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

Metabolic adaptations in prostate cancer

Prostate cancer is one of the most commonly diagnosed cancers in men and is a major cause of cancer-related deaths worldwide. Among the molecular processes that contribute to this disease, the weight of metabolism has been placed under the limelight in recent years. Tumours exhibit metabolic adaptations to comply with their biosynthetic needs. However, metabolites also play an important role in supporting cell survival in challenging environments or remodelling the tumour microenvironment, thus being recognized as a hallmark in cancer. Prostate cancer is uniquely driven by androgen receptor signalling, and this knowledge has also influenced the paths of cancer metabolism research. This review provides a comprehensive perspective on the metabolic adaptations that support prostate cancer progression beyond androgen signalling, with a particular focus on tumour cell intrinsic and extrinsic pathways.

Prostate cancer-derived extracellular vesicles metabolic biomarkers: Emerging roles for diagnosis and prognosis

Prostate cancer (PCa) is a global health concern, ranking as the most common cancer among men in Western countries. Traditional diagnostic methods are invasive with adverse effects on patients. Due to the heterogeneous nature of PCa and their multifocality, tissue biopsies often yield false-negative results. To address these challenges, researchers are exploring innovative approaches, particularly in the realms of proteomics and metabolomics, to identify more reliable biomarkers and improve PCa diagnosis. Liquid biopsy (LB) has emerged as a promising non-invasive strategy for PCa early detection, biopsy selection, active surveillance for low-risk cases, and post-treatment and progression monitoring. Extracellular vesicles (EVs) are lipid-bilayer nanovesicles released by all cell types and play an important role in intercellular communication. EVs have garnered attention as a valuable biomarker resource in LB for PCa-specific biomarkers, enhancing diagnosis, prognostication, and treatment guidance. Metabolomics provides insight into the body's metabolic response to both internal and external stimuli, offering quantitative measurements of biochemical alterations. It excels at detecting non-genetic influences, aiding in the discovery of more accurate cancer biomarkers for early detection and disease progression monitoring. This review delves into the potential of EVs as a resource for LB in PCa across various clinical applications. It also explores cancer-related metabolic biomarkers, both within and outside EVs in PCa, and summarises previous metabolomic findings in PCa diagnosis and risk assessment. Finally, the article addresses the challenges and future directions in the evolving field of EV-based metabolomic analysis, offering a comprehensive overview of its potential in advancing PCa management.

Change of glucometabolic activity per PSMA expression predicts survival in mCRPC patients non-responding to PSMA radioligand therapy: introducing a novel dual imaging biomarker

Purpose

The value of [18F]fluorodeoxyglucose ([18F]FDG) PET/CT in monitoring prostate-specific membrane antigen (PSMA) targeted radioligand therapy (RLT) is still unclear. The aim of this study was to identify appropriate prognostic dynamic parameters derived from baseline and follow-up [18F]FDG and dual [18F]FDG/[68Ga]Ga-PSMA-11 PET/CT for monitoring early non-responding mCRPC patients undergoing PSMA-RLT.

Methods

Twenty-three mCRPC patients of a prospective registry (NCT04833517), who were treated with [177Lu]Lu-PSMA-617 RLT and classified as early non-responders were included in this study. All patients received dual PET/CT imaging with [18F]FDG and [68Ga]Ga-PSMA-11 at baseline and after median two cycles of RLT. We tested potential biomarkers representing the "change of glucometabolic activity (cGA)" and "change of glucometabolic activity in relation to PSMA expression (cGAP)" composed of established parameters on [18F]FDG PET/CT as SUVmax, cumulative SUV of five lesions (SUV5), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) and its corresponding parameters on [68Ga]Ga-PSMA-11 PET/CT, respectively, for association with overall survival (OS).

Results

Kaplan-Meier analyses showed no significant association with OS for each tested cGA (cGASUVmaxp = 0.904, cGASUV5, p = 0.747 cGAMTVp = 0.682 and cGATLGp = 0.700), likewise the dual imaging biomarkers cGAPSUVmax (p = 0.136), cGAPSUV5 (p = 0.097), and cGAPTV (p = 0.113) failed significance. In contrast, cGAPTL, which is based on TLG and total lesion PSMA (TLP) showed a significant association with OS (p = 0.004). Low cGAPTL (cut-off 0.7) was associated with significant longer survival (17.6 vs. 12.9 months).

Conclusion

The novel biomarker cGAPTL, which represents the temporal change of whole-body TLG normalized by TLP, predicts overall survival in the challenging cohort of patients non-responding to PSMA-RLT.

Targeting the Metabolic Enzyme PGAM2 Overcomes Enzalutamide Resistance in Castration-Resistant Prostate Cancer by Inhibiting BCL2 Signaling

The next-generation androgen receptor (AR) inhibitor enzalutamide is the mainstay treatment for metastatic prostate cancer. Unfortunately, resistance occurs rapidly in most patients, and once resistance occurs, treatment options are limited. Therefore, there is an urgent need to identify effective targets to overcome enzalutamide resistance. Here, using a genome-wide CRISPR-Cas9 library screen, we found that targeting a glycolytic enzyme, phosphoglycerate mutase PGAM2, significantly enhanced the sensitivity of enzalutamide-resistant prostate cancer cells to enzalutamide both in vivo and in vitro. Inhibition of PGAM2 together with enzalutamide treatment triggered apoptosis by decreasing levels of the antiapoptotic protein BCL-xL and increasing activity of the proapoptotic protein BAD. Mechanistically, PGAM2 bound to 14-3-3ζ and promoted its interaction with phosphorylated BAD, resulting in activation of BCL-xL and subsequent resistance to enzalutamide-induced apoptosis. In addition, high PGAM2 expression, which is transcriptionally regulated by AR, was associated with shorter survival and rapid development of enzalutamide resistance in patients with prostate cancer. Together, these findings provide evidence of a nonmetabolic function of PGAM2 in promoting enzalutamide resistance and identify PGAM2 inhibition as a promising therapeutic strategy for enzalutamide-resistant prostate cancer.

SIGNIFICANCE

PGAM2 promotes resistance to enzalutamide by activating antiapoptotic BCL-xL and suppressing apoptosis, indicating that PGAM2 is a potential target for overcoming enzalutamide resistance in prostate cancer.

Role of monocarboxylate transporters and glucose transporters in prostate cancer

OBJECTIVES

Currently, research of new diagnostic approaches to detect clinically significant prostate cancer is relevant because of the importance of early detection of aggressive forms of the disease, often challenging, even when using modern diagnostic tools. The aim of this review is to present the current knowledge regarding monocarboxylate transporters' and glucose transporters' expression as a component of glycolytic phenotype definition in prostate cancer cells.

METHODS

We searched PubMed and Scopus databases. Twenty-six articles from 2003 to 2022 were included. Literature research and selection were carried out based on the recommendations of the PRISMA statement.

RESULTS

The presence of "lactate shuttle" in the tumor tissue is associated with a worse prognosis. Increased expression of MCT2, MCT4, GLUT1, and down-regulation of GLUT3 are associated with prostate adenocarcinoma. MCT4 expression level correlates with the grade of tumor malignancy and disease prognosis. Up-regulation of GLUT1 and MCT4 is typical for hormone-resistant prostate cancer. Inhibition of MCT1 and MCT4 and GLUT1 in prostate cancer cells reduces their metabolic activity and growth rate, a suitable novel approach for targeted therapy.

CONCLUSION

Review of the current studies showed that expression of certain MCTs and GLUTs types are associated with prostate cancer and some of them correlate with high malignancy and poor prognosis. Detection by immunohistochemistry of these transporters could represent a new diagnostic tool to identify aggressive forms of prostate cancer, and a novel therapeutic target for selective drugs.

Ciliary Neurotrophic Factor Modulates Multiple Downstream Signaling Pathways in Prostate Cancer Inhibiting Cell Invasiveness

BACKGROUND

Prostate cancer (PCa) remains the most common diagnosed tumor and is the second-leading cause of cancer-related death in men. If the cancer is organ-confined it can be treated by various ablative therapies such as RP (radical prostatectomy), RT (radiation therapy), brachytherapy, cryosurgery or HIFU (High-Intensity Focused Ultrasound). However, advanced or metastatic PCa treatment requires systemic therapy involving androgen deprivation, but such patients typically progress to refractory disease designated as castration-resistant prostate cancer (CRPC). Interleukin-6 (IL-6) has been established as a driver of prostate carcinogenesis and tumor progression while less is known about the role of ciliary neurotrophic factor (CNTF), a member of the IL-6 cytokine family in prostate cancer. Moreover, MAPK/ERK, AKT/PI3K and Jak/STAT pathways that regulate proliferative, invasive and glucose-uptake processes in cancer progression are triggered by CNTF.

