Nitric oxide-mediated inhibition of androgen receptor activity: possible implications for prostate cancer progression

In silico exploration of anti-prostate cancer compounds from differential expressed genes

Prostate cancer (PCa) is a complex and biologically diverse disease with no curative treatment options at present. This study aims to utilize computational methods to explore potential anti-PCa compounds based on differentially expressed genes (DEGs), with the goal of identifying novel therapeutic indications or repurposing existing drugs. The methods employed in this study include DEGs-to-drug prediction, pharmacokinetics prediction, target prediction, network analysis, and molecular docking. The findings revealed a total of 79 upregulated DEGs and 110 downregulated DEGs in PCa, which were used to identify drug compounds capable of reversing the dysregulated conditions (dexverapamil, emetine, parthenolide, dobutamine, terfenadine, pimozide, mefloquine, ellipticine, and trifluoperazine) at a threshold probability of 20% on several molecular targets, such as serotonin receptors 2a/2b/2c, HERG protein, adrenergic receptors alpha-1a/2a, dopamine D3 receptor, inducible nitric oxide synthase (iNOS), epidermal growth factor receptor erbB1 (EGFR), tyrosine-protein kinases, and C-C chemokine receptor type 5 (CCR5). Molecular docking analysis revealed that terfenadine binding to inducible nitric oxide synthase (-7.833 kcal.mol-1) and pimozide binding to HERG (-7.636 kcal.mol-1). Overall, binding energy ΔGbind (Total) at 0 ns was lower than that of 100 ns for both the Terfenadine-iNOS complex (-101.707 to -103.302 kcal.mol-1) and Ellipticine-TOPIIα complex (-42.229 to -58.780 kcal.mol-1). In conclusion, this study provides insight on molecular targets that could possibly contribute to the molecular mechanisms underlying PCa. Further preclinical and clinical studies are required to validate the therapeutic effectiveness of these identified drugs in PCa disease.

Stage-Specific Effect of Inositol Hexaphosphate on Cancer Stem Cell Pool during Growth and Progression of Prostate Tumorigenesis in TRAMP Model

Herein, we assessed the stage-specific efficacy of inositol hexaphosphate (IP6, phytic acid), a bioactive food component, on prostate cancer (PCa) growth and progression in a transgenic mouse model of prostate cancer (TRAMP). Starting at 4, 12, 20, and 30 weeks of age, male TRAMP mice were fed either regular drinking water or 2% IP6 in water for ~8-15 weeks. Pathological assessments at study endpoint indicated that tumor grade is arrested at earlier stages by IP6 treatment; IP6 also prevented progression to more advanced forms of the disease (~55-70% decrease in moderately and poorly differentiated adenocarcinoma incidence was observed in advanced stage TRAMP cohorts). Next, we determined whether the protective effects of IP6 are mediated via its effect on the expansion of the cancer stem cells (CSCs) pool; results indicated that the anti-PCa effects of IP6 are associated with its potential to eradicate the PCa CSC pool in TRAMP prostate tumors. Furthermore, in vitro assays corroborated the above findings as IP6 decreased the % of floating PC-3 prostaspheres (self-renewal of CSCs) by ~90%. Together, these findings suggest the multifaceted chemopreventive-translational potential of IP6 intervention in suppressing the growth and progression of PCa and controlling this malignancy at an early stage.

Bystander effect in photosensitized prostate cancer cells with a different grade of malignancy: The role of nitric oxide

Photodynamic therapy (PDT) is a therapeutic modality based on the simultaneous action of three elements: photosensitizer, light and oxygen. This triad generates singlet oxygen and reactive oxygen species that can reduce the mass of a tumor. PDT is also able to stimulate iNOS, the enzyme that generates nitric oxide (NO). The role of NO in PDT-treated cancer cells has been investigated in several studies. They showed that low iNOS/NO levels stimulate signaling pathways that promote tumor survival, while high iNOS/NO levels arrest tumor growth. There is increasing evidence that ROS/RNS control both proliferation and migration of cells in the vicinity of PDT-treated tumor cells (so-called bystander cells). In this work, we addressed the question of how NO, which is generated by weak PDT, affects bystander cells. We used a conditioned medium: medium of PDT-treated tumor cells containing the stressors produced by the cells was added to untreated cells mimicking the neighboring bystander cells to investigate whether the conditioned medium affects cell proliferation. We found that low-level NO in prostate cancer cells affects the bystander tumor cells in a manner that depends on their malignancy grade.

Chronic nitric oxide exposure induces prostate cell carcinogenesis, involving genetic instability and a pro-tumorigenic secretory phenotype

Prostate cancer is a leading cause of cancer death in men. Inflammation and overexpression of inducible nitric oxide synthase (NOS2) have been implicated in prostate carcinogenesis. We aimed to explore the hypothesis that nitric oxide NO exerts pro-tumorigenic effects on prostate cells at physiologically relevant levels contributing to carcinogenesis. We investigated the impact of acute exposure of normal immortalised prostate cells (RWPE-1) to NO on cell proliferation and activation of DNA damage repair pathways. Furthermore we investigated the long term effects of chronic NO exposure on RWPE-1 cell migration and invasion potential and hallmarks of transformation. Our results demonstrate that NO induces DNA damage as indicated by γH2AX foci and p53 activation resulting in a G1/S phase block and activation of 53BP1 DNA damage repair protein. Long term adaption to NO results in increased migration and invasion potential, acquisition of anchorage independent growth and increased resistance to chemotherapy. This was recapitulated in PC3 and DU145 prostate cancer cells which upon chronic exposure to NO displayed increased cell migration, colony formation and increased resistance to chemotherapeutics. These findings indicate that NO may play a key role in the development of prostate cancer and the acquisition of an aggressive metastatic phenotype.

Gasotransmitters in the tumor microenvironment: Impacts on cancer chemotherapy (Review)

Nitric oxide, carbon monoxide and hydrogen sulfide are three endogenous gasotransmitters that serve a role in regulating normal and pathological cellular activities. They can stimulate or inhibit cancer cell proliferation and invasion, as well as interfere with cancer cell responses to drug treatments. Understanding the molecular pathways governing the interactions between these gases and the tumor microenvironment can be utilized for the identification of a novel technique to disrupt cancer cell interactions and may contribute to the conception of effective and safe cancer therapy strategies. The present review discusses the effects of these gases in modulating the action of chemotherapies, as well as prospective pharmacological and therapeutic interfering approaches. A deeper knowledge of the mechanisms that underpin the cellular and pharmacological effects, as well as interactions, of each of the three gases could pave the way for therapeutic treatments and translational research.

Nitric oxide favours tumour-promoting inflammation through mitochondria-dependent and -independent actions on macrophages

Production of nitric oxide (NO) has been demonstrated in several malignancies, however its role remains not fully understood, specifically in relation to the metabolic and functional implications that it may have on immune cells participating in tumorigenesis. Here, we show that inducible NO synthase (iNOS) is expressed in cancers of the colon and the prostate, mainly by tumour cells, and NO generation is evidenced by widespread nitrotyrosine (NT) staining in tumour tissue. Furthermore, presence of NT is observed in the majority of tumour-associated macrophages (TAMs), despite low iNOS expression by these cells, suggesting that NO from the tumour microenvironment affects TAMs. Indeed, using a co-culture model, we demonstrate that NO produced by colon and prostate cancer cells is sufficient to induce NT formation in neighbouring macrophages. Moreover, exposure to exogenous NO promotes mitochondria-dependent and -independent changes in macrophages, which orientate their polarity towards an enhanced pro-inflammatory phenotype, whilst decreasing antigen-presenting function and wound healing capacity. Abrogating endogenous NO generation in murine macrophages, on the other hand, decreases their pro-inflammatory phenotype. These results suggest that the presence of NO in cancer may regulate TAM metabolism and function, favouring the persistence of inflammation, impairing healing and subverting adaptive immunity responses.

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Nitric oxide (NO) from the cancer microenvironment acts on tumour-associated macrophages (TAMs).

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NO induces a phenotypic shift in macrophages through mitochondria-dependent and -independent pathways.

