Prostate cancer prevention

Serum cytokine profiles in patients with prostate carcinoma

It has been suggested that various cytokines are associated with the pathophysiology of prostate carcinoma (Pca). We profiled ten cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IFN-γ and TNF-α) in the serum levels of 11 patients with organ-confined Pca, 15 with advanced Pca without cachexia, 8 with advanced Pca with cachexia (cachexia group) and 5 healthy males as controls. Cytokines were measured using a highly sensitive fluorescence microsphere system. Compared to the control group, serum levels of all cytokines were significantly higher in the cachexia group, and six cytokines (IL-1β, IL-2, IL-8, IL-12, TNF-α and IFN-γ) were significantly higher in the group with advanced Pca without cachexia. In the group with organ-confined Pca, only IL-1β and IL-12 levels were significantly higher compared to the control group. In the cachexia group, levels of all cytokines apart from TNF-α were significantly higher compared to the group with organ-confined Pca, and levels of four cytokines (IL-2, IL-4, IL-8 and IL-10) were significantly higher compared to the group with advanced Pca without cachexia. These results indicate that i) an aberrance imbalance of cytokine production was associated with the pathophysiology of Pca and cachexia, ii) cytokine profiles in Pca patients were distinct by disease stage, and iii) IL-1β and IL-12 may be applicable as early diagnostic indicators.

Chemoprevention of prostate cancer

Over the past two decades, many more men are diagnosed with prostate cancer then die of the disease. This increase in diagnosis has led to aggressive treatment of indolent disease in many individuals and has been the impetus for finding a means of reducing the risk of prostate cancer. In the past decade, there have been eight large trials of prostate cancer risk reduction using dietary supplements, 5α-reductase inhibitors, or anti-estrogens. The only two trials which have demonstrated efficacy are those involving 5α-reductase inhibitors: the PCPT (finasteride) and REDUCE (dutasteride). This review examines prostate cancer risk reduction, with emphasis on conclusions that can be drawn from these two landmark studies.

Natriuretic peptide receptor a as a novel target for prostate cancer

BACKGROUND

The receptor for the cardiac hormone atrial natriuretic peptide (ANP), natriuretic peptide receptor A (NPRA), is expressed in cancer cells, and natriuretic peptides have been implicated in cancers. However, the direct role of NPRA signaling in prostate cancer remains unclear.

RESULTS

NPRA expression was examined by western blotting, RT-PCR and immunohistochemistry. NPRA was downregulated by transfection of siRNA, shRNA and NPRA inhibitor (iNPRA). Antitumor efficacy of iNPRA was tested in mice using a TRAMP-C1 xenograft. Here, we demonstrated that NPRA is abundantly expressed on tumorigenic mouse and human prostate cells, but not in nontumorigenic prostate epithelial cells. NPRA expression showed positive correlation with clinical staging in a human PCa tissue microarray. Down-regulation of NPRA by siNPRA or iNPRA induced apoptosis in PCa cells. The mechanism of iNPRA-induced anti-PCa effects was linked to NPRA-induced expression of macrophage migration inhibitory factor (MIF), a proinflammatory cytokine over-expressed in PCa and significantly reduced by siNPRA. Prostate tumor cells implanted in mice deficient in atrial natriuretic peptide receptor A (NPRA-KO) failed to grow, and treatment of TRAMP-C1 xenografts with iNPRA reduced tumor burden and MIF expression. Using the TRAMP spontaneous PCa model, we found that NPRA expression correlated with MIF expression during PCa progression.

CONCLUSIONS

Collectively, these results suggest that NPRA promotes PCa development in part by regulating MIF. Our findings also suggest that NPRA is a potential prognostic marker and a target for PCa therapy.

Molecular genetics of prostate cancer: new prospects for old challenges

Despite much recent progress, prostate cancer continues to represent a major cause of cancer-related mortality and morbidity in men. Since early studies on the role of the androgen receptor that led to the advent of androgen deprivation therapy in the 1940s, there has long been intensive interest in the basic mechanisms underlying prostate cancer initiation and progression, as well as the potential to target these processes for therapeutic intervention. Here, we present an overview of major themes in prostate cancer research, focusing on current knowledge of principal events in cancer initiation and progression. We discuss recent advances, including new insights into the mechanisms of castration resistance, identification of stem cells and tumor-initiating cells, and development of mouse models for preclinical evaluation of novel therapuetics. Overall, we highlight the tremendous research progress made in recent years, and underscore the challenges that lie ahead.