METHODS

We investigate CNTF and its receptor CNTFRα expressions in human androgen-responsive and castration-resistant prostate cancer (CRPC) by immunohistochemistry. Moreover, we investigated the role of CNTF in proliferative, invasive processes as well as glucose uptake using two cell models mimicking the PCa (LNCaP cell line) and CRPC (22Rv1 cell line).

CONCLUSIONS

Our results showed that CNTF and CNTFRa were expressed in PCa and CRPC tissues and that CNTF has a pivotal role in prostate cancer environment remodeling and as a negative modulator of invasion processes of CRPC cell models.

Bicalutamide Anticancer Activity Enhancement by Formulation of Soluble Inclusion Complexes with Cyclodextrins

Bicalutamide (BCL) is a nonsteroidal antiandrogen drug that represents an alternative to castration in the treatment of prostate cancer, due to its relatively long half-life and tolerable side effects. However, it possesses a very low water solubility that can affect its oral bioavailability. In this work, we developed inclusion complexes of BCL with the highly soluble hydroxypropyl-β-cyclodextrin (HP-β-CyD) and sulfobutylether-β-cyclodextrin (SBE-β-CyD) to increase the water solubility and anticancer activity of BCL. The inclusion complexes were prepared using the freeze-drying method and were then characterized in a solid state via differential scanning calorimetry and X-ray analysis and in solution via phase-solubility studies and UV-vis and NMR spectroscopy. The BCL/HP-β-CyD and BCL/SBE-β-CyD inclusion complexes were amorphous and rapidly dissolved in water. Both the 1H-NMR spectra and molecular modeling studies confirmed the penetration of the 2-(trifluoromethyl)benzonitrile ring of BCL within the cavity of both cyclodextrins (CyDs). Due to the consistent improvement of the water solubility of BCL, the inclusion complexes showed higher antiproliferative activity toward the human prostate androgen-independent cell lines, DU-145 and PC-3, with respect to free BCL. These results demonstrate the ability of HP-β-CyD and SBE-β-CyD to complex BCL, permitting the realization of liquid formulations with potentially high oral bioavailability and/or possible parenteral administration.

Rapid nutrient depletion to below the physiological range by cancer cells cultured in Plasmax

Mammalian cell culture is a fundamental tool used to study living cells. Presently, the standard protocol for performing cell culture involves the use of commercial media that contain an excess of nutrients. While this reduces the likelihood of cell starvation, it creates non-physiologic culture conditions that have been shown to 're-wire' cellular metabolism. Recently, researchers have developed new media like Plasmax, formulated to approximate the nutrient composition of human blood plasma. Although this represents an improvement in cell culture practice, physiologic media may be vulnerable to nutrient depletion. In this study we directly addressed this concern by measuring the rates of glucose and amino acid depletion from Plasmax in several cancer cell lines (PC-3, LNCaP, MCF-7, SH-SY5Y) over 48 hours. In all cell lines, depletion of glucose from Plasmax was rapid such that, by 48h, cells were hypoglycemic (<2mM glucose). Most amino acids were similarly rapidly depleted to sub-physiological levels by 48h. In contrast, glucose and most amino acids remained within the physiological range at 24h. When the experiment was done at physiological oxygen (5%) versus standard (18%) with LNCaP cells, no effect on glucose or amino acid consumption was observed. Using RNA sequencing, we show that this nutrient depletion is associated with enrichment of starvation responses, apoptotic signalling, and endoplasmic reticulum stress. A shift from glycolytic metabolism to mitochondrial respiration at 5% O2 was also measured using Seahorse analysis. Taken together, these results exemplify the metabolic considerations for Plasmax, highlighting that cell culture in Plasmax requires daily media exchange.

Metabolomic Profile in Patients with Malignant Disturbances of the Prostate: An Experimental Approach

Purpose To identify metabolites in humans that can be associated with the presence of malignant disturbances of the prostate.

Methods In the present study, we selected male patients aged between 46 and 82 years who were considered at risk of prostate cancer due to elevated levels of prostate-specific antigen (PSA) or abnormal results on the digital rectal examination. All selected patients came from two university hospitals (Hospital Universitario del Valle and Clínica Rafael Uribe Uribe) and were divided into 2 groups: cancer (12 patients) and non-cancer (20 patients). Cancer was confirmed by histology, and none of the patients underwent any previous treatment. Standard protocols were applied to all the collected blood samples. The resulting plasma samples were kept at -80°C, and a profile of each one was acquired by nuclear magnetic resonance (NMR) using established experiments. Multivariate analyses were applied to this dataset, first to establish the quality of the data and identify outliers, and then, to model the data.

Results We included 12 patients with cancer and 20 without it. Two patients were excluded due to contamination with ethanol. The remaining ones were used to build an Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) model (including 15 non-cancer and 10 cancer patients), with acceptable discrimination (Q2 = 0.33). This model highlighted the role of lactate and lipids, with a positive association of these two metabolites and prostate cancer.

Conclusions The primary discriminative metabolites between patients with and without prostate cancer were lactate and lipids. These might be the most reliable biomarkers to trace the development of cancer in the prostate.

A Metabolism-Related Gene Landscape Predicts Prostate Cancer Recurrence and Treatment Response

Background

Prostate cancer (PCa) is the most common malignant tumor in men. Although clinical treatments of PCa have made great progress in recent decades, once tolerance to treatments occurs, the disease progresses rapidly after recurrence. PCa exhibits a unique metabolic rewriting that changes from initial neoplasia to advanced neoplasia. However, systematic and comprehensive studies on the relationship of changes in the metabolic landscape of PCa with tumor recurrence and treatment response are lacking. We aimed to construct a metabolism-related gene landscape that predicts PCa recurrence and treatment response.

Methods

In the present study, we used differentially expressed gene analysis, protein–protein interaction (PPI) networks, univariate and multivariate Cox regression, and least absolute shrinkage and selection operator (LASSO) regression to construct and verify a metabolism-related risk model (MRM) to predict the disease-free survival (DFS) and response to treatment for PCa patients.

Results

The MRM predicted patient survival more accurately than the current clinical prognostic indicators. By using two independent PCa datasets (International Cancer Genome Consortium (ICGC) PCa and Taylor) and actual patients to test the model, we also confirmed that the metabolism-related risk score (MRS) was strongly related to PCa progression. Notably, patients in different MRS subgroups had significant differences in metabolic activity, mutant landscape, immune microenvironment, and drug sensitivity. Patients in the high-MRS group were more sensitive to immunotherapy and endocrine therapy, while patients in the low-MRS group were more sensitive to chemotherapy.

Conclusions

We developed an MRM, which might act as a clinical feature to more accurately assess prognosis and guide the selection of appropriate treatment for PCa patients. It is promising for further application in clinical practice.

Beyond the Prognostic Value of 2-[18F]FDG PET/CT in Prostate Cancer: A Case Series and Literature Review Focusing on the Diagnostic Value and Impact on Patient Management

The role of 2-deoxy-2-[¹⁸F]fluoro-D-glucose Positron Emission Tomography/Computed Tomography (FDG PET/CT) in the management of prostate cancer (PCa) patients is increasingly recognised. However, its clinical role is still controversial. Many published studies showed that FDG PET/CT might have a prognostic value in the metastatic castration-resistant phase of the disease, but its role in other settings of PCa and, more importantly, its impact on final clinical management remains to be further investigated. We describe a series of six representative clinical cases of PCa in different clinical settings, but all characterised by a measurable clinical impact of FDG PET/CT on the patients’ management. Starting from their clinical history, we report a concise narrative literature review on the advantages and limitations of FDG PET/CT beyond its prognostic value in PCa. What emerges is that in selected cases, this imaging technique may represent a useful tool in managing PCa patients. However, in the absence of dedicated studies to define the optimal clinical setting of its application, no standard recommendations on its use in PCa patients can be made.

Personalized Medicine for Prostate Cancer: Is Targeting Metabolism a Reality?

