Toremifene for the prevention of prostate cancer in men with high grade prostatic intraepithelial neoplasia: results of a double-blind, placebo controlled, phase IIB clinical trial

Androgen receptor and estrogen receptor variants in prostate and breast cancers

The androgen receptor (AR) and estrogen receptor alpha (ERα) are steroid receptor transcription factors with critical roles in the development and progression of prostate and breast cancers. Advances in the understanding of mechanisms underlying the ligand-dependent activation of these transcription factors have contributed to the development of small molecule inhibitors that block AR and ERα actions. These inhibitors include competitive antagonists and degraders that directly bind the ligand binding domains of these receptors, luteinizing hormone releasing hormone (LHRH) analogs that suppress gonadal synthesis of testosterone or estrogen, and drugs that block specific enzymes required for biosynthesis of testosterone or estrogen. However, resistance to these therapies is frequent, and is often driven by selection for tumor cells with alterations in the AR or ESR1 genes and/or alternatively spliced AR or ESR1 mRNAs that encode variant forms AR or ERα. While most investigations involving AR have been within the context of prostate cancer, and the majority of investigations involving ERα have been within the context of breast cancer, important roles for AR have been elucidated in breast cancer, and important roles for ERα have been elucidated in prostate cancer. Here, we will discuss the roles of AR and ERα in breast and prostate cancers, outline the effects of gene- and mRNA-level alterations in AR and ESR1 on progression of these diseases, and identify strategies that are being developed to target these alterations therapeutically.

The adverse effect of anticancer drug toremifene on vascular smooth muscle cells is an important aspect of its tumor growth inhibition

PURPOSE

Toremifene (TOR) is widely used as an antineoplastic drug and has an inhibitory effect on angiogenesis in mesenteric desmoid tumors and vascular intracranial solitary fibrous tumors. However, no study has investigated the direct effect of TOR on vascular cells. This study aimed at exploring the effect of TOR on the behaviors of vascular smooth muscle cells (VSMCs).

METHODS

Human aortic umbilical vascular smooth muscle cells (HAVSMCs) were treated by TOR. Cell morphology, migration, adhesion, and proliferation assay were investigated. The cell cycle, apoptosis, mitochondrial membrane potential, and reactive oxygen species were assessed using flow cytometry. Caspase-3 and 9 activities were assayed using Caspase-3 and Caspase-9 Activity Assay kits, respectively. Immunofluorescence and Western blot assays were carried out to characterize protein expressions of PCNA, p53, and Rho/ROCK signaling pathway.

RESULTS

TOR damaged cytoskeleton, inhibited VSMC proliferation, migration, and adhesion, and induced abnormal cell morphology and apoptosis. The antiproliferative activity of TOR was associated with the induction of G0/G1 phase arrest, blocking the cell cycle. TOR disrupted intracellular reactive oxygen species and mitochondrial membrane potential, and enhanced p53 expression and the activities of caspase-3 and caspase-9. Thus, TOR-induced apoptosis by the mitochondrial signaling pathway. Additionally, TOR induced decreased Rho, ROCK, MLC, and pMLC proteins. Collectively, TOR may affect multiple behaviors of VSMCs by damaging cytoskeleton through the Rho/ROCK pathway.

CONCLUSION

The adverse effect of TOR on VSMCs could be considered as an important aspect of tumor growth inhibition.

The Transcriptomic Profiles of ESR1 and MMP3 Stratify the Risk of Biochemical Recurrence in Primary Prostate Cancer beyond Clinical Features

The molecular determinants of the heterogenic course of prostate cancer (PC) remain elusive. We aimed to determine the drivers predisposing to unfavorable PC outcomes anticipated by BCR events among patients of similar preoperative characteristics. The TCGA transcriptomic and clinical data of 497 PC individuals were used, stratified according to the risk of BCR by EAU-EANM-ESTRO-ESUR-SIOG. The relevance of the functional markers regarding BCR-free survival was examined by the cutp algorithm. Through UpSetR, subgroups of PC patients bearing an unfavorable signature were identified, followed by the hierarchical clustering of the major markers of the epithelial-to-mesenchymal transition (EMT). BCR-free survival was estimated with the Cox proportional hazards regression model. ESR1 significantly differentiated BCR-free survival, whereas AR did not. An elevation in KLK3 correlated with better prognosis, although PGR, KLK3, CDH1, and MMP3 predicted BCR better than the preoperative PSA level. Patients sharing an unfavorable profile of ESR1 and MMP3 together with lymph node status, Gleason score, T, and EAU risk groups were at a higher risk of BCR originating from mesenchymal features of PC cells. To conclude, we revealed an ESR1-driven unfavorable profile of EMT underpinning a worse PC trajectory. ESR1 may have a major role in PC progression; therefore, it could become a major focus for further investigations.

To block or not to block-hormonal signaling in the treatment of cancers

The breast and prostate glands are the two major organs that are highly dependent on the gonadal steroid hormones for their development and homeostasis. The cancers of these organs also show a large dependence on steroid hormones and have formed the basis of endocrine therapy. Estrogen deprivation by oophorectomy has been in active practice since the 1970s, and androgen deprivation therapy for prostate cancer was a major breakthrough in medicine in 1941. Since then, several improvisations have happened in these modes of therapy. However, the development of resistance to this deprivation and the emergence of hormone independence are major problems in both cancers. The lessons learned from rodent models have made it clear that the male hormone has a role in females and vice versa. Also, the metabolic products of these hormones may have unintentional effects including proliferative conditions in both sexes. Hence, administering estrogen as a method of chemical castration in males and administering DHT in females may not be the ideal scenario. It would be important to consider the status of the opposite sex hormone signaling and its effects and come up with a combinatorial regime to strike a balance between androgen and estrogen signaling. This review summarizes the current understanding and developments in this field in the context of prostate cancer.

Estrogen receptor expression is modulated in human and mouse prostate epithelial cells during cancer progression

Substantial data posit estrogen receptors (ERs) as promising targets for prostate cancer (PCa) therapeutics. However, the trials on assessing the chemo-preventive or therapeutic potential of ER targeting drugs or selective estrogen receptor modulators (SERMs) have not yet established their clinical benefits. This could be ascribed to a possible modulation in the ER expression during PCa progression. Further it is warranted to test various ER targeting drugs in appropriate preclinical models that simulate human ER expression pattern during PCa progression. The study was undertaken to revisit the existing data on the epithelial ER expression pattern in human cancerous prostates and experimentally determine whether these patterns are replicated in TRAMP (Transgenic Adenocarcinoma of Mouse Prostate) mice, a model for human PCa. Estradiol (E2) binding to the plasma membrane of the epithelial cells and its modulation during the PCa progression in TRAMP were also investigated. A reassessment of the existing data revealed a trend towards downregulation in the epithelial expression of wild-type ESR1 transcripts in high-grade PCa, compared to non-cancerous prostate in humans. Next, epithelial cell-enriched populations from TRAMP prostates (TP) displaying low-grade prostatic intraepithelial neoplasia (LGPIN), high-grade PIN (HGPIN), HGPIN with well-differentiated carcinoma (PIN + WDC), WDC (equivalent to grade 2/3 human PCa), and poorly-differentiated carcinoma (PDC-equivalent to grade 4/5 human PCa) revealed significantly higher Esr1 and Esr2 levels in HGPIN and significantly reduced levels in WDC, compared to respective age-matched control prostates. These patterns for the nuclear ERs were similar to the trend shown by E2 binding to the plasma membrane of the epithelial cells during PCa progression in TRAMP. E2 binding to epithelial cells (EpCAM+), though significantly higher in TPs displaying LGPIN, decreased significantly as the disease progressed to WDC. The study highlights a reduction in the epithelial ESR level with the PCa progression and this pattern was evident in both humans and TRAMP. These observations may have major implications in refining PCa therapeutics targeting ER.

