Preneoplastic prostate lesions: an opportunity for prostate cancer prevention

Exposure to pesticide residues in honey and its potential cancer risk assessment

Honey is the most recognized natural food by-product derived from flower nectar and the upper aero-digestive tract of the honeybees. Significance of honey for its medicinal importance are well-documented in the world's oldest medical literatures. However, the current urbanization, environmental contaminations and changes in agricultural, as well as apiculture practices has led to various types of contaminations in honey. Among all, pesticide contamination has become one of the major issues worldwide. This review focuses on the recent updates concerning pesticides occurrence in honey, as well as how the repeated use and long-term exposure to honey contaminated with pesticide residues could affect the human physiological functions, possibly leading to the development of various cancers. Our findings suggests that uncontrolled use of pesticides in farming and apiculture practices leads to the occurrence of pesticides residues in honey. Therefore, regular consumption of such honey will pose a serious threat to human health, since most of the pesticides has been reported as potential carcinogens. This review will draw the attention of honey consumers, scientific communities, apiculture farmers, as well as governing bodies to strictly monitor the pesticide usage in floriculture, agriculture as well as other related practices.

Evidence that EZH2 Deregulation is an Actionable Therapeutic Target for Prevention of Prostate Cancer

Chemoprevention trials for prostate cancer by androgen receptor or androgen synthesis inhibition have proven ineffective. Recently, it has been demonstrated that the histone methlytransferase, EZH2 is deregulated in mouse and human high-grade prostatic intraepithelial neoplasia (HG-PIN). Using preclinical mouse and human models of prostate cancer, we demonstrate that genetic and chemical disruption of EZH2 expression and catalytic activity reversed the HG-PIN phenotype. Furthermore, inhibition of EZH2 function was associated with loss of cellular proliferation and induction of Tp53-dependent senescence. Together, these data provide provocative evidence for EZH2 as an actionable therapeutic target toward prevention of prostate cancer.

GSTP1 and cancer: Expression, methylation, polymorphisms and signaling (Review)

Glutathione S‑transferase Pi (GSTP1) is an isozyme encoded by the GST pi gene that plays an important regulatory role in detoxification, anti‑oxidative damage, and the occurrence of various diseases. The aim of the present study was to review the association between the expression of GSTP1 and the development and treatment of various cancers, and discuss GSTP1 methylation in several malignant tumors, such as prostate, breast and lung cancer, as well as hepatocellular carcinoma; to review the association between polymorphism of the GSTP1 gene and various diseases; and to review the effects of GSTP1 on electrophilic oxidative stress, cell signal transduction, and the regulation of carcinogenic factors. Collectively, GSTP1 plays a major role in the development of various diseases.

Occupational Risk Factors for Prostate Cancer: A Meta-analysis

Prostate cancer is the second most common cancer in men worldwide. There are many occupational factors that have been suggested to cause prostate cancer. Our aim was to evaluate the evidence for causality by a literature review of occupational factors. We searched literature in Medline and SCOPUS from 1966 to June 30, 2015 to identify occupational risk factors for prostate cancer. The following risk factors were selected: farmers/agricultural workers, pesticides - whole group, and separately organophosphate and organochlorine pesticides, carbamates and triazines, cadmium, chromium, cutting fluids, acrylonitrile, rubber manufacturing, whole body vibration, shift work, flight personnel, ionizing radiation, and occupational physical activity. For each factor a literature search was performed and presented as meta-analysis of relative risk and heterogeneity (Q and I2 index). A total of 168 original studies met the inclusion criteria with 90,688 prostate cancer cases. Significantly increased risks were observed for the following occupational exposures: pesticides (metaRR = 1.15, 95% confidence interval [CI] = 1.01-1.32; I2 = 84%), and specifically group of organochlorine pesticides (meta relative risk [metaRR] = 1.08, 95% CI = 1.03-1.14; I2 = 0%), chromium (metaRR = 1.19, 95% CI = 1.07-1.34; I2 = 31%), shift work (metaRR = 1.25, 95% CI = 1.05-1.49; I2 = 78%) and pilots (metaRR = 1.41, 95% CI = 1.02-1.94; I2 = 63%) and occupational physical activity in cohort studies (metaRR = 0.87, 95% CI = 0.81-0.94; I2 = 0%). The literature review supports a causal association for a few of the previously suggested factors.

Voltammetric Application of Polypyrrole-Modified Microelectrode Array for the Characterization of DNA Methylation in Glutathione S-Transferase Pi 1

Direct and efficient label-free voltammetric detection of Glutathione S-Transferase Pi 1 (GSTP1) hypermethylation is reported using a custom developed 16-channel Microelectrode Array chip. The microelectrode array chip is used in a dipstick configuration allowing detection of DNA hybridization in a solution volume of only 0.35 mL. Platinum microelectrode disks (n = 16) 30 µm in diameter have been modified with a polypyrrole bilayer before any contact with the oligonucleotides. The attachment of the 15-mer Probe DNA to the bilayer is random but controlled by the presence of aliphatic tether groups allowing it to form a bidentate complex with the probe DNA. The voltammetric detection procedure of methylated GSTP1-specific target DNA is combined with bisulfite treatment of target DNA. Changes at the interface of the modified microelectrodes in an array configuration are used to record simultaneously cyclic voltammetry on all of the devices. The detection of the hybridization is evaluated statistically for a yes or no event by comparing the changes in recorded cyclic voltammograms before and after exposure to the Target DNA. All cyclic voltammograms of the methylated target show a greater percentage change than those with the non-methylated target exposure and show a greater change in cyclic voltammogram area after methylated target exposure. We observe an average percentage difference of 25.6% ± 4.9 with a variation of 19.1%. These results demonstrate that the fast sensing strategy possesses sensitivity and good specificity. Furthermore, this technology can potentially support rapid, accurate diagnosis and risk assessment of patients with prostate cancer.

Desquamation takes center stage at the origin of proliferative inflammatory atrophy, epithelial-mesenchymal transition, and stromal growth in benign prostate hyperplasia

In this commentary, we propose a relationship between desquamation, initially described as the collective detachment and deletion of epithelial cell in the prostate gland after castration, and proliferative inflammatory atrophy (PIA) and stromal growth in benign prostate hyperplasia (BPH). First, in response to diverse stimuli, including inflammatory mediators, epithelial cells desquamate and leave a large surface of the luminal side of the basement membrane (BM) exposed. Basal cells are activated into intermediate-type cells, which change morphology to cover and remodel the exposed BM (simple atrophy) to a new physiological demand (such as in the hypoandrogen environment, simulated by surgical and/or chemical castration) and/or to support re-epithelialization (under normal androgen levels). In the presence of inflammation (that might be the cause of desquamation), the intermediate-type cells proliferate and characterize PIA. Second, in other circumstances, desquamation is an early step of epithelial-to-mesenchymal transition (EMT), which contributes to stromal growth, as suggested by some experimental models of BPH. The proposed associations correlate unexplored cell behaviors and reveal the remarkable plasticity of the prostate epithelium that might be at the origin of prostate diseases.

Glutathione S-transferase and MRP1 form an integrated system involved in the storage and transport of dinitrosyl-dithiolato iron complexes in cells

Nitrogen monoxide (NO) is vital for many essential biological processes as a messenger and effector molecule. The physiological importance of NO is the result of its high affinity for iron in the active sites of proteins such as guanylate cyclase. Indeed, NO possesses a rich coordination chemistry with iron and the formation of dinitrosyl-dithiolato iron complexes (DNICs) is well documented. In mammals, NO generated by cytotoxic activated macrophages has been reported to play a role as a cytotoxic effector against tumor cells by binding and releasing intracellular iron. Studies from our laboratory have shown that two proteins traditionally involved in drug resistance, namely multidrug-resistance protein 1 and glutathione S-transferase, play critical roles in intracellular NO transport and storage through their interaction with DNICs (R.N. Watts et al., Proc. Natl. Acad. Sci. USA 103:7670-7675, 2006; H. Lok et al., J. Biol. Chem. 287:607-618, 2012). Notably, DNICs are present at high concentrations in cells and are biologically available. These complexes have a markedly longer half-life than free NO, making them an ideal "common currency" for this messenger molecule. Considering the many critical roles NO plays in health and disease, a better understanding of its intracellular trafficking mechanisms will be vital for the development of new therapeutics.

