Membrane rafts as potential sites of nongenomic hormonal signaling in prostate cancer

Statin use and mortality risk in Asian patients with prostate cancer receiving androgen deprivation therapy: A population-based cohort study

BACKGROUND

This study aimed to examine the associations between the use of statins concurrent with androgen deprivation therapy (ADT) and the risks of mortality in Asian patients diagnosed with prostate cancer (PCa).

METHODS

Adult patients (≥18 years old) diagnosed with PCa who were receiving any form of ADT and were being treated at public hospitals in Hong Kong from December 1999 to March 2021 were retrospectively identified, with follow-up conducted until September 2021. Patients who had received medical castration for <180 days without subsequent bilateral orchidectomy, those who had used statins concurrently with ADT for <180 days, and those with missing baseline total cholesterol levels were excluded. Statin users were defined as individuals who had used statins for ≥180 days concurrent with ADT, while non-users were those who had not used any statins. PCa-related mortality was the primary outcome, while all-cause mortality served as the secondary outcome. Inverse probability treatment weighting was employed to balance the covariates.

RESULTS

A total of 4920 patients were included, consisting of 2578 statin users and 2342 non-users (mean age 76.1 ± 8.2 years). Over a mean follow-up period of 4.2 ± 3.3 years, it was observed that statin users had significantly lower risks of both PCa-related mortality (weighted hazard ratio [wHR] 0.56 [95% confidence interval (CI) 0.48, 0.65], p < 0.001) and all-cause mortality (wHR 0.57 [95% CI 0.51, 0.63], p < 0.001), regardless of the type of ADT used. Notably, these associations were more pronounced among patients with less advanced PCa, as indicated by the absence of androgen receptor antagonist or chemotherapy usage (p value for interaction <0.001 for both outcomes).

CONCLUSION(S)

The use of statins concurrent with ADT was associated with reduced mortality risks among Asian patients with PCa. These findings suggest the need for additional research to explore the potential role of statins in the treatment of PCa patients.

Evidence on Statins, Omega-3, and Prostate Cancer: A Narrative Review

Dietary intake selections might play a crucial role in prostate cancer (PCa) occurrence and progression. Several studies have investigated whether statin use could reduce PCa risk but with conflicting results. Nevertheless, a significantly decreased incidence of advanced PCa has been consistently noted. Statins may also reduce the risk of biochemical recurrence (BCR) in men with PCa after receiving active treatment. However, the influence of statin usage on BCR and PCa progression in men with high prostate-specific antigen levels has been found to be insignificant. In contrast, the combined use of a statin and metformin was significantly related to the survival status of PCa patients. However, some studies have revealed that the intake of long-chain omega-3 fatty acid (ω-3) from fish or fish oil supplements may elevate PCa risk. Several meta-analyses on ω-3 consumption and PCa have shown controversial results for the relationship between PCa and ω-3 consumption. However, studies with positive results for various genotypes, fatty acid intake or levels, and PCA risk are emerging. This review highlights the association among statins, ω-3, and PCa. The findings summarized here may be helpful for clinicians counseling patients related to PCa.

Statin Use and the Risk of Prostate Cancer Biochemical Recurrence Following Definitive Therapy: A Systematic Review and Meta-Analysis of Cohort Studies

Background

Numerous studies have reported the role of statins on biochemical recurrence (BCR) among patients with prostate cancer (PCa) after definite treatment. However, the conclusions of these studies are contradictory. We aimed to determine the effect of statins on BCR of PCa using a systematic review and meta-analysis.

Methods

We searched PubMed (Medline) and other databases for cohort studies evaluating the effect of statins on the BCR of patients with PCa between January 1, 2000, and December 31, 2021. The random effects (RE) model and quality effects (QE) model were used to calculate the pooled hazard ratio (pHR) and pooled risk ratio (pRR) and their 95% confidence interval (95% CI).

Results

A total of 33 cohort studies were finally selected and included in this systematic review and meta-analysis. Statin use was significantly associated with a 14% reduction in the HR of BCR (pHR: 0.86, 95% CI: 0.78 to 0.95, I² = 64%, random effects model, 31 studies) and a 26% reduction in the RR of BCR (pRR: 0.74, 95% CI: 0.57 to 0.94, 24,591 patients, I² = 88%, random effects model, 15 studies) among patients with PCa. The subgroup analyses showed that statins could result in 22% reduction in the HR of BCR (pHR: 0.78, 95% CI: 0.61 to 0.98, I² = 57%, random effects model) among patients accepting radiotherapy (RT).

Conclusions

Our study suggests that statins have a unique role in the reduction of BCR in patients with PCa after definite treatment, especially RT. In the future, more clinical trials and in vitro and animal experiments are needed to further verify the effects of statins in PCa and the potential mechanisms.

The role of metformin, statins and diet in men on active surveillance for prostate cancer

PURPOSE OF REVIEW

A sound scientific basis has been emerging on the anti-neoplastic role of metformin, statins and dietary interventions. However, evidence in prostate cancer patients remains mixed owing to an absence of completed randomized trials. This overview examines the rationale for metformin, statins and dietary intervention for secondary prevention in men on active surveillance by summarizing current evidence base and biological mechanisms in influencing cancer progression and mortality.

METHODS

A comprehensive literature search was performed to identify studies that evaluated the role of metformin, statins and diet in the secondary prevention of prostate cancer as well as those that described the anti-cancer mechanisms of these agents. The search included Pubmed, MEDLINE, EMBASE and Cochrane library from inception till August 2021.

RESULTS

A total of 14 trials on metformin, 21 trials on statins and 13 trials on dietary measures were evaluated. Majority were observational population-based cohort studies or meta-analysis of them. Three ongoing prospective randomized controlled trials were also reported. Overall, mixed results were obtained.

CONCLUSIONS

The role of metformin and statins remains promising with several trials showing reduced rates of progression and cancer specific mortality. Combination therapy strategies have also been evaluated in more advanced patients showing synergism. Dietary interventions especially fruits, vegetables and fish intake has shown some benefit albeit with mixed results for others like legumes, red meat, coffee and multivitamins. Several ongoing randomized trials will provide stronger evidence in the future for secondary prevention.

Testosterone-androgen receptor: The steroid link inhibiting TRPM8-mediated cold sensitivity

Recent studies have revealed gender differences in cold perception, and pointed to a possible direct action of testosterone (TST) on the cold-activated TRPM8 (Transient Receptor Potential Melastatin Member 8) channel. However, the mechanisms by which TST influences TRPM8-mediated sensory functions remain elusive. Here, we show that TST inhibits TRPM8-mediated mild-cold perception through the noncanonical engagement of the Androgen Receptor (AR). Castration of both male rats and mice increases sensitivity to mild cold, and this effect depends on the presence of intact TRPM8 and AR. TST in nanomolar concentrations suppresses whole-cell TRPM8-mediated currents and single-channel activity in native dorsal root ganglion (DRG) neurons and HEK293 cells co-expressing recombinant TRPM8 and AR, but not TRPM8 alone. AR cloned from rat DRGs shows no difference from standard AR. However, biochemical assays and confocal imaging reveal the presence of AR on the cell surface and its interaction with TRPM8 in response to TST, leading to an inhibition of channel activity.