Prostate cancer invokes major shifts in gene transcription and metabolic signaling to mediate alterations in nutrient acquisition and metabolic substrate selection when compared to normal tissues. Exploiting such metabolic reprogramming is proposed to enable the development of targeted therapies for prostate cancer, yet there are several challenges to overcome before this becomes a reality. Herein, we outline the role of several nutrients known to contribute to prostate tumorigenesis, including fatty acids, glucose, lactate and glutamine, and discuss the major factors contributing to variability in prostate cancer metabolism, including cellular heterogeneity, genetic drivers and mutations, as well as complexity in the tumor microenvironment. The review draws from original studies employing immortalized prostate cancer cells, as well as more complex experimental models, including animals and humans, that more accurately reflect the complexity of the in vivo tumor microenvironment. In synthesizing this information, we consider the feasibility and potential limitations of implementing metabolic therapies for prostate cancer management.

The prognostic power of 18F-FDG PET/CT extends to estimating systemic treatment response duration in metastatic castration-resistant prostate cancer (mCRPC) patients

BACKGROUND

We aimed to test whether the prognostic value of 18 F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (FDG-PET/CT) in metastatic castration-resistant prostate cancer (mCRPC) extends to the estimation of systemic treatment response duration.

METHODS

mCRPC patients submitted to FDG-PET/CT in four Italian centers from 2005 to 2020 were retrospectively enrolled. Clinical and biochemical data at the time of imaging were collected, and SUV max of the hottest lesion, total metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were calculated. The correlation between PET- and biochemical-derived parameters with Overall Survival (OS) was analysed. The prediction of treatment response duration was assessed in the subgroup submitted to FDG-PET/CT in the six months preceding Chemotherapy (namely Docetaxel or Cabazitaxel, 24 patients) or Androgen-Receptor Targeted Agents (ARTA, namely Abiraterone or Enzalutamide, 20 patients) administration.

RESULTS

We enrolled 114 mCRPC patients followed-up for a median interval lasting 15 months. While at univariate analysis, prostate-specific antigen (PSA), Alkaline Phosphatase (ALP), MTV, and TLG were associated with OS, at the multivariate Cox regression analysis, the sole MTV could independently predict OS (p < 0.0001). In the subgroup submitted to FDG-PET/CT before the systemic treatment initiation, PSA and TLG could also predict treatment response duration independently (p < 0.05). Of note, while PSA could not indicate the best treatment choice, lower TLG was associated with higher success rates for ARTA but had no impact on chemotherapy efficacy.

CONCLUSIONS

FDG-PET/CT's prognostic value extends to predicting treatment response duration in mCRPC, thus potentially guiding the systemic treatment selection.

Dietary Phytochemicals in Zinc Homeostasis: A Strategy for Prostate Cancer Management

Studies have suggested an important role of the trace element zinc (Zn) in prostate biology and functions. Zn has been shown to exist in very high concentrations in the healthy prostate and is important for several prostatic functions. In prostate cancer (PCa), Zn levels are significantly decreased and inversely correlated with disease progression. Ideally, restoration of adequate Zn levels in premalignant/malignant prostate cells could abort prostate malignancy. However, studies have shown that Zn supplementation is not an efficient way to significantly increase Zn concentrations in PCa. Based on a limited number of investigations, the reason for the lower levels of Zn in PCa is believed to be the dysregulation of Zn transporters (especially ZIP and ZnT family of proteins), metallothioneins (for storing and releasing Zn), and their regulators (e.g., Zn finger transcription factor RREB1). Interestingly, the level of Zn in cells has been shown to be modulated by naturally occurring dietary phytochemicals. In this review, we discussed the effect of selected phytochemicals (quercetin, resveratrol, epigallocatechin-3-gallate and curcumin) on Zn functioning and proposes that Zn in combination with specific dietary phytochemicals may lead to enhanced Zn bioaccumulation in the prostate, and therefore, may inhibit PCa.

Follicle-stimulating hormone promotes growth of human prostate cancer cell line-derived tumor xenografts

Chemical castration in prostate cancer can be achieved with gonadotropin-releasing hormone (GnRH) agonists or antagonists. Their effects differ by the initial flare of gonadotropin and testosterone secretion with agonists and the immediate pituitary-testicular suppression by antagonists. While both suppress luteinizing hormone (LH) and follicle-stimulating hormone (FSH) initially, a rebound in FSH levels occurs during agonist treatment. This rebound is potentially harmful, taken the expression of FSH receptors (R) in prostate cancer tissue. We herein assessed the role of FSH in promoting the growth of androgen-independent (PC-3, DU145) and androgen-dependent (VCaP) human prostate cancer cell line xenografts in nude mice. Gonadotropins were suppressed with the GnRH antagonist degarelix, and effects of add-back human recombinant FSH were assessed on tumor growth. All tumors expressed GnRHR and FSHR, and degarelix treatment suppressed their growth. FSH supplementation reversed the degarelix-evoked suppression of PC-3 tumors, both in preventive (degarelix and FSH treatment started upon cell inoculation) and therapeutic (treatments initiated 3 weeks after cell inoculation) setting. A less marked, though significant FSH effect occurred in DU145, but not in VCaP xenografts. FSHR expression in the xenografts supports direct FSH stimulation of tumor growth. Testosterone supplementation, to maintain the VCaP xenografts, apparently masked the FSH effect on their growth. Treatment with the LH analogue hCG did not affect PC-3 tumor growth despite their expression of luteinizing hormone/choriongonadotropin receptor. In conclusion, FSH, but not LH, may directly stimulate the growth of androgen-independent prostate cancer, suggesting that persistent FSH suppression upon GnRH antagonist treatment offers a therapeutic advantage over agonist.

Resistance to Androgen Deprivation Leads to Altered Metabolism in Human and Murine Prostate Cancer Cell and Tumor Models

Currently, no clinical methods reliably predict the development of castration-resistant prostate cancer (CRPC) that occurs almost universally in men undergoing androgen deprivation therapy. Hyperpolarized (HP) ¹³C magnetic resonance imaging (MRI) could potentially detect the incipient emergence of CRPC based on early metabolic changes. To characterize metabolic shifts occurring upon the transition from androgen-dependent to castration-resistant prostate cancer (PCa), the metabolism of [U-¹³C]glucose and [U-¹³C]glutamine was analyzed by nuclear magnetic resonance spectroscopy. Comparison of steady-state metabolite concentrations and fractional enrichment in androgen-dependent LNCaP cells and transgenic adenocarcinoma of the murine prostate (TRAMP) murine tumors versus castration-resistant PC-3 cells and treatment-driven CRPC TRAMP tumors demonstrated that CRPC was associated with upregulation of glycolysis, tricarboxylic acid metabolism of pyruvate; and glutamine, glutaminolysis, and glutathione synthesis. These findings were supported by ¹³C isotopomer modeling showing increased flux through pyruvate dehydrogenase (PDH) and anaplerosis; enzymatic assays showing increased lactate dehydrogenase, PDH and glutaminase activity; and oxygen consumption measurements demonstrating increased dependence on anaplerotic fuel sources for mitochondrial respiration in CRPC. Consistent with ex vivo metabolomic studies, HP [1-¹³C]pyruvate distinguished androgen-dependent PCa from CRPC in cell and tumor models based on significantly increased HP [1-¹³C]lactate.

PET nanoplastics interactions with water contaminants and their impact on human cells

In recent years, many studies are focusing on the negative effects of plastic pollution, and in particular on the nanosized plastic fragments and their implications on the environment and human health. Nanoplastics in the environment interact with a great number of substances, many of which are dangerous to humans, but the interaction mechanisms, the complexes formation processes, and their biological impact are still poorly understood. Here we report a study on the interactions of polyethylene terephthalate nanoplastics, produced by laser ablation, with three different types of contaminants: glyphosate, levofloxacin and Hg²⁺ ions, and we demonstrate that the nanoplastics form complexes with all three contaminants through their favorable binding. Most importantly, this study highlights that to demonstrate the overall effect of the nanoplastics internalized by cells in vitro, it is important to combine alternative methodologies, such as metabolomics, with standard biological assays (i.e., cell viability and ROS production). In this way it becomes possible to better understand the body's response to this new class of pollutants and their possible chronic toxicity. Summary: PET nanoplastics, fabricated by laser ablation, interact with aqueous pollutants forming nanoclusters. The nanoclusters affect the cells metabolism, suggesting long-term risks.

