Molecular pathology of prostate cancer

Ornithine Decarboxylase Is Sufficient for Prostate Tumorigenesis via Androgen Receptor Signaling

Increased polyamine synthesis is known to play an important role in prostate cancer. We aimed to explore its functional significance in prostate tumor initiation and its link to androgen receptor (AR) signaling. For this purpose, we generated a new cell line derived from normal epithelial prostate cells (RWPE-1) with overexpression of ornithine decarboxylase (ODC) and used it for in vitro and in vivo experiments. We then comprehensively analyzed the expression of the main metabolic enzymes of the polyamine pathway and spermine abundance in 120 well-characterized cases of human prostate cancer and high-grade prostate intraepithelial neoplasia (HGPIN). Herein, we show that the ODC-overexpressing prostate cells underwent malignant transformation, revealing that ODC is sufficient for de novo tumor initiation in 94% of injected mice. This oncogenic capacity was acquired through alteration of critical signaling networks, including AR, EIF2, and mTOR/MAPK. RNA silencing experiments revealed the link between AR signaling and polyamine metabolism. Human prostate cancers consistently demonstrated up-regulation of the main polyamine enzymes analyzed (ODC, polyamine oxidase, and spermine synthase) and reduction of spermine. This phenotype was also dominant in HGPIN, rendering it a new biomarker of malignant transformation. In summary, we report that ODC plays a key role in prostate tumorigenesis and that the polyamine pathway is altered as early as HGPIN.

Multiple roles for UDP-glucuronosyltransferase (UGT)2B15 and UGT2B17 enzymes in androgen metabolism and prostate cancer evolution

In the prostate, approximately 50% of androgens are from adrenal steroids, mainly dehydroepiandrosterone (DHEA), its sulfate and androstenedione. These compounds are converted first into testosterone, and then into the active hormone dihydrotestosterone (DHT). After having activated the androgen receptor (AR), DHT is reduced into androstane-3α-DIOL (3α-DIOL) and androsterone (ADT), which are subsequently converted into 2 inactive and easily excretable metabolites: 3α-DIOL-17glucuronide (3α-DIOL-17G) and ADT-3glucuronide (ADT-3G). The formation of these last derivatives through the glucuronidation reaction involves 2 UDP-glucuronosyltransferase (UGT) enzymes, namely UGT2B15 and UGT2B17. The present review article aims at providing a comprehensive view of the physiological and pharmacological importance of these 2 enzymes for the control of androgen homeostasis. We will resume: (i) how UGT2B15 and UGT2B17 contribute to androgen elimination; (ii) how their glucuronidation capacity influences the androgen signaling pathway in prostate cells; (iii) how they contribute to the anti-proliferative properties of AR antagonists in prostate cancer cells; and (iv) how AR and its spliced variants regulate the UGT2B15 and/or UGT2B17 genes expression. Finally, whether the unexploited AR-UGT axis could serve as a prognostic maker or a pharmacological target for novel therapeutics in the treatment of prostate cancer is also discussed. This article is part of a special issue entitled 'Essential role of DHEA'.

Computer-assisted three-dimensional analysis of multifocal/multicentric prostate cancer

In order to study multiple contiguous prostate cancer lesions, we constructed computer-assisted, three-dimensional models of multifocal prostate cancer specimens obtained by radical prostatectomy. We then examined the genetic heterogeneity among the specimens by DNA microarray analysis. Cancer foci with high Gleason patterns were found to occur de novo, whereas those with low Gleason patterns occurred contiguously with cancers of low Gleason patterns. Three-dimensional analysis showed that distinct, noncontiguous cancerous foci were genetically independent and multicentric. In contrast some contiguous multifocal lesions had the same genetic origin.

Senescent remodeling of the innate and adaptive immune system in the elderly men with prostate cancer

Despite years of intensive investigation that has been made in understanding prostate cancer, it remains a major cause of death in men worldwide. Prostate cancer emerges from multiple alterations that induce changes in expression patterns of genes and proteins that function in networks controlling critical cellular events. Based on the exponential aging of the population and the increasing life expectancy in industrialized Western countries, prostate cancer in the elderly men is becoming a disease of increasing significance. Aging is a progressive degenerative process strictly integrated with inflammation. Several theories have been proposed that attempt to define the role of chronic inflammation in aging including redox stress, mitochondrial damage, immunosenescence, and epigenetic modifications. Here, we review the innate and adaptive immune systems and their senescent remodeling in elderly men with prostate cancer.