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NO favours pro-inflammatory cytokine production whilst decreasing macrophage function as antigen presenting cell.

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NO impairs repair function of macrophages.

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Presence of NO in cancer may regulate TAM metabolism and function, favouring tumour-promoting inflammation.

Testosterone in COVID-19: An Adversary Bane or Comrade Boon

COVID-19 is a pandemic disease caused by severe acute respiratory coronavirus 2 (SARS-CoV-2), which leads to pulmonary manifestations like acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). In addition, COVID-19 may cause extra-pulmonary manifestation such as testicular injury. Both high and low levels of testosterone could affect the severity of COVID-19. Herein, there is substantial controversy regarding the potential role of testosterone in SARS-CoV-2 infection and COVID-19 severity. Therefore, the present study aimed to review and elucidate the assorted view of preponderance regarding the beneficial and harmful effects of testosterone in COVID-19. A related literature search in PubMed, Scopus, Web of Science, Google Scholar, and Science Direct was done. All published articles related to the role of testosterone and COVID-19 were included in this mini-review. The beneficial effects of testosterone in COVID-19 are through inhibition of pro-inflammatory cytokines, augmentation of anti-inflammatory cytokines, modulation of the immune response, attenuation of oxidative stress, and endothelial dysfunction. However, its harmful effects in COVID-19 are due to augmentation of transmembrane protease serine 2 (TMPRSS2), which is essential for cleaving and activating SARS-CoV-2 spike protein during acute SARS-CoV-2 infection. Most published studies illustrated that low testosterone levels are linked to COVID-19 severity. A low testosterone level in COVID-19 is mainly due to testicular injury, the primary source of testosterone.

The probable destructive mechanisms behind COVID-19 on male reproduction system and fertility

PURPOSE

The present study aims to summarize the current understanding of probable mechanisms and claims of adverse effects of SARS-CoV-2 on male fertility potential.

METHODS

Our search was including original articles, reviews, guidelines, letters to the editor, comments on guidelines, and editorials, regarding the male reproductive system. We used the words SARS-CoV-2, coronavirus, severe acute respiratory syndrome coronavirus 2, "2019 ncov," testis, sperm, male factor infertility, fertility treatment, semen, assisted reproductive technology (ART), sexual transmission, and ACE2.

RESULTS

Data showed coronavirus affects men more than women because of more expression of 2019 nCoV receptors (ACE2 and TMPRSS2) in testicular cells. Also, "Bioinformatics Analysis" suggests that sperm production may be damaged, since "Pseudo Time Analysis" has shown disruption in spermatogenesis. "Gene Ontology" (GO) showed an increase in viral reproduction and a decrease in sperm production-related terms. Recently, SARS-COV-2 mRNA and protein were detected in the semen of patients that had recovered from SARS-CoV-2 infection. Therefore, the probable disruption of blood-testis barrier (BTB) in febrile diseases is suspected in the acute phase of the disease enabling viral entry into the testes. Not only is spermatogenesis disturbed, but also disturbs gonadotropin, androgens, and testosterone secretion during SARS-CoV-2 infection. No sexual transmission has been reported yet; however, detection of the virus in semen still makes the sexual transmission an open question.

CONCLUSION

There is a concern that male fertility may be disturbed after the SARS-CoV-2 infection. Therefore, follow-up of the reproductive functions and male fertility may be necessary in recovered cases, especially in aged men.

The Yin Yang Role of Nitric Oxide in Prostate Cancer

Nitric oxide (NO) is a ubiquitous signaling molecule in the human body with well-known roles in many different processes and organ systems. In cancer, the two-concentrations hypothesis of NO has dictated that low levels of NO are cancer promoting, while high levels of NO are protective against cancer. Although prostate cancer is a hormonally driven malignancy, research has been shifting away from androgen-responsive epithelial cells and evolving to focus on NO therapies, the tumor microenvironment (TME), and inflammation. NO is reported to be able to inhibit activity of the androgen receptor. This may prevent prostate growth, but low levels of NO could conversely select for castration-resistant prostate cells, creating an aggressive cancer phenotype. At high levels, nitrosative stress created from NO overproduction can be protective against prostate neoplasia. In this review, we discuss development and possibilities of NO-based therapies for prostate cancer.

Current Advances of Nitric Oxide in Cancer and Anticancer Therapeutics

Nitric oxide (NO) is a short-lived, ubiquitous signaling molecule that affects numerous critical functions in the body. There are markedly conflicting findings in the literature regarding the bimodal effects of NO in carcinogenesis and tumor progression, which has important consequences for treatment. Several preclinical and clinical studies have suggested that both pro- and antitumorigenic effects of NO depend on multiple aspects, including, but not limited to, tissue of generation, the level of production, the oxidative/reductive (redox) environment in which this radical is generated, the presence or absence of NO transduction elements, and the tumor microenvironment. Generally, there are four major categories of NO-based anticancer therapies: NO donors, phosphodiesterase inhibitors (PDE-i), soluble guanylyl cyclase (sGC) activators, and immunomodulators. Of these, NO donors are well studied, well characterized, and also the most promising. In this study, we review the current knowledge in this area, with an emphasis placed on the role of NO as an anticancer therapy and dysregulated molecular interactions during the evolution of cancer, highlighting the strategies that may aid in the targeting of cancer.

Sex differences in COVID-19: the role of androgens in disease severity and progression

PURPOSE

Throughout the SARS-CoV2 pandemic, multiple reports show higher percentages of hospitalization, morbidity, and mortality among men than women, indicating that men are more affected by COVID-19. The pathophysiology of this difference is yet not established, but recent studies suggest that sex hormones may influence the viral infectivity process. Here, we review the current evidence of androgen sensitivity as a decisive factor for COVID-19 disease severity.

METHODS

Relevant literature investigating the role of androgens in COVID-19 was assessed. Further, we describe several drugs suggested as beneficial for COVID-19 treatment related to androgen pathways. Lastly, we looked at androgen sensitivity as a predictor for COVID-19 progression and ongoing clinical trials on androgen suppression therapies as a line of treatment.

RESULTS

SARS-COV2 virus spike proteins utilize Transmembrane protease serine 2 (TMPRSS2) for host entry. Androgen receptors are transcription promoters for TMPRSS2 and can, therefore, facilitate SARS-COV2 entry. Variants in the androgen receptor gene correlate with androgen sensitivity and are implicated in diseases like androgenetic alopecia and prostate cancer, conditions that have been associated with worse COVID-19 outcomes and hospitalization.

CONCLUSION

Androgen's TMPRSS2-mediated actions might explain both the low fatalities observed in prepubertal children and the differences between sexes regarding SARS-COV2 infection. Androgen sensitivity may be a critical factor in determining COVID-19 disease severity, and sensitivity tests can, therefore, help in predicting patient outcomes.

Testosterone in COVID-19 - Foe, Friend or Fatal Victim?

The evidence derived from observational studies suggests male gender, diabetes and central obesity to be risk factors associated with an increased COVID-19-related case fatality. The precise pathophysiology behind this gender difference in mortality outcomes remains unclear at this stage, although it is worth exploring a possible role of testosterone as one of the contributory factors. The observed role of androgens in transcription of transmembrane protease serine-2, which facilitates COVID-19 anchoring to angiotensin-converting enzyme 2 cell surface receptors, seems to suggest that higher testosterone levels might be detrimental for outcomes. On the other hand, men with type 2 diabetes mellitus and central obesity have an increased prevalence of hypogonadotropic hypogonadism, with inhibition of gonadotropin-releasing hormone secretion induced by inflammatory cytokines being one of the postulated mechanisms. The increased COVID-19 case fatality in this cohort might perhaps reflect an underlying pro-inflammatory state, with low testosterone levels being either a surrogate marker of a poor metabolic state or playing a more active role in propagation of inflammation and thrombosis.

A preliminary observation: Male pattern hair loss among hospitalized COVID-19 patients in Spain - A potential clue to the role of androgens in COVID-19 severity

A preliminary observation of high frequency of male pattern hair loss among admitted COVID-19 patients and suggest that androgen expression might be a clue to COVID-19 severity.