Emerging Therapeutic Activity of Davallia formosana on Prostate Cancer Cells through Coordinated Blockade of Lipogenesis and Androgen Receptor Expression

Background: Prostate cancer (PCa) is the most prevalent malignancy diagnosed in men in Western countries. There is currently no effective therapy for advanced PCa aggressiveness, including castration-resistant progression. The aim of this study is to evaluate the potential efficacy and determine the molecular basis of Davallia formosana (DF) in PCa. Methods: LNCaP (androgen-sensitive) and C4-2 (androgen-insensitive/castration-resistant) PCa cells were utilized in this study. An MTT-based method, a wound healing assay, and the transwell method were performed to evaluate cell proliferation, migration, and invasion. Intracellular fatty acid levels and lipid droplet accumulation were analyzed to determine lipogenesis. Moreover, apoptotic assays and in vivo experiments were conducted. Results: DF ethanol extract (DFE) suppressed proliferation, migration, and invasion in PCa cells. DFE attenuated lipogenesis through inhibition of the expression of sterol regulatory element-binding protein-1 (SREBP-1) and fatty acid synthase (FASN). Moreover, DFE decreased androgen receptor (AR) and prostate-specific antigen (PSA) expression in PCa cells. We further showed the potent therapeutic activity of DFE by repressing the growth and leading to apoptosis of subcutaneous C4-2 tumors in a xenograft mouse model. Conclusions: These data provide a new molecular basis of DFE in PCa cells, and co-targeting SREBP-1/FASN/lipogenesis and the AR axis by DFE could be employed as a novel and promising strategy for the treatment of PCa.

TRPM8-androgen receptor association within lipid rafts promotes prostate cancer cell migration

In prostate carcinogenesis, androgens are known to control the expression of the transient receptor potential melastatin 8 (TRPM8) protein via activation of androgen receptor (AR). Overexpression and/or activity of TRPM8 channel was shown to suppress prostate cancer (PCa) cell migration. Here we report that at certain concentrations androgens facilitate PCa cell migration. We show that underlying mechanism is inhibition of TRPM8 by activated AR which interacts with the channel within lipid rafts microdomains of the plasma membrane. Thus, our study has identified an additional nongenomic mechanism of the TRPM8 channel regulation by androgens that should be taken into account upon the development of novel therapeutic strategies.

Osajin displays potential antiprostate cancer efficacy via impairment of fatty acid synthase and androgen receptor expression

BACKGROUND

Currently, antiprostate cancer (PCa) drugs, including androgen deprivation therapy (ADT), are initially effective; however, most patients with PCa who receive ADT eventually progress to deadly aggressiveness. There is an urgent need to seek alternative strategies to cure this lethal disease. Activation of lipogenesis has been demonstrated to lead to PCa progression. Therefore, targeting the aberrant lipogenic activity could be developed therapeutically in PCa. The aim of this study is to investigate the molecular basis and efficacy of osajin, a bioactive prenylated isoflavonoid, in PCa.

METHODS

PCa cells, LNCaP (androgen-sensitive) and C4-2 (androgen-insensitive/castration-resistant), were used in this study. Proliferation, migration, and invasion analyses were conducted by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method, a wound healing assay, and the transwell method. Lipogenesis was determined by a Fatty Acid Quantification Kit and oil red O staining. Apoptosis was assessed by annexin V-fluorescein isothiocyanate/propidium iodide staining, caspase enzymatic activity, and Western blot analyses.

RESULTS

Osajin inhibited fatty acid synthase (FASN) expression, a key enzyme for lipogenesis, in PCa cells. By inhibiting FASN, osajin decreased the fatty-acid levels and lipid accumulation. Significantly, osajin downregulated androgen receptor (AR) and prostate-specific antigen (PSA) in PCa cells. Moreover, osajin suppressed PCa cell growth, migration, and invasion. Through activation of the caspase-dependent pathway, osajin induced apoptosis in PCa cells.

CONCLUSIONS

These data provide a novel molecular basis of osajin in PCa cells, and cotargeting lipogenesis and the AR axis via impairment of FASN and AR expression by osajin could be applied as a new and promising approach for the treatment of malignant PCa.

Main Inflammatory Cells and Potentials of Anti-Inflammatory Agents in Prostate Cancer

Prostate cancer is the most common type of cancer and the leading cause of cancer deaths among men in many countries. Preventing progression is a major concern for prostate cancer patients on active surveillance, patients with recurrence after radical therapies, and patients who acquired resistance to systemic therapies. Inflammation, which is induced by various factors such as infection, microbiome, obesity, and a high-fat diet, is the major etiology in the development of prostate cancer. Inflammatory cells play important roles in tumor progression. Various immune cells including tumor-associated neutrophils, tumor-infiltrating macrophages, myeloid-derived suppressor cells, and mast cells promote prostate cancer via various intercellular signaling. Further basic studies examining the relationship between the inflammatory process and prostate cancer progression are warranted. Interventions by medications and diets to control systemic and/or local inflammation might be effective therapies for prostate cancer progression. Epidemiological investigations and basic research using human immune cells or mouse models have revealed that non-steroidal anti-inflammatory drugs, metformin, statins, soy isoflavones, and other diets are potential interventions for preventing progression of prostate cancer by suppressing inflammation. It is essential to evaluate appropriate indications and doses of each drug and diet.

Ganoderma tsugae Inhibits the SREBP-1/AR Axis Leading to Suppression of Cell Growth and Activation of Apoptosis in Prostate Cancer Cells

Recent research suggests that the activation of lipid biosynthesis (lipogenesis) is linked with prostate cancer (PCa) malignancy. Sterol regulatory element-binding protein-1 (SREBP-1) is a key transcriptional regulator controlling lipogenesis. Moreover, androgen receptor (AR) has been well defined to play an important role in lethal PCa aggressiveness from androgen-responsive to castration-resistant status. In this study, we showed that the quality-assured Ganoderma tsugae ethanol extract (GTEE), a Chinese natural and herbal product, significantly inhibited expression of SREBP-1 and its downstream genes associated with lipogenesis in PCa cells. Through inhibiting SREBP-1, GTEE reduced the levels of intracellular fatty acids and lipids in PCa cells. Importantly, GTEE also downregulated the expression of AR and prostate-specific antigen (PSA) in both androgen-responsive and castration-resistant PCa cells. By blocking the SREBP-1/AR axis, GTEE suppressed cell growth and progressive behaviors, as well as activating the caspase-dependent apoptotic pathway in PCa cells. These data provide a new molecular basis of GTEE for the development of a potential therapeutic approach to treat PCa malignancy.

Physiological implications of DHEAS-induced non-classical steroid hormone signaling

In the spermatogenic cell line GC-2, dehydroepiandrosterone sulfate (DHEAS), activates the Src/Ras/c-Raf/Erk1/2/CREB(ATF-1) signaling cascade. Since DHEAS is present in the gonads, and since spermatogenesis and maturation of spermatogonia to haploid spermatozoa requires activation of Erk1/2, the triggering of these signaling events by DHEAS might have physiological relevance. In the Sertoli cell line TM4, DHEAS-induces activation of Erk1/2, CREB, and ATF-1, stimulates expression of claudin-3 and claudin-5 and augments transepithelial resistance, indicating the formation of tight junctions between adjacent Sertoli cells. Thus, by influencing the formation and dynamics of tight junctions at the blood-testis barrier, which protects germ cells from cells of the immune system, DHEAS might play a crucial role in the regulation and maintenance of male fertility. In bEnd.3 brain-derived endothelial cells, DHEAS stimulates the expression of zonula occludens-1 and claudin-3 and promotes tight junction formation between neighboring cells, which at the blood-brain barrier protects the brain from harmful factors and cells. If DHEAS supports the integrity of the blood-brain barrier also in vivo, the current findings might lead to new strategies for the prevention or treatment of neurological disorders associated with barrier defects.