Molecular and metabolic imaging of castration-resistant prostate cancer: state of art and future prospects

Prostate cancer (PCa) represents the most common tumor in male and one of the most relevant causes of death in Western countries. Androgen deprivation therapy (ADT) constitutes a widely used approach in advanced PCa. When PCa progresses in spite of ADT and castrate levels of testosterone, the severe clinical condition termed as metastatic castration-resistant prostate cancer (mCRPC) takes place. The only approach to mCRPC has been represented by chemotherapy with taxanes for many years. Nevertheless, recently introduced treatments such as 2nd generation antiandrogens (i.e. enzalutamide and abiraterone), cell immunotherapy with sipuleucel-T or targeted alpha therapy with 223Ra-dichloride, have dramatically changed mCRPC prognosis. These novel therapies call for an unmet need for imaging biomarkers suitable for patients' pre-treatment stratification and response assessment. In this scenario, nuclear medicine can provide several metabolic and molecular probes for investigating pathological processes at a cellular and sub-cellular level. The aim of this paper is to review the most relevant findings of the literature published to date on this topic, giving particular emphasis to the pros and cons of each tracer and also covering future prospects for defining personalized therapeutic approaches.

Glutaminolysis is a metabolic route essential for survival and growth of prostate cancer cells and a target of 5α-dihydrotestosterone regulation

PURPOSE

Resistance to androgen-deprivation therapies and progression to so-called castrate-resistant prostate cancer (CRPC) remain challenges in prostate cancer (PCa) management and treatment. Among other alterations, CRPC has been associated with metabolic reprogramming driven by androgens. Here, we investigated the role of androgens in regulating glutaminolysis in PCa cells and determined the relevance of this metabolic route in controlling the survival and growth of androgen-sensitive (LNCaP) and CRPC (DU145 and PC3) cells.

METHODS

PCa cells (LNCaP, DU145 and PC3) and 3-month old rats were treated with 5α-dihydrotestosterone (DHT). Alternatively, LNCaP cells were exposed to the glutaminase inhibitor BPTES, alone or in combination with the anti-androgen bicalutamide. Biochemical, Western blot and extracellular flux assays were used to evaluate the viability, proliferation, migration and metabolism of PCa cells in response to DHT treatment or glutaminase inhibition.

RESULTS

We found that DHT up-regulated the expression of the glutamine transporter ASCT2 and glutaminase, both in vitro in LNCaP cells and in vivo in rat prostate cells. BPTES diminished the viability and migration of PCa cells, while increasing caspase-3 activity. CRPC cells were found to be more dependent on glutamine and more sensitive to glutaminase inhibition. BPTES and bicalutamide co-treatment had an additive effect on suppressing LNCaP cell viability. Finally, we found that inhibition of glutaminolysis differentially affected glycolysis and lipid metabolism in both androgen-sensitive and CRPC cells.

CONCLUSION

Our data reveal glutaminolysis as a central metabolic route controlling PCa cell fate and highlight the relevance of targeting glutaminase for CRPC treatment.

Revisiting prostate cancer metabolism: From metabolites to disease and therapy

Prostate cancer (PCa), one of the most commonly diagnosed cancers worldwide, still presents important unmet clinical needs concerning treatment. In the last years, the metabolic reprogramming and the specificities of tumor cells emerged as an exciting field for cancer therapy. The unique features of PCa cells metabolism, and the activation of specific metabolic pathways, propelled the use of metabolic inhibitors for treatment. The present work revises the knowledge of PCa metabolism and the metabolic alterations that underlie the development and progression of the disease. A focus is given to the role of bioenergetic sources, namely, glucose, lipids, and glutamine sustaining PCa cell survival and growth. Moreover, it is described as the action of oncogenes/tumor suppressors and sex steroid hormones in the metabolic reprogramming of PCa. Finally, the status of PCa treatment based on the inhibition of metabolic pathways is presented. Globally, this review updates the landscape of PCa metabolism, highlighting the critical metabolic alterations that could have a clinical and therapeutic interest.

Pyruvate-lactate exchange and glucose uptake in human prostate cancer cell models. A study in xenografts and suspensions by hyperpolarized [1-13 C]pyruvate MRS and [18 F]FDG-PET

Reprogramming of energy metabolism in the development of prostate cancer can be exploited for a better diagnosis and treatment of the disease. The goal of this study was to determine whether differences in glucose and pyruvate metabolism of human prostate cancer cells with dissimilar aggressivenesses can be detected using hyperpolarized [1-¹³ C]pyruvate MRS and [¹⁸ F]FDG-PET imaging, and to evaluate whether these measures correlate. For this purpose, we compared murine xenografts of human prostate cancer LNCaP cells with those of more aggressive PC3 cells. [1-¹³ C]pyruvate was hyperpolarized by dissolution dynamic nuclear polarization (dDNP) and [1-¹³ C]pyruvate to lactate conversion was followed by ¹³ C MRS. Subsequently [¹⁸ F]FDG uptake was investigated by static and dynamic PET measurements. Standard uptake values (SUVs) for [¹⁸ F]FDG were significantly higher for xenografts of PC3 compared with those of LNCaP. However, we did not observe a difference in the average apparent rate constant k_pl of ¹³ C label exchange from pyruvate to lactate between the tumor variants. A significant negative correlation was found between SUVs from [¹⁸ F]FDG PET measurements and k_pl values for the xenografts of both tumor types. The k_pl rate constant may be influenced by various factors, and studies with a range of prostate cancer cells in suspension suggest that LDH inhibition by pyruvate may be one of these. Our results indicate that glucose and pyruvate metabolism in the prostate cancer cell models differs from that in other tumor models and that [¹⁸ F]FDG-PET can serve as a valuable complementary tool in dDNP studies of aggressive prostate cancer with [1-¹³ C]pyruvate.

New findings on urinary prostate cancer metabolome through combined GC-MS and 1H NMR analytical platforms

INTRODUCTION

The inherent sensitivity of metabolomics allows the detection of subtle alterations in biological pathways, making it a powerful tool to study biomarkers and the mechanisms that underlie cancer.

OBJECTIVES

The purpose of this work was to characterize the urinary metabolic profile of prostate cancer (PCa) patients and cancer-free controls to obtain a holistic coverage of PCa metabolome.

METHODS

Two groups of samples, a training set (n = 41 PCa and n = 42 controls) and an external validation set (n = 18 PCa and n = 18 controls) were analyzed using a dual analytical platform, namely gas chromatography-mass spectrometry (GC-MS) and proton nuclear magnetic resonance spectroscopy (¹H NMR).

RESULTS

The multivariate analysis models revealed a good discrimination between cases and controls with an AUC higher than 0.8, a sensitivity ranging from 67 to 89%, a specificity ranging from 74 to 89% and an accuracy from 73 to 86%, considering the training and external validation sets. A total of 28 metabolites (15 from GC-MS and 13 from ¹H NMR) accounted for the separation. These discriminant metabolites are involved in 14 biochemical pathways, indicating that PCa is highly linked to dysregulation of metabolic pathways associated with amino acids and energetic metabolism.

CONCLUSION

These findings confirmed the complementary information provided by GC-MS and ¹H NMR, enabling a more comprehensive picture of the altered metabolites, underlying pathways and deepening the understanding of PCa development and progression.

GLUT1 is an AR target contributing to tumor growth and glycolysis in castration-resistant and enzalutamide-resistant prostate cancers

Castration-resistant prostate cancer (CRPC) displays a higher ¹⁸F-FDG PET SUV_max than hormone-sensitive prostate cancer, which suggests a greater need for glucose metabolism in CRPC. Targeting glucose metabolism in cancer cells remains attractive for cancer treatment. Glucose transporters (GLUTs) meditate the first and rate-limiting step of glucose metabolism. Here, we investigated the key mediator of glucose transporters and evaluated its therapeutic value in a preclinical model of CRPC. ¹⁸F-FDG PET showed a higher SUV_max in CRPC than in hormone-sensitive prostate cancer, and GLUT1 expression positively correlated with SUV_max and was associated with a worse CRPC outcome. GLUT1 inhibition significantly suppressed cell growth, glycolysis and tumor volume in a xenograft model both in CRPC and enzalutamide-resistant prostate cancer. Chromatin immunoprecipitation and dual luciferase reporter assay showed that androgen receptor (AR) directly bound to the GLUT1 gene promoter to promote GLUT1 transcription. Combining GLUT1 inhibition and enzalutamide remarkably suppressed proliferation and glycolysis and induced apoptosis in CRPC cells. Our results suggest that GLUT1 is an AR target and displays synergistic effects with enzalutamide. GLUT1 may act as a promising therapeutic target in CRPC and enzalutamide-resistant prostate cancer.