DNA hypermethylation in prostate cancer is a consequence of aberrant epithelial differentiation and hyperproliferation

Prostate cancer (CaP) is mostly composed of luminal-like differentiated cells, but contains a small subpopulation of basal cells (including stem-like cells), which can proliferate and differentiate into luminal-like cells. In cancers, CpG island hypermethylation has been associated with gene downregulation, but the causal relationship between the two phenomena is still debated. Here we clarify the origin and function of CpG island hypermethylation in CaP, in the context of a cancer cell hierarchy and epithelial differentiation, by analysis of separated basal and luminal cells from cancers. For a set of genes (including GSTP1) that are hypermethylated in CaP, gene downregulation is the result of cell differentiation and is not cancer specific. Hypermethylation is however seen in more differentiated cancer cells and is promoted by hyperproliferation. These genes are maintained as actively expressed and methylation-free in undifferentiated CaP cells, and their hypermethylation is not essential for either tumour development or expansion. We present evidence for the causes and the dynamics of CpG island hypermethylation in CaP, showing that, for a specific set of genes, promoter methylation is downstream of gene downregulation and is not a driver of gene repression, while gene repression is a result of tissue-specific differentiation.

Molecular pathways in prostate cancer

Objectives

Prostate cancer is a prevalent disease with a high impact on patients’ morbidity and mortality. Despite efforts to profile prostate cancer, the genetic alterations and biological processes that correlate with disease progression remain partially elusive. The purpose of this study is to review the recent evidence relating to the initiation and progression of prostate cancer in relation to the familial correlation of the disease, the genetic aberrations resulting in prostate cancer and the new molecular biology data regarding prostate cancer.

Materials and Methods

A Medline database search identified all the existing publications on the molecular events associated with the pathogenesis and evolution of prostate cancer. Particular emphasis was given on the specific genetic phenomena associated with prostate cancer.

Results

Like other cancers, prostate cancer is caused by an accumulation of genetic alterations in a cell that drives it to malignant growth. Specific genes and gene alterations have been suggested to play a role in its development and progression. Aneuploidy, loss of heterozygosity, gene mutations, hypermethylation and inactivation of specific tumour suppressor genes such as GSTpi, APC, MDR1, GPX3 and others have been detected in prostate cancers, but generally only at a low or moderate frequency. The androgen receptor (AR) signalling pathway may play a crucial role in the early development of prostate cancer, as well as in the development of androgen-independent disease that fails to respond to hormone deprivation therapies. Other alterations linked to the transition to hormone-independence include amplification of MYC and increased expression of ERBB2 and BCL2. Inflammatory changes may also contribute to the development of prostate cancer.

Conclusion

The identification of specific molecular markers for prostate cancer may lead to its earliest detection and better prediction of its behavior. The better understanding of the molecular events affecting prostate cancer progression may result in the introduction of new drugs to target these events thus providing a potential cure and a tool for prevention of this very common disease.

Unusual intronic variant in GSTP1 in head and neck cancer in Pakistan

In the present case control study mRNA expression of the GSTP1 gene, encoding a phase II enzyme that detoxifies via glutathione conjugation, was investigated using semiquantitative PCR followed by SSCP for 49 confirmed head and neck (HN) cancer and 49 control samples. It was found that GSTP1 was upregulated in significantly higher number of cancers (OR 4.2, 95% CI 1.2- 15.3). Grade wise correlation was also observed with more up regulation in patients with more advanced grades of HN carcinomas. We also found that 5 patients showed variation in mRNA with a larger product size than expected. Sequencing revealed insertion of an intronic segment between the 6th and 7th exon of the GSTP1 gene. Germline screening was performed showing mobility shifts which suggested mutation at the DNA level resulting in intronic portion retention. This study is of prime importance for drug design and treatment selection to overcome increased resistance of HN cancers to drugs due to alteration in the GSTP1 gene.

Variation in IL10 and other genes involved in the immune response and in oxidation and prostate cancer recurrence

BACKGROUND

To evaluate the association of variation in genes involved in immune response, including IL10, production and detoxification of reactive oxygen species, and repair of oxidative DNA damage with risk of recurrence after surgery for localized prostate cancer.

METHODS

We conducted a nested case-control study of men who had a radical prostatectomy in 1993 to 2001. A total of 484 recurrence cases and 484 controls were matched on age, race, and pathologic stage and grade. Germline DNA was extracted from paraffin-embedded unaffected lymph nodes. We genotyped candidate single-nucleotide polymorphisms (SNP) in IL10, CRP, GPX1, GSR, GSTP1, hOGG1, IL1B, IL1RN, IL6, IL8, MPO, NOS2, NOS3, SOD1, SOD2, SOD3, TLR4, and TNF and tagging SNPs in IL10, CRP, GSR, IL1RN, IL6, NOS2, and NOS3. We used conditional logistic regression to estimate OR and 95% confidence intervals (CI).

RESULTS

The minor allele (A) in IL10 rs1800872, known to produce less interleukin-10 (IL-10), was associated with a higher risk of recurrence (OR = 1.76, 95% CI: 1.00-3.10), and the minor allele (G) in rs1800896, known to produce more IL-10, was associated with a lower risk of recurrence (OR = 0.66, 95% CI: 0.48-0.91). We also observed associations for candidate SNPs in CRP, GSTP1, and IL1B. A common IL10 haplotype and 2 common NOS2 haplotypes were associated with recurrence.

CONCLUSION

Variation in IL10, CRP, GSTP1, IL1B, and NOS2 was associated with prostate cancer recurrence independent of pathologic prognostic factors.

IMPACT

This study supports that genetic variation in immune response and oxidation influence prostate cancer recurrence risk and suggests genetic variation in these pathways may inform prognosis.

Protection against oxidative DNA damage and stress in human prostate by glutathione S-transferase P1

The pi-class glutathione S-transferase (GSTP1) actively protect cells from carcinogens and electrophilic compounds. Loss of GSTP1 expression via promoter hypermethylation is the most common epigenetic alteration observed in human prostate cancer. Silencing of GSTP1 can increase generation of reactive oxygen species (ROS) and DNA damage in cells. In this study we investigated whether loss of GSTP1 contributes to increased DNA damage that may predispose men to a higher risk of prostate cancer. We found significantly elevated (103%; P < 0.0001) levels of 8-oxo-2'-deoxogunosine (8-OHdG), an oxidative DNA damage marker, in adenocarcinomas, compared to benign counterparts, which positively correlated (r = 0.2) with loss of GSTP1 activity (34%; P < 0.0001). Silencing of GSTP1 using siRNA approach in normal human prostate epithelial RWPE1 cells caused increased intracellular production of ROS and higher susceptibility of cells to H2 O2 -mediated oxidative stress. Additionally, human prostate carcinoma LNCaP cells, which contain a silenced GSTP1 gene, were genetically modified to constitutively express high levels of GSTP1. Induction of GSTP1 activity lowered endogenous ROS levels in LNCaP-pLPCX-GSTP1 cells, and when exposed to H2 O2 , these cells exhibited significantly reduced production of ROS and 8-OHdG levels, compared to vector control LNCaP-pLPCX cells. Furthermore, exposure of LNCaP cells to green tea polyphenols caused reexpression of GSTP1, which protected the cells from H2 O2 -mediated DNA damage through decreased ROS production compared to nonexposed cells. These results suggest that loss of GSTP1 expression in human prostate cells, a process that increases their susceptibility to oxidative stress-induced DNA damage, may be an important target for primary prevention of prostate cancer.