Cholesterol and Cholesterol-Rich Membranes in Prostate Cancer: An Update

Cells maintain normal structure and function by responding appropriately to cues from the surrounding milieu. Extracellular stimuli are transduced from the surface through the plasma membrane by a complex series of interactions between ligands, their receptors and intracellular signaling partners (e.g., kinases, G proteins). Cholesterol-enriched membrane microdomains, generally referred to as “lipid rafts”, exist within the lipid bilayer of all mammalian cells and play an important role in signaling from the cell surface to various subcellular compartments. Lipid rafts have also been implicated in tumor growth and aggressiveness. Epidemiological evidence suggests that the modern Western diet, which contains substantial levels of cholesterol and other fatty substances, promotes prostate cancer progression. Consistent with this idea, prolonged inhibition of the cholesterol synthesis pathway by pharmacologic intervention in men has recently been associated with reduction in risk of advanced prostate cancer. In this review, we discuss the possibility that membrane cholesterol promotes prostate cancer progression by a mechanism that involves dysregulation of lipid raft-resident signaling complexes. This hypothesis provides new avenues for mechanistic studies as well as therapeutic intervention.

Mapping the STK4/Hippo signaling network in prostate cancer cell

Dysregulation of MST1/STK4, a key kinase component of the Hippo-YAP pathway, is linked to the etiology of many cancers with poor prognosis. However, how STK4 restricts the emergence of aggressive cancer remains elusive. Here, we investigated the effects of STK4, primarily localized in the cytoplasm, lipid raft, and nucleus, on cell growth and gene expression in aggressive prostate cancer. We demonstrated that lipid raft and nuclear STK4 had superior suppressive effects on cell growth in vitro and in vivo compared with cytoplasmic STK4. Using RNA sequencing and bioinformatics analysis, we identified several differentially expressed (DE) genes that responded to ectopic STK4 in all three subcellular compartments. We noted that the number of DE genes observed in lipid raft and nuclear STK4 cells were much greater than cytoplasmic STK4. Our functional annotation clustering showed that these DE genes were commonly associated with oncogenic pathways such as AR, PI3K/AKT, BMP/SMAD, GPCR, WNT, and RAS as well as unique pathways such as JAK/STAT, which emerged only in nuclear STK4 cells. These findings indicate that MST1/STK4/Hippo signaling restricts aggressive tumor cell growth by intersecting with multiple molecular pathways, suggesting that targeting of the STK4/Hippo pathway may have important therapeutic implications for cancer.

Prostate cancer stem cells: the role of androgen and estrogen receptors

Prostate cancer is one of the most commonly diagnosed cancers in men, and androgen deprivation therapy still represents the primary treatment for prostate cancer patients. This approach, however, frequently fails and patients develop castration-resistant prostate cancer, which is almost untreatable.

Cancer cells are characterized by a hierarchical organization, and stem/progenitor cells are endowed with tumor-initiating activity. Accumulating evidence indicates that prostate cancer stem cells lack the androgen receptor and are, indeed, resistant to androgen deprivation therapy. In contrast, these cells express classical (α and/or β) and novel (GPR30) estrogen receptors, which may represent new putative targets in prostate cancer treatment.

In the present review, we discuss the still-debated mechanisms, both genomic and non-genomic, by which androgen and estradiol receptors (classical and novel) mediate the hormonal control of prostate cell stemness, transformation, and the continued growth of prostate cancer. Recent preclinical and clinical findings obtained using new androgen receptor antagonists, anti-estrogens, or compounds such as enhancers of androgen receptor degradation and peptides inhibiting non-genomic androgen functions are also presented. These new drugs will likely lead to significant advances in prostate cancer therapy.

The current evidence on statin use and prostate cancer prevention: are we there yet?

An increasing amount of data supports an inverse association between statin use and cancer risk. The findings for prostate cancer, particularly advanced disease, are the most promising of all cancers studied. Use of these agents seems to also be associated with improved prostate- cancer-specific survival, particularly in men undergoing radiotherapy, suggesting usefulness of statins in secondary and tertiary prevention. Some study results might be influenced by increased PSA screening and health-conscious behaviour in statin users but these factors are unlikely to completely account for observed beneficial effects. The epidemiological evidence is supported by preclinical studies that show that statins directly inhibit prostate cancer development and progression in cell-based and animal-based models. The antineoplastic effect of statins might arise from a number of cholesterol-mediated and non-cholesterol-mediated mechanisms that affect pathways essential for cancer formation and progression. Understanding these mechanisms is instrumental in drug discovery research for the development of future prostate cancer therapeutics, as well as in designing clinical trials to test a role for statins in prostate cancer prevention. Currently, sufficient data are lacking to support the use of statins for the primary prevention of prostate cancer and further research is clearly warranted. Secondary and tertiary prevention trials in men who have been diagnosed with prostate cancer might soon be performed.

Integrative Analysis of Subcellular Quantitative Proteomics Studies Reveals Functional Cytoskeleton Membrane-Lipid Raft Interactions in Cancer

Lipid rafts are dynamic membrane microdomains that orchestrate molecular interactions and are implicated in cancer development. To understand the functions of lipid rafts in cancer, we performed an integrated analysis of quantitative lipid raft proteomics data sets modeling progression in breast cancer, melanoma, and renal cell carcinoma. This analysis revealed that cancer development is associated with increased membrane raft-cytoskeleton interactions, with ∼40% of elevated lipid raft proteins being cytoskeletal components. Previous studies suggest a potential functional role for the raft-cytoskeleton in the action of the putative tumor suppressors PTRF/Cavin-1 and Merlin. To extend the observation, we examined lipid raft proteome modulation by an unrelated tumor suppressor opioid binding protein cell-adhesion molecule (OPCML) in ovarian cancer SKOV3 cells. In agreement with the other model systems, quantitative proteomics revealed that 39% of OPCML-depleted lipid raft proteins are cytoskeletal components, with microfilaments and intermediate filaments specifically down-regulated. Furthermore, protein-protein interaction network and simulation analysis showed significantly higher interactions among cancer raft proteins compared with general human raft proteins. Collectively, these results suggest increased cytoskeleton-mediated stabilization of lipid raft domains with greater molecular interactions as a common, functional, and reversible feature of cancer cells.

Cholesterol Sulfonation Enzyme, SULT2B1b, Modulates AR and Cell Growth Properties in Prostate Cancer

Cholesterol accumulates in prostate lesions and has been linked to prostate cancer incidence and progression. However, how accumulated cholesterol contributes to prostate cancer development and progression is not completely understood. Cholesterol sulfate (CS), the primary sulfonation product of cholesterol sulfotransferase (SULT2B1b), accumulates in human prostate adenocarcinoma and precancerous prostatic intraepithelial neoplasia (PIN) lesions compared with normal regions of the same tissue sample. Given the enhanced accumulation of CS in these lesions, it was hypothesized that SULT2B1b-mediated production of CS provides a growth advantage to these cells. To address this, prostate cancer cells with RNAi-mediated knockdown (KD) of SULT2B1b were used to assess the impact on cell growth and survival. SULT2B1b is expressed and functional in a variety of prostate cells, and the data demonstrate that SULT2B1b KD, in LNCaP and other androgen-responsive (VCaP and C4-2) cells, results in decreased cell growth/viability and induces cell death. SULT2B1b KD also decreases androgen receptor (AR) activity and expression at mRNA and protein levels. While AR overexpression has no impact on SULT2B1b KD-mediated cell death, the addition of exogenous androgen is able to partially rescue the growth inhibition induced by SULT2B1b KD in LNCaP cells. These results suggest that SULT2B1b positively regulates the AR either through alterations in ligand availability or by interaction with critical coregulators that influence AR activity.

IMPLICATIONS

These findings provide evidence that SULT2B1b is a novel regulator of AR activity and cell growth in prostate cancer and should be further investigated for therapeutic potential. Mol Cancer Res; 14(9); 776-86. ©2016 AACR.