Endocrinology of the Aging Prostate: Current Concepts

Benign prostate hyperplasia (BPH), one of the most common diseases in older men, adversely affects quality-of-life due to the presence of low urinary tract symptoms (LUTS). Numerous data support the presence of an association between BPH-related LUTS (BPH-LUTS) and metabolic syndrome (MetS). Whether hormonal changes occurring in MetS play a role in the pathogenesis of BPH-LUTS is a debated issue. Therefore, this article aimed to systematically review the impact of hormonal changes that occur during aging on the prostate, including the role of sex hormones, insulin-like growth factor 1, thyroid hormones, and insulin. The possible explanatory mechanisms of the association between BPH-LUTS and MetS are also discussed. In particular, the presence of a male polycystic ovarian syndrome (PCOS)-equivalent may represent a possible hypothesis to support this link. Male PCOS-equivalent has been defined as an endocrine syndrome with a metabolic background, which predisposes to the development of type II diabetes mellitus, cardiovascular diseases, prostate cancer, BPH and prostatitis in old age. Its early identification would help prevent the onset of these long-term complications.

Estrogen Receptors in Epithelial-Mesenchymal Transition of Prostate Cancer

Prostate cancer (PC) remains a widespread malignancy in men. Since the androgen/androgen receptor (AR) axis is associated with the pathogenesis of prostate cancer, suppression of AR-dependent signaling by androgen deprivation therapy (ADT) still represents the primary intervention for this disease. Despite the initial response, prostate cancer frequently develops resistance to ADT and progresses. As such, the disease becomes metastatic and few therapeutic options are available at this stage. Although the majority of studies are focused on the role of AR signaling, compelling evidence has shown that estrogens and their receptors control prostate cancer initiation and progression through a still debated mechanism. Epithelial versus mesenchymal transition (EMT) is involved in metastatic spread as well as drug-resistance of human cancers, and many studies on the role of this process in prostate cancer progression have been reported. We discuss here the findings on the role of estrogen/estrogen receptor (ER) axis in epithelial versus mesenchymal transition of prostate cancer cells. The pending questions concerning this issue are presented, together with the impact of the available data in clinical management of prostate cancer patients.

Epidemiology of Prostate Cancer

Prostate cancer is the second most frequent cancer diagnosis made in men and the fifth leading cause of death worldwide. Prostate cancer may be asymptomatic at the early stage and often has an indolent course that may require only active surveillance. Based on GLOBOCAN 2018 estimates, 1,276,106 new cases of prostate cancer were reported worldwide in 2018, with higher prevalence in the developed countries. Differences in the incidence rates worldwide reflect differences in the use of diagnostic testing. Prostate cancer incidence and mortality rates are strongly related to the age with the highest incidence being seen in elderly men (> 65 years of age). African-American men have the highest incidence rates and more aggressive type of prostate cancer compared to White men. There is no evidence yet on how to prevent prostate cancer; however, it is possible to lower the risk by limiting high-fat foods, increasing the intake of vegetables and fruits and performing more exercise. Screening is highly recommended at age 45 for men with familial history and African-American men. Up-to-date statistics on prostate cancer occurrence and outcomes along with a better understanding of the etiology and causative risk factors are essential for the primary prevention of this disease.

Molecular Mechanisms and Bioavailability of Polyphenols in Prostate Cancer

Prostate cancer is the one of the most frequently diagnosed cancers among men over the age of 50. Several lines of evidence support the observation that polyphenols have preventive and therapeutic effects in prostate cancer. Moreover, prostate cancer is ideal for chemoprevention due to its long latency. We propose here an equilibrated lifestyle with a diet rich in polyphenols as prophylactic attempts to slow down the progression of localized prostate cancer or prevent the occurrence of the disease. In this review, we will first summarize the molecular mechanisms of polyphenols in prostate cancer with a focus on the antioxidant and pro-oxidant effects, androgen receptors (AR), key molecules involved in AR signaling and their transactivation pathways, cell cycle, apoptosis, angiogenesis, metastasis, genetic aspects, and epigenetic mechanisms. The relevance of the molecular mechanisms is discussed in light of current bioavailability data regarding the activity of polyphenols in prostate cancer. We also highlight strategies for improving the bioavailability of polyphenols. We hope that this review will lead to further research regarding the bioavailability and the role of polyphenols in prostate cancer prevention and treatment.

Chemoprevention in Prostate Cancer: Current Perspective and Future Directions

Chemoprevention of prostate cancer aims to reduce the mortality as well as the public burden of overdetection, which increases anxiety, cost, and morbidity related to the disease. The role of 5-α-reductase inhibitors has been well investigated and shown to decrease the risk of prostate cancer. No current evidence exists to encourage the use of nutrients or vitamins as chemopreventive agents. The modulation of inflammation is one of the most promising targets for chemoprevention of prostate cancer.

Estrogens and prostate cancer

BACKGROUND

Hormonal influences such as androgens and estrogens are known contributors in the development and progression of prostate cancer (CaP). While much of the research to the hormonal nature of CaP has focused on androgens, estrogens also have critical roles in CaP development, physiology as well as a potential therapeutic intervention.

METHODS

In this review, we provide a critical literature review of the current basic science and clinical evidence for the interaction between estrogens and CaP.

RESULTS

Estrogenic influences in CaP include synthetic, endogenous, fungi and plant-derived compounds, and represent a family of sex hormones, which cross hydrophobic cell membranes and bind to membrane-associated receptors and estrogen receptors that localize to the nucleus triggering changes in gene expression in various organ systems.

CONCLUSIONS

Estrogens represent a under-recognized contributor in CaP development and progression. Further research in this topic may provide opportunities for identification of environmental influencers as well as providing novel therapeutic targets in the treatment of CaP.