Epigenetic markers of early tumor development

Cancer patients' outcome and survival depends on the early diagnosis of malignant lesions. Several investigation methods used for the prevention and early detection strategies have specific limitations. More recently, epigenetic changes have been considered one of the most promising tools for the early diagnosis of cancer. Some of these epigenetic alterations including promoter hypermethylation of genes like P16INK4a, BRCA1, BRCA2, ERα and RARβ2, APC, and RASSF1A have been associated with early stages of mammary gland tumorigenesis and have been suggested to be included in the models that evaluate individual breast cancer risk. In lung cancer, P16INK4a and MGMT gene hypermethylation was observed in sputum years before clinical manifestation of the squamous cell carcinoma among smokers. Loss of GSTP1 function by DNA hypermethylation together with changes in the methylation levels of repetitive elements like LINE-1 and Sat2 was reported in prostatic preneoplastic lesions. Also, DNA hypermethylation for hMLH1 and MGMT DNA repair genes was reported in precursor lesions to colorectal cancer. These epigenetic alterations may be influenced by factors such as xenoestrogens, folate, and multivitamins. Detection of these changes may help determining cancer susceptibility and early diagnosis.

The mutator phenotype in cancer: molecular mechanisms and targeting strategies

Normal human cells replicate their DNA with exceptional accuracy. It has been estimated that approximately one error occurs during DNA replication for each 10(9) to 10(10) nucleotides polymerized. In contrast, malignant cells exhibit multiple chromosomal abnormalities and contain tens of thousands of alterations in the nucleotide sequence of nuclear DNA. To account for the disparity between the rarity of mutations in normal cells and the large numbers of mutations present in cancer, we have hypothesized that during tumor development, cancer cells exhibit a mutator phenotype. As a defining feature of cancer, the mutator phenotype remains an as-yet unexplored therapeutic target: by reducing the rate at which mutations accumulate it may be possible to significantly delay tumor development; conversely, the large number of mutations in cancer may make cancer cells more sensitive to cell killing by increasing the mutation rate. Here we summarize the evidence for the mutator phenotype hypothesis in cancer and explore how the increased frequency of random mutations during the evolution of human tumors provides new approaches for the design of cancer chemotherapy.

Decreased expression of GST pi is correlated with a poor prognosis in human esophageal squamous carcinoma

Background

Glutathione S-transferase pi (GST pi) is a subgroup of GST family, which provides cellular protection against free radical and carcinogenic compounds due to its detoxifying function. Expression patterns of GST pi have been studied in several carcinomas and its down-regulation was implicated to be involved in malignant transformation in patients with Barrett's esophagus. However, neither the exact role of GST pi in the pathogenesis nor its prognostic impact in squamous esophageal carcinoma is fully characterized.

Methods

Immunohistochemistry was used to investigate GST pi expression on 153 archival squamous esophageal carcinoma specimens with a GST pi monoclonal antibody. Statistic analyses were performed to explore its association with clinicopathological factors and clinical outcome.

Results

The GST pi expression was greatly reduced in tissues of esophageal carcinomas compared to adjacent normal tissues and residual benign tissues. Absent of GST pi protein expression in cytoplasm, nuclear and cytoplasm/nucleus was found in 51%, 64.7% and 48% of all the carcinoma cases, respectively. GST pi deficiency in cytoplasm, nucleus and cytoplasm/nucleus was significantly correlated to poor differentiation (p < 0.001, p < 0.001 and p < 0.001, respectively). UICC stage and T stage were found significantly correlated to negative expression of GST pi in cytoplasm (p < 0.001 and p = 0.004, respectively) and cytoplasm/nucleus (p = 0.017 and p = 0.031, respectively). In univariate analysis, absent of GST pi protein expression in cytoplasm, nucleus and cytoplasm/nucleus was significantly associated with a shorter overall survival (p < 0.001, p < 0.001 and p < 0.001, respectively), whereas only GST pi cytoplasmic staining retained an independent prognostic significance (p < 0.001) in multivariate analysis.

Conclusions

Our results show that GST pi expression is down regulated in the squamous esophageal carcinoma, and that the lack of GST pi expression is associated with poor prognosis. Therefore, deficiency of GST pi protein expression may be an important mechanism involved in the carcinogenesis and progression of the squamous esophageal carcinoma, and the underlying mechanisms leading to decreased GST pi expression deserve further investigation.

Oxidative stress and DNA methylation in prostate cancer

The protective effects of fruits, vegetables, and other foods on prostate cancer may be due to their antioxidant properties. An imbalance in the oxidative stress/antioxidant status is observed in prostate cancer patients. Genome oxidative damage in prostate cancer patients is associated with higher lipid peroxidation and lower antioxidant levels. Oxygen radicals are associated with different steps of carcinogenesis, including structural DNA damage, epigenetic changes, and protein and lipid alterations. Epigenetics affects genetic regulation, cellular differentiation, embryology, aging, cancer, and other diseases. DNA methylation is perhaps the most extensively studied epigenetic modification, which plays an important role in the regulation of gene expression and chromatin architecture, in association with histone modification and other chromatin-associated proteins. This review will provide a broad overview of the interplay of oxidative stress and DNA methylation, DNA methylation changes in regulation of gene expression, lifestyle changes for prostate cancer prevention, DNA methylation as biomarkers for prostate cancer, methods for detection of methylation, and clinical application of DNA methylation inhibitors for epigenetic therapy.

Tumor-stroma co-evolution in prostate cancer progression and metastasis

Cancer development is complex and involves several layers of interactions and pleotropic signaling mechanisms leading to progression. Cancer cells associate with resident stromal fibroblasts, smooth muscle cells, macrophages, endothelium, neurons and migrating cells at metastatic sites and phenotypically and genotypically activate them. These become an integral part of the cancer cell community through activated cell signaling mechanisms. During this process, the cancer cells and cells in the cancer microenvironment "co-evolve" in part due to oxidative stress, and acquire the ability to mimic other cell types (which can be termed osteomimicry, vasculomimicry, neuromimicry and stem cell mimicry), and undergo transition from epithelium to mesenchyme with definitive morphologic and behavioral modifications. In our laboratory, we demonstrated that prostate cancer cells co-evolve in their genotypic and phenotypic characters with stroma and acquire osteomimetic properties allowing them to proliferate and survive in the skeleton as bone metastasis. Several signaling interactions in the bone microenvironment, mediated by reactive oxygen species, soluble and membrane bound factors, such as superoxide, beta2-microglobulin and RANKL have been described. Targeting the signaling pathways in the cancer-associated stromal microenvironment in combination with known conventional therapeutic modalities could have a synergistic effect on cancer treatment. Since cancer cells are constantly interacting and acquiring adaptive and survival changes primarily directed by their microenvironment, it is imperative to delineate these interactions and co-target both cancer and stroma to improve the treatment and overall survival of cancer patients.

Anti-tumor activity of oxypeucedanin from Ostericum koreanum against human prostate carcinoma DU145 cells

PURPOSE

Oxypeucedanin has been reported to have various biological activities. We investigated the efficacy of a coumarin compound, oxypeucedanin, from Ostericum koreanum against the human prostate carcinoma cell line DU145.

MATERIAL AND METHODS

Oxypeucedanin (C(16)H(14)O(5), mw: 286) was isolated through silica gel chromatography and characterized by NMR. The cells were treated with oxypeucedanin (25, 50, and 100 microM) for 24-72 hours, and cell growth and death were then assayed. The cell cycle progression and apoptotic effects were also assessed by western blotting.

RESULTS

Treatment with oxypeucedanin inhibited cell growth and induced cell death in DU145 cells. Furthermore, oxypeucedanin-induced cell growth inhibition was associated with an increase in G2-M arrest in cell cycle progression in DU145 cells in a dose and time-dependent manner. G2-M arrest by oxypeucedanin was associated with decreased levels of cyclin A, cyclin B1, Cdc2, and pCdc2. Oxypeucedanin-induced cell death was associated with significant increases in apoptosis and cleaved caspase-3 and poly-(ADP-ribose) polymerase.