Metabolomic analysis of prostate cancer risk in a prospective cohort: The alpha-tocolpherol, beta-carotene cancer prevention (ATBC) study

Despite decades of concerted epidemiological research, relatively little is known about the etiology of prostate cancer. As genome-wide association studies have identified numerous genetic variants, so metabolomic profiling of blood and other tissues represents an agnostic, "broad-spectrum" approach for examining potential metabolic biomarkers of prostate cancer risk. To this end, we conducted a prospective analysis of prostate cancer within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort based on 200 cases (100 aggressive) and 200 controls (age- and blood collection date-matched) with fasting serum collected up to 20 years prior to case diagnoses. Ultrahigh performance liquid chromatography/mass spectroscopy and gas chromatography/mass spectroscopy identified 626 compounds detected in >95% of the men and the odds ratio per 1-standard deviation increase in log-metabolite levels and risk were estimated using conditional logistic regression. We observed strong inverse associations between energy and lipid metabolites and aggressive cancer (p = 0.018 and p = 0.041, respectively, for chemical class over-representation). Inositol-1-phosphate showed the strongest association (OR = 0.56, 95% CI = 0.39-0.81, p = 0.002) and glycerophospholipids and fatty acids were heavily represented; e.g., oleoyl-linoleoyl-glycerophosphoinositol (OR = 0.64, p = 0.004), 1-stearoylglycerophosphoglycerol (OR=0.65, p = 0.025), stearate (OR=0.65, p = 0.010) and docosadienoate (OR = 0.66, p = 0.014). Both alpha-ketoglutarate and citrate were associated with aggressive disease risk (OR = 0.69, 95% CI = 0.51-0.94, p = 0.02; OR = 0.69, 95% CI = 0.50-0.95, p = 0.02), as were elevated thyroxine and trimethylamine oxide (OR = 1.65, 95% CI = 1.08-2.54, p = 0.021; and OR = 1.36, 95% CI = 1.02-1.81, p = 0.039). Serum PSA adjustment did not alter the findings. Our data reveal several metabolomic leads that may have pathophysiological relevance to prostate carcinogenesis and should be examined through additional research.

Overlapping nongenomic and genomic actions of thyroid hormone and steroids

The genomic actions of thyroid hormone and steroids depend upon primary interactions of the hormones with their specific nuclear receptor proteins. Formation of nuclear co-activator or co-repressor complexes involving the liganded receptors subsequently result in transcriptional events-either activation or suppression-at genes that are specific targets of thyroid hormone or steroids. Nongenomic actions of thyroid hormone and steroids are in contrast initiated at binding sites on the plasma membrane or in cytoplasm or organelles and do not primarily require formation of intranuclear receptor protein-hormone complexes. Importantly, hormonal actions that begin nongenomically outside the nucleus often culminate in changes in nuclear transcriptional events that are regulated by both traditional intranuclear receptors as well as other nuclear transcription factors. In the case of thyroid hormone, the extranuclear receptor can be the classical "nuclear" thyroid receptor (TR), a TR isoform, or integrin αvβ3. In the case of steroid hormones, the membrane receptor is usually, but not always, the classical "nuclear" steroid receptor. This concept defines the paradigm of overlapping nongenomic and genomic hormone mechanisms of action. Here we review some examples of how extranuclear signaling by thyroid hormone and by estrogens and androgens modulates intranuclear hormone signaling to regulate a number of vital biological processes both in normal physiology and in cancer progression. We also point out that nongenomic actions of thyroid hormone may mimic effects of estrogen in certain tumors.

Systems pharmacology-based drug discovery for marine resources: an example using sea cucumber (Holothurians)

ETHNOPHARMACOLOGICAL RELEVANCE

Sea cucumber, a kind of marine animal, have long been utilized as tonic and traditional remedies in the Middle East and Asia because of its effectiveness against hypertension, asthma, rheumatism, cuts and burns, impotence, and constipation. In this study, an overall study performed on sea cucumber was used as an example to show drug discovery from marine resource by using systems pharmacology model. The value of marine natural resources has been extensively considered because these resources can be potentially used to treat and prevent human diseases. However, the discovery of drugs from oceans is difficult, because of complex environments in terms of composition and active mechanisms. Thus, a comprehensive systems approach which could discover active constituents and their targets from marine resource, understand the biological basis for their pharmacological properties is necessary.

MATERIALS AND METHODS

In this study, a feasible pharmacological model based on systems pharmacology was established to investigate marine medicine by incorporating active compound screening, target identification, and network and pathway analysis.

RESULTS

As a result, 106 candidate components of sea cucumber and 26 potential targets were identified. Furthermore, the functions of sea cucumber in health improvement and disease treatment were elucidated in a holistic way based on the established compound-target and target-disease networks, and incorporated pathways.

CONCLUSIONS

This study established a novel strategy that could be used to explore specific active mechanisms and discover new drugs from marine sources.

RaftProt: mammalian lipid raft proteome database

RaftProt (http://lipid-raft-database.di.uq.edu.au/) is a database of mammalian lipid raft-associated proteins as reported in high-throughput mass spectrometry studies. Lipid rafts are specialized membrane microdomains enriched in cholesterol and sphingolipids thought to act as dynamic signalling and sorting platforms. Given their fundamental roles in cellular regulation, there is a plethora of information on the size, composition and regulation of these membrane microdomains, including a large number of proteomics studies. To facilitate the mining and analysis of published lipid raft proteomics studies, we have developed a searchable database RaftProt. In addition to browsing the studies, performing basic queries by protein and gene names, searching experiments by cell, tissue and organisms; we have implemented several advanced features to facilitate data mining. To address the issue of potential bias due to biochemical preparation procedures used, we have captured the lipid raft preparation methods and implemented advanced search option for methodology and sample treatment conditions, such as cholesterol depletion. Furthermore, we have identified a list of high confidence proteins, and enabled searching only from this list of likely bona fide lipid raft proteins. Given the apparent biological importance of lipid raft and their associated proteins, this database would constitute a key resource for the scientific community.

MicroRNA-449 suppresses proliferation of hepatoma cell lines through blockade lipid metabolic pathway related to SIRT1

MicroRNA (miRNA or miR) inhibition of oncogenic related pathways has been shown to be a promising therapeutic approach for cancer. SIRT1 might be a promoter factor on tumorigenesis of hepatocellular carcinoma (HCC). However, the mechanism is unknown. We investigated whether miRNAs regulate the SIRT1 and its downstream SREBP-lipogenesis-cholesterogenesis metabolic pathway in hepatoma cells. Human hepatoma cells were transfected with miR-449 mimics and inhibitors, and the effects of miR-449 on cell proliferation was assessed. We identified the miRNAs, miR-449, that control lipogenesis and cholesterogenesis in hepatoma cells by inhibiting SIRT1 and SREBP-1c expression and downregulating their targeted genes, including fatty acid synthase (FASN) and 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR). MiR-449 repressed DNA synthesis, mitotic entry and proliferation of hepatoma cells. Restoration of miR-449 led to suppression of SIRT1 expression and liver tumorigenesis. The newly identified miRNAs, miR-449 represents a novel targeting mechanism for HCC therapy.

Expression profiles and functional associations of endogenous androgen receptor and caveolin-1 in prostate cancer cell lines

BACKGROUND

In prostate cancer (PCa) patients, the protein target for androgen deprivation and blockade therapies is androgen receptor (AR). AR interacts with many proteins that function to either co-activate or co-repress its activity. Caveolin-1 (Cav-1) is not found in normal prostatic epithelium, but is found in PCa, and may be an AR co-regulator protein.

METHODS

We investigated cell line-specific signatures and associations of endogenous AR and Cav-1 in six PCa cell lines of known androgen sensitivity: LNCaP (androgen sensitive); 22Rv1 (androgen responsive); PC3, DU145, and ALVA41 (androgen non-reliant); and RWPE1 (non-malignant). Protein and mRNA expression profiles were compared and electron microscopy used to identify cells with caveolar structures. For cell lines expressing both AR and Cav-1, knockdown techniques using small interfering RNA against AR or Cav-1 were used to test whether diminished expression of one affected the other. Co-sedimentation of AR and Cav-1 was used to test their association. A reporter assay for AR genomic activity was utilized following Cav-1 knockdown.

