AMPK/SIRT1 signaling through p38MAPK mediates Interleukin-6 induced neuroendocrine differentiation of LNCaP prostate cancer cells

Neuroendocrine Prostate Cancer (NEPC) is an aggressive form of androgen independent prostate cancer (AIPC), correlated with therapeutic resistance. Interleukin (IL)-6 promotes proliferation and neuroendocrine differentiation (NED) of androgen dependent LNCaP cells. We treated LNCaP cells with IL-6 and observed for in vitro NED of cells and also expression of NE markers βIII tubulin, neuron-specific enolase (NSE) and chromogranin A (ChA). Here we investigated the proteins and/or pathways involved in NED of LNCaP cells induced by IL-6 and characterized their role in NED of PCa cells. We found that the altered proteins modulated AMPK signaling pathway in NE cells. Remarkably, IL-6 induces NED of LNCaP cells through activation of AMPK and SIRT1 and also both of these are co-regulated while playing a predominant role in NED of LNCaP cells. Of the few requirements of AMPK-SIRT1 activation, increased eNOS is essential for NED by elevating Nitric oxide (NO) levels. Pleiotropic effects of NO ultimately regulate p38MAPK in IL-6 induced NED. Hence, IL-6 induced AMPK-SIRT1 activation eventually transfers its activation signals through p38MAPK for advancing NED of LNCaP cells. Moreover, inactivation of p38MAPK with specific inhibitor (SB203580) attenuated IL-6 induced NED of LNCaP cells. Therefore, IL-6 promotes NED of PCa cells via AMPK/SIRT1/p38MAPK signaling. Finally, targeting AMPK-SIRT1 or p38MAPK in androgen independent PC3 cells with neuroendocrine features reversed their neuroendocrine characteristics. Taken together these novel findings reveal that targeting p38MAPK mitigated NED of PCa cells, and thus it can be a favorable target to overcome progression of NEPC.     

Interleukin-6

Autophagy reallocates nutrients and clears normal cells of damaged proteins and organelles. In the context of metastatic disease, invading cancer cells hijack autophagic processes to survive and adapt in the host microenvironment. We sought to understand how autophagy is regulated in the metastatic niche for prostate cancer (PCa) cells where bone marrow stromal cell (BMSC) paracrine signaling induces PCa neuroendocrine differentiation (NED). In PCa, this transdifferentiation of metastatic PCa cells to neuronal-like cells correlates with advanced disease. Because autophagy provides a survival advantage for cancer cells and promotes cell differentiation, we hypothesized that autophagy mediates PCa NED in the bone. Thus, we determined the ability of paracrine factors in conditioned media (CM) from two separate BMSC subtypes, HS5 and HS27a, to induce autophagy in C4-2 and C4-2B bone metastatic PCa cells by characterizing the autophagy marker, LC3. Unlike HS27a CM, HS5 CM induced LC3 accumulation in PCa cells, suggesting autophagy was induced and indicating that HS5 and HS27a secrete a different milieu of paracrine factors that influence PCa autophagy. We identified interleukin-6 (IL-6), a cytokine more highly expressed in HS5 cells than in HS27a cells, as a paracrine factor that regulates PCa autophagy. Pharmacological inhibition of STAT3 activity did not attenuate LC3 accumulation, implying that IL-6 regulates NED and autophagy through different pathways. Finally, chloroquine inhibition of autophagic flux blocked PCa NED; hence autophagic flux maintains NED. Our studies imply that autophagy is cytoprotective for PCa cells in the bone, thus targeting autophagy is a potential therapeutic strategy.     

