostate epithelium inversely correlated with degree of malignancy of prostate cancers, thus the role of Pyk2 in the regulation of prostate cells proliferation and differentiation was investigate in PC3 cells. Pyk2 can be activated by canonic stimuli such as tumor necrosis factoralpha and lysophosphatidic acid (LPA) in PC3 cells, in addition, LPA stimulated Pyk2 phosphorylation also induced extracellular signal-regulated kinase 1 and 2 activation in these cells. Proliferation of PC3 cell clones (PC3-PKM) expressing a dominant negative kinase-defective Pyk2 mutant is consistently decreased in respect to that of wild type PC3 cells. In addition, PC3-PKM clones underwent total block cell proliferation upon treatment with dibutyryl cAMP. Finally, in the presence of sustained levels of intracellular cAMP, PC3-PKM cells, but not wild type PC3 cells, acquired a neuron-like morphology. Taken together our results suggest that Pyk2 plays a role in the regulation of prostate cell proliferation and, more interestingly, its expression may represents a sensitive marker of prostate state of differentiation.