Evaluation of apoptotic effects of mPEG-b-PLGA coated iron oxide nanoparticles as a eupatorin carrier on DU-145 and LNCaP human prostate cancer cell lines

Many studies have so far confirmed the efficiency of phytochemicals in the treatment of prostate cancer. Eupatorin, a flavonoid with a wide range of phytomedical activities, suppresses proliferation of and induces apoptosis of multiple cancer cell lines. However, low solubility, poor bioavailability, and rapid degradation limit its efficacy. The aim of our study was to evaluate whether the use of mPEG-b-poly (lactic-co-glycolic) acid (PLGA) coated iron oxide nanoparticles as a carrier could enhance the therapeutic efficacy of eupatorin in DU-145 and LNcaP human prostate cancer cell lines. Nanoparticles were prepared by the co-precipitation method and were fully characterized for morphology, surface charge, particle size, drug loading, encapsulation efficiency and in vitro drug-release profile. The inhibitory effect of nanoparticles on cell viability was evaluated by MTT test. Apoptosis was then determined by Hoechest staining, cell cycle analysis, NO production, annexin/propidium iodide (PI) assay, and Western blotting. The results indicated that eupatorin was successfully entrapped in Fe₃O₄@mPEG-b-PLGA nanoparticles with an efficacy of (90.99 ± 2.1)%. The nanoparticle’s size was around (58.5 ± 4) nm with a negative surface charge [(−34.16 ± 1.3) mV]. In vitro release investigation showed a 30% initial burst release of eupatorin in 24 h, followed by sustained release over 200 h. The MTT assay indicated that eupatorin-loaded Fe₃O₄@mPEG-b-PLGA nanoparticles exhibited a significant decrease in the growth rate of DU-145 and LNcaP cells and their IC50 concentrations were 100 μM and 75 μM, respectively. Next, apoptosis was confirmed by nuclear condensation, enhancement of cell population in the sub-G1 phase and increased NO level. Annexin/PI analysis demonstrated that eupatorin-loaded Fe₃O₄@mPEG-b-PLGA nanoparticles could increase apoptosis and decrease necrosis frequency. Finally, Western blotting analysis confirmed these results and showed that Bax/Bcl-2 ratio and the cleaved caspase-3 level were up-regulated by the designing nanoparticles. Encapsulation of eupatorin in Fe₃O₄@mPEG-b-PLGA nanoparticles increased its anticancer effects in prostate cancer cell lines as compared to free eupatorin. Based on these results, this formulation can provide a sustained eupatorin-delivery system for cancer treatment with the drug remaining active at a significantly lower dose, making it a suitable candidate for pharmacological uses.

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In the current study, Eupatorin was efficiently encapsulated in mPEG-b-PLGA coated iron oxide nanoparticles.

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The nanoparticles bypass the limitations and provide a sustained release of Eupatorin into the human prostate cancer cell.

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The designed nanoparticles can be more effective in inhibiting cancer cell growth as compared to free form.

Alterations of tumor microenvironment by nitric oxide impedes castration-resistant prostate cancer growth

Immune targeted therapy of nitric oxide (NO) synthases are being considered as a potential frontline therapeutic to treat patients diagnosed with locally advanced and metastatic prostate cancer. However, the role of NO in castration-resistant prostate cancer (CRPC) is controversial because NO can increase in nitrosative stress while simultaneously possessing antiinflammatory properties. Accordingly, we tested the hypothesis that increased NO will lead to tumor suppression of CRPC through tumor microenvironment. S-nitrosoglutathione (GSNO), an NO donor, decreased the tumor burden in murine model of CRPC by targeting tumors in a cell nonautonomous manner. GSNO inhibited both the abundance of antiinflammatory (M2) macrophages and expression of pERK, indicating that tumor-associated macrophages activity is influenced by NO. Additionally, GSNO decreased IL-34, indicating suppression of tumor-associated macrophage differentiation. Cytokine profiling of CRPC tumor grafts exposed to GSNO revealed a significant decrease in expression of G-CSF and M-CSF compared with grafts not exposed to GSNO. We verified the durability of NO on CRPC tumor suppression by using secondary xenograft murine models. This study validates the significance of NO on inhibition of CRPC tumors through tumor microenvironment (TME). These findings may facilitate the development of previously unidentified NO-based therapy for CRPC.

Identification of an IL-1-induced gene expression pattern in AR+ PCa cells that mimics the molecular phenotype of AR- PCa cells

BACKGROUND

In immunosurveillance, bone-derived immune cells infiltrate the tumor and secrete inflammatory cytokines to destroy cancer cells. However, cancer cells have evolved mechanisms to usurp inflammatory cytokines to promote tumor progression. In particular, the inflammatory cytokine, interleukin-1 (IL-1), is elevated in prostate cancer (PCa) patient tissue and serum, and promotes PCa bone metastasis. IL-1 also represses androgen receptor (AR) accumulation and activity in PCa cells, yet the cells remain viable and tumorigenic; suggesting that IL-1 may also contribute to AR-targeted therapy resistance. Furthermore, IL-1 and AR protein levels negatively correlate in PCa tumor cells. Taken together, we hypothesize that IL-1 reprograms AR positive (AR⁺ ) PCa cells into AR negative (AR^- ) PCa cells that co-opt IL-1 signaling to ensure AR-independent survival and tumor progression in the inflammatory tumor microenvironment.

METHODS

LNCaP and PC3 PCa cells were treated with IL-1β or HS-5 bone marrow stromal cell (BMSC) conditioned medium and analyzed by RNA sequencing and RT-QPCR. To verify genes identified by RNA sequencing, LNCaP, MDA-PCa-2b, PC3, and DU145 PCa cell lines were treated with the IL-1 family members, IL-1α or IL-1β, or exposed to HS-5 BMSC in the presence or absence of Interleukin-1 Receptor Antagonist (IL-1RA). Treated cells were analyzed by western blot and/or RT-QPCR.

RESULTS

Comparative analysis of sequencing data from the AR⁺ LNCaP PCa cell line versus the AR^- PC3 PCa cell line reveals an IL-1-conferred gene suite in LNCaP cells that is constitutive in PC3 cells. Bioinformatics analysis of the IL-1 regulated gene suite revealed that inflammatory and immune response pathways are primarily elicited; likely facilitating PCa cell survival and tumorigenicity in an inflammatory tumor microenvironment.

CONCLUSIONS

Our data supports that IL-1 reprograms AR⁺ PCa cells to mimic AR^- PCa gene expression patterns that favor AR-targeted treatment resistance and cell survival.

High inducible nitric oxide synthase in prostate tumor epithelium is associated with lethal prostate cancer

OBJECTIVE

The aim of this study was to investigate the role of inducible nitric oxide synthase (iNOS) in lethal prostate cancer (PCa) by studying the iNOS immunoreactivity in tumor tissue from men diagnosed with localized PCa.

MATERIALS AND METHODS

This study is nested within a cohort of men diagnosed with incidental PCa undergoing transurethral resection of the prostate (the Swedish Watchful Waiting Cohort). To investigate molecular determinants of lethal PCa, men who died from PCa (n = 132) were selected as cases; controls (n = 168) comprised men with PCa who survived for at least 10 years without dying from PCa during follow-up. The immunoreactivity of iNOS in prostate tumor epithelial cells and in cells of the surrounding stroma was scored as low/negative, moderate or high. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) for lethal PCa according to iNOS category.

RESULTS

There was no association between iNOS immunoreactivity in stroma and lethal disease. However, when comparing high versus low/negative iNOS immunoreactivity in epithelial cells, the OR for lethal PCa was 3.80 (95% CI 1.45-9.97).

CONCLUSION

Patients with localized PCa have variable outcomes, especially those with moderately differentiated tumors. Identifying factors associated with long-term PCa outcomes can elucidate PCa tumor biology and identify new candidate prognostic markers. These findings support the hypothesis that high iNOS in tumor epithelium of the prostate is associated with lethal disease.