Interleukin-6: a bone marrow stromal cell paracrine signal that induces neuroendocrine differentiation and modulates autophagy in bone metastatic PCa cells

Autophagy reallocates nutrients and clears normal cells of damaged proteins and organelles. In the context of metastatic disease, invading cancer cells hijack autophagic processes to survive and adapt in the host microenvironment. We sought to understand how autophagy is regulated in the metastatic niche for prostate cancer (PCa) cells where bone marrow stromal cell (BMSC) paracrine signaling induces PCa neuroendocrine differentiation (NED). In PCa, this transdifferentiation of metastatic PCa cells to neuronal-like cells correlates with advanced disease. Because autophagy provides a survival advantage for cancer cells and promotes cell differentiation, we hypothesized that autophagy mediates PCa NED in the bone. Thus, we determined the ability of paracrine factors in conditioned media (CM) from two separate BMSC subtypes, HS5 and HS27a, to induce autophagy in C4-2 and C4-2B bone metastatic PCa cells by characterizing the autophagy marker, LC3. Unlike HS27a CM, HS5 CM induced LC3 accumulation in PCa cells, suggesting autophagy was induced and indicating that HS5 and HS27a secrete a different milieu of paracrine factors that influence PCa autophagy. We identified interleukin-6 (IL-6), a cytokine more highly expressed in HS5 cells than in HS27a cells, as a paracrine factor that regulates PCa autophagy. Pharmacological inhibition of STAT3 activity did not attenuate LC3 accumulation, implying that IL-6 regulates NED and autophagy through different pathways. Finally, chloroquine inhibition of autophagic flux blocked PCa NED; hence autophagic flux maintains NED. Our studies imply that autophagy is cytoprotective for PCa cells in the bone, thus targeting autophagy is a potential therapeutic strategy.     

Androgen deprivation therapy in combination with radiotherapy for high-risk clinically localized prostate cancer

Androgen deprivation therapy (ADT) has remained the main therapeutic option for patients with advanced prostate cancer (PCa) for about 70 years. Several reports and our findings revealed that aggressive PCa can occur under a low dihydrotestosterone (DHT) level environment where the PCa of a low malignancy with high DHT dependency cannot easily occur. Low DHT levels in the prostate with aggressive PCa are probably sufficient to propagate the growth of the tumor, and the prostate with aggressive PCa can produce androgens from the adrenal precursors more autonomously than that with non-aggressive PCa does under the low testosterone environment with testicular suppression. In patients treated with ADT the pituitary-adrenal axis mediated by adrenocorticotropic hormone has a central role in the regulation of androgen synthesis. Several experimental studies have confirmed the potential benefits from the combination of ADT with radiotherapy (RT). A combination of external RT with short-term ADT is recommended based on the results of phase III randomized trials. In contrast, the combination of RT plus 6 months of ADT provides inferior survival as compared with RT plus 3 years of ADT in the treatment of locally advanced PCa. Notably, randomized trials included patients with diverse risk groups treated with older RT modalities, a variety of ADT scheduling and duration and, importantly, suboptimal RT doses. The use of ADT with higher doses of RT or newer RT modalities has to be properly assessed.     

SIMBOSPROST: Prevalence of metabolic syndrome and osteoporosis in prostate cancer patients treated with radiotherapy and androgen deprivation therapy: A multicentre,cross-sectional study

AimTo assess the prevalence of metabolic syndrome (MetS) and osteoporosis in patients with prostate cancer (PCa) treated with radical radiotherapy (RT) with or without androgen deprivation therapy (ADT).BackgroundWorldwide, the prevalence of MetS is estimated to range from 20% to 25% of the adult population. However, prevalence rates are much higher in PCa patients (pts) who undergo ADT.Materials and methodsMulticentre cross-sectional study of 270 pts in Spain with PCa. Patients were divided into 3 groups based on the duration of ADT (6, 12–18, ≥24 months) and compared to a control group without ADT. MetS was defined according to NCEP ATP III criteria. Osteoporosis was assessed by DEXA.ResultsA total of 270 pts, treated from November 2011 to October 2012, were included. Of these, 122 pts (47%) fulfilled the criteria for MetS. The median age of this group was significantly higher (71.3 vs. 69.38 years, p = 0.028). MetS prevalence was 50% in the control group. In pts who received ADT, prevalence was 44.8% after 6 months of ADT, 45.3% after 12–18 months, and 50% after ≥24 months (pns). Most pts (168/270; 62%) underwent DEXA. Of those tested, 78 (46.4%) had osteopenia and only 11 (6.5%) had osteoporosis.ConclusionsThe prevalence of MetS in pts with PCa treated with radical RT was higher (47%) than in the general population. However, there were no significant differences in the duration of ADT administration. The prevalence of osteoporosis was low. These findings suggest that the prevalence of MetS in PCa patients may be higher than previously reported.     