GLUT1 expression in high-risk prostate cancer: correlation with 18F-FDG-PET/CT and clinical outcome

BACKGROUND

Tumour ¹⁸F-FDG-uptake is of prognostic value in high-risk and metastatic prostate cancer (PCa). The aim of this study is to investigate the underlying glucose metabolism mechanisms of ¹⁸F-FDG-uptake on PET/CT imaging in PCa.

METHODS

Retrospective analysis was conducted for 94 patients diagnosed with a Gleason sum ≥8 adenocarcinoma of the prostate at biopsy between July 2011 and July 2014 who underwent ¹⁸F-FDG-PET/CT imaging before radical prostatectomy (RP). ¹⁸F-FDG-uptake in primary lesion was measured by a blinded reader using maximum standardised uptake value (SUV_max). GLUT1, GLUT12 and HK2 expression were blindly scored after immunohistochemistry on specimens RP by three pathologists. Correlations between GLUT1, GLUT12 and HK2, and SUV_max were assessed using Spearman's rank correlation test. Survival probabilities were based on the Kaplan-Meier method.

RESULTS

With a median follow-up of 4.5 years, 56% (n = 53) of patients had biochemical recurrence (BCR), 7% (n = 7) progressed to castration-resistant prostate cancer (CRPC) disease, 13% (n = 12) developed metastasis and 6% (n = 6) died. Correlation was found between GLUT1 expression and SUVmax level (r = 0.25, p = 0.02). In addition, SUV_max was significantly higher in tumours with high GLUT1 expression (n = 17, 5.74 ± 1.67) than tumours with low GLUT1 expression (n = 71, 2.68 ± 0.31, p = 0.004). Moreover, a significant association was found between GLUT1 expression levels and SUV_max level (p = 0.005), lymph node status (p = 0.05), volume of cancer (p = 0.01), CRPC disease progression (p = 0.02) and metastasis development (p = 0.04). No significant difference between GLUT12 and HEX2 expression and SUV_max have been found.

CONCLUSIONS

GLUT1 expression in PCa tumours correlates with ¹⁸F-FDG-uptake and poor prognostic factors. These results suggest that this transporter is involved in the molecular mechanism of ¹⁸F-FDG-uptake in high-risk PCa and raise interest in targeting metabolic dependencies of PCa cells as a selective anticancer strategy.

Lipogenic effects of androgen signaling in normal and malignant prostate

Prostate cancer is an androgen-dependent cancer with unique metabolic features compared to many other solid tumors, and typically does not exhibit the “Warburg effect”. During malignant transformation, an early metabolic switch diverts the dependence of normal prostate cells on aerobic glycolysis for the synthesis of and secretion of citrate towards a more energetically favorable metabolic phenotype, whereby citrate is actively oxidised for energy and biosynthetic processes (i.e. de novo lipogenesis). It is now clear that lipid metabolism is one of the key androgen-regulated processes in prostate cells and alterations in lipid metabolism are a hallmark of prostate cancer, whereby increased de novo lipogenesis accompanied by overexpression of lipid metabolic genes are characteristic of primary and advanced disease. Despite recent advances in our understanding of altered lipid metabolism in prostate tumorigenesis and cancer progression, the intermediary metabolism of the normal prostate and its relationship to androgen signaling remains poorly understood. In this review, we discuss the fundamental metabolic relationships that are distinctive in normal versus malignant prostate tissues, and the role of androgens in the regulation of lipid metabolism at different stages of prostate tumorigenesis.

Sweet Cherry Extract Targets the Hallmarks of Cancer in Prostate Cells: Diminished Viability, Increased Apoptosis and Suppressed Glycolytic Metabolism

The present work evaluated the anticancer properties of sweet cherry (Prunus avium) extract on human prostate cells. Several sweet cherry cultivars from Fundão (Portugal) were methanol-extracted and their phytochemical composition characterized. The Saco "late harvest" extract was highly-enriched in anthocyanins and selected for use in biological assays. Non-neoplastic (PNT1A) and neoplastic (LNCaP and PC3) human prostate cells were treated with 0-2,000 μg/ml of extract for 48-96 h. Cell viability was evaluated by the MTT assay. Apoptosis, oxidative stress, and glycolytic metabolism were assessed by Western blotting and enzymatic assays. Glucose consumption and lactate production were measured spectrophotometrically. Saco cherry extract diminished the viability of neoplastic and non-neoplastic cells, whereas enhancing apoptosis in LNCaP. Cherry extract-treatment also diminished oxidative damage and suppressed glycolytic metabolism in LNCaP cells. These findings widened the knowledge on the mechanisms by which cherry extract modulate cell physiology, demonstrating their broad action over the hallmarks of cancer.

MCT4 promotes cell proliferation and invasion of castration-resistant prostate cancer PC-3 cell line

Prostate cancer (PCa) is one of the leading causes of cancer-related death in men. Blocking androgen receptor (AR) signaling is an effective treatment strategy for the treatment of advanced metastatic disease of PCa in men. However, the method of blocking AR signaling is not suitable for castration-resistant prostate cancer (CRPC), and the treatment of CRPC is still clinically difficult. It has recently been reported that MCT4 is a plasma membrane transporter that mediates the secretion of lactic acid from aerobic glycolysis by cancer cells. Its expression is up-regulated in PCa and plays an important role in the carcinogenesis of PCa, but the underlying mechanism is hardly known. The MCT4 gene of PC-3 cell line was knocked down by siRNA, then MCT4 mRNA and protein was detected by real-time PCR and western blotting, respectively. CCK-8, Transwell migration assay, Flow cytometry, and TUNEL methods were used to detect the proliferation, invasion and apoptosis of PC-3 cells by MCT4 knockdown, and the expression of invasion-related proteins (MCT4) was detected by western blot analysis. The treatment of PC-3 with candidate MCT4 siRNAs led to marked inhibition of MCT4 expression in both mRNA and protein level. MCT4 knockdown inhibits PC-3 cell proliferation and facilitates apoptosis. Furthermore, MCT4 promoted the invasion capabilities of PC-3 cells by regulating invasion-related genes, such as VEGF, CD147, MMP2 and MMP9. In conclusion, MCT4 promotes oncogenic process of PCa may, as least partially, by inhibiting cell apoptosis and accelerating cell proliferation as well as invasion abilities of PC-3 cells. VEGF, CD147, MMP2 and MMP9 are important downstream genes of MCT4 in facilitating cell invasion.

Cucurbitacin D Reprograms Glucose Metabolic Network in Prostate Cancer

Prostate cancer (PrCa) metastasis is the major cause of mortality and morbidity among men. Metastatic PrCa cells are typically adopted for aberrant glucose metabolism. Thus, chemophores that reprogram altered glucose metabolic machinery in cancer cells can be useful agent for the repression of PrCa metastasis. Herein, we report that cucurbitacin D (Cuc D) effectively inhibits glucose uptake and lactate production in metastatic PrCa cells via modulating glucose metabolism. This metabolic shift by Cuc D was correlated with decreased expression of GLUT1 by its direct binding as suggested by its proficient molecular docking (binding energy −8.5 kcal/mol). Cuc D treatment also altered the expression of key oncogenic proteins and miR-132 that are known to be involved in glucose metabolism. Cuc D (0.1 to 1 µM) treatment inhibited tumorigenic and metastatic potential of human PrCa cells via inducing apoptosis and cell cycle arrest in G2/M phase. Cuc D treatment also showed inhibition of tumor growth in PrCa xenograft mouse model with concomitant decrease in the expression of GLUT1, PCNA and restoration of miR-132. These results suggest that Cuc D is a novel modulator of glucose metabolism and could be a promising therapeutic modality for the attenuation of PrCa metastasis.

Prostate Cancer Energetics and Biosynthesis

Cancers must alter their metabolism to satisfy the increased demand for energy and to produce building blocks that are required to create a rapidly growing tumor. Further, for cancer cells to thrive, they must also adapt to an often changing tumor microenvironment, which can present new metabolic challenges (ex. hypoxia) that are unfavorable for most other cells. As such, altered metabolism is now considered an emerging hallmark of cancer. Like many other malignancies, the metabolism of prostate cancer is considerably different compared to matched benign tissue. However, prostate cancers exhibit distinct metabolic characteristics that set them apart from many other tumor types. In this chapter, we will describe the known alterations in prostate cancer metabolism that occur during initial tumorigenesis and throughout disease progression. In addition, we will highlight upstream regulators that control these metabolic changes. Finally, we will discuss how this new knowledge is being leveraged to improve patient care through the development of novel biomarkers and metabolically targeted therapies.