RESULTS

AR-expressing LNCaP and 22Rv1 cells had low endogenous Cav-1 mRNA and protein. Cell lines that expressed little or no AR (DU145, PC3, ALVA41, and RWPE1) expressed high endogenous levels of Cav-1. AR knockdown in LNCaP cells had little effect on Cav-1, but Cav-1 knockdown inhibited AR expression and genomic activity.

CONCLUSIONS

These data show endogenous AR and Cav-1 mRNA and protein expression is inversely related in PCa cells, with Cav-1 acting on the androgen/AR signaling axis possibly as an AR co-activator, demonstrated by diminished AR genomic activity following Cav-1 knockdown.

MicroRNA-185 and 342 inhibit tumorigenicity and induce apoptosis through blockade of the SREBP metabolic pathway in prostate cancer cells

MicroRNA (miRNA or miR) inhibition of oncogenic related pathways has been shown to be a promising therapeutic approach for cancer. Aberrant lipid and cholesterol metabolism is involved in prostate cancer development and progression to end-stage disease. We recently demonstrated that a key transcription factor for lipogenesis, sterol regulatory element-binding protein-1 (SREBP-1), induced fatty acid and lipid accumulation and androgen receptor (AR) transcriptional activity, and also promoted prostate cancer cell growth and castration resistance. SREBP-1 was overexpressed in human prostate cancer and castration-resistant patient specimens. These experimental and clinical results indicate that SREBP-1 is a potential oncogenic transcription factor in prostate cancer. In this study, we identified two miRNAs, miR-185 and 342, that control lipogenesis and cholesterogenesis in prostate cancer cells by inhibiting SREBP-1 and 2 expression and down-regulating their targeted genes, including fatty acid synthase (FASN) and 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR). Both miR-185 and 342 inhibited tumorigenicity, cell growth, migration and invasion in prostate cancer cell culture and xenograft models coincident with their blockade of lipogenesis and cholesterogenesis. Intrinsic miR-185 and 342 expression was significantly decreased in prostate cancer cells compared to non-cancerous epithelial cells. Restoration of miR-185 and 342 led to caspase-dependent apoptotic death in prostate cancer cells. The newly identified miRNAs, miR-185 and 342, represent a novel targeting mechanism for prostate cancer therapy.

Targeting membrane androgen receptors in tumors

INTRODUCTION

In the last decade androgen actions that are originated from non-genomic, rapid signaling have been described in a large number of cell models and tissues. These effects are initiated through the stimulation of membrane androgen-binding sites or receptors (mAR). Although the molecular identity of mARs remains elusive, their activation is known to trigger multiple non-genomic signaling cascades and to regulate numerous cell responses. In recent years specific interest is being paid to the role of mARs in tumors. Specifically, it was demonstrated that mAR activation by non-permeable testosterone conjugates induced potent anti-tumorigenic responses in prostate, breast, colon and glial tumors. In addition, in vivo animal studies further emphasized the potential clinical importance of these receptors.

AREAS COVERED

This review will summarize the current knowledge on the mAR-induced non-genomic, rapid androgen actions. It will focus on the molecular signaling pathways governed by mAR activation, discuss latest attempts to elucidate the molecular identity of mAR, address the plethora of cell responses initiated by mAR and evaluate the potential role of mAR and mAR-specific signaling as possible therapeutic targets in tumors.

EXPERT OPINION

mAR and mAR-induced specific signaling may represent novel therapeutic targets in tumors through the development of specific testosterone analogs.

Caveolin-1 and prostate cancer progression

Caveolin-1 was identified in the 1990s as a marker of aggressive prostate cancer. The caveolin-1 protein localizes to vesicular structures called caveolae and has been shown to bind and regulate many signaling proteins involved in oncogenesis. Caveolin-1 also has lipid binding properties and mediates aspects of cholesterol and fatty acid metabolism and can elicit biological responses in a paracrine manner when secreted. Caveolin-1 is also present in the serum of prostate cancer patients and circulating levels correlate with extent of disease. Current evidence indicates that increased expression of caveolin-1 in prostate adenocarcinoma cells and commensurate downregulation of the protein in prostate stroma, mediate progression to the castration-resistant phase of prostate cancer through diverse pathways. This chapter summarizes the current state of our understanding of the cellular and physiologic mechanisms in which caveolin-1 participates in the evolution of prostate cancer cell phenotypes.

Non-classic androgen actions in Sertoli cell membrane in whole seminiferous tubules: effects of nandrolone decanoate and catechin

Studies show a mechanism of action of testosterone, nandrolone and catechin as agonists of the membrane androgen receptor. The aim of this work is to investigate the non-classical effect of androgens and catechin in Sertoli cells from immature rats. The membrane potential of Sertoli cells in whole seminiferous tubules was recorded using a standard single microelectrode technique. It was performed a topical application of testosterone (1 μM), nandrolone (0.1, 0.5 and 1 μM) and the flavonoid catechin (0.1, 0.5 and 1 μM) alone and also after infusion with flutamide (1 μM), diazoxide (100 μM) or U73122 (1 μM). The immature testes were incubated for 5 min in KRb with (45)Ca(2+), with or without nandrolone (1 μM). The results were given as mean±SEM. The data were analyzed using ANOVA for repeated measures with Bonferroni post-test. Testosterone produces a depolarization in the membrane potential at 120 s after application. Catechin (1 μM) and nandrolone (1 μM) have shown a similar response to testosterone: depolarization at 120 s after the application. The same response of catechin and nandrolone was observed at different doses. The effects of testosterone, catechin and nandrolone were not affected after perfusion with flutamide. Perfusion with diazoxide and U73122 nullified the effect of nandrolone (1 μM) and catechin (1 μM). Nandrolone and testosterone increased (45)Ca(2+) uptake with or without flutamide within 5min. These results indicate that nandrolone and catechin act through a receptor on the plasmatic membrane, as well as testosterone, showing a non-classical pathway in Sertoli cells from immature rat testes.

Statin use and fatal prostate cancer: a matched case-control study

BACKGROUND

Statins are some of the most commonly prescribed medications in medical practice, and prostate cancer is the most common malignancy among men. Although there has been no consistent evidence that statins affect cancer incidence, including prostate cancer, several reports suggest they may decrease the rate of advanced prostate cancer. However, no study to date has specifically examined statin use and prostate cancer mortality. The authors conducted this population-based case-control investigation to examine this association.

METHODS

This was a matched case-control study. Cases were residents of New Jersey ages 55 to 79 years who died from prostate cancer between 1997 and 2000. The cases were matched individually to population-based controls by 5-year age group and race. Medication data were obtained identically for cases and controls from blinded medical chart review. Conditional logistic regression was used to adjust for confounders.

RESULTS

In total, 718 cases were identified, and cooperation was obtained from 77% of their spouses (N = 553). After a review of medical records, 387 men were eligible, and 380 were matched to a control. The unadjusted odds ratio was 0.49 (95% confidence interval, 0.34-0.70) and decreased to 0.37 (P < .0001) after adjusting for education, waist size, body mass index, comorbidities, and antihypertensive medication. There was little difference between lipophilic and hydrophilic statins, but more risk reduction was noted for high-potency statins (73%; P < .0001) compared with low-potency statins (31%; P = .32).

CONCLUSIONS

Statin use was associated with substantial protection against prostate cancer death, adding to the epidemiologic evidence for an inhibitory effect on prostate cancer.