Chemoprevention of prostate cancer in men with high-grade prostatic intraepithelial neoplasia (HGPIN): a systematic review and adjusted indirect treatment comparison

Background

High-grade prostatic intraepithelial neoplasia (HGPIN) is the precursor or premalignant form of prostate cancer. At least 30% patients with a confirmed HGPIN will develop prostate cancer within 1 year after repeated biopsy. HGPIN patients are the appropriate at-risk population for chemoprevention strategies investigation against prostate cancer. However the commonly used chemoprevention agents that targeted on hormonal imbalance or lifestyle-related factors showed varied results in HGPIN patients.

Methods

Literature searches were conducted in PubMed, EMBASE and Cochrane library according to Cochrane guidelines before January 31^st, 2017. Direct meta-analysis were performed to summarize the efficacy of candidate chemopreventative agents Dutasteride, Flutamide, Toremifene, Selenium, Green tea components, Lycopene and natural food products combination. Adjusted indirect meta-analyses were employed to compare the relative efficacy of these candidate chemoprevention agents head-to-head.

Results

The overall incidence of prostate cancer in HGPIN was slightly decreased by chemoprevention agents (25.7% vs 31.5%, RR = 0.92, 95% CI: 0.83-1.03, P = 0.183), with minor heterogeneity (I² = 22.3%, χ² = 15.08, P = 0.237), but without statistical significance. Subgroup analysis showed that green tea catechins significantly decreased prostate cancer in HGPIN patients (7.60% vs 23.1%, RR = 0.39, 95% CI: 0.16-10.97, P P = 0.044), with moderate heterogeneity (I² = 47.9%, χ² = 1.92, P = 0.166). The adjusted indirect meta-analysis favored green tea catechins over other chemoprevention agents, and significantly when compared to natural food products combination (RR = 0.355, 95% CI: 0.134-0.934).

Conclusion

The overall efficacy of chemoprevention agents in HGPIN patients is limited. But Green tea catechins showed the superiority to decrease prostate cancer in HGPIN patients.

Estrogen and Androgen Blockade for Advanced Prostate Cancer in the Era of Precision Medicine

Androgen deprivation therapy (ADT) has been widely prescribed for patients with advanced prostate cancer (PC) to control key signaling pathways via androgen receptor (AR) and AR-collaborative transcriptional factors; however, PC gradually acquires a lethal phenotype and results in castration-resistant PC (CRPC) during ADT. Therefore, new therapeutic strategies are required in clinical practice. In addition, ARs; estrogen receptors (ERs; ERα and ERβ); and estrogen-related receptors (ERRs; ERRα, ERRβ, and ERRγ) have been reported to be involved in the development or regulation of PC. Recent investigations have revealed the role of associated molecules, such as KLF5, FOXO1, PDGFA, VEGF-A, WNT5A, TGFβ1, and micro-RNA 135a of PC, via ERs and ERRs. Selective ER modulators (SERMs) have been developed. Recently, estrogen and androgen blockade (EAB) using a combination of toremifene and ADT has been demonstrated to improve biochemical recurrence rate in treatment-naïve bone metastatic PC. In the future, the suitability of ADT alone or EAB for individuals may be evaluated by making clinical decisions on the basis of information obtained from RT-PCR, gene-panel, or liquid biopsy to create a “personalized medicine” or “precision medicine”. In this review, we summarize ER and ERR signaling pathways, molecular diagnosis, and SERMs as candidates for advanced PC treatment.

Estrogens and Their Receptors in Prostate Cancer: Therapeutic Implications

A major challenge in clinical management of prostate cancer (PC) is to limit tumor growth and prevent metastatic spreading. Considerable efforts have been made to discover new compounds for PC therapy and recent years have seen promising progress in this field. Pharmacological approaches have been designed to achieve benefits in PC treatment and avoid the negative side effects resulting from administration of antagonists or agonists or new drugs. Nonetheless, the currently available therapies frequently induce resistance and PC progresses toward castration-resistant forms that can be caused by the androgen receptor reactivation and/or mutations, or derangement of signaling pathways. Preclinical and clinical findings have also shown that other nuclear receptors are frequently altered in PC. In this review, we focus on the role of estradiol/estradiol receptor (ER) axis, which controls PC growth and progression. Selective targeting of ER subtypes (α or β) may be an attractive way to limit the growth and spreading of prostatic cancer cells.

Estrogen receptor signaling in prostate cancer: Implications for carcinogenesis and tumor progression

BACKGROUND

The androgen receptor (AR) is the classical target for prostate cancer prevention and treatment, but more recently estrogens and their receptors have also been implicated in prostate cancer development and tumor progression.

METHODS

Recent experimental and clinical data were reviewed to elucidate pathogenetic mechanisms how estrogens and their receptors may affect prostate carcinogenesis and tumor progression.

RESULTS

The estrogen receptor beta (ERβ) is the most prevalent ER in the human prostate, while the estrogen receptor alpha (ERα) is restricted to basal cells of the prostatic epithelium and stromal cells. In high grade prostatic intraepithelial neoplasia (HGPIN), the ERα is up-regulated and most likely mediates carcinogenic effects of estradiol as demonstrated in animal models. The partial loss of the ERβ in HGPIN indicates that the ERβ acts as a tumor suppressor. The tumor promoting function of the TMPRSS2-ERG fusion, a major driver of prostate carcinogenesis, is triggered by the ERα and repressed by the ERβ. The ERβ is generally retained in hormone naïve and metastatic prostate cancer, but is partially lost in castration resistant disease. The progressive emergence of the ERα and ERα-regulated genes (eg, progesterone receptor (PR), PS2, TMPRSS2-ERG fusion, and NEAT1) during prostate cancer progression and hormone refractory disease suggests that these tumors can bypass the AR by using estrogens and progestins for their growth. In addition, nongenomic estrogen signaling pathways mediated by orphan receptors (eg, GPR30 and ERRα) has also been implicated in prostate cancer progression.

CONCLUSIONS

Increasing evidences demonstrate that local estrogen signaling mechanisms are required for prostate carcinogenesis and tumor progression. Despite the recent progress in this research topic, the translation of the current information into potential therapeutic applications remains highly challenging and clearly warrants further investigation.

Effects of Transdermal Testosterone Gel or an Aromatase Inhibitor on Prostate Volume in Older Men

CONTEXT

T replacement is being increasingly offered to older men with age-related low T; hence, monitoring prostate health is important during T therapy. Data suggest that estrogens have an independent effect on the prostate and some effects of T on the prostate might be mediated via its aromatization to estradiol. Although some studies have assessed the effects of T replacement on prostate volume, the differential effects of T and estradiol have not been delineated.

OBJECTIVE

The objective of the study was to investigate the relative effects of T and estradiol on prostate volume in older men with low T.

PARTICIPANTS

Thirty-one men, 65 years old or older with total T less than 350 ng/dL (measured by mass spectrometry) participated in the study.

INTERVENTION

The intervention included randomization to 5 g transdermal T gel (TT), 1 mg oral aromatase inhibitor (AI), or placebo daily for 12 months.

MAIN OUTCOME MEASURES

The primary outcome was prostate volume measured by transrectal ultrasound at baseline and 12 months. Secondary outcomes included prostate-specific antigen levels and lower urinary tract symptoms score.