Extracellular vesicles in prostate cancer: new future clinical strategies?

Prostate cancer (PCa) is the most common cancer—excluding skin tumors—in men older than 50 years of age. Over time, the ability to diagnose PCa has improved considerably, mainly due to the introduction of prostate-specific antigen (PSA) in the clinical routine. However, it is important to take into account that although PSA is a highly organ-specific marker, it is not cancer-specific. This shortcoming suggests the need to find new and more specific molecular markers. Several emerging PCa biomarkers have been evaluated or are being assessed for their potential use. There is increasing interest in the prospective use of extracellular vesicles as specific markers; it is well known that the content of vesicles is dependent on their cellular origin and is strongly related to the stimulus that triggers the release of the vesicles. Consequently, the identification of a disease-specific molecule (protein, lipid or RNA) associated with vesicles could facilitate their use as novel biological markers. The present review describes several in vitro studies that demonstrate the role of vesicles in PCa progression and several in vivo studies that highlight the potential use of vesicles as PCa biomarkers.

Endothelial nitric oxide synthase gene polymorphisms and prostate cancer risk in Serbian population

Genome-wide association studies (GWAS) have identified over 46 SNPs associated with human prostate cancer (PCa). Some studies have shown correlation of the nitric oxide synthase (NOS) NOS3 gene polymorphisms with the risk and/or progression of PCa. This study aimed to evaluate the association of NOS3 gene polymorphisms (-786T>C, -764A>G, -714G>T, -690C>T, -649G>A and 894G>T) with PCa risk and progression. 150 patients with PCa, 150 patients with BPH and 100 age-matched healthy controls were recruited in this study. Genotyping of promoter polymorphisms was performed by bi-directional DNA sequencing, and for 894G>T by RFLP analysis. There was no significant association between the alleles and genotypes of these genetic variants and PCa risk. For -786T>C polymorphism, we found that C allele is associated with absence of metastases, assuming dominant genetic model (P = 0.049; OR, 0.50; 95% CI, 0.25-1.00). It was found that, compared with NOS3 -690C>T variant CC genotype, CT and TT genotypes confer decreased risk of developing metastases (dominant model, P = 0.015, OR, 0.24; 95% CI, 0.07-0.88) and show association with low clinical tumour stage, compared with stages T3 and T4 (dominant model, P = 0.046, OR, 0.20; 95% CI, 0.04-1.02). Genetic variants -764A>G, -714G>T, -649G>A were not detected in our study group. There is evidence of an inverse correlation of the NOS3 894G>T minor allele with high serum PSA (>20 ng/ml) (dominant model, P = 0.013, OR, 0.37; 95% CI, 0.17-0.82). Our results suggest that NOS3 gene polymorphisms are genetic susceptibility factors for the progression of PCa and patient outcome.

Nuclear receptors and endobiotics glucuronidation: the good, the bad, and the UGT

The recent progresses in molecular biology and pharmacology approaches allowed the characterization of a series of nuclear receptors (NRs) as efficient regulators of uridine diphosphate glucuronosyltransferase (UGT) genes activity. These regulatory processes ensure an optimized UGT expression in response to specific endo- and/or exogenous stimuli. Many of these NRs are activated by endobiotics that also are substrates for UGTs. Thus, by activating their receptors, these endogenous substances control their own conjugation, leading to the concept that glucuronidation is an important part of feed-forward/feedback mechanisms by which bioactive molecules control their own concentrations. On the other hand, numerous studies have established the pharmacological relevance of NR-UGT regulatory pathways in the response to therapeutic ligands. The present review article aims at providing a comprehensive view of the physiological and pharmacological importance of the NR regulation of the expression and activity of endobiotics-conjugating UGT enzymes. Selected examples will illustrate how the organism profits from the feed-forward/feedback mechanisms involving NR-UGT pathways, but also how such regulatory processes are involved in the initiation and/or progression of several pathological situations. Finally, we will discuss how the present pharmacopeia involves NR-dependent regulation of endobiotics glucuronidation, and whether the unexploited NR-UGT axes could serve as pharmacological targets for novel therapeutics to restore endobiotics homeostasis.