CONCLUSION

These finding suggest a novel anticancer effect for oxypeucedanin, mediated via induction of G2-M cell cycle arrest and apoptosis in human prostate carcinoma DU145 cells.

Polyamine catabolism and disease

In addition to polyamine homoeostasis, it has become increasingly clear that polyamine catabolism can play a dominant role in drug response, apoptosis and the response to stressful stimuli, and contribute to the aetiology of several pathological states, including cancer. The highly inducible enzymes SSAT (spermidine/spermine N1-acetyltransferase) and SMO (spermine oxidase) and the generally constitutively expressed APAO (N1-acetylpolyamine oxidase) appear to play critical roles in many normal and disease processes. The dysregulation of polyamine catabolism frequently accompanies several disease states and suggests that such dysregulation may both provide useful insight into disease mechanism and provide unique druggable targets that can be exploited for therapeutic benefit. Each of these enzymes has the potential to alter polyamine homoeostasis in response to multiple cell signals and the two oxidases produce the reactive oxygen species H2O2 and aldehydes, each with the potential to produce pathological states. The activity of SSAT provides substrates for APAO or substrates for the polyamine exporter, thus reducing the intracellular polyamine concentration, the net effect of which depends on the magnitude and rate of any increase in SSAT. SSAT may also influence cellular metabolism via interaction with other proteins and by perturbing the content of acetyl-CoA and ATP. The goal of the present review is to cover those aspects of polyamine catabolism that have an impact on disease aetiology or treatment and to provide a solid background in this ever more exciting aspect of polyamine biology.

Loss of Nkx3.1 leads to the activation of discrete downstream target genes during prostate tumorigenesis

The expression of NKX3.1, a transcriptional regulator and tumor suppressor gene in prostate cancer, is downregulated during early stages of prostate tumorigenesis. However, little is known of the alterations in gene expression that occur as a result of this event. We combined laser capture microdissection and gene expression profiling to analyze the molecular consequences of Nkx3.1 loss during prostate cancer initiation using Nkx3.1-deficient mice. This analysis identified a cohort of genes (loss-of-Nkx3.1 signature) that are aberrantly overexpressed during loss-of-Nkx3.1 driven tumor initiation. We studied the expression of these same genes in independent loss-of-Pten and c-myc overexpression prostate adenocarcinoma mouse models. Nkx3.1 expression is lost in prostate epithelial proliferation in both of these mouse models. However, Nkx3.1 loss is an early event of tumor development in the loss-of-Pten model, whereas it occurs at later stages in c-myc transgenic mice. A member of genes of the loss-of-Nkx3.1 signature, like clusterin and quiescin Q6, are highly expressed in prostatic hyperplasia and intraepithelial neoplasia (PIN) lesions that also lack Nkx3.1 in the Pten-deficient prostate, but not in similar lesions in the c-myc transgenic model. Meta-analysis of multiple prostate cancer gene expression datasets including those from loss-of-Nkx3.1, loss-of-Pten, c-myc overexpression, and constitutively active Akt prostate cancer models, further confirmed that genes associated with the loss-of-Nkx3.1 signature integrate with Pten-Akt signaling pathways, but do not overlap with molecular changes associated with the c-myc signaling pathway. In human prostate tissue samples, loss of NKX3.1 expression and corresponding clusterin overexpression are co-localized at sites of prostatic inflammatory atrophy, a possible very early stage of human prostate tumorigenesis. Collectively, these results suggest that the molecular consequences of NKX3.1 loss depend on the epithelial proliferative stage at which its expression is lost and, that alterations in the Pten-Akt-Nkx3.1 axis are important for prostate cancer initiation.

Anti-proliferation Effect of Polypeptide Extracted from Scorpion Venom on Human Prostate Cancer Cells in vitro

BACKGROUND

Prostate cancer is a major cause of cancer-related death in men. Therefore there has been considerable interest to explore neoadjuvant therapy. Polypeptide extracted from scorpion venom (PESV), originally obtained from the East-Asian scorpion Buthus martensi Karsch (BmK), is being studied for both prevention and treatment of various human malignancies including prostate cancer.

METHODS

The present study was to investigate the effect of PESV on cell proliferation, cell cycle, and apoptosis in human androgen-independent prostate cancer cells DU-145 in vitro.

RESULTS

PESV treatment on these cells resulted in a significantly dose-dependent growth inhibition with a G1 phase arrest at 40μg/mL after 48h treatment. PESV treatment strongly induced expression of p27 (Kip1), but resulted in a decrease in cyclin E, one of cyclins involved in G1 progression. In other studies, PESV treatment also induced high apoptosis index (AI), confirmed by TdTmediated dUTP-biotin nick-end labeling (TUNEL) assay. Further, the apoptosis induction by PESV (40μg/mL) in DU145 cells was associated with an increase of pro-apoptotic protein Bax.

CONCLUSIONS

These results suggest that PESV modulates the expression of cell cycle-related and apoptosis-related proteins and induces growth inhibition and apoptosis of DU145 cells, providing a strong rationale for future studies to evaluate prevention or/and intervention strategies for PESV in pre-clinical prostate cancer models.

KEYWORDS

Prostate cancer, PESV, cell proliferation, cell cycle, apoptosis.

Genetic changes and DNA damage responses in the prostate

The integrity of genomic DNA is challenged by genotoxic stress originating during normal cellular metabolism or by external insults. Cellular responses to DNA damage involve elegant checkpoint cascades enforcing cell cycle arrest, damage repair, apoptosis or cellular senescence. The loss or alterations of genes involved in the damage response pathways have been reported in many cancer susceptibility syndromes and in sporadic tumors. Furthermore, this surveillance pathway is activated during early tumourigenesis presumably due to uncontrolled replicative cycles and has been recognized as one of the main barriers against the development of cancer. This review discusses the relevance of prostatic epithelial cells in prostate tumourigenesis and highlights common molecular changes associated with prostate cancer. Furthermore, DNA damage responses of primary cultures of human prostatic epithelial cells and fresh human prostate tissues are discussed providing evidence for alterations in crucial DNA damage checkpoint molecules. New insights connecting prostate tumourigenesis to alterations and defects in the pathways maintaining genomic integrity will be discussed.

Transgenerational effects of the endocrine disruptor vinclozolin on the prostate transcriptome and adult onset disease

PURPOSE

The ability of an endocrine disruptor exposure during gonadal sex determination to promote a transgenerational prostate disease phenotype was investigated in the current study.

METHODS

Exposure of an F0 gestating female rat to the endocrine disruptor vinclozolin during F1 embryo gonadal sex determination promoted a transgenerational adult onset prostate disease phenotype. The prostate disease phenotype and physiological parameters were determined for males from F1 to F4 generations and the prostate transcriptome was assessed in the F3 generation.

RESULTS

Although the prostate in prepubertal animals develops normally, abnormalities involving epithelial cell atrophy, glandular dysgenesis, prostatitis, and hyperplasia of the ventral prostate develop in older animals. The ventral prostate phenotype was transmitted for four generations (F1-F4). Analysis of the ventral prostate transcriptome demonstrated 954 genes had significantly altered expression between control and vinclozolin F3 generation animals. Analysis of isolated ventral prostate epithelial cells identified 259 genes with significantly altered expression between control and vinclozolin F3 generation animals. Characterization of regulated genes demonstrated several cellular pathways were influenced, including calcium and WNT. A number of genes identified have been shown to be associated with prostate disease and cancer, including beta-microseminoprotein (Msp) and tumor necrosis factor receptor superfamily 6 (Fadd).

CONCLUSIONS

The ability of an endocrine disruptor to promote transgenerational prostate abnormalities appears to involve an epigenetic transgenerational alteration in the prostate transcriptome and male germ-line. Potential epigenetic transgenerational alteration of prostate gene expression by environmental compounds may be important to consider in the etiology of adult onset prostate disease.