RESULTS

Serum T levels increased in both intervention groups; estradiol levels increased in the TT group, whereas it decreased in the AI group. At 12 months, prostate volume significantly increased (4.5 ± 1.76 cc, P < .05) only in the TT group. Increase in prostate-specific antigen levels were seen in both intervention groups at 6 months (P < .01 and P < .001). The lower urinary tract symptoms score increased only in the TT group (P < .05).

CONCLUSIONS

The tropic effects of T on the prostate are mediated via its aromatization to estradiol. Administration of AI for 12 months to older men was not detrimental to the prostate.

Premalignancy in Prostate Cancer: Rethinking What we Know

High-grade prostatic intraepithelial neoplasia (PIN) has been accepted as the main precursor lesion to invasive adenocarcinoma of the prostate, and this is likely to be the case. However, in an unknown number of cases, lesions fulfilling the diagnostic criteria for high-grade PIN may actually represent intra-acinar or intraductal spread of invasive carcinoma. Intriguingly, this possibility would not contradict many of the findings of previous epidemiologic studies linking high-grade PIN to carcinoma or molecular pathologic studies showing similar genomic (e.g., TMPRSS2-ERG gene fusion) as well as epigenomic and molecular phenotypic alterations between high-grade PIN and carcinoma. Also, this possibility would be consistent with previous anatomic studies in prostate specimens linking high-grade PIN and carcinoma in autopsy and other whole prostate specimens. In addition, if some cases meeting morphologic criteria for PIN actually represent intra-acinar spread of invasive carcinoma, this could be an important potential confounder of the interpretation of past clinical trials enrolling patients presumed to be without carcinoma, who are at high risk of invasive carcinoma. Thus, in order to reduce possible bias in future study/trial designs, novel molecular pathology approaches are needed to decipher when an apparent PIN lesion may be intra-acinar/intra-ductal spread of an invasive cancer and when it truly represents a precursor state. Similar approaches are needed for lesions known as intraductal carcinoma to facilitate better classification of them as true intra-ductal/acinar spread on one hand or as precursor high-grade PIN (cribriform type) on the other hand; a number of such molecular approaches (e.g., coevaluating TMPRSS-ERG fusion and PTEN loss) are already showing excellent promise. Cancer Prev Res; 9(8); 648-56. ©2016 AACR.

Toremifene, a selective estrogen receptor modulator, significantly improved biochemical recurrence in bone metastatic prostate cancer: a randomized controlled phase II a trial

BACKGROUNDS

Durability of androgen-deprivation therapy (ADT) for prostate cancer (PC) is limited. Additional selective estrogen receptor modulators (SERMs) may prolong the durability of ADT, because androgen and estrogen signaling drive PC progression.

METHODS

Men with treatment-naïve bone metastatic PC were randomly assigned in 1:1:1 fashion to receive ADT, toremifene 60 mg plus ADT (TOPADT), or raloxifene 60 mg plus ADT (RAPADT). The primary endpoint was the biochemical recurrence (BCR) rate, and secondary endpoints were changes of scores of the visual analogue scale (VAS) and the functional assessment of cancer therapy (FACT).

RESULTS

A total of 15 men, 5 each, were allocated to one of the three treatment arms. The basal serum prostate-specific antigen (PSA) level was 198 ng/mL (median, range; 30-8428). Bone metastases were graded as 1 (n = 11), 2 (n = 3), and 3 (n = 1) by the extent of disease. During the median follow-up period of 1370 days (range; 431-1983), BCR occurred in 3, 0 and 2 men in ADT, TOPADT and RAPADT group, respectively. The 5-year BCR-free rate was 30, 100 and 53 %, in ADT, TOPADT and RAPADT group, respectively (p = 0.04, ADT v.s. TOPADT, p = 0.48, ADT v.s. RAPADT and p = 0.12, TOPADT v.s. RAPADT). Scores of VAS improved in all groups and remained stable throughout the study. This analysis is limited as a preliminary result in a single center.

CONCLUSIONS

Toremifene with conventional ADT significantly improved the BCR rate in treatment-naïve bone metastatic PC. Further clinical trials are warranted to confirm the promising clinical efficacy of this combination therapy.

TRIAL REGISTRATION

The protocol was registered at the University Hospital Medical Information Network ( UMIN ID;0,000,064,000 ) in Sep 25, 2011.

Nano-Targeted Delivery of Toremifene, an Estrogen Receptor-α Blocker in Prostate Cancer

PURPOSE

Estrogen Receptor-α (ERα) expression is increased in prostate cancer and acts as an oncogene. We propose that blocking of estrogen hormone binding to ERα using the ERα blocker toremifene will reduce the tumorigenicity of prostate cancer, and nano-targeted delivery of toremifene will improve anticancer efficacy. We report the synthesis and use in an orthotopic mouse model of PLGA-PEG nanoparticles encapsulating toremifene and nanoparticles encapsulating toremifene that are also conjugated to anti-PSMA for targeted prostate tumor delivery.

METHODS

Human prostate cancer cell line PC3M and a nude mouse model were used to test efficacy of nano-targeted and nano-encapsulated toremifene versus free toremifene on the growth and differentiation of tumor cells.

RESULTS

Treatment with free toremifene resulted in a significant reduction in growth of prostate tumor and proliferation, and its nano-targeting resulted in greater reduction of prostate tumor growth, greater toremifene tumor uptake, and enhanced tumor necrosis. Tumors from animals treated with nano-encapsulated toremifene conjugated with anti-PSMA showed about a 15-fold increase of toremifene compared to free toremifene.

CONCLUSIONS

Our data provide evidence that blocking ERα by toremifene and targeting prostate cancer tissues with anti-PSMA antibody on the nanoparticles' surface repressed the tumorigenicity of prostate cancer cells in this mouse model.

In-silico identification and functional validation of allele-dependent AR enhancers

Androgen Receptor (AR) and Estrogen Receptors (ERs) are key nuclear receptors that can cooperate in orchestrating gene expression programs in multiple tissues and diseases, targeting binding elements in promoters and distant enhancers. We report the unbiased identification of enhancer elements bound by AR and ER-α whose activity can be allele-specific depending on the status of nearby Single Nucleotide Polymorphisms (SNP). ENCODE data were computationally mined to nominate genomic loci with: (i) chromatin signature of enhancer activity from activation histone marks, (ii) binding evidence by AR and ER-α, (iii) presence of a SNP. Forty-one loci were identified and two, on 1q21.3 and 13q34, selected for characterization by gene reporter, Chromatin immunoprecipitation (ChIP) and RT-qPCR assays in breast (MCF7) and prostate (PC-3) cancer-derived cell lines. We observed allele-specific enhancer activity, responsiveness to ligand-bound AR, and potentially influence on the transcription of closely located genes (RAB20, ING1, ARHGEF7, ADAM15). The 1q21.3 variant, rs2242193, showed impact on AR binding in MCF7 cells that are heterozygous for the SNP. Our unbiased genome-wide search proved to be an efficient methodology to discover new functional polymorphic regulatory regions (PRR) potentially acting as risk modifiers in hormone-driven cancers and overall nominated SNPs in PRR across 136 transcription factors.