Inflammation and Nitrosative Stress Effects in Ovarian and Prostate Pathology and Carcinogenesis

SIGNIFICANCE

Prostate and ovarian cancers are major contributors to cancer-related deaths worldwide. Recently, inflammation and nitrosative stress have been implicated in carcinogenesis, with the overexpression of NOS2 and concomitant release of nitric oxide (NO) associated with cancer initiation and progression. Recent Advances: An increasing body of evidence indicates an association between NOS2 expression and aggressive ovarian cancer. Research also indicates a role for NO in prostate disease pathology and prostate cancer. A therapeutic role for NOS2 inhibition and/or NO drugs exists for the treatment of both ovarian and prostate tumors.

CRITICAL ISSUES

Herein, we review the key molecular effects associated with NOS2 in ovarian and prostate cancer. NOS2 increases angiogenesis and tumor proliferation and correlates with aggressive type II ovarian tumors. NOS2 expressing tumors are sensitive to cisplatin chemotherapy, and NO may be used to sensitize cisplatin-resistant tumors to chemotherapy. NOS2 is highly expressed in prostate tumors compared to non-neoplastic prostate pathologies. NO may play a role in the development of androgen-independent prostate cancer via s-nitrosylation of the androgen receptor. Moreover, NOS2 inhibitors and NO donor drugs show therapeutic potential in ovarian and prostate cancer as single agents or dual drugs, by either inhibiting the effects of NOS2 or increasing NO levels to induce cytotoxic effects.

FUTURE DIRECTIONS

NOS2 and NO present new targets for the treatment of ovarian and prostate tumors. Furthermore, understanding NO-related tumor biology in these cancers presents a new means for improved patient stratification to the appropriate treatment regimen. Antioxid. Redox Signal. 26, 1078-1090.

JS-K, a nitric oxide pro-drug, regulates growth and apoptosis through the ubiquitin-proteasome pathway in prostate cancer cells

Background

In view of the fact that JS-K might regulate ubiquitin E3 ligase and that ubiquitin E3 ligase plays an important role in the mechanism of CRPC formation, the goal was to investigate the probable mechanism by which JS-K regulates prostate cancer cells.

Methods

Proliferation inhibition by JS-K on prostate cancer cells was examined usingCCK-8 assays. Caspase 3/7 activity assays and flow cytometry were performed to examine whether JS-K induced apoptosis in prostate cancer cells. Western blotting and co-immunoprecipitation analyses investigated JS-K’s effects on the associated apoptosis mechanism. Real time-PCR and Western blotting were performed to assess JS-K’s effect on transcription of specific AR target genes. Western blotting was also performed to detect Siah2 and AR protein concentrations and co-immunoprecipitation to detect interactions of Siah2 and AR, NCoR1 and AR, and p300 and AR.

Results

JS-K inhibited proliferation and induced apoptosis in prostate cancer cells. JS-K increased p53 and Mdm2 concentrations and regulated the caspase cascade reaction-associated protein concentrations. JS-K inhibited transcription of AR target genes and down-regulated PSA protein concentrations. JS-K inhibited Siah2 interactions and also inhibited the ubiquitination of AR. With further investigation, JS-K was found to stabilize AR and NCoR1 interactions and diminish AR and p300 interactions.

Conclusions

The present results suggested that JS-K might have been able to inhibit proliferation and induce apoptosis via regulation of the ubiquitin-proteasome degradation pathway, which represented a promising platform for the development of new compounds for PCa treatments.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3351-0) contains supplementary material, which is available to authorized users.

Stromal Androgen Receptor in Prostate Cancer Development and Progression

Prostate cancer development and progression is the result of complex interactions between epithelia cells and fibroblasts/myofibroblasts, in a series of dynamic process amenable to regulation by hormones. Whilst androgen action through the androgen receptor (AR) is a well-established component of prostate cancer biology, it has been becoming increasingly apparent that changes in AR signalling in the surrounding stroma can dramatically influence tumour cell behavior. This is reflected in the consistent finding of a strong association between stromal AR expression and patient outcomes. In this review, we explore the relationship between AR signalling in fibroblasts/myofibroblasts and prostate cancer cells in the primary site, and detail the known functions, actions, and mechanisms of fibroblast AR signaling. We conclude with an evidence-based summary of how androgen action in stroma dramatically influences disease progression.

Prolactin- and testosterone-induced carboxypeptidase-D correlates with increased nitrotyrosines and Ki67 in prostate cancer

BACKGROUND

Carboxypeptidase-D (CPD) cleaves C-terminal arginine for conversion to nitric oxide (NO) by nitric oxide synthase (NOS). Prolactin (PRL) and androgens stimulate CPD gene transcription and expression, which increases intracellular production of NO to promote viability of prostate cancer (PCa) cells in vitro. The current study evaluated whether hormonal upregulation of CPD and NO promote PCa cell viabilty in vivo, by correlating changes in expression of CPD and nitrotyrosine residues (products of NO action) with proliferation marker Ki67 and associated proteins during PCa development and progression.

METHODS

Fresh prostate tissues, obtained from 40 men with benign prostatic hyperplasia (BPH) or PCa, were flash-frozen at the time of surgery and used for RT-qPCR analysis of CPD, androgen receptor (AR), PRL receptor (PRLR), eNOS, and Ki67 levels. Archival paraffin-embedded tissues from 113 men with BPH or PCa were used for immunohistochemical (IHC) analysis of CPD, nitrotyrosines, phospho-Stat5 (for activated PRLR), AR, eNOS/iNOS, and Ki67.

RESULTS

RT-qPCR and IHC analyses showed strong AR and PRLR expression in benign and malignant prostates. CPD mRNA levels increased ∼threefold in PCa compared to BPH, which corresponded to a twofold increase in Ki67 mRNA levels. IHC analysis showed a progressive increase in CPD from 11.4 ± 2.1% in benign to 21.8 ± 3.2% in low-grade (P = 0.007), 40.7 ± 4.0% in high-grade (P < 0.0001) and 50.0 ± 9.5% in castration-recurrent PCa (P < 0.0001). Immunostaining for nitrotyrosines and Ki67 mirrored these increases during PCa progression. CPD, nitrotyrosines, and Ki67 tended to co-localize, as did phospho-Stat5.

CONCLUSIONS

CPD, nitrotyrosine, and Ki67 levels were higher in PCa than in benign and tended to co-localize, along with phospho-Stat5. The strong correlation in expression of these proteins in benign and malignant prostate tissues, combined with abundant AR and PRLR, supports in vitro evidence that the CPD-Arg-NO pathway is involved in the regulation of PCa cell proliferation. It further highlights a role for PRL in the development and progression of PCa.

Anti-inflammatory sesquiterpenes from the medicinal herb Tanacetum sinaicum

New sesquiterpenes tanacetolide A–C (1–3) were isolated from aTanacetum sinaicumextract together with known compounds (4–10).

Genetic variants within endothelial nitric oxide synthase gene and prostate cancer: a meta-analysis

Several variants within gene-encoding endothelial isoform of nitric oxide synthase have been reported to confer prostate cancer (PCa) susceptibility and/or progression. Nevertheless, studies referring to this issue have yielded inconsistent results. In order to elucidate the involvement of these variants in prostate carcinogenesis, we have conducted a meta-analysis of previously published case-control and relevant case-only studies. Eleven studies comprising in total 3,806 cases and 4,466 controls were included in the meta-analysis which yielded evidence of association of rs2070744 (ORCC = 1.43, 95% CI 1.04-1.97; p = 0.03) and intron 4a/b variant (ORab+aa = 1.47, 95% CI 1.00-2.14; p = 0.05) with PCa risk under recessive and dominant model, respectively. Furthermore, PCa patients carrying 4a/b a allele were found to have an increased risk of cancer progression to a less differentiated form, characterized by a high Gleason score (OR = 2.29, 95% CI 1.51-3.49; p < 0.01) and to higher TNM stage (OR = 2.55, 95% CI 1.71-3.81; p < 0.01). These results support the involvement of NOS3 variants in molecular pathogenesis of PCa.