Androgen-responsive and nonresponsive prostate cancer cells present a distinct glycolytic metabolism profile

Prostate cancer (PCa) progresses from an early stage, confined to prostate, to a more aggressive metastasized cancer related with loss of androgen responsiveness. Although, it has been recognized that PCa cells have unique metabolic features, their glycolytic profile in androgen-dependent and androgen-independent stages of disease is much less known. Hence, the main purpose of this study was to compare glucose metabolism in androgen-responsive (LNCaP) and androgen-nonresponsive (PC3) PCa cells. Cell culture medium was collected and differences in glucose consumption and, lactate and alanine production were measured using Proton Nuclear Magnetic Resonance ((1)H NMR) spectra analysis. The mRNA and protein expression of glucose transporters (GLUT1 and GLUT3), phosphofructokinase 1 (PFK1), lactate dehydrogenase (LDH) and monocarboxylate transporter (MCT4) were determined by real-time PCR and Western Blot, respectively. The obtained results demonstrate that androgen-responsive (LNCaP) and androgen-nonresponsive (PC3) cells consumed similar amounts of glucose, whereas PC3 cells present higher lactate production. This increase in lactate production was concomitant with higher levels of MCT4 protein, increased LDH activity and higher lactate/alanine ratio, also suggesting increased levels of oxidative stress in PC3 cells. However, protein levels of LDH, associated with lactate metabolism, and GLUT3, involved in glucose uptake, were decreased in PC3 comparatively with LNCaP. Androgen-responsive and nonresponsive PCa cells present distinct glycolytic metabolism profiles, which suggest that targeting LDH and MCT4 metabolic pathways may be an important step for the development of new diagnostic and therapeutic strategies in the different stages of PCa.     

Quantifying the Evidence for the Risk of Metabolic Syndrome and Its Components following Androgen Deprivation Therapy for Prostate Cancer: A Meta-Analysis

Background

No meta-analysis is yet available for the risk of metabolic syndrome (MetS) following androgen deprivation therapy (ADT) for men with prostate cancer. To summarize the evidence for the link between ADT and MetS or its components quantitatively with a meta-analysis including all studies published to date.

Methods

PubMed and Embase were searched using predefined inclusion criteria to perform meta-analyses on the association between metabolic syndrome, hyperglycemia, diabetes, hypertension, dyslipidemia or obesity and androgen deprivation therapy in patients with prostate cancer. Random effects methods were used to estimate pooled relative risks (RRs) and 95% confidence intervals (CI).

Results

A total of nine studies was included. There was a positive association between ADT and risk of MetS (RR: 1.75 (95% CI: 1.27–2.41)). Diabetes was the only MetS component present in more than 3 studies, and also showed an increased risk following ADT (RR: 1.36 (95% CI: 1.17–1.58)).

Conclusion

This is the first quantitative summary addressing the potential risk of MetS following ADT in men with PCa. The positive RRs indicate that there is a need to further elucidate how type and duration of ADT affect these increased risks of MetS and diabetes as the number of men with PCa treated with ADT is increasing.     

Expression and Functional Role of Orphan Receptor GPR158 in Prostate Cancer Growth and Progression

Prostate cancer (PCa) is the second-leading cause of cancer-related mortality, after lung cancer, in men from developed countries. In its early stages, primary tumor growth is dependent on androgens, thus generally can be controlled by androgen deprivation therapy (ADT). Eventually however, the disease progresses to castration-resistant prostate cancer (CRPC), a lethal form in need of more effective treatments. G-protein coupled receptors (GPCRs) comprise a large clan of cell surface proteins that have been implicated as therapeutic targets in PCa growth and progression. The findings reported here provide intriguing evidence of a role for the newly characterized glutamate family member GPR158 in PCa growth and progression. We found that GPR158 promotes PCa cell proliferation independent of androgen receptor (AR) functionality and that this requires its localization in the nucleus of the cell. This suggests that GPR158 acts by mechanisms different from other GPCRs. GPR158 expression is stimulated by androgens and GPR158 stimulates AR expression, implying a potential to sensitize tumors to low androgen conditions during ADT via a positive feedback loop. Further, we found GPR158 expression correlates with a neuroendocrine (NE) differentiation phenotype and promotes anchorage-independent colony formation implying a role for GPR158 in therapeutic progression and tumor formation. GPR158 expression was increased at the invading front of prostate tumors that formed in the genetically defined conditional Pten knockout mouse model, and co-localized with elevated AR expression in the cell nucleus. Kaplan-Meier analysis on a dataset from the Memorial Sloan Kettering cancer genome portal showed that increased GPR158 expression in tumors is associated with lower disease-free survival. Our findings strongly suggest that pharmaceuticals targeting GPR158 activities could represent a novel and innovative approach to the prevention and management of CRPC.     