A precisely substituted benzopyran targets androgen refractory prostate cancer cells through selective modulation of estrogen receptors

Dietary consumption of phytoestrogens like genistein has been linked with lower incidence of prostate cancer. The estradiol-like benzopyran core of genistein confers estrogen receptor-β (ER-β) selectivity that imparts weak anti-proliferative activity against prostate cancer cells. DL-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran (BP), a SERM designed with benzopyran core, targeted androgen independent prostate cancer (PC-3) cells 14-times more potently than genistein, ~25% more efficiently than tamoxifen and 6.5-times more actively than ICI-182780, without forfeiting significant specificity in comparison to genistein. BP increased apoptosis (annexin-V and TUNEL labeling), arrested cell cycle, and significantly increased caspase-3 activity along with mRNA expressions of estrogen receptor (ER)-β and FasL (qPCR) in PC-3 cells. In classical ERE-luc reporter assay BP behaved as a potent ER-α antagonist and ER-β agonist. Accordingly, it decreased expression of ER-α target PS2 (P<0.01) and increased expression of ER-β target TNF-α (P<0.05) genes in PC-3. ER-β deficient PC-3 (siRNA-transfected) was resistant to apoptotic and anti-proliferative actions of SERMs, including stimulation of FasL expression by BP. BP significantly inhibited phosphorylation of Akt and ERK-1/2, JNK and p38 in PC-3 (immunoblotting), and thus adopted a multi-pathway mechanism to exert a more potent anti-proliferative activity against prostate cancer cells than natural and synthetic SERMs. Its precise ER-subtype specific activity presents a unique lead structure for further optimization.

Selective androgen receptor modulators as improved androgen therapy for advanced breast cancer

Androgens were at one time a therapeutic mainstay in the treatment of advanced breast cancer. Despite comparable efficacy, SERMs and aromatase inhibitors eventually became the therapies of choice due to in part to preferred side-effect profiles. Molecular characterization of breast tumors has revealed an abundance of androgen receptor expression but the choice of an appropriate androgen receptor ligand (agonist or antagonist) has been confounded by multiple conflicting reports concerning the role of the receptor in the disease. Modern clinical efforts have almost exclusively utilized antagonists. However, the recent clinical development of selective androgen receptor modulators with greatly improved side-effect profiles has renewed interest in androgen agonist therapy for advanced breast cancer.

Designed modulation of sex steroid signaling inhibits telomerase activity and proliferation of human prostate cancer cells

The predominant estrogen-receptor (ER)-β signaling in normal prostate is countered by increased ER-α signaling in prostate cancer (CaP), which in association with androgen-receptor (AR) signaling results in pathogenesis of the disease. However CaP treatments mostly target AR signaling which is initially effective but eventually leads to androgen resistance, hence simultaneous targeting of ERs has been proposed. A novel series of molecules were designed with multiple sex-steroid receptor modulating capabilities by coalescing the pharmacophores of known anti-CaP molecules that act via modulation of ER(α/β) and/or AR, viz. 3,3'diindolylmethane (DIM), mifepristone, toremifene, tamoxifen and raloxifene. N,N-diethyl-4-((2-(4-methoxyphenyl)-1H-indol-3-yl)methyl) aniline (DIMA) was identified as the most promising structure of this new series. DIMA increased annexin-V labelling, cell-cycle arrest and caspase-3 activity, and decreased expression of AR and prostate specific antigen in LNCaP cells, in vitro. Concurrently, DIMA increased ER-β, p21 and p27 protein levels in LNCaP cells and exhibited ~5 times more selective binding for ER-β than ER-α, in comparison to raloxifene. DIMA exhibited a dose-dependent ER-β agonism and ER-α antagonism in classical gene reporter assay and decreased hTERT (catalytic subunit of telomerase) transcript levels in LNCaP at 3.0 μM (P<0.05). DIMA also dose-dependently decreased telomerase enzyme activity in prostate cancer cells. It is thus concluded that DIMA acts as a multi-steroid receptor modulator and effectively inhibits proliferation of prostate cancer cells through ER-β mediated telomerase inhibition, by countering actions of ER-α and AR. Its unique molecular design can serve as a lead structure for generation of potent agents against endocrine malignancies like the CaP.

Estrogen receptor beta in prostate cancer: friend or foe?

Prostate cancer is the commonest, non-cutaneous cancer in men. At present, there is no cure for the advanced, castration-resistant form of the disease. Estrogen has been shown to be important in prostate carcinogenesis, with evidence resulting from epidemiological, cancer cell line, human tissue and animal studies. The prostate expresses both estrogen receptor alpha (ERA) and estrogen receptor beta (ERB). Most evidence suggests that ERA mediates the harmful effects of estrogen in the prostate, whereas ERB is tumour suppressive, but trials of ERB-selective agents have not translated into improved clinical outcomes. The role of ERB in the prostate remains unclear and there is increasing evidence that isoforms of ERB may be oncogenic. Detailed study of ERB and ERB isoforms in the prostate is required to establish their cell-specific roles, in order to determine if therapies can be directed towards ERB-dependent pathways. In this review, we summarise evidence on the role of ERB in prostate cancer and highlight areas for future research.

Soy isoflavones and prostate cancer: a review of molecular mechanisms

Soy isoflavones are dietary components for which an association has been demonstrated with reduced risk of prostate cancer (PCa) in Asian populations. However, the exact mechanism by which these isoflavones may prevent the development or progression of PCa is not completely understood. There are a growing number of animal and in vitro studies that have attempted to elucidate these mechanisms. The predominant and most biologically active isoflavones in soy products, genistein, daidzein, equol, and glycetin, inhibit prostate carcinogenesis in some animal models. Cell-based studies show that soy isoflavones regulate genes that control cell cycle and apoptosis. In this review, we discuss the literature relevant to the molecular events that may account for the benefit of soy isoflavones in PCa prevention or treatment. These reports show that although soy isoflavone-induced growth arrest and apoptosis of PCa cells are plausible mechanisms, other chemo protective mechanisms are also worthy of consideration. These possible mechanisms include antioxidant defense, DNA repair, inhibition of angiogenesis and metastasis, potentiation of radio- and chemotherapeutic agents, and antagonism of estrogen- and androgen-mediated signaling pathways. Moreover, other cells in the cancer milieu, such as the fibroblastic stromal cells, endothelial cells, and immune cells, may be targeted by soy isoflavones, which may contribute to soy-mediated prostate cancer prevention. In this review, these mechanisms are discussed along with considerations about the doses and the preclinical models that have been used.