Effect of chronic Sildenafil treatment on the prostate of C57Bl/6 mice

Sildenafil is a potent and selective inhibitor of phosphodiesterase-5 (PDE5) and is considered first-line therapy for erectile dysfunction. Nowadays, Sildenafil is used extensively throughout the world on patients with pulmonary hypertension. However, few studies have evaluated the possible side effects of chronic Sildenafil treatment on the male reproductive system, specifically in the prostate. In the present study, it was demonstrated via morphological and ultrastructural analysis that chronic treatment with Sildenafil induced an enhancement of the glandular activity of the prostate. In addition, mice treated with Sildenafil showed a significant increase in testosterone serum levels. However, no statistically significant differences were observed in nitric oxide serum levels, or in sGC, eNOS, PSA and TGF-β prostatic expression. In conclusion, the present study suggests that chronic use of Sildenafil does not cause evident prostatic damage, and therefore, can be used pharmacologically to treat a variety of disorders.

Nitric oxide is a positive regulator of the Warburg effect in ovarian cancer cells

Ovarian cancer (OVCA) is among the most lethal gynecological cancers leading to high mortality rates among women. Increasing evidence indicate that cancer cells undergo metabolic transformation during tumorigenesis and growth through nutrients and growth factors available in tumor microenvironment. This altered metabolic rewiring further enhances tumor progression. Recent studies have begun to unravel the role of amino acids in the tumor microenvironment on the proliferation of cancer cells. One critically important, yet often overlooked, component to tumor growth is the metabolic reprogramming of nitric oxide (NO) pathways in cancer cells. Multiple lines of evidence support the link between NO and tumor growth in some cancers, including pancreas, breast and ovarian. However, the multifaceted role of NO in the metabolism of OVCA is unclear and direct demonstration of NO's role in modulating OVCA cells' metabolism is lacking. This study aims at indentifying the mechanistic links between NO and OVCA metabolism. We uncover a role of NO in modulating OVCA metabolism: NO positively regulates the Warburg effect, which postulates increased glycolysis along with reduced mitochondrial activity under aerobic conditions in cancer cells. Through both NO synthesis inhibition (using L-arginine deprivation, arginine is a substrate for NO synthase (NOS), which catalyzes NO synthesis; using L-Name, a NOS inhibitor) and NO donor (using DETA-NONOate) analysis, we show that NO not only positively regulates tumor growth but also inhibits mitochondrial respiration in OVCA cells, shifting these cells towards glycolysis to maintain their ATP production. Additionally, NO led to an increase in TCA cycle flux and glutaminolysis, suggesting that NO decreases ROS levels by increasing NADPH and glutathione levels. Our results place NO as a central player in the metabolism of OVCA cells. Understanding the effects of NO on cancer cell metabolism can lead to the development of NO targeting drugs for OVCAs.

Stilbene induced inhibition of androgen receptor dimerization: implications for AR and ARΔLBD-signalling in human prostate cancer cells

Background

Advanced castration resistant prostate cancer (CRPC) is often characterized by an increase of C-terminally truncated, constitutively active androgen receptor (AR) variants. Due to the absence of a ligand binding domain located in the AR-C-terminus, these receptor variants (also termed ARΔLBD) are unable to respond to all classical forms of endocrine treatments like surgical/chemical castration and/or application of anti-androgens.

Methodology

In this study we tested the effects of the naturally occurring stilbene resveratrol (RSV) and (E)-4-(2, 6-Difluorostyryl)-N, N-dimethylaniline, a fluorinated dialkylaminostilbene (FIDAS) on AR- and ARΔLBD in prostate cancer cells. The ability of the compounds to modulate transcriptional activity of AR and the ARΔLBD-variant Q640X was shown by reporter gene assays. Expression of endogenous AR and ARΔLBD mRNA and protein levels were determined by qRT-PCR and Western Blot. Nuclear translocation of AR-molecules was analyzed by fluorescence microscopy. AR and ARΔLBD/Q640X homo-/heterodimer formation was assessed by mammalian two hybrid assays. Biological activity of both compounds in vivo was demonstrated using a chick chorioallantoic membrane xenograft assay.

Results

The stilbenes RSV and FIDAS were able to significantly diminish AR and Q640X-signalling. Successful inhibition of the Q640X suggests that RSV and FIDAS are not interfering with the AR-ligand binding domain like all currently available anti-hormonal drugs. Repression of AR and Q640X-signalling by RSV and FIDAS in prostate cancer cells was caused by an inhibition of the AR and/or Q640X-dimerization. Although systemic bioavailability of both stilbenes is very low, both compounds were also able to downregulate tumor growth and AR-signalling in vivo.

Conclusion

RSV and FIDAS are able to inhibit the dimerization of AR and ARΔLBD molecules suggesting that stilbenes might serve as lead compounds for a novel generation of AR-inhibitors.

Modulation of nuclear receptor function by cellular redox poise

Nuclear receptors (NRs) are ligand-responsive transcription factors involved in diverse cellular processes ranging from metabolism to circadian rhythms. This review focuses on NRs that contain redox-active thiol groups, a common feature within the superfamily. We will begin by describing NRs, how they regulate various cellular processes and how binding ligands, corepressors and/or coactivators modulate their activity. We will then describe the general area of redox regulation, especially as it pertains to thiol-disulfide interconversion and the cellular systems that respond to and govern this redox equilibrium. Lastly, we will discuss specific examples of NRs whose activities are regulated by redox-active thiols. Glucocorticoid, estrogen, and the heme-responsive receptor, Rev-erb, will be described in the most detail as they exhibit archetypal redox regulatory mechanisms.

Prolactin/Stat5 and androgen R1881 coactivate carboxypeptidase-D gene in breast cancer cells

Plasma membrane-bound carboxypeptidase-D (CPD) cleaves C-terminal arginine from extracellular substrates. In the cell, arginine is converted to nitric oxide (NO). We have reported that up-regulation of CPD mRNA/protein levels by 17β-estradiol and prolactin (PRL) in breast cancer cells, and by testosterone in prostate cancer cells, increased NO production and cell survival. The CPD promoter contains a consensus γ-interferon-activated sequence (GAS) and 3 putative androgen response elements (ARE.1, ARE.2, ARE.3) that could potentially bind PRL-activated transcription factor Stat5 (signal transducer and activator of transcription 5) and the liganded androgen receptor (AR), respectively. This study showed that synthetic androgen R1881 and PRL elevated CPD mRNA/protein levels in human MCF-7 and T47D breast cancer cells in a time-/dose-dependent manner. PRL/R1881-elevated CPD expression was blocked by actinomycin-D, and a CPD promoter construct containing these GAS and AREs was stimulated by PRL or R1881, indicating transcriptional regulation by both hormones. Luciferase reporter assays showed that GAS and the adjacent ARE.1 only were active. Mutation of GAS in the ΔGAS-CPD construct (ARE.1 intact) abolished CPD promoter activity in response to PRL and, surprisingly, to R1881 as well. ΔGAS-CPD promoter activity was restored by PRL+R1881 in combination, and enhanced by ectopic Stat5, but abolished by Stat5 gene knockdown. Chromatin immunoprecipitation analysis confirmed binding of activated Stat5 and liganded AR to GAS and ARE.1, respectively. Activated Stat5 also induced binding of unliganded AR to ARE.1, and liganded AR induced binding of unactivated Stat5 to GAS. In summary, PRL and R1881, acting through Stat5 and AR, act cooperatively to stimulate CPD gene transcription in breast cancer cells.