Epigenetic regulation of the expression of genes involved in steroid hormone biosynthesis and action

Steroid hormones participate in organ development, reproduction, body homeostasis, and stress responses. The steroid machinery is expressed in a development- and tissue-specific manner, with the expression of these factors being tightly regulated by an array of transcription factors (TFs). Epigenetics provides an additional layer of gene regulation through DNA methylation and histone tail modifications. Evidence of epigenetic regulation of key steroidogenic enzymes is increasing, though this does not seem to be a predominant regulatory pathway. Steroid hormones exert their action in target tissues through steroid nuclear receptors belonging to the NR3A and NR3C families. Nuclear receptor expression levels and post-translational modifications regulate their function and dictate their sensitivity to steroid ligands. Nuclear receptors and TFs are more likely to be epigenetically regulated than proteins involved in steroidogenesis and have secondary impact on the expression of these steroidogenic enzymes. Here we review evidence for epigenetic regulation of enzymes, transcription factors, and nuclear receptors related to steroid biogenesis and action.

Association of serum cholesterol and cholesterol-lowering drug use with serum sex steroid hormones in men in NHANES III

PURPOSE

Low cholesterol levels and statin drugs may protect against prostate cancer with a worse prognosis. Their protective mechanism is unknown, but has been hypothesized to be related to cholesterol's role as a sex steroid hormone precursor. We evaluated whether serum testosterone and estradiol differ by cholesterol or cholesterol-lowering drug use.

MATERIALS AND METHODS

Testosterone and estradiol were measured for 1,457 male participants in the Third National Health and Nutrition Examination Survey. We estimated multivariable-adjusted geometric mean hormone concentration by quintiles of cholesterol concentration and by cholesterol-lowering drugs use.

RESULTS

Across quintiles of cholesterol, testosterone level did not differ (mean, 95% confidence interval (CI); Q1: 5.25, 5.02-5.49, Q5: 5.05, 4.76-5.37 ng/ml; p-trend = 0.32), whereas estradiol levels were lower (Q1: 38.7, 36.9-40.5; Q5: 33.1, 31.8-34.5 pg/ml; p-trend < 0.0001). Neither testosterone (no: 5.12, 4.94-5.30, yes: 4.91, 4.33-5.57 ng/ml, p = 0.57) nor estradiol (no: 35.9, 34.8-37.1; yes: 33.9, 29.4-39.2 pg/ml; p = 0.39) differed by cholesterol-lowering drugs use.

CONCLUSION

Testosterone did not differ by cholesterol or cholesterol-lowering drug use. Estradiol was lower in men with higher cholesterol, but did not differ by cholesterol-lowering drug use. Our results suggest that the lower risk of advanced prostate cancer among statin users is not readily explained by a cholesterol-mediated effect of statins on sex hormone levels.

Health behavior changes in white and African American prostate cancer survivors

Prostate cancer prognosis may be improved by healthy behaviors; however, little is known regarding whether prostate cancer survivors make health behavior changes after diagnosis, and there are no data on racial/ethnic differences. This study explored patterns of and factors that influence healthy behavior changes in diet, physical activity, and dietary supplement use among whites and African Americans (n = 30) aged 45 to 70 years, approximately 1 year after diagnosis with localized prostate cancer. Data were collected by telephone using semistructured qualitative interviews. The mean participant age was 59.6 years, 77% had attended college, 87% were married, and 22% were retired. Most (58%) had improved their diet since diagnosis, defined as eating more fruits/vegetables and less fat. Although 77% reported regular use of at least 1 dietary supplement before diagnosis, several discontinued use after diagnosis. Sixty-seven percent exercised regularly before diagnosis, and most of these (75%) continued after diagnosis; however, time and health constraints were barriers. Physician recommendation and family support strongly influenced positive changes. Except for more postdiagnosis dietary improvements in African Americans, there were few racial differences in patterns/motives for behavior changes. Most respondents were motivated to maintain and/or adopt healthy behavioral changes after diagnosis. Nurses/physicians are encouraged to inform their prostate cancer patients about the benefits of healthy eating and regular exercise and about the absence of scientific evidence regarding the benefits/risks of most supplements, particularly herbal formulations.