A novel role for raloxifene nanomicelles in management of castrate resistant prostate cancer

Of patients with castrate resistant prostate cancer (CRPC), less than 25-33% survive more than five years. Recent studies have implicated estrogen, acting either alone or synergistically with androgens in the development of castrate resistant prostate cancer. Several in vitro and in vivo studies, as well as a limited number of clinical trials, have highlighted the potential of selective estrogen receptor modulators, such as raloxifene (Ral) for the treatment of castrate resistant prostate cancer. However, the poor oral bioavailability and metabolism of selective estrogen receptor modulators limit their efficiency in clinical application. To overcome these limitations, we have used styrene co-maleic acid (SMA) micelle to encapsulate raloxifene. Compared to free drug, SMA-Ral micelles had 132 and 140% higher cytotoxicity against PC3 and DU 145 prostate cell lines, respectively. SMA-Ral effectively inhibits cell cycle progression, increases apoptosis, and alters the integrity of tumor spheroid models. In addition, the micellar system induced changes in expression and localization of estrogen receptors, epidermal growth factor receptor (EGFR), and downstream effectors associated with cell proliferation and survival. Finally, SMA-Ral treatment decreased migration and invasion of castrate resistant prostate cancer cell lines. In conclusion, SMA-Ral micelles can potentially benefit new strategies for clinical management of castrate resistant prostate cancer.

The strategies to control prostate cancer by chemoprevention approaches

Prostate cancer (PCA) is the most commonly diagnosed cancer in men in the United States with growing worldwide incidence. Despite intensive investment in improving early detection, PCA often escapes timely detection and mortality remains high; this malignancy being the second highest cancer-associated mortality in American men. Collectively, health care costs of PCA results in an immense financial burden that is only expected to grow. Additionally, even in cases of successful treatment, PCA is associated with long-term and pervasive effects on patients. A proactive alternative to treat PCA is to prevent its occurrence and progression prior to symptomatic malignancy. This may serve to address the issue of burgeoning healthcare costs and increasing number of sufferers. One potential regimen in service of this alternative is PCA chemoprevention. Here, chemical compounds with cancer preventive efficacy are identified on the basis of their potential in a host of categories: their historical medicinal use, correlation with reduced risk in population studies, non-toxicity, their unique chemical properties, or their role in biological systems. PCA chemopreventive agents are drawn from multiple broad classes of chemicals, themselves further subdivided based on source or potential effect, with most derived from natural products. Many such compounds have shown efficacy, varying from inhibiting deregulated PCA cell signaling, proliferation, epithelial to mesenchymal transition (EMT), invasion, metastasis, tumor growth and angiogenesis and inducing apoptosis. Overall, these chemopreventive agents show great promise in PCA pre-clinical models, though additional work remains to be done in effectively translating these findings into clinical use.

Risk adapted chemoprevention for prostate cancer: an option?

A high disease prevalence, the presentation in older age, a frequently slowly progressing course of disease, and high costs make diagnosis and therapy of prostate cancer a special challenge for urologists. Effective prevention of the disease may help to resolve some of the problems mentioned above. Two randomised, controlled studies prove that effective chemoprevention of prostate cancer is possible using 5-α reductase inhibitors (finasteride, dutasteride) (LoE 1) both in individuals at low and those at high risk developing prostate cancer. Furthermore, there is evidence that other compounds, e.g. selective estrogen receptor modulators (SERMs), non-steroidal anti-inflammatory drugs (NSAIDs) and statins might also be effective. This review investigates potential risks and benefits of chemoprevention including a consideration of health economic aspects. The authors conclude that chemoprevention in a high risk cohort using 5-α reductase inhibitors is a viable option and may even be cost effective. In consequence, the options of chemoprevention in prostate cancer should be further explored in an open and unbiased way.

[CYP17A1 inhibitors in prostate cancer: mechanisms of action independent of the androgenic pathway]

INTRODUCTION

The objective of this article is to review the mechanisms of action of abiraterone acetate, independently of the androgenic pathway.

MATERIAL AND METHOD

A systematic review of the literature was carried out on Medline and Embase databases.

RESULTS

Inhibition of CYP17A1 with abiraterone acetate induces changes in steroid metabolism, whose main component is the reduction of DHEA and androstenedione synthesis. This results in inhibition of androgen pathway in prostatic cancerous epithelial cell. Regardless of androgen activation pathway, abiraterone acetate could also act via an alternative mechanism of action not fully elucidated. Stromal cells, like tumor cells, could undergo the effects of CYP17A1 inhibition, resulting in blocking the production of secondary mediators that contribute to tumor progression. Similarly, it has been suggested that abiraterone acetate efficacy may be related to its ability to alter intratumoral concentrations of estrogen and progesterone.

CONCLUSION

The validation of these mechanisms could contribute to improved therapeutic strategies based on the use of abiraterone acetate alone or in combination.

Prostate cancer chemoprevention

Prostate cancer is a leading cause of morbidity and mortality in men and has significant treatment-associated complications. Prostate cancer chemoprevention has the potential to decrease the morbidity and mortality associated with this disease. Chemoprevention research to date has primarily focused on nutrients and 5 alpha-reductase inhibitors (5ARIs). A large randomized trial (SELECT) found no favorable effect of selenium or vitamin E on prostate cancer prevention. Two large randomized placebo controlled trials (the PCPT and REDUCE trials) have been published and have supported the role of 5ARIs in prostate cancer chemoprevention; however, these trials also have prompted concerns regarding the increase in high-grade disease seen with treatment and have not been approved by the US Food and Drug Administration (FDA) for chemoprevention. Conclusive evidence for the chemopreventive benefit of nutrients or vitamins is lacking, whereas the future role of 5ARIs remains to be clarified.

Preneoplasia in the prostate gland with emphasis on high grade prostatic intraepithelial neoplasia

There are a variety of morphological patterns and processes that have been implicated in the pathogenesis of prostate cancer. Prostatic intraepithelial neoplasia (PIN), inflammation with or without atrophy, and adenosis (atypical adenomatous hyperplasia) have all been given candidate status as precursor lesions of prostatic adenocarcinoma. Based on decades of research, high grade prostatic intraepithelial neoplasia (HPIN), a proliferative lesion of prostatic secretory cells, has emerged as the most likely morphological pre-invasive lesion involved in the evolution of many but not all prostatic adenocarcinomas. In this manuscript, we briefly discuss other proposed precursors of prostatic adenocarcinoma and then focus on the history, diagnostic criteria and morphology of HPIN. The incidence of HPIN and its relationship to prostate cancer is reviewed. The differential diagnosis of large glandular patterns in the prostate is discussed in depth. Finally, we summarise the recent clinicopathological studies evaluating the clinical significance of HPIN and discuss follow-up strategies in men diagnosed with HPIN.