Role of hormonal and other factors in human prostate cancer

American men have a lifetime risk of about 18% for prostate cancer diagnosis. Large international variations in prostate cancer risks and increased risks among migrants from low- to high-risk countries indicate important roles for environmental factors. Major known risk factors include age, family history, and country/ethnicity. Type 2 diabetes appears to reduce risk, while high birth weight and adult height are linked to increased risk of aggressive prostate cancer. Limited evidence supports an association with a history of sexually transmitted infections. A previous meta-analysis of eight cohort studies indicated no associations with plasma androgen, estrogen, or sex hormone binding globulin (SHBG) levels. However, there were dose-response relationships with baseline plasma testosterone levels in two studies that adjusted for other serum hormones and obesity. Finasteride (a drug that blocks testosterone activation) reduced prostate cancer risk by 25%. Low-frequency genes linked to familial prostate cancer only explain a small fraction of all cases. Sporadic cases were linked to relatively common polymorphisms of genes involved in (1) androgen synthesis, activation, inactivation and excretion, (2) hormone and vitamin D receptors, (3) carcinogen metabolism, and (4) DNA repair. Epidemiologic evidence supports protective roles for dietary selenium, vitamin E, pulses, tomatoes/lycopene, and soy foods, and high plasma 1,25-dihydroxyvitamin D levels. There is inadequate evidence that vegetables, fruit, carotenoids, and vitamins A and C reduce risk and that animal fat, alpha-linoleic acid, meat, coffee, and tea increase risk. Two major cohort studies found dose-response relationships with dietary calcium intake. Total dietary energy intake may enhance risk. Limited evidence supports a protective role for physical activity and elevated risk for farmers and other men with occupational pesticide exposure, particularly to organochlorine compounds and phenoxy herbicides. There is inadequate evidence for a relationship with alcohol or smoking. Most known or suspected external risk factors may act through hormonal mechanisms, but our review found little supporting evidence, and substantial further research is needed.

Age-related DNA methylation changes in normal human prostate tissues

PURPOSE

Prostate cancer is a leading cause of cancer death among the aging male population but the mechanism underlying this association is unclear. Aberrant methylation of promoter CpG islands is associated with silencing of genes and age-dependent methylation of several genes has been proposed as a risk factor for sporadic cancer. We examined the extent of gene methylation in pathologically normal human prostate as a function of age.

EXPERIMENTAL DESIGN

We used pyrosequencing to quantitatively analyze the methylation status of nine CpG islands in normal prostate tissue DNA from 45 organ donors and 45 patients who had undergone cystoprostatectomy for bladder cancer. We also analyzed 12 pairs of matched benign and prostate cancer tissue DNA from patients with prostate cancer.

RESULTS

Linear regression analysis revealed a significant increase in promoter methylation levels correlating with age for CpG islands at RARbeta2 (r = 0.4; P < 0.0001), RASSF1A (r = 0.27; P = 0.01), GSTP1 (r = 0.59; P < 0.0001), NKX2-5 (r = 0.27; P = 0.008), and ESR1 (r = 0.244; P = 0.023) in the normal prostate tissue samples studied. A calculated average methylation (z score) at all nine CpG loci analyzed in the normal prostate tissues showed a strong correlation with age (r = 0.6; P < 0.001). Comparison of the methylation level for the matched benign and prostate cancer tissues from individual patients with prostate cancer showed significantly higher methylation in the prostate cancer tissue samples for RARbeta2 (P < 0.001), RASSF1A (P = 0.005), GSTP1 (P < 0.001), NKX2-5 (P = 0.003), ESR1 (P = 0.016), and CLSTN1 (P = 0.01).

CONCLUSIONS

Our findings show aberrant hypermethylation as a function of age in the normal prostate tissues. Such age-related methylation may precede and predispose to full-blown malignancy.

Modulation of human glutathione s-transferases by polyphenon e intervention

PURPOSE

Green tea consumption has been associated with decreased risk of certain types of cancers in humans. Induction of detoxification enzymes has been suggested as one of the biochemical mechanisms responsible for the cancer-preventive effect of green tea. We conducted this clinical study to determine the effect of repeated green tea polyphenol administration on a major group of detoxification enzymes, glutathione S-transferases (GST).

METHODS

A total of 42 healthy volunteers underwent a 4-week washout period by refraining from tea or tea-related products. At the end of the washout period, a fasting blood sample was collected, and plasma and lymphocytes were isolated for assessment of GST activity and level. Following the baseline evaluation, study participants underwent 4 weeks of green tea polyphenol intervention in the form of a standardized Polyphenon E preparation at a dose that contains 800 mg epigallocatechin gallate (EGCG) once a day. Polyphenon E was taken on an empty stomach to optimize the oral bioavailability of EGCG. Upon completion of the intervention, samples were collected for postintervention GST assessment.

RESULTS

Four weeks of Polyphenon E intervention enhanced the GST activity in blood lymphocytes from 30.7 +/- 12.2 to 35.1 +/- 14.3 nmol/min/mg protein, P = 0.058. Analysis based on baseline activity showed that a statistically significant increase (80%, P = 0.004) in GST activity was observed in individuals with baseline activity in the lowest tertile, whereas a statistically significant decrease (20%, P = 0.02) in GST activity was observed in the highest tertile. In addition, Polyphenon E intervention significantly increased the GST-pi level in blood lymphocytes from 2,252.9 +/- 734.2 to 2,634.4 +/- 1,138.3 ng/mg protein, P = 0.035. Analysis based on baseline level showed that this increase was only significant (P = 0.003) in individuals with baseline level in the lowest tertile, with a mean increase of 80%. Repeated Polyphenon E administration had minimal effects on lymphocyte GST-mu and plasma GST-alpha levels. There was a small but statistically significant decrease (8%, P = 0.003) in plasma GST-alpha levels in the highest tertile.

CONCLUSIONS

We conclude that 4 weeks of Polyphenon E administration resulted in differential effects on GST activity and level based on baseline enzyme activity/level, with GST activity and GST-pi level increased significantly in individuals with low baseline enzyme activity/level. This suggests that green tea polyphenol intervention may enhance the detoxification of carcinogens in individuals with low baseline detoxification capacity.

Towards rational and evidence-based use of melatonin in prostate cancer prevention and treatment

Prostate cancer is a public health problem of the elderly men. It has been estimated that one in six men will develop prostate cancer in his lifetime in the USA. There is thus a huge clinical demand for effective therapies for the prevention and treatment of the disease. Here, the scientific evidence supporting the effectiveness of melatonin in inhibiting the development and progression of prostate cancer is reviewed. The rational use of melatonin in prostate cancer prevention, stabilization of clinically localized favourable-risk prostate cancer and palliative treatment of advanced or metastatic tumour is discussed within the context of the molecular pathogenesis of the disease.

Glutathione S-transferase pi (GSTP1) hypermethylation in prostate cancer: review 2007

Prostatic carcinoma is characterised by the silencing of the pi-class glutathione S-transferase gene (GSTP1), which encodes a detoxifying enzyme. The silencing of GSTP1 results from aberrant methylation at the CpG island in the promoter-5' and occurs in the vast majority of cases of high-grade prostatic intraepithelial neoplasia (PIN) and prostate cancers. We review the potential novel role of GSTP1 and its related expression in prostate cancer. The loss of expression (silencing) of the GSTP1 gene is the most common (>90%) genetic alteration reported to date in prostate cancer. Quantitative methylation-specific PCR assays allow detection of GSTP1 methylation in prostate biopsies and may improve the sensitivity of cancer detection. Advances in the epigenetic characterisation of prostate cancer have enabled the development of DNA methylation assays that may soon be used in diagnostic testing of serum and tissue for prostate cancer. Inhibition of aberrant promoter methylation could theoretically prevent carcinogenesis.