Targeting cholesterol-rich microdomains to circumvent tamoxifen-resistant breast cancer

INTRODUCTION

Adjuvant treatment with tamoxifen substantially improves survival of women with estrogen-receptor positive (ER+) tumors. Tamoxifen resistance (TAMR) limits clinical benefit. RRR-α-tocopherol ether-linked acetic acid analogue (α-TEA) is a small bioactive lipid with potent anticancer activity. We evaluated the ability of α-TEA in the presence of tamoxifen to circumvent TAMR in human breast cancer cell lines.

METHODS

Two genotypically matched sets of TAM-sensitive (TAMS) and TAM-resistant (TAMR) human breast cancer cell lines were assessed for signal-transduction events with Western blotting, apoptosis induction with Annexin V-FITC/PI assays, and characterization of cholesterol-rich microdomains with fluorescence staining. Critical involvement of selected mediators was determined by using RNA interference and chemical inhibitors.

RESULTS

Growth-factor receptors (total and phosphorylated forms of HER-1 and HER-2), their downstream prosurvival mediators pAkt, pmTOR, and pERK1/2, phosphorylated form of estrogen receptor-α (pER-α at Ser-167 and Ser-118, and cholesterol-rich lipid microdomains were highly amplified in TAMR cell lines and enhanced by treatment with TAM. α-TEA disrupted cholesterol-rich microdomains, acted cooperatively with TAM to reduce prosurvival mediators, and induced DR5-mediated mitochondria-dependent apoptosis via an endoplasmic reticulum stress-triggered pro-death pJNK/CHOP/DR5 amplification loop. Furthermore, methyl-β-cyclodextrin (MβCD), a chemical disruptor of cholesterol rich microdomains, acted cooperatively with TAM to reduce prosurvival mediators and to induce apoptosis.

CONCLUSIONS

Data for the first time document that targeting cholesterol-rich lipid microdomains is a potential strategy to circumvent TAMR, and the combination of α-TEA + TAM can circumvent TAMR by suppression of prosurvival signaling via disruption of cholesterol-rich lipid microdomains and activation of apoptotic pathways via induction of endoplasmic reticulum stress.

Integrins regulate microtubule nucleating activity of centrosome through mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase (MEK/ERK) signaling

Microtubule nucleation is an essential step in the formation of the microtubule cytoskeleton. We recently showed that androgen and Src promote microtubule nucleation and γ-tubulin accumulation at the centrosome. Here, we explore the mechanisms by which androgen and Src regulate these processes and ask whether integrins play a role. We perturb integrin function by a tyrosine-to-alanine substitution in membrane-proximal NPIY motif in the integrin β1 tail and show that this mutant substantially decreases microtubule nucleation and γ-tubulin accumulation at the centrosome. Because androgen stimulation promotes the interaction of the androgen receptor with Src, resulting in PI3K/AKT and MEK/ERK signaling, we asked whether these pathways are inhibited by the mutant integrin and whether they regulate microtubule nucleation. Our results indicate that the formation of the androgen receptor-Src complex and the activation of downstream pathways are significantly suppressed when cells are adhered by the mutant integrin. Inhibitor studies indicate that microtubule nucleation requires MEK/ERK but not PI3K/AKT signaling. Importantly, the expression of activated RAF-1 is sufficient to rescue microtubule nucleation inhibited by the mutant integrin by promoting the centrosomal accumulation of γ-tubulin. Our data define a novel paradigm of integrin signaling, where integrins regulate microtubule nucleation by promoting the formation of androgen receptor-Src signaling complexes to activate the MEK/ERK signaling pathway.

Activation of androgen receptor, lipogenesis, and oxidative stress converged by SREBP-1 is responsible for regulating growth and progression of prostate cancer cells

We previously reported that sterol regulatory element-binding protein-1 (SREBP-1) is involved in the transcriptional regulation of androgen receptor (AR) and formation of fatty acid through altered expression of fatty acid synthase (FASN). In this article, we provide a new finding that SREBP-1 induced oxidative stress in prostate cancer cells through increased production of reactive oxygen species (ROS) and expression of NADPH oxidase 5 (Nox5). We have shown that (i) expression of SREBP-1 protein is positively associated with the clinical Gleason grades in human prostate cancer; (ii) genetic overexpression or knockdown of SREBP-1 in prostate cancer cells resulted in corresponding increased or decreased AR, FASN and Nox5 expression, fatty acid and lipid droplet accumulation, and ROS generation; and (iii) SREBP-1 induces and promotes the growth, migration, invasion, and castration-resistant progression of prostate cancer cells in vitro and in vivo. Our data show a novel molecular mechanism by which SREBP-1 promotes prostate cancer growth and progression through alterations in the concerted intracellular metabolic and signaling networks involving AR, lipogenesis, and ROS in prostate cancer cells.

Old issues and new perspectives on prostate cancer hormonal therapy: the molecular substratum

Secondary hormonal therapy is a treatment option in patients with castration-resistant prostate cancer (CRPC); however, it is underutilized and is room for optimization and improvement. In this context, androgen receptor (AR) is the Achilles' heel, being critically important and various mechanisms ranging from receptor mutations to secondary signaling pathways are responsible for some of the biological heterogeneity, demanding a multimodal approach. A comprehensive review of the peer-reviewed literature is performed on the topic of molecular mechanisms supporting secondary hormonal therapies, including expanded alternative hormonal therapies for CRPC. Essential concepts in clinical treatment of patients with progression on primary hormonal therapy are maintaining the castrate state, accounting for the intermittency phenomenon and sequentially using oral antiandrogens and adrenolytics heading to androgen depletion microenvironment. Survival prolongation, pain relief or measurable improvement in tumor-related symptoms should be persecuted and are considered to be a tangible benefit of obvious worth to the patient. Understanding the underlying molecular substratum is of paramount importance to hormonal therapy optimization in this context once current androgen-depletion strategies are incomplete, and residual androgens as well as alternative routes contribute to sustained AR activity and disease progression to a lethal phenotype. One or many mechanisms may be playing a role, even within the same patient and lastly are potential targets for treatment. Five fundamental mechanisms mediated through the AR to promote tumor growth (three of which depend on ligand signaling) added to the stem cell pathway must be recognized in CRPC. They are persistence of intratumoral androgens as a result of in situ steroidogenesis or adrenal source; AR mutations that allow promiscuous activation by otherwise nonsignaling ligands; wild-type AR gene amplification; alterations in AR coactivator-to-corepressor ratio that impact transcription; outlaw AR pathways that bypass the need for androgens by signaling through crosstalk with other ligand-bound receptors, cytokines, or transactivation of activated tyrosine kinase receptors in the cytosol.

Statins and prostate cancer: molecular and clinical aspects

The field of the potential applications of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) beyond their unambiguous cardiovascular beneficial effects is steadily increasing. In this regard, statins have also been shown to possess anti-inflammatory, immunomodulatory, antioxidant and growth inhibitory properties. Regarding their role in carcinogenesis, both preclinical and clinical studies report conflicting results. Intriguingly, accumulating evidence suggests that statins may relate to decreased prostate cancer incidence and recurrence risk. However, data from clinical studies seem to be still weak and are confounded by several factors. Nonetheless, preclinical data suggest that statins might exert a chemopreventive role against prostate cancer by inhibiting the proliferation and inducing apoptosis of prostate cancer cells and also inhibiting angiogenesis, inflammation and metastasis. Cholesterol lowering as well as statin pleiotropy through inhibition of the synthesis of isoprenoids have both been implicated in their anticancer properties. In this review, we discuss the preclinical and clinical evidence supporting the preventive or potentially harmful effects of statins on prostate tumourigenesis and conclude that statins should not be recommended for the prevention of prostate cancer development or progression based on the current data.