Novel off-target effect of tamoxifen--inhibition of acid ceramidase activity in cancer cells

Acid ceramidase (AC), EC 3.5.1.23, a lysosomal enzyme, catalyzes the hydrolysis of ceramide to constituent sphingoid base, sphingosine, and fatty acid. Because AC regulates the levels of pro-apoptotic ceramide and mitogenic sphingosine-1-phosphate, it is considered an apt target in cancer therapy. The present study reveals, for the first time, that the prominent antiestrogen, tamoxifen, is a pan-effective AC inhibitor in the low, single digit micromolar range, as demonstrated in a wide spectrum of cancer cell types, prostate, pancreatic, colorectal, and breast. Prostate cancer cells were chosen for the detailed investigations. Treatment of intact PC-3 cells with tamoxifen produced time- and dose-dependent inhibition of AC activity. Tamoxifen did not impact cell viability nor did it inhibit AC activity in cell-free assays. In pursuit of mechanism of action, we demonstrate that tamoxifen induced time-, as early as 5min, and dose-dependent, as low as 5μM, increases in lysosomal membrane permeability (LMP), and time- and dose-dependent downregulation of AC protein expression. Assessing various protease inhibitors revealed that a cathepsin B inhibitor blocked tamoxifen-elicited downregulation of AC protein; however, this action failed to restore AC activity unless assayed in a cell-free system at pH4.5. In addition, pretreatment with tamoxifen inhibited PC-3 cell migration. Toremifene, an antiestrogen structurally similar to tamoxifen, was also a potent inhibitor of AC activity. This study reveals a new, off-target action of tamoxifen that may be of benefit to enhance anticancer therapies that either incorporate ceramide or target ceramide metabolism.

Genetic and molecular differences in prostate carcinogenesis between African American and Caucasian American men

Prostate cancer is the most common non-skin cancer and the second leading cause of cancer-related death for men in the United States. Prostate cancer incidence and associated mortality are highest in African American men in comparison to other races. The observed differences in incidence and disease aggressiveness at presentation support a potential role for different pathways of prostate carcinogenesis between African American and Caucasian men. This review focuses on some of the recent molecular biology discoveries, which have been investigated in prostate carcinogenesis and their likely contribution to the known discrepancies across race and ethnicity. Key discussion points include the androgen receptor gene structure and function, genome-wide association studies and epigenetics. The new observations of the ethnic differences of the ERG oncogene, the most common prostate cancer gene, are providing new insights into ERG based stratification of prostate cancers in the context of ethnically diverse patient populations. This rapidly advancing knowledge has the likely potential to benefit clinical practice. Current and future work will improve the ability to sub-type prostate cancers by molecular alterations and lead to targeted therapy against this common malignancy.

[Pharmaco and diet based prostate cancer prevention]

In 2010, in France, 8,790 men died from prostate cancer despite a low and decreasing mortality rate. The individual risk/benefit ratio of prostate cancer screening is the focus of controversy and currently not in favor of a systematic screening program. Therefore, only prevention could reduce incidence, side effects of treatment and related mortality. Interestingly, prostate cancer prevention is also a field of controversy mainly about 5-alpha-reductase inhibitors. However, it could be expected that pharmaco- or diet-based prevention will be a huge tool for cancer control, even more for prostate cancer burden. This review comprehensively analyses which molecules or compounds could be used in preventive trials. With regard to pharmaco-prevention, three different kinds of drugs could be identified. First drugs, which aim at mainly or even solely reduce prostate cancer risk such as 5-alpha-reductase inhibitors and selective estrogen receptor modulators. Drugs, which aim at wider preventive impact such as: nonsteroidal anti-inflammatory drugs or difluoromethylornithine. Lastly, drugs for which reducing prostate cancer incidence is merely a side effect such as statins, metformin or histones desacetylase inhibitors. With regard to diet-based prevention, two main approaches could be identified: aliments and nutriments, on one hand, and vitamin and minerals, on the other. Interestingly if compounds reach experimental plausibility, natural foods or even global diet seem to have a higher impact. Lastly, besides assessment of efficacy, effectiveness required the critical step of compliance, which might actually be the weakest link of the prevention chain.

Prostate cancer diagnosis among men with isolated high-grade intraepithelial neoplasia enrolled onto a 3-year prospective phase III clinical trial of oral toremifene

PURPOSE

Prostate cancer (PCa) prevention remains an appealing strategy for the reduction of overtreatment and secondary adverse effects. We evaluated the efficacy of toremifene citrate 20 mg in PCa prevention among men with isolated high-grade prostatic intraepithelial neoplasia (HGPIN) on biopsy.

PATIENTS AND METHODS

One thousand five hundred ninety men with HGPIN, or HGPIN and atypia, and no PCa on prostate biopsy were randomly assigned 1:1 to receive toremifene citrate 20 mg or placebo in a 3-year phase III, double-blind, multicenter trial. Men underwent annual biopsy until cancer detection or study end. Efficacy analysis was performed in 1,467 men who underwent at least one on-study biopsy. Baseline risk factors were evaluated to determine influence on cancer detection.

RESULTS

Cancer was detected in 34.7% and 32.3% of men in the placebo and treatment groups, respectively, with no observed difference (P = .39, log-rank test) in PCa-free survival. The 3-year Kaplan-Meier PCa-free survival estimate was 54.9% (99% CI, 43.3% to 66.5%) in the placebo group and 59.5% (99% CI, 48.1% to 70.9%) in the treatment group. Exploration of baseline risk factors demonstrated no subset in which a risk reduction was observed. In the placebo group, 17.9%, 12.9%, and 13.6% of men at risk at the beginning of years 1, 2, and 3, respectively, were diagnosed with PCa.

CONCLUSION

Although toremifene 20 mg did not lower the PCa detection rate, men with isolated HGPIN have a high likelihood of eventual PCa diagnosis, demonstrating they are ideal candidates for inclusion in chemoprevention trials and require surveillance by periodic prostate biopsy.

Small molecule tolfenamic acid inhibits PC-3 cell proliferation and invasion in vitro, and tumor growth in orthotopic mouse model for prostate cancer

BACKGROUND

Specificity protein (Sp) transcription factors are implicated in critical cellular and molecular processes associated with cancer that impact tumor growth and metastasis. The non-steroidal anti-inflammatory drug, tolfenamic acid (TA) is known to inhibit Sp proteins in some human cancer cells and laboratory animal models. We evaluated the anti-cancer activity of TA using in vitro and in vivo models for prostate cancer.

METHODS

The anti-proliferative efficacy of TA was evaluated using DU-145, PC-3, and LNCaP cells. PC-3 cells were treated with DMSO or 50 µM TA for 48 hr. Whole cell lysates were evaluated for the expression of Sp1, survivin, c-PARP, Akt/p-Akt, c-Met, cdk4, cdc2, cyclin D3, and E2F1 by Western blot analysis. Cell invasion was assessed by Boyden-chamber assay and flow cytometry analysis was used to study apoptosis and cell cycle distribution. An orthotopic mouse model for prostate cancer with PC-3-Luc cells was used to study the in vivo effect of TA.