The prevention of prostate cancer

From our better understanding of the natural history of prostate cancer, it is not unreasonable to believe that the disease is preventable. Prostate cancer has become a major healthcare problem worldwide, as life expectancy increases. Moreover, the cancer is slow growing, with a period of about 20-25 years from initiation to the stage when the clinically detectable phenotype can be identified. This review provides a simple overview of the endocrinology of prostate cancer and discusses some of the pharmaceutical agents that have been or are being tested to restrain, possibly arrest, the progression of this slowly growing cancer. Also discussed are many of the dietary factors that may influence the molecular or endocrine events implicated in its development. Dietary factors are considered responsible for the geographical differences in prostate cancer incidence and mortality. Since about 50% of all men worldwide, from both East and West, show evidence of microscopic cancer by 50 years of age, growth restraint would appear to be the pragmatic option to the possibility of preventing initiation.

Silibinin inhibits constitutive activation of Stat3, and causes caspase activation and apoptotic death of human prostate carcinoma DU145 cells

Transcription factor signal transducer and activator of transcription (Stat)-3 is activated constitutively in prostate cancer (PCA) suggesting that its disruption could be an effective approach to control this malignancy. Here we assessed whether silibinin, a flavanone from Silybum marianum with proven anticancer efficacy in various cancer models, inhibits Stat3 activation in DU145 cells, and if it does, what is the biological fate of the cells? At 50 muM or higher concentrations for 24 or 48 h, silibinin concentration dependently reduced constitutive Stat3 phosphorylation at Tyr705 and Ser727 residues under both serum and serum-starved conditions. Constitutively active Stat3-DNA binding was also inhibited concentration dependently by silibinin; however, apoptotic death together with caspase and poly(ADP-ribose) polymerase (PARP) cleavage was observed by silibinin only under serum-starved conditions suggesting that additional survival pathways are active under serum conditions. In other studies, cells were treated with various specific pharmacological inhibitors where phosphorylation of Stat3 was not reduced by epidermal growth factor receptor and Mitogen activated protein/extracellular signal regulate kinase kinase (MEK1/2) inhibitors, suggesting lack of significant roles of these in Stat3 activation in DU145 cells. Janus kinase (JAK)-1 and JAK2 inhibitors strongly reduced Stat3 phosphorylation but did not result in apoptotic cell death. Interestingly, JAK1 inhibitor only in combination with silibinin resulted in a complete reduction in Stat3 phosphorylation at Tyr705, activated caspase-9 and caspase-3, and caused strong PARP cleavage and apoptotic death of DU145 cells. Given a critical role of Stat3 activation in PCA, our results showed that silibinin inhibits constitutively active Stat3 and induces apoptosis in DU145 cells, and thus might have potential significance in therapeutic intervention of this deadly malignancy.

Promoter hypermethylation of GSTP1, AR, and 14-3-3sigma in serum of prostate cancer patients and its clinical relevance

OBJECTIVE

Hypermethylation of tumor suppressor genes (TSG) is thought to play an important role in tumorigenesis of prostate cancer. The main focus of research was the detection of TSG hypermethylation in cancer tissue. Our aim was to evaluate the feasibility of detection of hypermethylated genes in serum of prostate cancer patients and its correlation with clinicopathological parameters.

METHODS

One hundred twenty-five serum samples from 62 patients with hormone refractory prostate cancer (HRPC), 14 patients with early disease, and 49 healthy controls were examined. After DNA extraction and sodium-bisulfite treatment, conventional methylation-specific PCR (MSP) was performed for glutathione S-transferase P1 (GSTP1), androgen receptor (AR), and 14-3-3sigma.

RESULTS

In serum of HRCP patients, frequency of GSTP1, AR, and 14-3-3sigma hypermethylation was 32.2, 40.3, and 86.6%, respectively. In serum of patients with early disease frequency of GSTP1, AR, and 14-3-3sigma, hypermethylation was 21.4, 35.7, and 85.7%. In healthy controls, frequency of GSTP1, AR, and 14-3-3sigma hypermethylation was 0, 26.5, and 55.1%, respectively. There was a significant increase of frequency of TSG hypermethylation for GSTP1 and 14-3-3sigma in HRPC patients, in comparison with healthy controls. GSTP1 hypermethylation in HRPC patients was significantly correlated with differentiation of cancer and metastatic disease.

CONCLUSIONS

Hypermethylation of TSG can be detected in serum of prostate cancer patients. Some hypermethylated TSG can be detected in serum of healthy controls. GSTP1 was not detectable in controls and correlated significantly with Gleason score and stage of disease. Therefore, this gene may be a promising new tool in prostate cancer diagnosis.

Fractionation of high molecular weight tannins in grape seed extract and identification of procyanidin B2-3,3′-di-O-gallate as a major active constituent causing growth inhibition and apoptotic death of DU145 human prostate carcinoma cells

Several studies have documented the anticancer and chemopreventive efficacy of grape seed extract (GSE) against various malignancies including prostate cancer (PCA). GSE is a complex mixture of polyphenols including gallic acid (GA), catechin (Cat), epicatechin (Epi) and procyanidins-oligomers of Cat and Epi, some of which are esterified with GA. Initial studies to identify the GSE components cytotoxic to human prostate carcinoma (DU145) cells demonstrated that GA and several crude chromatographic fractions containing procyanidin dimers and trimers were biologically active. The focus of the present work was to purify 14 procyanidins from the fractions and to identify those with highest activity toward growth inhibition, cell death and apoptosis in DU145 cells. The most active procyanidin was identified by mass spectrometry and enzymatic hydrolysis as the 3,3'-di-O-gallate ester of procyanidin dimer B2 (Epi-Epi). B2-digallate exhibited dose-dependent effects on DU145 cells over the range 25-100 microM, whereas GA exhibited comparable activity at lower doses but was highly lethal at 100 microM. Structure-activity studies demonstrated that all three hydroxyl groups of GA are necessary for activity, but a free carboxylic acid group is not required even though esterification reduced the activity of GA. These data, and the fact that non-esterified B2 exhibited little or no activity, suggest that the galloyl groups of B2-digallate are primarily responsible for its effects on DU145 cells. Taken together, these data identify procyanidin B2-3,3'-di-O-gallate as a novel biologically active agent in GSE that should be studied in greater detail to determine its effects against PCA.

MYH mutations are rare in prostate cancer

PURPOSE

Oxidative stress is considered a risk factor for prostate cancer development and is associated with the production of reactive oxygen species (ROS). The base excision repair gene MYH protects against ROS-mediated damage to DNA. Inherited MYH mutations predispose to colorectal adenomas and cancer. A compromised base-excision repair function due to defective MYH may contribute to prostate carcinogenesis. Here, we examine the genetic contribution of MYH to prostate cancer risk.

METHODS

Patients diagnosed with high-grade prostatic intraepithelial neoplasia (HGPIN) alone (n = 45), prostate cancer alone (n = 123) or both (n = 82) were screened for the two most common mutations in the MYH gene using PCR-based RFLP analysis. A single patient with an inherited MYH mutation as well as a subset of 26 patients presenting with a family history of colorectal cancer were screened for additional MYH mutations by direct sequencing of the entire coding region.

RESULTS

Biallelic germline mutations in MYH were not detected among prostate cancer patients. Only a single patient was a heterozygous carrier for the Y165C missense mutation. Allelic deletion or somatic mutation of the remaining MYH allele was not identified in this patient's tumor DNA. Two patients harbored V22M polymorphism and three patients were carriers of Q324H polymorphism.

CONCLUSIONS

MYH mutations are unlikely to contribute to prostate cancer risk.