Subcellular localization of p44/WDR77 determines proliferation and differentiation of prostate epithelial cells

The molecular mechanism that controls the proliferation and differentiation of prostate epithelial cells is currently unknown. We previously identified a 44-kDa protein (p44/wdr77) as an androgen receptor-interacting protein that regulates a set of androgen receptor target genes in prostate epithelial cells and prostate cancer. In this study, we found that p44 localizes in the cytoplasm of prostate epithelial cells at the early stage of prostate development when cells are proliferating, and its nuclear translocation is associated with cellular and functional differentiation in adult prostate tissue. We further demonstrated that cytoplasmic p44 protein is essential for proliferation of prostate epithelial cells, whereas nuclear p44 is required for cell differentiation and prostate- specific protein secretion. These studies suggest a novel mechanism by which proliferation and differentiation of prostate epithelial cells are controlled by p44's location in the cell.

Anticancer activity of green tea polyphenols in prostate gland

Numerous evidences from prevention studies in humans, support the existence of an association between green tea polyphenols consumption and a reduced cancer risk. Prostate cancer is one of the most frequently diagnosed male neoplasia in the Western countries, which is in agreement with this gland being particularly vulnerable to oxidative stress processes, often associated with tumorigenesis. Tea polyphenols have been extensively studied in cell culture and animal models where they inhibited tumor onset and progression. Prostate cancer appears a suitable target for primary prevention care, since it grows slowly, before symptoms arise, thus offering a relatively long time period for therapeutic interventions. It is, in fact, usually diagnosed in men 50-year-old or older, when even a modest delay in progression of the disease could significantly improve the patients quality of life. Although epidemiological studies have not yet yielded conclusive results on the chemopreventive and anticancer effect of tea polyphenols, there is an increasing trend to employ these substances as conservative management for patients diagnosed with less advanced prostate cancer. Here, we intend to review the most recent observations relating tea polyphenols to human prostate cancer risk, in an attempt to outline better their potential employment for preventing prostate cancer.

Review: green tea polyphenols in chemoprevention of prostate cancer: preclinical and clinical studies

The prevention of prostate cancer (PCa) is a crucial medical challenge in developed countries. PCa remains surrounded by puzzles in spite of the considerable progress in research, diagnosis, and treatment. It is an ideal target for chemoprevention, as clinically significant PCa usually requires more than two decades for development. Green tea and its major constituent epigallocatechin gallate (EGCG) have been extensively studied as a potential treatment for a variety of diseases including cancer. In this review, we highlight the evidences of green tea polyphenols from preclinical and clinical studies in the chemoprevention/chemotherapy of PCa.

BP1, a homeoprotein, is significantly expressed in prostate adenocarcinoma and is concordant with prostatic intraepithelial neoplasia

BP1 is a member of the homeobox gene superfamily of transcription factors that are essential for early development. Significant mRNA expression and immunohistochemical reactivity of BP1 is present in a majority of breast cancers and in all cases of inflammatory breast cancer. This study attempts to determine whether BP1 expression is detectable in prostate cancer, another hormone dependent solid tumor, and whether this expression correlates with histopathologic and prognostic factors. Paraffin sections from radical prostatectomy cancer specimens and from tissue microarray sections of prostate cancer, obtained from the Prostate Cancer Tissue Registry (NIH), were assayed for BP1 immunoreactivity. Immunoreactivity scoring by two independent pathologists, using a three-tiered system (0, 1+, 2+), was recorded and correlated with Gleason scoring and prostatic specific antigen (PSA) biochemical recurrence. Ki-67 (MIB-1) immunoreactivity was performed to assess proliferation. Kappa and Cochran-Mantel-Haenszel statistical analyses were used to assess interobserver agreement and pathobiologic correlations. Significant BP1 immunoreactivity (2+) was identified in approximately 70% of prostatic adenocarcinomas, whether the analysis was performed on tissue sections (50 cases) or tissue microarray platforms (123 cases). BP1 immunoreactivity was seen in <5% of normal acinar cells. The agreement between two separate observers was very good, with kappa-statistics >0.7. In tissue sections, 12 cases with paired carcinoma and prostatic intraepithelial neoplasia (PIN) showed concordance with strong immunoreactivity. Gleason scores or prostatic specific antigen (PSA) biochemical recurrences were not correlated with strong BP1 immunoreactivity. Tumor proliferation, assayed with Ki-67 (MIB-1) immunoreactivity, was higher in cancer cells that were BP1 immunoreactive, relative to those that were BP1 non-reactive. These findings suggest that BP1 is an important upstream factor in the carcinogenic pathway of prostate cancer and that the expression of BP1 may reflect or directly contribute to tumor progression and/or invasion.