Direct visualization of phase separation induced by phenothiazine-type antipsychotic drugs in model lipid membranes

Lipid rafts constitute dynamic assemblies within a bilayer, engaged in, e.g., signal transduction, membrane trafficking and cell polarization. Despite wide interest in the process of domain formation in binary or ternary lipid model systems, only a limited number of papers are devoted to the influence of different additives on this process. In particular, works devoted to the role of drugs in raft formation are missing. In the present study, the influence of trifluoperazine, thioridazine and chlorpromazine on domain organization in raft-mimicking model membranes was investigated. Using giant unilamellar vesicles formed from an equimolar DOPC:sphingomyelin:cholesterol mixture, we found that phenothiazines elevated the number of domains, decreased their area and markedly increased the total length of the domain border. The impact of studied drugs on phase separation in the raft lipid mixture was also confirmed by Laurdan generalized polarization measurements. Alteration of domain organization induced by antipsychotic drugs was very likely to arise from selective accumulation of phenothiazines in interfacial regions between liquid ordered and liquid disordered domains. Interpretation of the results allowed us to demonstrate new aspects underlaying mechanisms of action of phenothiazine-type antipsychotic drugs. To the best of our knowledge, this is the first report demonstrating the influence of drugs on domain morphology directly visualized in giant unilamellar vesicles.

Characterization of androgen receptor structure and nucleocytoplasmic shuttling of the rice field eel

Androgen receptor (AR) plays a critical role in prostate cancer and male sexual differentiation. We have identified AR from a primitive vertebrate with a sex reversal characteristic, the rice field eel. AR of this species (eAR) is distinct from human AR, especially in the ligand binding domain (LBD), and its expression in gonads shows an increasing tendency during gonadal transformation from ovary via ovotestis to testis. eAR has a restricted androgen-dependent transactivation function after a nuclear translocation upon dihydrotestosterone exposure. A functional nuclear localization signal was further identified in the DNA binding domain and hinge region. Although nuclear export is CRM1-independent, eAR has a novel nuclear export signal, which is negatively charged, indicating that a nuclear export pathway may be mediated by electrostatic interaction. Further, our studies have identified critical sequences for ligand binding in the C terminus. A structure of three α-helices in the LBD has been conserved from eels to humans during vertebrate evolution, despite a distinct amino acid sequence. Mutation analysis confirmed that the LBD is essential for dihydrotestosterone-induced nuclear import of eAR and following transactivation function in the nucleus. In addition, eAR interacts with both Sox9a1 and Sox9a2, and their interaction regulates transactivation of eAR. Our data suggest that the primitive species conserves and especially acquires key novel domains, the nuclear export signal and LBD, for the eAR function in spite of a rapid sequence evolution.

Prostate specific antigen reduction following statin therapy: Mechanism of action and review of the literature

Prostate specific antigen (PSA) is a serine protease that is exclusively produced in the prostate, and its detection is the only laboratory test available for screening men for prostate cancer (PC). The interpretation of the assay is difficult since it is specific for prostate tissue and cellular growth, but not for PC. Pharmacologic therapy for hyperlipidemia, such as statins, may influence prostate cellular growth and subsequently PSA levels in patients. Dysregulated cellular growth in the prostate is mediated by inhibiting the rate-limiting pathway step in cholesterol synthesis, thereby decreasing isoprenylate intermediates, decreasing cholesterol rich cellular membrane domains, and down-regulating androgen and estrogen receptors. Statins, with variable efficacy, have been previously shown to inhibit cellular inflammation, angiogenesis, proliferation, migration/adhesion, and invasion, while promoting apoptosis in prostate cells by inhibiting the conversion of HMG-CoA to mevalonate. An individual statin's molecular structure, need for enzymatic conversion, bioavailability, and peripheral tissue concentration may partially account for differing properties. By inhibiting prostatic cellular growth and promoting apoptosis, statins may subsequently decrease PSA levels, an effect recently observed in cohorts. There is scientific and clinical evidence supporting the observations that statins are associated with an overall reduction in serum PSA in men, when used for greater than 6 months, and especially when used for greater than 2 years.

E3 ubiquitin protein ligase, E6-associated protein (E6-AP) regulates PI3K-Akt signaling and prostate cell growth

This study elucidates the role of E6-associated protein, E6-AP (a dual function steroid hormone receptor coactivator and ubiquitin-protein ligase) in the regulation of PI3K-Akt signaling pathway, prostate gland growth and proliferation. Here, we report the generation of transgenic mice and prostate cancer cell line, LNCaP cells that overexpress E6-AP protein. Using these models we show that the levels of total Akt and phosphorylated Akt (active Akt) are increased in E6-AP overexpressing prostate gland and LNCaP cells suggesting that E6-AP regulates the PI3K-Akt signaling pathway. The prostate glands in our transgenic mice are ~20% larger and produce preneoplastic lesions at the age of 18 months. Our data also suggest that E6-AP modulates PI3K-Akt signaling pathway by both androgen-independent and -dependent mechanisms. In the androgen-independent mechanism, E6-AP modulates PI3K-Akt signaling by regulating the protein levels of RhoA, a small GTPase, which is a negative regulator of the Akt signaling pathway. Further, we show that E6-AP, a known coactivator of AR, amplifies the androgen-dependent activation of PI3K-Akt signaling pathway. In addition, we show that stable overexpression of E6-AP in prostate cancer cells results in increased cell size and proliferation. Overall our data suggests that E6-AP regulates both the positive and negative modulators of the PI3K-Akt pathway in prostate cells which results in increased prostate cell growth, proliferation and decreased apoptosis.This article is part of a Special Issue entitled The 26S Proteasome: When degradation is just not enough!

Statin medication use and the risk of biochemical recurrence after radical prostatectomy: results from the Shared Equal Access Regional Cancer Hospital (SEARCH) Database

BACKGROUND

Although controversial, evidence suggests statins may reduce the risk of advanced prostate cancer (PC), and recently statin use was associated with prostate-specific antigen (PSA) reductions among men without PC. The authors sought to examine the association between statin use and PSA recurrence after radical prostatectomy (RP).

METHODS

The authors examined 1319 men treated with RP from the Shared Equal Access Regional Cancer Hospital (SEARCH) Database. Time to PSA recurrence was compared between users and nonusers of statin at surgery using Cox proportional hazards models adjusted for multiple clinical and pathological features.

RESULTS

In total, 236 (18%) men were taking statins at RP. Median follow-up was 24 months for statin users and 38 for nonusers. Statin users were older (P<.001) and underwent RP more recently (P<.001). Statin users were diagnosed at lower clinical stages (P=.009) and with lower PSA levels (P=.04). However, statin users tended to have higher biopsy Gleason scores (P=.002). After adjusting for multiple clinical and pathological factors, statin use was associated with a 30% lower risk of PSA recurrence (hazard ratio "HR", 0.70; 95% confidence interval "CI", 0.50-0.97; P=.03), which was dose dependent (relative to no statin use; dose equivalent<simvastatin 20 mg: HR, 1.08; 95% CI, 0.66-1.73; P=.78; dose equivalent=simvastatin 20 mg: HR, 0.57; 95% CI, 0.32-1.00; P=.05; dose equivalent>simvastatin 20 mg: HR, 0.50; 95% CI, 0.27-0.93; P=.03).

CONCLUSIONS

In this cohort of men undergoing RP, statin use was associated with a dose-dependent reduction in the risk of biochemical recurrence. If confirmed in other studies, these findings suggest statins may slow PC progression after RP.