Targeting androgen receptor-independent pathways in therapy-resistant prostate cancer

Since androgen receptor (AR) signaling is critically required for the development of prostate cancer (PCa), targeting AR axis has been the standard treatment of choice for advanced and metastatic PCa. Unfortunately, although the tumor initially responds to the therapy, treatment resistance eventually develops and the disease will progress. It is therefore imperative to identify the mechanisms of therapeutic resistance and novel molecular targets that are independent of AR signaling. Recent advances in pathology, molecular biology, genetics and genomics research have revealed novel AR-independent pathways that contribute to PCa carcinogenesis and progression. They include neuroendocrine differentiation, cell metabolism, DNA damage repair pathways and immune-mediated mechanisms. The development of novel agents targeting the non-AR mechanisms holds great promise to treat PCa that does not respond to AR-targeted therapies.

The impact of transcription on metabolism in prostate and breast cancers

Metabolic dysregulation is regarded as an important driver in cancer development and progression. The impact of transcriptional changes on metabolism has been intensively studied in hormone-dependent cancers, and in particular, in prostate and breast cancer. These cancers have strong similarities in the function of important transcriptional drivers, such as the oestrogen and androgen receptors, at the level of dietary risk and epidemiology, genetics and therapeutically. In this review, we will focus on the function of these nuclear hormone receptors and their downstream impact on metabolism, with a particular focus on lipid metabolism. We go on to discuss how lipid metabolism remains dysregulated as the cancers progress. We conclude by discussing the opportunities that this presents for drug repurposing, imaging and the development and testing of new therapeutics and treatment combinations.

GLUT1 protects prostate cancer cells from glucose deprivation-induced oxidative stress

Glucose, chief metabolic support for cancer cell survival and growth, is mainly imported into cells by facilitated glucose transporters (GLUTs). The increase in glucose uptake along with tumor progression is due to an increment of facilitative glucose transporters as GLUT1. GLUT1 prevents cell death of cancer cells caused by growth factors deprivation, but there is scarce information about its role on the damage caused by glucose deprivation, which usually occurs within the core of a growing tumor. In prostate cancer (PCa), GLUT1 is found in the most aggressive tumors, and it is regulated by androgens. To study the response of androgen-sensitive and insensitive PCa cells to glucose deprivation and the role of GLUT1 on survival mechanisms, androgen-sensitive LNCaP and castration-resistant LNCaP-R cells were employed. Results demonstrated that glucose deprivation induced a necrotic type of cell death which is prevented by antioxidants. Androgen-sensitive cells show a higher resistance to cell death triggered by glucose deprivation than castration-resistant cells. Glucose removal causes an increment of H₂O₂, an activation of androgen receptor (AR) and a stimulation of AMP-activated protein kinase activity. In addition, glucose removal increases GLUT1 production in androgen sensitive PCa cells. GLUT1 ectopic overexpression makes PCa cells more resistant to glucose deprivation and oxidative stress-induced cell death. Under glucose deprivation, GLUT1 overexpressing PCa cells sustains mitochondrial SOD2 activity, compromised after glucose removal, and significantly increases reduced glutathione (GSH). In conclusion, androgen-sensitive PCa cells are more resistant to glucose deprivation-induced cell death by a GLUT1 upregulation through an enhancement of reduced glutathione levels.

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Glucose deprivation carries an increase of free radicals in prostate cancer cells.

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The androgen receptor activation after glucose deprivation proceeds with GLUT1 overproduction.

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Treatment with hydrogen peroxide mimics the response to glucose deprivation.

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GLUT1-overexpressing prostate cancer cells are more resistant to glucose deprivation.

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Glutathione is more reduced in GLUT1-overexpressing cells under glucose deprivation.

Organelle-Derived Acetyl-CoA Promotes Prostate Cancer Cell Survival, Migration, and Metastasis via Activation of Calmodulin Kinase II

Although emerging evidence suggests a potential role of calcium/calmodulin-dependent kinase II (CaMKII) in prostate cancer, its role in prostate cancer tumorigenesis is largely unknown. Here, we examine whether the acetyl CoA-CaMKII pathway, first described in frog oocytes, promotes prostate cancer tumorigenesis. In human prostate cancer specimens, metastatic prostate cancer expressed higher levels of active CaMKII compared with localized prostate cancer. Correspondingly, basal CaMKII activity was significantly higher in the more tumorigenic PC3 and PC3-mm2 cells relative to the less tumorigenic LNCaP and C4-2B4 cells. Deletion of CaMKII by CRISPR/Cas9 in PC3-mm2 cells abrogated cell survival under low-serum conditions, anchorage-independent growth and cell migration; overexpression of constitutively active CaMKII in C4-2B4 cells promoted these phenotypes. In an animal model of prostate cancer metastasis, genetic ablation of CaMKII reduced PC3-mm2 cell metastasis from the prostate to the lymph nodes. Knockdown of the acetyl-CoA transporter carnitine acetyltransferase abolished CaMKII activation, providing evidence that acetyl-CoA generated from organelles is a major activator of CaMKII. Genetic deletion of the β-oxidation rate-limiting enzyme ACOX family proteins decreased CaMKII activation, whereas overexpression of ACOXI increased CaMKII activation. Overall, our studies identify active CaMKII as a novel connection between organelle β-oxidation and acetyl-CoA transport with cell survival, migration, and prostate cancer metastasis.Significance: This study identifies a cell metabolic pathway that promotes prostate cancer metastasis and suggests prostate cancer may be susceptible to β-oxidation inhibitors. Cancer Res; 78(10); 2490-502. ©2018 AACR.

GLUT1 regulates cell glycolysis and proliferation in prostate cancer

BACKGROUND

Glucose transporter 1 (GLUT1) plays a critical role in tumorigenesis and tumor progression in multiple cancer types. However, the specific function and clinical significance of GLUT1 in prostate cancer (PCa) are still unclear. Therefore, in this study, we investigated the role of GLUT1 in PCa.

METHODS

GLUT1 protein levels in prostate cancer tissue and tumor-adjacent normal tissues were measured and compared. Furthermore, real-time PCR and Western blot analysis were both used to detect GLUT1 expression levels in different PCa cell lines. Flow cytometry and cell-based assays, such as a glucose uptake and lactate secretion assay, CCK-8 assay, and transwell migration and wound healing assay, were used to monitor cancer cell cycle distribution, glycolysis, proliferation, and motility, respectively. Moreover, a mouse tumor xenograft model was used to investigate the role of GLUT1 in tumor progression in vivo.

RESULTS

GLUT1 expression levels are higher in PCa tissues than in tumor-adjacent normal tissues. The results from real-time PCR and Western blot analysis revealed a similar increase in the GLUT1 expression levels in PCa cell lines. Moreover, knockdown of GLUT1 inhibits cell glycolysis and proliferation and leads to cell cycle arrest at G2/M phase in the 22RV1 cell line but not in the PC3 cell line. In vivo experiments further confirmed that GLUT1 knockdown inhibits the growth of tumors derived from the 22RV1 cell line. In addition, we also showed that GLUT1 knockdown has no effect on cell migration in vitro.

CONCLUSIONS

GLUT1 may play an important role in PCa progression via mediating glycolysis and proliferation. Our study also indicated a potential crosstalk between GLUT1-mediated glycolysis and androgen sensitivity in PCa.

Inhibition of O-GlcNAc transferase activity reprograms prostate cancer cell metabolism

Metabolic networks are highly connected and complex, but a single enzyme, O-GlcNAc transferase (OGT) can sense the availability of metabolites and also modify target proteins. We show that inhibition of OGT activity inhibits the proliferation of prostate cancer cells, leads to sustained loss of c-MYC and suppresses the expression of CDK1, elevated expression of which predicts prostate cancer recurrence (p=0.00179). Metabolic profiling revealed decreased glucose consumption and lactate production after OGT inhibition. This decreased glycolytic activity specifically sensitized prostate cancer cells, but not cells representing normal prostate epithelium, to inhibitors of oxidative phosphorylation (rotenone and metformin). Intra-cellular alanine was depleted upon OGT inhibitor treatment. OGT inhibitor increased the expression and activity of alanine aminotransferase (GPT2), an enzyme that can be targeted with a clinically approved drug, cycloserine. Simultaneous inhibition of OGT and GPT2 inhibited cell viability and growth rate, and additionally activated a cell death response. These combinatorial effects were predominantly seen in prostate cancer cells, but not in a cell-line derived from normal prostate epithelium. Combinatorial treatments were confirmed with two inhibitors against both OGT and GPT2. Taken together, here we report the reprogramming of energy metabolism upon inhibition of OGT activity, and identify synergistically lethal combinations that are prostate cancer cell specific.