Evaluation of anin vitro model of androgen ablation and identification of the androgen responsive proteome in LNCaP cells

Proteins responsive to androgen and anti-androgen may be involved in the development and progression of prostate cancer and the ultimate failure of androgen-ablation therapy. These proteins represent potential diagnostic and therapeutic targets for improved management of prostate cancer. We have investigated the effect of androgen (R1881) and anti-androgen (bicalutamide) on the androgen-responsive prostate cancer LNCaP cell line using a quantitative gel-based proteomic approach. Prior to analysis, the in vitro system was evaluated for reproducibility and validated by appropriate molecular responses to treatment. Six replicate samples were independently generated and analysed by 2-D DIGE. According to strict statistical criteria, 197 spots were differentially expressed, of which we have successfully identified 165 spots corresponding to 125 distinct proteins. Following androgen supplementation, 108 spots (68 proteins) were increased and 57 spots (39 proteins) were decreased. Essentially no difference was observed between control and anti-androgen-treated samples, confirming the absence of "off-target" effects of bicalutamide. Identified proteins were involved in diverse processes including the stress response and intracellular signalling. The potential contribution to disease of these processes and identified constituent proteins are discussed. This rigorous, statistically supported study of androgen responses has provided a number of potential candidates for development as diagnostic/prognostic markers and drug targets.

Quantitative immunohistochemical detection of the molecular expression patterns in proliferative inflammatory atrophy

The proliferative inflammatory atrophy (PIA) is considered as a possible precursor of prostate intraepithelial neoplasia (PIN) or prostate cancer (PCa). In this study we assessed quantitatively the expression of AMACR, p63, COX-2, GST and iNOS in serial paraffin-embedded tissue sections obtained after radical prostatectomy of PCa patients (n = 30). The applicability of these markers to distinguish PIA, PIN and PCa was evaluated. We also compared the immunohistochemical expression profiles of AMACR, COX-2 and GST in the luminal and basal cells in lesions of PIN arisen in PIA or PIA alone. Two different patterns of COX-2 expression according to the p63 status of the basal cells were found. This observation gives us grounds to hypothesize that the diverse COX-2 patterns resulted from an initial basal cell damage which subsequently propagated to its luminal secretory cells progeny.

Decreased NKX3.1 protein expression in focal prostatic atrophy, prostatic intraepithelial neoplasia, and adenocarcinoma: association with gleason score and chromosome 8p deletion

NKX3.1 is a homeobox gene located at chromosome 8p21.2, and one copy is frequently deleted in prostate carcinoma. Prior studies of NKX3.1 mRNA and protein in human prostate cancer and prostatic intraepithelial neoplasia (PIN) have been conflicting, and expression in focal prostate atrophy lesions has not been investigated. Immunohistochemical staining for NKX3.1 on human tissue microarrays was decreased in most focal atrophy and PIN lesions. In carcinoma, staining was inversely correlated with Gleason grade. Fluorescence in situ hybridization showed that no cases of atrophy had loss or gain of 8p, 8 centromere, or 8q24 (C-MYC) and only 12% of high-grade PIN lesions harbored loss of 8p. By contrast, NKX3.1 staining in carcinoma was correlated with 8p loss and allelic loss was inversely related to Gleason pattern. Quantitative reverse transcription-PCR for NKX3.1 mRNA using microdissected atrophy revealed a concordance with protein in five of seven cases. In carcinoma, mRNA levels were decreased in 6 of 12 cases but mRNA levels correlated with protein levels in only 4 of 12 cases, indicating translational or post-translational control. In summary, NKX3.1 protein is reduced in focal atrophy and PIN but is not related to 8p allelic loss in these lesions. Therefore, whereas genetic disruption of NKX3.1 in mice leads to PIN, nongenetic mechanisms reduce NKX3.1 protein levels early in human prostate carcinogenesis, which may facilitate both proliferation and DNA damage in atrophic and PIN cells. Monoallelic deletions on chromosome 8p are associated with more advanced invasive and aggressive disease.

Progress in chemoprevention drug development: the promise of molecular biomarkers for prevention of intraepithelial neoplasia and cancer--a plan to move forward

This article reviews progress in chemopreventive drug development, especially data and concepts that are new since the 2002 AACR report on treatment and prevention of intraepithelial neoplasia. Molecular biomarker expressions involved in mechanisms of carcinogenesis and genetic progression models of intraepithelial neoplasia are discussed and analyzed for how they can inform mechanism-based, molecularly targeted drug development as well as risk stratification, cohort selection, and end-point selection for clinical trials. We outline the concept of augmenting the risk, mechanistic, and disease data from histopathologic intraepithelial neoplasia assessments with molecular biomarker data. Updates of work in 10 clinical target organ sites include new data on molecular progression, significant completed trials, new agents of interest, and promising directions for future clinical studies. This overview concludes with strategies for accelerating chemopreventive drug development, such as integrating the best science into chemopreventive strategies and regulatory policy, providing incentives for industry to accelerate preventive drugs, fostering multisector cooperation in sharing clinical samples and data, and creating public-private partnerships to foster new regulatory policies and public education.

Stromal-epithelial interaction in prostate cancer progression

Cancer is not a single-cell disease, and its existence and behavior are constantly modulated by the host. Cancer gene expression and genetics are also highly dynamic and are regulated epigenetically by the host through gene-environment interaction. In this article, we describe the molecular pathways leading to an unusual property of cancer cells: the ability to mimic the host microenvironment and, in particular, the characteristics of osteomimicry and vasculogenic mimicry, which are likely to be regulated by soluble and insoluble factors in the tumor-adjacent microenvironment. We also discuss the importance of host inflammatory and stem cells that contribute to the growth and survival of cancer cells. By understanding the salient features of cancer-host interaction, novel therapeutics might be developed to target the cancer and its host in the treatment of lethal prostate cancer metastases.

Conditional expression of human 15-lipoxygenase-1 in mouse prostate induces prostatic intraepithelial neoplasia: the FLiMP mouse model

The incidence and mortality of prostate cancer (PCa) vary greatly in different geographic regions, for which lifestyle factors, such as dietary fat intake, have been implicated. Human 15-lipoxygenase-1 (h15-LO-1), which metabolizes polyunsaturated fatty acids, is a highly regulated, tissue-specific, lipid-peroxidating enzyme that functions in physiological membrane remodeling and in the pathogenesis of atherosclerosis, inflammation, and carcinogenesis. We have shown that aberrant overexpression of 15-LO-1 occurs in human PCa, particularly high-grade PCa, and in high-grade prostatic intraepithelial neoplasia (HGPIN), and that the murine orthologue is increased in SV40-based genetically engineered mouse (GEM) models of PCa, such as LADY and TRansgenic Adenocarcinoma of Mouse Prostate. To further define the role of 15-LO-1 in prostate carcinogenesis, we established a novel GEM model with targeted overexpression of h15-LO-1 in the prostate [human fifteen lipoxygenase-1 in mouse prostate (FLiMP)]. We used a Cre- mediated and a loxP-mediated recombination strategy to target h15-LO-1 specifically to the prostate of C57BL/6 mice. Wild-type (wt), FLiMP+/-, and FLiMP+/+ mice aged 7 to 21, 24 to 28, and 35 weeks were characterized by histopathology, immunohistochemistry (IHC), and DNA/RNA and enzyme analyses. Compared to wt mice, h15-LO-1 enzyme activity was increased similarly in both homozygous FLiMP+/+ and hemizygous FLiMP+/- prostates. Dorsolateral and ventral prostates of FLiMP mice showed focal and progressive epithelial hyperplasia with nuclear atypia, indicative of the definition of mouse prostatic intraepithelial neoplasia (mPIN) according to the National Cancer Institute. These foci showed increased proliferation by Ki-67 IHC. No progression to invasive PCa was noted up to 35 weeks. By IHC, h15-LO-1 expression was limited to luminal epithelial cells, with increased expression in mPIN foci (similar to human HGPIN). In summary, targeted overexpression of h15-LO-1 (a gene overexpressed in human PCa and HGPIN) to mouse prostate is sufficient to promote epithelial proliferation and mPIN development. These results support 15-LO-1 as having a role in prostate tumor initiation and as an early target for dietary or other prevention strategies. The FLiMP mouse model should also be useful in crosses with other GEM models to further define the combinations of molecular alterations necessary for PCa progression.