Selective concomitant inhibition of mTORC1 and mTORC2 activity in estrogen receptor negative breast cancer cells by BN107 and oleanolic acid

Hormonal, targeted and chemotherapeutic strategies largely depend on the expression of their cognate receptors and are often accompanied by intolerable toxicities. Effective and less toxic therapies for estrogen receptor negative (ER-) breast cancers are urgently needed. Here, we present the potential molecular mechanisms mediating the selective pro-apoptotic effect induced by BN107 and its principle terpene, oleanolic acid (OA), on ER- breast cancer cells. A panel of breast cancer cell lines was examined and the most significant cytotoxic effect was observed in ER- breast lines. Apoptosis was the major cellular pathway mediating the cytotoxicity of BN107. We demonstrated that sensitivity to BN107 was correlated to the status of ERalpha. Specifically, the presence of functional ERalpha protected cells from BN107-induced apoptosis and absence of ERalpha increased the sensitivity. BN107, an extract rich in OA derivatives, caused rapid alterations in cholesterol homeostasis, presumably by depleting cholesterol in lipid rafts (LRs), which subsequently interfered with signaling mediated by LRs. We showed that BN107 or OA treatment in ER- breast cancer cells resulted in rapid and specific inhibition of LR-mediated survival signaling, namely mTORC1 and mTORC2 activities, by decreasing the levels of the mTOR/FRAP1, RAPTOR and RICTOR. Cotreatment with cholesterol abolished the proapoptotic effect and restored the disrupted mTOR activities. This is the first report demonstrating possible concomitant inhibition of both mTORC1 and mTORC2 activities by modulating the levels of protein constituents present in these signaling complexes, and thus provides a basis for future development of OA-based mTOR inhibitors.

Redefining hormone resistance in prostate cancer

Prostate cancer relies on signaling through the androgen receptor (AR) for maintenance and progression; and androgen-deprivation therapy remains a cornerstone of treatment for advanced prostate cancer. An effective clinical classification of prostate cancer should account for the extent of the disease as well as the mechanisms that are driving the growth of the tumor. The previous terms hormone-sensitive and hormone-refractory described response to treatment. It has become clear that these terms do not reflect the mechanism of disease relapse; however over the last decade there has been a better understanding of androgen-receptor mediated signaling effects and incomplete suppression of androgens in prostate cancer. The Prostate Cancer Clinical Trials Working Group 2 (PCWG2) now recommends addressing the spectrum of clinical states based on castration status as this ligand-centered terminology can more accurately describe the patients' disease, and ultimately provides a useful framework for patient management and drug development. Optimized use of androgen-deprivation therapy, low molecular weight inhibitors of adrenal androgen biosynthesis, and new AR antagonists are promising new therapeutics that can further define the meaning of castrate state. As hormone resistance is redefined to include patients that are refractory to treatments that ablate adrenal and in situ tumoral androgens, a meaningful new clinical state in patients will be forged. We propose a model for incorporating these patients into the current PCWG2 conceptualization of the disease.

Functional membrane androgen receptors in colon tumors trigger pro-apoptotic responses in vitro and reduce drastically tumor incidence in vivo

BACKGROUND

Membrane androgen receptors (mAR) have been implicated in the regulation of cell growth, motility and apoptosis in prostate and breast cancer. Here we analyzed mAR expression and function in colon cancer.

RESULTS

Using fluorescent mAR ligands we showed specific membrane staining in colon cell lines and mouse xenograft tumor tissues, while membrane staining was undetectable in healthy mouse colon tissues and non-transformed intestinal cells. Saturation/displacement assays revealed time- and concentration-dependent specific binding for testosterone with a KD of 2.9 nM. Stimulation of colon mAR by testosterone albumin conjugates induced rapid cytoskeleton reorganization and apoptotic responses, even in the presence of anti-androgens. The actin cytoskeleton drug cytochalasin B effectively inhibited the pro-apoptotic responses and caspase-3 activation. Interestingly, in vivo studies revealed that mAR activation resulted in a 65% reduction of tumor incidence in chemically induced Balb/c mice colon tumors.

CONCLUSION

Our results demonstrate for the first time that functional mARs are predominantly expressed in colon tumors and that their activation results in induction of anti-tumor responses in vitro and extensive reduction of tumor incidence in vivo.

Pleiotropic functional properties of androgen receptor mutants in prostate cancer

The androgen receptor (AR) signaling pathway plays an important role during the development of the normal prostate gland, but also during the progression of prostate cancer on androgen ablation therapy. Mutations in the AR gene emerge to keep active the AR signaling pathway and to support prostate cancer cells growth and survival despite the low levels of circulating androgens. Indeed, mutations affecting the ligand binding domain (LBD) of the AR have been shown to generate so-called "promiscuous" receptors that present widened ligand specificity and allow the stimulation of these receptors by a larger spectrum of endogenous hormones. Another class of mutations, arising in the amino-terminal domain (NTD) of the receptor, modulate AR interactions with coregulators involved in cell proliferation regulation. Besides characteristics of these well-known types of mutations, the properties of other classes of AR mutants recently described in prostate cancer are currently under investigation. Most interestingly, in addition to their potential role in the mechanisms which allow prostate cancer cells to escape androgen ablation therapy, data suggest that certain AR mutations are present early in the natural history of the disease and may play a role in many aspects of prostate cancer progression. Surprisingly, singular truncated AR devoid of their carboxy-terminal end (CTE) region seem to exert specific paracrine effects and to induce a clonal cooperation with neighboring prostate cancer cells, which may facilitate both the invasion and metastasis processes. In this article, we review the functional properties of different classes of AR mutants and their potential impact on the natural history of prostate cancer. Hum Mutat 0, 1-14, 2008. (c) 2008 Wiley-Liss, Inc.

Membrane androgen receptor activation in prostate and breast tumor cells: molecular signaling and clinical impact

In recent years, membrane androgen receptors (mARs) have been identified in prostate and breast tumor cells, and their activation by specific mAR ligands was linked to the regulation of crucial cell responses, such as cell growth, motility, and apoptosis. Analysis of the molecular signals triggered by mAR in the presence of anti-androgens has clearly differentiated mAR-dependent biological actions from those induced by the activation of the classical intracellular androgen receptors (iARs). In this review, we summarize the specific cellular events attributed to mAR activation and the experimental results on distinct non-genomic signaling cascades operating in various tumor cells independently of the iAR. Furthermore, we discuss the crucial role of actin cytoskeleton organization and signaling in mediating mAR responses. Finally, we assess the clinical impact of the reported mAR-induced apoptotic regression of prostate cancer cells both in vitro and in vivo and discuss the potential role of mAR as a novel therapeutic target.

Membrane androgen receptor activation triggers down-regulation of PI-3K/Akt/NF-kappaB activity and induces apoptotic responses via Bad, FasL and caspase-3 in DU145 prostate cancer cells

Background

Recently we have reported membrane androgen receptors-induced apoptotic regression of prostate cancer cells regulated by Rho/ROCK/actin signaling. In the present study we explored the specificity of these receptors and we analyzed downstream effectors controlling survival and apoptosis in hormone refractory DU145-prostate cancer cells stimulated with membrane androgen receptor-selective agonists.

Results

Using membrane impermeable conjugates of serum albumin covalently linked to testosterone, we show here down-regulation of the activity of pro-survival gene products, namely PI-3K/Akt and NF-κB, in DU145 cells. Testosterone-albumin conjugates further induced FasL expression. A FasL blocking peptide abrogated membrane androgen receptors-dependent apoptosis. In addition, testosterone-albumin conjugates increased caspase-3 and Bad protein activity. The actin cytoskeleton drug cytochalasin B and the ROCK inhibitor Y-27632 inhibited FasL induction and caspase-3 activation, indicating that the newly identified Rho/Rock/actin signaling may regulate the downstream pro-apoptotic effectors in DU145 cells. Finally, other steroids or steroid-albumin conjugates did not interfere with these receptors indicating testosterone specificity.

Conclusion

Collectively, our results provide novel mechanistic insights pointing to specific pro-apoptotic molecules controlling membrane androgen receptors-induced apoptotic regression of prostate cancer cells and corroborate previously published observations on the potential use of membrane androgen receptor-agonists as novel anti-tumor agents in prostate cancer.