Temporal changes in gene expression induced by sulforaphane in human prostate cancer cells

BACKGROUND

Prostate cancer is thought to arise as a result of oxidative stresses and induction of antioxidant electrophile defense (phase 2) enzymes has been proposed as a prostate cancer prevention strategy. The isothiocyanate sulforaphane, derived from cruciferous vegetables like broccoli, potently induces surrogate markers of phase 2 enzyme activity in prostate cells in vitro and in vivo. To better understand the temporal effects of sulforaphane and broccoli sprouts on gene expression in prostate cells, we carried out comprehensive transcriptome analysis using cDNA microarrays.

METHODS

Transcripts significantly modulated by sulforaphane over time were identified using StepMiner analysis. Ingenuity Pathway Analysis (IPA) was used to identify biological pathways, networks, and functions significantly altered by sulforaphane treatment.

RESULTS

StepMiner and IPA revealed significant changes in many transcripts associated with cell growth and cell cycle, as well as a significant number associated with cellular response to oxidative damage and stress. Comparison to an existing dataset suggested that sulforaphane blocked cell growth by inducing G2/M arrest. Cell growth assays and flow cytometry analysis confirmed that sulforaphane inhibited cell growth and induced cell cycle arrest.

CONCLUSIONS

Our data suggest that in prostate cells sulforaphane primarily induces cellular defenses and inhibits cell growth by causing G2/M phase arrest. Furthermore, based on the striking similarities in the gene expression patterns induced across experiments in these cells, sulforaphane appears to be the primary bioactive compound present in broccoli sprouts, suggesting that broccoli sprouts can serve as a suitable source for sulforaphane in intervention trials.

Centrosomal PKCbetaII and pericentrin are critical for human prostate cancer growth and angiogenesis

Angiogenesis is critical in the progression of prostate cancer. However, the interplay between the proliferation kinetics of tumor endothelial cells (angiogenesis) and tumor cells has not been investigated. Also, protein kinase C (PKC) regulates various aspects of tumor cell growth, but its role in prostate cancer has not been investigated in detail. Here, we found that the proliferation rates of endothelial and tumor cells oscillate asynchronously during the growth of human prostate cancer xenografts. Furthermore, our analyses suggest that PKCbetaII was activated during increased angiogenesis and that PKCbetaII plays a key role in the proliferation of endothelial cells and tumor cells in human prostate cancer; treatment with a PKCbetaII-selective inhibitor, betaIIV5-3, reduced angiogenesis and tumor cell proliferation. We also find a unique effect of PKCbetaII inhibition on normalizing pericentrin (a protein regulating cytokinesis), especially in endothelial cells as well as in tumor cells. PKCbetaII inhibition reduced the level and mislocalization of pericentrin and normalized microtubule organization in the tumor endothelial cells. Although pericentrin has been known to be up-regulated in epithelial cells of prostate cancers, its level in tumor endothelium has not been studied in detail. We found that pericentrin is up-regulated in human tumor endothelium compared with endothelium adjacent to normal glands in tissues from prostate cancer patients. Our results suggest that a PKCbetaII inhibitor such as betaIIV5-3 may be used to reduce prostate cancer growth by targeting both angiogenesis and tumor cell growth.

Identification of candidate prostate cancer genes through comparative expression-profiling of seminal vesicle

BACKGROUND

Prostate cancer is the most frequently diagnosed cancer among men in the United States. In contrast, cancer of the seminal vesicle is exceedingly rare, despite that the prostate and seminal vesicle share similar histology, secretory function, androgen dependency, blood supply, and (in part) embryonic origin. We hypothesized that gene-expression differences between prostate and seminal vesicle might inform mechanisms underlying the higher incidence of prostate cancer.

METHODS

Whole-genome DNA microarrays were used to profile gene expression of 11 normal prostate and 7 seminal vesicle specimens (including six matched pairs) obtained from radical prostatectomy. Supervised analysis was used to identify genes differentially expressed between normal prostate and seminal vesicle, and this list was then cross-referenced to genes differentially expressed between normal and cancerous prostate. Expression patterns of selected genes were confirmed by immunohistochemistry using a tissue microarray.

RESULTS

We identified 32 genes that displayed a highly statistically significant expression pattern with highest levels in seminal vesicle, lower levels in normal prostate, and lowest levels in prostate cancer. Among these genes was the known candidate prostate tumor suppressor GSTP1 (involved in xenobiotic detoxification). The expression pattern of GSTP1 and four other genes, ABCG2 (xenobiotic transport), CRABP2 (retinoic acid signaling), GATA3 (lineage-specific transcription), and SLPI (immune response), was confirmed by immunohistochemistry.