Function of JunB in transient amplifying cell senescence and progression of human prostate cancer

PURPOSE

Replicative senescence in cells acts as a barrier against excessive proliferation and carcinogenesis. Transient amplifying cells (TAC) are a subset of basal cell populations within the prostate from which cancers are thought to originate; therefore, we focused on prostate TAC to investigate the molecular mechanisms by which the TAC may be able to evade senescence.

EXPERIMENTAL DESIGN

TAC clones were isolated from each zone within the whole prostate and analyzed in flow cytometry. Prostate cancer cells were transfected with junB small interfering RNA (siRNA) and examined by chorioallantoic membrane assay for cancer invasion. Immunohistochemical analysis was done in primary and metastatic prostate cancer specimens.

RESULTS

TAC populations showed increased expression of p53, p21, p16, and pRb, resulting in senescence. TAC clones with reduced p16 expression successfully bypassed this phase. We further found close correlation between the levels of junB and p16 expression. Repeated transfection of junB siRNA in prostatic TAC allowed the cells to escape senescence presumably through inactivation of p16/pRb. The chorioallantoic membrane invasion assay showed much lower in invasive cancer cells with high expression of junB; conversely, silencing of junB by transfection with junB siRNA promoted invasion. We also found that metastatic prostate cancers, as well as cancers with high Gleason scores, showed significantly low junB immunopositivity.

CONCLUSIONS

JunB is an essential upstream regulator of p16 and contributes to maintain cell senescence that blocks malignant transformation of TAC. JunB thus apparently plays an important role in controlling prostate carcinogenesis and may be a new target for cancer prevention and therapy.

The impact of diet and micronutrient supplements on the expression of neuroendocrine markers in murine Lady transgenic prostate

BACKGROUND

Neuroendocrine (NE) differentiation (NED) in prostate cancer (PCa) is associated with morbidity and death; however, the underlying cause(s) promoting NED in PCa have yet to be determined. In this study, we examined the effect of both diet and micronutrient supplementation on the expression of NE markers using the Lady (12T-10) transgenic model of PCa. Lady (12T-10) transgenic animals develop advanced adenocarcinoma with NE characteristics that exhibits metastases in approximately 80% of cases. In this model a high fat diet has been shown to increase the severity of disease, while the use of micronutrients can inhibit this progression.

METHODS

In this study we used immunohistochemical analysis to determine expression of the NE markers: chromogranin A (CgA), neuron-specific enolase (NSE), bombesin, parathyroid hormone-related peptide (PTHrP), neurotensin and serotonin in prostates of PCa-bearing Lady (12T-10) mice.

RESULTS

High fat diet was correlated with significantly elevated expression of CgA and serotonin in prostate tissue of Lady (12T-10) mice. Addition of micronutrients to the control and high fat diet reproducibly elevated PTHrP and bombesin expression and suppressed NSE expression, while prostate tissue from the control diet supplemented with micronutrients exhibited significantly lower numbers of calcitonin- and neurotensin-positive cells.

CONCLUSIONS

These results highlight the importance of dietary control in management of disease and identify differential changes in NE marker expression, which may be diagnostically viable in monitoring the impact of therapies on disease status.

HRK inactivation associated with promoter methylation and LOH in prostate cancer

OBJECTIVES

Recent studies in selected human tumors have demonstrated reduced expression of HRK with hypermethylation. Because no similar study has been performed specifically in prostatic lesions, we examined whether the methylation status of HRK is altered in prostate cancers.