Emerging biomarkers in prostate cancer

Biomarkers may be proteins, RNA, DNA, autoantibodies or molecules that reliably diagnose cancer or serve as markers of prognosis. Prognosis is particularly important in prostate cancer, a disease many ‘die with’, but which kills only a minority of affected men. Prostate-specific antigen is widely used in screening for prostate cancer and has a significant false-positive rate, which leads to unnecessary biopsies, cost and anxiety. There is also a notable false-negative rate for prostate-specific antigen, with a significant number of high-grade tumors identified in men with a ‘normal’ prostate-specific antigen. Discovery and validation of improved diagnostic biomarkers is necessary. Biomarkers that would distinguish aggressive from more indolent forms of prostate cancer may be even more urgently required. High-throughput technologies that assay proteins, metabolites, DNA and RNA are generating candidate markers.

Genomics in breast and prostate cancer: assessment of the current state and future perspectives

Genomic approaches to cancer are beginning to have an important impact in unraveling the complex etiologies of this disease, as well as allowing us to rationally treat afflicted patients. In this article, we will focus largely on genomic approaches to breast and prostate cancer susceptibility, as well as pharmacogenomic approaches to treatment. Current genomic approaches to cancer susceptibility have led to some significant, if not spectacular, successes which include breast cancer. More modest achievements, if not outright failures, such as in prostate cancer, are also notable and will be discussed further. We propose interdisciplinary approaches involving basic, clinical and population scientists to vigorously attack the cancer problem scientifically and with more organization. We highlight recent successes and suggest new approaches with a personal, if not provocative, perspective.

Drug Insight: lycopene in the prevention and treatment of prostate cancer

For almost a decade researchers in the field of urology have investigated lycopene and the chemopreventive potential of the tomato. A potent antioxidant found in abundance in the tomato, lycopene has repeatedly been correlated with reduced risk of prostate cancer in numerous epidemiological and population-based studies. Researchers and clinicians continue to investigate beyond the potent antioxidant properties of lycopene for other mechanisms of action and chemotherapeutic potential. This review examines the preclinical and preliminary clinical evidence surrounding the tomato and the health claims based on lycopene. We have explored recent mechanistic insights and conclude that more clinical research is warranted. The scope and extent of scientific evidence accrued on lycopene and tomato extracts, reported molecular mechanisms of action, and its potential impact on the incidence and severity of prostate cancer are discussed.

Increased oxidative stress and oxidative damage associated with chronic bacterial prostatitis

AIM

To investigate whether chronic bacterial prostatitis might increase oxidative stress and oxidative damage in chronic bacterial prostatitis patients (CBPP), and to explore its possible mechanism.

METHODS

Enrolled in a case-control study were 70 randomly sampled CBPP and 70 randomly sampled healthy adult volunteers (HAV), on whom plasma nitric oxide (NO), vitamin C (VC), vitamin E (VE) and beta-carotene (beta-CAR) level, erythrocyte malondialdehyde (MDA) level, as well as erythrocyte superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) activities were determined by spectrophotometry.

RESULTS

Compared with the HAV group, values of plasma NO and erythrocyte MDA in the CBPP group were significantly increased (P < 0.001); those of plasma VC, VE and beta-CAR as well as erythrocyte SOD, CAT and GPX activities in the CBPP group were significantly decreased (P < 0.001). Findings from partial correlation for the 70 CBPP showed that with prolonged course of disease, values of NO and MDA were gradually increased (P < 0.001), and those of VC, VE, beta-CAR, SOD, CAT and GPX were gradually decreased (P < 0.05-0.001). The findings from stepwise regression for the 70 CBPP suggested that the model was Y = -13.2077 + 0.1894MDA + 0.0415NO - 0.1999GPX, F = 18.2047, P < 0.001, r = 0.6729, P < 0.001.

CONCLUSION

The findings suggest that there exist increased oxidative stress and oxidative damage induced by chronic bacterial prostatitis in the patients, and such phenomenon was closely related to the course of disease.

Glutathione S-transferase polymorphisms: cancer incidence and therapy

The super family of glutathione S-transferases (GSTs) is composed of multiple isozymes with significant evidence of functional polymorphic variation. Over the last three decades, data from cancer studies have linked aberrant expression of GST isozymes with the development and expression of resistance to a variety of chemicals, including cancer drugs. This review addresses how differences in the human GST isozyme expression patterns influence cancer susceptibility, prognosis and treatment. In addition to the well-characterized catalytic activity, recent evidence has shown that certain GST isozymes can regulate mitogen-activated protein kinases or can facilitate the addition of glutathione to cysteine residues in target proteins (S-glutathionylation). These multiple functionalities have contributed to the recent efforts to target GSTs with novel small molecule therapeutics. Presently, at least two drugs are in late-stage clinical testing. The evolving functions of GST and their divergent expression patterns in individuals make them an attractive target for drug discovery.

Fractionation of grape seed extract and identification of gallic acid as one of the major active constituents causing growth inhibition and apoptotic death of DU145 human prostate carcinoma cells

The anti-cancer efficacy of grape seed extract (GSE) against prostate cancer (PCA) via its anti-proliferative, pro-apoptotic and anti-angiogenic activities in both cell culture and animal models have recently been described by us. GSE is a complex mixture containing gallic acid (GA), catechin (C), epicatechin (EC) and several oligomers (procyanidins) of C and/or EC, some of which are esterified to GA. To determine which components are most active against PCA, an ethyl acetate extract of GSE was separated by reverse-phase high-performance liquid chromatography (HPLC) into three fractions. Fraction 1 was far more effective than others in causing growth inhibition and apoptotic death of human PCA DU145 cells. Of the components in this fraction, GA showed a very strong dose- and time-dependent growth inhibition and apoptotic death of DU145 cells, but C and procyanidins B1 (EC-C dimer), B2 (EC-EC dimer) and B3 (C-C dimer) were nearly ineffective. Mechanistic studies demonstrated a strong caspase-9, caspase-3 and poly (ADP-ribose) polymerase (PARP) cleavages by GA in DU145 cells. Procyanidin oligomers eluting in HPLC Fractions 2 and 3 were obtained in larger quantities by separating GSE into eight fractions (I-VIII) on a gel filtration column. All fractions were analyzed by HPLC-UV and negative-ion electrospray mass spectrometry. Fractions I-III contained the active compound GA and inactive components C, EC, B1 and B2. Fraction IV contained other dimers and a dimer-GA ester and was also less active than GSE in DU145 cells. Fractions V-VIII, however, caused significant growth inhibition and apoptosis with the highest activity present in the later fractions that contained procyanidin trimers and GA esters of dimers and trimers. Together, these observations identify GA as one of the major active constituents in GSE. Several procyanidins, however, and especially the gallate esters of dimers and trimers also may be efficacious against PCA and merit further investigation.

Epigenetic alterations in gastric carcinogenesis

Gastric cancer is believed to result in part from the accumulation of multiple genetic alterations leading to oncogene overexpression and tumor suppressor loss. Epigenetic alterations as a distinct and crucial mechanism to silence a variety of methylated tissue-specific and imprinted genes, have been extensively studied in gastric carcinoma and play important roles in gastric carcinogenesis. This review will briefly discuss the basic aspects of DNA methylation and CpG island methylation, in particular the epigenetic alterations of certain critical genes implicated in gastric carcinogenesis and its relevance of clinical implications.

Molecular pathology of prostate cancer

The molecular pathology of prostate cancer is complex; not only are multiple genes involved in its pathogenesis, but additional environmental factors such as diet and inflammation are also involved. The exhaustive research into prostate cancer to date has demonstrated a complex interaction of multiple genes and environmental factors, some of which may be more important in individual prostate cancer cases. This is an exciting era, with the emergence of new investigative tools such as DNA microarray technology and the application of the field of proteomics to the study of human cancers. Knowledge of genetic changes underlying the initiation, development, and progression of prostate cancer is accumulating rapidly. With increasing knowledge, it may be possible to distinguish indolent from aggressive prostate tumours by molecular fingerprinting. This review discusses the most consistently reported molecular pathological findings in hereditary and sporadic prostate cancer, together with new concepts and technologies.