Oxidative stress and androgen receptor signaling in the development and progression of castration-resistant prostate cancer

Aberrant androgen receptor (AR) signaling plays a critical role in androgen-dependent prostate cancer (PCa), as well as in castration-resistant PCa (CRPC). Oxidative stress seems to contribute to the tumorigenesis and progression of PCa, as well as the development of CRPC, via activation of AR signaling. This notion is supported by the fact that there is an aberrant or improper regulation of the redox status in these disorders. Additionally, androgen-deprivation-induced oxidative stress seems to be involved in the pathogenesis of several disorders caused by androgen-deprivation therapy (ADT), including osteoporosis, neurodegenerative disease, and cardiovascular disease. Oxidative stress can be suppressed with antioxidants or via a reduction in reactive oxygen species production. Thus, developing new therapeutic agents that reduce oxidative stress might be useful in preventing the conversion of androgen-dependent PCa into CRPC, as well as reducing the adverse effects associated with ADT. The objective of this review is to provide an overview regarding the relationship between oxidative stress and AR signaling in the context of PCa and especially CRPC. Additionally, we discuss the potential use of antioxidant therapies in the treatment of PCa.     

Differential Androgen Deprivation Therapies with Anti-androgens Casodex/Bicalutamide or MDV3100/Enzalutamide versus Anti-androgen Receptor ASC-J9? Lead to Promotion versus Suppression of Prostate Cancer Metastasis

Despite the fact that androgen deprivation therapy (ADT) can effectively reduce prostate cancer (PCa) size, its effect on PCa metastasis remains unclear. We examined the existing data on PCa patients treated with ADT plus anti-androgens to analyze ADT effects on primary tumor size, prostate-specific antigen (PSA) values, and metastatic incidence. We found that the current ADT with anti-androgens might lead to primary tumor reduction, with PSA decreased yet metastases increased in some PCa patients. Using in vitro and in vivo metastasis models with four human PCa cell lines, we evaluated the effects of the currently used anti-androgens, Casodex/bicalutamide and MDV3100/enzalutamide, and the newly developed anti-AR compounds, ASC-J9® and cryptotanshinone, on PCa cell growth and invasion. In vitro results showed that 10 μm Casodex or MDV3100 treatments suppressed PCa cell growth and reduced PSA level yet significantly enhanced PCa cell invasion. In vivo mice studies using an orthotopic xenograft mouse model also confirmed these results. In contrast, ASC-J9® led to suppressed PCa cell growth and cell invasion in in vitro and in vivo models. Mechanism dissection indicated these Casodex/MDV3100 treatments enhanced the TGF-β1/Smad3/MMP9 pathway, but ASC-J9® and cryptotanshinone showed promising anti-invasion effects via down-regulation of MMP9 expression. These findings suggest the potential risks of using anti-androgens and provide a potential new therapy using ASC-J9® to battle PCa metastasis at the castration-resistant stage.     