Maintenance of androgen receptor inactivation by S-nitrosylation

Antiandrogens target ligand-binding domain of androgen receptor (AR) and are used as first-line therapeutics to treat patients diagnosed with locally advanced and metastatic prostate cancer. Although initially beneficial as judged with actual tumor mass shrinkage, this therapy invariably fails and the cancer reappears as castration-resistant disease. Here, we report that increased intracellular nitric oxide (NO) levels lead to growth inhibition of both androgen-dependent and castration-resistant prostate tumors through a mechanism that involves AR function inactivation by S-nitrosylation of a single C601 residue present in the DNA-binding domain. AR S-nitrosylation does not impact its subcellular distribution but attenuates its ability to bind AR-responsive elements in promoter region of target genes. Mechanistically, AR is transnitrosylated by its partner HSP90 protein. Ubiquitous small-molecule NO donors promote the AR S-nitrosylation and inhibit growth of castration-resistant prostate tumors. These findings reveal a new mechanism of regulating AR function and suggest that sequential targeting of distinct domains of AR may extend therapeutic efficacy for patients with advanced prostate cancer.

Applications for nitric oxide in halting proliferation of tumor cells

Tumor resistance to cytotoxic therapeutics coupled with dose-limiting toxicity is a serious hurdle in the field of medical oncology. In the face of this obstacle, nitric oxide has emerged as a powerful adjuvant for the hypersensitization of tumors to more traditional chemo- and radio-therapeutics. Furthermore, emerging evidence indicates that nitric oxide donors have the potential to function independently in the clinical management of cancer. Herein, we discuss the role of nitric oxide in cancer and the potential for nitric oxide donors to support conventional therapeutics.

Increased expression of activated endothelial nitric oxide synthase contributes to antiandrogen resistance in prostate cancer cells by suppressing androgen receptor transactivation

Development of antiandrogen-resistance in advanced prostate cancer involves multiple androgen receptor (AR)-dependent and -independent pathways. Here, we demonstrated that endothelial nitric oxide synthase (eNOS) exhibited an overexpression pattern in hormone-refractory prostate cancer and several models of advanced hormone-resistant prostate cancer. We further established a novel in vitro model of antiandrogen-resistant prostate cancer (LNCaP-BC) by long-term bicalutamide treatment. Besides antiandrogen-resistant and other enhanced malignant growth phenotypes, LNCaP-BC cells exhibited an increased activated eNOS expression and NO production, and suppressed AR transactivation status. Treatment with a NOS inhibitor L-NAME could re-sensitize the growth response to bicalutamide and enhance the AR transactivation in LNCaP-BC cells. Together, our present findings indicate that increased NO production by acquired increased expression of activated eNOS could contribute to the antiandrogen-resistant growth of prostate cancer cells, via a mechanism of NO-mediated suppression of AR activity, and also targeting eNOS could be a potential therapeutic strategy for antiandrogen-resistant prostate cancer.

Effects of sorafenib on C-terminally truncated androgen receptor variants in human prostate cancer cells

Recent evidence suggests that the development of castration resistant prostate cancer (CRPCa) is commonly associated with an aberrant, ligand-independent activation of the androgen receptor (AR). A putative mechanism allowing prostate cancer (PCa) cells to grow under low levels of androgens, is the expression of constitutively active, C-terminally truncated AR lacking the AR-ligand binding domain (LBD). Due to the absence of a LBD, these receptors, termed ARΔLBD, are unable to respond to any form of anti-hormonal therapies. In this study we demonstrate that the multikinase inhibitor sorafenib inhibits AR as well as ARΔLBD-signalling in CRPCa cells. This inhibition was paralleled by proteasomal degradation of the AR- and ARΔLBD-molecules. In line with these observations, maximal antiproliferative effects of sorafenib were achieved in AR and ARΔLBD-positive PCa cells. The present findings warrant further investigations on sorafenib as an option for the treatment of advanced AR-positive PCa.

Nitric oxide synthase and breast cancer: role of TIMP-1 in NO-mediated Akt activation

Prediction of therapeutic response and cancer patient survival can be improved by the identification of molecular markers including tumor Akt status. A direct correlation between NOS2 expression and elevated Akt phosphorylation status has been observed in breast tumors. Tissue inhibitor matrix metalloproteinase-1 (TIMP-1) has been proposed to exert oncogenic properties through CD63 cell surface receptor pathway initiation of pro-survival PI3k/Akt signaling. We employed immunohistochemistry to examine the influence of TIMP-1 on the functional relationship between NOS2 and phosphorylated Akt in breast tumors and found that NOS2-associated Akt phosphorylation was significantly increased in tumors expressing high TIMP-1, indicating that TIMP-1 may further enhance NO-induced Akt pathway activation. Moreover, TIMP-1 silencing by antisense technology blocked NO-induced PI3k/Akt/BAD phosphorylation in cultured MDA-MB-231 human breast cancer cells. TIMP-1 protein nitration and TIMP-1/CD63 co-immunoprecipitation was observed at NO concentrations that induced PI3k/Akt/BAD pro-survival signaling. In the survival analysis, elevated tumor TIMP-1 predicted poor patient survival. This association appears to be mainly restricted to tumors with high NOS2 protein. In contrast, TIMP-1 did not predict poor survival in patient tumors with low NOS2 expression. In summary, our findings suggest that tumors with high TIMP-1 and NOS2 behave more aggressively by mechanisms that favor Akt pathway activation.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

IMPACT

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

Bacterium-generated nitric oxide hijacks host tumor necrosis factor alpha signaling and modulates the host cell cycle in vitro

In mammalian cells, nitric oxide (NO·) is an important signal molecule with concentration-dependent and often controversial functions of promoting cell survival and inducing cell death. An inducible nitric oxide synthase (iNOS) in various mammalian cells produces higher levels of NO· from l-arginine upon infections to eliminate pathogens. In this study, we reveal novel pathogenic roles of NO· generated by bacteria in bacterium-host cell cocultures using Moraxella catarrhalis, a respiratory tract disease-causing bacterium, as a biological producer of NO·. We recently demonstrated that M. catarrhalis cells that express the nitrite reductase (AniA protein) can produce NO· by reducing nitrite. Our study suggests that, in the presence of pathophysiological levels of nitrite, this opportunistic pathogen hijacks host cell signaling and modulates host gene expression through its ability to produce NO· from nitrite. Bacterium-generated NO· significantly increases the secretion of tumor necrosis factor alpha (TNF-α) and modulates the expression of apoptotic proteins, therefore triggering host cell programmed death partially through TNF-α signaling. Furthermore, our study reveals that bacterium-generated NO· stalls host cell division and directly results in the death of dividing cells by reducing the levels of an essential regulator of cell division. This study provides unique insight into why NO· may exert more severe cytotoxic effects on fast growing cells, providing an important molecular basis for NO·-mediated pathogenesis in infections and possible therapeutic applications of NO·-releasing molecules in tumorigenesis. This study strongly suggests that bacterium-generated NO· can play important pathogenic roles during infections.

JS-K, a glutathione/glutathione S-transferase-activated nitric oxide releasing prodrug inhibits androgen receptor and WNT-signaling in prostate cancer cells

BACKGROUND

Nitric oxide (NO) and its oxidative reaction products have been repeatedly shown to block steroid receptor function via nitrosation of zinc finger structures in the DNA-binding domain (DBD). In consequence NO-donors could be of special interest for the treatment of deregulated androgen receptor(AR)-signaling in castration resistant prostate cancer (CRPC).

METHODS

Prostate cancer (PCa) cells were treated with JS-K, a diazeniumdiolate derivate capable of generating large amounts of intracellular NO following activation by glutathione S-transferase. Generation of NO was determined indirectly by the detection of nitrate in tissue culture medium or by immunodetection of nitrotyrosine in the cytoplasm. Effects of JS-K on intracellular AR-levels were determined by western blotting. AR-dimerization was analyzed by mammalian two hybrid assay, nuclear translocation of the AR was visualized in PCa cells transfected with a green fluorescent AR-Eos fusion protein using fluorescence microscopy. Modulation of AR- and WNT-signalling by JS-K was investigated using reporter gene assays. Tumor cell proliferation following JS-K treatment was measured by MTT-Assay.