METHODS

We chose to analyze the hypermethylation status of HRK, the expression of HRK protein and mRNA with 12q13.1 loss of heterozygosity (LOH) and with p53 mutation, and lesion apoptotic indices as determined by transferase-mediated digoxigenin-tagged 16-desoxy-uridine-triphosphate nick end-labeling (TUNEL) assays in 53 prostate cancers.

RESULTS

Twenty of the 53 prostate cancers (38%) demonstrated hypermethylation in either the promoter or in exon 1 and, more significantly, the loss of HRK expression observed in 14 cancers by immunohistochemistry (IHC) was associated with promoter methylation. In addition, high apoptotic indices in tumors were related to positive HRK expression. Prostate cancers demonstrating HRK methylation also showed methylation of multiple other genes, such as p14(ARF), p16(INK4a), O(6)-MGMT, and GTS-P, but, with the exception of one case, p53 mutations were not detected. When compared to tumors having a Gleason score (GS) of 5-6, a significant difference in the apoptotic indices was found among prostate cancers of GS 7 (P < 0.001) or GS 8-9 (P = 0.007). We also detected a close correlation between the loss of HRK expression and decreased apoptosis in GS 5-6 and GS 7 tumors (P = 0.008, P < 0.001, respectively).

CONCLUSIONS

HRK appears to be inactivated principally by promoter hypermethylation in prostate cancers. We further suggest that the decreased expression of HRK may play an important role in tumor progression by modulating apoptotic cell death.

Integrative analysis of genomic aberrations associated with prostate cancer progression

Integrative analysis of genomic aberrations in the context of trancriptomic alterations will lead to a more comprehensive perspective on prostate cancer progression. Genome-wide copy number changes were monitored using array comparative genomic hybridization of laser-capture microdissected prostate cancer samples spanning stages of prostate cancer progression, including precursor lesions, clinically localized disease, and metastatic disease. A total of 62 specific cell populations from 38 patients were profiled. Minimal common regions (MCR) of alterations were defined for each sample type, and metastatic samples displayed the most number of alterations. Clinically localized prostate cancer samples with high Gleason grade resembled metastatic samples with respect to the size of altered regions and number of affected genes. A total of 9 out of 13 MCRs in the putative precursor lesion, high-grade prostatic intraepithelial neoplasia (PIN), showed an overlap with prostate cancer cases (amplifications in 3q29, 5q31.3-q32, 6q27, and 8q24.3 and deletions in 6q22.31, 16p12.2, 17q21.2, and 17q21.31), whereas postatrophic hyperplasia (PAH) did not exhibit this overlap. Interestingly, prostate cancers that do not overexpress ETS family members (i.e., gene fusion-negative prostate cancers) harbor differential aberrations in 1q23, 6q16, 6q21, 10q23, and 10q24. Integrative analysis with matched mRNA profiles identified genetic alterations in several proposed candidate genes implicated in prostate cancer progression.

Contemporary clinical management of isolated high-grade prostatic intraepithelial neoplasia

High-grade prostatic intraepithelial neoplasia (HGPIN) is a premalignant lesion associated with increased risk of coexistent cancer or delayed progression to carcinoma. Extended biopsy schemes have improved the ability to rule out concurrent cancers, increased the detection of isolated HGPIN and removed the routine necessity for immediate repeat biopsy. As the natural history of HGPIN is poorly defined, and no non-invasive marker allows monitoring of progression to cancer, routine delayed interval biopsy should be considered in all patients. In this article, we present an overview of the existing literature on HGPIN and a proposed strategy for clinical management.

Practical applications for epigenetic biomarkers in cancer diagnostics

Cancer represents a major global health problem and improvement of cancer treatment requires the development of new and useful molecular diagnostic tests that enable the detection of occult tumors, direction of personalized treatments, monitoring of patients during therapeutic intervention and prediction of long-term clinical outcomes. The ideal molecular diagnostic for cancer testing will be based upon non-invasive sources of DNA and will employ biomarkers that have excellent sensitivity, specificity and overall predictive value. Numerous genes are known to be hypermethylated during cancer development and progression. These methylation-sensitive genes represent potentially valuable epigenetic biomarkers for development of practical cancer molecular diagnostics. In fact, many epigenetic biomarkers have proven to possess excellent predictive value in assays designed to detect occult (or developing) neoplasms and/or forecast clinical course/outcome. The progress to date in this emerging area of cancer diagnostics suggests that we are not far away from a time when testing for epigenetic biomarkers will represent an integral part of cancer screening protocols that can be effectively applied to the general population and/or to groups of people with defined risk factors for specific cancer types.