Liquid chromatography-mass spectrometric assay of androstenediol in prostatic tissue: influence of androgen deprivation therapy on its level

Androstenediol (Adiol, androst-5-ene-3beta,17beta-diol) is suspected of being an endogenous proliferation agent of prostate cancer (PCa) even after androgen deprivation therapy (ADT). A liquid chromatography-electron capture atmospheric pressure chemical ionization-mass spectrometric (LC-ECAPCI-MS) method for the determination of Adiol in prostatic tissue was developed and validated for evaluating the influence of ADT on the prostatic Adiol level. After derivatization of Adiol with 4-nitrobenzoyl chloride, the detection response of the derivative was increased 150 times more than that of intact Adiol. The LC-MS method was specific and reliable for the measurement of a trace amount of Adiol in 30 mg of tissue. The clinical study using the developed method showed that the prostatic Adiol level was not changed by ADT. That is, the prostatic Adiol levels of PCa patients with ADT (n = 12), benign prostate hypertrophy patients without ADT (n = 8) and bladder cancer patients (without prostatic disease) (n = 6) were 0.83 +/- 0.28, 0.62 +/- 0.31 and 0.71 +/- 0.28 ng g(-1)tissue, respectively, and there was no significant difference between these groups.     

Anti-androgen receptor ASC-J9 versus anti-androgens MDV3100 (Enzalutamide) or Casodex (Bicalutamide) leads to opposite effects on prostate cancer metastasis via differential modulation of macrophage infiltration and STAT3-CCL2 signaling

Despite androgen deprivation therapy (ADT) suppression of prostate cancer (PCa) growth, its overall effects on PCa metastasis remain unclear. Using human (C4-2B/THP1) and mouse (TRAMP-C1/RAW264.7) PCa cells–macrophages co-culture systems, we found currently used anti-androgens, MDV3100 (enzalutamide) or Casodex (bicalutamide), promoted macrophage migration to PCa cells that consequently led to enhanced PCa cell invasion. In contrast, the AR degradation enhancer, ASC-J9, suppressed both macrophage migration and subsequent PCa cell invasion. Mechanism dissection showed that Casodex/MDV3100 reduced the AR-mediated PIAS3 expression and enhanced the pSTAT3-CCL2 pathway. Addition of CCR2 antagonist reversed the Casodex/MDV3100-induced macrophage migration and PCa cell invasion. In contrast, ASC-J9 could regulate pSTAT3-CCL2 signaling using two pathways: an AR-dependent pathway via inhibiting PIAS3 expression and an AR-independent pathway via direct inhibition of the STAT3 phosphorylation/activation. These findings were confirmed in the in vivo mouse model with orthotopically injected TRAMP-C1 cells. Together, these results may raise the potential concern about the currently used ADT with anti-androgens that promotes PCa metastasis and may provide some new and better therapeutic strategies using ASC-J9 alone or a combinational therapy that simultaneously targets androgens/AR signaling and PIAS3-pSTAT3-CCL2 signaling to better battle PCa growth and metastasis at castration-resistant stage.     

Effect of castration monotherapy on the levels of adrenal androgens in cancerous prostatic tissues

The mechanism accounting for the development of castration-resistant prostate cancer (CRPC) remains unclear. Studies in CRPC tissues suggest that, after androgen deprivation therapy (ADT), the adrenal androgens may be an important source of testosterone (T) and 5-alpha dihydrotestosterone (DHT) in CRPC tissues. To clarify the role of adrenal androgens in the prostatic tissues (prostatic tissue adrenal androgens) during ADT, we developed a high sensitive and specific quantification method for the levels of androgens in prostatic tissue using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Human prostatic tissues were purified using mixed-mode reversed-phase, strong anion exchange Oasis cartridges (Oasis MAX). Analysis of steroids was performed using LC-MS/MS after picolinic acid derivatization. The validation tests showed that our method of quantitative analysis was precise and sensitive enough for the quantification of dehydroepiandrosterone (DHEA), androstenedione, androstenediol, T, and DHT in the prostatic tissue. The levels of adrenal androgens in prostate cancer tissues after ADT were similar to those in untreated PCa. Especially, DHEA was the most existing androgen precursor in PCa tissues after ADT. The levels of DHEA were high in PCa tissues, irrespective of ADT. We assumed that DHEA played a significant role in the synthesis of T and DHT in PCa tissues after ADT.     