RESULTS

The NO-releasing compound JS-K was shown to inhibit AR-mediated reporter gene activity in 22Rv1 CRPC cells. Inhibition of AR signaling was neither due to an inhibition of nuclear import nor to a reduction in AR-dimerization. In contrast to previously tested NO-donors, JS-K was able to reduce the intracellular concentration of functional AR. This could be attributed to the generation of extremely high intracellular levels of the free radical NO as demonstrated indirectly by high levels of nitrotyrosine in JS-K treated cells. Moreover, JS-K diminished WNT-signaling in AR-positive 22Rv1 cells. In line with these observations, castration resistant 22Rv1 cells were found to be more susceptible to the growth inhibitory effects of JS-K than the androgen dependent LNCaP which do not exhibit an active WNT-signaling pathway.

CONCLUSIONS

Our results suggest that small molecules able to inhibit WNT- and AR-signaling via NO-release represent a promising platform for the development of new compounds for the treatment of CRPC.

Testosterone and prolactin increase carboxypeptidase-D and nitric oxide levels to promote survival of prostate cancer cells

BACKGROUND

Plasma-membrane carboxypeptidase-D (CPD) releases arginine from extracellular substrates. Arginine is converted intracellularly to nitric oxide (NO). This study determined the effects of testosterone (T) and prolactin (PRL) on CPD expression, and the role(s) of CPD in NO production and survival of prostate cancer (PCa) cells.

METHODS

LNCaP cells were treated with T and/or PRL. CPD expression was measured. Regulation by T (low doses) was determined using transfected cells overexpressing 5α-reductase type-1 (5αR1), which converts T to the more potent dihydrotestosterone. The effects of siRNAs targeting CPD (siCPDs) on NO production, cell viability, and apoptosis were determined using DAF2-DA, MTS, and Annexin-V assays. The effects of PRL/T on CPD/NO levels in PC-3, MDA-PCa-2b, and 22Rv1 cells were also evaluated.

RESULTS

In LNCaP cells, 10 nM T and 10 ng/ml PRL-upregulated CPD mRNA/protein levels. In pTRE-transfectants, 1 nM T-upregulated CPD mRNA levels by ∼2-fold over controls, whereas 0.1 nM T caused similar upregulation in pTRE-5αR1-transfectants. In LNCaP cells cultured in arginine-free medium, addition of furylacryloyl-Ala-Arg (FAR; CPD substrate) increased NO levels. NO production, with FAR, was enhanced by PRL and/or T. siCPDs decreased NO production and cell viability, but increased apoptosis. QPCR analysis showed T/PRL-upregulation of CPD in 22Rv1, MDA-PCa-2b, and PC-3 cells. NO production was doubled by T/PRL in 22Rv1 cells, tripled by T in MDA-PCa-2b cells, and marginally increased by PRL in MDA-PCa-2b and PC-3 cells.

CONCLUSIONS

T and PRL upregulate CPD and NO levels in PCa cells. CPD increases NO production to promote PCa cell survival.

Inhibition of glycogen synthase kinase-3β counteracts ligand-independent activity of the androgen receptor in castration resistant prostate cancer

In order to generate genomic signals, the androgen receptor (AR) has to be transported into the nucleus upon androgenic stimuli. However, there is evidence from in vitro experiments that in castration-resistant prostate cancer (CRPC) cells the AR is able to translocate into the nucleus in a ligand-independent manner. The recent finding that inhibition of the glycogen-synthase-kinase 3β (GSK-3β) induces a rapid nuclear export of the AR in androgen-stimulated prostate cancer cells prompted us to analyze the effects of a GSK-3β inhibition in the castration-resistant LNCaP sublines C4-2 and LNCaP-SSR. Both cell lines exhibit high levels of nuclear AR in the absence of androgenic stimuli. Exposure of these cells to the maleimide SB216763, a potent GSK-3β inhibitor, resulted in a rapid nuclear export of the AR even under androgen-deprived conditions. Moreover, the ability of C4-2 and LNCaP-SSR cells to grow in the absence of androgens was diminished after pharmacological inhibition of GSK-3β in vitro. The ability of SB216763 to modulate AR signalling and function in CRPC in vivo was additionally demonstrated in a modified chick chorioallantoic membrane xenograft assay after systemic delivery of SB216763. Our data suggest that inhibition of GSK-3β helps target the AR for export from the nucleus thereby diminishing the effects of mislocated AR in CRPC cells. Therefore, inhibition of GSK-3β could be an interesting new strategy for the treatment of CRPC.

Identification of clinically relevant protein targets in prostate cancer with 2D-DIGE coupled mass spectrometry and systems biology network platform

Prostate cancer (PCa) is the most common type of cancer found in men and among the leading causes of cancer death in the western world. In the present study, we compared the individual protein expression patterns from histologically characterized PCa and the surrounding benign tissue obtained by manual micro dissection using highly sensitive two-dimensional differential gel electrophoresis (2D-DIGE) coupled with mass spectrometry. Proteomic data revealed 118 protein spots to be differentially expressed in cancer (n = 24) compared to benign (n = 21) prostate tissue. These spots were analysed by MALDI-TOF-MS/MS and 79 different proteins were identified. Using principal component analysis we could clearly separate tumor and normal tissue and two distinct tumor groups based on the protein expression pattern. By using a systems biology approach, we could map many of these proteins both into major pathways involved in PCa progression as well as into a group of potential diagnostic and/or prognostic markers. Due to complexity of the highly interconnected shortest pathway network, the functional sub networks revealed some of the potential candidate biomarker proteins for further validation. By using a systems biology approach, our study revealed novel proteins and molecular networks with altered expression in PCa. Further functional validation of individual proteins is ongoing and might provide new insights in PCa progression potentially leading to the design of novel diagnostic and therapeutic strategies.

Inhibition of glycogen synthase kinase-3beta promotes nuclear export of the androgen receptor through a CRM1-dependent mechanism in prostate cancer cell lines

The androgen receptor (AR) is a ligand-dependent transcription factor belonging to the steroid hormone receptor superfamily. Under normal conditions, in the absence of a ligand, the AR is localized to the cytoplasm and is actively transported into the nucleus upon binding of androgens. In advanced prostate cancer (PCa) cell lines, an increased sensitivity to dihydrotestosterone (DHT), enabling the cells to proliferate under sub-physiological levels of androgens, has been associated with increased stability and nuclear localization of the AR. There is experimental evidence that the glycogen synthase kinase-3beta (GSK-3beta), a multifunctional serine/threonine kinase is involved in estrogen and AR stability. As demonstrated in the following study by immunoprecipitation analysis, GSK-3beta binds to the AR forming complexes in the cytoplasm and in the nucleus. Furthermore, inhibition of GSK-3beta activity by pharmacological inhibitors like the maleimide SB216761, the chloromethyl-thienyl-ketone GSK-3 inhibitor VI or the aminopyrazol GSK-3 inhibitor XIII in cells grown in the presence of DHT triggered a rapid nuclear export of endogenous AR as well as of green fluorescent AR-EosFP. The nuclear export of AR following GSK-3beta inhibition could be blocked by leptomycin B suggesting a CRM1-dependent export mechanism. This assumption is supported by the localization of a putative CRM1 binding site at the C-terminus of the AR protein. The results suggest that GSK-3beta is an important element not only in AR stability but also significantly alters nuclear translocation of the AR, thereby modulating the androgenic response of human PCa cells.

Usefulness of the top-scoring pairs of genes for prediction of prostate cancer progression

Prediction of cancer progression after radical prostatectomy is one of the most challenging problems in the management of prostate cancer. Gene-expression profiling is widely used to identify genes associated with such progression. Usually candidate genes are identified according to a gene-by-gene comparison of expression. Recent reports suggested that relative expression of a gene pair more efficiently predicts cancer progression than single-gene analysis does. The top-scoring pair (TSP) algorithm classifies phenotypes according to the relative expression of a pair of genes. We applied the TSP approach to predict, which patients would experience systemic tumor progression after radical prostatectomy. Relative expression of TPD52L2/SQLE and CEACAM1/BRCA1 gene pairs identified those patients with more than 99% specificity but relatively low sensitivity (approximately 10%). These two gene pairs were validated in three independent data sets. In addition, combining two pairs of genes improved sensitivity without compromising specificity. Functional annotation of the TSP genes showed that they cluster by a limited number of biological functions and pathways, suggesting that relatively lower expression of genes from specific pathways can predict cancer progression. In conclusion, comparative analysis of the expression of two genes may be a simple and effective classifier for prediction of prostate cancer progression. In summary, the TSP approach can be used to identify patients whose prostate cancer will progress after they undergo radical prostatectomy. Two gene pairs can predict which men would experience progression to the metastatic form of the disease. However, because our analysis was based on a relatively small number of genes, a larger study will be needed to identify the best predictors of disease outcome overall.