CONCLUSIONS

Our findings identify candidate prostate cancer genes whose reduced expression in prostate (compared to seminal vesicle) may be permissive to prostate cancer initiation. Such genes and their pathways may inform mechanisms of prostate carcinogenesis, and suggest new opportunities for prostate cancer prevention.

Cyclic adenosine monophosphate differentiated beta-endorphin neurons promote immune function and prevent prostate cancer growth

Pituitary adenylate cyclase-activating peptide (PACAP), a cAMP-activating agent, is highly expressed in the hypothalamus during the period when many neuroendocrine cells become differentiated from the neural stem cells (NSCs). Activation of the cAMP system in rat hypothalamic NSCs differentiated these cells into beta-endorphin (BEP)-producing neurons in culture. When these in vitro differentiated neurons were transplanted into the paraventricular nucleus (PVN) of the hypothalamus of an adult rat, they integrated well with the surrounding cells and produced BEP and its precursor gene product, proopiomelanocortin (POMC). Animals with BEP cell transplants demonstrated remarkable protection against carcinogen induction of prostate cancer. Unlike carcinogen-treated animals with control cell transplants, rats with BEP cell transplants showed rare development of glandular hyperplasia, prostatic intraepithelial neoplasia (PIN), or well differentiated adenocarcinoma with invasion after N-methyl-N-nitrosourea (MNU) and testosterone treatments. Rats with the BEP neuron transplants showed increased natural killer (NK) cell cytolytic function in the spleens and peripheral blood mononuclear cells (PBMCs), elevated levels of antiinflammatory cytokine IFN-gamma, and decreased levels of inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) in plasma. These results identified a critical role for cAMP in the differentiation of BEP neurons and revealed a previously undescribed role of these neurons in combating the growth and progression of neoplastic conditions like prostate cancer, possibly by increasing the innate immune function and reducing the inflammatory milieu.

Androgens and prevention of prostate cancer

PURPOSE OF REVIEW

This review provides a description of recent insights into the role of androgens in prostate cancer prevention.

RECENT FINDINGS

Many studies have elucidated a variety of molecular mechanisms involved in the initiation and progression of prostate cancer with many directly or indirectly related to the androgen signaling pathway. Both well known and novel agents for targeting the androgen pathway are under investigation, though very few are in clinical trials. After a review of recent papers describing these mechanisms, their results and implications were summarized.

SUMMARY

Finasteride remains the only agent proven to reduce the risk of prostate cancer, though there are currently two other ongoing phase III trials with vitamin E, selenium, and dutasteride. An enhanced understanding of complex interactions with the androgen pathways is leading to the exploration of additional promising approaches to mitigating the risk of prostate cancer.

5alpha-reductase inhibitors in benign prostatic hyperplasia and prostate cancer risk reduction

Androgens play an essential role in prostatic development and function, but are also involved in prostate disease pathogenesis. The primary prostatic androgen, dihydrotestosterone (DHT), is synthesized from testosterone by 5alpha-reductase types 1 and 2. Inhibition of the 5alpha-reductase isoenzymes therefore has potential therapeutic benefit in prostate disease. The two currently approved 5alpha-reductase inhibitors (5ARIs), finasteride and dutasteride, have demonstrated long-term efficacy and safety in the treatment of benign prostatic hyperplasia. Finasteride, a type-2 5ARI, has also been studied for its ability to reduce the incidence of biopsy-detectable prostate cancer in the Prostate Cancer Prevention Trial. Treatment with dutasteride, a dual 5ARI, has been shown to result in a greater degree and consistency of DHT suppression compared with finasteride. Two large-scale studies of dutasteride are currently investigating the role of near-maximal DHT suppression in the settings of prostate cancer risk reduction and expectant management of localized prostate cancer.

The evolving biology and treatment of prostate cancer

Since the effectiveness of androgen deprivation for treatment of advanced prostate cancer was first demonstrated, prevention strategies and medical therapies for prostate cancer have been based on understanding the biologic underpinnings of the disease. Prostate cancer treatment is one of the best examples of a systematic therapeutic approach to target not only the cancer cells themselves, but the microenvironment in which they are proliferating. As the population ages and prostate cancer prevalence increases, challenges remain in the diagnosis of clinically relevant prostate cancer as well as the management of the metastatic and androgen-independent metastatic disease states.