Biomarker Discovery in Human Prostate Cancer: an Update in Metabolomics Studies

Prostate cancer (PCa) is the most frequently diagnosed cancer and the second leading cause of cancer death among men in Western countries. Current screening techniques are based on the measurement of serum prostate specific antigen (PSA) levels and digital rectal examination. A decisive diagnosis of PCa is based on prostate biopsies; however, this approach can lead to false-positive and false-negative results. Therefore, it is important to discover new biomarkers for the diagnosis of PCa, preferably noninvasive ones. Metabolomics is an approach that allows the analysis of the entire metabolic profile of a biological system. As neoplastic cells have a unique metabolic phenotype related to cancer development and progression, the identification of dysfunctional metabolic pathways using metabolomics can be used to discover cancer biomarkers and therapeutic targets. In this study, we review several metabolomics studies performed in prostatic fluid, blood plasma/serum, urine, tissues and immortalized cultured cell lines with the objective of discovering alterations in the metabolic phenotype of PCa and thus discovering new biomarkers for the diagnosis of PCa. Encouraging results using metabolomics have been reported for PCa, with sarcosine being one of the most promising biomarkers identified to date. However, the use of sarcosine as a PCa biomarker in the clinic remains a controversial issue within the scientific community. Beyond sarcosine, other metabolites are considered to be biomarkers for PCa, but they still need clinical validation. Despite the lack of metabolomics biomarkers reaching clinical practice, metabolomics proved to be a powerful tool in the discovery of new biomarkers for PCa detection.     

Differential Utilization of Dietary Fatty Acids in Benign and Malignant Cells of the Prostate

Tumor cells adapt via metabolic reprogramming to meet elevated energy demands due to continuous proliferation, for example by switching to alternative energy sources. Nutrients such as glucose, fatty acids, ketone bodies and amino acids may be utilized as preferred substrates to fulfill increased energy requirements. In this study we investigated the metabolic characteristics of benign and cancer cells of the prostate with respect to their utilization of medium chain (MCTs) and long chain triglycerides (LCTs) under standard and glucose-starved culture conditions by assessing cell viability, glycolytic activity, mitochondrial respiration, the expression of genes encoding key metabolic enzymes as well as mitochondrial mass and mtDNA content. We report that BE prostate cells (RWPE-1) have a higher competence to utilize fatty acids as energy source than PCa cells (LNCaP, ABL, PC3) as shown not only by increased cell viability upon fatty acid supplementation but also by an increased ß-oxidation of fatty acids, although the base-line respiration was 2-fold higher in prostate cancer cells. Moreover, BE RWPE-1 cells were found to compensate for glucose starvation in the presence of fatty acids. Of notice, these findings were confirmed in vivo by showing that PCa tissue has a lower capacity in oxidizing fatty acids than benign prostate. Collectively, these metabolic differences between benign and prostate cancer cells and especially their differential utilization of fatty acids could be exploited to establish novel diagnostic and therapeutic strategies.     

The fat side of prostate cancer

Prostate cancer (PCa) metabolism appears to be unique in comparison with other types of solid cancers. Normal prostate cells mainly rely on glucose oxidation to provide precursors for the synthesis and secretion of citrate, resulting in an incomplete Krebs cycle and minimal oxidative phosphorylation for energy production. In contrast, during transformation, PCa cells no longer secrete citrate and they reactivate the Krebs cycle as energy source. Moreover, primary PCas do not show increased aerobic glycolysis and therefore they are not efficiently detectable with ¹⁸F-FDG-PET. However, increased de novo lipid synthesis, strictly intertwined with deregulation in classical oncogenes and oncosuppressors, is an early event of the disease. Up-regulation and increased activity of lipogenic enzymes (including fatty acid synthase and choline kinase) occurs throughout PCa carcinogenesis and correlates with worse prognosis and poor survival. Thus, lipid precursors such as acetate and choline have been successfully used as alternative tracers for PET imaging. Lipid synthesis intermediates and FA catabolism also emerged as important players in PCa maintenance. Finally, epidemiologic studies suggested that systemic metabolic disorders including obesity, metabolic syndrome, and diabetes as well as hypercaloric and fat-rich diets might increase the risk of PCa. However, how metabolic disorders contribute to PCa development and whether dietary lipids and de novo lipids synthesized intra-tumor are differentially metabolized still remains unclear. In this review, we examine the switch in lipid metabolism supporting the development and progression of PCa and we discuss how we can exploit its lipogenic nature for therapeutic and diagnostic purposes. This article is part of a Special Issue entitled Lipid Metabolism in Cancer.