Metabolic Differences in Glutamine Utilization Lead to Metabolic Vulnerabilities in Prostate Cancer

The new oncologic paradigm of precision medicine is focused on identifying metabolic, proteomic, transcriptomic and genomic variabilities in tumors that can be exploited to tailor treatments and improve patient outcomes. Metabolic changes are a hallmark of cancer, and inhibition of metabolic pathways is now a major strategy in medicinal chemistry for targeting cancers. However, non-invasive biomarkers to categorize metabolic subtypes are in short supply. The purpose of this study was to characterize the intracellular and extracellular metabolic profiles of four prostate cancer cell lines with varying degrees of aggressiveness. We observed metabolic differences between the aggressive prostate cancer cell line PC3 and the even more aggressive, metastatic subline PC3M assessed by hyperpolarized in vivo pyruvate studies, nuclear magnetic resonance spectroscopy, and carbon-13 feeding studies. On further examination of the differences between these two cell lines, we found increased glutamine utilization in the metastatic PC3M subline that led directly to sensitivity to glutaminase inhibitor CB-839. Our study supports the theory that metastatic progression increases glutamine utilization and the inhibition of glutaminolysis could have clinical implications.

Psoralen stimulates osteoblast proliferation through the activation of nuclear factor-κB-mitogen-activated protein kinase signaling

Osteoporosis is a systemic skeletal disease that leads to increased bone fragility and susceptibility to fracture. Approximately 50% of postmenopausal women develop osteoporosis as a result of postmenopausal estrogen deficiency. To reduce fractures related to osteoporosis in women, previous studies have focused on therapeutic strategies that aim to increase bone formation or decrease bone resorption. However, pharmacological agents that aim to improve bone fracture susceptibility exhibit side effects. Current studies are investigating natural alternatives that possess the benefits of selective estrogen receptor modulators (SERMs) without the adverse effects. Recent studies have indicated that phytoestrogen may be an ideal natural SERM for the treatment of osteoporosis. In Chinese herbal medicine, psoralen, as the predominant substance of Psoralea corylifolia, is considered to be a phytoestrogen and is used as a remedy for osteoporosis. A number of studies have demonstrated the efficacy of psoralen in bone formation. However, the pathways and underlying molecular mechanisms that participate in psoralen-induced osteoblast formation are not well understood. In the present study, hFOB1.19 cells were treated with psoralen at different concentrations (0, 5, 10, 15 and 20 µM) for 0, 24, 36, 48 and 72 h, respectively. Reverse transcription-quantitative polymerase chain reaction and western blot assays were performed to detect glucose transporter 3 (GLUT3) expression. A cell counting kit-8 assay was used to analyze cell proliferation. In addition the effects of mitogen activated protein kinase inhibitors on extracellular signal-regulated kinase (ERK), phosphorylated (p)-ERK, p38, p-p38, c-Jun N-terminal kinase (JNK) and p-JNK expressions and cell proliferation were measured, as was the effect of nuclear factor (NF)-κB inhibitor on P65 and GLUT3 expressions and cell proliferation. The results indicated that psoralen stimulates hFOB1.19 cell proliferation in a dose-dependent manner (P<0.05). Phospho-ERK, p38 and JNK were markedly increased by psoralen compared with the control group (P<0.05), and the specific inhibitors of ERK (SCH772984), p38 (SB203580) and JNK (SP600125) reversed the stimulatory effects of psoralen on signal marker phosphorylation (P<0.05). The rate of psoralen-induced cell proliferation was significantly suppressed by inhibitors of ERK, JNK and p38 compared with psoralen treatment alone (P<0.05). In addition, psoralen stimulated osteoblast proliferation via the NF-κB signaling pathway. Therefore, the present findings suggest that psoralen may be a potential natural alternative to SERMs in the treatment of osteoporosis and fractures.

Inhibition of prostate cancer proliferation by Deferiprone

Cancer growth and proliferation rely on intracellular iron availability. We studied the effects of Deferiprone (DFP), a chelator of intracellular iron, on three prostate cancer cell lines: murine, metastatic TRAMP-C2; murine, non-metastatic Myc-CaP; and human, non-metastatic 22rv1. The effects of DFP were evaluated at different cellular levels: cell culture proliferation and migration; metabolism of live cells (time-course multi-nuclear magnetic resonance spectroscopy cell perfusion studies, with 1-¹³ C-glucose, and extracellular flux analysis); and expression (Western blot) and activity of mitochondrial aconitase, an iron-dependent enzyme. The 50% and 90% inhibitory concentrations (IC₅₀ and IC₉₀ , respectively) of DFP for the three cell lines after 48 h of incubation were within the ranges 51-67 μM and 81-186 μM, respectively. Exposure to 100 μM DFP led to: (i) significant inhibition of cell migration after different exposure times, ranging from 12 h (TRAMP-C2) to 48 h (22rv1), in agreement with the respective cell doubling times; (ii) significantly decreased glucose consumption and glucose-driven tricarboxylic acid cycle activity in metastatic TRAMP-C2 cells, during the first 10 h of exposure, and impaired cellular bioenergetics and membrane phospholipid turnover after 23 h of exposure, consistent with a cytostatic effect of DFP. At this time point, all cell lines studied showed: (iii) significant decreases in mitochondrial functional parameters associated with the oxygen consumption rate, and (iv) significantly lower mitochondrial aconitase expression and activity. Our results indicate the potential of DFP to inhibit prostate cancer proliferation at clinically relevant doses and plasma concentrations.

Genetic polymorphisms in the telomere length-related gene ACYP2 are associated with the risk of colorectal cancer in a Chinese Han population

We investigated the association between single nucleotide polymorphisms (SNPs) in ACYP2, which has been associated with telomere length in several types of cancer, and the risk of CRC in a Chinese Han population. In a case-control study that included 247 cases and 300 healthy controls, 14 SNPs in ACYP2 were selected and genotyped using the Sequenom MassARRAY platform. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using unconditional logistic regression after adjusting for age and gender. We determined that rs843711 and rs843706 were associated with an increased risk of CRC (rs843711: OR = 1.376, 95% CI = 1.082-1.749, p = 0.009; rs843706: OR = 1.361, 95% CI = 1.069-1.733, p = 0.012). Additionally, rs6713088, rs843645, rs843711, and rs843706 were associated with an increased risk of CRC under additive and recessive models (p < 0.05). Finally, the "TTCTCGCC" and "CG" haplotypes decreased the risk of CRC, while the "AG" haplotype increase the risk of CRC. The association between rs843711 and CRC remained significant after Bonferroni correction for multiple comparisons (p ≤ 0.00036). Our data shed new light on the associations between genetic variants in the ACYP2 gene and CRC susceptibility in a Chinese Han population.

Ghrelin acts as energy status sensor of male reproduction by modulating Sertoli cells glycolytic metabolism and mitochondrial bioenergetics

Ghrelin is a growth hormone-releasing peptide that has been suggested to interfere with spermatogenesis, though the underling mechanisms remain unknown. We studied the effect of ghrelin in human Sertoli cells (hSCs) metabolic phenotype. For that, hSCs were exposed to increasing concentrations of ghrelin (20, 100 and 500 pM) mimicking the levels reported in obese, normal weight, and severely undernourished individuals. The metabolite production/consumption was determined. The protein levels of key glycolysis-related transporters and enzymes were assessed. The lactate dehydrogenase (LDH) activity was measured. Mitochondrial complexes protein levels and mitochondria membrane potential were also measured. We showed that hSCs express the growth hormone secretagogue receptor. At the concentration present in the plasma of normal weight men, ghrelin caused a decrease of glucose consumption and mitochondrial membrane potential in hSCs, though LDH activity and lactate production remained unchanged, illustrating an alteration of glycolytic flux efficiency. Exposure of hSCs to levels of ghrelin found in the plasma of severely undernourished individuals decreased pyruvate consumption and mitochondrial complex III protein expression. All concentrations of ghrelin decreased alanine and acetate production by hSCs. Notably, the effects of ghrelin levels found in severely undernourished individuals were more pronounced in hSCs metabolic phenotype highlighting the importance of a proper eating behavior to maintain male reproductive potential. In conclusion, ghrelin acts as an energy status sensor for hSCs in a dose-dependent manner, showing an inverse association with the production of lactate, thus controlling the nutritional support of spermatogenesis.