Elevated levels of the mismatch repair protein PMS2 are associated with prostate cancer

BACKGROUND

Defects in mismatch repair (MMR) proteins have been identified in various types of cancer. However, an association with prostate cancer has been controversial. Defective MMR results in genome instability with detrimental consequences that significantly contribute to tumorigenesis. This study determined alterations in key MMR protein levels in prostate cancer with the goal to identify prognostic markers.

METHODS

Prostatectomy samples were immunohistochemically stained and the relative presence or absence of key proteins MSH2, MLH1, and PMS2 determined. Cancer tissue of distinct grades was compared with the normal surrounding tissue. Microsatellite instability (MSI) in altered tissues was determined according to NCI guidelines.

RESULTS

In contrast to reports that associate a lack of individual MMR proteins with tumorigenesis, a significant increase in PMS2 levels was identified in PIN lesions and prostate cancer tissue. This elevation in PMS2 was independent of changes in levels in its heterodimeric partner, MLH1. Prostate tumors with elevated levels of PMS2 were genetically unstable, which was corrected by MLH1 co-elevation.

CONCLUSIONS

This is the first documentation of detrimental consequences associated with the increase in a MMR protein in human cancer. This study recognizes PMS2 elevation as a prognostic marker in pre-neoplastic and prostate cancer lesions. This result has significant implications for future diagnostic and treatment measures.

Integrative molecular concept modeling of prostate cancer progression

Despite efforts to profile prostate cancer, the genetic alterations and biological processes that correlate with the observed histological progression are unclear. Using laser-capture microdissection to isolate 101 cell populations, we have profiled prostate cancer progression from benign epithelium to metastatic disease. By analyzing expression signatures in the context of over 14,000 'molecular concepts', or sets of biologically connected genes, we generated an integrative model of progression. Molecular concepts that demarcate critical transitions in progression include protein biosynthesis, E26 transformation-specific (ETS) family transcriptional targets, androgen signaling and cell proliferation. Of note, relative to low-grade prostate cancer (Gleason pattern 3), high-grade cancer (Gleason pattern 4) shows an attenuated androgen signaling signature, similar to metastatic prostate cancer, which may reflect dedifferentiation and explain the clinical association of grade with prognosis. Taken together, these data show that analyzing gene expression signatures in the context of a compendium of molecular concepts is useful in understanding cancer biology.

Id proteins expression in prostate cancer: high-level expression of Id-4 in primary prostate cancer is associated with development of metastases

A major cause of treatment failure for prostate cancer is the development of androgen-independent metastatic disease. Id protein family, a group of basic helix-loop-helix transcription factors, has been shown to be involved in carcinogenesis and a prognostic marker in several types of human cancers. In this study, we examined the expressions of four Id proteins, Id-1, -2, -3 and -4, in 125 clinical prostate cancer specimens as well as 40 nodular hyperplasia specimens by immunohistochemistry. The expressions of Id proteins were correlated with Gleason grading and metastatic progress of the tumors. We found that Id proteins were dysregulated in prostate cancer. Id-1 and -2 expressions were elevated while Id-3 and -4 expressions were reduced in prostate cancers compared to nodular hyperplasia. Cytoplasmic staining of Id-1 (P=0.013) and nuclear staining of Id-2 (P=0.001) and Id-4 (P<0.001) were positively correlated with Gleason score. The results indicate that these Id proteins may play a positive role in the development of prostate cancer. In contrast, Id-3 might have an inverse relationship with prostate neoplastic transformation (P=0.002) and cancer progression (P=0.022). We found that Id-4 nuclear overexpression in the primary prostate cancers significantly increased the risks to the development of metastasis in the patients (odds ratio=3.215, 95% confidence interval=1.150-8.987, P=0.026). Our results suggest that in prostate cancer patients, differential Id proteins expressions may be a useful marker for poor prognosis, and Id-4 may be a potential prognostic marker for distant metastasis.