RESULTS

TA inhibited the expression of Sp1, c-Met, p-Akt, and survivin; increased c-PARP expression and caspases activity in PC-3 cells. TA caused cell arrest at G(0) /G(1) phase accompanied by a decrease in cdk4, cdc2, cyclin D3, and E2F1 and an increase in critical apoptotic markers. TA augmented annexin-V staining, caspase activity, and c-PARP expression indicating the activation of apoptotic pathways. TA also decreased PC-3 cell invasion. TA significantly decreased the tumor weight and volume which was associated with low expression of Sp1 and survivin in tumor sections.

CONCLUSION

TA targets critical pathways associated with tumorigenesis and invasion. These pre-clinical data strongly demonstrated the anti-cancer activity of TA in prostate cancer.

Current concepts and significance of estrogen receptor β in prostate cancer

An increasing amount of evidence points at important roles for estrogen receptors in prostate carcinogenesis and progression. Of the two estrogen receptors, estrogen receptor β is the most prominent within the prostate gland. Although there is much yet to be known, the findings from the discovery of the receptor in 1996 until now point at a role of the receptor in maintaining differentiation and reducing cellular proliferation in the prostate. Moreover, estrogen receptor β is the main target for phytoestrogens, perhaps at least partially explaining the difference in incidence of prostate cancer in the Western world compared to Asia where the intake of soy-based, phytoestrogen-rich food is higher. The tumor suppressive capability of estrogen receptor β makes it a promising drug target for the treatment and prevention of prostate cancer. This review will focus on different aspects of estrogen receptor signaling and prostate cancer.

Precursors of prostate cancer

High-grade prostatic intraepithelial neoplasia (PIN) is the only accepted precursor of prostatic adenocarcinoma, according to numerous studies of animal models and man; other proposed precursors include atrophy and malignancy-associated changes (with no morphologic changes). PIN is characterized by progressive abnormalities of phenotype and genotype that are intermediate between benign prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of prostatic carcinogenesis. The only method of detection of PIN is biopsy because it does not significantly elevate serum prostate-specific antigen concentration and cannot be detected by ultrasonography. The mean incidence of PIN in biopsies is 9% (range, 4%-16%), representing about 115,000 new cases of isolated PIN diagnosed each year in the United States. The clinical importance of PIN is its high predictive value as a marker for adenocarcinoma, and its identification warrants repeat biopsy for concurrent or subsequent carcinoma, especially when multifocal or observed in association with atypical small acinar proliferation (ASAP). Carcinoma develops in most patients with PIN within 10 years. Androgen deprivation therapy and radiation therapy decrease the prevalence and extent of PIN, suggesting that these forms of treatment may play a role in prevention of subsequent cancer. Multiple clinical trials to date of men with PIN have had modest success in delaying or preventing subsequent cancer.

A Summary of the Prostate Cancer Prevention Trials With a Focus on the Role of Vitamin E

Prostate cancer is the most common noncutaneous malignancy in men. It is an excellent target for primary prevention. Vitamin E trials conducted for prevention of prostate cancer have had conflicting results with a lower incidence of prostate cancer in the ATBC trial and a higher incidence in the vitamin E arm of the SELECT trial. Most of the clinical trials with vitamin E have been limited to the alpha-tocopherol isoform alone. An increasing body of evidence suggests, however, that the gamma- and delta-isoforms of tocopherol and tocotrienols are more promising with regard to cancer prevention. This review tries to justify our assertion that the gamma- and delta-isoforms of tocopherol and tocotrienol might be superior as prostate cancer preventers.

Epidemiology of prostate cancer and treatment remarks

Prostate cancer is one of the most common types of cancer and one of the leading causes of cancer death among men in the Western countries. The aim of the present analysis is to assess the cancer burden in order to ensure accurate strategies for chemoprevention and treatment, including the major therapeutic approaches for localized high-risk disease - surgery and radiation therapy - and quality of life issues related to each option.

Estrogen promotes prostate cancer cell migration via paracrine release of ENO1 from stromal cells

As a key glycolytic enzyme, enolase 1 (ENO1) is critical for cellular energy metabolism. Recent studies have revealed its important role in growth and metastasis of lung, head and neck, and breast cancer. However, the regulatory mechanisms of ENO1 expression and secretion remain unclear. We observed that conditioned medium from estradiol-stimulated prostate stromal cells significantly promoted the migration of prostate cancer (PCa) cells. Two-dimensional protein electrophoresis, mass spectrometry, and immunodepletion assays identified one of the major active factors in the conditioned medium as α-type enolase (α-enolase, or ENO1). Moreover, in prostate stromal cells, estradiol not only enhanced the stability of ENO1 at the protein level in an estrogen receptor-α-dependent manner but also promoted its secretion to the extracellular matrix. Furthermore, recombinant ENO1 bound to the surface of PCa cells and promoted cell migration via their plasminogen receptor activity in a paracrine manner. Immunohistochemistry suggested that stromal ENO1 levels increased in PCa compared with those in normal tissue.

Involvement of estrogen receptors in prostatic diseases

Accumulating evidence shows that estrogens participate in the pathogenesis and development of benign prostatic hyperplasia and prostate cancer by activating estrogen receptor α. In contrast, estrogen receptor β is involved in the differentiation and maturation of prostatic epithelial cells, and thus possesses antitumor effects in prostate cancer. However, the natural ligands of estrogen receptor β are not fully understood, and its mode of action according to its ligands and the binding sites located in the promoter regions of downstream genes remains to be elucidated. Here, we review recent experimental investigations of estrogen receptors and their urological relevance. Estrogen receptor-mediated signaling in the prostate is essential together with the androgen receptor-mediated pathway, providing a new therapeutic target for prostatic diseases.

Pharmacokinetic evaluation of toremifene and its clinical implications for the treatment of osteoporosis

INTRODUCTION

Toremifene is a triphenylethylene selective estrogen receptor modulator (SERM) that differs from tamoxifen in a single chloride ion addition on a side chain, resulting in a potentially more favorable toxicity profile.

AREAS COVERED

This article reviews the pharmacokinetics of toremifene and its potential use for the treatment of osteoporosis. This article was based on articles found through a literature search containing the terms 'toremifene' and 'SERMs.'

EXPERT OPINION

Toremifene can be administered orally with an excellent bioavailability. The overall pharmacokinetic profile is remarkably similar to tamoxifen. Toremifene is highly metabolized in the liver and is eliminated primarily in the feces following enterohepatic circulation. Some of its metabolites retain biological activity. This SERM was approved by the FDA for the treatment of estrogen receptor-positive metastatic breast cancer and is under investigation for its potential skeletal benefits in men on androgen deprivation therapy. Despite the positive preclinical and clinical evidences for the prevention of bone loss and fractures, the chemopreventive effect on prostate cancer remains to be confirmed and an increased risk of venous thromboembolism was evidenced in a large Phase III trial. Thus, additional data are required to establish the full clinical profile of this compound and its potential advantages over antiresorptive agents commonly in use for the treatment of osteoporosis.