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.

Genetic Alteration in Phosphofructokinase Family Promotes Growth of Muscle-Invasive Bladder Cancer

Aims

Metabolic alterations in cancer, including bladder cancer, have been addressed in recent years. We aimed to study the role of phosphofructokinase (PFK) in muscle-invasive bladder cancer (MIBC).

Method

By in silico analysis of the bladder cancer data from the Cancer Genome Atlas (TCGA) database using the cBioPortal platform, we studied genetic alteration of genes within the PFK family (PFKL, PFKM, PFKP, PFKFB1, PFKFB2, PFKFB3, and PFKFB4). In vitro studies were carried out using the PFK inhibitor 2,5-anhydro-D-glucitol-6-phosphate.

Results

Genetic alterations of PFK family genes were observed in ~44% of MIBC cases in TCGA. The main alterations were amplification and upregulation. Patients with altered PFK gene status were more likely to have a history of noninvasive bladder cancer. Altered PFK status was not associated with survival or disease relapse. Use of the PFK inhibitor significantly decreased the level of glycolysis and inhibited the growth and invasion of bladder cancer cells.

Conclusions

PFKs were critical genes in charge of glycolysis and were upregulated in bladder cancer. Targeting this pathway could inhibit cell growth in bladder cancer.

A Continuously Infused Microfluidic Radioassay System for the Characterization of Cellular Pharmacokinetics

Measurement of cellular tracer uptake is widely applied to learn the physiologic status of cells and their interactions with imaging agents and pharmaceuticals. In-culture measurements have the advantage of less stress to cells. However, the tracer solution still needs to be loaded, unloaded, and purged from the cell culture during the measurements. Here, we propose a continuously infused microfluidic radioassay (CIMR) system for continuous in-culture measurement of cellular uptake. The system was tested to investigate the influence of the glucose concentration in cell culture media on ¹⁸F-FDG uptake kinetics.

METHODS

The CIMR system consists of a microfluidic chip integrated with a flow-control unit and a positron camera. Medium diluted with radioactive tracer flows through a cell chamber continuously at low speed. Positrons emitted from the cells and from tracer in the medium are measured with the positron camera. The human cell lines SkBr3 and Capan-1 were incubated with media of 3 different glucose concentrations and then measured with ¹⁸F-FDG on the CIMR system. In addition, a conventional uptake experiment was performed. The relative uptake ratios between different medium conditions were compared. A cellular 2-compartment model was applied to estimate the cellular pharmacokinetics on CIMR data. The estimated pharmacokinetic parameters were compared with expressions of glucose transporter-1 (GLUT1) and hexokinase-2 measured by quantitative real-time polymerase chain reaction.

RESULTS

The relative uptake ratios obtained from CIMR measurements correlated significantly with those from the conventional uptake experiments. The relative SDs of the relative uptake ratios obtained from the CIMR uptake experiments were significantly lower than those from the conventional uptake experiments. The fit of the cellular 2-compartment model to the ¹⁸F-FDG CIMR measurements was of high quality. For SkBr3, the estimated pharmacokinetic parameters k₁ and k₃ were consistent with the messenger RNA expression of GLUT1 and hexokinase-2: culturing with low glucose concentrations led to higher GLUT1 and hexokinase-2 expression as well as higher estimated k₁ and k₃ For Capan-1, the estimated k₁ and k₃ increased as the glucose concentration in the culture medium decreased, and this finding did not match the corresponding messenger RNA expression.

CONCLUSION

The CIMR system captures dynamic uptake within the cell culture and enables estimation of the cellular pharmacokinetics.

The MCT4 Gene: A Novel, Potential Target for Therapy of Advanced Prostate Cancer

PURPOSE

The management of castration-resistant prostate cancer (CRPC) is a major challenge in the clinic. Androgen receptor signaling-directed strategies are not curative in CRPC therapy, and new strategies targeting alternative, key cancer properties are needed. Using reprogrammed glucose metabolism (aerobic glycolysis), cancer cells typically secrete excessive amounts of lactic acid into their microenvironment, promoting cancer development, survival, and progression. Cellular lactic acid secretion is thought to be predominantly mediated by MCT4, a plasma membrane transporter protein. As such, the MCT4 gene provides a unique, potential therapeutic target for cancer.

EXPERIMENTAL DESIGN

A tissue microarray of various Gleason grade human prostate cancers was stained for MCT4 protein. Specific, MCT4-targeting antisense oligonucleotides (MCT4 ASO) were designed and candidate MCT4 ASOs checked for effects on (i) MCT4 expression, lactic acid secretion/content, glucose consumption, glycolytic gene expression, and proliferation of human CRPC cells and (ii) growth of PC-3 tumors in nude mice.

RESULTS

Elevated MCT4 expression was associated with human CRPC and an earlier time to relapse. The treatment of PC-3, DU145, and C4-2 CRPC cultures with candidate MCT4 ASOs led to marked inhibition of MCT4 expression, lactic acid secretion, to increased intracellular lactic acid levels, and markedly reduced aerobic glycolysis and cell proliferation. Treatment of PC-3 tumor-bearing nude mice with the MCT4 ASOs markedly inhibited tumor growth without inducing major host toxicity.

CONCLUSIONS

MCT4-targeting ASOs that inhibit lactic acid secretion may be useful for therapy of CRPC and other cancers, as they can interfere with reprogrammed energy metabolism of cancers, an emerging hallmark of cancer. Clin Cancer Res; 22(11); 2721-33. ©2016 AACR.

Testicular lactate content is compromised in men with Klinefelter Syndrome

Klinefelter syndrome (KS) is the most common genetic cause of human infertility, but the mechanism(s) responsible for its phenotype remain largely unknown. KS is associated with alterations in body composition and with a higher risk of developing metabolic diseases. We therefore hypothesized that KS men seeking fertility treatment possess an altered testicular metabolism profile that may hamper the nutritional support of spermatogenesis. Testicular biopsies from control (46, XY) (n = 6) and KS (47, XXY) (n = 6) individuals were collected and analyzed by proton high-resolution magic-angle spinning nuclear magnetic resonance spectroscopy. The mRNA and protein expression of crucial glycolysis-associated enzymes and transporters were evaluated in parallel by quantitative PCR and Western blot, respectively. Our data revealed altered regulation of glucose transporters (GLUT1 and GLUT3); phosphofructokinase 1, liver isoform (PFKL); and lactate dehydrogenase A (LDHA) expression in the testis of KS patients. Moreover, we detected a severe reduction in lactate and creatine accumulation within testicular tissue from KS men. The aberrant levels of the biomarkers detected in testicular biopsies of KS men may therefore be associated with the infertility phenotypes presented by these men. Mol. Reprod. Dev. 83: 208-216, 2016. © 2015 Wiley Periodicals, Inc.

Suppressed glycolytic metabolism in the prostate of transgenic rats overexpressing calcium-binding protein regucalcin underpins reduced cell proliferation

Regucalcin (RGN) is a calcium-binding protein underexpressed in human prostate cancer cases, and it has been associated with the suppression of cell proliferation and the regulation of several metabolic pathways. On the other hand, it is known that the metabolic reprogramming with augmented glycolytic metabolism and enhanced proliferative capability is a characteristic of prostate cancer cells. The present study investigated the influence of RGN on the glycolytic metabolism of rat prostate by comparing transgenic adult animals overexpressing RGN (Tg-RGN) with their wild-type counterparts. Glucose consumption was significantly decreased in the prostate of Tg-RGN animals relatively to wild-type, and accompanied by the diminished expression of glucose transporter 3 and glycolytic enzyme phosphofructokinase. Also, prostates of Tg-RGN animals displayed lower lactate levels, which resulted from the diminished expression/activity of lactate dehydrogenase. The expression of the monocarboxylate transporter 4 responsible for the export of lactate to the extracellular space was also diminished with RGN overexpression. These results showed the effect of RGN in inhibiting the glycolytic metabolism in rat prostate, which was underpinned by a reduced cell proliferation index. The present findings also suggest that the loss of RGN may predispose to a hyper glycolytic profile and fostered proliferation of prostate cells.