Comprehensive identification and modified-site mapping of S-nitrosylated targets in prostate epithelial cells

Background

Although overexpression of nitric oxide synthases (NOSs) has been found associated with prostate diseases, the underlying mechanisms for NOS-related prostatic diseases remain unclear. One proposed mechanism is related to the S-nitrosylation of key regulatory proteins in cell-signaling pathways due to elevated levels of NO in the prostate. Thus, our primary objective was to identify S-nitrosylated targets in an immortalized normal prostate epithelial cell line, NPrEC.

Methodology/Principal Findings

We treated NPrEC with nitroso-cysteine and used the biotin switch technique followed by gel-based separation and mass spectrometry protein identification (using the LTQ-Orbitrap) to discover S-nitrosylated (SNO) proteins in the treated cells. In parallel, we adapted a peptide pull-down methodology to locate the site(s) of S-nitrosylation on the protein SNO targets identified by the first technique. This combined approach identified 116 SNO proteins and determined the sites of modification for 82 of them. Over 60% of these proteins belong to four functional groups: cell structure/cell motility/protein trafficking, protein folding/protein response/protein assembly, mRNA splicing/processing/transcriptional regulation, and metabolism. Western blot analysis validated a subset of targets related to disease development (proliferating cell nuclear antigen, maspin, integrin β4, α-catenin, karyopherin [importin] β1, and elongation factor 1A1). We analyzed the SNO sequences for their primary and secondary structures, solvent accessibility, and three-dimensional structural context. We found that about 80% of the SNO sites that can be mapped into resolved structures are buried, of which approximately half have charged amino acids in their three-dimensional neighborhood, and the other half residing within primarily hydrophobic pockets.

Conclusions/Significance

We here identified 116 potential SNO targets and mapped their putative SNO sites in NPrEC. Elucidation of how this post-translational modification alters the function of these proteins should shed light on the role of NO in prostate pathologies. To our knowledge, this is the first report identifying SNO targets in prostate epithelial cells.

DNA-binding properties of Drosophila ecdysone receptor isoforms and their modification by the heterodimerization partner ultraspiracle

Transcriptional activity of ecdysone receptor (EcR) isoforms varies considerably and is modified further by the heterodimerization partner and hormone treatment. To investigate whether differences in DNA binding of receptor complexes are responsible for these variations in transcriptional activity, interaction of Drosophila EcR isoforms, and variants of Ultraspiracle (Usp), the orthologue of RXR, with the ecdysone response elements (EcRE) hsp 27, PAL-1, and DR-1, were determined by electrophoretic mobility shift assays. Receptor proteins were expressed in vertebrate cells (CHO-K1) in order to rule out an influence of endogenous receptor proteins. In the absence of a heterodimerization partner, weak DNA binding of EcR was detected even without hormone with EcR-A and -B1, but not EcR-B2. In the presence of hormone, all three isoforms show increased binding to the hsp 27 EcRE. The heterodimerization partner Usp increased DNA binding considerably. The hormone effect of heterodimers is more pronounced with both EcR-B isoforms compared to EcR-A. Two specific bands were obtained for EcR-A and B1 but only one band is visible with EcR-B2. Deletion of the C-domain of Usp still allows basal DNA binding of the heterodimer, but in contrast to full-length Usp, addition of hormone decreases the intensity of the retarded receptor band of all EcR isoforms and the EcREs hsp27 and DR-1 considerably, whereas interaction with the EcRE PAL-1 is only slightly affected. Synergistic effects on transcriptional activity are associated with the formation of different receptor DNA-complexes observed with 1xhsp27 and 3xhsp27. Comparison of DNA-binding properties of EcR isoforms and EcR/Usp heterodimers revealed that binding of receptor complexes to hsp 27 EcRE is dependent on the AB domain of EcR and the AB-, C-, and D-domains of the heterodimerization partner. Interaction with the hsp 27 EcRE correlates neither with ligand binding nor with transcriptional activity of the various receptor complexes. We, therefore, conclude that the different receptor functions are regulated separately, for example, by interaction with co-modulators or post-transcriptional modifications.

Nitric oxide synthase gene polymorphisms and prostate cancer risk

Nitric oxide (NO) induces cytotoxicity and angiogenesis, and may play a role in prostate carcinogenesis, potentially modulated by environmental exposures. We evaluated the association of prostate cancer with genetic polymorphisms in two genes related to intracellular NO: NOS2A [inducible nitric oxide synthase (NOS); -2892T>C, Ex16 + 14C>T (S608L), IVS16 + 88T>G and IVS20 + 524G>A] and NOS3 [endothelial NOS; IVS1-762C>T, Ex7-43C>T (D258D), IVS7-26A>G, Ex8-63G>T (E298D) and IVS15-62G>T]. Prostate cancer cases (n = 1320) from the screening arm of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial were frequency matched to controls (n = 1842), by age, race, time since initial screening and year of blood draw. An antioxidant score [range 3-12; low (3-7) versus high (8-12)] was created by summing the quartile levels of vitamin E, beta-carotene and lycopene, which were coded from 1 to 4, respectively. The global tests for all eight single-nucleotide polymorphisms (SNPs) (excluding NOS2A-2892T>C, with low minor allele frequency) were statistically significant for prostate cancer (P = 0.005), especially for aggressive cancer (stage III-IV or Gleason score > or = 7) (P = 0.01). The NOS2A IVS16 + 88 GT/TT was associated with increased prostate cancer risk (odds ratio = 1.24, 95% confidence interval = 1.00-1.54), whereas the IVS20 + 524 AG/GG was associated with decreased risk (0.77, 0.66-0.90). The NOS3 IVS7-26GG was associated with increased prostate cancer risk (1.33, 1.07-1.64). All these SNPs showed significant associations with aggressive cancer and not for non-aggressive cancer. In the evaluation of effect modification, the effect of the NOS2A IVS16 + 88 GT/TT on aggressive cancer was stronger among subjects with higher antioxidant intake (1.61, 1.18-2.19; P(interaction) = 0.01). Our results suggest that NOS gene polymorphisms are genetic susceptibility factors for aggressive prostate cancer.

Inhibition of glycogen synthase kinase-3 in androgen-responsive prostate cancer cell lines: are GSK inhibitors therapeutically useful?

The glycogen synthase kinase 3 (GSK-3) is a serine/threonine kinase widely expressed in mammalian tissues. Initially identified by its ability to modulate glycogen synthesis, GSK-3 turned out to be a multifunctional enzyme, able to phosphorylate many proteins, including members of the steroid receptor superfamily. Although GSK-3 was shown to phosphorylate the androgen receptor (AR), its effects on AR transcriptional activity remain controversial. Analysis of short hairpin RNA (shRNA)-mediated downmodulation of GSK-3 proteins in prostate cancer cells showed a reduction in AR transcriptional activity and AR protein levels. Pharmacological GSK-3 inhibitors such as the maleimide SB216763 or the aminopyrazole GSK inhibitor XIII inhibited AR-dependent reporter gene activity and AR expression in vitro. Analysis of androgen-induced nuclear translocation of the AR was performed in PC3 cells transfected with pAR-t1EosFP coding for EosAR, a green fluorescent AR fusion protein. When grown in presence of androgens, EosAR was predominantly nuclear. Incubation with SB216763 before and after androgen treatment almost completely reduced nuclear EosAR. In contrast, the thiazole-containing urea compound AR-A014418 increased rather than decreased AR-expression/function. Although not all GSK inhibitors affected AR-stability/function, our observations suggest a potential new therapeutic application for some of these compounds in prostate cancer.

Androgens and prevention of prostate cancer

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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